texts: How do I calculate necessary mosfet turn on/turn off time?

texts:
I'm trying to measure capacitance of C1 using this design:

Everything works from 3.3V.

The mosfets is my addition to it - i want to discharge the capacitor after each half-cycle. Everything works OK in low frequencies, but i want to run it on 8Mhz and then it seems, mosfets do not turn on in time. Even more - performance depends on R3 - i had to lower it from 12K to 1K for this to work at 1Mhz.

If i want to discharge C1 in 62.5ns, how do I go about designing this - what mosfet parameters do I look up and what calculations do I make? How gate resistance influences turn on speed?

From what i see 2N7002 has

6ns turn on delay time
4ns rise time
20ns turn off delay time
5ns fall time

if I add it up - it's far less than 62ns.

Datasheet of 2N7002

Edit
Made an inverter as adviced by @rawbrawb


texts:
I have a 48V battery bank made up of 4 deep cycle 12V batteries in series. My charger only has 12V and 24V options.

I've considered using relays to put the batteries in parallel and charging at 12V. I'm assuming there has to be a better way. Ideally, one that allows all 4 batteries to remain in series.

Is there a common method to do this?
What effect would charging one 12V battery have on the other three in series?


texts: I have recently been looking at IR LEDs but having trouble in terms of finding the distance (in meters, cm or mm) the IR radiation travels through a medium such as air using the below diagram. Can someone help me to find how far this radiation can travel before its intensity is almost 0?


texts: why biasing an emitter follower with a transistor will cause the following transistor falling into active region?

texts:
My textbook says Q2 is not in the saturation region. I just think the Q2 transistor can be in the saturation region as long as R3 is small enough to provide the saturation current.

The author explained that is "because the signal on Q1's collector is always within the range of the power supplies, Q2's base will be between Vcc and ground, and therefore Q2 is in the active region(neither cut off nor saturated), with its base-emitter diode in conduction and its collector at least a few tenths of a volt more positive than its emitter." The book didn't include any values for the resistors, the transistors, and the power supplies. No matter what value these components have, Q2 will always stay in the active region.

I am doing self-study and hope someone could help me with this question. This is on page 83' upper right corner of the book named "Art of Electronics Third Edition".

simulate this circuit – Schematic created using CircuitLab


texts: Actuating a relay (either 5V or 12V) with 3V

texts:
I am trying to figure out how I can actuate a high amperage 12V relay with only the batteries I have on board.

Basically the idea is here to have a 3.7V lithium cell, a momentary switch to actuate the relay, and then let the current flow from the lithium cell through the relay to the load.

Is there any way I can do this? I'll be dealing with loads up to 60 ampere, and a lithium polymer battery that can support that kind of discharge.


texts:
I am trying to implement a phase control circuit for driving a TRIAC/SCR. I plan to use an xmegaA4U series microcontroller.

I already know that I can route the AC signal through a voltage divider and into the analog comparator, and route the output of the DAC to the other input of the analog comparator. From there I can select rising edge or falling edge triggering and that will allow me to control firing angle by programming the DAC (and the trigger edge).

The last bit of the puzzle is the firing pulse to the gate of the TRIAC/SCR. I figure I can route the output of the analog comparator to a timer channel via the event system, however, I am not sure that I can configure the timer to operate as a one-shot that can elicit a change on an output pin. Does anyone know if this is possible?

P.S. I know this could very easily be done in software with interrupt handlers, however I am trying to "kick the tires" on the xmega and event system, so I want to have minimal CPU intervention besides setting the pulse width once, and the DAC output when the firing angle needs to change. Beyond that, the hardware should take care of it.


texts:
I need a CCD camera that can be used inside vacuum. Not the flange mounted types used in XUV-X-ray applications, but small compact preferably less than 20 mm dia housing. Does anyone have experience in using standard CCD cameras in vacuum, or can anyone suggest possible sources/references?
Is it possible to set electronic exposure (aka electronic shutter) time, remotely through software, in a USB based CCD camera?


texts: Why does decreasing the voltage also decrease the circuit frequency?

texts:
In CMOS circuit design, we know dynamic power is propotional to \$V_{dd}^2Cf\$, so the best way to reduce dynamic power is to reduce Vdd.
However, according to the textbook,

Keeping the same clock frequency becomes unsustainable as Vdd is continuously reduced, because the rise and fall times of signals stop meeting the noise margin of the gate.

I don't understand why rise time and fall time increases as voltage decreases.


texts: By what factor would gate geometry have to be enlarged when VDD increases by some factor?

texts:
For integrated circuits, let us say that one wishes to increase  (contrary to current interests in trying to lower) operating voltage/VDD of integrated circuit.

If one increases VDD by some factor k, by what factor approximately would gate geometry need to enlarge?


texts: Controlling multiple triacs with microcontroller for light dimming: where to use optoisolators

texts:
I want to control (dim) multiple mains lights using triacs and a microcontroller. (One triac per light). I want to keep both the costs and component count as low as possible.

Is it necessary to have multiple optoisolators? (One per triac?) Under normal operation, could the triac gates be at significantly different potentials, for example when some lights are on and some or off, or perhaps during non-zero switching due to transient spikes due to the inductance of the lights? I would probably use a transistor (PNP) between the uC and triac, which would saturate to trigger it. The gate-side anode would be connected to neutral, as would the uC's ground.

I understand that the live part of the system should be isolated from interfaces such as programmers, as per this question. Such isolating would be less costly than one optoisolator per triac, so I'd prefer to isolate this way rather than one opto-isolator per triac.


texts: How to suppose the current directions for KCL?

texts: I know applying kcl but I dont know how to consider the directions of the current.What I do is I make a general current direction for the whole loop,then with the help of that I see the currents entrying the node or leaving it but I usually go wrong with this logic..Here's an example which includes my try an the real directions


texts: can you use a switching regulator from 120v AC (house power) 5 amp to output 5v DC 5 amp?

texts:
i am looking to power my high powered LEDs with and if i can switch from 30v dc to 5v dc with a switching regulator can i skip over using a power supply and just connect a switching voltage regulator directly to the 120v AC? When doing this, and i may need to convert AC to DC by using a full bridge rectifier... would it work?

EDIT:

ive been using buck switching voltage regulators to step down voltages from 30v DC to 5V DC at low current with little to no issues. They have a limit of 400mA or so and i now need to switch voltages from 120v to 5v ac or dc.. then convert to DC if it's AC. What can i use for bringing down the voltage?I prefer to use the buck switching voltage regulator because i have experience with them.
my load is 5 amps when it's 5v DC, so my question is can i use the buck converter (granted that i find one that can do 5 amps) to convert to 5v ac without it burning up? What alternative is there? Is this a time when only a transformer can do this? I prefer not to use a transformer because they are big and weighty on a PCB. Also i have seen phone chargers and even the raspberry pi charger put out 3.5amps from a wallwart in a very small space.


texts: Low power device in sealed unit -- design help

texts:
Main question: can I build an arduino-based sensor that'll use such low power that something like inductive charging will suffice to power it?

