texts: How low an insulation resistance is too low for a residential electrical system?

texts:
I have had occasion recently to test the wiring of a residential building for damage from a lightning strike. I opened all the breakers, removed all the loads, opened the panel, and meggered each hot circuit to neutral, and 220V circuits from hot to hot.  Many of the results maxed out my meter at 275 megaohms, but some did not. I got quite a few results ranging from 20 megaohms to 200 megaohms. I got a few as low as 1 megaohm. Since those were on kitchen circuits, I suspect contamination of the receptacles.

But this leads me to ask: how low is too low? Much below one megaohm I'd start to worry about heating. But I can't find any standard saying "thou shalt".  The best I've seen is ANSI/NETA MTS, which I can get an older 2011 copy of.
http://www.iemworldwide.com/pdf/ansi-neta-mts-2011.pdf

Table 100.1 recommends a resistance of at least 25 megaohms on circuits of 250 volts.  But it also says that there's no consensus standard, or at least there wasn't in 2011.

Is there a better answer than that?


texts:
I'm writing to a microSD card from within my firmware, but it's the lowest priority task, so it can be interrupted by other tasks while it's in the middle of reading/writing.

Now suppose I communicated with this microSD card using a UART. The problem during reads would be that the hardware RX FIFO would overflow, so the maximum delay I can effort would be (FIFO size × bytes/second), and during writes there would be no problem, because the other end would just wait until I send the next character.

How does this work now I'm using SPI? Is the situation the same that for writes it doesn't matter, and for reads it depends on the SPI FIFO size?


texts: I would like to power a 12 volt automobile radiator fan with a 110 volt generator.  I need to know what the amp draw will be on the 110 generator. At 12 volts the fan is rated at 24 amps.  If I use a transformer to go from 110 to 12 volts would that cause a 2.4 amp draw on the 110 volt generator? I realize that is approximate amp draw and the transformer may only have an efficiency of about 80%.


texts: Where to find 478 motherboard circuit schematics?

texts: I have searched for 478 motherboard circuit schematics on the internet, but have found none. Are any available publicly?


texts: Where would a pure inductive or capacitive load be placed on a Smith chart, assuming the TL impedance is real?

texts: I'm a new HAM operator, and just started learning about the amazing tool that is Smith charts; and it got me wondering what the edge case of a pure inductive or capacitive load would be? Since the normalized real part is 0, would they be plotted in the same spot?


texts: Looking for a circuit switch operated by velocity

texts:
I'm not at all electronically minded, but am looking for a small electronic circuit switch that is operated by velocity. Many years ago, I used to have a Casio watch that had some sort of switch for the light, where if you turned your wrist 90 degrees at a reasonable speed, the light would come on for 10-15 seconds.

I am now looking for some sort of component that would do the same job, and don't have a clue where to start.

Any help would be greatly appreciated.

Thanks.


texts: Help me modify this level-shifting circuit

texts:
I want to modify this circuit to output a 0-5V triangle wave.
It is currently configured to level shift a 5-10V triangle wave to
+/- 10V (for use in other parts the circuit), and the triangle wave output is taken from a voltage divider to give +/-5V.
Also, I will be using 12V power instead of 15V in the new circuit.
I haven't found any easy-to-understand tutorials on how to do this yet.


texts:
Transistors serve multiple purposes in an electrical circuit, i.e switches, to amplify electronic signals, allowing you to control current etc...

However, I recently read about Moore's law, among other random internet articles, that modern electronic devices have a huge number of transistors packed into them, with the amount of transistors that are in modern electronics being in the range of millions, if not billions.

However, why exactly would anyone need so many transistors anyway? If transistors work as switches etc, why would we need such a absurdly large amount of them in our modern electronic devices? Are we not able to make things more efficient so that we use wayy less transistors than what we are using currently?


texts: How do I connect a four way key in a potentiometer?

texts:
I asked this question in Physics stack exchange and had an answer, but I couldn't understand it well. A comment said this stack exchange was a better fit for the question.

Question:

How do I connect (which wire to which terminal) a four way key to a potentiometer, to compare the EMF of two cells. Circuit diagram and a four way key are shown in the pictures below.

A vague 3d representation of the whole circuit will be very much appreciated. I need to know where I have to connect the potentiometer and the cell and where do I connect the galvanometer?


texts:
I'm configuring the clock of the LCD which has a max clock of 30MHz as following. Plus I'm using the touch at I2C1, and USB at 48MHz.

The clearing and painting an image to the LCD is slow, and it's not that fast, also the operations that the CPU is using is really slow. I'm not sure what is configured wrong, or how do I configure the MCU to run at MAX Speed.

Here is the screenshot of the configuration:


texts: Is charge batteries in series faster than in parallel?

texts: I would like to know if charging 7 lithium-ion batteries in series with BMS 7S are faster than simply charge them in parallel. Please for your advice, thank you!


texts:
I can't understand what's the job of RCC_xxPeriphResetCmd() function in the stm32f4xx-rcc driver? in fact the thing that i can't realize is what happens to a peripheral when we reset it (by setting it's relative bit in the RCC AHBx(or APBx) peripheral reset register) ?

for example for AHB1 Peripheral :

the register is :

and stm32f4xx-rcc driver function is :

void RCC_AHB1PeriphResetCmd(uint32_t RCC_AHB1Periph, FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_RCC_AHB1_RESET_PERIPH(RCC_AHB1Periph));
  assert_param(IS_FUNCTIONAL_STATE(NewState));

  if (NewState != DISABLE)
  {
    RCC->AHB1RSTR |= RCC_AHB1Periph;
  }
  else
  {
    RCC->AHB1RSTR &= ~RCC_AHB1Periph;
  }
}


texts: What is the most effective way to prevent electrical arcs across resistors?

texts:
When building any kind of ultra high voltage boost circuit or transformer, the high voltage will often arc between components if the voltage is high enough and the distance between them is short enough. In many cases, it’s easy to fix this by increasing the air gap or coating with insulation, but not always.
In applications where resistors are employed in systems over a few hundred kilovolts, the resistor may offer a greater resistance than the insulator and the breakdown voltage of air over the length of the resistor may be far below the circuit operating voltages. In that case the insulator will fail and the current will arc around the resistor.
What’s the best way to fix that? In high power applications you can often use wire wound resistors. When doing that, the current could just arc between the windings if the insulation isn’t thick enough, or between the connector and the resistor housing. This is definitely a problem because bushings are often used in conductors in high voltage applications, but is there a way of fixing this for resistors?


texts:
I hope you could help me with this question.
Why would the voltage drop only by 0.2V when the forward voltage of this diode is 0.8V.
The Zener diode voltage is 10V
Thanks.


texts: I'm thinking of embedding a circuit into a jacket that I have, and I was wondering whether I could dry clean it with the circuit still attached to it. I read that dry cleaning could potentially dissolve items like plastic pens and was wondering if it could dissolve the PCB or the chip's shell...


texts: Crowbar circuit design: choosing the correct parts

texts:
I've designed a crowbar circuit with the aim of protecting my circuit from overvoltage (it cannot exceed 15V) and reverse polarity protection.
Looking online,Ii've found that a good solution for overvoltage is the "crowbar" circuit, and I've designed this:

This circuit is supposed to protect my circuit from overvoltage and reverse polarity (diode D7.)
The parts that I've picked are supposed to work for the following power needs:
The circuit normally works with 12V input and it will power two devices:

A low current device (that draws up to 500mA)
A step down converter (LM2596) that drives a high current LED strip (that draws up to 2A at 5V.)

Here comes the crowbar circuit. As you can see in the image, the netflag marked as +12V-POE powers the low current device, and has a maximum allowed voltage input of 15V, the VIN netflag is the voltage input of the LM2596 and steps down the voltage to 5V, allowing the high current LED strip to be powered.
I have some doubts about the components that I've picked from the JLCPCB library (I need to use their library in order to receive the board assemblied and ready to be tested.)
Do you guys think that with those components the crowbar circuit will work without any problems?
Leaving the resistor and capacitor aside, here are the datasheets of the thyristor, fuse and picked diodes:

Fuse
Zener
Thyristor
Schotty


texts:
The process:
I want to do a on-board-in-loop test. From simulink I want to send data via serial to ATmega 128, which will generate a PWM at 4kHz. This PWM will pass through a low-pass-filter so that the voltage across the capacitor will give the mean value of the PWM as output. This mean will be read by a data acquisition card (DAQ card) by simulink thus completing the loop.
The DAQ can read a maximum of 10V.

The low pass filter is simulating  acuator dynamics, which has some settling time after application of PWM (settling time - time required for the voltage across it it to become 99% of mean of applied voltage)

The problem:
The low pass filter has a ripple voltage.

Ripple voltage: voltage by which the final output of the low pass filter will oscillate about the mean of the PWM which is given at input. This ripple voltage is basically noise.

The ripple voltage comes to be of the order of the order of 1e-3V if the RC ratio is about 1e-3.

In the beginning of the simulation, the mean of the PWM voltages from my ATmega are about 1V. It then keeps decreasing till it becomes really low, of the order of 1e-5V(by keeping a really low duty cycle). I need to capture this entire range(the DAQ is capable).So I will need to amplify the PWM.

My question: Will a non-inverting OPAMP be able to do it? Asking this as an OPAMP has a slew rate (0.5V/microsecond). So will it be hampered when the PWM signal goes from LOW to HIGH or HIGH to LOW? If you can suggest any other way to achieve this, that would also help.

Edit 1: If I keep the RC product of the low pass filter as 40, I get a ripple voltage as low as 1e-6V. But is it advisable to build such a filter?

Website used for filter simulation: http://sim.okawa-denshi.jp/en/PWMtool.php

Edit 2: I want the settling time of the low pass filter to be around 400ms.


texts: MCP73833 suitable for charging battery and system at the same time?

texts:
I saw a schematic for the "USB LiIon/LiPoly charger - v1.2" by Adafruit. The schematic is shown below.

After reading the data sheet I am uncertain if the MCP73833 Charge Management Controller chip is safe to use when connected to the USB, battery and system at once.

The only line in the data sheet mentioning system load that I could find was:

  The TE input can be used to disable the timer when the charger is
  supplying current to charge the battery and power the system load.

This line indicates that it should be ok, but I feel this should be said more explicitly and not in one line that actually is about TE (timer enable) input.

So is this within the intended use of this chip?

