texts: multi device usb support for beaglebone black

texts:
I m using a beagle bone black in my project which controls a USB charger. My BBB is connected to another board which also powers the BBB through the header pins. The BBB's USB is expanded to connect multiple devices and also external power is supplied. so when i connect 2 or more devices even though the devices gets charged, the USB connection is not possible.

I also tried connecting a external powered hub to by beagle bone and connected a mouse and keyboard but still only one device gets detected. No multi USB support. Is this a problem with my kernel. i m using latest Debian image and my kernel is 3.8.13. Please help


texts: MIDI out waveforms very different between two devices

texts:
I have two MIDI output devices: an Axiom49 keyboard and a Korg SQ-1 step sequencer. The Axiom49 drives a MIDI input circuit that I've built using an Arduino just fine. The Korg SQ-1, however, does not work with it at all.

The Axiom49's output is simply 31.25k baud RS-232, which conforms with the MIDI specification. The output on the Korg SQ-1, however, is totally different than I was expecting and does not work with my MIDI input circuit at all.

So, I hooked both of them up to an oscilloscope (across pins 4 and 5 of the MIDI 5-pin DIN connector, coming from the MIDI OUT plug on both devices) to see what their output looked like (screenshots below).

Also worth noting is that I was able to hook the Korg SQ-1 up to a friend's computer using a MIDI-to-USB cable and drive a software synth.

So, does anyone know why the waveforms between two MIDI devices could be so different?


texts:
I want to use a shunt resistor to measure the current flowing though a section of my circuit. I am deciding between using an off the shelf shunt resistor or simply drawing a wide track on my PCB and calculating the resistance (and hence voltage drop) of that section.

What are the pros and cons or each method, and from your experience which method is best?. For my application the accuracy is not highly important (avg of 10A flowing and I need to detect current to an accuracy of 1A).

From what i can see the advantage of using an off the shelf shunt resistor is the precision and accuracy of the resistance, however it is more costly and the requirement of soldering will add uncertainty to the resistance.

Drawing a section of copper track on my PCB seems cheaper and eliminates the uncertainly brought by the solder joint.


texts: loopback using arduino to check LAN port connectivity

texts:
is there any way that I can use Arduino to send data to the LAN port (oscilloscope) to see the link and activity light but without using internet.. or maybe some programming that related to loopback. This is because the loopback cable that I've made are not working on the oscilloscope and only works on the pc.

Btw, I'm not using the LAN cable that connects between the wall and oscilloscope to avoid any virus. If possible I would like a solution that does not use any connection to the internet but can make the green and amber light at the LAN port to light up.


texts:
I have a basic doubt about charge transfer between pixels of a CCD. Let's consider this animation (picture taken from wikipedia):

A precise time sequence of applied voltages between gates and bulk allows to move the charge between a pixel (represented by a MOS element) to the next one.
But this picture shows the semplified situation in which only the pixel at left has some charge inside (i.e. only that pixel has been excited from light). What would happen if all three MOS are excited with light? How can we distinguish (in the external circuitry) which pixel has been excited (and how much it has been excited) if their charges are mixed (since the charge of one pixel goes to the next one etc) during the transfer mechanism?


texts:
I need to build an active crossover circuit for my 2-way speaker design. I decided to use TDA2009 as my audio amplifier. TDA2009 is shown connected below in the picture. My question is: how can I modify the TDA2009 circuit to implement the circuit in the gray box?

I know that C10 and C11 are need for the DC battery to minimize noise as well as C1 and C2 (2.2uF). So these 4 capacitors need to stay in the circuit. What about C4 and C5 do I need them? or I just connect the high pass filter of the gray box directly to pin 8 and 4 of TDA2009 and the low pass filter directly to pin 10 and 2 of TDA2009? What do you think?

Finally I need it to be active filter that is my TDA2009 need to be placed after the filtering circuit (gray box).

Please I need your help concerning this. I came to this forum after weeks of research because I am really stuck.

Thank you for your help in advance :)


texts:
I have an old Protek P-3502C Oscilloscope that I picked up second hand from my school. It has proven to be a great way to learn how to use oscillocopes, and has helped me with diagnostics as well.

But for as long as I have had it, I have had no clue what a couple of things on it are.

The first off is a section labeled COMP. TEST It has a single banana jack, and a button labeled in and out. (see image).

The other thing is two holes on the botton labeled CH A STEP BAL and CH B STEP BAL. (see image) From what I can tell from this document, it keeps the line from jumping around when I vary the volts/div scale. Is that correct?

COMP. TEST Connection

STEP BAL Holes


texts:
I got a task of building pure sine wave inverter, and I wanted to simulate my circuit before building it. File is in link. Problem is that the simulation stops after few seconds with error message:
I tried changing mosfet models, but it didn't help... Any ideas?

WRONG SCHEMATIC:
http://fifi.starkom.eu/rahchat/uploads/1593790276.asc
EDIT:
Solution was exactly right, thanks for fast help. There is working Schematic (looking a bit better, and also added deadtime)
NEW SCHEMATIC:
http://fifi.starkom.eu/rahchat/uploads/1593842342.asc


texts:
I'm new to EE.  I've made my first schematic:
To explain my project: I have 1 Nichia E21A LED that needs to be powered by any 5V power bank and be user dimmable via a dial (potentiometer.) The PCB and LED will be housed in different modules.
This is a colour sensitive use so I need to keep the LED running 90% of current output to maintain colour temperature, thus needing a PWM for dimming.
I've wired up a TLC555, however I need help with the duty cycle. I need the maximum duty cycle to be around 45% when the dial is turned to max so that I have around 110 lumens.
How can this be done?
Additional questions:

A bit of a rookie question but I'm having a lapse in logic:  Are my components wired up appropriately to the 5V out?
Is running the LED at 700mA but having the maximum duty cycle around 45% going to yield temperature issues? The LED is  going to be worn near the face.
Is my inductor value okay?

P.S. As shown on the schematic, all of the passive components values are final except the 'Switching controller' and 'Pot. Setup'
Datasheet for LED driver.
Datasheet for TLC555.
Datasheet for LED


texts: What is this circuit? It's from Yorkville powered sub nx720s input circuitry.


texts: I would like to simulate the effect of noise in a circuit built in Multisim so that I can make better component choices to improve my design. The main source of concern for me is that the circuit will be affected by noise created by ambient sources of electromagnetic radiation since there will be IR LED/phototransistor pair in the circuit, where the IR LED will modulate a 20kHz square wave signal. Can anybody make any suggestions as to how I would do this?


texts: Ideally, what sort of characteristics should a transistor have for a regular linear amplifier?

texts:
Most of us recognize the graph of \$I_C\$ against \$V_{CE}\$ for different base currents (\$I_B\$): -

And, ideally (as we are taught and believe) we would prefer the "constant current" part of the graph to be as flat as possible but, if we had a free-hand in choosing the "perfect" characteristic (irrespective of whether it could be manufactured or not), would we choose a different shape to the plots above?

I'm only thinking about a linear class A single output transistor audio amplifier.


texts: Conditions for maximum power transfer in an AC circuit

texts:
So, if we're given the circuit below:

Known values are:
\$E_g=35 \ kV\$
\$f=685 \ kHz\$
\$\underline{Z}_g=150 \ \Omega\$
\$\underline{Z}_p=(200-j300) \ \Omega\$

We have to calculate \$L\$ and \$C\$ to maximize the power transfer to the load \$\underline{Z}_p\$.
Aside from the impedance matching condition: \$Z_p=Z_g^*\$, is there anything else that can help me solve this circuit?


texts: How to vary the voltage output depending on the changes in temperature?

texts:
I am working with the Siemens Logo8! PLC (0BA8 version) and the purpose of my circuit seems to be simple:

If temp > 25°C then output voltage = 8V

If temp < 25°C and >15°C then output voltage = 5V

If temp <15°C then output voltage = 2V

Is there a possible way in a circuit of doing this?

I achieved a similar concept by using one Analog Input, then 2 Analog Threshold Triggers connected to a latching relay and eventually to a Digital Output. (Picture attached) However, the limitations of that system is that Voltage can be either 1 or 0.

The concept behind the circuit seems to be simple but I am really struggling to make it work and any hints will be much appreciated.


texts:
I am struggling to find the bits which dont matter when I have a memory mapped system with several devices connected.

The memory map is given by

I need to figure out which bits I should pass to the address decoder and which bits are "Dont Cares".

I know the answer to this question is : A15 - A4 are the bits that matter and A3-A0 are dont cares.

Can someone post a step by step method on how to find these?

Thank you!

P.S. I wasnt sure where I should post this question, Feel free to move it to another stack site as you see fit.


texts: Design questions regarding LM2735 (boost-converter) for DC-DC

texts:
I'm doodling with a future circuit. The application (Commodore 64) expects 5VDC (which I will provide with a pass-through) and 9VAC 50Hz. I do not have any working circuit or a schematic, because the circuit does not yet exist other than as an idea, but I have this very crude block diagram:

original

The circuit is fed by an external power supply, with 5V@10A and 12V@10A. I can use whichever I want. Even both. Since I want 9VAC in the final step (~13V û), I want some headroom for the H-bridge. So I pick 18V. That's what I want the DC/DC to achieve for me.

I think I need isolated DC/DC, but I'm not sure. What I'm sure about is that the 9VAC needs to swing around 0V, so no DC-components or offsets on it. With isolated DC/DC, I'm hoping (yes, because this area is completely out of my league) that the 9VAC will look like any 9VAC wallwart would produce. At least, that's my goal.

The 9VAC is supposed to be able to deliver 750mA continuously, so I will design for 1A. Bonus is if I can manage to double it.

There's a lot of new things here for me, so I need to break things down to make them graspable. At this point, I will put the PIC/Bridge/LC aside for a while and focus on the DC/DC.

Questions:

I know MAX1523 will work here, but it's way too expensive. Will LM2735 (datasheet) be of any use for my design?
What part(s) in my block diagram are responsible for the maximum amps at the outputs? The DC/DC, the H-bridge, or both?
Flyback topologies seem to use a transformer for isolation. Datasheet for MAX1523 suggests using a dual inductor with ferrite core (to save space). If this sort of isolation is used, will the 9VAC output be of the type I want (no DC-offets, etc)?


texts: Precautions for powering up an old oscilloscope?

texts:
I have a Phillips PM3264 100MHz 4 channel analogue oscilloscope, I have not powered it up in around 8 years.
I have not been able to find a users manual, nor service manual as of yet, only a few pages of specifications from a brochure [pdf].

I am concerned that due to the time it has spent in storage, and the overall age of the oscilloscope that merely plugging it into mains and turning it on may not be the wisest plan of action. There do appear to be reports that the line filtering circuit can be problematic on these oscilloscopes.

