texts: Atmega328p-pu (arduino bootloader) processor freezes/resets randomly

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I have updated the schematic of my project. The board for this was produced and all components are soldered to the board.
Now I am trying to make a "n20 gear motor" move using the motor driver, I have simplified my code, attached as image(screenshot).
Motor being used: n20 gear motor (produced in china, stalling current should be less than 250mA, normal current is approx 40-50mA.
When I run this code the processor sometimes resets and sometimes freezes completely, this happens frequently but randomly, almost within every minute.
The code itself is pretty simple, I think there is an electrical fault.
Does any of you have an idea what it can be? Thanks in advance.


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All I can find online are descriptions on how active buzzers have an oscillator built in so that you just need to feed them a DC and they buzz at the frequency set by such oscillator, but I haven't been able to find either a diagram, description or teardown of an active buzzer to see how is this usually done.
I can easily see how to build an active buzzer from a passive buzzer providing one of infinite possible ways of implementing an oscillator, but I wonder how is it actually done, specially on the tiny packages.
I've seen a teardown here, fantastic BTW, but I assume there are other much simpler/cheaper constructions.


texts: Connecting PIC32 through FT312D to Android tablet

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I need to connect my PIC32 to an Allview Android tablet over USB so that the tablet will charge from my PIC board and also be able to communicate at the same time.
I can connect the PIC32 to a FT312D using the UART.
The FT312D seems to support AOA.
Page 15 of theFT312D datasheet shows an example application that appears to supply the tablet with +5V.

https://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT312D.pdf
Is there any special setting or configuration I must do? Do I need an OTG cable? How does this work exactly?


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I am using a FT232RL chip with FTD2XX_NET.dll
I've made a program which writes and reads data to/from AVR atmega32 mcu.
First writes data, then reads data as answer.

Now, i want to make an event which indicated me if there's available unreaded data, only when AVR sends data to FTDI buffer and ONLY then. Whithout forcing my program to making loops for checking available data.
For my purpose, i want to do the mcu to sends data only when he wants, and the PC must to knows when there's new data in FTDI buffer's chip


texts: Where is data coming from a bus stored in a microcontroller?

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It might sound like a silly question, but somehow I am not able to answer this myself with confidence. Let's say we have a microcontroller (MCU) with a data/address bus and data is moving to and from the bus. "Where" exactly on the MCU is the data arriving on this bus temporarily stored? Is it in some RAM buffer or some IO data register for a particular address?

If it is not a data/address bus (that has addresses) and the data is coming on a random GPIO pin, where is this data temporarily stored in this case?

Thank you.


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I have basically no experience in electrical engineering or hardware design, but as an experienced software engineer, I recently took an interest in designing my own CPU. I followed the instructions/excercises presented in the book "The Elements of Computing Systems / Nisan & Schocken", which suggests a RAM design similiar to this:

CHIP RAM8 {
    IN in[16], load, address[3];
    OUT out[16];

    PARTS:
    DMux8Way(in=load,sel=address,a=a1,b=b1,c=c1,d=d1,e=e1,f=f1,g=g1,h=h1);
    Register(in=in,load=a1,out=aout);
    Register(in=in,load=b1,out=bout);
    Register(in=in,load=c1,out=cout);
    Register(in=in,load=d1,out=dout);
    Register(in=in,load=e1,out=eout);
    Register(in=in,load=f1,out=fout);
    Register(in=in,load=g1,out=gout);
    Register(in=in,load=h1,out=hout);
    Mux8Way16(a=aout,b=bout,c=cout,d=dout,e=eout,f=fout,g=gout,h=hout,sel=address,out=out);
}

So there is one "address" bus, which determines which address to read from. Optionally in the same cycle the value of the "in" bus is written to that memory address if the "load" bit is set.

Now I tried to take a spin on the architecture suggested by the book, where I would like to read instructions and data from the RAM in just one cycle (the book proposes a seperate ROM for the instructions). I came up with this RAM design:

CHIP RAM8 {
    IN in[16], load, address1[3],address2[3];
    OUT out1[16], out2[16];

    PARTS:
    DMux8Way(in=load,sel=address1,a=a1,b=b1,c=c1,d=d1,e=e1,f=f1,g=g1,h=h1);
    Register(in=in,load=a1,out=aout);
    Register(in=in,load=b1,out=bout);
    Register(in=in,load=c1,out=cout);
    Register(in=in,load=d1,out=dout);
    Register(in=in,load=e1,out=eout);
    Register(in=in,load=f1,out=fout);
    Register(in=in,load=g1,out=gout);
    Register(in=in,load=h1,out=hout);
    Mux8Way16(a=aout,b=bout,c=cout,d=dout,e=eout,f=fout,g=gout,h=hout,sel=address1,out=out1);
    Mux8Way16(a=aout,b=bout,c=cout,d=dout,e=eout,f=fout,g=gout,h=hout,sel=address2,out=out2);
}

So the only difference is basically, that I have introduced a second address bus, so I can read two addresses in parallel at the same time by also introducing a second mux into the chip design.

Now I have several questions concerning this design:

To me it seems, that the introduction of another mux seems rather cheap to read two items of data from the RAM in only one cycle. Also the hardware design seems totally sound to me (as a total hardware design noob) and simulating the chip seems to proof the design. Am I missing a big mistake/disadvantage of the design? Are there electrical contraints to the design?
Is this kind of design relevant at all, when reads from a lower hierarchy memory take up several cycles anyway?
Is this kind of design (reading multiple data items in parallel from RAM) used in any sort of existing, production-ready chips?
If yes... what kind of chips?
If no... why?

When googling, the only thing I could come up with was the topic of "PRAM", which refers to "parallel machines", not "parallel memory". Also there seems to be "DDR/QDR RAM" which I don't quite get, since they are still using a single bus to read data (are they reading different items of data on rising/falling clock edges?). But I guess these kinds of RAMs are not really relevant in regards to my design question anyways, since they need multiple cycles to read data anyways, while my design is register based and is able to read randomly accessed memory in only one cycle!?

I would appreciate any kind of information/clarification on this topic :)


texts: Battery switchover circuit when battery is being charged

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I would like to use two LM5050 in a typical redundant supply configuration for wall adapter and a battery. My concern is that when wall adapter is connected battery voltage goes higher because of the charging, effectively this circuit always operates on battery path.

One solution that comes to my mind is to connect SHUTDOWN pin of LM5050 driven by the battery to the wall adapter. Is that fine?

I don't understand why this answer suggests adding relays in sequence.


texts: How could a dental lab micromotor start at high current and torque without damaging anything?

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If you are familiar with dental micromotors, there are generally two kinds of them in foot pedals: simple switch or variable speed (like throttle.)
The simple one acts like a push button to be manually operated over and over again at very high speed (above 30,000 RPM for brushed motor handpieces and 70,000-90,000 RPM for brushless ones) without any problem.
I was wonder how to reduce the inrush current of a 12V 10A DC motor which I want to use to build a tool like a micromotor (using switch mode power supply.)
A couple of suggestions popped out but all of them is to lower the RPM (=low torque) to reduce the huge initial current; the other thing is giving the motor time to develop speed is good for long life and efficiency but we need high torque at moment to carve agates, so when there is a tool which can do it, there must be a solution for it. When we adjust the RPM on the control box in hand mode on 100% speed add up with the dial, so that's what a PWM speed controller does, but when we switch it to foot mode, each time we put the pedal down motor will start at the wanted speed.
I don't know how to do it without damaging the power supply or the motor, so if you know how or have ideas about, that would be helpful.


texts: Will a resistor be damaged if power rating is surpassed momentarily?

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I am using a power resistor to discharge an 82uF capacitor from 500V to 40V in 5 seconds.

Using this online calculator, the peak power on the 24k resistor will be 10W. Because the capacitor is discharging, this large power dissipation is only momentary, down to 6.33W after 500ms and down to 3.75W after 1000ms.

Because 10W resistors are massive, can I use a resistor with a lower power rating?


texts: Increasing the "range" of a potentiometer?

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For a recent project of mine, I wanted an adjustable resistance between 10Ω and 100kΩ, however none of the potentiometers I had went above 10kΩ. While I would have been able to put a few of them in series, that would be suboptimal as I would need to adjust all the potentiometers simultaneously.
I've tried connecting the potentiometer in series, parallel with resistors of other values, and different combinations of the two, but it seems like the "range" of the equivalent resistor (the difference between the maximum resistance and the minimum). It makes sense, as resistors in series increases the minimum and maximum the same amount, and parallel resistors (I think) always decrease the range, due to the formula R1R2/(R1+R2) being concave (negative second derivative).
In class, we've shown that using a transformer, one can transform a resistor of value R to (N1/N2)^2 R. However, my circuit is using DC, which makes the transformer method impossible.
Is there any way to transform a potentiometer with range [Rm, RM] to a potentiometer with range [Rm', RM'] where RM'-Rm' > RM-Rm in a DC-circuit?


texts: Why battery charge C rating is usually lower than discharge

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Why most (or all?) batteries can be discharged at an higher C rating than the charging C rating?

For example I have the following battery for my quad-copter:
https://hobbyking.com/en_us/turnigy-4000mah-3s-30c-lipo-pack.html

If you look at the specs tabs, you will see that the C rating for Discharge is 30C which means I can draw at max 120 AMPS continuously (which will last me about 2 minutes) and the C rating for Charging is 2C, which means I can charge it at 8 AMPS continuously (which will take about half an hour to charge fully).
All of the Lithium based batteries I found has significantly higher C rating for discharge than for charge.

What is the reason for this big difference? Is it limited to Lithium based batteries only or is it a common trend across most types of batteries?


texts: How to convert this single ended output to a precise impedance balanced output?

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This amplifier suits my purpose with one matter that I couldn’t figure out. Its output impedance is given as 0.01 Ohm.
The output of this amplifier will be coupled to a very high input impedance(more than 20Meg) and balanced DAQ input via a balanced STP cable.

So the receiver is balanced, cable is balanced but not the amplifier output. Signal interest range can vary between 100mV to 5V and freq from DC up to 30kHz.

I want to obtain an impedance balanced output from this amplifier. What could be done right at the output of this amplifier to convert it to a impedance balanced output?

I thought about adding resistors to signal and reference leads but resistors have tolerances. How about cascading the output with this line driver?


texts: Problems with extending camera module bus/cable?

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I like the idea of using a GoPro (or other action camera) as a helmet cam when I'm riding my motorcycle, but I don't like having a big box glued to my forehead. I'm imagining a camera with the camera module and lens being attached by a cable to a box with the microprocessor, SD card, screen, etc. That way, I can put the small camera lens up front, and the put the rest of the camera somewhere more convenient.

