texts: Is it safe to remove earthing from a scope?

texts:
I need to make some differential measurements on a device, but both nodes need to be floating from earth.

I found out the hard way that the negative clip of my oscilloscope voltage probes are connected to the mains earth conductor, but I don't have access to a differential probe.

I was wondering if there is an easy solution to this, and I figured this: inside the scope I have seen that the mains are only connected to a power, old style transformer, while the earth lead is screwed to the metal chassis. Since of course the transformer output is isolated from its input, I think that if I just remove the earth screw from the chassis and isolate the cable I can now connect my device to the scope, avoiding the pesky ground current that destroyed my first board.

The negative terminal I would hook to the probe clip is about 60V over earth, the maximum current it can source is just above 30mA. The input transformer can surely withstand a 60V offset, right?

I think that this is safe because the shell of my scope is all made of plastic, the only metallic parts are the BNC connectors and a couple of blade connectors that I use to calibrate my probes, but they should all be safe.

Is it ok to remove the earth connector from my scope to make such a measurement? I have seen this suggestion all over the web, so I think it must be safe, but I want to ask a board of professionals just to be extra sure.


texts: Is powering the Nuvoton N76E003 with just the UART0 pins legitimate?

texts:
I bought an 8 channel USB/UART controlled relay board from banggood.com:
https://www.banggood.com/2-in-1-DC-5V-8Channel-USB-Serial-Port-Relay-Module-UART-RS232-TTL-Switch-Board-CH340-for-Windows-Linux-MAX-OS-p-1624821.html?rmmds=myorder&cur_warehouse=CN
This board features a Nuvoton N76E003 1T 8051-based microcontroller to convert the serial commands (which come from either the UART hook-up or an on-board USB-to-serial converter) to actual relay switching action.
I was able to communicate with it using USB with no problems but I decided that I wanted to use the UART interface instead for my project. I bought an FTDI FT4232HL-based 4-channel UART breakout board to do just that:
https://www.electrodragon.com/product/usb-to-four-4x-serial-ttl-uart-module-ft4232/
I set the break out board outputs to be 5V using the solder-jumper pads on the bottom and hooked it up to the relay board and my computer USB port.
I found that when I plugged the USB into my computer, the N76E003 would boot up and work (read: communicate with computer over serial connection) even when DC power was not applied separately to the relay board.
I made some measurements and there are DC voltages on the TXD and RXD lines coming from the FTDI breakout board. And when the FTDI board is connected (only using the TXD, RXD, and GND lines) to the relay board I'm able to measure around 3.7V on the VDD pin of the microcontroller.
As a further note, the relay board has the UART breakout pins tied to the UART0 of the microcontroller.
Again, this scenario is without any external DC voltage applied to the relay board, and there isn't enough power to drive the relays. I tried toggling the relays with serial commands and I actually thought that making it do this would overload whatever this mystery power delivery mechanism is and kill either or both of the boards, but it didn't, just no relay action.
I poked through the Nuvoton datasheet and couldn't find any mention of a "Power-over-UART" capability. So my question is this: is this supposed to be happening, has anyone else seen this phenomenon of this uC chip, or have I somehow damaged the thing in a really interesting way?


texts: How does digital patch memory work on an analog synthesizer?

texts:
Not an electrical engineer, but kicking around ideas for a polyphonic analog synth with digital memory, a simplified/modernized update of an older all-analog design.

I've riffled through some of the patent literature, notably the one for the implementation of patch memory read/write for the Oberheim Four-Voice, but since I'm not an electrical engineer, can someone patiently explain to me like I'm five, how digital patch memory works exactly? Specifically, how are the states of analog potentiometers + switches stored and then "read back out" without physically moving the components?

I can imagine if the analog controls are entirely converted to rotary encoders, that the values could be set inside the analog "synth engine" by some sort of conversion from digital to voltage? If it doesn't touch the actual signal path per se, of course.


texts: I have an AC to DC converter that outputs 5V. I then run this into 2 regulators on my board. The 4.2V regulator goes into a cellular module, and the 3.3V regulator goes into a microcontroller. I noticed the micro resetting in the debugger and scoped the 4.2V and 3.3V on single mode. I saw this transient. It happens about 3 times a day. The frequency of the transient is very close to 100Mhz. My micro runs at 64Mhz, not sure where this transient could come from. The magnitude of the transient on the 3.3V has gone to 16V pk-pk. This would seem like it would cause severe damage to the electronics. How can I find the source of this transient? I emailed the maker of the AC DC converter. He said it is unlikely coming in on the AC line, and is more likely coupled downstream from the regulators.


texts: Is the spacing between Ethernet 10/100 Mbps and USB 2.0 traces critical?

texts:
I am designing a board with USB 2.0 and Ethernet 10/100Mbps. I found this layout guide with very helpful information.
In the layout guide, at p. 34 (Table 7), it says that the minimum spacing between MDI signals and other high speed signals should be at least 7.5 mm. In my design I will have to route a USB 2.0 differential near the Ethernet RX differential pair at approx. 3.8 mm for a length of around 10 mm.
So, my question: is this issue critical (will it lead to a non-working design)? In this case, what solutions can you recommend me (e.g., how to shield the Ethernet RX pair from the USB 2.0 pair)?


texts: How to measure DC motor (used as generator) efficiency using homebrew methods?

texts:
Background

I'll be making a "micro thermal power station" in the single-digit watt range at home (one-off, educational project. Bear with me).
A heat source, likely ethanol, will cause a stirling engine to turn a DC motor, used as a generator.
The topic of the educational part is to focus on efficiency. To this end I want to see where the energy is wasted on each stage.
Measuring the electrical part (after the generator) is easy. The problem is the previous stages (heat→motion and motion→electrical).
Also measuring the end-to-end efficiency is not hard (X ml of 95% ethanol is Y joules and so forth).
The biggest unknown is the heat→motion part. I tried asking the stirling engine manufacturers and they haven't measured it.
But if I figure out the generator part, then I can infer the heat→motion part.

Questions

Efficiency of DC motors when used as generators

I have several DC motors laying around at home, some DC (e.g. Mitsumi M36N-2), some BLDC (selected inrunners with Kv about 250).
From what I've seen in datasheets like the Mitsumi's it is expected that the motors have the highest efficiency (when used as motors) when they are lightly loaded (around 10% of the stall torque).
Is it reasonable to assume that the efficiency peak when used as generators will be in the same conditions?

Measuring efficiency with homebrew methods

Most of the motors I can use don't have datasheets, so their efficiency is unknown. I don't have a dynamometer, otherwise this part would've been easy. I came up with a method to measure the efficiency:

attach a spool to the shaft of the motor;
the spool has a known proof mass attached to the end of the thread;
the motor is loaded with known resistance (if it's the BLDC, then three equal resistors);
the whole setup is placed high near the ceiling;
as the mass is released, it unspools the thread, rotating the motor. Record the output voltage with a DSO;
integrate the power over time, and compare to the potential energy that the proof mass had before releasing;
changing the mass or load can simulate different load conditions.

So I have something, but seems too cumbersome, and it also introduces other unknowns.
I'm wondering about other approaches to this measurement problem. I may be missing something simpler. Any ideas?

Disclaimer

The question may be more appropriate for other SE sites. Please suggest if you think it's better asked elsewhere.


texts:
I was thinking why in oscillator circuits with only a DC source the capacitors and inductors don't reach a steady state where the first is an open circuit and the second a short circuit (so the whole thing behaves like a DC circuit).
My hypothesis is as follows: if the transistor were to always maintain a single state (i.e. Forward Active) then indeed the circuit would have reached a simple DC steady state (no oscillations after steady state is reached).
But if the transistors moves between Forward Active to Saturated (for example), there would be 2 DC steady states: one for the FA case, and the other for the Saturated case.
And as the transistor doesn't stay in either condition (FA or Saturated) long enough for the steady state of that condition to take root, the circuit keeps changing its behavior over time.
i.e.

FA state associated with DC steady state 1

Saturated state associated with DC steady state 2

When the transistor in FA it moves towards DC steady state one, but before 1 is stabilised, Saturation occurs.
At Saturation it moves towards DC steady state two, but before 2 is stabilised, the transistor is forward active again.
(In this example I used, FA and Saturated, but it can go through Cut off as well).
I wonder if this way of thinking is valid? Could people who understand this in depth please comment on the statement above. (I don't mind if it's not the best way to understand oscillators, but I do wonder if as far as it goes, the statement above is valid). Thanks!
(There is a separate question of why a Collpits oscillator, for example, produces a nice sine wave, but my question is more limited - only why it doesn't reach DC steady state regardless of what voltage pattern is produced as it oscillates).
Edits - added examples (click on image to see better):
This Collpits type oscillator goes from FA to Saturated:

But having reduced the resistor to 10 ohm, it stays FA, and oscillation no longer occurs (ordinary DC steady state instead):

A multivibrator also shifts between mostly Saturated and Cutoff for each transistor:


texts: Capacitance value - AC RC Circuit - Impedance Method

texts:
Here is the circuit:

simulate this circuit – Schematic created using CircuitLab

\$
V_i = \frac{8}{\sqrt 2} \angle0° V\\
V_c = \frac{6}{\sqrt 2} \angle45° V\\
R = 1000\space\Omega
\$

I'd like to know how to find the capacitance with these given values. What I've tried:

\$
V_c = V_i \times \frac{X_c}{R\space\space+\space\space X_c} \\
X_c = \frac{V_c\space R}{V_i\space\space - \space\space V_c}
\$

Here is the problem, just solving for Xc, I got a complex number with a angle different than -90°. So I forced Xc to be -90°, then when I solve for the capacitance c, I get a complex number:

\$
X_c = 1058.7141\angle 93.4716182° \\
\frac{1}{j\frac{500}{2\pi}c} = 1058.7141\angle 93.4716182° \\
c = -0.00001184768784 + j\space 7.18682779 \times 10^{-7}
\$

What am I possibly missing?


texts: Can someone help me on how to charge this Battery?

texts:
I have a ES cordless drill and it has a Li-Ion battery (model is ES GB118L20).

The original battery charger is missing and there is almost no way for me to get one in my country.

The Battery has 5 Samsung INR18650-20R 3.7v cells connected in series.

The battery pins are BATTERY+, BATTERY- and 4 pins marked BATTERY1, BATTERY2, BATTERY3 and BATTERY4 which are connected between + and - of batteries (probably used for balanced charging). Also there are T, BS and ID pins which I'm not sure of their role.

I tried charging the cells one by one by connecting a TP4056 charger to each battery pin (for example [BATTERY- and BATTERY1] or [BATTERY1 and BATTERY2], but was not successful. It didn't even start charging it.

Can anyone help me how to charge this thing?


texts:
I've knocked together a L297/L298 stepper motor controller and have a problem with what seems to be half the output. On the final 4 output lines after the L298 and diodes, I have 2 bipolar LEDs to help visualise what is going on without requiring a motor be attached at all times while debugging.

What is happening is odd and has got me stumped. One of the LEDs, the one attached to the CD / Inh2 lines works fine, however the other LED doesn't do anything. Grabbing my multimeter and measuring voltages on the Inh1/Inh2 outputs of the L297 show that the Inh1 output never changes and is always 0 whereas the other varies accordingly depending on if I'm in half or full stepping mode. I immediately thought it may be a bad chip but I've tried 3 different L297s now and all exhibit the same behaviour so it clearly isn't that.

