texts:
I'm following this project. More specific Step 7: Rainbow Pistil

https://www.instructables.com/Ever-Blooming-Mechanical-Tulip/

In the picture bellow. On the top left corner is how I should solder the leds.

The upper ring(Brass Wire) is the positive voltage
The lower ring(Brass Wire)

I am not sure if I should connect both 5V pin to the  positive voltage ( upper brass wire) and the two GND pins to the GND ( lower brass wire):
The other uncertainty is connecting the led lights daizy-chained. Can I use the middle OUT pin of one LED and connect it with the middle IN pin of the other LED.
I have tried to find a solution regarding this but there is no explanation  when it goes to connect them to a brass wire..


texts:
I am reading about dissection theorem and the part below is a bit confusing.

Could anyone one explain it?

  Any transfer function of a linear system is a bilinear transformation of anyone its circuit elements.


texts: Is there an optimal configuration or any way in which I can effectively connect

texts:
I currently have a 72V e-bike.

The configuration of the batteries directly from manufacturer is 6 12v 20AH valve regulated lead acid batteries connected in series. In taking the  limiter harness out of the mix my speed went up roughly 15kmh (this is being done strictly as a learning expierience and only driven on my own private property.) I have a 12V 14 Ah lead acid and another 12V 6.5Ah lead acid. I was wondering if connecting the two 14Ah and 6.5 Ah in a parallel circuit and then adding to overall power bank in series thus having 96V.  Will my speed increase any more? Is this an idea worth pursuing and if my configuration won't work is there any other that is worth pursuing?

Alternatively I'm taking one 12V to power an amplifier on bike.


texts:
Question:
Below figure represents an approximate equivalent circuit of a field effect transistor amplifier. Using KCL find the output voltage \$v_2\$ in terms of input voltage \$v_1\$.

My try:
I redrew the circuit as:

Here, \$i_1=\frac{v_1}{r+r_g}\$, \$i_2=\frac{v_2}{r_d}\$, \$i_3=\frac{v_2}{r_l}\$ and \$v_g=\frac{v_1r_g}{r+r_g}\$.
I applied the KCL at node x,
$$i_1+\alpha v_g+i_2+i_3=0\\
\implies \frac{v_1}{r+r_g}+\frac{\alpha v_1r_g}{r+r_g}+\frac{v_2}{r_d}+\frac{v_2}{r_l}=0\\
\implies \frac{v_1}{r+r_g}(1+\alpha r_g)=-v_2\left(\frac1r_d+\frac1r_l\right)\\
\implies \frac{v_1}{r+r_g}(1+\alpha r_g)=-v_2\frac{r_l+r_d}{r_lr_d}\\
\implies v_2=-\frac{v_1r_lr_d}{(r+r_g)(r_l+r_d)}(1+\alpha r_g)$$
But, in my book the answer is:
$$v_2=-\frac{\alpha r_gv_1r_dr_l}{(r_g+r)(r_d+r_l)}$$
Please check my mistake.


texts: Fake a panasonic battery to revive camera to copy photos from internal memory

texts:
Got this camera from a friend, battery door broken, no cables, no battery. There are some important photo's on this camera that I want to copy from internal memory to SD card. We first want to try this because USB requires an special USB cable we don't have and we even don't know USB will work when there is no battery at all.

The original battery is very expensive and because we didn't know the camera is fully operational, we want to try it first with an external battery (with some clip wires on contacts inside the battery compartment) to see it reacts on some juice. We verified the pin layout from a picture of the original battery, the DMW-BCG10E:

Connected our 4A powerpack ;-), must be enough and yep, we saw the first picture however the camera doesn't like the fake battery and shows us a message "This battery cannot be used" and turns off directly after this message. We also tried another battery, a LIPO, but same message.

There are some D and T pins on the original battery, this must be some kind of battery info data lines however we cannot find any info on this. We think it doesn't work because the camera cannot obtain some info from the battery or there is a problem with the camera itself. We want to know if we could use another battery, with same pin layout to fake the datalines. We don't know there is any standard. Before we try this, we want to know for sure there is no risk to damage the internals of the camera by doing this.

AC-adapter/DC coupler route

Panasonic also provides an AC-adapter/DC coupler with a case that fits inside the battery compartment, in fact a fake battery. I think there must be a (simple) trick (maybe a resistor or something, 'shorts' D and T for example) to let the camera think it is an AC-adapter/DC coupler.

Does anyone have experience with this or does anyone know where we can find more information?

EDIT/UPDATE #1:

very difficult to find info on these batteries, however, found the service manual!

They talk about "ID BAT DQ" (qualifier?) and later on "ID BATT DO". But what does it mean (unreg and DQ for example)?

Pin layout:

1. UNREG+
2. BAT THERMO
3. ID BAT DQ
4. UNREG-

Some schematics:

EDIT/UPDATE #2:

The creator of this video (thanks to @KalleMP) shows that the thermistor is only required to be able to operate the camera, however, tried the same and in my case it doesn't work. Hopefully nothing internally is damaged by doing some experiments. I ordered an original second hand donor battery for less than 3 euro's (still waiting for it to arrive) and will try it soon to figure out the chip is required or not, or if there is something wrong with the camera itself.

EDIT/UPDATE #3:

YES, WE'VE DONE IT, with success.
See also my answer.


texts: wrong operation result in shift right arithmetic in verilog

texts:
If I simply write following code:

module TOP;

wire [31:0] a = 32'b11111111_11111111_11000000_00000000;
wire [31:0] b = 32'b00000000_00000000_00010000_00011111;

wire [4:0] shamt;
assign shamt = b[4:0];

wire signed [31:0] signed_a;
assign signed_a = a;

wire [31:0] output;
assign output = signed_a >>> b;

This gives a correct result which is 11111111_11111111_11111111_11111111

However, if I use code that uses module, it always generates wrong result:

module TOP;

reg [31:0] a = 32'b11111111_11111111_11000000_00000000;
reg [31:0] b = 32'b00000000_00000000_00010000_00011111;

wire [31:0] out;

ALU alu(
    .A(a),
    .B(b),
    .C(out)
);

initial
begin
    #10 $display("out: %b\n", out);
    #10 $display("outout: %b\n", alu.outout);
    #10 $display("C: %b\n", alu.C);
end

endmodule

module ALU (
    input [31:0] A,
    input [31:0] B,
    output [31:0] C
);

wire signed [31:0] outout;

wire [31:0] signed_a;
assign signed_a = A;

wire [4:0] shamt;
assign shamt = B[4:0];

assign outout = signed_a >>> shamt;

assign C = outout;

endmodule

In above code, all result from $display shows wrong value which is

00000000_00000000_00000000_00000001.

Why it doesn't generate correct value like first code?


texts: How to solve practical OPAMP with finite differential resistance and finite offset current while other parameters can be considered ideal?

texts:
simulate this circuit – Schematic created using CircuitLab

Ip(bias)=200nA
rd=differential resistance=5Mohm
a=infinite
What should be its output?
I am confused if I should consider negative feedback and consider bias current gives only input offset voltage of straightway say that OPAMP is saturated.


texts: Connection a Low Amp wire to High Amp wire

texts: Suppose 5 Amps of current runs from point A to C.(20V) I want to connect a thin wire(I believe not for more than 1Amp) to a point B in between A and C. Will the amps melt the wire where it is connected to 5 amps wire? The wire will only be powering 350 milliamps load.


texts: Obtain an accurate DC value in an AC+DC signal

texts:
Background:
My goal is to use an Arduino with two proximity probe sensors to achieve some output.

It is worth mentioning that the output of the proximity probe has two components:

DC output that determines the position or the GAP
AC component on the top of that DC voltage to determine the vibration

I want to focus on the DC part.

The proximity probe sensor has a negative voltage output from 0 to -20 volt DC, as the Arduino accepts voltage only in the range of 0 to 5 volt, so I decided to use
a low-pass filter to remove the AC component and get just the DC component, as this DC component is in the range of 0 to -20 volt. I used an op-amp to invert and to scale down the voltage so instead of being in the range 0 to -20 V, it will be 0 to 5 V.

In this specific question my goal is to get the very accurate DC component. The circuit I implemented is very simple. Basically, it's a low-pass filter with a cut-off frequency of 1 Hz (assuming that my signal won't have a frequency component in the range of 0.00001 - 1 Hz) and then an inverting amplifier with a gain of 1/4 to invert and to scale down the DC voltage.

Here is the circuit:

The output is logical. I used a voltage source with AC and a DC component of -10 V DC offset to simulate the proximity probe signal, and here is the output:

The green line is the DC component which is almost -10 volt, and the blue line is the output inverted and scaled down. Which is almost 2.5.

The problem is with the output. It's almost 2.5 V, and it's oscillating and changing. My application needs an accuracy of millivolt, so this won't be acceptable.
How do I get a more stable and accurate output?

Here is the picture of a zoomed-in output:


texts: DMG4800 MOSFET running hot (while Si4804 runs cool)

texts:
I'm working on a BLDC control system for a micromotor, and have been using the Vishay Si4804 MOSFETs in output stage.

Due to availability issues, I ordered Diodes Inc DMG4800LSD-13 for a second board, since they were a bit cheaper, and the specifications match up well.

The problem: 4804 runs cool to touch, regardless of current draw. The 4800 runs WAY hotter, and one even blew during testing. Any idea what could be going on?

I'm running at a PWM frequency of 40kHz. The current draw during normal operation is only ~200mA.

EDIT:
The driver for this output stage is the Allegro A4964. I'm currently using a dead time of 1us.

Experimenting with gate resistor value, I can get the 4800 MOSFET to function without heating. Probably the slow turn-on and turn-off, and perhaps the small overlap, caused the heating.

Gate drive waveforms with 100 ohm gate resistor:

Gate drive waveforms with 33 ohm gate resistor:

Update:

I have switched to the 6016LSD MOSFETs and removed the GS resistors. They draw less current than the 4804's. These are the gate drive waveforms measured individually, since my cheapo scope doesn't to differential measurements. Both measured from Source to Gate.

Here I can start seeing quite some ringing on the high side gate. Does this warrant a higher value gate resistor again?


texts:
I'm using AMS1117 -3.3v regulator for providing 3.3v to my IO expander mcp23017, unfortunately some short circuit happened and my regulator gave 12v to IO expander, which burned my IC.

How can i prevent this?


texts: Is it a good idea to use a ceramic inductor for a DC-DC boost converter instead of a wire wound one?

texts:
I would like to use an SMD assembly service in order to pick and place the components directly to my PCB. There is a DC-DC boost converter (DD06AJSA) on the board which includes an inductor:

I need to boost a 3,7V lithium battery up to 5V with a current draw of 500mA.
Is it possible to use a ceramic inductor instead of a wire wound inductor with the same value, so 6.8uH, like in the following picture?