Details: I've got a "holding tank" on my boat ... a 3-foot tall polyethylene tank that's typically part-full of human waste mixed with salt water, which is a pretty horrible environment for electronics. I want to be able to know how full it is. External sensing hasn't worked well, so I'm considering putting some assembly into a piece of PVC plumbing pipe, with sealed ends, and sticking this in the tank. My plan is to use capacitive sensing (as in this design) with temperature compensation using a low-budget temp/humidity sensor I've got lying around. I plan to get information from this sensor to a display via bluetooth or some similar coupling. I typically need to know the tank-fullness about once or twice a day ... this doesn't require continuous monitoring.

My plan is therefore to use something like sleep mode most of the time, waking up now and then (or perhaps waking up in reponse to some sort of trigger -- I'm not clear on how to do this), and powering the thing from something like a lithium battery. But I need to recharge the battery, even if it's a very low power system overall. I was thinking that I could use inductive coupling (from a coil of wire outside the poly tank to a coil of wire inside the PVC pipe), and then take the resulting current and rectify and filter it a bit and use that to recharge the battery.

Any thoughts on

whether this is even slightly plausible? The PVC is probably 1/4" thick, and the poly tank is about 3/16"...so the inductive coupling would have to be over a distance that's on the scale of 1 inch, more or less, and
Whether there's an easy way to waken the system from low-power mode in response to some external signal, and
Whether using bluetooth, when the processor is going to be in sleep mode 99% of the time, is plausible, or am I going to be spending all my power in reestablishing the bluetooth connection?


texts:
Possible Duplicate:
  FCC and CE Testing / Failure Resolution

I am looking to do some pre-certification on several boards. I know several members here are quite experienced in this area. I would appreciate resources such as books/articles that talk into practical design and testing of PCBs before sending them to the test house. It would be nice if you could discuss the type of equipment you use to perform this tests, especially if it's relatively low cost and gets the job done.


texts:
I wanted to create my own PLC and PLC supporting software.

I would like to know how to get started.

Is there any software available to create background software?
What is a recommended controller for such applications?


texts: Microcontroller like the esp8266 with more gpio

texts:
I am looking for a microcontroller similar to the ESP8266, which has the following features:

1/ 36 dedicated gpio

2/ I2S for driving audio

3/ I2C for driving screens

4/ SPI

5/ WiFi Station and AP modes

6/ Any language will do

I want at least 36 pins gpio, all of which would be used and then additional pins for the other needs such is I2C, I2S SPI.

Spec wise it could be a bit more powerful than the esp8266, and need not be Arduino compatible, I just want it to be good value. Advice from enthusiasts with more experience than me would be appreciated.

Many thanks


texts:
What is virtual array antenna (VAA)?
I have searched it everywhere but i was unable to find direct answer to this question.
I know this concept was built from phased array antenna. Please explain this concept because i cannot find direct answer to this question.
Thank you.


texts:
I am analyzing the schematics of STM32F429 Discovery board, specifically power delivery circuit, here it is:

I have few questions that I couldn't get by myself:

Capacitors C26 and C25 are tantalum capacitors(used before ADC supply pin), they are 1 uF, but on the other hand capacitors C42 and C41 are 2.2 uF and are cheap ceramic caps(they are used for internal voltage regulator). The question is - why they use tantalum capacitors before ADC? Can I plug ceramic capacitors there or aluminium electrolytic? Tantalum are expensive and many people say unreliable, basically on any forum people say something like "stay away from tantalum caps". What are implications of using ceramic or aluminium electrolytic capacitors(or even through-hole electrolytes) in ADC decoupling?
The ADC power input is basically pi-network(assuming we have cap near the supply) with exception that we have not 1, but 4 capacitors. Why not just use two capacitors(big and small to cover more frequencies shunting to ground). Putting two of identical capacitors pairs seems redundant, it would make sense to use different values like Dave says.
Not longer relevant, see comments.
This question is more generic one, not only for this schematic. Often when it comes to inductors people just say "Oh, and here we have inductor". I am quite fascinated how people treat inductors like you can replace it with anything. How big the inductor should be? Does "bead" means that this is not actually an inductor, but a ferrite bead? Is it really so irrelevant and you can put in anything you have laying around, no matter if it is 10 uH, 10000 uH or small ferrite bead?


texts:
I am using the PSMC module in a PIC16F1782 to create a single-output PWM signal at 100 Hz.  I am having problems with the duty cycle glitching on a periodic basis.

The code main loop runs every 1.024 ms and the duty-cycle registers are updated on every pass of the loop.  The datasheet is quite specific in saying:

  The PSMCxLD bit of the PSMCxCON register is provided to synchronize
  changes to the event Count registers. Changes are withheld from taking
  action until the first period event Reset after the PSMCxLD bit is
  set. For example, to change the PWM frequency, while maintaining the
  same effective duty cycle, the Period and Duty Cycle registers need to
  be changed. The changes to all four registers take effect
  simultaneously on the period event Reset after the PSMCxLD bit is set.

In my case, the duty-cycle register may or may not be changed on each pass through the loop but the LD bit is set on every pass through the loop regardless if any changes were needed or not.

I suspect this is where my problems occur but I need to understand why this might be happening.  In particular, the datasheet appears to say that I can change any of the registers associated with the duty-cycle or period or phase at any time without affecting the current operating parameters.  Only after setting the LD bit do any changes made to those registers take effect.

Can anyone confirm this is indeed the case?  If this is NOT the case, can someone provide guidance on how and when to update the registers and/or the LD bit?

In particular, there is a several microsecond time period where the duty-cycle registers are being manipulated.  That is: initial values are loaded into the duty-cycle HI and LO registers, then those values are manipulated.  This might be a total time of 30us or so.  Only after the register values are stable is the LD bit asserted.

Obviously, the PWM output is active during this time.

The glitches are regular (not periodic) but random.  That might imply beating between the main loop period and PWM period - but then I would not expect the glitches to be random.

Any guidance appreciated.

Other information: no interrupts.

