texts: Do you need to perform an erase before a write with a HDD?

texts:
A simple question, the answer to which is surprisingly difficult to find. Does the internal controller in a HDD have to erase a sector on the hard drive if it already contains information, before it can be overwritten? This is what has to happen in flash memory and this is performed by the Flash Translation Layer. That is, a page has to be erased before being written to. The reason one must to erase before programming flash is because you can only write 0s. So first the data is erased and a block is all set to 1s. Then 0s are written as necessary. Does the internal controller (or any layer of the software) of a HDD also have to do this? Or on a HDD can you write both 0s and 1s?

Also what is the mechanism for read and write operations? I know data is stored as varying magnetisations, however what technology does the read write head use to sense the magnetisation and how does it modify it? I haven't been able to find a comprehensive description.


texts: Can you turn two inductively coupled conductors into a transformer?

texts: So I'm working on a school project, and to be honest. Don't know a lot about electromagnetism. I want to make a wireless charging station that could be plugged into the outlet. Of course I don't want to actually use 230V (I live in Europe), so I'd like to turn that into 12V. And for that you need a transformer. But I was wondering whether you can, instead of using a transformer, have the coils serve two jobs. And have them transform, and wirelessly transmit and receive energy at the same time. And if that is possible, would that work the same way as a transformer. By turning one coil a few more times?


texts: Why do we require isolated supplies for gate drivers in 3-phase inveters?

texts:
I have used isolated supplies while making optocouplers based drive circuitry for driving 6 IGBT switches in 3-phase VSI in my undergrad projects. I remember my professor kind of explained why exactly it was required but I kind of forgot the complete reason. I also remember at first using 6 isolated supplies for 6 switches and then reducing them to 4 as I learned from some application note which was probably from TI. Can anyone tell me what happens if I don't use isolated supply? Thanks in advance!

PS : I know there are other ways such as bootstrap drivers, but I'd really like to know what would happen if I supplied all optocouplers by deriving supply from a same transformer.


texts: Effect on the current by power factor correction

texts: When I make the power factor close to one, does the current in the circuit Change?


texts: Can you saturate a transistor with a foreign voltage?

texts:
Is it possible to saturate a transistor by applying a voltage on the base that is comming from a different source than the source of the voltages of the collector and the emmiter?

simulate this circuit – Schematic created using CircuitLab

Edit:

I wanted to start a desktop computer with an arduino that is powered by an adaptor.
I solved this problem by connecting the 2 ground pins with each other.


texts: What is the cause of this drastically different simulation behavior with slight variation in capacitor values?

texts:
This site uses Circuit Lab's schematic and simulation tool, for which I am grateful. Recently, I was attempting to modify a circuit present in this answer to a question.

simulate this circuit – Schematic created using CircuitLab
I kept getting rather strange results:

However, if I change the value of C1 from 5uF to 5.6uF, I get this result:

In each case, I used a step time of 0.01 seconds.
Would I be correct in concluding that Circuit Lab uses non-polarized capacitors by default when the value of the capacitor is standard, but polarized capacitors by default when the value of the capacitor is "odd"? Is there some other explanation for this behavior?
Edit: Some new data points:
Mattman944 suggested that the simulation would work better if I decreased the step size. I tested with a 0.001 sec step, and the running to the rails was not visible within 10 seconds. This suggests that the mathematical limitations of simulating the circuit may be at least partly responsible for the running to the rails behavior.
Bruce Abbot noticed that the + and - inputs of the second op amp are reversed from the original circuit. I tested with the inputs corrected, and the simulation did not show running to the rails within 10 seconds. This suggests that the circuit itself may be at least partly responsible for the running to the rails behavior. (I actually was a bit surprised that the circuit in this question gives as stable an triangle wave with the 5.6uF capacitor as it does.)
I am convinced that my original conjecture that the problem lay in two different capacitor models depending on whether the capacitor was a standard or "odd" size, is wrong. I am inclined to believe that:
a) the circuit as I drew it, is essentially unstable (as a triangle wave generator).
b) a finer step in the simulation allows a longer time before the instability becomes apparent.
c) I just happened "get lucky" that the instability was apparent after 5 cycles with the 5uF capacitor, and not apparent with the 5.6uF capacitor within 10 seconds.


texts: Operational amplifier - comparator with LED

texts:
I am trying to find the differential input voltage(Vd) for the circuit above.
Since this circuit is in open loop, Us is going to be either +Vsat or -Vsat.

Rt is a thermistance that varies with temperature

Rh is a variable resistor.

I am supposing that R,R,Rt,Rh are in series.

In this case,

The inverting input(V-) would be

V- = 15 * Rh/(2R+Rh+Rt).

The non-inverting input(V-) would be

V+ = 15 * R/(2R+Rh+Rt)

Thus,
Vd = (V+) - (V-) = 15*(R - Rh)/(2R+Rh+Rt).

I am not exactly sure if I am doing this right...
I am having difficult time with analyzing circuits... Could you help me?


texts: How to use rn42 bluetooth module with dualshock 3

texts:
I have a rn42 Bluetooth module with HID features, now how do I use it to connect to a DualShock 3 or 4 controller with an Arduino. Since the DualShock 3 pairs only to a particular mac address, how to store the rn42 mac address into the PS3 controller.
There are numerous solutions for connecting a DualShock 3 with Arduino but all use a USB shield and Dongle and I don't want to spend cash on them and want to achieve this only with the rn42. Please, someone help.


texts: Which edge is better for choosing a trigger?

texts:
I have a 100Hz signal with a fast rising time and slower falling time. This is the output from a zero crossing detector. The signal is connect to an Arduino input pin. Arduino can generate an interrupt on signal RISING or FALLING edge. I tested them and both works well (apparently), but I wonder if there is a reason to choose one edge over the other.

This is the signal:

Edit

This is based in this circuit, which I need for one particular project (controlling a HID lamp):

In my case the lamp is a 240V 250W HID with magnetic ballast (0.88 power factor) that flicker with SSR, so I must use an electromechanical relay, but with zero crossing. With this signal Arduino will wait for a right time to close the relay, minimizing arcing. It's not terrible important, as the relay only close once per day (you bet).

Suggestions are welcome.

A different approach

User @jonk suggested a different approach to my problem. While it serve best my needs, it's not an answer to my question and cannot be posted, nor accepted.

Anyway, jonk's approach doesn't deserve to be lost in the comments, so here it is:

The idea is to use a SSR and an electromechanical relay in parallel. The Arduino will switch on both the SSR (with built-in zero cross detection) and the relay (two pins) at the same time. The SSR will switch on inmediatly, powering the load. After some delay and a few cycles, Arduino will turn off the SSR. Then the relay, already closed, will take the load while the lamp is still being heat (and it will unaffected for any voltage mishap anyway).

Why it is best? I don't have to mess with mains. I don't have to adjust timings. I don't need an interrupt capable pin (Arduino only have two).


texts: USB connection dropped and "on" LED dims using Arduino + H-Bridge

texts:
Possible Duplicate:
  Arduino loses usb connection

When I connect the 5v power to an H-bridge I constructed the Arduino loses its USB connection to my computer and the "on" LED dims.

What's going on?


texts: Question about using N-channel MOSFETs in a current sharing controller

texts:
My question is specifically regarding LTC4353 :

Product link: http://www.linear.com/product/LTC4353
Datasheet link: http://www.linear.com/docs/41582

Looking at the diagram on the product link, or the first page of the datasheet, I noticed that it is using an N-channel MOSFET, but the current direction is labelled as from Source to Drain.
I'm wondering what is the reasoning behind this implementation? Is it done to make use of the body diode of the MOSFET?


texts: Using RS485 over CAT5e Foiled Twisted Pair (FTP)

texts:
I'm planning a system that has two sub systems that need to communicate with the PLC via RS485. The baud rates are 9600 and 19200 bps.
The cables are static (i.e. not moving) and placed inside of a electric cabin.
In the cabin area there are a few more electric appliances, such as PLCs and stepper motors. Those are placed in other electric cabins or behind metal separation. The cabin is not tangent to the motors or PLCs but in a few meters distance from the motors, with a metal separation and the cabin between them.
At first, I thought about using CAT5e FTP cables due to low cost and because I have read that this application is possible. Unfortunately, my lack of understanding if that is considered a 'harsh environment' and if the Foiled Twisted Pair will be good enough for running the applications properly.

Do you think using the CAT5e cables (with a proper termination resistors) will do a good job or should I consider other cable?
If one of my sub-systems is working with EIA-RS485, will that shifting away from the standard can cause issues?

Thank you.


texts: 2n3904 vs. Pn2222A for FM Radio Transmitters

texts:
My question is which is better for transmitting an audio signal on the common 88 - 108 fm band: the common 2n3904 NPN transistor or the PN2222A NPN or are they interchangeable. I have seen a lot of circuits and some have one and some have the other.

[EDIT]

I realized my question was not clear. For the time being I would be fine if you could tell me which of these transistors would be best for this circuit.  I know the 2N3904 is used but would the other one be better or could they be interchanged?

Image from http://i1.wp.com/cdn.makezine.com/uploads/2013/10/kogawa_simplest_transmitter.png


texts: switch on delay not working (capacitor, transistor)

texts:
I built a switch on delay with a 2n2222 npn transistor and a capacitor.

(I left out the base resistor (2k ohms) and the resistor for the led (330 ohms) in this simulation, but in real I added them for sure. The resistor before the capacitor is 1M ohm)
In theory, my 5V power supply should charge the capacitor slowly (because of the big 1M ohm resistor before the capacitor) and if the voltages reachs around 0.8V the transistor should switch on the led. Why is my circuit not working? I guess I forgot something since I have never seen such a small switch on delay on the Internet before. Or is the 1M ohm resistor in front of the capacitor too small to see a delay between plugging in my power supply and seeing the led going on? What is my mistake?


texts: How are crossing lines implemented on microchips?

texts:
I always imagined the photolithographic microchip manufacturing to be a 2D layer creation process without layering, thus creating a topological problem for circuitry when you have some \$K_{3,3}\$ or \$K_5\$ in it, which would certainly be the case for any non-trivial design.

And there are papers out there talking about producing "3D" chips with multiple layers to save space, thereby adding to the confusion.

Yeah, that's sad, but that is what I learned in school, a bunch of mysterious riddles.
It's no wonder people start conspiracy theories about aliens catering those technologies to us.

