texts: Could transmit/receive turnaround be improved by having a heterodyne receiver switchable between high-side and low-side injection

texts:
In some of the small radios I've worked with such as the Nordic Semiconductor 24LE line, there is a significant (100us+) delay between transmitting data and being able to receive a response.  By my understanding, a big factor in this delay revolves around the fact that a transmitter requires a PLL to be tuned to the exact desired transmission frequency, while a receiver requires a PLL tuned to a frequency which differs from the desired one by an Intermediate Frequency.  Thus, switching between transmission and reception requires retuning the PLL, and the need to retune the PLL represents a significant portion of the turnaround time.

Would it be practical to construct a radio such that the receiver could be configured to receive a frequency either above or below the PLL frequency, and then have a handshake sequence operate something like:

Transmitter sets PLL to 2315Hz, sets receiver mode to "100Mhz above"
Expectant receiver sets PLL to 2415Hz and receiver mode to "100Mhz below"
Transmitter listens for a little while to let its AGC settle.
Transmitter sends out packet at 2315Hz, while keeping PLL constant
Receiver hears packet which was sent 100Mhz below its PLL frequency
Transmitter switches receiver mode to "100Mhz above" while keeping PLL constant
Receiver sends reply at 2415Hz, while keeping PLL constant.
Original transmitter receives reply which was sent 100Mhz above its PLL frequency

When using a 100Mhz Intermediate Frequency (which I understand is normal for 2.4GHz communication) this approach would unfortunately be limited to using the upper and lower 50Hz of the 2.4GHz band, but it would seem that a reduction in transmit/receive turnaround time would be helpful.  Alternatively, use of a lower Intermediate Frequency would reduce the required separation between transmit and receive frequencies.

Are such approaches used at all, whether in 2.4Ghz radios or in other applications?  Do they have any particular problems?


texts: measuring vertical movement in a container

texts: I am looking for a non-mechanical means to measure the descension of a plate within a container about 3cm by 15cm by 7cm. The plate is not terribly well guided so there is a need for a lot of room for error, our resolution does not need to be high at all. We are measuring descension and ascension of about 3/4cm over the span of 15cm. Any thoughts on a sensor that could be good for my needs? it also needs to be rated to -20F and about 120F and be able to withstand fast acceleration and deceleration and shock. If you can help I will be very appreciative!


texts: Sensor Signal Open-Circuit/Short-Circuit Faults -- Trigger Shutdown Circuit

texts:
I am working on a project where I use the signal from 2 sensors in order to determine whether I want to trigger a timer circuit that then propagates a signal to latch an LED. The sensors give voltage output in the range 0.25 - 4.5 V, and I use a comparator to check if these voltages are greater than reference values. The output from the comparator goes to an AND gate and if both signals are high, the timer circuit is triggered. If the signal is high for a given amount of time, the LED turns on and latches (turning off LED requires a power reset).
I have all these steps working, but I need to figure out what to do if the sensors become disconnected/there is some downstream fault (open-circuit/short-circuit). Basically, I want the timer to trigger if either sensor is faulty or if both comparator outputs are high.
I have done a bit of reading and saw some mention of using pull-up/pull-down resistors with the comparator(s) but I am very much a beginner, so I didn't really understand what these were doing/how they were being used.
If anyone has an idea as to how to use these pull-up/pull-down resistors to accomplish the task, or if there are any alternative approaches, I am all ears!


texts:
I'm working on a project with an SG90 servomotor, that requires the use of PWM. However the motor works with PWM frequency of 50 Hz (20 ms period), and in my PIC16F690, when I try to calculate a value for the PR2 register (per page 129), I always get a value above 255, until I reduce the Fosc to less than 1 MHz, and also use a prescaler of 16.

So the question is: is possible to use post-scaler to achieve my desired results?

Thanks


texts:
Circuit (Mosfet Active Load Differential Amplifier):

Note: This is not homework. I want to be able analyze circuits well, and currently my understanding of circuits is weak.

In my textbook, I do not see the the \$1/g_{m}\$ resistance on transistor Q4, why is that?
Since a short exist between \$V_{o}\$ and \$V_{icm}\$, does that mean \$V_{o}=V_{icm}\$?


texts: 1.4V instead of 0V when Arduino signals a LOW

texts: I have motor controlling mechanism as the one shown in the image. I'm controlling the direction of a motor controller from three different sources. DIR1 and DIR2 form two of these sources and at any point in time one of them is the controlling source and is selected using the MUX. The third source OUT_2 is essentially connected to the motor controllers through the optocoupler directly and this source gets priority over the earlier two sources. OUT_2 is generated by an Arduino. In the real world implementation of this, when the external MCU signals OUT_2 to be LOW, I see 1.47V at OUT instead of 0V. Why is this and how do I resolve this?


texts: How does a pulsed laser diode driver circuit work

texts:
So i am looking at pulsed laser diodes, and i want to build a circuit for it to work. https://www.osram-os.com/Graphics/XPic7/00054198_0.pdf/Standard%20Pulsed%20Laser%20Diode.pdf
This is the article im using for my diode. I understand that the laser stores its electrical pulses in the capacitor but thats all i understand, maybe you guys can point me in a better direction of how the pulsed laser diode works and what it needs to drive. Also does the laser actually pulse or is it continuous wave with pulses of evergy in it?


texts: Can Transmission gates be used to implement 3 State Logic?

texts:
In my application i need to use a common line shared between two peripherals, i have to indicate to the devices whenever the bus is free or not, hence i can't have push-pull output where the output is either 0 or 1 , as these states are generally used for data transmission.

Instead i would prefer to have a open drain scenario, where the output "floats", to indicate to the device that the bus is free.

Now to achieve this, i want to use a transmission gate, where the third state(open) is used by controlling the enable pin, if enable is on (the normal 2- state logic, 0 or 1 where input flows to output), else the output pin floats.

Now my question is , if this setup is similar to the the way 3 state logic is used in microcontrollers/microprocessors , where an internal pull up resistor controls , the logic of the output pin , if it is different then in what way does it differ ?

Also have i missed something, do i have to read anything more to complete my understanding ??

EDIT

The Line is driven by a totem pole output, where only logic 1(5v), and Logic 0(0v) , signals are driven.


texts:
I just read the answer to this question asking how much a custom ASIC costs. It says that

When it comes to making an ASIC, the cost of the masks is HUGE. It is not uncommon at all for a set of masks (8 layers, 35 to 50 nm) to run US$1 Million!

I'm curious why the cost is so huge. Where exactly does all of that money go? Is it the material that's expensive, or does it take a lot of man-hours to make the mask, or something else?


texts: Charging a 9volt battery with a jst or dc plug

texts: I just want to make sure what I am thinking about doing will work and I will not cause a fire in the process. I would like to connect  a 9v rechargeable battery to a small dc motor in a plastic model (this part I can do). I wanted to know if I can solder a jst connector or a 2.1x5.5 mm  dc plug to the two leads on the battery while connected to the motor (motor off). I wanted to know if I could solder the complementary part of the dc plug to the appropriate charger.  The reason for this is I will not be able to get to the battery easily and wish to charge it so it is not one time use. If anybody has a simpler way or idea it would be appreciated.


texts: in some places when we are working with cables at home we get shock and therefore we are thrown away

texts: In some places when we are working with cables at home we get shock and therefore we are thrown away.. but in some places like Asia when you get a shock you are stuck with the cable until someone closes the breaker ..Why this sticking and throwing happens?


texts: Do electrolytic capacitors have a limited shelf life? I would like to know for both aluminium and tantalum.


texts: why the solution can just add or minus the degree directly when calculating the line voltage?

texts:
There is a three-phase electric power systems which is arranged in star (Y) ,and positvie phase sequence.

Now if the \$\bar V_{ab}=220∠60^∘ \$,then what is the \$\bar V_{bc}\$ and \$\bar V_{ca}\$?

The solution told me

\$\bar V_{bc}=220∠(60^∘-120^∘)=220∠(-60^∘)\$

\$\bar V_{ca}=220∠(60^∘+120^∘)=220∠(180^∘)\$

But i am curious about can we really do that?just calculate the degree part directly?

Because we can see the proof below in lots of books

\$\bar V_{AB}=\bar V_{AO}+\bar V_{BO}=V_p ∠0^∘- V_p ∠120^∘=\sqrt{3}V_p ∠30^∘ \neq  V_p ∠0-120^∘=V_p ∠-120^∘\$

So why the solution can just add or minus the degree directly?or can anyone tell me the original math formula about \$\bar V_{bc}\$ or  \$\bar V_{ca}\$?


texts: Analogue multiplexer using JFET for small signals

texts:
I'm working on a circuit with a non-inverting amp and I would like to switch between two reference voltages, both with low output impedance.

So in effect i want something like this:

simulate this circuit – Schematic created using CircuitLab

One thing: R1 is done using LM385 low power reference voltage, so voltage between anode and katode of D1 is 1.2V.
Output impedance of U1 is about 300 ohms.

I stumbled upon a thing called analog multiplexer and I think that it would suit this purpose quite OK. I would like to build it using basic components instead of buying IC. I thought about using JFETs, but would it make sense for such small voltages?

Please help!:)


texts: Fetching network time from simcon 800c gsm module

texts:
Is there any way to fetch the current time from the 800c GSM module. I tried the following commands:

AT+CENG=2
AT+CLTS=1
AT+CCLK?

Output:

+ceng:"4/01/01,00:35:+22

Not getting the updated date and time from network.


texts: Schematic of an amplifier with bandpass filter and impedance matching

texts:
I am having trouble creating a block diagram in PADS Professional Designer. My HMC414 amplifier (documentation: https://www.analog.com/media/en/technical-documentation/data-sheets/hmc414.pdf ) has IN input, two OUT outputs, and additionally VCC, VPD1, VPD2 and GND pins (there is also NC [Not Connected] pin). My DEA142450BT-3028A1 filter (documentation: https://product.tdk.com/info/en/documents/data_sheet/rf_bpf_dea142450bt-3028a1_en.pdf ) has 3 GND pins, one Input Port and one Output Port. I made a block diagram of the amplifier with the output matching and the filter, it looks like this:

I know of course that I have to connect all GND pins to ground, the VCC port to +5V, I've done impedance matching on the input (did I do it right?), I've connected my filter to the OUT1 port (does it look ok too?). I don't know what to do with the other ports though. What should I plug into VPD1 and VPD2? And should I do the impedance matching on the output the same way as on the input of the amplifier, only connect it to the filter port "OUTPUT_PORT"? I would really appreciate it if someone could guide me. Thank you in advance for your help.


texts: Do I need to filter before sending signal to an ADC?

texts:
I have an ADC that is capable of a 25kHz sample rate and I have a sensor whose bandwidth is 200kHz that I'd like to hook up to. This is a current sensor. Nyquist tells me that I need to limit the bandwidth of the sensor to 12.5kHz in order to be able to reconstruct a signal (and avoid aliasing). However I'm wondering if this is the right thing to do? In some sense I don't want to limit the sensor's bandwidth for applications like a peak detector where I want to measure peak sensor values and I might miss peaks if I filter them out..

