texts:
I need to make serial connection between regular PCs and a 3.3v TTL device, I using the Maxim 233 which has internal capacitors.
I have the PCs incoming TD connected to R1_IN and RD T1_OUT.
The ground pin5 is connected to the frame ground as well and its connected to the maxim233s GND.
What is unique in my setup that I running this chip from 3.3V instead of 5V because if I run it from 5V it will give out 5V on its low ttl part and can hurt the micro.
The outgoing data from the device to the PC works.
The incoming data from the PC to the device does not.
I can measure -10V if I check on the GND and the incoming wire.
Any ideas how to debug this any further? All the connections are triple checked and if it works one way there must be some minor issue. I use the same 9600 baud data rate for all tests on both ends. I have tried to replace the chip just in case that didn't solve anything.


texts:
I have a 1.1A, 33V resettable fuse in SMD 1812 package. To test it, I connected a 6A 20V source across it. It went up in a flame that lasted a few seconds. Should I conclude that the fuse is out of spec or this is this kind of known issue with resettable fuse of higher amp rating - 1.1A in this case?

A 250 mA, 24V SMD 1206 fuse from the same brand and a 500mA 60V SMD 1802 fuse from another brand held up well under the same test conditions.


texts: problem with using DAC with DMA and timer trigger

texts:
I'm trying to configure a  DAC with DMA and timer trigger to make a sine wave with 1KHz frequency(100 samples) and I'm using registers. my problem is that the DAC is not triggered when the timer value overflows. I wrote the code based on the reference manual and this site here what am I doing wrong here? is there something I'm missing?
my code has a main header and three other headers: DMA DAC and TIMER. this is the main
 #include "stm32f10x.h"
#include "TIMER.h"
#include "DAC.h"
#include "DMA.h"
#include  "math.h"

int main()
{
    TIM2_Init();
    calcsin();
    DAC_Init();
    DMA2_init();

while (1)
{

}

}

and this is my code for DMA
  #include "stm32f10x.h"
    #include "DAC.h"
    #include "usart.h"
     void DMA2_init(){

     RCC->AHBENR |= ( 1UL <<  1);            /* enable periperal clock for DMA    */

      DMA2_Channel3->CMAR  = (uint32_t)&sine_val; /* set chn1 memory address     */
      DMA2_Channel3->CPAR  = (uint32_t)&DAC->DHR12R1 ;      /* set chn1 peripheral address */
      DMA2_Channel3->CNDTR = sizeof (sine_val);         /* transmit word             */
      DMA2_Channel3->CCR   =

                               (1<<4)|   // Read from memory
                        (1<<5)|  // Circular mode
                                 (1<<7)|   // memory increment mode
                                 (2<<10)|      // size word
                                  (2<<8)|      // size word
                             (2<<12);  // Channel priority level High

      DMA2_Channel3->CCR  |= (1 << 0);        /* DMA2 Channel 3 enable  */

    }

the below code is for DAC
#include "stm32f10x.h"
#include "math.h"
#include "DAC.h"
uint32_t sine_val[100];
uint8_t Transfer_done;

#define PI 3.1415926

void Delay (uint32_t Time);

void calcsin ()
{
    for (int i=0; i<100; i++)
    {
        sine_val[i] = ((sin(i*2*PI/100) + 1)*(4096/2));
    }
}

void DAC_Init (void)
{

    RCC->APB1ENR |=  (1<<29) ; /* Enable DAC clock   */
    RCC->APB2ENR |=  (1<<2); /* Enable GPIOA clock */
    GPIOA->CRL &= ~0xF0000  ;
  GPIOA->CRL |=  0xB0000  ; // PA4  GPIO_Mode_AF_PP,Speed_50MHz

    DAC->CR |= (1<<0);   // DAC channel 1 enable
    DAC->CR |= (1<<2);   // DAC channel 1 trigger enable
    DAC->CR |= (4<<3);   // DAC channel 1 trigger selection timer 2 TRGO event
    DAC->CR |= (1<<12);   // DAC channel 1 DMA enable

}

and finally the code for timer is as follows:
   #include "stm32f10x.h"
int second;
int i;

void TIM2_Init (void)
{

RCC->APB1ENR |=(1<<0);

  TIM2->PSC   = ( 72 - 1);   /* set prescaler   = 1MHz  */
  TIM2->ARR   = ( 10 - 1);   /* set auto-reload = 10 us */

  TIM2->DIER = (1<<8);   //   update DMA request enable
  TIM2->DIER =(1<<14);   // trigger DMA request enable

  TIM2->CR1  |= (1<<0);   // 0x0001 timer enable

    TIM2->CR2 |=(2<<4); // trigger update event

}


texts: Are voltage transients on LTspice simulations significant?

texts:
I (incorrectly*) modeled this simple answer in LTspice IV and am seeing seemingly random instantenous voltage spikes up to +/-1kV on the output of the depletion nMOSFET.  Are these real?

If so, are they significant, and if so what standard practices are missing in this design to control them?

* Here is the correct model and output, which exhibits no voltage spikes.  (But I believe the question on the original circuit is still valid.)


texts: How to power up a project with 3 devices, between 0 and 12 volts

texts:
I'm working on a project which involves a DC heating element, a computer fan and an Arduino/ESP8266. I'd like to use one power supply for those devices.....

The requirements:

The heater needs a steady 12V / 1A DC
The fan needs 0 - 12V to operate
The Arduino/ESP8266 needs 3.3 or 5 volts
Here in Belgium, we have AC 220V mains electricity. I'd like to use 1 power supply (for instance of a laptop)

Here is a schema of the project:

I have 2 questions:

How much Volts/Amps does my power supply need, to get those 3 things working, safely, without overheating?
How do I connect the devices to the power source so that the Arduino/ESP8266 isn't getting to much volts/amps when the heater is switched off or the fan is shut completely down?

Looking forward to some suggestions!


texts: LM393N output doesn't behave as expected

texts:
I am currently working with the LM393N and am inconsistently getting a high output when it should be low. Below is a schematic showing the inputs and outputs of the IC.

VCC is coming from a "12V" rail supplied by a 12V zener with a 5K current limiting resistor and a 47uF cap in parallel (I know it's not ideal but I'm on a budget!).

The comparator is supposed to output a low signal, turning on the IL420 phototriac, when the capacitor (C1 on schematic) is discharged below around 1.5V. The expected output can be seen in the circuit simulation below. What's actually happening is the output stays high regardless of the capacitor voltage...... sometimes. Perhaps the most frustrating thing about this is that the problem only occurs occasionally, if I had to estimate it's probably around 10% of the time, the rest of the time the circuit performs its job admirably.

What I've already tried/checked:

The LM393N output is open-collector so I thought that the combination of the 3.3K resistor and LED internal to the IL420 may not be behaving as a suitable pull-up resistor, so I put a 4.7K resistor from VCC to the output. No dice.
The input common mode range is listed on the datasheet as 0 to VCC-1.5V max, so I put the 40K resistor in between the source pin of the 2N7000 and the comparator input to ensure that the voltage wouldn't exceeded 9.5V (the voltage across the zener occasionally dips to 11.5-ish but I believe the input voltage stays within range).
Maybe this goes without saying but I've checked that the cap is fully discharging, the (+) input is getting 1.5V and that the output is high when it shouldn't be.

Note - I know using an N-Channel MOSFET to drive a load on the source isn't necessarily best practice but this is a rough prototype at the moment.

Note numero dos - It's also worth mentioning that I am using both comparators on the chip and the other behaves as expected, at least so far.

Thanks for any and all help,


texts: Calculate power supply for step down modules

texts:
i'd like to build a system in which there will be step down modules that get their power from an ac-dc converter.

there are 5 modules connected to the ac-dc converter (each of them steps down to 5v/5a).
4 of the modules will power a peace of hardware that needs 5v / 3a
the 5th module powers an arduino or something like this.
i'm planning to input at least 24v (32 would be possible and preferred).

now the question: what power supply do i need? 220v ?a -> 24v or 32v ?a

i've been looking for calculators or discussions on this but it is a bit specific i guess.
so if anyone can help me i'd be really thankful!

Thanks in advance!


texts: Swapping Components and Reversing Polarity

texts:
I am having 2 DC motor, 2 Positive terminals & their negative Terminals. I want to build a circuit with 2 toggle switch so that when I toggle Both... It swaps the Motor and Change their polarity. That means

Before Toggle,

Motor-1

Left: +ve1
Right: -ve1

Motor-2

Left: -ve2
Right: +ve2

After Toggle,

Motor-1

Left: -ve2
Right: +ve2

Motor-2

Left: +ve1
Right: -ve1

I added an example so that it is easy for others to understand what I want. I tried to build the circuit but failed. Please Help.


texts:
To clarify what I mean by "in reverse" I mean in the context of something like an amplifier, if your input signal switches from +5v to -5v, does the output signal also switch polarity?
Coming from using transistors for computing I was under the assumption that transistors were more discrete than that. That if there is enough positive voltage on the control wire, then it becomes a conductor and if the voltage falls below a certain threshold it becomes a resistor. And it had never even occurred to me what happens when you reverse the polarity of the voltage on the control wire.
If transistors don't work in reverse as I described, then how do they work to amplify a signal like from a microphone where the signal fluctuates from positive to negative?


texts: mixing two different types of solar panels with different wattage

texts:
I have two solar panels (( Poly-100w(5.6A) - Mono-50w(2.6A) )) both have a voltage PmaX of 17-18v.

I want to connect the both of them in parallel and then insert them into a 10A solar charger.

Will I have any problem doing so, and will I have any reduction of the current in this state? please Help.


texts: 5V to 3V, calculate resistor value (or use diode?)

texts:
I want to connect this dv motor to the 5V output of an Arduino board. Of course I need to get the 5V down to 3V in order for the motor to function correctly. I've read that I could use a diode with the correct voltage drop for this, or just use a resistor.

Going the resistor way, I've got some trouble figuring out the correct resistor value.

From the datasheet I calculated that the resistance of this motor would be 40ohms at 3V (3 / 0.075 = 40). Is this correct?

The ratio between 5V and 3V is 0.6. So I figured I need a (40 * 0.6) = 24ohm resistor to get the correct voltage over the motor.

