texts: Differential amplifier and differential signals in small signal analyses

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I'm studying the differential amplifier on different books (Razavi and Sedra-Smith).

I've understood how this circuit works, but I have some questions. When authors analyze this circuit (2 identical mosfets or two identical BJTs with a current source below them, as shown in figure) for small signals, they always assume differential inputs, that is: v1 = -v2

Question: why is this assumption required? When this circuit is used as the first stage of an operational amplifier in a negative feedback fashion, who says that the inverting and non-inverting terminals will have v1 = -v2 ? Negative feedback says that the input differential input of the op-amp is very very small (and for a very very small differential input collector currents of the differential amplifier are linear), I don't understand then why v1 should be equal to -v2. Small signal analyses should (in my opinion) consider the case in which v1-v2 is very very small, but not necessarily v1=-v2

Thanks


texts: Locked Anti Phase PWM and BLDC makes sense?

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Locked Anti Phase PWM is used to drive brushed DC Motors,
but does it make sense to use it for a BLDC, e.g. 3 Phase Motor?


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I want to interface 8051 to a double gear box kit with comes with a dc motor. The motor spec is : "3-6 volts and draws up to a few amps"
The DAC is MAXIM 512  : And as per the data sheet, this is what i find : "
The latched digital output (LOUT) has a 1.6mA source capability while maintaining a (VDD - 0.4V) output level. With a 1.6mA sink current, the output voltage is guaranteed to be no more than 0.4V. "

And I need an amplifier to connect the DAC output to the motor. But how to design the amplifier circuit for this?

Thanks


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Which is the correct expression for the inductance of a single conductor? I see 2 different formulaes for the same in different sources.

Formula 1.
Ref: https://www.eeweb.com/tools/wire-inductance

Formula 2
Ref. https://www.electrical4u.com/inductance-in-power-transmission-line/

Note: In Formula 2,inductance is calculated for unit length. D is the distance upto which you need to consider the effect of magnetic flux (ideally infinite) for inductance calculation. Formula 2 is the one I have studied in college and I understand the derivation, but Formula 1 is from a reputed Electrical engineering online site. Now I am confused.


texts: Adding different voltage battery to same circuit

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I have 9 volt battery to get 5 volt using step down converter.
I want to enable the step down using a timer IC max input voltage 6 volt. I will use 3.7 v battery for this.

So my question is: Can I join the ground or negative pole of batteries in the same PCB or circuit, I will have problem with  signal voltage to enable step down and power off the timer from the MCU 5 volts ????????


texts:
I'm considering doing DIY SMT Reflow for production of my Super OSD project.

An overview of the component count:

Resistors: ~50 x 0603; precision 0.1% resistors as well as 1% and 5% components
Capacitors: 17 x 0603, 2 x 0805, 1 x 1206 (all ceramics), 2 x EIA-3216 (tantalums.)
Inductors: 1 SDR-0604 package
Chips: SOIC-8 (EEPROM), SOIC-28, TQFP-44, some SOT-23 (temp sensor + TL431.)
Transistors: 3 x SOT-23 (2 x N-ch mosfet, 1 x NPN)
Diodes: 2 x SOT-23, 2 x SOD-323
Misc: polyfuse 0805 x 1, LED 0603 x 1

As can be seen this going to be a monster to solder manually so I was thinking of doing DIY toaster oven reflow. Would this be suitable? Are there any pitfalls I need to be aware of?

Otherwise I'm going to have to solder them up myself but I see it being a real problem with almost 80 tiny components per board.


texts: for better isolation and because of sparking at the contacts, it is suggested using a separate supply with optoisolation like an image attached,  but in my design, I wave only one power supply and I have a limitation in adding another power supply, how can I isolated the power of relay from the power of micro with considering that I have only one power supply?


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I am trying to understand this circuit here.
I do not understand clearly how this works. I know that the PMOS is a current source but what impact does the resistor Rb have on this ?  Could anyone help me out with its working ?


texts: Resistor suggestions for colorblind person

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I'm a developer who has always had a love of the low-level electronis, but I have always been intimidated by it since resistors all seem to be color based and as a color-blind person, this is difficult to work with.

So my question to everyone here is if they know a good, practical way, to work with resistors (mark them, shelve them, etc).  This is the one thing that keeps me from doing more electronics hobby stuff since I hate spending an hour trying to find a 10K resistor in my collection of a few hundred.


texts: Can anyone explain how this 433MHz RF transmitter module works?

texts: I don't know the basic functionality of the circuit and I need a complete description of every component.


texts: Do pick & place machines require reels of components, or can cut tape be used?

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If I wanted to have a PCB assembled, would I have to give the manufacturer reels of components, or will pick & place machines also work with cut tape?

I ask because I'm thinking of having a low quantity of boards assembled (100-200), but most reels on Digi-Key have several thousand components or ICs on them.

I would rather buy cut tape with a few hundred ICs (even if it means a higher cost per component), since buying a reels with thousands would be a much higher upfront cost.

Tried Googling this but couldn't find an answer anywhere..


texts: Transistor delay switch equal to a SPDT Relay

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I have a circuit I need the functionality of a SPDT switch that is flipped a couple of seconds after power is applied.  It is just switching data lines on a USB port so there is no current being switched.

Actually, I need it to short the data lines on the USB port and then 2 or 3 seconds later connect the data lines to a USB hub.

Currently I am using a SPDT switch to accomplish this.

Thanks in advance!

INFO ADDED

I would like the process to be automatic.  i.e. plug the USB cable in and it just works.

Long explanation.
I have a windows tablet pc that has only one micro USB port on it.  It uses this port for charging as well as USB OTG to connect USB peripherals. The problem is it won't usually charge while in OTG mode.  Just applying 5v to the power lines of the USB port won't make it charge.. To get it to charge, you have to short the data+/- lines together.  Then as long as you keep power applied to the Power +/- lines it will continue to charge without shorting the data +/-.  You can then connect usb devices to the data lines and the PC and they work.

The purpose of this is so that I can charge the tablet and use USB devices at the same time.  As it is now, I have to plug the usb hub in with the SPDT switch in shorted position and then flip the switch every time I connect the hub.   I want to make it all automatic. It needs to have the lines shorted for a few seconds and then switch in the lines for the USB hub.

Detecting the USB plug in is easy, just use the USB shield and USB ground pin as a switch.. i.e. leave the ground wire disconnected in the USB cable. The shield wire is used to carry ground. When you plug it into the tablet pc it connects the shield to the GND wire (since they are tied together on the tablet's USB port) and completes the circuit.

Hopefully this makes this all clear. I'm not sure how this forum works to get your thread unlocked after its has been flagged as unclear. :/


texts: Multisim LF357N Op Amp Unity Gain - Questions

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Im working on a junior project in which we need to buffer an input signal from a RX antenna, pass the signal through 3 filters in parallel, and pipe the outputted signal into a RTL-SDR. It serves very little practical purpose as i know that the filtering could be accomplished digitally, but for the project we need to design an analog component.
My analog component is essentially going to comprise of:
-> Recieve signal from antenna
-> sma connector to pcb board
-> input buffer op amp(Ive read these are important at buffering our input)
-> active parallel filters(1 x band-pass, 1 x high-pass, 1 x low-pass)
-> op-amp summer
-> output sma connector (will be connected via short sma cable to SDR)
The frequency range we are going to be sampling is 700KHz - 1300Khz (part of the AM radio band).
This is my first exposure into looking at op-amps and researching the right ones to purchase for this project. In our lab i found a few LF357N op-amps and saw on the data sheet that they had a wide band-width of 20MHz. I figured i would try to breadboard a quick circuit to test the feasibility of this design. All i was trying to achieve was unity-gain using a simple non-inverting design. ** I understand that there are huge problems once we start getting into high frequencies in terms of signal distortion and loss on lines, especially bread boarding. This is why i wanted to make a mock up design before eventually trying my hand at creating a pcb for the final design of this project.
After i was having issues with this, i went to Multisim and started simulating the most simple circuit i could with the LF357N.
What ive seen is that while unity gain seems to work at very low frequency(10Khz), once i bumped my frequency up to 1MHz, the gain skyrocketed to tens of thousands.
Then i threw in 2 resistors to give myself a gain of 2, which worked very well. But as i increased the frequency in 1MHz increments, i noticed the gain was affected adversely again.
Now, my question is why? Is the LF357N not unity gain stable at high frequencies? Even though the datasheet said the bandwidth goes up to 20MHz? What should i look for in op-amps for buffer amps?
Will the same op-amps work for buffering and summing? Or will i need to find a different style op-amp for both of those operations. My understanding is that i will just need 1 kind, as long as the Unity-Gain-Bandwidth is high enough.
Thank you for any help you can give me! I know this may be fairly trivial information, but Ive been searching the web for a few weeks trying to figure all this out and figured i would finally ask a question on it.


texts: Driving a large, noisy, free-wheeling DC motor (cooling fan)

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I have an automotive cooling fan which is nominally 12v and draws about 15-25A with a BIG inductive spike at startup (will happily blow a 30A fuse).

These are traditionally wired via standard automotive relays, but I'd like to drive it from a FET or similar solid-state circuit, possibly PWM but that's a glory job for later, for now let's just switch it on & off with minimal magic smoke escape ;)

This device presents a few challenges:

Big inductive spike at startup / switchoff
When the vehicle is moving but the fan is NOT powered, we need to allow it to freewheel.
When the vehicle is moving AND the fan is powered, it may be driven "overspeed" by the motion of the vehicle, again we want to either disengage (freewheel) it, or at least not try to brake it.
In both cases the driver circuit will have to tolerate the conditions (freewheeling open-circuit the motor may generate far more than 12v, for example) as well as switch between them without letting the smoke out.

I haven't started doodling circuits yet as I suspect the answers to this question will dictate things like device choice & circuit topology. I'm assuming the freewheeling requirement will mean going down the H-bridge route (or at least half an H-bridge, there's no real call to reverse the rotation of your cooling fan!)

I mentioned that PWM control would be nice, other niceties would be soft start (to avoid the massive startup kick) and over-current protection (if the fan tries to kick in when something's jammed in it, the vehicle is 4x4 so the fan could easily be full of mud/sticks/squirrels at any given moment).