Are there inherently any problems with having a longer bus/cable between the camera sensor itself and the rest of the electronics?


texts: What is this miniature 2-pin D-shaped connector?

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In about 1992, I built a dolls' house and bought these connectors from RS to use as ceiling roses. The picture shows the 'plug'. The plug came with a cover that screwed onto the threaded section. There was a corresponding 'socket' with two pins (which I use as the actual ceiling rose).
The pin spacing appears to be 3mm (definitely more than 2.54mm) and the plug diameter is about 5mm. The pin diameter is <1mm. The socket fitted over the plug. Sadly time (and children) have taken their toll, and this is the last plug. The heat shrink section hides a pea bulb. The sockets are the actual roses and are all glued into the doll's house, so if I can't find more similar plugs, I'll have to re-wire the whole thing.
The only markings I can find are 'EM' in a rectangle, and the digit '3' beside that. The pins are marked 'A' and 'B'.
Thanks in advance.


texts: Is there a way to miniaturize cell-phone power adapter

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Is there a way to miniaturize a cell-phone power adapter to be not bigger than 1-3 cubic centimeters? Is there a way to do so by using more expensive parts or something like that?

I'm talking about usual cell-phone power adapters that transform 110 AC to 5V 1 A DC.

What are the limitation if it is not possible?


texts:
Bourns has various TVS diodes to protect Ethernet ports.
Most of them (for example CD143A-SR05) have GND, VCC and I/O pins.
I/O pins are for Ethernet signal line.
Why do these TVS diodes have VCC pin?


texts: Convert A weighted voltage output into sound pressure

texts: I have designed an A weighting network circuit. but i cant understand how to convert it's voltage output in to corresponding sound pressure level in dB. So How can I convert these voltage readings into dB?


texts: i want to use a Timer which generates a 40kHz frequency to toggle an output, when a start trigger arrived on an input. After a high signal was detectet on that input, the GPIO should be toggled 20 times with a frequency of 40kHz. Which timer mode is suitable for this application? Is it possible to do it within an GPIO interrupt? But how do i use the timer clock in t his GPIO interrupt to toggle the GPIO?


texts:
I'm planning to assemble x86-based computer equipment and place it outdoors, on the balcony, which has no protection from the elements, except for the concrete floor and roof. The temperatures here go approx. from -30C to +30C (-20F to +90F), with abundant snow and rain at times, and also direct sunlight.

The computer equipment needs power (230V AC), and at least ethernet connection (cat6 or similar). VGA and USB would be nice, but are needed only for random debugging. The system generates heat, which needs to transfered away.

What kind of weather proof enclosures would be suitable for this project? This far I've gathered from Wikipedia IP Code tables that IP67 or NEMA 4 / 4X would probaby be sufficient, but is that overkill? Typical 19" rack enclosure at approx 4U size would be pretty good, but non-standard similar sizes are OK as well. I failed to find any price information online, how much should I budget for this? I've never built anything like this, should I plan to purchase a piece or is it easy to do it myself?

(I realise this might not be the right forum for this question. Feel free to suggest a better suited forum or move my question.)


texts:
I need to identify two parts that I need to replace, but I'm having a hard time doing it.

These are the parts:

Part 1:

From my research I think it is a trigger switch (http://www.jiaben.com/en/pro.asp?BID=45&SID=30), but I don't know where to find one to replace it or how should I search for a replacement.

Part 2:

I think it is a 250Vac to 50Vdc converter, but I can't find one the internet anything resembling it.

Any help?


texts: Signal Generation with duration in VHDL?

texts: Im writing a signal generator in VHDL and I would like to set the duration of the signal generated to 75ms, it is an out signal and my clock is 100 MHz, I would be glad if you can help!


texts: Switching High-voltages with p-channel MOSFET

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I want to use a MOSFET to switch 400V to a circuit. I can switch low-side using an n-channel MOSFET, but it's more convenient to have the circuit with its ground fixed. So I want to switch high-side, but I don't see how I can use a low voltage for the switching (0 - 5V).

I am switching with a 0/5V square pulse and I need Vsg > |Vt| for the switch to be on (i.e. my load is to be connected to Vdd = 400V). With the configuration below, the MOSFET will be on regardless of if I have a HIGH or a LOW on my input pulse.

Does this mean my switching pulse needs to be 0/400V square pulse (a 400V on gate would give Vsg = 0V < |Vt|, turning the FET off)?

My MOSFET: 500V infeneon IPW50R190CE
Switching frequencies: 10 MHz


texts: Generating sinewave from a pulse train by using a micro-controller

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I want to create sine waves from 0.1Hz to 10Hz which are controlled from a software. For that I thought I can use micro controller as an interface between the PC and the sine wave signal.

But if I can be able to change the uC's frequency of the pulse train, how then I can convert those pulses to sines? Im not after high precision.

Is using RC filter recommended for such range and what RC values would be fine? The frequency range will be 0.1Hz to 10Hz.
Or is there more practical or bulit in solution?


texts: Can someone please help me with these questions on DC Chopper Circuits?

texts:
I had a quiz on power electronics and the following questions were asked:

Question 1: Consider the buck chopper in Figure 1, operating at 100 kHz frequency, with the switch duty ratio of 0.5 and input voltage of 100 V(DC). The load is resistive with R = 10 ohms, put across the filter capacitor. Load voltage is found to be nearly ripple free and inductor current is continuous. What should be the smallest value of inductor to keep peak value of the inductor current within 10% of its mean value?

Question 2: Consider the Boost chopper of Figure 2. With input voltage 10Volts and a fixed duty ratio of 0.8. The converter feeds a resistive load of 10 ohms and operates with continuous inductor current. Due to some fault, the load gets disconnected. What will be the resulting output voltage under the steady state? Why?

So, in the test, I was able to think and write only for the 2nd question:
My answer was: The output voltage across capacitor keeps on rising and rising since the diode will never be reverse biased thus the capacitor gets a continuous charge current from the inductor, which ultimately will lead to burning of the components of the whole setup.

As for the 1st question, I was just able to just find that the mean Inductor current will be 0.8 Amperes.

So, I was hoping if someone could help me with what might be the right answer for Question 1.

Also, did I write my 2nd answer right? What will be the correct answer?

Please, review and help.


texts: Deriving expressions from transfer function of state variable filter?

texts:
I have been trying to design a state variable filter based on a block diagram provided. The transfer function which I have is of the form:

$$\frac{K_1K_2}{s^2 + K_1s + K_1K_2}$$

I need to obtain and derive expressions for the natural frequency and quality factor of the state variable filter in terms of \$K_1\$ and \$K_2\$. In order to do so I need to compare my T.F with a 2nd order normalized T.F for state variable filters. Below is the T.F I am comparing with from this website.

$$\frac{V_{\text{out}}}{V_{\text{in}}} = \frac{A_o\left(\frac{f}{f_o}\right)}{\left[1 + 2\zeta\frac{f}{f_o} + \left(\frac{f}{f_o}\right)^2\right]}$$

I am getting confused since the 2nd order normalized T.F does not have an \$s^2\$ term.

For the natural frequency I have got:

$$\omega_n\text{ or }\frac{f}{f_o} = \sqrt{K_1K_2}$$

and for the quality factor:

$$2\zeta\omega_n = K_1s$$
$$\zeta = \frac{K_1s}{2\sqrt{K_1K_2}}$$

My question is: Am I comparing to the right transfer function since it does not have s squared terms? If so have I proceeded correctly? If not, are there any tips on what I could do to derive the above expressions correctly?


texts: Op amp rail splitter virtual ground shifts when LED is on

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I have a 9V power supply. I split it in half using a voltage divider buffered through a TL071 op amp. I use the +4.5V rail to power an ATmega328P. The microcontroller has one pin attached to an LED through a 330-ohm resistor.

The problem that I'm having is that whenever the LED is on, the voltage available to the microcontroller on the positive rail drops by about 570mV. The voltage on the negative rail also becomes more negative by 570mV. The voltage across the positive and negative rail remains 9V. It's the virtual ground that's shifting.

I think the reason may be that when the LED is on, the microcontroller+LED draw more current than the op amp can sink (any current drawn from the positive rail must be sunk through the op amp right? no where else for it to go) and so that causes the potential of the virtual ground to rise. Is that what's going on?

The microcontroller draws 17mA by itself when the LED is off. It outputs about 3.5V (the circuit isn't entirely accurate since it shows the LED being driven from the positive rail; it's actually driven from a microcontroller pin), and the LED requires 1.7V, so that's 1.8V dropped across the 330-ohm resistor, for an additional 5mA or so. I looked at the data sheet for the TL071 but was unable to find any information about how much current it can sink.

Is my understanding correct? How much current can the TL071 virtual ground handle? If the TL071 is the limiting factor, is there another op amp that would do a better job?

simulate this circuit – Schematic created using CircuitLab


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I have a device based on TMS470R1B1M from which I try to send CAN standard frames every second. As soon as I turn on the device, the device enters the error passive state.

How do I handle this error condition?


texts:
When inspecting the boards from electronics made in 1980s and earlier, one distinct feature is the extensive use of axial, electrolytic capacitors as power supply filter. Axial ceramic decoupling capacitors were used as well, to a lesser extent.

For example, this is a C64 motherboard.

Source: Wikimedia Common, by Gona.eu, license: CC BY-SA 3.0

This is a Tektronix 1720 vectorscope board.

Source: Flickr, by Toby Thain, license: CC BY-NC 2.0

However, although they are still being manufactured, it seems that axial capacitors largely disappeared in most devices since the 90s. Almost none of electronic devices we commonly see have a single axial capacitor. And it's certain that one is going to find something similar to this in a modern device...

