texts: Controlling 24-bit parallel RGB LCD with 16 bits

texts:
I'd like to run a 24-bit parallel RGB LCD with 16 bits using the LTDC controller of a STM32F469ZGT6.  The screen won't be displaying video or anything too intense, but there will be some anti-aliased fonts and images.  I thought of a few possibilities in how to configure the hardware:

Connect the LCD's LSbs (R0-R2, G0-G1, B0-B2) to GND
Connect the LSbs to the MSb of each color (R7 --> R0-R2, etc.)
Connect the LSbs to the MSbs (R7 --> R2, R6 --> R1, R5 --> R0, etc.)

Option 1 is out because full white could not be achieved.  Option 2 induces a higher overall error than option 3, the latter of which was recommended by a TI rep in their e2e forum.  However, when asked about performance comparisons, they replied:

  Sorry, we do not have any performance comparison between the two methods.

Is there any evidence -- empirical or otherwise -- that option 3 is superior?  Or is there another, prefereable scheme?


texts: Using an AC relay for DC switching, safe limits

texts:
I have an relay that's rated for a 250VAC, 16A load.
Would it be possible to also use the same relay for say a 25VDC, and less than 1A load?

From here,
relay power ratings - AC vs DC
,
it seems to imply that that due to arcing,
an AC relay would be able to support switching DC as long as the DC voltage is about 1/10 of the AC rating.

Would this apply as a general rule even if DC values are not explicitly stated on the relay's spec sheet, as in, there won't be long-term damage from implementing relays in this manner?
The particular relay I'm using is "G5LE-1A-E" with a rated load of 250VAC @ 16A, from here: https://www.digikey.com/products/en?keywords=%09Z2619-ND


texts: Logic Buffers for CPLDs Outputs (and Inputs?)

texts:
Today, I tried to use a ULN2003a darlington array as a buffer for my CPLD's outputs. While it works well, I have a concern. The max. voltage where the Max V is guaranteed to read a low is 0.8V. The darlington array's low level output was 0.7V. I was expecting closer to 0V, but that was not the case.

Because I'm operating near the logic level threshold, I'm not sure if using this darlington array is a good idea. Instead, I'm looking at other dedicated logic level buffers. My current requirements aren't that high - I think about 50 mA to 100 mA per pin would suffice.

I did find a 16-bit tri-state buffer, but I the Enable inputs control 4 outputs at a time. I need a way to control every output. I essentially require a open collector/drain at every output.

With that said, I did the 74LVC1G125. The advantage of this IC is that its max. output voltage for a low is 0.8V. The min. output voltage for a high is 2V. The voltage at which the Max V is guaranteed to read a high is 1.7V. I think this make it a good match.

Now, I haven't really used such a IC before and even though it has two inputs, am I correct in guessing that I could use this just by using the Output Enable (OE)? I could have a pull up resistor at the output, and the A input can be grounded. When the OE is low, the IC tri-states and the resistor pulls up the voltage. When OE is high, the IC outputs A, which was a low. Am I correct in my understanding regarding this or am I missing something?

The downside is that it's just one per package. The other issue is the limiting current of 50mA. SInce this is a absolute rating, I better get too close to this. I would definitely like to have some more legroom for this.

Anyone have any ICs in mind for logic buffering?

Finally, is it wise to have buffers on both ends of a long wire? The length is approximately ~10m. The wire feeds a signal from the output of the CPLD to the input of another CPLD.

EDIT:
The loads are just long (~10m) wires. So, capacitive + resistive load? On the other end, the wires connect to another CPLD. Because the other end has digital inputs, I don't think the load is going to be significant. The frequency of operation is less than 1kHz.


texts: This is out of curiosity. I am working with rf 433 MHZ transmitter receiver module. I just wanted to ask whether it affects health in any way. I have read that such radiation has carcinogenitic effects. Does the power transmitted by the transmitter has any effect?


texts: Add IR (infrared) remote control to simple audio amp?

texts:
is it possible to add some kind of a remote control receiver to a basic audio amp board that only has a manual volume knob?
The IC chip in the amp board is a TDA7498. A general view of the board is in the imageamp board


texts:
My brother is a senior in High School. When he visited our college. I've took him to a robotics event (inter college robotics competition). He got to see various bots designed by college students and got mesmerised. Now he too wants to design bots like that.

I told him programming is necessary. He already knows little bit and I'm helping him in becoming proficient. But I've no clue regarding this field.

Can any one kindly suggest a path & tiny projects to improve his interest.


texts: Can I create a fake keyboard using an Atmega chip

texts: I have been wondering lately if I can make a "keyboard simulator". I have an Atmel Atmega chip and I know it can communicate by serial because they are used in Arduinos. Is it possible to write some code for the atmega then connect it to the pc using USB and make the PC think that the Atmega is a keyboard, I could then send it data/commands. Is this possible, if so how could I go about it?


texts: ADS Simulation: Schematic to find input impedace

texts:
I'm following a paper, using ADS, to find the input impedance of a shunt Schottky diode. The paper's schematic is Fig. 1, and my schematic is Fig. 2. The point is that, I could not get the same result as the paper reported. Here is their steps and my corresponding results:

Their method: Shorterning the Impedance Matching tool, varying Pin. It was said the rectifier operates optimally when the diode's peak reverse voltage, Vr_max reaches Bv(6.4V as in the model). So, they found Vr_max = 6.4V @ Pin = 12.320 dBm (Fig. 3).
My results: Vr_max = peak(Vd). With Pin in the range (-5,15), my Vr_max could not reach 6.4V. At Pin = 12.320 dBm, my Vr_max = 4.509V while Vout = 2.599V (Fig.4). Therefore Zin (input impedance) is totally different than the paper's findings. Could anyone tell me what I did wrong?


texts: Avoiding false optical rotary encoder readings

texts:
I have an optical shaft encoder that has rather big resolution - 2500 pulses per rotation. The problem is that false pulses get registered from environmental vibrations - if I shake it in my hand or slap a hand holding it with other hand - I get several pulses forth, then several back, then forth again - it looks like decaying sinusoide.

One way to deal with that is to count some amount of pulses that are in the same direction before registering "ok, the rotation has started".

Does anyone know some clever tricks to deal with this kind of problem in microcontroller code?


texts: Using a pair of 220v-110v transformers together

texts:
I have two transformers (220v to 110v) which has a nominal power of 300VA. I want more than that for a specific application. Can I use both together to supply more current like this (?):

Any chance of going wrong or anything that I should take care?


texts: Could a pic32 run for thousands of years?

texts: By estimates based on known parameters of IC aging, could a standard pic32, if it is kept running in a vacuum or inert gas filled chamber, run for thousands of years or would effects like electro migration, dopant redistribution and thermal stresses(Ones that occur even in the stable  temperature environment) break the chip long before then?


texts: What is the shape of an antennas output?

texts:
I've been told that EM beams are "gaussian" beams that spread nonlinearly, so the spot size grows faster and faster as you travel further away.

However, when you talk about an antenna, it is defined by a beamwidth expressed in degrees, which makes it seem like there is a constant growth of the spotsize.

So do antennas not output gaussian beams, or does the beamwidth express something different than I am thinking?


texts: Is it possible to extract code from an arduino board?

texts: Is there a way to export code for an arduino even as a hex file?


texts: How to calclate Rb value for NPN transistor?

texts:
Here is a part of my schematic.
K pin from LCD is connected to NPN transistor.
A pin is connected to Vcc, 5V.
Base is connected to uController. It is Atmega16. 5V supply.
I am using BC547 transistor as it is showed at the picture.
Electrical Characteristics form datasheet:
Vcbo= 50V
Vceo=45V
Vebo=6V
Ic=100mA
hfe=110 min
So the question is how can i  calculate resistance of Rb?
I found some calculators online and there's always Vi, explained as the input switching voltage or the input trigger voltage. I am not sure what it refers to.
Also do i need resisor on collector too?


texts:
I'm planning to drive multiple RGB LEDs using a TLC5940 with PWM. These LEDs have the following specs:

Voltage Red: 1.8V
Voltage Green: 3.0V
Voltage Blue: 3.3V
Current per color: 20mA
Common anode

Since the TLC5940 is a current sink, how would I make sure each led gets the correct voltage. Hook up a resistor between each cathode and the TLC5940?

Please forgive me for asking such a simple question, I'm still learning :).


texts: I am working on drive to control the speed of motor using software PID. the output of PID will generate the reference for drive to run at particular speed. Here Kp and Kd will come from drive it self. The problem I am facing is that drive is giving integral time(Ti) instead of integral gain(Ki. How do I do the integral part if I have integral time(Ti) but not the integral gain(Ki)?


texts: What is the minimum supply voltage for the MC34063E in step-up (boost) configuration?

texts:
I need help determining the minimum supply voltage specification for the MC34063E in step-up (boost) configuration. I can't tell for sure by reading this datasheet.

First, on page 1 they say:

  Features:

  ...
  Operating from 3 V to 40 V

Then, in page 7, table 8, under section "Electrical Characteristics - Total Device", which I copy below, they say that the device start-up voltage (\$V_{START-UP}\$) is 1.5V, which is the "minimum power supply voltage at which the internal oscillator begins to work."

I understand that the start-up voltage is not necessarily the supply voltage at which the device starts regulating properly. It's the voltage at which oscillation starts. But then, what's the relevance of this information? Why would I need to know that the device starts oscillating at 1.5V if it is only guaranteed to regulate voltage properly at inputs above 3V? If I apply the lowest possible input voltage (3V), that's already above the start-up voltage (1.5V) so it will get the oscillation started anyway.

I understand that this parameter (start-up voltage) is relevant for other devices (such as the MCP1640) in which the start-up voltage is higher than the minimum input voltage. That means we must apply the start-up voltage when the device is initially powered on and then its input voltage may be lowered.

The specs for the MCP1640 are:

  Low Start-up Voltage: 0.65V
  Operating Input Voltage: 0.35V

But that's not the case for the MC34063E. Its start-up voltage is lower than its stated minimum input voltage:

Start-up voltage: 1.5V
Operating from 3V

My interpretation is that minimum supply voltage for the MC34063E is really 1.5V and not 3V as stated. Is that correct?

My question is: What is the minimum input voltage for the MC34063E to operate within its specifications in the step-up (boost) configuration?