So, I'm looking for guidance on what sort of topology I could use to drive it, which families of devices would be most tolerant of this sort of situation, parameters/configurations to look out for or avoid, and what's achievable or a right pain from the "wish-list".


texts: How to capture values displayed on 16x2 LCD

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I have an inexpensive in-line DC Wattmeter that I often use to measure yield from Solar Panels / Modules and other energy sources with reasonable accuracy and resolution. It has a 16x2 LCD display  (1602 STN) that displays 4 values simultaneously namely: Voltage (V), Current (A), Power (W) and Energy (AH). It uses a 8MIPS uC and has a Data Queue / Sequence time of 2 secs. It is rated for 0-60V and 0-100A DC. The wattmeter is a one stop solution as opposed to multiple DMMs or very expensive Data Loggers.

I am now trying to store the values displayed (Data Logging) for various downstream uses. The whole unit is sealed with only the 16 pins of the LCD remaining exposed (and thereby exploitable). All 16 pins are in use.

Is it possible to tap into those values being passed and either:

write them onto a SD card or
transmit to a PC/laptop over USB for display and storage.

The efficiency or accuracy of the unit should not be compromised in the due process.


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I was wondering what happens when VCE voltage becomes negative? suppose I am forwarding both junctions (no resistors). I know that saturation happens when VCE is between 0.1V- 0.3V but what happens below that range (V1 > V2) as in the following scheme?

simulate this circuit – Schematic created using CircuitLab


texts: If voltage can exist while current is 0...?

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In the following diagram voltage can exist without current since it's an open circuit:

simulate this circuit – Schematic created using CircuitLab

Can a voltage source in an open circuit with 0 current effect a circuit like so:

simulate this circuit

So that current would be equal to what is outputted from V-1, yet the voltage is increased to 15V due to V-2?

Because in this circuit voltage can increase even if it's an open circuit:

simulate this circuit


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I am trying to build an optimal circuit for Zero cross detection for PWM dimming using a microcontroller. I have gone through most of forums and their implementation varies.

I understand that the easiest option is to use an AC optocoupler with few resistors to connect to AC and then feed it to the microcontroller for zero cross detection. I have also tried that myself using Sharp PC814 and found working, however it gives slight flickering at low dim levels. (My input is 240V, 50Hz). The resistors also becomes hot despite using 1/4 watt x 4 connected in series ( 2x22K + 2x50K ) giving a total of 1W.

The other option suggested is to use a rectifier and then feed to a normal optocoupler. Does this solution have an advantage over the above solution of using an AC optocoupler directly ?

I have also found another forum suggesting two optocouplers in the reverse direction and feed their output(2 outputs) to a microcontroller. Again these has to be handled separately to find out zero cross. What benefits would this give ?

I have also seen forums suggesting a transformer, but I think an opto can do the job well considering the size, cost and efficiency.

Moreover I have referred one commercial boards and found it using a rectifier and an AC opto (H11AA1) which seems to be unnecessary since the opto itself can handle AC. However it gave smooth dimming at all levels (compared to the one I have build in the same AC source).

I would appreciate if someone can help me to identify the optimal solutions to find zero cross factoring the spikes, noise and some times the square wave from an inverter in the source. I understand that some programming would be necessary to make it better, however I want to ensure the circuit is good enough to handle most cases.


texts: Need some opinion about multiple power source switching

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I designed a simple circuit, which does the following.
Two voltage sources are attached, 5V USB plug and 7.5 V wall adapter with barrel jack plug.
5V USB source should get disconnected when 7.5 V source is active.
There will be another step-up converter (pololu 2115) on the output to bring the ca. 4.2 V output to the final voltage of 5 V.
I do not want to use the the barrel jack switch, because this would disconnect USB even if there is no power attached to the barrel jack plug.

So I use a single p-mosfet to do the job and it seems to work in general, except
for quite significant voltage and current spikes at the moment of switching the 7.5 V on and off. I made only a LTSpice simmulation without proper osciloscope.

Now my question is: Is it a usable solution? Should I care about the spikes? If I shoud care, how can I improve the response without a dedicated power path controler IC (which I know they exist)?

I attache the LTSpice circuit and the transient response graph as images.


texts:
In a recent question it was asked whether a boost converter could be used to "recycle" power output by a buck converter being tested. There are quite a few commercial regenerative electronic loads available on the market. However, a) they tend to be of the power-line tie in type, sending their power to AC mains, rather than to a DC line, and b) I have been unable to find schematics for either commercial or DYI regenerative loads.

In the circuit above, (from the question previously mentioned), \$V_{in}\$ is tied to the output of the buck converter. Whenever two power supplies are tied together, there may be contention for which power supply controls the voltage. For the circuit to work, and not settle at 0 volts as a stable point, the external power supply must "win" in any contention with the buck converter. The external power supply must provide power to make up all losses in the loop. One way to ensure that the external power supply is the "master" in this contention is to have the external power supply have a very low impedance, and the output of the boost converter a high impedance. Using an AC mains, or a lead acid battery for the external power supply satisfies the first condition. Using the boost converter in current regulation mode satisfies the second.
However, it would be nice to be able to use external power supplies which contain elements that block "back flow". Consider the following circuit:

simulate this circuit – Schematic created using CircuitLab
Provided the load can draw all of the current from the current mode boost converter (at the external supply voltage), the external supply will control the voltage. However, if the load cannot accept all that current at that voltage, the voltage across the load will rise.
Now, one may say "hold on a minute", the current into the load must be greater than the current delivered by the boost converter, else we would have a "free energy source". However, this is not so. It is only required that on average the energy supplied to the buck/boost loop equals the energy dissipated there. It is only required that on average the current from the boost converter must be less than the current drawn by the buck converter. However, both converters have elements that store energy, and simulations show that indeed, the buck may temporarily draw less current than the boost supplies, resulting in a significant rise in the tie-point voltage.
Ideas that immediately pop up as solutions are 1) use a bigger capacitor from \$V_{in}\$ to ground, or 2) use a shunt resistor from the buck \$V_{out}\$ to ground. A problem with 1) is that we don't know in advance how much energy might be stored in the buck converter, unless we know the details of the buck converter in advance. We might, but it would be nice not not have to rely upon such knowledge. A problem with 2 is that it reduces the amount of current recycled. Neither of these problems are a project killer. However, I wonder if there is a better way.
My question. Can anyone think of any other way to tie together an external supply which might restrict current back-flow, with a boost converter in current regulation mode, such that the voltage is determined by the external supply, even if the load does not accept all the current the boost converter is temporarily able to supply? Changes to the circuitry of the boost supply are absolutely acceptable. Adding a low-value sense resistor between the external supply and the tie-in point is also acceptable.


texts: Pro's and con's to using a pcb's middle layer (on a 4 layer board) as a heat sink?

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I'm finishing up a PCB design and it has a surface mount (TO-252) voltage regulator. I want the regulator to dissipate heat as much as possible however it will be within its thermal limit with just the top and bottom layers. So I was wondering if it will help to add a solid plane on the middle layer and/or will doing this weaken the PCB overtime or cause other issues?

Thanks


texts: How do I calculate, or measure, all values in a simple A.C. circuit?

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I'm trying to figure out how all the formulae fit together regarding A.C. currents. Given this circuit and equations:

I figured out the following:

E = 120 V (impressed EMF)
L = 0.160 H
X = L * 2π * f = 0.160 * 2π * 60 = 60.319 Ω
Z = X (no resistances, originally the square root of `R^2 + X^2`)
I = E / Z

So I have a few questions here:

Is the value '120V' actually the impressed EMF (total EMF) or is it the power/active component of the EMF?
How would I calculate the reactive/watt-less EMF?
Why do all the power formulae need \$I^2\$ or \$E^2\$, where does this come from?
Is it normal that the resistance of the conductor is not included in the calculations?
What values would I see if I used a voltmeter, ammeter, watt meter?

Thanks!


texts: Circuit to a/b switch like a relay would. So an analog or digital signal can be turned on or off or routed

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I need to build an arduino-based switcher / router for a multi-arcade to route controls to different game boards, and also switch 2 vga inputs into one output.  Without introducing any lag also.

3 increasinly complex examples of what I need this to do:

First is to take a bunch of leaf switch buttons (which technically are each connecting a pin on a jamma board to ground when pushed) and using arduino to route which pin on 2 different jamma boards is being connected to ground by the button push. It's basically button mapping for different games. I'll have some limited needs in this area but the biggest one is a/b switching between 2 full sets of controls based on what game is being played.

Example 2 is switching 4 pins from the leaf switch buttons to trackball outputs.  Which I think is still taking the lines low to ground but is more of a digital signal than a guy randomly smashing on a button.

Example 3 is a/b switching 2 vga outputs to a single vga output. And the lines in a vga are analog signals.

I'm not an EE so I still think in terms of a relay, which can a/b switch a single line no matter (within reason) what's on it.  So I would expect a relay could pass through any signal in either direction on that line since it's physically connecting the 2 pins together.

What is the digital circuit equivelant of a relay? I was considering optocouplers but that still functions like a transistor, right?  So not any signal could travel through it in either direction.  But maybe something like this would work for examples 1 and 2. Would it introduce any lag?

If I can do parts 1 and 2 I could always buy a vga switcher to do part 3 and hack the switch to still allow arduino to control it.

Any ideas?


texts:
I have an FPGA design that uses 2 outside clocks (INCLK and TXCLK) from an ADC to latch data also coming from an ADC (TXOUT) and a system clock.

A defined INCLK TXCLK and clk_sys as primary clocks in the timing constraints editor.

When i run the timing analysis, it appears that i have old time violation.

1) there a hold time violation for the path between the registers of U3 (LMreceiver) and U2 (capture) so i thought if added some logic between these registers i would solve the problem , but nothing changes.

2) there is a hold time violation for paths inside the modules fifo_generator_1, these modules have been generated by the IP catalog so i cannot modify them.. Is there anything i can do?

My understanding of hold time violation is that we can fix them by introducing in the path some logic to delay the signalenter image description here


texts: I do not know what "NM" indicates here under this inductor/ferrite bead label L5?


texts: Choosing resistors in series to make standard values

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I am working on designing a precision analog filter for a university electronics project.

The resistance values I am using (to meet the filter specifications) are not E96 values, so I am combining smaller value resistors in series to make the non-standard resistor. Is there any guidance for choosing these resistor values?

For example, to create an 11.9 kΩ resistor, I could use a 100 Ω resistor and an 11.8 kΩ resistor; or I could use a 7.15 kΩ resistor in series with a 4.75 kΩ resistor.

Intuitively I feel having the resistors a similar size may be better, but I am not sure if that is correct, or why it may be the case.

Also, would this change significantly based on the precision of my resistors? For example if I moved from 1% tolerance resistors to 0.5% or 0.1% values?


texts: LTSpice arbitrary voltage block (bv) simulating full wave bridge rectifier

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I'm creating a LTSpice simulation.  I need a voltage source that looks like the output of a full wave bridge rectifier.