If it is of any importance we have a mains ground circuit breaker (I was honestly shocked to discover that in some areas of the world it is not a legal requirement), and I do not have a variac (even so, I'm not sure that a variac would be the best idea at all). Mains power in the area is 240v at 50Hz, 240v is right at the upper end of the oscilloscopes power supply voltage range. I do not have probes for it at current, and I would prefer to at least get an idea as to whether it is still functional prior to purchasing probes given budget constraints, and location.

So, are there any precautions I can take when powering it up to prevent damage to the oscilloscope?


texts: Changing from 8 channel to 16 channel. Does change in voltage input affect upgrade?

texts:
I am going from a Numato 8 channel GPIO to a Numato 16 channel GPIO. The 8 channel I/O pins support 5V TTL signals but the 16 channel I/O pins support 3.3V TTL signals.

If the input to the I/O of the 16 channel GPIO is going to be 3.6V - 4.0V, will that be too high of a voltage to be able to use the 16 channel GPIO?

I posted this question on the Numato forum and put in a help ticket with Numato technical support but haven't received an answer.

Can anyone help me out?


texts:
I've bought a few 50MHz-6GHz directional couplers (SEDC-10-63+,) each for 75$. Here is a picture of this expensive coupler:

Unfortunately one of these couplers was not working from the beginning so I decided to take the cover off and get a glimpse of the insides.
The problem is I cannot understand what this big black component is (probably a ferrite,) what it does, and how it contributes to the coupling or directivity.
I also wondering if the cover is anything more than a simple cover. The top cover feels like a plastic but sounds like a ceramic object.
Coupler Inside

Cover

Update 1
What does this 1150 component do? connect output to the coupled port? Doesn't this decrease the directivity?


texts: Switching a sensor on/off; high vs low sided for low power consumption when connected to micro

texts:
I'm modding a PCB that has a CO2 sensor on it, powered by a battery (via a linear reg that also supplies the micro). The sensor is turned on and off to preserve battery power and the micro goes to sleep. I was surprised to see that the sensor has a permanent supply to it and ground is switched by the micro with an N-type MOSFET, rather than using a P-type MOSFET to switch its Vsupply on and off.

The C02 sensor is then connected to the one of the micro's UART's  Rx and Tx pins. I would have thought that the problem with this is that the micro could then provide a path to ground and be leaching current away as there is always power on the sensor's supply pin.

Am I unduly worrying about this?

Or, I'm not unduly worrying about this...if the pins were set as outputs and set high before sending it to sleep would that be the best way to minimise power consumption with the current set-up?

I would have had it high sided switching and set the Rx and Tx pins as GPIO pins configured as outputs with the pins being set low just before going to sleep. Is that a better way of doing it or am I overthinking this? (Or indeed just plain wrong?)


texts: Easily available alternative to anti static bags

texts:
I want to pack some electronic components, but I don't have an anti static bag. Are there any easily available materials that can be used instead.
Any frugal tricks ??
Thanks in advance.


texts: I am trying to design 9V-6.5A flyback SMPS using PI-Expert design tool. I used reference design to make flyback transformer. It gave maximum permissible leakage inductance of 16.38uH for design with ETD-29x16x10 core, but practically I got around 30uH of leakage inductance. Such vast difference between design value and practical value was not observed for higher voltage design say 15V,24V for same ETD 29x16x10 core. My analytical observation says.... Low voltage (High turn ration) -> High leakage inductance. It there theoretical relation for that????


texts:
I want to send a trig signal over a 9m cable, the signal is around 60Hz (each 15ms it sends a 1ms pulse). In order to avoid electrical interference I convert the 3.3V original signal with the following circuit:

I have a power supply of 24V available so this circuit is converting the 0 to 3.3V signal into 0 to 22V, my questions is: is it ok to send 1ms pulses using 24V or should I use a lower power supply of 12V? On the other side I have an opto-coupler and a current limiter of 10mA.


texts: STM32F103 timer behaves differently after hardware reset instead of st-flash reset

texts:
I'm learning to program the STM32F103C8 Cortex-M3 (on a BluePill board) and was playing around with the general purpose timers (TIM2 to TIM5) because I wanted to time some routines.

In my simple program I just set up the timer, set TIMx_CNT to 0 and loop until TIMx_CNT exceeds my target delay and blink a LED accordingly, to have a visible output. The relevant code is the following:

void setup() {
    /**********************************************************************
     ************************ Set up mcu clock ***************************/
    FLASH->ACR  |= FLASH_ACR_LATENCY_1;     // Set latency to 2 wait states
    RCC->CR     &= ~RCC_CR_HSEBYP;
    RCC->CR     |= RCC_CR_HSEON;            // Enable HSE
    while (!(RCC->CR & RCC_CR_HSERDY));     // Wait for HSE to be ready

    RCC->CFGR   |= RCC_CFGR_PLLSRC_HSE;     // HSE as PLL source
    RCC->CFGR   |= RCC_CFGR_PLLMULL10;      // PLL clock multiplier
    RCC->CR     |= RCC_CR_PLLON;            // Enable PLL
    while (!(RCC->CR & RCC_CR_PLLRDY));     // Wait for PLL to be ready
    RCC->CFGR   |= RCC_CFGR_SW_PLL;         // Select PLL as SYSCLK

    /**********************************************************************
     ***************************** Set up GPIO ***************************/
    // GPIOC configuration PC13, PC15
    RCC->APB2ENR    |= RCC_APB2ENR_IOPCEN;
    GPIOC->CRH  = 0x28200000;
    GPIOC->BRR  = 1 << 13;
    GPIOC->BRR  = 1 << 15;

    /**********************************************************************
     ***************************** Set up TIM3 ***************************/
    RCC->APB1ENR    |= RCC_APB1ENR_TIM3EN;
    TIM3->PSC       |= 1 << 11;               // PSC = 2048
    TIM3->CR1       |= TIM_CR1_CEN;

    /**********************************************************************
     ***************************** Call main() ***************************/
    main();
}

const uint32_t CYCLES = 39062;    // For 1sec on 1sec off blink

void main() {
    while (1) {
        GPIOC->BSRR |= 1 << 13;
        TIM3->CNT = 0;
        while(TIM3->CNT < CYCLES) {}

        GPIOC->BSRR |= 1 << (13 + 16);
        TIM3->CNT = 0;
        while(TIM3->CNT < CYCLES) {}
    }
}

To flash the board I am using the texane stlink utility.

After I flash the chip, the program runs fine, i.e. the observed blink frequency is the expected 0.5Hz. However if I then push the reset button, the LED no longer blinks (it is PWMing), and checking with the oscilloscope the blink frequency becomes 1kHz. Running the command "st-flash reset" returns everything to normal.

I've tried many things to no avail. I have also printed the TIMx_PSC register to a small GLCD and confirmed that even after the hardware reset the value is still 2048.

Also I know the APB1 bus is overclocked, but running it within spec doesn't change the observed behaviour.

Any help in understanding what is happening is greatly appreciated.


texts: Skin effect - resistance changes during DC/AC variation

texts:
I have a question about skin effect, skin depth to be exact.

Consider an AC system and a wire in it. Skin depth is, let it be, 0.2 radius of it.
We know that if it was a DC system, it would spread the current evenly and then the resistance would be lower than in AC system (according to  - bigger surface "makes" lower resistance).

My question is - is it possible to tell exactly how many times did the resistance decrease (comparing DC with AC)?


texts: Is there a color standard for painted toroidal magnetic cores?

texts:
Is there a color standard for painted toroidal magnetic cores ?

I noticed that yellow-white usually means a powdered iron core with a relative permeability of around 100 at frequencies below 10kHz.

What do the other colors mean ?


texts: Do thermal cutoff fuses wear out if used below rated temperature?

texts:
I tend to keep my electrical applicances alive for decades and have had several thermal fuses (the non-resettable axial kind) repeatedly wear out for no apparent reason, some of them in expensive devices from reputable brands. I know not to solder these things so I don't think I'm pre-stressing them when I replace them.
This is the kind of component I'm talking about: https://www.cantherm.com/wp-content/uploads/2017/05/SDF_JUNE_2016.pdf
Question: does the waxy stuff inside the fuse wear out at temperatures well below the rated temperature?


texts: I recently purchased an armax 230 ISOTRAN Model 1521. I can’t find it on the web anywhere, and from what I understand it is an isolation transformer that takes in 115 VAC and outputs about 210 VAC. (I’ve plugged it in and it does this) I’m wondering if it is safe to “play” with this device and try to make my own adjustable DC power supply from it. I am currently a Junior in college studying electrical engineering, but I have no experience with high voltages yet. Any advice would be appreciated.


texts: Can I increase my power output from my solar panel using a capacitor?

texts:
If I have a 3V, 70mA solar panel rated at max 210mW. If I design a RC series circuit with it, can I increase the power outlook to about 2W? If so, how can I determine the time it takes to charge? Also, how long will it take to discharge to get a 3V, 500mA output?
Below is an example of how intend to set it up.

simulate this circuit – Schematic created using CircuitLab


texts:
I am laying out a dual sided PCB, 1.6mm (62mil) thickness.  I'm wondering if I can drop a via on the feedline to a uFL connector and place another uFL on the other side.  Will this cause unacceptable signal reflections?
Additional info:
Design frequency is 2.4Ghz WiFi.  Board is a large LED sign (579mm x 186mm) which makes a 4-layer PCB cost prohibitive.  Because of this the feedline is not impedance-controlled, and it doesn't have a pi-network for impedance matching.  I understand that I can get away without impedance control as long as I keep the feedline very short.
Traces above ANT720 are RF grounds.  In addition entire area in brown box will be flooded with copper fill (GND) top and bottom, and stitched together with vias.  Traces that are visible are 0.5mm.


texts:
I want to make a circuit that turns on and off the light (LED) of a given time (eg. on 9 pm and off 6 am). I also want it to be adjustable.
My idea about the design:
I will be using an ATX computer power supply and 3 w LEDs. Control circuit is connected to +3.3 V or +5 V line for voltage conveniency. This part of the circuit will be responsible of opening the relay (switching on the light) at a given time of day and close it at a different time. It have to be adjustable, so I can change time settings.
The LEDs I'll be using is a cool white LED and a warm one, connected in groups like in drawing (one group being the same LED part).
Since the voltage of the LEDs is varying from 2-3 V I want to put 3-4 LEDs in serial, but I need to lower the voltage somehow (and regulate current?), because +12 V is too much.
(Cooling and heat sinks is no problem, I'll just connect fans to the +12V line and add a resistor.)
Summary:

Since the PSU is a switched-mode PSU, is the linear regulator not needed? How can I connect these LEDs in very safe and efficient way?

I don't think NE555 is the right IC for this project. The best thing would probably be to buy a micro controller (àla Arduino) and program it (I'd have to read up on that). Or do you have an idea of how I can make the timer circuit?

Should I use the Panasonic TX-S reed relay? I've also looked at TI TS5A3157, but I don't think that is what I need (The TI is an analog switch).