Source: Wikimedia Common, by Dave Jones from Australia, license: CC BY 2.0

Question

Why did Axial Capacitors Fall Out of Use in the Industry? I can imagine that axial capacitors were optimized for point-to-point wiring back in the pre-PCB era, not PCB assembly, and that the introduction of SMT was another shot. But it was just my imagination, backed by nothing. What were the exact sequence of events and/or rationale that led to the disuse of axial capacitors?


texts: Reason for High voltage difference between Ground and neutral wire in 3 phase system

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I have following reading of voltages:

RY  397V
RB  398V
YB  393V
RN  231V
YN  227V
BN  228V
RG  386V *
YG  385V *
BG  10V  *
NG  216V *

If you clearly observe data above phase-to-phase voltages are good and phase-to-neutral voltages are also good, but when I measure phase voltages with respect to ground unusual value is observed which should be actually somewhat equal to phase-to-neutral voltage. Also the neutral-to-ground voltage is too high, but should be minimum. Now the problem is it is not affecting the normal electrical equipment, but highly sensitive equipment like UPS doesn't take it as a healthy voltage. So what might be the cause behind it?


texts: Understanding Impedence when modifying a spring reverb

texts: So I found this spring reverb tank on Amazon for $17. I understanding that it is supposed to be used inside a guitar amp but I want to see if I can modify it to be a low-cost spring reverb for use with my keyboards. It says it has an Input Impedance of 800 Ohms and an Output Impedance of 2,575 Ohms. Would I be able to run the output of my keyboard into the input of the reverb and then just run the output of the reverb into an XLR mic input on my mixer to amplify the signal back to the proper level? Or would running the output through a DI box be better? I am not sure how the ohms relate to the instrument signals.


texts: Amplify .7Vpp square wave to 5Vpp square wave buffered to go over a 15-50 foot cable

texts:
I've got a sensor that outputs a .7Vpp square wave at 36kHz-60kHz.  I need to take that square wave and amplify it to 5Vpp, as close to 0V to 5V rails as possible.  Then I need to send that signal over a long cable, 6-50 feet depending on where I'm using the sensor and have that square wave still be nice and square when it reaches the other end.

I have a single +5VDC supply to work with.

Currently I can get a good square wave by using an LM311P comparator, but when I try to drive it over a long cable I end up with a wave that looks like a shark fin.

Should I be taking a different approach all together instead of the comparator, or is there something I can put between the comparator and the long cable to help the signal?

This is a little bit of a simplification of what I'm doing, but it's basically what I'm doing now.  NOTE: the BJT shown is actually part of the LM311P comparator.  Also, the 1V source is actually 5V.

simulate this circuit – Schematic created using CircuitLab

Here's the shark fin output at 36kHz, about 5Vpp, that I was describing:


texts:
I need a 12V 2A flyback diode for a solenoid and salvaged this unknown diode from a TR101 E-Panel (D5).
The markings on the diode are SN FE IB and a curvy U shape logo. 6.2mm long and 3.2mm diameter.

What are the specs of this diode and is it enough to use as a 2A flyback diode?


texts: Autodesk Eagle: How to design predetermined breaking points / line of breakage

texts:
How can you best design a line of breakage in Autodesk EAGLE that makes it possible to break the individual PCBs easy by hand?
Please see here what I would like to do (blue lines are the lines of breakage):


texts: How to measure isolation resistance between floating ground levels?

texts:
There a two isolated ground pins on an isolated dc-dc converter
  .

What method is used for measuring isolation resistance between input side ground level and floating (output side) ground level?


texts: how to control state space when it is not controllable?

texts:
I have the matrix A and B and I computed the controllability matrix and found the rank is lower than n. I know I can't apply pole-placement , how else can I solve the system?

n is the order of A


texts:
When I paid a visit to my component supplier I spotted a few GAL22V10 available there. Asked the price - CNY24 (about US$4) a pop, NOS.

Then I asked about EPM240T100C5, an 100-pin 240-LU CPLD and the price? CNY6 (about US$1) each, brand new. Even the bigger variant EPM570T100C5 costs about just $3.

Why? Why an immensely more powerful chip is sold at 1/4 of the price of a significantly older, way less powerful one?


texts:
In this design, the 2A motor "M", which is running at PWM=10kHz, creates a lot of noise in the ground as shown on the scope trace. Not only the ground is sinusoidal but more painful, the ground level raises up to 80mV when the motor is running.

Unfortunately, this noise and the fact that "ground is at 80mV" make it very difficult to detect the very little voltage variation of the sensor "S".

Only one big 3.7V battery powers the motor and the processor. A very small 3.0V battery is powering independently the op-amp.

All the ground traces are extremely thick and have been designed as much as possible like a star. There are a couple of 100uF on the big 3.7V battery as well as mutliple 0.1uF. There is one 4.7uF and multiple 0.1uF on the small 3.0V battery.

What could I do to minimize this noisy ground?


texts:
I am having a lot of Diamond symbols in my schematic named as Pxxxx. I am not able to find what it means as there are no legends mentioned in the file.

Also, are there any general conventions that govern the usage of symbols in schematics?


texts: Building a 50' string of LED lights for patio

texts:
I cannot understand the Ohm's law thing.  I'll make this simple and pray for an answer.

I have an adjustable "buck converter".  It can take 4-38 VDC into it and step it down to 1.25-36 VDC out.

So, I connected 12 VDC/3,000 mA to it and, with the tiny adjustment screw, adjusted it to put out 3.2 VDC (no idea what the mA output is) which is what the 100 LED lights are.  (3.0-3.2 Vdc rated)

I took a bread board and plugged in 100 of these LEDs and touched them to the "out" voltage of 3.2 and VOILA!  All lights lit up.  Is that it?  Don't need any resistor in the line.  Was it that simple?  Can I now build a 32' or 100' string and start hanging lights, with no further adjustments?


texts: Are MOSFETs better for high power applications than the BJT?

texts:
I was reading that the MOSFET is  more optimal for high power situations at low to medium supply voltages  than the BJT. However, I'm questioning this, because MOSFETs and BJTs           waste     little to no power while off.Mosfets         are  more prone to damage due static electricity            breaking    down the gate source oxide layer. Is it true that BJTs are better at high junction temperatures because they dont have an oxide layer?        .

Can anyone confirm whether or not this is true?


texts:
I look for a solution for a problem in my project.

The idea of the project is to create a smart library which help us to know where every book located in every period of time.

Picture :

The idea is to make a scanner which pass over the shelf and scans the books every 30 minutes.

I thought to implement that project with NFC tags and NFC scanner, but I found that there are limitations of distance between one tag to another.

Another problem is that I want to read radius of tags and not tag after tag (like QR code for example) because I don't know in which position the book will be on the shelf.

Picture of the problem:

The questions are

1. If the limit of NFC tags distance is more or fewer millimeters

2. If there is another cheap solution for reading some objects which are located in distance of 5-10 centimeter from some scanner


texts: Is it ok to use both rising and falling egde in this VHDL design?

texts:
I'm pretty new to designing hardware with VHDL, and I think I'm making a noob mistake. I'm making a CPU and my registerfile is rising_edge triggered. I had a problem though. I'll try putting some pseudo code to clear it up

on rising_edge {r0in <= 20; }
CLOCK CYCLE
on rising_edge {r1in <= r0out; }
CLOCK CYCLE

My problem is that r1in would be getting the old value of r0 instead of the appropriate 20. I then proceeded to change my code to use falling_edge instead of rising_edge for only the registerfile. A simplified version is below:

process(WriteEnable, DataIn, Clock)
begin
  if falling_edge(Clock) then --note the falling_edge instead of rising_edge
    if(WriteEnable = '1') then
      registers <= DataIn;
    end if;
  end if;
end process;
DataOut <= registers;

So now my registers are falling_edge triggered instead of rising_edge. All of the test cases I have pass with this configuration and it synthesizes without warnings... but is this correct?

I'm asking this question because I've long been told to only use both edges in a design if you really know what you're doing. I've been programming in VHDL for a few weeks, so I want to make sure that this is an appropriate case to ues both edges


texts:
So I was reading the chapter on Op Amps in Microelectronic circuits by Sedra, Smith, the topic on Differential Amplifiers to be exact.
Here's the amplifier: https://i.stack.imgur.com/3qWzi.png
To get this to behave as a differential amplifier, it had been proved that R1/R2 = R3/ R4, and the using this condition, the final gain turns our to be R2/R1.
That seemed simple enough, but I didn't get the following statement:

Note that if the amplifier is required to have a large differential gain, then R1 of
necessity will be relatively small and the input resistance will be correspondingly low, a
drawback of this circuit. Another drawback of the circuit is that it is not easy to vary the differential
gain of the amplifier. Both of these drawbacks are overcome in the instrumentation
amplifier discussed next.

Here, what exactly do they mean by "it is not easy to vary the differential gain of the amplifier"? It's just R2/R1, so that should be easy enough to manipulate, right?
Thanks in advance.


texts: we designed circuit using usb2240 when started USB side is working fine,sd card nothing shows up:

texts: we designed circuit using usb2240 when started the USB side is working fine. However, when I put in a micro-SD card (FAT32 formatted, with some sample files for checking) to the holder, nothing shows up. Linux put this as a device (/dev/sdb), but it can't be mounted. Windows device tree shows it as "Portable Device"-> E:, but likewise, no media is detected. Electrical connections seem to be fine, and the USB2240 disconnects & reconnects to the host computer when an SD card is inserted. I'm not sure if that part is expected.


texts:
I have to get two USB 2.0 ports connected to a single chip delivering data and power. If only one port is connected, this connection and power should be forwarded to the IC and if both are connected the second port must be completely shut down.

Can you help me out with that?


texts: Low voltage beak away/tension release connectors for building to building overhead cables

texts:
Are there low voltage breakway or tesion release connectors that should be used for overhead, building to building applications?
The background is we are running a single pair of speaker cable, and a single pair for relay input from one building to another building that is accross an access road.  Generally the speaker cables get screwed down on a terminal strip as are the wires to the relay contact.  The terminal is also the conection for wires that go to critial equipment.
The overhead cables that run accross the streat are high, but it is conceavable that they could get snagged by an unusually high truck, or caught in a tree fall.  In that case there seems to be chance that the cable would rip the terminal board, and other critical equipment off the wall, unless there is something between in that gives first.  Kind of like a fuse for tension.
Anyways, I'm sure there's something for this, but I've never seen it, and can't find it with a google search.
Thanks


texts:
I'm going to be powering some 20 m of LED strips at 24 V. After testing the strips, I can see that this will draw about 6 A.

Of course when inserting power from one side the voltage drop across the strip is large enough to make a significant difference to the brightness of the LEDs towards the end of the strip.

I would like to insert power from both sides of the strip, like shown below where I have modelled to resistance between across the power lines.

My concern in that the two 24 V lines might somehow compete with each other, having some unwanted power loss between them.

My question is whether this is a genuine concern or not? Would it be preferable to cut the 24 V line towards the middle of the strip?

simulate this circuit – Schematic created using CircuitLab

Edit: I think I was a bit ambiguous. To be clear, I will be using a single power supply, inserting power at both ends (not sure if that makes a difference).


texts:
I have 6 inputs that I want to insert in a 8-1 multiplexer. I just want to know how to modify the 8-1 mux to support only 6 inputs. I mean the last two rows on the truth table of the 8-1 won't be available.

