texts:
I understand that what I am doing requires the utmost care and that numerous precautions should be taken in completing a project like this.

Out of necessity, I am going to fashion a car battery charger from an ATX PSU. I need to draw ~14v to do this, I'm guessing from the +12v rail.

How can I tell if this will be possible for the PSU I have?

What I know:

This model uses HA17431PNA shunt regulators, which I have located on the circuit.
I will need to modify that IC's input circuit to adjust the regulator's voltage.
This may also require me to adjust the output caps, but given the step-up value it also may not.

What I don't know:

Precisely how to tackle this -- I have a decent soldering station and resistors, but this would be the first time I worked on something other than a phone/doing rework. I found the spec sheet from Hitachi for the regulator. What other resources should I consult?
What generates DC from AC in an ATX PSU? A transformer? Is the transformer able to generate this voltage for me without affecting other components?
How this will affect the current output on the rail.
Any other unknowns regarding how this modification might impact the performance of the PSU.

Can someone please help me accomplish this task?

Thanks for your time.


texts: Can a toroidal transformer be wired as a common mode choke?

texts: I am looking to build an ac power line conditioner. It was suggested that I use a transformer with dual 6.3v secondaries wired in a common mode choke configuration. This is done by using the in-phase ends of the transformer secondaries. The primaries will not be used in this configuration and are just taped off. Does this sound like a better option verses just using an already manufactured common mode choke for power lines?


texts: High Frequency Transformer Design and Materials

texts:
I have designed fly-backs and inductors and understand the basics about flux density, saturation and core losses. What I have never been very clear on is design of SMPS transformers. I get the concept that ideally you want to transformer to not hold any magnetic energy and instead to transfer it all, but what material properties allow this?

I’m assuming you want to have a high permittivity \$\mu_o\$ to transfer flux better but also a linear \$\mu_o\$ so there is a linear transfer of energy, what else? I have spent time over the years looking for good tutorials or information on this topic and never found anything very complete, there is a lot of information on inductors, or sometimes the application is not really clear but someone with a bit of experience can discern between true transformer design vs inductor based on if the design holds a lot of flux?

For instance I want to design an impedance matching transformer (1:3 step-up) for driving a load at ~300khz. I’m having a hard time selecting core materials, I was going to use a toroid because they are readily available but most of them are metal power instead of true ferrite. I know that metal powder “can work” but what properties of it should one look for it to be more ideal then other metal powder.

For reference I have posted images of some metal powder cores provided by Micrometals, For a high current inductor I would pick the -2 material, but for a transformer what would I want the \$\mu_o\$ curve to look like, and what is a good B-H curve for a transformer vs. inductor?

I guess my real question is, does anyone know of a book or good resource for high frequency transformer design that also goes into material property selection?


texts: Debouncing and hysteresis questions about a Schmitt trigger circuit

texts:
Above is a switching sensor which outputs ON OFF pulses by the 33k pull-down resistor. V2 and R_SW models the switching.
The sensor output is needed to be measured between 1Hz upto 150Hz.
I'm planning to use a Schmitt trigger circuit which can sharpen this sensor output pulses without letting switch bouncing effects.

Below is the circuit in LTspice where the sensor is coupled to the Schmitt trigger circuit at 1Hz sensor output(please left-click to enlarge images):

Here is at 100Hz (red is the circuit output):

Here is at 500Hz:

My idea was to prevent bouncing at the switching input, and I wanted to filter it by R1 C1 values.
So 47k and 10nF gives 339Hz cutoff frequancy. But as you saw in above figure circuit passes 500Hz pulses as well.

My first question is:

What R1 C1 combination could be used to prevent bouncing?
I emprically dont know what would bouncing frequency be when switching. I only know the pulse inputs will be between 1Hz and 150Hz.
So if I set the bouncing cut off at 340Hz then at 1Hz input if I have 10Hz bouncing pulses it will still be problem.
At this point I'm confused. Is there a typical remedy for this situation?

My second question is about the hysteresis amount and the voltage level at point B (inverting input).
As you see in the waveforms above, the green waveform represents the voltage at the point B(inverting input), the blue one represents the voltage at point A(non-inverting input),
and the red one is the output voltage. Here I set up the resistors such that the voltage at point B is almost half the voltage at point A.
And I set the hysteresis limits between 5.5V and 7V. Is there a rule of thumb or logic to set these levels for a better result? I mean is setting point B voltage to the half of point A is correct?
And is 2.5V hysteresis good? How about to setting hysteresis to 1V to 10V limit? Im asking because I couldn't find practical info about these issues in books?

I would appreciate your suggestions about this circuit.


texts:
I have a pretty simple application but not sure where to start on selecting parts
I have a 28 volt variable output that needs to drive a 14v dc motor. The direction of rotation of the motor is controlled by reversing polarity. Speed is adjusted by regulating the 28v input.  The motor runs at 300ma or so and stalls at 600 ma.
I can manufacture a bipolar 15v supply for an op amp.  I was thinking of using a differential amp design using a high output drive current feedback opamp.
https://www.ti.com/lit/ds/symlink/ths3121.pdf?ts=1607705909112&ref_url=https%253A%252F%252Fwww.ti.com%252Famplifier-circuit%252Fop-amps%252Fpower%252Fproducts.html%253Fpqs%253Dpaqs%2526familyid%253D3523
The 28v source signal can push 500 ma if needed.  The loop gain would be 0.5.   This is as far as my design skills take me.  Am I on the right path or is there a better approach? Even an off the shelf solution?
Thanks in advance
Tom


texts:
I recently read part of this 1986 "paper", Theory of Wireless Power by Eric Dollard. From what I understood, Tesla found the resonant frequency at which the energies of the electrostatic field and the magnetic field were equal.

In the above diagram, a virtual ground is established at one end of the terminal and the coil becomes a mono-polar transmitter.

With this set-up, can you transmit electricity through the ground?


texts: Operational amplifier circuit with one ac and one dc voltage source

texts:
The following circuit contains ideal operational amplifier, Vs voltage is sinusoidal with amplitude of 1Volt and frequency of 1kHz, where VE is a dc voltage of 2Volts.
I am trying to use superposition principle to find the output voltage. Also I want to draw a diagram of Vs(t) and Vout(t) versus time. First, suppose we ignore positive and negative
power supply of the op-amp(they are not shown on the circuit I was given).

Step 1: Let's ignore dc source and find the output. The equivalent circuit is:

So Vout1(t) = -(R2/R1) * Vs(t) = -Vs(t) (inverting amplifier)
Step 2: Let's ignore ac source and find the output. The equivalent circuit is:

So Vout2 = Vin * (1 + R1/R2) (non-inverting amplifier)
= VE * (R4/(R3 + R4)) * (1 + R1/R2)
= 2 * (2000/(2000 + 2000)) * (1 + 1)
=2Volts

Finally,
Vout(t) = Vout1(t) + Vout2 = 2 - Vs(t)
Is that method I followed correct?

Also, T = 1/f = 1/1000Hz = 0.001sec

So a graph I created is the following (supposing that Vs(t) is a sinusoidal signal with initial phase 0 degrees):

I know the graph is not very good but I want to know if it's correct. Thanks.


texts: I am trying to simulate high side MOSFET in Proteus using gate driver IC IR2112 but it does not work as expected when HIN is high. The mosfet should be turned ON when gate voltage is more than 10V but it gives across R4 the same voltage Vc as applied to IC pin 3 when HIN is high. I need to learn how to overcome the mentioned problem.


texts:
I would like to understand how can I determine the number of color of a STN screen.

For a TFT screen it is simple if I have 6R-6G-6B screen it is 262144 color, if it is 8R-8G-8B it is 16million colors. I just have to do the 2^n with n the number of bit.

But on STN there is usually 4 or 8 bits driven in the LCD. But if I understood well the functionment of this type of screen each bit is latch on 1 segment. Then with 8 bits you drive 8 segments so 2 and 2/3 pixel which for me mean that each segment can only be either on or off then you just have 8 color possible for a pixel. But I saw some description with STN of 4096 colors, how is that possible?
I think I missed something in the operation mode of a STN screen.

Is it a mater of duty cycle? How do I determine a number of color for a STN screen?


texts: Best tool bits for PCB cut outs (board shapes and slots) when prototyping with desktop CNC milling machine?

texts:
I have a cheap desktop CNC that I have successfully done some PCB prototypes on using 10 and 30 degree 0.1mm V-bits. When it comes time to doing the cut-outs I started with a 1.5 mm end mill with four flutes (Dremel branded bit) but found the fibreglass material made short work of killing the edges on the bit - so much so that by the end of the prototyping I had to revert to using the V-bits to cut out the last couple of attempts.
Was hoping someone with experience milling PCB prototypes could advise on the best bits (material, finish, flute count) for durability and minimum sizes to avoid wastage while not breaking the tips specifically with PCB materials?


texts:
I'm trying to fix this little electronic toy. It's really not much, 8 buttons, you push one, the lights go on, and a little melody plays. Now, I really don't know much about this, but really wanna fix that toy :)

There is a single controller, splitting to two circuits, one for diode lights, and another one to a speaker. The way it broke, as it's there is no sound. There is a transistor (or I think it is) for each circuit. For each, one (right) leg is straight to the batteries, the second (left) leg is to the chip (through a resistor), and the third one (middle) is to the outlet (from one it's to the speaker and from another it's to lights).

I was probing both the transistors to see what's going on when a toy is "activated". Dormant, controller leg has the same voltage that is coming from the battery, and the "out" leg has nothing on it. When the button is pushed, the voltage on the controller leg drops a volt or so, and the "out" leg starts showing some for lights. The out leg that goes to the speaker doesn't ever show any voltage, yet its leg that goes to the controller shows different voltage drops (I assume that's the controller "playing" music).

I believe the transistor for the speaker circuit just broke (IMO, sitting an hour in rain would do it). But, the only things I see on this transistor (again, I don't know what is it, really), are: C945 the first line, and P73C on the second line. There is absolutely no markings on this thing, and it has three legs and black solid body. It very much looks like this:

For the numbers that I see on it, I couldn't find a scheme that would tell me what it is, and what/where can I get as a replacement.

Some of the answers I've got tell me this is 2SC945, which is then, according to http://www.elexp.com/t_tranmk.htm would be NPN HF transistor. If so, and I were to order a replacement from, say RadioShack, how would I find one that would work?

UPDATE: I was able to replace this transistor with 2N3904 (I should've been more careful picking the replacement that had the same order of pins, but hey, this was the cheapest one available). Thank you for all your help, support, and explanations :)


texts:
we are working on a circuit containing a 8086 and 8x(2KB) external memories (6116). the problem is that all control signals are asserted correctly, the address and data is provided but they are not written to the memory.