Are these calculations correct? I'm still an electronics beginner so I'm not quite sure :).
And even if they are correct, would I be better of using a diode (or maybe even a voltage regulator)?


texts: Proper way for best fidelity to ground 1980's pro audio mixer, will grounding to the case create noise?

texts:
love this forum, this is my first post so "beer" with me.
I am modding an old 1989 tascam mixer.  I know its probably easier to just buy something nicer, but I got it for free and I want to use it as a learning experiance, both in soldering new parts in, and in theory.  I have limited study in electric circuits but was a long time ago. I know some basics.  The mixer came orig with 2 prong no ground.  Someone has modded to add a ground and bonded it to the case. Now I havn't turned it on becuase the caps are toast and I am building a new power supply that is in its own case with a new transformer/caps.  So I can change the power supply so it is isolated and then I wouldn't need to bond the case to the mains ground I think? I just don't want to have the mains ground bonded to the case if possible to keep unwanted noise out. The mixer has balanced and unbalanced circuits.  I am changing the op amps to LME49724, and changing some resistors and faders.


texts: whats voltage drop on 40 yards of ws2815 leds

texts: We are working on a project of using ws2815 led strips and our concern is how to handle the voltage drop?


texts: How does the formula for calculating Low and High Frequency in a Band-pass Filter occur?

texts:
Our professor told us that we should use the formulas below to calculate the
F-high and F-low frequencies that our band-pass filter should have.
$$F_\text{low}=\frac1{2π\,R_1\:C_1}$$ and $$F_\text{high}=\frac1{2π\,R_2\:C_2}$$
My question is how can someone mathematically explain those formulas.
How do these formulas come to be?


texts:
When I tried to plug my AC adapter was broke. Here you can see it:

It's only the wire so I can replace it without any problem from my AC adapter. But my question is: Can I use any wire (while it has the same connector) or I have to check the voltage too?

I have an old wire with the same connector, I tried with it and it works. But I don't know if I can use it or it can damage my AC adapter (sending different voltage for example, I don't know). Here you can see physical differences (the old wire connector looks like the same, but I found a little difference, the holes are a a little bigger than my actual wire): http://postimg.org/image/j1obisnzr/


texts: ATXmega128A1 USARTD0 RX not working, but F0 does with the same code

texts:
I have a problem with my atxmega128a1. I wrote a code using 3 usart interfaces. The init code is the same, but only two of the ports works fine.
The problem is with USARTD0 (and I tried USARTD1, but also fails)
The sympthom is the next: first USARTD0 inited to 9600bps, and after a few transmission, it has to init again to 115200bps. After setting up again to he new baud, it stops recieving. I can send via TX, but USART_RXCIF_bm never set.
It is so strange, beause the same code works fine with other ports. I have checked my code, and wiring many times.
Does anyone have any idea? I dig in erratas, alternative functions, etc. but haven't found any useful yet.
Thanks in advance, and sorry for my rough English.

void uart_init_d0(long baudrate){
usart_rs232_options_t options = {
        .baudrate = baudrate,
        .charlength = USART_CHSIZE_8BIT_gc,
        .paritytype = USART_PMODE_DISABLED_gc,
        .stopbits = 0 // 0=>1 stop bit
    };

    PORTD.DIRCLR   = PIN2_bm;   // (RXD1) input
    PORTD.DIRSET   = PIN3_bm;   // (TXD1) output

    sysclk_enable_module(SYSCLK_PORT_D, PR_USART0_bm);
    usart_init_rs232(USART_BAY2, &options);

}


texts:
Well I was learning transmission but I got a bit confused when I came to coaxial cables transmission at radio frequency.

What I am lost is how the waves are propagating in the cable, I was thinking that AC current just flows through the conductor just like a normal 2 wire system to the antenna. But the electric fields are not in the direction of the current but is in only between the two conductors (inside, and outside).

Why is this? I am so confused


texts: Charge and power distribution circuit with multiple batteries

texts:
I’m looking for solution for electric vehicle charge and power distribution system PCB.
For some reasons I want to split battery to several Li-Ion packs in separated units (hulls). I see the next possible setup for me, as shown in the Fig. 1 below.

The main question for me is the realization of such kind of “parallel” connections of chargers and power sharing between battery units and System Load. Is this a right way for such setup? I’m understand that batteries will try to equalize voltage between the units, but it is acceptable for me.
I want to use one of the Analog Devices (or another) charger IC’s and connect several chargers like as shown on Fig. 2 below. What could go wrong?

Also maybe there are similar on-the-shelf solutions or best ways?


texts: Insufficient ground supply on my circuit? Ground capacitive foil

texts:
I'm playing with a wireless sensor device (with atmega, xbee, and Capacitive sensor (simple foil)) that works fine with the lab power supply but as soon as I try it with AA batteries stops working. Wireless communication and atmega seems to work fine, but de Capacitive sensor (I use and arduino CapSense library) dosn´t work. It seems to have something to do with the GROUND from Capacitive sensor
I've also tried supplying power directly to the battery box, so no wires seem out of place neither...

Any tipps, recomendations, or saviour tests?? Sorry if I ask a basic concept... I´m newbie...

EDIT: I reformulate  ask and attach an image

Thanks,

Xavi

EDIT2: Thanks Ambiorix for explain me the problem on my circuit!


texts: I am working on a buck boost converter to buck from 24 V to 5 V and boost from 5 V to 24 V. When I have to boost the voltage, I am unable to boost it even pass the input voltage. I think it is due to the insufficient gate voltage as I only have 5V input and I am not allowed to have any other external power. I am using IRF540 for switching. This is my simulation diagram. As soon as I change the 'Pulse High Voltage' to 14V, the simulation works fine. What can I do now to get my circuit in a working state?


texts: Is it possible to approximate specs of a LED?

texts:
I am thinking about gutting a few infrared LED's from some old remote controllers and using them as part of a battery powered wii sensor bar. Obviously, I do not have the spec sheets for these LEDs, so I don't know the maximum and minimum voltage inputs, max currents, etc. Calculating the needed resistance required may not be possible.

Is there some kind of test that would allow me approximate said specs without destroying the LEDs? Or is reusing parts (without available specs) generally considered bad practice? I don't want LEDs to explode or catch on fire.


texts: When multiplexing audio do I need a pre-amplifier for each channel?

texts:
I am building a 16 channel multiplexer which will deliver the input from 16 microphones to a single ADC. I am clocking the ADC at 1.6 MHz and therefore sampling each audio channel at 100 kHz.

The ADC resolution is 12 bits, I cannot change the ADC because I am modifying a design, not starting from scratch. The ADC range is 2V. This is the microphone I am using:

http://www.farnell.com/datasheets/97498.pdf

I am realising this using 5 LMH6574 4:1 multiplexer chips, 4 used for the 16 mic lines then the fifth for the 4 outputs to produce a single output - The select lines for the first four are driven from a 2 bit binary up counter - a second up counter runs the 5th chip at CLK/4.

My question is this: Is it better to use an audio pre-amplifier for each channel - before being put through the multiplexer - or use a single pre-amplifier after the multiplexer stage?

I assume that if a single pre-amplifier is used it must have a bandwidth of at least 1.6 MHz, is this correct? - Will a high frequency pre-amp cause a loss in quality at the audio frequencies (compared with a hifi pre-amp chip)?

I also assume that the settling time of this amplifier is the all important factor, are there any rules/common practices defining what percentage I should be within (2%,1% 0.01% etc)?


texts: Iam doing a DC only backup system with ATMega328 MCU. It supplies full time DC to vaious devices. How can I measure the current usage of each device. The power loss for measurement is thought to be very less. Would you pls suggest a best way? Thanks.


texts: Predicting and Evaluating Connector Performance in a Capacitive Sensing Application

texts:
I have built a capacitance measuring system using the Texas Instruments FDC2214EVM evaluation module. The system is used to monitor the location of the user's hand in an enclosed space, where capacitance is mapped on to displacement.

Operating Principle

The FDC2214 device measures capacitance by determining the resonant frequency (40MHz or less -- in my case, roughly 5-10MHz) of an LC tank circuit connected to a capacitive sensor. As the sensor capacitance varies due to proximity of the user's hand, so does the resonant frequency of the circuit. Because all other parameters of the LC tank circuit are known, the resonant frequency of the circuit can be used to calculate the sensor capacitance, and therefore displacement.

System Configuration

Four capacitive sensors are connected to the FDC2214EVM -- one for each of the evaluation module's four inputs. Each sensor is a 5cm x 5cm piece of copper tape mounted on an acrylic plate. Each sensor is connected to the FDC2214EVM using 1m of coaxial cable.

At the FDC2214EVM-end of the coaxial cable, two jumper wires (small segments of 22759/32-22 wire terminated with Mini-PV connectors) are soldered to the conductor and shield, respectively, and plugged into female headers on the FDC2214EVM for sensor input and ground, respectively.

At the Sensor-end of the coaxial cable, one jumper wire is soldered to the conductor and plugged into an inline Mini-PV receptacle. On the other side of this inline Mini-PV receptacle is a wire that is soldered to the copper sensor.

Question

I am considering replacing the Mini-PV inline plug-receptacle assembly between each coaxial cable and each sensor. I am concerned that the use of these connectors might lead to reliability issues, because of:

Changes in connection quality after many mating cycles
Loosening of the connection due to mechanical disturbance

Ideally, the chosen connectors should not affect the noise-level of the capacitance signal. If a connector introduces a constant offset capacitance, this is manageable, as the offset can simply be removed during data processing.

I have decided that, because the capacitive sensors will be removed and stored each time the system is used, the chosen connectors should:

Be crimp connectors, which are, to my understanding, more tolerant of mechanical strain.
Be latched, to prevent loosening due to tugging, etc.

I am exploring the option of using Molex Mini-Fit Jr connectors (see my associated Digikey cart: https://www.digikey.com/short/ztdzv4) instead of the Mini-PV connectors. They meet both of the requirements above, and also have a relatively cheap manufacturer-approved crimp tool, unlike many other connectors. That being said, this sort of connector is often used for power supplies and the like, which is very different than my application.

I am curious to know if anyone has any advice regarding which type of connector would be best for this capacitive sensing application.

Thank you,
Dylan


texts:
I am building an audio crossover with time alignment based on Douglas Self's design. I desided to make an algorithm to calculate best resistor pair. The first part is easy:

Make a list of all resistors in E24 series.
Calculate parallel resistance for all combinations of two resistors.
Compare it to the target value and get error = calculated / target.
Return value with smallest error.

Now here's the part that I can't figure out. I use resistors with 1% tolerance. If I use two in parallel the combined deviation supposedly goes down. How do I calculate the exact value by how much the deviation goes down and how do I combine it with error from previous part to get the best pair?