Another thing that is annoying me is that the 3V minimum supply voltage doesn't appear in any other part of the datasheet. It only appears on what I consider to be the "marketing" section of the sheet. Is that spec stated in any other "more technical" part of the datasheet, such as a table under Electrical Characteristics section and I'm not seeing it?


texts: What is "pull the collector below ground" and saturation

texts:
I can't come up with any suitable title. I am reading about transistor from a book
Here's the 4 properties of an NPN transistor (for PNP, it is reversed)

  The collector must be more positive
  than the emitter.
  The base-emitter and base-collector
  circuits  behave like  diodes (Fig.  2.2).
  Normally the base-emitter diode is con-
  ducting and the base-collector diode is re-
  verse-biased, i.e.,  the applied voltage is
  in the opposite  direction to easy current
  flow.
  Any given transistor  has  maximum
  values  of Ic,  IB, and VCE that cannot
  be exceeded without costing the exceeder
  the price of a new transistor  (for typical
  values, see Table 2.1). There are also other
  limits, such as power dissipation (revCE),
  temperature, VBE, etc., that you must keep
  in mind.
  When rules 1-3 are obeyed, Ic is rough-
  ly proportional to IB  and can be written as
  \$I_C = h_FEI_B = {\beta}I_B\$.
  Where \$h_{FE}\$, the current gain  (also called
  beta), is typically  about 100.  Both \$I_C\$
  and \$I_E\$ flow to the emitter.  Note:  The
  collector current is  not due to forward
  conduction of the  base-collector  diode; that diode is reverse-biased. Just think of
  it as "transistor action."

and then here is the picture

it say when the switch is close then

  When the switch is  closed, the base rises to 0.6  volt (base-emitter diode is in forward  conduction).  The drop across the base resistor is  9.4 volts, so the base current is 9.4mA. Blind application of rule 4 gives Ic  = 940mA (for  a  typical beta
  of 100).  That is  wrong.  Why?  Because rule 4 holds only if rule  1 is obeyed; at a collector current of lOOmA the lamp has 10 volts across it. To get a  higher current you would have to pull the collector below ground.  A transistor can't  do this, and the result  is what's  called saturation - the collector goes as close to ground as it can (typical saturation voltages are about 0.05- 0.2V, see Appendix G) and stays there.  In this case, the lamp goes on, with its rated 10 volts across it.

What I have understood from this explanation is that here the lamp act as resistor that make the voltage at collector terminal 0 while the voltage at base is 0.6V (because \$V_B=V_E+0.6\$ and \$V_E\$ here equal 0) so it doesn't obey rule 1 and then rule 4 doesn't hold. But the after explanation is unclear. Why the collector must have higher current and what does "pull the collector below ground" mean and then how can collector can have 0.5 or 0.2 voltage while the lamp used up all voltage. So what is the use of the transistor in this case?


texts: Arduino and voltage divider plus N-MOSFET

texts:
I'm trying to control the keyfob from arduino/esp32 with N-MOSFET by basically bypassing physical switch on the remote with an esp32 controlled MOSFET. It works, but I wanted to add a feature of reading key fob battery level too (so I can replace it on time) and this is where problems started :-)
When trying to share the ground with battery, the MOSFET switch stops working. When I connect those circuits separately everything works perfectly. Any chance to have both circuits working together?


texts: Rotating Platform That Starts and Stops Incrementally

texts:
I'm not sure this is the right place to pose this question, as it probably encompasses more than one field - EE, ME, programming, etc.  But I'll ask the question anyway and hope that someone might have at least a general starting place.

Basically I would like to build a circular platform.  On the platform will be four different objects.  I would like the platform to rotate exactly 90 degrees when triggered via a computer (or by hand for a lower tech option) and then stop automatically.

Ideally it would be nice for the entire system to be automatic, but this isn't entirely necessary.

I'm assuming I will need some kind of electrical motor and belt for the rotation...  beyond that I'm not sure how to go about implementing the automatic stop at 90 degrees.  If someone were to start it by hand, I suppose they could also stop it, but it is importnt that it stop at exactly 90 degrees...

Any suggestions or ideas would be appreciated!


texts:
I am using HT12E, for a rf transmitter circuit. As per the datasheet HT12E is a 2¹² encoder.

Ideally such an encoder must have 2¹² inputs and 12 outputs. In addition to that all the inputs should be 1 exclusively.

When i look at the IC, I see 12 inputs A0-A7 + AD8-AD11, which go into the transmission gate circuit of the IC.

Can someone help me understand this part of the working ?


texts:
I am laying out a 2-layer PCB that has only through hole components, and I need it to be as small as possible. I was wondering how small I can set the clearance rule between the components?

When I searched I found very dense PCBs that has components nearly very close to one another like this one:

Does any component spacing work as long as pad to pad clearance is nearly 1 mm for easy soldering?
EDIT:
Here is a screenshot of my PCB:

I am leaving very small distance between the fuse holder, pin header and the diode (aprox. 1 mm), is there any thing I need to consider?


texts: Powering and operating dual electric linear actuators

texts:
I am in the process of building a height-adjusting desk. I am pretty good with computers (I'm a programmer), but I never learned much in the way of electrical engineering.

I recently purchased two Eco-Worthy brand linear actuators. They each have an 18-inch stroke and a 320 lbs. static load bearing capability. They just have two wires, the positive and the negative wires. They are supposed to operated at 12 volts with a 1 amp minimum and 3 amp maximum.

I intend to operate them both at the same time in the same direction. So what I am unsure of is primarily the power source. My understanding is that I would still use a 12 volt power supply to power both at the same time.

But will I need it to have a 3 amp output or more than that? Will the amperage be reduced as it is divided among devices? Am I misunderstanding how this should work?

Also, if I get a momentary rocker switch will I wire both together and then to the switch? Should I get a relay to run this through? Any recommendations on how I hookup the A/C power to it? Since it won't have any plug inputs.

Here is a link to the info about the actuators I purchased. Any help in figuring out the electrical setup is welcome.


texts:
I bought a small HD camera for a quadrocopter. It is dedicated for the specific model and supports filming motion JPEG movies and shooting stills. (photos not mine)

The connector is custom and have 4 pins. From what little I know about electronics (unfortunately), I guess, that one or two pins are the power ones and the other two are the control ones for start/stop recording and photo shoot.

My question is: how can I determine, which pins are used for which purposes? I'd like to create my own interface, which would simulate connection from the quadrocopter, such that I'll be able to use the camera without the aircraft. I'm owner of the quadrocopter as well, so I can use it for testing.


texts:
It it possible to have a passive NFC tag and a 125kHz RFID tag back to back in the same holder and not have one interfere with each other, reading one at a time? E.g Detect 125khz RFID tag, read it, disable 125khz reader, read NFC tag and then disable NFC reader, re-enable the 125KHz reader.

If this is possible, can both readers be active, reading their corresponding tag simultaneously?

For what application this would be used I'm not sure. I'm simply curious about whether or not this is possible.


texts: Gizduino atmega644 + Universal keyboard and display terminal (e-term)

texts:
I have a clone of Arduino which is GizDuino ATMEGA644 and a Universal Keyboard and Display Terminal (e-term). With this images

I connected the terminal to the microcontroller, after connecting that I tried to upload a sample program under the "LiquidCrystal" category "Hello world". After successfully uploading the program there was no display on the LCD and I also tried checking it to the serial monitor but it don't have the output too. I'm confused in searching what is the problem, I checked the com port and the selected board but there was no problem. can someone help me?


texts: STM32 & ST-LINK - Cannot connect to MCU after successful programming

texts:
I have built my own board with STM32F7-45VGT6. I have successfully programmed it with ST-LINK v2 (not the original one though) and now I cannot even connect with MCU.

I use ST-Link Utility from ST and SWD interface. It can be the case that I use SWD pins as output and in my code I set them as GPIO output. Can it be the case?

Nevertheless, I connect my reset pin to GND and set "Connect under reset" option in ST-Link Utility but it doesn't work... What can I do?

On the Internet, I have found something about using BOOT0 Pin, but I don't know exactly...


texts:
I'd like to know how a 'hand clap' switch works. You know, the kind where you *clap-clap* and the light turns on, *clap-clap* again and the light turns off.

How is the clapping sound detected? How can it be differentiated from whistling, people talking, a barking dog, ... ? Can it be another kind of sound?

What kind of components would I need to build such a sensor/switch, assuming everything works on DC?

Note: I am not interested in just buying a Velleman kit :-)


texts: In relation to a PIC, what is a debug header?

texts: In a recent question on which PIC to use, one answer mentioned that a particular PIC had the feature that of debug hardware being built in, so that a special debug header was not needed.  What is a debug header?


texts: Power-only USB connection to charge my phone - as simple as cutting the data lines?

texts:
In a pinch I bought a $3 "phone recharger" from the bin shown below, but now I am too scared to connect it directly to my phone, which costs orders of magnitude more. While a poor design could present undesirable qualities to the 5V power output, I have no idea if there's something inside connected to the data lines - part of the 21st century USB angst that has many people saying "not in my USB port you don't". See this security SE answer for some background on USB angst.

I'll check my "cable museum" drawer for a power-only USB link to connect it to my phone's power without connecting to the data lines. If I can't find one I am planning to just carefully cut into a USB cable and sever the two data lines which I am assuming will be a twisted pair, leaving the black and red power lines, and do whatever seems to be necessary to temporarily repair the mechanical and shielding integrity.

Am I missing something important here, or should this be as simple as I think?

above: From here.

above: From a USB 2.0 specification (update) at USB.org.

above: Image borrowed from this question.


texts:
I'm trying to just get timer based PWM output working on the F103 Nucleo board and I can't get the MCU to output anything. I spent a decent amount of time looking through the examples in the related questions relating to the F4 and F0 MCUs, but couldn't find an answer there. My code originally came from the CubeMX tool, but I changed the name of the PWM_MspInit function to match the function that HAL_TIM_PWM_INIT() calls.

My timer initialization and PWM inialization fuctions look like this:

/* 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 = 6400-1;
    htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
    htim3.Init.Period = 10000-1;
    htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    HAL_TIM_PWM_Init(&htim3);

    sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
    HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig);

    HAL_TIM_PWM_Init(&htim3);

    sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
    sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
    HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig);

    sConfigOC.OCMode = TIM_OCMODE_PWM1;
    sConfigOC.Pulse = 1000-1;
    sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
    sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;

    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1);
    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_2);
    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_3);
    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_4);
    HAL_TIM_PWM_Start(&htim3,TIM_CHANNEL_ALL);
}

void HAL_TIM_PWM_MspInit(TIM_HandleTypeDef *htim) {

    GPIO_InitTypeDef GPIO_InitStruct;

    if (htim->Instance == TIM3) {
        __HAL_RCC_GPIOA_CLK_ENABLE();
        __HAL_RCC_GPIOB_CLK_ENABLE();

        //Configure GPIO pins : PA6 PA7
        GPIO_InitStruct.Pin = GPIO_PIN_6 | GPIO_PIN_7;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

        //Configure GPIO pins : PB0 PB1
        GPIO_InitStruct.Pin = GPIO_PIN_0 | GPIO_PIN_1;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
        HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    }
}

Then my main() looks like this:

int main(void) {

    // Reset of all peripherals, Initializes the Flash interface and the Systick. */
    HAL_Init();

    // Configure the system clock
    SystemClock_Config();

    // Initialize all configured peripherals
    MX_TIM3_Init();

    // Infinite loop
    while (1) {

    }
}

The only part of my main.c not shown is the unmodified SystemClock_Config() function that CubeMX produced. To my understanding because of the 64MHz system clock this should produce a 1Hz PWM signal with a 10% duty cycle. When I probe PA6 or PA7 I get nothing.


texts: SPI, RS232 and DMX-512 data signals beneath the ESP8266-WROOM-02 Wifi antenna

texts:
I am working on DMX-512 Controller, which will accept commands for driving Addressable LED strip (GE60RGBW8812A) via ESP-WROOM-02 Wifi Controller and I have several data lines (SPI, RS232 and DMX-512) under ESP-WROOM-02's on-chip antenna:

Here is another, zoomed and layer-filtered image:

And another screenshot for clarification:

This is my first Wifi PCB design and my guts tell me I've done horrible mistake placing these data lines under the mentioned PCB antenna. Should I reroute data lines or is this design ok?


texts: Relay to control electrical plug and non-electrical wire

texts:
I'm not sure what I'm looking for, but what I need is a relay switch that will control two things, or maybe two different relays are needed, I'm not sure.