[Edit]
One section of the relevant code is as follows:

SetPWM_Auto
    incf        SPEED,W         ;add offset (can't have zero duty-cycle
    skpnz
      movlw     0xFF            ;don't allow speed to wrap to 0x00
    SETBSR      PSMC1DCH
    movwf       RBS(PSMC1DCL)   ;save speed in lo byte
    MULX132     RBS(PSMC1DCH), RBS(PSMC1DCL)    ;w *132 -> dcH:dcL

    bsf         BBS(_PSMC1LD)   ;load steering and time buffers
    rampg0
    goto        SetPWMdone

The multiply macro:

MULX132         MACRO   ACC1, ACC0      ;W * 132 -> ACC1:ACC0
; enters with multiplicand in W
; exits with result in ACC1:ACC0
; Written by Mike Rigby-Jones
    clrf        ACC1            ; Clear MSB
    movwf       ACC0            ; save W in ACC0
;    clrc                        ; use these instead of "lslf" for
;    rlf         ACC0,F          ;   non-enhanced PICs
    lslf        ACC0,F          ;C <- b7..b0 <- 0
    rlf         ACC1,F
    rlf         ACC0,F
    rlf         ACC1,F
    rlf         ACC0,F
    rlf         ACC1,F          ; ACC1:ACC0 = 8 * input
    addwf       ACC1,F          ; C + ACC1:ACC0 = 264 * input
    rrf         ACC1,F          ; divide by 2
    rrf         ACC0,F          ; ACC1:ACC0 = 132 * input  11 cy
    endm

My guess is that the registers within the PSMC are NOT properly double-buffered and that the duty-cycle is changing because the value in the DC register has intermediate values while the math is being done.  About to try fixing that.


texts: Maximum temperature of an electric motor and proper cooling system

texts:
I have found an electric motor in my home and I want to estimate how much time it can operate until its temperature becomes too high and eventually build a cooling system for it (I have seen that there are for instance many simple peltier cooling systems at fews $, like this one).

Unfortunately I have not found the datasheet of my motor on the web. I have only the following plate data:

Obviously it is not possible to make accurate evaluations without specific data, but it is sufficient for me a help to obtain a very rough estimation.

Basically, it is an AC 230V electric motor of 160W. It is structured in this way:

The metal rod on the left is rotated by the motor (inside the metal tube on the right). The motor theoretically reaches the end and then reverses the rotation; however I do not need this function and therefore I have removed the limit switch, therefore the motor can turn clockwise or counterclockwise indefinitely (therefore ignore the information: course 300mm).

What I want to know/estimate is:

which is the maximum temperature for this kind of device? I need only a rough estimation (like saying that for a generic Integrated Circuit we do not want to overcome 75°C). Then I may measure the temperature while using the motor and see when it reaches this critical temperature.
does the plate data give some informations about the maximum time of operation?
Is there a criterion for choosing the cooling system (in a rough way)? Is it a good idea to compare the power of the engine (160W) to the power flow offered by a certain cooling system?


texts:
Why is Arduino using AVR? I understand that they are the official processor but there isn't a reason the code couldn't be ported to an ARM or a Freescale architecture other than cost, right? As long as there is onboard memory, I figured there could be easy migration into those parts.

I see a lot of ARM in industry (seems like every vendor is pushing one into their designs) and was wondering why there wasn't more uptake in the Arduino developer world.


texts: How to provide enough current for my GSM circuit, and still use a LiOn battery?

texts:
I am very new to electronics.

I am building a simple GPS tracker prototype circuit that uses a 3.7 volt 500mah lithium ion rechargeable battery.

The circuit has 2 major components: a simple microcontroller that interfaces serially with a SIM908 GSM & GPS chip. When the SIM908 chip is active but not transmitting or receiving data, it uses only 80ma of current. But when I instruct the microcontroller to request the SIM908 to send or receive data, the SIM908 requires 2 amps of current during that period of radio transmission, then it goes back to utilizing only 80ma of current.

My idea is to send GPS location every 5 minutes to a website using the GSM cellular data. This solution is all working fine already, but the problem is that it drains the battery in about 2 hours.

I understand that could go for a much more powerful battery, but my project requires a small form factor, so the 500mah is the largest I can go, and thus, I need to stick with it.

So, maybe I am asking something impossible here, but my question is: does anyone know what would take to keep the same 500mah battery, still provide the circuit something between 3.3 and 3.7 volts, but have a way to increase amps to 2A during those current peaks for a lot lot lot more than 2 hours??... maybe 24 hours... would it be possible?

Hope this question makes sense, and someone can direct me to either a better solution or a more efficient way to provide power and current for many hours.


texts:
I am evaluating whether it can use "resistive touch film" in project-based cards using USBizi Chipset-100 in place of a conventional keyboard.
I would like to see some similar design to see howto make interface.
Any suggestions?


texts: It okay to use 12V 2.5A adapter instead of 12V 1A?

texts:
I have a piano keyboard that uses 12V 1A adapter . The adapter was not working anymore so i used another one which was 12V 2.5A but after 45 minutes of usage the keyboard got little heated up in the area where the adapter is plugged in.Now my question is :1) have it caused some damage to the keyboard?? Although its working fine.
2) Is it okay to use that adapter?


texts: Choosing the right MOSFET and diode for DPPM (Dynamic Power Path Management)

texts:
I am trying to implement a DPPM (Dynamic Power Path Management) system that uses a main voltage when it is present and a battery when the main power is not present.
The main voltage would be 12V and the battery would be a Li-ion (3.2-4.2V). The output voltage should not be less than 3V (when it is only the battery)
Have I chosen the components well, according to the use they are going to have?


texts: Switching loss in a synchronous converter (buck, boost or buck-boost) when light load occurs

texts:
When a synchronous converter operates in high load condition,if the inductor current is always positive, the switching loss of the Synchronous mosfet is minor in comparison to the switching loss of the Control mosfet.
This is because the Synchronous mosfet turns on and turns off in "soft switching" while the Controller mosfet turns on and turns off in "hard switching" (I have summarized a lot).
But when a synchronous converter operates in low load condition and the inductor valley current become negative , Control mosfet and Synchronous mosfet turn on in "soft switching" and turn off in "hard switching".
If I suppose that the 2 mosfets are matched, the switching loss  for both devices, is the same?
I'm sorry for my bad English, it's not my mother tongue, and it is not easy to express the concept that I want.
Thank you all for the attention.


texts: I use two desktop PCs and one set of wireless keyboard and mouse (Logitech with the 2.4 GHz Receiver). I got tired of plugging and unplugging the receiver so I took two old usb cables, a usb socket and a dpdt switch to make a  usb switch. Unfortunately neither pc will recognize the receiver when I plug it into my DIY switch. I have never done something like this so perhaps I’m missing something very fundamental. I’m hoping someone here has experience with home projects like these and may be able to tell me where I went wrong...


texts: Isolated step-down module for powering a Raspberry Pi from a speaker's 12V supply avoiding ground loop and interference

texts:
I have an older speaker with an iPod dock that I would like to extend with a Raspberry Pi as a streaming music player. At first, I tried powering the RPi from the dock connector with a Micro USB adapter cable but apparently this does not provide enough current.

Since I do not want to add another power supply to the setup, I have soldered a step-down buck converter to the power connector of the speaker's PCB. (I also replaced the original 12 V / 1.5 A power supply with a 3 A supply which should be sufficient for both the speaker and the RPi.)