On StackOverflow: 8086 can't access to external memory

original


texts: Mutually coupled inductor modelling in cadence

texts:
I used two methods to model two mutually coupled coils.

Method: 1) Using 'mind' cell from analogLib. It basically lets you define a coupling coefficient k value.
Method:2) Using 'Xfmr' cell from analogLib which basically lets you define turn ratio.

I am getting different results if I use method1 ('mind' cell) in Z11 plot.
The real part of input impedance (Re[Z11]) shows frequency dependent behaviour. But Re[Z11] = just the resistors and should be a constant line in Re[Z11] vs. f plot.
If I use method2, Re[Z11] is constant wrt frequency (as like a resistive response). So it is ok.
But the problem with method2 is I have only freedom of defining turn ratio, not the coupling coefficient(k). But I want to work with coupling coefficient(k) than turn ratio.
SO please suggest me, which method is best suited for WPT coil modelling in cadence.


texts:
I am trying to setup the SPI. I followed the logic from other tutorials but with no success. Can someone point me in the right direction?

void spi_setup(void) {

    RCC_AHBENR |= _BV(17); //IOPAEN
    RCC_APB2ENR |= _BV(12); //SPI1EN

    GPIOA_OSPEED |= 0x11<<7 | 0x11<<6 | 0x11<<5; //GPIO CLOCK SPEED
    GPIOA_MODER |= _BV(5*2+1)/*AFM*/ | _BV(6*2+1)/*AFM*/ | _BV(7*2+1)/*AFM*/;
    GPIOA_AFRL |= 0;
    //GPIOA_OTYPER = _BV(7) | _BV(6) | _BV(5); //output OPEN-DRAIN
    //GPIOA_PUPDR |= _BV(7*2+1)/*pull DOWN*/ | _BV(6*2+1)/*pull DOWN*/ | _BV(5*2+1)/*pull DOWN*/;

    SPI1_CR2 |= 0x111<<8/*8B data size*/;
    SPI1_CR1 = _BV(9)/*Soft slave man*/ | _BV(6)/*SPI Enable*/| (0x0<<3)/*BaudRate*/ | _BV(2)/*Master*/ | _BV(0)/*Clock Polarity*/;
}

void spi_tx (uint8_t send) {

    while ( SPI1_SR & _BV(7) ) {} /*while BUSY WAIT */

    SPI1_DR = send;
}


texts:
I'd like to ask for some help with performing a Load Pull simulation in ADS. I tried using the DesignGuide utility but am not sure how to connect the Load Pull Instr shown in the attachment and which voltages and loads to select initially. Anyone?

The circuit shown is my own and on which I'd like to perform Load Pull.


texts: How to short circuit with using push button

texts: I am testing the ability to charge and recharge battery circuit. I have been testing using a push button in order to short circuit the battery and drain the charge.  I would like to instead use an arduino to replace the push button.  I tried using a 2n222 and an irf150 mosfet but neither of these shorted the battery.  I basically want the current to follow directly from the drain to the source when the pin is active.  I cannot get this to work.  Do anyone have an idea of a design?


texts: Finding an empty slot in an array of registers

texts:
I'm working to implement an out of order processor in Verilog, and I'm trying to quickly find an empty slot in an array of reservation stations like so

reg [39:0]add_rStation[3:0];

Assume each station has a valid bit indicating whether it is full or not. By quickly I mean without big if else chain.
Does anyone know of way to do this Mathmatically (for lack of a better term)?


texts: I've been looking at DACs on Digikey and other electronics sites in hopes of finding a circuit to drive > 20 electrical nodes with ~10 mA per channel, 0->8V, with ~16-bit precision. I've seen evaluation boards from Analog Devices that offer 40 channels with the specifications, but they can only handle 1 mA load current. Does anyone have any suggestions for pre-made systems that could handle this sort of situation?


texts: I need to find a replacement transistor.  The only number I have to go by is a manufacturer (of the unit, not the transistor) part number from 1974 which of course leads nowhere.  I know it's a silicon NPN TO-220 case used as a relay driver.  I know the voltages, I can estimate the current, so I can search for all those parameters but get hundreds of candidates. Is there a way to further narrow down the field to just those with an EBC pinout without having to click through to every single data sheet?


texts: Switching DC-DC Buck converter voltage feedback

texts: When using 2 PSs for redundancy purposes we connect positive outputs through diodes, as I understand. Is it possible to connect voltage feedback network of the buck converter to diodes cathode, to let the IC compensate diodes voltage drop?


texts: Can I charge a NiCd battery with a NiMH charger?

texts:
I have an old NiCd RC battery pack. It was not used for at least ten years but when I tried to charge it with the old charger I was suprised to see it still had some capacity.

Now I just went and bought a new pack with a charger anyways, and it's NiMH.

Could I safely charge the old NiCd battery pack with that new charger? What could happen in the worst case?


texts: How to create isolation slots/gaps in eagle CAD

texts:
I'm new to PCB, how to create isolation slots or air gaps in PCB using eagle CAD.

Thanks


texts: I want to use a dc power jack in my circuit, and I chose this. After eagle does not have this schematic, I have to draw it on my own. Unfortunately I do not understand the pad size dimensions. It tells me that it should have the dimensions "4-3.0x2.0". Which size does that mean? In eagle I have the option to use the size "3.81x1.9304", which sounds as the best variant. Is that correct?


texts: Existing methods for bi-directional data transfers using no more than 4 wires?

texts:
I want to be able to exchange data between two units (in my case, two AVR processors), and I want to get away with using no more than 4 wires.

So what are the existing methods for doing this? I know there's USB, but that seems a bit overkill here since I don't need to for example support multiple connections over the same cable.

The requirements are not entirely set but I can at least give some approximations. The AVR processors I intent to use are ATTiny2313 and ATTiny13 which will run at 16 MHz (the ATTiny2313 will also run V-USB). Data throughput is extremely low since I will use this to implement a custom keyboard, so it will probably be something like a few hundred bits/s. The length of the wires will be something like up to one or two meters, maybe three.


texts:
In order to prevent heat (and to a lesser degree, preserve power) I'm exploring the idea of using latching relays instead of 'regular' relays.

I don't want to redesign and rebuild the application that uses these regular relays with ON/OFF toggle switches. So the latching relays must work on ON/OFF switches, not momentary switches.

In an older EE question, Russel McMahon mentions:

  A circuit could easily enough be devised to store power and apply it to the delatching coil when power was removed from the main input, thus making operation externally identical to a normal single coil relay.

What are some ways to use relays more efficiently? (scroll down a bit)

How would this work and how would such a circuit look like?

Thanks

EDIT: @TonyM, just your typical relay circuit:

[+]------ ON/OFF switch ------ + +----------[+]
                               } \
                         coil  }  \ NO
[-]----------------------------+ +
                                 |
                               load
                                 |
                                [-]


texts: Sending few commands with BLE without microcontroller

texts:
I am completely new to electrical engineering, but I am trying to build a small device with three buttons circuit, each one of them would send a different command to the mobile phone via Bluetooth low energy module (I would like to use EYSHSNZWZ Bluetooth Low Energy Module for its size).

So the main question, can I run this idea without any microcontroller? Can I even connect it without the microcontroller?


texts: How can the flip flop neglect clear when given output is given as feedback?

texts:
Here is how the circuet looks.

Initally the output the D flip flop is HIGH, when the there is HIGH to LOW input across the multivirator, it create a pulse of 200ms, which is connected to the Clear pin of the Flip Flop.

Shouldn't this happen?

Q outputs Low
Causes U5A to output HIGH
Which in turn causes the Flip-Flop Set to HIGH
Q outputs HIGH
Causes U5A to output LOW
Due to reset still HIGH causing Q to output Low
Cycle Repeats

But this does not happen, can anybody explain why?

Is it due to propagation delay time of each device?

Propagation of Flip flop is around 150ns whereas of NAND is 200ns, there are actually 4 more NAND (not shown connected as not gates).


texts:
I've been reading up on power electronics lately and as a challenge (and also a learning exercise), designed my first switching power supply - a buck converter in this case.

It is intended to supply 3.5-4.0V (decided by diode reference source) and up to 3A in order to drive some power LEDs with any DC source, ranging from a 5V USB charger up to a 9V PP3 battery.  I want an efficient supply, as heating and battery life will be a real issue (otherwise I'd be lazy and use a 7805+diode).
NOTE: I already noticed that I've got the switching logic the wrong way round, I need to either swap the connections into the comparator or use !Q to drive the MOSFETs.
My choice of MOSFETs instead of BJTs was due to the power losses in a BJT, and the thermal issues arising.  Is this decision to use MOSFETs over BJTs/IGBTs due to improved efficiency the right call?
Rather than using a PWM chip as many hobbyist forums suggest, I decided to use a comparator/clock/latch combination to rapidly switch between "charging" and "discharging".  Is there any particular disadvantage of this approach?
The CMOS latch (a D-flip flop) copies data to the outputs on the rising edge of pulses from the clock generator (a CMOS Schmitt inverter + feedback).
The choice of time constants / corner frequencies for the clock and the buck lowpass (10-100kHz and 10Hz respectively) is intended to support the small ripple approximation while also allowing the output capacitor to charge in a reasonable amount of time from power-on.  Is this the right set of considerations for deciding the values of these components?
Additionally, how would I go about calculating the value of the inductor?  I would assume that it depends upon the typical output current and the lowpass capacitor's value, but I can't quite figure out how.
[edit:]
In the past, I've used the shown MOSFET pair (in addition to software PWM) to create H-bridges for bi-directional, variable speed motor control - and as long as I kept the PWM period much larger than the MOSFET switching time, the power waste from shorting during switching was negligible.  In this case though, I'm going to replace the N-mosfet with a Schottky diode since I've never used a Schottky diode before and want to see how they behave.
I use a simple inverter+RC combo to provide the clock signal as I don't need a particularly consistent or precise frequency as long as it is considerably higher than the high-cut corner frequency of the buck-boost.
[edit II:]

I built it on a breadboard and to my surprise, it worked straight away without any issues, and at ~92% efficiency (compared to the 94% that I'd calculated from switching/component losses).

Note that I omitted the resistor in the output stage, out of laziness - also I can't quite recall why I put it there in the first place.

I omitted the reverse diode parallel to the P-MOSFET, and also used a 1N5817 Schottky diode (note: 1A rating) in place of the N-MOSFET.  It doesn't heat enough for my fingertips to notice.  I've ordered a higher-rated diode though for when I assemble the final unit, which will run with full load.