Can I run the 200kHz signal directly into the ADC? In what cases should the nyquist criterion not be followed?

Thanks


texts:
There is an instrument outputting pwm-like current pulse trains proportional to its rotation speed. I convert the output current pulses to voltage pulses by a shunt resistor to be read by a DAQ hardware.  Pulses are sampled with 12kHz. The software detects the rising edges and calculates the frequency for each pulse.
Above on the left figure is what I see from the output of the instrument.  P is the period, T is the pulse duration. Whatever the rotational speed the pulse duration T remains the same around 80us-120us(between 80 and 120 microseconds). Period P can be between 330us up to 2000us.

I have two questions:

1-  As shown in the right side of the above figure, I want to convert these pwm-like pulses to sharper ones. What kind of op-amp configuration would you suggest for this application.

2-  Since the frequency is counted between the rising edges what should be the sampling rate? My guess is 2*(1000000/80) = 25kHz. Would you agree?

3-  If I cannot reach up to that sampling rate is there  work around for lower sampling rates?


texts: Explanation for super-sensitive loose contact inside potentiometer?

texts:
Symptom

I have a mixing console, where one 6-pin stereo pot is errartic. When I turn it all the way down I sometimes can still hear the left channel at full volume.

Explanation

The circuit is a regular voltage divider where the wiper is connected to a JRC NJM 4580 op amp inverting circuit with 2 SMD resistors and one SMD capacitor (reverse enigneered).

The only explanation I have is that the pot sometimes looses its GND connection. I connected it to the GND of the other channel, but this didn't change anything, so the error is not on the PCB.

The pot appears to be an  ALPS RK12.

So the disconnection must be in the pot itself.

Mysteries

What I don't understand is the following: I can resolder the pot and the error disappears only temporarily. I can even bend the pin during resoldering and it does not change much. However, sometimes when the error is present, all I have to do is touch one pin of the pot with a screwdriver and the error disappears.

How can that be? There is no way a loose contact inside the pot can be that sensitive, or can it? It appears like the signal the screwdriver introduces makes to error go away. Also I am amazed because broken pots usually have a problem with the wiper. But a broken "bottom end" is kind of rare.

I wish I could imagine how a loose connection of the SMD op amp could cause such behavior. I am ready to buy that an SMD circuit responds to screwdriver tapping. I haven't resoldered the op amp yet.

And finally

I cannot easily replace the pot, because I need to take the whole device apart which may cause more harm than good. Also the pot is an industrial pot and not easy to get. And worst of all: I'm beginning to doubt that it is really the pot.

Am am aware that answers to my question may be speculative. But I am running out of ideas, so that'll be okay.


texts: what kind of display technology is this?

texts:
There is some kind of backlit display in the product markets which is most likely displaying behind the plastic. I don't know if this is related to LCD or electronic technology or maybe some kind of special plastic. I spent some time on the web to figure it out and finding wooden clocks that display numbers from the back of the veneer sheet but this is a different technology I think.
Does anyone know the name of this kind of display or any useful information about it?


texts: PTC or One time Fuse or fusible resistor for li-ion protection.any suggestion?

texts:
I designing a kind of portable device ,it contains 450mAh Li_ion or Li_Poly Battery (depends on space on PCB).
I design this system for mass production (10k-20K).

I want to add overcurrent protection in my design because it uses  Li_ion or Li_Poly batteries and safety should consider.

There is no input on this circuit just some LED and 7 Segment (Kind of indicator system.) ,All of the system placed in Box and just Vin jack is Available.

Its very Rare situation that Overcurrent and short circuit happend ,but as this  is a portable device and i use battery ,i should consider(maybe battery charger IC fails and short circuit happend!)

The charger input(Vin) is always about 6.5V ,D1 used for input jack reverse protection.

the system power just came from battery and i use Boost DC-DC converter to power MCU and All other parts.(4.2 to 5 DC_DC conv wire.)

Edit
4.2 TO 5V DC-DC Converter is turned OFF when MCP73831 is turned ON.(when Vin is connected all the system is turned OFF and just battery charger works.)

My question is :

1-which of PTC or One time Fuse or fusible resistor is better for my design and why?

2-Is the fuse(F1) in the right place(series with battery)?

Answer:
After i Study some Application notes here and here,I found out PCB mount PTC fuse is good option for my design.


texts: What does this symbol mean for this given circuit?

texts: I have circled the symbol in question (red). It looks like a variable resistor, but the rest of the circuit is attached to the tail of the arrow. I feel as though this circuit is trying to describe a voltage divider. Is this true?


texts: By replacing capacitor values with different ones in a circuit, will the circuit still work?

texts: I'm fairly new to electronics and following this schematic for a "Truth Meter", which detects sweat from your fingertips and a lights up an LED depending on the resistance of the skin, as one of my first projects. Anyway, I do not have the 10nF capacitor that I am supposed to use but I do have 22 pF, 10 uF, 0.1 uF, and 100 uF capacitors. What combination, if any, of the capacitors that I have, will make this circuit work. Also, does it matter if I use 1n4007 diodes vs the 1n4001 diodes I am supposed to use? Thanks.


texts:
I'm working with an STM32F103 device and am experiencing some strange behavior that I'm not so sure about where start with when it comes to debugging it.
I previously asked a question regarding DMA problems with this device that I never quiet resolved. I've come back to look at this, but now suspect my DMA problems are related to something else.
I'm working on a custom board that, at the moment is just the STM32F103 device connected over SPI to an STM32F405 discovery board. SPI works fine in polling mode and now I'm attempting to get SPI and DMA working again. My problem is that I can get it work intermittently but it seems to be dependent on initialisation of variables. For example, I can get SPI working with DMA well if I initialise some variable in my main() function.
EG:

int main(void) {
    uint32_t spiBase = 0;
    // etc, etc
}

However, if I then initialise another variable under this one DMA will stop working.
I'm really at a bit of a loss on how to go about debugging a problem like this!
Currently, I'm using the arm-none-eabi-gcc compiler with a Makefile I grabbed and modified that was originally intended for STM32F405 devices (from here: (http://liviube.wordpress.com/2013/04/22/blink-for-stm32f4-discovery-board-on-linux-with-makefile/), along with Texane's st-link utility.
It is entirely probable that my Makefile or linker configuration is a bit screwy!
Can anyone offer any advise on where I might start with strange problems like this?!


texts:
I have a number of simple LED strip lights, purchased to replace fluorescent tubes in a kitchen. Having installed the first ones, they have a noticeable flicker (to me, but not my wife!) on moving objects. I was wondering if it were possible to solder a smoothing capacitor across the dc drive to the LEDs.
The 1500mm strip is divided into 2 separate circuits each fed from 240v ac.
Each circuit consists of 5 blocks of 12 white LEDs (12 in parallel, then the 5 blocks in series). They are fed from 3 triac looking device circuits, with an output of 178v (on a cheap digital multimeter) so presumably 36v on each LED?
What uF of capacitor would I need? And will I need an extra leakage resistor too?


texts:
I have an Epihpone (Les Paul 100, fairly standard) electric guitar, which over the years have gotten to suffer from a non-functioning bridge pickup. I verified this using an ohm-meter, the result being that only the neck pickup gave a signal (also apparent from plugging it into my amplifier and playing) at 20K. In order to repair it or replace it, I am attempting to disconnect it from where it is soldered on; at its volume-meter (see pictures at the bottom).

I did attempt to remove the solder by heating it and the surrounding area, and use a solder sucker, but the solder would not melt - even after prolonged exposure to the heat from the soldering iron (30W, fairly standard). My question is, would I be better off using a solder gun? Clearly it gives off more temperature, hence making it easier to melt the solder, but I am somewhat concerned of also harming the nearby wiring (which mostly are not long enough to cut and re-solder on).

I made sure to let the iron reach peak temperature and to tip it with some solder beforehand, but the solder barely melted. I guess an alternative would be to cut the wire rather than melt the solder, but I would at any rate have to re-solder a new one on at some point.

Any suggestions on the optimal way of getting rid of this piece of solder would be appreciated.

Appendix: Results

I did the following:

Used a 175W solder gun to melt away enough solder to get a better hold of the wire.
Cut the black (hot) wire as close to the solder joint as I could.
Used the 30W solder iron (pointy tip) to melt away more around the remaining two black wires (bottom of picture 1).
Cut as close as possible to the joint for these two as well.
Melted the smaller solder joints for the white wire and red wires, allowing them to be pulled away.

In total I lost only 4-5 millimeters of wire from the pickup, and slightly toasted a few nearby wires, but not so badly that they took any substantial damage. Also, I tested the pickup (directly on the wires of the detached unit with 20K ohm) which showed that in fact the pickup is functional, giving ground to assume some fault with some other wire, part, or joint. At any rate, replacing the volume-meters and tone-meters is not costly, and re-soldering them should yield better connections.


texts: Netduino or Raspberry PI for my requirements?

texts:
I do not want to start a religious war, and believe that neither of them can be better in all circumstances. So, let' consider my circumstances.

My problem is that I am a software guy with no knowledge of hardware and Google is not my friend today, so I hope that I can get some advice here. In order not to start a religious war, let's confine it to which is more suited for my personal requirements, which is hopefully a question which can be answered (as opposed to a general "which is better?" which obviously cannot be answered).

It is, now that I come to try it, difficult to formulate exact requirements as I initially want to "play around and see what I can do", but here is as much info as I can give to help you to help me.

I do not want to take the effort to learn both systems as I have little free time. SO I seek advice which will help me to make a decision and stick with it.

I have 30+ years coding experience, am happy with both Windows (for Netduino's C# and .Net, although I have little experience either), and with Linux. I have no fear of new new concepts (in s/w) or programming languages.
But I am not very good with h/w, although I can handle serial port comms and an Atmel up board with no o/s (interrupt driven programming)
I am well versed in telemetry and SCADA, and am now becoming interested in "the internet of things", and aim to implement sensors/controllers for those.
After a few hobby projects, I might attempt a commercial project (so, think of licensing)
I need something that can be ruggedized to IP67, but guess that they both can.
I am not too concerned about price, probably more about flexibility. I would hate to build up knowledge of one system after 5 to 6 projects and then find that there is something that it cannot do, which the other can.
Since I know nothing about h/w, I am concerned about connecting peripherals. Does each peripheral have standard connections, or does it vary. Does one or the other system have more off the shelf" peripherals available?
Which can support the most peripherals simultaneously (or does that not make sense, with break out boards, USB, serial bus (MODbus), etc?) Also, CANbus support would be nice, but is not a hard requirement.
I do not require the display capabilities of the Raspberry Pi, not will I attach a keyboard. Strictly monitoring and controlling and communicating with a remote PC.
which has the wider support base (especially on the s/w side)?
while I am happy with Ethernet, I would not like to rule out WiFi or even Zigbee communications
Running on very long life battery/solar power might be interesting, but is not a requirement.