Schematic:


texts: 18650 Cell boost converter to 4.8v (not 5v)

texts:
I have a torch in which 3 AAA cells are put in (1.6 (new AAA) * 3 =4.8v). The problem is these are not long lasting and i have to change them after few days. What i am looking for is a rechargeable option. I cannot use 1.2v Ni-Cd(1.2 * 3 = 3.6v) regargeble as the voltage is too low and led is dim.
Recently i extracted 18650 (LGABD11865) batteries from my Old Dell Laptop.
I used powerbank module to test it out with my torch light. The output is slighltly over 5v (around 5.11) and the light consumes around 1.3Amps. When the voltage is reduced to 4.8v (checked through power supply) the amps are reduced to 1 Amp which is reasonable as it wont consume more battery and the torch wouldnt heat up.
Can someone please help me in this regard i have very basic knowledge of Electronics i need 4.8v CV with atmost 1 Amps.  Furthermore the torch can only take 1 18650 Battery along with 1 tp4056 charging module or small powerbank module (usb type A port removed).
Update: I used 3 new AAA  batteries in the casing which came with the torch. The voltage when measured showed 5.01v but the current at full brightness was 0.5amps. I need a resister MOSFET anything which can lower the current input to the torch. At present when connected with 5v supply the torch takes around 1.23 amps.


texts:
I was looking at a certain circuit in which there was the necessity of generating 3 DC current sources (10uA, 50uA, 250uA), starting from a given current source of 10uA. Let's consider firstly the circuit which has to generate 10uA (let's call it A).

1st question: can you explain me how does it works, in an intuitive way? Why is the current I4 copied to the transistor M10 (i.e. M10 is a current mirror 1:1)?

Now let's consider the circuits which have to generate 50uA and 100uA (let's call them B and C):

They are connected to I4 through the label VBN, as for circuit A. So B is a current mirror 1:5, C is a current mirror 1: 25. This result is reached by inserting 5 transistors in the first one (molteplicity = 5 so there are 5 transistors in series) and 25 transistors in the second one (molteplicity = 25).

2nd question: can you explain me intuitively why the number of transistors is equal to the multiplication factor of the current?


texts: Microcontroller freezing up when I connect a motor

texts:
The out pin is a PWM feeding into the npn transistor to control the speed of the motor. The motor is a small dc motor I found from a toy, and the transistor is the 2n2222. The microcontroller I'm using is a Tiva C. 3.3V and 9V are seperate power sources.

There is an Arduino to the left not drawn that generates a digital signal from an IR LED using the NEC protocol. The IR reciever filters out the carrier and feeds the raw digital signal to the microcontroller. The micrcontroller is coded to recognize two patterns; one to increase duty cycle and one to decrease.

When the duty cycle goes above some value, typically in the ballpark of 30%, the microcontroller freezes up and is not responsive to inputs. I have an LED that always blinks at 1Hz, but that also freezes when the motor is connected. As soon as I disconnect the motor, the microcontroller works fine and the duty cycle can vary the entire range and the LED resumes blinking. If I replace the motor with a resistive load, everything works fine.


texts:
It is required to find R=V/I given that \$V_{gd}\$ is zero.

Honestly, I don't know where to start. I don't think there is a current in the \$R_s\$ and \$R_g\$ resistors because the current has no way of coming back.(is that right?)


texts:
Im doing a project with a PIC18F452 and I will have to use USART. Thus, I bought a FTDI Basic breakout board (from Sparkfun) to make debugging easier. The board is the 5V version.

I already tested FT232R with a loopback circuit and Putty (on Windows) and it works well. I also tested PIC with a loopback circuit and it also works well.
However I can't get FT232R to work with PIC. In the microcontroller I have USART configured with 9600kbaud, 8bit, no parity (same as PC side), RX with interrupt. Im just sending data from PC to PIC. When PIC receives something prints it on LCD. The problem is PIC isn't receiveing anything.
So I picked up a osciloscope probe and the results are these:

The signal doesn't touch the GND!
Thats why PIC doesn't detect data arriving at RX pin, right?

However if I disconnect FT232 TX pin from PIC RX pin, I get:

I have both GND (ft232 and PIC) connected.

Any suggestions on how to solve this?

Thanks!


texts: Create a power supply that accepts 3.7 V - 5 V and outputs 5 V

texts:
Hello I was wondering if there is a solution for a power supply to accept a range of 3.7 V to 5 V and output a constant 5 V. Im trying to get a low powered circuit to be able to be powered from either 3.7 V lithium batteries or 5 V battery charger. will something like the modules based on the MT3608 do the trick?
Will something like MT3608 be able to provide 5 V when the input is also 5 V from a wall charger?


texts: Please explain in layman's terms how a PID accounts for inertia in temperature control

texts:
I'm building my own hobbyist microprocessor-controlled reflow oven. I'm using (mechanical) relays to turn the heaters (i.e. quartz tubes) on or off. I've noticed heating lags a couple of seconds before the temperature starts to rise.

For now I'm managing the temperature profile manually with the assistance of an Arduino, which just turns the heaters off when the set temperature is reached. For instance when I set the temperature to, say 120° Celsius and the heaters stop, the temperature still climbs 10-20 degrees so there is quite a bit of overshoot then some ringing, which decreases slowly.

I've read and watched many examples that make use of a PID for a better temperature control. Without that I would just stop the heaters, like 10-20 degrees below the set value and turn them on/off in short periods afterwards until the temperature stabilizes around the set value. I just know the delta varies with the temperature so it might not be as straightforward — I know about the exponential nature of temperature rise with a fixed set value.

So can anybody explain in layman's terms how a PID accounts for the inertia, e.g. what role the integral part and what the derivative part play in simple terms, as well as how/if I can figure out rather intuitively an estimation of the derivative and integral quantities without resorting to complex calculations.


texts: Power Amplifier (Darlington) with Power and current limitation

texts:
I'm designing a power amplifier and the following circuit is the output stage. My output stage consists of two complementary transistors for both, positive and negative waves but for better understanding, I will only show the one which handles the positive waves.

Vcc = 12V
Load = 8ohm resistor
Output current (max) = 1.1A
Output voltage (max) = ~ 8V
IN = Sinus with ~8V amplitude and an extremely low (~250uA) current
as the discrete Darlington needs a low input current.

As far as I know, R1, R3 & R4, D1 & Q3 are for current & power limitation. How does that work and how can I calculate these three resistors?

Thank you! I would be very happy for every help I can get.


texts: Suppose I have a DC/DC converter, Recom RPP30 for an example to hand. It lists an isolation voltage of 3000 VDC. How does this translate to an AC isolation voltage? Would this be equivalent to 3000 VAC RMS? 2121 VAC RMS (3000 peak)? Something else?


texts: Unknown "D" variable on datasheet's max pulse current description

texts:
I was reading the datasheet for an SFH4545 IR LED. In the "maximum ratings" category, the "surge current" value's conditions are: $$t_p=100\mu\text{s},\,D=0$$
What does the D mean? At first, I thought it could be the duty cycle, but it'd be strange if it was 0...


texts: Why does my MCU work better when powered to Vcc and PA1=D2 instead of Vcc and GND?

texts:
I'm making a MIDI processor, with its power coming ... directly from the MIDI signal itself, as done by the author of this page (see "Powered by MIDI" paragraph): it works well with a 100µF cap. I have assembled several units with no problem at all, perfectly working.

I'm using a ATtiny4313 and usually it's wired this way:

VCC (pin 20) => + of the 100 µF cap
GND (pin 10) => GND of MIDI sockets
RX/D0 (pin 2) => MIDI IN (with the usual MIDI IN schematics involving an optocoupler and resistors)
TX/D1 (pin 3) => MIDI OUT (with the usual MIDI OUT schematics too)

However on new units I'm currently assembling I noticed that it is not working very well (sometimes the MIDI signal is ok, sometimes it's not ok, and some notes are stuck, some are dropped).

Then, instead of the previous connection, I tried this way:

VCC (pin 20) => + of the 100 µF cap
PA1/D2 (pin 4) => GND of MIDI sockets
RX/D0 (pin 2) => MIDI IN (with the usual MIDI IN schematics involving an optocoupler and resistors)
TX/D1 (pin 3) => MIDI OUT (with the usual MIDI OUT schematics too)
and nothing connected to GND of the ATtiny!

And miracuously, everything works perfectly, the MIDI signal is perfect, no lost or stuck note! I tried it during a long time and it's perfect like this.

Question: What could be the reason of this thing: the MCU works better when powered on VCC (pin 20) and PA1/D2 (pin 4), instead of VCC and GND?

PS: In my code, I did nothing with pin #4, no digitalWrite, no pinMode. The only thing present in my code relative to a pin is pinMode(7, INPUT_PULLUP);, because I might add a push button later.

PS2: I thought it would be a oscillator problem with the internal oscillator a little bit too much "off" and that adding a crystal would solve it, but then why would doing PA1/D2 (pin 4) ==> GND solve everything perfectly well, even without a crystal?

PS3: I read a few parts of the ATtiny 4313 datasheet without any clue about this mysterious situation, i.e. power it in an uncommon way and it works 100%!


texts: How will I get the per-unit parameters when the data from the short-circuit test are shady?

texts:
Data from short-circuit and open-circuit tests of a 60-Hz, 100-kVA, 4600–230-V transformer are:

  VOC = 230 V
  IOC = 14 A
  POC = 60 W

  VSC = 172.3 V
  ISC = 20.2 A
  PSC = 1046 W

  Get (a) the magnetizing reactance referred to the high side and (b) the per-unit parameters.

ISC ≠ Irated, so how will I solve for (b)?

The problem is from the book with ISBN 0130612103.


texts:
I need to mount some relays that I have soldered wires to.  If I place them on a non-conductive surface and use a generous amount of standard glue from a hot glue gun, will that be relatively safe?  I'll be running mains level voltage through the relays.

According to this aricle  hot glue melts somewhere between 121 °C and 193 °C which I hope is much hotter than the relays would ever get.

Is there a better way to mount these relays?  Obviously using a PCB would be best, but the cost is a bit prohibitive for a custom designed PCB.


texts: cjmcu-3221 i2c problem - doesn't show on search

texts:
I have big problem and strange problem with the device,
I have connected it into Arduino
VS -  3.3V
GND - GND
SCL - A5
SDA - A4

didn't connect anything to ch1-3 and nothing to gnd\pow\vpu
using the simple i2cscanner code  - it get stuck .
I thougth maybe something wrong in the wirring
after disconnect the device - the code is running and say "No device found".
connected simple lcd i2c device - see the address correct
connected old display - see the address correct
so - no prboem in the wirring \ code \arduino  that is for sure 100% .
took 3 new cjmcu-322 - connect to the arduino with the correct pins, none of them works!
I have also try to add a 3.3K pullups resistors to the SDA\SCL lines - still can't see the them
what am I missing ?


texts: XMega waveform generation with DMA and USART

texts:
I'm using an Atmel XMEGA128A4U.

I need to generate a high speed digital waveform with minimal CPU overhead, and have set up a USART to output the waveform and DMA to transfer data from a table to the USART transmit register in background.

All is working just fine, except that the first byte of the table is transmitted repeatedly by the USART. The source address counter seems to refuse to increment.