This is what it looks like:

The problem that I'm now facing is that this creates a ground loop that adds switching noise to the output of the speaker. I could put an isolator between the RPi's audio connector and the speaker but there also seems to be a lot of interference coming through. Depending on the power supply, it can happen that the GPIO pins detect phantom phantom button actions when e.g. I turn the room lights on and off.

So my current idea is to replace the buck converter with an isolated one like this one.

My questions are:

Is my understanding correct that the isolated converter should remove both the interference and the ground loop?
What also makes me wonder is the fact that while buck converters are all over the place, it is hard to find even one of these isolated converters on amazon or ebay. Is this such an unusual application? Or do these isolated converters have another serious drawback?
Is the general setup OK? While I have basic electronics knowledge, I usually don't deal with power supply (and sure keep my hands off mains), so I want to be sure that I'm not missing anything that makes the whole thing a safety risk.

Thanks in advance for your input, it's highly appreciated.


texts: Control two different DPDT circuits with one DPDT switch

texts:
I have a HDMI switch (pictured below) and a USB 2.0 Switch both have dual inputs and a single output, with no external power input. Both from what I can see are switched via DPDT switch. What I want to achieve is have them both controlled by a single DPDT switch instead of their own switches, as I plan to put them together in a 3D printed case to make a crude KVM switch.

I’m not sure if I can just wire them up to the same switch or if I need anything additional to isolate the two circuits as I guess they will run on different voltages etc?

Any help is appreciated.


texts:
I am designing a board around the RBp CM3+ and would like to know more about how to wire the camera and USB pins. On the RBp CM3+ data sheet, it is stated that the USB pins like USB_P and USB_M must be routed as 90 Ohm differential traces. I also read somewhere that the camera pins (CAM1_DN0, CAM1_DNP, etc) need to be routed as matched length 100 Ohm differential pairs.
Does this mean that the differential impedance must be around 100 Ohms?
Other than ensuring that the differential traces have the same length and differential impedance, are there any other consideration I should have?
I'm also having trouble understanding the difference between an edge coupled microstrip, microstrips, and embedded microstrips


texts: High frequency Ultrasonic transducer for finer mist making

texts:
I am looking to make Mist/Fog from water using ultrasonic transducer mist maker. A typical mist making products in the market are using 1.7 MHz ultrasonic transducer to make 5 Micron size Mist/Fog. How ever, I am looking for 1 Micron size or below Mist makers. Do you think if I increase the frequency of the piezo ultrasonic transducer from 1.7 MHz to 2.4 MHz, 3.0 MHz or higher ones (5 MHz to 10 MHz) and may that lead to finer (1 Micron or below) mist/fog I am looking for?

Is there a corelation between the frequency of the piezo ultrasonic transducer and the density of the mist produced?

I would really appreciate someone input and advice on this. thanks

Jay


texts: Why is a lab PSU not suitable for driving a laser diode directly?

texts:
I'm looking to drive some laser diodes (50mW) at very modest powers (50%), using simple circuits no doubt less sophisticated than most lab PSUs.

Why does this site say it's not an option? I understand temperature changes, noise, pulses, spikes, inductances and so on, as the page itself describes.

But, since I'll have a lot if headroom, with a rough and ready constant current source that does that it says on the tin I guess, plus more than enough heat dissipation, what's the problem? How much noise and inductance can there  be?


texts: Create state transition diagram of a SSM that will output a "0" until the sequence 0, 1, 0 occurs.

texts:
As the title states, I'm trying to draw the state transition diagram of a sequential state machine that will output a "0" until the sequence 0, 1, 0
occurs. After the sequence occurs, the machine should output a "1" regardless of the input.

Here is my work, but I've encountered a problem. What happens when we get to state S1, and the sequence adds a 0? If I send it back to S0, we can then have "010" going back to S1, which is valid and would output a 1. I only intended for the output to be 1 once I get to S3. How can I fix my diagram?


texts: ngSpice Printing a lot of reference values instead of running the simulation

texts:
I have a project that uses ngSpice as a shared library. I fed a SPICE file to this project and the same file to ngSpice.exe. The ngSpice.exe finished execution within seconds however, the sharedlibrary goes on and on forever. It just keeps printing "Reference Value"

I have tried using the shared library with the same project before and it worked perfectly. This behavior started out of the blue. Could someone elaborate as to what is going on and why ngSpice.exe does not print this?


texts: Is it possible (and how) to program a PIC32MX chip with a pocket AVR programmer?


texts: Are these two circuits equal and what does the arrow symbolize?

texts: I'm not sure what the arrow means, anyway V+ and V- were given as 5V and -5V respectively and Vin changes from -6V to 6V (so maybe an AC voltage source would've been appropriate).


texts: Simple transistor motor driver does not work properly?

texts:
The transistor gets hot to the touch and the motor will continue to run when I disconnect the transistors base from 9v+ (I am trying to make sure the circuit works before I hook it up to an arduino). The motor will continue continue unless I disconnect the power supply.

Is this how the circuit is supposed to work like this?
I am using a 9v power supply, simple toy motor, 1uf cap, 1k resistor, and a PN2222a npn transistor.

I was following this instructables (http://www.instructables.com/id/Simple-Cheap-Motor-Driver-Board-for-Arduino/?ALLSTEPS). What am I missing with this circuit? Should I go through and do all the calculations for the circuit? Thanks!!!


texts:
This problem is asking for I/o function, i.e V2/V1.
I tried to solve this problem by first figuring out the Thevenin equivalents of input voltages and resistance before op-amp's input terminals but this approach is being discouraged by the question. Any insights on solving this problem will be appreciated.


texts: LED current limiting resistor and Ohm's Law

texts:
Yesterday I was trying to figure out how many ohms of resistor should I be using for my LED, and found this post right here in the forum.

The formula states that one should subtract the voltage drop of the LED from Vcc, and then divide it by the target current (A), in the example, it was (5-3.4)/0.005 = 320 ohms resistor should be used.

My question is this: why the resistance is calculated not with whole 5V but only fraction of it? Suppose the resistance of entire circuit would be at the lowest level of 320 ohms if LED is 0 ohms, and if I used Ohm's Law on this circuit: 5/320 = 0.015625 (A), which is way off the target current I was hoping for.

It's like a mystery for me, and I hope someone could really explain it to me.

EDIT: Another way to put it: If one imagine a blackbox payload consumes 5V, in order to supply 5mA through the circuit, the blackbox needs to be 5/0.005 = 1000 ohms. And I know the blackbox is composed of 2 components: the LED and resistor, and the sum of their resistance must be 1000 ohms. Let R of LED is x, and R of resistor is y, they have the relationship x+y = 1000. That means whatever resistor I put in it, the R of LED automatically changes to a fitting value so their sum is 1000, is that possible?