I hope that you can see that this is a question that can be answered, and invite counter questions asking me to further explain what I hope to achieve.


texts: I'm working on a Kenwood kr 5200 receiver and I came across some capacitors that need replacing, but I can't find anything online as to what kind of capacitor it is.


texts: I understand this until the final two lines. How does he get from 27.8766 to 1149.8hz and 7224.7rad/s?


texts:
I've recently gotten into eletrochemistry, and I found out that if you break through \$\epsilon_{0}\$ with a high enough voltage you can ionize various gasses. I've already wound a 1:1250 EE core that I plan to operate at 350 kHz on a 25 V supply which should give me 31.25 kV in the arctube, but there's this problem where I think I need to rectify the output and uh, I have yet to see a 50 kV diode.

Is there a way to do it that I'm just not remembering? I thought there was a way to do that back in the vacuum tube days.


texts: relationship between battery voltage and discharge rate

texts:
I guess my question roots from me not understanding what a load represents to the battery.

Is a 4V battery able to discharge at a higher rate (C rate) than a 2V battery?

Or does it completely depend on the load which will always extract current at the same rate regardless of the battery voltage.

In my current understanding I feel as if a higher voltage battery will allow for faster discharge rates if needed (higher C rates of discharge).

It's difficult for me to test this with a potentiostat because in my understanding it can always force negative currents on discharge (GCPL mode lets say) which can be higher than the maximum discharge rate a battery can deliver to a load.

Could someone please clarify this for me. I am very confused.


texts:
I am running small stm32/gsm module project and would need battery backup in it.
Is it possible to use cheap lipo charging module to do exactly that.

I would charge my battery through input terminals or usb, and be connected in the same time to battery. So if input goes away I get battery power.

Module is bought off eb..(no commercials):

And uses this particular IC (datasheet)


texts:
I was hoping that someone form here can help me with a problem.First I'll explain what I'm doing, then I will explain the problem.

Currently, I'm using 2 IRFB7530PbF MOSFET's as switches for an electric longboard that draws around ~10-20A continuous and has peaks of up to ~80A (all very rough numbers because it varies from EBoard to EBoard). Anyway, below is the schematic for the switch, it's very simple and just uses a 10K resistor for the gate and some resistors for the pretty blue LED on the pushbutton switch to control the gate state.

The problem that I've had is that the MOSFETs have drain-to-source shorted after turning them on and off a couple times without even riding the board. The switch IN+ &- are connected to the 10 cell LiPo pack which is at ~42V. The OUT+ & - are connected to the 4x ESC's (Electronic Speed Controllers) for the 4 separate hub motors. Each ESC has 3x 560uF 63V capacitors on them in parallel for a total capacitance of 1680uF for each one and 6720uF between all of them. I was thinking that when the MOSFETs are turned on and saturate the gate with the 10K resistors ,the caps pull a ton of amperage for a short amount of time and that is killing the FETs. I don't know if this is the case, but it looks like it's the only viable possibility.

Anyway, considering this was the problem,I decided to increase the gate capacitance so that it takes longer, around a second, for the MOSFETs to fully saturate so that the ESC caps can slowly charge. I added a 100uF 32V capacitor in between the gate and source to do so(32V if it's ok,because gate-source voltage is almost exactly half of the actual input voltage).

Anyway, before I test this and find out I'm wrong and kill 2 more FET's, I wanted to ask the community if they think that the capacitors are causing the problem and if not, what is causing the problem? Thanks!


texts:
What is the meaning of output current of the regulator.

For example, IC datasheet's written as "300-mA Output Current Capability", the maximum output current must be 300mA, isn't it.

What'll happen if I connect this regulator output to 4 ICs, which will consume about 100mA per each IC.

Or what'll happen if I connect this regulator output to 2 ICs, which will consume about 100mA per each IC.


texts: Advice to replace a discontinued battery

texts:
I'm looking for advice to how to replace a Duracell TR163 mercury battery in an old synthesiser I have (Oberheim OB-1 if anyone is interested).  The battery is no longer available, at least not in the UK, so I'm looking to see if I can replace it with a circuit or some other type of battery. The battery itself is rated as 4.05V and 500mAh so I'm thinking that using 3xAA batteries and reducing the voltage from 4.5V to 4.05V would work.  I'm very much a beginner with electronics and there seems to be several options (voltage divider, diodes etc) however I've not been able to find this specific situation to use as a reference.

My concern is that I don't know whether the load is fixed or variable so I'm not sure a voltage divider is sufficiently safe.  I believe the battery powers the patch memory when the device is powered off but I don't have any more details at the moment.

Ideally I'd like some sort of rechargable battery system that is charged from the main power board when the synth is running, but that's probably reaching too far!

Any advice would be most gratefully received.


texts: Making an operational amplifier out of a differential pair

texts:
I need to modify this circuit to serve as an operational amplifier with low output resistance

Because the operational amplifier that I'm familiar with uses this differential pair:

I thought about making my former circuit single-ended so we can use a common-drain amplifier and achieve low output resistance, maybe get rid of the degenerative \$R_{ss}\$ if we wish for higher -not as linearized- gain, then it was turn to think about if we really need to have that current mirror at the top with the reference being diode-connected, for a long time I thought we only did this for current mirrors to avoid the reference transistor from entering the linear region (I found out that when we do this, the small-signal circuit also changes and \$g_{mp}\$ shows up in the transfer function). Thus, I'm reluctant about whether I should include ditching \$V_{b}\$ and making \$M_{3}\$ diode-connected in my steps of transforming the original circuit to an operational amplifier.


texts: Wind turbine generator: brushed or brushless DC motor?

texts:
I am trying to use a DC motor as a generator for a wind turbine but then there are two possibilities for the DC motor which are brushed and brushless. Which one is more efficient to use?

I know that if I use a brushless motor then I need to use a 3 phase rectifier which includes 6 diodes. Will the voltage drop in these 6 diodes affect efficiency? But if I use the brushed motor then I don't need to use the rectifier. Can this be the advantage over the brushless motor?


texts: I have a relay that is controlling 220VAC input to a PSU. That PSU is controlling the relay coil at 5VDC so that when the PSU powers off the input is cut as well. Problem is how do I start it in the first place. I can wire up a small 4.5V battery with a button on the relay coil that when I press will allow power to the PSU and then the PSU will power the relay and everything will continue working as planned. I'm worried about combining 2 circuits like that, what I can do is I can put diodes on both the 5V from the PSU and the little battery circuit to not allow current from the other circuit to flow through but I'm wondering would it be a problem if I didn't? I'm not quite sure what will happen but I don't want to find out the hard way.


texts: Free spice Model to simulate integrated circuits design

texts:
I am using ltspice and I would like to simulate integrated full custom circuits for educational purpose.

I found the NMOS4 and PMOS4 models but there are not enough since there are too ideal there is i.e. no Early Effect.

Are there any possibilities to get a free spice model which includes the basic effects of the FETs and in which I can modify width and length like in the NMOS4 and PMOS4 models?


texts: RMS or effective ac voltage component of a full wave rectified sine (not filtered)

texts:
Ignoring the voltage drop on the diodes, for a full wave rectified DC,can I say that:
 1)  Vrms of the original AC = Vrms of the rectified DC. ( I have just flipped one polarity. Power is same)
2)   Vdc = V average = Vrms / 1.11072   ( the ratio between Vrms and V average) ( 0.7071 / 0.6366  =  1.11072) (0.6366 / 0.7071 = 0.9003)
If I view the rectified DC as a mixture of pure DC, and AC component, the V average is the pure DC component.
 3)  Since I know the Vrms and the Vdc, can I calculate the AC component voltage this way:

The Vrms of the AC component would then be Vrms of the original AC sine wave / 0.435.

If this is all wrong, what is the correct ratio? I am looking for an answer without using functions. Should the AC component be referred to as Vrms or V effective or both are ok?


texts: Building a passive ethernet hub with anti-parallel diodes

texts:
I've found several guides online on how to build a passive ethernet hub, the design is always the same:

I'm wondering what each of the 2 anti-parallel diodes do? For both positive and negative current there's always one diode conducting, so what's the difference to just bridging the wires directly?


texts:
I made a really simple scheme/pcb using Kicad (on Ubuntu 14.04). Now I'd like to print this and make my PCB, but I can't figure out how to properly plot the damn thing!

When I plot using gerber format and open files in gerbv, everything seems to be ok (measurements/scaling is ok), but when I try to export to PNG or any other format, the scaling goes wrong. If I try to print from gerbv, I get nothing (blank page).

So, what are the proper steps to create basic front and back Cu layers that I can print and then go on with making my PCB?

I've been stuck with this for days now, so any help is appreciated...

BR,
Newman


texts:
I have a STM32F051R8 (STM32F0 discovery board) I am trying to use to generate a PWM using a timer and change the pulse width at runtime. My code is:
// configuration
  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 0;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 65535;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

// runtime
  if(HAL_GPIO_ReadPin (GPIOA, B1_Pin)) {
    // Set The LED ON!
    HAL_GPIO_WritePin(GPIOC, LD4_Pin, GPIO_PIN_SET);
    HAL_GPIO_WritePin(GPIOC, LD3_Pin, GPIO_PIN_RESET);
    __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, 750);
    htim1.Instance->CCR1 = 65534/2;
  } else {
    // Else .. Turn LED OFF!
    HAL_GPIO_WritePin(GPIOC, LD3_Pin, GPIO_PIN_SET);
    HAL_GPIO_WritePin(GPIOC, LD4_Pin, GPIO_PIN_RESET);
    __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, 500);
    htim1.Instance->CCR1 = 65534/4;
  }

My problem is the signal looks like this:

Why are the waves like that? I thought they were supposed to be square. Am I doing something wrong, or is there some kind of setting I must apply?


texts: Working of Voltage-to-Frequency Converter

texts:
I have seen this circuit in a thesis "Voltage to Frequency Converter: Modeling and Design" submitted by Jyoti Ranjan Behra and Rajesh Kumar Barik (thesis abstract, thesis document).