Basically, from my Raspberry PI I want to control two things;

An electrical outlet and it's power, with NC side wired, so that my plug is on unless I turn it off from the PI.

Part 1 can I do on my 2 channel relay:

https://www.amazon.com/SainSmart-101-70-100-2-Channel-Relay-Module/dp/B0057OC6D8

I'm having trouble with part 2.

Have another wire interrupted also at the same time the plug is turned off. This wire is it's own power source and will not be powered by the wall electrical line like the plug, I simply want to interrupt the line when off.

Not sure if I need a second relay or something else for this purpose, as I don't want the power from the wall routed to this secondary line.


texts: Instrumentation amplifier and op amp V+ and V- shorted internally

texts: I have an INA2126 instrumentation amplifier and an OPA277 operation amplifier. I was trying to check if it is busted or not by using the continuity test of the analog multimeter. I'm  not sure if it's the right thing though. The weird thing was when I placed one probe in V+ and V- on the other probe the multimeter buzzed. Sometimes it does not buzz but the needle will move. Does this mean the IC is busted?


texts: How to determine the frequencies in which the L&C model of an artificial transmission line works?

texts:
I want to model an artificial transmission line with L & C. So far I used the following circuit and used the values of L=400 pH and C=0.16 pF so that Z=sqrt(L/C)=50 ohms. So, expected S21 and S31 could have a 3dB or 6dB drop from 1 to 2 and 1 to 3. (power divider).

But I am getting S21 and S31 as the following:

The gain is lower than 0 dB which I am not worried as of now as I will put some transistors in future (adjust the L values as well) and correct the gain.

But I am worried about the frequency independent behaviour. Well, I see that the input power flows from 1 to 2,3 well from 5-20 GHz. If I change the value of L to 1nH and C to 0.4 pF, then I see that it works at a different range.

During my design with transistors, I can figure out the capacitor parasitics that I would be getting (C_total) per node and then figure out the L depending upon the same formula Z=sqrt(L/C_total). But how can I be sure that the L value which I found works?

Am I missing something?


texts: Can metal electrical panels have a non-rectangular or squared shape?

texts:
Standard metal electrical distribution panels are rectangular or square shaped boxes.
Is there any standard - IEC, NEC, etc.- contraindicating  the manufacturing of a custom shaped box for an electrical panel, i.e. with round, elliptical or any other shapes?


texts: Identify an IC Found in a Garage Door Opener

texts:
Inside a defunct garage door opener I found this IC:

I tried searching for 33192C with variations of 'datasheet' and such keywords, but I got routed to the usual datasheet farms who are happy to let me know that they don't have it, and oh, by the way, here's an ad!

Can anyone identify this part, and even better, link to a datasheet?


texts: Resistor-Capacitor-Resistor configuration and layout differences

texts:
How you can explain the R-C-R configuration? Goertz zobel
link to the web-article

This looks to be used as a RF audio cable terminating, I suppose.
Which can be the electro-technical difference of having 10.2 ohm instead, or a R-R-C to ground, or C-R-R to ground?
To me a series R-C-R, R-R-C, C-R-R, C-2R, 2R-C all look to be electrically equivalent in any circuit.


texts: 1-channel GPIO from industrial PC over RS232 port

texts:
I am ordering a computer based on 4x4-R1000V motherboard (Ryzen Embedded, https://www.asrockind.com/overview.asp?Model=4X4-R1000V) for an industrial application.

I need a 1-channel GPIO (0 for zero, >1V for one). The board has on-board 1 x COM(RS-232/422/485).

My question is: is it possible to drive one (any) pin on the connector as a GPIO from Linux? Is it perhaps chipset-dependent?

I spotted Possible to use a 9 Pin Serial port as “GPIO” using ioctl()? suggesting it is shoudl work, but I'd rather have a confirmation from hardware folks here.


texts: How to close a serial port (16550 UART )

texts:
Have a 16550 UART serial port on an embedded CPU based computer. It is not used in this fielded environment, however, it is possible that someone could attempt to connect to it and send data.

Need to ensure that any data sent to it, has no impact whatsoever.

Is having no driver sufficient and/or necessary to "closing" a port?

Will the default settings on the 16550 UART chip itself still gather data, if it receives anything on the line?

...or is there a more proper way to do this? For example, some setting on the UART itself...or in the program that executes on the rest of the board?

Thanks.


texts: Why I don't get horizontally-polarized TVs in the satellite from time to time?

texts:
Something like once every 2 days I cannot watch horizontal SAT channels for about a half day. It says "no signal". During this "no signal" time I get very rarely watchable time. Like 1 minute in an hour. The after this "no signal" time ends there is no issue for about 1-2 days. That was for H.

On the other hand, I never have issues with vertically-polarized TV channels.

What might be the problem?


texts: Vcc drops on connecting variable resistor between it and ground

texts:
I have a VFD with a control board I am trying to fix. It requires an external variable resistor to be connected between the +10V terminal, analog reference terminal and ground. I found that on connecting the VR between the +10V terminal and ground, the voltage at the +10V terminal drops from 10V to around 8.78V. However, a similar board did not behave in this manner. What could possibly be the cause of this?

Many thanks in advance.


texts: How do I detect the signal and ground wire on a bluetooth earphone cable?

texts: I have a wireless bluetooth earphone, on which the left driver plays at half volume. I want to cut off the drivers and solder in a mmcx connector so that I can have options on the drivers. However assuming the color coding isn't standard or nonexistent, how do I detect the ground and signal wires without an option of doing a continuity test against 3.5mm jack ?


texts: What is the op-amp in this JFET-matcher circuit?

texts:
In the circuit diagram on this page, there appears to be an unspecified op-amp. Could anyone guess at a component I could use for this and/or explain why there is no specification?

Background: I am mildly clueless about electronics. I want to build this piezo preamplifier,

which uses a pair of matched JFETs. It lists possibilities for special matched JFET components which do indeed seem to be difficult to source, and alternatively suggests single JFET components which would have to be matched by hand. It recommends the above page as instructions for JFET matching. I'm trying to figure out what components I should get if I go down the hand-matching route.

Side-questions: (Apologies if these are too numerous, please ignore at your convenience.) Can I build the matcher on a breadboard or will it be better to solder together? Given the purpose of the circuit I'm matching the JFETs for (eg. it's run off 48V phantom power, not a 9V battery) should I make any adjustments to the matching circuit (ie. use a voltage source other than 9V battery; a different Rset value)? Or can anyone recommend a matched JFET component available in the UK?


texts: Datasheets do not mention and explain enough about current

texts:
I'm trying to build my first IoT project.
I'm using an L298 motor drive, an MCU-6050 6 axis gyroscope and accelerometer and an Arduino Due.
When going through their datasheets, most of the tables and information is about voltage or temperature. They barely mention details of how much current can be driven into a pin without damaging the pins.
What am I missing? Is current really not that important in lower voltages or I don't know how to read datasheets or maybe you have to calculate it?
The datasheets are:
L298
MCU-6050


texts: Do connectors with mounting tabs like this need to be grounded?

texts: The connector I have attached has these solder tabs on the side (red arrow). I think it's fairly common. The question is, when creating components for something like this, should I add two additional pins in the connector symbol for this? And if I should, should these be grounded in the design?


texts:
Background: I'm working on a project that involves tapping into the load cells of a scale and reading the differential output of the Wheatstone bridge. I need to keep all of the original functionality of the scale intact. The scales internal circuitry is running at 5v and it's powering the load cells at 5v as well, with either node of the bridge outputting 2.5v.

The setup so far: I have an Arduino Mega communicating with a 16bit ADC over the I2C SDA and SCL pins that's taking a single_ended reading from the output of a TI INA125P (Inst. Amp) that is amplifying the load cell's bridge output. When I disconnect the load cell from the scale and I supply power to it via the Arduino's 5v pin I get perfect, almost full-scale readings (awesome resolution with little noise to boot).

The issue: When I reconnect the load cell to the scale and I let the scales 5v circuit power the Arduino and my small amplifying circuit (via the Vin pin on the Mega) the scale's digital display outputs perfect weight readings, but all my Arduino reads is bogus values with no meaning.

At first I thought it might be an issue with conflicting supply voltages 5v from my computer and 5v from the scales circuitry, but from what I understand the Arduino's on board power regulator will automatically switch to the Vin supply voltage and disregard the usb's supply voltage.

Does anyone have any thoughts on what might be going on here? I'm not all that experienced with electronics so hopefully I'm overlooking something pretty simple!

Thanks!


texts: How to connect terminals like Ground Lugs and Feed-throughs?

texts: Feed-throughs, ground lugs, and similar terminals are often found on RF test equipment. What is the standard way to connect these to wires-- wrap stranded wire and solder? Is there a part that assists in making a repeatable and robust connection?


texts: I want to make a 220v rectifier and I want to draw 0.5 amps from it. I am using in4007 diode in full bridge configuration. The diode has a forward current of 1 amp and a power rating of 3w .My question is can I draw 0.5 A from it ? But if we see the power the diode should burn however it is still within the forward curent limit? Why is it so?


texts:
I'm creating a circuit with an infrared led and a transistor connected to a gpio pin on a Raspberry Pi. I'm currently using 5v with a 40 omh resistor (4 10 ohm resistors chained) but I'm not sure what resistor to put on the transistor.

The only transistor I have is the PN2222, will that work, and what resistor should I use?