UPDATE:
On @jonk 's recommendation:
r1_deviation_facror = 1 ( 1 + R1/R2)
r2_deviation_facror = 1 ( 1 + R2/R1)
combined_deviation = sqrt(r1_deviation_facror^2 + r2_deviation_facror^2)


texts: Signal response and settling time graph analysis

texts:
I have come across a datasheet of an instrumentation amplifier. I have a difficulty in understanding the signal response vs settling time graphs. Can someone please explain figure 28(page 10) of the provided datasheet in the link??

AD620 instrumentation amplifier datasheet


texts: Why can my body conduct electricity from a 9 volt battery?

texts:
I've created a scenario represented identically in the attached image . My question is this:

When I connect Jumper 1 to my left hand and Jumper 2 to my right, the LED turns on very faintly but I feel no shock. I have done much research that all seems to contradict itself and I simply cannot understand: How is the electricity travelling through my body, and at what voltage and amperage?


texts: I need helping understanding this VCO circuit

texts:
The two circuits of interest are described in pages 12-14 of Texas Instruments' Application Note 263, Sine Wave Generation Techniques PDF WARNING

I'm primarily concerned about the circuit in Fig. 15, but the circuit in Fig. 14 is its predecessor, which has some additional notes. I only need to understand the stages up to the triangle output. The logarithmic shaping stages aren't of interest to me.

The extent of what I DO know is the following:

Comparator = Square wave out put, obviously.
Square wave into integrator = triangle wave. So far, so good.

What I don't understand:

A lot.
How does the FET arrangement turn a simple constant voltage into an oscillatory behavior?
Why does the comparator need to be biased?

If you can ELI5, you'll be my hero. Currently I've only studied passive components and op amps. My knowledge of transistors (particularly the properties of real transistors) is essentially nonexistent. Thanks in advance for your help!


texts: Understanding a variable 220v AC to DC Power Supply

texts:
Can someone just please explain how and why the diodes D3 D2 and D4 are used?
Why D3 is single while D2 and D4 are in series?
How do we calculate the capacitance of capacitor required in a circuit like this?

Please, be a little descriptve I am a newbie.

Thanks to everyone in advance


texts: Magnetic induction on data lines from DC power lines

texts:
I have experienced failures of RS-485 links due to magnetic induction from ~52V battery power lines running very close in parallel. Standard shielding around the RS-485 cables did not solve the problem but a clearance distance of 1 inch did. The fault probably occurred when a high current such 90A was interrupted by the opening of a relay or a breaker. I have the following questions about such cases:

Standards: Is there any accepted guideline regarding clearance distances in this particular scenario? The recommendations I have seen are based on house wiring cases where there is a chance of shorting the data and power lines running through walls. Moreover, section 1.16 "Electrical Clearance" of IPC-A-620B (2012) leaves clearance spacing between cables up to design and only gives guidelines based on voltage. And while the IEC 61000-4-x tests appear to be very applicable here, they would apparently focus on protection at the transceiver level.
Calculations and simulations: What is the recommended approach for calculating the induced voltage or power in such cases? Which tools are prevalent in the industry for computer simulations of such scenarios? Are such calculations followed by experimental testing?
Behavior of DC current at trip: This is a more general question. For simulating scenarios like the one described, I will probably need to assume a maximum di/dt value. How fast and in what manner does a DC current terminate when its path is broken with an MCCB or a latching relay? Is it dependent on the source and load? Can waveforms from other cases be applied for this case or will I have to gather empirical data for my own system?


texts: More transmit power for 433MHz transmitter module by increasing voltage

texts:
I am using these 433MHz modules. According to the product information, I can supply the transmitter from 3-12 Volts. I am sending the data from an arduino (5V data) and want to power the transmitter with 12V that I am still be able to receive the data some meters away from the transmitter.

Can the transmitter still determine if it was a high or a low, when it is powered with 12V and the max data voltage is 5V or do I need a driver circuit?


texts: What software to graphically design a simple schematic?

texts:
I need to draw a schematic similar to that shown in the figure attached in this question.
Are there softwares that allow to graphically design a schematic like that?


texts: How to define a GATT profile for a BLE peripheral?

texts:
I have just bought a BLE device that can act as peripheral or central (a BLE mini).
Out of the box the device is like a wireless UART as a peripheral.

I looked at the example chat app under the hood and a TX characteristic is defined.

How can I now use the peripheral not for the example chat app, but for my needs, and define my own services/characteristics ? How do I setup the BLE peripheral with my own Gatt profile ? Is it a protocol that is used everywhere or is it proprietary to the BLE module maker ?

I just keep seeing on my web searches definitions about GATT and characteristics and how to use it etc, but never this info.


texts: Closed-loop position control with a stepper motor

texts:
Disclaimer: I understand this might not be the optimal setup for this application, but this is what I currently have available.
My controller is connected to:

a stepper motor with a lead screw for moving a load on a single axis;
a linear hall sensor for sensing the position of the load over the entire lead screw range.
an external MPU that is setting the target position.

Controller Requirements:

The system needs to work under a variable load. the variable load might almost reach the maximum force available from the stepper motor.
Minimize the settling time of moving from one position to the other.

After looking at the torque-speed curve of the stepper motor, these requirements seem to contradict each other: minimizing the settling time requires operating the motor at high speeds, but for getting a high force to overcome the high load, the motor should be operating at low speeds.
(Intuitively, I would say the motor speed should have a proportional error term; and a reciprocal of the error time integral term)
Are there any known feedback equations for this case?
It sounds to me like this problem should be very common, and probably has been discussed in books about servo control.
Are there any books you can recommend addressing this issue?


texts: Why no IEEE 802.11 version use 24 GHz ISM band?

texts:
IEEE 802.11 aka WiFi uses multiple ISM bands to transmit data,2.4,5 and 60 Ghz.The 24 GHz was never used in WiFi,why? Why did they jump from 5 to 60 and ignored 24? Why no wireless standard use this band?

I only saw this 24 band being used for car radar in older models,new cars use 77 GHz.The 24 GHz have big bandwidth and its worldwide avaliable ISM band,it seems perfect for some kind of short range domestic wireless aplication,it seems strange than nobody is using it.


texts:
I'm really confused in solving the following question.

  An isolated 50 Hz synchronous generator is rated at 15 MW which is
  also the maximum continuous power limit of its prime mover. It is
  equipped with a speed governor with 5% droop. Initially, the generator
  is feeding three loads of 4 MW each at 50 Hz. One of these loads is
  programmed to trip permanently if the frequency falls below 48 Hz. If
  an additional load of 3.5 MW is connected then the frequency will
  settle down to ?

Here, is my understanding of the question. At 15 MW load the frequency should drop by 50*0.05 = 2.5 Hz so the load would be working at 47.5 Hz. Now the new load is 4*3 + 3.5 MW = 15.5 MW which is above the maximum capacity and also the frequency would have fallen below 47.5 Hz, so one of the load has to trip. So the new load = 4*2 + 3.5 MW = 11.5 MW.

If we consider linear droop from the generator the linear equation relating frequency to power would be

$$ f = -0.05P + Constant(K) $$
To find the constant we put f = 50 Hz at P = 12 MW (given in the question).
So we get K = 50.6. So at 11.5 MW the frequency would be
$$ f = -0.05 * 11.5 + 50.6 = 50.025 Hz $$.
But the actual answer is 50.083 Hz. I know I differ slightly from the actual answer, I was wondering if my understanding of the question was right or wrong.


texts: Standard Peripheral Library and HAL drivers together in Keil

texts:
it seems that:

ST has moved to Cubemx code initializer and generates only HAL
drivers
Keil has introduced DFP and Manage-Run-time-Environment which
use HAL drives

although ST's cubemx and Keil's run-time-env so useful are so handy, but HAL drivers are somehow buggy yet. meanwhile there are lots of codes on git-hub,etc for Stm32F4 all written with Standard Peripheral Libraries(std_lib) .

Is it possible to use both Standard Peripheral Library and HAL drives together in one Keil project?


texts: Is it possible to use EL3 on an AllWinner SoC (R18)?

texts:
I have been looking for a cheap development board to play around with ARMv8 EL3 mode in the interest of writing a monitor. I stumbled across the PINE64 recently and it seemed like a great fit. It used the AllWinner R18 ARMv8 SoC and had JTAG support. However, I began searching about and discovered trace comments about essentially being locked out of AllWinner SoCs at EL3.

According to the PINE64 wiki page, the SoC's ROM will look for payloads over USB-OTG or an attached SDcard. Lots of talk about EL2/1 during this time.

However, there is also this mention of the ROM loading from sector 16 of the SDcard and executing it in aarch32 mode. It does not mention the ELx level, but perhaps it is from EL3? Unlikely, unless that was their intent. Does anyone know for certain?

Also, I've been unable to find an AllWinner R18 datasheet. I am unfamiliar with the company: do they typically require an NDA for this information? Older SoCs do appear online.

I have pending support emails to both companies at the moment, I just wanted to probe the community as well for real experience with AllWinner SoCs.

As an aside, and this one might go against the rules here, does anyone have experience with a decent ARMv8 development board that is debuggable and has EL3 support? I've found the Juno, but it's expensive and I do not need all the extra features.

More community conversation about the AllWinner SoCs and whether or not they support running user code in EL3. Several people chime in and report conflicting information. https://news.ycombinator.com/item?id=13397994


texts: How to combine and protect two 12V automotive signals into one?

texts:
In the below circuit, the DC component (6V) of a bridged car head unit speaker wire turns on a LM53601 buck converter. The LM53601 accepts voltages up to 42V. The +12V input into Q2 is protected to withstand the pulses described in ISO 7637. I have used this circuit in my car for some months now, and it works fine.

But now I want to extend the functionality so that the LM53601 is turned on either with the +6V speaker signal or when the ignition is turned on. The EN signal of the LM53601 accepts up to 42V, but I believe that I will have to protect this input for the pulses of ISO 7637 as well. My proposed solution is shown in blue where I suggest to use TVS-diodes and a reverse polarity diode. This seems like an overkill solution to me, but I have not found any other way to protect the input.

My question is regarding Q2. Should I put a diode (STPS2200U) or a resistor (or both) in the point where I have drawn a red arrow? The 3906 PNP transistor specifications are listed below.