This is the 8-1 mux I am using:

and its logic table:

I only want to use the D0 to D5 inputs.


texts: BH1750 Sensor ICs - Block Diagram - Why it has capacitor connect output to input of OpAmp?

texts:
The image from BH1750FVI datasheet. http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1750fvi-e.pdf (page 4)
I don't know why it has the capacitor connect output and input of OpAmp? Can anyone help me about this?


texts: components used to make a butterworth filter

texts:
I doing some amateur radio experimentation and want to create a bandpass filter. I believe that a Butterworth filter would be good because it has a flat frequency response in the pass band.

My center frequency is 1000Mhz and the bandwidth is 75 Mhz.

Since the the freq. is relatively high, I think the proper thing to do is use passive components in a ladder-type topology.

Does this seem like the right general path to follow for my design parameters?

Also, I'm going to build a circuit to do some testing. What should I on the lookout for in terms of my passive components (i.e. low ESR caps, etc.)

Thanks.


texts: Adjusting output bias of op amp is different with what I calculated and expected

texts:
Yesterday, I've posted attenuated and biased output from op-amp

And attenuation has been solved and bias remains.

After googling and with answers in stackexchange, I've built and improved the circuit:

simulate this circuit – Schematic created using CircuitLab

Well, the output is somewhat better than what I have got yesterday (Yellow - input, Blue - output):

But somewhat seems wrong and different with calculations:

Still, output is negatively bias a little bit while input is almost unbiased.
A resistance of compensation resistor R_COMP is different from calculations

In allaboutcircuits and youtube video from 10:14, a resistance of R_COMP is calculated as R_G||R_F.
According to them, R_COMP should be less than 47 kOhm. But, when I've put a resistor with a such resistance value, output is negatively biased much more.
Sorry, forgot to take a picture of it. Picutre down below is taken with a different circuit configuration, but it is a similar one with what I've seen.

Is there something that I am missing? In the youtube video from 23:14, he reduces resistances of R_G and R_F by a tenth while keeping their ratio the same and also reduces R_COMP by a tenth. Then output bias has eliminated significatly. Is it somewhat related with my situation?


texts: ltspice, simulate negative resistance, avalanche effect

texts:
I found some nice circuits here as a pulse generators
http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html

The author shows some scope pics and films from real world.. working.
But when simulated in LtSpice... does nothing :(((

What should be the problem?
Thank you.


texts: How to calculate RAM size from chip markings and number of chips

texts: I have a RAM with 8 TMS44400DJ chips on it. It says the word length is 1048576, so would it mean times 8 I have 8MB RAM on this module?


texts: How is current controlled in high power applications?

texts:
When working with electronics, it is quite easy to regulate current with a resistor, potentiometer, switcher, etc.

But take a simple high power application such as an electric stove. What method is used to control the current through the burners. They couldn't possibly use a variable resistor because the heat generated would be on par with the burner.

It is clear however that the controls are disipating very little heat and they certainly aren't using any electronic devices. So how do they do it?


texts: High Voltage MOSFET Controller - Random Failure

texts:
I have a 120V DC Motor that I need to control the speed of. I am doing this through a High Voltage PNP transistor (MJW21193) rated at 250V and 16A with a peak of 30A as I understand it from the data sheet. The Diagram below is the circuit in question. I am using an optical coupler to supply the required 5V signal from the 3.3V logic. The circuit works. There is some heat but not enough that you can not touch the back of the transistor... on my test bench. The unit only runs for 6 seconds at a time.

However, when I place the unit in the field the electronics randomly fail. Yesterday I lost D5 and possibly the transistor. Thought it test correctly. The only real difference between the bench and the field is the length of cable run. Test bench length is about 20ft. Field length is 250FT.

The stranger part--at least to me--is that there are identical circuits on my circuit board. Both with independent rectifiers feeding the IN and with separate outputs connected to the out. At first my thought was that the motor itself had a problem. However when I change the motors around (they have twist lock plugs on my control box) both resonators will run off the good circuit.

I ran the system for about 3 weeks on the bench testing both circuits. There were no issues. Intact I ran them about about 400% duty (timed runs) to attempt to verify the longevity of the circuit and associated field unit.

The motors have an steady state current draw of 1A at 120VDC. With a inrush current of 3A at the same power. At least that is the power that I see with my meter.

One NOTE: Due to the 5V logic needing to be connected to the 120VDC logic (for the gate to fire) I do see the negative side of the power (always on) on the output side of my optical coupler. About -50V. The diodes are there to prevent this from back flowing.

I am an Aerospace Engineer by education. So this is starting to get above my head. When all else fails ask for help right? Can any one help me out on this one?


texts: RC time constant in circuit with two caps with different potential

texts:
I'm trying to develop a model for the switching speed of a MOSFET. In reducing the equivalent diagram I have come up with this circuit with a resistor and two capacitors in parallel.

The catch is that there is a different initial potential across one of the capacitors. How would you go about deriving a time-constant(s) from such a circuit?

The two voltages should be arbitrary even though they have values in the diagram.

The purpose is to establish which parameters influence the speed, and to derive a formula to determine the maximum speed from such parameters.


texts: Can DAQ devices be used as Oscilloscopes?

texts:
Recently, I took computer architecture course, and got interested in analog electronics. At present moment, I can't afford good USB oscilloscope such as Agilent or Cleverscope (though, they are not that terribly expensive - $1500)

I am curious if USB Digital Acquisition Devices(DAQ) can be used as inexpensive temporary substitution for oscilloscope ? What would be drawbacks (apart from not having probes and having to record the data to PC) ?

Thanks !

Edit: some of the DAQ devices I have looked at:
http://www.ni.com/products/usb-6008/ (NI make an array of different USB DAQ)
http://www.keithley.com/products/data/multifunction/usb/?mn=KUSB-3100 (though it looks like this DAQ is better suited for power electronics)

Some USB oscilloscopes I am interested in:
http://www.cleverscope.com/products/CS320A
http://www.home.agilent.com/en/pc-1418982/usb-modular-oscilloscope?nid=-34492.0&cc=US&lc=eng


texts:
I am a bit confused because of a odd situation in part select operator in verilog. I had read about part select and vector part select operators. But there is a situation where I am having variable[0:0], as part select, though it can be written as variable[0], and I think both are correct. Please correct me if I am wrong.

Using the earlier convention means variable[0:0], I am getting segmentation fault in my program. So I just want to confirm that using this type of convention is ok to use or not?


texts: Why don't we see faster 7400 series chips?

texts: The 74HC series can do something like 20MHz while 74AUC can do something like maybe 600MHz. What I'm wondering is what sets these limitations. Why can't 74HC do more than 16-20MHz while 74AUC can and why can't the latter do even more? In the latter case, does it have to do with physical distances and conductors (e.g. capacitance and inductance) compared to how tightly packed CPU ICs are?


texts:
I'm in a bit of a pickle here.  I need to translate 3.3v to 5v ttl levels.  The devices I'm driving (12 total) are not low current devices so I don't want to interface directly, even with a current limiting resistor.

This is a reference design that I plan on selling and I want it to be as fault tolerant as possible.  My first pass was just to add 100Ohm resistors across each output from the microprocessor (3.3v output).  I'm rethinking that however and I was looking at voltage translation.  The two techniques that look most promising for me is either a pass through transistor interface using a MOSFET such as bs170 and the other is to use a dedicated chip such as the TXB0108 voltage translator.

Here is my conundrum.  I really want to keep the cost of these boards down.  I've sourced the mosfets at mouser for about .25$ each when buying in lots of 100.  The voltage translator ic's are a bit more expensive at about 4 bucks each, when bought in large lots.  My biggest issue is I only need 12 pins to be translated so it seems on the second IC I would be wasting 4 pins.  The mosfets are going to cost about 3 bucks per board (way less than the IC's) with a couple of resistors it brings up to 3.10 or so.  So, that cuts my BOM cost by about 6 bucks, but my issue is the space on the board.  Those 12 mosfets (and accompaning resistors) take up WAY more room than the two ICs (which take no external components).

TLDR; Does anyone know of another (cheaper and less room) than the two methods I mentioned above?  I need to translate 3.3v up to 5v.  It will only be output since the signal is unidirectional (always 3.3v -> 5v).


texts: Differential Pair Length Matching for DP83848I

texts:
I'm looking in the datasheet and layout guide of the DP838481 but I can't seem to find where it talks about length matching for the RX and TX differential pairs. It only mentions length matching for the MDI signals.

In this guide for 82579 Gigabit PHY chip (much faster than what my chip is operating at ~10/100 Mbps) it says to keep each differential segment within 5 mils. But in the MDI interface section it also says not to use serpentine routing!

"Do not use serpentine routing (zig zag of shorter trace)
to match the trace lengths. Serpentine routing to the RJ-
45 connector which connects to long out-of-system
unshielded cables can contribute to radiated EMI and
can decrease immunity to ESD" Page 18 of 82579 Datasheet

How close should my differential pairs match ? And should we really not use serpentine routing for these signals ?

Thanks in advance!


texts: Help identifying a sot-223 ldo voltage regulator

texts: I can't seem to identify this.  It's a 1117c but I need to find the correct output voltage.  I don't recognize the manufacturer logo.  Thanks in advance.


texts: Non-inverting amplifier with variable gain from 1 to 15

texts:
I need to design a non-inverting amplifier with gain from 1 (unity) to 15. From what I read, in theory this can be achieved by using a pot as the feedback resistor, but in practice this will only work depending on the open-loop gain of the op-amp.
Below is the circuit which I intend to use, using the AD8544 as an op-amp on single supply and RV1 used to set the gain from unity to 15. The input signal will have Vcc/2 as the base reference, hence why R1 is connected to Vcc/2. Input frequency can be anywhere from 5 to 600Hz.

The datasheet of the AD8544 shows a graph of the open-loop gain VS frequency (figure 30). Does this graph show that the gain could be up to 40dB for frequencies 5 to 600Hz ?

Is there anything which can be improved in the circuit shown below?


texts: DC-to-DC converter is giving weird output voltages

texts:
I am having an issue with an XL6009.

Basically I have 5v USB input to a TP4056 lithium charger which charges a single 3.7 lithium battery. Also from the output terminals of the TP4056 I am going into an XL6009 to step the voltage up to 5v to power an arduino. I use the pot on the XL6009 to get to 5v and this works perfectly when I have the USB plugged in.