The simulation includes a sine voltage source (voltage block) line to generate an "Input Voltage" and an arbitrary voltage (bv block) Rectified which uses the abs() function to "flip" the negative part of the input voltage waveform, thus creating the "Output Voltage" that drives the circuit.

Running the simulation generates an error message "Unknown symbol: line"

(Same problem if I use "V1" instead of "line" in the bv block formula.)

Help, please?


texts: In an intrinsic semiconductor, are there the same number of carrier electrons and holes? Or this is just exclusive for silicon?

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I am working with some polymers that behave like semiconductors when they are plugged into the current.
I am calculating the mobility of these polymers and I need the value of the current density (J) in order to achieve it.
I have found that the current density is the sum of the Jp+Jn.
Therefore, since for an intrinsic semiconductor the number of n and p is the same, then for Jp should I divide the total J by 2 or does this only apply to inorganic semiconductors?


texts: how to manually solder exposed-pad QFP package (Altera 144 pins)

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I need to manually solder an exposed-pad QFP Altera FPGA. This is crucial, since the pad is used for electrical purpose (not for thermal purpose)

I have tried the following but failed. I just put solder paste on the pad, then place the FPGA and solder the pins. After that, I use Weller hot station (http://www.rapidonline.com/catalogueimages/module/M300670P01WL.jpg) to head up the bottom, hope that it can melt the solder paste. But it can only burn and damage my PCB without doing the job.

I have conducive epoxy (that needs to mix a/b with 1:1 ratio). If I use that to stick the FPGA to the pad, will it work?


texts:
My question is why the concept of drift current or movement of minority charges is necessary while the pn-junction is formed. So drift current was explained to me in more or less this way

As the holes diffuse from p to n side due to concentration gradient, it leaves behind an ionised acceptor
which is immobile. Similarly when electrons diffuse from n to p side they leave ionised donors behind which too are immobile. As this continues the formation of the depletion region takes place, and due to the immobile charges an electric field sets in in the depletion region and this field leads to motion of charge carriers ie. the flow of electron from p to n and holes from n to p, this flow is regarded as drift current.

So let us assume there are two forces one that leads to diffusion of charge carriers which is due to the concentration gradient and other that arises due to the field generated, then why don't the diffusion simply stops when these forces become equal? Why do we need to introduce drift current?
Where did I go wrong or is there something I am missing? I've read answers on similar question that the diffusion is dominating but couldn't correlate with it my question if it is. Does this play a role somehow?


texts: How to keep the value in port until reset

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From experiments in simulation it looks like the signal, once set, is kept at the level of last write - at least in simulation and in waveform output. Is it actually guaranteed by the specification? I tried to find it in specification but I couldn't find it.

If this is not the case is the following code correct implementation of such thing?

template<typename T>
SC_MODULE(RegisterOut) {
        sc_core::sc_in<bool> clk;
        sc_core::sc_in<bool> rst;
        sc_core::sc_out<T> out;

        sc_core::sc_event _write;
        T val;

        void run() {
                while (true) {
                        wait(clk.posedge_event() | _write);
                        out.write(val);
                }
        }

        void write(const T &v) {
                val = v;
                _write.notify();
        }

        typedef RegisterOut SC_CURRENT_USER_MODULE;
        RegisterOut(::sc_core::sc_module_name, const T &v = T()) : val(v) {
                SC_CTHREAD(run, clk);
                reset_signal_is(rst, true);
        }
};


texts:
I have designed an SMPS circuit in which i have seen bulk capacitor getting damaged in a few cases (2-3 cases out of 100, which is still huge if I am aiming for a bulk production). The circuit has been running stable for over 6 months at some places and I have seen the capacitor failure within days at others. As such I feel that it could be an edge case between capacitor quality and power line stability. It could be that capacitor is just on the verge of failing and if there are minor surges or power line fluctuations, the capacitor gets damaged. Am I correct in thinking so or should I investigate something else in the circuit?

To mitigate this, I am planning to make two changes - (a) Use a branded capacitor like panasonic or so and (b) Use some sort of surge protection circuit as shown below:

This is an inexpensive circuit that I could come up with - a fuse in series and MOV in parallel to absorb spikes.

1) What current rating should I choose for the fuse? Taking care of circuit inefficiency and a little headroom, I guess 50 mA is a safe number. Shall I choose next higher rating available? Is there a better way to do this - like using a PTC?

2) How do I select MOV for my use case? On digikey, there are fields like Varistor voltage - Min, typ, Max, energy and Max AC volts. What values will be suitable for my purpose?


texts:
I have this wheatstone bridge:
Rmeasure is the impedance of my voltmeter between A and B. My goal is to have the equation of R1/R2. Because Umeasure changes if \$R_2\$ or \$R_1\$ changes.
the values of \$R_3\$ and \$R_4\$ are the same and known. E is known as well as Rmeasure. Only \$R_1\$ and \$R_2\$ are unknowmn.
I started with a Millman on point B
$$V_B = \frac{ \frac{V_A}{R_m} + \frac{V_D}{R_1} + \frac{V_C}{R_2}}{ \frac{1}{R_m} + \frac{1}{R_1} + \frac{1}{R_2}}$$
and then I get lost in my equations when I try to isolate $$\frac{R_1}{R_2}$$
Could you help me?


texts: Power Distribution to Greenhouse LED Lighting

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I'm working on designing a custom LED lighting control system for an agricultural research project. This involves supplying significant amperage to high power LEDs distributed over a wide area (e.g. hundreds of feet). I have some influence over all aspects of the design. Each lighting fixture could demand, say, 1 Amp; and lets say there could be 100 fixtures. I'm thinking of using a (PWM dim-able) constant current buck driver to run a number of fixtures, and supplying a high enough DC voltage to each driver that it can run a number of fixtures wired in series.

Power efficiency is of paramount importance to the project, and I recognize that the LED selection has a lot to do with that (i.e. luminous efficacy), but from a strictly electrical standpoint I'm seeking advice on how best to optimize power efficiency in such a system.

I need typical (i.e. 5V or 3.3V) control / logic voltages at the light fixtures, but I can also envision benefits in carrying higher voltage (e.g. 36V) throughout the system, and DC/DC switching it down locally, so that I can have a number of LEDs in series supplied by each driver so as to overcome the forward voltage burden of the LEDs.

Does anyone here have experience designing LED lighting systems like these, and can share insights on how to distribute power efficiently to them? I am wondering if I have the right idea, e.g., putting in Meanwell AC/DC power supplies at regularly spaced intervals to independently supply  power to regions of the system, and if so whether there are special considerations with regard to the type of power supply used in this application. I've read that power factor can be an issue in systems like these, but I don't understand why, or what is to be done about it. What kinds of power efficiency can I reasonably expect to attain?

Should I instead by thinking about running 110VAC (or 240VAC) to each fixture and doing the AC/DC conversions on the driver boards instead?


texts: Can we convert two type of USB ports by simply re-mapping the pins?

texts: So there's lots of different port (or plug) out there like USB type-c, micro USB etc. Where I'm curious to convert between those port is it just simply like re-mapping those pins to the correct position? Or a convertion requires some chips that modify the signal and can't be done by simply re-mapping the pins?


texts:
I'm designing a select-able gain circuit using a multiplexer and an inverting amplifier. Here's an example circuit, using a multiplexer.

I've read that if you provide a voltage larger than the supply voltage it can latch-up and/or damage the circuit due to too high of a voltage.

My question is do these effects occur when the multiplexer is switched to off? For example, if the input voltage has an amplitude of Va = 40V, the multiplexer is supplied with a 5V source, and the third switch (10k ohm) is the only activated line? I'm trying to target voltage ranges from 50mV <= Va <= 40V with gains of 0.02 <= G <= 20 and the output voltage from the op-amp should be ~1Vpp or ~2Vpp (referenced to the virtual ground). The frequency response should be anywhere from DC to ~20MHz.

If not, is there another way I can achieve this wide gain range (note: the value of R5 should be small since the circuit has to be able to handle high frequency signals)? I'd prefer to stick with only solid state components if possible.


texts: Communicate with 3 Sensors with the same I2C address

texts:
I got three sensors stick from sparkfun : https://www.sparkfun.com/products/10724
which each one got an arduino pro mini that filters the data before to send to a main Arduino.

Like this:

and until this point everything works, not even a issue.

But what I want to do next is to connect all the 3 arduinos via I2C to share the filtered data and at this point there is a big issue, the first arduino can acces to 3 Sensors via I2C and it crashes when I start to access to the unique address.

I wanted to make an independent I2C bus that exists only between the Sensor and Arduino pro mini and then another one that share the data to the main Arduino Uno.

So far I got no luck and what I came up to do, is to use a Serial cascade system

http://geodesicsphere.blogspot.co.uk/2012/12/daisy-chaining-serial-connections.html

There is anything I can do to use the I2C bus rather than Serial to share the 3 data filtered by each arduino and send it to the main Arduino UNO ?


texts: i want to calculate the uptime of LPC 1768 from when it begins running. for example a function like millis(); in arduino.


texts: Automation: How can I dispense thousands of paper sheets?

texts:
I am wondering if anyone has a good idea for a theoretical problem. Let's assume I have 3000 different designs printed on paper. I have about 100 pieces of each design. Each design is not a regular print you could print with a laser printer or inkjet printer.
Every design is stored in a little shelf so we have 3000 shelves with each 100 paper sheets in it.
Each day we have to pick designs from different shelves. We run from shelf 150 to 356 and then to 788 (just an example). This task uses a lot of time so I was wondering if there might be a clever possibility to automate it.

My thoughts so far: I use a linear system with 3 axis. A little mount with suction pads grabs the paper sheet from the shelves and dispenses it to a certain place.

Maybe this is not clever, maybe there is a better solution.

I appreciate your ideas and thoughts on this issue.

Thanks

Jo


texts: What's the easiest way to create a software-controlled 220V electricity interruptor?

texts:
As the title says, I'm looking for an easy way to interrupt a 220V electrical cable and to write a software that controls the interruption.

I imagine there are some kind of relays or contactors which can be controlled by the PC through a USB connection. I tried googling these, but did not find anything that promised to do what I need.

I'm a software developer, so I think I won't have problems doing the PC side of the thing. However, my knowledge and experience in EE is limited, so I'd prefer if I could just buy a device with a USB and power connection, instead of crambling something together manually.

