texts: Why is my atmega32u4 not showing up as a USB device

texts:
I have an atmega32u4 as part of a PCB that I designed.  The atmega32u4 comes with a USB bootloader and so I should just be able to plug it into my USB port and have it show up as a device.  It doesn't show up as a device, so clearly there is something wrong.

According to this website: http://www.hobbytronics.co.uk/usb-connector-pinout if my USB B has VCC =~5 V, D- =0 V, D+ = 3.3 V, then the computer should read that there is a USB device present.  I have measured that this is the case with a voltage probe (although D+ is only 3.14 V which I doubt is the problem).

Regardless of whether the board is functioning properly or not, if I'm measuring those values on the USB B pins, shouldn't my computer be recognizing that there is a USB device present?

Edit:
I've checked the signal with an oscilloscope and there is definitely a signal on the D+ line

note that the signal has a period of almost a second, which is weird.  It sometimes stays as that exact signal, but if I've just unplugged and replugged the USB connection it will do something interesting like this:

So I think that means my computer is at least trying to communicate with it and failing, but I don't know what to do with that information.

There are sometimes very short-width signals as can be seen at the beginning of the second picture.  I'm not sure why there are pulses that are so short and pulses that take almost a second.  Is one of those my computer and one of those the microcontroller?

Second edit:
So I'm starting to think that I just don't understand what is supposed to happen when I plug my board in.  I was under the impression that since the board comes with a USB bootloader I could plug it into my computer and immediately see it as a USB device, and also see it as an available port in the Arduino IDE.  Is this the case?


texts: Use a precision opamps or instrumentation amplifier for load cell application

texts:
I'm making a low power weighing scale with good precision. I'm contemplating if it'll be better to build a instrumentation amplifier with discrete OPAMPs of LPV821 which is low power (Iq 650 nA), high precision (Vos 2 uV typical, 10 uV max) and CMRR of 125 dB typical.

The other option is to use an instrumentation amplifier like INA333, which has characteristics like Iq of 50 uA, Vos of 10 uV typical, 25 uA max, and CMRR of 115 dB. I understand the laser trimmed resistances in the INA333 would make the gain precise.

What pros and cons should I consider for the two approaches?
Thanks!


texts:
I am trying to figure out the purpose of the gate resistor in this circuit:

Pictured are the UCC28700 flyback controller and the STD3NK80Z-1 MOSFET.
My understanding is that the resistor(s) serve two main purposes:

to limit the in-rush current that is caused by the parasitic input capacitance
to dampen the ringing on the Vgs signal when the drive pin pulls the signal low

At 14V, 10Ohms is not going to bottleneck the already current-limited DRV pin (datasheet says it is automatically current-limited to 25mA). My conclusion is that the resistor in the pictured schematic is to dampen the ringing, is that correct?


texts: Why motherboards have two pins for LEDs, led+ and led-

texts:
Very often you can find that there are two signal pins (+) and (-) for the LED in the motherboard.
1) Why not use one signal (+), and minus replace the ground?
2) What signal can be considered a common (+) or (-)?


texts: USB shield for analog and digital ground?

texts:
I'm new to Mixed-signal design and I'm having trouble deciding how to connect my digital and analog ground. I'm doing a 4 layer design, so I have a split ground plane.

As I understand, since I'm using the same supply the grounds should get together at some point. I'm inclined to use the USB shield as that point where the grounds come together, as I think this would clearly define the returning paths for the digital and analog currents.

I'm not sure if this is a good practice, or if there is a better solution.

I'd be glad to get any feedback on this. Thanks!

Edit: This is not a high frequency design (the main Microcontroller works at 16 Mhz). The different planes are required as the manufacturer states it as a requirement in the datasheet. The power comes from a USB connector that lowers the voltage to 3.3V through a regulator ADP3333. From there I get the "digital power" which comes directly from the regulator and then I get the "analog power"  which is the regulator output passing through a ferrite bead.

The IC is Analog devices AD5933 network analyser. http://www.analog.com/en/products/ad5933.html

Re-edit: My main question is:

Is it ok to connect both grounds through the USB chasis? Like this?


texts: How many capacitors do I need in my PCB design?

texts:
I have designed a PCB that includes an STM32L1xx MCU, a Micro SD Card, a pressure sensor, an accelerometer, a battery 18650 type and a buck-boost converter for a stable output of 3.3V (ISL9120IRTNZ).

I have followed the instructions from all the datasheets in order to connect the appropriate capacitors, make the correct connections etc.

I think that I have used too many capacitors for my design. Since every
module requires some capacitors, can I omit some of them?
Do you find any other error in the schematic?


texts: I am designing a MOSFET based H-Bridge to handle high current. I would like to place a SHUNT resistor in the circuit in order to detect over current. The voltage across the shunt resistor is to be read by a PIC micro controller (so the + voltage side cannot exceed 5V). The only place in the circuit i can think to add the shunt resistor is after the H-Bridge, however this means placing a tiny load on the source side of a MOSFET (as shown in image). Will this be a problem when considering the load is only 0.0001 Ohms? and is there a better place to position the shunt resistor?


texts:
I have a voltage divider feeding into an op-amp voltage follower buffer circuit. I'm trying to calculate the voltage level at the non-inverting input of the op-amp vs. the source voltage. The possible supply voltage is roughly in the range [0V, 5V].

First I tried using a simple voltage divider, so:

$$
V_A = R_2 / (R_1 + R_2) * V_S
$$

However, when I tried simulating this circuit in TINA-TI, the nodal voltages don't match those calculated.

I thought that was because the notion that there is no current flowing through the op-amp input wasn't truly non-zero, so I tried compensating for the op-amp input resistance and capacitance.

This time, the output voltage should be:

$$
V_A = (R_2 || R_3) / (R_1 + R_2||R_3) * V_S
$$

While this equation does match TINA-TI's simulation of the no op-amp circuit, it still doesn't match the op-amp circuit.

What else am I missing?

edit:

further information: I'm using the LMH6612 op-amp.

Suppose I want to target an output voltage of 2.5V. According to my first equation the required source voltage is ~2.82V. By recursively updating my simulation I calculated that the actual required source voltage is ~3.47V. Using the second circuit the required source voltage is closer, but only marginally at ~2.87V.


texts: Can you use an Arduino Uno as an ATmega328 programmer?

texts:
I don't have an Uno, but I was thinking of getting one and by the looks of it, you can remove the AVR microcontroller from the Arduino, right? It's just a DIP IC in a socket that can be pulled out, it seems like.

Uno http://egyrobots.com/image/cache/data/arduino-uno-500x500.jpg

So can you just load a program, remove the AVR chip, throw in another one, and load another program? Then you can have a permanent microcontroller solution for all your projects.

Is this possible?


texts:
So I have been designing a brushless motor and the circuit that drives it is based off of this Texas Instruments one here. The only problem is that this circuit runs off a minimum of 24v. I would like to use 12v, but I wasn't sure of the best way to go about doing this. The motor pre-driver (DRV8308) will work with 12v.

EDIT: Can someone at least explain to me why it is 24v minimum on the circuit i linked?


texts: electrical circuit contains elements with unique id

texts:
I want to build network (electrical circuit) which contains hundreds of elements (with unique IDs) based on some microcontroller.

Good example of that kind of network but much more expensive (and advanced) is Internet. For example I have main server (in my case microcontroller), nodes (computers with ethernet cards) and cables (e.g. cat 5e) which connect server with nodes. We can assume that network has  star topology.

Requirements according to above graphic:

I have x numbers of C (C could be circuit, cable or connection)
I have numerous number of elements with unique IDs which can be connected in to any place (C)
Element with unique IDs can be swap with another element, remove or add (if there exist C with no element)
I need to know ID of element which was connected to certain C.
I need to set ID by myself or can buy "element" that I know what is it's ID.

What are the easiest/cheapest way to make network like I explained above?


texts:
I'm reading over the history of British WWII radar systems, and one thing that really struck me was the improvement in crystal detectors. The were a vital component of microwave radars, and while the Germans had a magnetron literally fall into their hands in 1943, the lack of a useful receiver meant they were still struggling to make a working system when the war ended.

One point is interesting to me. While Crystal Fire recounts the development of diodes, mostly at UChicago IIRC, the British already had military-grade versions in 1940. The difference appears to be the noise level. The British version used in the Type 271 radar had 20 db of noise, while the US model in the Type 277 was 14.

Can someone familiar with these early devices explain where the noise was coming from, and how it was reduced?

And for comparison, can anyone offer a figure for the end-to-end noise in a modern radar system? I see that systems in the 1960s were 10s of MW and today they are replaced with ones using as little as 25 kW, and I suspect that is due largely to receiver improvements?


texts: Methods for removing solder from inside a header socket

texts:
While soldering a header socket I sometimes apply too much solder and it flows through, partially filling in one or two of the female sockets holes. This prevents the male headers from being inserted all the way. What are some methods for removing the solder from within?

I've tried to insert a jumper wire and then heat the wire with the soldering iron, but that did not seem to help. I do not own a solder sucker (yet), so I have not had a chance to try that yet.

Edit: I am attempting to remove the solder from within the header socket itself, not from the via/holes on the PCB.


texts: How and why is a magnetic field transmitted with alternating current?

texts:
I apologize for the basic question (or if it is incorrect in its assumptions,) but how does one account for magnetism in alternating current?

If I generate alternating current to a motor, why do my coil poles become magnetized, and why does the magnetic field rotate?

Looking at a graph of an AC waveform, can the magnetic properties be visually determined?


texts: PIC Microcontrollers, ambiguous quiz questions

texts:
I am taking a course in micro-controllers (PIC). I recently took a quiz but i am having hard time convincing my teaching assistant that the quiz he made is ambiguous as hell. What would your choices be? And could you comment of the questions themselves?

A little context: The quiz was supposed to be based on timers, it was taken after one lecture on timers and right before the lab on timers.

I am not even sure if i can ask these types of questions in this forum. But i am sure this is the only place i am going to get answers so here goes, be gentle

 1. The clock circuit (oscillator circuit) and reset circuit are internal circuits.

    True/False

 2. What is the roll over value of Timer1 when operating in normal mode?

 (a)0x10000
 (b)0xFFFF
 (c)255
 (d)none of the above

Note that Timer1 is a 16 bit timer.
Edit: TYPO IN QUESTIONS 2 OPTIONS.

The Pic that we used in our labs is 16F877A. It does not have an internal oscillator.

Answers according to TA were True and (b) 0xFFFF

My choices where False, because you could 'clock' the ucontroller with external crystal, external clock source, external RC oscillator, it did not matter if the second half of the question was true (0&&1 = 1). Mind you we were not formally taught about all the different clock sources of microcontroller.