I accidentally blew the LM393 comparator during testing, but an LM358AN took its place straight away without any issues.

As I can't find any decent circuit design+layout/routing software that will run on Arch Linux x64 (or even install, in the case of native Linux software), I've manually layed it out so it probably won't work by the time it's soldered...  But that just adds to the "fun" I guess!

Component values used: Clock gen { 1kR, 100nF }; Buck output { 330uH, 47uF }; Input capacitor [not shown] { 47uF }; P-MOSFET { STP80PF55 }; N-MOSFET { Schottky diode instead, 1N5817 - to be replaced with >=3A version }; ICs { 40106 NXP, 4013 NXP, LM358AN }


texts:
What is the proper way of repeating I2C/SPI blocks?

Since we know in the case of SPI blocks, MISO, MOSI & SCK must all be tied together in a single bus for communication to happen.

I have read the similar question on this forum regarding this issue but didn't found the answer satisfactory. The person who asked the question only had to place the block 3 times, so putting them directly on schematic made sense.

But in my project, I need 6-7 similar blocks for I2C and SPI. I don't know exactly at this point so using Repeat will be very beneficial for me in the long run.

Here is my top sheet:

I have successfully made Chip Enable into bus since they are all unique. But I need to tie the MISO/MOSI/SCK together for all repetitions.

Also I am getting these errors currently:

A generic answer on how to connect multiple SPI/I2C blocks together would be really appreciated. Or a definitive one that this is not possible.

Thank you for your help.


texts: Google Glass 3.5mm jack with battery neck strap

texts:
I'm thinking of improving my Google Glass by DIY building a micro usb to 3.5mm headphone jack with a battery connected to a neck strap out of parts from the internet.

I've already built the neck strap with gorilla clamps and a sewn in pouch at the back to house my 2600mAh USB pocket Power pack Charger External battery pack. It's nice and slim at 95mm x 25mm and round so sits on the back of the neck comfortably.

What I do want help with is the electronics. From what I have researched Google Glass uses a Maxim integrated MAX14532E chip to switch 3 functions, USB, TTY, Audio. In audio mode the pins represent the following.

Pin 1: +5V
Pin 2: Right audio out
Pin 3: Left audio out
Pin 4: Detect
Pin 5: GND

Also I've read that a 500kΩ resister will switch audio to stereo and 1mΩ will switch to mono.

Sooo my theory is that if I connect it all up like the following I should have a wearable addon battery pack that should double the battery life and a 3.5mm stereo jack for my beats earphones ?

Pin 1: + from battery pack
Pin 2: Right audio out
Pin 3: Left audio out
Pin 4: 470kΩ 1/4W 0.25W ±1% metal film resistor (Couldn't find 500kΩ)
Pin 5: GND (resistor and battery)

Total cost for this if it works is about £35, £70 with some good earphones ! Just I'm in the UK and don't want to brick my glass lol I can't get another pair.


texts:
I am writing a simple simulator for Mosfet and JFet. The equations governing these involve the important parameter "K". But, the data sheets normally do not provide the value of parameter K. So, I want my program to prompt the user to enter one or two other parameters they CAN find from the data sheet and enter. The program then should be able to compute the value of K using the parameter values the user entered.

(1) What parameter values the program should ask for the case of MOSFET?
(2) The same question but for JFET.

Thanks!


texts:
I've been making an audio amplifier, it works well so far after getting the correct components. I'm using a 10K potentiometer with switch for the volume but I've got a problem. The potentiometer increases resistance as I rotate clockwise... I need it to be the opposite, at the moment when rotating clockwise it works like this:

Off - 0 -> 10k

But I want it to be like this:

Off - 10k -> 0

If there a way to reverse the resistance, or have I purchases the wrong pot?

Thanks for your help :-)
Ben


texts:
I'm learning about step-down converter and I wanted to know what's the difference between continuous mode and discontinuous mode.

I know what they mean by deffinition (in the former the current through the inductor never reaches 0, while in the latter it does), but I would like to know what are the advantages and disadvantages that each mode present. What would lead me to design one or another?

EDIT:

After researching a little bit more, I read that, in discontinuous mode, higher current peaks could be needed. For the output average current to rise, the peaks in the inductor current would have to be higher in order to rise that average (given that there is a time where no current is flowing). So the transistor that acts as switch should be able to support that current that flows.

That is one point in favour for the continuous mode. I wasn't able to get completely other things I found out there, like something related to "pulse skipping" (which I don't know what it is by the way). Then, so far, I have one advantage of the continuous mode against the discontinuous one. Nevertheless, someone told me that discontinuous mode is more used than the another one, and that most flyback regulators operate this way. Is this true? If so, why is this? Why would someone choose discontinuous mode if transistors that support high currents (ergo, more expensive) are needed?


texts: Requirements for low voltage, low current MOSFET used in current source

texts:
I'm trying to determine the minimum requirements for a MOSFET that will be used in a op-amp based current source.  I've hit Google and this site and looked at multiple pages, but almost always, they are dealing with high voltage and/or current, so I'm not real sure they apply here.

This will be used in the output stage of an impedance analyzer.  While I've got op-amps that will easily source the 30 mA(or less) that are required, I'm trying to in essence buffer the op-amp from any capacitance on its output.

The input to the MOSFET is a 3Vpp(or smaller), biased at 2.5V 100Khz(or less) sine wave.  The application is a AFE for the AD5933 chip.

Please note, I'm not asking for a specific MOSFET, but for the things I should look for in choosing one.  Yes, I do know about the so called linear MOSFETs, but I really think that they would be a massive overkill(and a budget buster, to say the least) in this application.

Just as an example, the SI2300(and I have 30 or 40 of them handy) has my requirements firmly within its SOA chart(which has a decent DC area).  Is there anything else I should be looking at on the datasheet that would disqualify it for use here?

In any case, I'm planning on heat sinking the MOSFET however I can.  In the above MOSFETs case, I was going to increase the area of the copper pads it is soldered to, and give it copper right below it.  If it's a TO-220 or 253, it gets a real heat sink. Etc.

The power supply I'll be using has 5V(10A), 12V(3A) and -12V(800mA) available if that would make a difference.


texts: Question about MCU's, and Audio Manipulation

texts:
Ok, so I've been doing some research trying to find something like an audio MCU\DSP with a built in audio filter; for instance, something that I could manipulate audio with to get a final filtered output. So if I put audio through it, maybe the output will only be 5khz+, and 5khz- will be completely cut.

Basically, I'm going deaf in one ear (I had brain surgery to remove a tumor like 8 years ago, and the nerve is slowly dying continually taking more and more high tones with it), and insurance won't pay for a hearing aid to help boost the frequencies I'm losing back up to more normal levels. This all sucks too because I'm a musician with a very huge background in audio engineering.

Bottom line: I'm going to build my own hearing aid that does exactly what I need and want it to do. But I'm a little lost where to start and what IC's to get that will allow me to manipulate and filter the audio easily. I found one through TI, but I'm still looking into it. Plus size; it needs to be tiny. Thoughts?


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I'm interested in this purely from personal interest, I'm not a student.

Can I express 1024 bytes of information travelling over cat5e as joules (or some measure that fits into energy of e=mc^2 )? How?

Would this be radically different if it were travelling through a CPU?

I have no practical application in mind, but ideally we could express the mass of a gigabyte, and contrast it with waste from latency of an hour long transfer, or something like that. I'm sure the medium it travels over dictates a lot of this.


texts: LIN Network without Transceiver (for testing)

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My task is to implement LIN network on SPC560P microcontroller. This microcontroller does not have builtin LIN-transceiver, so it provides TX and RX pins. I know Lin network only has one LIN wire, but I tried to communicate two microcontrollers by connecting their TX and RX pins, like
MC1 TX to MC2 RX
MC1 RX to MC2 TX
But It does not work. I know Transceiver is necessary but I want to try it first just to test that my protocol is working or not.
It that possible to test it without a transceiver? I tried to find revelavent questions but I didn't find it.


texts: How do i get rid of a power-spike from consumer electronics?

texts:
Ive got a power-spike (im guessing here) when the amplification stage in a  speaker turns on, that temporarily disables my tv (black screen, but recovers in a second) and my question is how do i get rid of it? The speaker actively turns on its amplification (with an audible "click")  when it recieves a signal above a certain level.

Would a ferrite bead anywhere help?
Is it a grounding issue?
Should i attack the power lines, or is it related to signal cables?
Solder larger caps in the speakers power-supply? (not so accessible)


texts: How to choose input filter component value for power supply

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I understand that normally we'll modify the input filter after some measurement to meet the emission standard, but does anyone know on how we can estimate the initial value of this filter components especially during initial design stage (before the emission measurement was done)? Do we have any calculation reference to estimate this part value?

I read a lot of power supply guidelines from supplier however they don't cover so much on this item.

What I know is improper LC design could lead to oscillation to power supply, can anyone suggest any good method/approach to design the input filter?

Thanks


texts: Why do DC/DC switching controllers seem to favour the buck-boost topology over similar ones like Cuk, SEPIC and Zeta?

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I am looking at various DC/DC converter topologies for a power system I am designing. The most suitable topology for me is one that can perform both step-up and step-down functions, so I am looking into buck-boost and similar topologies like Cuk, SEPIC and Zeta.
While selecting the candidate ICs for the switching controller, I noticed a curios thing. On Digikey, where it is possible to filter by topology, the buck-boost & four-switch buck-boost topology occupies a large majority of the market. For instance, Digikey's catalog lists 471 active switching controller designs for a buck-boost topology, whereas for Cuk/SEPIC topologies there are only a handful of chips available (in the range of 15-20 chips).
Why is there such a preference for buck-boost topologies over Cuk and Sepic? Or is this just a shortcoming of Digikey's catalog?


texts: How would this circuit work? Would the LED behave like a strobe?

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I have placed a simple picture of the circuit I am trying to determine the behavior of. It is just a simple voltage source like a battery in series with a capacitor in series with an LED.
To my understanding, the capacitor would charge up, then release a large charge quickly which would make the LED very bright, but then begin to fade away quickly, and the process would repeat. However, I’m not sure this would be true. So what exactly would happen in this circuit?


texts: How to generate shortest/smallest/cheapest gate network for a set of functions?

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To make this most generic: I have a set of inputs I0, I1, ..., In, outputs O0, O1, ... Om and truth tables giving the desired values for each Oi for all input combinations.