Update: Here's the circuit I'm using, except with a 5v supply instead of a 12v

The LED has a forward current of 100mA and is found here (can't find a part number, specs are under description)
I've already calculated the value for the 2nd resistor, 40 ohms (with a 5v power supply)

The GPIO pin I'm using to control the transistor is 3.3 volts.


texts: Good solution for more interrupts on an arduino?

texts: I'm building a circuit with an Arduino Mega and simple IC chips (e.g. 7432) but I have many lines to monitor for interrupt conditions and not enough pins on the Atmel so I'm looking for a way to expand this.  Problems ensue because I need to be able to switch the trigger condition from rising edge to falling edge for some lines based on conditions, and some lines will remain high after having been serviced, so a priority encoder would suffer from the condition that a higher priority interrupt would mask a lower priority one.  For the latter problem, I am thinking of using a register and some gates to allow disabling of some interrupts, but I don't have a good solution for the former.  Does anyone have any suggestions?  I'm getting new chips as needed, so solutions involving extra 7400 series ICs or similar would be appreciated, but something more exotic would be OK as well.


texts: AC induction motor controlled by TWO TRIACS. They blow down

texts:
I am getting crazy with a board intended to drive an AC induction motor, which has two symmetrical windings (for the two run direction), a center tap, and requires a run capacitor.

The motor is rated about 900 watts, it can draw maximum 5 amperes, but until
now I used it with no load, so 1-2 amperes are consumed.

The idea is to drive a single TRIAC at a time, in the usual way, modulating
the pulses in order to control the speed (a rotary encoder provides feedback). Just to be clear, speed control/braking/reverse work well, my problem is that the board is not reliable, the TRIACs melt quickly even without big solicitations, but when they are sane, the results are good.

The schematic is the following:

By driving one or the other TRIAC it is possible to command the running
direction, and also decelerate (when pulsing the TRIAC opposite to the
running direction of the motor).

The circuit works as intended, but is very fragile. If the system is powered with low voltage (30 volts AC), everything is smooth; if the system is powered with the intended voltage (mains 230 VAC), it survives tens of seconds and then fuses blow and TRIACs burn.

If I mount only one TRIAC everything works well (of course, in one direction only): it does not burn. Mounting the second TRIAC, the opposite tap of the motor is no more free but it is connected to the circuit. Apparently the opposite tap develops high voltage and spikes which need to be canceled.

I used an oscilloscope to analyze what was happening: I was looking for
cross excitation of the TRIACs, extra voltage spikes and so on. Everything
seems normal, but the TRIACs keep to blow up. They are rated 800 volts. I
then tried to protect them using two 750V varistors in parallel to the anodes.
The varistors heat a lot, and this suggests me that there are high voltages
running around, even if I don't see them with the scope.

The next move has been to use 1.2KV rated TRIACs (don't have
the part number at hand now). Things go slightly better, but when the TRIAC
angle, from "low" power (near to right right end of the semi-cycle) is increased
to more power (near the middle of the semi-cycle), the TRIACs blow again. Fuses
blow also, but no other components are affected. My thought is that first a
TRIAC fails (or two TRIACs fail), then the short-circuit blows the fuse.

When the board fails, it seems that both the TRIACs melt, but I am
not very sure of this - I mean, until now I've never seen a single TRIAC
blown, always two.

I think I am missing something: to blow a 1200 volt rated TRIAC, a 1200 volt
voltage is necessary! I understand that windings can develop high voltage,
but I can not see it.

I tried to power that part of the board with 21 VAC (rms) from a transformer. The resulting sinusoidal wave has 67,2 volts peak to peak. The motor runs in the expected way (of course with very little torque). In no way I can see any voltage over 88 volts between any 2 points of the circuit. A pretty high voltage (peak to peak) is found across the motor capacitor: it can be as low as 44 volts with "low power" TRIAC angles, up to 85 volts (peak to peak) when exciting a TRIAC near the middle (top) of the semi cycle.

Calculating some proportion: if instead of 21 VAC, I use 230 VAC, then I should have around about 800/900 volts peak to peak. They would not be sufficient to burn the 1.2KV TRIACs, but it happens!

I don't know what to do. Somebody can help me please? Thanks, (many) thanks in advance.


texts: LDO getting hot on short circuit somewhere between Eth socket and LDO - how to best identify the short circuit spot?

texts:
I admit this is kinda "need a crystal ball" issue, however you might come up with some good hints that I can't figure out.

There's a Network Attached Storage unit (QNAP TS-219P+) that has a misfunctioning ethernet port (it doesn't connect to the the network, it's orange LED is on permanently regardless of whether the cable is attached or not).
I noticed that the 1.8V LDO (U30 GS1117AX18) gets really hot after 5 secs after power up and the Ethernet IC (U22 Marvel 88E1318) gets warm as well.

I measured all capacitors on Vout of this LDO and they all show a resistance of 0.5Ohm, the same is for the resistance between Vout of the LDO and GND, that clearly indicates the short circuit. C286 and C287 are decoupling the Vin and they are ok (indicating ~10kOhm), that would confirm the short circuit is a Vout side.

The PCB is clear of any physical symptoms.

I could take off the Marvel 88E1318 to check if it's damaged and replace it with a brand new IC but maybe there's something more suspicious that I should check first?


texts: Is it possible to use capacitor for isolation instead of optocoupler?

texts:
I designed a Buck converter which drives several LEDs. The PWM signal, which has a certain fixed duty cycle, is generated by a 555 timer IC. The circuit which drives the Buck MOSFET, including the 555, is boot-strapped and floating between 0V and 310V (rectified 220V AC). A current sensor measures the LED current and is supposed to send a pulse to the reset pin of the 555 to delay the next pulse.

The problem is, I can't find a cheap optocoupler which is guarantied to respond in less than one period of the PWM. If the current is not stopped within one period, the current through the Buck inductor would rise above the critical limit and damage the LEDs.

I decided to use a capacitor for isolation. I built up the circuit below to simulate it. However, I couldn't get a good response out of it regardless of what I tried. I would like to know if this method would actually work in theory and application. If it can work, what am I doing wrong here? And also, I would like to see if there is an example design.

simulate this circuit – Schematic created using CircuitLab


texts:
I have a 350kv BLDC motor and a 150 amp ESC. I'm using them to run a boat prop. It spins with plenty of speed in the air but as soon as I put it in water the ESC shuts down. The battery has plenty of power, I am using an Arduino connected to the ESC instead of a remote controller, I was wondering if there is anything in the code that I could change to give it more torque instead of speed, or do I need a higher amp ESC?
////////////////////////////////////////
#include <Servo.h> //Using servo library to control ESC Servo esc;
//Creating a servo class with name as esc
void setup()
{
esc.attach(10); //Specify the esc signal pin,Here as D10
esc.writeMicroseconds(1000); //initialize the signal to 1000
Serial.begin(9600);
}
void loop()
{
int val; //Creating a variable val
val= analogRead(A0); //Read input from analog pin a0 and store in val
val= map(val, 0, 1023,1000,2000); //mapping val to minimum and maximum(Change if needed)
esc.writeMicroseconds(val); //using val as the signal to esc
}


texts: How can I control Arc Lighter circuit with esp8266 d1 mini

texts: Here's an arc lighter that turns on when pressing down on the top left button. My question is, what is the easiest way to control the (on/off) of this lighter using only the esp8266 d1 mini.


texts: Does satellite radio use AM or FM or both?

texts:
Somehow, I cannot find an answer anywhere...  I am guessing both...
Several actual satellites had FM in their names, so perhaps that is a clue, but I want to know for sure...


texts: GM12-15BY-100 Stepper motor damaged,what caused it?

texts:
I have a dc stepper motor, GM12-15BYC:

2-phase,
unload typical current = 150mA,
Pull-out rate:800Hz,
Pull-out torque:120

I am using the driver DRV8834 to control it.

The configuration of the driver is:

MicroStep per step: 4
Step/Dir(Indexer) mode
xVref = 55.7mV,so the Itrip = 111mA.

First I managed to make the motor moving, however after playing around for sometime, the motor stopped moving, and seems died. I changed to another motor, the same thing happened again.

So for testing what is the problem, I applied a 10Hz frequency to the motor, then:

If I don't plug the motor in, then I can see the 4 windings all have signals of the correct frequency that I applied to it.

If I do plug the motor in:

The motor is not moving;
Checked the 4 wings, one of which phase has pulses, while another of the phase does not. For example, Black&Yellow is a pair, Red &White is a pair, I can see waves in Black and Red, but not in Yellow and White.
However, the frequency of the wave is changed significantly, now every pulse is 25 mircroSecond. while previously was about 1.5 second.

I thought this definitely indicates that there is something wrong with the motor.

So I checked the motor with multimeter, and find:
1. the resistance for each phase is correct. 30 Ohm.
2. no short or open circuit within each phase or between two phases.

My question is :

What might be the problem with this motor?
What might cause this damage of the motor?

Many thanks!


texts: Temperature stabilization with PWM , PID controller with delay system

texts:
I am doing a project to control the temperature with PWM. I use peltier, thermistor,mcu and h-bridge mosfet.

I want to reach a temperature with an error less than 0.05 and stay at that temperature without much (at most 0.05 C) oscillation. My first aim is to reach that temperatures in room temperature (no other effects than room temperature). Lets consider cooling mechanism, in room temperature, for example 14'C requires .285 PWM (out of 1) ,13'C requires .330PWM, and 20'C requires .180PWM. There is no linearity between them, and also changing PWM does not provide linear current change, ex: 1.0 PWM provides 2.15A, 0.5PWM provides 0.6A, and 0.2 PWM provides 0.16A across the peltier in room temperature.
My first cooling algoritm:Initially constant=0  Keep PWM 1.0 until temperature is close to set temperature (t_set) by 2, then lowering the PWM with, PWM=constant+ (temperature-t_set)/2, after temperature is set to a temperature constant=PWM, and then  PWM=constant+ (temperature-t_set)/5 and so on. And the system reaches steady temperature after 10-15 seconds after the PWM is changed, when PWM change >0.1

First question: How the mcu can can learn the PWM value that keeps the temperature constant? ( ex: 13'C requires .330PWM)

Second question: Is it possible to use PID algorithm to stabilize PWM value at set temperature without knowing the constants at first question?

Third question: If I find a good way that mcu to learn PWM values to keep temperature constant at different environments, and If I use good PID coefficients, do the PWM coefficients works for any environment, or are the PWM coefficients environment specific, ie: heat sink medium and differnt temperatures.

Thanks in advance.

--After 6 hours, from the answers

Q1- Learning that coefficient (I think) requires some algorithm when there is no PID.

Q2-Yes, with good PID coefficients it perfectly stabilizes, error term will be 0 and the only integrator term keeps the system stable, in noiseless environment.

Q3- If good PID coefficients are used and with educated (??) guess some level of stabilization can be accomplished.

To achieve good results in different environments (I think) it is needed to develop a auto tuning PID. My design criteria are keeping the temperature error minumum and keeping the reaching time for stabilization low (if possible).

From the result if it is approprite to ask here
my fourth question is: Q4: Which methods do you suggest me to find Ki, Kp and Kd coefficients in different environments (auto tuning PID coefficients when the mcu starts or restarts).


texts:
I have a RFID RC522 board that was working perfectly, until by mistake I tried to write it with a phone as if it was a RFID tag and now it stopped working, in the way that its led still turns on but it's not recognised by the code (it says firmware version 0x0).