Archived: Old, messy design drawing, newest drawing below:


texts: I want to two range values into a function and the function should return the larger range of the two. Can this be done in VHDL? By range I mean things like "7 downto 0". I want to use the returned range in declaration of an unsigned type.


texts: In another question I asked about ways one might obfuscate the design of a system, to prevent unauthorized cloning. One suggestion was that IC manufacturers are often willing to put custom labels on their chips. The idea is interesting, but my quantities are low enough that this would not be cost-effective. How might one remove or otherwise render unreadable the labels on ICs?


texts:
I have some VHDL code that has the following signal definition:

signal hcount  : integer range 0 to 235;

This is used as a counter throughout my system (so I believe it needs to continue as an integer and not be declared as a std_logic_vector for example), but I also need to use its least 3 significant bits to index an eight-bit signal like this (which does not compile):

signal somereg : std_logic_vector(7 downto 0);
...
somereg(hcount and B"00000111") <= <a bit value>;

What is the most appropriate way to index the "somereg" vector above?

Thanks


texts: Are binary adder and parallel adder same thing? I couldn't find any information about parellel adder in my book. Does anybody have an idea?


texts: Fuse detection in a lithium battery parallel connection

texts:
I really need your help in order to figure out a solution to detect a blow fuse in a 16S parallel connection.
The issue is: Despite a fuse has been blown, the voltage at the other side of the fuse is going to be the same just because it comes from the rest of the parallel batteries.
I would really appreciate your help to figure out a solution to send a signal when a fuse has been blow.
This is my battery project and the PCB:
The circuit diagram:


texts:
I'm wondering how to size a power supply for DC motors.

I have a 70W 24V brushed DC motor [Linix 63zy24-70-A I picked up from a surplus store]. I intend to control this using a PWM/MOSFET. If 10 bucks is 10 bucks, 70 watts is 70 watts. However, thinking of the inrush current, I measured a resistance of 6Ω, so with 24V/6Ω = 4A, and therefore I might need a 96W supply. I haven't worked with DC motors enough to know if that makes sense (seems low, but maybe not). My bench supply has a current limiter that tops out at 600mA, so I can't test it.

I am more familiar with sizing AC motors to the NEC, which involve an inrush current of 6 (or more) times the full load current, and any motors which can't be run at a locked rotor current are usually given an overload protection of 115-125% of the FLC.

I would imagine that using an obscenely large DC power supply would work, but I'm hoping more experienced folk can point me in a more reasoned direction.

As an example, I'm looking into something like this:
https://www.digikey.com/product-detail/en/LRS-150-24/1866-3321-ND/7705015/?itemSeq=298448846

Edit:
Thanks for all your answers. I wasn't realizing how much effect the controller can have on the power supply requirements.

Below is what I am planning on making. The PWM signal will be from a 555, ATtiny or Arduino. The BJT is there to (hopefully) make that choice irrelevant.

More application details:
The motor is magnetically coupled to a pump, so high-torque is not reasonably possible. Flow rate is currently controlled manually using an ball valve on the output of the pump attached to a single phase shaded pole motor. I'm looking to change that.


texts: PCB from washing machine, is it damaged?

texts:
I have simple question. Is it normal that coil attracts black dirt as you can see in the photo? Components seem to be good?
Thank you
Lukas

(Bosch washing machine PCB: AKO 547021-11)


texts:
I have a couple of questions regarding using a precision voltage reference on a DAC - AD7545A.

I am trying to fix an existing circuit that uses AD584  to provide a 5V DAC (AD745A) to provide an Analog Output between 0 to 5V using a circuit design similar to this figure 4 on the AD7545A datasheet.

And then it is stepped up (amplified to 0 - 12V) with a high current opamp OPA548 to drive a load.

Now, my question is can I use AD7545A to provide the 0 - 12 V output without going through an extra space? I will have to replace the AD711 in the figure with OPA548 to drive the load, and also I will need a precision voltage reference that can provide a 12 V reference to the DAC. AD584 has only 4 programmable outputs - 10,7.5,5 and 2.5. What would be a good replacement.

Well, and the second question is, that in case I have to use the existing circuit, the application notes I found on the AD584 datasheet shows it giving a -10V reference to DAC using the configuration of figure 16.

I would like to give it a +ve 5 V reference instead. Is it as easy as as just connecting the +5V pin to the Vdd of the DAC, providing the 15V Vin to 584 and grounding the common?

Sorry, I tried posting the figures here, but as a new user I cannot post pictures yet.


texts:
I want to install Cadence IC6.1.7 (Custom IC / Analog / RF Design) and Mentor Graphic Calibre tools on RHEL 8.2 server. I want to make the following things work after the installation:

Circuit Design: Virtuoso Schematic Editor

Circuit Simulation: ADE-L, ADEXL using Spectre simulator

Layout Design: Virtuoso Layout Suite L, XL, GXL

Layout Verification: Mentor Graphics Calibre: nmDRC, nmLVS, xRC

Where should I find documentation to fulfill the tasks?
Thanks!


texts: LTC4440 boosting in LTSpice, but not in reality

texts:
I have a simple LTC4440-5 circuit in both LTSpice:

(R1 is just a load resistor, which isn't present in reality)

And here in the matrix, there's:

And:

(Note that a few parts are slightly different from simulation to reality: The inductor is a 5uH part, the diodes are both DB2W40300L shottkys, and the mosfet is an AO3400A. However, I can plug any mosfet and any diodes into the simulation and I can't break it.)

I have tried running at both 1mhz, and 100khz input frequency. In LTSpice, everything's peachy; in reality, I get no change from a floating gate.

Now, in the LTSpice simulation, I get this on the boosted gate pin:

And in reality, I get this:

The gate floats at ~3v.

The mosfet seems to be half on, as the TS/inductor pin is at 4v, no load.

I've confirmed that all the rails are as they should be; 5v VCC, 12v on the mosfet, etc. I've tried swapping out 4440s, tested all the diodes, changed input frequency, etc. Nada. I've tried to break the LTSpice simulation to get it to approximate the behavior, but I can't get it to not charge pump.

What have I done wrong?

EDIT: Okay! Now we're getting somewhere. With a 100r resistor as a load in ltspice, I get a nice and stable charge pump. With a 130r resistor in reality, I get a sick 5khz oscillation in the charge pump:

(And zoomed)

Which... certainly wasn't the behavior I was expecting.


texts: Is quantum tunneling in transistors patterned?

texts: Quantum tunneling is a problem when engineering a nano scale transistor. Generating random numbers is a common issue in computer science. I'm not an expert in either of these fields, but to someone who might be, does it seem plausible that one could make a random number generator that consists of a 50% reliable transistor? Or would patterns arise?


texts: Gaussian Function Fourier Transform (Matlab)

texts:
I am trying to write my own Matlab code to sample a Gaussian function and calculate its DFT, and make a plot of the temporal Gaussian waveform and its Fourier transform.

According to the FT pair:

\$ e^{-at^2} \iff \sqrt{\frac{\pi}{a}} e^{- \pi^2 \nu^2 /a}, \$

The FT of a Gaussian is a Gaussian, and it should also be a real function.

So here is my graph:

So, why is my FT a flat line instead of being Gaussian?

And why is it that when I plot the argument of the DFT, the imaginary part is nonzero? Shouldn't the FT be real?

Any help would be greatly appreciated.

Here is my code:

clear; clf; clc;
a=5;
n=50; % Length of DFT
k=[-n:1:n];

x=exp(-a.*k.^2); % Gaussian function

subplot(221);
plot(k,x);grid;
axis([1.5,n,-max(-x),max(x)]);
xlabel('Data waveform');
hold on; plot(k,x,'o'); hold off;

xx=fft(x)/n;
subplot(222);
plot(k, abs(xx));grid;xlabel('Transformed, magnitude');
axis([1,n,0,1]);
hold on; plot(k,abs(xx),'o'); hold off;

subplot(223);

plot(k, real(xx));grid;xlabel('Transformed, real');
hold on; plot(k, real(xx), 'o'); hold off;
axis([1,n,-1,1]);

subplot(224)
plot(k,imag(xx)); grid;
axis([1,n,-1,1]);
xlabel('Transformed, imaginary');
hold on; plot(k, imag(xx), 'o'); hold off;

figure(gcf);


texts:
Apologies if this has been previously asked and answred, I did search but found nothing that provided the answer:

I have an HP Envy8, that came with a power adapter rated Output: 19.5V 3.33A. I also have a loan of an HP Envy x360, for which I don't have a power adapter to hand, but know the rating is 19.5V 2.31A.

My question is: Can I use the higher Amp rated adaptor (3.33A) with the lower rated machine (2.31A) without possible damage.  (I have checked and the adapters fit).


texts: Need help regarding power source for a 60V BLDC motor

texts:
I'm mostly new to electronics and stack exchange sites. I'm developing a small, lightweight, real life car (2 seater) for my school project. It is going to be run by a motor. I've chosen a brushless DC motor rated at 60V 1000W. That means its current consumption should be 16.66A according to my calculation.

I've chosen 5 x 12V 7.5A Lead-acid batteries as my power source. When connected in series-parallel , it should provide 60V 37.5A if I'm not wrong.
My car should run for at least 1 hour continuously at max. speed.

Now, my question is, will the motor be able to run for that amount of time with this power source? I mean, will the battery be completely dead before 1 hour or can it run for at least that amount of time? I need much help regarding this calculation.

I've searched for solution to this problem everywhere. But I've mostly found nothing or I couldn't understand anything.

I'm new here, so please pardon my mistakes and I might not understand many technical terms. It'd be highly appreciated if you could keep the answers basic.
The image shows info provided by the battery manufacturer.


texts: How to select specific programmer from multiple when using flashrom

texts:
I have 4 CH341A programmers connected to my laptop. They are all connected to the same USB hub. Reading the content of a SPI EEPROM works fine.
How do I select the programmer (of these 4) to be used for reading/writing in flashrom?

At the moment having 4 programmers fulfils no purpose for me, because flashrom has its own ideas about what programmer to use.


texts:
Is there a standard way in which 3 state, 6 pin slide switches are connected? I haven't been able to find any schematic online.

Originally, I assumed that each pair of pins corresponds to the in/out ports of each of the switch's three states. Having the switch in one of these three states would then close the circuit between the two corresponding pins. However, I have discovered that this is not the case.

I can attach a picture of my switch, but I don't have a model number so I don't know if it would be of much use.


texts: What type of vintage semiconductor device is this? Is it an SCR?

texts: I found this circuit board from an 1980s old humidity controlled chamber. This definitely looks like a temperature regulator of some sort. It has a M logo which means made by Motorola. It has the labels E03G-3-9 and 8739. Does anyone have any info on what this part is?


texts: Is there such a thing as an ultra low power solenoid?

texts: I am looking for a tiny push-type solenoid that can be driven with milliwatts. The plunger need only move 2-3 mm. Does such a thing exist?


texts: 5Vor 6V operating DC-DC for mobile battery?

texts:
For mobile battery, what voltage is suitable: 5V or 6V?