Doesn't one need to know the resistance of LED, or the LED's resistance is really dynamic?


texts: How does this PIC board achieve RS-232 communication without a line driver?

texts:
All the develooment boards I have seen yet with serial communication support usually have MAX232 line trasceiver. However, I have come across this Olimex PIC-LCD development board that does not have it. Rather, it seems to use discrete components to achieve the same aim. Below is the schematic. The RXD and TXD are connected to the PIC:

I am trying to understand how this works. For recieved data we would need to clamp the voltage to Vcc. For transmitted data we need to amplify the signal. I vaguely understand that there would be a simple clamp diode for the received data and a charge pump made up of capacitor and diode for the transmitter. The transistors are resistors are confusing me. What purpose do they serve?


texts: Altium: Routing in different layers brings me back to top layer

texts:
Routing on the top layer is fine. But whenever I try to route on a different layer, it automatically brings me back to the top layer and routes there. Am I missing a step?

Let me make this more clear.
 1. I can move from one layer to "next" using the +/- keys and the addition of vias
 2. I can add a route segment that is not connected to anything on all layers as well
 3. I can "SOMETIMES" add routes directly connecting it to a component, but that doesn't always work (not with all components).

on one of the components for example, I get this pop-out, then it immediately directs me to the top layer.


texts: Can a patch GPS-antenna be mounted in an inclined position?

texts:
I have just bought Globsat BU353S4 GPS-receiver. Now I have a doubt: it is mandatory to mount it in an horizontal position (i.e. facing the sky) or it can be also tilted of some angle with no perceptible loss in precision?

I'm talking about an ideal situation: two antennas with zero obstacles around them. One is mounted horizontally, while the other has some angle with respect to the terrain.

As I know, usually this patch antennas have a ground plane. Maybe that metallic plane can obstruct the view of one or more satellites... but I'm not sure, this is just a personal speculation.

P.S.
I'm struggling to mount it on a motorcycle, so there is not a big choice of places where the antenna can be mounted.


texts: Help identify missing component USB power

texts:
Can anyone help identify the component that is missing from this circuit board? The board is the main controller board for a music keyboard. The keyboard is meant to be able to be powered over USB but due to the missing component (presumably) this doesn't work. The keyboard can also be powered via a separate DC jack, which takes power from a 9V 200mA DC adapter (this does work).

Below is an image of part of the mainboard, the USB connector is centre-bottom. Just above that is the missing component, marked L19. The bottom pad of this is connected to the +5V pin on the USB connector. To the right of the USB connector is the DC jack.

Next to the missing L19 are two components labelled L20 and L21 - I presume these are the same as the missing component, but I don't know what they are. A larger image of these is below.

I have contacted the manufacturer but they won't tell me what the component is, so I'm hoping someone here might be able to help me.


texts:
I have a few questions regarding my understanding of circuits.

When you hook a battery up to a conductor does the chemical reactions which take place create a difference in charge between the terminals?

If so, is it the electric field created by this difference which exerts a force on charge placed in the circuit?

I know a 9V battery means a unit positive charge would deliver 9J of energy  if it were to travel between the terminals (from positive to negative), but does the size of the voltage affect the magnitude of the force exerted on the charges?

If this is right, is this why an increase in voltage increases current but also means a unit positive charge as it travels around the circuit can deliver more energy as it reaches a higher KE between collisions?

Thanks


texts:
I supposed there is a sense coil inside the RCCB (RCD)of this tankless water heater. But why is there a fuse inside one of the load side to the circuit? Isn't the round circle the sense coil where the 2 load wire passes? Why isn't the fuse in one of them?

Part of


texts: Is there a 16 bit version of the 74HC165

texts: Basically 16 bit parallel - in, then shift out, HC family.  Or do I need to just chain two 8 bit shift registers together?


texts: Will solder usually connect copper vias on a 2-sided PCB?

texts: I've seen videos where the board is suspended in a solution with an applied voltage to plate the vias, but I don't really have the resources to do that.  Is soldering parts a reliable method to ensure a connection on both sides of a double-sided board?  Some of the parts sit on the board in such a way that it's not possible to tell if solder melted onto both sides.  If this is not a reliable method, is there some other, simple way to connect the vias?


texts: Reworking a PCB - remove these components

texts:
I'd like to remove all the ICs from the below PCB, hopefully preserving them for future use:

This was a failed (ish) reflow attempt using paste and a hot plate.

I have a hot plate, a hot air machine and a soldering iron, plus soldering stuff: wick, solder sucker, and lead-free solder.

How do I do it?


texts: What kind of capacitor could build up, and maintain a charge acquired from lightning?

texts: The microwave tower next door has a lightning arrester attachment. The charge probably goes harmlessly to ground. If it were possible to siphon part of the charge as it went to ground, how would one choose the capacitor (capacitance rating, punch through voltage, etc)?


texts: Enhancing the bass response of an audio isolation transformer

texts:
Below is a simple buffer circuit using an isolation transformer:

The green trace is the output of the transformer and the blue trace is the input signal (20Hz to 20kHz sine wave.)
As you can see the bass response is not very good (I deliberately modelled a cheap transformer.)
I've heard of negative impedance drivers, but I can't find enough detail anywhere to implement one.
Can anyone tell me:

How to accurately model this transformer.

How to modify my buffer to increase the bass response.


texts: Is it a bad idea to use unsized integer constants in equality expressions in Verilog?

texts:
I noticed the following in the Verilog 2005 standard (5.1.8 Equality operators):

  If the operands are of unequal bit lengths and if one or both operands are unsigned, the smaller operand shall be zero-extended to the size of the larger operand. If both operands are signed, the smaller operand shall be sign-extended to the size of the larger operand.

and then in (3.5.1 Integer constants):

  Simple decimal numbers without the size and the base format shall be treated as signed integers

I've actually had a bit of trouble finding the bit size of integers in verilog, although this website says:

  integer is typically a 32 bit twos complement integer.

So, given that and the fact that the equality operation is performed bitwise (also stated in 5.1.8), does using an unsized integer cost more in the sense that the bit comparison is forced to use all 32 bits?

Take the following example as an illustration:

`default_nettype none

`timescale 1ns/1ps
module top;

   reg [3:0] ctr = 0;
   reg       clk = 0;

   reg some_reg = 0;

   always #1 clk = !clk;

   initial begin
      $dumpfile("top.vcd");
      $dumpvars(0, top);
      #20 $finish;
   end

   always @(posedge clk) begin
      ctr     <= ctr + 1;
      // if (ctr == 4'd5) // cheaper?
      if (ctr == 5)
        some_reg <= 1;
   end

endmodule

What are the implications for comparisons with parameters? ie

`default_nettype none

`timescale 1ns/1ps
module top;

   localparam SIZE = 5;

   reg [3:0] ctr = 0;
   reg       clk = 0;

   reg some_reg = 0;

   always #1 clk = !clk;

   initial begin
      $dumpfile("top.vcd");
      $dumpvars(0, top);
      #20 $finish;
   end

   always @(posedge clk) begin
      ctr     <= ctr + 1;
      if (ctr == SIZE)
        some_reg <= 1;
   end

endmodule

Should we specify the bit widths of parameters then? i.e.