Also: Unfortunately I have just 4.7uH as a choice, so would it still work as expected if I would choose a slightly lower one? In the datasheet for this IC FP6291 a value between 3.3uH and 4.7µH is recommended.


texts:
Basically what the title says. Cadmium is a toxic, environmentally harmful heavy metal that's banned under the RoHS directive, and even before RoHS its toxicity was well known. What makes cadmium selenide and cadmium sulfide such appealing semiconductors to make photocells out of?

Why not use silicon, which also drops in resistivity when exposed to light? Silicon does even respond to most visible light as far as I'm aware, though not as strongly as CdS/CdSe due to being an indirect bandgap semiconductor. But other direct bandgap semiconductors exist, too, including ones without any highly toxic elements, like gallium antimonide or tin sulfide, or any of the more complex compounds used for thin-film solar cells. What gives cadmium compounds such an advantage?


texts: Cannot determine address of connected I2C device (simple I2C scanner)

texts:
I have a 1602A V2.0 LCD display (16 chars x 2 lines) that I intend to connect to my  Kinetis MK26 ARM M4 MCU via a LCM 1602 I2C extender (which has a Philips PCF8574AT on it).

I'm trying to get it to work since this morning, but apparently, the address I calculated for the I2C extender (0x3F according to this datasheet, A0, A1, A2 are non-jumpered) is not OK, so I tried to scan for a valid address where the I2C extender would ACK me back, but I cannot find any.

I connected just the PCF8574AT to my board, the LCD is not connected and it still doesn't work.

I have the following piece of code (KSDK 2.0):

#include "fsl_gpio.h"
#include "fsl_port.h"
#include "fsl_i2c.h"

#include "Retarget.h"
#include "Log.h"
#include <stdio.h>

#include <stdint.h>
#include <stdbool.h>

int main()
{
    RetargetInit();

    i2c_master_config_t masterConfig;
    uint8_t status;

    /* Get default configuration for master. */
    I2C_MasterGetDefaultConfig(&masterConfig);
    printf("Got def. config\r\n");

    /* Init I2C master. */
    I2C_MasterInit(I2C0, &masterConfig, CLOCK_GetFreq(I2C0_CLK_SRC));
    //I2C_Enable()

    printf("Init\r\n");

    /* Send start and slave address. */
    printf("Starting...\r\n");
    // 0x70, 0x27, 0x38, 0x20, 0x3F

    uint8_t u8Addr = 0x3F;

    for(u8Addr=0; u8Addr<128; u8Addr++)
    {
        status = I2C_MasterStart(I2C0, u8Addr, kI2C_Write);

        LOG("sent address 0x%x", u8Addr);
        uint32_t u32Flags;
        /* Wait address sent out. */

        uint16_t timeout = UINT16_MAX;
        while(!((u32Flags = I2C_MasterGetStatusFlags(I2C0)) & kI2C_IntPendingFlag) && (--timeout))
        {
        }

        if((u32Flags = I2C_MasterGetStatusFlags(I2C0)) & kI2C_IntPendingFlag)
        {
            LOG("ADDRESSS 0x%x IS OK", u8Addr);
        }

        LOG("timeout is %d", timeout);

        //LOG("done address");
        status = I2C_MasterStop(I2C0);
        LOG("Stopped with status=%d", status);
    }
}

Could you please point out what I'm doing wrong, why my scan doesn't yield any results?

Or is there a problem with my I2C extender, phisycally?

I'd expect the output of the above code to contain a single "ADDRESSS 0x... IS OK" line with a timeout different than 0, but that's not the case.

Merry Christmas!

PS:
The LCM 1602 I2C extender I'm talking about is this one (with the Philips controller on it):

Which as as far as I can tell has this schematic (although the controller is not identical):
http://www.nexuscyber.com/Content/files/Schematic/I2C_Schematic.pdf

I connected the SDA & SCL to the properly labeled pins on my board (so I guess pull-up resistors are in place, I'd have to check to be sure), and the GND and VDD to a GND and a 3v3 on the board directly (I also tried connecting it to a separate 5v power source, results are the same).


texts: Need help getting at least +/-10 V from op-amp

texts:
I'm new to here and I did already some of the research but cannot really find an answer. I'm not very familiar with op-amps.

I have wired a LM358 op-amp as per the below example schematic in the MCP4725 DAC datasheet. The problem is that I'm getting only +2.7 V all the way to -2.2 V (I guess because I used 22 kΩ resistor instead of 20 kΩ) on the 12-bit DAC resolution.

However, I used bipolar supply with +/-15 V, and I was expecting the output voltage to be somewhere close to the 15 V both ways, or at least 10 V. Can somebody please explain what am I missing in order to reach my voltage output? Is the op-amp chosen wrong? If so, can you please recommend a device to use?

Thank you very much in advance for any help.

R1 and R4 are 22kΩ
R2 and R3 are 10kΩ


texts: how to switch between normal signal and modified signal with analog intput signals arduino?

texts:
I have a signal input like the sine V1 that is modified by the arduino and transformed it into a square signal. The value of the output depends on the value of a voltage reference given by a potentiometer. Both, the input signal and the reference are ADC inputs in the arduino. I put an interruptor just like the image, assuming PWM2 as arduino, and when the i put the interruptor in the position of the image i see the same voltage on the output as the potentiometer voltage reference, as is this where connected. Why is this happening ? can i do this in a different way ?

simulate this circuit – Schematic created using CircuitLab


texts: Why Micro-controller Pin is connected to ground via Capacitors?

texts:
I am analyzing a circuit which uses an Micro-controller to measure analog signals rms in digital form.  There is one connection of circuit that i am not sure what it does.

See the Figure. Here Vref of MCU is connected to ground via two parallel capacitors. This micro-controller is chinese made so its datasheet is avaiable but not very detailed. Data sheet shows that Vref is internally connected to VDD/VCC which is 3.3V. Though i am not sure because i think it should be zero, because it compares input analog signal to detect its +ve and -ve cycle.

(According to datasheet: Vref is an external voltage input pin)
Capacitor in question are in red rectangle...
I need to know these facts:

what would be the functions of capacitors if Vref is internally at VDD/VCC??

What would be the functions of capacitors if Vref is an Input Pin and it is grounded via these capacitors??


texts:
This is a follow-up question to What happens if I omit the pullup resistors on I2C lines?

In a digital wall clock I designed (using the DS1307 RTC and the ATmega328 MCU), I accidentally omitted the pull-up resistors that must be wired to both I2C lines. In the end I was lucky enough that the internal pull-ups on the ATmega I2C lines were enough to (barely) allow the communication between the devices. The result were long rise times on the I2C lines and speed reduction to 32kHz as seen in the scope shots below.

Edit: Actually, the frequency is exactly 100kHz - there are 2 peaks per 20us on the green trace. I initially thought there was a reduction to 32kHz because my scope calculated the frequency on the yellow trace.

What's puzzling me now is how the devices decided that 32kHz was enough for the communication to take place. The DS1307 datasheet says that the device supports 100kHz frequency on the I2C bus. How come it ended up using 32kHz instead? Is there some kind of handshake phase where the frequency is stablished?

In the end, my question really is this: How is the clock frequency established between master and slave in I2C protocol?

I couldn't find that information searching the Net.

In case this matters, I'm using Arduino IDE 1.03 and my firmware handles the RTC using the DS1307RTC Arduino lib (through its functions RTC.read() and RTC.write()). That lib in turn uses Wire.h to talk to the RTC.


texts: What happens to the energy stored in a short-circuited capacitor?

texts: Suppose we have an ideal capacitor with a certain voltage between its plates. We connect the two plates using an ideal (lossless) wire, so the capacitor discharges. Where has the energy having been stored in the capacitor gone?


texts: Flash memory : What are blocks and pages from a physical standpoint?

texts:
I would like to know the link between the physical layout of NOR and NAND flash cells and the concept of blocks and pages. I would also like to know the exact reason for why erasure only happens in regards to blocks.

I also don't get why NAND memory is not memory-mappable like NOR memory. I know that it comes from the fact that NOR cells are connected in parallel to the bit lines, but I don't get why you couldn't be able to read a whole word at once on NAND memory.

The word lines select which word is going to be read/written and the bit lines carry the data, isn't it ?


texts: How to make an mbed print text from ascii codes

texts: I want to send Ascii codes to an mbed and have it print Ascii characters which can be seen from Hyperterminal. How can this be done? I looked at the mbed website and found nothing about keyboard input or ascii characters.


texts: Designing a bus - Master at one end or in the middle?

texts:
I am laying out a data bus at the moment (initially on breadboard), and I am wondering if there is a 'right' way to lay it out.  I have a CPU acting as the bus master, and a number of devices (RAM, ROM, IO, etc) linked on to the bus.

We're talking no more than a few MHz of processor clock here - nothing incredibly fast.

Is it better to have the bus master device at one end of the bus (like this):

or is it OK to have the bus master in between other devices (like this)?

At the speeds we are talking, does it actually make any difference?  I can foresee possible issues at much higher clock rates, but at say 4MHz is it a design consideration I should be thinking about?


texts: How is it physically possible that there is no voltage drop across two pins of this DC jack?

texts:
I have a DC jack with three terminals. Terminal 1 is tip (+), terminal 3 is sleeve (-), and terminal 2 is a switch, my understanding of which is such that if there is no adapter plugged into the jack, terminals 2 and 3 are connected.

When I plug a DC adapter into the jack, I get the voltage drop I would expect across terminals 1 and 3, about 9V. However, there is zero voltage between terminal 2 and both 3 and 1. How is it possible that there is no voltage drop between either? Shouldn't there have to be a 9V drop between terminal 2 and 3 if there's 0V between 1 and 2?


texts: cut-off rates for error correcting codes

texts:
In pre-historic times, i.e., before 1990 or so, communications link designers used the concept of computational cut-off rates (instead of Shannon capacity) to estimate what could or could not be done in a dig-com channel. This idea goes back to Wozencraft and later promoted by Massey.

My question is: in the age of turbo codes, what, if any use and/or meaning is there for the computational cut-off rate beyond its very original meaning namely, it represents nothing more than the maximum rate that a sequential decoder can handle in finite time?


texts: Could I get some feedback on my circuit?

texts:
As someone who holds an engineering degree but is sort of new to circuit design/ electronics, I'm probably not aware of the many conventions and techniques that a more experienced circuit designer would assume are obvious. I would like to learn to become a competent circuit designer, however, and I was wondering if you wouldn't mind taking a look at this simple circuit I designed to test a pair of sensors. The sensors operate at 27V which is why I use MOSFETS to interface between the microcontroller and the inputs/outputs. The relay is there because those pins provide 27V power to the sensors so it would need to provide more current than the mosfet could, and also as a fail safe.

Specifically what I am not sure about is if I should place more diodes / caps to protect the circuit and reduce the chances of problems/ malfunctions arising.. I have placed diodes and caps on the input power, and a diode across the relay coil, but that is basically it, and I am not too confident about my cap choices.