What factor does influence on choosing different voltage for mobile battery?


texts: Supercap for Backup Power (10 hours Backup Time Min.)

texts:
I am using atxmega8e5 in a design and also utilizing its Real-Time Counter to act as a Real-Time Clock.

A lot of RT-Clock ICs can use a SuperCap to have backup power incase the device is unplugged or incase of power outage. Backup time requirement isn't huge: just a min. of 10 hours.

Is it possible to utilize a SuperCap to provide backup power to my MCU? If so, how would one go about it—what is the required circuity to switch from mains power to backup capacitor, and how would one charge it safely? The xmega8e5 does not have a dedicated pin for backup power and also lacks the 'Trickle Charge' capability of many RTCs.

Note: I am not asking about the various sleep modes. I am aware of them and will use them when the chip is using backup power.

If the required circuity costs as much as a RT-Clock IC, then might as well use that?


texts: Dynamically Configure FPGA From Host Program

texts:
I was wondering if anyone knows an efficient way to program the FPGA(PL) for a Xilinx Zynq-7 series or related devices,from a host C program (not on the SoC, but from the host PC). Is there an Xilinx API I can use/include in my program. As the only way I can think of doing it at the moment is invoking command line programming via Impact (which is not very elegant).

Basically I want to put the SDK "Program FPGA" functionality in my host C program where the user selects a prebuilt .bit file (and .elf file if possible) to program the FPGA/(SoC). This is just for a test of concept, later I would like to put this dynamic configuration onto one of the ARM CPU's.

Many Thanks
Sam


texts: Use diodes to obtain lowered DC voltage?

texts:
I am building a digital voltage gauge for my motorcycle for fun.  I am buying a nice little display which has common ground, so that I can provide 5 and 12 volts from the same source.  I was hoping to use a "7805" regulator to control the 5v, but do not want to provide the varying 12+- volts directly to the 7805.  I would like to drop about 7 volts before I apply the power to the 7805.  I looked at Using diodes to limit current to LEDs which seems to indicate that using diodes forward voltage drop is not a good idea for leds, and maybe using a zener diode is not either.  If I just use a series resistor, I would have to guestimate and experiment to get in the ballpark (as I don't know the current draw), and, as I understand it, the voltage dropped over the resistor would vary with the applied voltage.  Here are my questions:

Is using a diode(s) to drop the voltage independent of current a bad idea here? (Is it always a bad idea?)
Do I still get he same IIR loss for the voltage dropped whether it is a resistor or diode?
Is there a conventional "best practices" approach I should be using?
Lets go out into left field for a minute: other than heat-sinking the 7805, can I pot the whole mess with RTV silicon to vibration and moisture resist?

Always nice to know if the alternator is working OK.  Not an electronics guy, just a tinkerer.

Thanks!

==================================
Thank you Nick and Thomas.  I agree that a motorcycle is about the harshest environment one can choose-greater vibration, direct exposure to rainwater, probably greater variations in regulated voltage due to greater variations in engine (and so alternator) speeds. I had hoped to fuse and put the dropping resistor at the battery connection to provide the greatest protection for anticipated faults in the wiring run and/or the digital readout itself.  Based on your comments, I will fuse at the battery connection, run fine (#28?) wire to a MIC2945 and let it do all the voltage dropping.  I anticipate a mounting plate fastened directly to the 2945 heat sink, with the entire remainder of the assembly "glued" to the mounting plate with RTV silicon.  Waterproofing is a concern, for which I will rely on the RTV silicon.


texts: How to print in proteus console using the internal debug module on a CM3 device

texts:
how are you?. There are several ways to debug code in Proteus but I'd like to know another one that is shown in the CM3 help file of Proteus.
It has a section called "internal debug module" that has the following content:
In addition to source level debugging, model diagnostic messaging and other standard debugging windows, the Cortex-M3 module incorporates an internal debugging module which allows you to send messages to the ISIS simulation log from your firmware. This is implemented as a single read/write register (at address 0xFFFFFF00). the user would write some text to this address with a trailing zero and the text would then be displayed in the simulation log window.
Typical Usage:
#ifdef TARGET_PROTEUS
void print_str(const char* s)
{
    char* dbgout = (char*) 0xFFFFFF00;   // Addressing the debugging module
    while(*s)
    {
        *dbgout = *s;
        ++s;
    }
    *dbgout = 0;                         // Trailing zero – required!
}
#endif

I've tried several times to use that feature but the simulation is aborted by bus error or it gives a hard fault as soon as the function defined above is called and executed, I'm using a STM32F103C6 in the simulation. The first thing that I need to clarify here is that the STM32F103C6 doesn't have that memory position (it is internal to proteus) and last I'm compiling the program with STM32Cube IDE.
What I wish to know if someone has used this proteus feature and in afirmative case then if it only works with the Proteus internal IDE or it can be done from any compiler since the other compilers dimension the memory in function of the selected microcontroller.
NOTE: this question is only to know an additional way to debug a program.
Thanks in advance for the help.


texts: Photodiodes: Measuring Low Optical Power vs Dark Current Contradiction

texts:
Taken from: http://www.geni-uv.com/download/products/GUVV-T20GD-U.pdf
I'm trying to do some estimates here and I've run into something that seemingly doesn't make sense. In the table above, it states that the photocurrent is 14.7uA at 1mW/cm^2. To estimate the photocurrent at 10uW/cm^2, I scaled down that photocurrent to get 147nA. But 147nA is getting close to the dark 90nA current that is listed.
Yet, the minimum optical power source range that this photodiode is recommended to be used at is 1nW/cm^2 which is way, way below the 10uW/cm^2 that was being used in the estimate above.
Also, note that this is a huge 6.894mm^2 photodiode, yet 10uW/cm^2 doesn't seem like it should be an unreasonably low optical power to use such a photodiode at, but you can see from the estimate above it is already approaching the dark current.
Am I misunderstanding something?


texts: Where does this resistor appear in my nodal analysis? [BJT small signal analysis]

texts:
Here is my small signal circuit of a PNP common base amplifier with a resistor Rin at the emitter, Rl at the collector and a voltage source Vb at the base. Here is my large signal circuit:

simulate this circuit – Schematic created using CircuitLab
Here is my small signal equivalent.

simulate this circuit
Normally, this is an easy nodal analysis without the emitter resistance but i'm lost with it. Since it is connected to both nodes Vx and Vy, how would that even go? I think one of the currents leaving node Vx would both go through rpi and Re is that right? So that means rpi and Re would add up? But how about for Vy? Does Re matter for Vy or its just gmVx?


texts: Reducing voltage drop over 7805 regulator?

texts:
I have several projects (clocks) that require 12V and 5V supply. The 5V is for TTL ICs and the 12V powers a SMPS(Switching Mode Power Supply) to give HV(High Voltage) for a tube. The 12V pulls less than 100 mA, the 5V about 400 mA. The power source is a 15V 1A wall wart.

For my first project, I wired both the 7805 and 7812 with heatsinks to the 15V supply. The 7805 heatsink got to around 43.3C (110F). After the first build, I discovered the the heat produced by the 7805 depends on the voltage drop, and the current drawn, and I want to reduce the 10V being dropped over the 7805.

For my 2nd build, I was going to wire the 15V to the 7812, and run the 7805 off of 12V instead of 15V (giving 7V drop instead of 10V). I was wondering if there was a more efficient way to do this? Maybe using a Zener diode, or a voltage divider? I already have the 7805 and 7812 soldered, as well as the output caps, but I haven't soldered the inputs yet.

For the next clock, I am open to suggestions for using other regulator ICs.


texts: What is the filter and the transfer function that shown below?

texts:
May i know above is below to which type of filter?
is it a low pass filter?
and what is the transfer function for the circuit, may i know the step to drive it?

Thank you


texts: How do I use a PLL to multiply the input frequency by an irrational number?

texts: For integer multiples, I can use a frequency divider after the VCO to get a multiple of the input frequency. But how do I multiply the input frequency by an irrational number, say \$\sqrt2\$?


texts: Transformer with different kinds of loads

texts: How does the variation on the kind of the load of a transformer affects efficiency and regulation? If I use a capacitive load, will the efficiency be greater or lower than if I use a common inductive load?


texts: Having trouble to identify this capacitor, not for its values but its specifics. They're all being used in the AKAI reference series. This particular photo was taken from the power supply board of the AKAI AT 93L.


texts:
I was trying to make a sort of UPS circuit with a 12V DC 5Ah power supply and a 12V 5Ah seal-lead battery.

My question is that I don't know how to switch quickly from line supply to battery. I've tried a relay but while switching, power goes down and then up.

The load on this line consists of a microcontroller and an LCD display (1Ah 5V DC). What can I use instead of the relay?

Here is the schematic:


texts:
I am a bit confused with the implementation of a microstrip line to an u.FL connector. In order to maintain a 50Ohm line, the trace width would need to be ~0.1 inches wide, I have a pi matching network for 'just in case' implemented in line with the u.FL connector. Where I get confused is how would you do microstrip to something like a 0402 package resistor? Is this where co-planar wave guides perform better because they match up to component packages better? I would have to image a lot of reflection would occur hitting a component so much smaller then the trace width?

Also I have wondered this for a long time, and never found a good answer. For a very short run in terms of wave length, such as 1% the wavelength, is trace impedance control needed? My evidence for this though is the following:
$$
Z_\mathrm{in} (\ell)=Z_0 \frac{Z_L + jZ_0\tan(\beta \ell)}{Z_0 + jZ_L\tan(\beta \ell)}
$$

For a short wavelength say 1/100 \$\lambda\$, the equation becomes for following:
$$
Z_\mathrm{in} (\ell)=Z_0 \frac{Z_L}{Z_0}
$$

My antenna to be plugged into the connector is 50Ohm, so I believe that would be the load? or would \$Z_l\$ actually be the trace impedance?

The reason I ask is that I am basically running from a GSM modem to a u.FL connector, and It would be very easy to run a trace with ~100ohm impedance (using co-planar wave guide) instead of a huge wide 0.1 in trace for micro-strip.

update:
Since it was asked, my frequencies of interest are L1 GPS (1.575GHz) and GSM spectrum (800-2100MHz).


texts: Homework: AC circuit analysis correctness equations using nodal analysis

texts:
I've been struggling to find the equations needed to find \$V_o\$ and \$I_o\$ for the circuit given below. I came up with the following equations using nodal analysis and wanted to ask whether they were correct or not:

$$V_1: -2A \angle 0º + \frac{V_1}{-j} + \frac{V_1-V_o}{1} + I_o = 0$$

$$V_o: -\frac{V_o-6\angle-90º}{1} + \frac{V_o}{1+j} + \frac{V_o-V_1}{1} - I_o = 0$$

$$V_1 + 12\angle0º = V_o$$

Any help is appreciated!

