texts: Protection for transistor driving a coil

texts:
I recently purchased a few electromagnets. I want to drive these with transistors, but I want to build in protection, as these don't have any available specs re: max operating temp, duty cycle, etc. (It was all I could really find for a diy project)

Assuming a 1 amp NPN, standard driving circuit driving a coil with a flyback protection diode, how would I guard against possible fire if the coil fails as a short circuit? (Ie, I would assume that if the coil suddenly becomes a short circuit, the transistor would conduct too much current from C to E and would start smoking, and possibly lead to fire)

(LED to indicate fault condition would be nice also)

How could I, in addition, detect if the coil fails as an open circuit? (maybe just an LED to indicate this failure mode)


texts: What is the procedure to use ISCAS-85 benchmark Circuits for testing?

texts:
Could you please explain the detailed procedure about using ISCAS-85 benchmark Circuits for testing available at the below link http://web.eecs.umich.edu/~jhayes/iscas.restore/

How do we start, could you please explain in detail the steps how to use it


texts: Altium designer, The designator does not update when using update from libraries

texts:
I am fairly new to this forum and to altium designer. I am having a problem updating a transistor designator from Q? to T?. When I use the update from library in the tools menu, all the parameters update except the designator. Could some one assist me with this problem, please? I'vd looked in all the forums. But I couldn't find anyone who had the same problem as me.

Any suggestions would be appreciated.


texts: In hybrid systems, we can have DSPs, FPGAs, General purpose processors, etc on the same system operating together on the same application. How are the tasks distributed among them, and which unit manages this?


texts: Designing a simple energy-efficient communication protocol?

texts:
What is the required background knowledge in order to be able to understand and work on the design of a communication protocol which has to be robust, simple and capable of coping with short contact times between nodes?

The signal has to be simply BPSK-modulated and the communication should take place in TDMA fashion.

Additionally, it has to be implemented in C++. Is it hard to implement such protocols in C++.

Can you show me some pointers as introduction that may be useful for the above-mentioned task.


texts: Why do we ground the common probe on a 3 probe liquid level sensor?

texts:
I have a liquid level sensor with 3 probes, one us common,  the other is for low level and the third is for high level. On the liquid level control relay diagram,  I've noticed that the common probe is grounded. Why is this so?

Any information would really be appreciated.


texts: Connecting linear potentiometer to arduino

texts: Please help I am still a newbie. I would like to know how I can go about connecting a liner potentiometer to arduino .


texts: High precision distance between two GPS devices (may be GNSS-SDR)

texts:
I wish to get to high precision distance between 2 not moving points.

e.g. 1 cm accuracy for distance 1 km

I think if I will catch same GPS signal in two points then distance between resulting coordinates would be highly precise even if coordinates would not be precise.

Not sure how to catch same signal frame on both devices.

May be GNSS-SDR?

I remember there was project syncing 2 ublox GPS receivers but can't find either.

Any idea how to measure distance precisely ?


texts: How can I account for package trace length in KiCAD?

texts:
The documentation I got for the MCU provides "package trace length" (in micrometers) as well as "package trace delay" (in picoseconds). For example like this - 6535.15 um package trace length for M_DQ[18] trace with delay 44.47 ps. The MCU itself has rather a high number of high speed interfaces all of which suppose to be used according to the specifications (multiple SERDES lines, GbE, DDR3 etc).

Given this information, how can I easily account for it in my design if I am using KiCAD?

I know, I could use basic math and just keep track of each single trace on paper and add package length to ensure differential pairs are of matching length (in-pair and across pairs), but that seems like a headache. Is there any better option?


texts: Why do my outputs look exactly the same for the Allegro 3901?

texts:
I am trying to capture results shown in Figure 8 of Allegro 3901 data sheet .

My circuit looks like this:

The channels above coresspond to the oscilloscope screen captures below:

In the image above channel 3 is a PWM with Frequency = 467Hz and Duty cycle of 64%.
As you can see channels 1 and 2 are both low (but it looks nothing like Figure 8's Ireg+ and Ireg-).

In the image above channel 3 is low and channel 4 has a PWM with the same frequency and Duty Cycle (but again channels 1 and 2 do not look like Figure 8's Ireg + and Ireg - output).

Have I wired my circuit correctly?

I also noticed Figure 8 output is measured in Amps but I'm not sure how to get my oscope to measure in Amps.

I am using a Tektronix TDS 3014B.


texts: What can be the reason for the extra connections from this Wheatstone bridge to the amplifier?

texts:
This industrial amplifier is used for force transducers and here is the wiring diagram for the 6 wire transducers:
¨

And below is the terminals for the amplifier:

It seems 1 and 4 terminals are the output of the Wheatstone bridge to be amplified.

I'm kind of confused why there is two connection for the excitation voltage terminals of the bridge here. As you see 3 and 3' or 4 and 4' both are same points which are separately brought to the amplifier terminals. What could be the reason for 3' and 4'?


texts: Rigol DS2072A with compensated PVP2350 probes has overshoot at 100 mV/div. Bad?

texts:
With my new DS2072A I compensated the PVP2350 probes according to the instructions at 50 mV/div as chosen by the "Auto" button. Then, when I switch to 100 mV/div there's some overshoot with both probes on both channels.

It's more obivous at 2 ms/div:

Is that bad?
Is there anything I can do to fix it?
Is it a fault of the scope or the probes?
Could it be a factory reject smuggled out of the factory and sold by crooks?

I bought it from taobao.com  via superbuy.com (a taobao agent who orders from taobao who only ship to China and forwarded it to Austria), so I'm not sure what my warranty options are.

I unlocked the scope to 300 MHz and ran self calibration.
Software version: 00.03.06
Hardware version: 2.3


texts:
I have 8 cells (samsung icr18650-26f), and I want to build a battery pack 4s 14.8v (4x3.7v) to power an LCD Controller Board that requires a 12v4amp input

I have an idea of the design of this battery pack, but I'm not sure

I would also like to know if a 4s2p battery pack could do this?

Or this

I'm thinking of using this bms
https://es.aliexpress.com/item/4-strings-of-lithium-battery-protection-board-30A-high-current-four-strings-without-activation-of-automatic/32764959684.html
or this https://es.aliexpress.com/store/product/4A-5A-PCB-BMS-Protection-Board-for-4-Packs-18650-Li-ion-lithium-Battery-Cell-4S/3100001_32827571864.html


texts: Running electro-optic modulators in reverse

texts:
An lithium niobate electro-optic modulator allows one to modulate the amplitude (or phase) of an optical signal by applying a bias. But what voltage would I measure across the bias input if I applied a premodulated optical signal to the device? In other words, can they be run in reverse, as a way to probe the optical signal incident on them?

I would go get one and find out, but the relevant lab is locked until Monday, and I'm an impatient man.


texts: Find cause of diode destruction from destroyed diode itself

texts:
Is it possible to find the cause of power diode destruction, ie. if it was destroyed through:

reverse overvoltage spike (reverse breakdown and subsequent thermal destruction due to reverse overcurrent)
forward overcurrent (thermal destruction due to forward overcurrent)

But only by inspecting the destroyed diode itself?

Electrically it always had zero resistance between anode and cathode so far, so I mean some mechanical (destructive) way.

I know that there are ways such as X-rays or electron microscope to inspect  details of the destroyed P-N structure but these means I don't have at hand.

So I mean some less sophisticated means, such as to slowly decompose the diode package (slow grinding) and viewing the chip with normal microscope?

I also mean some common way, which does not heavily depend on diode type. The destroyed diodes I would like to inspect are SiC schottky IDH06G65C6 from Infineon.


texts: Driving an N-Channel MOSFET H-Bridge from a voltage doubler

texts:
I've been looking at driving an H-Bridge to raise the frequency of the mains voltage from 60 hz to somewhere between 60-120 hz.

I'm planning to use an Atmel Atiny84 to generate my clock frequency to drive an H Bridge. The mains voltage will be rectified by a full bridge rectifier, giving me nominally 240 VDC at up to 50 amps.

I have scavenged basically all the parts needed to do this, but from what I understand the highside of the H-Bridge requires either the use of P-channel MOSFETs or a voltage higher than the source voltage. This is because Vgs determines the conduction state of the MOSFET. So if the source is being fed at approximately +240 VDC, I need at least +252 VDC for most power MOSFETs to be saturated and fully conducting.

Most commercial circuits use a "charge pump" built into a large brick of silicion that spec. sheets are not available on. So my question is if I already have 240 VAC, can I just feed any of the common voltage doubler circuits and wind up with 480 VDC? The current I need for the gate is small, so capacitor size should not be an issue. I'd wind up with +240 V for Vgs if I did this, which is way too high for common power MOSFETs. But can I somehow feed this very high voltage into a common part like a 7815 to wind up with a Vgs of approximately +15 V ? This might require more components and be less effecient, but I don't really care.


texts: Increase low-frequency gain of a cascode amplifier

texts:
I've been designing a noise generator (for fun) with the goal of getting a smooth frequency response between 10Hz and 10MHz. Since I don't have any "fancy" op-amps, I decided to go with a discrete design that will eventually use a cascade of cascode amplifiers. I the first stage, I would like to use a single zener to bias the amplifier and act as the noise source.

Design Notes:

I chose the cascode amplifier because it is not subject to the miller effect
In order to take advantage of the avalanche effect, Vz > 6.5V (the 1N4737 drops 7.5V @ 30mA)
One option is to use the zener only as a noise source, and perform the biasing separately, but I would prefer not to take this route
The 1N4148 is used only for biasing and can be replaced with a resistor if necessary
The transistors are set to have a bias current of 10mA (max gain point for the 2N3904)
I realize op-amps can be used to do the same thing, but I wanted the additional challenge of coming up with a discrete design, and op-amps with a 100MHz bandwidth don't come cheap.

Questions:

Does my simulation provide a good approximation of the desired behavior? Recall that the goal is to amplify white noise between 10Hz and 10MHz.
How can I reduce the value of the emitter bypass capacitor (C2) while maintaining the desired frequency response and passband gain?
If I were to build this circuit using an aluminum electrolytic capacitor for C2, will I run into ESR problems at high frequencies?


texts: NFC tag interfere with hearing aid device

texts:
I want to add NFC tag to hearing aid device for a child to monitor on smartphone (or smatwatch - either carried by children) if the tag is in the range - if not it means that child lost it and I can remember GPS position to know where to find it.

Should I expect NFC to interfere with the device?


texts: Design for planar antenna that radiates in the plane of the antenna

texts:
Im trying to find a reference planar antenna design. The goal would be to design an antenna that radiates omnidirectionally on the pcb plane.

One solution would be to use an electrically small loop antenna. However, it might not radiate efficiently enough.

Can you recommend any other designs that would achieve a radiation pattern that is on the same plane as the planar antenna.

BR, Mikey


texts: How to generate an enable signal when a bus value is in a very small range?

texts: I am trying to build an MC68010 single-board system, and the first four 16-bit words (I am treating it as a 23-bit word-addressed system) of memory need to read a constant value (00100000h 00007C00h) so the CPU knows where to find the ROM. Is there a good way to determine when the address, encoded on 23 pins, is between 0 and 3? What I want to do is to OR together 21 of the address lines, creating an enable signal that is only active when the address is within range. Is this the best way to accomplish such a result, and if so, how do I do it efficiently? If not, what is the best way?


texts: Vertical USB connector, what is the best practice?

texts:
I have a board that is vertical to the ground, I need to provide a USB interface to the external world, due to the orientation, this needs to be vertical to the board. (i.e. think of my board standing up and USB connector protruding from the board). I looked around and it seems there are no micro B connectors that would stick out from a board, which made me think that probably the best practice is something else.

I am assuming best practice is to make a tiny board, assemble the connector to this board and connect USB via cable to the mother board. I like to get opinions from the crowd:

How did you deal with this problem?
When I am carrying USB signals from my board to a connector elsewhere, any precaution I need to take?


texts: I'm using a TPS54386 and currently designing a PCB layout. The data sheet says to avoid via's within a certain loop; I was wondering what would happen or if anything would if I went ahead and placed via's anyway to save space.


texts:
I'm trying to use the input capture module on a PIC32MX250F128B to measure the frequency of a square wave. The results I'm getting are both inconsistent and incorrect. All I'm trying to do here is measure the frequency of the input square wave by reading the capture value at every falling edge interrupt. Then I reset Timer2 and read the capture value again at the next interrupt.

Here's my ISR:

void __ISR(_INPUT_CAPTURE_4_VECTOR, ipl1) Capture4(void) {
    mPORTBToggleBits(BIT_10);
    capture_value = IC4BUF;
    mIC4ClearIntFlag();
    TMR2 = 0;
}

Here's my module configurations:

IC4Rbits.IC4R = 0;     // Assign peripheral pin RPA0 to IC4
mPORTASetPinsDigitalIn(BIT_0);
IC4CONbits.C32 = 0;    // 16-bit source timer
IC4CONbits.ICTMR = 1;  // Use Timer2
IC4CONbits.ICI = 0;    // Interrupt every capture event
IC4CONbits.ICM = 2;    // Simple Capture Event mode - every falling edge
IFS0bits.IC4IF = 0;    // Clear interrupt flag
IFS0bits.IC4IE = 1     // Enable IC interrupt
IFS0bits..IC4IP = 1;   // Set interrupt priority to 1
IC4CONbits.ON = 1;     // Enable IC module

T2CONbits.ON = 0;      // Disable while config
TCONbits.SIDLE  = 0;   // Continue in idle mode
TCONbits.TCS = 0;      // Use internal clock
TCONbits.TCKPS = 0;    // Set 1:1 prescale
TCONbits.TGATE = 0;    // Disable gated time accumulation
PR2 = 0xFFFF;          // set period register
TMR2 = 0;              // start counting at zero
T2CONbits.ON = 1;      // enable module

You'll notice the first line of the ISR toggles a digital output pin; I added this so I could monitor the activity to see if the interrupt was ever called. The interrupt does get called and I've viewed it on an oscilloscope. I would expect the ISR to be called consistently in line with the falling edges of the input square wave but this is not the case. Instead, the ISR is called inconsistently at seemingly random intervals. Also, the values being read from IC4BUF don't correlate at all with any adjustments to the input signal's frequency.

Clearly I'm missing something here. If you have any suggestions or can point out any obvious errors that I've made, that would be greatly appreciated. Also, I'm open to alternative methods for accomplishing the task of measuring the input frequency. I chose this route with the Input Capture because it seemed to make the most sense. Thanks!


texts: Clamper Circuit Without A Resistor Analysis

texts:
simulate this circuit – Schematic created using CircuitLab
We were given this clamping circuit and were tasked to plot Vc and Vout for varying input. The only given quantities are the forward voltage of the diode which is 0.7 and the Vin which is:

My general KVL equation (clockwise direction) for Vc and Vout are:
$$ Vc = Vi + 2V + Vd$$
$$ Vout = Vi - Vc + 2V + Vd $$
Using this equation, my analysis is:

At Vi = 0, Vd would be off because of its opposite polarity to the voltage source parallel to it. Vc would then be 2V. Vout would be $$Vout = 0 - 0 + 2V = 2V $$
At Vi = 10, Vd would still be off. Vc would be holding its initial charge. Hence, $$Vo = 10-2+2 = 10V $$
At Vi = -10 V, Vd will be ON. Vc would still be holding its initial charge. Hence, Vout would just be equal to 2V + the forward voltage 0.7 but because of the opposite polarity, it would be negative. $$ Vo = -2 - 0.7 = -2.7 $$

There is no resistor in the circuit so I'm unsure of the behavior of the capacitor. I just assumed that the capacitor would be holding the charge for a very long time since there is no resistor it can discharge to. The configuration looks like a clamper circuit but then my calculations don't show similar behavior. I'm guessing it has something to do with the capacitor carrying its charge to the next time interval? Should I be instead calculating for initial charge + new charge? So for eg., from an initial charge of 2V at t(0), at t(0+), Vc should be like this?
$$ Vc(0+) = (Vi + 2V) + V(0-) $$


texts: Say I want to design an n-bit system e.g. 256 bits. Can I generalize a 4-bit ALU which I think I know to 256 bits? These are my diagrams.


texts:
I have this circuit. I'm trying to find the \$I_{3}, U_{3}, P_{3}\$. For the nonlinear element I have this volt-ampere characteristics: \$ I_{3} = 3U_{3}^2 -U_{3}\$.

That's what I am doing. Using the KCL \$ I_{1} = I_{2} + I_{3}\$. So \$1= I_{2}+I_{3}\$.

Using Ohm's law for \$ I_{2}\$  I have \$ 1 = 0,2U_{1}+I_{3}\$.

Usings KVL the equation is: \$ 0=I_{3}.R_{3}+U_{3} +U_{0}-U_{1}\$ and then \$ 0=3I_{3}+U_{3}-U_{1}\$.

I'm replacing \$ I_{3} \$ with \$ 3U_{3}^2 - U_{3}\$.

\$ 0 = 9U_{3}^2 - 3U_{3} +U_{3} -U_{1}\$;

then I get

\$U_{1} = 2U_{3}+9U_{3}^2\$

And I'm not sure what to do next. I saw an example with quadratic equation but i don't know to form the equation.


texts: What will happen if you apply a AC Signal to a Programmable DC load(63600)?

texts: DC load consists of mosfet or many in parallel, for dc loads it arranges in series/parallel combinations to reach specifications of load. I have a doubt on it if AC load is applied,will it withstand or damage? If withstands what type of protection is used/ it behaves as specified. If it fails/damages for AC signal can it withstand for AC rectified signal? what about negative voltage input? it will be help full if explained for the device 63600.


texts: Accidentally made an analogue touch sensor from arduino digital pins

texts:
The other day I wrote a simple arduino script to switch on an LED when a pushbutton is pressed. Without connecting the pushbutton, the circuit created a make-shift analogue sensor that varies the LED brightness according to the distance you move your hand towards the input pin.

Dumbfounded, I rewired the circuit several times (also with different arduinos), and got the same results.

The LED was plugged in (no resistor), assigned as a digital output (13). A loose cable was plugged into a digital pwm pin (7) as input on the arduino mega 2560.

My understanding of electronics doesn't stretch far into electric/magnetic fields, was wondering if there was a rational explanation for this?


texts:
The pictured circuit comes from Build Your Own Transistor Radios: A Hobbyist's Guide to High-Performance and Low-Powered Radio Circuits (2012) by Ronald Quan, p. 73.

I am puzzled by Quan’s explanation about a part of this circuit.

L1_Primary and L1_Secondary are coils wound on a ferrite core and used as the receiving antenna for AM broadcasts.

He says on p. 73, “C1 provides an alternating-current (AC) short circuit at high frequencies (e.g., RF frequencies) but a low-pass filtering effect at audio frequencies.”

If I understand this correctly, Quan is saying that the RF portion of the signal is being shorted to ground while the audio frequency signal is being passed onto the connection to L1_Secondary.

The incoming signal at the left hand connection of C1 is a modulated signal.  For the sake of simplicity if I assume that the carrier (519.1 kHz, the tank circuit resonant frequency) is modulated by a 1 kHz tone, then the AM signal at C1 consists of sidebands at 518.1 and 520.1 kHz along with the carrier signal.  That is, there is no low frequency audio to pass along since no demodulating process has yet happened.  It seems to me that C1 kills the very signal which the circuit is trying to process.

What am I missing?

Thanks.


texts: Help wiring a pic processor to a FTD chip

texts: I have been trying to wire a PIC18f4620 to a FTD1232 using the MLCR reset. Below is my circuit. When I hit the reset, the short causes the processor and the FTD to lose power and I am unable to program to it. I am certain that this button to reset is possible, but I am unsure where I am going wrong.


texts: is 'Ok' important when sendin AT commands to modem

texts:
I'm currently using VHDL to program the FPGA Spartan 3AN Kit-set. The objective is create a programme to send an SMS to a mobile phone, using the Kit-set via the modem. I'm done with the transmit finite-state-machine (FSM) and started doing for the receive part.
However, I'm only required to send an SMS and the only thing to receive is the 'OK', which is send by the modem back to the device, after sending it an AT Command.

The question here is:

Is receiving the 'OK' from the modem important?
Can I substitute with delays in between each AT-Commands, assuming
the modem is functioning perfectly?

Thanks in advance!


texts:
I am using Arduino(does not matter) and 8 x 12 bit-ADCs to read some values. I created a prototype which consists of a Shift Register(SR) and all outputs of SR are connected to individual ADC's chip-select pin. During boot, I set all output of SR as HIGH.

I select the ADC by pulling the specific output of the SR as LOW and then talk to the ADC. As soon as my communication is finished, I again set all output of SR as HIGH. This is all working.

During some testing, I found that if all SPI (ADCs) are pulled HIGH (none should be talking) and if I read MISO, I was getting some random data. I realized that MISO was floating and added a 100K pull-down (weak pulldown!) which sorted this out. After this, if I listened the MISO while all ADCs were HIGH, all I get is 0s (Yey!).

My question is that does it make sense to pull down MOSI and CLOCK as well? Will it create any problem?


texts: How to design wireless charging coils so they are resonant?

texts:
I am continuing from this question: What can I use to increase efficiency of inductive wireless energy transfer instead of factory manufactured ferrite plates?

I am trying to make somewhat efficient wireless energy transfer for charging a 190mAh 3.7V battery. The plan is to use a rectifier, a voltage regulator and a charging IC MCP738312(datasheet) in the device and generate AC at a few hundreds of kHz from a 12V coming from a 1A regulated wall power adaptor in the charger device.

I am making my own coils because of the size I want them to be by etching multiple layers of copper foil:

A new question arose: how do I design the coils so that they are resonant? It would be great to get an answer that would be easy to understand for someone without education in electrical engineering, if that's possible, as much as it is possible.


texts: ESD/overvoltage protection with DM1231-02SO TVS array

texts:
I'm protecting a USB2.0 IC against ESD and overvoltage at the USB connector using a Diodes Incorporated DM1231-02SO TVS (dual) array. The datasheet labels the pins IN and OUT, but it's not 100% clear which of those should be on the USB connector side and which on the IC side. The datasheet refers to zapping at the OUT pins, which significantly implies that the OUT pins should be on the connector side.

My questions:

Is my assumption correct that the OUT pins should be connected to the USB connector pins (and that this is an appropriate device for USB2.0 protection)?
What is the electrical explanation for placing the device that way around?


texts: Test circuit to confirm RF receiver frequency? (315Mhz vs 433Mhz)

texts:
I've bought a 433 Mhz Transmitter/Receiver pair, or so I think. I cannot make them work, and I started to think that maybe the seller sent me a 315Mhz transmitter / 433 receiver pair by mistake (I've seen people online complaining about things like that, mainly because both types of modules look exactly the same and are easily confused apparently).

Here is a picture of my modules:

As you can see, the transmitter module (the one on the left), has a "R315" engraving. This suggests me this is indeed a 315Mhz transmitter. Is that so? I've seen pictures online of other transmitters with a "433" mark, so probably yes, I guess...

Now, the receiver module (the one on the right) does not have any special engravings or marks. On the back side it reads "XY-MK-5V" (which I googled but many articles are about "315/433 modules" so I don't think that's conclusive):

It also shows a table with three values "315Mhz", "330Mhz" and "433Mhz", but none looks specially marked.

How could I test in which frequency this receiver module is operating? Is there a simple test circuit I could build to do that?

Thanks!


texts: Can I drive a three phase induction motor with this method?

texts:
I have an idea to drive induction motors in a new way. I call it Variable Torque Drive (VTD). You are all familiar with VFD which utilize variable frequency and try to keep the torque constant. This method is vice versa. Let me explain.

Assume I have this weird delta configuration to drive phase coils. Keep in mind that I can control the drive currents RMS amplitude like in the figure, on right. For some reason I can not change the frequency, but I have full control over the amplitude. You are seing the waveform of each phase currents in the figure. As you know IF you increase the phase currents you increase the torque.

Now lets assume I have a constant frequency at 100 Hz and I can deliver 0 to 100 Amps RMS currents. Please try to put aside what you already know about classical driving methods. Like I said, I have full control over the amplitude and If I don't allow current flow on field coilds, no currents  will flow.

So since I can drive field coils at 100 Hz, its synchronous speed is 100*60 = 6000 RPM max. Now lets say I want to drive a loaded motor in 10 rad/s. Load is 10 KN and I can deliver up to 20 KN to the load. I also have speed sensors in on the rotor side. First I will deliver 15 KN to the load, and when I reach some speed close to 10 rad/s, I decrease delivered power to 5KN, then after the speed decreased down to some level below 10 rad/s, then I increase it to 12 KN, then 8 KN and it goes and on like this till I adequately regulate the speed at 10 rad/s. See the figure below to understand it better.

The question is, since my synchronous speed is 6000 RPM, can I drive an induction motor with this method and control the speed 0 to 5880 RPM(I figured the slip may be 2%). If so, does such method exist? If not, please explain why. Thanks.


texts:
So I'm doing experimental work on an unknown impedance.
I used a RLC meter for frequencies of 100, 200, 500, 1k, 2k, 5k, 10k, 20k, 50k and 100k Hz.
Now, I think the values I got for each frequency are not that relevant (tell me if they are and I can post them). What seems important is how they vary:

the absolute value always increases (varies between 404 ohm and 2.57k ohm). The increase rate is greater at mid-frequencies.
the angle starts positive and close to zero (7 degrees), increases until reaching a maximum of 47 degrees at 2k Hz and then it starts decreasing again until like 1 degree at 100k.

Now my attempt. What elements make my impedance and how are they placed?

The way the phase varies tells me that as frequency tends to zero and infinity, the impedance behaves as resistor.
The magnitude always increases.
The magnitude of the impedance of a resistor is constant
The magnitude of the impedance of a capacitor decreases with frequency. Therefore it's theoretically infinity at zero frequency and zero at infinite frequency.
The magnitude of the impedance of an inductor increases with frequency. Therefore it's theoretically zero at zero frequency and infinity at infinite frequency.

Because the impedance is low (but not that low) at low frequencies, the circuit must be equivalent to a resistor. Same for high frequencies.

I came up with an hypothesis of:

(resistor A in parallel with a capacitor C) in series with (resistor B in parallel with an inductance L). This seems to be the minimum that guarantees the absolute value scheme.

But does it verify with the angle?

Writing the transfer function of this circuit I get.

$$ \frac{R_AR_B + L(R_A+R_B)s + R_AR_BLC s^2}{(1+sCR_A)(1+s\frac{L}{R_2})} $$

Therefore I have 2 real poles and one pair of complex conjugate zeros. Of course without numerical values it is hard to guess if this is correct or not. But I know that the pair of complex conjugate zeros will guarantee me an increase of 180 degrees around the natural frequency and each real pole will guarantee me a -90 degrees fall. I know that the maximum I reach is 47 degrees (so around 45 degrees). Therefore I think my hypothesis can never be correct...
To increase the angle the first frequency to appear needs to be the zeros'one. However since the frequency only increases until 45 degrees and then decreases I need to have components that will get me at least -235 degrees of fall... My 2 poles only guarantee me -180 so it would only work if frequency never dropped. Therefore I'm stuck. Do I need more poles in my system? What components can I had to guarantee me that? Thanks in advance!


texts: Is it possible to pre calculate execution speed of micro controller for a given setup theoretically?

texts:
I need to work with 5x MPU9250 sensors, i2c 400kHz, Arduino nano 8MHz
also, I have HC-05 Bluetooth device 115200 baud rate serial.

is it possible to pre-calculate loop time to gather data from sensors (3x accelerometer,3x gyro, 3x magnetometer) and send through HC-05 serial Bluetooth module without coding and setting up the above setup?


texts: Why and When should we use the capacitor array instead of switch or capacitor in the timer control?

texts:
There is a schematic of precision timer control of the flip switch,about this,i have two question for that

1.What is the difference of the flip switch with the general switch?This switch is used in parallel SSHI,connect in series with the inductor.

2.Why is \$C_t\$ made into 4 bit capacitor array instead of switch or capacitor ?If it is let it become more accurate,then why don't he make \$C_t\$ into 5 bit or 10 bit ?


texts: How can I solve this exercise on Operational Amplifiers?

texts:
This is not really homework, but a self-study exercise. I have to solve the following questions (the solutions are in red):

I had no problem with part 1, so I will not ask about that. My problem is with part 2. It says the differential DC gain should be zero, so for me, since the DC part of V1 and V2 is the same, the condition is clearly that, from the transfer function $$\frac{R4}{R3}=\frac{R1}{R1+R2} \times (1 + \frac{R4}{R3})$$, and from that, simplifying, I get $$\frac{R2}{R3}=\frac{R1}{R4}$$. In the solution of the exercise, they seem to have an extra equation to make $$\frac{R2}{R3}=\frac{R1}{R4}=1$$, so that $$R2 = R3; R4=R1$$

Any idea on where this is coming from?


texts: CMOS Integrate circuit with output in Open Drain Technology

texts:
I can't understand a thing from my book, it say that since in integrated circuit with CMOS have an output of high and low current that is equal we can't use the wired-or connection, but we can use it with Open Drain technology.
I have some question:

What is the wired-or connection
Why if the I low and I high are equale we can't use a circuit like that:

But we have to use a circuit like that:

Thanks for read!Hope that you'll have a nice day!


texts: Is it worth modding an external audio jack to a camcorder?

texts:
I have a good HD camcorder that records low fidelity audio.

Instead of buying a new camcorder, I am tempted to try some external microphones on it, because the electret microphone wires are only 2 leads.

Is there a chance i'll still have low quality sound afterwards, because the microphone circuits are noisy and low quality?


texts:
I am getting confused with the working of the circuit. How will the expanded circuit look like?

Assuming the register is SISO, it will take (32-1) clock edges to get the output. What other information I can use?

How is the adder part working ?

Please help me with this. I am not posting this just to get solution to for my homework. I am preparing for an exam and such problems are repeatedly asked and I am not able to start from any where so I can't show my work. The official answer to the problem is option(A).


texts: Automatic switching to the changed set of TTL inputs

texts:
I have 2 sets of 4 logical inputs.
All inputs are active-low 5V TTL level lines with 4k7 pull-up resistors, as they may be pulled to ground by a a user pressing a switch or flipping a transistor with a rotary encoder, depending on what will be connected, if at all.
The goal
is to automatically pass the inputs of the set that changed to the output of the circuit;
If any of the inputs on a set changes then the outputs should reflect that set.
If there are successive changes on a set then that sets keeps being passed.
The inputs may be momentarily low, as in pressing a button. It may also kept low continuously, as in flipping a switch, during which time a change may occur in the other set. In such case the circuit should switch to that other set; a change in any set switches to that set.
Constraints
The outputs will be fed into one of the input sets of an existing 74LS157 multiplier on an existing PCB using 5V TTL logic, so perhaps TTL logic is best suited, and everything should run on 5V.
I like to optimise for minimising the number of ICs and passive components, and also for easy to obtain and cheap components.
What I came up with
is a flank detector circuit to generate a pulse on each flank of each input line.

For each set all 4 detectors are fed into an OR gate to detect change on any line, and then both set's detections are fed into a SR latch to remember the last changed set.
The Latch then feeds a 74157's selection input.  The 74157 then passes the changed set to its output.
All in all that takes around 6 7400 series IC's, 8 capacitors and 8 resistors.
I have a good feeling this can be done simpler.


texts:
I have a male type of plug with 4 exposed terminals that connects to a female plug of the same sort. 2 terminals are power, GND/VCC and two are data lines. With 4 exposed terminals, the chances are that a piece of metal or conductive material could easily short the VCC and GND.

To prevent this short I was going to put a MOSFET on the GND or VCC, and only enable those lines once a connection was detected.

The question is how to detect this connection? Assuming I can't measure it mechanically, only electrically. One method I was considering was to use similar to USB, and include pulldown resistors, on the data lines, and then apply a voltage and measure the corresponding voltage, however this still involves enabling the voltage line, when there's no guarantee there's not a short between the VCC and the GND. Is there a way to determine a valid connection or simply that there's not a short before hand?


texts: How do I choose which version of the IC MT8870 should I use?

texts:
I am following this guide to hooking up a phone to a circuit, depending on the DTMF tones. However, when I went to buy one, I realized there were lots of different "editions"/models.

Which one should I choose? Does it really matter in my case? To make this question more useful for future visitors, how did you get your answer?

Datasheet for MT8870


texts: How to find out which side of transformer the OC and SC tests were performed?

texts:
I have this problem which states that in a single phase transformer 2200/110 50kVA No load and short circuit specifications are like below, How to find out which side of transformer were the tests performed(I believe it means that the test may not be conducted on default sides( SC -> primary OC -> secondary) )

No load 400W 10A 110V
Short Circuit 90V 20.5A 808W


texts: What size of fuse do you put between 330w 9.08 solar and 12/24 auto charge controler

texts:
Please help me with my question. I have a 330w solar panel and how do i know the correct fuse size to put between the solar and the charge controller. Also fuse size between the charge controller and my 24v battery bank.
I have attached my solar data plate.
thank you


texts: What are the applications of external feedback for FPGA PLL's?

texts:
I see that most FPGA vendors allow users to use an external clock signal as the feedback input to a PLL. When provided external feedback (which originates ultimately from the PLL output), the PLL will adjust its own output skew until the feedback input is aligned with that of the reference input.
Why would we possibly want to do this? I understand in the abstract, that instead of aligning the PLL output with the reference, we can align another point in the clock tree with the reference, but in what kind of design would this be useful?


texts: How to find the time constant of a RC circuit with dependent sources

texts:
Given the following circuit, I would like to calculate the time constant \$ \tau \$.

I know that in an RC circuit \$\tau=R_{eq}\cdot C \$.

I've also found out that \$\frac{d v_{c}}{d t}=-\frac{2-\alpha}{R C} v_{c}(t)+\frac{E(1-\alpha)}{R C}\$, where \$E=e(t)\$. Let's define \$\lambda=\frac{1}{\tau}\$. My textbook considers \$\lambda=-\frac{2-\alpha}{RC}\$, so that \$\tau=-\frac{RC}{2-\alpha}\$.

Instinctively I would simplify the resistors so that I can find \$R_{eq}\$ in order to find \$\tau\$, but I don't know if that would be appropriate. Also why \$\lambda=-\frac{2-\alpha}{RC}\$?


texts: How can I make a motor turn extremely slowly?

texts:
I'm looking to have multiple motors rotating metal discs at different speeds (each motor would be for a single disc, which weighs maybe 100g and 20cm in diameter), ideally at the pace of a clock (I tried a clock mechanism but it wasn't strong enough to turn the weight of the disc).

The small motors I've found here in NZ seem to be the typical low torque, high speed, but these go much too fast. Initially I thought a potentiometer would do the trick because then I can vary the speeds on each motor/disc pairing, but then though a transistor could possibly achieve the same thing. However, I am brand new to this stuff and am really just fumbling around in the dark.

Short version: How can I best make a small motor that is 11000+rpm rotate as slowly as a clock?

Cheers


texts:
I want to use boost converter to to supply higher voltage to LED .I have confusion about which smps power supply to use on input side.
From specs. I am unable to understand why input current limitation is given??
and what happens if higher input current supply used?? Some websites blogs saying that in electonics devices donts consume power more than that they requires.
and What about linear voltage regulators??In datasheet of regulators they also mention input current limitations.

Below is of details of my project and spec:
1)SMPS spec.=12V 20 amps
2)led spec =35v 4 amps
I am using this boost converter
https://www.newegg.com/Product/Product.aspx?Item=2S7-00MH-02G82
 boost converter spec:

Input voltage : DC8.5V-48V []Input current : 10A (MAX) exceeds 8A please enhance heat dissipation []Output voltage : 10-50V continuously adjustable 12-80V fixed output [Output current] : 10A MAX exceed 6A please enhance heat dissipation

PLZ SEE BELOW IMAGE:


texts: Matrix of WS2812b powered in 24v (LEDs 5 by 5)

texts:
In order to reduce the power for a large quantity of WS2812b matrix, I would like to power it directly by 24V, by intuition, chaining in series 5 LEDs (for the power only, the data will be one by one to be able to address each LED).

As it's just an intuition, but I'm not really expert on it, can you please tell me what do you think about this solution?

Can you please help me to confirm the power consumption for a matrix of 100 LEDs, grouped by pack of 5 LEDs.

Will this improve consumption as compared to powering all 100 LEDs in parallel from a 5V power supply?


texts:
I'd like to buy one XBee Pro with Wire Antenna, and another with an u.fl connector. The problem is that, on the only website I can buy them, the U.Fl one costs 20 € less than the one with a Wire Antenna: I wish I could keep these 20 bucks.

On the other hand, I've already got two unused XBee with Wire Antenna: I wonder whether I could unsolder the U.Fl connector of one XBee Pro, and instead solder the wire antenna of one unused XBee.

So, Could I just replace an U.Fl connector with a Wire Antenna ? Won't this lower the range ? Are the XBee w/ ufl connector different from XBee w/ wire antenna, except for the antenna/connector ?


texts: Is there a continuous duty electric valve available?

texts:
I was searching and surprisingly unable to find a simple continuous duty electric water valve? Below is my requirement.

We get water from government. They release water only every 6th day., for few hours.  So most of the time our manual water valve is closed. Every 6th day, we manually open and  keep the water valve opened for few hours (typically 6 to 8 hours), because the timing is not consistent.

I want this process to be automated. If I have electric valve, I could simply connect to internet and schedule this. Only problem is, I see that solenoid valves cannot be activated for hours together. So I need a one (I don't care if its solenoid or anything, just something I could activate electrically), which I can activate and open electrically for few hours when needed.

Most of the aliexpress like platforms have valves, but not clear how long they can be operated. And numerous reviews suggest, even an hour of operation makes the coil/valve over heated, and even damaging the valve thereafter.

So can some one kindly suggest which device I should go after in the market? Do they have a different name than "continuous duty"? Kindly advice.

Update:
Kindly suggest something affordable (within $20 or so) if suggesting buying links. Kindly note, I am looking for ready made solution, not as a project. Something like plug and play. I intend to connect it to IOT, but that is separate(we have plug and play switches) so kindly focus only on suitable low cost continuous duty valves. Motorized valves are good fit as one of answers suggested,and am already searching for low cost ones but in vain so far.


texts: microcontroller external clock power option (pic18f)

texts:
when reading http://microchip.wikidot.com/8bit:ec

  The EC mode has three power modes to select from. The EC mode is selected in a configuration register. The three modes include:
  ECH - High-power mode, 4Mhz - 32Mhz
  ECM - Medium-power mode, 0.5 Mhz - 4 Mhz
  ECL - Low-power mode, under 0.5 Mhz

I'm confused as this is not a crystal oscillator that needs an amplifier to form an oscillating circuit. What is the "power" needed for if the clock is considered as:

  externally generated logic level signal and that signal used as the system clock source

Are the power options needed only when the OSC2 pin is used as an output? Maybe amplifying the signal to be re transmitted to other devices? Or is it necessary for amplifying the signal to drive the internal logic of the microcontroller?

Thanks a lot


texts: Cheap and simple solution for low frequency (period about tens of seconds) pulse generator

texts:
I need to generate a pulse each let's say 30 seconds. I don't need this period to be any precise (20...40 seconds fluctuation will be OK). The pulse duration should be about 1 ms.

I tried to implement NE555 for this but looks like NE555 don't intended for generation this low frequencies as it would need a relatively big capacitor (I'd like to stay within small and cheap CMD technology so 10uF cap is a maximum) and many MOhms resistors. This can lead me to the topology leakage problems.

So I tried to look for any counting solution but looks like that I will be able to get 100kHz divided by 64K as a maximum which is definitely not enough.

Next I tried to look at the watchdog timers. However after initial filtering I see that the longest period is 1.6 seconds and the lowest price is 33 cents.

Important note: I'd like to have this solution as cheap as possible. I hope to fit within 10-15 cents for BOM of this circuit.

Is there anything staying out of my sight? Any thoughts?


texts:
I'm designing a system that runs WS2182B signals down RS422 lines to LED strips powered elsewhere.
Where I'm stuck is that it makes sense to use the 5V power for the LEDs to power the RS422 receiver board since they're all 5V systems, but I can't figure out what connector(s) I would use. Ideally it would be something that just connects the power more or less directly to the LEDs and lets the tiny amount of power the PCB will need just draw off of that.
Is something like that even a good idea?


texts:
I am building a high power ZVS induction heater. I originally used this famous design. It worked like a charm when I used a 48v 31A power supply. But I want an upgrade. I recently got a few of these FCH072N60F 600v 52A power mosfets. They have a low Rds on, fast switching and low gate charge. All of which are needed for a good ZVS driver.

However, I recently got myself a 96v 30A power supply. I simply replaced the IRFP250N mosfets with the beefier FCH072N60F mosfets. I then realized that at double the voltage, my mosfets would burn out. The 470Ω 2w resistors were for the 48v version.

Could I simply double the resistance of these resistors or is it not that simple?


texts: Some trouble for drive a MOSFET(IRF540N) with driver(TC4427) (overheating)

texts:
I have some trouble about my MOSFET and its driver. I wanna operate my circuit around 4-5 Amps peak. For this purpose I drive two IRF540N MOSFETs parallel with one TC4427 driver by 62.5kHz PWM. But my MOSFETs are getting too hot. I checked related issues, maybe I using fake MOSFETs. I added my schematic.
Any suggestions ?

Thanks in advance


texts: questions on shielding static magnetic field

texts:
It seems that using ferromagnetic materials is the easiest way to shield  static magnetic field. But is it still working in strong field strength(up to 5T)?
Another question is that are mu-metal (iron-nickle) shield under magnetic force in the field?
I didn't see anyone considering this. Is it because the force is too small?


texts: Determine transmit and receive latency of a USB to EIA-485 converter

texts:
How could I determine the latency involved with transmitting data on a USB to EIA-485 converter?

The converter is a B&B Electronics USOPTL4 using the FTDI chip, and I know that there is a throughput latency from the time my Windows application calls WriteFile and data is actually transmitted.

The same question applies on the reception end of things. I know there's a latency from when the FTDI receives the serial data and it's provided to the OS for reading.

Has anyone successfully measured these latencies?


texts: which of the following will take min no of clock cycles?

texts:
Which of the following computation will take minimum no of clock cycles, if implemented on 8051 micro controller? following variabe declaration is in c-code:

unsigned int a,b;

A) b=a*a

B) b =a*3

C) b=a/3

D) b=a/4

This question was asked in ISRO Recruitment exam 2014. ans given is option D can you explain how to solve this and why the option is correct?


texts:
I have a very simple low-pass filter with an AC source a capacitor and a resistance in series. Now I set C and R so that R*C=100 but when I plot the diagram whit db(out), it looses 3dB at 156Hz instead of 100Hz.

Vin  in    0  DC 0.0  AC 1.0 0.0
C1   out 0   1uF
R1   in     out   1kOhm

ac dec 50 0.1Hz 100kHz

I'm just starting with this things, can someone help me?


texts: AC to DC power supply - earth ground capacitance on DC output

texts:
I have a mains to 60v DV power supply that I’m using for a project. Needless to say it managed to give me a bit of a shock. This surprised me as it’s supposed to be floating.

With no load the power supply seems to show a -60v potential to earth ground from DC -ve.

With the power supply off. Measuring Resistance between the DC -ve terminal and the earth ground there seems to be some capacitance as resistance goes from 1m to 0 ohms.

Measuring for capacitance there seems to be about 400uf capacitor between earth and the -ve terminal.

Putting a 5k ohm resistor between DC -ve and ground shows about 11mA flowing...

Obviously measuring anything with my bench oscilloscope is out of the question as this power supply -vs has a current path to earth.

Is this a poorly designed power supply?


texts: Unexpected behaviour of data memory in modelsim testbench

texts:
I am describing a very simple ram memory in VHDL and observing strange behaviour which I do not
understand nor am able to debug. I have similar code written elsewhere and I suspect that rewriting it would do the trick, but I am now very eager to find out what is wrong (having spent a fair amount of time on it).
Main code:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use ieee.NUMERIC_STD.all;
use ieee.NUMERIC_STD_UNSIGNED.all;

entity data_memory is

    port(
         data_address: in std_logic_vector(4 downto 0); -- data address
         clk : in std_logic;
         we : in std_logic;
         write_data : in std_logic_vector(31 downto 0);
         data : out std_logic_vector(31 downto 0)
        );

end data_memory;

architecture data_arc of data_memory is

    type ram_32x32 is array (31 downto 0) of std_logic_vector(31 downto 0);

    signal mem: ram_32x32;

    begin

        write: process(clk) -- o processo eh sensivel apenas ao clock
        begin

        if rising_edge(clk) then
            if (we = '1') then e
                mem(to_integer(data_address)) <= write_data ;
            end if;
        end if;

        end process write;

        read: process(data_address, clk, we, write_data)      -- sensivel a todos os sinais

        begin

            data <= mem(to_integer(data_address));

        end process read;

end data_arc;

Testbench:
library IEEE;
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use ieee.NUMERIC_STD.all;

entity tb_data_memory is
end tb_data_memory;

architecture tb of tb_data_memory is

    component data_memory is -- registrador de 32 palavras
        port(
        data_address : in std_logic_vector(4 downto 0);
        clk : in std_logic;
        we : in std_logic;
        write_data : in std_logic_vector(31 downto 0);
        data : out std_logic_vector(31 downto 0)
        );
    end component;

    constant clock_frequency : integer := 10e6; -- 10Mhz
    constant clock_period : time := 1000 ms /clock_frequency;

    signal we : std_logic := '1';
    signal clk : std_logic := '1';
    signal data_address : std_logic_vector(4 downto 0) := (others => '0');
    signal write_data : std_logic_vector(31 downto 0) := (others => '0');

    signal data : std_logic_vector(31 downto 0);

    begin

        uut: data_memory port map(
                                     data_address => data_address,
                                     clk => clk,
                                     we => we,
                                     write_data => write_data,
                                     data => data
                                   );

        clk <= not clk after clock_period / 2;

        test_bench: process

        constant period: time := 200 ns;

            begin

                data <= "00000000000000000000000000000000";

                wait for period;

                we <= '1';
                write_data <= "00000000000000000000000000000100";
                data_address <= "00001";

                wait for period;

                write_data <= "00000000000000000000000000000001";
                data_address <= "00010";

                wait for period;

                we <= '0';
                data_address <= "00001";

                wait for period;

                data_address <= "00010";

                wait for period;

        end process test_bench;
end tb;

.do file:
view wave
delete wave *
add wave *
run 1 us
property wave -radix unsigned *

current behaviour:

I have tried without driving the data output and obtained similar (altough slightly better looking) results.


texts: DDR3 SE signal, is 50Ohm impedance necessary?

texts:
I want to design a 6 layer PCB for an Allwinner H3 and DDR3, but the PCB workshop just have the stack-up shown in the image.

With this stack-up, The calculation for striplines impedance is difficult. The width of SE signal at 50 Ohm is 18 mils. So big for DDR3 signals.

Can I layout the DDR3 SE signal with 80 or 100 Ohm instead of 50 Ohm ?


texts:
I'm making a PCB in Eagle. First I found my components, and now I have to put them in Eagle so I can draw the actual board.

Now the problem is, I have found this power resistor (I need 0.5 Ohm dissipating at least 4.5W. This one dissipates more, but is apparantly the cheapest I could choose from).

As you can see, there is no CAD design associated with this component. In the datasheet there is a recommended pad layout, but this would mean that the resistor is layed down on the pcb, whilst al other transistors that might need  a heat sink are placed vertical on the PCB.

So my question is - how must I orient this component (horizontal/vertical/doesn't matter), and how an I find a CAD design to add this to Eagle?


texts:
I have a need to be able to connect a lead on a circuit to 1 of 5 different other leads. I think it’s obvious how I can accomplish this with jumpers or DIP switches or encoders.

The wrinkle here is that the voltage is somewhat high ~ 30V.

My question is: is there a electrically controlled way to accomplish this? I’ve looked at multiplexers and some other options but once you get into the 30V range these components seem to get too expensive to justify the cost.

What options are available in this situation?

To summarize, a good solution would:

Allow electronic control
Handle ~ 30V @ .5A
Be low cost — If one component handles mapping 1 to 5 lines, I’d need 5 of them on the board; each of 5 lines gets mapped to one of 5 lines.


texts: Why does a Category 5 rated jack have different solder tail positions than a traditional jack?

texts:
I am attempting to specify a replacement part for a modular jack used in an original design (I basically need something that will stick out farther than the original).  However, the part I would like to use specifies different solder tail positions than the original because it is designed for use with Cat 5.

The part is from TE and can be found here.

Here is the difference in the solder tail positions:

1. What is the reason for changing the positions of the solder tails for a category 5 jack?


texts:
The Star Delta Starter is a very common type of starter and is used extensively.

It is said that a star delta is used for a cage motor designed to run normally on the delta connected stator winding.

So If a motor is designed to run normally on the star connection, can we use the start delta starter with it?

How can we know if a motor can be connected in star delta starter from the motor nameplate?


texts:
I find it incredible how transistors per area keeps increasing. How has it been achieved so far? My ignorance tells me that if ICs were designed properly from stage to stage they should have got this far in a lot shorter a time, but at the same time I'm sure it's been a vast number of incremental improvements. The question is, what improvements were they? Were they all variations on a theme, or completely different improvements, it was probably a mix, but some enlightenment as to what kind of improvements they were, and why it's done in so many small increments.

Was it mostly improvements in the photo-lithography? Or transistor/circuit designs that allowed greater tolerance of imperfections? Or material science improvements which allowed higher quality materials in the transistors, tracks, and layering? Any other facets?

Thanks


texts: How to clean a power rail for sensitive ADCs

texts:
I am making a power management circuit for multiple sensitive ADCs that will get power from it.
The basic idea is kind of like this:
Where this circuit I'm about to make will be a power hub of 8 power sensitive ADC. The ADC circuit already has its own filters designed as recommended by it datasheet (PSRR 60dB@100kHz and 90dB@100Hz) which should be theoretically enough, but since I don't have much control and information on how clean the main supply is, it maybe total trash or really good.

Hence I would like to place something on the middle. The ADC circuits need 5V, hence I need a regulator and I found this which is advertised to be good at noise sensitive application TPS7A47. Is there something I can do to further give better protection against noise from the main supply? Also for inputs above 5V there is nothing to worry since the PSRR would kick in but for inputs that are exactly 5V (and output 5V)  from what I know an LDO does not have PSRR in these situations so how can solve this issue?


texts: Alternative recharging methods for a toy car

texts:
Question: I would like to know about alternative recharging methods for a rechargeable toy car.

Synopis
I have the Fisher Price Shake n Go Xtreme car and track set.  The cars are problematic in two key areas with regard to the electronics:

Recharging takes 40 minutes and provides 10 minutes of runtime
The recharging station is not AC powered, it operates off of 4 DC batteries

I would like to find an alternate way to charge the NiMH 3.6V 170 mAh batteries in the cars so that they can recharge faster, incorprating AC charging.  I believe the red and white wires simply supply power, while the yellow wires are connected to the bottom of the car and provide the positive and negative for charging

I am open to replacing the batteries with a higher amperage so that they hold a charge longer

Here are the pictures from the charging base, which takes 4 D-cell batteries.  I want to rewire this charging system to use AC power for charging more efficiently, and hopefully faster.


texts: Possible to drive a ULN2003 driver with a LM3914 Bar graph display

texts:
I would like to drive up to 10 LED's of each pin of a LM3914 Bargraph IC. In my toolbox I have a ULN2003 Darlington drive which should fit the bill. The Darlington driver seven open collector darlington
pairs with common emitters.

The LM3914 does this also. My premise is to connect the output pins of the LM3914 directly to the ULN2003 (see crude illustration)

Is this going to be possible? or am I going to have to invert the output of the LM3914


texts:
My question is in the title. I was looking for a component, but I can only find it with 5V. There is no data sheet provided so my question is in general:

Will a 5V crystal oscillator oscillate with a 3.3V supply?

Here is the component.


texts: Stability and Positive/Negative feedback

texts:
I often read that positive feedback is used to get oscillators (since the output of the circuit is summed up to its input signal and so leads to instability), while negative feedback to get amplifiers (since its output is subtracted to its input and so leads to stability).

But it seems to me that this intuitive reasoning is in contrast with the analysis of stability: in fact a negative feedback system is not always stable and a positive feedback system is not always unstable (we may check their stability by using the Nyquist criterion, for instance).

So why is it often used the first sentence?


texts: Matlab Digital filter not working, how come?

texts:
Before reading any further, to give you on some insight on the output level of the oscilloscope picture's
the ~340mV green signal is normal. If you know me I posted a question as to why its 340mV but for sake of simplicity 340mV is normal in this case. So attenuation is not being seen here.
trying to design some digital filters directly from matlab to be implemented in the STM32H7 using the CMSIS DSP library
I tried first doing a butterworth low pass filter with some criteria I made listed in the picture

Converted it to Direct-Form 1 and into second - order sections. Then generated to a .h header in single precision form as I am working with floats and not doubles.
Here are the coefficients
float32_t iir_coeffs[20] = {0.344617784f, 0.689235568f, 0.344617784f, 0.2994394898f, -0.6779106259f, // Biquad Stage 1
                            0.265586704f, 0.531173408f, 0.265586704f, 0.2307691127f, -0.2931158841f, // Biquad Stage 2
                            0.2259309888f, 0.4518619776f, 0.2259309888f, 0.1963121295f, -0.1000360623f, // Biquad Stage 3
                            0.2090389729f, 0.4180779458f, 0.2090389729f, 0.1816346198f, -0.01779049635f // Biquad Stage 4};

Once the coefficients where obtained, all I had to do in code was change the state variable length to 4*4 = 16 and number of stages to 4 as this is a 4 stage biquad filter implementation.
However this doesnt work! I have no idea as to why? There's no attenuation @ 20kHz should be -3dB down and at 40kHz should be a nice -100dB down but the picture says otherwise.
Oscilloscope pictures

CODE:
    #define ARM_MATH_CM7

#include "main.h"

#include "arm_math.h"

void init_Clock(void);
void init_I2S(void);
void init_Debugging(void);
void init_Interrupt(void);
void init_SpeedTest(void);

int32_t RxBuff[4];
int32_t TxBuff[4];
uint8_t TC_Callback = 0;
uint8_t HC_Callback = 0;

char uartBuff[8];
float32_t iir_coeffs[20] = {0.344617784f, 0.689235568f, 0.344617784f, 0.2994394898f, -0.6779106259f,
                            0.265586704f, 0.531173408f, 0.265586704f, 0.2307691127f, -0.2931158841f,
                            0.2259309888f, 0.4518619776f, 0.2259309888f, 0.1963121295f, -0.1000360623f,
                            0.2090389729f, 0.4180779458f, 0.2090389729f, 0.1816346198f, -0.01779049635f};

float32_t iir_mono_state[16];

float32_t inSample[4];
float32_t outSample[4];

arm_biquad_casd_df1_inst_f32 monoChannel;

void DMA1_Stream0_IRQHandler(void) {

    if (((DMA1 -> LISR) & (DMA_LISR_TCIF0)) != 0){
        DMA1 -> LIFCR |= DMA_LIFCR_CTCIF0;
        TC_Callback = 1;
    }

    else if (((DMA1 -> LISR) & (DMA_LISR_HTIF0)) != 0){
         DMA1 -> LIFCR |= DMA_LIFCR_CHTIF0;
         HC_Callback = 1;

    }
}

int main(void) {

    init_Clock();
    init_I2S();
    //init_Debugging();
    init_Interrupt();
    //init_SpeedTest();
    arm_biquad_cascade_df1_init_f32(&monoChannel, 4, iir_coeffs, iir_mono_state);

  while (1)
  {

      if (HC_Callback == 1){

         // GPIOA->BSRR |= GPIO_BSRR_BS3_HIGH;

          for (int i = 0; i < 2; i++){
              inSample[i] = (float32_t)RxBuff[i];
          }

          arm_biquad_cascade_df1_f32(&monoChannel, inSample, outSample, 2);

          for (int i = 0; i < 2; i++){
                TxBuff[i] = outSample[i];
            }

          HC_Callback = 0;

      } else  if (TC_Callback == 1){

        //  GPIOA->BSRR |= GPIO_BSRR_BR3_LOW;

          for (int i = 2; i < 4; i++){
              inSample[i] = (float32_t)RxBuff[i];
            }

                  arm_biquad_cascade_df1_f32(&monoChannel, &inSample[2], &outSample[2], 2);

                  for (int i = 2; i < 4; i++){
                        TxBuff[i] =  outSample[i];
                    }

          TC_Callback = 0;

      }

  }

}

Update 1: To show you how the coefficients are presented

UPDATE 2:
Tried doing it one biquad at a time comparing it to the bode plot in matlab as I go up a biquad and it works up till the 4th stage. Not sure if that helps.


texts:
I have this piece of circuitry that is supposed to protect a thyristor from spikes.
Is not clear to me how it is working and if the values suggested are ok.

The thyristor is a TIC106D
The trigger collect the signal from capacitive coupling with an high tension cable coming form an car ignition coil (about 14 kV), which waveform has very steep edges, so it need to be protected not to kill the thyristor.


texts: Controlling Servo motor SG90 from NodeMCU 1.0 development kit

texts:
I have a 5V "SG90 Servo motor" and would like to control it to move 0 degrees, 90 and 180 degrees, by sending it appropriate pulses from my NodeMCU Development kit.

Having searched on the net - I could not find a right example source on how to essentially program it.

Arduino IDE has some examples -but they are for Arduino hardware and not for NodeMCU/ESP 8266. ( I am using this to upload code to the NodeMCU )

There is a "sweep" sketch/program and I used/modified it a bit to suit the NodeMCU pin out, that did NOT work.
Hence reaching out to any engineers here who can share code snippet ( prefer python) and show how to control the Servo motor .

The Pins on the Node MCU I would like to use are D1..D4.
I have a 5V wall adapter from which I can power the Servo's Power ( Vcc) and GND pins.
The orange pin (i.e PWM ) on the SG90 Servo, is how I am trying to control the Servo from the NodeMCU's D1.. D4 pins.

Any help would be appreciated.


texts:
I was playing with qucs and noticed that capacitors are not simulated as I expected. I designed simplest circuit that illustrates that case.

AC Source: 2 Hz (2 times a a second)
Capacitor: 1pF
Simulation: 1 second

I expected to see different graphs on Probe 1 and Probe 2 BUT they are same.

Is it correct results? If not how do I get it to show correct results?
.. or how should I use qucs to simulate such circuit? (e.g. should I put some resistors)

PS I added 10 MOhm in parallel and it worked. Thanks @DaveTweed


texts: What determines the communication speed? is it the physical link's speed or the communication card speed?

texts:
Two IEDs (Intelligent Electronic Device),an electronic relay and a gateway, are connected with  Modbus RTU protocol over RS232.

In the relay's manual it states that a speed of 9200 bauds can be selected (typical for modbus serial)
In the gateway's Manual, I found that the communication card is rated at 115 kbps (actually I was considering two gateways, one with communication speed 115kbps and the other with 38 kbps)

My question is at what speed these two IEDs will communicate? is it 9600 bauds, or 115kbps (or 38 kbps)?


texts: Slow clock edge causing issues with D flip flop behavior

texts:
I'm trying to use a D flip flop and a pushbutton as a simple switch. My goal is this: every time I press the button, the output of the FF will switch state.

I put a circuit together in a simulator and it worked fine. I implemented a debounce circuit for the switch that works nicely on its own, with my scope showing a fast and smooth rise with no bouncing.

Essentially, I have the switch pulled low and attached to the CLK input. When the button is pressed, the clock is pulled high, triggering the FF on the rising edge of this signal.

The ~Q output is connected straight to the D input. When the FF is triggered by the clock, ~Q takes on the opposite value of D. Therefore, the FF should switch values on each button press. Because the FF is only triggered by the rising edge of the CLK signal, I don't have to worry about D changing faster than I can release the button. All good in theory (and in my simulator).

So I bought a D FF and hooked it up to my breadboard, attached my button and passives, threw an LED on the output and ... it's wonky. It would either turn on or turn off upon a button press, with a somewhat equal probability.

I examined the CLK signal with my scope and believe I found the culprit. As the clock edge falls, it reaches a certain voltage and then goes through a ton of small oscillations. It seems that these oscillations keep registering as "rising edges" on the CLK signal, which would rapidly change the value of ~Q (and consequently, D). I interpret this as the reason why I can't predict the output of the current set-up - because I have no idea how many dozens of oscillations occur during the falling clock edge.

Examining the ~Q / D lines shows similar oscillating behavior upon the CLK going metastable.

I've tried attaching capacitors on the CLK, D, and ~Q lines in all sorts of combinations to try to smooth out the behavior. Nothing has worked. It seems the metastable state is ruining my circuit, which I've read a bit about and understand it to be a pretty serious issue in digital logic.

Are there any tried and true methods to eliminate this metastable behavior? Or any suggestions to pull my CLK signal down hard enough that it doesn't want to oscillate?

Any suggestions are appreciated. I'll keep plugging away.


texts: How do I turn on a device with one momentary switch and off with another

texts: I've got this rev limiter I'd like to engage with one momentary switch and turn off with another (momentary) one. It would be turned on or off for extended periods of time. Ideally, this contraption wouldn't use electricity when the vehicle is turned off.


texts: Why are capacitor voltage ratings such strange values?

texts:
This is a similar type of question to this question about the use of the number 47.

I was looking at ordering some parts just like any other day and until now I've never really thought about it much, but I realised that the voltage ratings for capacitors seem really strange (to me at least).

The standard voltage ratings seem to be:

6.3 V
10 V
16 V
25 V
35 V
50 V
63 V
100 V
160 V

I've taken these values and plotted them on a graph to see if there was any correlation and it seems like there is an exponential correlation.

My actual questions are:.

How were these values initially decided upon?
Was/Is the voltage rating dictated by the material used and has just stuck over the years?
Are there any other components out there that use the same voltage ratings?


texts:
I'm using XDL file to analyze the bitstream of a spartan3e FPGA, I did the following steps:

I set up a single PIP for the XDL file and generate the bitstream file.
I set up a entirely empty XDL file with no PIPs in it and generate the bitstream file.
Compare the above two bitstreams bit by bit.

I do the above steps to all the PIPs in the FPGA to get a database of all the PIPs. however, when I tried to scan a normal FPGA design bitstream with this PIP database, I found inconsistency. for example: the following PIP:

pip CLB_X15Y7 OMUX2 -> BX0,

is not in the XDL description of the normal FPGA design, but all the 3 corresponding positions in the bitstream are "ON", which will cause a false positive detection of this PIP.

I feel very confused about this situation.


texts:
I want to make the same signal like the following images using an Arduino Uno. But I can't find the baudrate of this signal.
I calculated baudrate the same way as Wikipedia. But when I used the baudrate I got framing error.
The duration of the start bit: 0.2223 ms
1/ ( 0.2233 / 1000) = 4478 bit/s
What did I do wrong?

Update
The device has the following 4 pins.

VIN: 12 V
GND
GND
SIGNAL: 3.3 V

I don't have any documents like a datasheet or a manual. I think that it uses UART communication because there is only one signal pin.
I upload the logicdata file on my Dropbox account: Here!


texts:
I found that socket on a music device produced around mid 1970s in GDR and I was wondering what kind of socket it is. Unfortunately, someone painted the whole device, including the contacts. Therefore, I plan to replace the socket with an IEC-320-C14.

Additional Information

The device is a so-called "Kofferharmonium" (kind of a very big harmonica) manufactured by "VEB Klingenthaler Harmonikawerke". This page has some more information on it. The third picture shows the electrical internals of the device. My machine has no switch or regulator, but the motor is directly connected to the socket.

There is no schematic or any other hint on / inside the device.


texts: Why are always used N-Channel MOSFET on both High and Low side on BLDC applications?

texts:
As title, I always see an N-Channel MOSFET on both HIGH and LOW side of a 3-phase BLDC motor driver.

i.e.

Can you explain me why is better to use 6 n-channel instead of 3 n-channel and 3 p-channel?

p.s. In this case there isn't high side driver to PWM mosfets.


texts:
I cannot understand how the summation range has changed via substitution of m.

EDIT:

Full problem with solution (for context):


texts:
As the title says, I would like to interface an SJA1000 CAN controller to a Xilinx Spartan6 FPGA.

The SJA1000 has a shared 8-bit address&data bus with an address latch signal and either separate read and write strobes, or a read/!write signal and an enable strobe.  (ie. a total of 10 interface pins.)

The standard EMC interface core for the Spartan6 only seems to support separate address and data buses, as far as I can tell.

I probably could write something manually which implements the interface but before I go reinventing the wheel I wanted to ask about it -- interfacing to this sort of bus seems like it ought to be fairly common after all.

So is there some way to configure one of the standard Xilinx cores to serve as an interface to this device/bus type?  Or is there some other simple off-the-shelf solution?


texts: 15kV high voltage pulse generator circuit - how to have digital control?

texts:
First of all I'm fairly new to making a more complicated circuit.
I'm trying to make a PCB with an ATmega328PB chip on it. With that chip I want to control a high voltage pulse generator (arc lighter.)
Now I found the 15kV high voltage pulse generator that I want to use because of its size.
15kV arc lighter
I also found a schematic that can control this high voltage pulse generator.
Schematic of high pulse generator

I tried to make the same schematic for this forum but I'm not sure it is correct so please spare me on that.
This schematic is triggered by completing the power circuit.
Now I need some way to get this triggered by a high/low signal from the ATmega328PB (a digital signal if I'm correct.)

simulate this circuit – Schematic created using CircuitLab
Things I've thought of:
Adding a second MOSFET to the ground line.

simulate this circuit
Both schematics work that is the first thing. But with the second schematic,  once it is turned on it stays on. That is one thing I don't need. I've tried to do it with and without the pull down resistor but nothing works.
I'm sorry if some of the components in the schematic aren't right because the voltage or current they can handle but that is not what I'm trying to ask.
The only thing I want to know is how to control the on and off function of the arc lighter.
Thanks in advance if you need more info or I did something totally wrong please tell me because I need to learn a lot.


texts: How to ADD resistance with a push-button (Schematic Incl.)

texts:
Edit: New schematic, my apologies.

Background:
The circuit below shows a potentiometer "R1", which is not used until the normally open push-button "S1" is pressed. The second resistor "R2" is not used until the normally open push-button "S2" is pressed.

The orange square just represents a PCB I didn't design with components irrelevant to the issue.

Problem:
Obviously if both S1 and S2 are pressed at the same time, then R1 and R2 are in parallel. I need to make S2 increase the overall resistance even if S1 is currently pressed. The specific impedance is not too important, I just can't have R1 in parallel subtracting from the impedance of R2.

Basically I need S2 to override S1, either by somehow adding R2 in series with R1, or by having R2 replace R1 in the current.

Conditions:
S1 pressed: R1 only
S2 pressed: R2 only
S1+S2 pressed: at least R2 or both R1+R2
Default State: No current

Can this be done using only passive components and push-buttons?


texts:
I am looking to push a button and one led comes on when i push the same button again the first led goes off and the second light comes on. alternating lights each time the button is pressed.  one light should always be on.

I was hoping to use a microswitch as the button i want to use has a microswitch that i was going to switch.  Would this be a dpdt?  Does that exist in a latching pushbutton.  Any other  circuit ideas that would work?

I appreciate the input


texts:
In order to study the behavior of an RC circuit, I connected a resistor and a capacitor to an Arduino's I/O as shown:

The Arduino digital Output feeds the circuit with a square pulse of 2 sec duration. (one second HIGH, one second LOW)
for a charge time of 1 sec:
$$V_c = E(1-e^{-\dfrac{t}{\tau}}) = E(1-e^{-\dfrac{1}{0.83}})=0.7E$$
where E is the power supply voltage
Converting E value to a 10bit range, $$V_c = 0.7 \times 1024 = 717$$
Now, this is the graph I take from the analog input:

whose minimum value is 237 (0.23E), and maximum value = 784 (0.76E).
Assuming that the capacitor's value may differ a little, I may accept that 0.70E = 0.76E. But in that case, shouldn't Vc start from zero?
Assuming that the capacitor is semi charged, shouldn't in any case max-min=0.7E? (Before initiating, I discharged the capacitor connecting it with a resistor for several seconds.)
Any thoughts would be appreciated.
EDIT:
Using several values of charge time, every time the graph seems to be positioned in the middle, meaning Vc(min)+Vc(max) = E/2.


texts: A contradiction regarding flux conservation

texts:
Consider a simple circuit

Initially switch S was opened till steady state is reached and then it was closed. My understanding regarding inductors is that you can't have a SUDDEN change in current flowing through an inductor otherwise it would result in VERY LARGE (infinite) potential difference across it. (as the magnitude of time derivative of current will shoot to infinity!).

After switch S is closed, we're asked to find the current across inductor 1.
My teacher told me to apply flux conservation to find the current just after the switch S is closed. Flux conservation would say that current is suddenly changed as soon as switch is closed.

But how is it possible to have a SUDDEN change in current flowing across inductor 1, moreover I still don't understand exactly WHY flux is conserved.

Is my understanding regarding inductors wrong?

How to resolve this contradiction?
Why Flux is conserved?

EDIT: The flux conservation says that current will suddenly change because-

Clearly initial current (when switch S is opened and steady state is reached) isifferent from final (after switch S is closed).


texts: I am connecting 3 cells in series having 12volt each. So that I can acheive 36Volt as a output voltage. If i am charging these cells in series connected manner, which cell first gets charged? or all cells are equally chargerd? If first cell gets first charged mean, there is no current flow for next two cells. Am i correct? Please explain the charging operations of series connected cells...


texts: USB Type-C SMD connector PCB layout reference design

texts:
I am designing a board with a USB 3.2 Type-C connector from Molex, and I understand that at a possible 10Gbps, this design is going to need to be very well laid out.
Is there somewhere a reference design showing one example of the PCB layout around such a connector?
According to the whitepaper Managing Connector and Cable Assembly Performance for USB SuperSpeed:

System OEMs should get the optimized PCB launch designs from the connector manufacturer for their own PCB stack-ups.

Has anyone ever seen such a design from a connector manufacturer?


texts:
Being newbie to electronics, I'm unsure which SMD component to choose. I'm trying to build a step down voltage circuit using AMS 1117 (5 v to 3.3 v).

I want to know the SMD capacitor component (bypass caps) that I need to put across voltage regulator (AMS 1117). I know my voltage regulator's component ID : REG1117-3.3.

I think 10uF and 100uF would suffice across AMS 1117 voltage regulator. Can someone please suggest which to use?

EDIT 1: I want to power an ESP 12E using this.


texts: Error in third-party SPICE subckt of a MOSFET

texts:
I am simulating my circuit having a DMG1012T N-Channel MOSFET in LTSPICE XVII. My Circuit is given below:

However, after downloading the spice model of the MOSFET from this link and putting it in my schematics, the SPICE Software (LTSPICE XVII) shows this error

I tried to open symbol of mosfet included in standard library and found it's pins have been named D, G and S. I am not sure where is the problem and couldn't resolve it now. Please help.


texts: Solution for adding around 60V dc-offset on digital signal(0 and 5v) of 10MHz frequency

texts: I thought of using Opamp adder for this but the problem is high offset value which can saturate the Opamp. Can you please suggest some other solution ?


texts: Is there any way to comment a block in HSPICE?

texts: I know "*" comments the line. Is there any way to select a group and comment the whole block in HSPICE?


texts: How can I establish "frontiers" in the feedback resistor of an inverting opamp config, if I'm varying it with a pot?

texts:
simulate this circuit – Schematic created using CircuitLab

I replaced the feedback resistor of an inverting configuration by a pot. I'm meant to vary from edge to edge the pot so I can get a variable gain within -100 < A < -10 (I mean, without getting out from that range not even on the edges). Therefore, I need to fix the gain when the pot is at 0 Ohm and so for its max Ohm to avoid getting it greater than 100 times or minor than 10 times.

My first attempts were to put a resistor in series with the pot (both as feedback), later I tried with placing a resistor in parallel with the pot (again as feedback); at any case, I couldn't get the gain to be limited at 10, it tends to zero invariably.

What can you kindly suggest to me?

EDIT: opamp polarized with +12 and -12 V


texts: It's common to see 'solder mask' in PCB design. But sometimes, I see 'metal mask', such as in page 5 of this datasheet, does it mean I need to design a pad larger than the solder mask opening?


texts:
Could STM32S003F3 be flashed with SWIM interface only (SWIM, RST, VCC, GND, bare IC without any other elements)? I'm trying to flash it with ST-LINK/V2 and last version of IAR (Kickstart) and debugger reports that:

Errors while setting configuration with MCU name STM8S003F3: gdi-error [40409]: No answer from the SWIM: check chip connections and power supply; try a power on reset

So i'm wondering where could be the trouble :(


texts: Finding time constant for multi capacitor RC circuit

texts:
I need to derive an expression (with respect to time) of the current flowing through the short circuit. The capacitors are charged to some voltage value.

I know the solution but I am trying to understand how the time-constant of each capacitor in the circuit is determined only by the resistor in its branch. How come the other resistors have no effect?

I other words, how come the time-constant of C1 is 20uX100 and R2 and R3 have no effect on C1 time-constant?

simulate this circuit – Schematic created using CircuitLab


texts:
I have 2 stepper motors in my micromouse. Every so often one of the stepper motors will turn back one step. My set up is a PICAXE and a ULN2803A and to clock the pulses i just turn the outputs on or off on the picaxe. The stepper motors are back to back so if one is rotating clockwise the other must be going anticlockwise to make it go forwards. This leads me to powering my outputs using the following:

; Coil 1 of one stepper motor is output 0
; Coil 4 of one stepper motor is output 3
; Coil 1 of the other stepper motor is output 4
; Coil 4 of the other stepper motor is output 7
let pins = %10000001
wait 1 ;wait 1 second
let pins = %01000010
wait 1 ;wait 1 second
let pins = %00100100
wait 1 ;wait 1 second
let pins = %00011000

So why is it rotating backwards after 2 puleses? Have I got the coils the wrong way?
UPDATE:
I've just again checked that i have the correct coil numbers and this is correct. So the coils are the correct.


texts: How to determine the minimum proximity of magnet to an AC line for no electrical impedance?

texts:
As the title says, I am wanting to calculate the minimum proximity for a magnet to be near a AC line for no electrical impedance.

My scenario is this: I have a theoretical device like MagSafe (Apple's magnetic DC connector for laptops) however with one main difference, it would be with AC instead of DC. My understanding is that a magnet could cause the Proximity effect and create an electrical impedance.

To avoid the impedance but still use a magnet in close proximity in a "MagSafe" like device, I could simply move the magnet further away from the current. The part that I don't know is how to calculate the minimum distance required. I gather that I would need to determine the magnet's strength but I am unsure what other parts I need for the calculation (does the AC voltage matter for the proximity? can the proximity be affected by shielding the AC line somehow?).

The AC voltage in my case would follow the AS60038 standard (230v, +10% to –6% variation)

If this was a real device (rather than theoretical), I gather that I could simply measure the AC voltage etc and move a magnet around it to find out however I am curious how one could do this theoretically.


texts: Test 220V 50 Hz signal using oscilloscope

texts:
Can I test a direct electric signal wave AC 220V 50 HZ using an oscilloscope in safe mode and the schema for this testing.

The description in my oscilloscope say that the input AC pk and DC is Max 600V!?


texts: How was the design of active filter topologies arrived at, invented or discovered?

texts:
Active filters make use of Op-Amps. This can make it possible to avoid using inductors and get the same effect by "reversing" a capacitor. There are multiple topologies in existance for these active filters:

Chebyshev filter
Butterworth filter
Bessel filter
Elliptic filter

I can see that they have different role off and amount of ripples in pass band and stop band. What I do not understand is how these were discovered or invented in the first place. I fully understand passive filters made up of RLC. It is evident how they work and why they are the way they are. However, for the active filters it is not clear. Did the designers get a hypethetical transfer function first and then realize it in electronics?


texts: Loopstick (ferrite rod) antenna circuit model

texts:
A ferrite rod antenna circuit equivalent is usually given as so:

The numbers are made up, I didn't calculate the exact C you need to have to make it resonate at 1 MHz.
Here's a slightly more complicated model I found online that adds another implicit C, besides the variable one you add externally:

Here's my concern: no matter whether the LC is resonant or not, since it's in parallel to the "voltage source", it will be forced to take on its entire voltage.
I believe there should be a voltage division somewhere, so that if the LC (and the 10 Ohm wire resistances) are low impedance, most of the voltage will show elsewhere.

The above would work nicely.
I wonder what is the right circuit model for an ferrite rod (loopstick) antenna that demonstrates voltage division when the LC tank is out of resonance, and the voltage has to be captured outside of it ?
Is this a looptstick antenna as well?


texts: How can I trigger an LED with ultrasound

texts:
CASE:
I would like to trigger a few independent LED's wireless-ly as cheap as physically possible. It is simply a LED connected to a battery. (The LED-part must be cheap, the transmitter does not matter)
The best idea I could come up with was broadcasting ultrasound at an unhearable/minimal-interference frequency, such as 200KHz for example, and then trigger the LED "on" when it detects anything on that frequency band, else off. See simple sketch below:
It should turn on when the frequency is in a set range (180-220KHz). The transmission could be a simple sine wave.
I thought of using a really simple band-filter (like an FM radio design) but think that might be a bit expensive in parts? Could a simple coil work to trigger a transistor at a certain frequency or something?
Apologies for the poorly asked question, I am a bit confused as to what options I have in the electronic domain to implement this concept.
EDIT
The range will vary from 1 to 300 meters. Line of sight is not guaranteed so IR (which is easiest) is not an option.
The frequency could be anything, even in the range of FM, so it would act like a little radio receiver triggering the LED on if there is activity on that channel.
People I talked to in person suggested using piezo-sensors as receivers for the signal and then a PIC chip to process the signal and decide whether to be on or off.


texts: Common ground in low side current sensing

texts:
I've asked this question a while back and user/Transistor told me that the circuit will be floating and drift without a common ground, he suggested a virtual ground. but in this case we already have a ground connection between two voltage sources via 3 series resistor.
To measure current on the low side of circuit, do we still need to have a common ground between V1 and V2? Do the multimeters make a common ground with the source too?

simulate this circuit – Schematic created using CircuitLab


texts: I'm designing a power supply to deliver 6V DC with a zener diode acting as the regulator. I found out that there are two types of transformers that can be used. They can be center tap or a bridge. In center taps, we will use 2 diodes, while in bridge, we need 4. What are the pros and cons of each type and which is best suitable for my purpose? I think it's worth getting to know the advantage and disadvantage of using one or the other.


texts: Use Solid State Input Module for Output?

texts:
Below is a diagram of an "industrial" input module or also referred to as a signal conditional relay. Although it is dubbed an input module. Is there any reason I couldn't put a load between terminal 3 and terminal 4?  The load is a small device which draws approximately 200 mA.  My thought is that the DC power supply input Plus (+) of the device would be tied to Vcc and the power DC common (-) of the device to terminal 4.  Without a voltage on the field input (the off state), the logic output would be Vcc... so the device would not be powered since device's DC and DC common would be at the same voltage.  Unfortunately, the manufacturer does not supply the leakage current.
Thanks!


texts:
I have simple circuit with ada4891 op amp. I am using it to demodulate ASK modulated signal. But sometimes op amp is pulsing to ground for no reason. These pulses are short (about 1 us). I have oscilloscope up to 100 Mhz but I did not measured anything on input or in power supply rail. It just randomly jumps down. And now when I am measuring it again it is working normally, but I am scared it will start again. Could you help please? Do you know why it is happening? I have MCU 1.5 cm above. Could MCU somehow disturb op amp?
This is my schematics:


texts: Signal and power integrity - 4 layer board

texts:
Let's assume that we need to design Mixed signal PCB with 2 fast integrated circuits(tr_min = 1ns) operating at different voltage levels(3.3V and 4V). There are however other voltage levels on the PCB(5V, 12V) with low speed signals. Design must be done one 4 layer(i.e. sig-gnd-pwr-sig).

What voltage level should be used on PWR plane?

If i.e. PWR=3.3V then would return current path of the 4V high speed IC on bottom layer be GND or 3.3V PWR? I think it would be GND plane.
So if we keep PDN in mind what Rolf says then 6 layer would be more appropriate(i.e. sig-gnd-pwr-gnd-pwr-sig). According to Olin, we could remove PWR plane and used one GND plane as a return path for each and every signal on PCB. Therefore my stackup would be(sig - local gnd/sig - gnd - sig). I see some contradiction on those two approaches.

For further discussion, if some PDN tool is used to keep impedance below some value from i.e. 0-180MHz where should decoupling capacitors be located?

There are plenty of them, more than 60-70, so it's impossible to locate all of them near and around LQFP case. Is it OK to spread rest all over the board?

What are your thoughts?


texts:
I have a two battery banks on my boat.
The largest in terms of capacity is the house bank, which is made of deep cycle batteries that can be charged at up to 14.82V.
The engine start bank can only be charged at up to 14.7V.
My goal is to charge my house bank at the highest voltage in order to reduce engine run time, and without damaging my engine bank.
My plan is to charge the house bank at 14.82V and use a relay to combine the banks when the alternator is charging.
Can I use a diode with a 0.2V or so forward voltage drop? Would it require a heatsink?


texts:
I am monitoring a pushbutton with a microcontroller where I am trying to take care of four things together:

50-msec debounce upon push-begin and 25-msec debounce upon push-release
identify a short-press, defined as when button released within < 1 second
identify a long-hold, defined as when 1 second passes since button push-begin
sleep as much as possible when not doing anything else

Below is a short pseudocode of what I have implemented so far. I think it covers all of these cases.

Do you see any possible refinements or potential issues? (E.g., I am interested in any subtle cases that might be blindspots for my approach.)

Pseudocode:

Main loop {
  Sleep
}

Falling-Interrupt {
  Disable Falling-Interrupt
  Enable 50-millisecond-Debounce-Timer-Interrupt
}

50-millisecond-Debounce-Timer-Interrupt {
  if PushButton state is still LOW {
    Enable Rising-Interrupt
    Enable 1000-millisecond-Hold-Timer-Interrupt
  }
}

1000-millisecond-Hold-Timer-Interrupt {
  Register as Pushbutton long-hold
}

Rising-Interrupt {
  if (Time since Falling-Interrupt < 1000 millisecond) {
    Register as Button Short-press
  }
  Disable 1000-millisecond-Hold-Timer-Interrupt
  Enable 25-millisecond-Debounce-Timer-Interrupt
}

25-millisecond-Debounce-Timer-Interrupt {
   Enable Falling-Interrupt
}


texts: What is the correct European convention for annotating circuit diagrams?

texts:
I am compiling training material and would like to stick to the European symbols and convention in annotating circuit diagrams.

What is the correct way to mark currents and voltages?

I attach an example below showing possible annotations for the inductors.

Which annotation styles in this Circuitikz diagram is preferred or mandatory in Europe.  Can you provide a reference?

I also attach the Overleaf code for easy reference:

\documentclass{minimal}
\usepackage[european,RPvoltages]{circuitikz}
\begin{document}
\begin{circuitikz}
 \draw (0,2) to [short,i^=$i_1(t)$] (1,2) to [short] (4,2);
 \draw (0,0) to [short,f_=$i_2(t)$     ] (1,0) to [L, i_=$i_3(t)$, l_=$L_3$, v^<=$u_3(t)$](4,0);
 \draw (0,-2) to [short,f=$i_4(t)$     ] (1,-2) to [L, i^=$i_5(t)$, l=$L_5$, v<=$u_5(t)$](4,-2);
\end{circuitikz}
\end{document}


texts: what would happen if I used a rheostat in series with a motor to drop my 230v ac supply to 110v ac?

texts:
I realize that I would be running higher (a little more than double) current through the motor I'm just curious if it would damage my motor?

The motor is a 1 hp, 110V/60Hz driving a meat grinder.


texts: Cascode Current Mirror, Minimum output voltage

texts:
I can say that I understand simple current mirrors fairly well, but what i do not understant is the minimum output voltage requierd for the circuit to work properly...for the transistors to be in saturation.

Vout=V(D4).
Vds_sat is the saturation voltage of the transistor M2 and M4.
Vt is the treshold voltage.

Why is the minimum output voltage, on the drain of the M4, equal to the Vout_min=Vt+2*Vds_sat, why not only 2*Vds_sat?

From my perspective, separating the "output" and gorund (Vss=0V), there are only two transistors, both of whitch have a voltage drop of Vds_sat. Where does the Vt come from.

There is a second problem.

Vout=V(D4)

What is the formula for the minimum output voltage of a PMOS cascode current mirror? Is it just Vout_min=Vdd-(Vt+2*Vds_sat)?

Again, why or why not the Vt?

Thank you!


texts: NMOS Transistor Voltage Range For Specification?

texts:
I have a homework question I'm a little confused about. I was hoping for a point in the right direction. I am given the
\$K_n\prime\$ \$(400 \cdot 10^{-6} A/V^2)\$
and threshold voltage (0.4V) for an NMOS transistor, and told it should operate as a variable resistor (for small \$V_{DS}\$) between 200 Ohms and 1K Ohms. I need to find the range of \$V_{GS}\$ (maximum \$V_{GS}\$ already given as 1.8V) and the required width of the channel, W, knowing the the minimum channel length L is \$ 0.18 \times 10^{-6} m\$.

My approach thusfar is as follows: I assume it's a reasonable assumption that small VDS means operation in the triode region, since my given threshold voltage is 0.4V. Also, I could use the given upper limit of \$V_{GS}\$ in finding the parameters I need. So:

$$I_D = K_n\prime \cdot \frac{W}{L}(V_{GS}-V_t)V_{DS} - \frac{{V_{DS}}^2}{2})$$

But that leaves me stuck. I don't know VDS, or the current. I thought my reasoning for triode operation made sense, but if it is instead in the saturation region, that would spare me finding VDS, but with still two unknowns of the width and the current.

I feel as if I need to use the resistance values given in some way, but as I have not done a similar example before, I'm not sure how to incorporate them.

Any help would be greatly appreciated!