Also, any observations / recommendations regarding the circuit, or even ways to improve the schematic layout would be great!

Thanks in advance!

http://ge.tt/8EygOO32/v/0?c

Thanks to all the help, I have updated a schematic with the changes. I have replaced the linear regulator with a switching regulator, added bypass caps, fixed the relay placement/ made it a 24V relay, double checked that components will meet current/ voltage specs, added series resistances to fets, added TVS diodes on inputs, added fuse / on/off switch, tweaked the input voltage divider. added caps on inputs, and I think that is it.

Updated: http://ge.tt/2o9qXZ32/v/0?c


texts: How to make LC circuit just using Capacitor and Inductor?

texts: I am experimenting with inductor so I am looking for a simple circuit that will blink the LED with oscillator circuit. Basically turn on and off LED and finally diminish. How can I do so? For power input, I am using Raspberry Pi - 5V. Here is my circuit? what am I missing here?


texts: Driving a difficult load with an Op-Amp: high capacitance, high current, high speed

texts:
I've been banging my head against this problem all day. I have a bizarre load that I need to drive over 88 feet of SMA that is a 68 ohm pullup to 15V. The cabling adds 2.64 nF of capacitance. I've sketched it below.

simulate this circuit – Schematic created using CircuitLab

I'm driving negative-going analog pulses (worst-case from 0V to 3V and back) where both the amplitude and pulse width are important, with rise times down to 20 ns. Somehow I have to achieve:

Low overshoot (<135 mV)
High amplitude accuracy
Stability (this has been the most difficult!)

Because this requires sinking 18V / 68 Ω = 265 mA, I can't just use an opamp. So I tried a current-amplified opamp circuit like so:

I originally designed this without considering the capacitance of the cabling and I managed to get it perfect, but it oscillates once I add connect the 2.64 nF, as you can see below. I tried many different transistors and op amps, guessing at what parameter would affect this, but I can't get rid of the oscillation. I'm also stuck with a high-speed op-amp (BW > 50 MHz) because of the fast rise times.

Currently my only viable solution seems to be a simple voltage follower with no feedback. I'd have to calibrate out the VBE drop and temperature dependence, which makes for a terrible system.

My question is this. What causes this oscillation and what do I have to do during part selection to prevent it, or how could I damp the oscillation?


texts: Solution for refurbishing sealed switches

texts:
I don't know if this is the right stack to ask this in, but I could not find a match, but I feel this question may have enough common interest to find a solution anyway.

I am attempting to refurbish some old switches which can no longer be found. The problem is the switches are sealed by plastic rivets, so I cannot actually disassemble them, well I could, but I could only do it once ;)

The problem is oil has penetrated many of the switches, which leads to a lack of audible click and poor electrical connection. I have had a little success with ultrasonically cleaning in IPA, but the problem is getting the residue out of the switch.

The switches are ABS, and the contacts are nickle and gold coated copper. Do I have any hope in getting the oils out of the switch? Will I need to resort to degreasers, and if so, what can I use that would be safe to all the material types?


texts: Problem with voltage between a DC step up and Raspberry

texts:
I am working with a DC step up (XL6009) and a battery for the cell phone (3.8V), with a capacity of 2800mAh to power a Raspberry (10 minutes maximum). The output voltage of this module (XL6009) can be regulated by a trimmer (included), granting an output range of 5V-32V.

After using the trimmer to set the output to 5V and measure the output voltage of the module without having connected the Raspberry, I get 5V. Everything is normal.

The problem is that when I connect the Raspberry, the voltage goes up to approximately 7.30V ~ 7.38V, and I really do not understand the cause, since as I pointed out previously, it was configured the module -and tested- to 5V. When I unplug the Raspberry and retest, I get 5V again. What could be causing this voltage surge?

I used a Raspberry Pi B + (2014) and a Raspberry Pi 3B, and in both cases the same thing happens...
Both Raspberry have no connected peripherals, so their current consumption should be low, especially that of the year 2014.

Regards!


texts:
It is possible to set Vin(off) voltage for optocoupler. There is explained here:

TLP280-4 Optocoupler on 12/24V inputs

And in the appnote for TLP290 opto-coupler that can be downloaded from here:

http://toshiba.semicon-storage.com/info/lookup.jsp?pid=TLP290&lang=en

So, Is it possible to set Vin(on) threshold voltage?
I need to implement this:

ON voltage level > 18.0 VAC/VDC
OFF voltage level < 4.0 VAC/VDC

There is no explained in appnote for that opto-coupler.
While input signal is 24.0 VAC/VDC.
Additional requirement is keeping

Input impedance = 6.8 kOhm


texts:
i was doing some homework and one thing I had to do was to derivate the transfer function of a given bandPass. I have done it myself but i dont know if it is correct nor if i followed the right path / right assumptions. I'd be happy if someone of you could look at it and give me some feedback. Important: In my notes Ua = V(out) and Ue = V(in) the rest should be (I Hope) self explanatory.This is how I've done it:
And this is the bandpass:

Thank you in advance!


texts: Sizing a solar panel and battery for a simple solar application

texts: I am a novice. I want to correctly size a solar panel and battery for the following application. I will be powering 2, 6 watt cfl lights and a 40 watt incandescent light. I am planning on using 400 watt inverter from Northern Tool. I need the inverter because of the need for the 40 watt incandescent bulb which will be used as a heat source. The 40 watt bulb will be on 24 hours a day when the temperature is below 32 F. The two 6 watt cfl lights will run a maximum of 5 hours a day year round. I have done research on the internet, but so far some of the information I have obtained is contradictory. I live in southwestern Pennsylvania. What I need to know is the size of the solar panel in watts and the size of the battery Ah.


texts:
I'm reading an Atmel Data-sheet and it mentions using an LC filter for the Vref and Vadc pins, when simulating a simple small AC voltage with a 5V offset and using an LC filter with 10uH and 10uF the attenuation stays at 0dB until the SRF is hit at about 15.8kHz. The signal only starts to drop after that point, am I right assuming these types of filters are only meant for really high frequencies? (In power supply terms at least)

Also, if you get noise at the SRF of your filter won't that create other problems?


texts: How can I power mobile devices from my 36v or 48v battery safely?

texts:
I want to buy a rear rack battery for my bike, but not for powering the bike. Instead, I want to power other things, such as an action camera+gimbal, a mobile phone charger, grip warmers, lights etc for a prolonged period of time. A simple USB power bank (or several) is insufficient.

The battery typically outputs 36 or 48v and what I need is typically but not always 5V at 1 or 2 amps (depends on the device). I wouldn't mind using this battery to also power the front light which right now eats 36v directly. The speaker has a mains powered connection at 100-220v/300mA so I have no idea if it's possible to convert in this direction and if it's safe to do so.

What piece of hardware do I need to power USB ports? Also, how can I make sure that at no point in time the full 36/48v get fed into my devices... I assume I would need to put fuses somewhere?


texts:
I have a HDMI switch that I want to control with an Arduino.
It's working by pressing a button to change input signal.
The button is NC(Normally Close). By pressing the button you break the 3.3V going throw it.

I want so when you send 5V from Arduino you to break the switch of the 3.3V.
What component is best for doing this?
Will a transistor work? Doesn't it mean I need to apply 5V all the time except when breaking the switch.(Don't want that)

Is there any MOSFET that will work?
I have been looking at CMOS    4066?, is that a good IC for the job?
Or is there any relay IC that    work?


texts: Testing Chinese CR2032 Li-ion Battery Capacity

texts:
I recently bought a lot of cheap CR2032 batteries from aliexpress. Since there is no manufacturer stated on the package or the batteries, I would like to know if these batteries really have 220 mAh or are they as fake as they are cheap. I would like to use them for a project with the bluetooth SoC nRF51822 QFAA, which draws 3 uA in sleep and few mA when radio is active.

I made a constant current load, to draw the constant current over time and to calculate the total capacity, but I was unable to determine the correct capacity because the voltage on the battery went down to 0.1 V and current from the battery to 10 mA. I used this schematic from instructables.

http://www.instructables.com/id/DIY-Constant-current-load/

I changed the resistor to 10 ohm (around 11) and the voltage on the pot to 0.5 V (not exactlly 0.5V). With these calculations, I should have gotten 45 to 50 mA constant current, but when i measured it, it was 37 mA (good enough). But after a while (no more that 30 minutes) the current dropped to 10 mA and voltage to 0.1 V. After disconnecting the battery the voltage slowly raised to about 3 V. The same happened with the Chinese batteries and with some of the known battery brands.

Is there any other way (or a better schematic) to test CR2032 battery capacity, without buying some kind of battery measuring equipment??

Why did the voltage drop? Was it because of the "high" current I was draining?

Thanks!


texts: First PSU - need help with capacitor size

texts:
I am building my first power supply unit (my first project too) and need help in figuring the size of filter capacitor (and type, though I presume Electrolytic) I need to use after the rectifier diodes.

Specs:-
2 channels of 1.5VDC - 9VDC adjustable outputs with max 2.5A over both channels

Components sourced:-
229D12 Transformer - output is 12.6VCT (3.8A) at 60 Hz (65% = 2.5A) .... 4 x 1n5404 rectifier diodes (rated at 3A with Vf=1V) .... LM350 adjustable voltage regulator (rated at 3A with Vf=1.25V)

What I know so far:-
60Hz rectified is 120 cycles/sec so T=0.00833sec .... 12.6V - (2*1V diode drop) = 10.6V rectified - 1.25V (Vf of LM350) = 9.35VDC max .... Max current is going to be 2.5A (limited through LM350 and 3.74 Ohms of resistance)

I have tried sourcing the formula to calculate the size of capacitor needed, and I have seen many formulas regarding capacitors. Each one of them confused the heck outta me with funky symbols and abbreviations that I have yet to learn and each of the formulas was for something other than what I was wanting.

I speak basic English, understand average Mathematics, but still have no idea on most of the symbols and abbreviations used in EE. Please keep your answers simplified for this noob. :D

I appreciate any help ya'll can give.


texts: What are the dangers of a DIY fuse in a multimeter?

texts:
For the past few years I have been running my Fluke 79III without a fuse in its F44.100A 1kV fuse holder. This has meant that I've been unable to use the 40mA circuit.

When I blew the old fuse, I discovered that it had been previously 'repaired' with another fuse soldered to the original Buss DMM-44/100 fuse. Then I went to look for replacement fuses and was aghast to find them selling for £10 each, so I wasn't surprised that the previous owner had 'repaired' the fuse rather than replacing it.

What I now wonder is what the consequences of once more 'repairing' this fuse might be. I don't play with three phase, and I'm unlikely to play with more than about 260VAC, so could I safely use a 250VAC, 500mA fast acting fuse in its place?