EDIT: After solving the system of linear equations I got the following results:

$$V_o = -16-20j$$
$$V_1 = -4-20j$$
$$I_o = -30+4j$$

Don't know whether these values are realistic or not


texts: Solving RC filter by differential equation

texts:
I'm trying to solve the differential equation of a simple RC filter. What i got so far is:

$$CRV'+V=V_0\sin(\omega t)$$

Solving i get:

$$V == \frac{V_0 \sin(\omega t)}{1 + R^2C^2 \omega^2} -  \frac{RCV_0 \omega \cos(\omega t)}{1 + R^2C^2 \omega^2}  +c_1e^{-\frac{t}{RC}}$$

Can someone please help me understand how to interpret this with the usual concepts of reactance and impedance?

simulate this circuit – Schematic created using CircuitLab


texts: Should I use a voltage regulator on a desktop computer?

texts:
Should I use a energy regulator on a desktop computer?

I would like to know if I should use an energy regulator on my desktop, since I live in Brazil northeast region and I'm not sure about the quality of local electricity.

I'm asking because I've read some articles around the web telling that electricity regulators shouldn't be used at all, because they are useless and even destroy the equipment which are connected in them.

My goal is to preserve the equipment, so that they last longer and I could prevent equipment losses.


texts: Altium Designer: How to tell the auto router not to place vias too close to other components?

texts: My team is designing a very large PCB in Altium Designer (about four hundred 0603 components) and are using the auto router. The issue we're facing is that the auto router is placing some vias too close to other components (surface mount components, headers, etc.). Is there a way to configure the auto router not to set vias too close to other components?


texts: Why is it necessary to isolate MCU from the PoE part of the board?

texts: MCU is usually connected to a PoE controller via I2C interface. Most of the relevant documents show that I2C should be optically isolated in this application. What are the reasons to have such isolation?


texts: Send integer values through serial communication in PIC to PIC?

texts:
I need to pass integer values from one PIC to another through serial port

for char I can use the following code

char data1='a';
TXREG=data1;
while(PIR1.TXIF==0);

but when I try to pass int type variable it returns an ASCII equivalent..

Is there anyway to receive the data as integer instead of char type?


texts:
IKEA's LED drivers use cables with connectors that seem to be identified elsewhere as "mini AMP".

The socket appears to be a 6mm square, with a ~1mm wide and ~0.5mm high groove opening at the bottom centre and a 2 mm wide x 1 mm high rectangle in the upper right corner to ensure proper orientation.

Upper side of the connector has free space on one side which allows it to mate to the socket.

While I can find many examples on European websites, including Amazon, I can't seem to find anything similar in North America. Does someone know a standard name for the connector type in question?

By repeated searches, I've managed to find that "Dupont L813 male" is sometimes mentioned as well.


texts: Analog circuit design(amplifier with BJT) with abstraction(model)

texts:
I tried to cascade two circuit consisting of BJT transistor : Common Emitter stage, Emitter follower.
I do abstraction like belows, which means you just need to know only each unit block one by one and when you cascading these blocks, then whole system does sort of cooperating all blocks's function (like LEGO blocks, it might also called 'decomposition' or something).

As you know, each circuit has Input impedence, Output impedence, Voltage gain.

I want to know what relations each properties have when cascaded.

For example, I can guess that (Av_total) = (Av1) * (Av2).

But, what about Rin_total and Rout_total ? Are they related with Rin, Rout of each block, saying parallel connection of each Rin or something?


texts: Distance considerations between analog output and ADC input?

texts:
I have read about distance limitations of timing critical signals like communication over SPI.  In order to get more distance between my Pi and my sensor I am considering using an analog sensor and an ADC.

Question:
What should I know when considering the distance between my analog output and my ADC input?  I am, at the moment, considering the impact on:

Linearity of sensor output and ADC readings
Delay between sensor output and ADC reading

Details:

Sensor output voltage: 0.25 to 4.75 V
ADC input voltage: 0 to 5 V
I hope to sample the sensor output at 50 kHz (seems a bit fast and too fast for SPI over a 1m distance)
I'm not really sure how to calculate the amperage the ADC will draw from the sensor output.
Sensor.
ADC.

Insight and references are welcome!

Edit:

I think a minimum of 8 significant bits is what I can work with.  With a 500 unit range that's a measurement of 1/(2^8*500) = ±2 units.


texts: current source with high resistance load

texts: what happen if the load is a high resistance ( let's say 100K )


texts: Help me understand the relationship between positive, negative, neutral and ground in AC and DC

texts:
This question stems from notations on schematics and seemingly conflicting information I'm seeing. I suspect that I'm seeing different vernacular for the same concepts--but I'm in a place where no one's ever told me that an "elevator" is a "lift". Then again, I may have the concept completely off, and need to be schooled so I don't blow up my workshop. :)

With DC: Batteries have +/- terminals. Most schematics I see show the circuit with voltage in and ground. I've heard that most schematics don't trace the return path to the negative terminal because that's understood and it doesn't need to clutter everything up. I've also heard that on a DC circuit, ground is SYNONYMOUS with the negative terminal. On schematics, I've seen V-in and ground, I've also seen V-in, ground, and a separate trace connecting to the negative terminal.

Then, we move to AC. There's a hot wire (positive), a neutral wire, and ground. I ~assume~ that in an AC circuit, positive correlates to positive, neutral to negative, and ground to ground. Transformers will correlate the +/- when changing DC.

What are the facts and what are the myths? How can I tell if I need to ground something to earth vs. "ground" to the negative terminal? When do I ground to the chassis of my device? Are there standard conventions in a schematic that would indicate GROUNDED ground vs. return-to-the-source ground? Or is that something you know from experience and doing an analysis of the circuit? Is it generally safe to assume I can connect ground to negative? Or are there cases in which that would be a Very Bad Thing, and how do I identify those cases?

Just trying to wrap my head around +/-/ground in AC vs. DC, and how that voltage is used...


texts: electronically efficient breadboard wiring

texts:
I have checked stachexhange for my answer, but no luck. I hope I can be helped here.
I am building ben eater's 8-bit, and have a general question about wiring: Is it better (less impedance/resistance) to use ONE long jumper with bends, or should I use NUMEROUS as-short-as-possible jumpers to connect the end points?

example 1, in wiring ground and Vcc from one side of an 830 point BB, would it be better just to directly connect ground on one side, to the ground on the other side (same for Vcc)? OR would it be better to connect a small jumper from ground to column 1A, then another small jumper from column 1E to column 1F, then finally from 1J to the ground on the other side (and an analogous wiring scheme for Vcc). Ie one long bent jumper, versus multiple short straight jumpers?

Example two: (direct/bend) In connecting pins on chips from one BB to another is it better to use one wire between those chips, and bend the wire to accomplish this? OR (incremental) Would it be better to connect the pins on chips from different BBs using the incremental method as described above? Again, one long bent jumper, versus multiple short straight jumpers?

Any info would be helpful. Thanks to all of you in advance. Best...


texts:
I have a phenomenon which creates (small) displacements of charges (that I cannot quantify for now, this is the main problem, let's say that the charge surface density will be the same as when you rub an inflated balloon against your hair), and I want to measure it. My idea is to use a small capacitor (0.1 pF) which will store the displaced charges, linked to a precise oscilloscope. I need the oscilloscope to be interfaced with my pc hence someone advised me to get one on picotech.com. I guess I most of all need a very sensitive oscillo, which will be able to measure very small voltages. And I guess I need the smallest capacitance possible because of V = q/C.

What do you think of this approach ? I'm sure there are effects that I didn't take into account (I'm a mathematician, beginner in electronics), and could someone advise me which oscilloscope I could buy, please ? My budget is up to 400 euros. Thank you !


texts: Size of Decoupling Capacitors in Digital Circuits

texts:
There are plenty of questions about how to size decoupling capacitors in digital systems, but I have not found the answer to my specific question.

They are some capacitances that are usually put externally in circuits with MCUs or other digital circuits between GND and VDD. Their main role is that of reducing the power supply fluctuations. One of these kind of fluctuations is the so called ground bouncing, which is the drop of the voltage supply on the parasitic resistance of the supply line during the instants in which transistors absorb more current. It may be seen as a drop of VDD, or a rise of VGND, as shown in this graph.

I have seen in some datasheets (and the same has been written in some other questions) that usually they are chosen with 0.1uF capacitance (and surely not more than 1uF). But I do not understand the specific reason of putting this upper bound. I understand that their capacitance must be quite high (high capacitance = high smoothing effect), but why do we stop at 0.1 or 1uF? Why not 10uF, 100uF, ideally infinite F?

For instance, in stabilised DC voltage supply, I have always used (in parallel, after
Graetz Bridge and before the voltage regulator) an electrolytic capacitor of 15.000 uF, and its purpose was, at least conceptually, similar to that described before.


texts: Controlling power to a resistive load with AC

texts:
I have AC on an input (110V, 15A) and need to control the amount of power going to a purely resistive load.

Thyristor controlled by PWM seems like an option, but are there other/better ways to do this?


texts:
How can I solve this question?
In the circuit below, the n-channel MOS device operates according to the equation:
i(D)=K(v(GS)−vT)^2,
where K is 9.2 milli-siemens per volt, vT is 0.5 volts. The values of R1, R2, RS and RD are 657, 328.5, 11.6, 11.6 kilo-ohms respectively. Solve the circuit and arrive at the operating point of the MOS device. What is the value of I(D).


texts: STLINK V3 and Signal Integrity Considerations for a Debug Connector Which is Not Near the Processor

texts: We have a target designed to use SWDIO SWCLK SWO (and NRST). We have to move this connector to a location 6 inches away from the STM32F uC. I cannot find any documentation about signal rise and fall times.  Do I need to be concerned with signal integrity issues like matching trace impedance to ribbon cable impedance and using any series termination? Does anyone know of a document that addresses these concerns? I could not find any relevant material in the STLINK V3 documentation.


texts: Can Type-C device be configured as "Sourcing Device" without Power Delivery protocol?

texts:
I'm designing a device, that will be connected to various Android devices with either microUSB B or USB C receptables (in order to make it futureproof) and will be exposing some irrevelant ICs to the phone via USB 2.0 OTG. The most crucial thing however is that my device should be able to charge the phone while attached. I have learned, that with microUSB B the ability to charge while connected to OTG depends heavily on the phone itself. Some phones require specific resistor on ID pin pulled to the ground (e.g. Samsung Galaxy S3, Galaxy Note 8.0 - AFAIK they jump to one of docking modes, that orders them to accept power and be USB host at the same time), some do not require any resistor, but instead attaching the power source to the OTG cable before plugging into the phone (e.g. all Xiaomi phones I tried) and some didn't work for me at all (e.g. Samsung Galaxy S5 - has anyone succeded?).

For now I think of just simply putting two receptables in my device, both microUSB B and USB C and make either of them disabling the other on connection. The idea for microUSB B is that I will use 5-wire microUSB B plug - microUSB B plug cable (possibly custom, found only 4-wired so far) to be able to manage ID line connection to ground with some digital resistor on my device (the device will be configurable).