I have gone through the datasheet carefully, several times. I have tried all sorts of different initialisation orders, and added in checks for reset and busy even though other online DMA examples seem not to include them. I can get DMA working correctly with both pointers incrementing in a RAM-copy test.  I have checked the errata for the micro and there's nothing mentioned about any silicon bugs.

Can anyone spot what I may have missed?

/*******************************************************************************
  Function Name  : dma_out
  Description    : Initiates background memory write to port
  Input          : pointer to char source data
                 : length of block in bytes
                 : number of blocks to repeat (0 for continual transfer)
  Output         : None
  Return         : None
*******************************************************************************/
void dma_out (char *source, unsigned short len, unsigned char rep)
{
  // Enable DMA, no double buffering, round robin
  DMA.CTRL = 0x80;

  // Enable channel for configuration
  DMA.CH2.CTRLA     = 0x80;
  DMA.CH2.CTRLB     = 0x00;

  // Reset chnnel
  DMA.CH2.CTRLA     = 0xC0;
  while ((DMA.CH2.CTRLA & 0x40) != 0) // wait for reset complete
  {
  }

  // Set source and destination addresses
  DMA.CH2.SRCADDR0  = (char)((int)source);
  DMA.CH2.SRCADDR1  = (char)((int)source >> 8);
  DMA.CH2.SRCADDR2  = 0x00;
  DMA.CH2.DESTADDR0 = (char)((int)&USARTC0_DATA);
  DMA.CH2.DESTADDR1 = (char)((int)&USARTC0_DATA >> 8);
  DMA.CH2.DESTADDR2 = 0x00;

  // Wait while channel busy before setting ADDCTRL
  while ((DMA.CH2.CTRLB & 0x80) != 0)
  {
  }
  DMA.CH2.ADDRCTRL  = 0x50;  // inc source and reload each block, dest fixed

  // Set block length and repeat count
  DMA.CH2.TRFCNT    = len;
  DMA.CH2.REPCNT    = rep;
  DMA.CH2.CTRLA    |= 0x20;  // Set repeat bit only after REPCNT loaded

  DMA.CH2.TRIGSRC   = 0x4C;  // trigger on USARTC0_DRE
  DMA.CH2.CTRLA    |= 0x40;  // Trigger transfer
}

PS. No, I don't use ASF, or similar notation.


texts: Rise time for 2 MHz SPI clock signal driven by an Arduino Micro

texts:
Could someone tell me what a typical rise time would be for a 2 MHz SPI clock signal driven by an Arduino Micro (ATmega32U4), off the SCK pin? An actual measurement would be preferable, but I do not have the means to do that myself.

Am I right in assuming this would give me a lower limit for the rise times in a circuit driven by the Arduino SCK signal?

I could not find any useful information about the actual rise time on the web: not in the Arduino docs, nor on the Arduino forums, nor here on EE. The ATmega32U4 spec sheet only specifies an upper limit for SPI rise time at 1600 ns, as far as I can see.

Based on the clock frequency of 2 MHz I could assume a rise time of 1% of the clock period, i.e. 5 ns, but that would not be much better than a random guess.


texts: I am new to electronics and I am wondering how can I use my Vcc to produce a short single pulse.


texts: USB Abstract Control Model (ACM) interface capabilities

texts:
I'm never sure whether to post USB questions here or overflow... Anyway, I am trying to find a place that lists the ACM capabilities with the bmCapabilities value that corresponds to them.  My ACM functional descriptor (which works fine):
0x04,     // 0 bLength
0x24,     // 1 bDescriptortype, CS_INTERFACE
0x02,     // 2 bDescriptorsubtype, ABSTRACT CONTROL MANAGEMENT
0x06      // 3 bmCapabilities: Supports subset of ACM commands

I currently have a 6 for the capabilities because I saw it somewhere and it worked, but in other people's/vendor's descriptors I have seen everything from bmCapabilities = 0x01 to 0x0F (in the spec) but I can't find the document that lists out what the values actually mean.  Which document can they be found in?


texts: Is my solution to prevent leakage between power rails correct?

texts:
I have two boards with identical comparator circuitry (shown below). I want to detect in each board when the other is plugged in. My concern (in the picture) is that when I connect the two boards if the VDDA and VDDB are at different potentials (i.e., for example, one is at 12V and the other is at 10V), there would be leakage from VDDA to VDDB or vice versa.

Two questions:

Is my concern valid?
In order to work around this problem, I added the diodes D1. Would D1 solve this problem here?

UPDATED CIRCUIT with Component Values:


texts: Faulty relay(s), capacitor or power source?

texts:
I have this IKEA Bekant Sit/Stand electrical desk and all of the sudden today, it won't work properly. I push it to go up or down and it goes for a little bit and then stops. I can hear well the relays switching but I don't know if they are switching to ON and then place themselves on OFF. I disassembled the whole thing and I can say that all the mechanical parts involved work perfectly  (nothing is stuck) and then I have to conclude that is something electrical.
I have made a video so you can get an idea of what is happening.
Basically, I have  power source of 25V and 2.5Amps. When on "idle" the multimeter shows ~25V. When I press UP or DOWN on the desk controller the multimeter shows a drastic decrease and the voltage goes to ~2-3V (I have even seen it going to ~0V) and then when the relays switch back to OFF the voltage goes to ~35 and then slowly comes back to ~25.

Youtube Video


texts: CAN protocol : How to start with CAN interface with Microcontroller

texts:
I want to communicate with VFD (variable frequency drive) via CAN open protocol.

I have never used CAN before. So can anyone Guide me from where Should I start with ? Any link or Suggestions would really of great help.

I would be using dsPic/pic24 microcontroller. So, is there pre-written libraries that can make my design bit easier.

Also any suggestion for choosing a right controller ??

I am just looking for a right direction to avoid wasting time, as reading too many tutorial is also dangerous.

thanks


texts: How to tin a soldering iron after unboxing?

texts:
I have bought cheap soldering iron before but when I turn it on waited to heat up, it turned black and wont take a tin. Am I doing it wrong? I wasted 2 soldering iron like this. It turned all black and not tinning.
Please can you suggest what to do after plugging it for the first time .
I don't know how to tin a soldering iron thats why I wasted two soldering iron.


texts: If there exists a cascade of op amps, does the previous op amp's slew rate affect the later op amp's slew rates?

texts:
All op amps used are the same Texas Instrument LM348n. The datasheet says the op amp has a nominal slew rate of 0.5 V/µs, but gives no tolerance.

I have a square signal with an amplitude of 500 mV peak to peak being sent into a two op amps system. The first op amps is a unity gain op amp. It exists to prevent the wave generator's output impedance from affecting the second op amp's gain. The second op amp is a simple inverting op amp with a gain of -10.

When I measured the slew rate of the inverting op amp alone, I found a slew rate of 0.62 V/µs. However when the cascade circuit is created, the slew rate measured at the second op amp's output is now 0.589 V/µs.

Is this decrease in slew rate due to the fact that the signal was sent through two op amps, each with its own slewing effect? Do the slew rates combine in some way?

Lastly when I set the second op amp to a gain of -1, the slew rate decreases even more to 0.414 V/µs. Is unity gain instability the reason for the second decrease in slew rate?

I thought the slew rate was an intrinsic property of an op amp. Is there a variable that affects slew rate I am not considering?


texts: Single-ended to differential conversion, baluns (~200 MHz)

texts:
I'm currently working on a design where I use a multiplier chip with differential inputs and output. Now, in my application all external connections are single-ended, and some app notes (e.g. the one for the ADL5391 chip) talk about using baluns for single-ended to differential conversion (and vice versa). The data sheet for the AD834 also mentions using a balun as an option, albeit only on the output side.

Now, being all new to RF design (and EE not being my trade), I have a couple of questions:

What are the principal advantages of using a balun for this conversion instead of going the simple way of just tying one side to ground? (I have some vague ideas here, but a good reference for the basics would be very much appreciated.)
How relevant are these for my application in the low hundreds of megahertz?
Which side of the balun is to be preferred for the impedance matching/AC coupling stuff? The example circuits in the above data sheets differ in this respect.

Sorry for the broadness of the question, but I'm still struggling to wrap my head around the issues involved.


texts: Why will the current be zero between X and Y, the connecting wire between two loops, in this circuit?

texts: The existence of a voltage source between the two points indicates that there is a potential difference, so why would the two loops be independent and zero current flow through the connecting wire?


texts: Use capacitor to turn on led when power is off

texts: I have two LEDs in the circuit green LED turn on when the switch is on also capacitor is charged, Now I want to turn on the red LED by using capacitor when the switch goes off. Please help me, how I can do that. Thanks


texts:
For my circuit, I have mounted heatsinks to my mosfets to dissipate heat. I have below a crude drawing of how the heatsink/mosfet is placed on the PCB

I was thinking to integrate a LM35 to measure temperature, and to turn on a fan when the heat of the mosfet/heatsink gets too high, so that the air may cool down the mosfet/heatsink.

My question is, can I place a fan in some way that would cool off the mosfet/heatsink? If so, how? I was thinking to place the fan on top to suck air from the heatsink and blow the heat upwards?

Would this work? I don't think placing the fan to blow at the mosfet/heatsink would work since the heat would just dissipate into the board?

Would my mosfet/heatsink placement even allow for an effective fan to be placed?

UPDATE: So my design for placing the fan above the heatsink should work from what I'm gathering. Though I am still unsure of where I should direct airflow.

@Swonkie: If I enclosed the bottom of my fan into a shroud like WhatRoughBeast suggested, would the airflow be "directed"? If I implemented a shroud, would the air be drawn directly from the mosfet/heatsink strictly? If I did direct airflow to the mosfet/heatsink, wouldn't the heat dissipate through to my PCB board?