Any hint is welcome, thank you!


texts: Why is pull-up resistor disabled in OUTPUT mode

texts: I noticed in a lot of micro datasheets that the internal pull-up resistor is disabled automatically when the GPIO is in OUTPUT mode, but I'm not sure I understand why. Is a pull up resistor never needed in OUTPUT mode? Appreciate the explanation


texts:
I am trying to design an audio amplifier which provides a maximum gain of 20dB (or) 10V/V.

For the circuit I designed, the lower half of the amplified signal is being clipped.

I am also attaching the PSPICE student edition schematic file for review sendspace.com/file/5ntjl3


texts: Writing hex to several microcontrollers at the same time via ICSP

texts:
Is it possible to write a hex code to several microcontrollers via one ICSP and one program on PC at the same time ?

More specifically : I'm looking to program 10 PICs at the same time from the same ICSP (like extending ICSP each pin with 10 wires).


texts: If I am buying wire to be used in a damp environment, and I need a ground wire for an AC device, can an insulated third core act as a ground wire? I don't know what effect having no insulation has on the function of the ground wire. I was hoping to purchase SOOW cable as it fits my application, but none of the products I've viewed have bare ground wires. The NM-B wires I've viewed have them, but they are not heavy duty enough.


texts:
I am trying to understand how to implement up/down binary ripple counter.
Basically, I have a bunch of D-flipflops, and connect clk of next flipflop to ether Q or Q'.

So, if I want to change direction of counting, I just switch all clk multiplexors between Q and Q', and counter starts counting in opposite direction.

The problem though is that when I do switch inputs between Q and Q' flipflops do 1 count, so my counter is counting from different number.

I.e. I cannot have something like: 0->1->2->3(direction change)->2->1->0, it's getting like 0->1->2->3(direction change)->c->b->a->9...

What am I missing?


texts: Replacing 4 x 18650 batteries with 12 x AA batteries

texts:
I got an ILIFE V7S Robot vacuum that uses 4 x 18650 battery.
It is difficult to find a replacement even from the factory in China.

So I plan to replace this with 12 x AA battery. I plan to use Panasonic BK-3MCA24/CA eneloop AA 2100 Cycle Ni-MH Pre-Charged Rechargeable (https://www.amazon.com/gp/product/B07CWK26LG/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&th=1).

Based on the spec of Eneloop, each battery has 1.2V. So 12 AA would be 14.8 and that meets the required voltage of OEM battery pack.

Do you think I can use this ENELOOP AA or C-type batteries to replace the OEM ILFE battery pack?
Would it ENELOOP provide the same working hour?

The OEM can run for 3.5 hours non stop.

Thanks

The OEM battery pack spec is shown in the image


texts: How to find and decode a particular protocol

texts:
I'm trying to understand what protocol is used on a particular device in order to decode it and send custom values.
So far I was able to record the data with a logic analyzer but couldn't figure out what protocol it is and which baudrate. I'm guessing it is a protocol using K-line or LIN since it is using only one wire to communicate and voltage levels are close to the input voltage levels.
But I want to make sense of the data to be able to replicate it using some microcontroller.
I tried to level shift the voltages to 5V volts and try to read with Arduino but with no success.
I think I should make a hardware capable of reading K-line variants but couldn't find any reference for that (I should mention that this protocol is not using 5-baud init or something since it sends the request almost immediately. Or at least I think that I doesn't).
Photo1:First Frame only, the request without the response

Photo2:Complete Messages Including the first Frame found in the Image above

I know that from the images it is hard to understand so I'm uploading the Saleae Logic Saved capture
https://drive.google.com/file/d/12WzHQq_dCJ9NLyXMu-7z73zewajVO33a/view?usp=sharing


texts: Cheapest Bidirectional NFC With Android Phone

texts:
I'm trying to build a handheld device which can communicate bidirectionally with an NFC-enabled Android phone. Generally, the phone will send some arbitrary command, and the handheld would then respond with some data.

The cheapest NFC chip I've found is this one from ST.

Can this chip be used to implement bidirectional communication? If not, what features/standards do I need to be looking for in an NFC chip?

Still trying to wrap my head around the technology. The words MiFare and Felica keep coming up, but the chips seem to be more expensive, and I'm not sure if they are necessary.


texts:
I just put together a buck bonverter PCB that I designed and am using the SiC437 from Vishay. DataSheet

I am using a power supply to control and measure the input supply voltage and current. I am using a multimeter and resistors to measure and control the output current.

I have started testing the performance of the buck converter:

Supply voltage and current: 10 Volts at 0.55 Amps

Output voltage and current: 5 Volts at 1.03 Amps

So far I was happy with the results. I then bumped up the supply voltage to 25 volts and put the same 4.8 ohm load on the output. This time, it seems the buck converter shut down, as it was drawing 0mA. (Its idle current draw was around 16mA). I attached a 24 ohm load to the output at 25 volts and it was functioning correctly.

I am assuming that the buck converter is going into one of its many shutdown protection modes. I touched the buck converter with my finger during operation and had no noticeable temperature difference so I don't think it was a thermal shutdown. I believe that I may have picked the wrong external components and it is going into a shutdown mode.

I have attached the schematic that I have used for the buck converter circuit as well.

Also, is there a better way of being able to test discharge current performance other than twisting a bunch of 24 ohm resistors together and burning my fingers? Thank you!

Edit: Here are the Waveforms taken from my oscilloscope. The first one is when the supply voltage is 8.0 Volts and the load on the output is 3.3 Ohms.

The second is when the supply voltage is 12.0 Volts with the same 3.3 Ohm load.


texts:
I bought a soldering station a while back and was practicing on a kit and had the website on assembly up while I was soldering using 60/40 tin-lead solder. Should I worry about splatter on the surfaces causing contamination? Or from using my keyboard/mouse while I was soldering? I occasionally snack in there and was wondering if I was slowly poisoning myself.

Edit: is there any way to clean it the contamination from the room?

Edit 2: Possible duplicate doesn't quite answer my concern on surface contamination and transfer of contamination I feel. For example when I touched a door knob after soldering but before washing my hands, would I have transferred any amount of lead contamination to the door knob in which case I could be unknowingly ingesting lead by touching the door knob and eating/drinking in another room?

Edit 3: question was not properly answered I feel, does lead transfer to surfaces after my hand touched the solder because if so wouldn't door knobs and light switches in my house be contaminated


texts: Dimension Engineering's Sabertooth 2x32 Analog DIP Switch Settings

texts:
My goal is to control two DC motors using
the Sabertooth 2x32 motor driver with the driver's DIP switch settings set on analog mode. I read the driver's manual, but there is a couple of things I don't understand with the documentation on the analog mode DIP switch settings.

There are two DIP switches which confuse me: the DIP switches 4 and 6. I tried to understand them and at first I thought I understood how they work so I tried something but it didn't work. So I tried playing with the switches to find a configuration which would work but each time the motors ended up acting weirdly and far from what I was expecting. Then I decided to focus on a single position of the DIP switches. So I tried to understand how the motor would behave with the DIP switch 4 ON (Mixed) and the DIP switch 6 OFF (Unidirectionnal). Though I ended up getting even more confused, but at least I knew why I was confused.

So here is what I understand:

At this point, I'm not even gonna try to understand how the other configurations work since they seem even more confusing. So I guess I'm just gonna keep trying things until I understand or until a very kind person explain me how it works. ;)

I know there are libraries available but I don't want to use them.

Note: I have a background in computer programming and not in electrical engineering. I do this as a hobby and I'm a complete beginner in electrical engineering. So please apologize for my lack of knowledge.


texts:
I am using a qtr8-rc sensor array on a line following robot, When I use it on a black line on a white surface it works but when i try to use it on a black surface with white line i can't get correct results, i have extracted the following code from my robot to test it separately but no matter what i do i can not get it to detect white line on a black surface...

include "PololuQTRSensors.h"

PololuQTRSensorsRC qtr;

void setup(){
  Serial.begin(9600);
  qtr.init((unsigned char[]) {2,3,4,5,6,7,9}, 7);

int i;
  for (i = 0; i < 250; i++){  // make the calibration take about 5 seconds
    qtr.calibrate(QTR_EMITTERS_ON);
    delay(20);
  }
}

void loop(){

unsigned int val[7];
  qtr.readCalibrated(val);
  int line = qtr.readLine(val,QTR_EMITTERS_ON,true);

Serial.print(line);
  Serial.print(" R< ");
  Serial.print(val[0]); Serial.print(" ");
  Serial.print(val[1]); Serial.print(" ");
  Serial.print(val[2]); Serial.print(" ");
  Serial.print(val[3]); Serial.print(" ");
  Serial.print(val[4]); Serial.print(" ");
  Serial.print(val[5]); Serial.print(" ");
  Serial.print(val[6]); Serial.print(" ");
  Serial.print(val[7]); Serial.print(" ");
  Serial.println(" >L ");

}

Some sample reading I am getting,

3200 R< 553 473 397 113 120 533 304 104  >L
3432 R< 567 514 474 113 120 393 82 104  >L
3494 R< 572 625 544 94 100 487 69 104  >L
3418 R< 543 421 506 88 93 305 64 104  >L
3407 R< 529 403 487 69 73 290 50 104  >L
3403 R< 524 397 480 62 67 284 46 104  >L
3506 R< 538 561 474 37 40 264 27 104  >L
3503 R< 538 543 455 18 20 248 13 104  >L
3519 R< 558 567 474 44 46 269 32 104  >L
3537 R< 577 590 500 69 73 290 50 104  >L
3545 R< 577 614 532 94 100 310 69 104  >L
3466 R< 611 497 397 94 100 310 69 104  >L
3534 R< 572 584 500 62 67 284 46 104  >L
3534 R< 572 584 500 62 67 284 46 104  >L

All numbers are way too close so readLine does not return a correct position.  One of the pins on my arduino does not work so I skipped connecting one of the sensors(sensor 7)


texts: Importance of Source-Body Connection In MOSFET Cascode Amplifier

texts:
While reviewing cascode amplifiers, I found an image on Wikipedia of a MOSFET amplifier, which I reproduced here:

The image on Wikipedia has the following caption under the image:

  Since each MOSFET transistor has gate (sic) and source connected, this configuration is valid only for discrete 3-terminal components.

First off, I assume the caption meant to say body instead of gate, but even with that correction, I don't see how the second half of that sentence follows from the first.

My question is: How important is it to specifically connect the body and source in each MOSFET in a cascode amplifier?

