texts: Minimize Current Sensing Loss in LED Driver

texts:
Design voltages and currents:

Vo = 100V. Iout = 50mA. Po = 5W.

R4 is the output current sense resistor. The reference voltage for the error amplifier is 2.5 V which implies that under the target output current, this resistor will be 50 Ohm. With a current of 50 mA, this resistor will be dissipating 125 mW of power!

My application is for just 5W output power which means that 125 mW is 2.5% of this! How can I minimize the power dissipation? Will I have to move to a different topology (single stage PF is important)?


texts: Connecting nine LEDs in series.. why the results?

texts: I asked this before but I'm having problems still. I need to connect nine LEDs in parallel with a 9 volt battery. The wire leading away from the 9V separates into three and on each three are three LEDs in series. A calculator told me that if I have 2.25 volt, 28 mA LEDs on each branch I need an 82 ohm resistor. If I have an 82 ohm resistor and 9/82 is .10976... wouldn't my current be too low? I just don't know how to do it. How do I decide which resistor I need to use with an LED?


texts:
I'm trying to design an audio amplifier output stage to drive a speaker load. I'd like to start with the design of this stage in order to calculate the input impedence to the output stage so that I can proceed to design a buffer stage with an appropriate output impedence and a gain stage before that. My speaker impedence is \$8\Omega\$ and I'd like to deliver a minimum of \$1W\$ to the load and keep total harmonic distortion below \$1\%\$. One possible class AB output stage configuration is given below. I looked at a few different configurations but this one is nice in that it doesn't require a constant current source for the biasing which makes it simpler:

I first began by calculating the peak voltage over the load:

\$Vp = \sqrt{2R_LP_l} = \sqrt{2(8)(1)}=4V\$

From this I calculated the maximum output current through the load to be \$2mA\$ using ohms law. Assuming \$R_3\$ and \$R4\$ to be 0 for the time being (I can add these values back if I notice any thermal runaway effects later)

Since the voltage gain of this output stage is approximately unity the output current which I calculated as \$2mA\$ is related to the input current through the current gain given by

\$A_i = \frac{i_o}{i_i}=\frac{(1+\beta)R}{2R_L}\$

The textbook I'm using has made the assumption that all of the transistors, NPN and PNP, are perfectly matched when they derive the current gain. This is obviously not true in reality. The 2N3904 NPN transistors and the 2N3906 transistors I'd like to use have very different current gains.

My question is how can I solve for my bias resistors R1 and R2 such that I keep the total harmonic distortion low while still supplying the output current that satisfies the power requirement. What is a more practical/real-world design approach for designing this output stage. I find that the theory in the textbook is often quite useless when it comes to design for real applications.


texts: Verilog - Wiring multiple hardware instances together

texts:
I am very new to Verilog and digital hardware implementation.

I want to instantiate multiple instances of a hardware block, place them side-by-side, then wire them together (ie. one block's output is the next block's input). What makes it complicated is that I want to create a 2D array-like layout of these hardware instances. Thus, each instance would propagate a signal to its lower and right-side counterpart.

This block is instantiated once below:

alg_unit alg_unit_inst (
.clk(clk),
.rst(rst),
.init(init_temp),
.in_a(in_a_temp),
.in_b(in_b_temp),
.valid_D_in(valid_D_in_temp),
);

To instantiate multiple, I am using 2 generate loops.

generate
        for (i=0; i<N; i=i+1) begin : alg_unit_generate_i
                for (j=0; j<N; j=j+1) begin : alg_unit_generate_j

                        wire init_temp;
                        wire in_a_temp;
                        wire in_b_temp;
                        wire valid_D_in_temp;

                        assign in_a_temp = A[0];
                        // other assign statements here ...

                        alg_unit alg_unit_inst (
                        .clk(clk),
                        .rst(rst),
                        .init(init_temp),
                        .in_a(in_a_temp),
                        .in_b(in_b_temp),
                        .valid_D_in(valid_D_in_temp),
                        );

           end
end
endgenerate

I need a way to refer to previously instantiated alg_unit blocks. That way, I can hook up the input signals of the alg_unit blocks generated "later" to the output signals of the alg_unit blocks generated "earlier".

Should I be assigning/storing output signals from the earlier-generated alg_unit blocks to intermediate "wire"s? Alternatively, is there a way to refer to previously instantiated alg_unit blocks?

Ie)

// alg_unit_inst[0] was a previously-instantiated block
// I feel like using the approach below may require hard-coding some instantiations ???
alg_unit alg_unit_inst[1] (
.in_a(alg_unit_inst[0].out_a),
.in_b(alg_unit_inst[0].out_b),

);

Thanks in advance.


texts: How do I calculate the total quiescent device current draw for eight years if the the device had a 20 µA quiescent current?

texts:
I have a D-type flip flop (CD4013B) connected to a lithium battery with 240 mAh capacity, and it is stored for eight years at room temperature.
May I know how much quiescent current will be drawn from the battery during eight years storage time?
Let me expand
Maybe let me put to you all a better view of my current scenario:

The quiescent current of this device is ~20 µA

I have four batteries connected in 2S and 2P (that is, two in series and then parallel with another two in series) => 480 mAh @ 8 VDC

Each battery has a capacity of 240 mAh @ 4 VDC and from the graph of capacity vs OCV, it will have a capacity loss of 20% after eight years storage at 55 °C.

My circuit can work at minimum voltage of 5.7 VDC

Hence, I would like to know how much current is consumed from the IC and the self-discharge of the batteries during the eight years storage.
Will the batteries be able to operate my circuit after eight years?


texts: How to wire an RCE225 Dual Ended Switch for Series/Parallel switching

texts:
I have a model locomotive that uses an RC Truck engine to power an alternator. The AC current goes through a bridge rectifier and then a RCE225 Bigger Dual Ended Switch (from Servo City) for Forward/Reverse control of two traction motors.  I would like to send the power through another RCE225 dual ended switch to change the motors between series (for power) and parallel (for speed) wiring.

I need help with the wiring - I don't want to destroy an expensive component.

Thanks for your help!

Bob


texts:
I  first open circuited the 50 mA source and used Ohm's law to find \$V_1\$
$$V_1= 20 ∠0°  \frac{j50 \times (-j25+40)}{j25 +40}$$
but the answer is not correct. Also, how do I find \$V_1\$ when the 20 mA source is opened?


texts: Powering ESP8266 from pc atx power supply

texts:
I am powering my ESP8266 from an orange/black wire from my pc power supply. When i remove and reattach the CH_PD pin from +3.3V (orange wire) both leds, blue and red, flash shortly then start to dim and the ESP8266 powers off i guess.

What could be the problem?

EDIT:
I am using an Arduino as FTDI, powered from USB.

ESP       ARDUINO     ATX
--------------------------------------
TX        RX
RX        TX
VCC                   3.3V ORANGE WIRE
GPIO2                 3.3V ORANGE WIRE
GPIO0                 3.3V ORANGE WIRE
CH_PD                 3.3V ORANGE WIRE
RST                   3.3V ORANGE WIRE
GND       GND         BLACK WIRE
          RST         BLACK WIRE

I could not find the datasheet for the power supply but the model is SL500 SW117XC.
It says it can handle 30A on the 3.3V wire. There is one laptop size HDD and an SSD on the same wire. I just connected in parallel inside the PC case. My PC is on during this.

I also had a CD4050BE as a logic level shifter between Arduino(FTDI) TX and ESP RX but thought that was the problem so I removed it.


texts:
I'm using an ATxmega64A3U, I've connected a 4MHz external crystal and two 18pF load caps. I'm using the ASF module for clock configuration, however when starting up I can see that the code hangs in the following spot:

static inline void osc_wait_ready(uint8_t id)
{
    while (!osc_is_ready(id)) {
        /* Do nothing */
    }
}

The while waits for the clock source to stabilize but that never happens. Does anyone have any suggestions why this could be?

Addition

The code I've posted above is from the ASF, to make sure I know what I'm executing I wrote the following code and could see that the code gets stuck in the while loop that waits for the oscillator to stabilize.

OSC_CTRL |= OSC_XOSCEN_bm;
while(!(OSC_STATUS & OSC_XOSCRDY_bm));
CCP = CCP_IOREG_gc;
CLK_CTRL = (CLK_CTRL & ~CLK_SCLKSEL_gm) | CLK_SCLKSEL_XOSC_gc;
OSC_CTRL &= ~OSC_RC2MEN_bm;

I enable the external oscillator, wait for it to get stable, disable lock on register, switch over to external oscillator, disable internal 2MHz oscillator.


texts: Calculating resistor values for RPi circuit detecting AC current using H11AA1 and PNP transistor

texts:
I've got an electronic doorbell system (Aiphone IE-1AD) that sends a ~15Vac signal when the button is pushed.

I used this blog post on detecting a signal on a similar door bell using a moteino (arduino) to create this wiring schematic for the raspberry pi.

Question 1:  I think I need to make the circuit run using the 3.3v in my diagram rather than the 5v from the blog post - correct?

The moteino uses a 5v power for the circuit, but I think I need to change it to 3.3v.  When the optocoupler (H11aa1) is closed (connected), I understand the input voltage to be then sent to the GPIO pin (either directly, or via the capacitor).  Because the Pi GPIO pin expects a 3.3v (whereas the moteino could handle 5.5v), I want to be using 3.3v to run the circuit.

Question 2:  if I'm using 3.3v, what resistor values?

I'm not sure how to go about figuring out the resistor values.  The LED has a voltage drop of 2v and a runs well on about 10-15ma, but how do I handle the capacitor in parallel?

From this youtube at about 3 min in, it looks like the PNP has a .7v drop from B to E, but do I need a resistor between the optocoupler and B as the video would suggest?

Question 3:  An extra resistor?

It looks like there's a pathway, when the optocoupler is closed and the transistor is allowing current from E to C, that directly connects the 3.3v source to the GPIO pin without a resistor on the route (via the transistor) - is that a problem?  Wouldn't it cause too much current to the GPIO pin?  What resistor and where would address it?

I'm as interested in the why behind  the answer as I am in what to do make this work


texts: I have measured the output of a triangle wave using a spectrum analyser. This is controlled via digital, but oscillates completely by analogue circuitry. It is from the design of a music synth. I am trying to understand the spectrum completely. I understand the harmonic frequencies, but there are a lot of small spikes in between. What could be causing this?


texts: Need help understanding this op amp/BJT configuration to troubleshoot why I'm reading different voltages than expected

texts:
I am building this VCO in an attempt to study it and I'm having trouble understanding the references section seen bellow.

I have used a KIA431 that I 'stole' from a broken switching power supply on the breadboard in place of the specified LM4041CZ-ADJ and it is giving me the +5V I was expecting. I am using the LM336Z-5.0 as a substitute in Multisim because I couldn't find a part model. Besides this, the rest of the circuit is quadruply checked to be as specified in the schematics and as seen in the Multisim snippet.