I guess writing it fried the chip, but is there any way to check if it's actually fried or just a software problem?


texts:
Here the schematic of a very simple circuit

I know I don't have the flyback diode on the motor. And the MIC4422 is flipped in the schematic.

I want to control the high power motor with this high power mosfet while using PWM.

To drive the mosfet(AUIRFS8409-7P), I got a MIC4422 to increase the mosfet switching speed, but I still get some extreme heat after only a few second of running and there is no load on the motor. For sure no heatsink can dissipate this heat.
I didn't put any resistor at the gate of the mosfet to increase the switching speed.

I try lowering down the pwm frequency. At about 50 hz, the heat is OK with heat sink, but the frequency is too low for the motor to run smoothly and it's vibrating a lot. Maybe I could find a equilibrium point between the ''vibration'' and the heat output.

Do you know anything to reduce the switching time even more, when the motor will have load, it will be even worst. Is my circuit ok?

BTW, when the mosfet is not under pwm, the mosfet is not even a little bit warm. The problem is really with the switching time.

Thanks a lot,
Bernard


texts: Can every logic ic output be connected directly to ground or Vcc in any case?

texts:
One day, someone here, I forgot who, wrote: "On modern ic's, every input and output pin can be connected directly to either ground or Vcc." Talking about ologic ic's.
Is it true? And is true all the time?

I read also many comments recommending not to do that and always add a resistor of several KOhms.
Adding a resistor protects the pin even when technically it's allowed to do so. But is adding a resistor at every pin permanently connected to ground or Vcc worth it? What would be the level of protection considering that neither ground or Vcc has a resistor? Advantages?

Connecting an output to a low impedance circuit to ground or directly to ground will make the pin transfer maximum current when it turns high. Can it be bad for the ic?
And similarly, can it be bad when an output is low while connected to a quasi-infinite source of current?

(This question does not qpply to open-drain pin, which de facto require a pull-up resistor.)


texts: Is it feasible to use one flyback controller with two transformers, yet only one feedback? The primary winding of the transformers would be connected in parallel, isolated feedback would be taken from the most loaded output, then others would be less regulated, but yet in required range.


texts: How to find Setup time and hold time for D flip flop?

texts:
I am simulating D flip flop in cadence, how to find set up and hold time in d FF?

And I have design negative D FF using Pass gate and Inverter when i change same circuit to positive D FF by changing ck to invClk and invclk to clk.

invclk=not(clk)


texts: Are radioisotope HRNGs commercially available?

texts:
I figure if they use Americium-241 pellets to make commercial smoke detectors, there's no reason they cannot use such pellets for hardware random number generators. I read an unconfirmed anecdote that casinos often use them in their digital gaming machines. Even though they don't have nearly as high of a bitrate as the optical HRNGs, radioactivity is quite reliably random.

There have been a few hobbyists who built their own but that's a bit too risky for me right now.


texts:
Right now I am using KiCAD to try make a 6.35mm Headphone jack to BNC converter and am confused as to how to wire rn, tn and sn.

What do they do? This is my current KiCAD schematic.


texts:
With all the technology available today with being able to boost voltage efficiently using SMPS, why do we still use 9V batteries? Is there some secret advantage with them that I am unaware of?

If you look at the size as well, the 9V is just big and bulky and I have designed projects where I can use 2xAA batteries and boost the voltage, which will give me longer battery life than a 9V. And it takes up the same amount of space.

A lot of circuits today also need regulating, and the easiest way to do that with a 9V is a linear regulator (usually to about 5V) and I am aware this is not the case for every design, but that right there is energy wasted, and yet again, boosting the voltage from 1 or 2 AA batteries will probably give your product a better shelf life.

I saw a comparison between a 9V battery and some AA batteries, where someone found the energy available, and ended up with this data:
NOTE: These results were from Energizer Alkaline batteries. The page can be found HERE.

So with all this data, why are 9V batteries still used in designs? Are there some applications where it would be advantageous to use them? Or is it usually a better idea just to go for the AA or AAA solution?

There have been times where I have considered using a 9V battery for some of my projects but it always seems after doing my calculations, they just don't hold up as well as others, so am I missing something?

For reference, the datasheets for the compared batteries are here:
AA
9V

EDIT: I am not intending this to be an 'opinion-based' question, rather, I was intending to ask from a practical point of view, if there were advantages to choosing a 9V over any other solution (such as boosting AA batteries). Just wanted to make that clear!


texts: What is the meaning of these motor characteristic keywords?

texts:
could anybody please explain the following terms?

Speed, rated load (RPM)
Rated load (N)
Rated voltage (V)
Max Static Force (N)
Max Current (A)
Max Load (N)


texts: Ground Loop RS232 between PC and Breadboard

texts: I have a microcontroller circuit on a breadboard that I want to to connect to my PC via a RS-232 interface through a MAX232 IC. The breadboard is connected to an external power supply.  One of the pins from the RS-232 needs to be connected to ground.  When I connected it to the ground of my breadboard I blew out the fuse in my power supply.  I replaced the fuse and did the same thing and it worked.  I'm confused about how the power supply in my PC has one ground and the power supply in my breadboard has another, and how the connection could ever work when there are two grounds in the system.  When I connect the ground pin of the serial port to the ground rail of my breadboard doesn't this cause a ground loop b/t the PC and the breadboard?  Can this fry my PC?


texts: Is it safe to run long I/O wires to a microcontroller?

texts:
I'm contemplating using an MCU sitting in my garage to read data from a couple of sensors, one of which may be as much as 10m distant. I'm not using analog sensors, as this question asks, instead, I'll be using Maxim OneWire devices (used in non-parasitic power mode).

I believe the actual digital signal and power should be fine at these distances (I'll probably use something like CAT5, and I can tie multiple conductors together if I really need to), but I'm concerned about other issues, mainly EMI, and at the top of my list of worries is exactly what happens when lightning strikes nearby? Doesn't this wire act as a large antenna, and could pick up meaningful voltages when lightning strikes?

It may or may not be relevant to state that the wire(s) in question would be run inside the building (in the attic), and not out in the open air. I'm not worried so much about a lightning strike directly on the wire, as I am about the large EMI voltages that could (would?) be generated in the wire upon a nearby strike.


texts: Constant current for phone charging with boost converter?

texts:
I am using the TPS61236P from Texas Instruments to charge a phone from a 3.7V Li-ion battery.  I have gotten it working to the point where I have a ~5.1V output through a USB port, going into the phone.  The phone recognizes that it is charging, but AIDA64 outputs a very low charging current (20-100mA).

I am wondering if the problem is the fact that I am using the constant current mode of the boost converter, which I have set to 2A.  I have used the TPS2514 from Texas Instruments as a USB port controller (2.7V to D+ and D-), and have even shorted the D+ and D- lines (after removing the TPS2514), with no better result.  Is the constant current mode causing this issue, or would that not be a problem?

If not, is there anything else that could be related to the USB port/controller itself that would limit the amount of current the phone can draw?

EDIT: I should note I am using a Nexus 6P as the phone to charge, with the cable being a USB-A to USB-C M/M cable.  I have had no problems with the cable when used with a commercial grade phone charger.

Schematic:


texts: How to mount electronics on a vehicle chassis safely

texts:
I want to implement a control system I designed for a light electric motorbike. I would like to mount it as professionally as possible on the chassis. It consists of a power system pcb and a SAMC21 development board which I'll merge later once this all works properly. I have tried screwing it directly on the aluminium chassis but have found that shocks and vibrations from the horn disturbed the system or even destroyed it upon large shocks like a few hammer hits. Is there a specific way car and motorcycle manufacturers mount their electronics to make their system as robust as possible?
Thank you for your help!


texts: Zener Diode Circuit Sees Voltage without source applied

texts:
I have a circuit into an optical isolator which is used to detect the status of a contact in the field.

Zener diodes are used in series to drop the voltage to the optical isolator as well as as series resistor to limit the current to about 3mA when the Zeners breakdown.

The puzzling phenomenon is that with field contract open in that there is no source voltage, one can read the sum of the Zener voltages at the input to the circuit.

Is it possible that the wire to the field contact provides enough "noise" so that it is possible to read a voltage at the input even though the contact is open and no source voltage is being applied?


texts: Knife Blade On/Off Switch for an A/C circuit

texts:
I'd like to build a fun audio amp. Its a blue tooth module, so there are no controls.  I just want a simple on/off switch. This amp is to be used in a workshop, and because I live in Las Vegas (where it gets quite hot in the summer) I don't want to leave the power supply engaged all the time. I'm not all that worried about speaker pop on startup.  I'd like to shut off power upstream of the switching power supply.  I was considering using this switch,  just because it looks cool.  I intend to use it in this circuit

What I'm not clear about is safety using this switch.  I'm guessing the power supply output is approx 2 or 3 amps at 14v.  I don't know the input power ratings. I'm thinking worst case is that somebody might bridge the open knife blade to blade seat with a sweaty hand?

The parts aren't all on hand yet, so I don't know the actual operating current in a single leg of that A/C circuit.

The other option is to use a double pole, single throw switch of the same design, to shut off both legs of the 120v wiring, but that seems much more dangerous to me. Somebody could bridge the 120v terminals on the hot side of the switch.  (In fact, why do they even make a double pole single throw switch like that?  That just seems unsafe.)

Note: the intent here is that this amp assembly hangs on the wall, about ten feet from the door of the shop.  I am not worried about tossing a tool on the workbench and having that short out the switch. I am not worried about hitting the switch with my hands when I enter the dark shop (while trying to find the light switch)

Your thoughts here?  Is this crazy unsafe?


texts: Oops: shielded inductor very close to a crystal. Problem?

texts:
I've got a design that worked great on the two boards I hand assembled, but more than half of the boards from the local assembly shop are bad.

I've traced the most common failure mode to an unstable reference clock from my processor to the ethernet PHY.  I guess the PLL is not locking properly in some cases.

About the only thing I've found (and it's possibly a big thing) is that in an effort to squash the area down I somehow ended up with the 24MHz crystal for the system clock (that is fed to a PLL for the Ethernet reference clock) -very- close to the DC/DC converter's shielded inductor. The shielded inductor is at 45 degrees orientation to the crystal, but one corner is within 20 mils of the side of the crystal! Oops.

I've been able to move this crystal to about 160 mils away now, which is the best I can do without some serious rework.  I've seen a layout example in the processor's layout notes that appear to show the crystal about 100 mils away from the inductor (the DC/DC is integrated in this processor package), so I'm thinking that's okay.  The evaluation board has them about 250 mils apart, but it doesn't look like that distance was a significant factor in that design (although it could have been).  It just looks like a convenient spot for both components.