`default_nettype none

`timescale 1ns/1ps
module top;

   localparam [3:0] SIZE = 5;

   reg [3:0] ctr = 0;
   reg       clk = 0;

   reg some_reg = 0;

   always #1 clk = !clk;

   initial begin
      $dumpfile("top.vcd");
      $dumpvars(0, top);
      #20 $finish;
   end

   always @(posedge clk) begin
      ctr     <= ctr + 1;
      if (ctr == SIZE)
        some_reg <= 1;
   end

endmodule

Are there any good guidelines about when its safe to use unsized integer constants in expressions? For instance, I use them on the rhs of expressions above since the standard states (5.6 Assignments and truncation):

  If the width of the right-hand expression is larger than the width of the left-hand side in an assignment, the MSBs of the right-hand expression will always be discarded to match the size of the left-hand side.

I assumed this means that ctr <= ctr + 1 adds ctr to 1'b1 or 4'd1. Or, does it add ctr to 32'd1 and then discard the top 28 bits?


texts:
simple model of a diff opamp with an independent differential signal source

figure 1

how does current flow through the transistors since V1 and V2 and referenced to each other and not to vee? i understand how the circuit is supposed to work for example in a case where V1 and V2 are each referenced to vee, but need some help to understand figure 1 where there is no reference of the differential ac source to the opamp vee rail.

figure 2


texts:
I have been coding and using Arduinos for quite some time now.  However I am ready to move up to using straight AVR chips without the arduino bootloader.  My question is what are resources to do this?

I want to use linux / mac so winavr is out of the picture as is avrstudio.  If there is no such thing as what I am after I will settle for a windows virtual machine.  But until I know for sure.  What I want is some type of IDE that uses avr-gcc.

As a bonus to this question does anyone have any good resources on learning C for avr?  Specifically how to configure Makefiles etc for the various different chips?


texts: How to Drain Heat from a High Intensity Lightbox (2200 watt)?

texts:
As you may know, I'm working on designing a "lightbox" that will contain 3 high intensity metal halide bulbs - consuming a total of 1600 - 2200 watt. The purpose of the box is to generate ~40,000 lux of light in an area that's 24 inches by 24 inches.

The box is meant to open/close in 1 minute intervals. This will be accomplished through a series of "microcontrollers" and "servo" motors. The box will open from the front (the "door") and be lifted upward through the servo motor.

While the box is closed, no light will be emitted. While it is open, the goal is to cause as much light as possible to escape from the box. For this purpose, another series of "servo" motors will cause the bulbs to move forward slightly out of the box (closer to the subject).

The box will be built out of wood and the dimensions of the box will be about 18 inches, by 12 inches by 12 inches.

This is all background information. My main concern (and the reason for this post) is about "draining" the heat from the box so that the wood doesn't catch on fire.

Currently (based on several suggestions from SO members), I will be taking the following precautions:

I will be placing a 240 CFM fan UNDER the box to filter out the heat.

My question is about this is: How much can I expect the wood to heat up in 1 minute with such a fan present?
Furthermore, I want to design the box so it can last for 15 and 30 minute open/close phases as well - how much more would

the wood heat up in 15/30 minutes compared to 1 minute?

If this would present a problem, would using a 400 CFM fan eliminate the problem? If not, would using 1 CFM fan on bottom (of 240 CFM) and another on top (of 100 or 240 CFM), help to enhance air flow and reduce heat  in the box?

To protect the wood from heat/fire I plan on spraying No-Heat Spray. Will this help? Is it enough or are there other "coatings" I should apply?
I plan on coating the inside with a mirror like substance to project as much light as possible. Will this cause the wood to absorb more heat or less? (I assume less..)
Is there any other way to "fire proof" the wood (without converting it into metal which would cost $1,000 +) or perhaps my entire design is flawed?

Another question: Part of the plug from the bulb will be inside the box (around 8 inches) - will the heat damage the plug (which will be made from plastic I presume)?

As a side note, someone will be present whenever the bulbs are on so if there is a fire it will be seen. My primary goal is to avoid a fire in the first place but perhaps more importantly I want to avoid significant damage to the wood..


texts: Should I solder the shielding wire (braiding) on USB cable for better data transfer?

texts:
So Ive cut the USB wire of my racing wheel (like xbox controller) and joined them again, to skip the breakaway USB cable part. While splicing, I Ignored the shielding wires, just picked them off and twisted only the 4 main wires of USB, since the guys on youtube recommended not to worry about shielding, just only the 4 wires.
Now when I connect the wheel, the windows doesnt even recognize what kind of device it is, it says the device is malfunctioned. Ive tried all software related solutions and ruled them out, which comes down to the final question :
Should I solder the braiding wires also for better data connectivity ?? If so how do I solder the braiding wire since it is supposed to surround the whole usb.Can I twist them into single mesh and solder them without any problems ? Should I retain the aluminium foil too ?
P.S:I have no knowledge about ECE, EEE so forgive me for my biased questions.


texts: Is an external oscillator for MAX2769 GPS receiver needed?

texts:
I am designing an RF frontend for GPS using MAX2769 chip. However, due to lack of theoretical and practical background in signal processing, I am unsure how to interpret the documentation when it comes to the usage of an external oscillator.

The docs say in the Crystal Oscillator section:

  The MAX2769 includes an on-chip crystal oscillator.
  A parallel mode crystal is required when the crystal oscillator is being used.

If an internal ostcillator is included, why would I need an external one?
Can I not use the internal crystal oscillator (to avoid needing an external one) but still achieve the desired functionality or receiving I and Q data?
Do I need an external oscillator to keep the internal one in check because of its lower quality (PLL)?
Does XTAL (pin name) stand for external?


texts: PCB Design position of flyback diode for motor

texts:
I have a simple question:
If I design a PCB, does it physically matter at what position my flyback diode for my motor is? Does it matter if it's "in front" of my MOSFET or not?
I made two examples to demonstrate my question:
Example 1:

Example 2:

Is example 1 equal to example 2?


texts:
Use Schmitt trigger to design a 1 kHz square wave oscillator. Assume the Op Amp supply voltages to be +15V, and the maximum bias current of the Op Amp to be 500nA. Assume that the maximum output of the oscillator to be +-14V.

This is what I have solved so far,
The bare circuit i have drawn is as below,but what does the 500nA use for?

simulate this circuit – Schematic created using CircuitLab

For R1 and R2 is it true for me to set any value but the same magnitude?


texts: So I basically have a 2 AWG power wire, but I want to end up with about 5 or 6 14AWG wires so I can put the power through a connector. Does anyone have methods of going from a 2AWG to multiple 14 AWG wires?


texts:
I recently started learning assembly and came to know about linker scripts and other low-level details of hardware programming. I am also teaching myself computer architecture and somewhere along the line I came to fear that my picture of the memory model might have been wrong all along.