To make this as clear as possible, I need the following things:
a) to know what this op amp/bjt configuration is meant to achieve and why a simple buffer (or amplifier with a gain of 2) wasn't used to acquire the +-10V reference
b) the name of the bjt configurations
c) why I am reading different voltages than what is specified (+-10V). I am reading +13.85V and -13.18V on the breadboard and +12V and -11.3V on the simulation

One thing that's also really bugging me to understand is that in both cases we see one diode drop difference between the positive and negative output voltages.

P.S. I am assuming that the only reason this op amp/BJT configuration is used is to feed the CA3280Es at the Tri to sine converter on page 6 of the linked PDF. I would appreciate a confirmation on my assumption (or the opposite) and a link to any resources that might help me get my head around this. (This is not part of the question in the title so it will not be considered in my answer acceptance.)


texts: Measuring 150kHz, ~30V peak waveform with good resolution

texts:
I am trying to choose test equipment for a systems test application and I am running into a road block with one of the specs I need to meet.

The device features an H-bridge output similar to the circuit shown below, but instead of a motor we will use some sort of load power resistor (20 ohm, I believe). VBUS in our application is ~30V and the FETs are driven such that the output seen across the load is something close to a +/-30V peak, 150kHz waveform (approximately a square wave)

I am just interested in measuring the peak voltage of the waveform, but with relatively good accuracy. I need resolution down to about 1mV, ideally (I believe this would be 15 or 16-bit).

What sort of test equipment would be best suited to handle this measurement?

An oscilloscope seems to typically have poor resolution at its higher volts/div ranges (5V or 10V divisions in this case, likely), but would probably be preferable if affordable enough. A digitizer can have lower bandwidth and lower sample rate, but would seem to get me the resolution I need (PXI-4080 was one option I looked at, but the 0.1dB bandwidth is only 20kHz).


texts: Why does Samsung include useless capacitors?

texts:
I do component-level repair of tablet mainboards, and I have seen this puzzling situation on two different models of Samsung tablet mainboards so far (SM-T210, SM-T818A).  There are ceramic chip capacitors on the PCB that are clearly connected to the ground plane on both ends.   Resistance checks confirm, plus it's pretty obvious just looking at them.

SM-T210 -- This looks like signal conditioning of some sort.  It's on the reverse side of the PCB from the SD slot but SD uses more than two signal lines so I dunno.

SM-T210 -- This is on the reverse side of the PCB from the USB commutator IC.  It's right next to the battery connector.

SM-T818A -- This is the AMOLED power supply.  The mystery cap is actually located at the edge of an EMI shield (removed for the photo) and the shield frame had to include a cut to clear the cap.  So they went to some trouble to have the cap right here.

The only scenario I can come up with is that during Capture the design engineer placed a bunch of caps for eventual use, but connected both ends to ground so the DRC module wouldn't complain about floating pins.  Then they ended up not using them all but didn't delete the extras from the design.  The design gets sent to a Layout engineer, who simply places and routes the design they've been given.

I'm willing to allow for somebody doing something so intelligent and wise that it's beyond my ken (filtering terahertz-band noise from the ground plane?), but I don't think this is an example of that*.

*Of course, that's exactly what I'd say if it was an example of that.


texts: How i can store 64 byte data into flash faster as 1 ms?

texts: I have one problem with store data into flash on my uC LPC1759. I need to save 64 byte data into flash, but when i use IAP-Interface, it takes more than 1 second. Is there a way to make it faster than 1 ms ? It is possible use DMA for copy data from RAM to Flash? Or write data to flash less than 256 Byte ( UM10360 - minimum size - 256 Byte).


texts: 5V tolerant - tolerant to 5V and how many more ? Harsh environnement

texts:
There is a lot of questions about this subject... Nevertheless this is not clear to me and clearly I m afraid of putting a signal at the input of a microcontroller which is higher than this supply voltage (ie 3V3). Nevertheless I would really happy if it works. So I have a microcontroller which is supplied with an LDO which converts 5V into 3V3. Nevertheless I need to use the 5V for driving "loads" thank to the microcontroller by using microcontroller outputs configured in open drain. Nevertheless when the transitor is open, the microcontroller sees 5V from the LDO. Nevertheless as I am working into a harsh environnement, I am afraid of  seeing momentary the 5V to be higher than 5V. I have clearly a very bad knowledge about EMI, so I won't take any risks.

Apparently if I correctly understand the datasheet, a standard I/O ("TC") pin has a maximum voltage equal to Vddio (3V3) + 0.3 which gives 3V6. I know actually from previous projects into my firm that there were no failure due to broken microcontroller. So the voltage at the input pins never exceeds 3V6 due to the harsh environnement. When I look at the "5V tolerant pin", the margin is higher ! They are tolerant to 5V5 ! So I have not a margin of 0V3 but a margin of 0V5. So it should work ? What do you think about it ? Did I correctly understand the datasheet ?

Here is the datasheet if you are interested in : https://www.st.com/resource/en/datasheet/stm32f030f4.pdf

Thank you very much and have a nice day ! :D


texts: meaning of having harmonic on special signal

texts:
my question maybe seems very simple but, I'm not familiar with the answer of that;

what is the meaning of harmonic of the signal exactly?

I know the harmonics of the signal are signals whoes frequencies are multiple of the frequency of the fundamental component of the main signal but I want to know about the deep concept of that, actually; my exact question is:

what is the meaning of having harmonic?

or

some signal has harmonic and some other not; what is the difference between these two signal in properties?


texts: Correct design for large contactor circuit?

texts:
After some advice here I'm wondering if this is the correct design of my circuit.

I'm now using a SSR as the control device to the contactor. The diode, I believe, should not only protect the SSR from back EMF, but also the capacitor as well. I know I will also need a resistor or thermistor prior to the capacitor so the capacitor itself does not cause a large inrush current, both when the system is turned on, and again after the switch is opened again.

The value of that resistor is something I'm still somewhat unsure of how to calculate.

For application details, the system will be on for at minimum 2 minutes before the relay is closed to engage the contactor. The contactor will then be on for up to 60 seconds before being disengaged. The capacitor needs to be able to recharge within 60 seconds to be able to close the contactor again if necessary.

If I'm understanding correctly, upon startup, the resistor/thermistor will suppress the capacitor inrush and slowly charge it (charge time depending on resistance value). As soon as my switch is closed, the capacitor will provide the full energy required to close the contactor coil. From that point on, the 24V source will provide enough energy to hold the contactor in, while also slowly charging the capacitor.

Once the switch is re-opened, the diode with suppress the back EMF, while the capacitor recharges.

Does this design seem reasonable? If so, how do I determine the value of the resistor to complete the design?

http://www.kvc.com.my/EnterpriseChannel/SharedResources/Datasheet/0/?ProductId=1000066755&Filename=SCHNEIDER-LX4-FH024.pdf
http://www.mouser.com/ds/2/293/e-nt-15067.pdf
https://www.us.tdk-lambda.com/ftp/Specs/dpp120-240.pdf


texts:
Before some days I have taken a look at circuit which controls AC current's frequency. That circuit was a VFD which looks like:

simulate this circuit – Schematic created using CircuitLab

But this circuit is for controlling 3 Phase motor.

So, I tried to make a similar one that can control a single phase load, like a bulb.

So, I created the below shown circuit:

simulate this circuit

And here is the sketch of arduino to give pulses to Gate of IGBTs:

int Phase1TransistorA = 2;
int Phase1TransistorB = 3;
int Phase2TransistorA = 4;
int Phase2TransistorB = 5;

int t = 4; //time in seconds
int T = 1000 / t;
int p = 1028; //number of duty cycles of pwm to create half ac-cycle.

void setup()
{
  pinMode(Phase1TransistorA, OUTPUT);
  pinMode(Phase1TransistorB, OUTPUT);
  pinMode(Phase2TransistorA, OUTPUT);
  pinMode(Phase2TransistorB, OUTPUT);
}

void loop()
{

  for (int i = p; i >= 1; i--)
  {
    digitalWrite(Phase1TransistorA, HIGH);
    digitalWrite(Phase2TransistorA, HIGH);
    delay(T / (p * i * 2));
    digitalWrite(Phase1TransistorA, LOW);
    digitalWrite(Phase2TransistorA, LOW);
    delay((T/ (p * 2)) - (T / (p * i * 2)));
  }

  for (int i = 1; i >= p; i++)
  {
    digitalWrite(Phase1TransistorA, HIGH);
    digitalWrite(Phase2TransistorA, HIGH);
    delay(T / (p * i * 2));
    digitalWrite(Phase1TransistorA, LOW);
    digitalWrite(Phase2TransistorA, LOW);
    delay((T/ (p * 2)) - (T / (p * i * 2)));
  }

  for (int i = p; i >= 1; i--)
  {
    digitalWrite(Phase1TransistorB, HIGH);
    digitalWrite(Phase2TransistorB, HIGH);
    delay(T / (p * i * 2));
    digitalWrite(Phase1TransistorB, LOW);
    digitalWrite(Phase2TransistorB, LOW);
    delay((T/ (p * 2)) - (T / (p * i * 2)));
  }

  for (int i = 1; i >= p; i++)
  {
    digitalWrite(Phase1TransistorB, HIGH);
    digitalWrite(Phase2TransistorB, HIGH);
    delay(T / (p * i * 2));
    digitalWrite(Phase1TransistorB, LOW);
    digitalWrite(Phase2TransistorB, LOW);
    delay((T/ (p * 2)) - (T / (p * i * 2)));
  }

}

When I tried to power up the bulb, the first pair of IGBTs died silently even without heating. I would like to know Why this happened and the steps to solve the problem.

The pair of IGBTs that died:


texts: Differential Amplifier constant output voltage

texts:
SE-Members,
The past few days i've been figuring out why my circuit does not work.
It is a simple differential amplifier with a gain of 2.
The OpAmp is the "TLE2027CDR".
My problem: The output voltage "v_out" is always at 3.57V. Even if both V1 and V2 are at ground potential.
By the way: V2 >=V1 of course.

simulate this circuit – Schematic created using CircuitLab

Datasheet: https://www.component-hk.com/datasheets/ab/MAX9938TEUK+T.pdf
I couldn't find anything in the datasheet either.


texts: Do I need to terminate extremely short traces (< 0.5 inches)?

texts:
Some background: I have a little hobby project running that basically interfaces a 64 pin ARM mcu (the STM32F405RGT6) to a stereo codec (a TI PCM3010) via I2S interface. I'm deriving the master clock for the I2S bus from the MCU (the stm32f4 series apparently has a PLL for this purpose), which runs at 12.288 MHz (256 times the sampling frequency, which in this case is 48kHz). The bit clock and respective data in/data out lines run at approximately 3MHz. I'm currently looking at routing the design on a 2 layer board, since it doesn't really have a huge amount of I/O. So far I've been able to locate the codec literally right next to the MCU, so that trace lengths to respective pins are 3 to 13mm in length (and as a plus, the analog/digital halves are nicely segmented). The ground plane is unbroken, except where I have to use a via for the data out line.