But then I unplug the USB so that I am running solely on the 3.7v battery the output from the XL6009 goes up to around 39V. If I plug the USB in again it drops back down to 5v. The only load I have across the output of the XL6009 is a multimeter.
I understand that the XL6009 should deliver a 5v output regardless of a varying input voltage as long as it is within range.
I dont have much experience with these so I am betting I am doing something wrong but would like some help to point me in the right direction.

thanks
Sos


texts: Any way to monitor current sourced by USB?

texts: I need an easy way to monitor the current being taken from a USB port on a PC. Is there any s/w that can do that? The alternative is wire cutting, which is a last resort.


texts: Re-programming PIC microcontrollers with USB through smartphone

texts:
I want to be able to reprogram my microcontroller through my smartphone. My microcontroller will be sending data to the phone through USB with a built-in USB module. However, I will run into the problem of wanting to update my firmware without changing the unit completely.

If I were to send a .hex file through USB, would I need to have USB OTG capabilities to re-program my microcontroller?

Can I get away with just a USB slave device to send data, and be reprogrammed through it?

I am hoping to use just the PIC18F45J50 to get this done. However, it only has full-speed USB device capabilities.

The other one I'm looking at is the PIC24FJ32GB004.

Can I update the firmware of PIC18F45J50 with just that chip by sending it a .hex file with a smartphone?

If not, could the PIC24FJ32GB004 be what I'm looking for?

An example would be the Arduino Uno. It uses an ATMega8u2 as a FTDI chip to communicate with the computer, and I'm assuming this is the device that flashes the ATMega328's memory. The smartphone is able to read data accurately from the Uno through Physicaloid.

The Arduino Micro uses an ATMega32u4, which has a built in USB module. It is able to be reprogrammed and is supported in the Arduino IDE as well. However, when using the Micro to communicate with the smartphone, it only sends the phone garbage data. Is there a workaround for this?


texts: How to convert 8 bit binary to BCD using logical gates on multisim?

texts:
I have a task to convert analogue signal to digital on multisim. But multisim have no Ic to convert 8 bit binary to BCD. Now I have to make logic circuits to convert 8 bit binary to bcd. I have used kmap technique to minimize first 4 bits than second four bits

then I have designed logic circuits through minimized expressions.
 I have made two sets of 4,4 bit converters on ADC output pins like this.

 I have made this circuit on multisim but this is not converting a complete 8 bit binary to 8 bit bcd and not showing correct value of analog to digital

how I could convert a complete 8 bit binary to 8 bit bcd through single combinational logic circuit ?


texts:
I disassembled a cheap digital tire pressure gauge that had quit working (leaking silver oxide cell, as I discovered).  After deciding it was unrepairable I removed the circuit board, which had the LCD display on the back.  It fell off and seemed to be completely unattached. There was a ribbed rubber strip between a plastic "step" on the the display and the row of contacts.

Here are some images of the LCD:

Front ↑

Back ↑

Edge view showing the "step" ↑

The rubber spacer ↑

I happened to view the display under bright light with a specular reflection from the plastic, and saw this:

Since the ribbing on the spacer runs "vertically" from the contacts on the PCB is that how power and signal are delivered to the faint, almost invisible traces on the display?  I don't see any embedded wires in the rubber... is each rib designed to conduct along its length but be insulated from its neighbors?  The spacer looks and behaves just like a simple piece of rubber.

What is this technology (both the "spacer" and the invisible traces on the LCD) called?


texts:
I'm using an SIMCOM, SIM800. This module was working perfectly fine, but suddenly it stopped posting and while debugging I found out that AT+CSQ was returning "+CME ERROR:604" which according to Telit means can not allocate control socket

What does that mean? What does the control socket do? It's strange to see the CSQ command fail.
Design question
Has my power block somehow damaged the module?


texts: Choosing The Right IR Emitter for a Photodiode

texts:
I am working with the following IR photodiode http://www.mouser.com/catalog/specsheets/bpv22nf.pdf

However, I am having some trouble figuring out what sort of IR emitter I can use with this. I am trying to setup simple IR data transfer between microcontrollers.  The datasheet makes me think I could use either a 950nm emitter or a 830-880nm emitter but I'm not entirely sure. Also, how closely should I match the rise and fall time? The beam angle? I'd like to use a through hole package, which may limit my choices.

Thanks for the help.


texts: What is the theory behind the coded magnet sensor?

texts: I see that Banner has coded magnet switch. The switch would NOT be active by any magnet but one. Why this happen?


texts:
I recently found myself soldering more than usual up to a point where I'm willing to buy a fume extractor to mitigate long term health effect. However, the price range of all the products I could find is quite drastic. From a couple of bucks to well into the thousands. I'm not shy on spending a bit, but I'm not willing to go all out either.

My current estimated usage is about 5 hours a week, but could rise up to 10 quite easily.

What characterestics should I look for when doing my shopping? Is there a better type of filter to look for?

I know that this question is on the verge of opinion, therefore if an admin flags it as inappropriate, I will remove it right away.


texts: What is the function of the capacitor \$C_\infty\$ in connecting the DC supply of a common-emitter amplifier to ground?

texts: this circuit using voltage divider but I don't know why there is \$C_\infty\$ connecting to ground and DC voltage supply. Also, normally, many CE models I have seen don't have \$R_L\$ included to serve as load. Can the variation of \$R_L\$'s value changes the gain?


texts: Schematic Symbol Help Possible Antiquated JFET Symbol Conversion

texts:
This is an old schematic, and the MPF102 JFET in the picture is confusing me.

Can someone help me identify the Gate, Source, & Drain connections to this symbol, please!

My guess is that the bottom right pin is gate, but it is not intuitive for me.

Here is the old symbol, from the schematic:

Since the MPF102 is no longer available, I chose to replace it with a J113, and here is how I typically see it drawn:

Would someone be willing to map the equivilent pins of both of these two symbols so I can see whats going on.


texts:
I'm looking to use the D1N914 diode in a netlist for use with ngspice. Thankfully I've found the model for free here: http://ppd.fnal.gov/experiments/cdms/old_files/electronics/FLIP/3U/QampDiscrete/proto/schematics_layouts/DIODE.LIB

Problem is, I don't know how I can add such a model to work with gschem or even ngspice. I'm wondering if anyone is familiar as how to use models in ngspice or SPICE in general.

The circuit I'm describing is a just a voltage source connected to a D1N914 (anode to positive, cathode to negative). Nothing special, I'm just doing a small DC analysis.


texts:
The usual rule with LC circuits is to use the lumped model if the circuit is considerably smaller than the wavelength, or if the propagation time is considerably smaller than the rise time.

With RC circuits however, using the distributed model is important no matter the wavelength and there are relations between the lumped and distributed models. For example, the time to reach 63% of the final voltage is half for the distributed model (the Elmore delay).

I'm concerned about the difference in terms of ringing period and peak ringing amplitude between the distributed and lumped LC, not considering any wave behaviour (the circuit is much smaller than the wavelength). I couldn't find any relation between the two approaches. It would be useful to simulate it as lumped and use a simple conversion to get the real behaviour, like for distributed RC.

So my questions are:

1.What are the relations between distributed and lumped LC?

2.If the circuit is much smaller than the wavelength, is it true that all the voltages measured on the line have the same phase? Is the LTspice (or PSpice) simulation accurate?

later edit: in the picture above the voltages are in phase because it is not long enough or it doesn't have enough inductance or capacitance. I've managed to get the same delay as for the transmission line component by using 10 LC elements and enough inductance.


texts:
I am not an electrical engineer, but because I broke the 3.5mm jack of my headphone, I decided to mod it to have a removable cable.

It's a headphone with mic (hyperx cloud2).
It's working well when I plug a 3 conductor audio cable into it (left and right speakers working properly)

The issue is when I use a 4 conductor audio cable, the sound becomes really weird, kind of echoish.

I m wondering what could be the issue.

Did I solder wires on wrong pins?
Are some cables still insulated?

How could I test this to know where this issue is coming from?

Thank you!


texts:
Many times during reading about Power Supplies, I came to this word and couldn't find it's meaning? What does generally burst mode mean? What is the advantage of a power supply if it has burst mode.
To be more specific in Buck converter.


texts: What's the goal of diode and resistor in parallel on SMPS?

texts:
While reading schematics diagrams from several switch mode power supplies of LCD TVs, I noticed that the pin which delivers the PWM pulse to the gate of a MOSFET has a diode and resistor in parallel.

Some diagrams don't have it. But there are lot of which they have it. I guess it's some protection to the driver to the IC controller.

Although I'm not sure. In first diagram there are diode and resistor in parallel, and in second there is not.


texts: Reasons for a simulated circuit to oscillate when the physical circuit does not

texts:
I am building a circuit to drive a solenoid with current control. I am driving it with a circuit based on the improved howland current pump.

Interestingly my simulated circuit displays a large amount of ringing on fast step inputs and I spent a good deal of time trying to stabilise the circuit by adding a capacitor across R5 (this worked but slowed down the response more than I would like), however when I physically build the circuit the ringing did not occur even without the extra capacitor.

I am used to this working the other way around with the "ideal" simulation exhibiting stability and the physical circuit oscillating.

What factors can lead to this.

I am suspicious of a few candidates.

Poor spice models (However I am using TI Spice with TI's own component models)
Stray capacitance damping things (this is constructed on a breadboard)


texts: Given bode plot, determine the poles and zeroes

texts:
Ultimately, I want to figure out the transfer function $$H(s)$$

But to know that I would need to know where the poles and zeroes are.

Looking at this, I know $$ H(20j) = 0  $$ but that's pretty much it. Where are the poles?


texts:
I'm trying to find a ripple/pulse/edge counter chip that can record rising edges from a wind anemometer while my AVR sleeps. The signal is typically 0-50 Hz. I want to read it every 10 minutes, so it needs to be 14/15/16 bit or more.

I'm hoping to find a chip that can keep track of the number of rising edges at a lower power cost than waking up the AVR at each pulse.

Does anyone have a suggestion for such a chip? I'm obviously searching for the wrong keywords. Any help is greatly appreciated :)

I'd like the to read the data serially, if possible.

Edit: I found the DS2423 Maxim chip. It seems like a good fit, but it is discontinued: http://www.maximintegrated.com/en/products/comms/one-wire/DS2423.html


texts: What is the value of the node voltage, V1?

texts:
The value of the Vz (voltage across the Zener-diode) is 4V. There is also a current flowing against the diode. We know that when a diode is in the zener region, Vd = -Vz. I tried a simple KVL and got the equation 5V + V1 -(-4V) = 0. Is this correct?

simulate this circuit – Schematic created using CircuitLab


texts: Suggestions needed to replace relay on this circuit

texts:
I am designing this circuit for testing purpose to test the following conditions.

1.When +12V is applied to the test circuit,my Circuit B should be activated for 2ms and trip open.CKT B is already designed and working fine.During this condition,my CKT A should be inactive.
2.When no power is applied ,my CKT A should be activated.