I know this is possibly a bit vague for someone who doesn't understand a L297/L298 driver, but I'm hoping it is some easy rookie mistake that I can fix in seconds with the correct hint? Here's a schematic of the circuit I've replicated roughly:

from RepRap Stepper Motor Driver 1.2


texts: Reading SPI flash W25Q128FV with raspberry pi, what am I doing wrong?

texts:
This is the pinout I have for the flash memory W25Q128FV which I'm trying to interact with

I'm trying to control it with a raspberry pi 3 B+.
Here's how I wired everything:
CS - GND
D0 - SPIMISO
WP - nothing
GND - GND
VCC - 3.3v
HOLD - nothing
CLK - SPISCLK
DI - SPIMOSI

CS is in GND because datasheet says that in LOW, we can write/read from the chip.
I also enabled spi on raspberry and I'm using the library wiringPi with channel 0.
I'm writing like this:
wiringPiSPISetup(0, 2000000)
wiringPiSPIDataRW(0, data, 4)

but I get no changes in data. I suspect something is wrong but I don't know if it's on the chip, on the wiring or on the software. This is a brand new chip by the way.
What are the raspberry pins SPICS0 and SPICS1 for?
I'm trying to read the manufacturer id, here are the instructions:

here's what I did:
    data[0] = 0x90;
    data[3] = 0x00;
    data[4] = 0xEF;
    data[5] = 0x17;

I don't know what those MF7-MF0 and ID7-ID0 are but I substituted them by some numbers I found on the datasheet
datasheet link: http://www.xmcwh.com/Uploads/2020-09-03/5f50d26953af2.pdf
Here's my Rust code with everything ready to test and dockerized, just ./run.sh, compile the Wiringpi/wiringpi with ./build and cargo run in w25qxx_spi: https://github.com/lucaszanella/w25qxx_spi/blob/68a7f993a6572e177d9b4d60a7cfac02ccb016ff/w25qxx_spi/src/w25q.rs
If you help me you're helping open source, I'm interfacing with wiringpi in Rust and creating a library to read from W25Q spi flash memory.
Pins information:


texts: Colpitts Oscillator- Extract Signal with emitter follower

texts:
I designed a circuit as shown in wikipedia:colpitts
which runs at about 500kHz, L=680uH and C_1=C_2=100pF (+ some tuning caps in parallel to L). When looking at it with an oscilloscope it works just fine, now I want to decouple the signal from the oscillator (the scope's probe's capacity alters the frequency for example). What circuit would do that? I tried an emitter follower but as soon as the collector of the oscillator circuit "sees" a base, oscillation stops. I tried what resistance to GND would not influence the signal and found out that 100kOhm attenuate the oscillation to about half and 1MOhm may just be right. So I tried this(imagine all missing parts of the left bjt as in the link above):

simulate this circuit – Schematic created using CircuitLab

I tried some combinations of values of the resistors but nothing seemed to deliver the signal to output. Either it was destroyed right away (when R_B was low, no oscillation even occurred) or nothing came out of the transistor (when R_B was large, 10k-100k).
Why is that? Can anyone propose a circuit that may buffer the signal for further use so to speak?
Last but not least if anyone has an idea of how to reduce phase jitter of the oscillator itself, that would be great. Thanks

Edit: Hey I played around a bit. The emitter (as expected) has a lower impedance and is more loadable, but I put no transistor behind it yet as an amp stage because the signal is not as sinusoidal as the collector output (lower half waves are cut off partly). How can this be fixed?

To increase stability I tried to make a Clapp version out of my circuit by doing this:

simulate this circuit

Notice the cap in series with the inductor and the new large signal bias resistor.
The stability did not increase. Did I do it right?

Since the emitter did not give enough sinusoidal a signal, I tried to lower R1 (4.7k down to 470 Ohm) to provide more current and therefore making the collector signal "stronger" (more loadable) but the circuit stopped working completely. How could this be predicted (is there a formula or something? All formulas for Colpitts I found are that gm*R_E > C1/C2 and the obligatory f_osc=1/(2pi sqrt(LC))). Is there some good paper about Colpitts with an extended mathematical approach?

Further more, which configuration is more stable (and if so, why?): common base or common collector?
I looked at the ham radio circuits (and I am not through yet) but they seem to use mostly Colpitts in common collector configuration. Is that hinting to that this is more stable?

Attempts to decouple the source voltage more did not make the circuit more stable (more and closer caps of various capacities). Wrapping the whole circuit in aluminum foil did not help either (it only produced smoke:-). No, kiddin, that was not the point, it really didn't help...).

Thanks, tomorrow more tests.

Update: So I changed the large cap of 100nF (C3) to 100p and the feedback caps to 470p. Larger values didn't work (which I tried to make C3 the only frequency-defining cap, at least almost). The stability increased. What also increased the stability was to lower the base bias voltage almost to the point where the circuit stops oscillating. Further more the wave form got more clean a sinus. This was to expect, since we give only as little amplification as possible to sustain oscillation.

The circuit oscillates now at 655kHz and only changes slowly in the sub-10Hz region.
My goal is to get an oscillator, which should be short-time stable and not wildly oscillate around its center frequency (so to speak, the frequency at which the frequency alters should be low...). I only have 200mVpp left at the emitter, but I think it can be loaded a little with a common emitter stage that amplifies the signal. So instead of an emitter follower there will be a common-emitter amplifier.

Surprisingly (to me...) a better coil with less resistance did have no effect on stability. Why?

If you are interested I will post some pictures and screenshots of the scope.
Let me know.


texts: UART is garbled when running at more than 9600 bps

texts:
I'm connecting 2 MSP430F5529-based boards (running at 1 MHz) using UART and MAX3232 (MSP430F5529 -> MAX3232 -> cable, a few cm long - will be longer in our final application -> MAX3232 -> MSP430F5529).

It works as long as the bit rate of the UART is under 9600 bps. If this is raised, I start getting many errors (usually the MSB is flipped).

If I remove the MAX3232 and connect the boards directly, the problem goes away. It doesn't happen if I loopback, too.

I am running the MAX3232 at 3 V, which the datasheet says is enough:

  Transmitter outputs will meet EIA/TIA-562 levels of ±3.7V with supply voltages as low as 2.7V.

What am I doing wrong?

My code on the TX side is:

void UART_Initialize() {

    UCA1CTL1 |= UCSWRST;
    UCA1CTL0 = UCMODE_0; // UART
    UCA1CTL0 &= ~UC7BIT ; // 8 bits, no parity, 1 stop bit
    UCA1CTL1 |= UCSSEL_2; // Source 1 MHz

    UCA1BR0 = 104; // 104 ~= 9600 bps
    UCA1BR1 = 0;

    UCA1MCTL |= UCBRS_0 + UCBRF_0; // Modulation
    P4SEL |= BIT4 + BIT5;
    UCA1CTL1 &= ~UCSWRST;
    UCA1IE |= UCRXIE;
}

void UART_send_data(unsigned char character) {
    while (!(UCA1IFG & UCTXIFG));
    UCA1TXBUF = character;
}

unsigned char UART_get_char() {
    while (!(UCA1IFG & UCRXIFG));
    return UCA1RXBUF;
}

void UART_shutdown() {
    UCA1IE &= ~(UCRXIE|UCTXIE);
    UCA1CTL1 = UCSWRST;
}

int main() {
    unsigned char received_data;

    P4OUT = 0x00;
    // Disables the watchdog
    WDTCTL = WDTPW + WDTHOLD;

    // CPU clock to 1 MHz

    UCSCTL0 = 0x00;
    UCSCTL1 = DCORSEL_3;
    UCSCTL2 = FLLN5_L;

    __enable_interrupt();
    UART_Initialize();

    while(1) UART_send_data(0x55);

}

On the RX side the code is similar except for main() (which just receives the value and compares to 0x55).


texts:
I am currently reading about Pulsed Latch Circuit. And there is a frequent mention of "hold time violation". Like:

  For latch, "...data must be held for a longer period of time,
  increasing the likely number of hold time violations".

Please explain what hold time violation is in the context of Latches.


texts: Confusing Parallel/Series Arrangements in Application of Thévenin's Theorem

texts:
I'm learning from Paul Scherz's Practical Electronics for Inventors (2nd ed.) and I've become confused at what was I thought I was comfortable with: namely parallel and series resistors. The offending example is:

Looking at the uppermost diagram and working out the simple Thévenin equivalent circuit for the circled loop, I don't understand why the total Thévenin resistance is the sum of individual parallel resistors and not series resistors.

My reasoning tells me that since the other half of the circuit has been shorted, then an equivalent current flows through both resistors in this loop i.e. implying a series arrangement. Going further, even if the circuit were complete, these two resistors would still be in series, so I'm confused as to why the Thévenin resistance has been calculated as if this is a parallel arrangement.


texts: Modifying an amp evaluation board to bias the coax?

texts:
I'm normally a software guy, but a recent project requires me to dip my toe in the ocean of electrical engineering.
I'm trying to (cheaply) capture GPS signals to process in software, and I have an amplifier (TRF37C75 Evaluation Module from TI) for use with an active antenna. What I don't have is a way to inject DC to the coaxial. I'm finding bias tees rated for the appropriate frequency to be too expensive or too hard to get. I'm not of the skill level to build my own from scratch.
An acquaintance of mine suggested that by adding an inductor to the amplifier module, the same as L1 between the VCC and the RFIN side of C1, would have to effect of a bias tee.

This sounds doable, but L1 for this module is a 100nH from CoilCraft; components with this inductance are all SMD, so how do I get it to reach? Can I attach leads to it?
On the other hand, I was also pointed to this blog, where a DVB dongle was modified to add DC to the coaxial. He effectively did the same thing, by adding an inductor between the power supply and the coaxial. By the looks of the images, he just used an insulated copper wire to carry the DC and then soldered the inductor onto the PCB between the capacitor and the coax.
Does this sound reasonable to try with the amp module? It seems rather quick and painless to do, and much cheaper and easier than having to add Yet Another Device (bias tee).


texts: How to receive audio from Arduino into Max

texts: I'm a beginner with Max and what I'm trying to do is take the the audio input signal going into my Arduino and hear the receiving audio playing through Max. There's a photo below of the patch that I'm working with. If anyone knows how to do this, It would be much appreciated.


texts: For my application I have two AD633 Analog Multipliers that need a ground referenced +-15V supply. I have a 24VDC and a 8 VDC supply to use, but i would prefer to use the 24V supply. I've looked at several options, But most used too many components, So am after a solution that uses as few components as possible and will last for a long time.


texts:
How can the Eagle control panel pane sizing be set per user preferences?
When opening Eagle my left pane is consistently too small. How can this be set so that upon starting Eagle a different left pane size can be set in the control panel?


texts:
I am constructing a system in a solar car, and need to have capaitors large enough to power the Telemetry system for about 15s after power down.

I need to use capacitors instead of the batteries, due to race regulations.

The Telemetry system takes about 1 amp at 5v leading to a power consumption of approximately 5 watts. The minimum operating voltage is about 4.5 volts.