ALSO: As I am using an LM35 for temperature sensing, should I place the LM35 so that it's touching the heatsink or the mosfet itself? Which would be more effective implementation for temperature reading?


texts: What is the material of AC outlet plug pins? Is it standardized? Are they usually just stainless steel?

texts: ^ The title. I want to know if the material is food safe and wanted to know if it would be toxic if introduced into a material that will be consumed. It will be exposed to liquid constantly and I don't want it to start rusting or putting heavy metals in my mixture.


texts: I want to create a part in Eagle for Bourns PEC16 series rotary encoder. I can follow online tutorials, but I'm not sure what the standard rotary encoder symbol looks like. Is there a diagram or specification I can follow to make the part more useful?


texts: Is there any more subtle convention for GPIO pin labelling between overlines, asterisks, and/or inverter symbols?

texts:
As a firmware developer, I've been given an old schematic that seems to have an inconsistency between pin naming conventions. Some of the signal lines from the microcontroller are labeled with an overbar e.g. \$\text{ENCABULATOR}\,\overline{\text{POWER}}\$ while others are labelled with an asterisk like \$\text{Warp Core On*}\$.
In both cases, inspecting the circuit downstream, it is often apparent that the "sense" of the pin is inverted whenever either notation is used. That is, I would need to drive both the "Encabulator" and the "Warp Core" pin low to turn the respective device on.
My suspicion is that this schematic was edited by multiple people, and some of them knew how to add overbars to labels in whatever app they were using, while others simply typed in an asterisk instead — perhaps alluding to the pin plus inverter symbol "dot" convention?
Regardless, is it most likely that this is a simple inconsistency within the schematic? Or might there be a more subtle meaning, like declaring different intents regarding pull-ups or drive levels or other pin sourcing/sinking behaviors?
Of course only the original team could answer for sure but before I pester them about it I'm curious if there's any convention here that would already be recognizable to someone less on the software and more on the hardware side.


texts: How to make a high current bi-directional motor driver circuit

texts:
I have a 14.4V DC drill motor that can draw 10 amps when under full load. I need a circuit that can control the speed and direction of the motors, using an Arduino with PWM. We are using relays instead of a H bridge is because of the high current. My first attempt at a circuit is shown bellow:

Ignore the yellow pen, this was a suggestion by someone else. Pin 1 and pin 2 of the relay are connected to the same digital-out pin on the arduino. The relay module I have has built in optocouplers and pull down resistors for the direction switching.

The FET is a IRL3705N. It has a threshold voltage of min 1V and max 2V. It has a sufficient heat sink attached to it, as shown in the picture, along with the motor and gear box bellow.

Issues with this circuit

The FET acts strangely. In my very first attempt at this circuit RG was 100 ohm and I had another 900 ohm resistor between the optocoupler and the 12V source. This potential divider meant that the gate to ground voltage was a 10th of the 12V, i.e 1.2V, which according to the datasheet should be sufficient to create a conducting path between the source and drain, however it didn't. We removed the 1K resistor so that the gate gets the full 12V and it then worked. Our guess was that this is because the Gate to Source voltage needs to be at least 1V higher than the voltage across the motor, and not just 1V higher than ground. But we are not sure. Is the left half (the gate turn on circuit) of my schematic correct?

The other issue is that we have blown a few of the MOSFETs, and I'm not sure if its because the diode is in the wrong place. When the motor is a generator, the diode is initially reverse biased. This is because the position of the relay switches when driving the motor determines the polarity the generator will be, and this position always means the diode is reverse biased when the motor is a generator. Therefore in the code we have it set so that every time the speed becomes zero, the relays change position. This then allows the energy in the circuit to be returned to ground. The problem is that this does not work when the motor is quickly reduced from full speed to low speed.

Is there a better circuit that will not have these issues? If my circuit is fine, please also leave a comment.

Thanks!


texts: How can I switch multiple lines using a single switch?

texts: I am looking to make a switchbox for my 34 pin floppy drive (I know you can't hotswap) but I don't know what to use. I have heard of a multiplexer but I think it is only one way. I need to be able to switch the single "B" line from a DOS computer between a 5.25" floppy drive, and a floppy drive emulator. How can I achieve this?


texts: What are the voltages noted next to the C-rates?

texts:
I am looking at a brochure/datasheet for some lead acid batteries, Hoppecke deep cycle gel, OPzV (link to brochure).

Below you see two snippets from it:

I have some problems understanding the C-rate concept in general, and I think the answer might lie in the noted voltages. So, what are the voltages noted next to each C-rate in the top of the columns?


texts: MAX31855 and Type K sensor seem to top down at -60°C (should be measuring -80°C)

texts:
As a prelude, I'd like to offer that I have obviously read the famous question here: Sensor for ultralow (to -85°C) freezer monitor

I have set up a K-Type probe from Adafruit and their MAX 31855K breakout board with SPI. I can read the data all right, and get consistent results at room temperature.

What is problematic is that when I put this sensor in a -80°C freezer, the probe seems to bottom out at ~-65°C, whereas the actual temperature probe of the freezer shows -80°C.

I though my computations were false (the 14 bit temperature is tricky to bit-shift and 2's complement convert), but I have made the math myself by printing the bits and using paper and I find consistent results with my code.

So yeah.. do you guys know if this is a non-linearity of the sensor at these temperatures?
Is the K-Type thermocouple not adapted? (I thought it could go down to -200°C)
Could this be a problem on the MAX 31855K side?
Any hint at what could be wrong?

I'm planning to check different places in the freezer (right now the probe is on the top compartment, I'll try the bottom tomorrow), and another freezer too to eliminate any "freezer-specific" influence, but if there is something I overlooked, can you help me?


texts: Digital logic input with very wide input voltage range

texts:
We are developing an industrial controls product that will be used to monitor the presence or absence of voltage ranging from 5V to 480V.  Since the unit will be generic and programmable, this input may be used in a variety of unpredictable ways.

The problem I have been wrestling with is how to monitor such a wide range of voltages with a single circuit design.  For example, if I drive an optocoupler LED directly, I can't get the 5V to turn it on without the 480V destroying it.  Voltage regulators typically operate on much lower voltage than 480V, so I'm in a bit of a dilemma.

The industrial controls solutions I've seen get around this problem by saying, "purchase this other model for high voltage input" or "buy this high voltage input converter and add it on."  Is that really the only solution here?  Am I trying to do the impossible?  Any input would be appreciated, no pun intended!

A possibly related question


texts: How to safely test a Lithium Battery Management System board

texts:
I'd like to design a Battery Managements System board (based on TI bq40z50-R2) for my own small (2-4s) lithium battery pack, but I am still unsure how can I test it safely.

I am worried that an error in my board design or in the configuration of the bq40z50 might cause a short circuit or some other unsafe condition to the batteries.

The tests would also include batteries short circuit, undervoltage, overvoltage, overcurrent.

I was thinking of buying for the first tests  a 2s or 3s commercial Lithium battery pack with protection (short circuit, overvoltage, undervoltage per cell,…) already integrated (unspecified IC).

I am unsure whether that protection circuit might interfere with the normal operation (measurement accuracy,…) of the bq40z50, invalidating the test.

I could also use stricter protection thresholds for the bq40z50:
for example I'd set 4.23V for overvoltage on the bq40z50, whereas the protection IC in the commercial battery pack is set for 4.35V. This way I'd see if the bq40z50 sets the appropriate flag during an overvoltage test.
During such a test, can I also use a multimeter to monitor the batteries voltage or would this also interfere with the protection ICs?

Once these first tests are done, I'd proceed using the designated batteries for my battery pack  (branded 18650 Li-Ion or RC LiPo without protection IC already in them).

Could this work or do you suggest an other procedure/hardware?

Is there another way to simulate a Lithium battery without actually using one?

Thanks in advance for you help

Sincerely


texts: LTspice MOSFET stops charging capacitor past Vt

texts:
I'm building a buck-boost converter that transfers C1's charge to C2. In the schematic shown below, C1's initial charge is 4V. When I use switches instead of MOSFETs in the circuit, everything works smoothly and C2's final voltage is somewhere around 3.5V (losses due to parasitics).
However, when I replace those switches with MOSFETs, C2's voltage starts to taper off around the threshold voltage of that MOSFET. In this scenario, the Vt is 0.843V, which is where C2 caps out around. What am I missing here? I initially thought it was turning off since the voltage at the source node is rising over time, but even if I drive the MOSFET with 15V at the gate (Vgs >> Vt), the results don't change. That also rules out the MOSFET dipping into saturation mode, since Vds << Vgs - Vt as well.


texts: Constant value required for VHDL array indexing?

texts:
I basically have a line like this in a vhdl code.

entity my_entity is
   port(x : in std_logic_vector;
        y : in std_logic_vector;
        ...);
end entity my_entity;

architecture arch of my_entity is
   -- declarations...
   signal delta : unsigned(...); --correct sizing
   signal aux_signal : std_logic; -- correct sizing
   signal another_signal : unsigned(...); --correct sizing
begin
   delta <= x - y; -- x > y
   aux_signal <= or_reduce(std_logic_vector(another_signal(to_integer(delta) downto 1)));
   -- other stuff
end architecture arch;

the syntax is fine (checked by ncvhdl), however when i try the synthesis the compiler complaints of assignement like "aux_signal" saying that it needs a constant value.

Since i need an assignment like that... is there another way to achieve the same result?


texts: Best PC interface for simple custom hardware

texts:
What interface of your PC do you use in order to connect to simple custom hardware?

The most commonly used interface was RS232 some while ago and today is probably USB, but wouldn't it be simpler for beginners to use the parallel port to control really simple circuits like step motors or LEDs? I have the impression from what I have read so far that the parallel port was not really designed for things like that, but I am not sure about possible limitations with respect to that.

Unfortunately, I can find very little literature on how to use the parallel port probably because it is somewhat outdated for professional hardware.

Does it make a difference for the decision on the most suitable interface whether I will just use output or also input?

I should add that I do of course know about Arduino, but I don't want to have any complexity hidden from me.

Moerover, I am using Linux and have a parallel port available.
So I am currently biased towards the parallel port.


texts: Is it really necessary to manually clear the XMEGA timer overflow interrupt flag?

texts:
As some of you may know, Atmel provides a software framework (mainly as part of Atmel Studio) that provides drivers and examples and is updated on a more or less regular basis.

In a recent update they explicitly point out, that it is important to manually clear the overflow interrupt flag in the interrupt callback function.

 // * \subsection xmega_tc_qs_ovf_setup_code Example code
 // *
 // * Add a callback function that will be executed when the overflow interrupt
 // * trigger.
 // * \code
 static void my_callback(void)
 {
    // User code to execute when the overflow occurs here

    // THIS WAS ADDED IN LAST UPDATE
    // Important to clear Interrupt Flag
    tc_clear_overflow(&TCC0);
    // THIS WAS ADDED IN LAST UPDATE

 }
 //\endcode

According to the XMEGAA data sheet:

  OVFIF is automatically cleared when the corresponding interrupt vector is executed. The flag can also be cleared by
  writing a one to its bit location.

Is there a scenario/reason where manually clearing the flag may be required?


texts:
I'm searching for ways to simplify prototypes, specially the requirements to create an II (input Interface) or UI (user interface). No need to drill holes for buttons or create a button array because it's not easy to experiment with this, espescially when you want to change or extend it. Yes, you can use a touchscreen (with or without display) for this but it is more difficult to change or maintain because it depends on the firmware and it needs additional hardware that pushes product costs. So, why don't use existing (obsolete) devices that got it all already to reduce costs but is also environment friendly.

Got a couple of phones lying around with great capabilities though but unusable for advanced tasks (like Nokia's for example) and want to reuse those to be a part of projects. All of them got a touchscreen, a browser that can display (offcourse) HTML and an audio/mic socket.  Came up with the idea to create an extendible HTML interface with buttons that produce sounds (frequency instead of measure button resistance) to measure input/selection.