I am using Normally closed relay in the place of switch(SW), so that my CKT A is always on and inactive when +12V is applied.The minimum response time of the relay I found was approximately 0.5ms.I want to reduce this response time as it will have an impact on CKT B activation time.

Is there any option to use any other switching device to satisfy this condition.


texts: Why add a diode to a transistor controlled DC motor circuit?

texts:
I'm new to the world of circuits.  I have only a basic level of understanding.  I know how to use resistors, know the difference between NPN and PNP transistors, and understand the one-way flow control offered by a diode.

But I don't understand why a diode has been introduced into the circuit (and many similar diagrams I've seen) when using a transistor to switch a DC motor on and off when it runs at a higher voltage than the controlling source (ie. an Audrino or PC).

Here's an example from Adafruit:

I recognize that the 5v source current powering the motor would not short to ground because of the orientation of the diode.  But I don't see why you would do that rather than just have the 5v run directly (and only) to the motor.

Is there something about the rotating nature of the DC motor that causes reverse current or something, and the diode is there to protect the audrino?

Appreciate any help offered.  Thanks.


texts: Why is the frequency domain representation of an integrator 1/s?

texts:
I am taking a linear systems and signals course and we are currently looking at system transfer function realization. The textbook states the following,

  A transfer function \$H(s)\$ can be realized by using integrators or differentiators along with adders and multipliers. We avoid use of differentiators for practical reasons discussed in Sections 2.1. Hence, in our implementation, we shall use integrators along with scalar multipliers and adders. We are already familiar with representation of all these elements except the integrator. The integrator can be represented by a box with integral sign (time domain representation) or by a box with a transfer function \$\frac{1}{s}\$ (frequency domain representation).

I'm not entirely sure i understand why \$\frac{1}{s}\$ is the frequency domain representation for an integrator. When i hear the word integrator i'm thinking 'integration, finding the area underneath the curve, summing of areas...'. Could anyone explain to me why \$\frac{1}{s}\$ represents integration? I am not seeing the link.

Thanks in advance.


texts: Is the CAN bus protocol a master and slave protocol?

texts:
I am investigating if the CAN bus will work for the projects I am building at the moment.

I want to create a bunch of input/output controllers that will accept/buffer commands, execute them and then report back progress. My feeling is that a master and slave setup will not work best for project, but I am not sure if the CAN bus works on that principle.


texts: Recently I was designing a PCB for my project using 89c51. I am using a 12V battery to run motor and 7805 to give 5V to 89c51. When going to ARES for PCB designing I realised the VCC pin of 89c51 is not connected to output of 7805. While this pins are hidden in ISIS. How do I unhide this hidden VCC and GND pins to manually connect them to output and COM of 7805?


texts:
How does DMIPs apply to clusters or multi core systems.

My understanding is that DMIPs is a benchmark w.r.t how long it takes to run the benchmark program on a processor. So it should not matter if it is multi-core cluster or operates in different ARM modes like Split, Lock-Step etc.

Is this correct ?

Will running the cluster in Lock-Step config result in a different DMIPs than split mode?


texts: What are the most common failure modes of Solid State Relays?

texts: Doing an FMEA and this question came up, for both AC and DC SSRs


texts: Which surface finish for edge connector plating to increase number of mating cycles with sliding spring contact?

texts:
I'd wish to insert a small 12x33mm PCB into a USB slot multiple times a day. Because of that high number of expected mating cycles, the surface finish of the edge connector should be chosen wisely.

The PCB will draw 2 microamps of current in power-down mode, and up to 8 milliamps at peak levels. And the components are likely to last for over 20 years, so it the PCB.

The contact wear will be caused by spring contact and the wear is sliding.

"Common" surface finish options for increased mating cycles are:

ENIG - Electroless Nickel, Immersion Gold
ENEPIG - Electroless Nickel, Electroless Palladium, Immersion Gold
electrolytic nickel gold - (sulfamate) nickel with hard (or soft) electrolytic (acid) gold layer on top (often 3:1 layer height ratio)
galvanic gold a.k.a. hard (plated) gold a.k.a. electrolytic gold a.k.a. electroplated gold. This is gold with hardening additives (like cobalt) without the nickel base layer.

The "Blackpad effect" seems possible with hard plated gold and ENIG. So these PCB finishes can only be applied selective not over the complete board, or when applied full board, loose the rework capability.

I do need an edge contact connector (a.k.a. "finger") finish mainly for high mating cycling low wear. I do not necessarily need to meet any spec its contact resistance upper limit value. Still having a connection that works, and doesn't do harm to the spring contacts of the USB female connector is sufficient. There is no soldering to be done on these contacts.

Which (sufficient, not the best) surface finish to choose for these contact fingers, and why?


texts: Can I use 2 Flop synchronizer to migrate a pulse from one clock domain to another provided that clocks phase shifted but of same frequency?

texts:
I want to migrate this signal from CLKA to CLKB. Frequencies of both the clocks are same but they are out of phase.

Can 2-Flop synchronizer be used for this? Please note that the signal can be low/high for one CLKA clock cycle (pulse).


texts: Is possible to modulate the upper and lower sides of a carrier with two distict signals?

texts:
I would like to modulate in amplitude the upper and lower sides of a carrier with two distinct signals. Would it be possible?
There is a specific name for this scheme of modulation?

The detection will be made using the sampled data (in the digital domain).


texts: How do I get a stable 15V signal without a variable power supply?

texts:
I'm studying mechanical engineering (inb4 easy major), so my knowledge of EE is limited and sequestered to blind application.

I need a stable 15V supply for a wheatstone-bridge strain sensing circuit, and I can't use a power supply (too bulky). I wanted to use a battery bank and just step up the voltage, but I'm given to understand they output some sort of PWM signal, not a stable DC signal. My thought was to use a boost converter to step up to 18V, and then use some kind of LC smoothing filter to get a stable 15V. Is this a bad idea? How would you guys approach this? Is there any sort of cheap IC package that will do all of this for me? Thanks in advance.


texts: Does "Common Mode Noise" only affect single-ended signals?

texts:
In the above illustration the common mode noise is hitting to both + and - wires.

Here is my understanding of the "common mode noise":

In a Single-ended system: the - wire is GND and + wire is carrying the actual signal, so the noise will only affect the + wire but not the - wire since it is GND. Noise then will appear at the output (difference of the + and - wires).

In a Differential-ended system(differential signalling):* the - wire and the + wire both are carrying signals which are mirrors of each other, so the same noise   will simultaneously be added to the + wire and the - wire. Noise will not appear at the output.

If my understanding is correct; does that mean if one talks about "common mode noise", he is talking about a single-ended system?


texts: What is the purpose of a filter consisting of a capacitor and two inductors?

texts:
I have the following filter in a single device:

It looks like a ceramic capacitor, but with 3 legs, and also states capacitance like such capacitor (only 103 printed).

What is the typical purpose of such filter? How would it usually be connected?


texts: Turn a load on with a pulse of power, keep on until (NO) button is pressed

texts:
I have a device that sends a pulse +12V when access is confirmed. I would like to keep a relay live until a button is pressed to close the circuit.

This is used to start up a cars (acc) and allow it to start. Then when I exit I will press the button and it's all off. I am lost as to what to search for and the ways to make this happen.


texts:
I'm aware of how Zener diodes can work as voltage clamps, but how do TVS diodes work in terms of physical construction?

The Wikipedia article explains what they are used for, and a bit about their capabilities and parameters, but doesn't really explain how they're constructed or what their detailed physical behaviour is.

Is there a way to describe them with a discrete representation, or are they a unique construction?


texts: OpenOCD throws "JTAG scan chain interrogation failed: all zeroes" error

texts:
I am trying to install openWRT on a router using my Raspberry Pi Zero. I am following the exact steps as explained in http://www.alfredklomp.com/technology/experia-v8/
However, for some reason I keep getting the following errors:

Warn : gpio 11 is already exported
Warn : gpio 25 is already exported

Error: JTAG scan chain interrogation failed: all zeroes

Full output:

    Open On-Chip Debugger 0.10.0+dev-01242-g11c5efd2-dirty (2020-05-15-17:51)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
DEPRECATED! use 'adapter srst delay' not 'adapter_nsrst_delay'
Info : auto-selecting first available session transport "jtag". To override use 'transport select <transport>'.
force hard breakpoints
flash_file
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : SysfsGPIO JTAG/SWD bitbang driver
Info : JTAG and SWD modes enabled
Warn : gpio 11 is already exported
Warn : gpio 25 is already exported
Info : This adapter doesn't support configurable speed
Error: JTAG scan chain interrogation failed: all zeroes
Error: Check JTAG interface, timings, target power, etc.
Error: Trying to use configured scan chain anyway...
Error: vrx200.cpu0: IR capture error; saw 0x00 not 0x01
Warn : Bypassing JTAG setup events due to errors
Info : starting gdb server for vrx200.cpu1 on 3333
Info : Listening on port 3333 for gdb connections

Does anyone know what is going wrong? I have been searching for ages, but this is my first time doing this and I am not finding anything useful.
Thanks for taking the time to look at my issue! I really appreciate it :)

I am thinking the connections might be incorrect, but I am doing the exact same as described by him and I used both his schematics plus the image to match his wire placing.


texts: What could be the target applications for these BJTs?

texts:
NXP recently introduced a new family of BJTs with switching capabilities of up too 100V, 10A , see "The toughest bipolar transistor - 100 V in LFPAK/Power-SO8".
I cannot think of a switching application where these (or any other similar) BJTs would be preferable compared to a MOSFET. Also I am very sure that there is a commercial objective behind these devices and thus there must be at least one worthwile application.

So, in what kind of application would these BJTs actually have benefits over a MOSFET?

(NB: I am referring to switching applications, not linear applications like voltage regulators.)


texts: type I phase detector - analog vs digital inputs

texts:
Section 13.13.2.A of the Art of Electronics (3e) describes a type-I phase detector. It is explained that the analog version of this circuit uses a multiplier and the digital version uses an xor gate. Additionally, this quote seems to indicate that the xor gate is a digital "version" of an analog multiplier:

  The type I phase detector is applicable to either
  analog- or digital-input signals, and performs a simple multiplication of the inputs. For digital signals this is just an exclusive-OR gate...

I fail to see how an xor gate gives the same result as an analog multiplier with digital inputs. Here's the digital circuit and corresponding voltage output as a function of phase.

How this circuit works and why it functions as a phase detector make sense to me. However, I don't see what the analogous analog circuit would be. For instance, replacing the xor gate with a mixer produces the following circuit:

If I assume that the RC lowpass filter produces a perfect average of the mixer output over a period (and for simplicity both input signals have identical frequency), then the relation between \$V_{out}\$ and \$\phi\$ is shown in the following plot.