0x10000 because 255 was obviously wrong, timer1 being 16 bit and because of the fact that the timer rolls over after 0xFFFF.


texts: Two ports of the same PowerBank on series

texts: I have a power bank with 2 USB ports, each one is a 5V/2A, is it possible to put the two ports on serie so I can have a 10V/2A output?


texts: Error setting up timer HAL PeriodElapsed Callback STM32F334R8T

texts:
I'm trying to create a microsecond delay function using the STMs regular timer. I wanted to set a timer to fire an interrupt every microsecond and then increment a variable in the call back function which gets called at the end of the interrupt and if that variable has reached the desired value stop the counter with HAL_TIM_BASE_STOP_IT().

Normally when using the HAL library for STM32 at the end of an the interrupt, the interrupt handler calls a callback function. The callback functions are already declared but are left blank. The driver makes use of a nonstandard keyword weak which allows you to overload the callback function, by simply writing your own definition. I've successfully done this with the callback functions for the interrupts for I2C, UART, and SPI communication, but for the timer I get the following 3 errors.

Error[Pe079]: expected a type specifier C:\projects\automated_testing\voltage measurement node\Src\main.c 610

Error[Pe147]: declaration is incompatible with "__interwork __softfp void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *)" (declared at line 1558 of "C:\projects\automated_testing\voltage measurement node\Drivers\ C:\projects\automated_testing\voltage measurement node\Src\main.c 610

Error[Pe141]: unnamed prototyped parameters not allowed when body is present C:\projects\automated_testing\voltage measurement node\Src\main.c 610

My function at the moment is literally just toggling a pin to see if it works. If I comment it out, it compiles fine.

void HAL_TIM_PeriodElapsedCallback(&htim3)
{
  HAL_GPIO_TogglePin(N_CS_GPIO_Port, N_CS_Pin);
}

Here's the configuration code for my timer created by STMCube to be in "Output Compare No Output" mode. I'm using HAL_TIM_Base_Start_IT(&htim3) to start the timer and does call the interrupt routine and get to the correct blank callback function when I don't create my own definition of the function.

* TIM3 init function */
static void MX_TIM3_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 0;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 72;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_TIM_OC_Init(&htim3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sConfigOC.OCMode = TIM_OCMODE_TIMING;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_OC_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

Any ideas as to what I've done wrong would be very helpful.


texts: How can i make f(a,b,c) = \$A \cdot B \cdot \overline C + A \cdot \overline B\cdot C\$ using only XORs and NANDs?

texts:
i have this problem where i need to make the Logical Function represented by :

f(A,B,C)= \$A \cdot B \cdot \overline C + A \cdot \overline B\cdot C\ \$ using only XORs and NANDs

The function was as the beginning a 4 Variables Function

$$F(A,B,C,D)= (A \cdot B\cdot \overline C \cdot D + A\cdot \overline B \cdot C + A\cdot B\cdot \overline C \cdot \overline D)$$

And i simplified it by a simple factorisation of \$A \cdot B \cdot \overline C\$ and now i'm stuck,don't know how to make it out of XORs and NANDs.

Thanks in advance for your help !


texts:
I need to design the hardware to load my custom programs into a STM32F051C8T6 microcontroller and I'm not sure of which pins should be connected to what and I wouldn't like to do things wrong.

I've found some good information in the web about the software part, but not about the hardware part.


texts:
So I have several TEG peltiers, and the main issue that arises is the peltier tile neutralizes in heat over time. Applying my hand's heat to one side will soon affect both sides of the tile, therefore no longer producing voltage. What is the best way to produce a constant voltage? A heat sink on the opposite side perhaps? (if so, suggestions on what type of heat sink)

To summarize, how can I produce a constant voltage in my peltier TEG, or what is the best/closest way to do this?


texts: Logic Level Conversion. Different Voltages on High Side

texts:
I've used this circuit before to do logic level conversion.  The diagram is labeled to reflect I2C however I am using it for UART.
Usually my scenarios have been where the low side is 3.3v and the high side is 5v and this circuit has always been fine.

Currently I have a scenario where the low side will be 3.3v and the high may be 5v or 3.3v.  I'm wondering if this circuit is still ok in this case.

Any comments are appreciated.

thanks!


texts:
I am going to buy A6 GSM module for connecting to my Raspberry PI and making a little research here. Will I be able to power up this module purely from PI or external power source is a must?

A6 data specification says it requires from 4.9 to 9 volts.
Can it be powered up, for example, from GPIO port, which seem to be provide 5V?  Some sources say about 5V battery, but maybe it's just a a recommendation?

I am totally newbie in electronics and had no experience with PI before. I have Raspberry PI 2 model B revision 1.1.

UPDATE: I found out that module specified in my first link is not actually a SIM900 module so I corrected the title. It is A6 tagged as a replacement of SIM900 and seems to be based on GSM/GPRS A6 chip.

Also in the web I found several modifications tagged both as SIM900 and A6 (1, 2, 3), and all of them have different power consumption (1.3mA, 1.5mA, 2mA). As I have no particular preference in one GSM module over another during the purchase, opinions on any of them are appreciated. Real experience is highly appreciated.


texts: Trying to make fuzz factory with CV inputs

texts:
I'm trying to construct some kind of fuzz factory modular from regular fuzz factory pedal.

Circuit of the original pedal is pretty easy, but I've tried to add some VCAs based on LM13700. Honestly, I'm a little noob in electrical design, so I've just combined fuzz circuit with VCA circuit and got this:

Here I tried to make working CV inputs for stab, gate, comp and drive parameters with LM13700 VCAs.

So the qestion is: will it work, or how can I check it for performance (besides constructing it?)


texts: Start learning FPGA programming with a real FPGA

texts:
I want to start developing with a FPGA and I have no idea about them. I have found a Xilinx-spartan-6-FPGA but I'm not sure if it is a good choice to start learning with.

Any advice?

This question is not a shopping recommendation, it is more about with which FPGA I can start to learn.

I want to start with a real one, not with a simulator. This is why I've asked it a Xilinx-spartan-6-FPGA is a good one to start.


texts: Why is length matching performed with the clock trace length as the target length?

texts:
Length matching is performed mainly to avoid the skew generated among the parallel data lines/data bus width.
All the high speed PCB design guideline suggest performing length matching with the clock trace length as the target length and trace length tolerance of the data, address, command lines has to be maintained with respect to clock signal. May I know the particular reason for this?
As I understand it, the clock appears continuously. There will not be any data loss in the clock, hence it is a periodic signal. Data will consider the positive edge or negative edge of the clock and it will appear initial sequence in the timing waveform.
Any insight would be greatly appreciated.


texts: Design of circuit to reduce flickering of LED

texts: I want to Design a circuit to reduce flickering of LED(1.6 v) powered by a DC motor acting as a generator .Mechanical input is kinetic energy of water.Plz suggest me a circuit .What if we employ two condensers,one will charged for sometime and then it will be discharged through a 1 watt LED and the other being charged simultaneosly when the LED is getting discharged.Voltage generated at the end of LED is 1.6volts.


texts: How load sharing can be done in AC mains and inverter?

texts:
I want to do load sharing in between ac mains and inverter? But How it can be done, I have no idea.
In the above line, many experts will not understand the question, so I am just explaining a simple example below:-
Suppose we need to drive a load of 10 kW (load can anything or mostly all the loads are combined to form the 10 kW) in our household. But in my area, the utility sector provides only 5 kW to drive the load. but if I go above beyond this we need to pay for this extra. But in my home, I have an inverter (inverter can be any type may be a solar or conventional system with battery) which is rated of 6 kW, so why we will purchase extra energy from the utility sector if we have an inverter. so what we will do we want to share the power or bypass the load, in simple terms if we set the limit of ac mains to 4 kW and after beyond going to 4 kW my power will be shared by the inverter which will 6 kW.
Now this power distribution will be done by the microcontroller and some hardware apparatus (e.g.IC's, gates).
So I explain everything that I need to do.
SO first I thing I need to do share the power, mean to say how I can minimize the power transfer from the grid, and allows maximum power from the inverter well grid is still ON, no power cut.
I request to all please kindly share me some basic ideas on this.
Recommend me any book/reference paper for this, please? I apologize for not posting any pictures or any code. because this is a practical question that I need to do.


texts: 74LVC and similar... can a logic 1 output sink current?

texts:
Say I am running my 74LVC125 at 2.5V. At the A input I have a logic 1 and at the nOE input, I have a logic 0, so the device should be driving a logic 1 onto the Y output.

With no load connected to the Y output, I should observe 2.5V at the output, obviously.

Now say I have a load along the lines of 1kohm to 5V. What happens? I choose 74LVC125 for my example because for tristate LVC logic, in the high-Z state (nOE high), applying higher voltage than Vcc on an output is allowed. But what about with the output enabled?

Will it sink something like (5.0V - 2.5V) / 1kOhm = 2.5mA?
Will very little current flow?
Will it sink more current than I would expect? The TVS diodes of the LVC device will not yet flow current, but will some kind of reverse bias damage happen to the rest of the LVC driver IC?

I want the first thing to happen, that is for the 'LVC125 to sink something like 2.5mA into 2.5V. Using a logic circuit like 74LVC125 is cheaper and than applying several MOSFETs for this purpose. Can it be done?


texts: Can I rip the screen off the Adafruit Mini Color TFT with Joystick FeatherWing?

texts: I'm looking for a small color screen, and I came across  the Adafruit Mini Color TFT with Joystick FeatherWing. But I want it to be a bit smaller, and I don't need the joystick and buttons on it. Would it be safe, and if so, how would I take off the screen and use that separately?


texts:
I have a design is that over-stressing (EOS) a PFET's (PMDT670UPE,115) rated Vgs by 50% (Vgs -12V, limit is -8V), I want to consider PWM'ing this part with 50% duty cycle in hopes of increasing the part lifetime!

We still would be saturating FET and providing EOS Vgs just trying to

reduce time spent at the EOS condition and
reduce temperature which (slightly) increases permittivity.

Can you conjecture if how PWM would impact the population of FETs operated at the unrated Vgs?

Would it counter-intuitively reduce part lifetime (perhaps due to switching losses)
might PWM'ing have a proportional extension of lifetime
might PWM'ing have a significant / nonlinear extension on the PFET lifetime.


texts:
As you know, msp430 launchpads have their own debugger, nothing else required to debug,on the other hand fet-debuggers are sold in high prices on ti.com,what the hack is that? and if i buy only MSP430G2x53 what should i use to debug and make it work.