Now for the actual question; is it even required to terminate transmission lines under a certain length? I've seen in some literature that this is case (as in you don't have to terminate anything), but why is this exactly? I know it really depends on the edge rate (and source/destination/trace impedance), but would I gain any benefits by doing it anyway? Due to the layout of the codec chip, it would be possible to series terminate the lines, but really only by moving it further away, and by introducing more vias and broken ground planes into the equation. I realize this is a sort of low speed/edge rate design and I could get away with routing the board with my eyes closed, but I'd actually like to design something properly for once!


texts:
I need a 5v 2.5A output in a handheld device and have settled on the TPS61235P.  Its 2.5mm QFN package was very hard to solder, but I finally got a board fabbed and tested it out.  After roughly a few minutes of constant on-time @ 2.5A, the input traces started to burn up.

Now for the next PCB I'm planning on using the wider traces with solder mask left off so I can tin the entire trace up to the chip.

But once I solve this, I'm left wondering, how do I keep the chip cool?  It seems way too small for a heatsink, and doesn't have a solder pad similar to other chips I've used.

I assume a schematic won't be necessary, but I am attaching a pic of the current prototype pcb.


texts: Is it normal for the OC2 vacuum tubes to glow bright orange during operation & OA2 to flicker while running?

texts:
I just got this vintage Heathkit IO-10 oscilloscope from ebay. Just tried powering it up and it seems to be working fine. But I noticed that the OC2 tube seems to glow very bright orange and the OA2 glows purple and works fine. Occasionally there is flickering in the OA2 tube as shown in the video. Is this normal for both the tubes?

I've added a video to help understand better.
https://youtu.be/SlazPn6tTwo

Also I've a question regarding replacing the two can electrolytic capacitors. Can the first cap be replaced with a 250V- 100MFD and the second one with 450v-68MFD?

First capacitor: 150V-100MFD(3 caps in one)

Second capacitor:400V-350V-250V-150V - 40-40-30-40MFD(4caps in one)


texts: SMPS minimum rating / type calculation - how?

texts:
Looking for some help in defining the specifications of SMPS required to power an embedded project around (rather surprisingly, may be), Intel Atom motherboard. The plan is to run the system fan-less (or try to do so, if possible), with minimal peripheral count, in a closed-box fashion, i.e. without exposing capability to add additional peripherals, yet run on least amount of grid power. All of the following would be housed inside a custom-made (non-standard, i.e. nothing like mini-ITX etc.) cabinet.

Considering the power requirements specified by following blocks --

Dual-core Atom 1.8GHz, Mobo+CPU combo   - ~ 15W ( some articles talk about ~13W )
2GB DDR-III 1333MHz RAM module (single) - ~ 1W ( not sure, just guessing )
16GB USB thumb-drive                    - ~ 1W ( not sure, just guessing )
Teensy+ USB connected (bus powered)     - ~ 3W ( assuming 500mA @ 5V from USB)
315MHz ISM Rx/Tx module w/ Teensy       - (included in Teensy's power requirement)
USB Bluetooth dongle                    - ~ 1W
USB WiFi dongle                         - ~ 2W

Sum of operational power = ~ 25W

So the questions -

Does the above calculation and assumed power values seem reasonable ?
Can I really add up the power values as I've done to arrive at the required SMPS rating ?
Can I target a 30W SMPS, or say a 50W SMPS (to take the cold-start current draw into account) ?
Most standard desktop SMPS's available today seem to be rated for at least 400W, and very rare few at 250W (which BTW seem quite expensive). Is there something significantly different between such SMPS's and some of the other SMPS's found on electronics distributor sites which seem to supply a single DC rail (usually I've seen 12V) ? I believe standard PC mobo requires 3.3V, 5V and 12V (both +ve & -ve rails), but are all of those required by Mobo, or for the peripherals ? Does typical Mobo have onboard voltage regulators to convert 12V to 3.3V / 5V if required by say the processor / memory ?


texts: 5-pin DIN socket advertised as MIDI, not the same as on my MIDI gear

texts:
I bought a 180-degree 5-pin DIN chassis-mount socket dirt-cheap for a project, but I saw that it looks quite different from the MIDI outs on my MIDI gear; I did some research but couldn't find any info on MIDI plugs being any kind of specialized DIN shape, just 5-pin 180-degree DIN.
I just ordered another chassis-mount socket from UK, advertised on their site specifically as being for MIDI, but it's the same as the cheap one I got before, and doesn't appear to be the same as on my gear. I currently don't own a cable, so my own tests are pending. But when they say MIDI is 180-degree 5-pin DIN, is it really exactly the same or is there some other specification that needs to be made between different layouts of 180-degree 5-pin DIN? Diameter of the semicircle? Size and shape of the aligning nub?
I can easily believe no one has ever actually ordered this product and tried to use it since the UK online store has been running! What I can't believe is that this information doesn't exist anywhere within Google's reach. It's out there somewhere.


texts: Working principle of a MOSFET Transistor

texts:
I was just reading a blog entry regarding the power conflict of the Arduino and trying to understand everything, when I came to a point where I could not understand the working principle of the circuit vs the explanation of the MOSFET I found online anymore:

In the drawing above it shows that the gate voltage of the MOSFET is 5V and that it does not conduct in that state which also makes total sense, since a barrel connector is plugged into the device and it sources the power from the voltage regulator and not the USB. I checked out the datasheet for the FDN340P and it turns out being a P-channel Enhancement type, which is also visible in the schematic. Now I wanted to read more about MOSFETs and the first overview I saw looked like this:
Here it says under P-channel MOSFET enhancement type that it does not conduct if the voltage is 0 and that it conducts the higher the voltage is. This does not make sense to me considering the first schematic ... I also saw a second overview stating the same. I would be very happy if anyone could explain this to me and maybe the four types of MOSFETs in general since it is not clear to me after this. English is not my first language so I am sorry for any mistakes


texts: STM32 Rotary Encoder with Hardware Interrupts

texts:
I'm trying to get a rotary encoder working on my STM32.

I have channel A & B being pulled up to 3V and debounced with 1uF capacitors.
The board has channel A & B connected to PA11 & PA10 respectively and have configured hardware interrupts for both
I've tried a number of different algorithms to decode the direction of rotation but no matter what I do I can't get consistent alternating interrupts (ie. ABABAB)
I've tried triggering on both edges, just falling, just rising and no matter what I get the interrupts triggering seemingly randomly.

Is there something I'm doing wrong? Are the interrupts not enough to keep up with the speed of the encoder? Is the debouncing not enough (Looks okay on a scope but maybe the interrupts are more sensitive)? Is there a better way to do this in general? I've been stuck on this for a while so any help would be great. Let me know if more info is necessary.

*Code Edited to reflect changes (working algorithm)

INTERRUPT HANDLER

static int8_t states[] = {0,-1,1,0,1,0,0,-1,-1,0,0,1,0,1,-1,0};
uint8_t RotaryCurrentState = 0x00;
uint8_t RotaryTransition = 0;
int8_t RotaryPosition = 0;

/*Rotary Encoder Interrupt Handler
Channel A (IRQ11) & B (IRQ10)

              CW --->
 A (IRQ11)  ¯|___|¯¯¯¯|___|¯¯¯¯
 Interrupts  ^   ^    ^   ^
 B (IRQ 10) ¯¯¯|___|¯¯¯¯¯|___|¯
 Interrupts    ^   ^     ^   ^
                  CCW <---

void EXTI4_15_IRQHandler(void)
{
  RotaryCurrentState = (Read_IO(ROTARY_A) << 1) | Read_IO(ROTARY_B);
  RotaryTransition = (RotaryTransition <<2 ) | RotaryCurrentState;
  RotaryPosition = RotaryPosition + states[RotaryTransition & 0x0F];

  EXTI_ClearITPendingBit(EXTI_Line10);  //Clear Channel B
  EXTI_ClearITPendingBit(EXTI_Line11);  //Clear Channel A
}

MAIN.C

//Initialize
RotaryTransition = Read_IO(ROTARY_A) << 3 | Read_IO(ROTARY_B) << 2 | \
                   Read_IO(ROTARY_A) << 1 | Read_IO(ROTARY_B);

while(1)
{
  //CW Transition
  if (RotaryPosition == 4)
  {
    STM_EVAL_LEDToggle(LED4);
    RotaryPosition = 0;
  }
  //CCW Transition
  else if (RotaryPosition == -4)
  {
    STM_EVAL_LEDToggle(LED3);
    RotaryPosition = 0;
  }
}


texts:
Using a PIC, I got a signal oscillating around 2.5V +-[0,2.5]V approximately. This is intended to generate a simple sound through a small speaker.

The speaker, unfortunately works with 0V +-[0,2]V, and I expect the direct usage of 0-5V not resulting in the same sound (or even breaking the speaker). Consequently, I would need to displace the ground to 2.5 for the speaker.

simulate this circuit – Schematic created using CircuitLab

Could someone indicate me the direction for a solution?

Current status:

I did not managed to go very far,

Using opamp, but they mostly threat the input voltage, so a negative voltage source is required. I should probably reminder how they work in case it is the solution.
Splitting the voltage with resistors, but that did not convinced me due to attenuation.
I finally looked for some LM317 to generate a ground at 2.5V; However, I am not sure if it would work when the wave provide "negative" values.


texts: Help compare my results to the maximum power transfer theorem and explain using algorithms

texts:
So below is an image of the relationship between efficiency of a circuit and the resistance of the load, as you can see the maximum efficiency occurs when the two resistances are equal.

here is a graph of my recorded data, it is clear that it follows that above model, however it is graphing the ability of varying wires to heat water. That is, it is essentially graphing the ability of the wire to transfer energy to the water.

Why do my results follow this path? also how can I explain using theory and maths that there is a maximum power and beyond that when you increase the resistance power drops?


texts: STP16CPS05 Sink Driver External Resistor does not change output current

texts:
Have a 10 x 10 LED array sourced with CD74HC154 Decoder/Demultiplexer to PNP Transistors (rows)  and sinked with STP16CPS05 Sink Driver (columns).  This is driven with an Atmega328P.  Rows and columns are multiplexed. It works great.

Problem:  I want to adjust LED brightness by increasing sink current through STP16CPS05 via the external resistor R-EXT pin 23.  Using data sheet Table 11, when I change R-EXt from 1K to 215 ohm there is no change in brightness.  This is still true when I light just one row and turn of multiplexing. If I disconnect an LED from an STP16CPS05  output and go straight to ground it gets much brighter.

See attached schematic. Note: I am using an inverter gate from Latch LE/DM1 pin 4 to Output Enable pin 21. This was to eliminate random flickers when multiplexing.  Only turns on outputs when Latched.  Also works great.

Source: Row Current is 200mA with transistor Base resistor at 2.5K. Dropped this down to 215 Ohm to make sure I was not restricting current here. Transistor is  Fairchild SS8550.