The solution is also very cheap because you can use any existing device that is able to play a soundwave and you only need an audio cable to process commands. You can even use dumb phones to do the 'trick'. Another nice thing is that you can 'record' commands, play a sequence of commands, for example with a MP3 player. Could be very nice.

Also experiment with remote controls, to reuse old remote controls. Problem with these is detection, different brands use another 'frequency' and it requires allot more work to get it working. So an 'App' is easier to develop, an App that produces just soundwaves (like DTMF) - see also: http://onlinetonegenerator.com/dtmf.html

If you can use the microphone, you can develop an bi-directonal i/o system, you can interact with the UI on the cheap. But okay, first things first.

I like to build an audio socket (with help of an Arduino) to measure frequencies. Found this - https://www.arduino.cc/en/Tutorial/SimpleAudioFrequencyMeter - but is very limited in handle frequenties. I really like to see the frequenties are above hearing limits, above 18.000 hz for example so you are able to make it a sort of wireless in the future (speaker -> microphone)? When playing music or other sound it doesn't disturb 'button' detection.

Is it possible to measure high audio frequenties anyway? What is the best way (without or less external components) to do this? Any idea's or links?

UPDATE:

Just found this:
http://www.instructables.com/id/Arduino-Audio-Input/

And:
Have experiment done with this device, a DTMF decoder:
https://nl.aliexpress.com/item/wholesale-1pcs-MT8870-DTMF-Voice-decoding-module-phone-module/32643931980.html
and converted the header into a dual line resistor network, works pretty well but you still need this device to decode the tones/frequenties.


texts: Understanding class A amplifier waveforms

texts:
I am working on an audio amplifier but got stuck on to a basic of npn transistor circuit.

Attaching a class-A amplifier circuit. Take a look here or here. I tried to simulate the circuit but as everywhere on net it is said that this can amplify whole sine wave , in my P Spice simulation it is not. Only one half of input signal is getting amplified.

My question is how I can get full sine wave (as all the schematic of class a amplifier over the internet claims)? Also please explain why exactly I am getting attached waveform in my circuit.


texts: How can I tell if an antenna is a dipole antenna

texts:
Background

I'm trying to select an antenna for an FCC/IC-approved cellular module, SIM7000A. Apparently, to meet IC modular certification, you need to select an antenna which has

a) equal or less gain and

b) which is the same type

as the antenna that was used during FCC/IC testing of the module.

Question

I'm new to RF wireless and I'm trying to find a dipole antenna, since this is the type of antenna that SIM7000A used in its certification testing. I also know what frequency bands I need and what maximum gain I can have in each band. When I research on Digikey and Mouser there are a lot of antennas which are classified as PCB, or chip, or blade, etc. My problem is that I can't tell if an antenna is a dipole antenna or not: is there an easy way I can tell? For most of them, it doesn't mention the words dipole or monopole anywhere on their datasheets.


texts: Source-free, under-damped, parallel RLC with 2 intial conditions

texts:
I think I'm suffering from brain-drain. I'm trying to solve a 2nd order differential equation for the natural response of an under-damped parallel RLC circuit with initial conditions of \$I_L\$ and \$V_C\$ but I'm falling (apparently) at the final hurdle.

All the solutions on the web that I have found seem to skirt over the solution to finding B1 and B2 in this type of formula. Most (if not all the solutions) seem to solve for output voltage but I also want to know how the inductor current decays.

The best single picture I have found shows this: -

And, I am happy that I can use this to solve for the voltage waveform if my initial condition was just the capacitor voltage BUT, I need to know what B1 and B2 are for the intial conditions of BOTH capacitor voltage and inductor current.

So, in short: -

What is the formula for \$i_L(t)\$ for a parallel RLC
How do I formulate the B1 and B2 values taking into account BOTH initial conditions
Ditto for \$v(t)\$


texts: How can i make a 3.3v ouput from 9v battery?

texts: I'm a newbie in embeded system and basic electronics ,Yesterday i purchased a esp8266 wifi module from amazon along with ftdi usb driver i'm also have an Arduino uno, esp8266 require 3.3 v . Arduino and ftdi driver has a 3.3v pin but the tutorial i watched suggest that not connect esp with arduino or ftdi ,so how can i start working with esp from a 9v battery?


texts: Altium doesn't let me place anything on schematic

texts: When I left click the mouse to place a component, nothing happens. I can't place the components.  How can I fix it?


texts: Deriving the NOT logic gate using PMOS logic

texts:
I recently started learning about Field Effect Transistors (FET's) and about the MOS circuit family. From my understanding NMOS is made from a p-type substrate and n-type source/drain, whereas the PMOS is made from a n-type substrate and p-type source/drain. However, I'm not so sure as to how we can derive different logic gates from PMOS and NMOS. Let's say we have the following diagram, where x and y are the inputs and z is the output:

The current in PMOS flows from the Source to the Drain terminal, and that can only happen if the Gate terminal is set to Low. Silly question, but why is that so? Furthermore, how can we use this to get the NOT logic gate (As shown in the second image)?


texts:
I have a medical office call box/light system that is older probably 20 year old and they moved the main panel that the Drs see to know when there are patients waiting and since they moved it, it is intermittently not working. The system uses a signal that is transmitted over the AC connection/plug.
I am new to oscilloscopes but purchased one to see if I could observe if the signal is too weak in the new location (it’s about 250 feet from where it was originally) or if it’s getting too much interference.
I have found that the system needs to be on its own circuit and have a 2700 UH choke installed on the circuit feed but that’s about all I can come up with since apparently the manufacture has gone out of business. They do still have a website but only very limited information and no schematics.
http://www.varitronics.com/ts-cs2install-nc.htm

My problem seems to be when I look at the pattern all I can identify is the 60hz signal and don’t see any changes when energizing one of the boxes and would like to know if anyone has any suggestions for blocking out the 120V 60Hz signal so I can see the signal that is used to operate these boxes over the 120V line. I believe I need a high pass filter but not sure what components I would need to achieve blocking the unwanted signal but still be able to pass the triggering signal I am looking for to identify the problem.
Thanks in advance for any help you may be able to provide.


texts:
I am not sure if I used the right forum to ask this question. If it is wrong, please point me the right one.

I understand in general how A-GPS works with cell towers, and how it depends on the data signal. But there are some thing I don't understand fully yet.

I have one phone primarily used in cities, and it is equipped with A-GPS only. My service provider has certain coverage. But even I drive outside my service provider's coverage I am still able to navigate with offline map.

I have another phone equipped with A-GPS only, I used it to travel in other countries thus I don't even bother to insert a SIM card or use roaming service. Basically it is a just a mini tablet. But in cities I was still able to find myself on offline maps, see myself moving on the maps and so on. In one case I was deep is the Amazon rain forest I had no way to locate myself.

So my questions is if A-GPS depends on cell towers to obtain the locations, does it mean as long as there are towers around, it does not matter I can have service with them or not, then I can use A-GPS?


texts: Low-pass filter for high power application

texts:
I'm designing a LP filter that should be used for a load of up to 2000W. I want to filter the AC voltage that supplies a controlled heater which uses a TRIAC for control. I've tried one approach but found it useless. First, such an inductor, on series with 13A must be very big and possible costly. Second, high losses of power. Third, since I'm working with DC I should use a non-eletrolytic capacitor so, for 220V and such capacitance, it will be very big. Clearly, although I got good filtering on o'scope, it's not the best approach for high power loads.

So, finally, is there a better way to design a LP filter for high power that is more electrical efficient and cheaper?

Also, my cutoff frequency was about 60Hz (planned higher, but had to adjust the inductor to guarantee the right current on load). Is there any rule of thumb of which fc should I use when planning to filter AC voltages?


texts: Import changes from selected schematics not all in Altium

texts: At the start please note that I'm new in Altium. I'm having 7 schematics and 2 pcb documents. For first document I want to import changes only from 1,2 and 3 schematics, but if i go to `Design->Import changes from project_name` I only can import from all project schematics and I have a list of unused items to choose.This situation causes that i need to slide up the list and search needed element and finding element is longer. If anyone knows the answer, I would be grateful for your help.


texts: How to identify the type of modulation and data rate of an RKE system transmission

texts:
Many devices that measure frequencies of key fobs, can inform, in addition to the frequency measurement, also the type of modulation, FSK or OOK, and the data rate in bps. Previously in this forum, I made questions about methods of how to measure frequencies and reverse engeneering of a hardware of a device able to perform these measurements. Based on the discussions, I decided to use the Prescaling method. In this method, the signal received would be amplified, its frequency would be divided and then it would go to a controlled gate and a counter. I will put the links of these previous discussions at the end of the post for those who wants more information.
I only know that the main modulation methods used by transmitters of the key fobs are OOK and FSK. I don't have any additional information about protocols or how these modulation are implemented in these transmiters.
So, to differentiate OOK from FSK, I imagined the following circuit:

simulate this circuit – Schematic created using CircuitLab
The idea with this circuit is to monitor the activity of the signal. If the signal is pulsating it will means that the modulation is OOK, but, if after a determined interval of time no pulses are detected, it means it is FSK.
The range of fequency is from 100MHz to 915MHz, so, for the calculus of the capacitor's discharge time, I take the worst case, the longest period, that happens at the lower frequency, It means 0,01\$\mu\$s. I took arbitrarily 3 times this period to be the time of discharge,Td, of the capacitor.
So, we have:
Td = 0,03\$\mu\$s = 5*R2 *C
Considering R2 = 1k\$\Omega\$; we will have C = 6pF.
Doing this, I had the following concern: This period of 0,03\$\mu\$s is 27 times longer than the smaller period, of 1,09ns in 915MHz. So, to detect a low level of a pulse(switch-off) in 915MHz, this low level will need to have a duration of at least 27 cicles of carrier.
Doing reverse engeneering at a hardware that can do these measurements, I came across with the folowing circuit, Which I think is the circuit to check signal activity: (Onservation: In the original hardware, the value of C2 was 18pF and R6 was 10K. I just changed it to the value that I calculated here )

simulate this circuit
Based on this explanation. I have the following doubts:

Only frequency counting is sufficient to know the data rate and modulation ? If not, which of the circuits above would be better to discover the modulation ? Is there a better solution ?
How can I know, or estimate, the data rate ?

Below, are the previous discussions that I mentioned at the beginning of the post.
Discussion about methods of how to measure frequencies:
Which frequency measurement method is more suitable for RF signals from 200MHz to 915MHz?
Discussion about a reverse engeneering of a hardware of a device that can do these measurements:
Digital Frequency Measurement


texts:
The blue highlighted values are the answers, but can sombody explain how my teacher got 120v for the 4k resistor and 60v for the 2k resistor? the only one I could figure out is the right side where I showed 1 calcuation....