In the thesis, they are not explaining the working of this circuit in detail.
Can someone please explain the working of this circuit to me? What is the use of those two BJTs in it?


texts: Issue with parallel resistors in LTSpice

texts:
I'm trying to build a reactive load box, so I can run a guitar amplifier without a speaker. It's basically a device that simulates the impedance/frequency curve of a relatively high power speaker.

I need 4Ω nominal impedance, but my local electronics store does not sell 4Ω 100W resistors, so I though of getting four 16Ω resistors and put them in parallel.

On the right it's the correct impedance curve using a single 4Ω resistor, and on the left, the same circuit but using four parallel 16Ω resistors.

Why are the simulation results different? I thought these circuits were supposed to be equivalent.

Edit by Steve G.: The following circuit gives the same results as the 4 x 16Ω resistor circuit (note the floating wire):


texts: How to use electrically isolated weak signal for Arduino interrupt?

texts:
I'm trying to use the signal generator from a DSO Nano v2 to drive an Arduino interrupt for testing purposes. I have measured the output of the signal generator at approximately 13mA @ 2V DC.

I have tried using a 4N28 optcoupler alone but I found that the voltage differential at the output was nowhere near enough to trigger the interrupt (it was ~0.4V), I assume there is not enough input current for the IR LED to saturate the transistor.

How can I make this work? Also, would this solution apply for other comparatively weak signal sources.

Would an opamp be able to boost the output signal?


texts:
if we have a circuit with a bjt like this one

and we know that the I is 1.1mA in 25 Celsius , with Vbe=680mV and Ie=1mA , and β=100 in 25 Celsius. If we know that the TC (thermal) of Vbe for constant Ie is -2mV/C how much would TC for Ve be? For 75 Celcius what is Ve?

I have calculated that for 25 Celsius Ib=9.9μΑ the current in R2 is 0.2mA going down and the current in R1 is 0.1mA going down. Also Vb=-13.6V and Ve=-14.28V . However I don't know how to calculate TC and the other question for 75 degrees. How could I do that?


texts: I want to make a digital timer that counts to 99 minutes 59 seconds the problem is that i want to use 4 digit 7 segment display so i have to oscillate the input of the bcd to 7 segment display between the four digits so i have to control the decade counter 74160 so i use mux to choose which counter to work and counter 5 oscillate switches the mux quickly . How to control f/f wheather to output or to keep the output for itself for now till it`s turn?


texts: Wireless radio reception power vs distance

texts:
I found a PDF online that says:

  The diagram shows that one unit of power is required to achieve a given data rate over one unit of distance. But to maintain the same data rate over x the distance, a traditional wireless network requires not x but rather 16x the power.

It refers to this diagram:

Shouldn't it have been 9X the power (instead of 16X) or 4X the distance (instead of 3X)?


texts: How to generate crosstalk between 2 wires?

texts: I'm trying to recreate a situation where crosstalk is occurring. I'm having a bit of trouble trying to inductively cross couple two parallel wires that don't have any shielding or insulation and aren't twisted together. I basically have 2 oscillator circuits that are connected to an inductor since I want to measure the two inductors frequency.


texts: Reverse polarity protection for analog input pin

texts:
I am designing a PCB with a PIC 16 microcontroller. The purpose of the PCB is to measure the voltage of a button cell battery, before the battery is placed in its device (assume this batterytesting is involved in a mass production line, so its used very much, and very quick). Now i am using a sort of clothspin to clamp the battery on the top and bottom side (anode and kathode). But the mistake to reverse the polarity of the battery is very easy to make. For that reason i want to include a reverse polarity protection, so that if the battery is placed wrong (negative voltage on the analog input) it doesnt fry my microcontroller.
What is the best option i can use? A diode wont do the trick in my opinion since that makes the voltage that i want to read drop, But i also dont want to make a very difficult circuit for this RPP.

Thanks in advance!

This is the circuit. The Battery wire is going to the analog INPUT. The resistorValues are not right yet. They will be something like 100, 1000, 1000 ohm


texts: How do I figure the I2C timings for a peripheral?

texts:
The I2C timing specs are confusing me a bit. Here's a few timing characteristics from my peripheral :

It's basically the same as I2C timing specs provided by NXP. I am looking at specs at 100khz mode. The max rise and fall times for example are given, but not the minimum. Should I program my I2C controller on MCU for 1000 ns rise time only or could I go lower?
Similarly the specs for,say, START condition Hold time is given by a minimum 4 us. The max value is left as blank.
Do I go just by min and max values? Or if I can program differently, how high/low can I go?


texts: Find current and power factor in circuit

texts:
This is a picture of a homework question that I do not understand all too well. The question is below:
The power supply in Fig. P9.59 generates 50 kW
the line impedance is 0.095 . If the load consumes
43 kW and the voltmeter leads 220 V rms, determine
the ammeter leading and the power factor of the inductive load.

I don't know how to start. I know some functions that are most likely to be used:
P = Vrms x Irms x cos(theta) with cos(theta) being the power factor. Also, I extracted the information and I don't understand how to find the current. That being the obvious first step. I tried using P = VI => 7kW / 220 = I. But, I checked the answer my professor put online and it's not the same. He somehow got Irms = 271.4 Arms. I don't understand it. please help. Thanks.


texts: Star Delta Motor Starter, at higher ampere in Delta Configuration

texts:
Here is a dilemma. The electrician in my village isn't so much internet savvy as I guess(and I am not electrical expert) so I am asking this question here on his behalf. It's just similar to another question asked on stack exchange, but as I am novice in electricity, I am attaching the images also

Problem : We have a motor with this specification which is in star delta configuration. When we start in star it's ampere reads around 4, and when in delta it goes up to 30 ampere and then mcb cuts the power after 6-10 seconds.

It is a 15 hp motor.
In the below image is the panel . The lower part of the panel is for this motor.

Interestingly we have another motor in star delta configuration(upper part of panel) which works fine.  It's of different hp.

PANEL :

[![enter image description here][4]][4]


texts:
I need some help confirming what my answer sheet is indicating regarding the output waveform.

So far, everything I have matches up with the answer sheet except the last peak from output 'U'. The SET signal is pulsed so shouldn't the output 'U' be HIGH until the RESET signal is pulsed? If so, then why does the answer sheet show it pulsed and then returns to LOW?


texts:
Recently some one asked me 'Why ammeter (based on moving coil principle) has a non-linear scale?' In multimeters (not based on moving coil principle) which we uses in digital lab, I didn't found any non-linearity in scale?

Can someone provide any reason why this is happening?


texts:
Well, I have a little problem, I'm out of resources for the next month (read: funds for electronics) and I ordered a 12V accumulator/lead battery. The motors I have are rated for 7.4 Volts and are 165W. Full spec's are not available (cannot find them) but I do have a link to the motor.

Here is a quote from the seller page:

Supply Voltage       7,2 - 7,4 V
Nominal Voltage      7,2 - 7,4 V
Turns                12
RPM (no load)        32000 min^-1
Power                165 W
Manufacturer number  2310072
Use as               Tuning-part

Now, I have a motor schield which is 0.018 Ohms and I assume the DC motor has something around just that. I do not have such small resistances to drop the voltage from 12V to 7.4, so what are my options?

Is there any DIY voltage regulator thingy?

The resources I do have are (from the arduino starter kit):

5 x Resistor 220 ohm
5 x Resistor 1K ohm
5 x Resistor 2K2 ohm
5 x Resistor 10K ohm
5 x Resistor 330K ohm
2 x 100 nF Capacitor
2 x 10 nF Capacitor
2 x 100 uF Capacitor
6 x LED
1 x Piezo speaker
1 x 10 KOhm POT
2 x PCB button
1 x LDR
1 x Thermistor
1 x IR Receiver
2 x Transistor
2 x Diode
1 x MOSFET

and some other scrap which is lying around (broken DVD players etc).

Any thoughts on dropping the voltage to 7.4V without losing too much power?

I did look at 30A voltage regulators but some are even in the price as high as $500, but I can't find any 12 to 7 volts 30A regulators, so I think I'm on my own with this?

Anyway, I hope someone here can guide me in the right direction!


texts:
I have an application involving an ATmega328 which may be powered while the ATmega is not.
The circuit is an led driver (operating at 24V) which can be controlled either by potentiometers or digitally with the ATmega. In the latter case, the circuit will be connected to a controller board, providing the ATmega with 3.3V. In the first case, though, only the driver and the potentiometers are powered from a 24V PSU and as the pots and the ATmega control the same pin on an IC, the ATmega will see up to 3.3V on some GPIOs while not being powered.
Each pot has additional 680 kΩ in series and the current will therefore be limited to ~30 µA, which should be fine (according to this document). I'm not concerned about the current through the clamping diodes, because I'm bypassing those with Schottky diodes anyway, but I'm clueless about how the ATmega will behave in such a situation. My guess is, that it will boot as soon as there's sufficiently high voltage on the rail (how should it know about a current limitation of the supply).
I'm thinking of a software solution, something like "wait until capacitor is charged above threshold", but that would still require the MCU to show predictable behaviour.
Another idea is to pull down the 3.3V, maybe with a MOSFET, so I don't waste power in the "digital version" operation.
At the moment it is hard for me to decide on a solution because I have not much experience with it and I also couldn't find much information about it either.
So my questions are mainly:
Is there a way to keep the ATmega in a reset state by hardware (from my undestanding, the RESET pin requires a pulse to trigger a reset)?
Is there a chance, that the firmware or data in EEPROM/RAM gets corrupted or that the MCU shows unpredictable/erratic behaviour when the µC is power cycled continuously?
Do microcontrollers include "features" that avoid problems in such a scenario (brownout detector)?


texts:
I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit I am talking about (part of this circuit is amplitude control though, but still).

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: I know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

But, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shorted in this case.)

I don't know how is that possible since we have resistor Rf and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example.

How come then this expression still happens to be correct in all textbooks, what am I missing?

EDIT: Values of Va and Vb are such that these diodes are off.


texts: Wires from car battery to solenoid catching fire after connecting a second solenoid

texts:
I have two solenoids connected to my AVR and car battery:

simulate this circuit – Schematic created using CircuitLab

But when I start switching them the circuit burns up (literally there was fire).

The lines connected to the solenoid is what caught fire.  The switching frequency is probably like 1 or 2 Hz.

Here is some data on the solenoids (I unfortunately cannot find a part number on them any where):

Switch at 12V
.58 Amps running
2.94 Amps switching
16V spikes when switching

What did I do wrong here?