Thanks in advance


texts: Inferring BRAM with unused addresses efficiently

texts:
What is a correct way to infer a RAM with some unused higher addresses (using block RAMs)?
Using the code below (default values for generics, Xilinx synth and map) I get a RAM sized the same as if depth was set to 2**ADDRWIDTH:

entity foo is
    generic (
        DATAWIDTH : positive := 8;
        DATADEPTH : positive := 5000;
        ADDRWIDTH : positive := 13
    );
    port (
        clk_a  : in std_logic;
        we_a   : in std_logic;
        addr_a : in std_logic_vector(ADDRWIDTH-1 downto 0);
        di_a   : in std_logic_vector(DATAWIDTH-1 downto 0);
        do_a   : out std_logic_vector(DATAWIDTH-1 downto 0)
    );
end foo;

architecture bar of foo is
    type myram_type is array (DATADEPTH-1 downto 0) of std_logic_vector(DATAWIDTH-1 downto 0); --! type for ram content
    shared variable myram : myram_type; --! ram
begin
    process (clk_a)
    begin
        if rising_edge(clk_a) then
            if we_a = '1' then
                myram(conv_integer(addr_a)) := di_a;
            end if;
            do_a <= myram(conv_integer(addr_a));
        end if;
    end process;
end bar;

For example, I want a RAM with DATAWIDTH = 8 and DATADEPTH = 5000, so the address has to be ADDRWIDTH = 13 because ADDRWIDTH = 12would only allow to address 4096 RAM locations. Lets assume one block RAM ressource on my FPGA can hold 8192 bits.
If I handcoded this I required 5000*8/8192 rounded upwards = 5 block RAM ressources.
However, with the code above, synthesis and map of Xilinx results in 8 block RAM ressources being used, because thats what can be addressed by 13 bit wide addresses...
Nontheless, this is not really efficient use of ressources since 3 of the 8 block RAMs will never be used.
I tried to check if the address at the input is larger than DATADEPTH and then assign don't cares for the data, but that results in the whole ram being implemented as distributed RAM / LUTRAM.
Am I missing something important or do I have to use one big ugly generate for this?


texts:
I would like to design a RC filter to prevent reset to a SoC during a ESD strike. Assuming the reset net is by default low.

And the reset comes from a separate board which connects to the main board (where SoC resides) using a Board to Board connector.

In case there is air discharge on the daughter board. I want to avoid changing the state of reset line during the ESD strike and avoid trigger of reset to the SoC.


texts: What is the magnetic field due to an electromagnet at a point that is not along its axis?

texts:
For e.g. at a point below(or perpendicular) to a cuboidal/cylindrical core electromagnet?
I am confused whether the magnetic field for an iron-core electromagnet is limited to the axis passing through it because if that is the case how can it be used for the various applications that requires applying force on other metals?
Please specify the method to calculate the field,if any.
I am a beginner so kindly pardon any mistakes.


texts:
we have found a design of screw terminal that we really like but we are having lots of problems trying to source this specific part, I was hoping somebody here may recognize the design and know where to find the part. I have attached some images of the terminal opened and closed. With a typical screw terminal the screw clamps down onto a wire securing it, in this style the screw pulls up a nut that clamps the wire. I hope the pictures are clear and show what I'm describing.

tb1 http://www.rtdcontrols.com/images/TB1.jpg
Terminal block closed:
tb1 http://www.rtdcontrols.com/images/TB2.jpg
Terminal block open:
tb1 http://www.rtdcontrols.com/images/TB3.jpg

Any info about this would be appreciated, Thanks


texts: Raising Op Amp Supply Voltage Without Affecting Output Voltage

texts:
I have an existing analog input circuit on a device that utilizes an op amp (TI LM2902) as a buffer. There is a reference voltage of 9V and the Op Amp is powered by 5V. The input signal to be read by the ADC originates at an off-board sensor.

I am wanting to make a new device with more inputs and re-use the existing circuit. The new device I am making does not have any need for 5V, so I am wondering if it is possible to raise the Op Amp supply voltage to 9V without affecting the ADC values? I want the A to D readings to be consistent between the two device.

My understanding is that the supply voltage just dictates the ceiling of the output voltage. Is this correct and the ADC values will be the same whether I power the op amp with 5 or 9 volts?


texts: How to prevent a resistor receiving a too high power?

texts:
If a circuit was creating 0.3 watts, and resistors rated for 1/4 watts were used, what would be the easiest way to make it stay inside the rating? Would it be to, say, connect two resistors of twice the resistance in parallel, thereby cutting the watts applied to each in half?

Also, I've experienced that when connecting a 1/4 watt resistor of approx. 50 ohms in series with a 10V supply, it gets hot and its resistance increases a LOT (To a couple of kilo-ohms). Is this normal, and shouldn't the resistance stay the same within the limitation?


texts:
I have this problem to solve and I have the answers, but I'm trying to understand the concepts behind it.

A paging system has the following parameters: 2^32 bytes of physical memory; page size of 2^10 bytes; 2^16 pages of logical address space.

  1. How many bits are in a logical address? 26 bits
  2. How many bytes are in a frame? (?)
  3. How many bits are in the physical address specifying the frame? 22 bits
  4. How many entries in the page table? 2^16
  5. How many bits in each page table entry? Assume each page table entry contains a valid/invalid bit. 23 bits


texts: What is the "CV" unit for leakage current in a capacitor datasheet?

texts:
I've looked at a few leakage current specifications for electrolytic capacitors, and they all seem to specify the value as something like this:

  I < 0.01 CV or 3 (μA) after 2 minutes, whichever is greater

Here are a few example datasheets: Panasonic, Multicomp, Nichicon, Rubycon.

Am I right in thinking that the leakage current is a product of capacitance and voltage, i.e. for a 100µF cap on a 5V supply I'd be looking at a leakage current of \$I = 0.01\times100µF\times5V=5\times10^{-6}A = 5µA\$.

Or is that CV unit something totally different?

Additionally, why the long time delay for this rating when a capacitor typically charges in seconds or less?


texts:
I'm thinking of doing a small-scale Solar off-grid setup 1-2 80 Watt panels with a 12v 40Ah Deep Cycle battery. I have questions for those parts in another thread, but for now, my question is about understanding what to look for in a battery controller. Kindly see the example on this link.

I will copy paste the specs written:

Technical date SMR05
Nominal voltage 12V/24V, automatic recognition
Max solar current or load current 5A
Over charge voltage14.6V/29.2V
Over charge release voltage 14.0V/28.0V
Over voltage protection 15.6V/31.2V
Load disconnect voltage 10.5/21V
Load reconnect voltage 11.5V/23V
Over voltage protection 15.6V/31.2V
Lighting hours 0-18hours
Night/day detect 3.0-7.5V/6.0-15.0V
Battery type Liquid,Gel
Max solar voltage 55V
Max battery voltage 40V

Kindly correct me on my understanding of this specs:

Model
The battery to be putted can either be a 12 volt or 24 volt?
the solar panel's current can not exceed 5A (Solar panel in Parallel should not total over 5A)?
14.6V for 12V is the indicator that the battery is 100% charge?
14.0V is the time where the controller will pass the excess energy to the Load?
Protection for the battery.
If the controller detect the drop of v taken from the panel is at 10.5, the load part will be disabled? Or if the voltage drops at 10.5 the controller will not charge the battery?
Battery will charge at 11.5V? or the Load (excess energy) will be re-activated?
??
??
??
??
??
??


texts: OpAmp impedance matching for multiple measurement devices

texts:
I am planning a custom circuit incorporating an operation amplifier. The circuit will either be connected to a 50 Ohm oscilloscope input or an 1 MOhm oscilloscope input. Transferred (analog and digital) signals will have a frequency up to ~1GHz. Now I know that the output impedance of the custom circuit should be equal to the input impedance of the oscilloscope in order to transfer the signals in the best way possible. The (ideal) opamp has an output impedance of 0.
Thus I was now wondering: Is it necessary to put one resistor after the opamp, two (switchable, depending on target), or none? Serial, or parallel?


texts: Coin cell battery retainer, problems and best practices

texts:
I use Memory Protection Devices BK-913 CR2032 Through hole battery retainer.

I use Adafruit's CR2032 PCB footprint, which is almost identical to the recommended footprint in the datasheet for the retainer. It is has a square 4x4 mm center pad defined as negative. Around the center pad is a 15.24 mm circle defined as "no solder mask".

When the PCB is manufactured it looks like this:

Is the square center pad and the surrounding circle electrically connected? If I understand the footprint correctly, they should not be? But the little breaks in the black square surrounding the center pad suggests that they are connected anyway?

I have experienced some problems with this footprint, the connection with the battery sometimes fails. I have to readjust the battery, and some batteries only works if halfway inserted into the retainer. Not very reliable.

It worked perfectly with the batteries I had, but when I got a new batch of the same batteries (same manufacturer, same supplier etc.), they are extremely difficult to make proper contact in the retainer. I guess the batteries from the new batch are a tiiiiny bit different physically..?!

Are there any best practices for footprint design for coin cell battery retainers? For example, I have noticed that the pad under the battery retainer on the Texas Instruments SensorTag looks like this:

What is the reason for this? Are the little solder dots there to help make better contact with the battery?

How can I modify my footprint to be more reliable?


texts:
I have an antenna which runs at 917MHz located inside a metal structure that measures in at 6m long, 2m wide and 1.9m high. The exact location of this antenna will be in the center against the length of the metal structure. I would like to know how do I mathematically predict the behavior of the EM waves emitted from the antenna at any given point inside the container, without the use of any simulation software?

My objective is to determine the effect of enclosing an antenna inside a metal structure to illustrate the effects of super positioning mathematically not the entire process but just a few iterations to see and understand how the you can achieve the same goal as the simulations.

I feel like all I know is to fill in the parameters in the software and click run simulations but without fully understanding whats going on in the background. And sadly this is not a good way to grow academically.

This is purely for my own understanding not for any project or deadline. If anyone wants to criticize me for not using simulations, please refrain from commenting has I have mentioned my reasons or if you think this is stupid and a waste of time.


texts:
I am trying to create a custom PSOP footprint in Altium designer using the IPC compliant footprint wizard. The datasheet of the ic says that it is a PSOP (plastic small outline package). In the wizard there is an option for a SOP/TSOP package with Gullwing leads, but not for PSOP. The included packages are SOP, TSOP and TSSOP.

Can I select this option to create my footprint for the PSOP package. The ic I am using is an NCV7729 8A H-bridge driver from ON semiconductor.


texts: What's a reference text on analog design?

texts:
I'm looking for a intermediate text that covers (discrete) amplifier circuit theory using BJTs and FETs and circuit elements such as current mirrors, differential stages, feedback theory, etc. My applications are wideband and the book should cover BJT charge control models. A chapter to two on device physics would be helpful.

I do not need to review Ohm's / Krichhoff's laws, passive componets, etc., and I already have books that cover digital.

I've seen a chapter from Donald Neaman online and this book seems ok. Can anyone recommend this text or another one?


texts:
I have to drive a solenoid with the following schematic:

It works great but sometimes the MIC5020 or the input pin of microcontroller fails and can therefore no longer be pulled high, but I can't quite understand why.
VSOL: 48V DC.
VSOL_MEAS: measurement pin to see if 48v is present.
SOL_SENS: measurement pin to see if solenoid is present.
Does anyone have an idea what's wrong?


texts:
Modules of 3 LED

Simple LED strips or bars that are using 12V input voltage often have the following layout:

They consist of modules with 3 LED each, all connected in parallel to the input voltage.
A single module consists of three LED and one resistor in series with the input voltage.

(This answer has an example picture and schematic: Cuttable 12V LED strip)

High resistance after one LED breaks

The whole module goes dark, and all other LEDs get a tiny bit brighter because they no longer share the power supply and it's connections resistance with the broken module.