So how can we build complex processors and chips just using a 2D topology ?


texts: What determines the current consumption in LEDs?

texts:
I analyzed some data obtained for some experimental LEDs, and I have asked myself why in some LEDs, the current and current density is higher than others.
Obviously, I am using different materials with different thicknesses in these experiments, which is one reason. Nevertheless, I wanted to analyze by taking the hole mobility in one of my tests. One of my LEDs has lower charge mobility, and as a result, the current and current density is higher than the other LED model.
My theory is that due to the lower charge mobility, the holes and electrons move slower to inside the LED, but they recombine effectively once they achieve the recombination layer. That is one of my arguments, but more points of view are more than welcome, if anyone has any different opinions.


texts:
I tried out op-amp level shifters on web. The ones recomended here as well but there is a problem when no input applied. The output voltage is no seperable from the case voltage applied. As i understand it is called op-amp biasing. I am trying to apply reference voltage with shift voltage but calculation isnt simple. So i am guessing there is a commoon way to do it.
How can i sense opamp level shifter has no inputs or how to bias that shifter?

And my biasing idea is like that:


texts: What is the operating principle of this single-transistor constant current source?

texts:
Sorry if this has been asked before; I'm still learning about electronics and probably don't have the right vocabulary to describe this part's functionality.

I came across an interesting part made by NXP when looking for simple ways to get a constant current source of around 20mA for trickle-charging some nickel batteries. The part is the 'PSSI2021SAY', from NXP:

https://assets.nexperia.com/documents/data-sheet/PSSI2021SAY.pdf

It is currently out of stock on Digikey, but glancing at the datasheet, it looks like it should be simple to make a similar circuit out of a PNP transistor, a couple of diodes, and a few resistors:

My questions are, how does this topology work? Does it require a stable input voltage or other external factors? Does the transistor need any special properties? What about the diodes/resistors?

It looks like it is somewhat cheaper than most other parts with a similar function, so in a nutshell, what's the catch?


texts:
Inexpensive noise-cancelling headphones use a single microphone located in a little lump between the plug and the earphones. They seem to work fairly well for ambient noises, but not for handling noise or touching the headphones themselves.

I want to build a pair for myself, but with a mic inside each earpiece. They will be closed-back, with large drivers. The idea is to compare the source material with the sounds in the space closest to the ear.

idealized schematic:

simulate this circuit – Schematic created using CircuitLab

Obviously a simple resistive feedback network is wishful thinking. Or is it?

What are the phasing considerations for this environment? Not looking for a complete calculated answer, more like "do I need to continuously recalculate the feedback network based on different ear shape/position?"


texts:
I recently purchased a Velleman Sound to Light soldering kit. I thought it would be easy to understand even as a beginner electronic hobbyist but I am having some issues.

Please take a moment to check out the kit schematics:

I have limited knowledge about how all these works but there are some parts of the circuit that are particularly troublesome for me to understand. Here are a couple of questions:

What is the purpose of the C4 capacitor? Is this what it's known as the bulk or smoothing capacitor?
Why does't the T3 transistor have a resistor on the emitter leg? Don't you need that resistor (for negative feedback) to be able to stabilize the transistor such as preventing thermal overrun, minimize beta variations effects between transistors etc?
What is the purpose of resistor R8? It looks like its on a weird place being in series between the power supply positive lead and and half of the circuit, what is up with that?
What is the point of having R12 and R5 as two separate resistors? Can't those two resistor be replace with a single resistor and achieve the same affect?
Why aren't the biasing resistors (voltage dividers) on T1 and T2 not identical? Its the exact same transistor so why is the voltage divider biasing different (specifically on R2 and R10)?

Thanks.


texts: Finding a transfer function by voltage division

texts:
If I have the following circuit:

I know that I can find the transfer function by doing voltage division.
However, in this example, where does the negative sign in front of R1 come from?
$$T(s)=\frac{-Z_2(s)}{Z_1(s)+Z_2(s)}=\frac{-R_1}{R_1+R_2+L \cdot s}$$


texts:
I'm installing surge arrester to protect a server room full of machines using the following page as a guide

http://engineering.electrical-equipment.org/electrical-distribution/how-choose-surge-protection-device.html

It said that it is required to put surge arrester devices between the low voltage input and the machines that want to be protected if the distance between them is more than 30 meter. My question is, what it the distance is less than 30 meter? Do I install only in the input?


texts: Problem of transistor thermal runaway in parallel connection

texts:
simulate this circuit – Schematic created using CircuitLab
I wanted to use two transistors in parallel to increase current rating.
So I simply put two transistors in PCB design. Later I found thermal runaway in transistor which will create problem in parallel. For which general solution I find is to use resistor in emitter. But I didn't put it in design.
So is there any other way to solve this problem except to use resistor at emitter?
I search for it and found that using a shared heat sink will keep both transistor temperature same so current will increase in both together and current will be shared equally. Is it right ?
I also want to turn on transistor only for 3 seconds. So does I even need any solution for this or I can go without any solution as no constant current is flowing for long time?


texts: Remove brown/yellow resin around electronic components

texts:
A fuse socket in my Edifier sub-woofer stopped connecting (I accidentally damaged it when I was replacing a fuse) and I want to replace it.

When I opened the rear panel I found out all high voltage components are in black rubber tubes and are sealed by some brownish resin.

Is there some way beside bruteforce to remove it?

Image for reference:


texts:
I want to discharge a capacitor (0.47μF) through a led (red led: 2V, 15mA) but I want the discharge remains for a while e.g. 60s or 30s. I charged the capacitor with 10V then I calculated the resistance's value (533Ωhm) to have 15mA current but the discharge was very quick.The led lighed up for just a moment. I know that if I put a bigger capacitor the discharge will remain for a longer time. But, I want the specific capacitor to use with 0.47μF capacitance and if it is possible to change the resistance.

So I try to use the function V(t)=Vo*e^(-t/RC) to calculate the RC.

The values for the function are: t=60s Vo=10V and V(t)=2V as a result RC=186,45s

So, if I put in the function C=0.47μF, the value of the R is calculated 79MΩhm but I can't succeed 15mA current with this resistance.

As a result the led never light up! Could you recommend a way to have the above capacitor but with a little bit longer discharge?


texts: Switching between power supplies - USB dominant

texts:
I'm trying to create a data logger. I want the data logger to be able to run in 2 modes.

Bench mode (usb powered 5V)
Field mode (externally powered 3.3 - 12V)

Bench mode is active whenever power is supplied to the usb port. In the other case Field mode is active. i want this because the data logger will be used in battery powered projects and i don't want the data logger to leech from the host project if it can get it's power from usb.

So basically i want to create a power multiplexer that switches the external power supply off whenever usb power is supplied.

The datasheet of the micro controller I'm planning to use gave the following schematic.

The working thou is exactly opposite of what i had in mind. So i tried to adjust it.
I know this should work as long as the external power supply is lower the 6-7V, but what about higher voltages?

simulate this circuit – Schematic created using CircuitLab
Note: Only an example.

Either configuration should have an as low as possible current consumption, and a small footprint.

I have seen a lot of topics related to this but they haven't given me the answer how to do it.

so my question(s):

Is it possible?
How can i switch off a 3.3V - 12V power supply using USB power supply.
How to determine needed resistor / capacitor values.
Which parts would you recommend.

New Edit

thou ORing is an option it doesn't prevent my circuit (behind the LDO) to leech from the host project.

I also understand the restrictions set by the usb standard.

i probably should use mosfets instead of BJT's but i wonder if this would work.

simulate this circuit


texts: Selecting a transistor for high-side switching at 5V with a 2A load current

texts:
I'm doing a high side switching of 5V 2A load and will be ON or OFF for long time(1-10 hours).

Now I'm confused about which transistors should I use ? or MOSFETs ? Do I need heatsink ? I really prefer SMD transistor or MOSFET, if its possible ?

I also want 5V on other side of transistor/MOSFET too. I'm sure there will be voltage drop, is there any way to get back the voltage drop ? First I thought to use bit high voltage in switching like 7V then put voltage regulator on other side so I can get right 5V. But since the load is 2A. The power will be 10W if I'm not wrong. Then I think its too much heat.


texts: How to translate analog inputs at [-15,+15V] to [0,+3.3V] without ±15V rails?

texts:
Title says it all, but to provide some context: the goal here is to design a 12-channels ADC system. Input signals varies between -15 and +15V. The acquisition system will probably be a mid/large arduino, but this is not a constraint.

Constraints:

High input impedance (downscaling through resistor networks is excluded)
Small footprint (once 12x count taken into consideration), low part count. Trying to keep this as simple as possible to assemble for a hobbyist
Only supplies currently present: +3.3V (microcontroller), +5V (USB charger), +12-14V "automotive", non-regulated.
Using an 12-to-1 I2C multiplexer as a first stage is an option, and this could free a lot of space, but this is not my preferred option

Exotic ICs easily sourced from major suppliers are fair game.

Goal is ~20 acquisitions per second, with acquisitions on the various channels as synchronous as possible. Accuracy requirement is low: +/- 50mV (on source) would do, in line with an 10-12bit ADC.

I've tried weird configurations with op-amp in summing configuration, but I'm out of ideas.

Thanks


texts: I want to make an ideal diode using a comparator and one p-channel mosfet. I'm looking for a cheapest method to add a few millivolts (25mV - 50mV) as an offset to one of op-amp's inputs just to ensure that the mosfet would be forward biased.


texts: Shorting Triac gate to ground doesn't turn it off

texts:
In the below circuit, 170 is a Q401E3 Triac: http://www.mouser.com/ds/2/240/E2Triac-18233.pdf

The capacitors are ceramic disc.

The Triac is rendered normally conducting when S1 is open.

When I close S1 the Triac is still conducting when I don't want it to be.

I'm not sure what is wrong or how to fix it; would appreciate any help. The only thing I can think of that is happening is that the path from Engine Magneto to ground through the S1 switch is of a lower impedance therefore making the Triac useless in the circuit below. The point of the circuit was that when S1 closes, it allows the spark plug to ignite.

Edit: circuit based on patent US5190019 https://www.google.com/patents/US5190019


texts: When should ESD Protection Diodes be used?

texts:
I'm working on a heated glove project that uses a Buck-Boost converter to step-up/step-down the voltage across the heating element. This is something that has just occurred to me, but I'm not sure if my fabric will cause any ESD issues. The fabric itself will be sewed to a polyester glove liner inside a fleece glove, so ESD may or may not be present. The PCB itself will be coated with a conformal silicon coating and placed into the inside padding of the glove, but I feel that the DC/DC converter IC could still get damaged from possible static of the fabric discharging into the output pin of the IC.

So would this be a situation where a ESD diode should be used? And if so, should it be used with a DC/DC converter?


texts: Maximizing efficiency in synchronous boost converter

texts:
simulate this circuit – Schematic created using CircuitLab

The aim is to design a synchronous boost converter using a microcontroller ATMega 2560 switching at 31.25 kHz.