Watch Big Clives Things you should know about fuses. (including a 15kV one) video if Spehro Pefhany's answer hasn't already convinced you not to try this.


texts: Contact resistance is messing with the transistor switch

texts:
Hello I have a circuit board here that detects when a plug is detected on a 3.5mm audio jack and a LED is lit up. Since the audio jack has switches, I am using the ring contact and switch since it is unused in the plug.

Here is my circuit for the LED:

The problem now is, after some investigating it would seem (my theory only) that the ring contact and the ring switch is not "pushed" enough to each other to form a solid connection. I know this since when I try to test both contacts my multi-tester detects a continuity.

In the picture below you can see the LED is on:

Now if I try to push it in it turns off. Picture below:

Now I could just easily bent that flap so it would stay in place but when a jack is plugged and unplugged it reverts to its old state. Can the contact resistance be overcome by changing the circuit without changing the actual jack itself ?


texts: How do devices/appliances draw more current when needed?

texts:
Suppose I have a desktop computer and I decide to do something that requires more processing power. In this case my computer will draw more current to increase power. How is this increase in current performed? Does my computer open up more parallel circuits so the total resistance decreases? or do they have electronic potentiometer or something completely else. Is the technique used in a desktop computer the same as if I were changing the oven's temperature?

Any help is greatly appreciated.


texts: How can I control things without using delay?

texts: I have always hated that you couldn't do other things while you used the delay(); function. However, I want to blink a LED or do whatever while using serial, but how does this work? How do I do this without using the delay function?


texts:
I'm working with this blower, https://www.mouser.com/ProductDetail/ebm-papst/D2E097-BE11-77?qs=DB9cKZ5ZWfV%252B%252BcGyCSU1bQ%3D%3D.
Is there an simple way of slowing down the speed without any adverse effects on the life of the motor?


texts: Does an Electron really travel thousands of Miles when I use a server in another Country?

texts:
When I press a key on my keyboard, it will alter the flow of electrons in a wire connecting to send data to my computer. Let's say it sends the bits: 100000000100000000100000000100000000, which is a few letters encoded in binary and ASCII.

These electrons somehow move down the wire, to a chip, that detects where my data should go with transistors, or as I understand it, little switches that can be controlled with another wire. The chip will detect where my data is heading, and send it in the right direction.

So the question is, if I make a HTTP request from Europe to a server in USA, do some of electrons from my PC, in 200 ms the response takes, travel across the Atlantic ocean to USA and come back to me?


texts: How is the closed loop transfer function defined for an oscillator?

texts:
an electronic oscillator is a device which can generate some signals without input signals. It is an unstable system realized with positive feedback, as shown in the following scheme:

Now I have two questions:

How is the closed loop transfer function of this device defined? The input signal does not exist.
How can we implement negative or positive feedback, if the input signal does not exist?
I know that in negative feedback the feedback signal is added to the input signal, in positive feedback is subtracted. So in the first situation we use and adder circuit, in the second one a subtractor circuit. But what do we do in this case?


texts: Can breakout board still be used if the pad gets ripped out?

texts:
In a desoldering incident, my beautiful board ended up like this:

Other side:

The guy doing the desoldering says there is no chance this board is usable since he claims he ripped through the connection between the pad and the board. To me it looks like the pads have been ripped out.

Is this board usable? How can I safely find out? I apologize if it seems stupid. I wanted to make sure that I don’t damage my MCU board by connecting to it, as I don’t have much time left before my deadline to get replacements.


texts: How does Stitching capacitor provide shortest return current path between plane splits, as we know that it blocks DC current?

texts: I heard that Stitching capacitors are used to provide shortest return path whenever a signal is routed along the 2 power plane splits. As we know the return current path will be right under the trace. So how does the stitching capacitor provide shortest return path? As we already know that capacitor blocks DC current. So when I connect a stitching capacitor, how does return current flows through the capacitor?


texts:
I have a capacitor rated 15000 µF, 35V.

So, I charge my capacitor to 15V with no problems using a charging resistor.
Now while discharging, I am using thyristor (2N6509G) as my switching device and a coil as my discharge resistor. Coil resistance is about 2 Ω.

Using the discharge equation of capacitor, I calculated the discharge time in this setup, which comes out to be around 81 ms for (assumed) final voltage of 1 V.

In my application, I wish to discharge the capacitor only for 20 ms.
But when I do that, the capacitor voltage drops down to 0.9V in just this 20 ms duration instead of the calculated 7.7V (using discharge time calculators online).

If I am not doing anything wrong in the setup, what is it that I am not understanding conceptually? How do I go about discharging capacitors only to some fraction of the stored charge?

Edit: Thank you all for your comments, I am sorry for not being very clear with the details.

So, this is a coil gun model basically.
Coil :- Copper magnet wire: AWG 20; no of turns: 650; Coil resistance: 2ohms

I actually used an online calculator for capacitor. Discharge Time Calculator

I used another calculator to get the inductance of this coil which came out to be 8.88mH. Coil Calculator

*Note: This circuit is not my original work.


texts: Using the same components for two 555 timers

texts:
I am building a circuit to operate a Linear Actuator to open and close a lid.

The open and close times are the same.

The standard monostable circuit works.

There is one switch to tell if the lid is open or closed, it shows 12v+ when open and is grounded when closed.

I have built one timer unit. It works to specs.

I was wondering, since the timers will be the same, would it be possible to use the same components for both timers.

Pins 2 and 3 would use different triggers and the outputs would go to different places as well.

I would use jumpers between the two 555 Chips.

Basically my thought would be to connect all pins but 2 and 3 in parallel with each other.

Would this fly, or am I missing something.

It would be impossible (I trust) to trigger both timers at the same time.


texts: How to calculate the maximum data rate or frequency of a bus driver

texts:
I'm searching a suitable bus driver for a project. I found the Nexperia 74VHC244D. On the website they say the maximum frequency is 60MHz (here).

But how do I calculate the 60MHz? Because it's not mentioned in the datasheet. Is it just the inverse value of the propagation delay?


texts: Embedded Applications Software Testing Life Cycle

texts:
I have no JTAG and I can not afford it for my ARM Cortex M3 Chip.

I'm wondering, how professionals debug their applications ?

Do you flash your uC every time, frequently, then you run and test, then change? is that a bad practice ?
Do you only use UART or LCD for writing logs on the screen ?

I need tips and tricks from the professionals :)


texts: Rated voltage vs rated power on lamp holder

texts:
I bought a string of lights from America (110V, 25W per socket, 50 sockets (1250W total) to use in South Africa (power supply is 220/230V 50Hz).

I thought I could just use a converter (220V to 110V) and 25W incandescent bulbs.

But now I wonder if I really need a converter? The resistor is the actual bulb, which I will buy here and will therefore be rated 25W at 220V.

Surely that will be fine? I figure 1250W/110V=11.4A for the string or 25W/110V=0.23A for the socket. Or 1250W/220V=5.7A for the string or 25W/220V=0.11A for the socket.

Does current make a difference? These are just lights, not electronics, right?


texts: How should I use 3.3V + 5V in KiCad without getting an ERC error?

texts:
Below are parts of my design.

Using KiCad, I have problems using both VCC (5V) and 3.3V power, both from Arduino Mega pins.

If on U6 (flash) I connect 3 and 7 I get a similar error, so I guess I did something wrong regarding the PWR_FLAG settings. I also tried using the VCCQ (it also has a round symbol like VCC), but then I get different errors.

What should I change in my schematics to use both 3.3V and 5V without any ERC errors?


texts: Using Multisim to Measure Thevenin Resistance

texts: Using probes, it is easy to find the Thevenin voltage, and Norton Current of a circuit. We could simply divide Vth / In = Rth, but is there a way to find Rth through a simulation?


texts:
VSAT is the saturation region boundary in the MOSFET characteristics.

In the text book it says VSAT=VGS-VT0 but I can't see any explainations. Is there any reason for it?


texts:
I built waveform generator using AD9833. It can produce sine and triangular wave with amplitude about 1.6 V and square wave with amplitude of 4.5 V. I'm searching for some circuit which can control amplitude of output wave and this amplitude can be set by arduino so something like PWM should be used.
In conclusion I am searching for a circuit which has:
First input - square, triangle or sine signal, frequency 1Hz to 1MHz. Signal is produced by AD9833. Its impedance should be 200 Ohms. Amplitude is 1.6 V for sine and triangle and 4.5 V for square.
Second input - signal from arduino about set amplitude
Wanted output - input signal with modified amplitude between 0 - 12 V. This output amplitude should be set by arduino.
I would like to hear some ideas which circuit should I use. I'm still a beginner and I need your help. Thanks for reply. I look forward to your ideas for solving my problem.


texts:
Good day,

I'm a 2nd year electronic engineering student prepping for an upcoming test and i ran into some trouble with the analysis of this particular circuit. I'm trying to find the currents i1(t) and i2(t) for t>0. Whilst this question appears in chapter 7 (first order circuits), looking at it i would argue that it is actually a second order circuit due to the two inductors which are neither in series nor parallel. I can't see a way of getting a single equivalent inductance in this case straight away.

I have calculated the initial currents i1 and i2 using current division as shown below:

We know that the current through an inductor cannot change instantaneously so, therefore i1 and i2 at t=0+ (just after the switch changes) will be the same.
Am i correct in saying that when the switch changes we have a short circuit and so the source current will flow in a loop bypassing the 6ohm resistor and the RL portion on the right. Would the right-hand portion with the 5,20 resistors and two inductors then simplify down to a series RL circuit for t>0?

Any help much appreciated.

Regards,


texts: Connecting `signal ground` to `earth`: should I?

texts:
We usually have 3 wires in the outlet: L (line), N (neutral) and PE (protection earth). It is pretty common that the N is tight to PE in the distribution board or power plant.

If the device have conductive case, this case should be connected to PE to make the device safe for a human. However I still have a question: should be signal ground network connected to PE or not? Or it should be connected through let's say 10meg 1W resistor?

If the device don't have galvanic isolation there should not be any connection between SGND and PE. Right?

If there is a galvanic isolation the question become tricky for me. For example - if it is a RS-485 transsiever - I should have a return path for diferential pair. This means that the isolated signal grounds of the transsievers should be connected to each other. This connection can be done through a third conductor in the cable or - if it is absent - it can be a PE, right? So in this case I should directly connect the SGND to PE.

I suppose that in some cases SGND should be connected to PE through a 'big' resistor (for example 1MOhm / 1W) to prevent the schematic from float (to drain the static or any charge).

I examained some similar question on Stack I was able to find (one, two, three). They have some useful information which I included in this question, but they actually asked for some particular cases (say RS-485 usage in the first question) and don't have general information on the subject.


texts:
For architectural reasons, we have a need to take a twisted pair (of an RS485 bus) into a PCB and then out. The PCB traces would add about 2 cm (just less than an inch) of length to the bus. The stubs connected to this differential trace pair in the PCB are very short (<1 cm).