The secondary damage here is that more LED stay dark than are actually broken.

Low resistance after one LED breaks

Then, one module consists of only two LED and the standard resistor, which is now way to small for limiting the current in the normal way. So the two other LED in the module ret much more current, and are possibly much brighter. The other modules should get a little darker, because they need to share the power supply with the broken module, which now uses more current.

The secondary damage here is that the two LED which get higher current will break soon too.
In the end, more LED will stay dark than were actually broken - because they broke too, in this case.

Workarounds?

Of course, in both cases, repairing would mean replacing the broken LED.

But what do to best, in each case, if no replacement LED is at hand?


texts:
I was asked to find the four colour stripes of a 1M ohm (tolerance of 5%)

My question now is don't we have 2 options? I came up with:

Black(0) Brown(1) Blue(x1M) Gold (5%)
Brown(1) Black(0) Green(x100K) Gold(5%)

Is there one right and one wrong or are both of these correct?


texts:
I'm designing a network of wireless sensors for an outdoor enviroment. It will consist of aprox. 30 sensors powered by battery (6 months autonomy), taking measurements with a low frequncy (max 10 times per day), distributed in a radius of 100m, with a central node as a gateway. The gateway will be powered by battery and solar panel.

What is the recommended communication protocol to cover a radius of 100m, star topology, in an outdoor environment (farm) and with the nodes being powered by battery? I think LoRa is for larger areas and ZigBee for smaller areas.
How do I estimate the solar panel and the battery capacity, once I have the total power consumption, for the gateway?. I think that the solar panel must provide enough energy to power the station during the day, plus the energy to recharge the battery. What about cloudy days?. Is there a rule of thumb for this?.
The gateway will be always listening for new communications, but the nodes will be 99.9% of the time in sleep mode, so all the communications must be initiated by the nodes. Is there a way for the gateway to wakeup the nodes using a wireless signal and start the communication? Or the only way would be to wakeup the nodes periodically with an internal RTC and poll the gateway for new messages?
The power consumption of the communication module of the gateway in "listening" mode is the same as the Rx power consumption specified in the datasheets? Or the Rx power consumption is for when the module is actually receiving data?


texts: Li-Po shield for Arduino with in-line recharging, soft-off and voltage protection?

texts:
I'm looking for a shield for my Arduino (or a breakout board that I can adapt for the purpose). It should have these abilities:

JST connector for my single-cell battery.
Over- and Under-current protection
Voltage boosting to 3.3v or 5v level. (preferably 5v)
Recharge from USB or external power.
transparent switching from battery to external (and back)
Battery gauge with low-power alert. (MAX17043G+U or similar)
Soft-off so my application can turn itself off.

Of all of these things, it looks like the SparkFun LiPower shield meets the most of them, but it cannot turn off my device. Pololu has a nifty push-button power switch that can turn off the supply by pin input, but I want to cut off the battery too. I've also checked out the Liquidware Lithium Backpack, but it doesn't switch seamlessly from vSupply to vBatt, nor can it turn itself off or monitor the battery level, and it requires ugly wires from one end of my board up over the sides, so is difficult to use with shields.

Has anyone seen anything better?


texts: SDC constraints for two flop sychronizer

texts:
I have doubt, What should be proper SDC constraint for CDC module, i.e., two flop synchronizer.
between "dat driving by aclk to bdat1 driving by bclk"
Note: aclk and bclk are not the same, also question for what if same too?

Is it false path?

Following is SDC constraints file I have used,

# Input ports
# -----------------------------------------------------------------------------
set_input_delay $ACLK_IN_DELAY  -clock $SCLK [get_ports dat ]

set_input_delay $V_CLK_1_IN_DELAY     -clock $V_CLK_1    [get_ports srst_ni]
set_input_delay $V_CLK_1_IN_DELAY     -clock $V_CLK_1    [get_ports drst_ni]

# Output ports
# -----------------------------------------------------------------------------
set_output_delay $BCLK_OUT_DELAY  -clock $DCLK [get_ports bdat2]


texts: What's the difference between using 3.7v and 9v as phantom for electret mic?

texts: I'd like to pass from a mic/filter/amp circuit with the LM386 and powered by a 9v battery in single supply to a 3.7v equivalent using the PAM8403. In hi-fi audio the phantom DC is 48v. Is there any downside in using a voltage as low as 3.7?


texts: How to find a datasheet for a part that doesn't exist on the manufacturer's website?

texts:
While bored recently, I decided to take apart a few old pieces of electronic equipment and attempt to reverse-engineer them.  I've been doing pretty well, but I've come to an IC that I can identify but doesn't seem to exist on the manufacturer's website.

Specifically, it's an SOP20 package marked "I87-0205-000 1202S7E", with Microchip's logo on it.  I'm fairly new to this, but context clues (looking at the board) suggest that this is some kind of MCU, which makes sense, given the manufacturer.  I've tried googling these numbers, and while I get about 8 billion results on Alibaba with vendors willing to sell me hundreds of them, none of them actually tell me what it is, or offer any datasheets.  I've tried contacting a few of these vendors asking for datasheets, but none have gotten back to me yet.

So, anecdotes aside, are there any good methods of figuring out the name of a chip/finding the datasheet for a somewhat unidentifiable chip?


texts: How to change step pulses into PWM pulse synchronously?

texts:
I am driving a stepper motor using microstepping techniques.
For the input signals to the driver, step and dir are used.
More than 100,000 steps/second speed is target.
The PWM frequency is below 100KHz. How to convert the step pulses into PWM pulses synchronously ? I want the rate should be same even though the constant buffer delay exists.
At this moment, ISR routine for step pin handles counting up/down pulse.

But when i mill something for test on my CNC with my stepper drive, the 3D output quality isn't pretty good compared to with other vendors high performance closed loop stepper.

So i guess there is an input jitter on step pulses.


texts: Connecting a device to a CPU via USB PCB tracks

texts:
I have a device that should be connected to the CPU via USB 3.0, and I am planning to put both the CPU and this device on the same PCB, so I am thinking of using PCB tracks to connect them.

My questions:

Is there any problem in the above way of connecting the two devices?
What type of consideration do I need to take of?
Can I do just connect the wires to each other, or do I need some type of interface?
Do I need all the normal surge/over voltage and ... on this design?
Is there any sample schematic that I can use as reference?


texts: Detect alternating current using one contact only and arduino analog input

texts:
I am trying to setup an arduino so it can detect an AC where it only has access to one pole.

(kind of like these "electricians screwdrivers" that you put in one of the connections of an electric outlet, and then it lights up by completing the circuit through the users body)

I have access to a simulated ac power source, a pin from a different controller with a different power source that is toggled between high and low every 10ms.

Now, when I connect the arduinos analog input and gnd to the ac power source, and print out the value of it every 5ms to the serial monitor of the arduino, all i get is zeros.

However, I know that current is flowing, because when I put a buzzer between the one ac pin and the arduinos gnd, I hear a sound from the buzzer.

Why am I not detecting the current here? Do I have to build my detector differently? below is a simplified drawing of my setup.

Thanks

(Sorry I am not an electrical engineer, please forgive the limited language and knowledge)


texts:
The following system is given and I'm asked to find the transfer function $$\frac{Y(s)}{U(s)}=G(s)$$ $$\bar {\dot x}=\begin{bmatrix} 0 & 1 & 0 & 0 &0 \\0 & 0 & 1 & 0 & 0 \\ 0 & -1 & -2 & 0 & 0 \\ 0 & 0 & 0 & -2 & 0\\ 0 & 0 & 0 & 0 & -3\end{bmatrix} \bar x + \begin{bmatrix} 0\\0\\1\\1\\0\end{bmatrix}u=A\bar x + Bu \\ $$

$$y=\begin{bmatrix}0 & 1 & 0 & 0 & 1\end{bmatrix} \bar x $$

I haven't practised that much on state space models and I don't remember that much from matrix algebra but here's what I've thought.

I found the eigenvalues seeing the matrix as a 2x2 diagonal matrix with matrix elements therefore getting the denominator of my transfer function $$s(s+1)^2(s+2)(s+3)$$.

I also have my backdoor $$G(s)=C(sI-A)^{-1}B $$ but this includes many calculations and I guess that there is a faster solution.


texts:
I am designing a RGB LED matrix of 1:4 scan 16x32 pixels
As it is 1:4 I have 2 options

Option A: Use A,B,C,D pins direct address to control the display

or

Option B: Use A,B pins only and use a decoder to control the display

Which option would be faster? I have to chain many panels so I have to optimise speed.
Can option A generate more noise in comparison to option B?
It is very important to have minimum noise for the display to have good quality.

As I have to chain 10 displays. If I use a decoder for every display there will be 10 decoders required. Is that delay per display negligent?
But if I use those C and D lines, there will be 2 more lines running through the display.

Explanation for 1:4 scan rate

As my display is of 16 rows, 1:4 scan rate means only 4 rows will be lit every cycle i.e 25% of the total display. 1:2 scan rate means 50% 8 rows will be lit per cycle. So for 1:4 Address lines are used to decide will set of rows will be lit. That is why I have 2 options. Either use 4 pins for direct addressing. Or use 2 pins and use a decoder.

I am designing something similar to this display:

Led matrix

Thanks!


texts: Commercial 1.5m / 5' LED light fitting parallel LED arrangement

texts:
I am reviewing LED light fittings for an industrial premises refit. As with most of the experienced users on this site I like to understand what I'm purchasing and have opened up a sample fitting to have a look. To my surprise I find that the LEDs are arranged on three PCBs as shown in Figure 1.

Figure 1. LED light fitting comprising of three PCBs in parallel connection, with 12 series connected rows of 6 parallel LEDs on each board.

The array is driven by a constant current power supply which looks OK but I've never seen an array of LEDs driven like this and here on EE.SE we advise people all the time not to do this.

The distributor is giving a 50,000 hour warranty on the lamps (which is good). He also says that if a chip dies the "circuit will compensate" which I take to mean that the others in the row will have to pass more current. The build quality looks good with a much larger PCB than other brands with most of the copper left on the board which should help with heat dissipation.

Can anyone comment on the likely reliability of this arrangement and how, if one were manufacturing this fitting, if LED selection and matching would be carried out?


texts:
I'm building a charger for a set of LiPo cells. My circuit needs to make sure they get fully charged to their maximum level of 4.35V. At the same time, the circuit should protect the cells from overcharge. The charging stops when the 4.35V level is reached.

Tolerances on components might cause a tiny overcharge, for example 10mV. Can this be harmful for the battery?

From what overvoltage does the battery get damaged?


texts: I know that aircraft sometimes employ a 400Hz AC system to save weight on transformers, so I'd imagine that spacecraft might employ a similar technique. I'm wondering if anyone in the aerospace field can confirm 400Hz or higher frequency operation in space.


texts: Why doesn't the RMS current and voltage give me average power?

texts:
Apologies for the multiple bridge rectifier questions.