I am thinking of using a 5 farad capacitor, but I don't know if this will work. Could someone please shed some light on how this is calculated?


texts: Is there a way to build a software defined radio using the PC's DSP chip?

texts:
I'm looking to build a radio controller for a few DIY robots and was wondering if anyone knew of a way to utilize the onboard DSP in PC's as a SDR. The reasoning for this direction is I remember reading a related project back in my BBS days for ham radios.

The project would preferably be on Linux, yes I'm vaguely familiar with GNUradio, and use as little hardware as possible.

Update:

After google-ing I found the reference document I was refering to at amsat.

However most documentation I've found is geared to Windows/DOS based projects.


texts: How to calculate aging tolerance of Resistor?

texts:
I wanted to calculate the worst case minimum and maximum value of Resistor 1K by considering all  the
tolerances(initial tolerance,temperature,environmental factors and aging).

Here is the link for the datasheet:

http://www.bourns.com/docs/Product-Datasheets/CHPREZTR.pdf

Based on the datasheet, I found

initial tolerance - 1%

temperature - 100ppm/deg C - Calculated as +0.45% and -0,4% (Based on my system operating temperature range which is between -15 deg C AND 70 deg C)

Environmental factors -10.5%

But I do not know how to calculate the aging tolerance based on the Load Life data which is given as 1% under this condition (+70 °C; 1.5 hours “ON”,
0.5 hours “OFF”; 1000 hours)

Any suggestion how to interpret the datasheet for aging tolerance?


texts: Can linearity of photoreceptor be improved by calibration?

texts:
I am trying to determine if equipment I already have can be used to take a reading in mcd/m2, for a quality control test. I have a sensor which meets all the requirements listed in the standard test method except that it has a linearity error of <1% instead of linearity error ≤0.5%. Could a better calibration correct the linearity of this sensor so that it is within tolerance or do I need a better sensor?

https://www.intl-lighttech.com/products/ilt5000-researchlab-radiometer
https://www.intl-lighttech.com/sed033-broadband-silicon-detector
https://www.intl-lighttech.com/products/ilt5000-photometer-sed033yr-detector-luminancebrightness-measurement-system
https://www.intl-lighttech.com/products/ilt5000-sed033yw-research-lux-measurement-system

According to the mfg, this system satisfies all the following requirements except for linearity:

spectral error, f1' ≤5 %
UV response, u, ≤0.5 %;
resolution at least 0.1 mcd/m2;
resolution 1.0 lux;
linearity error, f3, ≤0.5 %
signal-to-noise ratio: at least 10:1 for all measurements.

EDIT: MORE INFORMATION

Data Mfg provided when asked about linearity:

Distance 1: 1 meter (lm/ft2) Distance 2: 2 meter (lm/ft2) Expected
Value % Deviation
2.42E+02 6.00E+01 6.050E+01 -0.8%
2.32E+01 5.75E+00 5.789E+00 -0.8%
2.20E+00 5.56E-01 5.509E-01 0.9%
2.60E-01 6.49E-02 6.510E-02 -0.3%
3.98E-02 9.86E-03 9.956E-03 -0.9%
4.66E-03 1.16E-03 1.164E-03 -0.5%
5.14E-04 1.28E-04 1.286E-04 -0.3%

Cal Values from this specific equipment:

No device found at COM port 3
Device found at COM port 4

Type help for a list of device commands
Type exit or quit to close console

getinfo
Base Serial Number = 00000000000000000
Vendor Serial Number = ILT500000000
Model Name = ILT5000
Friendly Name = NOT-DEFINED
Generation = 3
FW Version = 3.1.2.8
Dark mode (0=No,1=Factory,2=User) = 1
Rf Setting (0=Auto,1=Rf1,2=Rf2,3=Rf3,4=Rf4) = 0
Rf value R1 (kOhms) = 3
Rf value R2 (kOhms) = 1000
Rf value R3 (kOhms) = 10000
Rf value R4 (kOhms) = 10000000
Rf value in use (KOhms) = 10000000
eCal: Enabled
eCal values = 1.016e-12 4.965e-12 1.002e-11 5.044e-11 1.011e-10 4.963e-10 9.982e
-10 4.997e-09 1.000e-08 4.992e-08 9.991e-08 4.970e-07 9.946e-07 5.014e-06 9.994e
-06 5.007e-05 9.993e-05 5.002e-04 1.001e-03
Sample time (ms) = 2000
Auto Sample Time: Enabled
4-20mA mode (0=Auto/log, 1=min-max/linear, 2=manual) = 0
getvx1 = 0.081090
getvx17 = 1.381653
getvagc3 = 3.281837
Active voltage gain stage = 2
TIA voltage = 0.064558
getcurrent = 6.443e-12
Factory dark = R1 192 13 6 R2 172 47 65 R3 205 52 69 R4 17529 17299 14838
User dark = R1 160 0 0 R2 146 1 0 R3 159 1 0 R4 9272 9503 9558
Ambient level = 0.000e+00
Logging: Disabled
Wireless/Auxiliary Listening: Enabled
Peak Tracking: Disabled
Fast Integrate: Disabled
Multidrop: Disabled
Sensitivity: 1.475000e-09

Sorry if this question seems confused or is missing any needed info, I am just a tech, not an engineer.

Thanks.


texts: What exactly are the tradeoffs between terminating a transmission line carrying a digital signal in 50 ohms versus high impedance?

texts:
I have a black box that outputs a 1.28 MHz clock signal that I need to buffer and distribute. If that signal is terminated into 50 ohms the voltage is so slow <1.5V it won't register as high for the logic family and voltages I want to use. Into High-Z it swings up to a full 3V which is well above the 2V threshold for TTL and CMOS.
What is the tradeoff from switching to 50 ohms to High-Z? Is it noise? Ringing?


texts:
Using a mobile device so I can't upload a picture.  I need to find Z_total in a circuit. I will simplify the circuit description so that its easily pictured.

The simple circuit contains  The  5<20 phasor current source ("<" representing angle here).  The source is in series with a 10ohm resistor and an inductor labeled 30ohms.  This is a simple single-loopb.

I've never seen this before.  Normally I see diagrams with inductors as impedance values (ex: j30), or in henry's, with which I would calculate impedance with j-omega-L.

How can I find Z_total for such a circuit?

I tried just summing 10+30 =40 ohms, but that is wrong.  I also considered maybe its reactance, meaning omega-L = 30, and multiplying by j to get Z_inductor, then summing that with the resistor to find Z_total, but that is also wrong.

This is on an exam review and we have the answers, but not procedures.
 I don't have the answer to my described circuit, as the actual circuit is more complex and contains more elements. The common problem though is all the caps and inductors are labeled as ohms, not reactance, impedance or farads/henries.  Not sure how to interpret this.

I will try to log on later and attach the actual circuit.

Thanks


texts:
I feel kind of stupid asking this question, but after unsuccessfully searching for papers and then starting to draw my own solution with a lot of XORs to the following problem, I started wondering about how fundamental the problem was, and that literature must already have an solution:

Imagine you have got two controllers, one being a master and one being a slave. Some outside power can tell the slave to be the master at any time, e.g. when the current master is unreachable. As both controllers are connected to some actuator there must be some kind of safe form of mutual exclusion that prevents all foreseeable error scenarios. To accommodate for loss of power or the current master not reverting his master status after a new master was crowned (e.g. if it never received that information) I tought about letting each controller produce additional output signals, e.g. signaling that the controller is the master, and mixing them between logical 0 and 1 (to filter some illegal constellations e.g. 1 & 1 which may be produced through short circuits and the like, or 0 & 0 in case of power loss). These addional signals should then determine which signal path (the actual control signal for the mutually exclusivly accessed actuator) should be blocked and which one shall let the signals pass.

Is there a name for such mechanisms and are there any good papers describing these methods / exclusive access strategies?


texts: Do I need to use a diode when combining two usb 5 volt lines?

texts: I want to use a USB bus powered device with my laptop. However, it draws to much current from the laptop and won't work. Do I need to use a diode(s) if I solder another 5 volt line powered by a wall wart to the original cable?


texts:
I was going through the following link which describes the "I2C address allocation table"

http://simplemachines.it/doc/IC12_97_I2C_ALLOCATION.pdf

Upon reading the aforementioned information table I was thinking that the device address "0x5x", where "0x5" is the group ID is not used for any of the I2C devices.

Is it possible that I am referring to a very old information?

If NO, then I recently came across a ST product (the below link), which has the address as "0x5x"!

http://www.st.com/resource/en/datasheet/vl53l0x.pdf

I am confused now.

My doubt is: Is it possible to assign a group ID of "0x5" to any I2C device?


texts: As a hobbiest with trying to learn what exactly would a bench oscilloscope do for me?

texts:
I'm overwhelmed by all the stats and options out there and I'm not exactly sure what I would even do with one as a day to day basis.

I have a little dso138 kit that I can see simple waveforms on currently and I'm still not quite sure how I would do something useful with this information.

What does a bench oscilloscope bring to the table for a beginning hobbies in this field?

(I am not asking for a recommendation on any specific brand or unit, more in general usage)


texts: Is it right to define ground as a pool of surplus free electrons, like a metal?

texts:
In a dipole antenna or any other pole like antenna, there is supposedly a ground on one side causing the current to flow away and towards the ground towards the feed, but if the whole antenna itself is a good enough conductor with free electrons, how does the earthing work?
Is it necessary to have an antenna such that it's resistance is higher than the ground?


texts:
Im searching for a very cheap/simple UART to Bluetooth (LE) module, but all I can find are modules like the BlueGiga BLE112, which seems like complete overkill (USB, GPIOs, ADCs, etc). I also came across the Nordic nRF8001, but it's only a chip, and not a complete module with shielding, antenna, etc.

So does anyone know of a cheap and simple module?


texts: Does anyone know the name of this 8 pin connector?

texts: I accidently cut this too short, does anyone know the name of this connector?


texts: How do I find out which current/voltage to use for an unlabelled LED panel?

texts:
I have a 600mm x 600mm LED panel with 576pcs 3014-type SMD LEDs in some unknown configuration/topology (edge-lit, similar to this one here: http://i01.i.aliimg.com/wsphoto/v0/1990066259_5/Wholesale-3PCS-Lot-48W-Led-Panel-Lights-60x60cm-Led-Panel-600-600mm-Ceiling-Panel-lights-LED.jpg ). I thought the standard way to power it would be a constant current driver, like the one I use for my smaller COB lights. I tried a 300mA driver, which resulted in 34V voltage drop (for the whole panel). The panel was fairly dim and clearly needs more power, but I don't know how much, as I have no data sheet of the panel or the individual LEDs.

How do I find out how best to power this panel without damaging it?

One idea was to try varying the current in a friend's lab (with his adjustable power supply), but where to stop? Is there perhaps a voltage limit over a single (white) LED that I could watch out for? Or is there some other useful measurement I could make with a standard multimeter?

I am looking for a method that does not involve a soldering iron because I do not have one suitable for SMD to re-assemble the LEDs.