Question: How to match the PCB differential trace pair impedance to that of the twisted pair cable (~120 Ohms)?

Given the low bit frequency (about 250kbits/s), the first answer that comes to mind is that the trace pair impedance does not really matter, since the shortest wavelength within the relevant bandwidth is so much larger than the trace pair on the PCB (say, a couple of meters vs. a couple of centimeters). This also appears to be true for CAN buses entering PCBs, given some of the discussions that I have seen in this site.

Having acknowledged that, if we still wanted to get as close to 120 Ohms differential impedance with the trace pair on the PCB, how can we compute the trace width and separation? Edge coupled micro strip calculations that one can find on web sites such as eeweb.com incorporate a reference ground plane on which the common-mode currents can return. In our case, it is just a twisted pair (no ground wire or shield) entering the PCB (i.e., no common-mode current return path on the wire), so should we even use a ground plane under the trace pair?


texts: How to interpret the CMRR at the data sheet of an amplifier?

texts:
Here is the data sheet of an AE101 amplifier http://www.hbm.com.pl/pdf/a0114.pdf

At page 46 there is a line as such:

Common mode rejection

0... 300 Hz    dB   >100

  300 Hz       dB   >85

Do these mean for AE101 the common mode voltage will be rejected more than 100 dB or %100 for the frequencies more than 300 Hz?


texts: Purpose of a capacitor between op amp input and output

texts:
what is the purpose of using a 1 uf capacitor between input and output of this op amp?

this is a current source circuit .


texts:
Peripherals in Micro-controllers usually provide a way for us to send and receive data from it. Usually this are memory mapped registers.

I have come across few terminologies. The most often used one is a buffer and probably a FIFO. But when working with CAN controllers, I came across Mailboxes.

Now I am confused.

What is the difference between a buffer and a mailbox. Or a FIFO and a mailbox.

Thanks!


texts: Lighting LED using keypad and microcontroller

texts:
So I am working with Gizduino (Arduino clone), keypad and led. What am I doing is getting the value of keypressed and then light up the led according to the value (eg., when I pressed 2 on the keypad 2 LEDs will blink). I know this is just basic but please bear with me. I have this code (I will not include some really basic things like keymapping or something that is not related to my question).

int led1 = A0;
int led2 = A1;

void setup()
{

pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);

}

void loop()
{
   char keypressed = myKeypad.getKey();

   if(keypressed != NO_KEY)
   {

       if(keypressed > 47 && keypressed < 58)  // is between '0' and '9'
       {
           if(!mySwitch)
           {
               num1 = (num1 * 10) + (keypressed - 48);
           }
           else
           {
               num2 = (num2 * 10) + (keypressed - 48);
           }

           if(keypressed = '1')
           {
               digitalWrite(led1, HIGH);
               delay(500);
               digitalWrite(led1,LOW);
               delay(500);
           }
           if(keypressed = '2')
           {

               digitalWrite(led2, HIGH);
                delay(500);
               digitalWrite(led2,LOW);
               delay(500);

        }
    }
}

What's happening is that when I press '1' in the keypad the first led will blink and after that the second one will too. Why is this happening? Is there a problem in my code?


texts: Generating Rolling Code with Arduino for RF Switch

texts:
I am working home automation using Arduino and TX/RX module.
From various sources I learned that Rolling Code based RF Switches are having better security.

I have following queries

How suitable it is to use FIXED code RF relays for Home automation. I need it for switching on and off lights and not for key locks.
Is it possible to generate rolling code using arduino for a given receiver working on rolling code RF.

Please help.


texts: RGB LED Strip - Variable Voltage Vs. PWM

texts:
I am going to install an Analog RGB (non adressable) LED strip in my room and need to make a driver for it.

The LED strip specs are:

10 cm segment
12V @ 60mA max per segment

I would be using 330cm of the strip (33 segments => 2A max => 0.7A max per channel)

My initial thought was to use a microcontroller with 3 PWM channels for red, green and blue. But then I realized I could probably get away with using 3 variable resistance to provide variable voltage to the 3 channels and the color can then simply be changed by altering these resistors.

Would this way be okay ? After all PWM does the same thing ... generate analog voltage levels from digital.

The only thing i can think of is that the variable resistors need to be able to handle that much current (vs PWM solution where a mosfet/bjt would take care of it).

Any thoughts ?


texts: Can a phone battery be used to power Arduino or Motors

texts:
I was wondering whether it would be possible to use a rechargeable battery from an ordinary cell phone to power some electronics such as a motor shield for Arduino?
Can that be done and if yes then how?

Cheers


texts:
I try to read some value from CT. Everything is alright but sometimes I read some really high value on my arduino pin.
I was looking some information about the CT protection. People talked about diode because we don't want a value higher than 5V ( if it is higher we could burn the ATMEGA). Which type and where can I put it? I'm actually using this schematic:


texts: Fake microstepping in A4899 and LV8729 stepper-drivers?

texts:
I built a test jig to experiment with a friend's 16-pin A4988 stepper driver, and even added bi-directional LEDs to the outputs and, regular LEDs to the inputs, to see if it behaved as expected.
By default, it does a full circle in 200 steps, and both coils were always driven.  Fine.
If MS1 is set, every other step features a coil off.  200 steps rotate it half-way.  Expected.
But in any jumpered "microstep" mode, and pulsing VERY slow, I can see and feel that it MERELY COUNTS steps, before the last two.
For instance, at Sixteenth Stepping, the first 14 steps do nothing whatsoever.
Step 15 advances a half-step, and Step 16, the next full step.
No PWM, no fractional voltages.  Just counts until the final two steps, and half-steps.
So I ordered a pair of LV8729 controllers of the same 16-pin RAMPS-style from BigTree on Ali.  Certainly these would microstep ... but no.  Precisely the same behavior.
Anything above half-stepping, they just count until the final two pulses in the sequence.
No modulated PWM, and no in-between. Half-stepping is the finest resolution available.
Does anyone have the same experience?  Is there some secret to force this style of stepper driver to do real microstepping?
Have found no online references to fake microstepping on cheap stepper drivers.
It is hard to imagine that millions of these are being sold, without true PWM fractional steps.  Someone would notice, eh?  At regular speeds though, it is difficult for a human to see.
My expectations may be amiss.


texts: Problems using Servo.h and VirtualWire.h in arduino

texts:
I'm using an Arduino Uno. My motive is to control a servo via wireless transmission using RF. So for that I have to use both Virtual Wire.h and Servo.h. But when I am compiling it shows me errors that is not defined and other problems. When I studied on net it shows that both uses Timer1 so we have to change the timer of Servo. So there are some suggestions and fixes found on net that guided me to use a new library called ServoTimer2.h.

http://arduino.cc/forum/index.php/topic,21975.0.html

Now when i use this library it doesn't seem like its been included in the arduino library. Also the color of Servotimer2.h doesn't change also.

Errors showed while compiling

#include <VirtualWire.h>
#include <Servo.h>

void setup(){}

void loop(){}

Servo\Servo.cpp.o: In function `__vector_11':
C:\arduino-1.0.3\libraries\Servo/Servo.cpp:103: multiple definition of `__vector_11'
VirtualWire\VirtualWire.cpp.o:C:\arduino-1.0.3\libraries\VirtualWire/VirtualWire.cpp:568: first defined here


texts:
I am really confused about how several books and videos handle Pulse Shaping.In order to avoid ISI (Inter Symbol Interference: Energy from one sample leaking into the energy of the other, creating uncertainties)  and have finite bandwidth, Nyquist suggested using a Sinc impulse response.

Every System (not recorded) is Causal in nature. Overhere the impulse comes later while the output starts producing the Sinc impulse response so its peak comes ontop of the sample point. Also somehow the future impulses tend to affect current values.

Can someone explain me how is this possible?


texts: Small 5V BLDC motor controller - 6 mosfet IC

texts:
I am creating follow focus system (motor with gears that moves camera lens ring). I think the best choice is BLDC motor (DC geared are too loud, stepper don't have enough torque or too  big).

I need a motor to rotate at ~100RPM. The torque needs to be at least 1kgcm. I found some bldc motors that satisfy my needs (like emax 66KV + magnetic encoder for feedback) - most of them are used in gimbal systems.

Now onto the controller. It needs to be small - not bigger than 4cm in any direction. I believe 10W is more than enough. I'd like to be able to power it with 5V - directly from power bank - there is no need for more voltage since it is low RPM low torque project. I did some research and couldn't find any drivers that satisfy those requirements. They are either too big or require at least 7.2V to be powered (RC escs).

I therefore think the only way is to create my own controller. I based it off of this solution (https://simple-circuit.com/arduino-sensorless-bldc-motor-controller-esc/).

My questions are:

Since I am using 5V to power motor and arduino also outputs 5V from its pins can I skip IR2104S gate drivers? 4.3V should be enough motor voltage.
6 mosfets bridge take up a lot of space. Is there an IC that provide same functionality? As stated before the motor should only need about 10W.
If you notice any mistakes in my plan or explantions let me know


texts: Common emitter, o.p. set by feedback resistor

texts:
I am analyzing common emitter amplifier where operating point is set by feedback resistor between b-c.

Voltage gain showed by symulator is much lower than (-)R2/R1 and input resistance is lower than B*R1 (B is beta, hfe).

What is R3 impact?
I am looking for exact formulas (for "by hand" calculating) for k and R_inp. Knowledge about R_out would be also educating.

My goal is understanding voltage and input impedance drop in circuit like below:

Predicted: k=U_Rc/25mV=6V/25mV=240 V/V, R_input=(25mV/Ib || 1k)*B || 82k=109k || 82k=47k

Simulated: k=113 V/V, R_input=13k


texts:
I did try to set this up in Mouser Blue Edition. Apparently vb and vs become connected at some point so the bootstrap capacitor can discharge itself. I haven't been able to see that happen in my simulator yet Mouser Blue encounters an unrecoverable problem and can't simulate anything (The second schematic is from Fairchilds):

I'm not sure I have it down really but if VB and VS are connected inside the IR2104 then it should look like this I think:

Thank You


texts: Anode potectial in industrial electroplation operation

texts:
I am modeling a large (physically 125' x 12' x18") electroplating line.

The line has a common anode (industrial plain carbon steel 1 x 1-1/2" x 1/4" floor grate) with multiple pairs of rectifiers that provide current to cathode conductors that support the product as it is transported through the operation .

The rectifiers provide individually up to 12,500 amps each through a combination of copper buss and flexible 2-1/2" OFHC connectors.

I have completely to my satisfaction and to readings taken during production modeled the IR drops along the cathode conductors and in the product being electroplated.

My question relates to the andoe side of the process. Because the rectifiers 'float' essentially up to the location where they are either 'commoned' together along the 125' length or where the first point in the circuit where they contact 'tank potential' (tank sits on the 'ground' and is steel).