My big concern at the moment is... did I fix the problem?  How likely is it that a crystal 20 mils from a shielded inductor could cause problems?  The odd thing is I have 6 boards that have so far behaved perfectly, and about 5 that have this reference clock PLL problem.  I'm not sure why it's not all of the boards, unless it's just how individual tolerances add up.

I could have bigger signal integrity issues here...  but then much more demanding parts of the processor layout (DDR2 memory) seem to be behaving well.  No boards show any hint of problems there or anywhere else.

The most likely cause of my woes has been the local assembly shop.  I have a very low confidence level in the boards I got from them.  I've found a large number of mistakes. One board's been working since I replaced the crystal... I didn't see any oscillation on the scope, but under a microscope it definitely appeared to have connectivity. However, replacing crystals didn't help any of the other boards.

I just wish I had a concrete, fixed problem for this next board revision instead of a bunch of "It'll probably work now"...

Here's a picture of before and after (the crystal is slightly larger in Y than it's footprint):


texts: USB Voltage auto selector (Prioritise VUSB)

texts:
I'm trying to design a auto voltage selector circuit to prioritise USB voltage when the USB is plugged in. The power goes through some voltage regulators which then powers a MCU (ATMEGA32U). I have two circuits for this, one that goes to the 3.3V voltage regulator and another that goes to a 5V voltage regulator. VIN varies from 3.7V to 15V.

Voltage selector for 3.3V

When there is no VUSB present the P-Channel MOSFET allows current to go through from VIN. When VUSB is present, it turns on the P-channel MOSFET which blocks the current from VIN and allows the current flow through via the diode. The switch is just there so that I can bypass this entire circuit if necessary.

Voltage selector for 5V

Similar to before when no VUSB is present, the P-Channel MOSFET allows current to go through from VIN. When VUSB is present, it turns on the P-Channel MOSFET which block the current from VIN and allows current to flow through to the 5V rail bypassing the voltage regulator via the diode.

So my question is, is there any problem with this circuit and will it work? I know there are similar questions like this before but none has been exactly what I need. Thanks in advance.


texts:
I have been working with TI's PRUs on the am335x, equipped on the BeagleBone Black. I would like to know if other hardware manufactures offer similar systems. I am doing my Bachelor Thesis on this topic. So, it would be nice if I had some other system to compare to.

So far I have found nothing like it. The BeagleBone Black seems to be somewhat of a hybrid between a Raspberry Pi and an Arduino.

Edit:
I'm not looking for a recommendation to buy anything. For my thesis I need to compare the system that I'm using with their possible competitors. I think it's interesting to know what systems are out there apart form the one that I'm working with (the am335x).


texts: What happen when input changes the same time clock pulse changes in edge triggered flip flop?

texts:
For example take positive edge triggered D flip flop.If input (D) changes from 1 to 0 at the same time when clock pulse goes from 0 to 1(positive edge of clock pulse), what will be the output (Q).Will it be 1 or 0?

Assume setup time and hold time to be zero


texts: Identify relevant parameters of Transformer Spec. for Audio Application

texts:
Upon the advice of this question/answer I have added a 1:1 audio isolation transformer to my circuit.

I picked up a transformer at the local radio service shop and dropped it into my bread-board prototype; it's a Shaffener IT237 as shown in the spec sheet below. It works well in my application. I'd like to purchase an SMD equivalent, but I'm not sure what paramaters are most relevant for this circuit.

I don't fully understand how this transformer affects the circuit, but I do know that it fixes the issue outlined in the post linked above.

The circuit shown below is a simplified version of my project. The input is the line-level AC coming from a CD player, ChromeCast, or similar appliance. The output of the Class A amplifiers is sampled by an Arduino.

What parameters of the existing transformer shown in the specs sheet below should I consider when looking for an alternative SMD version of this component? I would guess that I need a low impedance device as this is for use with very low voltages (5-50mV), but beyond that I have no idea what I'm looking for.

simulate this circuit – Schematic created using CircuitLab


texts: measuring ac voltage drop across a resistor with a solenoid in series with it

texts:
I wanted to measure the phase difference between the current (magnetic field due to the solenoid) and the system response. I am doing this by measuring the voltage drop across the resistor in series with the solenoid and using this as the reference frequency of the lockin amplifier.

On increasing the frequency of the source (function generator), the impedance of the circuit is increasing and decreasing the current in the circuit. This reduces the amplitude of the reference frequency to the point where the lockin amplifier is not able to lock to the reference.

I wanted to amplify the drop across AB using an op-amp. I am not sure if a differential amplifier will do the job for this purpose. One this that caught me off-guard while designing the differential amplifier was what do i consider as ground here, if i make V1 as A and V2 as B.

I am not sure if i can even do this here. There is another doubt I got while looking at some datasheet like the one for OP27 (snippet below). It says the maximum differential input voltage between the terminals is just 0.7V. This can't possibly mean that the op-amp can only amplify voltage difference between the terminals that are below 0.7V..

I do get the feeling that I am doing a lot of stuff wrong. Any help would be greatly appreciated.
Cheers! :)

Edit:

I got a hint from Bruce's comment and Metacollins answer. So now I have a common ground for the entire experimental setup. Is this the way i should go about it?


texts:
Background
I'm currently digging into STM32L0 series and I stumbled something I couldn't answer.
According the the datasheet page 58 we can see all the peripherals are clumped into a section of 512 MB, now in that section the IOPORT bus resides, this bus handles all the GPIO ports according to page 56.
According to the vendor software each PORT is offset by 0x0000 0400 starting from 0x5000 0000 being PORTA
0x5000 0400 being PORTB and so on..
I tried looking through the compiled memory map and register view, but didn't get any smarter.
Question
Why does each port(A,B,C,D,E,H) have 1 kB allocated, when according to the datasheet/vendor provided SW they only have 11 x 32bit registers associated with them adding up to 44 bytes?
What could this be - Am I completely off ?
typedef struct
{
  __IO uint32_t MODER;        /*!< GPIO port mode register,                     Address offset: 0x00
  __IO uint32_t OTYPER;       /*!< GPIO port output type register,              Address offset: 0x04
  __IO uint32_t OSPEEDR;      /*!< GPIO port output speed register,             Address offset: 0x08
  __IO uint32_t PUPDR;        /*!< GPIO port pull-up/pull-down register,        Address offset: 0x0C
  __IO uint32_t IDR;          /*!< GPIO port input data register,               Address offset: 0x10
  __IO uint32_t ODR;          /*!< GPIO port output data register,              Address offset: 0x14
  __IO uint32_t BSRR;         /*!< GPIO port bit set/reset registerBSRR,        Address offset: 0x18
  __IO uint32_t LCKR;         /*!< GPIO port configuration lock register,       Address offset: 0x1C
  __IO uint32_t AFR[2];       /*!< GPIO alternate function register,            Address offset: 0x20-0x24
  __IO uint32_t BRR;          /*!< GPIO bit reset register,                     Address offset: 0x28
}GPIO_TypeDef;


texts: LC circuit with AC-supply - current through the coil

texts:
A parallel LC-circuit is connected to an AC-supply as in the figure below.

  \$I_{tot}(t)=I_0sin(\omega t+\phi)\$, \$\phi\$ is the phase angle between \$V_{tot}(t)\$ and \$I_{tot}(t)\$

  a) Determine \$\phi\$.

  b) What current \$I_L(t)\$(Amplitude and phase) runs through the coil L?

  Use the following information: \$R=10 \Omega, ~C=30\mu F,~L=10^{-3}H,~I_0=2A,~\omega =300\frac{1}{s}\$

I was never good with LC-circuits, which is why I picked out this one out of my textbook.

How do I approach this type of exercise?

I was thinking that since it's an LC-circuit then because of Lenz's law the phase is \$\phi =90°\$? Is that also the case here? And the resistor \$R\$ kind of bugs me in the circuit. Does it have any influence on the current or the phase?

How do I get the amplitude and phase in b)? Although I still think that the phase should be \$90°\$. But what about the amplitude?

I guess part of the current would flow through R, right? Meaning the 'amplitude' of the current in L is a little less. But how would I get the value of \$I_R\$? I don't have a value for the voltage V.

Sorry for my lack of work here. My knowledge on curcuits in general is really slim.


texts: Transformers as Inductors (Weird Results)

texts:
If a transformer's primary and secondary are connected in series, then the total inductance of the result, is greater than the summation of each coil separately.

That is to say: \$ L_{total} > (L_p + L_s) \$.

I've seen the math for this and understand it well enough; but the thing is, if I connect an xfmrs coils in series and then short the primary (so that there is a direct path to the secondary) the result is significantly greater than the inductance of the secondary by itself: this I don't understand.

I understand that the short is not zero (unless one is using a super conductor), and that there is going to be current through the primary, but there seems to be more to it. For instance, if I short the secondary (instead of the primary), the LCR meter reads MUCH higher than as if the coils were just connected in series!

I want to make sure that my LCR meter is correct, because if this phenomenon holds true, then I would like to take advantage of this in a filter circuit.

Can someone help me to understand what's going on?


texts:
I'm taking my first course in electronic circuits and I'm a little lost when it comes to combining NMOS transistors with capacitors. In particular I am having trouble with finding the steady state for Vo(t) in the following diagram.

Can someone point me in the right direction? My thoughts go as far a recognizing that steady state means there will be no current going though the capacitor as it acts like an open circuit.

The intial conditions are Vin = 0 V and Vo(0) = 0 V (cap is initial uncharged) and phi(t) is turned low(0 V) to high (5 V)

Edit : the parameters of the nmos: \$V_{Tn} = 1 V\$ and \$k_n=1 \mathrm{\frac{mA}{V^2}}\$


texts: Can someone identify this old round connector?

texts:
I am trying to develop something to control an old antenna rotator, and it has a connector like this one:

It does not seem to be a simple audio connector, but is more or less of the same size. What it its name? Is it possible to find a male connector for it nowadays?

Thank you in advantage!


texts: Why do we use a transformer on some heating element projects when the wattage is the same on both sides of the trasformer?

texts:
On some projects involving heating elements there's a transformer being used.
The explanation given is "we are using a transformer because we need more current."
The watts on both sides of the transformer are supposed to be identical.
Wouldn't the heating element dissipate the same energy with and without the transformer?


texts: Dividing Current to 10 outputs from 5V source

texts:
I need to create a simple power supply circuit to feed 10 external boards, similar to a USB power hub.

My power source is an AC to DC adapter measured to output 5V 10A. I need to limit the maximum amount per output to 1A. The external boards (U1, U2, etc) are audio boards, they have an MCU, an audio player, 5W amp and speakers. Each board uses from 300mA to 700mA (they vary due to music/frequencies), so 1A max should be enough.