I can understand that w/ a 4-terminal discrete MOSFET, one can bias the body to enable the implicit BJT and diodes present in a MOSFET. But for an integrated circuit MOSFET, where the body is typically connected to ground for all transistors (and thus neither the body-source diode or implicit BJT would be enabled), how much of an effect would not connecting each transistor's source and body have on the amplifiers behavior, assuming the IC designed such that the shared body is always at a lower or equal voltage to each source terminal?

Would the body effect be significant in this case, as alluded to here?

  If the body is at a lower voltage than the source, then you must consider body effect.

Perhaps I may be overthinking the Wikipedia caption (or maybe the advice applies to analog amplifiers in general), but I just want to be sure.


texts: What does a wifi antenna look like in a Hotspot?

texts:
I have a 2014 T-Mobile ZTE Hotspot which is no longer holding a signal. After tearing down the hotspot it is NOT clear to me which hardware component is the wifi antenna.

I have posted pictures below hoping someone could call out which component is the wifi antenna.

Thank you in advance!

For reference the photos below are of a T-Mobile 2014 ZTE Hotspot Model: Li3728T42P3h774771

Here is a detailed view of what is inside one of the plastic caps which could be the antenna.


texts: DCF77 (AM 77.5 kHz) receiver in discrete components?

texts:
I'm looking to better understand basic RF receiver circuits, and I thought building a basic AM 77.5 kHz receiver seemed like a good challenge. I do however have had quite a challenge in finding any resources on this. Do you know any good starting points for the basic circuits involved in building this, in discrete components if possible, as I would like to understand the details of the system?

If I understand correctly it should be possible without any kind of phase locked loop, and just with "simple" envelope detection as it is low frequency amplitude modulation?

Don't worry about the actual demodulation, I'm going to sample the signal and do it digitally. This is what I know how to do. ;) So I'm only looking for the RF to baseband part.

Thanks in advance.


texts: Why is the power supply terminal is not connected to ground in this bridge rectifier?

texts:
Above is two identical bridge rectifier circuits. Input is a 12V sinusoidal voltage source. Red is the source. Blue is the output from the circuit on the right side.  Green is the output from the circuit on the left side. It seems like the left circuit is wrong and the one on the right side has true output. But I don't understand why it is not the other way around.

The only difference is that the circuit on the right side has a ground between the load and two diodes.

On the other hand, the circuit on the left side has a ground connected to the negative terminal of the supply.

Normally I connect the negative terminal of the power supply to the common ground.

An example to this is the circuit on the left side.

But when I plot the output for both circuits, the circuit on the left side acts weird for negative alternating input.

But my logic says:

When V2 goes positive the current must flow through D7 R2 D6 and finally to the supply terminal.

When V2 goes negative the current must flows throug D8 R2 D5 and to the supply terminal.

So I would expect the same output as in the circuit on the right side. Hence I would expect a rectification for negative halves as well.

What is wrong in my logic here?

Regarding the working circuit in the right side:

I dont understand the circuit on the right side by the way. Because:

When V1 goes positive the current must flow through D3 R1 and finally to the ground or to D2 ???.

When V1 goes negative the current  must flow through D4 R1  and finally to the ground or to D1 ???.

Why do we need ground here? Current still should flow to the terminal of the supply without a ground there.

My question is:

Why is the common ground connected like in the circuit on the right?


texts: I am creating an Arduino compatible with minimal parts (ie chip, caps crystal) and since it was available from Adafruit's EagleCad library decided to use the Arduinor3-noioref component for the pad layout.  When I went to build the board I was surprised to see that instead of just having the pads in the right place for a shield it also had a "dimension" layer and drill holes. I am now trying to understand what that means for me when it comes to the actual board dimension since the component already has what I could consider board dimensions.  Should I take the board dimensions and just line them up with the component dimensions as close as I can?   Would appreciate it if someone in the know could help me out.


texts: Understanding data transmission rates over copper wire

texts: I've been researching the different ways to connect sensors to an Arduino, and i2c seems to be a popular method. I've read that it's only reliable at short distances (a few metres, at most), with a data rate of 400 or 100kbps.  I'm having a hard time understanding why the limits of this protocol are so low in comparison to other data transmissions over copper, such as gigabit Ethernet.  I've seen reasons like capacitance, voltage drop, and resistance given, but isn't Ethernet over cat5/6 subject to all those same issues?  Basically, I want to know why pulsing some voltage down some copper wire doesn't yield more consistent results (bandwidth, distance) when comparing these different methodologies.


texts: ST-Link refuses to find my STM32F3 discovery board

texts:
The ST-Link Utility software I installed doesn't recognize the board. It looks like I connected the board before installing drivers and even after multiple trials of installing and uninstallling the drivers the problem remains. The device manager shows an unknown device with broken driver. My OS is Windows 7.

I am using Atollic IDE for development.

Is there anyway to solve this problem?


texts: Atmel Chip not recognized as USB device. How to troubleshoot

texts:
I've soldered the AT90USB1286 Chip on a PCB like on this circuit: Imgur

If I measure the pins, caps, resistors etc. with a multimeter, everything seems to be powered and fine. Reset button pulls to ground. And yet, the computer doesn't recognize any USB device when I plug the USB cable in.

I've tried it on Mac and a Linux PC. lsusb doesn't show anything new after plugging in. Same goes for Mac.

Does anyone have an idea how to troubleshoot this? How to get this chip recognized over USB? Thanks a lot.


texts: Short Distance Board to Board Communication

texts:
My MCU runs a SPI bus with about 4 devices. I'd like to extend this bus to be off board as well  i.e. have some PCBs connect to the "main" board and extend the functionality. The "pad to pad" distance would be:

trace length of main board + Cable length + trace length on the extending board

3" + 6" + 3" = about 12"

In my experience, even a 1 MHz signal, with about 7 ns rise times, over this distance via a ribbon cable was overshooting by over 1 V (but there was no excessive ringing). The boards will be powered by the same power supply.

Note: You can't see the rise times here but you can see the excessive overshoot - this is a 3.3V signal. And yes, this was measured properly with a very short wire from the probe to ground. Much like it's often recommend on this site. I don't think it's a measurement error.

I'd like the system to work at 4 MHz but 2 MHz is also acceptable. The max. number of boards I'd like to connect would be about 4 and this would extend the SPI bus to have about 12 devices. I don't think this would be too difficult to manage via code as I already have something working like this. Having the additional slave select lines is also not an issue.

However, my concern is how to send the SPI data from one board to another. Should I just send straight SPI or convert it to LVDS at one end and then convert it back into SPI on the other end?


texts: AC alternative for DC diode short-circuit protection

texts:
I have two sensors (represented in the schematic below by a switch) connected to a light. If one of the sensors trips, I would like the light to switch on.

The sensors and light are directly on AC, and there is where my problem is. In the DC alternative (on the right), I would put diodes behind my switches to prevent a short circuit when two switches are on at the same time. But on AC, diodes won't work. So how do I prevent a short circuit when two switches are on at the same time in an AC setup like on the left?
Cheers,

Dolf.


texts: I need to identify what I think is a voltage regulator. It is a TO-220 package with 023499 at the top and 8509 below it with KAG below that. Can anyone help with this? It is in a battery charger.


texts: Why 12v batteries but not 110/240 corresponding with the mains?

texts:
I have a basic curiosity question while I trying to learn/figure electrical "things" while I trying to size my UPS.

I know that an UPS will convert power from mains (240v in my case) into 12v battery and then convert back to 240v when in use.

1) May I know why is it 12v is the most "Standard" for batteries? Why not just 240v or 110v? That will do away all all those Ah conversion and inefficiency during conversion right?

Is the capacity stored inside a 12v 100ah battery is actually lesser (due to conversion) than a 120v 10ah battery if the output is 240v?

One of the reason that I could only thing of is probably safety? If safety is not an issue, then this will not happen right?

Out of so many voltages, why 12v is the chosen voltage?

2) May I know the conversion formula and explanation on each value and meaning on the conversion? I found many formula but having a hard time comprehend those values.

Thank you very much!


texts: Detect if usb device is connected on the other side of the cable

texts:
Is it possible to detect that there is a device connected on the other side of the cable without using any current sensor? I simply want my arduino to do something when i plug my phone to charger.

I have tried to use 4N35 without success as shown on the picture, even with some resistors.

I know i could use something like ACS7xx current sensor but i think it could be done without it.

Another way to do this would be to use DATA lines of the usb since they are pulled either HIGH or LOW but i'm not sure if i want to mess with that.

Any help or advice would be highly appreciated.

Thanks.

EDIT
I have tried to detect the device on DATA line and it works, unfortunately only when the device is on since i need to read HIGH signal.


texts: PCB - Altium designer resistor voltage divider calculation

texts:
Good evening,
I have a problem, I'm not really studying EE or know anything about EE, but I'm doing an optional course in PCB design, in my schematic document, I have a place (picture), where I have this text written next to it:

  Calculate voltage divider for 1.8V output voltage

I really have no idea how to do this, and I might find resources how to calculate it, I'm a bit scared I might find a wrong answer. I would like to know for sure, so that's why I asked here.

If anyone could help I'd be happy. Also, if this picture isn't enough to calculate, I can edit and paste a bigger picture of the schematic. Thank you in advance.


texts: Can I use an external antenna with JY-MCU arduino bt board?

texts:
I have a couple different Bluetooth boards similar to this one I took a photo of. It works fine but I can seem to find any info on if I can hook up an external antenna to it or not?

The documentation doesn't seem to mention it.

I know what the VCC GND TXD AND RXD pins do.

I have successfully used it. Is there a way to hack in an extra antenna?


texts: Can some one tell me what this type of switch is? It seems kind of like a trigger in action.


texts: Use PCF8574 switch selection multiple SPI slave devices, is it possible?

texts:
My project use esp8266's SPI communicate with MCP3208 and SDCard, to select which device to be communicated, that device's CS pin need to set low, and set high to another device to disable, right? My esp826 is out of pin, so my question is can I use PCF8574 to select spi device communicate with esp8266?

Thanks


texts: I need to verify the power law in this question

texts:
Question.

I suppose the value of Vx must be positive. So how do I manipulate the equation such that Vx becomes positive?