(This question is related to Easy way to figure out a LED's Vf in order to pick an appropriate resistor but not quite the same, so I have opened a new question.)


texts: Relay coil suppression with unknown switching tolerance

texts:
I'm sorry if the title is confusing - I'm not exactly sure how to pose this question/concern.  I'm rewiring a 12 volt automotive engine control harness to be used stand-alone outside the original vehicle.  Part of the process is to eliminate the rest of the original vehicle harness & unnecessary components of the relay & fuse box that are intertwined with the engine harness.  The factory service manual gives me the following diagram (reduced to show only necessary fusing/relays for my application), but I'm concerned that it is oversimplified and may not show the necessary relay coil suppression to protect the ECM (engine control module).  The "CPU" in the diagram is not the ECM I'm concerned about.

I had planned to use TE V23232-D0001-X001 relays for the throttle control motor, ECM relay, fuel pump relay, & starter relay.  The coil resistance is 46ohm, and the relays have no built-in suppression.

For the ignition relay I planned to use a TE V23132-A2001-X30 (used on multiple BMW models).  I cannot find exact specifications for this OEM model, other than seeing it listed as 130A and with the schematic printed on the relay housing.  It appears to have a resistor in parallel with the coil.  The general version of this relay has a coil resistance of 37ohm, with a resistor for coil suppression.  The coil rating has a footnote indicating the ratings are "with resistor". The coil does read 37ohm across the terminals.

My questions, as general as they are:

What coil suppression method(s) should I use to protect the ECM considering I don't know if it has any built-in protection?  Switching speed isn't a concern, but I'd prefer to get decent contact life from the relays.

If the ECM already has protection built in, does adding another layer cause complications?

If the V23132-A2001-X30 relay has a resistor built in, is any other suppression necessary, and what method would be used if so?  The FSM schematic as shown has a series diode & resistor in parallel with the ignition relay coil, but this is not built in to the components I'm using and would have to be added if necessary.


texts: Female-female connector, but what is it called?

texts:
Question
What is the "official" name for this type of connector? (the large black box in the image)
More info...
I need the connection to connect two PCBs together as one was missing from a system that I purchased.
The connection links between the male header pins on two circuit boards and therefore needs to be female-female.
After an extensive search on-line I've come to the conclusion that without knowing what it is called I'm not going to be able to find them.


texts: bare-metal software and FreeRTOS run in ARM Cortex A9

texts:
Is that possible to run bare-metal software in CPU0 and FreeRTOS in CPU1 since the ARM Cortex A9 is a dual core processor. I am asking this out of curiosity. If anyone has accomplished this before, do you mind sharing how you did that?

I am using Zedboard FPGA with ARM Cortex A9 PS.


texts:
I'm building the circuit of this article:

C7 is rated 1nF 2kV. Is this right, does this capacitor need to be able to handle 2kiloVolt? Why is that? Is ethernet dangerous?


texts: I'm interacting with a computer and the return high (1) is at 12V but I need it to ~5V. What is the best way to lower the voltage without affecting the signal (serial) ? I already thought of a voltage divider but I was wondering if there is a better way ...


texts: Can an IR camera be used in broad daylight?

texts:
I am wondering if it is at all possible to have an IR camera that can be faithfully used in broad daylight. I have already seen this question here, but I am looking to understand if a full blown camera can even have this capability.

What I would like, is to be able to make out cars (that are on), and humans, against a background using an IR camera in broad daylight. Is that even possible? I would think so, but I am not sure of the physics/electronics constraints in this regard. Thank you.


texts: Is it practical to build a wearable project that draws 9A @ 12V?

texts:
When plugged into wall warts, the flexible LED strips I want to make into a wearable display draw 3A @ 12V per 5m.

To do a 30 x 15 pixel display that's 15m, or, 9A @ 12V running around my body. Is this prima-facie unsafe? If it's not, am I going to need to carry the batteries around on a trolley?

I believe the LEDs will light at 9V and just not be as bright (which may be what I want, anyhow) and I'll be running PWM'd patterns so it won't be a 100% duty cycle but I'd at least like to establish a lower bound.


texts: Splitting 12V power supply into 12V, 9V and 5V outputs

texts:
Apologies if I butcher the terminology. I'm a new hobbyist trying to learn the rope.

I have 1 power supply that I'd like to use to power 3 devices:

Commodore 64 motherboard: 9V 1.5 Amps
Commodore 64 peripherals: 5V 1 Amp
LCD Module: 12V 2.5 Amps

From doing some research, it looks like I will need at least a 12V, 6 Amp power supply.

From there, I know I need a switching regulator to down step the voltage.

My questions are:

How do I split the power supply into 3 outputs?
Once I have it split, do I need 1 switching regulator for each output that needs to be down stepped?

Thanks!

EDIT: The C64 needs 9V AC, not DC as @RJR pointed out.


texts: How to create a system where battery power exist as backup power source

texts: This mainly applies to design of a clock but can be applied to many other circuits. The idea is that a device with PIC microcontroller is usually powered via external DC power supply which obviously passes through a voltage regulator; if this power source is lost, the device should switch to run from a battery power source but suspend most of its operations and enter a "minimum operations mode" having detected loss of main power. Are there any application notes on how to do this for PIC or any other microcontroller?


texts: Wake-up PC from sleep mode using PIC24FJ256GB106

texts:
I am trying to wake-up the PC from sleep mode, using PIC24FJ256GB106.

I am using Windows 7. I have installed "Microchip Solutions v2012-04-03" and I used the firmware from "Device - HID - Custom Demos" directory as a starting point.

When I connect my USB device, it shows up in Device Manager, in "Human Interface Devices" tree. (I am using Windows 7) But there is no "Power Management" tab from which I can check the "Allow this device to wake the computer".

Anyways, I figured out some kind of a solution for my device to wake up the computer from sleep. So I have to:

connect a USB mouse on the same root hub with the device
I have to check the "Allow this device to wake up the computer" for the mouse
and in the USBCBSendResume() function, I had to remove the if(USBGetRemoteWakeupStatus() == TRUE) condition

How can I wake-up the PC only using the device, without the mouse connected on the same root hub?


texts: Verilog test bench incorrectly reading test vector

texts:
I'm trying to use a test bench to simulate a 4-input XOR function. I've specified the test inputs and expected outputs in a test vector file. This isn't homework, just for personal interest. For the first 8 (0000 through 0111) inputs, the expected output is being misread from the test vector. The final 8 are okay.

I used the test bench to verify a different combinational circuit, and it worked fine. I modified slightly to simulate my XOR function, and now it is not working as expected.

Any help, comments, suggestions, etc. are appreciated!

XOR module:

module xor_4(input [3:0] a,
                output y);

assign y = ^a;

endmodule

Testbench:

module testbench3();
reg clk, reset;
reg a, b, c, d, yexpected;
wire y;
reg [31:0] vectornum, errors;
reg [3:0] testvectors [10000:0];

// instantiate device under test
xor_4 dut({a, b, c, d}, y);

// generate clock
always
    begin
        clk = 1; #5; clk = 0; #5;
    end

// at start of test, load vectors
// and pulse reset
initial
    begin
        $readmemb("xor_4.tv", testvectors);
        vectornum = 0; errors = 0;
        reset = 1; #27; reset = 0;
    end

// apply test vectors at rising edge of clock
always @ (posedge clk)
    begin
        #1; {a, b, c, d, yexpected} =
              testvectors[vectornum];

    end

// check results at falling edge of clock
always @ (negedge clk)
    if (~reset) begin
        if (y !== yexpected) begin
            $display ("Error: inputs = %b", {a, b, c, d});
            $display (" outputs = %b (%b expected)", y, yexpected);
            errors = errors + 1;
        end
        //$display (" %b %b %b %b %b ", a, b, c, d, yexpected);
        vectornum = vectornum + 1;
        if (testvectors[vectornum] === 4'bx) begin
            $display ("%d tests completed with %d errors", vectornum, errors);

            $finish;
        end
    end

endmodule

Test vector:

0000_0
0001_1
0010_1
0011_0
0100_1
0101_0
0110_0
0111_1
1000_1
1001_0
1010_0
1011_1
1100_0
1101_1
1110_1
1111_0

Output from iverilog script:

C:\iverilog>iverilog -o test testbench3.v xor_4.v
C:\iverilog>vvp test
 WARNING: testbench3.v:17: $readmemb: Standard inconsistency, following 1364-200
.
 WARNING: testbench3.v:17: $readmemb(xor_4.tv): Not enough words in the file for
the requested range [0:10000].
Error: inputs = 0000
  outputs = 0 (1 expected)
Error: inputs = 0001
 outputs = 1 (0 expected)
Error: inputs = 0010
 outputs = 1 (0 expected)
Error: inputs = 0011
 outputs = 0 (1 expected)
Error: inputs = 0100
 outputs = 1 (0 expected)
Error: inputs = 0101
 outputs = 0 (1 expected)
Error: inputs = 0110
 outputs = 0 (1 expected)
Error: inputs = 0111
 outputs = 1 (0 expected)
        16 tests completed with          8 errors


texts: Order capacitors by leakage rate in Cockcroft-Walton voltage multiplier

texts:
Looking at a system like the Cockcroft-Walton multiplier posted here: https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/voltage-multipliers/

To use 400V 100uF electrolytic capacitors running at 110VAC (the first capacitor cannot be electrolytic: it has to run in both polarities), do you think there is any advantage of measuring the leakage in each capacitor, and ordering them in the chain?

The reason to do this would in theory be to reduce the build-up of voltage within the capacitor chain: Supposing I have N capacitors, and I order them from lowest leakage to highest, would that give me a more stable combination than mixing them up in a more alternating order (hi, lo, hi, lo, etc)?

I do understand that there should be balancing resistors in parallel. Just wondering if there is any value in ordering them, since there is a huge variation in the capacitors I have looked at.


texts: Variance in ECG lead resistance ; its effect ; CMRR

texts:
We are designing custom ECG electrode with flexible printed wires as to reduce wires clutter from different electrode. The manufacturer has made the patch but the resistance variation between all the three electrode varies, which is 20 ohm, 5 ohm and 30 ohm respectively.

Is this variation acceptable or resistance of the electrode and the the lead as seen by the amplifier should be same. Considering the electrode-skin interface in which variation is in the order of 1000 of ohm, is variation of lead resistance by 15 to 50 ohm acceptable. If we consider common mode noise variation across leads with different resistance, will amplifier amplify common mode noise, thus amplifying noise.

Will using the right leg drive can help to reduce the noise.


texts:
On the Wiki site re: Amplitude Modulation, see:

http://en.wikipedia.org/wiki/Amplitude_modulation

-it states, "It is assumed that  \$\omega_m \ << \omega_c\$,"

...which means that the frequency of the modulation is always lower than the frequency of the carrier.

Anyhow, my question, what if we did not assume that?

Is the reverse possible ?

more question added, 12/14/2013 Dan Jenson

Guys, thanks so far, I am coming along in my understanding because you all articulate precisely; and so with good respect to you all I would like to continue a little further.

Please let me go on and detail my question  more precisely.
I guess that my aim is a mathematical question per wave theory and I am using AM theory as a starting point.

Question: In wave theory, when one wave amplitude modulates another in a non-linear mixer the "signals" multiply and the frequencies add, and (as far as subtracting goes), the higher freq, subtracts the lower since we are dealing in semi-conductors and vacuum tubes which deal in like charges, namely electrons.