I'm a beginner who understands a voltage divider quite well, but that is the first time I have to apply a current divider. I had a look at some tutorials/books, the math seems simple in my context, but it's still not clear to me what resistor values I should use and if I'm connecting the outputs correctly (I'm not used to do things in parallel). Below is how I think it should be:

simulate this circuit – Schematic created using CircuitLab

About the resistance, if I use the general formula IBRANCH = IS(RTOTAL/RBRANCH) I will get 1A for any kind of resistance as long all values are the same (for example, they could all be 100ohms or 1K)..So what value is best for this application?


texts: RN42 Bluetooth Module - Entering command mode from C code

texts:
I am using a PIC32MX795F12 microcontroller together with a RN42 bluetooth to UART module.

I can send text to the UART with no problem at 115200 baud.
Using Putty I can also enter the command $$$ to enter the command mode and get the CMD response.
Unfortunately I've not been able to enter the command mode using the C code.
My command to do this is as follows:

  "UART3WriteString("$$$");"

where the function is defined as:

void UART3WriteString(const char * str) {
while( *str ) {
    U3TXREG = *str++;
    while( U3STAbits.TRMT == 0 ); //wait for the transmission to be done)
}

}

When I do this, the RN42 does not go into the command mode. It just outputs $$$ without the CMD response.

Any ideas?

Thanks!


texts:
I have an application where I will be taking serial signals will need to level shift the signal to 3.3V. The input signal will be from 15 to 5V for a high input and I need them all shifted down to 3.3V.

I understand how to do this when there is one constant input voltage but in this situation, depending on what is connected to my RS232 connector I could have..

-10 to 10V

0 to 5V

0 to 15V

on the input side. Does anyone know a good option to make sure that all of these 3 different signals can be shifted down to 0-3.3V?

I'm struggling to find a solution.

Thanks in advance


texts:
These amplifiers tend to shape the current and voltage waveforms using their respective harmonics .

The goal is to minimize the area of overlap between drain (or collector) voltage and drain current to maximize efficiency.

My question is:  Would that make sense and work only if the transistor is meant to operate at full swing into the compression region ( almost as a switch but not quite) or otherwise?


texts: TIVA TM4C123G Driverlib Function Question

texts:
I have a question about how to use a basic GPIO function from the TIVA driver library to set an output pin high. See the below image for more detail.

The red underline on the code on the left hand uses GPIOPinWrite. On the right is the datasheet for the driver library which shows a description of the function.

Can someone explain how this sets pin 2 high? I understand the first two values passed into the function but not how the last Ui8Val sets the pin high?

EDIT

I see in the GPIO header file that GPIO_PIN_2 is defined as 0x04.

Thanks!


texts: Is there a way to control the PWM duty cycle of a 555 timer without using a variable resistor?

texts:
I need to control the duty cycle of a Pulse Width Modulation (PWM) circuit from a DC voltage input. To do this, I've been looking into 555-timer circuits - but every circuit I've come across involves controlling the duty cycle by using a variable resistor/changing resistor values (e.g. changing the value of Rb in the diaram shown below).

I've researched and thought about it a lot, but I can't find a way to use a certain input voltage to give a certain duty cycle in a PWM cicruit with the 555-timer, so any suggestions I may not have thought of or letting me know it can/can't be done would be appreciated.

Thanks

As a note: The requirement of controlling a PWM circuit duty cycle with an input voltage and not by other means is necessary for what I'm doing... I'm not trying to make my life difficult

Also, I forgot to mention I'm also not allowed to use microcontrollers!


texts: Writing STM32F7 code without external files?

texts: How to start coding for STM32F7 platform without any external files despite of assembler startup file. Is there a header file with memory mapped registers which does not include any other header files (for example core_cm7.h)?


texts: I have Arduino Mini Pro 5v and need to know if the Vcc will drive a 5v Relay. My Voltage output measure on the Vcc is 4.2v. Will the 5v Relay be triggered?


texts: Buck converter without inductor in a NiMH charger (Zilog AN0259 application note)

texts:
After doing some reading online, it seems that you can't really build a step-down converter with only a filtering capacitor and without an inductor, because the losses occuring during charging of the capacitor would lead to low efficiency.
However, I'm looking at a application note from Zilog: "AN0259 - Low-Cost NiMH Battery Charger Using the Z8F0830": https://www.zilog.com/docs/z8encorexp/appnotes/AN0259.pdf which is using exactly that circuit - a capacitor is charged with a 10 kHz PWM signal, which in turn charges the NiMH battery. No inductor is present in the circuit.

What makes this circuit work in that situation? Or maybe it acts as I described above - it has high losses, but the designers just roll with it?


texts: How to create Spice / LTSpice repeatable damped sinusoid

texts:
Is there a more elegant and/or simpler method to model a repeating, damped sinusoid from SPICE or LTSpice rather than chaining the damped SINE sources in series?   Below is a schematic and the waveform I am attempting to recreate ad infinitum.

I'm attempting to simulate switching noise from a DC/DC converter from within LTSpice.  The area of interest is the PCB parasitics which cause a repeating, damped sinusoid superimposed on the switching frequency output ripple.

The only method I have found to model a repeating, damped sinusoid is to use a series chain of SINE sources, each offset in time by 1/2 the switching frequency, and include a damping factor for the decay.   For a short chain length this is manageable;  however for a longer transient sim, the thing would become unwieldy.

Any ideas how to make this repeatable forever?


texts:
Can some one explain this terminology please I think I understand it but not completely sure.

I think pull down is where you place a resistor between +V and the other component and pull up is where you place the resistor between 0v and the component.

If I am completely wrong then let me know!


texts: FreeRTOS priority and its effect on Thread

texts:
I am learning basics of Free RTOS wth a STM32MCU. I defined two threads, each one take mutex, wait for 1000ms and give the mutex again. I have noticed that when the priorities of the threads are not the same, this delay will be different for each thread. This made me wonder because the delay periods are defined the same. Could somebody explain the reason of that? You find a piece of my code here:

void StartDefaultTask(void const * argument)
{
  for(;;)
  {
    xSemaphoreTake(Mutex1Handle, portMAX_DELAY);
    LCD1602_setCursor(1, 1);
    LCD1602_print("ThOne1");
    HAL_Delay(1000);
    LCD1602_clear();
    xSemaphoreGive(Mutex1Handle);
    osDelay(10);
  }
}
void StartTask02(void const * argument)
{
  for(;;)
  {
    xSemaphoreTake(Mutex1Handle, portMAX_DELAY);
    LCD1602_setCursor(2, 1);
    LCD1602_print("ThTwo2");
    HAL_Delay(1000);
    LCD1602_clear();
    xSemaphoreGive(Mutex1Handle);
    osDelay(10);
  }


texts: How does a sine choke exactly function? In most high power inverter systems, the primary side of the output transformer is always driven by a PWM signal. The secondary output which is sent to a load should also come out to be PWM. How does a pure sine wave inverter exactly convert this PWM into a pure sine wave? What if we fed SPWM directly to the primary of the ferrite transformer, how to filter the secondary output to get pure sine wave?


texts: Early solid state radios used Ge diodes as a detector .Si was not available then so this makes sense .Impedances were much lower than the Valve stuff.A 5k Log volume control   pot was common for early solid state where 500K was common for a valve detector .Also the solid state radios had lower output voltages than their valve counterparts . Prebiasing the diode was essential to keep distortion down .When Si transistors arrived I would still often see a Ge detector diode present .Was this because they in the day had lots of glass Ge diodes in the store ? If a Si diode is prebiased it should have low distortion too? Does the more gradual VI curve of the Ge diode give less distortion ? Is the distortion cancellation that prebiasing achieves not as good for Si because there is more distortion to begin with ?


texts: I'm reading about a microprocessors at the moment and wondering if I could get started with an 8-bit microprocessor. What would I need to get started. I understand that they need external RAM and ROM. I don't know whether it is still possible to get an Intel 8-bit one as my book is from 1980. So are there any other recommendations?. I am looking for the circuit diagrams for creating my own PCBs, is this advisable? Something like a single board computer is what I'm looking for.


texts: Is it possible to create Altium PCB footprints without designator labels?

texts:
I'm pretty new to Altium, have years of experience with Orcad.
At the moment I'm in the process of filling a PCB library. Among them there are no-BOM footprints like test points, mounting holes and breadboard snippets. These are copper-only components. And I really don't need designator labels for them on the silkscreen. (For the test points I only want the comment field). I tried a lot but found no way to create a footprint without a designator label. Is it possible? Having to remove them manually each time is annoying.


texts: LT-Spice RL circuit simulation ill behaved current

texts:
I am trying to simulate a RL circuit in DC with LT-spice as follows:

NOTE that the inductance is 0.0229 H although in the picture you see 229

Now, according to my calculation, what I would expect is that, because of the inductor, the current needs some time, say 4.4 tau to be close to the theoretical value of V/R = 1.497 A.

Below you can find the data of the circuit:

Inductance (H):     0.0229

Resistance (Ohm):   3.34

DC voltage (V):     5

Current (A):        1.4970059880239521

Tau:            0.006856287425149701

Critical time (s):  0.03016766467065869

Now, when I simulate the circuit in LT-spice, this is not what happens, the current jumps up to 1.497 immediately, not showing the exponential behaviour it should have in a circuit like this. What am I doing wrong I checked and doublechecked but I cannot find out what I am missing! As you can see with LT-spice I looked very close to t=0 to check whether I was missing out on the timescale, but the current behaviour is not exponential at t = 0 + dt either!

From my calculation, the theoretical behaviour before 0.03s should be the following:


texts:
Note: This is a followup to a previous question that was left unanswered. The circuit has been remade on a breadboard and the symptoms are different

I have been trying to make a voltage limiter circuit work for ages now, there must be something I don't get about transistors. In the following circuit that takes a low frequency high voltage (50V max, 20V typical) sinewave to produce a stable 5V later on, the voltage limiter protects the big capacitor (16V breakdown).

simulate this circuit – Schematic created using CircuitLab

As simple as it is on breadboard (power supply DC in, no load), no matter the setting on the potentiometer the capacitor does not charge (Gate of Q2 is always the input). Is there anything I am doing wrong? I am tempted to make a PCB to rule out wiring as 2 breadboards have 2 sets of symptoms, but I'd like to be sure it's supposed to work.

Wiring:

On a front view, the MOSFET's pinout is gate-drain-source.


texts: What is the best wired protocol choice for home automation?

texts: I know the X-10 protocol. X-10 is a good choice or is there better?


texts: I have some basic diode questions. When we forward bias a diode the electrons in the N region cross over the depletion region and enter the P region. Here they are supposed to recombine with the holes which are abundant in the P region. However my issue is this. When electron and holes recombine dont they form an ion? And ions are not mobile. So what mistake am I making here?


texts:
I am using 1N5408 diode in a rectifier circuit. The datasheet can be found here.

I find myself in a very bad state while understanding symbols and meanings while reading datasheets. Can anyone have a look and explain to me what the following terms signify, that is, what do you mean be them?