Question: Why doesn't R-EXT value change LED brightness?

update:

I took the measurements as shown in the image below.  While multiplexing is paused, measuring the single LED in a column that is on Anode = 4.84V Cathode =0.80V.  Transistor Emitter = 5.06V   Collector = 4.88V.  At the pin for this column on STP16CPS05 = 0.69V

Looking at the Datasheet graph of FWD Current vs FWD Voltage for a blue LED, if my FWD Voltage is 4.0 Volts then the current must be 69mA?  I added the dashed lines to the graph.


texts:
My father recently brought home an old identification card, and after cracking it open I found that it consisted of  simply a large coil of wire, connected to a small electronic chip (which was so small that I sadly lost it - it looked something like this but a lot smaller. Incidentally, it was so small that when I was cracking open the ID tag it actually got a bit damaged).

It works as an identification card, in that when you swipe it close to a detector, it registers your identity. I could (and have) made some guesses as to how it works (probably involving a magnetic field?) but many times my guesses turn out to be wrong, and I can't seem to be able to find a good physical explanation online as to how these identification cards function, and how they store your identity.


texts:
Today, I saw a very old historical piece of lab equipment at the university. It had a large number of dials, although not as large as you would see in an oscilloscope. The size was similar to an oscilloscope, though, although it isn't as deep due to the lack of a CRT. The text "impedance bridge" was written in the label of the device.

I couldn't find an impedance bridge page in Wikipedia. There is impedance bridging page, but I assume that is for an entirely different purpose.

Loosely related, although I believe the impedance bridge may be distinct from a universal bridge: What is a "universal bridge"?

So, what is this historical piece of equipment that is called "impedance bridge"? Is it different from "universal bridge" (please feel free to mark as duplicate if not)? What does it do? For what purposes is it used? Is an impedance bridge needed in modern times too, or is it just some obsolete historical equipment?

Edit:  Ok, sorry for the shaken picture (should have used DSLR instead of a mobile phone camera), but here's it:


texts: Is transformation from one state representation to other state representation changes the transfer function of the system

texts:
I was reading about designing of controller by state state model  from book by Norman S. Nise
And author suggested that if state space representations  given in problem are of form other than phase variable form then best method to design a controller would be
1.transform given system to phase variable form
2.then design the feedback gains
3.then again transform the designed system back to original state space form
So my question
1.when we transform from one of state space representations to another , isn't zeroes of system may changed?
Or in other words
isn't transfer function gets changed due to transformation
As I try to figure out myself here is my attempt

And after all this calculation to me it seems that both transfer function may not be equal always
but
example given in book shows that it has same transfer function in both transforms so I thought it(example) may be a special case
So can anyone explain
Mathematical expression I got can be solved further to obtain a relationship between both transfer function ?
Or
my conclusion is right that transfer function may or may not changed due to transformation?


texts: I'm using LCD display and keypad to control my stepper motor. My stepper motor uses a 12Volts, 2Amperes power supply and I used L298N as its driver. My code functions well but the problem is everytime I plug in the power source for the stepper, the LCD starts malfunctioning. The display texts disappears but the light is still on. LCD gets its power source in arduino mega 5v, the l298N driver also utilizes the same 5v source from it. I think that's the problem, currents jamming in because l298N also has a pin connected the the 12Volts, 2Amperes power source..... I'm not sure if that's the problem guys pls help me fix it. THANKS


texts:
I started building a DIY portbale speaker out of a douk audio tp 3116 and an old pair of sony speakers.

The spec on the ebay site of the amp says that it operates between 12-25 volts, but for the 60 watts sony speakers I would need around 24 volts.
So my question is how should I power the amp?
 I wanted to use 2 gel batteries, but if fully charged it would output around 28v, so i would need a dc-dc converter, and its capacity is small as well, so i thrashed this idea.
 If I used 18650-s I would need 5-6 cells, (I realised that 20v is enough for what I want it to use) but i dont know how long will it last with this kind of setup.
Should I use 2-3 packs in paralell in order to get decent batterylife or it is hopeless to make something this "powerful" battery powered.

Could you tell me what should I do in order to make this project work?


texts: Calculation of Euler angles. But gets a change (delta) in change and not a constant value

texts:
What I've done will now:

I'm using an IMU (MPU6000) to calculate the Euler angles of an object and for this, I'm using Madgwick AHRS algorithm. The MPU gives acceleration due to gravity (a) about the axis and angular velocity (g) about the axis and I feed these values to calculate the quaternions which are converted to Euler angles using this function found on Wikipedia.

So what's going wrong:

I'm getting the Euler angles to be yaw-pitch-roll: 0.001518, 0.001626, 0.003990. This isn't in degrees or radiance. Whats the dimension here?
I'm feeding in, the accelerometer reading about each axis (so its m/s^2) and after calculating the angle of rotation from the gyro, the theta value (in degrees) about each axis.

MadgwickAHRSupdateIMU((float)tx, (float)ty, (float)tz,(float)ax, (float)ay, (float)az);

where tx,ty,tz are the angle and ax,ay,az are in G.

    tx = gx * timestep;
where gx is the raw gyroscope reading. And timestep is the time between gyro readings.


texts: Using a resistor to help regulator heat dissipation

texts:
I designed a circuit that consumes about 0.7 to 0.9 amperes depending on the state of its components.

I use a 7805 regulator to feed the circuit with 5V and the regulator is connected to a 12V adapter.
The regulator has to drop about 7 volts at 0.9 amperes maximum and it means about 6.3 watts of heat generated in the regulator. Changing the adapter is not an option because this circuit is a part of another circuit that needs 12V.
My question is: Is it possible to use a resistor to drop a couple of volts before the regulator? This may split wasted power between resistor and regulator. Am I right?


texts:
I am making an DC to AC converter circuit in LTSpice. The schematic is posted below.

When I plot the current across the transistors, I get huge spikes in the current, as seen in the diagrams below.
We want to get rid of these spikes in the current.
When we built this circuit in the lab we saw that these large currents were messing with the power supply's output voltage. The power supply can only handle 5 amperes. The current (without the spikes) decreases exponentially with time and soon becomes less than 5 A, but the spikes remain unchanged.
Is there any way to get rid of these spikes?
If so how?


texts:
I have realized what I thought was a classic zero cross detector circuit using an H11AA1 chip:
https://www.digikey.com/product-detail/en/on-semiconductor/H11AA1SR2M/H11AA1SR2MCT-ND/2094174

My circuit is the following:

Note, I am using a H11AA1SR2MCT chip in my physical circuit (linked above) which should give me all zero-crossings.

I am now probing with an oscilloscope; I did not attach this circuit directly to 110VAC, I am using a toroidal transformer that gives a ~42V peak to peak isolated output. In the following image, the yellow trace is the transformer output, the green one is the signal at "PAD3" in the above circuit referenced to the local GND. I am using a 3.3V power supply.

I was planning to use that signal to generate an interrupt on a microcontroller very close to zero crossing, but so far it's simply unusable, voltage only goes down to 2.1V instead of zero and the timing characteristics are very far from the actual zero-crossing, even if they stay in sync with the wave. Is there an obvious mistake I am not seeing? Thank you


texts: Trying to simulate the linear region of a MOSFET

texts:
I wanted to simulate the linear region, so I tried this:

simulate this circuit – Schematic created using CircuitLab

I expected the triangle wave to be curved, but it didn't have those features. Am I doing something wrong or am I expecting the wrong results?

How does one usually simulate the linear region in SPICE?

Or do I have to make a lumped model of an NMOS for it to display the linear region?

EDIT:

simulate this circuit

I suppose this would be the more appropriate setup. The triangle \$V_{ds}\$ no longer creates a triangular \$V_{ov}\$. Making everything clearer to think about. Still, as in the previous schematic, the question remains, I was expecting curves, instead of straight lines.

EDIT:

Has anybody tied breadboarding the fist circuit and measured it with an oscilloscope? I just realized that it might not actually have significant curves. As the \$V_{in}\$ varied in phase with \$V_{ds}\$, that might compensate for the the expected upside down parabola of a varying \$V_{ds}\$, making it a lot less curved.


texts:
I've got a lenovo tablet (lenovo ideapad miix 300) from my friend, upon opening it, i found a burned out smd component that is the same component shown in the picture. I need help identifying this component, because I want to fix the tablet. Thanks.
I've tried to google the part number, but no luck.

The burned component:

The component caused the tablet to show that its charging when the battery connector is plugged in, even without no charger attached. Other effect is that the cpu heatsink becomes warm, but no picture is shown and the tablet cannot be turned on.
Here is picture of other components around the burned component. (red are pads of the burned out component that is desoldered at the moment)

Here are some pictures that show where the components are located at the tablets motherboard.

Sorry for my English, I am not native English speaker.


texts: How to check if a 3 phase motor is shorted or has problems

texts: How can I test using an analog multimeter if this 3 phase motor is shorted? It has a hard time starting( turn a little then hums) if there is a load connected, but if you remove the load (removing the belt from the pulley), it will start turning. My multimeter has X10k, x1K, X100, X10, & X1.


texts: How does k-nearest neighbor apply to wireless network positioning?

texts:
I'm trying to gain some insight into the variety of positioning algorithms for wireless networks. Apparently there are three categories of algorithms: distance estimation, scene analysis and proximity.

As far as I understand, distance estimation algorithms use certain metrics (e.g. signal strength or signal propagation time) from multiple sources to determine the location of the target. The proximity technique assumes that the target has the location of the receiver from which it is getting the strongest signal.

That leaves scene analysis. The document offers a brief explanation of the k-nearest neighbor algorithm but that didn't do it for me. I looked up the algorithm on Wikipedia but I don't have a clear view as to how this applies to wireless positioning.

How is k-nearest neighbor used as a wireless network positioning algorithm and what makes it different from distance estimation techniques?


texts: Why use an antistatic solvent dispenser bottle?

texts:
What reasons are there to have an antistatic solvent dispenser bottle (for cleaning your PCBs after soldering) as opposed to a solvent dispenser bottle that is not antistatic rated? I am specifically asking about the kind of bottles that have a stainless steel dispenser, such as the R&R Lotion bottles seen here: http://rrlotion.com/product/anti-splash-pump-solvent-dispensers-esd/

I have found several standards that suggest keeping anything that is not ESD safe at least 12 inches away from your ESD sensitive items, which is a good rule, but are there any other reasons why a dispenser bottle should be antistatic? Is there a reason why I shouldn’t purchase a solvent dispenser bottle that is not ESD safe and keep it further than 12 inches away from my ESD sensitive things?


texts:
I was testing some things on my protoboard to learn a little about transistors.
I made this:

The batteries are two AA 1.5V in series.
The resistor is a 1Kohm.
The transistor in a TIP122 npn darlington.

I uploaded a code that just put Pin9 as OUTPUT and HIGH, so I can test the currents on the circuit.

1.Current beetwen the Pin9 and the Resistor: 1,32mA.

2.Current beetwen the Baterry(+) and the Colector: 0,43A.