FYI: We were able to get this to work (without fire) with just a single solenoid, but adding the second causes these issues.


texts: Order of Physical Proximity for Decoupling Capacitors

texts: I have completed a schematic for a PCB and selected a series of decoupling capacitors for usage with a variety Xbee format radios on one board (i.e. one at a time, but changeable). I have included in decoupling capacitors of various sizes as specified by data sheets. As I begin the the physical layout my question is: does the physical order of these capacitors have any importance? (i.e. 8.2pF closest, then 1uF, then 10uF, then 100uF furthest from the power pin OR 100uF closest and 8.2pf Furthest)


texts: Why is there a discrepancy in the E192 series?

texts:
For all series from E48 through E192, this holds true:

$$
value = 10^{\frac i n}
$$

where i is the zero-based index in the series and n is the length of the series. The one exception is E192[185]:

$$
listed = 9.20
$$

$$
expected = \text{round}\left( 10^{\frac {185} {192}} ,2\right)
= \text{round}\left( 9.19479... ,2\right)
\approx 9.19
$$

It seems that industrially, 9.20 is indeed much more common, but to muddy the waters even further, Vishay offers both of these parts:

RN55E9191BRE6
RN55E9201BRE6

What is going on here?

There is a random post on EDAboard that talks about the same issue.

This is related to, but not the same as, A question about E12 series resistors - it's well-known that E24 and below differ from the exact logarithmic formula for historical reasons, but no such historical reasons are listed in (for instance) the Wikipedia article for the higher series.


texts: Bluetooth frequencies possible to Jam with Wifi routers?

texts: Since Bluetooth operates at the 2.4 GHz with 1Mhz width and 79 channels would it be possible to Jam with a few 40 dollar routers at the 2.4 spectrum default I believe the channel width is 20MHz and there are 11 channels. So all you have to do right is make sure that every router is overlapping by minimum 1mhz to block all connections to a bluetooth connection given that the wifi has a higher power then the bluetooth connection at the connection point. I understand that this is probably not the case but I'm confused on why it doesn't work so any help would be appreciated.


texts: Measuring differential signal with single ended probe

texts: I have a differential signal(a +/- signal) to measure. Can I use a single ended probe to measure it and then just multiply whatever I read by 2 to get the actual amplitude?


texts:
I have a signal I am interested in obtaining power from. The best way to describe the signal is that it is random.

In the graph, the voltage fluctuates from negative to positive with an RMS of 0.5 volts. What circuit would be useful to obtain power from a voltage signal similar to this one?

I am interested in knowing how to obtain power from a signal similar to the signal in the graph. It is random.
The max impedance of the source at 1 kHz is 3.5kOhm. The signal will fluctuate at around 0.5 to 2Hz. Will impedance increase or decrease? The source is a piezoelectric transducer. The max voltage will be from 4 to 12 volts.

Source of image: USC, Doug Button
https://slideplayer.com/slide/6121107/


texts: MCU RAM - Why accessing RAM across the boundary causes Bus Fault?

texts:
My question is best explained by an example. There's an evaluation kit from Infineon that uses ARM Cortex-M4 and has a total of 80 kB of RAM. There is also 512 kB of Flash memory. [However, it seems that due to large areas within RAM being "reserved" (as per board's reference manual), the maximum RAM size is below 20 kB. What could be the cause of such behaviour?] After further investigation, the problem appears to be that the RAM allocated for program data passes the boundary between the two regions, and does so in a misaligned fashion. This may cause problems even if code size is well below RAM size.

To give a little context to the problem, here is the output of arm-none-eabi-size with SysV option enabled:

section               size        addr
.text                 5628   134217728
Stack                 2048   536854528
.data                  116   536856576
.bss                 16386   536856692
USB_RAM                  2   536873078
.no_init                32   536936384
.debug_aranges        2208           0
.debug_info          43565           0
.debug_abbrev         3389           0
.debug_line          11094           0
.debug_frame          9968           0
.debug_str           30489           0
.debug_loc           21316           0
.debug_ranges         2064           0
.build_attributes      472           0
Total               148777

Unless I am mistaking, the only parts that go into RAM are .bss, .data(as it goes both into RAM and Flash). The relevant linker map section is as follows (i.e. shows exactly the point where the .bss section goes out of its bounds):

.bss            0x1fffc874     0x4009 load address 0x0c0016a8
                0x1fffc874                . = ALIGN (0x4)
                0x1fffc874                __bss_start = .
 *(.bss)
 *(.bss*)
 .bss.resultsArray
                0x1fffc874     0x4000 ./main.o
                0x1fffc874                resultsArray
 .bss.resultsArrayIndex
                0x20000874        0x2 ./main.o
                0x20000874                resultsArrayIndex
 *fill*         0x20000876        0x2
 .bss.oversamplingResult
                0x20000878        0x4 ./main.o
                0x20000878                oversamplingResult
 .bss.numberOfOversamplingSamplesCollected
                0x2000087c        0x1 ./main.o
                0x2000087c                numberOfOversamplingSamplesCollected

Note that per user manual, PSRAM ends at 0x1FFFFFFF and DSRAM begins at 0x20000000. Running this program generates a Bus Fault when the startup sequence reaches 0x1FFFFFFD. Reducing the size so that it fits in PSRAM makes the program compile and run without any Faults. The question is not as much about this particular program; instead, I am genuinely curious as to why so little RAM is available for the actual program variables and uninitialized data and everything else that goes into RAM?

Below is the screen capture from the reference manual outlining the memory organization at the boundary.


texts: Why can't I declare and assign a logic type in one step in SystemVerilog?

texts:
I can declare and assign a wire in one step in SystemVerilog.
Eg.: wire y_and = a & b;
I can't declare and assign a logic type in one step in SystemVerilog.
Eg.: logic y_and = a & b;
But this works:
logic y_and;
assign y_and = a & b;

Why can't I declare and assign a logic in one step in SystemVerilog?


texts:
I designed a simple board based upon the ds of the TPA3118.
Here the actual schematic:

When I power the device, even with no input signals, coils (L1..L4) and op-amps (IC1..IC2) reach a quite warm temperature:

I understand it's not such an high temperature, but I would like to understand if it's normal. Especially for op-amp I don't understand what they are doing. With no input signals there's only a DC offset (provided by R4 and R6).
The coils are NRS8040T100MJGJ (10 uH, 3.1A, 34 mOhm, 22 MHz).

I checked with the oscilloscope and there are no oscillations in the input pins.
Of course I have the high-frequency "PWM" on the coils - here I can understand the heat.

I measure 135 mA at 24V in this condition.
The board is working. But I want to be sure this is its correct behavior or I missed something in my design.


texts: Using a 12V battery while simultaneously charging via Heavy Duty battey charger

texts:
Very similar to a question asked and answered but using solar panels..
BUT this time I'm asking, Can I use my 135Ah deep cycle battery to power a 2000W inverter and at the same time charge my battery with 50A 7 stage battery charger.

So connected in parallel.  I don't expect to be drawing more than 300-400 watts 240v from the Inverter.  Think of it as a home made UPS for my office

Thanks


texts: How do for loops work in verilog? Why can't I achieve what I want?

texts:
This is my code for a simple 2-1 8 bit multiplexor, where SW[17] is my selector.

If it is on, show Y = SW[15:8], if it is off, show X = SW[7:0].

module part2 (SW, LEDR, LEDG);

    input [17:0] SW; //inputs
    output [17:0] LEDR; //light every switch
    output [7:0] LEDG;  //byte desired

    //All switches to red leds.
    assign LEDR = SW;

    //Green leds get the desired byte.
    assign LEDG[0] = (~SW[17] & SW[0]) | (SW[17] & SW[8]);
    assign LEDG[1] = (~SW[17] & SW[1]) | (SW[17] & SW[9]);
    assign LEDG[2] = (~SW[17] & SW[2]) | (SW[17] & SW[10]);
    assign LEDG[3] = (~SW[17] & SW[3]) | (SW[17] & SW[11]);
    assign LEDG[4] = (~SW[17] & SW[4]) | (SW[17] & SW[12]);
    assign LEDG[5] = (~SW[17] & SW[5]) | (SW[17] & SW[13]);
    assign LEDG[6] = (~SW[17] & SW[6]) | (SW[17] & SW[14]);
    assign LEDG[7] = (~SW[17] & SW[7]) | (SW[17] & SW[15]);

endmodule

This code is simple, but I am trying to optimise it and replace the 8 lines.

I wanted to use some sort of loop, but I failed:

integer index;
initial
   begin
   for(index = 0; index < 8; index  = index+1)
       begin
       assign LEDG[index] = (~SW[17] & SW[index]) | (SW[17] & SW[index+8]);
       end
   end

I also tried this, and I failed:

//Green leds get the desired byte.
always @(SW) begin
    if (~SW[17])
        assign LEDG = SW[7:0];
    else
        assign LEDG = SW[15:5];
end

I am getting an error saying that the left part of the assignment must have a variable data type.


texts: I am using an AC Power supply, and the frequency of the wall plugs is around 50hz. Is there a way to increase this frequency keeping everything the same?


texts: Laplace and time domain transform confusion with respect to RC LPF

texts:
I am a bit confused with Laplace domain and its equivalent time domain conversion

Consider the s-domain of first order LPF filter which is \$V_o(s)/V_i(s)=1/(1+sRC)\$. Now for a second order LPF filter in s-domain is simply the multiplication of the transfer function by itself i.e \$V_o(s)/V_i(s)=1/(1+sRC)^2\$
The implmentation of such a transfer function with resistor and capacitor are two RC filters cascaded like shown in the figure

Now for analysis of the above implemented filter in time domain.Considering a step input the analysis of this filter is \$V_1(t)/V_{in}(t)=1-e^{-(t/RC)}\$ and \$V_o(t)/V_1(t)=1-e^{-(t/RC)}\$, and hence \$V_o(t)/V_{in}(t)=(1-e^{-(t/RC)})^2\$

But in time domain the multiplication of Laplace domain transfer function should be convolution, yet the second order RC filters are implemented as multiplications. Also the Laplace transform of \$V_o(t)/V_{in}(t)=(1-e^{-(t/RC)})^2\$ is not \$V_o(s)/V_i(s)=1/(1+sRC)^2\$

What am I missing here??

EDIT:

Ok here is an exercise I tried.
Assuming \$V_i(t)=u(t)\$, unit step function, which in s domain is 1/s the Laplace transfer function for a first order LPF is \$V_o(s)=V_i(s)\times 1/(1+sRC) = V_o(s)=1/s(1+sRC)\$ The inverse Laplace of this function is \$V_o(t)=u(t)\times (1-exp(-t/RC))\$. This checks out which I verified in Matlab in time and s domain.

Now for the second order LPF and step input with a buffer in between like in the circuit by MatteoRM. The Laplace transform \$ V_o(s)=1/s(1+sRC)^2\$ right? If i follow the same exercise as before, the inverse Laplace is \$1 - (te^{(-t/(RC))})/RC) - e^{(-t/(RC))}\$. Now this does not check out in time domain. Again what am i doing wrong?


texts: Is Arduino suitable to be a Humanoid Robot controller?

texts:
I am not a Arduino developer here. However I would like to ask if any developer out there who have experience on the capability of Arduino, is Arduino suitable to develop a humanoid robot? Humanoid robot consists of visual camera, sensors and servos, wireless transceiver, compass, accelerometer and so on.