5V PWM signal is fed from the microcontroller to the high and low side driver (IR2101).

My current output is about 15A max and I read somewhere that ideally, diode current should be limited to 7A max to prevent high power dissipation.

I would like to minimize power dissipation through the diode and maximize efficiency.

I tried turning on the high side switch with NOT gate signal from the low side PWM signal.

High side mosfet turns on when the low side is turned off but the voltage remains at 4 volt and does not increase.

What could be the cause of this problem?


texts: What will happen if 1/0 condition appears in microcontroller?

texts:
I need to implement the following function in a microcontroller:
\begin{equation}
\ k= (v_{(n)} - v_{(n-1)})^{-3}
\end{equation}
Here, 'v' stands for signal amplitude and 'n' for sample number. If the difference bettwen two successive samples becomes zero, what will happen?
Will the corresponding data register will be saturated or it will create junk value or create any problem?


texts: Why is slip necessary in an Induction motor?

texts: Why should the rotor of a 3-phase induction motor not rotate at synchronous speed?


texts: In a 4 phase dc motor control application, I have to excite the coil using Mosfet with the pwm of 12.5 Hz with the train of pulses of 12 khz on each phase. So I am in a position to create 4 different pwms each with the above mentioned frequencies. I have planned to use Pic 18f45k80 which has four CCP modules. But these modules use only two timers TIMER 2 and TIMER 4 for PWM. So I could create only 2 different pwm at a time. Is there a way to create 4 pwms using PIC 18f45k80 with using CCP modules? I like to create a pwm waveform like the image that I have added.


texts: How do I know I have the right Bootloader Installed on my ATMega328P-PU?

texts:
I got an ATMEGA328P-PU , already bootloaded , but when I tried to upload the program
(a simple program for blinking the LED on pin 13 ) I'm getting an error as :

  avrdude: stk500_getsync(): not in sync: resp=0x00

I have googled a lot and have tried numerous way to get rid of this error viz :

-press reset just before selecting Upload menu item

-correct Serial Port selected

-correct driver installed

-chip inserted into the Arduino properly

and followed every instruction on www.arduino.cc
but heck


texts: Can AC voltage phase change across an SSR?

texts: I got an SSR (Picker PCS15-D-240A-25ZL) to control a single phase 240VAC North American circuit going to a heating element on a homebrew setup. One of the load wires goes through the SSR and the other goes straight to the output so that the circuit can only be completed when the SSR connection is closed. I tested the heating element plugged directly into the wall circuit and it works fine. Then I moved to testing through the SSR and noticed the heating element wasn't producing any heat. I decided to see what was up with a multi-meter. Checking the output I noticed that difference between the two load wires was approximately zero volts which was odd. Then I decided to check from one post of the SSR to the other when it was closed and noticed a voltage difference of 240v. So is the SSR changing the phase of the power somehow and if so how can I resolve the issue?


texts: Modelsim - Weird verification problem with DDR and Xilinx UNISIM

texts:
I am doing verification of VHDL component using OVM and ran into serious problems. I have found that problem is in one specific component and created environment specifically for it. It's a RGMII to internal interface converter (from DDR to SDR) using Xilinx UNISIM components to simulate special FPGA chip parts behavior.

BUFG_inst : BUFG
port map (
    O => INTERNAL_CLK,
    I => RGMII_CLK
);

IDDRDATA0_inst: IDDR
generic map (
    DDR_CLK_EDGE => "SAME_EDGE_PIPELINED",
    INIT_Q1 => '0',
    INIT_Q2 => '0',
    SRTYPE  => "SYNC"
)
port map (
    Q1 => data(0),
    Q2 => data(4),
    C  => INTERNAL_CLK,
    CE => CE,
    D  => RGMII_DATA(0),
    R  => RST,
    S  => '0'
);
-- several more instantiations

I generate transactions and send them to DUT using driver:

forever
begin
my_transaction tx;

@(posedge dut_vi.clock);
seq_item_port.get(tx);

dut_vi.ctl   = tx.ctl;
dut_vi.reset = tx.reset;
dut_vi.data  = tx.data;

@(negedge dut_vi.clock);
seq_item_port.get(tx);

dut_vi.ctl   = tx.ctl;
dut_vi.reset = tx.reset;
dut_vi.data  = tx.data;
end

In Modelsim wave, this input (watching DUT input ports) is just fine.. But internally, it takes previous value of data - for example previous value of CTL was 0, on rising edge it's 1, but DUT samples with rising edge that previous 0 as it didn't actualize inside modelsim.

I tried using "little hack":

TMP_CLK <= RGMII_CLK after 1ps;

BUFG_inst : BUFG
port map (
    O => INTERNAL_CLK,
    I => TMP_CLK
);

It solved the problem (partially). DUT was now sampling correct values.. But it created problem with output and monitor. Now everything is correct in wave, but monitor sees wrong values (but only sometimes - usually with beginning of packet - valid signal changed from 0 to 1). So it's similar problem as with input. My monitor looks like this:

forever
begin
dut_out_transaction tx;

@(posedge dut_out_vi.clock);
tx = dut_out_transaction::type_id::create("tx");

tx.dv    = dut_out_vi.dv;
tx.err   = dut_out_vi.err;
tx.sof   = dut_out_vi.sof;
tx.eof   = dut_out_vi.eof;
tx.data  = dut_out_vi.data;

$display("DUT_OUT EOF: %b", dut_out_vi.eof);

if (dut_out_vi.eof == 1)  // this never happens
    ovm_report_info("out_monitor", "EOF");

aport.write(tx);
end

Since it's similar bug, I tried similar hack - I added #1ps right after @(posedge dut_out_vi.clock); and it truly helped.. But new problem arisen - now monitor never sees EOF signal in 1 even though it is in 1 in wave several times.

I use Modelsim 10.5 with resolution of 1ps. Any ideas what could be causing it or how to fix it?


texts: I am trying to choose a right DC adapter for SNC-VB630 CCTV Camera but the only specs I could find in the official documentation was 'INPUT 12V DC'. Nothing about amperage. I have a 12V dc adapter with 400mA current at hand and I was wondering if that would suffice. How can I find out?


texts: Does Crystal/Oscillators package matter?

texts: I design a lot of PCBs that uses microcontrollers with external clocks. For some reason a lot of the example designs always tend to use the big generic HC-49 package. Even factory made modules that I purchase tend to use that package. I typically source my components from LCSC which has a large variety of components. Are there any disadvantages to using the smaller packages for crystals other than price and availability?


texts: ULN2803 relay driver working for high loads

texts:
I am trying to understand the working of this Darlington transistor array. I am using it for inductive loads and for driving the loads of my relays, but now I am trying to understand the part of its ability to drive high loads.

What for the high current drive is needed, if the use of the load driving is just to have a current path and to energize the inductor by the COM supply?

For my relays (min switching power 5V, 100mA,) I am using AC/DC power adaptor + buck converter, so the output power is around 5V, 3A load.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm writing software (for ATMega32) that reads pressure from Bosch BMP280 sensor. I'm using I2C bus. I have found this library: https://github.com/BoschSensortec/BMP280_driver

and I have a question about inizialization of I2C:

int8_t rslt;
struct bmp280_dev bmp;
/* Sensor interface over I2C with primary slave address  */
bmp.dev_id = BMP280_I2C_ADDR_PRIM;
bmp.intf = BMP280_I2C_INTF;
bmp.read = user_i2c_read;
bmp.write = user_i2c_write;
bmp.delay_ms = user_delay_ms;

What function should I use as user_i2c_read/user_i2c_write and user_delay_ms?


texts:
I'm having an issue on an FPGA project I'm working on. I'm unable to write to defined memories within the FPGA, but writing to registers works fine. I was thinking about working around this problem by simply using registers as memory. I only need to store a max of ~1024 bits at a time, and there is plenty of register space available on the FPGA. The FPGA in question is an Altera Cyclone III model if that makes a difference.

Are there any disadvantages to using registers versus memory that I'm overlooking?


texts:
Inside a Nintendo Switch I spotted some traces that take a meandering path to the RAM chips.

What are the benefits of designing it this way, instead of taking the shortest path?


texts:
I'd like to control 3x L6234 IC's (3x BLDC motors) with the cheapest microcontroller/board/lauchpad but I'm a bit confused about the requirements needed for the microcontroller. As I understood each motor needs 3 PWM control signals so I'd need 9 PWM's, but I'd also need 9 timers in the microcontroller right? Or can I use just 3 combined with prescalers?

I was thinking about using Arduino boards but they are still more expensive than texas launchkits (MSP430 launchpad and stellaris could do the work?).


texts: Reduction by factor of 3 in non-linear grounded-emitter amplifier distortion from Art of Electronics, 3rd edition

texts:
I've been going over the basics reading the Art of Electronics (3rd ed.) by Horowitz & Hill. I am currently reading  about the shortcomings of the single-stage grounded-emitter amplifier. Precisely, their non-linearity.  I'm kinda lost in that part where the authors say (on p. 94):

  Because this represents the extreme variation of gain (i.e., at the peaks of the swing), the overall waveform "distortion" (usually stated as the amplitude
  of the residual waveform after subtraction of the strictly linear component) will be smaller by roughly a factor of 3.

Where does that 3 come from? How did they derive it?


texts:
I've connected my LED to 1K resistor. When I tested it out on a breadboard it worked fine, the LED was very bright. Now, when I soldered it to the board, the LED light is poor. I did everything the same, so it confuses me what it could be. Everything else works fine, so that means the connection is good. Could the problem be in the tin or paste I use? Does anyone have an idea?
Edit: The voltage is 5V. I am using the same USB programmer.


texts: Rotate Eagle CAD component about its origin

texts:
Could someone help me redefine the center of rotation for a component please?
When I open the component in Eagle library I can see there is a little cross on one of the pins and at the moment when I rotate it turns about this point. I would like the cross in the middle of the part (it is a PCB-mounted potentiometer so between the 2 outer ground pins) so I can rotate about the center of the actual part.
Does anyone know how to move the little white cross to the center so I can turn the part around this point instead please?


texts: What does this component do in this series pass regulator

texts: I'm wondering what the 1.2k resistor does in the following circuit series pass voltage regulator.  I should also mention, \$Q1\$ is a Darlington transistor.


texts: Installing a "battery controller" on my desktop motherboard

texts:
I'm currently working on a DIY tablet project which involves a low power desktop motherboard and a huge 40 Ah 12 V Lithium battery. My set up ATM involves:

8* 3.3 V 20Ah batteries (series of 4, two of them connected in parallel)
pico-PSU can take input of 12~25 V, 80~120 W ATX PSU
Mini ITX motherboard KTQM77/mITX

Now, I think this set-up is pretty simple, but I cannot think of a way to check the battery remaining and other stuffs over the Windows. Sure, I can get a battery display with a small micro-controller to check the remaining battery and so on, but I really want to get that laptop-like battery control interface. Can this be done?