Can this be the solution to this question?


texts: Recover correct value from unstable memory through read operation

texts:
We are given a memory with 32-bit width for each word. it has the length (N - number of rows) which is not relevant for the question. we know that the memory has a problem where at any row, one bit could be replaced with a different value (it's not necessarily that all rows must have this unintended
wrong replacement).
What can we do for the memory (by adding FF's, Gates, etc.) in order to detect while reading from memory if we have a wrong value for a certain bit? and what can we do in order to recover the correct value?
my approach was that when we write something to that memory, to do XOR operation on all the bits and save it at some register, then if a bit changes, we can perform XOR again on the read value and compare it with the value saved at that register, if they are unequal then we detected an error.
I'm just not sure this is the right thing to do, and I don't know yet how to draw a schematic for such circuit. I would be glad for some insight.


texts: Impedance calculation from voltage and current (exponential) waveforms

texts:
If we want to find the impedance across two terminals (a port) at a frequency \$\omega_0\$ using the voltage waveform across \$v(t)\$) and current through (\$i(t)\$) the terminal, general intuition is to use discrete Fourier transform for both voltage and current waveforms and take the ratio
 $$Z(\omega)|_{\omega=\omega_0}=\frac{V(\omega)}{I(\omega)}|_{\omega=\omega_0}.$$
To my understanding, the answer should not depend on the shape of the waveform as long as there is a \$\omega_0\$ frequency component in the waveforms. - Please correct me if I am missing any point here.
But this doesn't seem to be true when the waveforms have an imaginary frequency component (growing/decaying in time).

Example:

For example, let's take \$i(t)=I_0 \sin(\omega_0t)e^{\alpha t}\$ and suppose we have an ideal inductor \$L\$ to measure the impedance (in fact, an ideal inductor is chosen to explain my question). Now we have,
$$v(t)=L{di(t) \over dt}=L I_0 e^{\alpha  t} \left(\alpha    \sin ( \omega_0 t)+ \omega_0  \cos ( \omega_0 t)\right),$$
and the Fourier transforms,
$$
I(\omega)=-i\sqrt{\frac{\pi }{2}} I_0\big( \delta (i \alpha -\omega +\omega_0)-  \delta (-i \alpha +\omega +\omega_0)\big)
$$
$$
V(\omega)= \sqrt{\frac{\pi }{2}}  I_0 L\big(i \alpha  \delta (i \alpha -\omega +\omega_0)+ \omega_0 \delta (i \alpha -\omega +\omega_0)-i \alpha  \delta (-i \alpha +\omega +\omega_0)+ \omega_0 \delta (-i \alpha +\omega +\omega_0)\big)
$$

Obviously, we cannot find \$V(\omega)/I(\omega)\$ at \$\omega =\omega_0\$ but if we put \$\omega =\omega_0+i \alpha\$, and consider one-sided Fourier transform we have

$$\frac{V(\omega)}{I(\omega)}|_{\omega=\omega_0+i \alpha}=(i\omega_0+ \alpha)L$$

This is, in fact, equivalent to the impedance of an inductor when \$\omega =\omega_0+i \alpha\$. But here, I am interested in finding the impedance at \$\omega_0\$.

If we use Laplace transform, we will get \$V(s)/I(s)=s L\$, and then we can simply put \$s=j\omega_0\$ to obtain the impedance across the terminals (inductor in the example). However, to my knowledge, we can't use Laplace transform for the discrete set of numbers (i.e. voltage and current signals in the time domain).

Even if we use z-transform (which said to be more like discrete Laplace transform), we will still be ending up with \$V(z)/I(z)=(i\omega_0+ \alpha)L\$

My questions

What is the physical meaning of the real part \$(\alpha L)\$ observed in the Fourier transform in this example?
How can we obtain the equivalent impedance across a port using voltage and current waveforms when the waveforms are exponentially growing (or decaying)?


texts: STM32F7 Discovery LTDC unit - changing system clock

texts:
I have strange experiences with display on my F7 Discovery board. When working with 216MHz system clock, the display (LTDC) works properly. However after changing to 120MHz (using CubeMX, so the app ensures other clock buses are correctly configured, LTDC works with 25MHz) I can see only tearing as in a photo below.
Should I change something else in addition to changing clock frequency?


texts: I need to do a membrane pcb for a keyboard or a flexible PCB like a membrane PCB

texts:
I need to design a membrane PCB for a keyboard and/or flexible double sided PCB that works like a membrane PCB.  My problem here is that I don't know how to do the buttons, with one contact of the button in one layer and the other contact in another layer.  Similar to what can be seen in this image:

Also: Which software is better for doing this, Proteus or Altium?


texts:
I'm using a modern NI USB-GPIB adapter with NI-MAX 19/488.2 to query an Agilent E8361A VNA with SCPI commands.

Commands such as *IDN? and SENS:FREQ:START? -- basically any command ending in a question mark -- returns the proper string with no hiccups. The problem is that anytime I send a command such as SENS:FREF:START 100mhz , the VNA sets the start frequency to 100 MHz but the VNA window displays the SCPI error -420 "Query Unterminated" and causes the NI-488.2 terminal to time out. I've tried setting the terminating character to CR, LF, and manually sending them both to no effect.

Any ideas how to eliminate those -420 errors?


texts:
I need to design an ALU with two 8-bit inputs A and B and control inputs x, y, and z that supports the following operations:

x  y  z  |  operation

0  0  0  |  S = A-B
0  0  1  |  S = A+B
0  1  0  |  S = A*8
0  1  1  |  S = A/8
1  0  0  | S = A NAND B (bitwise)
1  0  1  | S = A XOR B (bitwise)
1  1  0  | s = reverse the bits of A
1  1  1  | S = NOT A (bitwise)

This is supposed to be done with an 8-bit adder and an arithmetic-logic extender. Reading through my textbook, I see that the purpose of an AL-extender is to alter the input bits so that an adder, rather than a lot of extra components, can be used to do everything (or at least that's what I understand from it). For example, the AL-extender could put the bits in two's complement so that the adder does a subtraction. Likewise, for the bitwise logical operations, the bits could be altered appropriately and one of the adder inputs could just be zero so that the result comes through properly.

But what exactly do I do about multiplication? My book is very vague, so I'm not sure if an AL-extender would require me to do something clever to make the adder do the work (just add 8 times in my case? ...ha ha), or if I can just throw a multiplier in there. I'll have to read up on division, but I bet it's similar to multiplication.

Well, anyway, the bottom line is still, what is an AL-extender "allowed" to be/able to have in it? Is its only purpose to alter input so that it can be fed to an adder?

*EDIT: Well, it is multiplication/division by 8, so this can be easily performed with shifting left or right by 3. Would I still have a real/proper AL-extender if I added some shifters in there? (Maybe I'm overthinking this as a complete beginner...)


texts: Why does the voltage drop when connected to loads and what's the solution?

texts: I have thermoelectric modules and set it in series, then I connected to a DC to DC step up (CN6009) to enhance the voltage. Then I connected to my phone with usb charger to try charge with it, but the voltage suddenly drops. Should I change the step up or increase the amount of the module?


texts:
My device uses a silicone keypad to detect a key press rather than a physical button.

After setting up, it works smoothly, even without applying much pressure to the keypad.

However, after a while ( say 2 months), you will need to apply much pressure on the key pad before a key is detected. It continues like this for a while, and then no keys can be detected again.

So we open, clean the PCB keypad traces with "methylated Spirit". And it works back as new. Sometime, we see black residue on the keypad PCB traces, which appears to come off the conductor of the silicone keypad. We wipe this off and  everything is back to normal.

My question is how to avoid this problem.


texts:
I have to design a power input filter of consumer device. It is powered with desktop AC/DC 12V power supply. Max current consumption - 1A. Device has a full metal enclosure. I am considering putting ESD and reverse polarity protection diodes in front, then use a cap-common mode choke-cap filter. Problem is that it is not clear to me how to approach selecting actual component values. Device may function as non grounded, but may get grounded through associated equipment, connected to a random enclosure spot.

I have a prototype with only a cap and inductor in series with positive lead. Negative lead is connected to chassis. Touching the prototype with a grounded wire scares uC. As there is only one wire coming to the device from power supply, I assume it is a common mode stuff that causes trouble.

I might as well isolate electronics from the metal enclosure and only connect input filter cap or a resistor from negative lead to the enclosure.

If anyone could guide me to the right direction, I would be very grateful.


texts: How to calculate the power requirements of a fan motor?

texts:
I bought a fan from the USA to use in Europe. The fan's specifications states the following:

  Requires a grounded electrical supply line of 120 volts AC, 60 Hz, 15
  amp circuit.

Here we use a 220V, 50-60Hz supply. I've managed to find a step down transformer at a local electrical store that is a 220V-110V transformer for home use. They have a two models — 50VA and 100VA.

Which one would I need to power my fan? Is the 50VA, sufficient?


texts: Current spikes when MOSFET turns on and voltage spikes when MOSFET turns off

texts:
I studying for my Power Electronics course and have come across something which I can't seem to wrap my head around.

In a lab, we built a buck converter with an inductive load and measured various transients during its operation, specifically focusing on the transient currents and voltages that occur during switching of the MOSFET.  At the end of the lab, the following question was asked:

  Describe why a current spike is produced when the MOSFET is switched
  on, and a voltage spike is produced when the MOSFET is switched off

I am familiar with the fundamental formulas for inductors and capacitors, and from those I would expect that a voltage spike could occur when switching an inductive load, because of a near instantaneous change in voltage across the inductor.
However, this doesn't seem to fit with the question that is being asked, which implies a current spike when switching on and a voltage spike only when switching off.

These are the only two slides I could find from the lectures that show this kind of behavior, but I can not understand how the shown circuits would produce that behavior:

Switching on:

(note: U_CE is the voltage across the MOSFET and Ic is the current through it)

What is the source of this current spike when the MOSFET turns on?

Switching off:

(note: U_CE is the voltage across the MOSFET and Ic is the current through it)

What is the source of the overvoltage when the MOSFET turns off?
The inductive load is pictured with a flyback diode, so I don't see how this would be caused by the inductor.  And I would think that the capacitor just gets charged up to its capacity and then maintains a constant voltage.

Any help would be appreciated, thanks in advance.


texts: What causes unequal phase-to-neutral voltages in three-phase distribution systems?

texts:
A four-wires cable runs into an apartment building to supply it with three-phase 380/220V alternating current. Each apartment is connected to one phase, different apartments are connected to different phases with interleaving so that phases are hopefully loaded equally.

Now it turns out that voltage between phase 1 and the neutral is something like 215 volts and the voltage between the other two phases and the neutral is about 203 volts each.

One of the tenants is connected to a phase which is 203 volts relative to the neutral and has problems with appliances malfunctioning because of undervoltage. He calls a serviceman and the serviceman claims the substation transformer feeds such voltages and the only thing he can do is to disconnect the tenant from his phase and connect him to the phase with 215 volts.