According to what I understand currently, all the code and data resides on the non-volatile memory just after we 'burn' the binary onto a processor - the RAM being volatile contains nothing upon reset. When the program begins 'executing' it does so from the address 0x0000 which is almost always (AFAIK) the lowest address in Flash. So, instructions are latched onto the bus connecting Flash to the CPU core and that is where the actual execution takes place.
However, when we talk about the CPU retrieving or storing data from the memory, we're usually talking about RAM - I am aware that we can read/write data from the program memory as well (I've seen this done on AVRs) but is it not as common? Is it because RAM is faster than ROM that we prefer to store data there?

The accepted answer to this question says that most pieces of code execute out of RAM.

Does this mean that the start-up runtime code (which itself executes from Flash) has to copy all the program opcodes from Flash to RAM and somehow maps the addresses in Flash to point to RAM so that the CPU fetches opcodes from there? Is it similar to the process in which we move the .data sections from ROM to RAM on startup?

I can imagine this to be simpler in von Neumann architectures where the program and data memories share a bus but in Harvard architectures wouldn't this mean that all the code and data have to pass through the CPU registers first?

As you can probably guess, I am a little too confused by this whole business. Having always programmed at a higher abstraction level I am easily troubled with such details. Any help is appreciated.


texts: How to make a multi emitter BJT transistor?

texts:
Im trying to create the 74XX series IC's from scratch, using just transistors, resistors and diodes. I intend to chain them together and create some logic systems. Right now i'm trying to create a basic NAND gate but i can't find any transistors with at least two emitters. Why? Can i just take two transistors and solder together first the bases and then the collectors? Or maybe create it from diodes?

What i want to know is where can i obtain such a transistor or how to make one. I know how it works and where its used.

Here is an image of a NAND TTL gate:


texts: How can I check the level of charge left in a battery?


texts: Is there a wiring design that would protect a person in bath from electrocution when a powered appliance is dropped?

texts:
Hairdryer falling into bath is a Hollywood cliche already. Jokes aside, is there a wiring design that would protect a person in this case?

Overcurrent protection will trip too late, residual current will not help - current through phase and neutral can be equal. Shaver sockets are great, but they output limited power.

Is there a wiring design that would allow using high-power mains-powered appliances and still protect a person against electrocution?


texts: Circuit protection component arrangement

texts:
I was reading this thread and decided that in general it's better to place the reverse polarity protection diode D2 after the TVS rather than before it, and to instead use a bidirectional TVS for D1 (note that it is unidirectional in the image):

In this configuration, the TVS will prevent reverse polarity through itself under normal operating conditions and not cause the fuse to blow. Further, in the event of a negative surge, the reverse polarity protection diode will not be in the surge path and have less risk of damage.

Is there any drawback to this configuration in terms of protection?


texts:
Is there a standard for putting a circuit schematic inside an IEEE paper? I can't find the documentation about it.

I hope someone can help me with that.

edit:
Can i for example show a simplified version of my schematic? or do I need to put the whole schematic in the paper?


texts:
I'm trying to identify this IC. It's on the motherboard of an Epson 5040UB 4K HD projector. The projector tries to boot and then shuts off after 4 mins. A flir thermal image of the MB during this boot sequence shows IC 4706 at 204°F hot. I'm looking to replace this IC, but I cannot identify it. The printed marking on the IC is "AY 7397"
UPDATE: according to user Diah on badcaps.net forum:

AY are DC to DC PWM (Pulse-width modulation) step down. with easy
language of my...the boot didn't receive signal LAMP ON, it will not
step down. it keep on high pulse ( FAN High SPEED ) ( ERROR BLINKING )
this why they become warm.

So, perhaps the problem is with the ballast and this chip is operating as expected within tolerance and just heating up because its holding the load until the shutdown occurs? If so, would its twin IC4707 not exhibit similar thermal reaction?


texts: On the possibility of steel nails as EMI filters

texts:
I live in a place where ferrite beads for EMI suppression are hard to get.
I thought steel had a very high iron loss, especially at high frequencies.
So is it possible at least theoretically to use hard steel nails to attenuate high frequency noise in, say, power supplies?


texts:
Does alternating current mean any variable voltage or only specific case of it when polarity (e.g. current flow direction) gets reversed?
I want to understand what AC really is, and if PWM or AC passed through a rectifier (which is essentially \$\lvert sin(x)\rvert\$ if \$sin(x)\$ was passed on input) is an AC voltage?
If not - what is it?


texts: Max watt bulb for an old "660w 250v" table lamp?

texts:
I have an old table lamp that's imprinted "LEVITON / MADE IN USA / 660W 250V / LAMP HOLDER".

I'm used to lamps with stickers that specifically tell me what max-watt bulbs I can use, usually 60W, 75W, or 100W.

Why is this lamp printed "660W", and what's its actually safe, maximum-wattage bulb?

Photos below. There's a UL sticker, but otherwise nothing else is printed or stuck on the lamp sides or bottom.


texts: Why don't some 2S LiPo packs include a balancing connector?

texts:
I have been looking at several 2S LiPo batteries for my project. The charger that I have has a balancer output to balance the cell voltage in batteries, but a lot of 2S packs on the market don't include a balance connector at all. For example, this one:

Why is that? Isn't it unsafe to charge a 2S (or any multi-cell battery) without proper cell balancing?


texts: When changing the rotation of 3 phase motor, does it affect the cooling of the motor?

texts: I had to change the direction of 3 phase motor rotation, it's working great, but does it affect badly any thing, like the cooling of the coils?


texts: Why is my IR sensor giving wrong high voltage output?

texts:
I've picked up some IR sensors from a local electronics shop. The shopkeeper had no idea about the specification/part-no of the sensor. I've assumed it to be TSOP38238 as my sensor looks exactly like this.

I am providing 3.3v (2A) to the sensor on the rightmost pin and have connected the center pin to the ground. I've used an household AC's IR remote to test it.
The output is consistently 3.15-3.20v when no IR light is pointed to it.
Strangely the output ranges between 2.7v to 3.00v when i point IR from my remote to it.

I want to hook this sensor to ESP8266 to an interrupt pin but i don't think the MCU will detect an interrupt (change) with such ouput.


texts: Heating a tube of aluminium electrically

texts:
I need to regulate the temperature of the surface of a tube of aluminium. The tube is used as a mandrel for composite molding/curing, so the target temperature is below 100C.

Currently, there is no type of heating element attached to the tube. I have done a little bit of research, and these are some of the possibilities I found:

Peltier module. Its hot side would be glued with thermal grease to some areas of the tube, the cold side would be brought to room temperature with a heatsink + fan.
Resistive heating element. Nichrome wire would be wrapped around the tube and heat it by thermal conductivity. However, it seems to be challenging to electrically isolate the wire from the aluminium tube.
Joule-heating the tube. Voltage between the extremities of the tube would heat it by Joule effect. The problem is the current requirement is huge, since the tube resistance is low.
Hot air. It is simple to setup up with a fan and heating elements, but the heating would not be uniform due to convection currents.