Update: The transient protection circuitry was taken from a TI reference design using a similar buck converter that has the same voltage input range (see below). This passed ISO 7637 testing so that is why I thought it was smart to use the same design. The design uses a smart diode controller (LM74610) for reverse polarity protection, but I have used a 200V Schottky instead which I believe should be ok.


texts: I understand that Preset and Clear inputs are asynchronous inputs which means whenever Clock signal is low one of them can immediately set the output to 1 (Preset) or to 0 (Clear) (assuming they are active high inputs). But I wonder what happens when one of those inputs has been set to 1 when Clock was 0 and then Clock goes 1. Does J and K ovewrite Preset/Clear or they have to be released to let J and K affect the output?


texts: How can aluminium cables be lengthened for automotive environment?

texts:
My company's business is stretching and armouring cars. In the former process we must also lengthen all the wires. We've just come across aluminium cables, which pose a problem — until now we used to cut and solder the cables together with the extension.

The sections we have to deal with are (in mm²):

0.5
0.75
1
1.5
2.5

I'd like to know what [industrial] options are available to stretch aluminium cables. There is one possibility that is out of question: replacing entire cables with longer ones. We don't have all the connectors since not every single of them is available, some are proprietary and brand-specific. So we're left with actually "stretch" the cables.

So what are the available options?


texts: Could somebody please tell me where to find wire in the NI Multisim to connect logical gates to the VCC? I cannot find it.


texts: What defines Volts, Amps, Watts and mAh?

texts:
My current understanding is as follows:

Volts: Speed of electron flowing.
Amps : Number of electrons flowing.
Watts: Amps x Volts measured for "some" time. mAh: Very confused to
come up with anything at all.

I don't think these definitions are correct, what should they be?


texts: Is a single FET a good way to drive a 100kHz signal through short coax?

texts:
I'm trying to transfer a small (1V)  variable frequency signal over about a metre of coax.  I'm not interested in anything above 100 kHz. One thing to note is that my signal already comes with a +24VDC offset.  So I have this:-

based on this from a proper coax driver datasheet (Intersil HA-5002 driver):-

The HA-5002 is essentially a current amplifier, so I have my FET set up as a voltage follower.  The Spice simulation seems to suggest that it works, with the expected 50% signal reduction at the end of the coax.  The response is -5dBV over the 100kHz bandwidth.  R1 (1.5k) runs a little warm as it's getting towards the top end of its power dissipation, but heat sinking a coax driver doesn't seem unusual.

This circuit seems very simple and the question is, therefore, is it too simple?

PS.  I've looked at many driven coax arrangements here and elsewhere.  The way it's done seems uncertain with 50Ω resistors, here or there. Sometimes there's just one 100Ω resistor at the source.


texts: Receiver and transmitter with the same antenna

texts:
I want to build a simple transceiver (half duplex) for 433.92 MHz ASK modulation. I have found a transmitter chip and a receiver chip that I want to use. I want to use the same antenna for RX and TX but I am unsure of how to approach this (The receiver can handle the full output power of the transmitter). I do not want to buy a ready-made circuit for this, I'm doing this mostly to learn.

The antenna is 50 ohms but the receiver and transmitter both have their own impedances and need some matching network. If I used separate antennas this would be simple (say a PI attenuator).

But I’m unsure of how this would work with having both RX and TX on the same antenna. My very naïve approach to this would be to use a splitter/combiner after the matching networks and accept the -3 dB loss from this. This way every side sees 50 ohms.

But this feels very wrong and any input here would be much appreciated!


texts: Effect of temperature on Radio Components

texts: Just starting to gain understanding on how various Radio components work (PA, LNA, LO, Mixer, etc.). Every component has ratings from the component manufacturer. I am curious to know, what effect we may see when these radio components are exercised to extreme temperatures. How does temperature affect the Radio performance?


texts:
Can you please help me converting following to standard POS

A(A + C')(A + B)

I have done the following so far

(A+AC')(A+B+C.C')
(A+AC'+B.B')(A+B+C)(A+B+C')
(A+AC'+B)(A+AC+B')(A+B+C)(A+B+C')


texts: Can I put negative voltage to the signal input of the ADS8317 A/D if I use a sufficiently large series resistor?

texts:
The datasheet of the ADS8317 A/D converter shows that it has protection diodes on the signal inputs, which have a VF of 0.35V. The maximum ratings say "Input current to any pin except supply: -20mA to 20mA" It also says "Analog input voltage: –0.3V to VDD +0.3V"

I have seen similar absolute maximum ratings before where both maximum voltage and current were given, with a comment saying that some overvoltage is fine as long as the current doesn't get too high, but this isn't explicitly said here.

My input signal is in the range of 0V to 0.8V at the times I want to measure it, but between those times it regularly goes down to -0.8V. Currently I plan to protect the ADC from this negative voltage with an additional op amp that is explicitly tolerant of over/undervoltage (indicated in the way I mentioned above), working from a 5V single supply so that it can't produce negative voltage at the output.

However, this has the drawback that I can't measure all the way down to 0V, even though the op amp is Rail-to-Rail. I don't actually need to measure that far down as part of my application, but it would be great for easy calibration of system offset. The extra amplifier also adds its share of errors and signal delay (which isn't really a big issue, but less of that is always better :))

Do you think it's OK to put negative voltage to the analog inputs as part of normal operation, as long as you don't exceed the current limit? Given the RC network I already plan to place at the input, the current should be 1mA maximum under normal circumstances, and that only for 100µs each millisecond.


texts: How do I know where I need decoupling capacitors?

texts:
I'm building a motor driver shield for the Arduino. Here's the schematics (please forgive the messy layout):

And here's the PCB layout:

I'm testing it out by breadboarding it while running a simple 'run for 5 seconds then reverse' procedure on the MCU, and I'm experiencing some odd issues with decoupling capacitors. If I leave them off, the motor stutters rather than moving smoothly, presumably due to the motor's power rail dropping. I put a 100uf electrolytic capacitor across it (shown on the board), and it started running smoothly.

Now, however, the motor reverses seemingly at random, I presume as the MCU is being reset for one reason or another. Following the 'more capacitance is better' mantra, I installed the second electrolytic cap, between the 5v and ground rails. Now, weirdly, we're back to step 1: the motor stutters.

Finally, I added a third, 0.1uf ceramic cap across the motor terminals. Suddenly, everything is fine: The motor runs smoothly, and it reverses when it's supposed to.

Adafruit's shield seems to solve the issue by just throwing lots of caps, both electrolytic and ceramic, at the problem. Unfortunately, as you can see, I have quite limited PCB space, so I can't afford to do that. I could take the cargo-cult approach and say "it's working now, great" and stop, but I'd rather understand what it is that caused each of these symptoms, and what I should do to ensure they don't happen on the real board.

The first answer to this question answers most of my obvious queries about capacitance, but I have a couple of remaining ones:

Is the 100u and 0.1u cap between the 5v (logic) rail and ground that Adafruit's shield has necessary? Removing it on my breadboard seems to have no effect.
Do I need the 0.1u ceramic caps across both the motor rail on the H-Bridge input and directly across the motor terminals?

Edit: I've updated the schematic and PCB layout with the proposed positions of caps, based on the advice of those kind enough to answer my question.


texts: Looking to drive an ST-Link in standalone mode

texts: At present I have one connected to interface the IAR EWARM s/w running on a PC. Does anyone do a standalone program just to take an output file and burn it to flash? [I'm using STM32F303x MCU]


texts: What negative Gate to Source threshold voltage means in MOSFET datasheet?

texts:
I have seen certain MOSFET data sheets with a negative threshold voltage, like:

Si2301DS Gate-Threshold Voltage \$V_{GS(th)}\$ = -0.45 V
AO4425 Gate-Threshold Voltage \$V_{GS(th)}\$ = -3.5 V

Does it mean the MOSFETs are depletion type? Does it mean that if I do not apply any gate voltage and pull the gate to 0 or ground, they will still conduct until it is made below -3.5 V? Can someone please explain?

I am looking for MOSFETs that will switch off when Li-ion cell voltage reaches 3.3 V or lower.


texts: "Halt and Catch Fire" BIOS cloning scene unrealistic?

texts:
The first episode of the TV series "Halt and Catch Fire" (inspired by the early days of Compaq) has two characters starting to clone the IBM PC BIOS in 1983 by creating a circuit that would display the binary contents of an address with lights, one guy reading off the contents of each of the 65,536 addresses as hex values, and the other guy writing them down. A later scene implies that they then entered the data in some other system and printed it out on a line printer.

Would it really have been a significant technical challenge at that time to read the contents of the chip and write it to diskette?

The BIOS was documented in the "IBM PC Technical Reference Manual" so there was no need to do that anyway, but I'm still curious about how realistic the scene was otherwise.

PC Magazine 1982 article The Key to the PC from Google Books


texts:
I'm working with MODBUS interface, based on a usb dongle which converts usb to RS485, then, in my board the rs485 half duplex is passed to max3362, as shown.

The data is passed to NXP K64 controller. My problem is that at the end of the modbus package the CPU is sending there's sometime an extra byte which causes the receiver to show an error.
For example:
This is the data the controller should be sending to the host:
0B 03 02 0F FF 65 F5.
The bold 65 F5 is the crc.

Instead, sometime, it sends:
0B 03 02 0F FF 65 F5 C0

So, apparently, there an extra byte C0, which causes an error at the host side.
I've tried with various USB dongles, at some, it seems ok, at some, it seems there's an error.
I do not know what is the cause of the error, is it the board, FW, or dongle?
Any ideas?
I'm really stuck here.


texts: How can I convert a pulsed signal to an analog voltage?

texts:
I would like to measure the speed of a DC motor using a phototransistor and get as an output a voltage which varies linearly with frequency.

The motor speed can vary from 0 to say 3000 RPM. Using the phototransistor I can easily get a signal whose frequency varies from 0 (DC) to 50 Hz. I would like to convert this signal to a voltage which varies from 0 (or close to zero) to 5 V linearly with the speed of the motor (and therefore with the frequency of the signal obtained from the phototransistor).

I know that a simple solution would be to use a microcontroller to calculate the period of the signal from the phototransistor and then output the corresponding PWM voltage, but I'd like to keep things analog and not use a microcontroller, if possible. What circuit can I use to achieve this?


texts:
And, I honestly have no clue as to where to start. I've gotten about as far as downloading and installing CodeSourcery Lite...and that's about it.

I'm comfortable with C, I'm comfortable with vim, couldn't do a make file if my life depending on it. Most of my C projects have been small enough to not really require build scripts, which is probably the key reason I haven't learned make.