What causes such unequal voltages? Is it unequal load on different phases or anything else? Also has the serviceman done the right thing or did he just put extra load on the higher voltage phase and induce risk of distribution failure?


texts: How to intuitively understand the bode plot of \$e^{-30 t}\$

texts:
Everyone knows that \$ e^{-30 t} \$ is a rapidly decaying function. In fact, a little too fast to be useful.

Which is amusing why this function would have the following properties as displayed by the bode plot.

Can someone explain how the Bode plot of this function correspond what we see in the time domain?

Why do we have a large negative drop off in the Bode Plot when we
have a large positive rise in the time domain?
Is it possible to observe the effect of the pole in the time domain?
Finally, how do we understand the phase of this function? I can't see
any phase effect in the time domain at all.


texts: Calculating battery current during charging in CCCV

texts:
I am researching how (lithium-ion) batteries are charged using CCCV. Specifically, I am interested in the "constant-voltage" part of the process:

My question is - how do I calculate current \$i\$ during constant-voltage? I have found idealized simple R-only or RC circuits as possible battery models. I have found multiple definitions for open circuit voltage (\$V_{ocv}\$) as a function of capacity (\$Q\$). Assuming a simple R-only equivalent circuit such as the following:

I have found variations of the following formula including terminal battery voltage (\$ V_t \$) and internal impedance (\$ R_i \$) of a single battery cell 3:

\$ V_t = V_{ocv} - R_i * i \$

where

\$ V_{ocv}(Q) = V_0 - \frac{K*Q_{nom}}{Q_{nom}-Q} + A * e^{-B * Q} \$

Thus, should following not hold?

\$ i = \frac{V_{ocv} - V_t}{R_i} \$

To my understanding, \$V_t\$ is constant (say \$4V\$ or \$4.2V\$) during constant-voltage. \$V_{ocv}(Q)\$ is assumed to be known, see plot and sample reference below. In the literature, \$i\$ is always shown with an exponential decrease during constant-voltage but not how it is actually calculated. I am unsure as to whether \$R_i\$ is constant.

My background is in Computer Science so please feel free to recommend literature for additional reading - I feel like I'm probably missing something obvious here.

3 Marra, F., Yang, G. Y., Træholt, C., Larsen, E., Rasmussen, C. N., & You, S. (2012). Demand Profile Study of
Battery Electric Vehicle under Different Charging Options. In Proceedings of the 2012 IEEE Power & Energy Society General Meeting IEEE.

EDIT: Added \$V_{ocv}\$ equation and CCCV plot.

EDIT 2: Added R-only circuit diagram.

EDIT 3: For posterity, here are two helpful lectures on how CCCV may be simulated by describing a circuit as a system of differential equations and converting them to a discrete time model that can be simulated easily:

First, converting differential equations to discrete time

Next, how to simulate the constant-voltage portion


texts: Should I always have holes in my PCB pads?

texts:
The drilled holes aren't always perfectly centered. For single sides boards this doesn't make much difference, but for plated through holes having a hole in the pads copper could mean that the pad only partly connects to the through-hole metalization if the drill doesn't match the hole perfectly.
Are through-hole pads without hole in the copper allowed?

edit
About the larger annular ring (re Leon's comment): it's not the outside I'm worried about. I've never had an annular ring so small that the drill comes outside of it. If the drill goes a little bit to the west, then possibly on the east side the copper of my pad doesn't connect to the through-hole metalization. This wouldn't be noticed when the board is tested, since there's still a (partial) connection, but it may have a higher resistance.


texts: Am I correctly concluding that these two AC/DC adapters are interchangeable

texts:
I'm in the US with 120V mains. I have a "heavy" style AC/DC adapter (weighs a pound or so) and a lighter one (weighs a couple of ounces) which came off a 1TB Seagate NAS. Can I replace the heavy one with the light one?

Here are the specs for the heavy one:

AC100V  50/60Hz 19VA
DC 12V 1000mA

and here are the specs for the light one:

AC INPUT: 100-240V~ 50-60Hz, 0.65A max, 51-80 VA
DC OUTPUT: 12V  2A

If I understand correctly, the DC output of the lighter one is 12V and is capable of handling a draw (e.g. from a DC motor) up to 2000mA, so in that regard it is just as capable as (more capable than) the heavy one.

But I know pretty much diddly about electric, so I don't know how to interpret what 0.65A max, 51-80VA means on the AC input side.

P.S. The writing is so small, I can't tell if that is a tilde ~ or a minus-sign after the 240V.


texts:
I am using a B-L072Z-LRWAN1 board (which has a STM32L072 MCU) and I want to get data from a DHT11 sensor. To achieve this, I need a microseconds delay which I am not able to obtain.

The libraries provided by ST have a millisecond delay function but not a microsecond function.

I need some help.
Thank you in advance!


texts: What exactly lies between an HDL and a circuit?

texts:
I'm trying to learn basics of hardware design process to get a better understanding of how CPUs, microcontrollers etc  work and how are they made.

My googleing gave me many articles with info like "HDLs are now used to design CPUs", but every manual for dummies I've found talks about Verilog usage with FPGA, which is absolutely not what I need, 'cause there is no transistor-level (CMOS, for example) circuit involved in the process (FPGA itself is an already designed and producted device), so it's not "hardware design" in terms of my understanding of the word.

The question is: are HDLs really used to design digital devices from scratch? If so, what exactly happens between the HDL code and a transistor-level circuit implementation? Are the logical gates (as a result of synthesis) translated to circuit diagram (for some tech process usage) with some other tools? What are those tools?

Or, maybe, am I taking a wrong direction in my study?


texts:
Anyone know of a good source for capacitive touchscreens in low quantity at a reasonable price? Just something to play around with in projects, I'm interested in either small (eg for portable applications, 3-5") or large (eg for kiosk or standalone applications, 10-20"). I know I can get a resistive touchscreen for pennies these days, but I want a capacitive one (for various reasons).

EDIT: The reasons I'm interested in are basically just the main reasons people use capacitive screens in general. Things like more durable (a solid piece of glass instead of a flexible piece of plastic), Multitouch capable, etc.


texts: I have a circuit that normally runs at 3-5v and then when triggered, it gets pulled to ground (around .1-2 mv leakage). I want to use this to trigger a relay to close a different low voltage circuit. Can I use the "Sainsmart DC 5V Relay Module for Arduino PIC ARM DSP AVR MSP430 TTL Logic" board to achieve this?


texts: Following is from a PCB that I am presently working on. That particular path signals are of 100-400kHz signals. Is there any problem in having routes of this kind?


texts:
I'm using a Shinyei PPD-60PV particulate sensor in a product and I've noticed something very odd in testing, and I don't know how to explain it. It's connected to a WildFire board by way of cabling to an interface adapter board. The WildFire is powered by 5V through its USB port. The PPD-60PV has two 5V/GND connections made through the interface adapter board, and an analog output that is wired to the A7 ADC input of the WildFire by way of the interface adapter board.

My product supports two fundamental modes of operation: (1) Wi-Fi connected, and (2) Offline. What I've discovered is that in Wi-Fi mode, the analog output of the PPD-60PV sensor appears to rise by about a volt. What I discovered (and painstakingly narrowed the symptom down to) was that this voltage rise happens somewhat gradually (over several seconds), only after the ESP8266 connects to a Wi-Fi network. It also recovers to a normal baseline value gradually (over a similar period of time) upon resetting the ESP8266 (and hence disconnecting it from the Wi-Fi network).

Further diagnostic experiments reveal that this voltage rise on the analog output of the sensor occurs even if I disconnect the analog output from the WildFire altogether leaving the 5V / GND connections in place and probe it with an oscilloscope.

Also if I have two assemblies plugged into the same power source, with one of them in Wi-Fi mode, and one of them in offline mode, the offline mode unit exhibits the voltage rise phenomenon. The rise is certainly there, and also noteworthy that it's to a lesser degree than when the unit itself is in Wi-Fi mode, e.g. 600mV - 700mV.

An offline unit connected to an isolated power source (e.g. a battery pack) does not experience the voltage rise, e.g. despite physical proximity to a Wi-Fi connected unit.

I wondered if maybe it was a ground path resistance issue, but everything is pretty short lengths here, and I measured the resistance from both sensor ground connections back to the WildFire ground at 0.2 ohms each, and I measured the total current of the system at about 300mA (displayed on a the LCD of a conventional benchtop 5V power supply). That certainly doesn't account for a 1V rise as far as my reasoning goes.

My understanding was that the PPD-60PV analog output is a low-impedance buffered output, but that's not entirely clear from the datasheet. I'm kind of stuck / perplexed at the moment, and I'm not sure what to do next.

So, on to my forlorn question. What could be the root cause of what I'm observing here? What advice do you have as to what I might do next to drive this issue to ground, as it were?


texts: Pros/Cons/differences of High pass inductive vs capacitive filter

texts:
A simple high pass filter can consist of a capacitor in series with a resistor or a resistor in series with an inductor. Why would I use one over the other? I also wonder the same thing about low pass filters. Do capacitive high pass filters have less energy usage or increased speed, or clearer filtering capabilities compared to inductive high pass filters?

Thank you!


texts: Role of the Schottky diode (power supplies)

texts:
In the figure below I have two power supplies (+ VS, -VS) of 100V to power a PA107DP amplifier.
The 2 power supplies must be supplied by an external voltage of 24V (the connector of the external power supply is just above the 100V power supply (R24-100B)).

At the connector output of the external power supply there is a Schottky diode (D5.)

What is the role of the Schottky diode in this case?
How do I choose the Schottky diode? This diode is 50V / 10A.  Why was a diode with these characteristics chosen?


texts: Getting Connection Refused error upon running openocd

texts:
I'm having a bit of trouble setting up an openocd debugger in Eclipse.
Upon running debug configurations, I get:
Error message from debugger back end:
localhost:3333: Connection refused.
Failed to execute MI command:
-target-select remote localhost:3333

This is what the debugger tab looks like:


texts: Zener over voltage protection from DC hand crank generator

texts:
I have a board powered by a hand crank generator. Under normal conditions the voltage peaks at 18-20 volts. However spinning the handle violently will peak higher at 30+ volts. The generator runs through a schottky bridge rectifier and into a 5 volt regulator rated at a max of 26 volts. The circuit as a whole pulls less than an amp.