But the real struggle begins with phones that have USB C connector. I have read some documentation and found out that the decision about setting host and slave in USB C - USB C connection is made based on CC pin pulling up/down with specific resistors. The same resistors also seem to resolve power delivery roles.

My question is: do I have to use USB Power Delivery protocol (so a specialized IC) in order to achieve a state in which the slave (my device - UFP) is powering the host (phone - DFP) or is it achievable with some pulling resistors setting/swapping?


texts: Is there a reason phase information isn't given for RF wideband amplifiers?

texts:
I have an application where I would like to amplify a HF signal (25 MHz) by around 20dB.  The signal can't be inverted (it sits within a PLL loop where the phase is important).  I considered building my own, but then I figured this component ought to be fairly common and will be much better than anything I'd build myself, with everything on a small die.
I checked the datasheets of many wideband mmic amplifiers offered by my local distributor and I noticed that none of them actually said whether the amplifier was inverting or not.  I suspect that most are based on some kind of collector feedback arrangement (common for RF amplifiers) but I can't be sure.  That would make them inverting.
None of the datasheets I examined offered non-inverting as a distinguishing feature, so I'm wondering if I'm missing something obvious?  I realize I could cascade two low attenuating amps together, but that's a bit of a pain.  A quick search on the internet threw up the NE5205, but like many RF components it seems to have gone the way of the dodo.  Is there a reason phase isn't important or relevant in RF wideband amps and what do you do when you require a non-inverted signal?


texts: My application has a max Amp draw of 56@24Vdc, if I use a Circuit Breaker that is rated 60A@48Vdc, will it "trip" 60A@24Vdc? If not, what do you suggest?  The Minn Kota MKR-19 Circuit breaker is rated 60A@12/24/36V how is this possible (Ohms Law)?


texts: Why are the pinouts of LPC21xx all over the place?

texts:
I am working as a winter intern at a robotics company. My job is to assist the lead embedded developer in... whatever he wants my assistance in.

About a week back, I was handed a NXP blueboard with LPC2148 on it. Although I loved the more processing power (compared to the ATmega32s I had been working on), I found something very odd about the ARM7 based controller. If you look at the pinout here

you would notice that the port pins are just all over the place. In the AVR series everything is arranged cleanly with all the port pins together. Why is it not so in the LPC21xx? I cannot find any logic at all, they are not arranged by pin number or by functionality (like all the JTAG pins together). It seems like the designers just stacked the pins in a random form.

Can any body please explain the reason behind this?


texts: Undriven element when connecting coax to ground?

texts:
In playing around with some RF beacons I noticed that there is generally just one driven element, with the other elements connected to ground if present. I'm having some trouble wrapping my head around this idea, for example, when connecting a simple transmitter to a half wave dipole one element would be driven and the other would always be connected to ground.

This is contrary to how I believed radio waves were generated, that is, by having alternating currents in different radials. Other designs have a transformer on the output with the secondary connected to the antenna. This makes a whole lot more sense since both elements of a dipole are then driven. So my question is, does it really make a difference if both elements are driven or if one is simply connected to ground and the other swings around it?

This might be where the balanced/unbalanced thing comes in, which I've never been able to wrap my head around?

Something like the Pixie 2 Transceiver for example, which seems to be fairly popular among the DIY QRP crowd.


texts: How does Quartus pin planner know about voltage in each I/O bank?

texts:
It is possible to specify a range of I/O standard options in Quartus pin planner. I am trying to understand a few things:

How does Quartus know what voltage is supplied to each bank?
Why does Quartus give a long list of I/O standards for each pin and not limit them based on the supply voltage for that specific I/O bank?

Also,

What is the difference between "3.3V LVTTL" and "3.3V LVTTL (default)" in the pin planner?


texts: Can anyone here help me build a capacitor?

texts:
Here's the project: I'm building a capacitor by hand to essentially measure the permittivity constant. I am doing so by building a capacitor of known dimensions, setting up an RC circuit and plotting the cap. discharge. With the known resistance, the cap. should discharge according to the model

V(t) = V0e^-t/RC

where V0 = the battery voltage (i'm using a 1.5V Dcell), R = the resistance of the circuit (i'm using megaohm resistors - between 3-22MΩ - i have 10 of each), and C = the capacitance = KEA/d where K = dielectric constant (3.85 for paper), A = plate surface area, d = distance between the plates (im separating the plates with paper but may try other materials) and E = the permittivity of free space.

I'm measuring v(t) with a program called logger pro. It basically does exactly what i need; it plots voltage over time.

So here's my problem. I can get everything to work perfectly with a pre-built capacitor. The circuit works, the resistors work as predicted, etc.

But when I hook my one of my many attempts at a home-made resistor (one in which i can actually know the dimensions), I start seeing really weird things.

I hook up the cap. to the battery, and the voltage across the cap goes up to about 1.5V so the cap is storing charge. But as soon as I disconnect it from the battery, the voltage drops instantly. Then rises. Sometimes it rises to a voltage greater than 1.5V! It goes through these really random curves. Keep in mind, at this point, the circuit isnt even completed! its just a cap with a voltage meter and open wires!

The actual circuit design has resistors on a switch so that I can charge the cap, flip the switch, and once the switch is flipped, current flows through the resistors and i can track the discharge. Whenever i try that, again i see really random patterns. As soon as i flip the switch, the voltage across the cap drops into the negatives, then starts gaining voltage, and even gains positive voltage!

I've tried a few different cap designs, but i think I'm clearly missing something. My current model has two small strips of copper tape across a piece of paper. I made sure that the copper sheets are not in contact, and since there is a voltage across the cap, it must work.

I've also tried aluminum foil sheets over paper; similar results. but again, the curves and voltage fluctuations are different every time.

Can anyone think of solutions? Perhaps a better cap design, or a better circuit design?

thank you guys so much! again, i dont know if this really belongs on this forum but i appreciate any help u guys can offer!!


texts: How to use reed switch to change operating modes?

texts:
I have a circuit of LEDs - say L1-L10.  My requirements:

No visible switch
Illuminate the LEDs successively (only ever one at a time) every time the user passes a magnetic "wand" over the switch.  (Mode 1-10)
Using the same "wand" permit the user to set the circuit to an automatic mode whereby an LED lights for a few seconds then the next, etc.  Again only one LED at a time.  (Mode 11)
Permit the user to turn on all LEDs simultaneously.  (Mode 12)
The circuit should remember which Mode was last enabled when reactivated.
Battery operated 9V.

I've seen kits advertised with this type of feature using a reed switch.  Thus far I've been unable to locate any information on how such a switch is used to change modes.  Can anyone help me find out how this is done?


texts: Does the temperature of a processor influence its energy consumption?

texts:
I don't have a very strong background in physics and electrical engineering but just from knowing that the major or basically all energy consumption of a processor comes from switching its transistors and from the the electrical resistance, which is very high I would say as a processor is basically a very thigh cable at very low voltages and very high currents, and that the resistance and hence the wasted heat is lower at lower temperatures, I would conclude, that a processor in a cooler environment also consumes less energy.

This also leads to another other question: assuming that a CPU has a specific power consumption at a specific level of utilisation, would the power consumption be much more than twice as high at "double" utilisation (although this is hard to define in practice) as the overall temperature would increase and the same "work" would lead to more energy loss due to more resistance?

To give a short background on the question: I was wondering if my notebook battery life lasts longer if I'm using it outside in the winter for example. Of course this is hard to answer as there are many other factors like the behaviour of the battery itself at different temperatures and the display, but this has lead to the basic question described above.


texts: How does a switch's series voltage affect discharge time in a relaxation circuit?

texts:
I made this relaxation oscillatory circuit in LTspice using a voltage controlled switch (sw) that switches off at \$ 100V \$ and back on at \$ 50V \$. To the left, the sw has \$ V_{ser}= 0V \$ series voltage and it takes the capacitor \$ C_1 \$ approximately \$ \approx 0.7ms \$ to hit the drop-out voltage at \$ 50V \$. The math confirms the discharge time I measured in the LTspice trace:
\$ V_{d} = V_{c}* e^{-t \over R_{th}C }  \$
\$ t = -\ln {V_d \over V_c} R_{th}C_1 = -\ln{50V \over 100V} * 10^6 * 10^{-9} = 0.693ms \approx 0.7ms\$
where \$ V_d \$ is the drop-in voltage and \$ V_c \$ the cut-in voltage. \$ R_{th} \$ is the Thevenin resistance the capacitor sees - that is, \$ R_2+(R_1||R_{on}) \approx R_2 \$.
Now if I add a series voltage (\$ V_{ser} = 20V \$) to the switch sw (schematics on the right), I spotted no difference in the charge-up time but a significant increase in the discharge time (\$ \approx 1ms \$. I don't understand either case.
If the capacitor starts discharging at \$ 100V \$ and there's this series voltage of \$ 20V \$, the capacitor is effectively discharging a \$ 100V - 20V = 80V \$ of initial charges. The capacitor should then hit the drop-out voltage quicker than that without adding the series voltage in the switch.
\$ t = -\ln {V_d \over V_c} R_{th}C_1 = -\ln{50V \over 80V} * 10^6 * 10^{-9} = 0.47ms \$
But the simulation gives \$ \approx 1ms \$
How does the switch's series voltage affect the relaxation circuit - specifically, why does it increase discharge time, whereas the charge-up time seems not to be affected?


texts: I thought that the ground was different from “earth”!

texts:
According to Paul Scherz in his Practical Electronics for Inventors, he mentions in Chapter 2, Theory, the following:

  Typically, the earth, with its infinite charge-absorbing ability and net zero charge, acts as a good point for comparison. It is considered the $0-V$ reference point or ground point.

I thought that ground in any circuit was a point in the circuit with respect to which other voltages were measure. And it was literally the connection to the earth (for safety purposes in house wirings, etc.) that earth meant.

But the text suggests that I’m wrong.

I just want to know what is correct.


texts: Finding the number of bytes written in a larger array

texts:
How can I read the total number of the bytes written into a larger array?
For example if 10 bytes are written in a uint8_t array[100], how can I check if the written bytes are 10 and not 20 or 80 or 100

Since sizeof(array) would give us the total number of the array (100 bytes), we cannot know how many bytes are actually written in the array and how many array cells are empty.


texts:
I want to add a relay or transistor, what fits the need best, to a simple switch, so I can control the switch by a micro computer but also keep the already installed switch so I can still operate the mechanism by hand.

Here a little sketch of what I thought of (sorry, I'm new to electronics so forgive me if this is a dumb question :D)

(on the left side is the current situation and on the right side is what I thought of, the blue box is the "electronic switch" (transistor, relay, ..), I didn't add its control wires to keep the sketch simple.

As long as the "box" can handle the load this should work, right? Am I missing something here or is it safe to start building?