Example: full adder

I0 I1 I2 O0 O1
 0  0  0  0  0
 0  0  1  0  1
 0  1  0  0  1
 0  1  1  1  0
 1  0  0  0  1
 1  0  1  1  0
 1  1  0  1  0
 1  1  1  1  1

Now I know how to use a Karnaugh diagram to generate min terms for each output and build them with NOT, AND and OR gates. But in reality I only have gates with 2, 3, 4 or 8 inputs so for more inputs gates have to be chained in a tree leading to a lot of gates and long signal paths and I also have more gate types to take advantage of.

So my question is: How do I generate a gate network using any kind of gates optimized for either shortest path (fastest), least number of gates/wires (easiest to assemble) or least number of 7400 series chips (I'm running out of space :). Considering fanout limits would also be nice.

Is there something better than brute forcing all possible gate networks to see if any one of them gives the right result?

Note: Target goal would be something that can handle at least 16 inputs and 16 outputs.


texts: After realizing the l293d output won't suffice and the voltage drop of the l298 is quite high, I believe learning to construct a simple H-Bridge to suit would be beneficial. Before starting with tests, am I correct in assuming the voltage drop of the below circuit would be calculated by the data sheets Rds(On) of each mosfet in the high/low path multiplied by drain source current? If so, a theoretical n/p-channel pair with Rdson .4ohms with 2A would be a .8V drop. Round to 1V. Are there other obvious factors I am ignorant of that would affect voltage drop available to motor besides thermal characteristics? Thanks


texts:
I'm working on a project using this stepper motor it is rated at 1.5 A/Phase current. Initially I planed of using this driver, so I checked if it can provide enough current for the motor. The website says:

  can deliver up to 2 A per coil with sufficient additional cooling

however further down it says:

  can deliver up to approximately 1 A per phase in full-step mode

I assume the difference if only significant in the case of 6-wire stepper (unipolar) and each coil is two phases?

The linked stepper has 4 wires (bipolar) so current per phase = current per coil?
Can the stepper be used with this driver?


texts:
The diagram above shows my circuit. It is actually an AC Voltage Controller with PWM controlling the output voltage and a 1:2 transformer stepping it up to 230V. A 1.8uF capacitor is used as a filter which works fine to quite an extent.

The problem here is that the output voltage when fed back to the controller via a step down transformer and a voltage divider to bring voltage within safe limits of controller and an offset circuit (since controller doesn't bear negative voltages, contains a lot of spikes although there is no such spike at the load.

ADC waveform is given below

I have tried changing the step down transformer, ADC circuit components, MOSFET and optocoupler but noise/spikes is still there and gets even worse some times.


texts:
Given the design of a PCB with some 16 pin connectors, the routing became so messy to the point that every route must crossover other routes, like in the attached screenshot

So, is there any known technique that allows crossover connections for PCB design? Is there any integrated circuit that handles with this problem?


texts:
I'm working on project that involves 100 white and 100 RGB leds, controlled with 25 TLC5940.
I've managed to connect three TLCs to Arduino MEGAv3 and so far so good.
I've found out that I have to add 0.1uF capacitors( ceramic, but I can only get film) between TLCs VCC and GND to smooth out voltage drops and 1uF / 100uF caps along the positive, negative rails. (to not burn down TLCs)
I'm using these LEDs: RGB and WHITE
So, from TLC5940 basic use example, i calculated that i have to use 1,5kohm resistor on each TLC to provide 26,04mA per LED channel. So at full on, all this should pull 26.04x400=10.416Amps!
As this is going to be freestanding installation I'm thinking on using 12v 105Ah car battery. (not connected to car) with this buck converter DC/DC 12V-5V 15A 75w
So the questions, that I haven't found answers to, are:

How to calculate resistors for TLCs? Or are there not needed any..?
And how to calculate resistors for LED? It's stated I = 39.06/R(in ohms) (i don't know why U is 39,06..)
U = (Vc-Vled)/ILed = (5-3,4)/0,03 = 53ohm ?
How to protect TLCs from any possible overheating that i'm not aware of ?
Are my LED mA calculations correct ? as i measured with single led turned on, between arduino 5V pin and breadboard it shown ~36mA on multimeter.
I have attached sketch below, it's only showing two TLCs, but this wiring will continue as shown.

UPDATE:
This is my scheme as it is now on breadboard.
I went with MeanWell 12->5V converter after consultations in arduino forum. I cannot take risks of running out of voltage because of voltage drop in system.
Changed my white LEDs to more efficient model. Added SN74HC04N inverters for signal strength. I hope scheme is somewhat understandable.. It actually works as is and I plan to start soldering this to veroboards soon. There are definitely improvements to be made that i'm not aware of and maybe someone can point out some?


texts: Reverse polarity protection on AD623 inputs used to measure low voltages on a sense resistor

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This circuit used to measure low voltages on a sense resistor is part of my current meter in arduino that measures currents from 0.005ma to 5A.

I configure the gain of the instrumentation amplifier with a value of 100.
On the sense resistor the min voltage on its terminals is 0.00005v and max voltage 0.05v.
Actually I have the circuit working ok but I need is a way of reverse polarity protection on the inputs of AD623 to protect for example if I connect the wrong way the inputs to measure current on a Li-Po battery.
Is there a way to get that protection and keep the accuracy of the circuit?


texts: How do you determine what the circuit that determines the next state looks like?

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This is a homework question. I've only started to learn about circuits and it's just that I'm completely lost on what the circuit to determine the next state would look like. I'm looking for the process of how to make the circuit that determine the next state so I can apply it to other similar problems rather than just the circuit for this problem. So first I had to simplify a truth table.

I got

I got this circuit from translating the truth table to a Karnaugh map

Moving on, I had to use the circuit I made to try determine the next state which in turn lights up an LED. Something like:

The state transition table:

which I once again converted to two separate karnaugh maps and made a circuit for them which leads me to:

This was a bit iffy because I wasn't sure how I was supposed to connect the two bit register to the circuit that resulted from the karnaugh map

The FSM has one input, the input from the very first simplified Karnaugh map

it will count the number of ones
if it sees a 0, it will reset the count to 0
if it seeas a 1, it will increase its count
if it sees at least 3 1s in a row, it will turn on an LED
The LED will stay on until it sees another 0.

For the last part of the problem, I have no idea how to create the circuit that determines the next state. I'm relying on truth table and Karnaugh maps to make my circuits quite heavily and I'm not sure what to do without it. Any help would be appreciated.


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I have a device with 3 different power supplies in one of my product. Now the complete device is powered using an IEC filter connector with following circuit digram.

I have two questions:

What is the role of resistor here?
What will be the effect of changing value of Cy here (if I increase or decrease it?) ?


texts:
I have a project coming up that requires serial data comms across a large vehicle with two trailers connected in train. The total length of the vehicle is 100ft, and I need to install several nodes along the length of the vehicle that all need to communicate with the master node at the front.

I plan to use RS485, and have no problem using proper twisted pair cable throughout the body of the trailers.

My concern is connecting across the drawbars of the trailers. Ideally I want to use a standard 7 PIN trailer lights connector because of its robustness, and the availability of a curly/stretchy cable that expands and contracts as the vehicle travels around corners, but this is not twisted pair!

I can use a low baud rate as I’m only transmitting commands, not huge amounts of data.

Will it still be reliable if a section of the data line is not twisted pair?


texts:
I've finally understood the purpose of the second solenoid in the above GFCI.

How it works is when Reset was pressed. The contacts come to the top (attracted by the top solenoid). And in the second solenoid (actually the main one), there is a pin with spring that locks the contacts (in top position) into place. When the SCR and main solenoid (the right horizontal one) triggers, it pulled the pin to the right magnetized metal hence the contacts come down (with spring inside). This is an ingenious electronic reset design, I wonder what GFCI receptacle in the USA used it. Mostly you have mechanical Reset only wherein if you press Test, the Reset button would pop up. Why doesn't USA GFCI receptacle used electronic reset too. What is the advantage and disadvantage of electronic Reset button?

original:

A GFCI outlet usually has 1 solenoid only.. such as this Leviton teardown:

But the following has 2 solenoids,

I'm double checking and reverse engineering the circuits. Anyone has any idea why two solenoids. The top solenoid probably attracts the contacts upward, but why is there another solenoid on the right.

This is the circuit diagram for both (they use identical chips):


texts: What will happen if I drive 2 TEC-12715s and 2 CPU fans off a 12v/30a power supply?

texts:
I'm planning an addition to my liquid cooling system for my computer.  I would like to use two TEC-12715 peltiers, which pull up to 15a @ 16v, and two CPU fans, probably pulling around 5W total power.  However, for pricing and other reasons I was considering this power supply, which supplies 30a @ 12v.

I know that the peltiers will work at 12v, though I suspect at a lower efficiency and higher amperage(?).  What my novice electronics understanding is struggling with, though, is understanding what will happen given that my devices can pull more amps than the power supply can provide.

I suspect all four devices (2x peltiers, 2x fans) will just get less power than they can handle, and the peltiers will dissappate less heat than their capacity and the fans will run at a slightly lower RPM.  Is this correct?  If so, will the power loss be a constant percentage of total power across all devices (everything runs at 90% power), or will the fans still get all the power they need (since their load is so small) and the peltiers will just run at lower power?  Or is this all a really bad idea that will cause the PSU and devices to fail in bad ways?


texts:
I use Wheatstone bridge as a dual voltage divider to feed both inverting and non-inverting inputs of differential op-amp:

Theoretically voltage can be calculated using voltage divider expression: Va = V1*(R2/(R2+R1) = 7.5 mV. Following the same reasoning Vb = 6.0 mV. When I use LTSpice to calculate these voltages for the bridge alone without op-amp, everything is fine. However, when I connect bridge to op-amp circuit, Va = 6.5 mV and Vb = 4.8 mV. If LTSpice doesn't give erroneous results, how should I calculate voltages Va and Vb?


texts:
I am trying to implement carry chain with Cyclone IV FPGA. I will use carry chain as delay line so here is quick explanation of my program: When input signal "cin" goes high, signal starts to propagate through chain and in moment when STOP occurs, propagation is sampled by registers. To do so, all it takes is to set all the bits of the first operand (input a) to ‘1’ and the bits of the second operand to ‘0’ (input b). Code which works fine for me is :

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity SignedCounter2 is

    generic (

    DATA_WIDTH : natural := 10

               );

    port (

             cout   :out std_logic;
             izlaz: buffer signed ((DATA_WIDTH-1) downto 0);
             a: in signed ((DATA_WIDTH-1) downto 0) ;
             b: in signed ((DATA_WIDTH-1) downto 0) ;
             clk1: in std_logic;
             clk2: in std_logic;
             cin: in std_logic

          );

          end SignedCounter2;

architecture rtl of SignedCounter2 is

SIGNAL reg: signed ((DATA_WIDTH-1) downto 0);
SIGNAL buf: signed ((DATA_WIDTH-1) downto 0);
SIGNAL STOP: std_logic;

begin

STOP<=clk1 and clk2;

process (cin,clk1,STOP)
    variable s : signed ((DATA_WIDTH) downto 0);
    begin
    s := ('0' & a) + ('0' & b) + ('0' & cin);
    buf<=s((DATA_WIDTH-1) downto 0);
    cout <= s(DATA_WIDTH);

    if (rising_edge(STOP)) then
        izlaz<=buf((DATA_WIDTH-1) downto 0);
    end if;

    end process;

end rtl;

With such structure of code i get exactly what i need; carry chain with fast paths as is show in next picture.