Correct me if I mentioned anything wrongly.


texts:
I would like to simulate a simple oscillating circuit involving an unijunction transistor. I do not find such component in LTspice so I figure I need to import one. Could please show me step by step on how to do it ?
I googled LTspice UJT , and there is this text file:

*Programable Unijunction Transistor pkg: TO-226AA
.SUBCKT X2N6027 1 2 3
************** K1 G K2
Q1 2 4 3 NMOD
Q2 4 2 1 PMOD
.MODEL NMOD NPN(IS=5E-15 VAF=100 IKF=0.005 ISE=1.85E-12 NE=1.45
+ RB=10 RE=0.5 RC=0.5 CJE=3.5E-11 VJE=0.75 CJC=1.1E-11 VJC=0.75 TR=4.76E-8
+ TF=16N VJS=0.75 )
.MODEL PMOD PNP(IS=2E-15 VAF=100 IKF=0.005 ISE=1.9E-12 RB=10 RE=0.5
+ RC=0.5 CJE=3.5E-11 VJE=0.75 TF=1.6E-8 CJC=1.1E-11 VJC=0.75 TR=5.1E-8
+ TF=16N VJS=0.75 )
.ENDS X2N6027

I saved this text file and named it 2N6027.sub . But it didn't show up in component selector. What can I do with this text information ?


texts:
I am still in the process of flashing my very first micro controller (an ATmega32U4). In the whole process of learning and exploring how to get this done I also used a multi meter several times on the ATmega to see if a certain pin was high (to check if my program was active, in other words, if I finally successfully written the flash memory).

Since I am still a bit clumsy with electronics, I put the probe on two pins at the same time; ground and VCC.

I noticed that suddenly stuff reset, and my power supply started to make a different sound. I didn't even realise straight away what I did, but after a while I finally realised, "oh $@!#, I am creating a short with my probe...".

Now aside from the fact that that was a rather stupid thing to do, is there any way I can test of the ATmega chip itself is still OK?


texts: Heat Transfer of Aluminum Plate with LEDs

texts:
I'm building an LED grow light for an, um, indoor vegetable garden, and I'm trying to figure out what dimensions I can get away with for the aluminum sheeting I'm going to use for the mounting plate. I've been trying to use this heat transfer calculator, but unfortunately the physics is a little above my head.

I will be using 11 high intensity LEDs (data sheet), wired in series running at 700 mA. Due to build constraints, I plan to use an aluminum sheet that's 12" x 5", 1/16" thick (0.30m x 0.13m, 1.5mm thick). So that works out to a surface area of 60 [sq in], but the manufacturer recommends at least 9 [sq in] per LED (thus 99 [sq in] total for this project), so I'm significantly under that.

TL;DR - Here's the question - I have an aluminum sheet 12" x 12", 1/16" thick, if I cut it in half, and then use thermal epoxy to bond one half on top of the other, would that sufficiently increase the heat transfer capacity of my heatsink? Sorry if this is a dumb/obvious question, I really should have paid more attention in physics class :)


texts:
simulate this circuit – Schematic created using CircuitLab

Today I saw an led dimmer product. the driving circuit was like in the schematic. it was a cheap one but the circuit looks inefficient to me. when the bjt not conducting, R1 pulls the gate high, and mosfet starts conducting that's ok. but when the bjt conducting(high signal on gpio) bjt shorts the gate to gnd. thats actualy commonly used circuit. but large amount of current (12V/150 = 80mA) flows through the gnd on R1. is it okay for a commercial product?

pwm frequency is seen as 500Hz on scope. obviously when they increase the R1, rise time of the mosfet get very high and switching losses dramaticly increase. they claim that this product can handle up to 20 amps(of course there is a heatsink on mosfet).

so the question is, is there any efficient solution to drive a gate without gate driver? is it the right way to drive a mosfet?

I don't have the products document but here are bjt and mosfet.


texts: What is the current flowing through the resistor in this circuit?

texts:
I have to find the current flowing through the resistor connecting node a to d. I know it's a current divider problem, but I'm having a hard time finding the correct expression. I presume R5 is obsolete, since it's connected to an open circuit.
Since \$R_{1}\$, \$R_{2}\$, \$R_{4}\$ are connected in parallel, their equivalent resistance \$\frac{1}{R_{T}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{4}} \$. Since we have to find the current through through \$R_{3}\$, the current \$i\$ should be:

$$ i = I_{0} \frac{R_{T}}{R_{3}+R_{T}} $$.

Is this correct? Am I doing something wrong?


texts: How to achieve large gain in the transfer function with OP-AMPs?

texts:
My transfer function is:

$$ \frac{-115.298}{1+5\centerdot10^{-4}s}$$

To achieve the denominator I used an inverting op-amp with Rf = 1k, Cf = 0.5uF (ceramic, and both in parallel) in feedback and R = 1k at the input. I am using TL084 OP-AMP.But is it possible to get a large gain of 115.298 in any possible way? Can any one suggest any ideas.


texts: How is energy consumed when charging a battery?

texts:
When I charge my battery at a constant voltage and current, the energy supplied is constant throughout the charging process. If it takes 1h to charge to 80%, the next 20% takes another 1h.

Since I supplied the same amount of electrical energy during the first and second one-hours, is a significant part of energy wasted during the second one-hour?

I understand the battery internal resistance increases by the degree of charge. Does it mean we waste a significant of the electrical energy supplied in the form of heat?


texts: Resonance Frequency of system with two inductors

texts:
I am trying to derive a formula for the resonance frequency of the following circuit:

The piece that is giving me trouble are the two inductors, that (although I might be wrong) cannot be further simplified. Therefore, it is not possible to use the known/basic formulas for RLC circuits which either are completely in parallel, or in series (https://en.wikipedia.org/wiki/RLC_circuit).
I hope that one of you will be able to get me going by providing some hints, or pointing me to a source where I can look up the answer. In any case, thank you for your trouble.


texts: Combination of four half-bridge load cells

texts:
I have a kitchen weight scale containing four half-bridge load cells, each cell associated to one foot of the scale.

I want to hack it to use it as a pressure sensor and link it to an Arduino microcontroller.

With resistance measurement, I have deducted the sensors were linked using this configuration:

I have removed the original PCB and connected the sensors together the same way and also to an opamp (INA122) using the E+, E-, S+ and S- connections.

However I do not have consistent values according to the place where the pressure is applied.

I am now thinking about building four parallel bridges, each containing one load cell and three regular resistors. Each bridge would be connected to its own opamp. This would allow to better calibrate the output of each bridge and improve the balance between all of them.

Is it a good way to combine the sensors and get a position-independant measurement ?
Is there a better combination ?

Thank you in advance.


texts:
This is my very first big project. I have to build a laser engraving machine for date stamping. I'm using Arduino Uno microcontroller and a CNC shield with GRBL control.

Being fairly new to G-code, I looked up articles about writing one for daily date change. I found http://www.microtechstelladata.com/TextToNCcode.aspx where they convert date to G-code directly.

My concern is, how do I generate G-codes daily in an autonomous way? I am going to use another Arduino Mega for programming a keypad and an LCD screen and use it for controlling an RTC module for daily date update. Can I use the output of the RTC module somehow and feed it to the G-code generator in Arduino mega which will generate a G-code daily and provide it further to the other Arduino Uno board with the CNC shield.

RTC module (daily date update) --> Arduino Mega (generation of g-code for date provided by RTC module) --> Arduino UNO equipped with CNC shield and GRBL control --> stepper motors and laser diode driver --> laser engraving

Am I going in the right direction here? Any help will be appreciated.

Cheers!


texts: How to shorten fall time of NPN transistor

texts:
I have built a circuit containing a 2N3904 NPN transistor.  I am using this to amplify a signal to send it longer distances and then drop it back down to 5V.

simulate this circuit – Schematic created using CircuitLab

While debugging the circuit, I noticed the resulting square wave has a longer fall time than expected.  Below are screenshots of the resulting waveform: red is the original and blue is the result (measured at TX_DATA_5V_AMP).

Resulting waveforms

My questions are:

Why is the fall time so much longer than the rise time on this waveform?
How can I shorten the fall time on this circuit?  Can I shorten it by changing the resistor values or the transistor?


texts: Measuring resistance at every point in multiplex circuit with analog-to-digital IC

texts:
Here I have basic LED multiplex IC (HT16K33). I want to add different resistors in my multiplex circuit and measure them at each x,y position with my ADC IC (ADS1115).
For some reason it won't register any measurements (values oscillate in sine as usual when nothing is attached). I tried with adding another transistor, but without changes. I'm really new in this, so any help appreciated. Is this possible at all, or I have to try different approach?

PS. These IC's are as complete modules with all the resistors and capacitors they need to function, I didn't bother to draw them.


texts: How to run electric match and microcontroller from a single power supply

texts:
We have a fairly large system that's been built up over the years for running a fireworks show from a computer (see here for the first generation software and hardware) using a pretty simple XBee-based wireless system.  I'm in the process of working on a replacement system and I'm trying to tackle one of the annoying things in the current system...which is current.

Ideally I'd like to be able to run both the local microcontroller (I'm using a version of the XBee that has an on-board Freescale) and fire the electric matches with a single power supply.  The problem, of course, is that firing the matches takes all current away from the uc, causing it to reset.  I've tried thinking about how to isolate the matches, which are essentially shorts in the circuit from the uc, but I'm afraid I'm woefully out of my depth in this area.  I'm assuming some capacitors would be involved but I don't know exactly what it would look like.  The firing current of an electric match is around 1A and extremely rapid.  Ideally we'd have up to 16 matches per system.  Bonus points if the solution could also be used to power an on-demand flash :).


texts: What does this schematic symbol mean (similar to solder bridge)?

texts:
this symbol is similar to solder bridge, but there is a connection on both end.

what does this symbol mean, and what is the equivalent pcb for this symbol


texts: How to receive bytes from SPI with interrupts using HAL on STM32?

texts:
Background

I am trying to make a SPI connection between two STM32F103C8T6's.

Measurements

According to my logic analyzer I get a signal that looks ok (sending 10 bytes with values 0x55):

Results

My receiver's callback function for RX Complete also stops in the breakpoint (last line in code below):

void HAL_SPI_RxCpltCallback(SPI_HandleTypeDef *hspi)
{
  /* Prevent unused argument(s) compilation warning */
  if (hspi1.RxXferCount == 10)

Problem

I sent 10 bytes, however, the RxXferCount has value 0. Instead, RxXferSize has value 10, but pRxBuffPtr is empty.