Also, if you see any problems or suggestions with my rig, let me know-like 40Ah battery being a bit of overkill and so on.


texts:
I'm planning on buying a Raspberry Pi  and I want to power it using solar energy. Since the voltage input needed by the Raspberry Pi is 5 Volt, I need to build up the relative low voltage power input of the solar panels (I guess they'd be around 1-2 Volt?).

To tackle this problem I build a little circuit, see below.

If S1 and the middle switch are closed, Voltage will be build up by the inductor until 5 Volt is reached. Then a timer will automatically open the middle switch, causing current at 5V to flow to the capacitor, here current will be build up. As the capacitor is loaded with current S3 can be closed, powering the Pi.

I've got very basic knowledge on designing circuits, so my main question is: Will it work, or not? If not, what am I missing?


texts:
I am trying to understand the difference of pulse operating.
How I get there is two ways.

For example.

Bias procedure:

Set \$I_D\$ limit to 400 mA, \$I_G\$ limit to 4.5 mA
Set \$V_G\$ to -5.0V
Set \$V_D\$ +25V
Adjust \$V_G\$ more positive until \$I_{DQ}\$ = 40 mA.
Apply RF signal

Here are the options:

Pulsing the DRAIN

Applying desired bias voltage to the GATE (it's about -2.5V ) and pulsing only DRAIN voltage (+25V).

Pulsing the GATE

Applying maximum bias voltage to GATE (-5V), applying DRAIN voltage (+25V) and starting to pulsing GATE voltage from desired bias to maximum bias  (-5V to -2.5V).

I want to understand when to use which way, and what are the differences.

Second question:

How to more accurately design the current limits for \$I_D\$ and \$I_G\$?  How to make sure that when you turn the system on or off tgat the GATE voltage will appear first and be there when DRAIN comes?


texts:
As I know, the direction of current in N channel mosfet is from drain to source. Now, how this current can be pass in this circuit????
SO, why most of the reference books say, in n-channel current flows from drain to source, and for p channel from source to drain??


texts: What complications arise when designing a USB device sharing switch?

texts:
I wish to design and build a USB switch capable of transferring one USB keyboard between one of two computers.   I wish to automate the process of unplugging the device from host A and plugging it into host B and vice versa.
What are the complications that arise when trying to do so, and what different solutions are there on an analog (i.e. just mechanically switch all 4 or 8 cables from one side to the other) or digital level?

If we choose an analog design, it should be straightforward to completely interrupt the connection between the device host A and establish a connection between the device and host B. I understand that this necessitates USB re-enumeration and so on, but from an outside perspective, there is no obvious reason why this should not work as well as unplugging and replugging.
I am aware that commercial solutions to this requirement exist.

Most commercially available devices on the other hand seem to opt for a digital switching solution instead. What are the benefits of doing so, and what additional drawbacks are there (the possibility of unintentionally feeding voltage to upstream ports comes to mind)?


texts:
I'am doing some small IOT device and want to use power source 2 x AA elements which gives ~3V. It should be power efficient, so in schematic included TPS61025 as output requirement is fixed 3.3V. First PCB revision didn't worked, possible of bad PCB layout. Could you check if such layout is optimal for TPS, any suggestions for improvements ? FB left floating as its fixed voltage TPS.
L1 used LQH32PN6R8NN0L
C2 used GRM21BR71A225KA01L
C3 low ESR 40mΩ T520B107M006ATE040


texts: How do I find the best DC motor for my rack and pinion system?

texts:
I need enough electric power to produce about 0.289 Nm with a rack and pinion system and compress 24 mm of a 110 mm x 21.6 mm, 0.99 N/mm steel spring.
What I have so far is that for a 10mm pitch diameter gear with ten 1mm gear modules and an angular velocity of about 15rpm (or 1.571 rad/s) I could use a 12 V power supply to deliver 37.8 mA and do this job with a DC motor:
I didn't know where to start from so I arbitrarily decided that the rack would slide the 24 mm with 3/4 of the gear full rotation in 3 s. That brought me to a 10 mm pitch diameter gear with ten 1 mm gear modules. The angular velocity I obtained is:
$$
\theta =\frac{3}{4} 2 \cdot \pi \cdot \text { rad } \quad w =\frac{\theta}{3}=1.571 \frac{\text { rad }}{s}
\\
$$
Is that reasonable? Should I reconsider this decision?
Then, I assumed the torque on the gear to be the same as the work done by compressing the spring and set this to be the electrical power consumed:
$$E \cdot w=0.454 W$$
$$ V=12 V \quad I =\frac{(E \cdot w)}{V}=37.837 \mathrm{~mA}$$
Are these last equations correct? If so, how do I go about combining an adequate DC motor with the optimal gear ratio?
Any corrections, comments and/or suggestions are welcome!
For a more thorough description of my problem go to here


texts: Regulatory considerations for 500W, 400V DC power tether

texts:
I'm working on a robotics project where we intend to deliver ~500W of power over a 1000 ft tether. The current plan is to run ~400VDC down the tether on a pair of 16 AWG wires. These power wires will be bundled with other control wires as part of a cable assembly.

We are intending to include basic safety features like fuses and overcurrent/overvoltage/temperature sensors. We're considering including some type of DC Ground Fault Interrupter. Additionally, this is not a consumer product, it's an industrial tool for infrastructure maintenance work.

I have seen in this post that many of these standards are handled by UL standards, but I am not sure if complying with UL standards is a legal requirement, or only necessary if we are pursuing a UL certification.

What sort of regulatory standards do we need to comply with to distribute power to our robot in this manner?


texts: Is the output of a smoothed rectifier same as the DC output of a battery?

texts: When rectifying an AC signal to DC through full wave rectification and smoothing using capacitors, is the output same as that of a DC battery?


texts: Can I run a program, on an ATtiny85 with micronucleus bootloader, without usb connected?

texts: I have managed to put micronucleus bootloader on an ATtiny85. Using it, I can successfully upload programs to my ATtiny through USB and they run as they should, as long as they are connected to USB. When I only connect the Tiny to +5V and GND, it does not run the program. How can I change that? How can I make it so that my programs run even without connecting the ATtiny85 to USB?


texts: Turn S R Latch Using a NOR gates into NAND

texts:
I can't post a picture so the question will use Boolean Algebra. For me an SR Latch is

S NOR Q' = Q
R NOR Q  = Q'

I will represent Q' as P since Q' might be mistaken as NOT(Q).

S NOR P = Q
R NOR Q = P

If I want to turn it into a circuit using only NAND gates it turns into

NOT(NOT(S)*NOT(P))
NOT(NOT(R)*NOT(Q))

When I build the circuit it seems that I have way too many NAND Gates. Random pictures online show that I only need 2 NAND gates. This does not make sense to me, specially if it can be built with 2 NORS then with Boolean algebra I should get 8 or 6 NANDS.

That is what I came up with, which happens to reduce to 4 NAND gates. Is that correct?


texts: Can 2.4GHz antenna radiate through a small enough enclosure opening?

texts:
I am designing a device with two stacked parallel PCBs of which the top one serves as a front panel (with touch pads), while the bottom PCB holds all the components. I need to add a Bluetooth LE module to the bottom PCB and since the top PCB is mostly covered in copper, and the enclosure will likely be metal, I need to find a way for Bluetooth to radiate.

I see two options here:
1. Choose a Bluetooth module with U.FL connector. Mount it together with all the components on the bottom side of bottom PCB. Mount another U.FL connector on the bottom side of front panel. From there I could draw a PCB antenna on the front panel either on the top side (and make a via to U.FL) or on the bottom side.
2. Choose a Bluetooth module with chip/PCB antenna and mount it on the top side of bottom PCB. Make a opening in the copper layers of the front panel large enough for bluetooth to work.

The second approach will be much cheaper than the first (U.FL connector and cable add up to $7.50 on Mouser) but I'm worried it will make my bluetooth radiation pattern too directional, and I can't imagine what is the reasonable size of the opening in copper layer? I can't afford to spend much front panel area on that feature. OTOH, if the opening area required would be about the same as area required for a PCB antenna + keepout area (approach 1) then I can do it.


texts: Amplitude demodulation on receiver receiving higher frequency than initial message tone

texts:
I'm using an envelope detector to demodulate my AM signal with the schematic below.

I'm expecting to hear a 1Khz tone at V_demod but when I listen in on the signal, the frequency of V_demod in real life sounds higher in pitch compared to 1kHz. Does this mean I have a bit of Frequency Modulation? Can this also be the result of not having the circuit closely tuned to the specific carrier frequency? I thought if the circuit isn't tuned very closely to the carrier frequency, I would get a bunch of static and the amplitude will drop (like how if you tune an AM radio slightly outside of the frequency, you get this kind of response)


texts:
How does for example a generic signal detector (E.G. this cellular frequency detector circuit) actually pick up on a specific range of frequencies? (for 4g im assuming its around 900Mhz?)

In regards to that, could this circuit be changed so that it picks up other ranges/specific frequencies (E.g. 500Mhz)?
P.S Please bear in mind I am very new to this.
Thanks!


texts: What are FIT's and how they used in reliability calculations?

texts:
In Military, Medical, Space, Professional eqt. design there is a need to be able to prove that your device can last a certain length of time with a certain confidence level.  Or that reliability must be used in design to inform the design direction, either through component selection, component testing and sort or in amelioration techniques (like redundancy, FEC's - Forward Error Correction etc.).

How are FIT's (Failure In Time) used in the reliability aspect of design and verification? Examples of calculations?

How are FIT's determined/derived?

How is this related to MTTF (Mean Time To Failure) and MTBF (Mean Time Between Failures)


texts: What exactly does Close Loop Speed Control System control?

texts:
I'm working on a project about controlling Brush-less DC Motor using PI(Proportional Integral) Close Loop Speed Control Method.
3 Phases Motor is driven by 6 MOSFETs, Rotor speed is sensed and feedback to the control IC, this IC will compare the reference speed (target speed) with the sensed speed and adjust the control of the 6 MOSFETs.
Schematic is as below:

Calculation and controlling can be done inside the IC itself, but I want to know what signal the PI Close Loop Speed Control will control to archive the target speed? Eg: when rotor speed is lower than ref speed, the controller will increase the Duty cycle of PWM or will it increase the phase switching frequency?
Thank you all for reading.


texts: Arduino - Stop execution of code definitly

texts:
I've got a big problem with my new Arduino. I made a big mistake, and now I can't anymore connect to my arduino. Is there any possibility to recover the Arduino, or to stop the execution of code definitly?