I was running through practice problems that my teacher provided for us to prep for the coming exam... but I cant understand how he came to those voltage values.


texts: Source potential for MOSFET with grounded substrate

texts:
Considering the configuration below, the source's potential should be invariant with respect to Vg (as long as Vg>Vt). So Vs is equal to Vdd.

But if the substrate is connected to the source, as shown here, when Vs reaches Vg-Vt, the transistor switches off, and Vs remains at Vg-Vt.

Is this correct? I am asking because I read in a material that in the first situation Vs depends on Vg.

EDIT (quote from a lab guide):

  If the M1 transistor is in cut-off stage, for the case in figure 4.2b, the output voltage will depend on VGG and the threshold voltage, following a relation that contains also elements (parameters) specific to the intrinsic structure of the basis substrate.


texts:
simulate this circuit – Schematic created using CircuitLab

I'm creating a hand-held device with a momentary push button that will activate an LED and play a sound or MP3 (I didn't include the sound card/speaker in the schematic because I couldn't find a symbol that would correspond) when the switch is down to complete the circuit. Is there a component that would let me play this MP3 when the push button is down and repeat the sound as long as the push button is down?


texts: Properly earth grounding benchtop supply

texts:
A DC benchtop supply is usually ground free, i.e. the negative output is floating wrt earth ground. I used to use HP E3630A which has an additional "Earth Ground" pin and to which I shorted the "-" pin.

Now I have a power supply (Keysight E3648A) that has only four outlets: "+", "-" for each "Output 1" and "Output 2". I need +/-5V for testing a PCB so I put them into track mode and short "Output 1 -" with "Output 2 +", calling this "ground".

This "ground" and the supply voltages go to my test PCB which has its grounds (indirectly) connected to other devices over SMA cable shields (signal generators, signal analyzers).

Now I am not sure how to best connect "ground" to earth ground or if I should keep it floating in the first place?

Interestingly the manual does not discuss earth ground at all and how to properly connect it. Any recommendations?


texts: difference between crystals in applications

texts: I am trying to use a crystal for a MCU. The xtal is 32.768KHz. This will be scaled up by the internal PLL or FLL to a much more higher level. I was looking at some crystals of the same value in some websites and saw a crystal of the same value. But, it was mentioned that it is a good xtal for RTC applications. So, my doubt is that, can I not use them as XTALS for my MCU. Is there a massive difference in a xtal usage for the 2 different scenarios . If so, what are the parameters I should be aware or rather concerened about please.


texts: Measuring voltage drop across a diode in a switched circuit

texts:
I have the below circuit where the input voltage is 8V and a PWM pulse is given to the base of the Q101 transistor.

From what I have measured,

The voltage at the anode of the diodes D102 and D103 is constant like around 8V. But when I measure the voltage at the cathode of the D103 and D103, I get a PWM waveform whose peak value is 7.7V.

Voltage measurements are done using oscilloscope.

My questions :

How to measure the voltage drop across the diodes D102 and D103 in this senario?
Why am I getting a PWM voltage waveform only the cathode of the diode and not at the anode?
Why is there a 0.3V voltage drop across the diode? Shouldn't it be typ. 0.7V?

BOUNTY EDIT :

-The 8V is the voltage source. SBATT is connected to a load which draws a minimum current of 80mA and a maximum of 100mA.

-The temperature of the circuit , which I have measured is not 150degC. The temperature is around 85degC

-The diode is not a schottky diode.


texts: I'm reading through Jim Williams' "Analog Circuit Design: Art, Science and Personalities", and a mysterious component called a crysistor is mentioned. There are a few clues in the text, like the fact that it was a superconducting magnetic memory that "showed promise of revolutionizing the computer world". I can't find any reference to the crysistor aside from this book. What was the crysistor and how did it work?


texts: How do I use a quartz crystal in an oscillator?

texts:
How can I get a quartz crystal to make square waves at 4.096MHz? So far I have the 4.096MHz quartz crystal and this schematic I saw:

Where can you find an amplifier with a single input and what voltage should I use?


texts: ATmega168 circuit not working without Arduino regulator?

texts:
I am having this very strange issue with my stepper motor driver circuit which uses an Atmega168 an L293 h bridge that appears to not want to function without an Arduino (Uno) connected to 3V3 and ground.

Some more detail would be that the h bridge is powered by a 12V dc power supply that is "chopped" to about 3V with a mosfet and pwm from the Atmega. Whilst developing the circuit VCC (for the Atmega and L293) was provided from the 5V pin on the Arduino. I should mention that this circuit works fine with the above setup.

My issue came in when I tried to make it standalone by hooking up a 3V3 regulator (TS1084) to the 12V supply in order to provide VCC because once doing that nothing seems to be really going on after powering up the circuit, very feint vibrations can be heard from the stepper but the pwm pins that should be feeding the h bridge all seems not be outputting anything though.

This all seems like some strange problem caused by the regulator or the different voltage but the strange thing is that after another few attempts I accidentally left the 5V pin of the Arduino connected to the 3V3 rail in the circuit as well as the ground connected to the ground and the moment I powered on the circuit everything starting working and the Arduino also went on. The moment I disconnect the 5V of the Arduino though everything stops and upon reconnecting it everything starts again. I have checked though and with the Arduino connected the VCC across the circuit still remains at 3V3, so the Arduino isn't making 5V somehow.

This whole thing has got me rather baffled and the only thing I can think of is that the Arduino's regulators are doing something but that does not really make any sense.

ALSO, I have no idea if this is related but whilst operating the 3V3 circuit with the Arduino connected the regulator gets extremely hot and constantly goes into thermal shutdown after a while if I do not put a fan on it.

If any of you have ever seen something like this or know of any way to do so please help!

EDIT:
I have now tested the circuit with a 1A 5V regulator rated for up to 35V input and it does work with this regulator (NCP7805TG). What I have noticed with the 3.3V one though is that it might the problem seems to come from connecting the pwm pin of the atmega to the mosfet, once I disconnect it or place a large resistor on it the atmega starts reading voltages on its pwm pins again. I am therefore guessing that this is somehow putting to much strain on the regulator but it still does not explain why hooking the arduino up in parallel has any effect what so ever.

PS. I will probably only come around to making a schematic some time tomorrow if it is really needed but I think everything is described properly enough.

ALSO, the fact the it is on 3.3V does not seem to be a problem because it works fine if I use the first setup mentioned in the post but running from the 3V3 pin on the Arduino instead of the 5V pin.


texts: Rectification of Micro DC voltage levels?

texts:
I am building a payload for a high-altitude Balloon launch in the club I started which will be measuring DC voltages (electric field) at different altitudes using a wire dipole or two metal plate formation.

I obviously need a low noise amplifier to even register any data in the logger, and we are not worried about polarity, only magnitude.

To do this, I am thinking an instrumentation amplifier fed from the metal plates to the data-logging device, but I am facing a problem, how can I assure the DC amplifier is only measuring positive values? Even some good diodes have a few hundred millivolt drop, which would not be suitable for the experiment. A transformer would not work because this is only DC we are working with (even if it was AC, the high input impedance requirement would not be fulfilled).

Any ideas on rectification or ways to amplify the small DC signals which we can't be 100 percent sure the polarity is constant.


texts: Alternatives to Large Transformer or PSU for Driving DC Heater

texts:
I have a 3D printer heated bed, instead of 3d printing I want to use it for reflow soldering. The bed is intended to operate at 70c, using 12v or 24v. It can be wired in series or parallel depending on the input voltage, it's 0.8 ohms wired in parallel, and 3.2 ohms wired in series.

I want to reach 260c, and the power demand will be at least proportional, so I think I'll need at least 90W * (260c-25c)/(70c-25c) = 500W. Lets say 700 to be safe. To push that through the 0.8ohm heated bed I'll need about 24v at 29A.

So that means I need either a large and expensive 24V PSU, or a large and expensive transformer.

But is there any way around that? For example, could I connect the heated bed directly to AC, and then use a triac to carefully ration the on cycles? I'm hesitant to do this because of the low duty cycle (15%), and high peak wattage (4.5kW).

Are there any other options? My first choice was to buy a cheap 30A 24v PSU on ebay, but that just blew up so I'd like to try something else.

Edit: To clarify what I'm asking: Is there a way to drive a high current, low voltage resistive load from 120v AC without using a transformer, or a full blown switching power supply?


texts: Transistor pinout - how to read the datasheet

texts:
Is the capsule's straight face visible? Or the round one? Is that top view or bottom view?

Do all datasheets use the same orientation?

This is the datasheet. I'm not looking for an answer specific to this datasheet. I want to know how to identify pins when there's a representation like this shown. Some datasheets use 3D images with pin labels, but not this one.


texts: stm32f401 I2C does not send byte after repeated start

texts:
I am programming an I2C master on a STM32F401 nucleo board. I program it without HAL, just using registers.

I am interfacing a peripheral, that has to be read like the following:

Start
Write Address with R/W 0
Write register address
Send repeated start condition
Write Address with R/W 1
Read data from peripheral

The first 3 steps work totally fine, but I can't send the address with R/W 1 after the restart condition.

Here you can see the timing diagram using a logic analyser. The restart condition is sent, but afterwards SCL and SDA are just low.

Here is my code

    i2c_start();
    if (i2c_sendAddr(TLC2991_ADDR)) { //returns != 0 if NACK
        fault = true;
        i2c_end();
        I2C1->SR1 &= ~I2C_SR1_AF;
        return -1;
    }
    i2c_sendByte(VOLTAGE_REG_OFFS + 2 * ch);
    i2c_wfw();
    i2c_start();
    i2c_sendByte(TLC2991_ADDR | 1); //tried i2c_sendAddr too
    u8 msb = i2c_recvByte(1);
    u8 lsb = i2c_recvByte(0);

And the functions called

void i2c_start() {
    I2C1->CR1 |= I2C_CR1_START;
    while (!I2C1->SR1 & I2C_SR1_SB);
}

int i2c_sendAddr(u8 addr) {
    I2C1->DR = addr;
    while (!(I2C1->SR1 & I2C_SR1_ADDR))
        if (I2C1->SR1 & I2C_SR1_AF)
            return -1;
    I2C1->SR2; //generates a read, clears ADDR
    return 0;
}

int i2c_sendByte(u8 data) {
    while (!(I2C1->SR1 & (I2C_SR1_TXE | I2C_SR1_AF)));
    I2C1->DR = data;
    return I2C1->SR1 & I2C_SR1_AF ? -1 : 0;
}

//wait for byte transfer
void i2c_wfw() {
    while (!(I2C1->SR1 & (I2C_SR1_BTF | I2C_SR1_AF)));
}

The TXE bit is high before setting the DR after the restart, afterwards it is low, but the I2C does not transmit anything. Please point out what I missed.