Edit:
I'm thinking of 2 scenarios here:

1st: Add a remote controlled power button to my pc (since it's a small DC a small transistor would be enough). Of course I would have to turn it off again after a few milliseconds.

2nd: Add a relay to a light switch (230V AC), but here I could have the problem winny mentioned (if one switch is on, the other one cant turn it off), so this wouldn't be the first application to start


texts: How to cut a nano SIM out of a 8-pin SIM?

texts:
I have a 8-pin SIM, which I want to cut into a nano SIM (which only has 6 pins).
Looking at the Wikipedia X-Ray image,  I assume I should cut the lower 2 pins.

Is this correct?


texts: Determine the value of Ic (sat) and the value of Rb in a simple circuit

texts:
I need help with my homework I do not understand how to find the resistance for the Rb in the for this problem.

simulate this circuit – Schematic created using CircuitLab

Here is the question:

In this circuit, the transistor has a gain of 80 and a voltage Vce (sat) of 0.1V Rb is adjusted to have a transistor saturation. Determine the value of Ic (sat) and the value of Rb. Vcc=25V

I found Icsat with the following calculation.

Since the voltage is the same in parallel circuit I know that Vin = Vcc

Vin -Vcc-Vce(SAT)=0

25-RcIc-0,1=0
25-220Ic-0,1=0
-220Ic=-24,9
Ic=0,113A
=113mA

Now the second steps us to find Rb how can I do so?


texts: What is the best way to connect two decoupling capacitors to an MCU?

texts:
I was watching an STM32 PCB layout video by Phil’s Lab. At 1:55:19 he routes the traces between the STM32 MCU and the two decoupling capacitors. Here is a screenshot:

He goes on and recommends to always connect decoupling capacitors like he did (from the MCU pin, into the two capacitors, and only then into 3V3), in order to maximize filtering.
My question now is whether this indeed is a better way to wire up decoupling capacitors when compared to this layout:

I know that the closer the decoupling capacitors are to the MCU, the better. So in the end the answer might just be, that the routing solution that results in the shortest traces between MCU pin and decoupling capacitor is optimal?


texts: Making a replacement 5V reference g sensor

texts:
I'm looking to make a replacement G sensor for a vehicle for which the sensor is no longer available. Here is some background on the system.
The Gravity (G) sensor is a vertical low-g (gravity) acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the powertrain control module (PCM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition the PCM misfire detection diagnostic will be deactivated.
The G sensor at rest output should be between 2.35V - 2.65V (+1g). During a rough road condition the voltage output can vary between 0.5V (-1g) and 4.5V (+3g).
What could I use to replicate this? I've attached a wiring diagram as well.


texts: Can't get this schmitt oscillator to work...did I goof somewhere?

texts: Below is my attempt at a schmitt oscillator circuit that uses a 74HC14 and lights up three LEDs in sequence. I built it on some breadboard, but nothing lights up. I'm really at my wits end...can anyone tell me where I went wrong?


texts: How to find properties of time varying voltage?

texts: I need to find amplitude and phase angle of 5th harmonic component. But I can't understand how to do that. I have already calculated amplitude for 1st harmonic component. My calculation is as follows.


texts:
I have a generic VHDL entity and I have this code:

--- in testbench
const bits : integer := 13;          -- number of bits
const pow: integer := 8192;          -- 2^bits
const squared : integer := 67108864; -- pow^2

In where I pass those 3 constants to the entity. What I would really like is something like:

--- in testbench
const bits: integer := 13;

--- in architecture (generic bits:integer)
const pow : integer := 2^bits;
const squared : integer := pow^2;

Since bits is known at synthesis time is there any way to do it without using hardware?


texts: Spark Transmitter with flyback driver and good arcs

texts: I recently built a Fly-back Driver with a fly-back transformer and a primary voltage input of 12 volts and the arcs are about an inch long ( i don't know the exact output voltage because I don't have the ability to measure it ). I have heard that in the 1900's they used arcs to transmit Morse. I want to replicate this. I am wondering how I would hook up the antennas to the arc and hooking up the ground and how the arc relates to all of this. I know that there might be some legal issues to this, but I live in the mountains far from many people, maybe a few FM radio users but I just want to test this for a second and I will not be continuously running this, in other words don't restrict me to information because of legal issues because I know the warnings. So how should I connect the arc up to ground and the antenna and is there any other components I need for this?


texts: How could you transfer data over an audio line?

texts:
I'd like to pass some data over an audio cable (i.e from audio card to my cellphone) with a short cable.

I'm looking for some ideas for algorithms for achieving this. They of course should include the proper modulation technique to transfer the data over audio signal, so the cellphone could interpret it over it's microphone jack.

Ideas? ;)

(P.S - my current idea is using Biphase mark code. is it any good for this?)

Thanks.


texts: Modding a doorbell to a transceiver but need timer

texts:
What is the best way to accomplish adding a switch with a 5 second 'on' feature (where the circuit is closed for 5 seconds then opens thereby turning it off)??

I was thinking of using a digital doorbell and hard wiring it between the 9VDC source and the digital transceiver, but am seeking advice on the timer (trying to create what I believe is called a monostable circuit)


texts: What R, C values to use in an RC Snubber to reduce output ringing in switching regulator?

texts:
I am using a simple buck switching converter (AP3211) to convert 5V-12V to 3.3V.

The issue I am trying to resolve is the output ringing.  I see a 800mV P-P ringing on the output, with a frequency of 185MHz.  I've read details that I could possibly use an RC snubber to reduce the ringing.

Some references I found:

http://www.ti.com/lit/an/slyt465/slyt465.pdf

onsemi.com/pub_link/Collateral/TND396-D.PDF

The schottky diode has a Junction Capacitance of 120pF.  A few different articles have a slightly different approach to calculate the R and C values for the snubber, however I've come to the following values:

R = 7 Ohm
C = 270 pF

My question is:  If I don't care about power consumption (to an extent, and not enough to use a linear regulator), could I use lower R and higher C to reduce the ringing even further?  If so, what are suitable values for R and C?


texts: I have a motor driver interfaced to an arduino using AnalogWrite() for PWM, for some strange reason it only spins the motor from values 210 to 255(full on) with analogwrite, anything lower will make the motor hum very aduible PWM and not spin...any ideas on how to correct this? Do I need Fast PWM?a


texts:
I am looking for a mechanical 2 way selection switch which is rated up to 30kV / 10 A (pulsed, pulse length 100 micro-secs). It could be something like mechanical switches (e.g. the polarity switch of the old Fluke HV supplies https://www.ebay.com/itm/FLUKE-410B-HIGH-VOLTAGE-POWER-SUPPLY-0-10K-VDC-0-10-MA-/361503203404). I do not have any special performance criteria (switching time, etc.) and it does not need hot-switching capabilities.

I searched already for some time, but did not find anything fitting my needs in the web.


texts:
When making a BOM I used a component which goes by part number BC847BW,135. It is available on Mouser and Digikey.

An "alternative", is listed on Farnell: BC847BW,115

The datasheet doesn't seem to mention what ",135" or ",115" means. I've seen this suffix on other Nexperia parts but it never made a difference to me until today, when it caused me some inconveniences with an assembly house.

So I'm curious as to what those numbers mean, and if the parts are different at all, or if its a packaging issue (reel size), etc.

p.s.: the issue I had with the assembly house is unrelated to the question, I had to suggest the ,115 part as an alternative to the ,135 part because on their database BC847BW,135 is listed as SOT23, so I just had to suggest a different part number with SOT323 footprint - the W suffix clearly indicates SOT323 on the datasheet but anyway)

update to the p.s.: they corrected their model on their database and will proceed with the ,135 part.


texts:
I see a lot of Bluetooth adapters OBD-II reading speed, temperature, etc. Does that adapter read from the CAN bus with standard broadcasting?

If read with standard broadcasting from the CAN bus, where can I find this standard table of broadcasting? I need the speed value address.


texts: complementary transistor pair npn/pnp in the Kapustinsky circuit

texts:
I need to create an old circuit that reproduces fast impulsion, the Kapustinsky circuit (see the picture).
This circuit is 33 years old, and a transistor (or equivalent) does not exist anymore, the PNP RF transistor BFT92, which as a transition speed of 5GHz.
As described in the article 10.1016/0168-9002(85)90622-9, it's in a complementary pair transistor with a NPN BFR93, which is not a Darlington or Sziklai transistor (Am I right?).
I have two questions:

I don't fully understand what the pair does exactly
Is it possible to replace the PNP transistor, and how?

Thanks for your help


texts:
I my new design I need to use SD card communication.
I would like to match all the impedance traces and control the length of the traces.
Regarding the controlled length, is there a rule of thumb to determine which can be the maximum difference between two uncoupled traces?


texts:
Being the stiffness of the grid its capability of maintaining the voltage constant despite small variations on load. Whereas, a weak grid would be easily affected by load variation and the voltage would change.

So here it comes my question, how do you quantify how stiff a grid? Is there any formula to calculate this?


texts:
Design a counter: 12-10-8-6-4-2-0-1-3-5-7-9-11 using D Flip Flop.

My first approach is designing a 8 - 6 - 4 - 2 - 0 - 1 - 3 - 5 - 7 - 9 - 8 - 6 ...  counter and display them on 7segment LED.

After writing down the binary code of these numbers above, I realize that they seem obeying a rule

  1 0 0 0 (8)
  0 1 1 0 (6)
  0 1 0 0 (4)
  0 0 1 0 (2)
  0 0 0 0 (0)
  0 0 0 1 (1)
  0 0 1 1 (3)
  0 1 0 1 (5)
  0 1 1 1 (7)
  1 0 0 1 (9)

It can be seeen that the LSB of the even numbers are always 0, while they're always 1 for the odd numbers. As for 3 left bits, they are symmetrical. So my idea for this problem is after counting from 8 downto 0, the LSB would change from 0 to 1, and start counting up (using 3 or 4 D-Flip-Flop and logic gates). But after writing down Next State Table, I face with the way to force my starting number to be 8.

  Present State ---- Next State
  0 0 0 0 ------------ 1 0 0 0  (next state is 8 if starting number is 0)
  1 0 0 0 ------------ 0 1 1 0 (display 8, next state is 6)
  0 1 1 0 ------------ 0 1 0 0 (display 6, next state is 4)
  0 1 0 0 ------------ 0 0 1 0 (display 4, next state is 2)
  0 0 1 0 ------------ 0 0 0 0 (display 2, next state is 0)
  0 0 0 0 ------------ 0 0 0 1 (display 0, change LSB into 1, and activate counting up)

The problem here is that the state 0 0 0 0 is used twice (once for forcing starting number to be 8 and once for change LSB into 1) and I think my counter would get confused. So I wonder there are any ways to implement this kinda counter?

Thanks in advance for any of your answers.