I guess I could invert the output (e.g. amplifier with gain=-1) to get a roughly analogous result. Is this what is done? If not, how can I implement an analog type-I phase detector (presumably with a mixer)? Did I misinterpret the phrasing used, and what was really meant was that a mixer is used as part of the phase detector but is not actually analogous to the xor gate?

Something else I've missed?


texts: On STM32F4xx: Can I trigger a timer by itself so it goes through a list of periods updated from an array?

texts:
I need things to happen at precise (down to the clock, ~5.5ns at 180MHz) periods of time based on a list; let's say 5 periods of 444444, 555555, 666666, 777777 and 888888 timer clocks (obviously a 32bit timer clock).

I propose the following:

I set TIM2 "TIM_Period" with the first period. I set clock to system clock. I set it to trigger itself (is that possible?). I also set up an ISR to get fired at same time
I start TIM2.
I pre-load the next "TIM_Period" in the timer, somehow that it will only be "effective" after it "fires/updates".
In ISR I increment an index through the array of values: If a next value exists I pre-load it into "TIM_Period" so TIM2 loads it next time. If no next value I turn off the self triggering. Other things might be done in the ISR as long as short enough to end before next timer firing.

If this works, could I (in the ISR, based on some list) also set up other timers to be triggered by this main timer?

Thank you for answers so far but soft timers are out of the question.
Also, I don't need many; I need 3-4.
I'd prefer hard answers from somebody that actually did trigger one timer from another.


texts: How can I use 2 TP4056 to safely discharge 2 18650 cells in series

texts:
I am new to electronics. I have made a robotic car type thing with arduino and L298N and I want to power it using two 18650 cells in series. I have watched videos on youtube where guys use 2 18650 cells in series without any over-discharge protection board (e.g. TP4056 ). But I don't think it is safe and I think there should be over discharge protection circuit (e.g. TP4056). I don't know how to do that with two 18650 cells. Should I connect two 18650 cells with two TP4056 and connect TP4056 in series and use it across load?
Is is safe? What is the proper way to use two 18650 cells with over discharge protection?
below screen shot shows what I am thinking of donig.
Edit : I am not worried about charging. I have different charger for that.

Thank you


texts: How can I invert a solar-powered oscillator's frequency?

texts:
I have a hobby project that's been on the backburner for about 3 years now. It's very simple - just a solar-powered oscillator hooked up to a speaker, that changes frequency in response to the level of sunlight.

This is the circuit I'm using right now. It's mostly designed by Wilf Rigter from the BEAM circuits mailing list:

The thing is I'd like to invert the frequency/sunlight response. At the moment in dark light it's a quiet tone with low frequency, and in bright light it's a loud tone with high frequency. Instead, I'd like to have a high-frequency tone in low light and a low-frequency tone/pulse train in bright light.

I'm really up against my knowledge limit in understanding this circuit as it is. What I do understand is that the 10nF capacitor charges through the 22k resistor until its voltage reaches the Vbe threshold for the NPN transistor on the bottom left, at which point the transistor opens and the capacitor discharges through the speaker, making a click. Then something happens to reset the system and it starts again. With more light the capacitor charges faster and so the tone has a higher pitch.

Inverting the frequency/light level response, though, is beyond me. I think I'd need to somehow slow down the charging of the timing capacitor here as the light increases by diverting the current somehow, and I suspect that I'd want to be storing this diverted current in another storage capacitor to be discharged through the speaker, instead of discharging the timing capacitor through the speaker. Actually building this into a schematic, though, is too difficult for me right now.

Any help much appreciated!


texts: How can I use power over ethernet to transmit data and power to the OpenMV Cam M7?

texts:
I'm trying to make the OpenMV Cam M7 PoE enabled. See the link below for the camera:

https://openmv.io/collections/cams/products/openmv-cam-m7

It has USB interface, SPI, UART and CAN buses. My initial thought is to use a PoE splitter and send power through the USB and then convert the ethernet to SPI or UART, but I'm looking for more ideas. The network switch conforms to the IEEE 802.3af standard, and the splitter steps it down to 5V, which the microcontroller board can tolerate.


texts: Driving High Power LEDs with this circuit

texts:
I've just completed building this circuit (thanks alexan), times 3 for each RGB channel.

R1 = 4.7k
R2 = 1K
R3 = 10K

Q1 = BD140
Q2 = BD139

This circuit is used to power 4x20mA RGB LEDs in parallel and am happy with the result. They're using 510/470/470 resistors for the RGB channels respectively.

Now I'd like to do the same but power a much higher power LED but I have a few questions before I go ahead and purchase it.

What's the reason for not having a common cathode, instead having +/- for each channel? Can the cathode go to a common ground in my circuit, while each of the anodes go to the emitter of each Q1?
Would the schematic above be sufficient to drive these LEDs? (remember the schematic represents a single channel)
How do I calculate the resistor values for each channel for a 12VDC power supply? Is the 350mA current for all 3 channels or is it per channel?

If it's per channel, then each channel would need 166.67mA of current. The calculation I'm using is:

Typical Forward Voltage R/G/B (datasheet) = 2.4/3.5/3.4

Red = (12V - 2.4V) / 166.67 = 57 Ohm (1.6W)
Green (12V - 3.5) / 166.67 = 50 Ohm (1.4W)
Blue (12V - 3.4) / 166.67 = 51 Ohm (1.4W)

This doesn't seem right to me at all, because the total power comes to 4.4 Watts.

So, where am I going wrong?


texts: Why does a GPIO pin always return logic low when devices are connected to it?

texts:
I made myself a transceiver in which I want a microcontroller to control.

I created a microcontroller test circuit where some GPIO pins are pulled up via 10K resistors and when I tested them with this code, the correct data returns:

cpl P3.5
mov A,#30h
jnb P3.5,theend
inc A
theend:

The reason why I use 30h and 31h as values is because I hook the micro to my computer and 30h and 31h are hex codes for the numbers 0 and 1.

I use the same code and connect each individual GPIO pin to each individual input circled in my circuit below. The problem is 30h is always returned which means to me, somethings always sending that pin to ground, yet I don't have anything else connected to the two GPIO pins except for each circled input in the circuit below. The two GPIO pins are not connected to each other either.

What could be the cause as to why the GPIO pins don't work the way they should? Do I need diodes or something between GPIO pins and a device input pin such as any circled input in my circuit?

UPDATE

The microcontroller in question is an AT89C2051 and the voltage source in all cases is 5VDC.


texts: What is "gain" a measurement of in electronics?

texts: I'm familiar with the term "gain" used in sound and music, but I'm having difficulty finding the definition in electronics.  I'm seeing the term low gain and high gain being used in the description of the Panasonic Grid-Eye infrared sensor.  What exactly is gain a measure of in electronics?


texts: PWM to synth control voltage improvements

texts:
Just built this little circuit to control my Moog Werkstatt. The plan is to make a MIDI-to-CV converter and add more CV outputs and of course a GATE output later. But before going further, I thought I'd ask if this circuit could be improved.

CV in this context stands for "Control Voltage" and is used to control the frequency of the oscillator in the synth. The Moog Werkstatt changes the pitch by 1 octave per volt.

The Atmel chip sends a 0–5V PWM signal at 133.333kHz. After filtering the PWM output it is scaled to -5-+5V (which is what the Werkstatt expects). I want to be able to tune the signal so therefore I let a voltage divider turn the signal down to roughly 4.5V and then I have an amplifier which can turn it up to 5.5V (and be adjusted by a potentiometer).

It works well and I'm quite satisfied with the performance but maybe there are some obvious faults with the design that might affect stability? Perhaps there should be a buffer somewhere in the circuit? Will R2 and R3 change value over time and cause unbalance?

I would greatly appreciate any suggestions. Thanks!


texts: How to do theoretical calculation of S parameters

texts:
I created a test bench for bond wire in ADS EM simulator and got the following graph in the picture I attached. I'm trying to compare the values which I got in ADS with theoretical one. But I'm confused how to do calculation of S-parameters in a two port network.

Kindly help me to calculate the S parameters and compare with the practical one.


texts: Software definable battery controller to be able to re-use various laptop batteries

texts:
I'm looking to retro-fit an older small netbook Toshiba NB100, by replacing the logic board with the single core Atom 1.6Ghz with an up-board core.

A hardware/software solution for re-using the battery for this laptop seems to be among the hardest task. Ideally I'm looking for some kind of programmable battery controller whereby the a particular battery can be defined in software.

I'd want to be able to charge while using the machine. I'd want battery level to be reported in the usual Windows way (ACPI drivers would be needed).

I think that there might be a good market for the upboard for re-using most of the parts of old laptops in this way: environmental particularly.

Related question, but appears to be specific to another battery: Battery charging for DIY laptop


texts:
Basically, I'm wondering if the size of a via pad and drill has any effect on my circuits. For example, let's look at two vias:

One via has a smaller drill and more copper around the edges, while the second has a larger drill and therefore less copper around the edges. Both vias take up the same amount of space on the board.

Which type of via is generally preferred, and why? Is there a difference if I choose to fill the vias with solder?


texts: Crowbar Circuit for 35V OVP - What parts should I use?

texts:
Please excuse my confusion, because I really don't understand what the "150mA max continuous cathode current" means on the datasheet for the LM431. I'm also not sure it'll work in the crowbar circuit I intend to build. (I suspect it will, seeing as it's rated for 36V).

I have the following circuit diagram, based on a Wikipedia description of a crowbar circuit:

simulate this circuit – Schematic created using CircuitLab

D3 leads to a(n) LM3481 used as a SEPIC (Pg 26) to output 7V for a load that draws between 500mA to 1A (1.25A to be on the safe side).

This leaves me with a number of questions, assuming I want the crowbar to reject (short out) input voltage higher than 35V:

If the input voltage at D1 is higher than 35V (unlikely, but possibly as high as 40V), will the LM431 become damaged or will the fuse burn out first?
Will a polyfuse/PTC work for F1? What part type/specifications should I look for?
To what should I connect the wiper for R1, GND? Does R1 need to be a POT or can I use a fixed resistor?
What are the values for R1, R2 and R3?
DI1 is a TRIAC. What specifications should I look for?
Does the 150mA mentioned in the data sheet have anything to do with the load after D3? What is it actually telling me?
I know that I can use Vout ~= (1 + R1/R2)Vref to work out what R1 and R2 should be, but I don't know how I work out Vref. Is that Vin from D1 or from the LM431?