Each of the individual rectifiers has a single output shunt which is used by the SCR fire circuit to meet set current value. Voltage varies to meet current.

So essentially each rectifier is a source of electrons, and the desired outcome is for the electrons to plate the metallic species in solution onto the product in a uniform and repeatible 'controlled' process 24/7/365.

Now enter reality.

is the anode grate reasonably to be expected to be at 'zero potential' - i.e. Do electrons that have participitated in plating process return to a ground state such that when they 'go to' the grounded anode grate they see 0V?

Or in the same way that on the cathode side there is an IR drop caused by the liner/positional resistance and the high currents. BTW the plating process is a non-linear electron sink which I am modeling as a function of concentration, activity, and chemicals.

Maybe my question is like asking on a power distribution AC utility line is the nutral leg always at zero along its multiple-mile length?

Thank you

Hope I have provided sufficient context and detail for replies.

Also there are 22 rectifiers , each two are paired and supply power to cathode conductors through different length conductors - i have this modeled and results in a potential difference across the product being processed.


texts:
I'm intending to capture the signal lines of an audio mixer (XLR, 16 channels).

Each channel can be a microphone (order of mV range), or line signal (upto around 1 V).

I want all lines (16 channels x 3 XLR (GND + 2 signal lines)) to either JST or pin headers (2.54mm).

I don't know in front which will be microphone/signal lines (or at least I don't like to be dependent on it).

When I will use Arduino ADCs or other ADCs, will I get problems (like crosstalk) of I try to read a signal of a few mV next to a signal of 1V? Is there a minimum space? Or is it best to put the GNDs in between like:

Pin   1   2    3    4   5    6    7
     Ch1 Ch1  Ch1  Ch2 Ch2  Ch2  Ch3...
     Gnd pin2 pin3 Gnd pin2 pin3 …

So the minimum space between e.g. Ch1 pin2/3 which is 2 mV and Ch2 pin2/3 which is 1.0V is enough? (2 * 2.54 = 5.04mm) ?


texts: Should I design a high-power switched mode power supply with surface mount components?

texts:
I'm designing a SMPS for a fairly high-power application (2kW, 50A).  In looking at the available components, sometimes almost the exact same components are available in surface-mount and through hole versions, for example: FDB035N10A in D2PAK and FDB036N10A in TO-220.  The specs are very similar, except the surface-mount component has a higher power dissipation rating.

Is it preferred to use surface mount components in this case?  What is more common or industry-standard?  What are some of the pros and cons?


texts:
Hello I am trying to communicate with TI BQ28Z610 by using Nucleo-F746ZG. All I do is trying to read data from TI chip. I am sending 0x08 to slave address 0x55.I2C frequency is 80kHz and pull ups are 10 K. Here is the related part of the trial code:

while (1)
    {
        /* USER CODE END WHILE */

        /* USER CODE BEGIN 3 */
        //READ VOLTAGE FOR TESTING

#define I2C_Slave_Address (0x55) // Receive 0x55+1    0x55
        uint8_t I2C_Data[16];
        uint8_t I2C_DataToSend;
        char statusString[255];
        int statusStringLength;
        I2C_DataToSend=0x08;

        if (HAL_OK != HAL_I2C_Master_Transmit(&hi2c1,(uint8_t)I2C_Slave_Address,&I2C_DataToSend,1,1000)){
            statusStringLength = sprintf(statusString,"Transmit failed");
            CDC_Transmit_FS(statusString,statusStringLength);
            HAL_GPIO_WritePin(LD1_GPIO_Port,LD1_Pin,1);
        }

        if (HAL_OK != HAL_I2C_Master_Receive(&hi2c1,(uint8_t)I2C_Slave_Address + 1 , I2C_Data,1,1000)){

            statusStringLength = sprintf(statusString,"Receive failed");
            CDC_Transmit_FS(statusString,statusStringLength);
            HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin,1);

        }
        statusStringLength = sprintf(statusString,"Voltage: %d", (int) I2C_Data[0]);
        CDC_Transmit_FS(statusString,statusStringLength);
        HAL_Delay(100);
    }

Here is the oscilloscope image:

Here is the logic analyzor view:

So what might be the reason behind it? For me everything looks fine. Thank you beforehand.
Edit: Here is the logic analyzer capture for 0xAA slave address:


texts: adding a yagi antenna to a bluetooth dongle

texts:
I want to set up a Bluetooth link between devices that are over 2000 feet apart.  Yagi antennas for 2.4GHz that can connect to routers are available.  A cheap Bluetooth dongle that can be easily taken apart can be found on DealExtreme (see the insides of one at http://we.easyelectronics.ru/Stress/prikruchivanie-usb-ustroystva-k-vnutrennostyam-noutbuka.html [In Russian] ).  The cheap Bluetooth dongle has an antenna on its PCB.  How can the internal antenna, with its single wire connection, be disabled and the external Yagi, with its coax wiring, be connected for strong signal strength?

This is an example of the type of dongle I'd like to modify.  The antenna trace can be seen on the right side of the PCB.


texts: What is the risk of using only ESD gloves?

texts:
I am working on a project where I am quite uneducated in the aspects of ESD. Our equipment is automated & grounded and the electronic components which will are loaded into the automation are nested in ESD trays. Once the operator loads the trays with the components into the automation, they are not touched again by humans.

If I am only wearing ESD gloves and am only touching the ESD trays, how much risk is there to damaging the electronic component?

The end product is very low cost and non-technical in nature, and I’d like to minimize the expense of mats, straps, etc.


texts: Can I use a common mode choke as a coupled inductor in a SEPIC converter

texts:
I do not really understand the difference between common mode chokes and coupled inductors. They are both 2 coils wrap around the same core but I know they have different purposes.
I want to design a SEPIC converter with a coupled inductor but it requires high current ratings and inductance value around 1 mH. However, coupled inductors do not have these specs whereas common mode choke have.
Is it okay to use a common mode choke as a coupled inductor in the SEPIC converter if the inductors are connected such that their flux are in the same direction?
Reference document from Texas Instruments


texts:
I am having a bit of trouble trying to figure this out. The equation I come up with keeps canceling Omega out.

$$Attempt$$

Converting the circuit to the frequency domain the capacitor becomes \$\frac{4}{j\omega}\$

I then used a current divider to find \$\underline y(j\omega)\$ = \$\underline u(j\omega)\$ 6 \$\frac{2+\frac{4}{j\omega}}{6+(2+\frac{4}{j\omega})}\$

Final Equation: \$\frac{12+\frac{24}{j\omega}}{8+\frac{4}{j\omega}}\$ = \$\frac{3x+6}{2x + 1}\$

Simplifying this I get the frequency response to be \$\frac{1}{2}\$. I am fairly certain that his is not correct.


texts: Current Source Dissipating Power or Providing Power?

texts:
In my Electric Circuits Analysis class, I came across this problem asking the value of the current sources dissipating power. Here's the diagram I got.

I'm pretty sure the current source is dissipating power. How did I get this wrong?
In the problem they stated I = 5.

Here's my crude but sufficient work


texts:
I implement a communication between two stm32f4 discovery board. I was trying to get some errors of hcan->Error (ESR in bxCAN) as much as i can to see how STM32 handles CANbus error management.
I shorted one of tranceiver's CAN L to the VDD and VCC respectively and after doing that communication disappeared. I traced one of mcu. It enters init and normal mode well. While transmitting process TEC incrementing and Bus off, error warning and error passive flags set. Last error code indicates bit dominant error.

My tranceivers was working at that time. I used simple board which includes 2xSN65HVD251DR IC, 2x100nf, 2x120 ohm.

NOTE: Damaged bxCAN worked on  LOOPBACK mode.


texts: How to find power, delay, and area of a synthesized design using Design Compiler?

texts:
I have a huge design that is synthesized and mapped to 45nm Nangate library. Is it possible to read the mapped Verilog file in design compiler and find estimates of power, area, and delay without running any optimizations or elaboration in DC? (The original synthesis is done using another tool and I would like to compare its synthesis report with that of design compiler).

The reason I am asking this question is that because the design is so big, DC takes a lot of RAM during elaboration which is beyond the capabilities of my machine. So, I would like to avoid elaboration step and get estimates of power, area, and delay in a simpler way.


texts: In magnetically coupled coils, what is the difference between coefficient of coupling and the percentage of a flux linked to the other coil?

texts:
I have encountered this problem.

A coil A of 400 turns and another coil B of 500 turns lie near each other so that 20% of the flux produced in A links with B. It is found that a current of 5 A in coil A produces a flux of 0.33 Wb, while the same current in coil B produces a flux of 0.15 Wb. Determine the coefficient of coupling between the coils.

The solution given to me had the coefficient of coupling being different as it had to be computed. L1, L2 and M were all computed first and then solving for k.
I have not seen any source clear up this confusion. This is because an alternative formula for k is the ratio between the number of flux linkages between A and B over the flux linkage of A. So what is supposed to be the difference?


texts: Did Capacitative Loading Kill My Op Amp?

texts:
I've been playing with various constant current source configurations to help control the current output of my bench power supply and my latest efforts centred around the op amp and MOSFET approach.  I breadboarded the circuit shown below and got a pretty reasonable max Vref of 40mV at the + input to the op amp and both op amp inputs had equalized, so things looked good. Keen observers will notice the crucial missing components, but more on this later.  I decided to wire up a current meter between Vcc and MOSFET to check the current, expecting < 1/2 an amp flowing through the MOSFET.  I can't remember exactly what the current measurement was before I switched off the meter, but I don't believe it was high (probably a bit low, if anything).

A split second after turning off the meter (the circuit was still powered), the op amp went up in smoke.  The MOSFET was very hot and the op amp was warm-to-hot.  At first I thought it was the action of turning off the meter, but now I'm not so sure.

I considered that turning the meter off left the source / drain leg OC. This would have made Vsense 0V. The op amp would drive hard to make the - pin equal Vref, but so what??  No current is flowing through the MOSFET and the gate has a very high impedance, the op amp is putting out a high output voltage, but that shouldn't kill it surely and it's also a very valid test case for this circuit.  The whole idea is that it protects against load shorts.  If the circuit was operating correctly then a short between Vcc and MOSFET should still result in a controlled current through the FET.  I started looking on the internet for other possible causes and I hit upon HF oscillation as a possible cause.

Here's my take of what may have happened: the capacitative load that is the gate of the MOSFET introduces a delay into the negative feedback loop.  Starting with a Vsense voltage that is slightly too low, the op amp puts out a stronger output signal to correct the difference on its pins but this signal is delayed whilst the MOSFET gate charges.  Now, I'm not completely sure what happens next, but the gate will eventually reach the voltage intended by the op amp and I'm guessing that the extra time spent charging the MOSFET gate causes the gate voltage to overshoot (is this true? what really happens here?).  This causes a higher than Vref voltage to appear across Vsense and the op amp acts to correct this by pulling the output low.  This causes the gate capacitor to discharge slowly through the op amp output, which again causes a delay since the effect of pulling the output low isn't appearing across Vsense as quickly as it should.  So, we have oscillations back and forward, constant over and under shooting.