Here my code:

void setup () {
  Serial.begin(9600);
}

void loop () {
  Serial.write("Hello World!");
}

My problem is, that this code is executed so immediatly after booting the Arduino, and I can't upload something different to the Arduino...

Please help me.


texts: How to switch an output based on specified voltage difference (outside of rail tolerance)?

texts:
I'm designing a CAN circuit that will connect a series string of 12V batteries together. The first battery will be tied to a common ground (think vehicle chassis) that will connect to the CAN ground which is shared separately across the batteries.
I'm trying to design a circuit that will activate a GPIO pin if CAN activity is detected. At it's simplest, I believe this is achievable with the use of a differential amplifier with low gain - such that the inputs are buffered and summarised independent of the amplifier circuit's ground.
What happens however if the CAN voltages are offset - i.e. if we consider CAN to be +2.5V and -2.5V relative to the source ground - in the 4th battery in the string the difference becomes 38.5 and 33.5 relative to that batteries ground (and well above rail voltage)
Is an instrumentation amplifier or differential the right circuit for this application? Ideally I want a buffered circuit where if the difference between Vin(A) and Vin(B) > 4V, an output gets pulled high.


texts:
Firstly apologies for any naivete in this post. I am not an electrical engineer, I just have a problem I am trying to solve.

I have a 12v power supply connected to a 5v "reducer" (which started off life as a car lighter port -> USB converter) connected to a device which draws 500ma and has an internal battery. In the event that the connection from the 12v -> reducer is lost, currently will flow in the opposite direction to the reducer. I'm not sure what is drawing current, there is an LED "on" light which remains lit when the 12v is disconnected, but for this application I want no current to flow from the device -> reducer as it is important to conserve the device's battery supply.

So I thought a need a diode, rated for 500ma / 5v forward and maybe also a reverse rating (let's say 10ma / 3v - the device's battery is 3v and the reducer draws 10ma).

Searching for "5v 500ma diode" on eBay comes up with no results, mainly Zener diodes which I don't want. "assorted diodes" is flooded with listings for LEDs and "junction diodes" returns quite a few listings for rectifier diodes but my supply is already DC so I don't know if these are the right solution.

When I search for "assorted resistors" I can pick what I need, but when searching for diodes I can't find any listings for standard "PN" or "junction" diodes.


texts: I have the Xilinx Spartan-3AN Starter Kit and I need to use the on board DDR2 SDRAM (MT47H32M16CC-XX). Until now I only used Static RAM and this type of memory is new for me. Can someone explain me how this memory works? What are the differences compared with a SRAM?


texts: Transient Response and s-plane root location

texts:
A second-order system has the closed-loop transfer function T(s)=Y(s)/R(s). The system specifications for a unit step input is as follows:

I managed to solve the problem until this step. But I am stuck at solving the permissible area for the poles in the s-plane as per the question mentioned in the given image.


texts:
I'm currenty working on a 4 layer PCB that requires two parallel memories.My question regards the distribution of the traces in the PCB. Is it better to trace them like a bus:

or is it better to take only one trace to both ic's? Like this:

Does it affect the perfomance of the circuit?
Thank you very much.


texts: I have an old RCA VCR (model number VR501) which contains a fuse in the power supply I am repairing. From the markings on the fuse I can only tell that it is a 1.6A 250VAC glass 5x20mm fuse, however I am not sure how to tell if it is a slow-blow or fast-blow. There is no available service manual for it that I can find either. Would anyone know which of these it would be?


texts: How to read serial data from oscilloscope

texts:
I have a microcontroller (PICAXE 20X2) and a pot meter. I programmed the micro so that it sends any change of pot meter to serial port of PC. Obviously it is a 8bit ADC. Now the interesting thing for me is being able to decode this serial data on the oscilloscope.

Here are two pictures, the first is when the micro is sending "0" to PC and the next one is when it sends "255". The data is being transmitted using 9600 buad and I can receive them at the PC terminal.

First Pic

Second pic

So my question is, did I capture the right data on my scope, and second how one can read and decode this pulses into a hex or ascii format. I mean how to read this rising and falling pulses (0/1).

Thanks.


texts: Microcontroller GPIO status when switched off ? Can current flow from internally in microcontroller from one gpio to other gpios when switched off?

texts:
I am using arduino nano GPIOs to switch multiple devices (16 devices) using MOSFET (IRF540N).

I have configured my switching circuit in such a way that my device will remain ON even if even if high signal is not given to but to switch off those devices nano needs to give LOW signal (I have implemented this circuit using resistor divider).

My requirement is to keep the devices on even if nano is not powered which is been achieved only when one device is connected but 2 or more devices are connected then devices are switched off.

I am also isolating the GNDs of nano and devices using relay.

Still my devices are getting Off when multiple devices are connected? Is it because of even if both the GNDs are isolated some amount of current flowing via nano controller internally?

Is there any other solution to achieve the same?


texts:
Hi fellow electronics enthusiasts.
I'm currently working on vibration detection machine used to detect unbalance from a rotating shaft, rotating from 300-2500 Hz. I have both the tacho signal ( 1 PPR ) and the vibration from transducer.

Now I'm really confused. After the transducer there is sweep filter that uses the tacho signal as center frequency so at 1 kHz the output sine wave is 1 kHz.

How do i extract useful data from this signal ?

I've read for the past week on the internet about order analysis and different methods but im so confused about how to implement it, how fast should the ADC sample rate be for the order tracking?

Should I do Fourier transform over the sine wave?

How to transfer the signal to angular domain?

Everything is just confusing. A little help on order analysis, or how to extract information from rotating shaft would be very appreciated!


texts: Serial 2's Complementer with One Input and One Output

texts:
I know this question has been asked and there already are answers to this question on the Internet. I just want to ask you where I am wrong in my way of thinking.
When I first saw this question, the shortcut -keep copying until you see a 1 and then complement the rest- hadn't occurred to me. So I thought I would just complement the bit, add 1 to it and if I get a carry then I would keep it in the flip flop to add it to the next bit coming from the input.
Meaning that,
In State-0

if the input is 0 then I should output "0" (after complementing) and keep that carry "1" in the flip-flop so flip-flop goes from state-0 to state-1.
If the input is 1 then I should output "1" but the flip-flop remains in the same state which is state-0.

In State-1

if the input is 0 then I should output "1" -since 2's complement would be 10 and I have a carry "1" in the flip-flop- I would get another carry so the state remains the same.
If the input is 1 then I should output "0" and the flip-flop remains in the same state as well.

Here is my state diagram :

+---------+-------+-------+--------+
| Present |       | Next  |        |
| State   | Input | State | Output |
|    A    |   x   |   A   |   y    |
|    0    |   0   |   1   |   0    |
|    0    |   1   |   0   |   1    |
|    1    |   0   |   1   |   1    |
|    1    |   1   |   1   |   0    |
+---------+-------+-------+--------+

After getting the equations from the table above. I get a circuit like so:

simulate this circuit – Schematic created using CircuitLab
Can you please help me to figure out what's wrong with my way of thinking?
Thank you in advance. :)


texts: Pulse generator with single op amp and diode

texts: I want to design pulse generator with specific period and duty cycle. I found a pulse generator with single op amp and diode. I couldn't find information about how to calculate period and duty cycle. If you have any suggestion about pulse generator design with single op amp (not comparator or 555 timer). You can find my schematic in figure below.


texts:
In just about every design guide I saw, the formula for primary inductance of flyback is:

However in "SMPS Design" by Pressman/Billings the equation for CCM is:

To bring second equation to the first form Kr should be = Vin/(Vin-Vds), which is always > 1. Does not look right.

Question: Which equation should I use?

UPDATE: I'm accepting @andy-aka answer because it prompted me to verify the derivations in Pressman's book. Turns out that at some point they use DCM formula dI = 2 x Iedc (instead of CCM dI = 2 x Iedc x Kr) to substitute dI in Lp equation.

So, the answer is: First formula is correct, second is wrong. Although I suspect one of the two Vin(min) in it can be substituted for Vin(min) + Vds to account for voltage drop in a switch, like it is done in the book.


texts:
I'm facing a strange issue which I can not identify.
The circuit is the basic PT2399-based echo.
My components setup is based on the research of similar circuits:

The problem is that I'm not getting any feedback echo effect with this at all, and also I'm not able to hear the delay effect when I'm turning the corresponding pot (connected to the pin6).
I can hear the delay effect when I remove the connection between the feedback pot and pin16 (which is supposed to create a feedback loop) while placing the audio probe right after the feedback pot out.
The similar, but the simpler circuit was working for me (unfortunately I don't have it), a difference is in the LPFs with the internal op-amps in the chip and some capacitors.
Am I missing something?
UPD:
My audio probe is a simple jack with positive/ground wires, connected to the headphones.
By connecting the circuit output to the audio interface, I'm able to hear the desired effects and it seems to be working properly. But I'm still confused about why it is behaving in that way.


texts: Smoothing unregulated DC input voltage to a voltage regulator

texts:
I am building a USB mobile charger powered by manually rotating a 12V DC motor shaft. This voltage goes as an input to a LM7805 voltage regulator and the output of the voltage regulator is used to power the mobile device.
When I measure the input voltage to the regulator, it varies from 7V to 11V. Since this is a high fluctuation of input to the voltage regulator, the mobile charger is rejecting the current.
However if I place a battery as an input to the 9V regulator, the mobile is getting charged with a current of 240mA.
I have tried placing capacitance of 4700μF at the input but to no avail.
I would like to know how could the input to the voltage regulator be smoothened so that the charger accepts the current.


texts: DIY radio burns components when using shared power source

texts:
first of all: noob disclaimer: sorry for the unprofessional sketch and my limited understanding of what I'm doing. I'll try my best to make myself understandable.
I'm trying to make a radio receiver that uses an external audio amplifier, but when I try to use the same power source (the AC-DC adapter), either the DC-DC buck converter or the FM receiver blows out because of over voltage or over current (smoke and sparks effect). Luckily those asian modules are cheap..
But if I use different AC-DC adapters for the FM receiver and the amplifier everything works. Why? How could I use a single power source for powering everything? I suspect the problem is some kind of ground loop etc, but I can't understand how to fix this.
In the below image the AND-gate is supposed to be a 3.5 mm audio jack and not an AND-gate.

simulate this circuit – Schematic created using CircuitLab


texts: Switching 120V AC with Digital Logic on Isolated Power Supply

texts:
Context: A digital phase-controlled light dimmer system.