Most of the tutorials that I've googled up are for something different (and I don't know enough to make the changes for what I have) or just not very good.

My goal as of now, is the make the LEDs blink.

I can break it down (I think) into two questions:

Where do I find documentation for this thing? I have the example code, but is that it?
What exactly ARE the compilation to hex to board steps?


texts: What causes saturation in a Bipolar Junction Transistor

texts:
Given above is a familiar picture of the output characteristics of a Common Emitter Transistor, it is clear that collector current,\$I_c\$ at first increases linearly with Base voltage,\$V_{cb}\$ and then attains saturation.

What is the cause of this phenomena?

Does it have to do something with threshold current?

Also at equilibrium, when no current is flowing through the transistor, is there the presence of depletion layer?


texts:
Lets say I have a 500 watt, 12 volt DC power supply. This means I should be able to draw roughly 41 amps (12V*41A =~ 500).

This is far more current than my mains power can provide. My circuit breakers are like 15 amps.

Well, also the supply side is at a different voltage. It supplies power at 120 volts AC. So, 500W / 120V = 4.1A, it should draw about 4.1 amps to supply the required power. Well within my mains power spec.

Here's where I get confused. Since the ampere is a measure of "charge per second" does this mean there is more charge coming out of the PSU than going in?


texts: Do I need to make a DC path at the input of an op amp?

texts:
I've heard that a DC path is needed
at the input of an op amp,or the op amp
won't be functional because there is no
path for the input bias current.
(in the image below,R1 provides a dc
path for input bias current)

But if I use MOSFETs to design an op amp,is there still input bias current(the gate of MOSFETs have no current)?Or do I still need to add R1 to make op amp functional?

if R1 is needed,can it connected to a DC voltage source or it must be connected to gorund?


texts: Opto-coupler circuit - selection of resitor

texts:
I have a circuit like below.

I wanted to know how these resistance values were calculated. I wanted to use 12V/24V in place of 9V.

Let me know selection of opto-coupler and resistance value.


texts: Is the following USB connection possible: Host USB to converted to serial (FTDI) and then converted back to USB (FTDI)

texts:
I am trying to connect a host USB device on one board to an endpoint USB device on another board, but I am required to send the link between the two devices as a serial (UART) connection between the two boards. The USB to Serial and Serial to USB converters would be housed on the individual boards that house the respective host and endpoint devices.

I need the host USB device to recognize the endpoint device as a USB endpoint just the same as if it were a direct USB connection.

Is it possible to get this work in the way I need? I understand the communication speed would be much slower than conventional USB. I have seen FTDI conversion chips that claim to work up to 3Mbaud, (like this one: https://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT234XD.pdf)  and I would think ~2Mbaud would be sufficient for what I am doing. The chip I linked seems to be exclusively for USB host devices to convert to serial out, I have not been as successful at finding a device expected to work in the opposite direction (serial to USB endpoint).

Has anyone done something like this successfully before, or perhaps can identify to me that this is impossible for reasons X, Y, Z?


texts: How to safely ground a switching power supply with floating outputs?

texts:
I just received a 120VAC to 5VDC (20A) switching power supply (the kind with a passively ventilated metal casing) for use with a microcontroller project I'm working on (driving long LED strips).

I've wired up Line-Neutral-Ground correctly to a 3-prong plug. It tests out fine (and the case IS bonded to ground internally) but I see the outputs are labeled DC- and DC+ and indeed DC- is not bonded to ground so the outputs are floating (though I'm not detecting a high voltage differential).

Is there any danger in bonding the DC- output to Ground with a short wire, to ensure my circuit ground is also referencing the home ground? I'm not sure simply letting the outputs float is wise, but I don't want any dangerous side-effects if I ground DC-. (The circuit sharing this power will at times be connected to my PC which is itself quite thoroughly grounded so I'm inclined to emulate that behavior.)

Side-note: I have an after-market laptop supply that's two-prong... it works either way, but if I plug it in one way the metal trim on the laptop has an interesting "buzz" to the touch. Not shocking, but definitely noticeable. I suspect that when it's plugged in the right way the output ground is weakly referencing neutral, and the "buzzy" way has the output ground weakly referencing line voltage (it's floating - it'd be quite a bit more than buzzy otherwise). The OEM supply with the 3-prong plug? Fully grounded to the shield of the DC power cord.

So I suspect that when it comes to AC to DV power, getting Line and Neutral wired up wrong is far more risky than letting the output float, and that grounding the output is preferable to letting it float if you're working in an environment where you'll interface directly to grounded equipment. I just want to be sure...


texts:
I am trying to find the simplest way to mill this PCB with an Othermill:

Image 1

Image 2

I currently have both images saved in the R13 DXF format.

Basically, I'm trying to force the Othermill to behave like a ShopBot.

In EAGLE; Is there a way to bypass the schematic process, convert those DXF files into traces, accurately place drill points, and export the finished design as a .brd or .gbr?


texts: How does this wireless transceiver work?

texts:
While messing with Arduino I came across this wireless transceiver. As a newbie in all this stuff, it's written that it operates at 2.4 GHz, so the transmitter crystal and receiver crystal must operate at 2.4 GHz, right? From the photo I can see that the crystal is 16 MHz which is 0.016 GHz. Probably I'm not getting it right, where am I mistaken?

NRF24L01+ 2.4GHz Antenna Wireless Transceiver Module


texts:
I'm developing a small knob that can be controlled by both the user and a microcontroller. My current design is a modified servo. I'm removing most of the gearing to keep the motor's torque low. I'm using the pot to keep track of knob location and an H-bridge to drive the motor.

If the user tries to turn the knob while the microcontroller is also trying to turn the motor, I'd like to maintain constant torque and not let the current spike. Essentially I want to let the user "win" but I don't want to turn off the motor or damage it.

Do I need protection circuitry here, or is a motor fine with being forced backward while it's trying to run forward? This is my first non-trivial use of a servo, and I'm still learning how they and DC motors work.


texts: How to properly use an OPB917BOCZ photoswitch?

texts:
I am building a weather station with an anemometer. I have an OPB917BOCZ photoswitch on-hand that I would like to use as the tachometer if possible. However, I can't seem to have any luck with it.

The device has five leads: anode, cathode, GND, Vcc, and output. From the diagram it looks like the anode and Vcc can be hooked together, same with GND and cathode. I tried the reverse as well (cathode and Vcc; anode and GND). I tried measuring the output with a multimeter, but I cannot see anything. My father suggested that it generates pulses and doesn't simply open a gate, so I tried measuring those pulses with a DSO but I don't see any pulses either.

He has used one of these devices successfully for a similar purpose, a tach for a spindle on a CNC lathe. He has it wired the same way I tried. Why can't I measure any output? I am getting pretty frustrated. Any suggestions?

Thanks.


texts: How do I tell if my Thermistors are 10k or 100k?

texts: Is there any way to determine if your Thermistors are 10k or 100k?  I need to set the settings in my Marlin firmware.  I tried one with the 100k setting, it worked, nothing blew up, but I still don't know if the readings were accurate.


texts: simple induction heating circuit problem

texts:
Update: got it working... Fix: replace diodes for proper schottky. Result: got oscillation but no resonans. Fix: replace cap with 1 uF polystyrene. result: got resonans.

But now my problem is i cant get any power out of it! I know the freq is a bit high to properly heat steel, its around 330kHz. But it draws 3.5A running empty peaking at 50V, and only goes to 5A at 20V when i insert a workpiece.

How to upp the effect?
or is this generally an ineffective design?

old question
I´m getting a bit interested in resonans and found a circuit for a very simple self oscillating inductuiong heating circuit. im new to using powertransistors.

In addition i put a 12V zener diod and an a 10kR between node R1,T1,D1 and ground to protect my gates from overvoltage

My problem being the circuit wont oscillate. One MOSFET turns on, stays on. The circuit draws ca 3A at 12 V. And nothing much more happens.

I have a hard time understanding why..

Im was thinking that the mosfet needs a negative flank with respect to drain in order to turn of proper (enhancement mode?). But the page explaining uses STP30NF10 which are similar to mine. I am using IRF540 enhancement mode Mosfets 100v 28A.

Anyways... below is schematic of my current non-functional stup. .. please help as to what might be causing the problem.

simulate this circuit – Schematic created using CircuitLab

actually, while doing the drawing s i noticed that my diodes d3,4 are not schottky diodes. but have a 0.6 Vdrop. would that do it? the circuit is theoretically supposed to osc @ 240kHz.


texts: Interfacing HEDS 9700 optical encoder with AVR atmega32

texts:
I'm trying to interface an HEDS 9700 optical encoder using an HCTL-2020 IC (or anything else) with my Atmega ( atmega128, atmega32, atmega16, atmega8 or any AVR-family based microcontroller, don't matter for me ).

But I don't know what should I do. I read datasheets of both devices. What pins from HCTL must connected to my microcontroller (and which one ?) ? Basically, I don't know what to do with this encoder.

Please help me find out the way.

Thanks.


texts: PWM of 2.8v LED input (high-side driver IC selection)

texts:
I'm trying to control brightness of some commercially obtained instrument panels (for a mock aircraft cockpit). The panels have some internal LED strings (presumably, anyway) which are explicitly rated to a 2.8v input (and no more), and unfortunately must be switched on the high side. Maximum current draw I've measured on the bench is about 60-70mA.
I have an existing PWM module used for various other tasks in the system, which has spare outputs. The PWM chip on the module is a PCA9685 which can sink a decent amount of current, but 60-70mA is beyond what it can cope with.
Therefore my plan was to establish a 2.8v power rail using a small linear regulator, and use my PWM input through some kind of driver/switch to give the final 2.8v-PWM-ed signal to the backlight input. The problem is I can't find a suitable driver which works in the correct voltage range, but has a fast enough response time for PWM.
There's plenty of 'slow' solutions,(< 100 hz) even toggling the enable line of the 2.8v regulator, and there's plenty of fast solutions (designed for PWM) for automotive, but which need 12v output.
(I don't think I can use simple BJTs because of the junction voltage drop: below 2.8v the backlight is much less bright). In case it's relevant the PWM signal is at 5V.


texts:
What if I use second order RC filter instead of LC filter in Buck, even it gives roll-off of 40db/decade.
Why is LC preferred?


texts: Is it possible to use a Zener diode as a High Pass Voltage

texts:
I'm trying to ensure a minimal Vin to solar powered (incl. battery ) ESP8266 project.