Cell structure with fast lines:

Problem is that operands "a" and "b" need to be declared somehow else then input signals. When I try to declare them fore example as SIGNAL or CONSTANT carry line gets deformation (fast paths are not used or cells are placed at strange way).


texts:
https://i.stack.imgur.com/mjF4e.jpg

This is in a 2004 manufactured motherboard, Sanyo brand capacitor

Can anyone help me identify the mf rating and volt. And why it’s written like this


texts: Digital output of the STM32L152RE: toggling between +/- V?

texts: Is it possible to get the digital data output from the STM32l152RE microcontroller to toggle between +/- volts? where the +V will represent the logic-1 and -V will represent the logic-0, instead of conventional 0 V as logic-0 and +V as logic-1.


texts: Should my NiMH battery powered circuit/device switch power sources when charging?

texts:
Details

Battery Supply: 2.4V (2x NiMH 1.2V - 1500mAh batteries )

Charging Supply: 5V (USB Power Adapter / Wall Wart)

Switching Regulator/Controller: NCP1450A 3.3V Step-Up Boost Supply Voltage

Circuit Description

Power Consumption: The circuit will be fully on for 12 (15 second) intervals every day consuming 150mA of current (3 minutes total in 24 hours). The circuit will consume approximately 50uA of current while sleeping.

Circuit Composition: Put simply, the circuit is composed of an MCU that reads sensor values and controls output to peripherals based on sensors and timing intervals.

Battery Charging: The primary MCU, or optionally a dedicated secondary MCU, will control the battery charging and maintenance.

Usage and Application: The device is primarily intended for battery operation, but may just as easily be placed within range of a power outlet where it can remain plugged into the provided dedicated 5V power supply for extended periods of time or even indefinitely.

Questions & Concerns

Concerns: In a circuit engineered to constantly pull current from the batteries, even when the optional dedicated power supply is connected for charging and maintenance, the battery life will be reduced and the batteries damaged from being subjected to a constant charge and drain. Also, accurate battery capacity may be difficult to ascertain once the initial charge sequence is completed which may lead to over or under charging.

Question 1: Are my concerns founded? Or, alternatively, will any potential life-reduction/damage be sufficiently inconsequential to omit the necessity for an alternative design solution?

Question 2: Assuming my concerns are founded, what will be an appropriate design to isolate the batteries from the circuit while the device is plugged into the dedicated power supply yet will still facilitate the charging and maintenance of the batteries?

Please reply with your ideas and design considerations. Your input will be greatly appreciated as I do not have much experience in this area.


texts:
I have a dual voltage 115/230v universal motor, which I need assistance connecting to DC power.
The model is a Model D671B FASCO 1/15 hp 1550 RPM 115/208-230V with Industry number 1231.GE.
The motor works fine in AC, but, I have not been able to get it to spin on DC. The wiring diagram shows only AC connections.
I have been able to test leads where can get 16ohms, these are blue to black, blue to orange, and red to yellow. With the ohm meter connected, each coil pair changes resistance showing brushes attached. another connection between black and orange gave 1 ohm.
In addition, I have tried attaching the red coil in series.
Any advice? The motor cannot be disassembled, so I cannot identify the wire connections.


texts: Transistor PWM Generator (No ICs) for practical application

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I want to produce a good quality PWM signal with transistors(BJTs, FETS, etc..). I do not want to use an IC at all(learning to use transistors properly). I'm currently using a BJT Astable Mutivibrator

@Source pin is a mistake I meant drain

As you can see the signal is fine until I attach the mosfet.

I've tried the configuration using 1N4148s to improve rise time, however due to the current limitations of the switching diode the signal isn't strong enough, I've tried various amplification techniques I found online, but the results were so horrible they weren't worth posting.
The DC-DC converter works like this, however it is not the subject of the question.

How can I stabilize this signal for practical general purpose use or is this an exercise in futility?

EDIT
To Newbies, DO NOT BUILD THIS!
If you want to build a boost converter from jellybean parts, use an NE555 and an OP-AMP or (better) comparator to regulate the voltage via the CV pin, even then there's a nasty ripple voltage. However the answer to the question is correct emitter follower(pushpull amp), etc was the best way to go. Oh and please don't use an autotransformer, it does lower the stress on your MOSFET, however the voltage isn't controllable without a switching regulator on the output end.(Which should probably be implemented in any case.
)


texts: Controlling a 220V European outlet from Arduino

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I want to use an Arduino to control my 220V outlet.

I have searched the web and stack a couple of hours and all I found was this product from Sparkfun and Adafruit, but it does only take 110V and it is an American outlet.

Neither the Weemo will work here in Denmark.

Our outlets in Europe (Denmark) look like this.

I want to avoid to work with high voltage (and possible a fire). How?


texts: Need to implement a phase locked frequency converter from 32768Hz to 36000Hz. How would I go about it?

texts:
I am building a timecode-related application and need to generate a square-wave clock pulse of 36000 which is integer-dividable down to 24,25 and 30. My source clock is 32768Hz which does not divide down to integer values. I believe therefore I need to convert the 32768Hz clock to 36000Hz.

There's also options to convert up from 1Hz, 1024Hz, 2048Hz or 4086Hz although I suspect the approach would be similar.

How would I best go about this?


texts: How do I benchmark and compare Simulink models when it comes to resources usage and performance?

texts:
I am trying to implement a model with different levels of complexity in Matlab Simulink. I would like to perform a comparison between the different models in terms of computational cost, resource usage (RAM), number of operations and CPU time and possibly any other useful performance metrics.

What is the right procedure to this? Are there are useful functions I can use? Thanks in Advance (I am using Matlab 2015b)

All the models are Simulink models


texts:
I am trying to match a gsm antena, doing it on a pcb, first time in practice. I understand the whole process to adapt it, I've done it in simulators. However, I don't understand the need for a pi matching network, since (theoretically) and LC circuit is enough, or a series and shunt capacitors. So why the extra component?

Plus, I understand even less the suggested pi matching network on the uC datasheet. It shows 2 shunt capacitors with a normally 0-ohm resistor in between. Aren't the capacitors redundant?

When working on a pcb which components should I prefer to do the matching? Are stubs a bad idea? I never see them referenced to do the matching.

I forgot to add:
I'm going to do this with a vna, the configuration I have is the antenna pin from the uC directly connected to the matching network and then the antenna. Should I do this with the uC powered or turned off.

DataSheet: https://cdn-shop.adafruit.com/datasheets/sim800h_hardware_design_v1.00.pdf

Suggested pi-network:

Hope was clear enough,

Regards,

Pedro Lopes


texts: Via stitching removes solid ground plane

texts:
I read in some places that having a solid ground plane is needed . Does not via stithing causing the solid ground plane to become broken? Is this okay?

Also when everyone talks about return current, are they talking about the current flowing underneath the trace itself or the plane beneath the trace?(because skin effect makes a trace a 3d structure, can return current flow below on the same trace?)


texts:
I have the following problem:

Consider the graph below

What is the power dissipation in a 75 \$\Omega\$, when the voltage across it is the plotted voltage above?

Okay, so my idea was to split the power dissipation into three parts.
From [0-5]us, from [5-7]us and from [7-13]us.
The power dissipated from 5-7us must be: \$P=\frac{U^2}{R}=\frac{2^2 V^2}{75\Omega}=0.0533 W\$
The power dissipated from 7-13us must be: \$P=\frac{U^2}{R}=\frac{(-4)^2 V^2}{75\Omega}=0.2133 W\$
But how do I calculate the power dissipated from 0-5us? Do I have to find an average voltage or?


texts:
I am searching for a way to use a comparator with possible negative voltage on its inputs.

My thoughts and attempts so far:

Op amps and comparators with V+, V- and GND: the circuit utilizes a single LiPo battery.
LM339/393: works correctly only when Vin >= V- - 0.3V, which is not enough.
Diodes: too low voltage, I suppose

Requirements are:

Vin range -2.0V .. + 2.0V (and around 0.1V on the reference)
Max. current provided for comparator input: around 500 uA

Recently I have found an interesting comparator - LT1716 (datasheet/website). It provides a "Valid Output with Either Input 5V Below V– ". If there is one, then the idea is not new and there should be more, right?

(I am new to electronics, and I am sorry if I did not provide some related info - please let me know what I forgot)


texts: Keyed access in PIC config settings for the WWDT

texts:
I'm playing around with the settings for the windowed watch dog timer (WWDT) for the PIC18F24K40.

In chapter 3.7.3 (page 37) about device configuration, the DT Window Select bits are briefly described, but there is no explanation in chapter 9 (page 106) (which treats the WWDT).

Searching internet on "keyed access" only give me more datasheets different PIC's, but none of them have it explained in more detail.

So, what does "keyed access" mean?
And what does "Software control of WINDOW" mean? And how can I manipulate the window in software?


texts: I was going through a problem on inverting Amplifiers and got the output voltage of the op amp as -10V. Can someone explain how the load current flows upwards from a grounded terminal? I know the output is at -10V so the load current flows from higher to lower potential, but isn't the - sign there just to indicate the 180° phase shift between the input and output voltage? Practically how can a current flow from a ground terminal, upwards?


texts:
My question is that does the energy efficiency for Li-Ion battery varies for different C rates ? For e.g if a battery is charged and discharged at a lower C rate, would it's energy efficiency would be higher than the one being charged with a higher C rate ? If yes, why ?

I have searched about it, and i know the fact that the battery's capacity depends on the current amplitude extracted from it. At higher discharge rates the capacity is lower, and so will be the output energy. Same is the case with charging, with higher charging current amplitude, the battery wont be charged to its full capacity and the maximum cut-off voltage is reached. But what about the energy efficiency ? Would it also differ for low and high charging and discharging case scenarios ? Or does it remain the same ? Because in high C rate case, we are extracting less energy (capacity x voltage), but we also provided it with less energy while charging it. So doesn't the energy efficiency need to be same for high and low C rates charging/discharging case ?