I have a 230V/9V 10VA transformer, and I want to know how much DC current I can draw from this circuit. From this I assume that the \$I_{rms\_max} = 1.1A \$.

I ran the simulation for various values of C1 and R1, and this seems to give the greatest possible DC current (I think).

Because this was going to be fed to a boost converter, I allowed 2V ripple.

The following values were obtained from LTspice:

\$V1_{rms} = 9V\$
\$I_{V1(rms)} = 0.96A\$ <- Less than 1.1A
\$V_{out(rms)} = 10.15V\$
\$I_{R1(rms)} = 0.40A\$

This gives me:

$$
 \eta = \frac{P_{out}}{P_{in}} = \frac{10.15*0.4}{9*0.96} = 47\%
$$

However, this is the power graph:

The average values of the graphs give me 4.9W and 4.13W, which gives me an efficiency of 84%.

Which value is correct?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm using the A9 module from Ai-Thinker in a logger project. It has 2 ADC pins and I need to measure 2 analog inputs (not at the same time) from my 2 sensors. Right now I'm prototyping with an Arduino Uno and an A6 module. I'm using the Arduino AREF pin to get accurate measurments from my sensor.

If I would move on to the A9 module then if and how could I use one of those ADCs as an AREF? For the sensors I would use just one of those ADCs and a multiplexer.

If anyone could suggest an even simpler way of doing what I need then I would be grateful.

I added a circuit, I did the best I could, don't hate, I'm not an electrical engineer.


texts:
I'm looking into improving an existing battery driven design with a PMIC chip. The device runs from a single LiPo cell, sleeps most of the time and wakes up every 20 minutes or so to update an ePaper display with data loaded over WiFi. It's based on the ESP32 chip since the ESP32 is easy to programm and has the WiFi module built in. The battery is charged over the USB port.

Currently the device has separate chips and circuitry for charging the battery, measuring battery voltage (through a voltage divider) and uses an LDO to get to the 3.3V voltage to drive the ESP32.
I checked the available TI chips but I'm a bit overwhelmed by the options. Can somebody recommend an efficient PMIC chip which ideally integrates charging logic, battery voltage monitor over I2C and LDO or Buck/Boost converter? The ESP32 has peak currents of 500mA. Is it better to use a chip with LDO or with Buck/Boost converter? Would you recommend separate chips for these purposes over an integrated PMIC chip?


texts:
I am using an LT1716 comparator in the inverting mode. So, I am simulating it in LTSpice. I understand that the Vout is Vcc when Vin,at the inv terminal is less than Vref at the non inv terminal and vice versa.

But in my simulation its not so. I am attaching the screenshots with this post.
For eg / the Vref is 4V, Vin is 1V. The Vcc to the comp is 7V and the Vss is ground.

But in this case, ideally I should be getting Vout of about 900mV.
Or do I need the whole hysterisis compensation resistors to make it work _


texts: So, I'm remembering that back in school, I managed to make a 555 signal create a tone signal, and that another 555 could trigger the 555, such that I had a variable toned signal that could be pulsed. IE, I could change the frequency, and pulse the frequency. IE, I could have 3 pulse per second of a 1Kz tone. I've been trying to figure out how to do this circuit today, and have been having problems with one small portion of it. I can create the tone, create the pulses, but I can't seem to make the pulses trigger the higher frequency signal, I can't figure out how to trigger it. What am I missing?


texts: Why negative feedback (common source degeneration) increases linearity range?

texts:
From this online lecture (page 190-20), I see that the negative feedback (Rs in common source degeneration) helps increases linearity range.

I am wondering if anybody know an explanation for this intuitively or mathematically.

Another question is what is the difference between the left and right hand pictures in the image below?
For small signal, they are exactly the same.

Thank you.


texts: How do I tell Modelsim to not create a wlf file when I carry out simulation?

texts:
The wlf file contains the wave dump data. For some reason I get this message on my computer:

#           File in use by: leader  Hostname: DESKTOP-LEADER7  ProcessID: 14602
#
#           Attempting to use alternate WLF file "./wlftnzmqtm".
# ** Warning: (vsim-WLF-5001) Could not open WLF file: vsim.wlf
#
#           Using alternate file: ./wlftnzmqtm

Why it can't open the file I do not know. Basically I have commands to compile all files and then invoke vsim. I just invoke these .do files and soon I start seeing this error. I just want Modelsim to stop creating wlf files as I do not need them and because of this error, Modelsim ends up creating a lot of wlf files.


texts:
In the schematic below, I would like to know the best way to dissipate the FreeWheel Current in the very shortest time possible.

simulate this circuit – Schematic created using CircuitLab


texts: STM32F7 Discovery Board STemWin examples

texts:
I've tried compiling the included ticker example with the STemWin_HelloWorld project included in STM32CubeF7. Functionally, it works OK but the draws seem to be corrupted.

Take a look at the video I've uploaded onto YouTube:

I suspect it as something to do with the configuration of the memory but I cannot be sure. This was compiled using SW4STM32.


texts:
The circuit has 12V SMPS & 3.3V LDO supplies.
Does connecting the Schottky diode SD2 to 24V supply is advisable?
If so, is there any advantage over connecting to 3.3V supply?

The Zener diode ZD is added as an extra protection.
Is this required just in case of a worst scenario?

Edit: Typo Error: 24v. There is only 12v & 3.3v supplies. The left side of Optocoupler is connected to AC Neutral. The 12v & 3.3v supplies are to be considered as labels. Should I connect the SD2 to 12v or 3.3v. The 3.3v is from a LDO connected to 12v.(which is not shown here)

If there is any serious mistake, can someone pls help with a better schematic?


texts: Voltage Regulation: Cascading vs. Individual

texts:
Consider my design:

Input power is either 8.4V (VBAT) or 15V (Wall Wart).

From there I need several voltages to power all the components on that board. Here is a list of voltages:
5, 3.3, 2.5, 1.85, 1.8, 1.5, 1.25, 1.2, 1.0 and 0.75.

Without going into the merits of what is required for each one of those voltages (current, noise, and etc), is there an intrinsic advantage in cascading switchers versus tying them all to one front end switcher (in this case a 5V output)? I'm mainly talking about overall efficiency, but I'm interested on other considerations.


texts: Understanding Source Peaks with Half-Wave Rectifier with Capacitive Filter

texts:
We started going over simple rectifier circuits in my electronics lab yesterday. When I implemented this circuit I was a bit confused by the source signal on the oscilloscope:

and the readout:

I believe the stunted peak of the wave has to do with the the source crossing the forward voltage of the diode and the capacitor starts charging and in this process, sinking the current from the source, essentially shorting it, never allowing the source to reach its peak.

That's probably wrong but it's the only thing that makes sense to me at the moment.

We used a 47 microFarad electrolytic cap and a 1k ohm resistor.


texts: Trouble understanding an amplifier and filter circuit

texts:
First time poster and a beginner at electronics, please tell me if any formatting is wrong.
I implemented this amplifier and filter circuit and connected it with a function generator as input to see if it worked. It did, but I do not understand it's behaviour. At about 70k frequency, input 272mV gives me 1.56V as output. But the gain starts to be less than 1 when I put anything above 1V as input. For example, 4.8V gives me 280mV as output. All this was observed on an oscilloscope. Would anyone please  explain how that happens?


texts:
I've a PCB with quite some electronics including a few motor drivers (30V, 100kHz PWM), and a few brushed DC motors 1 meter further away. These motors each have a quadrature encoder, so next to their 2 motor leads, they also require wiring for a 5V supply and have 2 channel outputs (wrt the ground of the 5V supply).

Without going in details why, I cannot use one long bundle of cables to directly connect the PCB to the motor.
Instead I need to use a long, small PCB in between to interconnect the main PCB and the motor.

      _________
              |
        main  |         _________________________          _________
        PCB   |_________|   long, small PCB     |__________| motor |
              |  wires  |_______________________|   wires  |_______|
              |
      ________|

Normally I would twist the motor leads, but how to implement wire twisting on a PCB?


texts:
I have a Yamaha DTX Multi-12 drum pad. It's great, but its fatal design flaw is it doesn't support samples over ~5 sec/ ~100 KB. I would love to be able to import pop-song-length CD-quality samples (+5 min. @ 192 Kbps).

I don't really know where to start with this. My first guess: Find a compatible 16GB+ SSD 2.5" hard drive, attach it to the motherboard, then tweak the software so it can recognize and accept importing larger file sizes/longer sample lengths. How you actually do all that is beyond me.

Anyone have any insight into a fairly advanced project like this? Thanks!


texts:
I have a NAND logic gate, the top 6 pins appear to be working fine (4x Input, 2x Output) However the bottom 6 pins on the IC appear not to work.

I was testing the IC via an LED, connecting two high currents to the input and then the output to the LED, it works fine for the top half and not for the bottom.

In relation to the pin map above, I have tried pins KCD, LFE, placing a high current into pins C & D expecting a high input from K and also E & F expecting a high input from L.

Is the IC damaged or am I missing something?

The IC is a Texas Instruments CD4011B

Data Sheet: http://www.ti.com/lit/ds/symlink/cd4011b.pdf

Jacob.


texts:
I have a basic quesiton about circuit theory in general.
Consider the following circuit:

I understand that the resistor will have a constant voltage of 1V across it as it takes the DC component of the input voltage source. The capacitor will take the AC part of the input voltage source (the 0.5V peak-peak signal).

There's my first question: How can there be 1V across the resistor and 0.5V peak-to-peak across the capacitor when both devices are in parallel? Don't they have the same voltage across them?

The second question is when the capacitor current goes negative, it's supplying current to somewhere -> where does it supply current to if top node is at same voltage?

I feel like I'm missing some basic rule here?


texts:
Can a low-cost, low-resolution RDAC and a precision voltage reference by used to make a coarsely adjustable high-precision DC voltage reference? Consider for example the AD5121 7-bit RDAC with ±5ppm/°C drift and 8% resistor accuracy driven by the ADR4525 reference with 1.25μVpp from 0.1 to 10Hz and 4pmm/°C drift. Assume that the output will be buffered with a zero-drift amplifier.

The initial resistor accuracy aside, will this circuit give me an adjustable voltage with DC performance nearly as good as the reference on its own? The reference will be used to periodically null the input of a 24-bit ADC for precision DC voltage measurements at the 5ppm level.

I ask this because only high resolution DACs and RDACs provide DC (1/f) noise specifications like the voltage references do. If the low-resolution DAC can really act as a resistor with 5ppm/°C TC then I would expect it to work fine.

On a related note, there are no SPICE models for these RDACs so do they really behave enough like a discrete resistor/pot to simulate as such?


texts: I am using Cadence software to design a CMOS circuit and I am using the GDPK180 library. Can I modify the length of the transistor to be different for the transistors or it should be the same for all?


texts: Tutorials on embedded programing using Zynq 7020 with ARM processor

texts:
Just as the question states. I have been having trouble being able to just test out the programming side of the ARM processor on the TE0720 board. I have been searching online for how to setup the board, and get into some SDK where I can program the thing, but everytime I try something, I run into errors (which I cannot find any fixes for).