120V AC mains
I use an isolating transformer (and rectifying circuit) to generate +12V and +5V DC rails.

I want to use reverse phase control (I've read that this produces less EM noise), so I'm looking to switch the AC mains using 2 Power MOSFETS (e.g. FDB14N30) with the source pins connected together.

In order to put the MOSFETs into the "on" state, I need to raise Vgs to 10V-30V, but in order to do this, I think I need to hook up the MOSFET source pins to my isolated ground rail, and the gate pins to my +12V switching signal.

By doing this, have I defeated the whole purpose of an isolated power supply, in terms of danger of death and damage to components?


texts:
I'm actively looking for a solution about this since nearly 2 months: I need to build a USB SD card reader slot for my project www.samplerbox.org.
I tried various solutions:

buy some cheap USB SD reader on ebay and dismantle them : I tried at least with 3 of them : unfortunately, the chip is always under a black glue (epoxy?) and it's impossible to see which chip is used.

Moreover I don't see how I could attach an existing SD reader to my own PCB

Use a ready-to-use SD module (SPI interface) like this one:

But as discussed in another topic, this works with SPI, and thus, this is not suited for my case, because transfer rate would be far too slow with SPI (~ 1 MB/sec)
So none of these solutions have worked.
How would you provide a SD card slot to your device, on you own PCB, with high transfer rate (thus using USB instead of SPI)?


texts: Simple question: What is your favorite breadboard, and why? I'm looking to upgrade mine, and am curious to see what other people use.


texts: Why is any general cutset equation a linear combination of fundamental cutsets?

texts:
I have currently started studying circuit theory and my professor introduced graphs to form kvl and kcl equations. When we form the cutset matrix using fundamental cutsets it is easy to understand that equations corresponding to fundamental cutsets are linearly independent. But as soon as we add any cutset equation to the matrix which is not a fundamental cutset, the sum of entries of a column become zero signifying that the equation set is no longer linearly independent. My professor told us that each cutset can be written as a linear combination of fundamental cutsets and he showed this using an example. It wasn't quite satisfactory as no mathematical insight was given. Since I have just been introduced to graph theory, I couldn't come up with a formal proof of this. I looked up on the net and could not find any good material which adresses this. It would be very helpful if someone could explain why this is the case.

The same goes for fundamental loops that is every loop can be written as the linear combination of fundamental loops. It looks obvious but I still am not able to prove it.


texts: MOSFET only turns partially off when overheated -- why?

texts:
I've recently wired up some large 12V fan PWM controller with a 11A rated n type MOSFET and a gate driver IC. Testing the MOSFET without its heatsink (probably a bad idea...), I noticed that it would respond to overtemperature in a way that I have difficulty explaining: by entering a partially-on state, where even with 0V at the gate, about 700mA of current were still going through the fan. I found that surprising; testing with different loads and scenarios showed that
1) 10W LED array load shows the same effect
2) 2W LED array load does not show the effect
3) an open circuit (no load) does not show the effect
4) A hot MOSFET will stay off if the circuit is interrupted externally.

My question is now why. It should be noted that the MOSFET is not damaged; after cooling down, it switches the fan just fine. Also, the fan did always have an adequate snubber diode in place, so I don't think the back emf is the expanstion here. I've also tested different MOSFETs that consistently show the same effect.

My question is now: What causes the MOSFET to behave that way? If it were simply free carriers generated by thermal excitation, wouldnt those continue to be there after interrupting and reconnecting the load circuit (#4)?

(Note this is purely academic -- I understand that the MOSFET is running out of spec without its heatsink and should be expected to fail one way or the other, but I want to understand the physics behind this particular failure mode.)


texts: Creating a delay using TIMER0 module on PIC16F1939

texts:
Suppose we are using an external  oscilaltor at 8 MHz and needed a voltage high for approximately  1 second at pin RA0. One instruction cycle takes  0.5 \$\mu s\$. I made a subroutine that takes 25 ms, with the prescaler set to \$\frac{1}{256}\$.

delay
clrf TMR0
L0
movf TMR0,w
xorlw d'195'
btfss STATUS, Z
goto L0
return

This subroutine( accounting for the call and return instructions that use up two cycles each) takes up 49924 cycles.

So, to create a one second delay, all I need to do is to call this routine 40 times.

   counter equ 0x21
   movlw d'40'
   movwf counter

   bsf LATA, 0
   bcf BSR, BSR1
   L1

   call delay
   decfsz counter
   goto L1

   bsf BSR, BSR1
   bcf LATA, 0

However, in MPLAB's logic analyzer I get some strange results, the RA0 pin doesn't even go to HIGH!
I am self teaching on this subject, and if you know any good online articles on this subject I would be very happy to read them. Also how can we do this using the INTCON register?

HERE is the datasheet of the pic I am using. The OPTION_ REG is on page 187, and the INTCON regsister is at page 90.


texts:
I googled deeply but couldn't find any cpu constructor simulator.
I'm specifically hoping to learn about the operation of the northbridge, but When I googled "bridge simulator" or "bridge (the construction game)" is the result.

I don't want to simulate existing architectures. İ need to create my own.

Question: Do you know any free project (ideally C++) with this flexibility:

Place ALUs, FPUs, etc arbitrarily
Make the instruction fetcher width 8 bytes
Allows operation with an arbitrary set of components (E.G, build a system that doesn't utilize L2/L3 cache)
Designate instruction pipeline length
Run the simulated hardware at various frequencies
Can simulate a GPU (or GPUs)

Is there a utility that would allow me to experiment with hardware design in a click-and-drag CAD manner? If there isn't, how complicated would it be to make such a simulator for 8-bit systems?


texts: Voltage used to charge a UPS-Inverter and its usage

texts:
I'm new to this area and know very little about electrons and how electrical components work. I'm always curious about Inverter/UPS usage.

I'm from India and we have a inverter at home. It is attached with two batteries which will supply the power for my home for 8 hours (TV, 4 ceiling fans, 4 lights). When there is interruption in power supply I drain out the inverter completely and when power comes back it gets charged fully in 2 hours.

I was always thinking that if it can charge up fully in 2 hours and supply power for 8 hours then I can save electricity for 6 hours which I'm paying to supplier by disconnecting power supply after my inverter charge up completely.

I know this is silly thinking but I want to have some explanation from experts saying that my thinking is incorrect, because if that happens then everyone in this world can save lot of power.


texts: What does EKR(ROE) mean in capacitor markings?

texts: I have a L4960 regulator. In its datasheet on page 9 there is a typical application circuit. Under notes, it says C1, C6, C7: EKR(ROE). What does that mean?


texts: How does a cable tone-and-probe kit work?

texts:
A useful tool for someone installing electrical cabling of any sort can be a Tone and Probe Tool: it allows one to find individual leads among a possibly hundreds in a cable trunk, without having to either strip or connect the remote end.

With the tone generator part connected to the start of the wire(-s), the probe tool typically generates an audible tone once its tip is in close proximity of the correct wire.

Can someone explain how these work in theory, perhaps with a high-level sketch of the basic circuits of such a tool?


texts: replace individual 1n4148 with diode array

texts:
I have a side job with OhKeyCaps building mechanical keyboards. We use a amoeba single switch pcb which at the bare minimum (IE no rgb) requires a switch and a single 1n4148 diode. Fairly common stuff and easy to figure out. We've talked about having someone make us a flexible PCB to speed up the building process. So that is the problem at hand. We could easily just get some SMD diodes  between each switch and the trace and be done.

Since I build keyboards all the times both my kids wanted a mechanical keyboard so I started them off with the iris. (Iris is just a brand and style of keyboard, not important to the question). When I got the PCB for the iris I noticed that there wasn't a multitude of diodes like I had expected from when I hand wire my keyboards. Instead there are 7 diodes installed and 28 switches per PCB half. I did some probing around and found that the diodes have 6 pins on it but the markings are too small for me to read. From what I can tell the IC is just 4 diodes configured like so:

I'm not sure how the they all tie together but I know that the two cathodes eventually go to the controller (atmega32u4) in the end. I wanted to know how this could be accomplished so I started looking around with my limited knowledge on how to make said diode. I eventually found a small article which told me what I was searching for was diode array which then led me to digikey... but when I searched for a 7 segment common cathode I couldn't find one nor did I know how or where to search. The end game of this is that it is a hassle to wire up 70+ diodes on a keyboard and we have been talking about someone to make us a flexible pcb to simplify and speed up our building process, although making/building the flexible PCB is unrelated to my questions. I need to be able to find a solution before I present it to my boss so how do I google for buying a diode array, or does it have another name? My only requirements of the diode array is same size or smaller than the same number of 1n4148 diodes it is replacing, and that it isn't too small where I can't hand solder this. A nice to have would be that I can have a single chip to replace 6 diodes. I hope this edit clears up confusion


texts:
I have 6 nodes that I want to connect on the same CAN Bus. All the nodes are installed in the same 19" rack, so each segment will be less than 2 ft (0.6 m). The CAN Bus connection on all the nodes is on a terminal block with screw terminals.
The CAN Bus speed is 50kHz.
The cable used will be twisted pair.
The nodes at each end will be terminated with 120 Ohm resistors.

All documentation I have ever seen for CAN Bus shows the use of drop cables, but I would like to daisy chain the CAN Bus like it is shown in the above drawing.
I would like to know if anyone has any experience in doing the connection this way?
(This is for a SCADA system. 5 of the nodes are EtherCAN modules)


texts:
I have a six T8 Fluorescent light fixture. The 2 inner bulbs are powered by a 2 bulb ballast GE232-120RES-DIY, and the 4 outer bulbs, 2 on each side are powered by a 4 bulb ballast GE432-120RES-DIY. 2 of the bulbs from the outer bulbs only light up a drop. I can see power going through but not enough to light it up.
What can the issue be? I checked the wiring and the sockets, they seem good.
What else should I look for?

Edit: Both ballasts are new and all bulbs are new. I tried swapping the bulbs to see if there is a issue with the bulbs. It doesn't help.


texts:
I'm creating a soft-latching circuit for my project, using a 2N3906 PNP transistor and an N-Channel IRLZ44N MOSFET. The circuit is fairly simple; Once switch one is pressed, it brings the gate of the MOSFET high, which turns it on, which also brings the base of the 2N3906 low, effectively turning it on allowing for current to flow from the emitter to collector then to the gate of the FET latching it on. However, I need a little help understanding the 2N3906.

In my previous circuit, R2 wasn't there, and the circuit was not working. In fact, the circuit was pulling around 200mA, and measuring between V+ and drain showed around 2.4 volts. This 2.4V was also present between V+ and drain even before I pressed the button. Then I placed 2.2K resistor where R2 is, and the FET was no longer 'on' before the press of the switch. After pressing the switch, V+ to drain raised to 4.1V. Then I increased R2 to 22K and I was seeing the full 4.2V between V+ and drain.