I have seen this as a proposed solution, but apparently the MOSFET doesn't short to ground (according to one of the comments).


texts:
Suppose I have the following circuit image of an example XORD gate using AND, OR, and NOT gates:

Are there any open source tools that are capable of converting this into text characters, so that I can show the diagram inside text documentation without having to link to the image? An example of a square being drawn using ASCIFLOW would be:

+-----------------+
|                 |
|                 |
|                 |
|                 +------------------>
|                 |
|                 |
|                 |
+-----------------+

But I'm trying to see how to create basic circles, triangles and other gate-shapes.


texts: Rectifiers operation when there is a sudden voltage drop

texts:
Currently studying rectifiers and came along a paragraph in a book that left me puzzled.

"In a full-bridge rectifier supplying an inductive load, if there is a sudden drop on the AC voltage at the input of the rectifier, the firing angle will immediately drop to zero degrees".

I'm very puzzled about this. What is the evidence on that? My suspect is that it has something to do with the current continuity on the inductive load, the current can't simply have a sudden drop. But how does that makes the firing angle go to zero? Why should that happen?

Another question I have is related with the firing circuit of the thyristors, that makes them transition to conduction. Now if there is a breakdown and the gate current/voltage of the thyristors suddenly drops to zero, they will cut off, right? What happens now with the current /voltage on the inductive load? Then again it can't simply just drop to zero, in the case of the current. But where to does the inductive load discharges? To the thyristors? Do I simply create a spark and the circuit is ruined? Maybe with a freewheeling diode in anti-parallel with the load, I could solve the hazard?

Thanks in advance!


texts: The constant time value for an electronic device

texts:
i am working in a data science project that require certain information about electronic devices. So I know that for each electrical circuit there is a permanent regime and a transient regime and while passing from the transient regime to the permanent regime there is a certain characteristic value of time T which is constant for each circuit. what i need to know is for domestic electronic devices is there an average or maximum value of T (the device is unknown) after which we are sure that the transient regime is probably over.
i will appretiate any information that can help me .


texts:
I am trying to simulate a basic inverter circuit in LTspice. For some reason I am unable to obtain 48V peak to peak across the resistor R1 which only shows about 6Vp-p (indicated by the blue square wave). V(first) and V(second) are the pulse signal going to the base of the BJT switch. What changes should I make in order to obtain higher voltage across R1? Any help would be highly appreciated.
EDIT: I simulated the circuit using nmos, managed to get the waveform but the p-p voltage is too low (24mV as opposed to 48V). What might be the reason for this?


texts: Help with wiring a temperature controller and a solid state relay

texts:
I have a problem that's probably patently obvious to someone in the know but alas, that's not me.

Long and short- I have a 240v heating table (aluminum table with silicone heating pads underneath) that is about 40 years old and it just died.  Unfortunately all of the old parts no longer exist and the original design was part specific.  So after a lot of reverse engineering and brain storming I (with some help) found a solution.
 The table will be controlled by a Watlow pm3c1cj-aaaabaa, with a simple relay switch to turn the controller on, and a solid state relay to power the heating elements.

I have successfully wired everything according to the diagram my helper gave me but the solid state relay hung me up. Here's the wiring diagram (incomplete) :

Relay is the relay switch to power on the Watlow

Watlow is the pm3c1cj-aaaabaa

The Watlow has the following contacts available: T1, X1, W1, Y1, Cf, Cd, CE

"THC" is the thermocouple

SSR is a Continental rvda/6v40

The SSR has the following contacts: 1/L1, 2/T1, 3/A1, 4/A2

I'm at a loss as to finish up the wiring.  Any help would be massively appreciated.


texts: Obtaining varying voltage from a constant voltage power supply

texts:
I have a 24V 20A power supply. 24V is constant not variable.

I want to use a heating wire such as nichrome one for an experiment.

It means I need to pass around 4.5 or 5A through a pure resistive element. I need to find a way to adjust the current through the heating wire.
I can do it by varying the voltage across it. The heating wire has resistance about 1.5 ohm.

So I guess I have two options: First one is to add a series power potentiometer which can handle currents up to around 10A.

And the second option could be using an opAmp and 24V as its rails.

Since I cannot find such power potentiometer how can I implement a 0-12V varying output with max current upto at least 6A from the power supply I have?

Or any other ideas to vary the current through the resistor?


texts: Analog input like in a PLC: Thermistor or 0-10V

texts:
Depending on the configuration, PLCs can often measure 0-10V, resistance or 0-20mA on the same set of screws.

How to use the same screw terminal to measure resistance of an NTC element, voltages in the range of 0 to 10V or current in the mA range?

Any suggestions how I would go about this?

I know how to measure resistance, I know how to measure voltage, but I'm not quite sure how to combine these. Also it'd be nice to make something that won't break if you try to measure resistance on a 10V signal or the other way..


texts: Why is MPLABX reporting the wrong amount of program memory used?

texts:
I've been using XC8 v1.34 for a while, and since v1.41 got released I upgraded to that version instead. Just for the sake of nothing-ness, I recompiled a mature project and saw that the value under "Program Used" (in dashboard) decreased by one, so I got really curious what was optimized away (both compilers used PRO-mode optimization).

I found the menu option Windows -> Debugging -> Disassembly listing in MPLAB and in there was a clean assembler code (below each C-statement) so I cut-n-paste the contents from v1.34 and v1.41 to two separate files and ran a diff. The only thing differing is the timestamp, which was weird since MPLAB says "Program space used: 142" for v1.34 and 141 for v1.41, but the disassemblies are exactly the same.

I then try with stripping all C-lines and the header from the output with:

$ grep -v '^[0-9]*\:' 134 | grep ^[0-9] > 134_2
$ grep -v '^[0-9]*\:' 141 | grep ^[0-9] > 141_2

In the stripped files are nothing but pure assembly code. So I check again:

$ wc -l *_2
 139 134_2
 139 141_2
 278 total

$ md5sum 134_2 141_2
b6aa911111d43cf5251cda7d4e871fdb  134_2
b6aa911111d43cf5251cda7d4e871fdb  141_2

I.e exactly the same code. 139 op-codes too, not 141 or 142.

Why is MPLABX reporting the wrong value?


texts:
This is my first post here, hope you all doing well. I'm a CS student, having my first class on circuits. I've been given this problem (see picture) where I'm asked to find V2. I'm missing one equation, which I can't seem to find? In the first equation, with the currents, I'm assuming that all the currents are flowing away from V2.

I know that this may be very basic, but it's all very new to me.


texts: Flashing multi chips with JTAG using openocd

texts:
I'm newbie in this field. My task is I have to flash 6 devices with JTAG like the picture below. I'm currently success with flashing one device.
Can someone give me advice how to flash all 6 devices?
As I understand, when a device is being flashed, other will be in BYPASS mode, right? Then how can I control the devices? Just in case when flashing 6 devices and one fail, I can know which one is fail and flash it again.
If can, please explain to me like I'm a 5 years old boy would be very helpful.

Edited 1:
These are my 2 config file.

source [find target/kinetis_generic.cfg]

$_TARGETNAME configure -event reset-init {}

flash bank pflash.0 kinetis 0x00000000 0x20000 0 4 $_TARGETNAME

proc program_device () {
 # halt the processor
 halt
 wait_halt
 # write file to flash memory
 poll
 flash probe 0
 flash write_image erase unlock "C:\\Users\\tung\\Desktop\\flash program\\OpenOCD-20170821\\sa2_can_195_init_boot&device.srec" 0x00000000
 #start execution of the program just downladed
 reset run
 #exit OpenOCD
 shutdown
}
init
reset init
program_device ()

and

source [find target/swj-dp.tcl]

if { [info exists CHIPNAME] } {
    set _CHIPNAME $CHIPNAME
} else {
    set _CHIPNAME kinetis
}

if { [info exists ENDIAN] } {
    set _ENDIAN $ENDIAN
} else {
    set _ENDIAN little
}

if { [info exists CPUTAPID] } {
    set _CPUTAPID $CPUTAPID
} else {
    set _CPUTAPID 0x4ba00477
}

set _TARGETNAME $_CHIPNAME.cpu

swj_newdap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf -expected-id $_CPUTAPID

target create $_TARGETNAME cortex_m -chain-position $_CHIPNAME.cpu

$_CHIPNAME.cpu configure -event examine-start { puts "START..." ; }
$_CHIPNAME.cpu configure -event examine-end { puts "END..." ; }

# if srst is not fitted use SYSRESETREQ to
# perform a soft reset
cortex_m reset_config sysresetreq


texts: What is the physical meaning of the characteristic impedance of a transmission line?

texts:
If it was per unit length, I'd understand, but apparently it is a constant of the whole line.

Consider if I change the length of the transmission line, the impedance of the whole thing should increase since more power is dissipated, but the characteristic impedance doesn't change. So, what exactly is the characteristic impedance?


texts: 8-bit binary U/D counter with rotary encoder

texts:
Im trying to make 8-bit binary counter using CD4516 / HEF4516 (doesnt matter, both act same).

My circuit works well excepct one error.
I can successfully go from 00000000 to 11111111 and over again, i can do the same in backwards direction.

Error only occurs when i have 1000 on lower counter go to 0000 and back to 1000, then the second IO acts weird.

Error is not in arduino, nor the PISO, id does the same with directly connecteed LEDs.

Anyone have an ide? Thanks.

EDIT: working circuit:


texts:
I've some basic knowledge on how to program PIC microcontrollers in the past I've used a LCD and a keyboard to make a clock alarm.

Recently I really got into Web development, mostly on SQL, PHP, HTML and some other basic stuff.

What I want to achieve is to create a GUI using web languages, that I can access using any computer within the same network. ( I don't know wether I should host the server in a computer that is connected to a PIC or if I should host the web server in the pic).

So the real question is: Where do I start so I can get documentation on some projects that used a similar set up to what I want to achieve.


texts:
I have built a valve/tube tester. To provide the various screen and plate voltages I'm doing this:

The required voltage is selected by a rotary switch down the stack of zeners.  The momentary button is pressed to test the tube. The MOSFET is a 500V device that can handle more than 7 amps.  It has protection zeners built in but I've added an external one to the gate anyway.  Datasheet here
R2 represents the ESR of my power supply.  At 150mA its already sagged to 260v but thats fine; the tubes I'm testing draw less than that.

It works as expected. There are two instances, one for screen volts, the other for plate.  But every so often I find the MOSFET has failed in one or the other, shorted source to drain.

There is sometimes a 68nF capacitor 'downstream' (depends on configuration), the MOSFETS are mounted on an aluminium heatsink but never get even warm to touch (they only run for a few seconds at a time) and the device itself seems to be well protected and rugged to boot.

What have I missed?  Whats the most likely way I'm destroying these MOSFETS and what can I do to mitigate this?