3.Current beetwen the Emissor and the Ground: 0,32A.

I can`t understand this currents. I was expecting 3mA ((5-2)/1000) on the 1st case and 3A (1000(gain)*3mA) on the 2nd and 3rd.

Am I doing something wrong?
Is this circuit going to damage my Arduino, since there is 0,32A going to the Ground Pin?


texts:
after I worked for a while with the PIC16 microcontrollers, I wanted to get known to PIC32 microcontrollers.
But I have a problem.
If I try to run a simple program on the PIC32MX110F016B or on the PIC32MX220F032B I get always the same error message:

  Failed to program device
   Selected device and target: memory    mismatch.

I use the PIC Kit 3 combined with MPLAB to program the PICs and with the PIC16s it worked always pretty well.
The PIC is powered from the PIC Kit 3(3.25V) and I connected it this way:

(PC3 = PIC Kit 3 pin, MC = Microcontroller pin)

  PC3 MCLR -> MC MCRL
  PC3 VDD -> MC VDD
  PC3 VSS -> MC VSS
  PC3 PGD -> MC PGED1
  PC3 PGC -> MC PGEC1

I also connected a 10K resistor from MCLR to the VDD pin.
And I think the only important config I set in the program is right, too:

#pragma config ICESEL = ICS_PGx1        // ICE/ICD Comm Channel Select (Communicate on PGEC1/PGED1)

Here the full console output:

  Connecting to MPLAB PICkit 3...

  Currently loaded firmware on PICkit 3  Firmware Suite
  Version.....01.36.10  Firmware type..............PIC32MX

  Programmer to target power is enabled - VDD = 3,250000 volts.
  Target device PIC32MX110F016B found. Device ID Revision = A1

  The following memory area(s) will be programmed:  program memory:
  start address = 0x0, end address = 0xfff boot config
  memory configuration memory

  Device Erased...

  Programming...  Failed to program device  Selected device and
  target: memory mismatch.


texts: how to avoid brownout caused by a multimeter on esp32

texts: I am using the VOLTCRAFT VC130 multimeter for measurement of current through my esp32. The microcontroller runs perfectly with two 1.5V batteries(~3V as read by multimeter in voltage mode). But when I put the multimeter in current mode between power supply(batteries) and esp32 in series for the monitoring the current. The brownout detector triggers. The brownout voltage level is 2.43 V +/- 0.05 for the esp32.


texts:
What is the memory map of w65c02s?
The datasheet is not clear at all compared to the atmega328p.
Can someone put up a chart and explain the memory space of this microprocessor?


texts: Routing the signal across the slot opening in the power plane

texts: What happens when we rout a signal trace across the slot opening in the underlying power plane ? Can you please explain the signal integrity issues generated by this mistake ? And what will happen if we rout a differential transmission line across a slot? Will the above issues be presented with the differential line ?


texts:
In the datasheet the battery is directly connected to pins 3.
But in some breakout boards I see this circuit:

simulate this circuit – Schematic created using CircuitLab
What is the purpose of this circuit? It's worth to use it or it's an "overkill" for this application?


texts:
I got a question about BUS isolation circuits.

Is this a correct design?
Looks not to me.
The book said that if POWOK is high, two SMBUS will connect together.
But I think it's wrong, the NMOS should be turned on when POWOK is low.....

The other circuits is like shown below.
I think its purpose is to isolate two power plane of the BUS.
When no power, the MOS is off to prevent the current from the outside ( to the SOC), and when power on and R/W data, if the data is high, the MOS will be off, and the other side will be pulled-up to the level as its power. and when data is low, it can pass through the NMOS to the other side.
Please correct if anything wrong here.


texts:
I am having a basic doubt regarding the working of preset and clear inputs.

Consider these two figures:-

Here in figure 1, if clear is 0, then Q will be 0 from 1.

But if its active low signal as shown in figure 2 then if clear is 0, then it will be inverted and clear input will be 1. So how will the output Q be 0 if clear input =1 ? I think it should not be inverted so that we can directly pass the clear input which is 0 and get output Q as 0.

I am not able to understand the meaning of active low signal and it's use here. What is the actual meaning of active low signal ? Is it just like attaching a NOT gate for input or does it mean that circuit will be active for low inputs but the inputs remain the same and not get inverted?

Please help.


texts:
I have here a circuit that I would like to find the transfer function ( call it \$H(jw) )\$ of so that I may map the input voltage (V_in) to the output (V_out) as:

$$V_{out} = V_{in} * H(jw):$$

I am not yet sure why it is not just the frequency response of a high-pass filter.

Namely: \$H(w) = jw / (jw + 1/\tau)\$ with \$\tau = R_2 C_2\$

For those interested in a physics paper, this paper at https://arxiv.org/abs/1602.06080 is basically a much more in-depth look at the problem I am trying to solve but with a lot more info that is not so relevant to this specific problem.

Those in the paper were able to decouple the performance of R1xC1 and R2xC2 by having them be limiting cases of one product being much larger than the other. I can not make that assumption and am wondering how it effects the total frequency response or if it is still mainly the high pass filter bit.

My V_in will also be a pulse with fast rise time and exponential decay but that is info I can multiply this transfer function by.

EDITS:

I did make a typo and switched V_in and V_out in the first equation (thanks for pointing it out, the definition you provide is the one I meant)

And as mentioned in an answer my V_in would indeed have a large impedance (somewhere in the 10 MOhm range) for this problem.

So I believe the real circuit (in terms of a voltage source) would be something like:


texts:
I am using an TI PCM1804 to convert my audio signal.

The PCM1804 is configured as follows:
Master Mode, with 12.288MHz input clock
Sample rate: 48kHz

The testsignal is a 440Hz sine with an amplitude of 4.5V_pp. In order to get a balanced signal from the signal generator, I use a circuit which is identical to the one in the PCM1804 evaluation kit:
http://www.ti.com/lit/ug/sleu015/sleu015.pdf

The circuit looks as follows:

After analyzing the ouput, unfortunately there is no 440 Hz sine but a distorted signal. I can post a picture of it in the next post.

Can anybody help with this issue? I have no idea where this comes from.
Thanks in advance!
audio_horrible

Output picture:


texts: How to locate FCC ID of a bluetooth device

texts:
I'm trying to find the FCC ID for a super common bluetooth trigger, the one used on all the selfie sticks.

I went through each manufacturer name I saw on Alibaba and input their company names into FCC site, but none of them show this specific product.

How is it possible that these companies manufacture this trigger and send it to US without the FCC certification? The devices show the FCC logo.

What else can I do to locate it? I tried opening the devices from 2 different manufacturers, but can't find it.

It is possible that they all ripped off some patent and all use 1 FCC ID that belonged to the original manufacturer of the device? Hence, the reason why when I search for individual manufacturers I can't find FCC application for that device.


texts:
I found a CNA1011K photocoupler laying around and I wish to try it out. Could someone explain what the parameters from the datasheet mean and how to use them for particular circuit parameters?

LED maximum current If: 50mA - that's understood. How about the voltage across it? Standard LEDs have nominal voltage and current ratings, but not this one.
Reverse voltage and current: why should I care about them?
Forward voltage: @ If= 50mA is 1.2V. How do I ensure a 50mA current? If I use a 50Ohm resistor, as in the circuit diagram, the current will be 24mA, right?
Is it better to alter the light intensity by increasing the voltage or the current through the LED?
How do I know what base current range I can generate with LED? How to choose the RL value based on an arbitrary Vcc voltage, what is the Vcc range?


texts: Battery lifetime about a fifth what it should be

texts:
I have an esp8266-201 hooked up to an LM3671 buck converter breakout that is in turn connected to a 3x AAA battery pack.

The capacity of the battery pack should be at least 1200 mAh at 4.5 volts.

The apparatus draws about 100 mA while awake and about 0.175 mA while sleeping (taken with a multimeter), and it is programmed on a 60 s sleep, 3 s wake cycle. This corresponds to an average current draw should be 100*(3/63) + 0.175*(60/63) = ~5 mA.

The device only runs for approximately 2 days or about 48 hours meaning that it is registering an average current draw of 25 mA.

What is going on here?

EDIT:

I powered the device using batteries from the same pack as the ones that failed earlier. I made sure all the batteries had voltages of ~1.6 V before placing them in the pack. I loosely monitored the voltage of the battery pack over time.

N.B. I realized a flaw in my firmware was causing the ESP8266 to draw more power than needed for my application. I changed the settings and managed to about half the wake current to ~55 mA. The average current is now about 2.5 mA

Although I halved the wake current the device did not last twice as long. It ran exceptionally until about the 50 hour mark where it began to drop off quickly. Does this signify bad batteries or something else?

It seem like the batteries discharged in the manner that they should, they just exhibited a much lower mAh then they should. I am particularly perplexed that halving the current did not double the run time. What is happening here?


texts: I'm trying to get a MPU-9150 motion sensor running with my FPGA-Board. The problem is that my I2C-master library doesn't support writing single bits. According to the Register Map there a for example bit 6 and 7 in register 26 reserved. What happens when I write (let's say 0's) to them and is it recommended to do so?


texts: Maximum current and voltage of Small Ceramic Capacitors?

texts:
Small ceramic caps are nasty because their markings, such as ceramic monolithic leaded "104M"(yellow-brownish) and epoxy ceramic monolithic leaded "223", do not reveal max values. Since I do not know their manufacturers, I cannot google for their max voltages or max currents.

What is a typical maximum I for the smallcap?
What is a typical maximum V for the smallcap?


texts: How to store custom ltspice symbols/schematics in a subfolder?

texts:
I made a simple inverter INV.asc and associated symbol file INV.asy, which I am using in my top-level test file, Top.asc. I would like to store my INV symbols in a subfolder (or somewhere else). I tried to do this by adding the sub-folder res to my path (both Symbol & Library search paths), which lists the component in the component select window, and I can place it in the top-level schematic; however, when I do this, I get the error that LTSpice "cannot find schematic". This is despite that, when I right-click on the part in my top-level, I can select "Open Schematic" and it opens fine.

I'm okay with doing it a different way; my end goal is to just get all of my individual parts in their own folder, so that my top-level schematics don't get cluttered with my own parts. How can I do this?

Link to the files:
https://drive.google.com/file/d/1c5If1WNBPw-w9pMh5-f55B_HYko3VJTw/view?usp=sharing

UPDATE 1/23/2020 1:41pm
I moved the .asy and .asc files to my LTSpice\lib\sym\Alex folder, but I still get the error, even after closing/reopening LT. I deleted the part from the Top and re-added using the one in my LT folder.

I still get the error:


texts: Voltage and current during the first cycle of RL circuit

texts: I have a simulation of RL circuit connected with an ac source. Any one can tell me please that why the peak of the current during the first positive half cycle is higher than the peak of current during the  first negative half cycle although both halves of the cycle come from the same voltage source and current goes through the same components in both positive and negative half cycles?


texts: PIC16: How does one enter sleep mode using C?

texts:
The datasheet of my PIC16 refers to the "SLEEP instruction". I'm programming the PIC16 in C using MPLAB X and the XC8 compiler.