But now what if, let’s say the vacuum tube rf amp was a little gassy and glowed blue with some plasma when transmitting thus ionizing the actual gas atoms and (once again) “thus” bringing a proton gyro-magnet into the equation.  Since this mentioned particle is opposite in charge to the electron can we now bring into our applied math equation my forwarded “B-A”namely the ‘missing’ lower freq. wave modulator minus-ing the higher freq. carrier thus giving a negative resultant ?

My question again, re: wave theory, given the needed parameters, does the “B-A” math exist in reality or even virtual?

added 12/15/2013

My question launches from an electronics understanding of heterodyning to wave theory itself. I was simply wondering why the author of the referenced wiki site stated the equation as an "assumption" ?

I 'believe' that if hypothetically an opposite charge were included into the equation then maybe my proposed math could find validity.

Please, in wave analysis can we describe the why and where-to-fore of the
\$\omega_m \ << \omega_c\$,  equation mentioned above in essence as a simplistic intuitive of why this is true in wave theory ?

AM is the perfect example and so the question remains valid.

Granted the question goes on to model a yet untested hypothesis related to plasma physics,
but (!) I do not wish to conjecture this far I merely am looking for some sounding board commentary on how we can assume to conclude our understanding at this mentioned assumption?

Gentlemen, please,
sincerely, Dan Jenson


texts: System Generator: How to configure the pins for the signals of your design?

texts:
I am programming a FPGA by System Generator. I have done this design:

I don´t know what are the respectives pins of my FPGA for the blocks of my design called 'Gateway In' and 'Gateway Out'. I would like to check I would check the design made in my FPGA through a generator waves and a oscilloscope.
Does anyone know how to assign pins of your design if you made it using System Generator?
Thank you so much.


texts: Powering a USB Host with MCP1253 Charge Pump

texts:
I'm a SW head trying to design a circuit that can switch 5V to a USB Port for embedded Host Operation and switch it off for USB Device operation. Microchip have a few schematics which show the use of their MCP1253 Charge pump for this.

Obviously they know what they're doing but looking at the specs for this device  it can supply 150mA of Output current. That seems very light weight for USB Host? In addition it provides a regulated output power but since my input Voltage would be 5V power rail of the board I'm not sure I need a regulator. Obviously I'm missing something.

I'd be very grateful if somebody could explain why this is used to power USB Host at such low current.


texts: Can a capacitative touch switch provide multiple response levels?

texts:
After recently discovering the ESP32, I've been inspired to attempt my first electronics project. It will be a very simple wifi-enabled light.
I thought I would take advantage of the capacitative touch pins on the ESP32 and add two on-device touch buttons to increase/decrease the brightness.
Then I thought I might be able to save a pin if the buttons are able to return different capacitive values, and if my code can consistently detect these different threshold levels.
After much searching around, I have not been able to find any examples of capacitative switches used in this way, or any switch components that provide graduated capacitive values.
Is this a bad idea? Or is the capacitance range for these switches sufficient that I could be able to achieve this kind of multi-state set up?


texts:
I'm driving a 12V brushed DC motor using an A3941 full bridge mosfet driver. The setup is controlled using an STM32F407. Since the A3941's logic inputs need 5V, I'm using a MC74VHCT125A buffer between the STM32 and the driver.
There is also a wireless remote using an nRF24 and its data is parsed by the STM32 as well. Its a simple remote that transmits a 32-byte array. If array[0] = 1, turn the motor CW, if array[0] = 0 then stop the motor. If array1 = 1, then turn the motor CCW and if array1 = 0, then again stop the motor. This partially works and this is where the strange behavior comes into play. When I press the button for CW on the remote, I hear a low whine and the motor does not turn or turns very very slowly. If I press the button for the CCW, it turns but not at the set duty cycle. For the motor to turn, you need to keep pressing the button on the remote. This means that the PWM Start function keeps getting called again and again. If this causing this weird behavior?
Can anyone help me understand what is happening here?
To test if the motors are working properly, I added a small while (1) loop where I turn the motor CW, wait for 2s, stop the motor, reverse the direction and start the motor again, wait for 2s and the stop the motor again. This works just fine without any issues. So I know that the motor driving circuitry works okay.
The functions for turning the motors CW, CCW and OFF are as follows:
void Start_M1_CW(void)
{
    HAL_GPIO_WritePin(DIR_M1_GPIO_Port, DIR_M1_Pin, CW);  // Sets the direction by setting the Phase pin to 0
    HAL_GPIO_WritePin(PWM_L_M1_GPIO_Port, PWM_L_M1_Pin, GPIO_PIN_SET); //PWML = 1. Pg. 9, Table 2 of the datasheet
    HAL_GPIO_WritePin(SR_M1_GPIO_Port, SR_M1_Pin, GPIO_PIN_SET); //SR = 1. Pg. 9, Table 2 of the datasheet
    HAL_TIM_PWM_Start(&htim5, TIM_CHANNEL_1); // PWMH. 95% duty cycle, 20Khz frequency
    Motor_M1.flag = 1; // a simple flag to tell if the motor is ON or OFF
}

void Start_M1_CCW(void)
{
    HAL_GPIO_WritePin(DIR_M1_GPIO_Port, DIR_M1_Pin, CCW); // Sets the direction by setting the Phase pin to 1
    HAL_GPIO_WritePin(PWM_L_M1_GPIO_Port, PWM_L_M1_Pin, GPIO_PIN_SET); //PWML = 1, Pg. 9, Table 2 of the datasheet
    HAL_GPIO_WritePin(SR_M1_GPIO_Port, SR_M1_Pin, GPIO_PIN_SET); //SR = 1. 9, Table 2 of the datasheet
    HAL_TIM_PWM_Start(&htim5, TIM_CHANNEL_1); // PWMH. 95% duty cycle, 20Khz frequency
    Motor_M1.flag = 1; // a simple flag to tell if the motor is ON or OFF
}

void Stop_M1(void)
{
    HAL_GPIO_WritePin(SR_M1_GPIO_Port, SR_M1_Pin, GPIO_PIN_RESET); //SR = 0
    HAL_TIM_PWM_Stop(&htim5, TIM_CHANNEL_1); // PWMH = 0
    HAL_GPIO_WritePin(PWM_L_M1_GPIO_Port, PWM_L_M1_Pin, GPIO_PIN_RESET); //PWML = 0
    Motor_M1.flag = 0;
}

This is the code for operating the motor based on what the remote payload contains. This works fine btw. I can see the button as 0 or 1 while debugging.
void Parse_Remote_Payload(void)
{
    //M1 CW
    if (nRF24_payload[0])
    {
        Start_M1_CW();
    }
    if (!nRF24_payload[0])
    {
        Stop_M1();
    }
    //M1 CCW
    if (nRF24_payload[1])
    {
        Start_M1_CCW();
    }
    if (!nRF24_payload[1])
    {
        Stop_M1();
    }
}


texts: Increase 74LS TTL gate's output current to drive multiple high-power LEDs

texts:
If have several 1 watt LEDs that I want to drive off of a TTL gate's ouput. What can I do to increase a 74LS TTL logic chip's output fan-out (current) to be able to produce a true 5 V output that is capable of driving as much as 500 mA (or more if possible) worth of devices (at 5v)?

As a side question to this one, is it better to use a TTL chip's high output with the cathode of the LED connected to ground or vice versa (use a low output with the LED anode connected to +5 V)? Also, on which leg of the correct orientation should the current limiting resistor go, if that matters? Finally, to complicate things more, should the LEDs be connected in series or parallel for higher output?


texts: How can I float a pin that otherwise should be low?

texts:
I want to enable/disable a TI TPS54302 buck regulator with a microcontroller. The enable (EN) pin should float to enable the device, or be tied low to disable it.

I currently have the EN pin connected to a GPIO pin on the MCU. At startup, before the pin state can be set low, it will sometimes already be floating, so the regulator operates for a brief time before the pin is intentionally set low.

I'd like to add an external pull-down resistor to ensure the regulator stays off until it is supposed to be on, but that would prevent floating the pin.

I presume I could simply pull the pin high (instead of floating it) and achieve the desired result. The TPS54302 datasheet says:

  The EN pin has an internal pullup-current source which allows the user to float the EN pin to enable the device. If an application requires control of the EN pin, use open-drain or open-collector output logic to interface with the pin.

If I tie the EN pin to ground with a 10kΩ resistor, and pull the MCU pin high when I want the regulator to operate, is that a viable solution?

I'm not concerned about small (≥1mA) constant current usage as this is a line-powered device.


texts: Generalized Power Equation, Ohm's Law and Ohm's Power Loss?

texts:
I'll try to state my questions precisely as I can.

I'm a beginner in Electronics and since I have a background in Physical Chemistry and basic Calculus, the book Practical Electronis for Inventors, 4th Ed. suited very well my needs. Not too deep in maths but also not superficial. And that's the book I'm using for.

On the part about the Generalized Power Law (GPL, for short), that's \begin{equation}P = IV \qquad(\text{W/A})\end{equation}
It's said that

  provides a general result, one that is independent of type of material
  and of the nature of the charge movement [...] The generalized power law
  can be used to determine the power loss of any circuit, given only the
  voltage applied across it and the current drawn, both of which can
  easily be measured using a voltmeter and an ammeter. However, it
  doesn’t tell you specifically how this power is used up

What I don't understand is exactly what he means about power loss. Is it about producing heat or another form of energy not intended for that device? So if that's true this power calculated its not the useful power produced by that device, but the difference between the input and the output?

So this GPL can be applied only and only for this purpose of power loss calculation (aka heat production), correct?

Now the Ohm's Law (OL, for short):
\begin{equation} V = IR\qquad (\text{W}/\text{A}^2) \end{equation}

Which we use if the resistor or another device has a linear relationship of \$I\$ and \$V\$ while \$R\$ is constant --or have a linear area on its graph, like LEDs, I think--, and then we can calculated its useful (?) power. Correct?

IF and ONLY IF all the power is converted to heat of something like that, the OL can be substituted on GPL, giving us the Ohm's Power Loss (OPL, for short)
\begin{equation}P = VI = V(V/R) = V^2/R \end{equation}
or
\begin{equation}P = VI = (IR)I = I^2R\end{equation}

The books says

  In this form, the power lost due to heating is often called ohmic heating, Joule heating,
  or \$I^2R\$ loss.