In trying to keep the simple circuit simple I was thinking about a 20 volt zener (D5) and a tiny 10 ohm series resistor(R1). When it comes to protecting a voltage regulator is this the most ideal method or should I be looking at something different?


texts: How to find inductance of a burnt inductor of a RF matching circuit

texts:
I have an Android headunit for my car with wifi, gps, 3G, etc. At some point the GPS stopped working. I replaced the antenna connector because the pin was bended and could not connect anymore. At the beginning the gps was working for a while and then dead. GPS can see satellites but gets not SNR. I took apart the HU and see that there is a burnt inductor at the matching circuit of an active the antenna (see photo). I think it makes sense that it was working fine but after a while it burnt and had that behaviour. Now it gets no SNR at all. I guess if burnt badly after all.

Here there are a Ohm resistor (top) , burnt inductor (middle), inductor (bottom right), and a capacitor of 4.7uF (bottom left).

I have the schematics of this, but it corresponds to a part that is "optional" (see schematics).

I'am no expert at all in electronics, so I need help here. I think that the burnt inductor is M5002, which the description says is 10nH 300mA. The M5003 says nothing, there is no info there. How can I be sure that the burnt one is M5002? (I have no LCR meter at the moment).

Any help will be highly appreciated.
cheers.

Update 1 :
I am quite sure what is burnt is an inductor see photos attached.

enter image description here

Then, @JRE  in this photo it seems as if the empty pad is connected to the antenna pin (I would say GND?)  can you confirm?


texts:
I'm trying to get rid of this heat problem , I know that I have to use heat sinks according
to it's specification , but the problem here is there's no space for that heat sink.

So I do have to need a method to calculate and get a idea about it's switching loss
to compare these two MOSFETS to select the better one. The design that I speak is a
push-pull topology and it does drain 20A peak current , switching frequency is 50KHz and
how could I calculate the power dissipation due to the switching losses?

I have compared these two MOSFETS,

Is that calculating the operating point from that graph is a good idea here?
Regarding the 20A in mind so there will be 1V between Drain and the source. So
which means approximately 20W as heat on it's peak. Regarding the Ipeak reaches
linearly so approximate heat dissparation is around 10W per two MOSFETS, so 5W per
a one. So do I still need a heat sink there?

What other options that I should concern,

Voltage ringing.
Hi voltages causing by leakage flux. (use a clamp drive)
Reverse and forward switching delays. (use a gate drive)

5W is still too hot for a design regarding without heat sink. Could somebdoy suggest
any other MOSFET which does the job with less heat. Ron is very small device.

EDIT: My supply voltage is 24V and I am not using a gate drive here. I'm using 5V TTL
output to drive these two MOSFETS.


texts:
I have a HIP4082 full bridge MOSFET driver driver driving a full bridge. After some experimenting with the circuit prototype i found out that the driver heats up to over 60 °C after a short while of running, which concerned me but it worked fine. However as I decreased impedance across the load (which was originally connected to primary coil of a transformer) the driver started acting in a weird way and i found out that it has blown out. This is already the second driver i destroyed this way and they're expensive as hell, so I need a solution.

I think what's causing the driver to blow out is that when I decrease impedance across the load I basically create a short circuit between the driver's bootstrap pin and ground, which kills it. By adding a resistor across the load or the whole bridge and ground, I could easily solve the issue, however I do need low impedance on the load because I need high current (up to 20A).

I thought about adding a resistor across the driver's bootstrap line, but I have concerns about it affecting the bootstrapping functionality.

EDIT: I'm actually using IGBTs in place of MOSFETs (specifically IRGPS4067DPBF) Also I'm not posting a layout because the full bridge is not on a PCB but it's simply bridge-soldered to the driver circuit.
The full bridge operates at 150 kHz square wave.Both circuit and load voltage is 12v

Also here's my circuit schematic:

The full bridge is connected as in the driver's datasheet, except the feedback loop and shunt resistor:

Here's the control circuit layout:

And here's the picture of the bridge:


texts:
I'm a mechanical engineering student and I have a little home project I'm hoping to work on. Unfortunately the only electric circuits class I had to take taught plenty of theory but very little about practicality so I am still at a loss when it comes to designing more complex circuits than the basic ones to prove class concepts.

I'm trying to create a simple circuit that will have multiple leds connected to it (those leds will have fiber optics running off their tops). It seems like connecting them in parallel would be the way to go. If I have a prototype board,a power supply, and a method of turning on and off the power, could I simply solder those leds to wires and create a parallel circuit without any additional elements? I've heard I should include a resistor before each led, but how would I go about choosing which resistor to use, the smallest possible? Would this circuit need any diodes or bridge rectifiers?


texts: Using srf05 ultrasonic sensor to detect changes only

texts:
I am using the SRF05 sensor to detect distance, so far so good. Now we need to detect only changes, which means, the sensor will have some close object to it, but than when some other object which is more far, is moving, I will have to detect that.

My concern was that if I get a distance from a close obstacle, a movement of other far obstacles will not affect him because I don't get linear signal, but just the distance of the close object that reflects the sound signal.

I am little bit confused, because the signals are going around the room, and when it gives you a distance, it's a mix of many reflections from objects around. So how a far object will affect it, if I have a more close object?

Am I completely wrong?


texts:
I have implemented DC-DC converter with mic5158 (schematic like in datasheet, no current limit, adjustable output), all work fine, except mosfet heating while medium load.
After investigation of this problem, i have found that gate-source voltage always keep near threshold (~4v). So mosfet always partially open instead of close-open cycle. With higher load voltage raising, so charge pump working.
I wondeder why Vgs does not fall  below threshold and not raising to full-open mosfet level.
Any idea how to make mosfet fully open-close to avoid heating?


texts:
It could sounds odd but I am trying to find a switch for my inverter that is an isolator.

My batteries are 12 V and my inventer can do over 5 KW, but I found a switch at 48 V, rated 300 A.

If I use it on 12 V what would be the max rated current for it?


texts: Coordination of mechanical and electrical power in electric drives

texts:
I want to ask a question to respected specialists in electric drives.
It is known that the mechanical power of an electric motor is determined by a simple formula:

\${P_{mech}}= M {\omega}\$;

Electric power is determined by the basic ratio, as the product of current and voltage (if, to a first approximation, the properties of alternating current machines, etc. are not taken into account):

\${P_{el}}= U I\$;

The ratio between these powers depends on many factors (losses in the steel of the stator, rotor, losses in the converter, etc.).

Suppose we have a low-speed torque motor (in a gearless electric drive) with a torque of \$100 Nm\$ and a rotation speed of \$0.1 rad/s\$. Mechanical power of the motor will be \${P_{mech}}= 100*0.1\$;

In order to have a high efficiency of, say, \$90\$%, we must have an electric power of \$10/0.9 = 11.1 Wt\$.

Therefore, our product \$UI\$ should be equal (to a first approximation) \$11.1 Wt\$.

This means that we must have:

1) a relatively high voltage and at the same time a very small current;

2) a relatively high current and at the same time a very small voltage;

3) voltage = current;

In all three cases, we risk not providing the required high torque (which depends on both the current and voltage), therefore, we must significantly increase the current and voltage. But then the electric power will increase significantly, and the efficiency will not be equal to \$90\$%, but \$10\$% - \$30\$%.

The question is this: are my arguments true and it is impossible to design a high-performance low-speed high-torque engine in this way? Or are there ways to make good coordination between electrical and low mechanical power in such gearless electric drives?


texts: STM32 DMA short data burst buffer speed limitation

texts:
I had gone through few texts on this topic (listed below), but was not able to figure out the speed limitation of STM32´s DMA.

What is needed:
Take 8bit parallel burst input from external ADC (20 kB per burst). Frequency of input signal - 22,5 MHz. Buffer one burst send it to PC with slower speed via USB and wait for another burst. No data processing on MCU side. MCU will know about comming data by trigger on GPIO pin.

Delay between bursts is higher than 1 second.

What is limit of input signal frequency if I would like to use higher frequency?

STM32 family has many types and I feel completely lost in this. Is any of the STM32 capable of such a task? If yes is it available on any dev board? I´m not very familiar with HW designing so dev board seems like a better solution for me.

FPGA is maybe better for this but definitely harder to HW(PCB) design. Also FPGA devboards are more expensive.

AN4104 App Note - Using the STM32F0xx DMA controller

AN4031 App Note - Using the STM32F2,F4,F7 Series DMA controller

AN4666 App Note - Parallel synchronous transmission using GPIO and DMA

How to use STM32 DMA

embedded.fm DMA - Alittle help from my friends

Discovering the STM32 MCU

External ADC & DMA

Deska STFM32F746ZG

Using DMA in STM32 projects


texts: How to make Kicad alow P-MOSFET as switch without ERC problems?

texts:
I have a P-MOSFET which is acting as a switch. However, I get errors as seen in the image. How should I resolve this issue? I know i just could don't bother since i know it will work but I rather not.

I have tried using PWR_FLAG but that do not work either. Is all PWR_FLAGS connected and that is why that results in strange behavior?

/Johan


texts: DC Current Density and Voltage in a Finite-Length Conductor

texts:
Assume you have a rectangular bar of copper with finite length L.  You apply a voltage difference at two points on the top surface of the bar; (x1,y1) and (x2,y2).  Because the bar is finite in length, I believe that the current will not be uniformly distributed.  How would you go about calculating the voltage and current density at an arbitrary point within the bar?

I have tried to think through a few models that would approximate this, but I keep falling short.  I think there must be a better way.  Ideally, there would be an actual equation that I could derive that would give me the voltage and current density at any point within the bar.  I have also wondered if a finite element method approach is best here.

If the bar is relatively thin in the z direction, I wonder if the problem can be simplified by instead considering a copper sheet with no thickness.

If anyone could point me in the right direction, I would really appreciate it.


texts: Electric potential energy of charge relative to 2 metal plates

texts:
Let’s say I have a positive electric charge in middle of two plates, one is positively charged, the other one negatively with total intensity of electric field of 5 N/C.  If the charge has 2 Coulombs, and is 3 meters from positive plate and 3 meters from negative plate, it will have potential energy relative to negative terminal 30 Joules, right?

But what potential energy will that charge have relative to the positive plate? -30 Joules? And what does that even mean? Can we speak of potential energy when comparing the positive charge with positive plate?


texts:
the servos that came with the kit have connectors that are too small to remain seated in their socket.
they do fill up all three pins, but they don't cling to them tightly enough to remain electrically connected. were they intended to be wider or was it just designed poorly?
is there a way I can fix this?

(I don't know which site has miscellaneous hardware questions so I took a guess.)
edit:
here's a picture of the board in question:
(Click for larger view)

the sockets look like the kind made for larger connectors with tabs,but instead are receiving 2 smaller ones.