I hope i am able to make my question clear.
Your helpful suggestions and comments would be appreciated.
Thankyou


texts: Using a switching DC-DC converter in high dynamic range current/voltage sensing

texts:
I'm thinking of making a power meter circuit which will have a high-side current-sensing amp (LTC6102), a resistive voltage divider for sensing the voltage, a dual op-amp (OPA2365) as a buffer for the current and voltage signals, a 2 channel simultaneously sampling ADC(LTC1407), an FPGA for multiplying and keeping a running sum and a blue-tooth UART module for transmitting to a phone.

The ADC and the rest of the digital circuit will be powered from 3.3V, and will draw 70mA.
This will be measuring an e-bike's consumed power with the maximum supply voltage of 54.6V.
I would use a liner regulator but then I need a radiator because I need to dissipate 3.5W considering the high voltage drop.

So I'm considering using one of these DC-DC converters with a built-in inductor to save space with less dissipated power.

My concern with these switching converters is noise.

I can estimate the impact of the power supply ripple based on the converter's specs and the PSRRs of the op-amp and the ADC (the current-sense amp will powered directly from the supply)

What I don't know is how to estimate is the impact of the radiated EM noise from the inductor in the converter.

My understanding is that when it comes to EM-induced noise I should be concerned about the places with low currents/high input impedances.

In my case these are the connections:

from the output of the current-sense amp to the buffer op-amp (1LSB
is 2.5V/4096=610uV or 1mA/4096=244nA for the current sense amp's
output)
from the resistive divider to the buffer op-amp (same 610uV LSB)

I understand that the actual currents into the op-amp inputs will be lower, but not sure how to estimate those.

This might be a broad question but as a ball-park estimate is 0.5 LSB of noise achievable in my case with a switching DC-DC converter considering the EM noise from the inductor of the converter?

(Now I'm thinking maybe the bluetooth module is a bigger EMI concern)


texts: What causes servos to get damaged from high voltage?

texts: I have 6 volt continuous servos. I needed to run them, but had no 6 volt power source nearby so I tried using a 9 volt 280mah rechargeable battery. The motor made weird sounds, but didn't work? I checked later and it still works with 6 volts. What caused it to malfunction?


texts: Continuing execution after ISP in LPC81x series

texts:
I am uploading software via serial ISP in to an LPC81x series microcontroller. This is a Cortex-M0+ chip. After software upload, I would like to start the execution of the uploaded software without having to reset the CPU externally.

There is a "Go  " command in the serial ISP and the "lpc21isp" software uses it as such: "G 0 T\r\n". However, this does not seem to work as it has several problems:

The part of the program residing at address 0x00000000 is the interrupt vector table, not program code. Starting thumb mode execution at that address is just going to fault. However, I do not know what the "go" command really does.
Somebody needs to set up the interrupt table pointer (VTOR), reset all the pin configurations and invoke the reset handler. This is quite different from starting execution at a certain address.
The documentation says that using the "go" command on an address below 0x00000200 is not supported. In my case atleast the reset handler resides below that address.

I am open to any suggestions that would allow me to continue execution after ISP.

Just as extra information: the reason I wish to do this is that I do not have spare communication lines for reset or forcing ISP. I can, however, toggle the power to the chip. I would like the chip to unconditionally start in ISP mode, so I can update the software on every chip bootup if I wish.


texts:
If I am using a CMOS switch, how much do I have to slow down the switch time so that I don't experience a pop in my audio signal out of my amplifier and how would I accomplish that?

The switch time is currently on the order of nanoseconds which is unnecessary and causing a loud click/pop. The switch basically alternates between two input signals as fast as possible. Currently I'm using the ADG1419, but I can be open to using other chips. I do not want to experience any latency, which I believe is a 3-5ms audible threshold. Thanks!

Update: Here is a picture of my oscilloscope capturing the switch when both audio inputs are the same. I read that in pedal design, if the switches switch to quickly there will be a pop/click.

Update: Here is Input (CH2) vs output (CH1) during switch.


texts: Does the Rds(on) of a MOSFET vary based on source-drain voltage?

texts:
The Rds(on) of a MOSFET decreases when you apply higher gate voltage, but does it typically vary based on the source-drain voltage?

I will be using a MOSFET to switch very low voltages (10's to 1000's of µV) and was wondering if normal MOSFETs will work as long as the gate voltage is high or if the low source-drain voltage means I will need something special.


texts: How could this transistor be in saturation?

texts:
For this RTL circuit (RTL inverter with active pull-up):

The textbook says that in the output high state, Qp is in saturation and the circuit looks like:

I wonder how this is possible?
$$Rcp = Rc/10$$ and usually $$R_B > R_C$$ so we expect that the voltage at the base is less than the voltage at the collector. And for saturation, we need $$V_{BC} = 0.6V$$


texts: How to measure a short of power amplifier in car?

texts:
Recently my old amplifier in car has got a defective contact on one of the switches, so I decided to unsolder the old one and solder a new one. Unfortunately the amplifier caused a short as I connected it to the battery again (I don't know how this could happen, maybe I damaged some component or something, or maybe there was suddendly a wrong connection due to soldering althought I don't think so).
What I've done next is to unsolder the switcher again and bypassed the needed conducting paths by soldering some kind of bridge (I don't need to switch it again, it's ok for me when it just works with a specific adjustment). But before I try to connect it to the battery again, I'd like to test if this is save. So I thought about using an ohmmeter. My idea is when I connect it to the plus pin and minus pin of the amplifier, the resistance must not be 0 Ohm, because this would cause a short since 12V / 0 Ohm means infinite current. Are my thoughts correct? Or do I miss something important?


texts: Trouble with Turning Off/Powering Off two systems at once, how should I approach this?

texts:
I have an overall that I want to shut off completely with a flick of a switch; however, the system I want to shut off is comprised of two smaller, completely separate systems.

Let me give you an example,

If you can see, the two smaller systems are completely separate; however, I want to be able to flick a switch and have the entire system turn off (both peltier-battery combinations). Basically, how can I connect the two systems without getting into the messy territory of parallel batteries.

In addition, I also want to add a thermostat control that controls the entire system's Peltiers (both of them in sync, together), so I need a way to link the two smaller systems together to have it under control of one thermostat controller.

Thanks Guys


texts: How to wire a normally open switch to a recoil start engine with no external battery?

texts:
I am making an engine toggle switch for a recoil-start engine using two switches wired in series for safety. The engine will shut off only when two "kill" cables on the front have been connected. In the picture below, I have lengthened the wire to make it more noticeable and easier to work with.

Unfortunately, the switches are built to be normally open and cause the engine to shut off when both switches are on (hereinafter called "switch box"). The ideal situation is that the engine status reflects the switch box status: both switches ON activates the engine and turning either switch OFF in the switch box shuts down the engine.

Thankfully I was able to find some answers on how to flip the switches to act normally closed from using concepts from this  kill switch post. I also viewed a post about  latching relays  to potentially use for hooking up to the engine. I spent some time prototyping these ideas and it works exactly as I need it to. Below are the schematic and pictures of the functioning prototype, whenever the LED is ON the engine is OFF because a connection has been established:

LED OFF means Engine ON

simulate this circuit – Schematic created using CircuitLab

For my question, I would have been able to hook up this circuit and been done with it except a recoil-start engine does not utilize an external battery like this prototype circuit and most of the engine kill-switch questions on this forum do. I've noticed through testing that the battery is crucial for making the circuit work. Given that the kill cables from the engine are wired with its spark plug, how would I be able to implement the Normally-Open to Normally-Closed wiring without having a battery? Is there some way to wire the same path the battery creates without using a battery?


texts: Single Channel ADC with DMA giving garbage results on STM32F7

texts:
I'm looking to implement ADC and DMA with HAL on a F767. I want the ADC to be always converting and storing to memory via DMA until it reaches the buffer limit of 320 and then I want to go to a conversion complete callback function. ADC seems to be enabled fine and it converts values up to the buffer limit and then it goes to the conversion callback routine. The problem I'm having is when I check the ADC buffer in the conversion complete callback function is that the first half of the ADC buffer (exactly the first half, 0 to 160) is full of these values when the ADC input is ground:

I'd expect values anywhere from 0 to about 15 at the worst, so it is partially consistent.

When I connect the ADC to 3V I would expect close to 4096 but instead I get:

As the values ARE lower when the ADC is connected to ground and higher when the ADC is connected to 3V they're not completely garbage values, it's not just random values stored in memory. Also, after the first half of the buffer, everything is just zeroes so I'm thinking that maybe I've configured the ADC wrong or reading it wrong. I'm assuming that because the DMA stores the values in the array I just need to check the array during the conversion callback function but this doesn't work.
The buffer size and DMA call

//this code before main
    #define ADC_BUFFER_LENGTH   340     //5000khz signal / 1.67 Msps = 334 samples

uint32_t ADC_Val[ADC_BUFFER_LENGTH];

//this code after main but before while loop
HAL_ADC_Start_DMA(&hadc1, ADC_Val, ADC_BUFFER_LENGTH);

And the ADC initialisation:

static void MX_ADC1_Init(void)
{

  /* USER CODE BEGIN ADC1_Init 0 */
//ADC operating @ 1.6MHz - 100MHz/4 = 25MHz
//25MHz/(12+3) = 1.67Msps
  /* USER CODE END ADC1_Init 0 */

  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC1_Init 1 */

  /* USER CODE END ADC1_Init 1 */
  /** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

and my conversion callback function:

    void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
    //chop out sample window 1 and 2
    //sample window 1
    //Pulse Tx is 50 uS wide, there is a settling delay of 20us = 70us
    //with a sampling rate of 1.67Msps 70*1.67 = 119 samples
    uint32_t ADC_SW1_Temp[ADC_SW1_LENGTH] = {0};
    //30us sampled window @ 1.67Msps = 50 samples
    for(int i = 0 ; i < ADC_SW1_LENGTH; i++)
    {
        ADC_SW1_Temp[i] = ADC_Val[(ADC_SW1_START + i)];
    }
    ADC_SW_1 = 0;
}

Is there anything here that is obviously incorrect? If not, what is the best way to approach debugging of the DMA and the ADC?


texts: How do I reduce the frequency of electric current for part of a circuit that has variable frequencies?

texts:
I want to reduce the frequency of electrical current that is operating in the 220 to 240 khz range, to being a maximum of 20khz.  I want it to still be variable though, and the magnitude of variation to be the same (so 240 kHz for the part of circuit operating at high frequency becomes 20 kHz on the low frequency part,  and 220 kHz becomes either 0 kHz (subtracting the frequency to get it below the maximum), or about 18 kHz if we scale it down by 12 (240/12=20, 220/12= appr. 18.33).  Really I just want to know how to isolate a part of a circuit and have it shift the frequency of the electrical current down to a frequency that is compatible with being heard when sent through a speaker.  The magnitude of the reduction for each side doesn't matter, it doesn't even need to be equal, as long as it remains variable but is reduced to a hearable frequency.