Using this analogy, I have glimpses of understanding around why placing a resistor between the op amp output and the MOSFET gate (and/or a capacitor between the op amp out put and ground) acts to reduce this effect, but it's by no means clear.  So, here's my challenge to you guys with more experience and knowledge: can you provide a decent intuitive anatomy of this disaster so that I fully understand what happened (the word "pole" is banned!)?  Can these oscillations really kill the op amp?  I'm thinking that the amount of current sloshing back and forward between the op amp and MOSFET is quite small considering the capacitance involved.  Also, can you explain in a nice intuitive way why the resistor and cap solution mitigates the problem?


texts:
See image - I dont have any idea on how to start calculating this circuit using Kirchhoffs laws. There isnt any kind of this circuit anywhere on the web as far as I can see. I would be very thankful if someone had a formula (sorry for my english, but what I mean is something like this U(V)=R*I to calculate with). You cant make a triangle out of three resistors cuz of the power source between them (as far as I know), the resistors arent in parallel either. I know I firstly need to calculate R, then use 1. Kirchhoffs law on joints/points (?), then write circuit mesh 1 and 2 and from those formulas calculate all the currents. But the best thing about this is that Ive never in my school calculated this type of circuit (believe me, I would have just asked my classmates if they knew the answer to this).

node where all currents go to: I3-I1-I2=0 => I3=I1+I2

S1: -V1+I1*(R1+R5)+I3*R3=0=-2.1+I1*45+(I1+I2)*15

S2: +V2-I2*(R2+R4)+I3*R3=0=1.8-I2*20+(I1+I2)*15

Still working on how to calculate using two unknowns

Those should be the results:

I1=24,8 mA

I2=40,8 mA

I3=65,6 mA


texts: USB Type-C: Are CC1 and CC2 interchangeable?

texts:
The schematic bellow is a USB controller, designed to be used to change USB's VBUS voltage:
Question: Are CC1 and CC2 interchangeable, meaning that red-marked labels could be switched between them, i.e, is there any difference for the controller whether CC1 or CC2 are connected to the pins 10/11?


texts: I do not understand why the direction of I3 is to the right, I am supposed to find Vs which the solution is 36V, my only problem is the direction of current for kirchoff current law, so I would like to know why I1 and I2 are the direction they are.


texts:
I'm asking here another question in relation to my previous one.

I would like to know how would one proceed when you want to control a heavy robot with differential wheel drive. When it comes to sending PWM values, I cannot control the robot, i.e, I cannot make the robot go into a straight line.

Another issue would be, braking the robot. Think 100Kg at its maximum weight, so It will have a LOT of momentum and inertia. Knowing this, what would you do to control its movement, with a differential drive system, and how would you control is breaking?

Note: This isn't to be considered as a hobby project. Think of this as the best way to implement it.


texts:
This was the slide that our professor displayed in class regarding the closing of a capacitive circuit.

Why is the amplitude(after a certain while) different in both cases? Shouldn't it be the same either ways?

Edit: Haha, I just realized from the answers that I was reading the wrong scale. Thanks though.


texts:
I have a relay model RM40-3021-85-1005 (datasheet), and according to datasheet it has a minimum switching current = 10mA

The coil resistance is 125 Ω, and when I connect it directly to 5V it works as expected. The current is \$I = \frac{V}{R} = \frac{5}{125} = 40mA\$.

Considering I have a limited power source, and as my understanding the relay only needs 10mA and I'm providing 40mA, I tried to include a 100 Ω in series with the coil. So the current will be \$I = \frac{V}{R_{coil} + R_{1}} = \frac{5}{125+100} = 22mA\$

With the 100 Ω the relay doesn't operate and I believe it is because the voltage over the coil. According to datasheet, the minimum for the coil operate is 3.75V, and with the extra resistor I get 2.75V. \$ V = R * I = 125Ω * 22mA = 2.75V \$

It is not clear to me. Is my understanding correct? If so, how can I operate the relay with a current lower than 40mA? For example 20mA.


texts: Common drain small signal analysis and unresolved question for fet

texts:
question:

There is an amplifier circuit obtained between JFET and MOSFET.
For the FET used in the circuit, IDSS = 8 mA, VGSoff = -3V and working point current is 1.42 mA.

Use MOSFET parameters as Kn = 1 (mA / V ^ 2), VTN = 1V, gm = 0.75 mA / V.

The voltage gain of the first floor in the circuit is calculated as 0.7,
and the voltage gain of the second floor is calculated as -100.

R7 = 101(R8) and R8 + R9 = 4.462 KΩ.

According to this; Determine the resistance values in the circuit to be KΩ.

Hi
It is desired to calculate the resistance values according to the parameters given in the question (in kilo ohms). I will use re model to solve this. However, jfet is composed of common drain. The resistance of R3 is confused. Books have common drain gain but no R3 resistance. can somebody help me with the jfet's gain formula and question?
@G36


texts: Are the ground wires and the earth creating a loop in this system?

texts:
Below in the photo both SMPS power supplies powers some DAQ boards. I named them as 12V PSU1 and 5V PSU2. As you see the PSU1 and PSU2 are daisy chained at their mains entry(line, neutral, earth):

And here is the basic diagram:

Above both power supplies powers the different parts of the remote device Device 1. In real there are six of them but or simplicity I draw one device. The PSU1 directly powers the device, the PSU2 powers the 5V part of the device through a USB Hub.

I named the nodes as A, B, C, D and E.

Knowing that in SMPS A E and C D nodes are capacitively coupled, is there a loop for high frequency across A B C D and E?

If there is can I eliminate that by cutting the daisy chain earth between  D and E?

Edit:

Block diagrams of the power supplies:

And here is the power line filter.


texts:
I'm not very experienced with electrical soldering, but I decided to give it a go. I don't have any kind of clamp to hold the protoboard in place, so I used electrical tape to hold it down to the table. While I was soldering, I noticed a whiff of nasty stench, and when I turned the board over, I realized I had melted a hole right through a strip of electrical tape.

I was outside, so I guess you could say the area was well-ventilated, but I'm still worried. Could this have caused any lasting effects on my health? What are the risks of electrical tape fumes?

Thanks, any input appreciated.


texts: Game Boy Camera – How to identify this connector?

texts: I want to get another male socket for the JST-looking connector that the 1998 Game Boy Camera uses.  I haven't been able to identify it though – the pitch looks to be exactly 1.5mm center-to-center.  Can I still buy this connector?


texts: How to repair a solder pad that came off a ribbon cable?

texts:
I've similar questions on  how to  repair solder pads however all the questions so  far only talk about solid PCBs.
For  some reason the solder pad  came off this ribbon  cable after I had soldered it onto the board. Is there anyway to fix this pad or is this cable just faulty? The other bits are fine but the person who sold the cable says  its my fault.


texts:
I have this circuit built and it keeps blowing up my bridge rectifier when I power it.

Is it because I have connected the chassis/system ground to earth ground?  I cannot figure out what is happening and every time it blows a fuse and destroys the rectifier.

click for schematic


texts: Which is faster for an MCU? Calculating Steinhart-Hart or search in Look-up Table?

texts:
Let say we are to measure 0-100 degree Celsius in 0.1 degree resolution by using an NTC. For a particular MCU which is faster (takes less time to reach the result) :
a) Reading NTC value via ADC and calculate the result using Steinhart-Hart algorithm?
or
b) Reading NTC value via ADC and compare it with the entire pre-constructed look-up table to find the result?


texts: Can someone help check my solution for this timing diagram?

texts:
I've been working on some timing diagrams and I keep mixing up the behaviors for the different flip flops.

EDIT:

I think I have the logic correct. If someone could please let me know if I'm anywhere close, I'd greatly appreciate it! Here's what I believe is how Y2, Y3, and Y4 should behave.

If anyone can let me know if I'm close, it'd make my day! Thanks.

Black is what was given and red is what I've done so far.


texts: Dramatically increasing voltage in a circuit

texts:
Suppose I have a small AC generator, which produces an unstable current at 1 volt. How can I transform this into 10000 volts, decreasing the amperage accordingly? It does not matter if the output is AC or DC, nor does it matter if the output is stable.

Is there a small, inexpensive way to do this in a circuit, rather than having a huge transformer box?


texts: How do you remove negative voltage from a sin, triangle or square wave?

texts:
I need square wave without negative voltage.

Considering a source which produces square wave (could be function generator or from other circuits) has no ability or I don’t have the control required to do this. So I need to use an extra circuit which can block the negative part.

What circuit would you use?

My simplest idea is to use a diode in series to block the negative voltage. However it doesn’t work. I have tried high and low frequency. Simulation in multisim’s oscilloscope doesn’t show any difference.  I have no idea why this is happening. Being relatively new to semiconductor devices, I am hoping to learn something new from this as it goes against my basic understanding of diodes.

Why the diode can’t block negative voltage? Is it because the diode’s p-n junction works like a little capacitor?

Multisim schematic and oscilloscope result:

Edit: After applying Olin Lathrop’s answer and Venny’s diode suggestion oscilloscope shows exactly what I want.


texts: Why can’t i use a supermesh analysis on this circuit?

texts:
Hi I want to ask you why i can't use a supermesh like this blue line.
The answer of this question is io=3.1 A.
I tried several times to use a supermesh but It doesn't work.
Is it because of the dependent current source?
Please tell me the reason....


texts: Why is the current in the resonant load in my H-bridge only sinusoidal for low current amplitudes?

texts:
I am attempting to drive high-current (~1000 amps) at high frequency (10~30 kHz) through a coil. I am not an electrical engineer but a student working in a small lab where we have to build everything we need ourselves (which is pretty fun), so I may not understand some basic things that might be obvious to the EE community. Prior to several months ago, I had only worked with voltages and resistors (in year one of undergrad).

My attempt: attach a capacitor in series with the coil so that it would have a resonant frequency and then drive that load with an H-bridge, supplied by a large capacitor bank. For testing, I am currently using two 400amp and two 600amp IGBTs that we already had for the switches, but will eventually upgrade to 1200amp IGBTs if I get everything working properly. These IGBTs are controlled by gate drivers that are optically isolated from their inputs coming from an FPGA. I have configured the FPGA to create 4 square waves, 2 of which are in-phase with each other and that are out of phase with the other two. This will be a pulsed system, and a trigger signal to the FPGA controls when the system fires.

The H-bridge is basically as below. In reality, there are currently two inductors, the main coil and a second to adjust (with the capacitor) the resonant frequency. The signals from the gate drivers, which are floating, are applied across each IGBTs gate and emitter. I have not included my control circuits to avoid unnecessary clutter; they work exactly as I intended.