I have also checked the SDA line with an oscilloscope and there are no glitches or similar.


texts:
I want to design a circuit that powers a motor on under certain criteria, and off under other criteria.  I built my circuit using switches and a 74ls04 (Inverter) and a 74ls08 (AND) gates.  The circuit is quite simple, and works properly  when I hook the output up to an LED.  My circuit runs properly off of an input of 5v, 9v, or 12v.

However, I encounter problems when I hook the output to a motor rather than an LED.  The motor that I am using is a Fishertechnik component which accepts 6v-9v.  When I replace the wire to the LED with the wire to the motor, nothing happens.

I used a digital logic probe to try to pinpoint the problem.  When the wire connecting the motor is connected to the breadboard in the output position and NOT connected to the motor it produces a digital "high".  However, when that same wire is in the same output position on the breadboard and the other end IS connected to the mootor it produced a digital "low".

I hooked the motor directly up the the 9v battery and it worked.  It just doesn't work when hooked up to my circuit!  But my circuit works just fine when hooked up to an LED rather than the motor (for an output).

I also tried using a multimeter to try better understand what is happening.  It appears that the output of the IC which is hooked up to the motor is at .75v when the motor IS connected, but at 7.6v when the motor is NOT connected (with a 9v battery hooked up to the input of the circuit).

I consider myself a beginner with electronics, so any help you may be able to provide is great!  I know that it is not my circuit, but I just can't figure out why the motor is acting so weird with the circuit, but fine with a battery!!


texts: Is the RESET signal in this LCD required pull-up resistor?

texts:
I'm designing a circuit which includes this LCD display.
There is no information about an internal or external pull-up resistor for the RESET signal. the only thing that the datasheet says about the RESET signal is active LOW.

So, I wonder, what should I do?

What will happen if I'll put pull-up resistor when internal pull-up is presented?

thanks.


texts: How to end sending data over I2C by Slave or Master?

texts:
Let us say a Slave or Master is sending multiple bytes to the receiver on I2C bus and the number of bytes is not defined before hand. So then how will the sender tell the receiver that it has no more data to send?

So far what I understand is that for the case when the sender is Master then it sends a NACK to tell the Slave (Receiver) that there is no more data to send. And after sending NACK then it sends the STOP condition to finish the session.

But I wonder how does this handshaking takes place between a Master and Slave when the Slave is sender and the Master is receiver and only the Slave (sender) knows when there is no more data to send to the receiver?


texts: Help with understanding the power supply schematic

texts:
Below picture is the schematic of a Chinese power supply:

What's the top rectangle circuitry is for with negative voltage? and whats is RL1,RL2?
Why there's two resistor (R15-R20) in parallel? (to increase wattage?)
What R46 and C8 is doing there?
Why there's a zener diode between inputs of the opamps?

There's whole lot more that I don't understand about this schematic, so any extra explanation is appreciated.


texts: Calculate right number of supply and ground contacts per connector

texts:
Just silly question, but not clear for me.
For example, I have some device with 20A DC consumption. I have to connect this device to power source by some multicontact connector, 20 pins for example. Each pin can carry 2A of DC current.
How much VCC and GND contacts I should use to handle 20A to the device?
Variant 1: 10 VCC pins and 10 GND pins, because connector should pass 20A through VCC pins to the device and then return the same 20A to the power source by GND contacts
Variant 2: 5 VCC pins and 5 GND pins, because each pin can handle 2A, so 2A*(5vcc + 5gnd) = 20A


texts: Buck converter LC output filter contribution to phase margin

texts:
I'm trying to develop a better understanding of how my power distribution network can affect the stability and performance of buck converters, which has lead me to documents like this one.

The main point of the document is pretty obvious, and I think I understand it: if the total phase response of the control loop is -180 degrees when the gain is >= 0dB, the regulator will probably become unstable. This matters to my design process because the LC output filter contributes to the control loop's phase response, and my power decoupling network contributes to the LC output filter.

My question: After running a few simulations, it looks like any reasonable LC output filter for my application will have a phase response of -180 at a pretty low frequency. Is my LC output filter having a phase response of -180 an automatic showstopper for a buck regulator, or would you expect a "modern" buck regulator to have enough internal compensation in its error amplifier to handle this issue?

This is my super low-resolution model of my LC output filter. I've included about 2nH / square parasitic inductance for my power plane as well as some roughly fudged ESL numbers for the decoupling caps, and a 50 ohm resistor for my low power microcontroller.

And here is a frequency sweep that goes from 1kHz to about 250MHz


texts: Use of LED driven over-current in a strobe lamp

texts:
I'd like a strobe lamp using RGB LEDs as it's light source. I want to pulse the LEDs with very short duration pulses (ideally microseconds or less) at around 100 Hz.

The total on time for the LEDs per second is likely to be less than 1/1000 of a second. If the LEDs are driven at nominal power, the total light output will be low and the resulting illumination will be very poor. I'm interested in the idea of driving very short pulses through the LEDs that are constant power, but with a current well over the nominal. Ideally, 10x or even 100x over nominal.

A thread here: High Current Pulse on LED suggests that a few times over nominal current for short pulses is probably okay, but I think they're talking about longer pulses than I am imagining.

Could anyone comment on whether the LEDs are likely to survive long enough to be useful? I don't mind a drastically reduced total life. As long as they'll survive for a few tens of hours of usage (total on time probably less than an hour), that's fine.


texts:
a bit of specific question. I want to build my own cable based on pins stated in the manual of an old camera, so I can capture the video (composite video) and audio signal.

Question: Is there something I should do to mitigate possible signal interference, when choosing the wires of the cable, even thogh there are already pins reserved for the shielding?

Recently I bought a analog camera, which has a 8 pin din connection. This combines the output for the video and and power supply for the camera. To display the camera output, I have other devices that work with composite video input. So for this to work, I want to build a cable with 8-pin din connector on the camera side and analog video and 12 v (6.5W) power supply on the display side. I know all the pins of the 8-pin camera side, they are stated in the manual. There are also explicitly pins reserved for shielding.


texts:
I researched that starting from Bluetooth v4.1 a BLE device can be either a master or a slave.
I was curious if anyone has tried it? And how to go about it.

Also I am new to hardware and would like a starting point to build a prototype, any suggestions on that?


texts:
I pulled an AT28C16 from an old KVM switch and have managed to wire it up like so:

A0-10 -> GND
CE -> GND
WE -> 5V
OE -> GND
VCC -> 5V
GND -> GND
I/O0-7 -> Floating. Plugged by hand to level meter one by one.

With all of the address bus lines hooked to GND, I am able to read the first 8 bits as 01110000. This is all well and good, however the datasheet says this is a 16K EEPROM, and this chip has 11 Address Bus line, which equates to 2048 combinations and therefore 2048 bytes or 2048*8 bits. Thats not 16,000 bytes. How to I read the full 16K with only 11 Address Bus lines?


texts: Questions regarding an upconverter topology (biasing network and small overdrive problems)

texts:
This following diagram is taken from the textbook “RF Microelectronics” by Prof. Razavi.

I have a number of questions regarding this upconverter topology.
Q1
How can we tell from this upconverter (or any other mixer topology) whether the output is a double-side band signal or a single-side band signal?
Q2
It is mentioned that the gate of M5-M8 should be biased at 0.6V. However there is no biasing network connected to the gate of M5-M8. So why can we make sure the common mode voltage at M5-M8 is 0.6V?
Q3
If the M5 gate has to be biased at 0.6V and the gate of M1 is fed by an LO with a 1.2V swing, then why M1 will suffer from a small overdrive?
Q4
How the small overdrive of the M1-M4 degrades the performance of the upconverter?
Q5
Can increasing the width of M1-M4 help to solve the small overdrive problem?
Thanks.


texts: Finding the DFT size in relation to an OFDM encoded signal

texts: I am completely lost here. How do I go about determining the size of the DFT matrix used in conjunction with an OFDM encoded signal? I have researched this a lot but cannot find a solid answer? Is it determined by the number of subcarriers, frequency of the signal or other characteristics?


texts: how to properly save an architecture in a fpga ic forever

texts:
Considering I made an architecture to do some specific thing, wrote in vhdl, for example.

Can I 'burn' it in a fpga chip, forever? Or how should I do it, protecting the intelectual property knowing the fact it can be read from the serial flash memory?


texts:
I want a circuit in which I get the following sequence:

0001,
0010,
0100,
1000,
0001

I know that it's 4-bit shift register. But what is my approach to design this circuit?


texts: Arduino I2C bus fails when one slave is powered down

texts:
I have a set of Arduino Nano units where one is I2C master broadcasting messages to a number of slaves. It works perfectly fine when they are all powered on.

The Arduino units are all interconnected with wires between A4 (SDA), A5 (SCL) and GND. All of them have separate 5V lines. I have tried with internal pullups (as configured by the Wire lib) and by external 4.7k resistors.

The problem is when I cut the 5V line on one of the slaves. That slave will then pull the A4 and A5 lines to GND. My pullups doesn't do enough to pull it back. How can I circumvent this behavior?

My ideas range from using some kind of solid state "relay"/analog multiplexer to ensure the I2C bus is electronically disconnected from the Arduino when powered down, to using some opto-decoupler. I have not used such methods before and perhaps there are better ways of doing this. I'd prefer not to add extra hardware unless I have to. By the way, I don't necessarily need to have bidirectional communication over the bus. I only need the master to broadcast messages to all slaves at once.


texts: Can two PCIe endpoints communicate with each other through PCIe switch?

texts:
Figure shows basic architecture of PCIe. From what I understood, Root complex block will convert data into PCIe format. That means PCIe endpoint to endpoint communication will happens through Root complex block.

Am I right ? If yes what is the purpose of Switch?


texts: Do "blown" fluorescent lights still use electricity?

texts:
When a fluorescent light fixture goes out, it often flickers and then after a while stops shining altogether. When this happens and when it finally dies is the circuit broken and does it still use electricity?

I don't understand too much what exactly is spent or breaks in a fluorescent light bulb when it is at the end of its life and I would appreciate any explanation. Here's a video about what I'm talking about:

https://www.youtube.com/watch?v=NDnKEOeFJn0


texts: What does it mean to have dual input range?

texts:
Hi guys I am looking for a wide range input voltages DC-DC Converter as my inputs would vary from 12,24,36,42Vdc. I found this, the Murata NCS12 series which have an input ranges of 9-36V and 18-75V. Now what does that mean? Could it be I can input from 9-75V? Because it only has 1 pin for the input voltage.

Also what does the 10% load efficiency mean? Because I might need only 300mA but a peak of 1A for my application.

I might use the NCS12S1205C.