What is going on here? I would like to try to use some math to calculate these values and not just throw in something that works. I'm very curious why it didn't work without R2, and why I was seeing 2.4V at the gate even though I hadn't pressed the switch.

Also in order to calculate a base resistor for the 2N3906, you need to know the current that is flowing through collector-emitter junction, however, since MOSFETs are not current driven, how do I calculate this?

Thanks!

simulate this circuit – Schematic created using CircuitLab


texts: Powering a STM32 Nucleo board using batteries/power bank

texts:
I was wondering if it's possible to power a STM32 Nucleo L073RZ using a power bank via USB or a battery.

I tried using the power bank to power the board however, LD1 would constantly flash red. I even tried using a wall socket to power the device however the same issue would occur.

There was a answer which has the same issue but the answer which was to put a jumper on JP1 didn't work for me. It would still constantly blinks red at LD1.
Possible to power STM32 Nucleo boards with USB battery pack?

Is there any other ways to power via power bank?


texts:
I don't know if this belongs here or stackoverflow. I assume here as although verilog looks like software it's actually describing hardware connections?

I have a Spartan-3AN evaluation board and I'm trying to implement a simple rs232 port interface on it which I can't get to work. I'm an experienced software developer but new to verilog and digital design. I want to move up from flashing a single LED to the next step.

I've tried to implement it like this -
1) Generate a clock pulse "serclock" at the baud rate, so at the start of each bit.
2) Implement a state machine that once it's told to start steps through the states at the correct speed.
3) Implement a lookup to output the correct data bit depending on the state that 2) is in.

If there is a better way I'd appreciate any help. However I would expect this to work but I get nothing at all. Can anyone spot anything stupid that I've done? I'd appreciate any advice.

// Serial port demo program
//
// Assumptions: 50Mhz clock rate

module SerDemo(input clk, output ser);

// Start signal tells it to start sending bits
reg start;

//The bits of data to send
reg [7:0] data;

/////////////////////////////////////////////////////////////////////////////
// Serial port clock generator
// Generate a 9600 baud clock signal for the serial port by dividing the
// 50Mhz clock by 5208

reg [14:0] clockdiv;

// Count from 0..5207 then reset back to zero
always @(posedge clk)
begin
    if (clockdiv == 5207)
        clockdiv <= 0;
    else
        clockdiv <= clockdiv + 1;
end

// The serclock is a short pulse each time we are reset
wire serclock = (clockdiv == 0);

/////////////////////////////////////////////////////////////////////////////
// Serial port state machine
// Only start the state machine when "start" is set. Only advance to the
// next state when serclock is set.

reg [3:0] state;

always @(posedge clk)
begin
   case (state)
        4'b0000: if (start) state <= 4'b0001;
        4'b0001: if (serclock) state <= 4'b0010;    // Start bit
        4'b0010: if (serclock) state <= 4'b0011;    // Bit 0
        4'b0011: if (serclock) state <= 4'b0100;    // Bit 1
        4'b0100: if (serclock) state <= 4'b0101;    // Bit 2
        4'b0101: if (serclock) state <= 4'b0110;    // Bit 3
        4'b0110: if (serclock) state <= 4'b0111;    // Bit 4
        4'b0111: if (serclock) state <= 4'b1000;    // Bit 5
        4'b1000: if (serclock) state <= 4'b1001;    // Bit 6
         4'b1001: if (serclock) state <= 4'b1010;   // Bit 7
        4'b1010: if (serclock) state <= 4'b0000;    // Stop bit
        default: state <= 4'b0000;                  // Undefined, skip to stop
    endcase
end

///////////////////////////////////////////////////////////////////////////////
// Serial port data
// Ensure that the serial port has the correct data on it in each state

reg outbit;

always @(posedge clk)
begin
    case (state)
         4'b0000: outbit <= 1;              // idle
         4'b0001: outbit <= 0;              // Start bit
         4'b0010: outbit <= data[0];        // Bit 0
         4'b0011: outbit <= data[1];        // Bit 1
         4'b0100: outbit <= data[2];        // Bit 2
         4'b0101: outbit <= data[3];        // Bit 3
         4'b0110: outbit <= data[4];        // Bit 4
         4'b0111: outbit <= data[5];        // Bit 5
         4'b1000: outbit <= data[6];        // Bit 6
         4'b1001: outbit <= data[7];        // Bit 7
         4'b1010: outbit <= 0;          // Stop bit
         default: outbit <= 1;          // Bad state output idle
    endcase
end

// Output register to pin
assign ser = outbit;

///////////////////////////////////////////////////////////////////////////////
// Test by outputting a letter 'd'

always @(posedge clk)
begin
    data = 100;
     start = 1;
end

endmodule


texts:
Here is schematic for DC motor control. Using this I can drive motor in both directions and also send short pulses to motor, to move it only a little bit in desired direction.
Let me explain schematic in detail.

PWM controller is powered using 12V DC (Vin). Modulated signal (Vout) is input signal of first DPDT relay. Depending on which relay is energized, direction of rotation of motor is changed.

D1 and D2 are there because of back EMF protection.
D3 and D4 are there to enable me to drive motor in opposite direction when it goes to limit in one direction.

Using left 4PDT (ON-OFF-ON slide type) I choose whether motor will be powered for long time (as long as one of relays is energized) or for short time (one of relays is energized for short time using pulse signal generated using 555 circuit).
Lets say that we choosed on left 4PDT that voltage which drives motor is "long" (lets call this first ON position of left 4PDT, it is of type ON-OFF-ON).

Using right 4PDT (ON-OFF-ON, momentary) I choose which relay will be energized. Pay attention that in whatever "ON" position is right 4PDT, it will short one part of 555 circuit (one side of C2 with pin 2). You will see soon reason for this :)

When left 4PDT goes in second ON position, then 555 circuit gets power supply (12V DC) and it is ready.
Right 4PDT now has not only function to choose specific relay (thus driving motor in desired direcion), but also to cause process of generation of short pulse using 555 circuit by short connecting one side of C2 with pin 2 (here is where I found this pulse generator http://www.doctronics.co.uk/555.htm#triggering). Generated pulse energize specific relay for short time so motor rotates in specific direction only for short.

Is this ok? :) Is there something what should be changed? I didn't choose values for capacitor and resistor in 555 yet because I still don't know exactly what will be pulse duration. I have normally closed wtiches, DPDT relays and PWM controller.

Motor is linear actuator (http://www.ebay.com/itm/Linear-Actuator-Motor-DC12V-24V-750N-50mm-100mm-200mm-300mm-600mm-For-Electric-/281749055276?var=&hash=item41998d672c:m:mCviYhnG5aL1LRiI4QsowiA), it should arrive in few days.
I should buy other components. Motor amperage is 3A max.

This is PWM controller I have http://www.ebay.com/itm/162002954574?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

DPDT relays are http://www.ebay.com/itm/Relay-Omron-LY2NJ-Small-relay-10A-8PIN-Coil-DPDT-12V-DC-/371102969959?hash=item566775f067:g:hmoAAOSwKsRWFmAP .
Which diodes should I use for D1, D2, D3 and D4?

Is this power supply (12V DC) good for this application http://www.ebay.com/itm/AC100-240V-to-DC-12V-2A-3A-5A-6A-8A-10A-Power-Supply-Adapter-Fr-Led-Light-Strip-/331146532722?var=&hash=item4d19df1772:m:mmYVpw9kxcePGAlVHiBpCWQ ?


texts: How can I implement a solid state relay in LTSpice?

texts:
I want a specified DC input voltage or above input voltage of a solid state relay to activate it.

I want 3V or above DC input to turn on the relay's output switch.

Here is the simple diagram:

Is there a way to implement it in LTSpice?


texts:
I have some project what requires all GPIO pins of attiny10 so I have to program RSTDISBL fuse. But only programmer I have is low voltage USBasp (with latest firmware supporting TPI interface).

The datasheet offers the way to re-program attiny10 by applying +12V to RST when RSTDISBL are programmed:

15.3.1. Enabling
The following sequence enables the Tiny Programming Interface:
• Apply 5V between VCC and GND
• Depending on the method of reset to be used:
– Either: wait tTOUT (see System and Reset Characteristics) and then set the RESET pin low.
This will reset the device and enable the TPI physical layer. The RESET pin must then be
kept low for the entire programming session
– Or: if the RSTDISBL configuration bit has been programmed, apply 12V to the RESET pin.
The RESET pin must be kept at 12V for the entire programming session

The USBAsp programmer doesn't supports 12V operation but I assume I could use simple inverting (because at normal operation it pulls logic low during programming and I need to pull it up to +12V) level shifter for this?

Should a circuit like this work? RST_OUT are RST pin from USBasup while RST_IN are RESET pin of ATtiny10.

Another question here is about the common ground. +5V are coming from Vusb via USBasp and +12V are coming from some sort of other PSU. Is it acceptable to combine grounds here? Or is is better to get +12V from PC PSU (same where Vusb comes from)?


texts: implementing a capacitor TDR using a transmition line

texts:
In this simulation example they show that a capacitor causes impedance drop in TDR.
But i can see why? maybe its somthing to do with rise time of the source?
Also using Z0 and length of the transmission line ,how do i see the amount of capacitance and inductance in that TL?
Thanks.


texts:
All,

Lately I've been thinking more about bulk capacitance in my designs. Previously, I've been careful about part selection and placement for decoupling and filter capacitors during design. Once a board is fabricated, I double check voltage sag on each power rail and make adjustments from there.

I'm not really happy with this approach. I'm not a big fan of crossing my fingers and making adjustments on the fly. Are there any rules of thumb out there or good references on calculating the amount of cap that's needed in a design? As an aside, I work on mostly digital designs, so there are no inductive loads to worry about.


texts: I am using the MCP73831 along with a Lithium Ion battery to supply an Arduino Mini project. Is it safe to supply my project directly on the battery? Or should I use a transistor to protect the project from the high charging voltage? Please mind that I need to keep the power consumption at a minimum for this project.


texts: Wiring 434mhz transmitter to Explorer Hat

texts:
I'm trying to hookup this transmitter module http://cdn.sparkfun.com/datasheets/Wireless/General/TWS-BS-3_433.92MHz_ASK_RF_Transmitter_Module_Data_Sheet.pdf to the Raspberry Pi Explorer HAT...

As you can see from the data sheet, pin 3 is the data input. The HAT provides outputs which sink to ground when they are ON...