VRPM
I F(AV)
IFSM
VF
IRR

Also, can anyone confirm that the rectifiers can be used for converting 9V AC to 9V DC?


texts: Continuous frequency grid to discrete grid

texts:
I am designing a controller for a system using several methods, one of which is a discrete method. In the continuous time I am looking at a logarithmically spaced frequency grid in the range $$\omega \in [0.1,1]$$Now I want to design a controller in the discrete time, but I want to evaluate the h-infinity norm (which I am minimizing) over the same frequency grid as in the continuous time.

How can I minimize the norm over the same frequency grid in discrete time?


texts: Software timers using hardware interrupt

texts:
I have to implement a counter for upto 30 minutes on my microcontroller. However the hardware interrupts maximum time is nowhere close to this. So I think I would be using the interrupt and increment a variable everytime the interrupt is called by the hardware. However I would like to know if there are already any such open source timers available which I can port and use more easily rather than writing evertything from scratch. The second question is :

interrupt timer()
{
/increment a count

}

Other than setting a flag when my required counter value is reached is there any more efficient way of doing this?


texts: Running 5v 4A device using 18650 batteries

texts:
I'm working on a project involving a SBC, IR LED's and a screen. All of them together draws 3.5 to 4 Amps and voltage of-course is 5v. I'm hoping to run this using 18650 (3.7v), I have a couple of them lying around.
I'm confused on what would give me the most efficiency - connecting batteries in series and using a buck converter or parallel batteries with boost circuit. Either way i'm not familiar these circuits, can anyone give me a lead.


texts:
I have a requirement to make a BT2.1 adapter, which I have to connect to a balance scale via serial port. The weighing scale transfers weight data to the adapter via serial port. This BT adapter has to pair to any mobile phone. The application running on the BT based mobile phone should display the weight measured on the weighing scale.

Keeping this in mind, can anybody suggest me the profile that i should implement on the BT adapter?

Also, Is anybody aware of a single chip based BT solution which I can use for building the adapter?

I am new to the world of Bluetooth...


texts: How can I drive 12v LEDs from my Arduino Nano?

texts:
Background
I am building a scale RC helicopter and ordered a bunch of 3mm LEDs to give it some nice navigation and strobe lights which I plan to drive with an Arduino Nano.
Problem is that I goofed and didn't notice that the LEDs are 12v until they arrived.  I know that the Arduino Nano can accept 12V on pin 30, but I think the voltage output on any of the "D" or "A" pins is always 5v (correct??).
Question
If the voltage output of the Arduino pins is 5v, then how can I drive the 12v LEDs using the Arduino, or is it impossible?


texts: Constant current source to heat thermistor rapidly

texts:
My goal is to heat a thermistor as rapidly as possible.

The thermistor has a resistance value of 10k Ohms at 25 degrees C, and a negative temperature coefficient.

If I apply a constant voltage of 12V, the thermistor requires 30-50 seconds to heat up by 5-10 deg C above its starting temp. I would like the thermistor to reach 5-10 deg C above its start temp in less than 3 seconds, preferably within 1 second.

I am using a power source that can provide up to 30V, with a max draw of 3A.

I am considering using a constant-current source to try to achieve this goal, such as http://www.instructables.com/id/Constant-Current-Source-with-Operational-Amplifier/, but modified to provide greater current than the example project. Will this work toward my goal? Or are there better circuit options I could consider?


texts:
Following up on my previous question, I tried this simple circuit to ensure that there is a minimum load on my power supply (to prevent the unloaded supply from rising above Vmax of a part).  I actually built this and it works as I expect, but I wonder if there are any additions that should be made to improve its performance?

simulate this circuit – Schematic created using CircuitLab

My idea is, if the load (Rload) is disconnected or not drawing at least a minimum current, the supply rail will rise because of inadequate current through Rsource.  When the voltage reaches 9.6 (Vzener + Vbe), Q1 will start to turn on, and will sink enough current (and turn on the "Overvoltage" LED) to keep the rail below about 9.6V.

If the load is drawing enough current, the zener/transistor circuit will be inactive.

Incidentally, I believe that just a zener alone would be sufficient, except that it would have to shunt all the excess current itself.  By adding a higher-power transistor Q1, a lower-power zener can be used.


texts:
I was doing some exercises on transfer functions and ran into this RC Circuit.

I thought that I was allowed to add up the two resistors since they are in series.
Which makes that the voltage across all elements would be equal and Vin = Vout.

Although I am not completely sure if this is correct, could someone please verify or point me out my mistake?


texts: Does a VSR current rating affect the size of leisure batteries that it can charge?

texts:
(Apologies if this is a silly question, I don't do much electronics.)

I'm converting a van into a camper. I've bought three 12V 95Ah AGM batteries (which, incidentally, will be hooked up to a solar panel) that I want to be charged by the engine when I'm driving. I'll be hooking them up in parallel, meaning that essentially I'll have a 285Ah leisure battery.

It seems that the split-charging system I want is a VSR (Voltage-Sensitive Relay) between the starter battery and the leisure batteries. When looking into buying them, I see that they have different current ratings.

What is this rating relative to? Lower-rated ones are, of course, cheaper, but I don't want to sacrifice safety by shaving off some cost. Would a 140A VSR be okay? Do I need a 300A one?

(If I haven't provided enough information for an answer, feel free to ask for more details via a comment and I'll include them.)


texts: Errors in pin assignment for a SPICE file in Altium

texts:
I'm trying to simulate the following circuit in Altium before going to PCB route:

But I get the following pin errors:

I found the SPICE model and tried to assign them to this footprint:

Here is how I link the .ckt file:

Here is the how I made the pin assignments:

the rest of assignments:

And finally here is the SPICE ckt file's code:

*
*
* (DUAL) RETRIGGERABLE MONOSTABLE MULTIVIBRATOR
* Pulse Width Tw = 0.5 * R * C
* tpd R,A,B->Q     30n
* Tpulse 75n, C=0, Rext=5k
.SUBCKT 74HC123  A B CLR  CGND RC  Q QN  VCC VGND  vcc1={vcc} speed1={speed} tripdt1={tripdt}
.param egain=1/{vcc1}
.param td5=1e-9*(5)*4.0/({vcc1}-0.5)*{speed1}
.param td2=1e-9*(2)*4.0/({vcc1}-0.5)*{speed1}
*
XINA    A Ai  VCC VGND  74HC_IN_1  vcc2={vcc1}  speed2={speed1}  tripdt2={tripdt1}
XINB    B Bi  VCC VGND  74HC_IN_1  vcc2={vcc1}  speed2={speed1}  tripdt2={tripdt1}
XINCLR  CLR CLRi  VCC VGND  74HC_IN_1  vcc2={vcc1}  speed2={speed1}  tripdt2={tripdt1}
XINRC1  RC RCi  VCC VGND  74HC_IN_0  vcc2={vcc1}  speed2={speed1}  tripdt2={tripdt1}
*
* Model of a 74HC123 derived  from SGS-Thomson data sheet.
* Helmut Sennewald, 13.9.2002
A4 DHIGH 0 N014 0 N004 N006 N005 0 DFLOP   tripdt={tripdt1}  td={td5}
A3 0 N015 N016 N023 0  N014 0 0 OR  tripdt={tripdt1}  td={td5}
A1 Ai 0 0 0 0          0 N015 0  SCHMITT  Vt=0.46 Vh=0.02  tripdt={tripdt1}  td={td5}
A2 Bi 0 0 0 0          N016 0 0  SCHMITT  Vt=0.46 Vh=0.02  tripdt={tripdt1}  td={td5}
A6 0 N008 0 N006 0     N007 0 0  AND  tripdt={tripdt1}  td={td5}
A5 0 N009 0 N007 0     N008 0 0  AND  tripdt={tripdt1}  td={td5}
A14 0 N003 0 N021 0    N004 0 0  AND  tripdt={tripdt1}  td={td2}
A13 0 N003 0 N005 0    0 N030 0  AND  tripdt={tripdt1}  td={td5}
A12 N005 0 0 0 0       N012 0 0  BUF  tripdt={tripdt1}  td={td5}
A21 0 N010 0 N011 0    0 N009 0  OR  tripdt={tripdt1}  td={td5}
A22 0 N005 0 N007 0    N010 0 0  OR  tripdt={tripdt1}  td={td5}
A11 0 N013 0 N012 0    0 N003 0  OR  tripdt={tripdt1}  td={td5}
A7 0 N007 0 N018 0     QNi Qi 0  AND  tripdt={tripdt1}  td={td5}
A20 RCi 0 0 0 0        N011 0 0  SCHMITT  tripdt={tripdt1}  td={td5}  Vt=0.44 Vh=0.2m
A10 RCi 0 0 0 0        0 N013 0  SCHMITT  tripdt={tripdt1}  td={td5}  Vt=0.1 Vh=0.2m
A32 0 N006 0 N021 0    N022 0 0  OR  tripdt={tripdt1}  td={td5}
A31 0 N022 0 N023 0    N021 0 0  OR  tripdt={tripdt1}  td={td2}
A33 N021 0 0 0 0       N019 0 0  BUF  tripdt={tripdt1}  td={td5}
A30 CLRi 0 0 0 0       N023 0 0  BUF  tripdt={tripdt1}  td={td5}
A34 0 N007 0 N006 0    N020 0 0  AND  tripdt={tripdt1}  td={td5}
A35 0 N020 0 N018 0    N017 0 0  OR  tripdt={tripdt1}  td={td5}
A36 0 N017 0 N019 0    N018 0 0  OR  tripdt={tripdt1}  td={td5}
M10 RC N001 VGND VGND NMOS1
M30 RC N024 VCC VCC PMOS1
D1 RC VCC DIO1
D2 VGND RC DIO1
R10 N001 N002 100
R30 N024 N029 100
R3 CGND VGND 1
E4 RCi 0 RC VGND {egain}
E7 N029 VCC N018 0 {vcc1}
E8 N002 VGND N030 0 {vcc1}
V1 DHIGH 0 DC 1
.MODEL NMOS1 NMOS ( LEVEL=3  W=500e-6  L=1E-6  VTO=1
+ VMAX=1E6  RS=10  RD=10  CJ=0.002  MJ=0.4
+THETA=1E-6 ETA=0.01  KAPPA=2.2)
.MODEL PMOS1 PMOS ( LEVEL=3  W=500e-6  L=1E-6  VTO=-1
+ VMAX=1E6  RS=10  RD=10  CJ=0.002  MJ=0.4
+THETA=1E-6 ETA=0.01  KAPPA=2.2)
.MODEL DIO1 D (IS=10p RS=10 N=1.75 M=0.4 Cjo=6p TT=20n)
*
XOUT0  Qi  Q   VCC VGND  74HC_OUT_1X  vcc2={vcc1} speed2={speed1}  tripdt2={tripdt1}
XOUT1  QNi QN  VCC VGND  74HC_OUT_1X  vcc2={vcc1} speed2={speed1}  tripdt2={tripdt1}
.ends
*
*
*

I couldn't figure out where I am doing wrong. What can I do to solve this issue?