My circuit works, bases on @Trevor's circuit
Thanks all for your amazing ideas.


texts: Center-tapped Full Wave Bridge Rectifier

texts:
I'm designing a high-voltage power supply for a plasma experiment.  I have a center-tapped ignition transformer (50:1) that I'm using to step up the voltage from 120VAC to 6kVAC and then using a full wave bridge rectifier to get +/- 6kVDC.  The problem is, the design of the experiment requires me to have 0 and -12kVDC outputs, not +/- 6kVDC (essentially, the positive terminal on the device I'm using needs to be grounded).  My basic understanding of this concept is that I somehow have to connect the center tap of the transformer to -6kV, which is called "floating" the transformer.  How can I modify the basic rectifier circuit:

to fulfill this need?

Thanks,
Noah


texts: Instead of using wye delta transformation I tried redrawing the following circuit but I do not understand where I made a mistake. The circuit appears to have the same voltage current relationships at the nodes, a, b, and c. I have shown all my steps to calculate the equivalent Thevenin resistance. Could someone explain what is wrong about my method of redrawing the circuit?


texts: ESP8266: Differentiate wakeup due to sleep interval vs button press

texts:
I have an ESP8266, ESP-12F modules that is in deep sleep mode.

It wakes up every 6 hours to read the humidity sensor, display it on LED and then post to IFTTT. Because it is every 6 hours, it actually wakes up every hour just to check an EEPROM stored counter to see if the 6 hour has elapsed. Otherwise, it will increase or reset the EEPROM counter accordingly.

I also want the user to press a button to wake up the ESP, read the humidity sensor, display it on the LED and send to IFTTT even if the 6 hours have not elapsed.

Is there a way to differentiate wakeup due to sleep interval vs a button press reset? In both cases the reset reason is 5.

I'm open to both hardware and firmware solutions.

I have also tried to simulate a possible circuit. But the GPIO12 (which I am trying to read as LOW right after ESP wakes up) does not hold on to the LOW value long enough for me to read it right after wake up.


texts: Accidentally outputting to an optoisolator

texts:
It's your friendly electronic hobbyist again.

I am designing a board where I am reading input from an optoisolator like this.

IN7 is connected to a peripheral parallel port chip of an old 8-bit microprocessor, which is supposed to be set as an input.

I just realized, however, that a user could accidentally have IN7 set as a 5V TTL output instead of an input.

What happens in a case like this?  Could doing so cause damage to the circuit?  If so, is there a way to protect it?

I'm afraid I don't understand optoisolators (or transistors) well enough to know what would happen.


texts:
Is it possible that the schematic shown here is wrong?

I would expect something more like that...

It seems like that he inverted the feedback wires, but I'm quite suspicious because he made the circuit and it works, I'm a bit confused.

EDIT: as said in the comments this is not a flip flop, but a latch, sorry for the error.


texts: How does charge/discharge current increase battery temperature?

texts:
I already know that charging or discharging a battery causes it to heat up, and that increase in heat is proportional to the current. But what physical process is behind this?

My back-of-the-envelope explanation would be that the battery has internal resistance, and the current must overcome this resistance. In doing so, the electrical energy is converted into heat. In other words, the electrons crash into poorly-conductive parts of the electrodes, heating the material up.

But is it really as simple as that?


texts: Collector Doping Concentration and Current Gain

texts: I was wondering, in a BJT why does the collector doping concentrarion have no effect in determining the current gain? I am trying to understand this conceptually but I can't seem to wrap my head around it.


texts: Is the isolation necessary in this circuit?

texts:
I am designing a circuit to control LED drivers. The main characteristics are the following:

The circuit is powered through the electrical network (230 VAC)
It has three types of dimming outputs: 0-10V, PWM and DALI.
In addition, the circuit has a mechanical relay to control the AC supply for the LED driver.

I have a prototype that works acceptably well but I have questions about the isolation. I have read in the forum about isolation (link1;link2) but I can not solve my question. I had thought of using two isolated GNDs and two isolated converters: one to convert 230 VAC to 12 VDC and another from 12 VDC to 12 VDC to obtain an isolated power supply for subcircuits: DALI, PWM and 0-10V. A simplified schematic is shown below.

I have many questions, but mainly these two:

Is the insulation correct? If not, what should be corrected?
Is isolation unnecessary or is it only necessary to isolated a part of the schematic?

simulate this circuit – Schematic created using CircuitLab

Thanks!


texts: Control theory: What is the physical interpretation of asymptotic stability

texts:
For Bounded Input, Bounded Output stability (BIBO), there is a very nice interpretation. All it means is that if for any finite signal the system produces a finite output signal, then the system (cellphone, radio, lamp, etc...) is BIBO stable.

But what about asymptotic stability? Asymptotic stability states that without an input signal, any initial internal state of the system will lead to the internal state decay to zero.

Can someone come up with an example that illustrate this effect?

More interestingly is the case that a system can be BIBO stable without being asymptotically stable. Are there any realistic system that can achieve this?

Thanks


texts: Proximity sensors interfacing with microcontroller

texts:
I'm trying to connect this proximity sensor GX-H8A to interface with my microcontroller STM32L4R5. I just want to make sure if my design will work and will not damage the micro.

I'm planning to connect the Brown wire to 24VDC, Blue wire to Ground, and the Black wire to the input signal on my microcontroller, and a 3.3V pull up with a 10K resistor on the Black wire as well. So when the sensor detects the object, it will get pulled to ground and the micro will receive a 0 signal.
Is this configuration and theory correct? I'm scared that somehow the 24V will got connected to the microcontroller and damage it, and I'm not sure why they connected the Output node with the 24V node in the circuit diagram.
Thanks.


texts: Say I’m planning to prototype some circuits (filters, oscillators, etc.) by soldering the component leads together in a “hairball” construction.  If I use typical 10% or 20% tolerance inductors, how small an inductor can I design with before worrying about the component lead inductances becoming a larger issue than the component tolerances?


texts: How do I remove the offset from the DAC output and change the range?

texts:
This DAC has an output range of 1-3 volts. Here's the datasheet:

Datasheet

I'm getting pulses with different amplitudes, frequencies, duty cycles and widths varying from 0.2 ms to 2 s from the DAC. I want an output range of 0-4 volts instead (Vcc=5v). I tried a high-pass RC filter, and then amplified it with an op-amp, but the output doesn't look like a pulse anymore. Also, I tried the circuit suggested in the datasheet (page 8) with no luck. I'm not sure what values I should assign to this circuit, since I don't understand how it functions.
How should I go about this?


texts:
I have a monitor that is no longer working. It had an intermittent problem where it would go "pop", the black out for a little while, then come back on. Then recently it went "POP" a little louder, and hasn't been working since.

I have looked at the PCB to try to identify the broken component. And I found this:

Could it be the top one that is fried? if so, what is it? and Can I change it myself?

EDIT:
As someone mentioned, the broken component may not be the one in the picture.

The monitor in question is an AOC U2868PQU.
I did look for the service manual, the only one I could find was behind a paywall.

The panel of the monitor is a m280dgj-l30

The controller is a 715G6355-M1A-000-005K, apparently, this controller is also used in a philips monitor.


texts: How to calculate necessary resistance to dim some LEDs?

texts:
Here's some nice LED's packaged in strips which can be cut apart and used for projects.  Voltage is up to 12 volts, and many people are using 3S 11.1 lipo cells to power them.

Some people comment that they are too bright, or that different colors (e.g. red and green) do not match in intensity.

Can I solder a resistor in series to reduce the current flow to match the brighness?  Will that improve the battery life?  If I get a dial resistor, can I dial in the desired brightness and then measure the amperage flowing through the circuit to determine the needed resistance?

  http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8941

  (source: hobbyking.com)


texts: break-beam sensor to detect low paper supply

texts:
all. I know enough about soldering and circuits to be dangerous, meaning I can follow instructions, but I could not design my way through an open door.

I am interested in using an IR Break Beam Sensor (3.3v 20ma to power it--details https://www.adafruit.com/products/2167 ) to cause an LED to turn ON when the beam is detected, not when the beam is broken. Basically, I want to detect when a roll of paper is NOT between the two sensors and then have an LED stay on (or blink would be better). I should be able to do this simply, no?  It needs to run 24/7 but the beam most of the time will not be broken. Any circuit guidance would be appreciated and then I will try to figure out what kind of battery power i would need. Oh, when the paper is replaced, I would want the circuit to turn off the LED. The paper is definitely thick enough to block the beam.
Thanks for any guidance/resources.
-Bob


texts:
I need a series component to isolate a 2440MHZ antenna for testing purposes-- it can either be a a high quality 0402 RF capacitor (Johansen) or a zero ohm resistor.

The series component will remain on after the product is shipped.

I do have any experience with zero ohm jumpers at RF but I have used 8-10pf high quality RF capacitors in the 0402 to make a short..the impedance of this device must be quite negligible on paper when connected to a 50 resistive load.

If I want minimum variation in the product due to the jumper, should I use a zero ohm jumper or high quality capacitor?


texts: How to test if a bipolar stepper motor is working?

texts:
I have this stepper motor:

I write the code below for a PIC16F877 microcontroller for a continuous movement in stepper motor:

    LIST P=16F877A
include "P16F877A.INC"
__CONFIG _RC_OSC & _WDT_OFF & _PWRTE_ON & _CP_OFF & _BODEN_ON & _LVP_OFF  & _CPD_OFF & _DEBUG_OFF;
ERRORLEVEL -302

cblock 0x020
    d1
    d2
endc

    org         0x00
    goto        start
    org         0x04
    retfie

start
    bcf         STATUS,RP0              ;BANK 0
    bcf         STATUS,RP1
    clrf        PORTB

    bsf         STATUS,RP0
    bcf         STATUS,RP1              ;BANK 1
    clrf        TRISB
    bcf         STATUS,RP0              ;BANK 0

    call move

move
    movlw   b'00001010'
    movwf   PORTB
nop
    call    delay
nop
    movlw   b'00000110'
    movwf   PORTB
    call    delay

    movlw   b'00000101'
    movwf   PORTB
    call    delay

    goto    move
return

delay
    movlw   0xFF
    movwf   d1
delay_0
nop
nop
nop
nop
    nop
    nop
    nop
    decfsz  d1,f
    goto delay_0
    nop
    return

idle_loop
    goto        idle_loop

end

But the stepper motor isn't working. I connect: red:RB0, green:RB1, yellow:RB2 , blue: RB3
and i have a ULN2003A  darlington transistor.

Is there an alternative way to test it to see if it is not work properly?


texts: Why is line-ground voltage higher than line-line at the output of a variable frequency drive

texts:
I am using a Fluke 87V, reading AC voltage with the low pass filter activated. I have also used a stray voltage eliminator and the readings are the same.

Between each of the phases I read about 38VAC. Between each of the phases and ground I read about 68VAC.

The VFD is connected to a load.

Could this be caused by voltages induced by ground loops? And how can I check to test if this is actually was is causing the strange readings?