I have all of the Xilinx tools/SDK's and Vivado downloaded, but I just need some sort of tutorial to help me get started working with these things. At this point I am just trying to run a simple "hello world" or blinking LED test code. Are there any tutorials that are specifically for what I am trying to do, or at least to bring the board to life?


texts: Calculating the gain in a differential amplifier

texts:
I have a specific question regarding this circuit:

I need to calculate the gain of this amplifier. However, when I do this, I get the value two times bigger than the simulation of this circuit, which I run in Multisim, suggests.

My line of thought is this:
The gain should be equal to R1/((re1+R2)+(R4||(R3+re2)), where re1 and re2 are the thermal resistances of the corresponding transistors.

Calculaing gives me the value of approximately 6.2, when the simulation suggests that the gain is 3.3. I have double-checked and the simulation circuit has no errors in it.

Thanks for your help!


texts: Question about logic gate optimization and CMOS implementations

texts:
I am struggling with a conceptual question surrounding logic gates and how they're efficiently implemented in CMOS circuits.

For example, let's say I want to implement a NAND gate. If I didn't know anything about CMOS, I could build it on paper at the level of logic gates with an AND gate followed by an inverter. However, it turns out that NAND gates are efficiently "directly" implemented in CMOS; there is no need for an individual AND gate or inverter.

Similarly, some compound gates (like a 2-1 AOI) are actually simpler and more efficient to implement "directly" in CMOS than with the individual gates (an AND and a NOR gate). If I understand correctly, using a "direct" AOI gate instead of the individual gates saves me an entire level of logic!

What other complex gates are more efficiently implemented "directly" in CMOS than with the individual gates? Suppose I build a rather complex yet optimized gate/chip using only basic gates as the building blocks. How do I know there isn't a more efficient way to implement that chip "directly" in CMOS in a single level of logic?

If it turns out that my big complex chip has a simpler "direct" implementation in CMOS than with the individual gates (maybe my chip is just a 2-2 AOI!), why design at the level of individual logic gates? How are large complex chip designs (designed at the logic gate level) implemented efficiently in CMOS?

Thanks!


texts:
I am working on a circuit that uses power from the wall outlet (50hz and 60hz) and I would to calculate the amount of power at different time between
(0 and pi).  The circuit has a power Factor of 1.

So, for example, if I wanted to know at what point between (0 and pi) the power would be say 10% of the total power, how would I calculate it?
Or, how would I know the level of the power at say pi/4 or pi/6?

Thanks very much for your time guys.


texts: Two flyback diodes in parallel for higher current?

texts:
I'm trying to use a water pump that says 12V and 1200mA. I read somewhere that I need to put a flyback diode to handle current when it turns off, but looking around I only have 1N4001 diodes, which can handle 1A max.

Can I put two of those in parallel so each one only have to handle 600mA? Or should I buy a bigger one?


texts: How to power an LED when a circuit isn't complete

texts:
I'm an electronics beginner trying to carry out a project similar to this one: http://www.techwillsaveus.com/shop/diy-kits/diy-thirsty-plant-kit/.

I'm having a difficult time understanding how it is that the LED is powered when the circuit is not complete (the sensor detects no water) and then turns off when the circuit is complete (sensor detects water/wet soil). Also, would it be possible to create something such as what I just mentioned but in addition to the LED turning off when water is detected another one turns on?


texts: Making a simple 4 bit adder into a 4 bit adder with carry in & out

texts:
I have coded a simple signed 4 bit adder. It doesn't have any carry in or carry out so it easily overflows.
Below you can see my code.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity four_bit_adder_simple is
        port(
                A, B : in std_logic_vector(3 downto 0);
                Sum : out std_logic_vector(3 downto 0));
end four_bit_adder_simple;

architecture signed_impl of four_bit_adder_simple is
begin
        sum <= std_logic_vector(signed(A) + signed(B));
end signed_impl;

Port mapping:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity four_bit_adder_tester is
    port(
            SW : in std_logic_vector(7 downto 0);
            LEDR : out std_logic_vector(3 downto 0));
end four_bit_adder_tester;

architecture tester_impl of four_bit_adder_tester is

begin

i1: entity work.four_bit_adder_simple(signed_impl)
    port map(
    A => SW(3 downto 0),
    B => SW(7 downto 4),
    Sum => LEDR(3 downto 0)
    );
end architecture;

How can I add a carry-in and a carry-out by using the resize function to change the bit size of the vectors before adding them together?


texts: How would I go about converting a change in capacitance into a voltage?

texts:
Just starting out with electronics here as a physics student- I appreciate the help!

In a simple LCR circuit with a variable capacitor, how would I go about detecting the change in capacitance and converting that change into a measurable voltage signal? What kind of circuit/ components will I need?


texts: MQ Gas sensors - can heater coil be run 24/7?

texts:
I am building a Hydrogen Sulphide gas detector for battery charging rooms using a MQ-136 sensor. I have searched everywhere for the answer to this question:-

Can the sensor be powered continuously? I saw a forum comment (in french) on stack exchange saying if the MQ sensors are left powered on they will burn out in less than a week. No-one seemed to challenge this statement.

I'm wanting to leave the sensor heater powered 24/7 so it can detect for gas as batteries are often left on charge over weekends and overnight. The system will disconnect the chargers if gas is detected from an overcharged or faulty battery. I could write code to take readings every hour with the sensor turned off in between but the sensor would not last long if it only has a lifespan of a week.

I'm thinking more that the forum post is wrong but I need confirmation from someone who has used the MQ series of sensors. There's nothing in the datasheet to suggest you can't power them continuously.

Can anyone offer any advice?


texts: Comparison of 180nm and 65nm CMOS technology in consideration of delay, power and energy consumption

texts:
how would each of them typically compare with respect to delay, power and energy consumption?
(Used in digital circuits)


texts: Determine output filter using the bode approximation

texts: Given that the carrier frequency Fc and modulation input frequency Fm are known, how would I use the bode approximation to determine an output filter, if the carrier frequency component must receive less than 35dB interference from the other frequencies?


texts:
I have a circuit breaker for my house as this one:

Each time we turn on 3 ACs , the breaker turns the current off and I have to lift the circuit breaker switch which is far down stairs in my basement. I need a mechanism to lift the lever automatically when electricity goes off. I can't change the circuit breaker, so I am thinking of a attaching motor,battery, and an arduino board to get my job done. Do you have any better ways to lift the switch ?


texts:
I have the basic knowledge about multivibrators, but I did not understand the working principles of the circuit schematic provided down below.

I have done the basic research about how it works, but I could not understand this particular BJT Astable Multivibrator circuit. Could someone please explain why 470 ohm and 10K ohm resistors are used and why the outputs of the circuit are not the emitter legs of the transistor but the collectors of the transistors.

And the most important question is : I put LEDs to the outputs. Does that changes the duty cycle of the Multivibrator (or frequency)?


texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to make a BCD to 7 segment decoder, but I can't make it work. I have a 7 segment with a common anode and I have connected a 1 kΩ resistor to each one of its segments.

I am using a 9V battery to power it.

How should I connect the DIP switch in the circuit?

Also, in the circuit, when I try to test my ICs (74LS32 and 74LS08), by connecting the ground to the inputs and  output to a LED light, but it's not working properly.
All of my 7408 ICs are only producing a high output when both inputs from switches are off, and when one or two are on, it will have a low output, while my 7432 ICs are acting like AND gate (only high output when both inputs are high).
I have tested the same ICs on a digital trainer and it was working fine, but when I try to put it in my circuit, it's back to not working properly.
What could have I possibly done wrong?


texts: Measuring pulses, options for accumulate samples after trigger

texts:
I have a circuit that amplifies pulses and the goal is to measure them with a MCU's ADC in lowest possible power. The pulses width are about 100uS and I am interested about their peak amplitude.

Now I added a HW trigger (comparator) and the plan is to wake-up the MCU, do some conversions, compute peak then sleep. Particularly, I plan to use SAM21L (Atmel) which have some 5uS wake time from a idle mode (not sleep). The speed is not so important, I'll be glad if I can take 10 samples, so 1 at 10uS.

The problem is that I don't know if MCU approach can be realistic, since most of them wakes up quite slowly so pulse can be missed or wrong measured. As can be seen in image, from trigger to peak I have only 40uS or so.

Now I wonder what options do I have?

use other smaller MCU only for ADC that can wake very fast
build a sample and hold circuit
build a precision rectifier (so sample and hold naturally)
try a HW tiny ADC but no idea how to catch the peak (so convert and accumulate stand alone)

I'd like some opinions, thank you.

EDITED:

The GREEN trace represents (amplified) signal + some induced noise in first stage. The last stage is a non inverting DC coupled OA, with (+) forced to 0.3V reference for maximal swing to 3V3.
The BLUE is my comparator reference, little above reference.
The LIGHT BLUE is my comparator output which I plan to use as trigger for MCU.

The tolerance for measuring is not so tight, I just want to measure the peak. Since the MCU will consume much more compared to amplifier, the trigger is supposed to wake-up, do some burst (blind) conversions up to 100uS, then store one result as peak found.

Overall, the peaks are non-repetitive (great idea to predict) but luckily, the normal periodicity is slow, one per minute or so (particle detector). However, in practice can appear multiple pulses in bursts and I need to count them, so I presume that pulses will come next to each other.

The S&H idea or rectifier, came up in case MCU isn't able to respond fast enough.


texts: Presence of 555 square wave generator breaks the rest of the circuit even when not connected.

texts:
I have a pretty bizarre problem with Multisim. I have a larger circuit which works perfectly when the inbuilt square wave generator for Multsim is used. I wish to replace the square wave generator with my own.

I have a 555 square generator circuit which works perfectly when I test it by itself, the moment I recreate that circuit in the main circuit and connect it to a 5V source the output of the main circuit just stops after a few milliseconds. This only occurs when the square wave generator is connected to a source without even connecting it to the rest of the circuit, when I remove the 5V source the circuit simulates for a few seconds and then just stops the only way to get the correct waveform is to completely[![enter image description here][1]][1] remove the 555 square wave circuit.

When I do connect the 555 timer I get an incorrect output for a few milliseconds and the circuit stops anyway. I have no idea why the presence of the timer breaks the rest of the circuit and I was hoping someone could enlighten me on this.