So the GPL and the OPL are the same thing?...
I'm days struggling to understand these equations and it's meanings but I just can't. May be stupid questions but I just can't understand who is who and what is what.


texts: Help needed using convolution to calculate a system's impulse response

texts:
I have a circuit with the transfer function \$G(s) = \frac{1}{(s+1)^2}\$ and I'm asked to calculate the impulse response of the circuit. After looking into it I know that I need to use convolution with the delta function to solve this.
I've managed to get as far as forming the integration to solve this, but I'm struggling as it seems to be quite a complex integration. I'm not sure if I've gone wrong somewhere leading up to it, so I was hoping someone could have a look through what I've done so far, and also help me with the final integration. I'll post my working first and I'll explain the integration problem at the end.
So the transfer function \$G(s) = \frac{V_o(s)}{V_i(s)} \therefore V_o(s)=G(s)V_i(s)\$, where \$V_o(s)\$ is the output response and \$V_i(s)\$ is the input impulse.
To find the output as a function of time: $$v_o(t) =L^{-1}\{G(s)V_i(s)\}=g(t)\ast v_i(t)\\ g(t) = L^{-1}\{\frac{1}{(s+1)^2}\}=e^{-t}t\\v_i(t) = \delta(t)\\ \therefore v_o(t) = g(t)\ast v_i(t)=e^{-t}t\ast \delta(t)$$
So the convolution integral will be:
$$\int_{0}^{t}g(t-\tau)v_i(\tau)d\tau = \int_{0}^{t}e^{-(t-\tau)}(t-\tau)\delta(\tau)d\tau$$
This is where I get stuck as I can't solve this integral. Firstly I'm not 100% sure about the integral of \$\delta(\tau)\$, but I believe it equals 1? Is this correct?
I'm also not sure if I should be including that second \$(t-\tau)\$ bracket, I thought maybe the integral should be \$\int_{0}^{t}e^{-(t-\tau)}\delta(\tau)d\tau\$. This seems much easier to solve.
Can anyone point me in the right direction/correct me if I've made an error?


texts: I'm starting an Arduino project where I plan to turn on some LEDs using analog pins on the arduino. My plan is to use a transistor to turn on the LEDs. I know I can turn on low power ones directly, but I want to use brighter ones (perhaps a 12v LED). I dug up some transistors I had bought years ago from Alltronics, but I have not had luck identifying them. I'm familiar with resistor color codes but haven't found anything standard like that for transistors. Thanks for any help.


texts: How to see benefit effect of BJT current mirror in the load?

texts:
I don't arrive to see benefit effect of BJT current mirror in the load.
I would get twice ic (ic1+ic2 = 3mA) with the same sources (both with phasing =0). But here I(RL) = -29µA.

link
Origin diagram :

The VB(Q3)-REF1 is 0V :

The VB(Q3)-REF1 is 52mV with V1 180° phasing :

Replacing with RC


texts: Transistors, explanation of current gain

texts:
At this first picture i have a NPN transistor with Beta=75, 2N222A transistor, both Inputs are 5V. it was very simple to calculate the current that will flow through the LED. as it is simply I1 * Beta = I2, and I3 = I1+I2.

But if i replace it with a resistor of value 5k for example the I1*B = I2 relationship is not valid anymore.

My question is, I1*Beta = Maximum I2 current, would that be a better explanation of a relationship or i don't understand something ?


texts: Is a 90V output spike normal for a 45V buck boost converter?

texts:
The LT5176 buck boost converter outputs a short 90-91 volt spike at at the output in the 2nd second after startup, applying power to Vin.
Schematic

More details at Why does this buck boost with dual MOSFETs fails output at certain input voltages at light load? (board is populated with single MOSFETs: 4 pieces)
Measurement setup

100 kHz LMG95 (Zes-Zimmer precision power meter)
Input resistance: 1MOhm, 20pF
50 cm cable
clip probe tip

Regression

this overvoltage spike happens at all input voltages (33-55V)
this overvoltage spike happens at different loads (1ma, 10ma, 100ma, 1000ma)
also happens unloaded

Questions
Is it normal to measure such a voltage spike at the output? In case this is expected behaviour, why? Which design/IC would not suffer from a short overvoltage spike on startup?


texts: How does an IR LED turn on and how can I test to see if its not broken?

texts:
I'm an electronics beginner.

Does an IR LED turn on like how regular LEDs turn on or does it only turn on when you've assigned a specific code for it to transmit?

The reason why I ask:

I bought some IR LEDs (940NM). I'm just trying to get them to turn on and view them with my phone camera. Do I have to use an IR sensor or can i just apply some sort of voltage and it turns on?

What is the easiest way of doing this? I'm using an Arduino.

Here is a link of the LED i bought:

https://www.amazon.ca/Gikfun-Infrared-Launch-Emission-Arduino/dp/B0154HHAKG/ref=sr_1_1_sspa?ie=UTF8&qid=1544379560&sr=8-1-spons&keywords=gikfun+ir+led&psc=1


texts:
I would like to determine the position of a motor based on its radio emissions, I do not have access to said motor but I am trying to reverse engineer it.

Here is what I know about it :

It has X amount of positions (X being finite and somewhere around 50).
It is a stepper motor.
It is not very large or powerful, but it is not a tiny RC motor.
The whole structure is not encased in metal, which is good for my case.

Sorry I cannot provide more information, but with this, is it possible to determine through enough experimentation, the position of the motor based on the EMI it generates ?

Suppose it rotates at a constant speed, then depending on the length of the emission (t x 1, t x 5, t x 24,...) I should be able to determine where it landed right ?

I know Stack Exchange is not for theoretical questions but I am going to invest in an SDR for this and I would like to first know if it is feasible.


texts: Making own transformer from 0.5mm 1020 steel sheet?

texts:
I need a high power transformer with 240VAC primary at 10-16A and secondary of 6VAC 350-400A. I calculated that I would need a transformer core with cross sectional area of about 45cm2 to able to use about 1:1 windings per voltage.

My question is, how well will 0.5mm thick 1020 steel with 10-50micron zinc plating compete as tranformer core? I have two choices: take apart a bunch of microwave transformers or make one myself, and getting silicon steel sheets is impossible at any sensible price for me.

For getting 45cm2 CSA im planning on making a transformer EI type with core size 95x50mm, as using 100 pcs stack of 0.5mm plates.


texts:
On our summer scouts camp, I need to power a tablet (it simulates the computer from The Lost, and the children must activate it every 108 minutes). It requires 4.3 - 5.3 V and about 650 mA. I need to power it for 6 days, but the problem is, there is no electric outlet or something nearby. So basically we must make the electricity or use batteries. And for it to be harder, the financial limit for this project is 18 EUR (20 USD), which isn't a lot obviously. I would also like to note that we have a 1000W electric generator, but it can run for only about 2-3 hours/day.

So I came up with two solutions how to power the tablet:

Solution 1: Use batteries

I can buy and use a bunch of batteries. Problems:

Capacity - I need 15,6 Ah/day, which is a lot for batteries and
this financial limit.
Charging - I can use the electric generator, but can I charge a battery in 2 hours?

Solution 2: Generate electricity ad-hoc

I have a dynamo from old Czech car, which (according to the internet) can output 12V 55A (is it possible?) and maybe connect it to a stationary bike, and children will have to use the bike to charge 18650 lithium batteries, which will then power the tablet.

I like the second option more. What do you think? Do you have more solutions? Any advice appreciated. Or feel free to ask for more details. Is it even possible?

Notes:

My level of knowledge of electronics is low-medium, but I don't have much practical experience.
I made a practical test. 4 AA NiMH 2300 mAh batteries charged the tablet for 8 hours. Those numbers don't make sense, theoretically it should have been 15 hours!


texts: Control Speed of 3 phase induction motor

texts:
Let me start by saying pardon my ignorance on the topic.  I have knowledge in electrical wiring but not so much in the technical engineering aspects of motors and micro-controllers.

I just purchased a Lincoln conveyor oven for a startup I'm working on.  (They're are no electronics on the motor). The oven has a conveyor that has a slow and fast speed.  I want to put a speed control on the motor to achieve a conveyor speed in between the two factory speeds.  Basically set the motor to high and then have a separate control to slow down the motor (Not looking to double or triple motor speed).

This is the specs on the motor:

6 Wire harness to motor

Gry | Red | Blk
------------------------------
Brn | Wht | Wht

I've been digging around the internet but I wan't to make sure I'm doing this in the way that will ensure the full life of the equipment.  I know voltage control is not a good method with a 3 phase motor.  Any suggestion on how I could achieve the preferable with some type of rotary pot switch for granular control over the speed and no electronics.

Any help is greatly appreciated.


texts:
This is probably a stupid question, but please bear with me.
I'm making a boost inductor for PFC and I just wanted to make sure I'm calculating for the voltage correctly. Is the equation:

\$N =  \frac{V\times10^8}{4fA_eB}
\$

Or does that only apply to transformer windings?

If it does apply to inductors, should \$ V =V_{boost}\$ or rectified \$ V_{in}\$?


texts: Ohmmeters don't appear to make LEDs conduct which gives overestimates in the resistance measured (tested with a R1//(R2+LED) parallel circuit). So what is the voltage they apply to the circuit, assuming it is conventional? I assume it depends on the range selected (I seriously doubt it will apply 1V to a mOhm branch), but to what extent?


texts: How can I prevent lead free solder from ruining my soldering iron tip? Can I re-tin my tips?

texts:
I have been using a Weller WLC 100 for about 10 years, and I have always used this conical tip from Apex Tool Group: https://www.mouser.com/ProductDetail/apex-tool-group/st-7/?qs=fKX4t1ubQE95bthTEmHMHA%3D%3D&countrycode=US&currencycode=USD

Recently I have been using tin/silver/copper (Sn96.5Ag3Cu0.5) lead free solder -- I've been using this solder: https://www.digikey.com/en/products/detail/multicore/796065/2498924

I am able to use a new tip and this solder for about 3 - 4 months before the tips become dull and grey and no longer have solder cling to them. After that, they will melt the solder, but the solder will ball up and just fall off.
From reading other posts here, it appears that perhaps I am cleaning the tip too abrasively and removing the iron plating. For instance, my soldering routine is:

Turn on iron/let solder previously left on tip become molten
Wipe off molten solder on damp sponge
Do soldering
When tip appears to be dirty, wipe it off on a sponge
When tip appears very dirty, pull it through my copper scouring ball
When soldering done, cover tip in solder
Turn off iron

I think on step #5 above, I may be damaging the tip. On the other hand, when I use leaded solder I don't have any problems, and I have use the copper scour ball for a long time with no issue.
I have also written to Weller and they could not make any suggestion about why my tips were ruined.
Attached is an image of my soldering station, which can only control temperature by potentiometer (I keep knob just below 5 as that appears to melt solder easily, and a bit below takes solder too long to melt). Also attached is an image of two "dead" tips.

Can anyone suggest why my tips become dull when I use this lead-free solder, and why solder will not cover them any more?
Is it possible to re-tin my tips? If so, how?


texts:
I would like to transform 5V 500mA (from USB power) into 12V with a few cheap components.

Is this possible with the help of some generic parts (and not with the help of some expensive transformer, etc.)?

Also, how many milliamps would this provide?


texts: Supplying power to a 12V motor with 5V and 2A adapter

texts:
A very elementary power supply question but i couldn’t find the answer with Google, so I would appreciate a response.

I’m using a 12V, 340W DC brushed motor for a personal project. While the motor is relatively powerful, I don’t need the full capacity of the motor, but I do not want to buy a new motor as I already have this lying around.

For the purpose of my project I only need it to operate it at 5V (required RPM from the data sheet). I have a 12V, max 3A, cont. 2A, 30W driver lying around too. I was wondering if I used a 5V, 2A power adapter (that I already have), will it only supply 2A even if the motor tries to draw more than that and will this damage the adapter by any chance?

I really don’t want to buy any additional parts and I have all these components lying around. If I supply 5V to the driver, even if the motor tries to draw more than 2A, will the power adapter limit it, or will it supply more and damage the adapter and driver? Is this okay to do or will I damage anything?