Extra Details:  The circuit I have already converts DC current into pulsed current using Schmitt triggers.  This pulse is sent into an induction coil to create a pulsed em field at the same frequency.  If a conductive material or ferrous metal goes within the effective range of the pulsed em field, it induces current in the material and generates its own em field, which affects the pulse going through the induction coil, changing the frequency that the current is at.  I want to be able to detect that change in frequency.  Most methods involve converting it into sound through various means, one being to wrap some wire from the circuit around an AM radio, another being directly connecting it to a speaker of some sort along with an amplifier, but only after converting it to frequency that the speaker will output within the human hearing range.


texts: Arduino + PWM + LED Buck Regulator / Flashing not smooth

texts:
I am trying to use an Arduino + PWM to control a 100w LED using a Sure Electronics 300-3000ma buck regular - Product Here

The chip being used is LM3409

The buck regulator is powwered by an external 36v suppply to VCC + GND, and a 100W led is connected to the LED +/-.

This configuration is working fine without PWM but I can not understand how to control it with PWM from an Arduino without flicker.

The arduino is connected to to a 4n35 Optocoupler.

The Arduino Digital Pin 2 is controlled (AnalogWrite) after reading the value of a Potentiometer (0-1024 mapped to 0-255) and is connected via a 200 Ohm Register to Pin 1 of the Optocoupler. Pin 2 of the optocouler is connected to the arduino ground.

int led = 2;           // the PWM pin the LED is attached to
int last = 0;
// the setup routine runs once when you press reset:
void setup() {
  // declare pin 9 to be an output:
  Serial.begin(115200);
  pinMode(led, OUTPUT);
}

// the loop routine runs over and over again forever:
void loop() {
   int sensorValue = analogRead(A0);
   sensorValue = map(sensorValue, 0, 1023, 0, 255);
   if (sensorValue != last)
  {
    last = sensorValue;

    analogWrite(led, sensorValue);
    Serial.println(sensorValue);
  }
}

The LED buck device says that the EN pin - PWM terminal when applied with ground or suspended, full amount of current will be output and when connected with +5v or VIN, output current will be 0.

I have tested this, if I connect the 36v from the LED power supply to the EN pin the LED goes out. If I connect to ground or leave floating it runs at 100%

I do not know how to connect the other side of the Optocouler to the EN PIN properly.

I have connected pin 4 of the optocoupler (EMITTER) to the EN PIN, and connected pin 5 (COLLECTor) of the optocoupler to 36V from the VCC on the buck regulator.

This seems to work as it does go up and down in relation to changing the potentiometer.

0 from analogWrite on the arduino and the LED is running at 100%\
128 from analogWrite on the arduino and the LED is running at 50%
255 from analogWrite on the arduino and the LED is running at 0%

But it is not a constant brightness, it is flashing terribly and not usable.

Any help appreciated as I do not know how to move on with this.


texts: Multiple PCIe Functions in Real User Applications (EP mode)

texts:
According to PCIe specification, a PCIe device may contain a collection of up to 8 functions. If a PCIe is configured to a specific endpoint, under what circumtances does it need multiple functions? Why single function is not sufficient, it is a implementation option or it is a must to have a multi functions EP in certain usage models?

Can any expert correlate this usage model to a real life PCIe user application?


texts:
I am trying to understand the difference between a MOSFET current mirror with and without compensation (Replace Q3 with a short circuit).

In the case of a current mirror without compensation, V1 needs to be increased for Q2 to enter the saturation region.

The addition of compensation means that the increase of V1 is no longer required.
What is causing this to happen??


texts: CAN line collision detection with XOR gate

texts:
I want to connect multiple devices via UART but want to benefit from CAN physical layer its noise resistance and mutlimaster capability. Also I need to detect whether or not there is collision on the line and if so cancel my outgoing transmission. I have figured out that I can achieve this by simply adding XOR gate between RX and TX lines between CAN transceiver and uC. But after looking into some datasheet data it comes with a problem: XOR's propagation delay is up to 10ns (worst case scenario) and CAN transceiver's propagation delay form TX to RX is ~200ns which would result in generating false collision detection signals when transmitting data while the line was idle. What should I do in such a case? I can see 3 possibilities but I am not fully convinced to any of them (maybe there is a better solution):

delay TX input of XOR gate with simple RC low pass filter tuned to match CAN transceiver's propagation delay.
delay output signal of XOR gate with simple RC low pass filter to filter out spikes shorter than CAN transceiver's propagation delay.
Use some hardware in uC to digital filter short spikes on collision detection input.


texts: Voltage follower with a pair of matched FETs

texts:
I am studying for an exam and as a part of a question I have to explain biasing and operation of the voltage follower that uses two matched JFETs in the following arrangement:

I am not sure that I understand the self biasing of T2.

Vgs of T2 can't be positive because of the voltage drop across R2 when a current I flows, so T2 will never be fully "on", putting a limit on the maximum current I regardless of the input voltage, correct?

If that is so, is that maximum current I in practice lower than what is needed to achieve the desired drop, for the output to be equal to input?


texts:
I'm working on a project where I want to very accurately (+/- 1 degree) determine the angle at which a finger is bent.

One of my main constraints is that my sensing mechanism can't interfere (much) with the normal positioning and movements of the hand.

I'm trying to determine the best sort of sensing mechanism for this project. I looked into a lot of rotational encoders but I can't find any small enough to fit between two fingers and this wouldn't work for the first knuckle joint.

My next thought was to use flexible strain gauges across the top of each joint but I don't think I'll be able to get anywhere near the amount of accuracy that I need.

Another thought I had was to place a hall effect sensor on top of the finger joint but I'm not super sure how accurate I'd be able to get with this.

Any thoughts on a good way to do this?


texts: How can I shield signal cables in an electrically noisy environment?

texts:
I have been playing with a four-channel EEG neurofeedback device. There is some evidence, not conclusive  but respectable, that coding performance is improved by neurofeedback on the ratio of beta power over theta power. I would like to see if that is true for me.

My question concerns cable shielding or other noise reduction techniques. I work in an old building with two-wire electricity. So there is no accessible quality ground, and we had to shell out some extra money for extra-high-end surge protectors as a result. And there is a lot of electrical noise around my work station -- fluorescent lights, a laptop, desktop, and server, printer, several screens, plus miscellaneous other equipment, all within six feet of my head  The result is a much noisier signal than I get using the same equipment at home.

The EEG is battery powered, so there is no direct coupling to the building power supply. The output goes to my computer via USB cable, so there might be some noise from there, but the same is true at home. So it is the incremental noise, induced by office equipment in either the leads to my head or the USB cable, that I want to shield against.

Is there a good way to do that? I would try grounded coaxial cable, but I don't have a ground.


texts: what's the maximum output voltage of my soundcard?

texts:
I have measured the voltage of some files with an oscilloscope, and they max out at 1.2v pk-pk when I set my volume on loudest.

However, how can I make sure that's the maximum voltage that's possible?
Would there be any case where it would produce more voltage?
I'm going to hook it up with a digital-analog converter, and I don't want to burn it.
I guess I could always check the signal with an oscilloscope before I connect it to the DAC, but that would be too much of a hassle...

Also, I read that I should be looking at the RMS voltage because that will determine whether it'll burn it or not. Why is that?


texts: MXM to PCIe connector - help in understanding some of the MXM pins

texts:
I am trying to build a board to bridge the MXM slot in my laptop with a PCIe riser. Have just started working out which pins from the MXM slot should connect to which pin on a PCIe slot. I have put my initial planning work on github - https://github.com/gautamz/mxm3-pcie-rise-connector.

I need help with the following MXM pins,

PWR_GOOD & PEX_RST# - PWR_GOOD indicates to the board that
the internal power state of the endpoint is fine. On PCIe this is
indicated by PERST#. So I am connecting these two. But then what do
I connect the PEX_RST# pin on the MXM slot to? Can I just leave this
unconnected? Setting PWR_GOOD is important to ensure I get PCIe v3 speeds, or else the system will default to PCIe v1.
PEX_STD_SW# - This determines the swing for the
MXM GPU. However I saw nothing for this in PCIe specifications.
There the swing appears to be managed by the REFCLK signals. In the
MXM specs if I connect this to ground I am indicating standard
(desktop) swing. Should I connect this to ground, or leave it
unconnected?
3V3 - Do I need to connect the PCIe 3.3V pins to the 3V3 pins on the MXM slot?
I am planning to only connect to the following MXM pins - WAKE#, PWR_GOOD, SMB_DAT, SMB_CLK, PEXRXn & PEXTXn (n = 0 to 15), PEX_REFCLK, PEX_CLK_REQ#, PEX_RST#(?), PEX_STD_SW#(?). This should be enough for the PCIe card since I will power it with an external PSU. Any other MXM connections are mandatory?

In the github repo I have a spread sheet where I am working out the needed pin connections before I begin working on the PCB layout. If you have any other advice for this, it would be appreciated. I will also put up the PCB layouts on the github repo.


texts: Mesh current method question here?Is this correct?

texts:
We have the circuit in the figure.I have to find Vo in terms of Vi.

So I have the system of equations
{-Vi+ (1k+1k)I1- 1kI2-5=0

5+1k*I2+I2*1k-I1*1k=0

and Vo=1k*I2

We have 5-Vi=2kI1-I2 and 5=I1-2kI2 and Vo =1k*I2.I know that I should find I2 in terms of Vi from the first and second equation and then replace it at Vo ok?
So I do that,and I have

I2=(-5-Vi)/3

Now I have Vo=I2*1k= (-5-Vi)/3 Volt

I think that I have made a mistake and Vo should be equal to Vo=-1k* I2?


texts: Effective differences between MAX485EESA+T and MAX485ESA+T?

texts:
Is anyone able to explain to me the effective difference between the MAX485EESA+T and the MAX485ESA+T?

The datasheet points out that is more tolerant of ESD discharge up to 15kV, nothing more.

Can it be used as drop-in replacement for the standard MAX485?