I've got an LED switching on and off by connecting 5V to it's input and then connecting it's output to one of the HAT's outputs (which alternate between sinking to ground and not) but I can't get the transmitter working despite trying different wiring configurations. For the record, the transmitter does work and can be seen to be working, if I simply connect another 5V to the chip's data input.

My question is: how do I wire up the RF transmitter's input pin to one of the Explorer Hat (github.com/pimoroni/explorer-hat) 's output pins?

The output pins do not provide voltage, they only sink to ground when they are turned ON (programmatically - I've got this bit covered, I'm just unsure of the wiring).


texts:
Hi I plan to build charger circuit to charge high capacity nicd battery. The charger will output 40A , is it safe to limit and reduce the current using pwm  IGBT/mosfet so the output will be pulse ?
!


texts: Altium: How to change several components at once in order to save time and effort?

texts:
I am drawing a schematic in Altium Designer. Sometimes, I need to change some components from one value to onther. For example, I have 10 capacitors of 1 pF and need to change them all to 2 pF. Is it possible to do it at once instead of change each capacitor separately.
This will of course help me to save time and effort !!


texts:
I'm trying to measure a fork's lift battery by an ADC.
The problem that the output voltage isn't predictable and not constant, so that I can make a constant voltag divider.
What I have measure is it goes from 7 to 30VDC, and the max input voltage of my adc is 1.2V.
How would I design the voltage dividers and the op-amps in that case?


texts: Boost converter output still active when boost IC is turned off

texts:
Am using the tps61175 boost converter ic in a project. per the datasheet here

i noticed when i pull the EN(enable) PIN LOW and the boost converter ic turns OFF , i still read voltage at the output Vout and the voltage corresponds to my input voltage Vin.

To further elaborate, say i connect a 3v battery to Vin and pull the EN(enable) PIN HIGH for the boost converter ic to start working with a Vout of 5.1v. When i pull the EN(enable) pin low, the Vout is becomes 3v.

The first picture shows what i did to turn the circuit off completely. That approach also lead to loss of about 400mA and the output voltage broke down to 4V instead of the desired 5V.

I need help about how to make the output Vout 0v when the boost ic is OFF, thus
turn the circuit of completely.


texts:
I have a signal that should have this theoretical shape:

The signal I am receiving experimentally has the following shape:

And here is a plot that better shows the shape of the waveform (I have clipped off most of the excess data):

Notice the large amount of what seems to be high frequency noise in the second plot and third plot.  I am trying to figure out how to filter out the noise of the the experimental waveform with keeping the overall shape.  I have considered using a low-pass filter or a voltage regulator but I am not sure if they will have the desired affect.  Basically I need to keep the shape (and ideally magnitude) of the peak while filtering out the channel noise.

EDIT:  Don't be concerned about the reflection of the theoretical peak in plot 1.  This is just a direction change and is on no concern.


texts:
I have a dumb question. My textbook says \$\beta I_B\$ current flows into the collector terminal.
Isn't Collector-Base path shorted by the external wire? Since base and collector regions are semiconductors, they offer very high resistance compared to the external wire path. How can more current flow into the collector terminal of the bjt compared to the external shorted wire?

In below two diagrams I put resistors. Which connection is correct and why?

simulate this circuit – Schematic created using CircuitLab


texts:
I still have an understanding problem with impedance matched coaxial cable and its behaviour.

We do impedance matching to prevent reflections.

How does my signal source see the whole cable? At a certain frequency it sees only 50 Ohms. How do I calculate that frequency? What does my signal source see at lower frequencies? A capacitive load, depending of the length of the cable?

I already read many articles and posts, but it is something which is still not clear to me.

simulate this circuit – Schematic created using CircuitLab


texts:
I am currently required to study different ways of reducing the transistor switching time. From what i understand, the two most used methods are speed-up capacitors and Using a negative, non-linear voltage reaction to avoid saturation.

Unfortunately, i don't really understant how either of them work and I haven't been able to find any useful resource online.

Could anybody explain them to me or point me to some useful material ?


texts: Circuit for finding engine RPM using the magneto's coil ground wire

texts:
I'm looking to see if there's a solution without using a microcontroller to find the engine RPM (perhaps spark frequency is a better term?) using only the magneto's coil grounding wire. This wire kills the engine when you touch it to the block. I believe this wire carries an AC current (correct me if I'm wrong) and a high voltage, so I was not sure how I could go about designing a simple circuit that won't be killed by these two factors.

I basically want to turn a transistor off once a certain frequency has been achieved. The transistor is normally on until this frequency has been reached.

I've seen engine hour meters and tachometers that clip onto or wrap around the spark plug wire, but that isn't what I'm trying to do in this case. I'm pretty sure there is a frequency on the grounding wire too, but correct me if I'm wrong.

I'd appreciate any help offered.

Here's a crude picture of the magneto setup:


texts: Can you sum and difference in a single op-amp?

texts:
I want to take two independent differential signals (audio line inputs with unknown properties which may be present or not), remove any common-mode noise from each of them (they could each have different common-mode noise), then sum the desired signals together. I believe I can do this all with 1 op-amp.  (Actually I want to output the desired signal differentially, so I will use two of these with inverted output polarity.)

You can assume Rfeedback = Rground and all the input resistors are equal.  So then I believe the output is:

$$V_\mathrm{out} = {R_\mathrm{f} \over R_\mathrm{in}} ( A + B )$$

with all the common-mode noise cancelled.  Correct?

Are there any problems with this op-amp configuration?

This page calls it a "generic linear operator":

Will the CMRR be reduced by summing on the non-inverting node or anything?  I did the math, and CM sources are completely cancelled out at Vout, but I feel vaguely uneasy about it.  :)

The input impedance of the inverting inputs varies with the signal, as explained here, but shouldn't matter as long as it's much larger than the source impedance.  The common-mode impedance is the important part, and should be the same for all input pairs.

If I weren't trying to do it all in one, I'd use two diff amps followed by a summing amp (followed by an inverter for the differential output).  Does that method have any benefits over the single op-amp method?


texts: What does an ADC DNL specification mean, exactly?

texts:
I'm looking at the differential non-linearity specification for an Analog-Digital converter. The spec sheet claims that the DNL ranges from -1LSB to +1LSB, with a typical value of \$\pm\$0.6LSB. What exactly does that mean? Is this some value that's taken statistically? Does this mean the 3 \$\sigma\$ value is 0.6LSB? I.E., for any given code, the range of voltages over which it has jurisdiction is 99.7% likely to be no greater than 1.6LSB or less than 0.4LSB?

Suppose I wanted to model a 16-bit ADC with these specifications. How would I go about injecting DNL into the output codes? The spec sheet is completely unclear as to what 0.6LSB means. Is there some statistical convention? Or would it just be some random number which caps at \$\pm\$1LSB for every single code?


texts: Control single-light LED strip with Raspberry pi and MOSFET

texts:
I'm trying to make my LED strip fade-in and fade-out by using Raspberry-pi 4, unfortunately for me, I am not an electronic expert. Every tutorial I saw so far was for RGB LED strips and I have a single-color (3000 K) LED strip with just 2 pins (+ & -).
I have:

LRS-50-24 datasheet
30N06L datasheet
4m LED strip single color (3000K) 24V
Raspberry Pi 4

My question is how to connect the MOSFET and the LRS-50-24 to the PI in order to control the fade-in/out by GPIO python code?
Appreciate any help


texts: Does USB cable quality matters (affects in someway the signal) on audio interface (or DAC)?

texts:
I was wondering this for quite a while.  Usb cables are purely digital signal so in theory no one should care about its quality if it does the job well and transfer the signal to the end (ones and zeroes).  But then again... Why do some cables have double shielding for interference?  And when we are talking about recording and audio interfaces I started thinking that perhaps interference could bring noise to the recorded signal or some 'impurities'?  I know that gold coating is just a cheap marketing trick and practically is not important at all. Cable resistance - this I do not know (on digital cables).

So how (if it does) a good quality, double shielded, cable "improves" the sound?

Is there ANY advantage of using it over a cheap, single shielded (or not even shielded at all..) cable when we are talking about high quality DAC, Audio interfaces and other devices which transfer signal that is video, audio or anything familiar.  Should I run and purchase a good quality usb when I'm recording? Or good quality cables are only good for reliability?

Haven't solved the mystery myself. I know that you guys are always helpful and will solve it  :)

P.S.     I am asking specifically for audio interfaces or DAC.  I know that if you'd pay 50$ for an iPhone cable it would be simply dumb as it does not matter expensive or rather cheap.  Audio interfaces and specifically audio recording is what I am not sure about..   (and didn't quite found the information I was looking for on the internet or forums)


texts: How to theoretically determine ESR of a capacitor and DCR of an inductor for a buck converter?

texts: How can we determine ESR of the capacitor and DCR of inductor theoretically in the design of buck converter, without using an LCR meter?


texts: How to Show Voltage Inputs Without a Net in EAGLE

texts: when I am creating a schematic in EAGLE I would like the ability to show inputs from another area. I think this should be a possibility, as it is used widely. I have an example of an image below that I found (I didn't highlight) that shows what I am talking about. Look at DRAM_VREF for example. It's showing that the pin of the same name on the SoC should go to the 0.01UF capacitor, and then be grounded. Is thee any method for doing something similar in EAGLE?


texts: mV difference not detected by LM741 opamp comparator

texts:
I've made this comparator circuit, it has a changing current going through the photodiode and when lighting changes sufficiently it should trigger a 5V signal at the opamp output terminal.

When the photodiode is in low light conditions the non-inverting opamp input terminal has a voltage of 2mV. When I illuminate the photodiode I get a voltage of 20mV. I've adjusted R2 so that the inverting input terminal of the opamp is set to 10mV.

When I illuminate or darken the photo diode nothing changes to the output voltage of this opamp. Also nothing changes when I disconnect or switch the input terminals. It remains high (4.7V) at all times.

(I've measured all voltages directly to the opamp pins)

Is there a design error? Or is the voltage difference too small?

simulate this circuit – Schematic created using CircuitLab


texts: Why don't they use zener diodes in high frequencies?


texts: Correctly Configuring and Using DAQ Device Digital TTL I/O

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I am using a National Instruments USB-6000 DAQ to control some equipment that accepts TTL inputs.

Specifically, I have to pull a pin (normally 5V) to low. As I understand it, to do this, I can use my DAQ's digital output configured as open collector operation. Is this correct so far?

Furthermore, I'm confused as to the use of a pull-up resistor in this case. Looking at this example, there is a pull-up resistor on the path to Vcc. In my case, there is already 5V on the pin by default. So do I still need a pull-up resistor? I can only think that I would need one in series to limit the current going into my DAQ.