So would this be great for my application of inputs 12,24,36,42V 300mA peak 1A ?


texts: Does an iron nickel core work at high frequencies?

texts: I have a toroidal Iron nickel core, which upon research I found was used in an amplifier transformer, I couldn't get much info in it but I want to know if I can use it in a boost or buck converter circuit as the core, will it work as well as a soft iron ferrite core or is it just meant to be used at low frequencies as a transformer.


texts: Op-Amp analysis without using op-amp gain

texts:
I have a question concerning this op-amp problem for which I need to find an expression for \$v_{out}(t)\$, where \$V_B\$ has a constant value:

simulate this circuit – Schematic created using CircuitLab

So far, I've found that we can describe \$v_{out}(t)\$ by the following equation :

$$v_{out}(t) = R_2 \times I_{R_2} $$

And I know that :

$$V^{-} = V^{+}$$.

Now, I have some problems to use \$R_1\$ in the analysis, since I know that the current passing through it is \$0 A \$.

Therefore, I tried to use another equation with the gain of the op-amp :

$$V_{out} = A \left( V_{in} - V_B \right)$$

But I don't think I can find an expression. Therefore, I wanted to know if it's possible to find an expression without using this last equation ?

Edit : Added the original problem. The text is the following :

Pour ce circuit VB est constante. Déterminer vout(t) en fonction de
vin(t) et des autres paramètres. Calculer sa transformée de Laplace
en fonction de Vin(s).


texts:
I am trying to build an LC meter for measuring capacitance variations based on an LC tank Oscillator and an LM311 comparator. I took the circuit from this source (https://www.schiessle.de/emt1/MessKleinKap/MessKleinKap1.htm), and I would like to stick with that circuit as much as possible.
I first simulate the circuit in LTspice to get an idea on how the circuit works. I want the LC circuit to oscillate around 100 kHz, and in the simulation, the results are good.

However, when I built the circuit, the results differ from the expected values. As a first step I made the circuit on a protoboard, and I checked it with a nScope USB oscilloscope.

I included a bypass capacitor from the power supply to ground, I connect the balance and strobe pins of the LM311, and I also used a different L1 inductance value of 2.7mh (therefore the oscillating frequency should be around 96Khz) that is not ideal (it has a 23ohms component). The components that I am using have, except the capacitor C3, 10% tolerance value.

The problem is that the circuit becomes damped and noisy after a few seconds, and I can not find why. I try modifying the C3 value. The bigger the value of the C capacitor, the longer it lasts in a stable way. I tried placing another 1mF capacitor in parallel to C3 and it works.

video here: https://youtu.be/F3j8kqEoxcw

Could these issues be caused because of building the circuit in a regular protoboard and not on a PCB? What else could be the problem? Any comments will help!

Thanks in advance!


texts:
I am using a sensor having high impedance and have been suggested by the manufacturer to use a buffer (unity gain buffer) so that when we measure the values on ADC, they don't vary.

Now i am using LM324 Quadruple Operational Amplifier as a unity gain amplifier using this circuit and this link page 9 (but not using RL and CL).

Input on the V + of the circuit is 1.37 but the output V out is coming to be 1.41 or 1.42 instead of 1.37. I am not able to find out why this gain is coming and how to resolve this.


texts:
I designed a buck converter on breadboard as shown in the picture. I am applying PWM from my microcontroller. I am not sure why this circuit is not working, I have spent so much time on it. Is there any problem with the connections? Or have I picked the right MOSFET and MOSFET driver? The MOSFET is N-type and the MOSFET driver is low- and high-side compatible. How do I know if the MOSFET driver is working as high-side or low-side? I guess PWM input from microcontroller is not a problem as I have tested it with a signal generator also.

MAX627 data sheet**


texts: Why must the VCCA be powered in Cyclone 10 LP even if PLLs are not being used?

texts:
The device documentation related to the Cyclone 10 LP FPGA states that "you must power up VCCA even if the PLL is not used".

We were comparing the power dissipation of a Microsemi IGLOO2 FPGA with the Cyclone 10 LP. The core power dissipation of the Cyclone 10 LP was significantly lower than the IGLOO2. However, when we measured the VCCA we found that although we were using no PLLs in the design the power dissipation was quite huge on it. So eventually we gave up on the idea to use Cyclone 10 LP in place of the Flash based IGLOO2 FPGA.

Why is VCCA so important? Can't Intel make FPGAs where the device can work with VCCA grounded when PLLs are not being used?


texts: Using a radio board with Contiki-OS on lpc1347 mcu

texts:
I am trying to build a port for Contiki on my lpc1347 board. So far I have been able to run a basic LED blinking/Hello_World Contiki process/program on my board. My next goal is to use a cc2530 radio that I have, the problem is I do not know much about this. I see that that there is already a port for cc2530, but I want to use cc2530 as a radio, so is it necessary to port contiki in that too?
I am sorry for my naivete.

Thank you.


texts: 3.3 V through a 2 m cable : can it work?

texts:
I have to develop a system composed of 2 PCBs :

The 1st PCB is supplied by a 3.7 V LiPo battery. A 3.3V DC-DC converter converts the battery voltage to 3.3 V to all components on this PCB (microcontroller, LED, etc.).
The 2nd PCB includes sensors. It receives the supply from the 1st PCB. It is about 2 meters away from the 1st PCB, they are connected via a cable.

I was thinking of passing the 3.3 V output of the DC-DC converter through the cable from the 1st PCB to the 2nd PCB, and using a boost converter on the 2nd PCB to ensure that I have 3.3 V in the end.

Is that the right way to do it? I am afraid of the voltage drop due to the cable. Is the boost converter necessary? Would you consider adding extra components or using a different method to supply the 2nd PCB?

Thank you for your advice.


texts: What if you enable both DMA and Interrupt for a STM32 ADC

texts:
Imagine this scenario:

You are using a timer driven ADC in DMA mode, nothing special. Now, because you are interested in having a Watchdog, you also enable the ADC Global Interrupt in CubeIDE (enabling this is necessary so the watchdog triggers the interrupt).

Now imagine the DMA finishes transfering: the DMA will call "HAL_ADC_ConvCpltCallback", BUT since we also enabled global interrupts for the watchdog, HAL_ADC_IRQHandler will also be called, and this function will also call "HAL_ADC_ConvCpltCallback".
So, do you end up having "HAL_ADC_ConvCpltCallback" called twice? One by the DMA and another one by the IRQ handler?
Things get more confusing when DMA fails and an overrun happens in the ADC. The DMA will by itself call "HAL_ADC_ErrorCallback" due to transfer error, BUT because we also have an overrun, HAL_ADC_IRQHandler will also call "HAL_ADC_ErrorCallback" due to overrun error.
So, you end up having "HAL_ADC_ErrorCallback" called twice? One by the DMA transfer error and another one by the IRQ handler due to overrun?
I have tried to find the answer for this in the STM32 manual, also the HAL manual and by directly looking at HAL code but could not figure it out.


texts: Can a 9v battery or AA batteries be used instead of a bench power supply?

texts:
Do I have to get a bench power supply to work on electronics on a breadboard?  I know I can power an LED from a Raspberry Pi, but once you get more stuff on the board you need external power.  I don't want to spend money on a power supply yet.  Can I use a battery?  These would be small projects for learning.  I also saw a kit with the that will connect to the wall for cheap, but that looks dangerous.

Edit:  The kits I've seen use the LM317, but again, it's a screw down block for wires from the wall (I think).  I'm not sure that's good.


texts:
I'm trying to make a circuit with Op-Amps so I can get readings from a PT100 temperature sensor with an Arduino ADC.

I have based my design on this design: RTD Temperature Sensing

I want to read from 0°C to 500°C with the greatest resolution possible.
I'm using a LM2902NFS-ND Op-Amp
I'm using a single 5V supply
The PT100 has a 4.7kΩ pull-up resistor
The 1kΩ and 47kΩ voltage divider so 0°C will output 0V
The gain should be 19.6 so I have an output of 3.309V at 500°C

After a lot of verification, it seems like the circuit does not behave as expected. The voltage offset at 0°C seems to works, but the gain doesn't. I have taken multiple readings between the PT100 and the output, and it seems like the gain drops after the output is 1.2V, so about 200°C.

At 490°C, I should have an output voltage of 3.25V, but I have 1.35V.

From 0°C up to 200°C, the gain is about 15 and is pretty stable.

I have tried powering the Op-Amp with 12V without success. The rest of the circuit was still powered at 5V using a LDO 5V regulator from the 12V supply.

I have the same set-up for 5 sensors and they all behave like the same.

I'm not an expert in electronics and I would be really happy to learn what is wrong with this setup!

Many thanks

Edit:
Here are some measurements:
R_RTD - V_RTD - VOA2_out - VOA1_out - VOA3_out
100 - 0.107 - 0.107 - 0.105 - 0.002
138 - 0.147 - 0.107 - 0.145 - 0.754
175 - 0.185 - 0.121 - 0.183 - 1.194
212 - 0.221 - 0.154 - 0.219 - 1.263
247 - 0.255 - 0.186 - 0.253 - 1.306
280 - 0.287 - 0.216 - 0.285 - 1.339

As you pointed out, the VOA2_out is problematic. I will try the fixes proposed!

simulate this circuit – Schematic created using CircuitLab


texts:
How do I go about identifying an unknown connector, either from spec or measurement?
For example, I've got a GM4632-730 DC motor, which unfortunately came without the cable (and to make things worse, the connector partially broken)

All that's obvious to me is number of pins (and number of rows), pitch, and 'shape'. The latter is tricky to describe or search for.
Finding The JST Connector You Need (YouTube) gives a good understanding on relationship between pitch size and JST model numbers. Wikipedia is even better, with links to relevant datasheets. While I measured the pitch at about 2.5mm, the shape doesn't seem to match any of the JST datasheets, and those I've got on hand don't quite fit.
Molex seems the next thing to try, but Wikipedia is not nearly so helpful covering only PC connectors. Where do I go next to work this out? What other common formats are there?
The Banggood.com page even includes a picture of the appropriate connector, and makes it clear it differs from those I've got here and have tried. Is there anything else I can do with this end?

While this came about because I'm trying to find a specific connector and that remains my immediate issue, I'm more interested in how in general one can identify such connectors; short of holding stock of a variety and trying them all.


texts: Types of wire and applicability for guitar amps

texts:
I'm working on a DIY project for a tube amp. Next step will be to buy the right components and then actually mount everything.

I have some experience with amplifier theory but have never built one. What kind of wire should I buy, and what is the applicability of these wires in relation to guitar amps?

Silicone Jacket Wire
Teflon jacket
Cloth jacket
PVC jacket


texts:
I am doing a project at a local fair which is one of those 'steady hands' games. I am adding a twist that if you touch the wire with the loop you are dragging through it once, distractions will start.

Is it possible (using no ICs) to make a sort of trigger where when the loop touches, the trigger is triggered and the trigger output goes forever?