The circuit is supposed to count up until the green wave form reaches the red and then it resets and starts again.


texts: Unable to generate device simulation libraries from Quartus Prime

texts:
I am using Quartus 18.1. I am trying to generate device simulation libraries as per the procedure here:
https://www.intel.com/content/www/us/en/programmable/support/support-resources/knowledge-base/solutions/rd06182013_21.html
I also tried to use the GUI that comes with Quartus to do the same. However, I end up getting error every time.
Here is the output:
C:\My_Designs\Test\counter>quartus_sh --simlib_comp -tool questasim -family cycloneive -language vhdl -gen_only
Info: *******************************************************************
Info: Running Quartus Prime Shell
    Info: Version 18.1.0 Build 625 09/12/2018 SJ Standard Edition
    Info: Copyright (C) 2018  Intel Corporation. All rights reserved.
    Info: Your use of Intel Corporation's design tools, logic functions
    Info: and other software and tools, and its AMPP partner logic
    Info: functions, and any output files from any of the foregoing
    Info: (including device programming or simulation files), and any
    Info: associated documentation or information are expressly subject
    Info: to the terms and conditions of the Intel Program License
    Info: Subscription Agreement, the Intel Quartus Prime License Agreement,
    Info: the Intel FPGA IP License Agreement, or other applicable license
    Info: agreement, including, without limitation, that your use is for
    Info: the sole purpose of programming logic devices manufactured by
    Info: Intel and sold by Intel or its authorized distributors.  Please
    Info: refer to the applicable agreement for further details.
    Info: Processing started: Fri Jan 01 23:54:43 2021
Info: Command: quartus_sh --simlib_comp -tool questasim -family cycloneive -language vhdl -gen_only
Info: Quartus(args): -tool questasim -family cycloneive -language vhdl -gen_only
------------------------------------------------
invalid command name "cmdline::getFunctionOptions"
    while executing
"unknown_original cmdline::getFunctionOptions ::quartus(args) {{family.arg #_default_# {The name of the Quartus Prime device family, without any spaces..."
    ("eval" body line 1)
    invoked from within
"eval unknown_original $cmd $args"
    (procedure "::unknown" line 7)
    invoked from within
"cmdline::getFunctionOptions ::quartus(args) $function_opts"
    invoked from within
"array set optshash [cmdline::getFunctionOptions ::quartus(args) $function_opts]"
    (file "c:/intelfpga/18.1/quartus/common/tcl/internal/simlib_comp.tcl" line 1446)
------------------------------------------------
Error (23031): Evaluation of Tcl script c:/intelfpga/18.1/quartus/common/tcl/internal/simlib_comp.tcl unsuccessful
Error: Quartus Prime Shell was unsuccessful. 1 error, 0 warnings
    Error: Peak virtual memory: 4717 megabytes
    Error: Processing ended: Fri Jan 01 23:54:43 2021
    Error: Elapsed time: 00:00:00
    Error: Total CPU time (on all processors): 00:00:01

I do not understand why this is happening at all. I would be grateful if anyone can shed some light on this.


texts: Can I use the wrong end of a voltage regulator?

texts:
Let's say I wanted to power two circuits: a 12V circuit and a 3V circuit.  Could I use a 15V power supply and a 12V voltage regulator with three pins: Input, Output, and Ground.  Input to Ground would be 15V, Output to Ground would be 12V, and presumably Input to Output would be 3V.  Can I use the Input to Output voltage difference to drive a circuit?

EDIT:
It sames the answerers agree that this would not be advisable.  I'm trying to think of a good alternative.  I could use a 12V power supply to power the 12V circuit and in parallel power a 3V LDO.  However, that seems like it would waste a lot of power.  Am I forced to using two separate power supplies?


texts:
Why is AC current inversely proportional to voltage?

I think that current should be proportional to voltage, because according to \$V=IR\$, when \$R\$ is fixed, the bigger \$I\$ is, the bigger \$V\$ should be. But according to this simulation, the relationship between \$I\$ and  \$V\$ is negative. Is the software the problem? I use Virtuoso Cadence to simulate the circuit.

I have another question. The direction of the arrow should be the direction of the current. Why is the first half wave negative?

Is the meter "flipped around" in 1 (below)? Or, should I modify something in 2? I had tried simulating 1, but it didn’t change the relation between the voltage and current.


texts:
Working with the STM32H753ZI I am following the sequence of setting the "VOS" into Vcore boost mode or "VOS0" to achieve the highest clock speed as possible.
In the reference manual a sequence is to be followed in order to get there.

As requested, I have followed all the procedure to get to "VOS0", however I am stuck at step 4. "Wait for VOSRDY" to be set. This bit never sets for me. I have tried everything. Re arranging orders. Any ideas?
Code:
void init_Clock() {

    //Obtaining 480 MHz
    //DIVM1: 4
    //DIVN1: 60
    //DIVP1: 2
    //D1CPRE: 1

    // FLASH_ACR
    // MASKING: FLASH_ACR
    FLASH -> ACR &= ~FLASH_ACR_LATENCY;
    FLASH -> ACR &= ~FLASH_ACR_WRHIGHFREQ;
    // WRITING: FLASH_ACR
    FLASH -> ACR |= FLASH_ACR_LATENCY_4WS;
    FLASH -> ACR |= FLASH_ACR_WRHIGHFREQ_2;
    // CHECKING:
    if (((FLASH -> ACR) & (FLASH_ACR_LATENCY_4WS)) == FLASH_ACR_LATENCY_4WS){

    } else{
            //NO
    }

    // PWR_D3CR
    // MASKING:
    // PWR -> D3CR &= ~PWR_D3CR_VOS;
    // WRITING:
       PWR -> D3CR |=  PWR_D3CR_VOS1;

    // RCC_APB4ENR
    // MASKING:
       RCC -> APB4ENR &= ~RCC_APB4ENR_SYSCFGEN;
    // WRITING:
       RCC -> APB4ENR |= RCC_APB4ENR_SYSCFGEN;

    // SYSCFG_PWRCR
    // MASKING:
       SYSCFG -> PWRCR &= ~SYSCFG_PWRCR_ODEN;
    // WRITING:
       SYSCFG -> PWRCR |= SYSCFG_PWRCR_ODEN;

    // PWR_D3CR
    // WAITING:
       while (((PWR -> D3CR) & (PWR_D3CR_VOSRDY)) == 0){};

    // RCC_CFGR
    // MASKING:
    RCC -> CFGR &= ~RCC_CFGR_SW;
    // WRITING:
    RCC -> CFGR |= RCC_CFGR_SW_PLL1;

    // RCC_PLL1DIVR
    // MASKING:
    RCC -> PLL1DIVR &= ~RCC_PLL1DIVR_P1;
    RCC -> PLL1DIVR &= ~RCC_PLL1DIVR_N1;
    // WRITING:
    RCC -> PLL1DIVR |= RCC_PLL1DIVR_P1_2;
    RCC -> PLL1DIVR |= RCC_PLL1DIVR_N1_60;

    // RCC_PLLCKSELR
    // MASKING:
    RCC -> PLLCKSELR &= ~RCC_PLLCKSELR_DIVM1;
    RCC -> PLLCKSELR &= ~RCC_PLLCKSELR_PLLSRC;
    // WRITING:
    RCC -> PLLCKSELR |= RCC_PLLCKSELR_DIVM1_4;
    RCC -> PLLCKSELR |= RCC_PLLCKSELR_PLLSRC_HSI;

    // RCC_D1CFGR
    // MASKING:
    RCC -> D1CFGR &= ~RCC_D1CFGR_D1CPRE;
    RCC -> D1CFGR &= ~RCC_D1CFGR_HPRE;
    RCC -> D1CFGR &= ~RCC_D1CFGR_D1PPRE;
    // Writing:
    RCC -> D1CFGR |= RCC_D1CFGR_D1CPRE_DIV1;
    RCC -> D1CFGR |= RCC_D1CFGR_HPRE_DIV2;
    RCC -> D1CFGR |= RCC_D1CFGR_D1PPRE_2;

    // RCC_D2CFGR
    // MASKING:
    RCC -> D2CFGR &= ~RCC_D2CFGR_D2PPRE1;
    RCC -> D2CFGR &= ~RCC_D2CFGR_D2PPRE2;
    // WRITING:
    RCC -> D2CFGR |= RCC_D2CFGR_D2PPRE1_DIV2;
    RCC -> D2CFGR |= RCC_D2CFGR_D2PPRE2_DIV2;

    // RCC_D3CFGR
    // MASKING:
    RCC -> D3CFGR &= ~RCC_D3CFGR_D3PPRE;
    // WRITING:
    RCC -> D3CFGR |= RCC_D3CFGR_D3PPRE_DIV2;

    // RCC_PLLCFGR
    // MASKING:
    RCC -> PLLCFGR &= ~RCC_PLLCFGR_PLL1RGE;
    RCC -> PLLCFGR &= ~RCC_PLLCFGR_PLL1VCOSEL;
    // WRITING:
    RCC -> PLLCFGR |= RCC_PLLCFGR_PLL1RGE_8_16;
    RCC -> PLLCFGR |= RCC_PLLCFGR_Wide_VCO_Range;
    RCC -> PLLCFGR |= RCC_PLLCFGR_DIVP1EN;

    // RCC_CR
    // MASKING:
    RCC -> CR &= ~RCC_CR_PLLON;
    // WRITING:
    RCC -> CR |= RCC_CR_PLLON;
    // WAITING:
    while ((RCC -> CR && RCC_CR_PLL1RDY) == 0){};
}

UPDATE: Got it working
As Brhans answer was setting the LDOEN bit first before touching the VOS bit.


texts: Short circuit parallel to current source

texts:
So, I have to find the initial conditions for the following circuit with a switch. For \$t<0\$, the switch is closed, so we draw the inductor as a short circuit and the conductor as an open circuit. I have to find the voltage drop across the conductor, which would be equal to the voltage drop across the \$R_2\$ rezistor, as well as the current through the inductor.

Here comes the problem, since the current source \$J_2\$ is short circuited, how would I go about solving this? From what I know, the source wouldn't be eliminated and the current flowing through the short circuit would be equal to the source, \$i_L(0-) = 4 A\$. However, I'm not sure how I could go about finding the current flowing through the \$R_2\$ rezistor, as the current source parallel to the short circuit is confusing me.

Any input would be much appreciated. Thanks in advance!


texts: what happens with diode voltage drop when connected directly to constant voltage supply?

texts:
The diodes usually have voltage drop of about 0.7V or so, which is said to be constant for some type of diode (ie. not depending on voltage/current).

So what would happen if one connected a diode directly across the power source (for example, over the 1.5V battery), oriented so it conducts?

On the one hand, one would expect to measure 0.7V across diode, as it is its voltage drop. On the other hands, that same points are also directly across power source, so one would expect to measure 1.5V of the power source. And due to KVL (and no other elements in the circuit), they cannot differ but must be the same.

I'm primarily interested what would happen in real world and why (although I'd appreciate ideal diode theory and/or simulations in addition to it).

What would voltmeter across diode read (in the short time before diode self-destructed due to excessive heat)? And where would be missing 0.8V (1.5V-0.7V) actually be (it must be somewhere according to KVL)?


texts:
Can you please explain this function whether it is odd or even step by step:

\$x(t) = cos(t) + sin(t) cos^2(t)\$


texts: Could I create Peltier cooling module from iron and copper?

texts:
I want to create a tiny, easy to maintain one-purpose distilation unit. It's supposed to distilate expensive tetrachlorethylene to clean it from whatever is dissolved in it.

There are millions of ways to heat something up - you can burn it by candle, heat by short circuit or keep it in sunlight (at least now in summer). But till today, I have known only one way to cool something down - the one that is used in the fridges.