Using Rogowski coils I measure the current in the two branches of the H-bridge, through the coil, and I also check the signal being sent to one gate for reference. If I charge the capacitor bank to a low voltage the current waveform looks perfect. It creates a nice sinusoidal waveform just like I want but the current is low .

However, when I increase the voltage of the capacitor bank source and drive more current (> 5amps) the current waveform becomes worse and worse.

What is the reason I am not getting a sinusoidal current through my coil at max currents greater than a few amps? I need an amplitude of 1000amps, not 2! Am I misunderstanding something fundamental or doing something silly?

I realize this is a long post. Thank you for your time in reading and considering it!


texts: Fan voltage fluctuating with potentiometer

texts:
I am driving a two side by side fans (original Xbox 360) from 20v, 4A source via a 12v regulator and a 10k trim potentiometer. The goal is simply to adjust voltage between 3v-12v, nothing I havent done before but shortly after setting the fans to the speed I want (say 6v), they begin slow down, around 4v. Then I adjust the pot to speed them up and then sometimes they will randomly go full speed ahead.

The pot doesnt get warm, the regulator output voltage is stable 11.96v. I have noticed that if the pot outputs 7v with the fans unplugged, the voltage sags to below 5v when plugged in.

The fans pull roughly 320mA @ 12v and 170mA @ 5v in this setup so 3.85W maximum.
Ive read a lot of trimpots have a max rating of 3.00W but this happens at power levels below that?


texts: Why Wouldn't I Buy A Diode With The Highest Reverse Voltage?

texts:
I'm only just beginning to read about diodes. I'm looking at the 1N400x series, where all specs are the same except the reverse voltage (link: https://www.mouser.com/ProductDetail/Diodes-Incorporated/1N4003-T?qs=rGAXPo9uwV0nfQ36LZW%252BLg%3D%3D for example). The reverse voltage increases as x increases, all else is the same (even price).

From what I understand, the reverse voltage is the maximum voltage drop the diode can have (in reverse) before it fails. My question is, is there a reason I shouldn't just buy the highest reverse voltage I can find? Is the N4001 not the same in every way as the N4003 except that the N4003 can work with higher voltages without failing?


texts: Identify components in an audio circuit schematic

texts: In the attached image you can see a circuit part of a commercial audio amplifier. I'm trying to determine what kind of component is R-CH and what role it plays in the circuit. I'd also like to figure out whether this circuit is on the audio signal path of the amplifier or not. What clues would give that away?


texts: How do I know what power rating pots need?

texts:
EE novice here. In this post on reddit, the author wonders if 125mW-rated potentiometers are usable in the MFOS Noise Toaster. The Noise Toaster drives analog audio circuitry off a single 9V battery and AFAIK there's no voltage boost circuit involved.

I believe that despite the specification of 250mW-rated pots, it may be safe to use 125mW-rated ones. My reasoning is this:

125mW at 9 volts implies ~13.8mA; a 660 ohm resistor on 9V will limit current to that level. A 1K ohm resistor will limit current to ~9mA, for 80mW, comfortably lower than the rated 125mW value.

In all but one place in which potentiometers are used in the circuit, I see on the schematic that they are in series with resistors, the smallest of which is 3K, so even with the pot turned to minimum resistance, it will pass no more than 3mA or 27mW.

The exception is on the audio output end of the circuit, in the case where the Toaster is driving line out instead of its built-in speaker, and R66 (a 100K pot acting as the master volume control) is turned to zero resistance. There's no fixed resistor in series there, but I think current should be limited in this case by the Q7 FET and/or the U2-A op-amp feeding it.

So my questions are:

Is my overall analysis reasonable, or am I misunderstanding things?

Could either the LM324 op-amp or the 2N5457 transistor drive more than 13mA through R66?

Would a 1K resistor in series with R66 make it safe to use 125mW-rated pots throughout?


texts: Due to overcurrent, shouldn't I be extremely cautious when setting an I/O pin as Output?

texts:
The question can be applied to any microcontroller with I/O capabilities, but I’m currently working with the popular ATmega328p. Consider the following circuit: A simple SPST Normally Open switch with a 10k pull-up resistor and a ceramic capacitor attached, connected to any I/O port.
The specific pin should be obviously configurated as INPUT in the respective DDRx. The datasheet describes, inside the DC Characteristics section, an Input leakage Current I/O pin \$ (I_{IL}/I_{IH})\$ of 1µA, while far in the horizon the DC current per I/O pin caps at 40.0mA. Not a problem at all.

DDRD = 0x00;    // Entire port as INPUT

Now consider that I forgot the fact that the given pin has to be set as Input, I set it as Output and set the Port HIGH.

DDRD = 0xFF;    // Entire port as OUTPUT
PORTD = 0xFF;   // Entire port HIGH

While the datasheet doesn’t provide an Output Impedance it can be estimated to be 25Ω, based on the given graphs.
Now at the time the button is pushed the current finds its way through the microcontroller from the 5V source with a 25Ω resistor plus negligible resistance due to the copper trace. This theoretically produces an overcurrent of 160mA above the DC current per I/O pin ceiling. Could this fry the port and the device?

Analogously, if I switch over to positive logic and set the port to LOW the same problem could be encountered:

DDRD = 0xFF;    // Entire port as OUTPUT
PORTD = 0x00;   // Entire port LOW

Considering this type of circuit is avidly encouraged, how it doesn't seem to bring any troubles? Now, back to the original question, shouldn’t I be extremely cautious when setting an I/O pin as Output? Or at least attach a small series resistor as a primitive protection?

Note: Not a native English speaker, feel free to edit the post if you see something awkward.


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texts: STM32CUBEIDE stuck in Reset_Handler when attempting to debug

texts:
I'm having some trouble debugging my STM32.

Since last weekend, I had to rebuild my Ubuntu 19.10 workstation from scratch, so all of my tools are newly installed and at whatever the latest version is (as far as I can tell). Everything was working fine before the rebuild.

I'm running STM32CUBEIDE with the following version details:

Version: 1.3.0
Build: 5720_20200220_1053 (UTC)

Whenever I attempt to flash and debug the microcontroller, the bits are uploaded and verified correctly, but the μc gets stuck inside of the Reset_Handler, defined inside of Startup/startup_stm32l412c8tx.s.

This happens even with a newly generated sample project. I have not physically changed the breadboard I'm programming in any way from when it was working.

I'm using the STLINK-V2 USB programmer over SWD.

I can pause, step and play from the debugger, but execution is trapped inside the Reset_Handler loop.

I can manually reset the device (with the momentary switch) and the state changes are reflected in the debugger as follows:

[256.299] Device_GetStatus():  ST-LINK device status: RESET_MODE
[256.572] Device_GetStatus():  ST-LINK device status: RUN_MOD
If I tail the debugger output log, I see the following (repeating eternally unless paused):
[14.655] write():  <12> Tx: $60000020006800400068004000800000000000000000000000000000f09f00200d05000800000000000000000000000000000000f09f00204b3900081602000800000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000ffffffff000000000000000000000000000000000000000000000000f09f002000000000#e6
[14.656] read():  <12> Rx: $qXfer:threads:read::0,bfb#fb
[14.656] write():  <12> Tx: $l<?xml version="1.0"?><threads><thread id="1" core="0" name="main"></thread></threads>#8b
[14.656] read():  <12> Rx: $z1,8000216,1#95
[14.657] write():  <12> Tx: $OK#9a
[14.657] read():  <12> Rx: $m800050d,1#5b
[14.657] handlePacket():  Reading 0x1 bytes of memory from addr 0x800050d
[14.658] write():  <12> Tx: $f8#9e
[15.083] read():  <12> Rx: $qXfer:threads:read::0,bfb#fb
[15.083] write():  <12> Tx: $l<?xml version="1.0"?><threads><thread id="1" core="0" name="main"></thread></threads>#8b
[15.083] read():  <12> Rx: $qXfer:threads:read::0,bfb#fb
[15.083] write():  <12> Tx: $l<?xml version="1.0"?><threads><thread id="1" core="0" name="main"></thread></threads>#8b

This is where the debugger points inside Startup/startup_stm32l412c8tx.s

.equ  BootRAM,        0xF1E0F85F
    .section    .text.Reset_Handler
    .weak   Reset_Handler
    .type   Reset_Handler, %function
Reset_Handler:
  ldr   sp, =_estack    /* <-- DEBUGGER HERE */

I'm hopeful that there's some simple setting or software version that I've lost or missed.

Any tips or pointers would be greatly appreciated.


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texts: Need a switching device. Should it be a relay?

texts:
I am trying to build a system where first i would charge the battery (3.7V,40A), and then discharge it through a high wattage Resistor. For this purpose i will be connecting a power supply (15V-50A) with my AC mains. It would be followed by a synchronous buck converter which would charge the battery (being controlled via PWM signal by the micro-controller). The purpose of using a synchronous buck converter is its bidirectional current nature, which mean it would be able to supply the current from the power supply to the battery (during charging) and from the battery to the Load (during discharging). I chose IR3553 from International Rectifier Synchronous Buck Converter to be used. The rough idea i have drawn, and it can be seen in the image below.

As can be seen in the image there's a switching device which would help me  (by the help of my micro-controller) to select between the power supply (during charging operation) and Resistor (during discharging operation) drawn in red. So my questions are :

1) What device would this be ? Is it a relay ?

2) I was going through relays online and they are used for these purposes. But what i also found was that there are different kind of relays mainly Electro mechanical relays and solid state relays. I also found in one article online that electro mechanical relays are  used when current is upto 15A. And solid state relays have higher currents upto 100A. So if my power supply is providing a max of 50A current, does that mean that i will have to use Solid state relays ?

3) Also I found out that relays are present with different no. of poles for eg 2,3,4,6,8 pole relays are there. In my case i think a single pole relay would do the job, am i right ?

4) What other things should one look for in relays data sheets ? for eg in my case (15V-50A) what things i should be concerned about when i am selecting a relay ?

Thank you.


texts: How to select offset frequency for phase noise measurement?

texts:
When reviewing datasheets or papers on oscillators, phase noise is obviously an important parameter, but I see that the phase noise is highlighted at one offset frequency from the carrier in particular, usually selected to be somewhere between about 1 kHz out to 10 MHz.
If you have an oscillator, how you pick the offset frequency at which to specify your phase noise performance?  Do you aim to provide a measurement in the \$1/f\$ or \$1/f^2\$ regions, for example (or one of the other regions illustrated on this page)?


texts: Do standard 3.5mm plugs short the terminals when plugging or unplugging?

texts:
I need an inexpensive connector to deliver positive, negative, and signal. I was considering using a standard 3.5mm audio style plug.

However, I am concerned that when plugging in the connector, it could possibly short tip to sleeve for example, just from looking at how the jacks are usually constructed.

Is this true? Is there a better connector style to use then, something "hot swappable"?