How can I execute a SLEEP instruction on my PIC16 using C?


texts: Mosfet controlled LED strip not bright enough

texts:
So, I'm trying to control a LED strip with a NodeMCU using N-MOSFETs FQP30N06L, one for each channel. However, the strip is not nearly as bright as with the original IR controller. (I saw the similar question, however my transistors are definitely logic-level)

The main problem SEEMS to be the mosfets, as if I connect the LED strip chanels directly to ground i get a much much brighter light. Also, there seems so be a quiet high pitch sound when using the transistors.

The circuit is very simple, strip (5m, 30 leds/m) runs on 12V and should take 1.5A, so 0.5A for each channel, and that's what the power supplies. Looking at the datasheet for the MOSFETs, it looks like at 3V G_gs is should let through 10A, way more than the 0.5 I require. (However it is my first time looking at a datasheet so that's probably where my mistake is, though I have no clue what).

I have a multimeter, just wouldn't know where to even start measuring things.

Also I'm not connecting the MCU to 12V as I know that's too much for the voltage regulator, I just couldn't find a good enough cirtcuit drawing tool, so any suggestion for that is welcome as well.


texts: buck converter with a simple bypass schematic mode?

texts:
in my design i need to place a buck converter 10-30V input with a fixed 12V output. my concern is that when the battery volatge level is low (for instance 10v) the device will stop bucking. so i want to make my buck converter to bypass the input voltage when it is lower than the required output(which in this case 12).
any ideas on such designs? or which components to use?


texts: Why have the neutral wire in house current

texts: In Canada anyway and i assume around most of the world, two wires come from the electrical company to your house. The hot and the neutral. ( there is also another hot 180 degrees out of phase with the first one but forget about that for now)What i am wondering is simple, why don't they just send the hot wire and you connect it to the ground (after passing through some resistance obviously). This would complete the circuit fine and save them so much money in installing the wire.


texts: How does the OV(Overflow flag) of the 8051 work and how does it differentiate between signed and unsigned digits?

texts:
If a number is 8 bit, the maximum value it can have is 2^8 or (1111 1111).
In the OV flag, the last digit or the MSB decides the sign, but how does the overflow flag know if it is the "signed MSB" or a normal MSB ?
eg. (1111 1111) is the number 256, but I read somewhere that as the MSB is set to 1, it is a negative number. I do not understand this as it is very confusing if the MSB is used as a sign bit or as an ordinary number with a place value.


texts: Not Understanding Grounding in an Electrical Circuit

texts:
This might be a stupid question but i am just a little confused about grounding/earthing. Specifically for example in a home when some electrical appliance faults, the current will go to ground since i assume it is then the path of least resistance/easiest path. From my understanding, this current then goes through ground and back to say the power pole ground and the current will go back into the circuit. However here are my questions:

When the current flows through the ground and say i am standing 1 m away from the grounding pole, why isn't it possible for some of that current to go back through my body (assuming i was touching something positive in this scenario)? Is it since the human body is of a much higher resistance when compared to ground? (~100000 Ohms compared to around 7 Ohms).
When current goes through the ground pole from a house in this scenario, why does it go back to say the power pole ground, rather then the neighbors ground pole as it is closer? Is it since the neighbors ground is on a different circuit?
When current goes to ground through the house ground pole, it does go back to the power pole ground pole right? Then the current will go back into the power pole circuit or no? I am a bit confused as where the current goes after it goes to the ground?

4. Updated Question: If the houses are on the same transformer, if they both faulted at the same time, where does the current go then. Does it go to ground, then house 2 goes to house 1 then goes to the power pole ground?

Also Is it bad for the ground current to go back through to the source current? As in typically inst the fault current caused much higher or not typically for a household appliance failing like a toaster?


texts:
I use 24V control circuit is showed as follows.

If I connect a 10k resistor as load the transistor works.
5V control signal => 0V collector voltage
0V control signal => 24V collector voltage.
But if i connect a dc motor as load the transistor damaged permanently.(DC motor draw 0.15A at 24V. It's power is about 3.6W.)
5V control signal => 0V collector voltage
0V control signal => 3V collector voltage
After that, even if I connect 10k resistors again, the output does not change between 0-24V.
Output voltage changes between 0-3V with 0-5V control voltage(the transistor doesn't seem to turn off completely again). Where am I doing wrong?


texts: How to build an electric rat trap / deterrent

texts:
I am looking to build an electric rat trap that acts like an electric fence, one that that can deter or block rats from climbing up a tree.  Not interested in killing them.

I have a large orange tree that we love, unfortunately so do all the neighborhood rats. Every night they run up into the tree, eat into several oranges, leaving debris all over the ground. In a couple months time, all our oranges could be gone.

I don't want to poison them (we have dogs), snap traps are mostly useless, and if they work, it gets just one. There are always a bunch more in the area that follow.

I'd like to build an electric "fence" that can shock them as they climb up the tree.  I saw on youtube how they do this:

Take a 12V battery, connect it to a 150 uF AC Capacitor, which then connects to two sheets of aluminum/steel (positive to one piece, negative to the other). Each piece of aluminum/steel will wrap around the base of the tree, spaced an inch or two apart, so when they climb up, they get shocked, and fall off.

This is one example of a setup that I found:

The negative line of the batter goes straight to one piece of metal/aluminum, the positive goes into one capacitor, then into another, and then to the other piece of metal/aluminum.

As I got this off of YouTube, I was hoping for clarification on a couple things.

Would this setup work? If not, what changes would be needed?
How to make it safe? I would disconnect battery at night and reconnect in morning. I don't want my tree to catch fire, and I don't want to electrocute myself.
What kind of shock would I expect if I personally triggered it - touched both pieces of wire.
How long would battery last, if nothing touched it? I assume I would have to recharge the battery at some point?


texts: Short circuit test on long coaxial cables

texts:
In a building infrastructure there is coaxial cables for TV. The first end of all the cables is on the roof. The second end for each cable is in different apartment.

The problem is that I don't know which cable is connected to which apartment. So I thought that doing short circuit test might do the job. But:

The cables lengths are [20m-50m]
I can't get the two ends near each other (DUH!)


texts: Maverick probe causes ardiuno to reset when touches grounded electrical item

texts:
I have a Maverick 732 probe connected to an Arduino for measuring temperature. The outer shield of the probe is connected to the ground pin on the Arduino, and the other wire is connected to an analog pin on the Arduino, and to a 220k ohm resistor and then 5V:

Using a variety of off the shelf 12v and 9v DC AC/DC adaptors to power the Arduino, the external wire of the probe touching an earthed appliance such as the metal shell of an electrical oven or a slow cooker causes the Arduino to reset.

The one thing that all of these transformers have in common is that they only have 2 real pins connected at the plug (UK 3 pin plug with a plastic pin where the earth pin would be or a metal pin with no earth wire connected). So the transformer is only connected to live and neutral at the plug socket.

On a power adaptor that uses a 3 pin plug and includes an earth connection in the plug, the resetting of the Arduino when the probe sheathe touches an earthed appliance does not happen. If I use a battery instead of a transformer, this issue also does not happen.

I then modified the transformer to include an earth connection to the outer part of the barrel connector (-) that provides power to the Arduino. This also solves the problem - the reset no longer occurs.

I don't understand what I can change in my circuit, short of using an earthed ac/dc adaptor to provide power to avoid this issue. Is there anything that can be done to stop this happening?


texts: Superposition theorem for transient analysis

texts: Can we apply superposition theorem in transient analysis of circuits? I don't think it can be used since during transient state the input and output relation is not linear and is rather explained by exponential functions like in case of RL and RC circuits. Please consider a case having two different sources with different frequencies.


texts:
I'm trying to design my own USB 3.0 hub based on this commercial design,

I can understand everything in this design except the usage of IC "ASM1543".
Unfortunately there is no datasheet available, however a product brief is available at https://www.asmedia.com.tw/product/85ayqa4SX4XSewIf/230yQc0rgeGp9TJ4
According to the brief this IC is a,
ASM1543 is a one Four to two differential channels mux switch with integrated Type-C
Configuration Channel Logic Circuitry, using for USB3.1 type-C mux and CC detection
application

The IC looks like to be connected between USB 3.0 hub IC and USB C port. I wish to have a USB C connection on my design. Yet I'm confused if I should use this IC. Since there is no datasheet available I prefer to avoid using it if it's not necessary.
My question is what is the purpose of this IC? Would I have proper USB C functionality without using this IC by directly connecting a USB C port to bridge IC? After all as per my understanding USB C is only a form factor. Technically I don't need any soft of circuitry to convert USB 3.0 Type A to Type C?


texts: Problem with aop subtractor with simple power supply

texts:
I am using a LM324 with a simple power supply like you can see in the picture below as a subtractor.

It subtracts \$Vs = V1 - V2\$, and my problem is, when the subtraction is positive I have no problem but when it's negative I thought I would have 0V but I always get 0.6V wathever the result of the negative subtraction is. Can someone help me please?


texts: Output of 4.8V due to reverse polarity series schottky diode?

texts:
I was reading through the Data Sheet for the Photon, an IoT dev board: https://docs.particle.io/datasheets/photon-datasheet/ and under the Power section it says:

  When the Photon is powered via the USB port, VIN will output a voltage of approximately 4.8VDC due to a reverse polarity protection series schottky diode between V+ of USB and VIN. When used as an output, the max load on VIN is 1A.

How is it that it outputs 4.8V due to the "reverse polarity protection series Schottky diode"? How does the Schottky diode influence Vin in such a way that it outputs 4.8V?
Also what does it mean when it's between "V+ of USB and VIN"? Is it that it's connected across the positive terminal of the USB pin, to VIN?


texts: I want to connect 3 wire pt100 sensor with arduino uno, without using any amplifier or op-amp. What could be the circuit of the same?


texts: how to implement Ethernet with PIC, PIC18F97J60, PIC32MX(795F512L), ENC624J600, LAN8720A

texts:
My project is a data logger board which must mount a PIC of some kind to provide USB and Ethernet as a means to communicating with the board. I can develop this system into two products a low-end version which provides 10Mbps (10BaseT) and a more featured one which must provide 100Mbps (100BaseT) for compliance with LXI (LAN eXtension for Instrumentation).

For the low-end version I use

PIC18F97J60

This part offers the path of least resistance. I get everything in one chip including the PHY layer. I just need to add magnetics and use the free MICROCHIP TCP/IP stack in the firmware to get the job done. However, this provides 10Mbps (10BaseT) only and the product based on this solution cannot be LXI compliant.

For the more featured version I want to use a suitable member from

PIC32MX

With the PIC32MX I could use one of the following PHYs

LAN8720A/LAN8720Ai
ENC424J600/624J600
LAN9220, LAN9221 or similar

In a few words what are the main differences and use cases between these PHYs?