I will be using PWM to slow down the motor and average it out to around 3V or less. The motor draws around 2.4A at 3V when I checked with a bench top PSU and DMM. I don’t want to supply more than 2A and I don’t mind it losing a bit of torque. It only spins a threaded rod and the load is pretty much static once it starts. Do I have to take any additional methods to be safe or will the power adapter limit the current supplied?


texts:
Sounds a daft question but I got thinking about another question and this cropped-up.

Background - In a conductor electrons move seemingly in a random fashion and more so when the conductor is warmer. When a voltage is applied there is a general tendency for electrons at one end of the conductor to start pushing electrons out at the other end i.e. there is a current flow.

But, as we are informed at school, the atom comprises mainly of empty space and, electrons appear to be a tiny object in that empty space so (with faint recollection of Heisenberg's uncertainty principle) and (ignoring anything I have previously learnt about how a BJT works), my question is this....

Question - If the plates of a capacitor were close enough would DC current flow?


texts: Influence of incident signal on antenna S-parameters

texts:
I'm interested in determining the phase of an incoming signal using a 1-port Vector Network Analyzer (VNA). The antenna would be receiving a signal while connected to the VNA. I know that the S11 parameter determined by the VNA will have an amplitude and phase (from), but I would like to know if the incident signal will have any effect on the phase of that S11 parameter, or if it is solely a product of the antenna properties.

Thanks in advance.


texts:
I recently built this circuit, but didn't understand why these resistors connect voltage-out to ground. My logic would say the path would either go like...

or


texts: I have a TIG welder that quit working on me the other day, when I took  it apart I found a blown resistor. I had just turned it on for the day, did about a 1 inch weld and when I stopped I heard a pop and saw a flash from the corner of my eyes. The said resistor is 62K ohms +/- 5%. i have a resistor that is 68k ohms +/- 5%. would it be OK to use that or not? It is physically a little smaller than the one that popped though, so I am not sure if that changes anything or not. Help please.


texts: Increase the pulling force of a solenoid with a permanent magnet

texts:
I have a number of solenoids I would like to use in a project. The problem is that they're not quite powerful enough so I've been trying to come up with ways to increase the their pulling force without increasing the voltage.

I was thinking that I could add a permanent magnet to the bottom of the plunger so in addition to the the core being pulled into the coil the magnet would be repulsed by the coil and add to the force the plunger has.

Would this actually work? And if so what strength of magnet should I use? Should the magnet sit on the outside of the coil or just inside?


texts: What kind of band stop circuitry is this?

texts:
I have found this band stop circuitry:

It gives this transmission function:

It has a band stop behavior at 230Hz. The last opamp is a simple high amplifying lowpass. The first opamp feedback gives a lead compensator behavior. But especially the feedback over C9, R5, C11, R6, C12 is very unclear to me.
Have you ever seen this topology? I have searched the web for various kinds of band stops, but I have not found anything similar.
Does this circuit look familiar to you? If so, how do I calculate it? I mean I can use LTSpice to adjust the values by trial and error to my needs, but I want to understand what I am doing :)
Thanks in advance for your help!
Update
The second Opamp feedback loop is obviously a simple lowpass filter. Here I want to add some details to the first opamp feedback loops:
Taking only one feedback loop at the first opamp, like this

We get a typical lead compensator (https://ctms.engin.umich.edu/CTMS/index.php?aux=Extras_Leadlag) behavior in the transmission:

If we now add the second feedback loop, like this

We get this notch, high pass like behavior:

Whereas, this is not a real highpass. For a highpass for low frequencies, the amplitude should drop to -infinity dB. Here it stays at 0 dB. Strange
Can someone help me to calculate the transfer function of this circuitry? Or give me a good tutorial to calculate the transfer function for such kind of circuits?
Thank you very much
Question of Ady aka:
What happens when you delete resistor R5:
A highpass filter like behavior


texts: How to short certain pins on a 7x9 array

texts:
I’m planning to control an 80s electric typewriter via a Raspberry Pi. I want to emulate the keyboard matrix by shorting one of seven 5V pins to another one of nine that feed into a microcontroller. Eg, shorting pin 0 and 16 prints out a full stop; 5 and 12 print ‘w’ etc.

How can I best control this?


texts: Why would a computer power supply output 5.2V on the 5V rail?

texts:
I am using a computer PSU as a lab power supply. In the current setup, I am drawing about 1ma on the 5VDC rail. And still the multimeter indicates 5.18VDC. I can upload a scope show if needed, but this seems too large of an error for a multimeter.
Is this normal? Why would a regulated power supply output a very incorrect voltage value?


texts: What is the purpose of the capacitors between 5V and ground on the power pins of the op-amps?


texts: Calculating Resistor Wattage for Voltage Divider?

texts:
Background:

I am monitoring the voltage of a 4 cell LiPo battery (max voltage 16.8V, maximum advertised current output = 60A) using a sensor with a maximum input of 3.2V.

I am using a 2-resistor voltage divider with R1 = 22KΩ and R2 = 4.7KΩ.  This maps the maximum battery voltage to approximately 2.95V.

Vout = (R2 / (R1 + R2)) * Vin = (4.7KΩ / 26.7KΩ) * 16.8V = 2.95V

Question:

Once I have these values, how do I calculate the required wattage of the resistors R1 and R2?

As a practical matter I see many people using 1/4 watt resistors, but I'm interested in understanding the calculation myself.


texts:
When finding parameters for electromagnetic waves and transmission lines, we can find various characteristics including attenuation and characteristic impedance.
\$\alpha\$ is attenuation constant.

1-With \$\alpha\$ as an attenuation constant for propagation we can determine:

\$ \displaystyle \alpha = \frac{1}{R_0}(R+G|Z_0|^2)\$

2-We can also determine the characteristic impedance.after that we can determine
\$\alpha\$ for distortionless lines or low-loss lines from these equations:

\$ \displaystyle Z_0= \sqrt{\frac{R+j\omega L}{G+j\omega C}} = R_0 + jX_0 \$

\$ \displaystyle\ \gamma = \sqrt{(R+jwL)(G+j\omega C)}\$

How can we prove that the attenuation constant, \$\alpha\$ in first equation, is equal to the  \$\alpha\$ that we can determine from second equations??


texts:
I need to electrically "sense" when a brick is thrown through a vertically-oriented pane of breakaway glass, breaking it.

My first thought was to paint a thin strip of clear conductive ink/paint/gel across the back of the glass, then treat it as a normally-closed switch to trigger the rest of the circuitry.

I need this to be reliable and reproducible.  Are there any reliability drawbacks to this solution, and if so, can you suggest something better?  I'd like the solution to be as passive as possible at the point of the glass (that is, I don't want to do something like mount a tiny digital accelerometer unit on the glass, as this would require much more effort than I believe is necessary).


texts: Best way to AND all connected inputs to one output

texts:
I have an CNC router with 7 x SN04-NPN sensors connected in parallel with one control board input. The problem is obvious, i got random false endstop triggers due leaking of SN04. I know i should have one sensor per input but inputs are lacking and i can't connect them all individual, i don't need the individual control/info anyway. I come with an idea to overcome the problem but still connect them all in parallel by using optocouplers, schemantic below:

For simplicity i only have draw 3 pairs but there will be 7 of them.
Is my drawing ok? Or there is any IC i can use to AND all inputs into one output?
PS: Control board have optoisolated inputs, VCC is 24V
Sensors use same power supply as control board (24V), power is shared


texts: How to solve AC fan induction motor jammed possibly due to magnetic locking/cogging?

texts:
I have a single phase ac fan motor (from a regular household stand fan) which operates on 240V 50Hz power source. It has a start capacitor.
The problem I am facing is the motor is not spinning or jammed. If I spin the motor by hand, the motor spin freely (not yet turned on), meaning that it is not mechanically jammed (bearings etc), but rather possibly electrically. When I let the motor spins fast by hand, then I switched on the power, the motor immediately stopped. It looks like the magnetic field is causing the rotor to be attracted to stator and get locked, preventing rotation. This is not suppose to happen. The magnetic field is supposed to be rotating. I have removed the capacitor and try to start by hand with power switched on, but still jammed.
What caused this phenomenon to occur? How to solve it?


texts: How can a magnetic circuit with an airgap have a higher e.m.f in the secondary coil than the same circuit without the air gap?

texts:
I have a magnetic circuit with the same configuration as in the image, the primary coil has 203 turns and the secondary has 406 turns, how do I get a higher eletromotive force when there is an air gap across the magnetic circuit?
If the reluctance is increased and the permeability is reduced shouldn't the emf also be less than without the air gap?


texts:
I have a JR1738RX-12V remote control system in my child 4WD car. We noticed that it's too slow/weak so we decided to put 4xRS-570 motors to give it more juice but they are 65W compared 45W from original ones.
Car is barely moving now and the culprit in my (newbie) option are the mosfets inside of the unit. Two of them are fnk3070pa (http://www.fnk-tech.com/comp/file/download.do?id=375) and can generate max 50W, while other two are http://www.chinesechip.com/chipFile/2015-07/100N03-18026-0.pdf and they can go up to 180W. My idea is to just try to replace these with the ones that can produce more power like this one https://docs.rs-online.com/f35b/0900766b812cf73f.pdf
Is this a good enough replacement? Am I missing something big?
Battery used:
https://greencell.global/en/other/1108-green-cell-battery-agm-12v-20ah.html
--- EDIT ---
Motors now: RS570 65W 40k rpm, before RS390 45W 15k rpm (https://www.dhgate.com/product/children-s-electric-car-dc-motor-kid-s-ride/496410887.html#redirect_detail=WAP2PC) cannot find more details about the engines themselves.
Even tho I messed up and taken the "high speed" motors which in reality give less torque which I actually wanted they should still be improvement from current setup.
Currently car (https://leantoys.com/product-eng-2824-Jeep-XJL-588-Electric-Ride-On-The-Car-White.html) with 4 of these barely starts moving then shuts down after 1 meter of driving. After cca 15sec you can hear the relay that turns it back on. We suspect it's the fuse that's protecting the plus wire on the battery.
Original battery on the car was replaced with this one. Original one was 10Ah max 2Amps while this one is 20Ah max 6Amps.


texts:
Some say Ground is just a reference point for measuring voltages, some say ground is a safety device for appliances and some say ground is just a bare piece of metal regardless if its even connected to the actual earth (as in dirt)

I have multiple questions about ground:

This one is about appliances and is taken from howstuffworks, "Let's say that a hot wire comes loose inside an ungrounded metal case,the metal case then becomes hot so anyone that would touch the case would be fatally shocked. By having a ground wire attached to the metal case, electricity from the hot case will flow straight to ground and will trip the breaker"

Can you not be safe just by touching a hot wire alone, granted you don't touch neutral?
What if you touch a hot wire then, stick you other finger in the dirt (soil)?
So its telling me that the current flow from a hot wire, to the grounding wire-> (connect to some rocks and dirt/poop) is so high, it can trip a breaker?
In a DC situation there is no hot wire, and (correct me if i'm wrong) but if I have a 350v Capacitor fully charged, there is absolutely no way for me to get electrocuted unless I touch both terminals. Why doesn't AC behave this way?

And how about this:
people say step 4 is to ground that wire, How? The car is insulated from the earth All I see is an open circuit.