Question

How can I receive the correct bytes?

Values from the register SPI1 and variable hspi1

Relevant code

Initialization (using a GPIO for defining Master and Slave):

/* SPI1 init function */
static void MX_SPI1_Init(void)
{

  hspi1.Instance = SPI1;
  hspi1.Init.Mode = (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_12) == GPIO_PIN_SET ?
    SPI_MODE_MASTER : SPI_MODE_SLAVE);
  hspi1.Init.Direction = SPI_DIRECTION_2LINES;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}

Main function:

int main(void)
{
   ...
   MX_SPI1_Init();
   ...

   _transmitter = (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_12) == GPIO_PIN_SET ?
                  SPI_MODE_MASTER : SPI_MODE_SLAVE);

   while (1)
   {
      if (_transmitter)
      {
      uint8_t data[] = { 0x55, 0x55, 0x55, 0x55, 0x55,
                         0x55, 0x55, 0x55, 0x55, 0x55 };
          HAL_SPI_Transmit_IT(&hspi1, data, 10);
      }
      else
      {
         HAL_SPI_Receive_IT(&hspi1, _spi_data, 10);
      }
   }
}


texts: Assumptions in the Calculation of Noise Vrms

texts:
I was doing some reading on noise analysis and its calculations.

The SRS lock in amplifier specifies input noise levels only at a certain frequency and not the entire spectrum itself.

For example: \$ 6 nV  \backslash  \sqrt{Hz}\$ at 1kHz,

But with such data, I can only estimate input noise using the assumption that the PSD is "flat". Are electronics usually to be assumed as "flat" when it comes to input noise?

Here is the link to the data sheet of the lock-in amplifier. Thanks. (https://www.thinksrs.com/downloads/pdfs/catalog/SR810830c.pdf)


texts: Why is transistor gain measured in terms of current?

texts:
Why is gain of a transistor measured in terms of current ratio instead of voltage?

Signals are often measured in volts and it makes sense as potential can exist without any load.


texts: from this three which one is the best best current measuring method?

texts:
so i'm planning to build a battery power meter where it will measure voltage,current,mAh,WH ,and i have created the voltage divider for voltage measurement ,but i cant decide which current measuring method to use,i have 3 method that will work,but which one is the best , i want it to be as accurate as possible ?

also the microcontroller i will be using is an atmel atmega328p-pu used as standalone micro controller

the first method (A) is by simply using a power resistor as current shunt on negative rail and when its under load there will be a little voltage drop on the resistor and the mcu will measure the current from the vdrop

second method (B) is by using a CT and an op amp

third method (c) is by using custom callibrated ebay current shunt since the current shunt will only gives out few millivolt it will require an op amp,and because this kind of shunt was very sensitive to temperature change a thermistor is required to compromise the temp changes ,because temp change may cause the reading to go off so badly example: current shunt output is 1mV/A at 36c it may change to 1.1 or even up to 2.6 mV/A due to temperature change.


texts: What is the difference between TFT LCD interfaces?

texts:
I am looking at driving a small TFT and have found that the driver chip supports various interface methods, however I can't see why I would choose one over another.

The options are:

i80
SPI
VSYNC
RGB

Can anyone describe the pros and cons of the different interfaces?

In my specific case I want to drive an ILI9320 with a PIC32 via the Parallel Master Port.


texts: Measure the leakage current of a CMOS inverter

texts:
I would like to measure the leakage current of a CMOS inverter. As this current depends on the input, I decided to measure something average, namely, the leakage current of a ring with two CMOS inverters so that both PMOS and NMOS devices have an opportunity to be in both on and off states. I am using a SPICE simulator for this purpose. My circuit is as follows (not-that-relevant instructions are omitted):

X1 in  int dd ss bn bp inverter
X2 int in  dd ss bn bp inverter

Vdd dd 0 1
Vbp bp 0 1
Vbn bn 0 0
Vss ss 0 0

.ic V(in) = 0
.probe dc Ileak = par('abs(I(Vdd)) / 2')

where inverter is a subcircuit based on BSIM4 (v4.7) devices.

Since I have little experience in this area, I cannot really tell if what I am doing makes sense. I would be grateful if somebody could confirm that the circuit serves the desired purpose.

There is one more aspect that I would like to clarify. My global target is to get a rough estimate of the leakage current of a larger circuit based on the measurements of this little ring. I understand that this estimate will probably be (very very very) vague and abstract. Nevertheless, such an approach is good enough for me. However, I would like to push this estimate as far as I can, and I am wondering if it would be better to include some loads in the circuit between the two inverters as shown below:

.subckt load in dd ss bn bp
X1 in  int dd ss bn bp inverter M = 3
X2 int out dd ss bn bp inverter M = 12
.ends

X1   in int dd ss bn bp inverter
X1_1 int dd ss bn bp load

X2   int in dd ss bn bp inverter
X2_1 in dd ss bn bp load

Vdd dd 0 1
Vbp bp 0 1
Vbn bn 0 0
Vss ss 0 0

.ic V(in) = 0
.probe dc Ileak = par('abs(I(Vdd)) / 2')

where load is a subcircuit with a couple of slightly enlarged inverters.


texts: Altium: Component Clearance constraint won't go away after setting rule

texts:
I am using Altium 18. I ran a DRC check and got the following error:

This is saying i don't have clearance between J2 and MH2. This can be seen in the PCB:

However, i have set the following rule:

Surely this should get rid of this error? What am i missing?


texts:
Currently adding a house extension which will have a roof lantern. I want to run a strip of WS2801 LEDs around the inner bottom edge to have some fun with (think "disco lantern"!). Electricians are currently on-site and I want to get the right cables in the walls.

I'll be using 2 x 5m reels meaning 320 leds. If I've understood the power needs correctly, WS2801 is about 60 milliamps per LED max meaning a 20amp supply should be enough. Is that right? I don't think they'll ever be all at full power but I want to allow for it as changing cabling later would be disruptive and expensive.

The power supply and controller are going to be in the corner of the room - about 5m away from the lantern in terms of cable run. I was considering running a small 2-core cable for data and then appropriate cable for power.

I have two questions about this. For the data - what is an appropriate cable? I've no idea what the issues may be around data loss over a 5m length. The controller will be small (Arduino or PI) so I could find a home for it up in the lantern, but I'd prefer to keep it more accessible if I can.

Regarding power - I'm expecting to need at least one connection per LED strip, more likely two. Question is, should I spur from a single power cable run to the base of the lantern (If I'm right about 20amp this should do) or am I better off running multiple, smaller cables direct from the power supply?

My electricians should be able to advise on this stuff I know but they've clearly not come across someone wanting to do something this ridiculous before and I'm getting blank faces from them.

thank you!


texts: Is it possible to have voltage across an inductor without having current through it?

texts:
Example : In certain cases in transformers we do assume so having zero current in the secondary but there is still a voltage across it due to mutual flux .

Also we do similar things while calculating the thevenin equivalent of the secondary in the tranformer circuit .


texts: When converting 120vac to 12vdc, does the wattage & amperage change?

texts:
I'm trying to calculate how long my UPS will power my cable modem and router.

I know that together the two draw 2.25 amps at 12 volts (27 watts), but this is on the DC side of the power brick.  Does the wattage increase linearly with the voltage increase?

Basically, how many watts will my devices draw from the wall?


texts:
So there are several types of transistors:

BJT
JFET
MOSFET

Combine all that with the various flavors of each (NPN, PNP, enhancement mode, depletion mode, HEXFET, etc) and you've got a wide array of parts, many of which are capable of accomplishing the same job.  Which type is best suited for which application?  Transistors are used as amplifiers, digital logic switches, variable resistors, power supply switches, path isolation, and the list goes on.  How do I know which type is best suited for which application?  I'm sure there are cases where one is more ideally suited than another.  I admit that there is some amount of subjectivity/overlap here, but I'm certain that there is a general consensus about which category of applications each of the transistor types listed (and those I left off) is best suited for? For example, BJTs are often used for analog transistor amplifiers and MOSFETs are generally used for digital switching.

PS - If this needs to be a Wiki, that's fine if someone would like to convert it for me


texts:
I'm 15 and recently started electronics and I'm having trouble understanding voltage.
I've read so many articles and watched so many videos about voltage and they all give different answers. Some of them say that voltage is like pressure, others say that voltage is is like gravitational potential energy and then some say its a measure of electric field strength. So as you can see, I don't know what to think.
Could someone please explain it to me because I've been trying to find an answer for like 2 months and it's kinda driving me insane :)
And also if voltage is like gravitational potential energy, how does more voltage mean more current?


texts: What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?

texts:
For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the on-resistance would have to be deduced from the IDS curves?)

Is there a difference in the way these are designed and manufactured?  Can one type generally be used in the other application, but not vice versa?

Related, for BJTs: What's the difference between small signal bipolar junction transistors (BJTs) marketed as switches vs. amplifiers?


texts: Where is the electric field in an \$LC\$ circuit?

texts:
Suppose we have an ideal \$LC\$ circuit with an open switch at time \$t=0\$ where the capacitor is initially charged to a voltage \$V\$.
The instant the switch is closed, the typical \$LC\$ oscillations will begin.
What electric field actually causes these oscillations to begin?
At time \$t=0+dt\$ the electric field in the circuit should appear as follows:

Note that there is no electric field inside the superconducting wires and similarly no field in the superconducting inductor. If this is the case, where is the electric field that supplies the initial force to get the electrons in motion?
We know that \$F=ma\$ and electrons have a nonzero mass so they can only gain speed (they are initially at rest at \$t=0\$) if there is a non-zero electric field at their position.
Where is the electric field that supplies this force?
My second and primary issue is that there does not appear to be any location where an electric field can exist to supply the back EMF.
It is this back EMF which must be overcome in order for the creation of a magnetic field within any inductor.
That is, when we wish to create a magnetic field, we must do work against an electric field that opposes the motion of the charge and that energy supplied in opposition to the back EMF materializes as energy within the magnetic field that we create.
There does not appear to be any field that could possibly provide that resistive back EMF to oppose the motion of the charge of the current.
Think about it this way:
Imagine a positive charge moving from the positive plate to the negative plate as the capacitor discharges. In its traversal of the circuit, not once does it encounter an electric field to take away the energy it possesses and transform that energy into magnetic field energy. Where is the location of the electric field providing the back EMF?


texts: Limiting current without generating (MUCH) heat (efficient)

texts:
I need to Limit my current without changing voltage.
I need this for a few things, one of them is protection against short circuit without damaging a fuse or generating heat if that short circuit is going to last a long time.
second one is charging a phone at 5v and 1A/0.5A. the reason is the Lithium battery I'm using is not rated for that much current draw.