Is there a member of the PIC32MX family that is equivalent to the PIC18F97J60 by offering MAC and PHY all integrated in one chip?

Thank you for your help

Regards


texts: Using of RF transcieivers to communicate over 230VAC powerline

texts:
Initially I need to communicate between several devices placed within one appartment (or a building). All those devices will be connected to 230 VAC power line.

I'd like to skip any wireless communication as it will not guarantiee that neighbours will not interfere with each other.

And I'd like to have a cheap and small solution.

Initially I stuck with TDA5051A which is created directly for what I need. In addition its datasheet including detailed application schemes:

However the chip is moderately big (10mm long SO16 package) and a bit pricie (about $3/piece not including price of additional needed components).

So this is why I turned to figure out how to do this with in the same way as RF-wireless communication does. But instead of the air I will use 230VAC power line as the medium:

So my questions are:

Is it enough to use a capacitor between the powerline and the
transceiver?
Which wire is better to use for communication: line of neutral?
How can I be sure that the signal will reliably transmitted within
one single powerline wire AND will not be transmitted wirelessly with any
significant power to the neighbours electrically isolated powerline
wires?
Is it possible to place any filter at the apartment (or building)
inlet to restrict data transmission to/from neighbours?
I will be very appreciated if anyone will share ready-to-use
schematic
Is there anything else I should think about or take into account?

Thank you in advance!


texts: Mutually exclusive headphone and speaker

texts:
I have a device that has only one set of analog audio out signals that are amplified for headphone usage. I want to be able to use these signals to output to a set of speakers OR a headphone jack, but not both at the same time.

The headphone jack has a detect pin that goes high when a jack is plugged in.

I have found a simple amplifier circuit for amplifying a headphone signal for an 8 ohm speaker.

I have created a test circuit (image below) with the headphone jack and the amplified speaker circuit on the right and the output for the right channel of the audio on the left. My thinking was that when the detect signal goes high, the LM386 Vs pin would receive voltage from Vcc. Feel free to delete parts of my circuit that are bad.

Using the detect signal from the headphone jack, I would like help designing the circuit that fits the following truth table:

Detect | Speaker | Headphone
   0   |   1     |    X
   1   |   0     |    1

If you know how to use 123D Circuit you can fork my circuit and pick up where I left off.

Edit 1: Turns out this isn't as complicated as I thought because I (finally) found some information about the detect switch states:

"The switch is closed when headphones are absent. The switch opens when headphones are inserted."

Here is the (presumed) working photo:


texts: Washing machine / microwave motor - AC or DC

texts: If I take an old washing machine motor and try to convert it into a generator would it work and if so would it generate AC or DC? Same question with a microwave motor. I know it uses permanent magnets but would it generate AC or DC?


texts: Transformer and IC heating in Viper22a SMPS design

texts:
I have designed an SMPS using viper22a IC. This gives an output of 9.8V and on adding a 10 ohm load resistor, voltage drops to 9.6V, thus giving an output of almost 10 watts. Here is the circuit that I am using:

Initially I used EE core transformer and it was performing excellent. I am not sure whether it was EE-13 or EE-16. However, due to height consideration, I had to switch to some low profile transformers. I chose EPC-13 and EFD-15 and tested the circuit by replacing the original transformer. Here are the images of original and new transformers I got for testing:

At no load, the circuit gives an output around 9.8V. However as soon as I put a 10 ohm load, the voltage drops to 5.6V i.e. a net output power of around 3 watts.

In this case, there is heating observed in transformer as well as Viper22a IC.

Kindly give your opinions about what might be wrong and suggestions regarding what should I do?


texts: Find potential difference between nodes A and B in circuit below

texts:
By KVL and KCL
Ix = 4A and Iy=Iz=6A

The potential difference between A and B = Va - Vb = 6 +8Ix =38V
I don't understand how we calculated the potential difference using KVL and KCL


texts:
I've been looking for a viable means of communication under water (other than sonars), be it short or mid-ranged, and I have come across MM and MI.
I am no engineer, so I need help with this, and I guessed you guys would be helpful.

In this case, the emitter would be located in an AUV (Autonomous Underwater Vehicle), so the power input to the comm system can't be too high, let's say no more than 20 or 25 WH/dm^3, and it should last for more or less 30 hours.

The question is: What would the maximum range of this system be?

Thanks in advance!


texts: How can a DFIG have total control of reactive and active power?

texts: I'm confused with the power flow of the rotor to the grid, specifically the both-way direction


texts: Deciding between ULN2804 or ULN2803 with 74HC595

texts:
I'm making a circuit with Arduino + 74HC595 + (ULN2804 / ULN2803) to drive a few 12 V Motors.
I'm trying to decide whether to use the ULN2804 or ULN2804. On testing, performance of both is fine, except Vout is around 11.46V for the ULN2804 and around 11.10V for the ULN2803, using a 12 V Supply.
On the two datasheets, almost everything seems to be same except for a few values - all related to the input of the IC:

TTL vs. CMOS drive
2.7K vs. 10K input resistor
5V vs. 6-12V specified input voltage range

Which of the two parts is more suitable when used with the 74HC595 (CMOS) to drive 12 V motors, in the sense of long term reliability?
Or, is there no important difference between them in my application?


texts:
I bought some SOM modules with AM335x on board (PH8700). The SOM is completely blunk (both eMMC and EEPROM). So I have to build u-boot spl first and load it via XMODEM. The problem is that u-boot spl hangs between board_init_f() and board_init_r(), it seems that the bad thing happens while relocating the stack from SRAM to DRAM. Specificaly when I comment the following code in ctr0.S:
# ifdef CONFIG_SPL_BUILD
#   /* Use a DRAM stack for the rest of SPL, if requested */
    bl  spl_relocate_stack_gd
    cmp r0, #0
    movne   sp, r0
    movne   r9, r0
# endif

u-boot SPL goes further. Does it mean that I have some problems with DDDR3L? Do I have to retune it in u-boot? Why is that? The board doesn't seem to be changed, and the previous versions worked fine...  P. S. I've tried different versions of u-boot (mainline, TI, some custom versions for PH8700 module, TI versions, etc.). The result is always the same - SPL freezes between board_init_f() and board_init_r(). How can I resolve that issue?


texts: What's the purpose of the full wave diode bridge in this DC-DC power supply?

texts:
In the following power supply circuit, there is a full wave diode bridge (full wave rectifier?) after the DC Input. I can see how we need a full wave rectifier after an AC input, but why after a DC input? Is it to smooth out power signal?

Thanks

Circuitlib Schematic


texts:
I'm trying to simulate a basic voltage-doubling rectifier circuit:

But my time graph looks like this:

Is there something wrong with my circuit? Am I using the simulator wrong?


texts: Troubles with mic preamp for headphones with integrated microphone

texts:
I am designing a preamp intended to interface with a microphone in common headphones (e.g. apple earpods, or sony headphones with a microphone) which will then connect to my ADC's inputs.
I've developed a circuit based on a reference design, however the reference does not take into account the need to bias the microphone. From what I gather, I need to provide ~1.65V to the mic.
My circuit is using an AC voltage source @ 4mVrms to simulate output from the microphone (not sure if that's a fair model) and I'm not including any mic resistance.
My questions:

How would I bias this mic? providing power to net 8 does not show a bias (in simulation).
How do I ensure the gain of this pre-amp is correct? Finding datasheets for the mic in apple earpods is next to impossible so I don't have any real specs to go from.
Are there any reference designs that perform the same task?


texts: Why is a common LED failure mode to flicker astably or oscillate?

texts:
There are many cases of LED lights failing by beginning to flicker intermittently.  I am not talking about the intentional duty-cycle modulation utilized in many driver circuits.  I am referring to visually evident strobing on the order of 10 Hz.  This failure mode is common to flashlights, desklamps, and ceiling lamps.  What is it about the electronic circuits contained within commercial LED lamps which causes this to be a common failure?

Is this something fundamental to the way white LEDs behave when they overheat?  Do they intermittently go open-circuit?

Is this due to the action of a safety circuit in the driver?

It is not due to a failure in the switching supply, because it is often observed in battery-powered flashlights.

It is not due to a failure in the dimming circuit, because it occurs in lamps not powered through a dimmer.

It appears that there is some common oscillatory or astable failure mode in which component values on the "hairy edge" (especially capacitors?) combined with:

increased resistance in connections due to corrosion; -AND/OR-

increases in current drawn by LEDs as their temperature rises

shift the effective value of components used in the circuits, leading to this flickering failure mode often being induced in the lighting circuit.

Will someone "in the know" please cast some light (so to speak) on the apparently common shortcoming in the electronic design of commercial LED driver circuits which is the root cause of this ubiquitous problem?

Thank you very much.


texts: How to solve Transfer function with step function appplied to the input?

texts:
I'm trying to solve this problem of the book "Automatic Control Systems" by Benjamin Kuo.

I really don't get the answer the book has:

Since I thought the answer would have to be:

$$
F(s)=
\dfrac{880(s+6.818)}{s(s+6)(s+10)}
\dfrac{1}{s}
$$

or

$$
F(s)=
\dfrac{880(s+6.818)}{s(s+6)(s+10)}
E(s)
$$

since \$e(t)=u(t)\$

My question is why in the answer it seems they multiply \$F(s)/E_c(s)\$ by the step function since in the original function it is multiplying by the other side of the equation and there's only one instance of \$u(t)\$.
$$
\dfrac{1}{s}
G(s)
$$


texts: Suggestions on simulating fuse characteristics electronically?

texts:
Assume that we have an isolation transformer 230V in 230V out and that we measure the output current with a current transformer with known transfer function. We compare the current to a settable value and if over, then we trip a relay that disconnects the output. This kind of fuse will be almost infinitely fast, something that is not always desireable. So, what about this:

simulate this circuit – Schematic created using CircuitLab

U1 is a true RMS ic such as the AD 8436. The values of the RC link should be something else, the comparator a real comparator etc. I just drew to illustrate the idea, being that I could vary the characteristics of the "fuse" by changing the RC time constant. Now the time taken to reach the trip point will depend on how much larger the measured current is or t = -LN(1-(1/n)), where n is by how much we have overcurrent.

If we assume that the time constant is 10s, then the fuse will trip after 7s if the current is 2x over, 2.8s if 4x and 1s if 10x. One could also change the time constant to be something else on discharge by adding a diode and resistor over R1

Would this be a workable idea for an electronic fuse?


texts:
I am new to microchip but I build an circuit with PIC12F629 and wrote this program:

#include <xc.h>
#define _XTAL_FREQ 20000000
#pragma config WDTE=OFF , BOREN=OFF , PWRTE=ON , MCLRE=OFF , FOSC=INTRCIO

void main(){

TRISIO    = 0;
GPIO   = 0;
    while(1){
        __delay_ms(1000);
        GP0 = 1;
        __delay_ms(1000);
        GP0 = 0;
    }

}

I compile it with XC8 MPLAB X and I have transfer hex file to chip, then I connect pin num1 to positive voltage and pin number 8 to ground, then pin num7(GP0) to positive side of led and grounded other side of LED.