Can anyone explain to me the effective electrical difference that distinguishes the two?


texts: SPICE model for one terminal spherical capacitor

texts:
I have a circuit where at least some of the capacitance is coming from large, non-radiating, spherical conductors.  I would like to model it in SPICE to better understand its operation-- is such a thing possible?  The capacitors I have available are all two terminal devices...

I know that the capacitance of my sphere is \$C=4\pi\epsilon_0 r\$, where \$r\$ is the radius of the sphere.  I'm trying to figure out how to represent that in a SPICE circuit.

Updated to address points made in comments and answers:

Here is what I originally meant by "not coupled":

The self capacitance of a sphere is \$4\pi\epsilon r\$, where \$r\$ is the radius of the sphere.

If I have two spheres of equal radius the capacitance is:

\$2\pi\epsilon r \sum_{n=1}^\infty \frac{\sinh\left(\ln\left(\frac{d}{2r}+\sqrt{\left(\frac{d}{2r}\right)^2-1}\right)\right)}{\sinh\left(n\cdot\ln\left(\frac{d}{2r}+\sqrt{\left(\frac{d}{2r}\right)^2-1}\right)\right)}\$, where \$d\$ is the distance between sphere centers.

The summation limits to 1 as \$d\$ goes to infinity, and the remaining terms can probably be interpreted as the self capacitance of each sphere in series.  So the total capacitance is the self capacitance of each in series, plus, what I will call a "mutual capacitance" caused by interaction of the electric fields and which is a function of distance.

By “not coupled”, I’d meant that this distance dependent mutual capacitance term is  arbitrarily small, leaving only the self capacitance.  Probably the wrong choice of language.  The capacitance value is not dependent upon anything else in the circuit, but obviously Gauss’ Law still holds.


texts: Determining the correct power rating of a braking resistor

texts: Braking resistor on AC servo motor driver is not working, and I cannot find power on it, but it is 100 Ohm (It burned up). Power on driver is 200W. Can I put 400W (100 Ohm) braking resistor on that motor?


texts:
I just bought this power supply for a project.
I just went in with a multimeter to test the voltage and pins, which gives me a 20V reading as expected.
However, after I remove the power supply from the wall, I still see 20V initially, and then I see the voltage dropping quite slowly, over a fairly long period; I'd say around half a volt per second, or even slower.
Is there any way to discharge this voltage this fast, or any other circuit to not have long discharge times from powersupply as it causes problems to switch to my battery?


texts: I have a power P-channel MOSFET that can produce a max of -34 A and whose datasheet does not include parameters W or L. How can I model this PMOS without W or L if I only have \$R_{DS_{on}} \$ and \$Q_g \$?


texts: Spectral analysis with RF signal generator

texts:
I need the spectral analysis of an LC circuit which oscillates in UHF band. I have a rough idea about its resonance peak but I need to observe it. As equipment, I have at my disposal Aeroflex 3020 RF signal generator, Aeroflex 3035 RF digitizer. Each uses a 3010 RF synthesizer as local oscillator.

My question is that, can I use this setup for spectral analysis purpose ? If yes, what would be the strategy to follow ? Should I sweep the frequency range via script? Should I send signals which contain many harmonics to excite the circuit ?

Thanks in advance,


texts: Is this DIY high voltage AC generator safe to use?

texts:
Making a DIY type high voltage AC power supply from 40 W soldering iron, 220 V AC to 12 or 6 V AC step down transformer and 5 A fuse.
These things are ALL connected in series to the 220 V AC mains.

Am I doing this "high voltage AC generator" circuit right?

I am making a high voltage alternating current power supply of 10 - 15 kV enough to generate strong electrostatic influence on deionized water to construct a water bridge and investigate its physical properties for a research.

The circuit consists of a 40 W soldering iron (used as dummy load or sacrificial load in case the transformer fails), 5 A Fuse, and finally a step-down transformer of 220 VAC to 12 VAC or 6 VAC with center tap all connected in series to the AC mains 220 VAC

BTW I am at a beginner level when it comes to controlling high voltages.


texts: Radio interferes with I2C bus communication

texts:
I have a PCB with a Microchip PIC18F97J60 on it and every time I key a 5 watt radio transmitting at 144 Mhz next to the board it resets the processor. The processor resets when it’s attempting to communicate over the I2C bus. The watch dog timer times out waiting for the MSSP (Master Synchronous
Serial Port) interrupt flag to be set. This happens most often when waiting for the interrupt flag after the master (PIC18F97J60) sends a restart or a NACK.
I’m using 2 kOhm pull up resistors and running the bus at ~96 kHz. On the oscilloscope it looks as though the interference on the bus is bad enough where it can pull the SCL and SDA lines down from 5V to 2.6 V.  What can be done to protect the i2c bus signals from interference so the processor does not reset while waiting for an interrupt from the MSSP module?


texts: Can someone help me with a basic LED set up?

texts:
I'm going to make a simple cluster of identical LED's, tight together in a circle. I want to use between 15 and 25 LEDs.  The LEDs are near IR (830 nm) with 1.45 V drop at 100 mA.

What is the optimal approach? Should I wire all in parallel, series, or a mix?

I would like to power from the wall, so I want at least 2.5 A if using 25 x 100 mA LEDs right? And what would be the best voltage?


texts: DAC based voltage supply (current buffered) with current monitoring: shorting/instability?

texts:
I'm using a DAC to generate a 16-bit voltage supply, using a current buffer (unity gain amp) to enable high current draw and protect the DAC output, and then sensing the current delivered to a load using a current sense amp. Please see schematic.

With an open circuit load (should draw no current) the buffer seems to be pulling a lot of current (the solder job is fine, tested on multiple boards).

Is there something wrong with performing the current sensing operation the way I'm doing it? i.e. is there something wrong with this circuit that I'm not understanding?

Some useful information

buffers I'm using are unity gain stable


texts: Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?

texts:
In this video, the electrical engineer and youtuber Mehdi Sadaghdar (ElectroBOOM) disagrees with another video from professor Walter Lewin.

Basically, professor Lewin shows in an experiment that if we have two different resistances connected in a closed loop, and if we generate a changing magnetic field using a coil, the voltage at the endpoints of the two resistances will be different, contrary to the expectations from Kirchhoff's Voltage Law (KVL).

simulate this circuit – Schematic created using CircuitLab

According to the experiment, the left voltmeter VM1 shows a voltage different from the second voltmeter VM2. Lewin then concludes that KVL does not hold when there's a changing magnetic field. The mathematical reason that he gives is that the magnetic field is non-conservative, and KVL can be derived from Maxwell's equations only when the field is conservative. He then says that this experiment is a proof of his claims.

Mehdi, on the other hand, points out two things: first, that the way the probing was done is incorrect. The changing magnetic field has an effect on on the probe wires, and that's one of the reasons why the voltmeters change value depending on the position.

Second, he says that because there's a loop, then the loop is behaving like an inductor, and together with the coil it's forming mutual inductor:

simulate this circuit

I understand Lewin's derivation of the KVL, so I understand that there's an issue with the non-conservative magnetic field, but at the same I think Mehdi is right: that loop is an inductor, and the way Lewin is probing the circuit looks wrong to me. So where is the mistake here?

Does KVL hold in the circuit above?
Is the probing being done right?
Does the circuit have a mutual inductor that should not be ignored?


texts: AVR external interrupt triggering by the falling edge: for how long should I keep signal low to guarantee triggering?

texts:
The question header appeared to bee too long. I'm sorry for that.

So I have a schematic generating a short LOW on INT0 pin of ATmega48PA. From the simulation I figured out that the LOW level will be there for about 800 ns. I plan to clock the AVR from internal RC with 1:8 divider which means 1 MHz Fosc.

How do I make sure that the interrupt will be triggered?

I make some reading of the datasheet but I was looking in a wrong chapters or there is no such information.

Could you please point me into the right direction to find needed info?

Thank you!


texts: Acceleration of sequential computation over time

texts:
I am looking for a model (or "law", as in Moore's law) to describe the acceleration of sequential computation over time. By sequential computation I mean, for example, repeated applications of a hash function (e.g. SHA256). (Another example would be repeated multiplication modulo an unfactorisable RSA modulus.)

In his keynote David Patterson has a chart about "single program speed" (see here) which more or less captures what I am looking for. Does this metric have other names, and have there been studies about it?

Below is an image from "Computer Architecture: A Quantitative Approach":


texts: Sony Xperia Z1 - Camera Module Datasheet

texts:
I'm writing to inquire about technical data related to the Sony IMX220 image sensor, as found in the camera module of the Xperia Z1.

I will be interfacing with the module and require a datasheet including timing information, registers, etc; is this data publically available? Thanks for any assistance with this matter.


texts: Speed measurement of brushless dc motor with hall sensors with STM32

texts:
I have difficulties understanding and finding a solution to find the speed of a BLDC motor. Here is the specs:

3 Phase BLDC with 3x Hall sensors in 120 degrees, 2 pole-pair

The image below shows the situation:

I have setup a timer in XOR mode in the micro. The PSC is [19 - 1] and the Counter Period is [10000 - 1] while the timer clock is 80MHz.

My motor has the maximum speed of 3000RPM.

The timer is setup in XOR mode and with each transition generates an event. According to STM32F407 reference manual, in this mode each transition resets the CCR register to 0. It means if I add up this register 6 times, I should get one complete "Electrical Rotation" or half "physical rotation" since the motor is 2 pole pairs.

My questions:

A)
I just picked that numbers for the timer PSC and counter period randomly...how these number are going to affect my measurement? e.g. with those numbers can I cover speeds from 1 to 3000 RPM?

B)

I have the following code inside the XOR ISR... does this code make sense?

static uint32_t speed = 0;
static uint32_t time = 0;
static int isMeasuring = 0;

void XOR_ISR() {
     uint8_t state = readHallStateFromGPIO();
    if(state == 0b101 && isMeasuring == 0) {
        time = 0;
        isMeasuring = 1;
        time += TIM4->CCR1;
    } else if(isMeasuring == 1 && state != 0b101) {
        time += TIM4->CCR1;
    } else if(isMeasuring == 1 && state == 0b101) {
        time += TIM4->CCR1;
        speed = time;
        isMeasuring = 0;
    }

Here, the speed (suppose my code is correct, should add up timer values for a whole period of hall sensor). Then I am going to convert it to RPM by converting frequency to time and multiply by 2 because of pole pairs.

Is this correct?


texts: Interrupt trigger on presence of a pwm signal

texts: In order to detect the presence of a pwm signal using a microcontroller from an external sensor (an interrupt), say the sensor is a hall sensor rotary encoder that is used to count the number of rotations and the direction of rotation of a motor shaft using a magnet attached to the shaft, what is the most trivial way to accomplish the task?