When battery voltage drops under a certain value , MCU enters an undefined state, which prevents it from wakening again when voltage is as needed ( tried both with 3v3 unregulated input and 5v regulated ).

My question is - is there a way to use a Zener Diode ( in some combination or else ), to ensure that when voltage drops under 3.0v or 4.5v ( as an example ), a cut-off will occur, preventing entering this state ?


texts: Replace this yellow capacitor 205K 300V with different type?

texts: I've been trying to find a replacement capacitor for the one in the attached picture. I have been looking for a 2uF 300V according to the indication of the 205K (2,000,000) and what I can usually find on many different websites is a 2.2uF and 400V. From what I remember, the voltage doesn't matter as long as it is higher but 0.2uF more is already 10% higher. I'm also confused with the different names I find, axial film, metallised polyester film, polypropylene film etc. etc. From the image I even found the Taiwanese manufacturer (apparently called Tenda). My question is can I replace it with another type of capacitor, e.g. electrolytic. This capacitor is on a circuit which belongs to a Scholl foot massager and is near where a small fan gets its power from an RB157 rectifier. The fan is used to produce cool air to sooth the feet. The symbol on the circuit board is that of a non-polarised capacitor. The physical size is 31mm x 14mm x 10mm (it is an oval shape). Thanks.


texts:
I'm the owner of an old 2nd world war bunker. To imagine it, a short overview: Imagine they drilled 50 meters into a mountain, then drilled out a big hall, in which they built a regular building. It has an emergency exit, like a chimney.

I'm evaluating a system to get 3G inside. So the easiest way to do that is by putting a yagi antenna at the end of the chimney-exit. The other end will be in the room inside.

Do I need to use a GSM repeater or is yagi-antenna/20mcalbe/inhouse-antenna enough for a standard smartphone to connect to the outside world.

In other words, is it working just with antenna and cable without a repeater?


texts:
Good day, we were tasked to design a transistor based RF oscillator to be used as a VCO for our design experiment. In the picture shown below I have seen many tutorials on how to set the L1, C2, C3 values. I also already know how to set R1 and R2 as they are only used to bias the transistor. I would just like to ask

  What are the C1 and C5 capacitors, and the L2 inductor for and how do I set them to a certain value?


texts: What does it mean for reactive power to be delivered / consumed?

texts: Real power makes sense since there is actual consumption, but regarding reactive power; what is consumed / delivered? And how does the circuit change once this happens?


texts: Fixed voltage drop (current and temperature independent)

texts:
simulate this circuit – Schematic created using CircuitLab
Is there a clever way to create a fixed voltage drop say 2V that is not affected by current or temperature?
Voltage stability should stay within 1-3%(5% at most) over -40...60C.
Specified drop should be at few hundred microamps and it should endure atleast 50mA per LED.
As you can see a 2V zener voltage varies greatly due to current and temperature:

The problem is that I need to adjust the brightness of 24V LED-s. I have 24V supply voltage and want to adjust LED voltage from 2 to 15V using DCDC converter. Very few converters have such a large adjustment range, so I need to chop off extra 2V from DCDC output to make the LED really dim. Individual LED-s are controlled by NPN transistors in common emitter mode.


texts:
Is it recommended to ground the neutral line in an off grid solar system?

A nonisolated inverter would be by definition wired this way, right?

I believe that in home electrical systems neutral is connected to ground in one location. There is a ground bus and a neutral bus and they are linked in one location near the main home supply and the earth connection.

As I understand it when grounding the neutral line,

If there is an earth fault on the neutral line nothing happens
If there is an earth fault on the live line the inverter circuit breaker will trip. (if no other protection trips first)

If you do not ground the neutral line a GND fault will either ground the neutral line or the live line. I believe the disadvantage being that if the live line is grounded it is confusing for future problems unless there is an indication of the fault.

In a home system is there more danger because of the higher voltage transmission lines?

Would there be a difference if there was or was not a GFDI (Ground Fault Protector)?

REF-1
REF-2


texts: Placement of signal, power and ground lines within a ribbon cable

texts:
Just a couple of assumptions before I start as this is a theoretical question

All signals are <1MHz digital signals
All signals are single ended, no differential pairs
The 3 power lines are +5V, -5V and 12V
The ribbon cable is unshielded
The ribbon cable is inside a system with various other wiring looms carrying voltages/signals

What is the best placement for signal, power and ground lines within a ribbon cable with regards to EMI.

I have drawn up the two possibilities I could think of which are:

Interleaving ground lines between each signal/power line
Using the ground lines to create a barrier between the power and signal lines

Is one of these a better practice than the other or is there an even better solution which I didn't think of?


texts: How to design a discrete linear regulator with an opamp and an N-channel MOSFET?

texts:
So as far as I understand, the basic idea of a linear regulator is to use a series-pass element along with an opamp with negative feedback to stabilize the output. This is what I usually see as an example:

simulate this circuit – Schematic created using CircuitLab

Now, to use a MOSFET in place of the BJT, can I just do a direct replacement like this:

simulate this circuit

Or should the gate of the MOSFET be driven by another BJT like below?

simulate this circuit

Or does it not make any difference? Is one more stable than the other?

Also I remember reading somewhere on the internet that in order for the opamp to regulate correctly, a small current should flow out of the output through the negative feedback loop, but a MOSFET gate doesn't allow any current in, which is also confusing.


texts:
I am using 7805 and 7815 for the voltage 5 V and 15 V respectively. I provide 24 V to 7815 it is giveinng me output voltage 18.5 V instead of 15 V. According to 18.5 V to input to 7805, its output is 6 V. It should have to provide 5 V output. similarly, the output of 7815 should be 15 V.

I don't know what is happening. Can you tell me what will be the error in the circuit?

I am using this schematic in hardware.


texts: Problem Implementing high side P channel mosfet power source selector

texts:
I have build the above circuit on a breadboard and it is almost working but not quite.  I've spent a number of hours on the problem to no avail. My background is not electrical but I've been building projects and circuit boards using arduinos, esp8266 and esp32 for a number of years.  This is my first ever post....
The problem I'm trying to solve is negotiating two possible power supplies for the PCB, input 1 from linear regulator and input 2 from the USB bus.  I do not want the USB bus providing power to the regulator as it currently does which back powers the 12V supply.  I realise I could use diodes to achieve this, but I would like to get this to work!
I'm using LEDs at input 1 and 2 to confirm which power source is active.
If I only connect power to input 1 then load lights up and the LED at input 2 does not : intended behaviour.
If I only connect power to input 2 then load lights up and LED at input 1 does not: intended behaviour.
In reality power is likely to be supplied at input 1, then power supplied by input 2 and I want input 1 to be disconnected.  This appears to happen.  However then, when I disconnect power from input 2 leaving power on input 1, load does not light up: not intended behaviour.
I would like input 1 to be passed through to the load when input 2 is disconnected.  If I measure the voltage at A it reads 0.8V which is enough to keep the logic level AO3402 on.  If I then connect input 2 directly to ground, forcing the gates of Q7 and Q13 to 0V, the load lights up.
I am uncertain as to why the gates are kept at 0.8V.  I have tried a lower value pull down at R36 but this does not work.
Any ideas appreciated, or different approaches also welcome.  I do realise the two diodes would achieve the same result, but there may be significant power draw so I would like efficiency to be good.


texts: How to read & interpret the hall sensor or get the dashboard odometer readings for an electric scooter?

texts:
We are working on an electric scooter (moped) project and would like to get the distance reading (that goes to the odometer from the hall sensor / bldc controller) on our IoT device.
The scooter uses a BLDC Motor Contoller (JH Brand model A6080B8P3 M TMK6) with a voltage of 60 V DC.
The odometer (instrument cluster) on this electric scooter is a Chinese and we cant figure out the brand. So the controller is sending some signals to the odometer / instrument cluster which is how the distance is displayed on it.
We want to be able to use our IoT to calculate the distance for each trips. We don’t want to use a GPS based distance measurement but would love to get the signal from the controller or read the odometer / instrument cluster somehow.
We also want to refrain from adding a new pulse counter to the scooter.
Any ideas would be appreciated. Please feel free to ask us any questions and we would be happy to reply.


texts: Placement of Vias to Connect Ground Planes

texts:
I've been wondering a lot about grounding practices on PCB layouts. My first question about it deals with vias. I've noticed that on a simple 2 layer PCB with ground planes on both sides, there will typically be a few or several vias spaced out to connect them with minimal impedance between the two copper pours.
However, on an RF board the via placement looks much more deliberate and I'm wondering about the theory behind this. The vias connecting the ground planes often border the RF trace. See this differential coplanar waveguide example:

I also have a second question about grounding on PCBs. When is it appropriate to "isolate" ground planes from each other? And how does having the ground planes on one layer (let's say top) isolated from each other help when both of those ground planes are connected to the same ground plane on the bottom through vias. When we have these isolated ground planes, does the via placement differ from either of the above cases?
Note: I'm aware of the possible duplicate here but I'm not satisfied with the answers and think my question asks for more detail.
Thank you for the information.


texts: Stochastic Processes wtih respect to the electric load demand

texts:
I am required to look at the statistics (stationarity, mean, standard deviation etc) of the electric load profile.  I decided to use the load data for the IEEE reliability test system as it has all the data for an entire year.  More specifically I have data for all 24hrs * 7 days * 52 weeks = 8736hrs of the year.

From this data, I then produced the 24 hrs load profile for each of the 364 days of the year.  At this point, I have 364 realizations of the stochastic process.  Then using this data, I fixed time (eg. at 1am, 2am, … 1pm, 2pm) and stored all 364 data points for each time of day.  Therefore, for 1am, I have 364 data points, similarly at 2am and so on.  Therefore, I end up with 24 random variables (in terms of stochastic terminology) and created the best fit probability density function in MATLAB using this data shown below:

I have also found the mean, for each hour and this produces the following:

As we can see from this, the mean does vary with time, therefore, the process is not Wide Sense Stationary and by extension it also not Strict Sense Stationary as indicated by the different PDF's in the first image.  Furthermore, I have concluded that the process is not ergodic because the time average of one realization (i.e. the load profile for one day) is not equal to the average of the ensemble at different time as the average/mean changes over time and is not constant.

Now I understand, that if the process is not WSS, then automatically it cannot be SSS and by extension ergodic.  But I am merely pointing out by observation, ways I think I can identify WSS, SSS or ergodicity.