The circuit doesn't work, how could I fix it? I don't quite get timing in the code, any idea?

I measure voltage at LED sides, it is about 1 but incoming voltage is about 5.

I also removed all timing to lite GPO all time but still no luck:

#include <xc.h>
//#define _XTAL_FREQ 20000000
#pragma config WDTE=OFF , BOREN=OFF , PWRTE=ON , MCLRE=OFF , FOSC=INTRCIO

void main(){

//init GPIO pins
TRISIO    = 0;
GPIO   = 0;
    while(1){
       // __delay_ms(1000);
        GP0 = 1;
        //__delay_ms(1000);
        //GP0 = 0;
    }

}

Update

It strangely worked by adding positive voltage first and negative second in to the circuit, any idea why? It even works by just grounding pin3! I think it needs something in the circuit.


texts: how to calculate the total power dissipation of below circuit


texts: How can I silence this noisy SMPS board?

texts:
I have a receiver and it's  SMPS board is making a constant hissing sound which is noticable from a few steps away, so I'm sure it's not normal. The source is probably the ferrite transformer on it, but I'm not 100% sure because it's hard to tell. What components are the most likely to cause this problem (and why)? Because they all measure ok, but I only tested them with a multimeter and in circuit. Or what can I do with the transformer if that alone is responsible for the noise? The noise is there whether or not the SMPS is loaded, there is only a little difference.
The schematic is here (page 112):
https://www.manualslib.com/manual/950375/Denon-Avr-3311ci.html?page=112#manual
Should I just change all electrolytic caps and hope it will go away? If not, then what?


texts: How to automatically disconnect from battery when USB +5v is present

texts:
I'm creating a SMD PCB where space is extremely limited.
Usually, the application is powered by a battery (Single cell 3.7v lipo).
To charge the battery, I'm using a USB cable.

What I'd like is for the application to automatically switch to USB power instead of the battery whenever power from the USB is present.

A normally closed "switch" between the battery and load sounds ideal. The +5v from the USB would be used to open the switch. When the USB is disconnected (left floating) the switch would close and connect the battery again. Is there a simple way to achieve this? Am I overcomplicating it - would a diode on the positive terminal of the battery serve the same purpose?

As I say, space is extremely limited so I'm trying to achieve this with as few components as possible. I'm hoping I can find a single solution in say a SOT23 package or similar.

Here is a simplified schematic drawing.


texts: How can I describe the behavior of an inductor without reference to a magnet?

texts:
In class we have been given an exercise to simulate capacitance, inductance, and resistance without reference to - well, without refernece to much of anything. The resistor is straightforward, likewise the cap - a voltage is created, energy is stored. Now, how about the inductor? Most inductance descriptions I've seen so far involve either a magnet or an iron rod. How does the generated magnetic field in and of itself affect the current?

Thanks much in advance

Joe


texts: Buck Converter - Calculating Line and Load Regulation

texts:
I have a buck converter with a PWM circuit and Control Circuit in LTSpice.
I'm wondering, how do I simulate values for load regulation and line regulation?

I was thinking for line regulation I could sweep the input voltage?
But for load regulation, all I can think of is having a switch with an extra resistor that turns on and changes the output resistance.


texts:
I have one basic question, because I don't know much about tube amps. I live in a country where during winter, voltage can be from time to time low (around 160V-180V). I decided to keep my amp safe using an automatic voltage regulator, which keeps it around 220V-230V, which is good. Can those devices do any harm to a tube amp?

I also noticed that when there are voltage oscillations during the day, the amp tends to be slightly lower sounding. Is that normal behavior for tube amps?


texts: Do transparent electronic paper displays exist as a commercial product?

texts:
Is there a such thing as a transparent electronic paper display that is commercially available ?

I've found that Samsung has a transparent LCD, but I haven't been able to find any examples of transparent e-paper.


texts:
In the case where you hit a power line with your car, is it possible if you

a) touch the frame of the car [(i) either one or (ii) both hands] and your body has no contact with the ground, you will not be electrocuted.

Similarly, if you b) open the car door and have one foot on the ground and the other foot still remaining in the car. (keeping in mind that that the body is not in contact with the frame of the car)

I may have misunderstood something, but is the reason that you do not get electrocuted due to the negligible potential difference for scenario a) with both hands and that one hand touching the frame will result in the same reasoning for scenario b) where you are not completing the circuit that you won't get electrocuted?

Thank You!


texts: How can I generate overflow condition from a 74'283 or 74'181 adder without an output pin of the carry-in of the MSB?

texts:
I've been building my own CPU from low level chips, using the 74LS283 adder. And I've been wondering about how to set the overflow flag. Finally I seem to have grasped that the overflow flag is the carry-in of the MSB xor-ed with carry-out of the MSB. See also https://stackoverflow.com/questions/29330787/signed-overflow-why-carry-in-and-carry-out-of-msb-should-match. But I wonder how I could even know the carry-in of the MSB when I use the 74LS283 adders?
I suppose with the '181 ALU, there are signals !P and !G. From the datasheet:

P (Carry Propagate) and G (Carry Generate). In the ADD mode, P
indicates that F (result) is 15 or more, while G indicates that F is
16 or more. In the SUBTRACT mode, P indicates that F is zero or less,
while G indicates that F is less than zero. P and G are not affected
by carry in.

this sounds like it might come close, but if I interpret the 4-bit numbers as two's-complement signed numbers, then 15 is already -1. In subtract mode this might work. But what about signed addition overflow?
There is another related question here: How to determine if a Carry Look Ahead Adder Overflows but it seems to have only allusions and comments that speak about precisely the problem that the carry-in to the MSB is hidden inside the package.


texts:
I have a question about the circuit below. I want to find Vo in terms of Vi. But I don't fully understand the principles about an ideal op amp's output. You will see my questions in bold at the bottom of the page when I first explain my process.

So first I assume the ideal op amp has infinite input impedance so no current flows into either input of the op amp.
Next as the non-inverting input is connected directly to Vi, I can assume that the inverting input will also be held at Vi.
Now because both sides of R2 are held at Vi, no current will flow through R2.
Finally to find the current flowing through R1, I use nodal analysis to say the current through R1 will be (Vi-Vo)/R1. Now the answer I have been given is Vo=Vi, or the nodal analysis equation equals 0.
But how does this equation equal 0? Is it because both inputs are at the same potential of Vi, so Vo will also be at the same potential of Vi, so no current can flow?
Or is it because Vo must equal Vi in order to hold the inverting input at the potential of Vi?
I thought that if there was no voltage difference in the inputs, then Vo would equal to 0V?
Thanks


texts:
I'm looking for a little help understanding this circuit:

http://i1316.photobucket.com/albums/t607/blueturnsred1/Capture_zps5150bde6.jpg

Details of the circuit:

1 IRF510 Power MOSFET N-Channel

1 1M Ohm Resistor

The sensor is made from plaster of paris

About the circuit:

Basically what we have is a mosfet connected to an LED and a 6 volt solar cell.  The sensor is a piece of plaster of paris with two nails in it. The whole kit can be seen here:

http://technologywillsaveus.org/resources/thirsty-plant/

The idea behind the circuit is that you put it in a plant's soil, and when the plaster of paris "sensor" dries out the led comes on, and you know it's time to water the plant.

I have been trying to wrap my head around how this switch works.  What I have been able to understand so far is that in a typical switching application. when five volts is applied to the gate of the the MOSFET it will switch on and allow the circuit to function.

The way I think that this circuit works is that the current is shorted through the "sensor" when the plaster of paris is wet. I believe this keeps the current from going to the gate of the MOSFET, and keeps the LED off.  Then when the "sensor" dries out the current goes to the gate and switches the MOSFET on.

Can anyone tell me if I am on the right track?

I have read a lot of tutorials, but I can't find anything that will help me further understand this.


texts: Dynamic range of voltages for ADC input controlled by software

texts:
I'm trying to build an interface that can take the readings from level sensors and provide a small enough voltage that a 3.3V microcontroller can read.

I've done this successfully using the following circuit, which will give me a reading in a fixed range of voltage inputs. The circuit is simply a voltage divider -> rail-to-rail buffer -> RC filter.

simulate this circuit – Schematic created using CircuitLab

BUT, I want to be able to interface with sensors with different voltage-output-ranges, without sacrificing resolution on my ADC. That is, I want different sensors to be compatible such that interfacing a different sensor only requires you to specify what the sensor's output range is in the microcontroller's software.

For example, some of the sensors I'm looking at have output ranges of:

0-2.5VDC
0-3.3VDC
0-5VDC
0-10VDC
0-12VDC
0-24VDC
4-20mA

My immediate thoughts were to replace one of the resistors in the voltage-divider network with a digi-pot, but high accuracy (low resistive tolerance) digi-pots are expensive. Are there any cheap ways to achieve this? (I'm not too concerned about circuit complexity, just cost.)


texts: High Impedance Load Driving with Mosfet as Common Source Configuration

texts:
I am just trying a design ac switch with mosfets which are connected as common source. Mosfets will drive 16.2A load in normal conditions. When I try to drive 10 ohm load with 162V (peak, 400hz), as you can see in picture 1, there is no problem in load voltage. ( Green wave : Load Voltage, Red wave : Gate-Source Voltage)

I just try to increase load to 100k, I saw the almost 162V on load without gate firing. What is the reason of this ? Leakage current, drain-source parasitic capacitance etc.. and How can we handle this problem ? Is this really problem ? In addition, frequency is affecting the load voltage in off-state. I see almost nothing on load when I used 162VDC source in off-state of mosfets. It just happens with AC sources.

By the way, I saw the same thing on real circuit, not just a simulation.
I am waiting your kind comments,
Thank you,


texts: What is making this noise (Ultrasonic sensor output)?

texts: I have an ultrasonic sensor, operating in continuous mode, that is providing a 0-10 V DC output signal. It is connected to an ADC. We are using a cheap power suppy to power the sensor. The ADC has its own wall plug supply. The node where I connect the the ADC input to the sensor output reads the DC voltage just fine, but it also has an unwanted frequency component which causes my ADC readings to fluctuate. I will be isolating components, and using coupling caps and/or RC filters to attempt to isolate the noise, but I would like to know if anyone can identify this type of noise immediately so I can get rid of it. I am suspecting one of our power supplies/bad ground right now. It appears that this 100 Hz noise is the lowest frequency. Any ideas what this noise is, or other ideas about how I can stop it? Thank you in advance!


texts: is there anyway to increase an output voltage 100V DC to 110V DC using caps the source available is 110 V RMS?

texts: simulate this circuit – Schematic created using CircuitLab


texts:
I've got a Weller soldering station with settable temperature and interchangeable tips.

Is there a table or general guidelines for temperatures and tips for different soldering tasks, such as:

wire-wire, thick
wire-wire, 20 gauge
wire to PC board
through-hole chip on PC board