I was googling and thinking though, and I've learned about Peltier effect. If effective, this would be the most awesome solution, providing both heat and cooling.

In serious business though, Peltier coolers are made of semiconductors and I can't afford one. Also, their shape doesn't really suit my needs.

So I was thinking of creating many connections like the one you see above. Would it work? Would it work well?


texts: How to find the positive wire on wall charger

texts:
i have a TPLINK wall charger from my old router. It's almost new and i would like to use it for my 5V regulator project. The prboem is that i dont know which of the 2 wires is positive and which negative. If i connect it wrong the 3 polorized caps on the circuit will blow up.

Charger specs:

Model: T090085-2C1
Input: 100-240V~
Out: 9VDC .85 Amps

I know tha using a LM7805 with this adaptor is not very efficient but i'm doing it for the science :)


texts: Im confused about signals. I can absorb time domain but not frequency domain. How does one converts a time domain signal into frequency domain signal by just looking and analyze(without using math like fourier).thanks


texts: How to drive 1MHz Ultrasonic Transducers

texts:
I have 2 ultrasonic transducers (see below picture)  facing each other with spacing of 10cm (adjustable). I would like to supply 1 MHz sine wave (from function generator) to one transducer (transmitter) and measure signal amplitude on the receiving transducer (using an oscilloscope).

Can someone please advise the circuitry needed to achieve the above test ?

The transducers are rated for 3Vp-p, not sure about the current they consume.

Below is the transducer specification that was provided by the Manufacturer.


texts: Does direct GPIO communication between 2 microcontrollers requires pull up/down

texts:
If I want to use GPIO pins of two microcontrolles as a mean of simple communication (e.g. reporting an event by sending 1 or 0), Do I need to enable internal pull up or pull down resistors on any of the MCUs?

I Want to put 2xSTM32 on the same board and need a way to signal the other chip that something has happened. I want to do this using a single GPIO pin on each device (hence no I2C/SPI/etc.)

Can you please tell me how what configuration should I do to the GPIO on each side? e.g.

SENDER:
GPIO Mode = output push-pull OR output open drain?
Pull Up/Down = Pull up or pull down or NONE?

RECEIVED:
GPIO Mode = input mode
Pull Up/Down = Pull up or pull down or NONE?

I mean what is the difference between push-pull and open drain and what will enabling pull up or pull down resistors do anyways?


texts: What is the steepest roll-off achievable for an analogue low-pass constructed with a single op-amp?

texts: I was wondering about this question. What if the only design requirement is having the highest steepness of the roll-off but using only one op-amp? I know it's possible to construct approximations of second order low-pass filters with one but what about higher orders?


texts:
I have 5 or 6 individual Proteus files that have been made to create individual subsystems of a bluetooth speaker. I'm now looking at unifying these onto a single motherboard. Unfortunately, copying and pasting doesn't capture sub-circuits so it would be a pain to copy and paste the contents of each file individually.

Is there any way that I can add a proteus file as a subcircuit/child-sheet on a new project?


texts: Why can phasors be used simplify getting instantaneous power from instantaneous curent and voltage?

texts:
If instantanoeus power is p(t) and instantaneous voltage and current saying for a resistor are v(t) and i(t), then p(t)=i(t)*v(t). But if you convert v(t) and i(t) to their respective phasors and multiply them, the product is NOT the phasor of p(t).

For example, for R=3 Ohms,$$v(t)=6*cos(120\pi+30^{\circ})$$ and $$i(t)=2*cos(120\pi+30^{\circ})$$. Therefore, $$p(t)=12*cos^2(120\pi+30^{\circ})$$, or $$p(t)=6(1+cos(240\pi+60^{\circ}))$$.

The problem is if I try to multiply $$V=6\angle{30^{\circ}}$$, which is the phasor of v(t), by $$I=2\angle{30^{\circ}}$$, the phasor of i(t). The resulting product $$P=12\angle{60^{\circ}}$$ is  equivalent to $$p_1(t)=12cos(120\pi+60^{\circ})$$.

p1(t) is not equal to p(t). What did I do wrong?


texts: What causes these artifacts in my electrophysiology recording? Large power spikes at many frequencies

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I'm a biologist who does a fair amount of computational work, but has little electrical engineering experience, so please excuse my ignorance.
I'm recording electromyography (EMG) signals from muscles in moving rats for an experiment. The electric signal at the muscle is picked up by silver wires (which are insulated but not perfectly so). The signal is passed through a cable to an amplifier (which low-pass filters <1000 Hz I believe), and then to a digitizer and computer to be recorded at a sampling rate of 512 Hz. The Fourier transform of a 10-second segment of signal looks like this. As you can see, the signal has relatively even power at all frequencies.
 However, there will occasionally be a great amount of noise in the signal. In the Fourier transform, you see large spikes of power at many frequencies: 50 Hz, 100 Hz, 150 Hz, 200 Hz, 250 Hz, but also smaller spikes at other frequencies.
And here is the same noisy signal, zoomed in on the Y-axis:

I figure that the multiples of 50 Hz must have something to do with the utility frequency (I'm in Europe), and maybe the other frequencies are due to interference of overtones or something. But I don't understand why the artifact comes and goes. Most animals have no problem at all, in some animals it appears and disappears, while in others it's present almost all the time. Browsing StackExchange, I've read something about voltage resonance, but I don't really understand it well or know if it's relevant.
Any ideas about the source of this problem? And about how I can prevent it?


texts: How to access parameter values in transient simulation and/or NGSPICE interactive interpreter

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I want to make the time-step and stopping-time in a trasient simulation scale automatically by using the parameter values (.PARAM lines) in the netlist. Here is a minimal ngspice etlist to demonstrate my use case.

How to access parameter values in transient simulation and interactive interpreter

.PARAM R = 1kOhm
.PARAM C = 1nF
.PARAM pi = 3.14159265359
.PARAM fb = {1/(2*pi*R*C)}  ; Q1. Why does pi need to be defined above?
.PARAM amplitude = 5V
.PARAM pointsPerCyle = 20
.PARAM numCycles = 1.5

VDD 1 0     SIN(0V {amplitude} {fb})
R1  1 2     {R}
C1  2 0     {C}

.TRAN {1/159kHz/20}         {1.5/159kHz}
* .TRAN {1/{fb}/{pointsPerCyle}}        {numCycles/fb}  ; Q2. How to access the parameter values defined above in tran sim?
.PLOT TRAN V(1) V(2)

.CONTROL
    run
    plot V(1) V(2)
    * plot {V(1)/{amplitude}} {V(2)/{amplitude}}    Q3. How to access the parameter values defined above in interactive interpreter and/or ngspice scripts?
    * print $fb
    * echo $R

.ENDC

.end

The netlist will run as is, producing a transient simulation plot. The commented lines are where the errors occur. So I have 3 questions here.

Why do I need to define pi in order to calculate some parameters? If it is already defined, I cannot access it at this point in the netlist (.PARAM lines)? Why?
How do I access the .PARAM values to define the time-step and stop-tim in a trasient simulation?
How do I access the .PARAM values in interactive interpreter and/or ngspice scripts?

Thank you!


texts: Why is a non-rechargeable cell a "primary" cell, and a rechargeable cell "secondary"

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I was relating the Digi-Key Trivia Thursday question to my friend today and he was confused why a rechargeable cell is "secondary", and all I could reply with is "it just is".  The Wikipedia article for rechargeable batteries only mentions:

  It is technically known as a secondary cell because its electrochemical reactions are electrically reversible.

That connection still seems totally arbitrary; I can't find anything about "secondary electrochemical reactions" or "secondary redox". What is the connection?


texts: Amplifying Small Signal With Solid State Relay

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I am trying to control an electromagnet with a signal from a small microcontroller (a BeagleBone Black). Obviously, I need to amplify the signal. I have a lead from a power source that I want to pass through to something when the pin on my board goes High (3.3v). I think that a relay is what I want here (correct me if I'm wrong), but have no idea how to find one that will do what I need. The separate power supply will range anywhere from 5 Volts 0.5 Amps to possibly 20 Volts 3 Amps. Because of the circumstances where I'll be using these relays, I would rather use solid-state relays so that there aren't more magnets than there needs to be in the vicinity.

Are relays what I'm looking for? If so, are relays that fit these specs available, and what exactly am I looking for?

EDIT: To add some more detail, it will be High for approximately 50-100 ms. For most of the time, the separate supply will be at 20 Volts 3 Amps, but I will be testing my stuff with it, so I may try it at higher or lower values.


texts: Does anyone know what these marine radio pot/switches are or what they do?

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I enjoy re-purposing misc items and components to make neat gadgets etc. I have salvaged these two "switches" from an old marine radio. The rods on each click in and click out and rotate in both clicked-in position and clicked-out position. The only writing on them is "503B 33 3F" on one. And "800503B 33 3F" on the other.

I know most people talk about looking up data sheets for things like these, but I am unable to find a data sheet for them. Any description of their function or a link to a data sheet would be greatly appreciated. Thanks!


texts: Arbitrary Function Generator or DAC with memory IC help

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I am trying to look for a hardware solution to my current problem. Currently I am using an AFG preprogrammed with a signal (example below, 8bit resolution is OK, using 30 or more data points each 1us in duration). I would like to replace this AFG with an IC that I can program through SPI or similar. Then when I want a signal trigger it with TTL or equivalent.

I have found a few IC's that are similar to what I want, specifically a SPI DAC, with memory for one data point MCP4725.

Also I have found a few sweep programmable square and sine wave systems but not anything that can satisfy my needs.

I understand there may not be a solution, but I am hoping that it is just that I am using the wrong search terms.

Terms used;

"DAC with memory and frequency"
"IC AFG"
'IC arbitrary function generator'


texts: Does a very small via reduce the drawbacks of a non-filled via-in-pad?

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I have been doing a lot of vias in pads on my 2 layer prototypes (which I hand-solder) because I save a lot of space and the end result looks very compact and neat.

However, I have been researching on vias in pads for production, and it seems that unless I am willing to pay the extra cost to have them filled and plated over, they will give me only headaches.

So, my question is: is there any low-cost compromise between avoiding vias in pads all together and having filled vias in pads? I was thinking about using 0.3mm vias (I have low currents) to reduce the amount of solder they suck in.

Also, I tend to place double vias in pads. That is, most of the time my vias in pads have pads on both side. For example two capacitors in parallel on each side of the board.

So, even with small vias. Would I still have problems of solder on one side overflowing the other side and making a mess of my board?

I have not the means to test this cheaply my-self, so I was hoping some of you could give me some insight and tell me about your experience. Note that for these boards I am not working with BGA components. Only SMD components in the range of 0805, 0605 and QFNs.


texts: What is the difference between flux and flux-linkage? how to calculate inductance of transmission lines?

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in calculating inductance of a single current carrying conductor how flux linkage is calculated?why flux is multiplied by a factor (X^2)/(r^2) to get flux linkage.
see the following images: