texts:
simulate this circuit – Schematic created using CircuitLab

I have this case where my V1 supply voltage is constant at 14V.

The C1 capacitor now charges up to 14V and assume my capacitor C1 is 35V rated.

But I have this condition where I need to check my circuit in case of high voltage say.

This is the pulse I need to apply.

My questions :

V=E.(1-e^((-T)/(R.C))) - This is the formula I use to calculate the voltage at the capacitor after 50us. If I plug in my values of R (2ohms - should in the circuit which represents the resistance mentioned in the pulse specification), C(123.2uF - taken considering ALL tolerances),E and T, I get a value around 20.937V.

I have a query. My capacitor is rated properly if I measure this voltage after 50us. Suppose I measure like instantaneously, say after 10us, my capacitor fails. Should I not measure after 10us? If not, why should I not measure after 10us?

If I measure the voltage before that 50us, the voltage is going to be higher than the capacitor rated voltage. It won't fail? Or is it very small time for the capacitor to handle or accumulate?

After 50us, my input V1 voltage goes back to 14V. But now my capacitor is holding 20.937V. What happens to this 20.937V? Assume I have connected a load across the capacitor. Does the excess voltage go to the load / source?
If I have a reverse protection diode between the source and the capacitor, then where would this 20.937V go when the input voltage has come back to nominal 14V?


texts: Trouble controlling LED strips with n-mosfets on 2 power supplies

texts:
I have 2 equal power supplies and I try to control LED strips using arduino and n-channel mosfets. I've split the strips between the supplies, strip A + arduino is on one power supply, strip B is on the other.

The problem is, that the other circuit is behaving randomly, and seems to be always open. I'm thinking if it's design problem. As arduino-mosfets for strip B are not on the same circuit (arduino is on different power supply, thus base is +5V on power supply 1 and it opens the circuit on supply 2). Is there a way to fix this without buying one big power supply (I cannot buy them here without waiting too long)?

Power supplies are the same: Meanwell LPV-100 (100W).
LED strips use 2x72W, so there should be plenty of power.
Mosfets are IRLB8721, from China. But they seem OK.

Thank you!


texts:
Hi looking for a manufacture part ID which matches the socket in the pictures attached.

Measurements are:-
inner black plastic diameter 12.5 mm
outer metal case 14 mm
metal screw nut (for connecting to the plug) 16 mm

It is a 3 pin connector with '1 2 3' written on the inner black plastic to identify the pins.

There are screw attachments for fixing each of the parts together. One is located under the metal screw nut. The other two are located to hold the cable grip together.

I have identified it to be a circular cable connector with an P68 SGS rating.


texts: How to get more info about promotional video mini-board

texts:
As a promotional stunt, a content delivery network firm I won't name here, mailed a booklet that contained a small display that automatically started a video when opening the cover.

I was unable to temper my curiosity.

To the back of the display is a board with just 3 IC's, I would guess:

one labeled E200, which might be something like this one: Power Architecture e200 z0 Core
flash RAM
a video/audio controller (since it sits right on the strip to the display).

The printed text on the back of the board reads:

SY_AK2005
A_V1.2
2013/04/25

Is there a way to get more information about this set-up? There's a mini-USB port, is it only for charging the battery, or could I interface with the software/firmware on it or flash alternative firmware on it?


texts:
I am using this DC-DC buck converter.
Schematics :

Buck converter specifications :

Input voltage - 18V to 32V
Switching frequency - 300kHz
Output voltage 9V
Load current - 0mA to 200mA maximum.

When measuring the inductor leak current, I get the following waveform:

Can someone tell me what causes the glitches circled in red in the inductor peak current waveform?


texts: How much time to wait before sampling new data from soil moisture sensor?

texts:
I am working with some cheap soil moisture sensors, as the ones on the picture below.

One of the problems of these kind of sensors is that they must not be powered on at all times. If you neglect to do so and leave them powered up at all times, electrolysis will take place and corrode the anode probe, thus releasing unwanted materials into the soil that you are probing.

To overcome this problem I intend to keep the board without power until the system needs to acquire new data.

This is the schematic of the board:

My question is, how much time after powering up should I wait before the voltage from the A0 output is stable?

The RC constant of the 51K resistor and the A0 capacitor is 5.1 ms. Should I at least wait 5.1 ms?


texts: is a voltage regulator required for atmega328p when powering from boost converter at a set voltage?

texts:
I know that linear voltage regulators are more accurate at holding the required voltage but the boost converter i am using seems to keep a pretty steady one. the voltage will of course be within the chips requirements.
what would be the main drawbacks of not using one?


texts: Can voltage regulators deal with negative output current?

texts:
Let's say I have a supply of 12v, and a 7805 5v voltage regulator. If we use this 7805 between the 12v and GND we get an additional 5v line. Now can we use the 12v and the 5v to power a load that requires 7v (=12v-5v)?
I'm asking because this would mean that 7805 has to deal with current going in the opposite direction than in the more "usual" circuits. If this is possible, does that hold generally for most voltage regulators or is that highly dependent on the particular model?


texts:
I'm doing a practice problem from https://6002.catsoop.org/F19/ex11/mechanical_analog

The problem is as follows: A mass m = 10 kg is at rest on a horizontal plane with viscous friction coefficient B = 20 N-s/m (which creates a damping force proportional to the velocity \$v_m\$). A short impulsive force of amplitude 200 N and duration 0.01 s is applied

The electric circuit analog is as follows:

Ultimately, I want to find what the voltage across the capacitor is(aka the velocity). I'm planning to use the formula for RC circuits:
$$v_c = v(final) - [v(init) - v(final)]e^{-t/\tau}$$
where \$ \tau = m/B\$ in this case
Substituting in values, \$ \tau = (10kg)/(20Ns/m)\$
Now all I need to do is find \$v(init)\$ and \$v(final)\$

A capacitor is going to look like a short at the very beginning so the voltage across the capacitor is going to be zero, \$ v_c = 0\$ while a capacitor towards the end will look like an open circuit. When the capacitor is an open circuit, the voltage across it will just be the voltage across the resistor. So,

$$v_c(final) = F*\frac{1}{B} = 200N * \frac{1}{20} = 10$$

As a result, my answer should  be

$$v_c(t) = 10 - 9.8*e^{-2t}$$

However this doesn't seem to be the answer, where did I go wrong?


texts: Difference between electronic component and passive component

texts: I am confused about the difference between a passive component like resistor and an electronic device like diode. I know about their functionality. But my question is why resistor is not called an electronic device? Because as far as i know, resistors deal with electrons so do diodes.


texts: How to calculate the total resistance of this electrical circuit

texts:
I'm a programmer and I'm making an Artificial Intelligence for a boardgame called Hex. Since I am not that familiar with electrical engineering, I need your expertise on this subject.

I am now working on the evaluation function of the board. I have represented the board as a graph, since that is what a computer needs as input. But in this case you can also see it as an electrical circuit. The circuit usually looks like this, only then 11x11 hexagons:

The edges/resistors are all either 0,1 or INF (infinity).

My goal is to give a score to the board. I want to apply an electrical voltage to the two boundary opposite nodes and then check the total resistance between them.

I have made a possible scenario on a 2x2 board. The dots are nodes, the edges are resistors, the numbers the resitor values, and the arrows are my current-stream assumptions:

So the way I understand it is, I have to do something called nodal analysis. So i made for each node an equation where the voltage going in a node is the same as going out. So here are the equations I made:

$$V1 :  \frac{(V1-V2)}{0} + \frac{(V1-V3)}{1} = 10  $$
(From what I understand the voltage source number doesn't matter so I picked 10).

$$V2:\frac{(V1-V2)}{0} = \frac{(V1-V3)}{1} + \frac{(V2-V4)}{1}$$

$$V3: \frac{V1-V3}{1} + \frac{(V2-V3)}{1} = \frac{(V3-V4)}{2} + \frac{(V3-V5)}{\infty}$$

$$V4: \frac{(V2-V4)}{1} + \frac{(V3-V4)}{2} = \frac{(V4-V5)}{\infty} + \frac{(V4-V6)}{1}$$

$$V5: \frac{(V3-V5)}{\infty} + \frac{(V4-V5)}{\infty} = \frac{(V5-V6)}{\infty}$$

$$V6: \frac{(V4-V6)}{1} + \frac{(V5-V6)}{\infty} = 10? $$
(I assume the current leaving out here is 10, but I'm not entirely sure)

So with some algebraic manipulations I put the numbers into a matrix, where the voltages are the variables ofcourse: (I also assumed dividing by zero is the same as multiplying by Infinity, I don't know if that is the correct way).

$$\infty -\infty  -1   0    0    0   = 10$$

$$\infty -\infty  1    1    0    0   = 0$$

$$1    1   -2.5  0.5   0   0   = 0$$

$$0    1    0.5 -2.5   0   1   = 0$$

$$0    0    0    0    0    0   = 0 $$

$$0    0    0    1    0   -1   = 10 (?)$$

If you solve this you get:

$$V1: NaN  $$
$$V2: NaN  $$
$$V3: 0.05 $$
$$V4: 0.05 $$
$$V5: 0  $$
$$V6: -0.05$$

I have two questions now:

1.Where is my mistake in? (because I don't think voltages can be NaN or negative)

2.If I calculated these voltages correctly, how do I then compute the total resistance?


texts: Why is the voltage across the depletion layer higher than the reverse bias voltage across the diode?

texts:
So if I apply a reverse bias voltage across a diode, the voltage across the depletion layer is the sum of the voltage across the depletion layer at 0 bias voltage plus the reverse bias voltage as the figure b in the image shows.

What I do not understand is that if I apply a (reverse bias) voltage across the diode, given the only 'resistive element' is the depletion layer, all of the voltage should drop across the depletion layer hence the voltage across the depletion layer should be equal to the applied voltage. So why instead is it equal to the applied (reverse bias) voltage plus the barrier voltage at 0 bias?


texts: I came across the concept of analog and digital signals in my data communication course. We studied that analog signals are continuous signals and teacher presented a diagram like the sine wave and that digital signals are discrete; He showed a diagram of digital signal too. I am not an electronics student but I would like to know how these signals are generated and what is meant by continuous and discrete signals in reality. Please tell me something more about these signals.


texts: 32 Bit Increment Circuit and Verilog Program

texts:
I have to build a circuit that stores a 32-bit number. The circuit features a control signal inc that, when active, increments the stored value by 3 in each cycle. If inc is 0, the circuit simply stores its current value without modification. The input clock governs the state transitions in the circuit upon each falling edge, the input clear is used as an asynchronous reset for the stored value, the input inc is a control signal that activates the values increment and the output value is a 32-bit signal that can be used to read the stored value at any time.

I have no clue how to make a circuit diagram for this, but here's what I have for the verilog code so far:

 module increment(input clock,
             input clear,
             input inc,
             output [31:0] value);

     reg [31:0] value;

     always @ (posedge clock or negedge clear)

     if (clear) begin
        value=32'b0;
     end
     else if (inc == 1) begin
        value = value + 2'b11;
     end
     else begin
        value = value;
     end
endmodule

Would this make sense given the parameters? Any help on how to make a circuit out of this?


texts:
I would like to upgrade a software simulator from DDR4 to DDR5. I was looking for a document that describes in detail the changes of the DDR5 standard but I couldn't.
Is there any source that explains in detail what changed and what is new (e.g., RFM command)?


texts:
The specs of TI TLC5944 LED driver says "constant current sinking"  capability is 60-mA.(LED Power supply voltage up to 15 Volts, and Vcc=3.0V to 5.5 V )

My understanding is if Sink current is low, then its better as it will not heat-up my LED driver chips.

1- I want to understand What is the importance of High (or Low) LED driver Sink current?

2- Why we do not talk about sourcing Current instead?

Any comments?


texts: I'm working on a project which will contain lots of smaller modules written in VHDL, how in quartus can I make this manageable also to the point that I can test the smaller modules. I am trying to implement the DES encryption algorithm in VHDL, and for example one of my modules is the initial permutation. How can I achieve the unit testing of all my modules?


texts: Optimal voltage range for A/D Conversion

texts: Why the voltage corresponding to the ADC  result of 25 is 1.07 v (for a 10 bit A/D converter with a low reference voltage of one and high reference voltage of four) shouldn't the A/D conversion result be as it is , meaning 25 volts? In the manual it says  the ADC result is more accurate if the value of the analog signal covers the whole voltage range from VRL to VRH.


texts: Modifying a Boss DS-1 Distortion pedal, possible lifted pads

texts:
My apologies if this is in the wrong place, seems like the people on this section would know what to do in this situation. I am brand new to circuit bending and electronics work in general, really starting to realize how much of an art it is to do things right.

The first project I decided to tackle before messing with the board on a Roland TR-505 drum machine I have (I will need to be much better with my soldering) is the Keeley Mod for the Boss DS-1. Well documented so it seems like a good start. ANYWAYS...

I started desoldering (Using a chisel tip, 40 watt iron and a desoldering pump) and was running into constant problems using the pump. I'll be getting a wick soon, but in the process, a few pads have lifted, exposing copper (but it doesn't look like it exposed the board itself). Is there an easy way of fixing this? I've heard scraping away the guard on a little bit of the tracing and soldering to that is a standard fix.

Also, one thing I have heard is to always be careful around the IC chip. I haven't touched it with my iron, just removed a few caps and resistors nearby. I kept touching the IC chip to see if it was getting warm, and at a point it was (but not hot, just a light warmth). How do you guys know if something like that is fried until you are totally done with your modifications?

Thanks


texts: I found that my heat sinks are not large enough for the surface it is being used on, so I am wondering how to connect multiple to each other. My goal is to connect 4 side by side to each other, and to possibly stack one on top of the other as they are very thin. The question is, what material can I use to do this while still maintaining full conductivity? If I stack two on top of each other, but just use glue to connect them, I fear that the stacked one will not be conducting the full amount heat capable as the glue will interfere. What can I use to properly do this?


texts: Mini jack microphone only works in headset

texts:
This is so weird. I have never seen anything like this before. I have a Kingston HyperX headset. The microphone is detachable and looks like this. When I plug this directly into my PC or USB adapter (with a mini jack for microphone), it does not detect any sound what so ever. Literally none.

However, when I plug it into the headset and use the mini jack from the headset, it works just fine. This makes me think that Kingston did something weird with their wiring. I spliced open a mini jack I had laying around, and I tried hooking it up directly to the microphone, but no matter which combination I tried, I couldn't get any sound. I set Windows to listen always, so I heard a lot of jittering and buzzing when I accidentally shorted them. It works just fine with the headset, though.

So this is basically what it comes down to:

I hope that makes sense. The headset is not powered by USB or anything. How do I make this microphone work in a regular AUX/mini jack port, so I can "ignore" the headset?


texts:
Oli used this circuit

in an answer, and it pops up a lot on Google images too. But does it work? If it does a theoretical explanation will be welcome.


texts: How to mount pcb with IEC320-C14 power entry connector inside enclosure

texts:
I am making a PCB which has one IEC320-C14 and one IEC320-C13 connector on it (Like this one). The PCB will be quite small, just large enough for some sensing circuitry; between 5 and 8 square inches. This PCB senses the presence or absence of power, and switches power with a relay.  It will need to switch up to 6 Amps of 120VAC power. I'd like to get better than IP45. This will be inside a larger case (IP24 rated) that's exposed to the elements 24/7.

I want to have this PCB inside an enclosure with a single removable faceplate. I plan to put the C14 plug into the face plate, screw it in, solder it to the pcb, and then put it inside the case and secure the faceplate. Below is a cross-sectional "cartoon drawing" of what I'm describing.

The problem now is that the PCB is just dangling there inside the case.

If I solder the C14 plug to the PCB and then screw the PCB to the inside of the case, then the faceplate cannot go over the plug (it hits the flange).

If I assemble the faceplate + plug, then mount the PCB, it's impossible to then solder the plug into the PCB.

What's the "industry correct" way to use these C14 plugs with flanging?  Is it ok to just leave the PCB dangling inside the enclosure, attached only by the plug?


texts: Is there something wrong with the circuit below?

texts: I have built a 2 bit counter, so it normally counts from 0 to 3, but I want it to count up to 2. I have added a hex display and I can see 3 displayed there. The circuit is below:


texts: I have a keypad circuit, when I press and hold a key, the signal "key_pressed" is always high, as long as I keep the key pressed, which is normal, when I leave it, it gets low again. But I don't want this signal to be constantly high, no matter how long I press the key, I would like to be detected as a single short press. In other means I should find a way to set this key_pressed to low after lets say 10ms. I'm doing everything in VHDL, no resistors capacitors... I also can't wait for a falling edge then it makes no sense, no key will be displayed on the LCD until the key is released which does not make sense.


texts:
I have a seemingly simple question but I've been doing a lot of searching and can't find an answer.

What is a simple or standard way to achieve a 90 degree phase shift of an RF signal in the frequency range of ~1 MHz up to a few 10s or 100s of MHz? In the minicircuits catalog I see Hybrid couplers as low as 25 MHz so I would say 25 MHz and up is covered (though I don't know the cost) so the question can be narrowed down to how to achieve a 90 degree phase shift for a signal below 25 MHz?

In particular, in my specific application I have a signal which can be fixed in the range of 1-3 MHz that I would like to shift by 90 degrees. The 90 degree shifter doesn't need to necessarily need to work over a very large frequency range.

Ideas that I think would work but I don't know how well:

putting in a time delay with a length of cable. This is a bit inconvenient because it's a long length of cable (~10 m or more) and I don't have incremental control over the phase shift.
Put the signal through the stop band of a filter. This will give it a 90 degree phase shift but unfortunately it will also necessarily suppress the signal amplitude by a lot.. I've only thought about the case for a simple single pole filter
Digitizing the signal, somehow implement the phase delay digitally, then re-synthesize an analog output.

It seems like this should be something not too difficult, but in terms of commercial solutions I have only found products for higher frequency ranges. I can't tell if I can't find what I'm looking for because it's something so simple it's just not sold or if I'm searching for the wrong things or if there is some genuine difficulty with what I need. Any tips are appreciated!

I am asking for potential use in a modulation transfer spectroscopy system in which I need to generate a phase modulated (at ~3 MHz) signal at 80 MHz and then subsequently demodulate to extract the phase quadrature of a new signal generated at the modulation frequency. Both the phase modulation and phase quadrature detection could be done with the assistance of a 90 degree phase shifter and mixers.

edit: Clarification. I do NOT need a wideband phase shifter. I am curious about a general technique which could be used to phase shift a narrow band signal whose carrier may be anywhere in the range from 1-100 MHz. That is, say I have a narrowband 3 MHz signal. How can I give this a 90 degree phase shift? Say I have a narrowband 80 MHz signal. How can I give this a 90 degree phase shift? I do not need a wideband phase shifter. Apologies for the confusion. If different techniques are suitable for different frequencies within the range I have indicated then that is ok. I am at present most interested in a way to give a 90 degree phase shift to a signal which is like 3 MHz.


texts: How hot can a dremel get during normal operation and what happens if it stalls? I use a dremel 200 at home and when it's been running for longer periods of time (5 min continious) I notice that it get's hot and seems to run faster.


texts: How do I calculate the resistor R2 in this current limiter?

texts:
How can I calculate the resistor R2 of the above circuit?

I know how to calculate R2 to control the base of Q2 but I don't know what I have to do to take into account the current from the collector of Q1.

I must keep the current consumption low.


texts: Why do voltage regulator ICs have big ripple rejection ratio?

texts:
The LM7805 voltage regulator has a ripple rejection of 73bB (minimum is 62dB.) My textbook says that this gives a tremendous advantage because we do not have to use any bulky
LC filters in the power supply to minimize the ripple.
I don't understand how this IC can reduce the ripple that much.
A sample of the internal circuitry of LM7805:

I don't see any block that will act like a filter capacitor for the input voltage to reduce that ripple that much.
Why do voltage regulator ICs have such a big ripple rejection ratio?


texts: Op-amp astable multivibrator with single supply

texts:
I want to create a simple circuit to flash a LED with one op-amp. I already simulated the circuit  (astable multivibrator) but there is one problem with the supply. I don't know what to change so that it works for single supply. However, when I use dual-supply it will burn my LED when placed like on the circuit below. The output will oscillate between 10V and -10. Unfortunately, -10V is below the max. allowed voltage for an LED (which is maybe 5V?).

I have two questions now:

What would I have to change when I want it to work with dual-supply (currently it would kill my led)?
How do I need to change the circuit to get it work with single supply?

Thank you!


texts: How to design a switching circuit with minimal voltage drop?

texts: I am using a high side switch with BSS84 MOSFET. This is used to power on and off all the sensor and actuators during deep sleep of the uC. All the sensors are working except the SG90 servo. There is a.vpltage drop from ~3.26V to ~3.04V. Which MOSFET could I use which has a low droupout voltage? Would IRLML2244 fit for this purpose?


texts: Will my circuit charge the battery and power Arduino?

texts:
I am currently attending High School, so I don't expect too much here. I simply want to know all the recommendations for this circuit (Capacitor values, etc).

But I mainly want to know if this circuit will take 120V AC and charge a battery in parallel with the load which will be a future bare-bone Arduino circuit.

NOTE: Bridge Rectifier Will Be A NTE5326.

Circuit Image:

Data Sheets:

Mcp73831
LM2576
NTE5326 Bride Rectifier


texts: Capacitor Maximum Frequency of Operation

texts:
The correct answer is 760kHz.

My Solution is:

First find self-resonant capacitor frequency.
Self-Resonant Frequency = 1/(2pi*sqrt(LC)) = 758kHz.
From our second condition, we have that the capacitor must be operated less tahn 75.8kHz.
Capacitor Impedance 1/(2*pifC) > 10r, this leads to f < 72kHz.

Thus, I take the lower of these two conditions. Hence, my answer is 72kHz. What am I doing wrong?


texts: How to power an Attiny from AA batteries?

texts:
I am working on a project where I would like to power an RGB Led in a ambient light situation. I have prototyped this using an Arduino Leonardo and the led. Currently the project is plugged into the USB port of my computer, however I would like to use an Attiny 45 or 84 and AA batteries. I was originally thinking of using 3 AA non rechargeable batteries which would provide about 4.8 volts when fully charged. The issue is that the voltage will drop over time and I would like the led to be a constant brightness. A voltage regulator came to mind, but it would need to be efficient since I would like the batteries to last quite a while. I looked at some but was not sure the best one for my situation.

The led I am using is from SparkFun - SparkFun RGB led.

Another route would be to use two AA batteries and a step up board like is here SparkFun 3.3v breakout but again battery life is in question. I am not sure how to calculate battery usage through a step up board.

Long battery life in this situation means it would last for weeks, maybe months, of on and off use. I may be asking for the impossible with only 2 or 3 batteries though.

So my questions are would one of these options be better than the other? Would the brightness not change that much with 3 AA batteries and no voltage regulator? Would the batteries last a long time with the second option? Is there another option I have missed?

I am new to the hardware side of things, so any help is much appreciated!


texts: How to enter into ISP mode through 'reinvoke ISP' in LPC1759

texts:
In LPC1759, I entered ISP through "reinvoke ISP" with the following steps

Disable PLL
Reset timer 1
Re-map interrupt vectors
Set watch dog timeout
Reinvoke ISP

After entering into ISP, What exactly happens in the controller?
How to check if it is in ISP Mode?
After entering ISP, How to get out?

void init(void){

Chip_Clock_DisablePLL(SYSCTL_MAIN_PLL, SYSCTL_PLL_CONNECT);

Chip_TIMER_Reset(LPC_TIMER1);

Chip_SYSCTL_Map(REMAP_BOOT_LOADER_MODE);

}

int main(void)
 {

uint32_t wdtFreq;
wdtFreq = Chip_Clock_GetPeripheralClockRate(SYSCTL_PCLK_WDT) / 4;

init();

Chip_WWDT_Init(LPC_WWDT);

Chip_WWDT_SetTimeOut(LPC_WWDT, wdtFreq / 10);

Chip_IAP_ReinvokeISP();

DEBUGSTR("HELLO\n\r");

return 0;
}


texts:
I am having some troubles to simulate a Buck converter in LTSpice.
I added a picture of my schematic in which a use an IGBT (IRGP20B120U-EP from International Rectifier) and a fast recovery diode MUR8100E (from On Semiconductor). The diode current is green and the IGBT current is blue.

As you can see, the reverse recovery current of the diode is really enormous. It's a peak higher than 150 A, when the 'normal' current (I mean after the reverse recovery time) is about 5 A.

I am not that familiar to simulating circuits with LTSpice so is it possible that I am doing something wrong? If noticed that if I increase the gate resistance, the peak becomes a little bit smaller. Probably because the gate capacitance charges more slowly.

Is there anyone who could tell me how this is possible because the peak current seems too high for me, which means that my simulation is not really realistic.

: LT Spice files


texts: How does the voltage difference develop when MOSFET is biased with Current Source?

texts:
I have a circuit in LTSPICE which is performing as desired but I could not understand the working of it. Basically I have an NMOS circuit shown below (fig a):

Here are some values which I calculated previously for this specific transistor: (By DC sweep of Vgs at Saturation condition(Uds>Ugs-Ut)):

When Vgs=0.8V, Id=63uA
When Vgs=1V, Id=104uA
When Vgs=1.2V,Id=151uA

Now, If I wanted to do current biasing, I set the current (current biasing) and get the corresponding Ugs in the same Transistor and then would distribute this Ugs to a nearby transistor for biasing (voltage biasing). I am not sure if this links with the concept of current Mirrors.

The concept which I am not able to understand is "How does the Transistor develop the Ugs with given current?" More specifically, in the given schematic, How does the Vgs(=0.8V) gets developed automatically with the given current of 63 uA) - This seems obvious if I link the calculated value at 0.8V to be 63 uA but I am not able to understand how this voltage is getting developed by MOSFET.

Is it like, when we are sending a specific current to the transistor, the transistor then sets up a resistance (Equal to Vgs/Id) and creates this voltage at Gate?

So, in MOSFET at saturation region, the internal channel structure looks like: (fig b)

In the above circuit, Vgd=0. So, as per this post, Why MOSFET Pinchoff occurs, even though the channel is not formed at the Gate-Drain point, there is no restriction on current flow. So, is the voltage getting developed due to the shape of the channel (More at Source and less at Drain)?

Now, the KVL should be, Total voltage, Vt=Vgd+vgs. Since Vgd=0, Vgs=Vt-(threshold voltage)?. So, in the whole, I see that the MOSFET is acting like a resistor (whose value changes as per the current driven) or like a medium which allows current in a specific manner (slope in the p-substrate in the fig(b)) that creates a Gate-source potential with the given Id.

Is the above analysis correct? or Am I missing something? (And to the curiosity, why the source current has a negative direction?)


texts: Baseline PIC 12F508 Delay Loop Goto Instruction

texts:
I have been experimenting with a PIC 12F508 and have just begun writing my own delay loops in assembler. Nothing fancy yet just toggling an LED connected to GP1 (set as an output) on and off to verify the code.

I finally got my loop to work but I don't understand why it has to be written a certain way for it to work.

I have copied part of the code that doesn't work below I omitted the input / output TRIS setup and configuration bits for clarity.

When the code is written as it is below and dly4 loops back on itself the LED doesn't flash it just stays on solid.

I can't understand why this is because according to the datasheet after the variable count4 reaches 0 the goto dly4 should be skipped. The next instruction goto main_loop should then be executed which returns to the start of the code toggles the led again and the process repeats.

main_loop

movf    sGPIO,w
xorlw   b'000010' ; toggle LED on GP1
movwf   sGPIO
movwf   GPIO

movlw   .80
movwf   count
movwf   count2
movwf   count3
movwf   count4

dly1    decfsz  count,f
        goto    dly1
dly2    decfsz count2,f
        goto    dly2
dly3    decfsz count3,f
        goto    dly3
dly4    decfsz  count4,f
        goto    dly4
        goto    main_loop
END

To make the code work I have to modify the goto at the end of the loop from:

goto    dly4   to    goto    dly1

Why would I want to go back through all four loops again? Wouldn't decrementing the variables from 0 by going through again reset them to 255? Even though the code works with the modification above I can't understand how the loop is even being exited.

Thanks For Any Help In Advance.


texts: Circuit analysis of active LP-filter with 2 OP amps

texts:
So this is our diagram:

We want to find C1, C2, R1, R2 so that our frequency cut-off is 1kHz.
We also need to have R2C2 = 2 * R1C1.

So, my first instinct is to:

Use KCL nodal analysis
Set C1 = C2 and R2 = 2* R1
Somehow calculate the values of the components involved with the characteristics of the filter V_out/V_in and the given cut-off frequency of 1kHz.

Right now I'm stuck at the part with the nodal analysis. I've never tried nodal analysis on this kind of diagram before, so I don't know if I've done it correctly. I end up with a very messy result, especially when I replace my Z1, Z2, Z3,Z4 with the 1/jwc etc. I've set Z2 = z4.

Have I done this analysis correctly, or is there something I missed? Where do I go from here so that I don't get a hairy equation for V_out/V_in?


texts:
UPDATE

I've provided a full outcome report in one of the answers below with an updated schematic and description of the operating principles as I've come to understand it.

I'm studying switching converters to feed a strange craving to understand how
they work. I'm just getting to the part about off-line AC-DC converters in the
books, but being a practical sort, I thought I'd open up one I have handy and
see what I could explain so far.

Here's what it looks like after opening:

And here's the schematic I reverse-engineered from it:

[click to expand]

Here's what I think I understand so far. All component labels are as printed on
the PCB:

C1 gets charged to roughly 170V DC by the line bridge rectifier and supplies
the input current.
B1 is the transformer (no idea why it's not T1). B1P12 is the primary winding
terminating at pins 1 and 2. I believe this is the main primary
inductor/winding.
R3, C3, and D7 comprise a snubbing network for the main inductor. The "R1A"
designator signifies a "rectifier-style diode, about 1A in size". I'm not
able to see the markings without desoldering it, which I wanted to postpone
for now. Also, given the provenance of the other parts, I'm not sure I'd
discover much.
R6 provides base current for U2, the main switching transistor (a TO-220).
U1 is a base driver for the main switch, shunting base current when turned
on. This is a TO-92.
Moving to the output, D10 (LED) and R11 provide indication when output
voltage (nominally 12V) is present on the output.
C8 is the output capacitor.
B1S (secondary) is the only secondary winding and pulls current out of the
negative end of C8 during the off stroke, providing the output energy. D9
blocks reverse current through the secondary.

Here's what I don't understand yet:

There's no clock/oscillator. How the heck does it switch periodically? The
only thing I can think of is some resistor and capacitor make up an RC
circuit or something.
What does B1P34, the second primary winding (on pins 3 and 4) do? I've heard
of these being used to power a \$V_{CC}\$ rail, but there are no ICs in the
circuit to power. Maybe it provides bias current for the opto and base driver
or something?
I expect that D11 is a zener, maybe 11.5 V or something. I can't tell by
inspection; it just looks like a signal diode package. But it makes sense to
me in that location to turn on the opto when \$V_{out}+\$ goes above 12
V or so. I don't get what R10 does though.
I also don't get what C5 or C7 do, but I've probably asked enough.

Can a more experienced eye help me decode some of this?


texts: WS2812B strip glitches or flickers. What's the cause?

texts:
I've rebuilt the Project Piano LED Visualizer but I'm experiencing some issues with the LED strip that I don't understand.
I'm using a 10A/5V power supply to power a strip of precisely 180 WS2812B LEDs while powering the Pi-Zero seperately with an "adequate phone charger".

simulate this circuit – Schematic created using CircuitLab
At first, I used 0,3mm solid Wire for GND and the PWM-pin, which worked fine, the LEDs lit up and everything was good.
Until the wire broke, because it was quite fiddly and bound to break given the necessity of mounting the project to a Piano.
So I changed the wiring to a 0,5mm stranded wire, which is more flexible and thus made positioning and such way more easy. I also made it a bit longer to better position the pi, so the wire has about 30-45cm of total length (more guesswork as I'm currently not there to check)
However, when hooking everything up, the played notes lit up correctly with an "extra LED" along with slight flickering.
Before only a single LED lit up as it should.
A short clip of the problem
The problem appears to be worse when white-color is used then when a single color is used.
The functionality still was ok, but the glitchy behaviour was odd and also not constant on every note played. That randomness also makes it a bit distracting.
I was wondering...

..does this come from the stranded Wire?
..is there some other error in the setup, that's been overlooked in the project?
..is it the length of the new Wire?
..is it a problem in the programming?

I should mention that this project includes a HAT for controlling the strip:

Waveshare LCD TFT 1,44'' 128x128px


texts:
I found that inVerilog, the array can only be declared in reg.
And I found that it seems like if can only work in for loop such as

integer i;
reg [3:0] a [0:3];
for (i=0; i<5; i=i+1)
a[i] <= i;

what if I want to run in case?

module testrun(

input [7:0] b,
input clk, rst,
output reg [7:0] c , d, f

);

reg state = 0;
reg [7:0] a = 5;

reg [7:0] e [0:128];

integer i = 0;
//reg [7:0] command = 0;

always @(posedge clk, posedge rst)
begin
    if (rst)
    begin
        c<=0;
        d<=0;
    end

else begin
    if (state == 0)
    begin
        case (i)
        i: begin
                e[i] <= a + 1;
                f <= a + 1;
                c <= e[i];
                i <= i + 1;
                a <= a + 1;

                state <= 1;
            end
        endcase
    end

    if (state == 1)
    begin
        d <= b + b;
        state <= 0;
    end
end
end

endmodule

above is the code I test to see if the value of a + 1 can write into e[i], then write it into output c in the next clock.
However, what I get is the output c is zero all the way. but it shows the expected result of output d. Means case actually working just that array is not working.
What is the problem? Or this can only be sone in SystemVerilog?
By the way, I use University Program VWF to monitor the result.


texts:
I have an external library which works fine for LTspice IV. To add this external library, I simply overwrote (added) the corresponding files in the lib folder in the installation directory. Hence, I have a lib folder of the following structure:

lib:
  - cmp
    |-standard.dio
  - sub
    |-myPart.mod
  - sym
    |-Misc
      |-myPart.asy

When I do the same in LTspice XVII, it doesn't work. This means, that if I open a schematics which uses myPart the error message "Couldn't find symbol(s): myPart" pops up. I also can't find this part in the "Component browser" in LTspice XVII but it is available in LTspice VI.

How can I add this library in the XVII version?


texts: SystemVerilog: S-R Latch doesn't work correctly

texts:
Here is my gate level description of an S-R latch:

module SR_Latch_Nand(input S, R, C, output Q, QB);
wire s1, r1;
nand #8 n1(r1, R, C);
nand #8 n2(s1, S, C);
nand #8 n3(QB, R, Q);
nand #8 n4(Q, S, QB);
endmodule

and here is test bench for this S-R latch:

module SR_Latch_Nand_TB();
logic s, r, clk;
wire q, qb;
SR_Latch_Nand sr(s, r, clk, q, qb);
initial begin
  s = 0; r = 0; clk = 0;
  #100 s = 1;
  #100 clk = 1;
  #100 clk = 0;
  #100 clk = 1;
  #100 s = 0;
  #100;
end
endmodule

When i check waverform, value of Q is x at most of the times. other times it's mostly incorrect. I've tried to preset values of q, qb but it still doesn't seems to work.

So can you tell what's the problem with this code?


texts:
I am working on a project where I need a relay, and bought an NO HKE CMP8-S-DC48V-A relay for the job. This is my first time working with relays though, and while I more or less understand what they are and how they work, I can't seem to figure out how to wire it, and most tutorials I've looked at don't demo this type of package.

I'm testing the relay on my breadboard. By looking at the diagram on their site, I've connected my "controlling" circuit to the pins at the bottom for the coil (the ones to the side that are close together) and I've connected the circuit that I want the relay to switch on the other two pins (the bigger ones close to the middle). Both circuits are just resistors hooked up to the same power source for the moment, with a switch on my controlling circuit. Apologies for making it look so sloppy, the package is not breadboard friendly.

So what I expect is that when the switch is off for the coil of my relay, that there will be no current flowing the red wires, and through the 10K resistor. Yet, when the switch is off and the power is connected, I get ~12V across the 10K resistor measuring with my multimeter, while no current is flowing through the resistor in my controlling circuit with the coil. If I toggle the switch on, current obviously flows through both resistors.

I find it confusing that an NO relay is passing current while its coil isn't energized. What am I missing here?

Edit:

Here is the schematic of the circuit

simulate this circuit – Schematic created using CircuitLab


texts: Floating analog input using Arduino with 1m cable

texts:
I use an analog input from an Arduino to read the value from a piezo plugged in parallel with a 1M ohm resistor.

I followed this tutorial from Arduino: https://www.arduino.cc/en/Tutorial/Knock

Here is my schematic:

It worked perfectly until I decided to use a 1m cable between the piezo scheme (piezo || resistor) and the analog input.

With a short cable, I read 0 when there was no vibration nor activity. But when I change the length to 1m, I always read values higher than 0... This input is floating.

What would be the solution so I can read a precise value and stop this input from floating?


texts:
Because the Example Virtual Serial Device project from NXPUSBLib contains a space in it's directory structure (specifically Example_VirtualSerialDevice/LPC43xx M4/...) I can not successfully download code through the GUI programming tool in LPCXpresso.

So, I have attempted to compile a binary file, and download to my LPCXplorer4330's M4 core. This results in the error included at the end of this post.

Do you have any suggestions as to how I can get some code downloading? I'm running Ubuntu 12.10 x32, and the LPC-Link JTAG programmer.

I have quadruple checked file permissions, and have tried multiple combinations of AXF files or BIN files.

Thank You!

$ crt_emu_lpc18_43_nxp -wire=winusb -pLPC4330 -vendor=NXP -flash-load-exec=~/Desktop/Example_VirtualSerialDevice.bin -load-base-address=0x14000000
Ni: LPCXpresso Debug Driver v4.0 (Sep 19 2012 09:15:29)
Nc: Looked for chip XML file in /usr/local/lpcxpresso_4.3.0_1025/lpcxpresso/bin/LPC4330.xml

Nc: Looked for vendor directory XML file in /usr/local/lpcxpresso_4.3.0_1025/lpcxpresso/bin/nxp_directory.xml

Nc: Found generic directory XML file in /usr/local/lpcxpresso_4.3.0_1025/lpcxpresso/bin/crt_directory.xml

Nc: Emu(0): Conn&Reset. DpID: 2BA01477. Info: LPCLINK_1_1
Nc: SWD Frequency: 3000 KHz. RTCK: False. Vector catch: False.
Nc: Packet delay: 0  Poll delay: 0.
Nc: NXP: LPC4330  Part ID: 0x00000000
Cr:v Registered license, download limit of 128K
Et:58: Cannot open binary file 'Example_VirtualSerialDevice.bin'


texts:
I am using 415 V supply. Line to phase neutral is 240 V. I have 110 V appliances that I want to use. I have created 11 different points for which I want to use this appliances, and want to install a three phase panel for it.

What three phase step-down transformer should I use that will give me phase to neutral voltage of 110 V?


texts:
On a datasheet for a single pole, multiple contact switch, I see that there are a few contact ratings: non-switching (50VDC, 100mA), switching (5VDC, 100mA) and minimum (20mVDC, 1uA). What are these different specs describing?

If I anticipate my system to draw 3VDC at around 100mA (300mW), am I good to use this switch since it is rated for 500mW or must I obey the current and voltage specs independent of each other?


texts: PIC Microcontroller - __delay_ms() no effect

texts:
I am newbie to C programming on a pic microcontroller. I am slowly working my way through the various tutorials and literature available to try and apply my knowledge.

I am currently trying to  blink an LED with the pic16f1619 using the curiosity board using MPLAB IDE X, specifically pin A5.

My code is as follows:

#include <xc.h>
#include <stdlib.h>
#include <stdio.h>

#define _XTAL_FREQ 32000000 //internal oscillator of pic16f1619 is 32MHz

// Above is header files - xc is for compiler, stdlib is for general  function             and stdio is for I/O
// Below is the bit configuration - this is taken from the curiosity mcc    generated bit configuration

// CONFIG1

#pragma config FOSC = INTOSC    // Oscillator Selection Bits (INTOSC    oscillator: I/O function on CLKIN pin)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)

#pragma config MCLRE = ON       // MCLR Pin Function Select (MCLR/VPP pin    function is MCLR)

#pragma config CP = OFF         // Flash Program Memory Code Protection    (Program memory code protection is disabled)

#pragma config BOREN = ON       // Brown-out Reset Enable (Brown-out Reset    enabled)

#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is    disabled. I/O or oscillator function on the CLKOUT pin)

#pragma config IESO = ON        // Internal/External Switch Over (Internal    External Switch Over mode is enabled)

#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable (Fail-Safe    Clock Monitor is enabled)

// CONFIG2

#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write    protection off)

#pragma config PPS1WAY = ON     // Peripheral Pin Select one-way control (The    PPSLOCK bit cannot be cleared once it is set by software)

#pragma config ZCD = OFF        // Zero Cross Detect Disable Bit (ZCD disable.  ZCD can be enabled by setting the ZCDSEN bit of ZCDCON)

#pragma config PLLEN = ON       // PLL Enable Bit (4x PLL is always enabled)

#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)

#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)

#pragma config LPBOR = OFF      // Low-Power Brown Out Reset (Low-Power BOR is disabled)

#pragma config LVP = ON         // Low-Voltage Programming Enable (Low-voltage programming enabled)

// CONFIG3

#pragma config WDTCPS = WDTCPS1F// WDT Period Select (Software Control (WDTPS))

#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled)

#pragma config WDTCWS = WDTCWSSW// WDT Window Select (Software WDT window size control (WDTWS bits))

#pragma config WDTCCS = SWC     // WDT Input Clock Selector (Software     control, controlled by WDTCS bits)

void main(void) {
TRISAbits.TRISA5= 0; // set pin as output
LATAbits.LATA5 = 1;  //set pin as high

while(1)
{
LATAbits.LATA5 = 1;  //set pin as high
__delay_ms(1000); //delay of 1second
LATAbits.LATA5 = 0;  //set pin as high
}

}

At the moment there is no effect on the output of pin A5. I have tried changing the function of the pin with the different registers. Any help would be greatly appreciated!
I am sware of this code - LATAbits.LATA5=~ LATAbits.LATA5; // Toggle Bit of Port A5

Any help would be greatly appreciated as I am really stuck!


texts: Is a varistor basically two diodes in series, with opposite polarities?

texts:
The typical curve for current vs voltage for a varistor:

looks a lot like the 2 reverse voltage regions of a normal diode:

Is this equivalent the following, and if not, why not?

simulate this circuit – Schematic created using CircuitLab


texts: UAV-towed gradiometer: magnetic signal decay with water depth

texts: I want to use an unmanned aerial vehicle to tow an airborne gradiometer. Goal is to detect historic anchors buried in the sea floor. What is the effect of (sea)water depth on the magnetic signal? Any standard equation(s) I can use to determine max detection depth in relation to size (weight) of ferrous target? Sensitivity and resolution of the potassium sensor are 0.0003 nT @ 1 nT and 0.0001 nT, respectfully. Thanks!


texts: Can anyone identify this 40-pin SMT socket on the Silicon Labs BRD4180A board?

texts:
This socket appears on the Silicon Labs BRD4180A board and it might be nice to reuse the module on our projects after programming it.  The socket appears to have 50-mil spacing between pins.  What is it?  There are no apparent markings on the plastic itself.
Male/female:

From datasheet (probably 3d render):


texts: I have two node voltages that I wish to plot against each other, similar to the XY mode on an oscilloscope. How do I achieve this via LTspice? LTspice only plots quantities against time.


texts: Using a PC PSU instead of a dedicated professional "brick"?

texts:
Usually when choosing a PSU for a scientific instrument going into production I will go to one of the major distributors and buy something like this, which is rather expensive but well specified.

However, I note that PC PSUs with the same ballpark ratings are a fraction of that price. What are the pros and cons of using the PC PSU?


texts: Regulating 220v AC voltage for halogen lamp with Arduino

texts:
I am making a project based on Arduino which is about regulating the brightness of 220v AC halogen lamp. I've read that halogen lamps are the easiest ones to regulate the brightness. However, electronics is my weakest spot.

I've read that a TRIAC regulator can be used for this task, also from this other question (220v AC Fan regulator) it seems that sometimes it wont work. Can it be used for my project?

Thanks in advance.


texts: ATMega8: why do VCC and AVCC have to be connected?

texts:
I often read that it is good practice to connect VCC with AVCC. Even in the ATMega8 datasheet it says so:

  AVCC is the supply voltage pin for the A/D Converter, Port C (3..0),
  and ADC (7..6). It should be externally connected to VCC, even if the
  ADC is not used. If the ADC is used, it should be connected to VCC
  through a low-pass filter. Note that Port C (5..4) use digital supply
  voltage, VCC.

But nowhere I can find an explanation as to why they have to be connected.
A simple circuit for blinking a LED works without connecting VCC and AVCC.

Do I just have to accept it, or is there a good reason?


texts: Hi I built a simple LC low pass filter and I supply it with a 1 volt peak to peak ac voltage at 200 Hz from a function generator. My cutoff is set at 700 Hz and I have selected my circuit components based on this cutoff. However, when I hook up my circuit to the Oscilloscope both the input and output seem to be attenuated when measured on the Oscilloscope. The input and output shows up to be around 150 mv Peak to Peak instead of 1Volt Peak to Peak. I believe the capacitors have something to do with this attenuation.  What are your suggestions to solve this problem ? Thanks


texts: Using 18650 batteries to power TV during power outage

texts: I have a ton of 18650 batteries. As a fun project, mostly to learn. I would like to build a battery pack with these batteries, and power my TV when there is an outage. Can I just match the AC 120 V ~ 50/60 Hz 3.2 A with a battery configuration?


texts: noise/rpm/cpm values of 12V fan on 5V voltage

texts:
I am using Sunon HA40101V4-1000U-A99. This is 12V DC fan, but I am using it with 5V DC (according to specification).
But I am not able to find values for audible noise, rpm, cpm, current on 5V. Datasheet just provides these values for 12V.

Is there any way how to find it out? Or to deduce it?
I would like to get some table with values for specific voltages, how they are influenced (or at least for 5V in my case).


texts: Determine the current i through the 4 ohm resistor

texts:
Due to different frequencies, i applied superposition by shorting the right source
and applied voltage division rule to get the voltage across the resistance.
Vr=3 ∠0° * 4/ (4 + 6j) = 1.666∠-56°, and Ir=Vr/R
But the answer is not correct (for the right source also). What did I do wrong?


texts: Drive Capacitive load with toroidal transformer

texts:
this question is related to my previous post:
Toroidal transformer voltage breaks down
I am trying to build a circuit that drives a capacitive load (approx. 9nF) through use of a toroidal transformer. My circuit generates a 2Vpp sine wave with variable frequency (50 - 500 Hz) and feeds it into a power amplifier OPAMP (OPA548), which is able to supply around 2 A at approx. 14V output voltage. My goal is to control the voltage on the capacitive load to increase and decrease both frequency and voltage.
My problem is that if I increase the frequency of my sine wave, my load impedance will decrease and draw more current. The primary winding inductance however will increase its impedance and therefore, I will get less current on this side.
Therefore, if I try to design the circuit for 50 Hz, I would need aprox. 0.06 A of input current, which is no problem. But when I then increase the frequency, I would need 10 times this current but the impedance on the primary side of the transformer will increase and thus I can not draw more current while maintaining the voltage levels.
Does anyone have a clue what I could do to prevent this?
EDIT: I use the transformer in reverse, meaning that for my application, the leakage inductance on the secondary winding is 10 H and gets shorted out by the capacitive load. My leakage inductance on the primary side will be around 9 mH. My problem is that for 500 Hz, I would need approx. 20 mA to drive my capacitive load at 400V which means I need to supply 666 mA at 12 V through my OPAMP. But when I decrase the frequency to 50 Hz, this would result in 6,6 A at 12V from my OPAMP and thus burning my OPAMP. Now since I do not have much experiance with using transformers over a this frequency range, are there any actions I could make to somehow "match" my input impedance or so to not burn my OPAMP while still being able to drive my load. Or is a sigma-delta amplifier better since amplifying different frquencies is more like audio technology?
A better schematic:


texts:
There is a plethora of information on motor sizing on the internet discussing the rated voltage, current, torque and power of the motor, and how these parameters should be selected based on the load the motor's driving. Some articles went deeper discussing the moment and the torque. Then, HP = (torque x speed)/5252.

But how often is all this information available? If you're sizing a motor for a conveyor in an industrial plant, what other data other than the voltage (likely 480V in north america) and the mass of the load do you have readily available. Companies that manufacture conveyor systems probably have software tools that calculate the motor size for them.

But for someone who doesn't have this software, how does one go about determining what size motor they need to drive a 6000lbs load over a conveyor of length 20 feet.  Let's assume 1800RPM since that's what most conveyor motors at our plant are, and 480V 3phase across the line start.

I guess I could start with calculating the torque required: torque = force x radius. Is the radius in question that of the conveyor roll?
And force = mass x acceleration. Mass = 6000lbs. Acceleration = (1800 - 0)/t. Assuming starting from rest and going to full rated speed. Not sure what "t" is since the motor is direct on line start (and not controlled by a VFD so there is no ramp up time)

I want to get a good grasp on the subject so a detailed answer would be much appreciated.


texts: Activating a circuit based on change of resistance

texts:
I am looking to use a sensor, such as photoresistor, to activate a circuit only when there is a significant change in the input. Such as when the light incident on the photoresistor changes significantly (e.g. something suddenly blocks or unblocks the light source).

What would I need to make this circuit? Ideally when the resistance changes by a certain amount quickly it would activate a transistor or switch.

I'm not sure where to start with this one without using a computer to process the time taken and calculate a  derivative.

edit:
It must be a microcontroller free solution. I'm not fussy about the tolerance or what-ifs from environmental variables, so long as the circuit can detect large resistance changes.


texts: in question below I couldn't' evaluate the initial state for inductors and capacitor in order to do the s domain analysis. If you can also show me how can I draw the circuit for inital state, I would be really greatful. Thank you!


texts: Control of a D.C. motor reversing contactor

texts:
I've got a forklift with a partially functional motor controller. As I've got a bit of experience with electronic engineering (as opposed to electrical), I have a few questions that I was hoping to get some help with.

The current setup looks like this:

The original controller is very hard to get hold of. A close alternative with very similar specs is available. However, it doesn't have the "FWD Input" or "REV Input". For the original controller, the internal block diagram is as follows:

The new controller is as follows:

The contactors that the "FORWARD" and "REVERSE" control are Albright DC182.

I guess, my question is, what might the "F/R Contactor Driver" (in the block diagram) do? Because as far as I can tell, the contactors works by connecting completing the circuit across the coils.

Any help would be greatly appreciated.


texts:
I am trying to design a circuit that enables me to use low voltages to control an actuator that works with high voltage. I think I need to use an opto-isolator.

How can I get a 150V square wave output from with an opto isolator?
I appreciate any type of help or comment.
Thank you.


texts: Efficient spike detecting Microprocessor or DSP architecture

texts:
I am looking for microcontroller or DSP (or its architectures) which are efficient in terms of power as well as performance in detecting spikes. I want to run an algorithm which detects spikes and processes them. So, I am looking for architectures which are efficient in this type of performance.

Any hints, suggestions, etc would be really helpful. Thanks in advance.

UPDATE: I am getting the input signals in digital format. I am not looking for an extremely real-time performance also. Even if I get some delay, thats fine. Also, I am not only interested in just the spike detection, but also a number of characteristics like its height, etc. In short the algorithm in quite complex. I am trying to do this for ECG/EMG signals, etc. Algorithms are not so straightforward, and hence I am looking for an efficient architecture.


texts: What factors cause the harmonic distortion in ADC at high signal amplitudes?

texts:
I have been studying about the ADC's SNR vs amplitude relation. A sample curve is shown below:

I am interested in the region rounded (orange) of the gray curve. At that region, we expect to see harmonics in the spectrum and thus define the SFDR.

I found that at that region, there are 2 effects happening:

Increase in noise floor (due to Jitter) (green arrow)
Harmonic distortions (due to Non-Linearities) (magenta rounded)

I am interested in (2). I am trying to understand what kind of non-linearities causes these harmonic distortion. I am aware of effects like feedback DAC mismatch, amplifier saturation - but they generalize to one concept - saturation. (Of course this non-linearity sometimes is used in diode mixers for frequency conversion)

Is there some different non-linearity which causes these harmonic spurs (magenta rounded)?


texts: What should be the voltage divider resisor values in units?

texts:
I'm trying to build a circuit that lights up a LED when a battery connected to it is full charged. I found LM358 lying around so I plan to use it as a comparator. I want a 3.7v using a voltage divider, I don't mind if it's less or more a little. I already have some 470ohm resistors. so the other resistor I want is around 165ohms and the standard value resistor is 160ohms and I will get around 3.73v across the 470ohm resistor.

What I wanted to know is how do I choose the resistor values in ohms or kohms, or in mohms? since there are 47k and 16k I also can use them right? but what is the drawback? I know that a comparator/op-amp use a little bit current in its inputs, so what should I be care about choosing the resistor values?
Is there something in the LM358 datasheet that it can help to choose me the values between ohms,kohms,mohms ?

LM358 Datasheet


texts: Analyzing/designing positive feedback amplifier

texts:
I've been searching all around to find a tutorial on analyzing/designing a positive feedback amplifier, especially a single transistor in common collector mode, but with no luck...

So, lets say I have this circuit:

simulate this circuit – Schematic created using CircuitLab

I was able to design the DC part of the oscillator, the operating point. But I just cant get my head around, how to design the AC part.

How would I calculate the values for the positive feedback capacitive divider network? Also, is there any universal way of analyzing transistor feedback circuits? I would really appreciate a step by step guide.

Thanks in advance!


texts: What is this plastic chip packing material called?

texts:
When I order ICs from larger retailers, they are delivered in a plastic housing that prevents the pins from becoming bent during shipping.  With a chip included, they look like this:

I would like to buy more of these so that I can store and ship some ICs I have that didn't come with one, however I am having no luck finding any for sale so I must be using the wrong search terms.

I have looked for chip/ic + carrier, housing, packing, storage, etc. but not found anything remotely like this.  I've tried the same retailers that sell the chips as well as places like eBay but I can't find anything at all.

What do retailers call these items when they are up for sale?


texts: Way to connect test points on circuit board when both sides of board must be accessible?

texts:
I have a commercially made circuit board with multiple 7-segment displays (HSP-H103) soldered into it. I need to test the displays to make sure all of the segments work for each one.
The problem is that it is difficult to hold wires or leads against the necessary test points which still being able to view the display.
I thought of maybe trying to use a mirror, but getting the mirror at the right angle is not easy.
Is there any easy way to hole a lead to a solder point on the back of a circuit board?


texts: Resistor network in between SAW Filter and Power Amplifier

texts:
I am going through user guide of Microchip's LoRaWan Gateway. The manual is over here. At page 48, I am struck at one resistor network and unable to understand it's use. I can make a guess and I think it is for reducing signal strength to a level acceptable by power amplifier at it's input. Below is the screenshot of the schematics page on page 48 of the manual:

According to current knowledge I have for RF designing, I have listed the blocks in above picture (encircled by different colors) with their functions:

Green: Resistor Network to attenuate signal so that Power amplifier can accept the signal power
Red: Impedance Matching Network
Blue: DC Blocking Caps.

Am I correct?


texts: Surface scratch between neighbor SMD components

texts:
I recently started an advanced SMD soldering project. I hqve a couple smaller projects under my belt, so I'm raising the bar this time.

I was pre-tinning some 0603 resistor and capacitor pads and must have accidentally scratched the surface of the pcb between 2 neighbor components. The result is that solder flows between the pads of 2 different neighbor components (resistor and capacitor) and now there is continuity between both pads. When I look at the schematic, these 2 components are actually serially connected, but I'm not sure how to confirm that these are the 2 poles that are meant to be connected. So first question is how to go about making this diagnostic?

Second question is how to fix such a mistake? It's amazing sometimes how easy it is to scratch the surface of a pcb without even noticing. I have searched quite a lot online and haven't found a technique specifically for such a problem.

Thanks

from KiCad:


texts: Where do I find electrical power transmission grid data?

texts:
I am looking for websites which provide datasheets of 3 phase electrical power transmission networks with information about their grid topology. My aim is to first transform this data into following format:
topo = [[0,0.25,0.25,0.5,0],
        [0.25,0,0,0,0],
        [0.25, 0, 0, 0, 0],
        [0.5, 0, 0, 0, 0.01],
        [0, 0, 0, 0.01, 0]]

introduce power consumers and power generators and use it for load flow calculations. This particular (theoretical) grid consists of 3 nodes (1 to 3), 1 slack node (4) and 1 fake slack node (5, which is required in this case for specific reasons). The values in topo describe the distances between the nodes in the grid in km. It would be very handy, to have datasheets with similar topology information.
This is my first post in this stack, I am very sorry for potential flaws.


texts: Is there a voltage regulator IC that takes PWM input?

texts: I am looking for a small IC that provides a regulated dc voltage based on the duty cycle of the input. This is probably asking for a lot but does anyone know if one exists. Essentially I need a low pass filter but I need to conserve board space as much as possible as I am VERY limited. Also, I have done LPF's in the past with just a resistor and capacitor but I can never seem to get the noise out. I usually end up with at least 20mA of ripple. My PWM would likely be 3.3V pk-to-pk but I could also manage 5V as well. Any ideas?


texts: Why BLDC are DC motors as basically they work on ac by using inverter? Can I directly give AC supply to BLDC motor?

texts: What I have heard is BLDC is workhorse in industry even laptop fans they work on BLDC but why they are called DC motor as eventually they use inverter to get ac as input? Can I directly give AC supply to BLDC motor without inverter? Is BLDC a misnomer or does it has some significance ?


texts:
A problem reads "A single phase 50 Hz generator supplies an inductive load of 5000 kW at a power factor of 0.707 lagging ... "
How can there be real power loss from an inductor?


texts: How are power flows between multiple power systems (tie-line flows) determined?

texts:
In Europe, for example, there are multiple transmission system operators (TSOs), which are responsible for their own region of the grid. These TSOs must exchange power to ensure reliable operation of the whole system.

Does anyone know how the amount of power exchanged is determined? Is there some forecasting of demand in each region that gives each TSO and ballpark of how much power they need/how much excess power (generation capacity) they have?

If anyone has any reports that describe this process it would be greatly appreciated!

Edit: A reason that I'm wondering is because it seems like in some regions tie line flows (between areas) are scheduled as a set point to be maintained. Any idea how these scheduled flows are determined? Specifically the note "maintenance of the scheduled interchanges" in this link.


texts: What is the maximum frequency to use diodes for distortion?

texts: What is the maximum frequency to use rectifier, Schottky or Zener diodes for cut off sin wave to square wave?


texts: How do I calculate the Power deliviered to an electronic component by using the information found in the datasheet?

texts:
I am studying mechanical engineering and is trying to design a product that will contain an electronic component with this Datasheet.

I am trying to figure out is how to calculate the heat dissipation from this component when it is going at full load to get a sort of worst case scenario. I am aware that this could be done by using the power equation, as in this example

P=V*I    Where V = Vin-Vout

My problem is that I - not being well versed in electronics - do not understand what values to use from the datasheet. I'm sorry if I haven't provided enough information.

Your assistance would be very appreciated!


texts: A question about digital scope input and common mode noise

texts:
Data acquisition systems' ADCs use differential amplifiers at inputs. So with respect to a common ground(for example earth-ground reference), I apply 3V to one input and 1V to the other input of the differential amplifier;
and the amplifier will measure the difference which is 3-1 = 2V. And if perfectly balanced system is used I guess it will reject 50Hz common mode noise which is capacitively coupled to both input wires from mains for instance.

When I approach a live mains cable to a scope's coax cable input, I see 50Hz noise appears on scope screen. So I guess the system is balanced since no input is connected and the system is balanced.
Since I still see this 50Hz noise I wonder how does a digital the scope subtracts the voltages. It doesn't use a differential amplifier? Why wouldn't it use a differential amplifier, so it could reject common mode inferences like in an ADC input?


texts: Currently I am using an Allen Bradley Analog output card to get a variable -10VDC to +10VDC output as defined by the PLC program. However the PLC will only supply 100ma with that voltage. The device that I am providing power to requires 350ma. Is there a way I can "Amplify" the current output to the required 350ma while still providing the -10v to + 10v (variable) range required by the device? (The device in question regulates speed and direction of a hydraulic unit. It currently operates, but at a reduced speed due to the lack of current).


texts: Interfacing TSOP IR Receiver with Arduino

texts: How do I send signals from a 38 kHz Vishay's  TSOP series  IR receivers to an Arduino and make the Arduino act accordingly(eg. move a motor)?


texts: draw 30W @ 5v to run LED light string and Arduino from a car battery?

texts:
I've got a set of LPD6803 LED lights controlled by an Arduino that I'd like to connect to a 12v system powered off an auto battery.  The lights can run off 5-12V but this particular Arduino board is spec'd for only 4-8V Vin.

The total draw of the lights will be something under 30W.  My guess is significantly lower, but I'm basing this on the spec sheet.  (In testing I can run them off a 5V/2A AC adapter and it works fine)

Any ideas for the simplest way to power both from the single 12v source?  It seems like the lights can run off a 12V circuit while the Arduino runs off a 5V circuit.  Or I can run them both off 5V, if the 5V source can provide this power.  I'm pretty sure a 12v->USB plug probably wouldn't.  Does a 7805 apply here?

(I also have an inverter + AC adapter solution I could use but it's quite a hack!)

Thanks!


texts: Splitting Digital RGB Signal Line to multiple LED strips

texts: I am trying to connect multiple strings of WS2812B RGB LEDs to the same signal line (so that they will all behave the same way, display the same colors, etc). The WS2812B is very time sensitive, so I am looking for input on the most effective way to take the single signal line, and split it to all 4 strips. All of the strips are identical. Thanks for any help!


texts: Why is 50/60Hz interference is also called RFI interference?

texts:
I encounter sayings like this everywhere:

  RFI interference is unintentional radiation from sources such as
  electric power transmission lines.

My confusion comes from my following thinking:

1-) First of all, power transmission lines work with 50/60Hz which is not radio frequency.

2-) Electric power transmission lines produce electromagnetic fields not radiation like antennas, so calling it radiofrequency interference doesn't make sense to me. It should be called electromagnetic field interference?

I'm sure I have lack of knowledge somewhere but couldn't figure out.


texts: Current draw at digital output pin differences in two equally coded segments -probable cause?

texts:
I measured the current output of an Arduino Duemilanove (with an ATmega168) in two cases and found out that the currents differ strongly.

The following code creates an output of 72mA at pin 13 measured in my case on a digital multimeter (Tenma 72-7745). Note that it is almost the double of the max. current of 40mA.

void setup()
{
  pinMode(13, OUTPUT);
}

void loop()
{
 digitalWrite(13, !digitalRead(13));
 // digitalWrite(13, digitalRead(13) ^ 1); // this works as well
 delayMicroseconds(58);
}

the code below about 36.5mA:

void setup()
{
  pinMode(13, OUTPUT);
}

void loop()
{
  digitalWrite(13, HIGH);
  delayMicroseconds(58);
  digitalWrite(13, LOW);
  delayMicroseconds(58);
}

The measured frequency at pin 13 (+) and ground for both examples is around 8kHz.
The current draw doesn't change too much when I make the frequcey lower for example with  delayMicroseconds(1000); it is in this case 493Hz and 68mA in my condition (temperature and microinstructions which effects the clock I suppose).

I tried to google this, but could not find any sources. Do you have any idea?

Is this somehow related to the digitalRead() instruction? Does this function need a current to read? What about current sink and source? I need help..


texts: Using AVRDude to program AtTiny via Arduino-as-ISP

texts:
As I understand, I can use Arduino as ISP. Most instructions start with "load ArduinoISP from examples".

But then I want to load existing .hex file to the target chip. E.g.

AvrDude -> ArduinoBoard+ArduinoISP -> targetChip

And I fail miserably to find proper instructions though I believe this is possible and perhaps even already explained somewhere. I could not find instruction mainly because keywords yield instructions on many related but different topics.

I suspect that as Arduino uses avrdude I can sneak how it works when programming via ArduinoISP... At least I'm trying in this direction right now, but I would be glad if someone can help me to save the time.

UPD I've succeeded with the help of the answer below. The last thing to mention - I hate arduino's instruction for giving an image instead of specifying wiring. As I understand it is like:

pin 10 to reset
pin 11 to mosi
pin 12 to miso
pin 13 to sck


texts: Hall effect current sensor and proximity to EMI

texts:
I am preparing to layout a PCB. I have an ACS723, that I want to use to sense the current going through a relay. In addition to the relay I have a Meanwell IRM-12-20 to supply ac to dc voltage to the board.

According to the ACS app note:

  The ACS723 works by sensing the magnetic field created by the current
  flowing through the package. However, the sensor cannot differentiate
  between fields created by the current flow and external magnetic
  fields. This means that external magnetic fields can cause errors in
  the output of the sensor.

Since the ACS will be detecting mains voltages, and that I want to have enough spacing between the high and low voltage sides of the circuit, the layout I had in mind restricts the placement of the ACS.

Overall, I am curious as to whether or not close physical proximity to either the AC/DC converter or relay will cause enough interference wrt the ACS readings?

Here is a partial of what I have come up with to give you an idea of the current layout.


texts: Modeling one Current limiting cuircuit with two BJT

texts:
I trying to better understand one article related to current limiting with two BJT. The link is here: https://www.planetanalog.com/seemingly-simple-circuits-user-proof-external-supplies-circuit-3-the-two-bjt-current-limited-supply/#
The schematic is this one:

Extract of the blog:
*Analysis is simplified by the observation that the emitter current of Q 1 consists of two components: the currents of RE1 and IB2 . The base
current of Q 1 has both components, and IB1 from IB2 is IB2 /(β1 + 1)
or IC2 /β2 x (β1 + 1). This current and IC2 flow through RB to
contribute to VB and they are proportional, through the β values.
The total current in RB caused by Q 2 is
<img src="https://i.stack.imgur.com/dDqKT.png" alt="
" />
*

Question
In this equation IRE1 is missed.
Is it true or not?
Thanks jonk for reading my post.
Trying to clarify my my question.
The equation stated in the blog is supposed to give the current flowing through RB resistor. Trying to find the way this relation is established, I used Kirchhof
law at the node located upon intersection between Q1 base and Q2 collector.
IRB = IC2 + IB1 = IC2 + IEQ1/(BetaQ1 + 1) = IC2 + (IB2 + IRE1)/(BetaQ1 + 1) [A]
In the blog, the result is : (1 + 1/(BetaQ2.(BetaQ1 + 1)).IC2 = IC2 + IC2/(BetaQ2.(BetaQ1 + 1)) = IC2 + IB2/(BetaQ1 + 1) [B]
At this point comes my question: Why IRE1 is missing from [B]
It is as if this assumption has been made: IBQ2 = IEQ1 and IRE1 = 0.


texts: Vector monitor, purpose of a third "green gun" connection

texts:
I recently came into possession of a vector monitor, as shown below (Vector Monitor, Model: IO-1128, from Heathkit). Its got a red, blue and green "gun" connections. However, I am not sure about its third green connection.

From the schematic ((https://archive.org/details/HeathkitIO1128VectorMonitor), the red and blue connections are related with vertical and horizontal display positions respectively.
What would be the purpose of the "green gun" connection?


texts: What is the meaning of the second value in the ESP8266 bootloader output?

texts:
When connecting an esp8266 to a serial port at 74880 to flash or inspect it, depending on what pins are held down there are a series of diagnostic boot messages.

The line looks something like this:

rst cause:2, boot mode:(3,6)

The rst cause - the reset cause is very easy to find documentation on and has been useful in diagnosing low power or error conditions.

The first boot mode number is pretty well documented as being derived from (gpio15 << 2 | gpio0 << 1| gpio 2), and the device will be expected to load code via the UART or from flash based on this value.

The second boot mode value, in this case 6 (I've seen 0, 1, 3 and 7 here), seems to be elusive and I've been unable to turn up documentation on what this diagnostic means. What should it do and where is there further documentation on it?


texts: In an isolated SMPS feedback design, how could optocoupler latency be higher than the switching period?

texts:
I often see this in practical SMPS designs. An optocoupler & voltage reference pair is used for informing the controller section about the output voltage level. However, when I read the datasheet of the optocoupler in the circuit, I see that the given signal characteristics "rise time" and "fall time" are higher than the switching period of the controller circuit.
Example
See this circuit in this article.

In the schematics, it says that the switching frequency of this circuit is 250kHz, which means the switching period is 4us. In the optocoupler datasheet, the rise time is given as 4us (typical) and 18us (maximum). The fall time is 3us (typical) and 18us (maximum). The signal has to rise and then fall, so it takes typically 7us (36us at maximum) for a pulse. An engineer must make his design considering the worst case circumstances, so we should take the maximum pulse time as 36us, which is 9 times the switching period.
Wouldn't it mean that the controller will respond to an output change 9 periods late? Is this much latency acceptable, doesn't it cause output voltage level controlling problems? Or, is there anything I'm missing here? Can you please explain me how does this kind of SMPS designs work with all these slow optocouplers?


texts:
I want to run a number of sensors up the length of a flex circuit, they all communicate via SPI and I will run chip selects individually to each device.

I need the flex circuit width to be minimal so its likely I will have tracks in close proximity running the entire length of the flex circuit.

Im concerned with how this will affect the SPI comms with increasing length.

EDIT: The SPI will run at a maximum speed of 1MHz, data will be active on both MOSI and MISO, One mircoprocessor will sit at one end of the flex circuit as master, comunnicating with the chain of sensors.

I'm not looking for an exact figure just ball park, so that i can decide o na length to test with first.
This answer SPI max distance gives the max length for cables, but i think that this is not applicable to that of a flex circuit.

How long can I go with the SPI on a flex circuit?


texts: Using Data Visualizer with Atmle-ice with SPI Physical interface

texts:
I am trying to output some debug strings from an AtMega328P to a terminal window on AtmelStudio using the DGI. I would like to use the 6-pin 100-mil connector of my Atmel-ICE Basic Kit, which I currently use to program the uC.
On my scope I see the ASCII character 'S' as expected:

So the uC is doing the right thing. I think that the problem is chip select pin. It is reported on the DGI SPI Pinout but I cannot use it because it is not present on the connector.
There is an option on the SPI configuration windows of AtmelStudio to "force the startup synchronization on CS". I tried in both ways but nothing changed.
Am I doing something wrong or is it necessary to connect the debugger with the full 10 pins connector to use the Data Gateway Interface?


texts: Proof of Thevenin's and Norton's Theorem?

texts:
Googling this gave me a number of proofs, but almost all of them assume the load is a linear component.

Could someone give me a proof for these theorems assuming the load can be anything (a linear or non-linear component)?


texts:
By accident I placed an imported bitmap on tStop instead of tPlace. How can I remove it?
Unfortunately I noticed it too late to simply undo it.


texts: What affects the design of a SOC or uC to offer XIP or RAM for code execution

texts:
I have been trying to understand the factors in controller / SoC design such that it can execute code from either XIP flash or from a RAM. There are controllers that support an XIP flash of around 5MB and there are SoCs where there is no XIP at all, there is only external memory present. The code is executed from the external DRAM in these cases (which I can relate to how PC works).

Some conclusions observed so far include:

Using a XiP is no longer efficient after a certain size/speed,
considering both the cost and the actual operation.
The manufacturing process affects the design too?
Some hybrid solutions are also present, where the instruction bus can fetch from a XIP or an External DRAM

In summary the question would be where is the line drawn between the two solutions : execution in RAM and execution in place from flash (XIP).


texts: Is voltage an accurate metric for testing the charge of an NiMH battery?

texts:
I regularly use rechargeable 1.2v AA NiMH batteries, and I'd like to be able to use my multimeter to test both how much charge they have when I've finished charging them, and how much charge they have left at any one time. However, being an electronics newbie and doing some research, I'm left confused as to just how directly voltage is correlated with a battery's level of charge, due to there being lots of conflicting voices surrounding the topic.

A highly-rated EE answer here claims that voltage is directly related to a battery's level of charge, stating:

  NiMH cells start at about 1.5 V right when fully charged, drop to about 1.2 V most of their discharge life, and are pretty much empty at 900 mV

Then this answer here claims the exact opposite:

  It is not possible to measure or guess the capacity of a battery with
  a single set of instantaneous measurements, like voltage, current, and
  temperature.

  At best you can tell how much current is going into or out of the
  battery a what voltage. However, there is no way to infer capacity
  from that. If you can control the load, you can get some idea of the
  internal resistance, but even that would take at least two
  measurements separated in time and therefore can not be done
  instantly. And, battery voltage and internal resistance does not tell
  you capacity.

The FAQ at GreenBatteries.com also claims voltage is inaccurate:

  ...a NiMH (or NiCd) battery stays at about 1.2 volts until it is
  nearly completely discharged.  This makes it almost impossible to know
  the amount of capacity left based on its voltage alone

Elsewhere on the internet, opinion is divided at best.

So, I'm here for a final, definitive answer on the topic - are voltage and similar measurements accurate for assessing a battery's level of charge?

If they aren't, then what is?

N.B. In order to make this a definitive question for the topic, please ensure that any and all answers are well-sourced.


texts: Why did my micro-controller short out even though the alligator clip of the oscilloscope was connected to a ground pin?

texts:
I have a STM32F407G-Discovery board, and I bought a DS1054Z oscilloscope for the purposes of debugging.

Before I did anything, I went through videos and articles about how to use it. From my very basic understanding of them, I gathered that since my MCU was connected to my computer through a USB, it was a mains earth reference, and so I need to be careful about where I plug the alligator clip of the oscilloscope.

As such, I made sure to connect the alligator clip to a pin titled GND. However, as soon as I did, the LEDs on the MCU faded away and they just stopped working. I can no longer flash any code onto my MCU.

Here's a picture of the board:

This is where I connected the alligator clip: the far right side of the board. The GND pin above the 5V pin which is above the 3V pin which is above the PH1 pin.

My plan was to connect the alligator clip to this GND pin, and then use the longer probe (not sure what's it called) to hook onto the PE3 pin (since I'm trying to debug a SPI issue). Was my logic incorrect?

What did I do wrong?


texts: Why is wireless charging safe for phone circuits?

texts:
Wireless charging is done by electromagnetic induction, by continuously changing magnetic field in a coil, i.e. by passing AC current through it.

I have always been told by others to keep magnets away from electronic devices (more specifically, one shouldn't move a magnet fast, near a electronic device, that's what I have learnt). The reason being:

  Strong changing magnetic field, can induce high EMF and high currents in circuits, causing them to blow-up.

So, how do they save circuits of phone when is charged wirelessly?


texts: We are looking to add to a product software-controllable pullups on sensor signal lines. Currently the signal lines we hardwire to a pullup of 5V via a 2K7 resistor, but other systems allow software-selectable pullups instead of having certain input channels always pulled up. How could we accomplish this electronically? (we can assign an MCU pin to "command" to pullup, thats fine) Is it simply a buffer that outputs when on (5V) then Hi-Z when off? Open for ideas...


texts:
Using a PIC32MM0064GPM028, how is Pickit 3 supposed to connect to it? Reading page 3 of the datasheet I see no PGC/PGD-pins at all, and in this document (PICkit™ 3 In-Circuit Debugger/Programmer Guide) it says all PIC32 are supported.

I cannot figure out how.


texts: Recommendation for simple path management circuit for backup lithium battery

texts:
I am using a lithium ion (~100mAh) battery in my application, which is almost all the time powered up by 12 V source. The 12V gets converted to 4.2 V through SMPS, which then further powers up the 3.3V through LDO. The purpose of battery is to act as an alternate power source for the LDO, when the 4.2 V output is absent. The battery also comes with an inbuilt circuit which is described in the diagram below

The reason for choosing 4.2V as the SMPS voltage, is that the charging voltage of the battery +circuit combination is recommended to be 4.2-4.3 Volts.
Now, given the above circuit, the under voltage, over voltage protection is already present. I am looking for a simple circuit which can do following purposes
1)  Control the charging by enabling / disabling the 4.2 V output fed to battery+circuit combo.
2)  Switch the power input from battery, in absence of the 12V input (hence the 4.2V SMPS output).
Hooking the battery all the time on 4.2V output looks to be a workable, but not-so-safe option. Also, the 3.3V logic powers up a MCU, so the logic can also be controlled by MCU especially for purpose 1.


texts:
I am an engineering undergraduate student.
I am currently working on a project to implement a sensing package on a quadcopter for the deployment in the canopy of tropical rain forests. This package needs to measure temperature, humidity, pressure and light intensity. All these have been taken care of, but it also needs to precisely obtain the position of the quadcopter and I am not sure how to achieve this. As it will operate in a rain forest, a standard GPS will probably not be accurate enough in part due to the bad signal (forest means a lot of trees and vegetation around). I am building everything on an Arduino Mega 2560 board. I was thinking on using D-GPS but I am not sure how to implement it.

Does someone know how I could obtain a precise (submeter precise) position of the quadcopter?


texts: What is the difference between the Euler and Tustin method, when going from time to z- domain?

texts: When we going from time domain to Z-domain we can use Euler of Tustin method for the same purpose I just wonder Which one is most accurate and Why?


texts: Can voltages be different if watts are the same? Does DC vs. AC change this?

texts:
I'm currently building a home in a van, it's my first tango with electrical engineering.  I watched a video on voltages and amps and my understanding is basically like so:
  a battery is like a water tower, voltage is the pressure, amperage is the size of the pipe, and watts is how much water comes out per second.

So now I'm wondering what the big deal with amperage and voltage is when it seems matching wattage should be enough.  If a motor were a water wheel, it shouldn't matter whether it's water rushes through a small canal or lazily passes by in a large creek so long as the amount of watt-er per second is the same... or so I imagine.

Does AC vs DC have something to do with this?  Certainly the moving water metaphor totally breaks down there.

{And, in the context of my project, my current plan is 12V DC (car battery) -> 12V DC to 15V AC (inverter) -> 15V AC to 15DC (Mac Book Pro charger [which I think is a converter]) -> 15V DC input on computer...  in the end it seems like my mac just wants x amount of watts.}


texts: Why is channel capacity a factor of bandwidth instead of frequency?

texts:
I'm trying to understand the concept of capacity for a wireless channel.  Some help would be appreciated.

For a AWGN channel capacity is calculated as:

$$C=B \cdot log_2(1 + S/N)\text{ bits/sec}$$

B = bandwidth.  This is what I don't understand.  Why isn't it a factor of frequency? To me considering bandwidth only makes sense in cases where the system changes frequency.

Bandwidth is the difference between an upper and lower frequency range.  Well, what if I'm using a fixed-frequency signal?  Fupper and Flower would be the same value, right?  So does that mean B=0?  So a fixed frequency signal can't carry any data?  We know that's not true, AM radio does it.  So what am I missing?
According to this formula, a fixed-frequency signal would have the same performance regardless of whether it's at high or low frequency.  This makes no sense to me.  For example say my bandwidth is 1Hz at a fixed frequency of 1Hz.  Compare this with a bandwidth of 1Hz at a frequency of 2.4GHz.  It's plainly obvious that I can cram way more bits into 2.4 x 109 cycles/second than I can with just 1/sec.  But according to this formula I can't.  Please help.
What about fractional differences?  Waveforms are analog in nature, so we could have a 1Hz signal and a 1.5Hz signal.  Likewise at the high frequency range.  Say 2.4GHz minus 0.5Hz.  There is an infinite amount of space between 1 and 1.5.  Could not 1Hz and 1.001Hz serve as two separate channels?  In terms of practicality I realize this would be difficult, nearly impossible to measure this difference with modern electronics, especially with noise added, but in pure theory you could have two channels.  So in that sense, shouldn't there be an infinite amount of bandwidth between two frequencies?  Or do we only count in 1Hz whole number increments?


texts: Switching a solenoid between 2 different AC/DC adapters?

texts:
I have build a circuit to turn a solenoid on and off with an Arduino (actually it's 10 solenoids, but that's not important right now), and now I would really like to make it possible to choose between 2 different AC/DC adapters because that would give me possibility to have 2 velocity levels that I can trigger from Max/msp. Of course I never want the positive side of the two different AC/DC adapters to connect, so I would have to make sure (in my Arduino code), that never happens.

Here's a rudely made schematic hopefully spreading some light on what I'm trying to achieve:

As the picture shows, I am unsure as where to connect the positive side of the solenoid. At first I thought this was easy to do, but I don't think connecting the positive side of the solenoid to each of the AC/DC adapters positive sides would work out, although I'm not sure.

NOTE: In the end I want to be able to control a minimum of 10 solenoids - each with the possibility to choose between 9 and 24V.


texts:
For a project at my university we have to improve the design of a processor (more specifically, the Plasma CPU. The design is generated based on a description written in VHDL.

We have to identify weak spots in the design and improve them. The most obvious points that can be improved are the are the multiplier (the default multiplier takes 32 cycles) and the clock speed (which requires lowering the delay encountered on the critical delay path).

Currently, I'm trying to improve the cache, but I found this to be very complicated (but it could just be my lack of experience with hardware projects). I tried to improve the cache by using cachelines of 4 words instead of 1, but I am unsuccesful in doing so: I can't understand the (undocumented) protocol that the DDR controller follows and every attempted change results in the DDR controller refusing to read or in corrupted data.

Is there a plan of attack for understanding and/or improving hardware design in VHDL? I think one of my problems is that the improvement I want to implement requires changes in a lot of modules (DDR controller, memory controller, cache, CPU and changes in signals in some higher-level modules) and I can't comprehend all of them at the same time. Also, I was hoping that there might be easier targets for improvement (besides the multiplier and the critical delay path).

If anyone wants more information, just ask.


texts: Transmission lines in paralell for RS485

texts:
I have a system with two RS485 transceivers connected by a 300 meters long cable, with 6 wires inside it. In this case, 3 paralell wires of this cable are being used for the "A" signal and the other 3 paralell wires for the "B" signal, resulting in 3 identical transmission lines in paralell, and it's known that the characteristic impedance of this arrangement is 100 ohm, which is good for RS485.
The characteristic impedance for RS485 systems is between 100 ohm and 150 ohm, nominal is 120 ohm.
I want to use only one of this wires for signal "A" and other for signal "B", and I need the impedance of this new arrangement. How can I calculate this?
Old arrangement:
Z_0=100 ohm
New arrangement:
Z_0=?
Complete system:

Edit:
All internal wires are 26 AWG and 300 meters long. They are all paralell to each other, not twisted pair. Also, the whole cable is shielded, just like it was in the old arrangement.
About the remaining wires, two will be used for a DC signal, one for RS485 signal ground, and the last one is not connected to anything. The updated image with the new arrangement is the following:

Signal ground is connected to both ends grounds, with a 100 ohm resistor between the cable and grounds. Shielding is grounded at only one end without any resistor, like it was in the old arrangement.
Thanks for helping.


texts: Does an external interrupt interrupt ADC or does ADC stall interrupt?

texts:
I'm working on an RTC application with a 1Hz clock attached to the external interrupt pin on a PIC16f887. I also have continuous ADC operations happening along with the 1Hz clock.

My question is whether the ADC or the interrupt would get priority if both occur at the same time? What if the interrupt occurs during an ADC operation? Is the operation halted to allow the interrupt to be executed? This would obviously invalidate the reading.
Or does the interrupt wait for the ADC to finish?


texts:
I just began digital technology in my school and im struggling with one task my teacher gave me. Since I have holidays right now I cant ask my teacher (living in Germany). So I hope I'm at the right spot here!

This is the task he gave me:

  Create a circuit (functional block diagram) which only has a permanent output signal K2 if the input S1 was temporary activated. If the input S1 is temporary activated again the ouput K2 should go off.
  Please note: The output K2 should not flicker if S1 is permanently activated.

I also have to create a functional equation. Dont know if mine is actually correct:

Thanks for any help!