Can someone, confirm if my analysis of the stationarity property makes sense or is incorrect.


texts: In a sound recording studio 11 microphones are placed at different locations. The data from each microphones are brought to a processing center over wires and are sampled, quantized, binary coded and time-division multiplexed. The multiplexed data are now transmitted to a master recording station. Assuming each signal bandwidth is 20 KHz, the acceptable error in sample amplitude is 0.25% of the peak signal amplitude and a sampling rate of twice the Nyquist rate. Determine the minimum cable bandwidth needed to transmit these data.


texts: Connector suitable for use in oven at 125°C

texts: I'm designing a PCB that needs to be tested in the oven at 125°C (potentially 135°C). This board has a 64 position connection (split into 4 x 16 connections) to another board which will be placed outside the oven. What style of connector could I use which would be able to survive this high temperature condition? I have found high temperature ribbon cable rated to 200°C but I'm struggling to find a suitable connector. Perhaps an IDC/IDT connector would be best but I have been unable to find any rated above 85°C. I have considered soldering the ribbon cable directly to the board but this is fiddly and not very robust.


texts: Cannot establish a communication between two nRF24L01+ modules

texts:
I’m willing to experiment with nRF24L01+, so I have bought a set of modules from China, and I’m trying to establish a communication between an Arduino Nano and a Raspberry Pi 3.

At first, I tried to write my own sending program (in C++) for the Arduino and my own receiving program (in Python) for the Raspberry Pi, but I could not receive anything.

I thought it might be a problem with some missing initialization, so I decided to try using a dedicated library. I tried the example scanner programs, and it seems to work fine on both the Arduino and the Raspberry Pi sides: it detects some activity that corresponds to my WiFi network. So I tried the pingpair_dyn examples. The sender side appears to send data, but the receiver does not see anything and the sender times out. I tried both directions with the same result.

I read that there might be some issues with the 3.3V pin of the Arduino Nano that may be insufficiently stable to power the nRF24L01+ chip, so I tried to power it from the 5V pin, through a L33CZ LDO regulator, and with decoupling capacitors, with no success.

I thought it might be a cabling issue, so I double- and triple-checked. The chip respond as expected, so I think the SPI signals (MOSI, MISO, CSN) are correctly connected. And since the scanner also works, I think the CE signal is fine as well.

I thought it might be a problem with my WiFi network interfering: even if I took care to choose a channel away from the WiFi channel, the antennas of the WiFi AP and of my laptop were close the the nRF24L01+ modules, and I thought that might result in a low gain of the LNA. So I trieed shutting down my WiFi (both the AP and my laptop’s), and I still could not establish a communication.

My first tests were with a few meters and a wall between the modules, but I also tried with only a few centimeters, and I still could not get any successful communication…

Any idea what I may be doing wrong? Is there a chance I bought some counterfeit nRF24L01+ chips or bad modules?


texts: Question Regarding Full-Rated (100%-Rated) Circuit Breakers

texts:
When specifying circuit breakers, it’s customary that breakers protecting down stream equipment and feeder conductors should be rated at no more than 80% of their maximum rated load current downstream at the bus voltage for the devices/feeders.

But I’ve come across applications where 100%-rated breakers are used/specified. These are usually in high voltage power distribution scenarios.

I understand that using 100% rated breakers permits the use of smaller downstream feeder conductors. But does anyone know where using such breakers makes sense? They are more expensive than regular breakers.


texts: Can you put a 120vac positive line into a breadboard?

texts:
Is there anything I need to know about putting a 120vac positive line in my breadboard? (Like, for example, if it's a bad idea to do that to begin with.) It will just be a christmas lights strand at less than a quarter amp. I will only be putting the positive line into a DIP relay. I've only heard a few instances where people have done this and my only electrical experience deals with 5vdc so i've never been shocked. I know that I will not be touching this while it is actually plugged in as well.

I also will have 5vdc control wires on the other side of the breadboard. Should I throw in some diodes to protect my Arduino, or should the relay keep the power isolated pretty well?


texts: Diode circuit analysis with constant voltage drop model

texts:
For this circuit I have to find the V_out/V_in ratio and my problem lies on one instance and that is ,
if V1 is negative (for the case  V1< Diode on Voltage) all the current flows through the diode and diode acts like constant voltage source which in turn causes some current flow through R_1. My question is ,Why Diode On voltage is the only cause for the current flow through R_1 ? Does  V_1 not have any role on causing current flow through R_1 since V1 is in magnitude greater than Diode_On voltage?


texts: Do linear thermistors exist on the market?

texts: I'm working on a project right now that requires me to use a thermistor to sense the tempertaure change with an op amp comparitor with hysteresis. Because of the non-linearity of a normal NTC or PTC thermistor, I wanted to know if there existed any thermistors whos resistance changes linearly to the amount of heat applied. A quick google search shows me that a Silistor is exactly that, but there isn't a product that I found that has that name. So do these linear thermistors exist on the market, and do they exist in a through-hole format? Side note, I'm not making this a product recommendation. I just want to know if they are sold and if they have a specific name.


texts:
I have a basic question about directional couplers.

In this scheme each port is represented by one wire. What does it mean? The other terminal of each port is GND for all?


texts:
This is a AD620 instrumentation amplifier for single supply operation
when i tested the below circuit on a bread board , it is giving zero voltage output   for input of  0V to 1V input and then giving offset voltage . For example if i give 3 volts it is giving 2 volts at pin 6.. But when i connect it in dual supply mode its working fine, please some one help me. when i simulated the circuit on multisim it is working fine for both the modes


texts:
I am going to build 8x8x8 LED cube. Before I do I need to figure out a good driver circuit. I came here because I have very little knowledge about how a lot electronic parts fit together.

So here's my plan.

I will be using the Arduino UNO to run the animations.

The cube itself will be made with 512 3mm Diffused Blue LEDs. These LEDs have a Vf = 3.4vand maximum current of 20mA. I want to be able to provide that maximum current. The cube will be setup so that the 64 columns will be the anodes of the LEDs and the 8 layers will contain all the cathodes of the 64 LEDs in that layer.

I have decided to use nine 74HC595 shift registers to expand the Arduino's I/O to the required 72 outputs. From here I don't know what to use to connect the shift registers to the cube. The first 8 registers will control the columns (anodes) and the last will control the layers (cathodes).

Some have suggested I use the UNL2803 to "anti-drive" the 64 anodes and 8 transistors or MOSFETs to turn the layers on and off.

I don't understand how to connect the UNL2803 or the other parts so could someone provide me with some clarity, a simple schematic perhaps? I just don't get how to use a UNL2803 to source current...

Schematic Below For CubeDriver:


texts: Effect of internal series resistance of solar cell

texts:
Above is the equivalent circuit of a solar cell with internal series resistance. Also the photo generated current \$I_L\$ is constant.

I want to understand how the load resistance changes the terminal characteristics of the solar cell. This is what I have been able to infer so far -

The terminal current expression can be written as -

\$I=I_L-I_S(exp(\frac{V+IR_s}{V_T})-1)\$

\$I_S\$ is the reverse saturation current of the diode.

Now the open-circuit voltage can be found by putting \$I=0\$.

\$V_{oc}=V_Tln(1+\frac{I_L}{I_S})\$

Similarly the Short circuit current can be found by putting \$V=0\$.

\$I_{sc}=I_L-I_S(exp(\frac{IR_s}{V_T})-1)\$

Clearly, if the series resistance is changed, \$V_{oc}\$ will remain the same but \$I_{sc}\$ goes on decreasing. Is this correct? I understand that for small values of \$R_s\$ there won't be any change in \$I_{sc}\$, but after certain value of \$R_s\$, \$I_{sc}\$ is bound to change. I want to know if this is correct or not. Thanks.


texts: Know the transmission speed between PICAXEs with Radio module

texts:
I was wondering if I could know the transmission speed between 2 PICAXEs using an Radio Module.

At the moment I tried to send data between 2 PICAXE 40x2 only with the 433MHz Radio Transmitter. The transmission works but its speed is very slow, like 1 package every 5 seconds.

Is it possible to increase this transmission speed?

I also read I should use the NKM2401 Radio Encoder/Decoder.


texts:
I'm simulating NiMH cell discharge from 1.5V to 1.0V. The circuit I drew is supposed to draw a constant current from the battery.

I simulate a DC Sweep in circuit lab but somehow the current draw is not constant. I get the following plot for the current draw from the battery.

Is there a problem with the schematic?Can the schematic to draw constant-current be reduced to use less components?

EDIT: Also noticed a strange behavior of the simulation tool. I simulate another constant current circuit and do a DC sweep. Here is the video

EDIT (02062013):

Changed the transistors to 2n2222 and sense resistor.

Simulated again with same DC Sweep parameters. Notice the Y-Axis on this plot below.

Later simulated the same circuit in geda+gnucap+ngspice and plotted.

Click2Zoom

Looks acceptable now :-)


texts:
My APC UPS stopped working. I have had it for many years and it was serviced once by APC while in warranty and never opened again.

Now since it is not in warranty anymore I opened it and saw two very suspiciously looking resistors.

What are those? Any tutorial on how to replace them (for a non solder iron friend)?

Here other pictures:
Large area
Small area

After reading the comments I gave another detailed look at the board with magnifying lenses and the only other suspicious thing I found is a capacitor that looks like it was hand soldered into place. May be when it was serviced by APC. Notice it has glue attached which I think indicates it was previously flush to the board. The place in the board immediately below where it should be glued to still has a mark of the glue. It is very far from the resistors place.

The visual underneath the smoked traces does not look bad although lightly darker:


texts: Behringer Pro Mixer DX 500 Needs to match new power supply adapter

texts:
I'm quite unfamiliar with the electrical side of things, so I'd appreciate it a lot if I can get some basic help.
I have a Behringer Pro Mixer DX 500 at home which would be used mostly in Bulgaria - where the voltage is at 220V. It came without a power supply adapter, in the photo (where it's a bit blurry) it says:
POWER SORCE: 2 * 19 VAC 30W
Here's also the manual for the mixer if it's helpful:
https://manualzz.com/doc/29044519/pro-mixer-dx500

Turned out a power supply adapter is close to impossible to find quickly on the web and in a bit of a rush, I purchased the following from the US:

The model (which is cropped out in the picture) is MXUL2 specifically.
Only later I realized it says 2 * 17.5 VAC.
So I wanted to ask if that's gonna be in any way a problem and, in case it is, can I somehow compensate by purchasing a precise Down Voltage Transformer (which I need to get anyway for transforming 220 V to 115V)?
Even if the 2 * 17.5 VAC discrepancy wouldn't be a problem (I so hope it wouldn't), feel free to suggest a respective Down Voltage Transformer, if you have something in mind that is a good choice on the low price end of things.
Thanks a lot!


texts: Arduino Motor Shield for 12v stepper motor

texts:
I'm making a basic rig for timelapse photography using arduino.
It is a panning system for a DSLR camera, so I went with the motor shield from Arduino with the L298 chip and a 12V, 1.7A stepper motor. Before I could power the motor shield externally I noticed that the motor was running fine off of the 5V USB supplied to the Arduino board. It was able to fully move the DSLR around at different speeds and hold it in place.