Please help, Thanks!


texts: what does bandwidth in a channel really mean?

texts:
I'm new to EE, just a question on bandwidth in a channel. The book I'm reading describe the definition of bandwidth as

  The term bandwidth can refer to the number of bits per second that a channel, a link, or even a network can transmit.

Below is a picture to illustrate:

Below are my questions:

Since bandwidth refer to the number of bits per second that a channel can transmit. So in the picture, the channel/link can move/transmit 5 bits in one second(inside the channel/link), shouldn't the bandwidth be 5bps?
If "transmit" means how many bits the receiver receives in one second, then it make senses that the bandwidth is 1bps, but it also raises another question, the bandwidth is 0bps for the receiver in the first five seconds(since the first bit hasn't reached the receiver's end), after 5 secs, the bandwidth is 1bps. So strictly speaking, the receivers has no bandwidth in the first 5 secs, but since we are talking bandwidth in a broad picture, the initial no bandwidth state can be ignored, is my understanding correct?


texts:
I'm building a sort of homemade tablet out of a 10" touchscreen (designed for RPi-like devices) and an Asus TinkerBoard SBC. The SBC takes the standard 5V 2.5A power source, but the screen requires 12V 1.5A (it can power the SBC from a built-in driver board). I've come to the part where I need to design the battery, but I'm stuck wondering how to get 12V out of a battery that will fit in a tablet.

Do normal 10" tablets have similar 12V power requirements for their screens? That seems unlikely, given that I can't figure out how a 4C LiPo could fit and still provide hours of use. But I'm not sure how else to approach the power problem.


texts: Input common mode voltage of AC coupled differential pair

texts:
I was reading OnSemi's AN8173 app note and couldn't understand why input common mode voltage of AC coupled line is equal to VTERM.
My thought was each input of the receiver, D and \D, will swing between VTERM and VTERM-400mV, thus the common mode would be VTERM-200mV. Indeed, when I simulated the circuit with LTSpice, input of CML receiver, D and \D, initially swing between VTERM and VTERM-400mV and input common mode voltage is VTERM-200mV. However the common mode starts to drift to final value of VTERM, D and \D swinging between VTERM+200mV and VTERM-200mV.
Why is that so?
Thank you.


texts: Is this logic correct to determine whether this extension is safe to use with my induction cooktop?

texts:
I'm having a hard time understand ampere, power and voltage. I'm not a science student, but want to understand this basic thing.

The max power (I don't know if power is correct to say or not, but max 1200 W is written on it. So I guess this power) of my induction cooktop is 1200 W.

I have a Philips extension which have following written on its back:

6A 250V~ 1500W (Max).

So I assume this means: P = VI So 1500 W = 250V x 6A

It makes sense.

Now, Indian electricity comes at 220 V.

So in that case, my induction cooktop will have the following power relation, when I'm using it at its max power (i.e., 1200 W):

1200 W =  220 V x I
I = 1200/220
I = 5.4 approx.

So let's say 5.4 A (ampere) (AM I CORRECT TO CONCLUDE THIS?)

Now, what I've written above is correct, I will assume this basic concept and meanings of voltage, ampere and power are somewhat clear to me.

Now, main question: According to extension specifications, I can use it for a load (is it called load?) of 1500 W. But my load (induction cooktop) is 300 W less, so technically there won't be any problem?

I've seen my friends who use extensions for coolers and they burst/damaged. I don't want that experience.


texts:
I was searching today for a new 24V transformer, and I found that some of them have a "fuse" symbol on their label, and I was wondering what this fuse symbol means?

Does the fuse symbol on a transformer (toroidal or not) mean that the fuse is integrated in the transformer's winding?

Or does the "fuse" symbol try to suggest what kind of fuse has to be used with that transformer?

Here you can find an image with the transformer label:

(Image source: RS Components - 2 Output Toroidal Transformer, 120VA, 2 x 25V ac)


texts: dB SPL Calculation is not making sense- values are seemingly too high

texts: I am using an electret with a sensitivity of -38.44 dBV to make sound measurements at a distance of 1m. I decided to add an amplification circuit with a gain of 125. So in the end to convert to SPL, I first used my sensitivity which is 11.967mV/Pa (in SI units) to convert the measured voltage to pressure. P=V/S, where V is the voltage before amplification (i.e. output value divide by 125) and S is sensitivity. In the final step, I then convert this to dB SPL using a reference pressure of 20e-6 Pa and the formula dB SPL=20log(Pa_rms/Pref). However, with this formula, I get values ranging around 100 dB, I believe that I am supposed to be getting values around half that, what I am doing wrong? any help would be appreciated.


texts: Initial values of the dsPIC30F registers under the ICD3 debugger

texts:
Ok, I created a simple project that consists of just a few assembler files and it is not using any libraries. What is it doing is not important here. After that I have put breakpoint in ICD3 right on the reset entry point and after booting I see the following:

Controls stays on the address 3c6. If I browse to the beginning of the program memory, I see the following:

This confirms that 3c6 is really the reset entry point. At the same time I see on the registers:

The W15 is 0x800, as it is written in the documentation, but SPLIM is not zero as it should be according to the docs. I would guess that ICD3 has set it. Is that right? Even more, ICD3 shows the first 80 bytes of the RAM  as reserved:

My guess is that I should not use the stack setup that I inherited after reset (because it points right into the reserved area and seems co cover it all) but replace it with my own one.

So my questions:

Will ICD3 work fine on any stack? I cannot change W15 and SPLIM in one step, so there is a chance that stack will be inconsitent for a short while. Is this simply a small risk that I should take or there is something more there behind?
What other resources are used by ICD3?
What should I do/not do to cooperate nicely with ICD3?
Is it right that in the release version of the build there will be no 80 bytes reserved area?

p.s. Here is the build log:

It suggests that this 80 bytes area in the RAM are not a single piece of data. But SPLIM covers them all... Does anybody has any clue what this all might mean?


texts:
I have a 393B04 PCB specs and a drawing denoting a "10-32 UNF 2A Coaxial Electrical Connector".

This is the same than a SMC Connector?. Can i purchase an standard SMC connector which supposedly fits the 10-32 UNF 2A thread?, or i must purchase 10-32 coaxial connectors?

Edit:

The spec only focus on the thread, not on the electrical connector. I guess this is for commercial purposes, for selling built expensive cable,
As definitions: jack: thread outside, plug: thread inside, male: a pin contact, female: a covering contact,
As indicated, clearly this is not a regular SMC connector, which is a male jack,
Unless i should seek for a SMC reversed polarity (this is, a female jack), which i dont think exist, or perhaps as rare as a 10-32,
An SMA has a 1/4-36 thread, An SSMA has a 10-36 thread, and the SMB no thread at all :),
CDInt sells both 10-32 to SMA and 10-32 to SMC cables.....!,
The device shows a female jack.

So i should finally purchase a 10-32?

Thanks in advance.


texts: "Modulation" effect of collector current on DC current gain

texts:
I've found that it is typical for a BJT NPN transistor to exhibit current gain \$h_{FE}\$ which varies up and down as \$I_C\$ increases. The reason is probably trivial, but for some reason intuition tells me that \$h_{FE}\$ should decrease monotonically with \$I_C\$.

This image is taken from a 2N3904 datasheet.


texts:
I just finished soldering a QFN package to a breakout board, and was about to go at it with my multimeter in continuity testing mode to check for bridges, when it occurred to me that some semiconductors can be damaged by negative voltages. I presume that continuity testing works by applying a small voltage, in line with a large resistor, and checking for a voltage drop... could that small voltage damage the IC? I only have the one multimeter so I can't exactly check what voltage it feeds in, but I assume it's large enough to get through your average diode's forward drop.

I'm probably just being paranoid, but it would be nice to get a categorical answer to put my mind at ease. Is the voltage applied by a run-of-the-mill DMM in continuity mode ever enough to risk damaging an unpowered digital IC?


texts: Input offset voltage for microphone circuit

texts: Does anyone know what's the input offset voltage (oscillated 2.5V) to the op-amp in the circuit for? From my understanding, the input offset voltage needs to be extremely small so that output DC offset can be reduced. But for this circuit, the input offset voltage is big, therefore, it is making the output offset voltage high. Hope someone can help me!


texts: In jfet voltage divider bias how can Vgs be negative with out knowing the resistor values?

texts: With out referring to particular values of the resistors, my textbook states that Vgs in below circuit is negative. How is this possible? If I increase R2, it increases Vgs, right?


texts: Schrödinger and electrical measurement issue

texts:
During the 19's, Schrödinger state that it is impossible to make a measurement without disturbing a system. To illustrate his statement, he made the famous experiment of the cat and the box. Poor cat btw..

This is also true in electronic nowadays. A multimeter is use in parallel of a load for a voltage measurement. This "add on" will change the equivalent resistor value and then change the "true" voltage value. This is also true for current or other kind of measurement.

How is it possible to compensate this lack of precision? I don't need to be that accurate, but I ask that question by pure curiosity


texts: Amplitude modulator for a sine wave generator

texts: I have a home made, mostly using the design in a magazine article, radio frequency signal generator, and I would like to be able to modulate (AM) the sine wave output, which is up to 8 MHz, with an audio sine wave. Is there a simple design for a module that I can insert in the output lead to accomplish this?


texts: Which one is more accurate: Digital oscilloscope or Analog oscilloscope?

texts: I know it is some sort of wide question, but nowday I usually only see digital oscilloscopes around. I want to know if their digital nature will affect the accuracy of measurements? (Something like digitization error in sampling signals). Or asking other way are they any specific applications which accurate measurement requires using only analog ones in current time? I guess flexibility of digital oscilloscope grows trend to using this type of oscilloscopes, but I will be happy if you correct me.


texts: What is the purpose of the ic pin in a nixie tube? For example, the Z573M? Knowing how to drive one, this pin seems to have no purpose.


texts: PIC programmer, need to replace few components

texts:
I am building a PIC micro-controller programmer named Brenner8: http://www.sprut.de/electronic/pic/projekte/brenner8/

Although, it needs a BF959 transistor for (Q8), and BAT43 diodes for (D1,D2,D4) As this diagram:

I don't have these components in my country. All I have here: BF759, BF859, BF869, BF871, BF872, BF891, and BF981 for transistor.

Any suggestions?


texts: Are polymer tantalum capacitors safe for use in new designs?

texts:
I want to expand this post to cover polymer tantalum caps.  In my application I have an older switching regulator that outputs 24V and needs large output capacitance (220uf), so ceramic or polymer aluminum caps are not an option.  I have to remove the MnO2 tantalum caps and I'm thinking of using polymer tantalum caps.
Kemet's papers seem to indicate that these caps would be a better alternative to the regular tantalum caps.  They don't have the same failure rates and do not present the ignition failure.  Has anybody seen any other issues with this type of caps?


texts: Interfacing to a differential signal with isolation

texts:
For diagnostics I need to monitor a differential data signal similar to RS485. For safety the signal need to be fully isolated. The thought that I had was to use a pair of opto isolators across the signal. In this fashion one opto will be active in one direction and the other opto will be active when the signal is in reverse. Then a micro will convert the stream to something legible. Assuming the opto won't load the signal and the optos are fast enough to react, will the setup work or am i missing something?

simulate this circuit – Schematic created using CircuitLab