I used a MOSFET, a sense resistor and a transistor to limit the current. it's cheap and works well! it's good for powering LEDs as they don't change resistance that much to burn the MOSFET or empty my battery fast.

but for my application it'll be incredibly inefficient! for example my 5000mah battery could be charged at 4A but I want to charge it at 1a or 0.5A.
or charging a Super Capactior as they have small internal resistance from alithium battery (that gives as much current as you need, but it might blow up!)

Anything I can do? The voltage has to stay the same or otherwise the device will not work


texts: Possible to run nichrome at very low voltage?

texts:
I want to operate a 1-inch length of nichrome 80 wire, 26 gauge, at 200-600 degrees Farenheit. This type of wire has 2.657 Ohms of resistance per foot. So, for 1", there would be 0.22 Ohms of resistance in the wire. According to my amperage chart I will need between about 1 amp and 2 amps to operate in my desired temperature range.

The problem is that according to my calculations I would have to run at 0.5 Volts if using 2 amps and 0.25 Volts if using 1 amp. This seems like a very small voltage to me.

For example, my power supply, a standard benchtop supply has 0-3 amps and 0-50 volts. The Voltage meter on my power supply has gradations in 2 volts. In other words between 0 and 10 there are 5 tick marks. So, to run at 0.25 Volts, for example, I would have to have the gauge at 1/8th of tick mark--a tiny amount on the gauge. It seems like if I just nudged the Voltage knob a tad too much I could blow out the wire.

I am doing something wrong here? Do I need some kind of special, ultra-low voltage power supply, or are my calculations wrong in some way?

What if I put a resistor in series with the wire? That would increase the voltage needed, but I would still need to operate at a very exact voltage, right? For example, if I added a 5-Ohm resistor, then operating at 1 Amp would seem to require 5-Volts, a more normal voltage, but once again am I risking a burnout if I nudge the know slightly too far?


texts: Are the terms "Sheet Resistance" and "Sheet Resistivity" interchangeable?

texts:
This website has a calculator used to determine the resistance of conductive ink traces.
http://circuitcalculator.com/wordpress/2006/06/14/conductive-ink-traces/
The calculator lets you put in the values for trace width, length, thickness, reference thickness (as specified in the data sheet of a given conductive ink), and sheet resistivity (also specified in the data sheet of a given conductive ink).
The data sheet on this website gives the sheet resistance of a conductive ink.
https://www.dycotecmaterials.com/wp-content/uploads/2019/02/Dycotec-DM-GRA-9100-Datasheet.pdf
The Wikipedia page on Sheet Resistance says “Sheet resistance, often called sheet resistivity, is a measure of resistance of thin films that are nominally uniform in thickness.” https://en.wikipedia.org/wiki/Sheet_resistance
This entry on Wikipedia seems to be saying that sheet resistance and sheet resistivity are used to mean the same thing - so can I use the value for sheet resistance given on the data sheet as the value for sheet resistivity in the calculator?


texts: Unknown component connected to white wire of rechargeable battery

texts:
I want to replace a battery for a TDK A26 speaker. (You can see a picture of the battery here). In the country where I live it is no possible to find a replacement, so I decided to replace the individual batteries. However, there is a component I am not sure how to replace. At first glance, it seems a diode. I tried to test it using a multimeter but it is 'open'. I did attach another picture of the battery which shows the 'diode'. It is conected to a thermistor  jk-d175.

I found a video in Ytb  where they conect directly the white wire to the negative terminal, I was tempt to do the same but I am sure there are better alternatives.

I will apreciate any suggestion about how to replace that component.


texts: Chosing XTAL Capacitors for Microcontroller

texts:
I am trying to chose the parallel capacitors for the crystal on my micro-controller. The crystal is a 9.6MHz quartz crystal (chosen because 9.6MHz is good for UART communication). Going through the equations I get a value of 32.29pF. This seems higher than what I typically see on boards. This value is also higher than the 15pF recommended value in the Clock App note (image below). Can someone explain to me if I am doing the calculations correct?

MCU = ATXMEGA128A1U
MCU Clock App Note = here

Crystal = 407F35E009M6000

From application documents for the micro controller I get these numbers and equation:

Ce = 2CL - Ci - Cs

where:

Ce - is the external capacitance needed

Ci - is the pin capacitance

CL - is the load capacitance specified by the
crystal vendor

Cs - is the total stray capacitance

ATxmega128A1 IBIS file (typical values):

C_comp = 4.44 pF

C_pkg = 0.27 pF

Ci = C_comp + C_pkg

Ci = 4.71 pF

Cs = ~3pF (typical of board traces)

CL = 20pF (specified for crystal).

Using that equation and Ce works out to 2*20 - 4.71 - 3 = 32.29pF.


texts: LR tunnel diode relaxation oscillator question

texts:
I have 1 question relative to the LR tunnel diode oscillator.
If we increase the inductance of the inductor frequency is reduced but shouldn't the output voltage be increased as well? I am running simulations on falstad but cannot detect any changes, has anyone else encountered this issue before me?


texts: How to calculate the amount of smoke output from the mq2 sensor?


texts: How is the voltage and current plot for a matched transmission line constant?

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When the transmission line is terminated with a matched load the voltage on the line is given by V(z)=E e^(jβz).
where β is the phase constant of the line.

1)How is the voltage plot a constant for this transmission line?

2)How is e^(jβz) represented on the line?

The voltage and current on the matched transmission line can be seen in the above figure, Fig 7-6 (c)


texts:
I had a little project running with an arduino pro mini. had external psu connected and connected my programmer with power onto it. smoke came up. hole in the diode. now my question:

Is a dead diode actually a short in the circuit? So that i have to desolder it?


texts: 7432 behaves like an AND gate & 7408 behaves like an OR gate

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Ok. First of all, I'm an absolute beginner about IC and circuits.
If you will view the pictures, you will notice that the 7432 behaves like an AND gate and the 7408 behaves like an OR gate.
PS. I tried the circuit on a 7487 XOR gate and 7404 NOT gate and it works fine.

So my question is. Is there something wrong with my circuit or is it with the IC?

Switches are on the 1st and 6th on the dip switch. BTW. Disregard the IC on the center of the pictures. That's a 7404 NOT gate. Thanks in advance Sirs.

1: off ---
6: on ---
LED: off

1: on ---
6: on ---
LED: on

1: off ---
6: on ---
LED: on

1: on ---
6: on ---
LED: on


texts: Whoever knows how that circle terminations called (part number)?


texts: Lead acid battery increasing current under constant voltage

texts:
I've found an old lead-acid battery and decided to check if it still is in a decent condition. I've opened all rubber caps and checked that the water level was still OK. It measured 10.5 V before I started charging.

I programmed a controllable power source to provide 13.15 V under a 1.4 A current limit. Differently from what I expected, charging current started at about 100 mA (constant voltage) and it's slowly increasing for 2 hours. It has just passed 600 mA.

The battery is not heating or noticeably releasing gases.

Is this expected? It's different from the behavior we normally see on deeply discharged batteries (current limited first, than constant voltage).


texts:
I've got a question, and I just keep getting myself confused when I try to solve it.
The problem asks to find voltage and current and resistor currents transients (the switch is opened at t=0). Before commutation the circuit is in steady-state condition.
 I've solved it quite for a long time, and checked each my calculations by solving with different methods. This is why I was sure about my answers, but when I did PSIM simulation, different results were shown. Now I'm puzzled. Please, can anyone help me to solve this?
** p.s. for closed switch I found that Vth=5v, Rth=3/8 Ohms. I suppose I made a mistake in finding resistor currents


texts: if connect a diode to an AC signal can it be kept forward bias with increasing voltage at n-side?

texts:
if I connect a diode to an AC signal can it be kept forward bias with increasing voltage at n-side?

Is Vx going to be Vi even after Vi>4.5 because it seems to be reverse biased. here's my circuit and assumed output.


texts: How to calculate a laser diodes amps from its wavelength?

texts:
I am building a laser driver circuit.

Every laser diode requires a different amount amps to run correctly without burning. So instead of me coming on here and asking what each laser diodes amps are, is there an equation that maybe takes the nm wavelength and the output power into hand and allows you to figure out the amps required to power it? In this circuit I use V = IR where V = 1.25 and r has to be calculated. the resistor are in series so 2x10 Ohm lasers are 5 Ohms output. 1.25/5 = 0.25A or 250mA. But that is for this red laser diode. So how do i calculate the amps needed for all different laser diodes?
Also how do i calculate what capacitance i will need based off the laser diode?


texts: Where are all the multiterminal discrete transistors?

texts:
Looking at all the various schematics of op amps, regulators, etc. I see lots of multicollector or multiemitter BJTs (and why no multibase?). How come these (or their MOSFET equivalents) aren't seen in discrete form? Is there a practical reason beyond "no one wants them"?

EDIT:

An example of what I'm talking about:


texts: Detecting absence of current in transformer secondary

texts:
Beginner here. I'm trying to build a circuit which charges a capacitor to an arbitrary voltage in the shortest possible time. I want the high voltage part of the circuit to be galvanically isolated from the low voltage part. To this end, I'm using a flyback transformer. The "on" time, during which the core is magnetized, is determined by a monostable 555 timer. To have as little "dead time" as possible, I would like to determine the moment at which all of the energy in the core has transferred into the capacitor, so I can restart the 555 timer.
Whenever there is current flowing from the transformer into the capacitor, there will be a voltage equal to Vcc + Vcap / N present at the drain terminal of the MOSFET. After the core has demagnetized, the voltage will be just Vcc.
Such a feedback circuit must satisfy a few requirements: First, it should not draw excessive amounts of current from the transformer, since that would decrease the efficiency. Secondly, it must be able to handle a relatively large range of voltages. Assuming a turn ratio of 1:10 and a maximum voltage of 370V on the secondary side, the voltage at the drain terminal is 37V + Vcc. Initially however, when the capacitor is discharged, the voltage is as low as Vf/10 + Vcc, where Vf is the diode forward voltage.
The following circuit seems to work, at least in the simulation. The output of the common-base stage is zero for any input voltages below Vcc. The complementary pair of emitter followers ensures that the voltage at the trigger input of the 555 is always between ground and Vcc.

simulate this circuit – Schematic created using CircuitLab
While I can verify that this works in the simulation, the functionality seems to be very dependent on the choice of R3. Am I correct in assuming that this circuit, especially the common-base section, is very non-linear and thus quite unpredictable. Is there a method I can use to roughly determine the required value for R3, without relying on trial-and-error?
There are additional problems with the circuit, such as the low input resistance due to the common-base stage and the large base-emitter voltage at Q3.
I can't help but think that there is a simpler way of achieving what I'm trying to do.