The problem arose when it was asked to do a single step at a time (I assume setting up any speed here will do). I noticed that not all steps are equal. Sometimes, there would 2 small steps followed by a larger step or even the other way around. From my understanding, stepper motors have fixed step size, and either it will fully do it (provided with enough power), or it will fail, is that correct? I thought it will fully overcome the inertia, and not get stuck half way, and then work fine other times.

So is the motor/5v power or my code is at fault here? Providing external power would require me to cut a trace on the shield so I'm holding out on that till I'm sure. (also having a single power supply would be nice!)

Here is the generic code I'm using:

#include <Stepper.h>

 const int stepsPerRevolution = 1024;
 Stepper myStepper(stepsPerRevolution, 12,13);

// give the motor control pins names:
 const int pwmA = 3;
 const int pwmB = 11;
 const int brakeA = 9;
 const int brakeB = 8;
 const int dirA = 12;
 const int dirB = 13;

 int times = 120;//420
void setup() {
 Serial.begin(9600);
 // set the PWM and brake pins so that the direction pins  // can be used to control the motor:
pinMode(pwmA, OUTPUT);
pinMode(pwmB, OUTPUT);
pinMode(brakeA, OUTPUT);
pinMode(brakeB, OUTPUT);
digitalWrite(pwmA, HIGH);
digitalWrite(pwmB, HIGH);
digitalWrite(brakeA, LOW);
digitalWrite(brakeB, LOW);

// initialize the serial port:
Serial.begin(9600);
// set the motor speed (for multiple steps only):
myStepper.setSpeed(2);
}

void loop() {
  while(times>0){
    myStepper.step(1);
    Serial.println(times);
    times--;
    delay(12000);
   }

  }


texts: Inserting compile date/time into the code in XC8

texts:
I'm in the process of writing code for a real time clock, and I want to compile the code with constants for the date/time of compilation to burn onto the clock immediately upon programming.

I believe I have seen this done before, but my searches have proved fruitless. Is there some kind of compile time macro that would do this? Something like:

rtc.second = __COMPILE_SECOND;
rtc.minute = __COMPILE_MINUTE;
rtc.hour   = __COMPILE_HOUR;
rtc.date   = __COMPILE_DATE;
rtc.month  = __COMPILE_MONTH;
rtc.year   = __COMPILE_YEAR;


texts:
This is not an assignment I'm prcaticing for my mids
Can someone solve this problem for me. Will the node betweeb R4 and R3 be equal to Vi? If so what case will there be a virtual ground and what case will a node be in some reference voltage like Vi.

How I went about solving it i. Used nodal equation in node between R3 and R4 , R3 and R2 and R2 and R1 and then substituted value of Vi until there were only two V terms one Vi and one Vo to get the expression of vo and Vi. However my expression was too long and now I doubt my method.


texts: What resistor should I use for connecting seven segment to Arduino?

texts:
I am planning to use Arduino with a 4 digit 7 segment that uses TM1637 driver chip, which has 4 pins, and uses 2 pins for data with i2c protocl.

Here is the code and datasheets:

https://github.com/avishorp/TM1637

Here it says that pull-up resistor is needed. How can I choose appropriate resistors for the 7-segment?

  The second problem also arises from the code snippet above. I2C is
  wired-and bus, meaning it should never be driven high.When a logic '1'
  is desirable, the output of the Arduino should be put in
  high-impedance state allowing the pull-up resistor to pull the line to
  its high level. This is unlikely to cause an immediate problem, but in
  the long term it may cause the reliability of the components to
  degrade.

In some part of the datasheet it says:

Electrical character (Ta = -40 - +85℃, VDD = 4.5 - 5.5 V, Vss = 0 V)
Output pull down resistor - Typical ~10KΩ (Test condition K1~K2)


texts: Reverse engineer a TSOP 1730 IR Receiver Module?

texts:
I'm trying to reverse engineer a small IR Receiver module to interface it to a new uC board, I'm designing for it. The original uC mother board got blown. It's for a mate who wanted to use the same Remote control transmitter and as the module was on a standard 4 pin 2.54mm pin header it seemed an easy option, when I said I'd have a look.
So I've drawn up a sketch in Kicad of the existing IR Receiver Module on the Left and the circuit I was trying to use on the right. The existing module used a 5V Supply to the IR Receiver, so I'm repeating that for simplicity and as I'm using a 3v3 uC I isolated the data from the receiver through an LTV356 Optocoupler.
That Opto coupler isn't giving me the output I'd expect. Just bread boarding this module the data line, (Pin 4) is held idle high and pulses low as data is received. When I connect to the optocoupler through a current limiting resistor the line is just constantly low all the time. So I'm misunderstanding something there between the data line and the optocoupler.
My main question thought is about Pin 2 of the module. I can't see what it does. In the previous blown uC module that pin went straight to a uC, I assume to a digital GPIO and can't for the life of me see what this pin does. It's basically connected to 5V supply through a resistor and a diode in series so what does it do? Looking at it logically the uC should be able to control the illumination on the LED, which is in the same part of the circuit but that LED is straight to GND so no way to control it. Obviously I'm misunderstanding something there too :(
I'll try add the schematic:


texts: VHDL: Is it possible to have a "variable length" string in VHDL like in programming languages?

texts:
According to the package named Standard in VHDL, the string is actually declared as array of character type where the character type itself is also defined within the package.

Provided that I am filling in a string with data which shall then be written to a file and the size of the string cannot be known in advance, how do I declare a "variable length string"?

I am aware that the Line type exists from textio. However, I don't know if it is possible to actually concatenate different line variables and then write them to a file. If this is possible then my problem can be solved.


texts: Flexible-PCBs: what data is needed for manufacturers?

texts:
Can someone explain more about how you generate data for flexible or flexi-rigid PCBs for manufacture? Do I just make more layers and export more gerber files? Is there anything I need to keep in mind when sending these to be manufactured?

I've made a decent number of medium-complexity 2-layer boards and had them manufactured by producing gerber files. I use Pulsonix, but am familiar with Eagle as well.


texts: I'm trying to build a Common Emitter Amplifier, but nothing is working

texts:
My transistor model is BCx19, and I'm trying to get a 10 times gain.

I am honestly kind of lost. COuldn't get a lot of info from my teacher, I was just more confused when I asked him.


texts: How does this oscillator work under a constant DC voltage?

texts:
Consider:

How does the oscillator in this circuit work? A tank circuit can't oscillate when there is a constant DC voltage, am I wrong? I simulated the circuit in NI Multisim and couldn't observe any oscillation. But the circuit works pretty well in real life.

Please help me understand how do this and how the negative feedback work.


texts: Would the "Min 10A DPDT 240Va" relay on this page be appropriate for controlling a 240V AC UK power supply using 5v from an Arduino?


texts: How can I convert a 4-digit BCD number to Binary in hardware? (using 74LS ICs and GAL22V10 ICs)

texts:
As the title suggests, I need to convert a 4-digit BCD number to binary.
I am aware of the doubble-dabble algorithm (https://en.wikipedia.org/wiki/Double_dabble), and that if you use it backwards you can convert from BCD to binary.
The algorithm works on paper but, as the title says, I need to do this on hardware using ICs from the 74LS family, and I can control them using a GAL22V10 by making my own state machine.
Below is an initial idea on how I would do it (this would be for only a 2 digit BCD number):

The problem here is that I dont know how I would subtract the 3 from the input digits without changing the number first into 2's complement and then back to binary and feed it into the register.
Would this be possible? Or is it more of a task for a microcontroller?


texts: How to do redundancy for a DC/DC converter? So that if one of the converters fails the other gets switched on

texts: I have a DC/DC converter that gives 3.3 V output.In our system it is the most important part.So we need a redundancy for this.So that if one of the converter fails the other should automatically get switched on. What kind of circuitry do we need to get this kind of logic.


texts: Unable to read data from MCP9808 using i2c

texts:
I have a MCP9808 temperature sensor and a Raspberry Pi 3B plus.  I had great success reading the temperature from this sensor via i2c on an Arduino Uno, but am not able to read the temperature with the Raspberry Pi.  There are several libraries available to read the sensor through Python and C, but I get error messages with all of them.  Therefore, I'm attempting to use simple command line tools to diagnose the issue.

Datasheet can be found here:
http://ww1.microchip.com/downloads/en/DeviceDoc/MCP9808-0.5C-Maximum-Accuracy-Digital-Temperature-Sensor-Data-Sheet-DS20005095B.pdf

I have already enabled i2c on the Pi, and am able to detect the sensor (default address 0x18):

root@raspberrypi:~# i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- 18 -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
...etc...

Furthermore, I can probe the registers of the sensor:

root@raspberrypi:~# i2cdump 1 0x18

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
00: XX 00 00 00 00 80 00 04 03 60 a0 27 00 XX XX XX    X....?.??`?'.XXX
10: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
...etc...

But I can not get individual bytes or words from the sensor:

root@raspberrypi:~# i2cset -y 1 0x18 0x05
Error: Write failed
root@raspberrypi:~# i2cget -y 1 0x18 0x05 w
Error: Read failed
root@raspberrypi:~# i2cget -y 1 0x18 0x05 b
Error: Read failed
root@raspberrypi:~# i2cget -y 1 0x18 0x05 i
Error: Invalid mode!

Nor can I set the config register of the sensor:

root@raspberrypi:~# i2cset -r 1 0x18 0x01 0x0000 w
Error: Write failed

I've read the relevant portions of the datasheet (i think), yet I don't understand why I'm not getting data. If I understand correctly, I don't have to write anything to any registers to prepare the sensor (the power-on defaults render it ready to go).

What am I doing wrong?


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