I am looking to some answers about:

The Peltier module is widely used to cooling applications, do they have a down-side when used the opposite way, to heat things up?
Could the nichrome wire be isolated electrically but not thermically easily?
Would it be easier to switch to a steel tube and heat it by induction? By coiling the tube and applying AC current?


texts: Can multiple Schmitt triggers in series fully debounce a switch?

texts:
After dealing with software debouncing for a while, I find it takes a huge toll on the system, so I thought of initially making a hardware debouncer with one Schmitt trigger (74HC14), a capacitor, button and resistor as shown below from talkingelectronics.com:

But I read that the Schmitt trigger is half as nasty as a regular inverter when determining when to output a high or low, because it switches state at the 33% and 66% mark where as a normal inverter would switch closer to the 50% mark (but with the HC version it's probably more at 55%).

I was wondering, because the Schmitt trigger is six inverters in one package, would debouncing substantially improve with any button of my choice applied to the first input if I made six of the circuit on the right hand side with the same component values and connected all of them in series? (Example: output of the first circuit to the input of the second circuit where the capacitor and resistor meet.)


texts:
I'm building a system based on one of the old Raspberry Pi model B's (yes, first series) into a very small enclosure. I need to run an Ethernet cable from the POE splitter I have in this enclosure to the RJ-45 connector on the Pi's board, but I find I don't have enough room to do it (at least, not without creating a very small -- three inch -- cable.) I'm wondering if I can simply desolder the RJ45 jack and solder the Ethernet cable directly to the board itself, but I find that there's a lot going on in that jack:

Given all this "stuff" in there, would soldering the wires directly to the board even work?


texts: Permanent magnet synchronous motor (PMSM) equivalent circuit

texts:
I am trying to model a PMSM (permanent magnet synchronous motor) in LTspice and in order to do so I need to form an equivalent circuit. Through some research I believe the circuit should be formed in the dq reference frame as follows:

ref. https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6508040

with a back emf source along with resistor and inductance components.

Using the equations below and through the parks transformation I have made some progress:

I have tried rearranging the equations but the derivatives of the flux $$\frac{d\psi}{dt}$$ being unknown has confused me. Has anyone done something similar or can point me in the direction of some more comprehensive reading than I have found so far.

I have values for Ld, Lq, torque, resistance, initial values for va, vb and vc and the torque constant, voltage constant, speed and number of motor poles. Is this enough to work out the other values in the circuit. Are there any other parameters I require?

Any help would be much appreciated


texts: In my professional life, I sometimes need to create timing diagrams for protocols: UART, SPI, etc. However, I can't find any good programs available. What programs can be recommended for this and what is the experience using them?


texts: Creating an Input bias current return path (for an amplification circuit)

texts:
I have passive sensors (pyranometers that consist of thermopiles and measure sun irradiation, sensor specs are attached at the bottom of this question) that output a low voltage signal so I need to amplify them using an instrumentation amplifier.
My passive sensor has only two wires, one named HI and one named LO. I'm attaching the sensor differentially to the instrumentation amplifier.

I have chosen the AD8237 for this task: Datasheet

The datasheet of this In-Amp says:

  When the source, such as a thermocouple, cannot provide a return
  current path, create one, as shown in the following figure.

Question:

Can I just add a 10 MOhm resistor for each of the two inputs in parallel to ground to provide the required bias current return path like I did in the following?

Are there disadvantages to this approach? I still will be able to measure fully differential I guess as im applying the same resistor to both paths?

Any potential problems regarding impedance matching possible here?

simulate this circuit – Schematic created using CircuitLab

The sensor specs:


texts: Boost Converter - How the diode keeps conducting?

texts:
In the OFF state (SW Open) the voltage across the inductor changes its polarity and "pushes" current through the diode. So we have a voltage source in series with the inductor, producing a voltage that is greater than the voltage source Vs.

My question is: How the diode keeps conducting if the voltage across the load will have the same value as the voltage across the Switch (0 V across the diode)?


texts:
I am designing a high voltage DC/DC converter that is for an aerospace application and therefore I am focusing on reducing the size and weight, so switching at a high frequency possibly integrating wide band-gap semiconductor devices. However, switching at high frequencies with the typical wire wound transformers has its limitations. Therefore I started to research the use of planar transformers.

However with high voltage applications (in the kV range, with low current in the 100’s mA range), planar transformers are not typically used because of the insulation ratings and the like.

My question is: how viable is it to design both high voltage and high frequency transformers? What will be the main things to be worried about?

If anyone has any references/guides for designing high voltage, high frequency planar transformers, or any reference designs, please do guide me to them. Any general tips for their design, how to insulate them, manage eddy currents and proximity effects at these levels etc will also be appreciated.

The SMPS topology will likely be a form of parallel resonant converter to enable reduction of switching losses.


texts: Altium through-hole type, "slot" vs "rectangle", effect on copper pour

texts:
I am drawing a board which will fit in an enclosure with batteries. The battery terminal tabs should come up through slots in the PCB, and solder to a pad around the slot perimeter.

I created a new connector in our parts library as a through-hole with the dimensions of the slot I need. The three choices for hole types are "round", "rectangle", and "slot". I want to use "slot", but you can see below that it has a really weird effect on the copper pour.

Rectangle through-hole:

I don't want a rectangle, but it has a predictable effect on the copper pours. The ground plane on the bottom layer connects to the pad, and the top copper is pushed away beyond the region where solder mask will be removed.

Slot through-hole:

The slot-type through-hole pushes the top copper layer out in a weird blown up and rotated version of the actual slot.

Why is this happening?


texts: Indicator LED to Case - mechanical design

texts:
I got a board for which I need several indicator LEDs and I cant decide on the best solution for the mechanical design of these.

The board and the casing currently have a gap of 15mm to each other.

So far I came up with the following ideas to get the indicator LED's out of the case.

a) solder the LED in through holes and bend it 90deg
b) put pad like for a SMD LED to the top and solder the LED flat to these
c) put a pad to the top and the bottom of the PCB (1.6mm PCB fits exactly to a standard 3mm LED)
d) SMD LED with light pipe
e) extend (unnecessarily) the whole PCB 15mm and use a 90deg SMD LED

So here are my questions:

Did I forget any viable (or even better) solution?
I want to make about 1000 of these. Is there a major difference in the assembly cost (I guess for example that b should be quit a struggle to solder in the right position)?
What would be best practice in this case?
For the 3 through hole LED solution - what is the best practice to cover / isolate the long free LED legs from each other or is this unnecessary?


texts: Weird current in Push-Pull converter for high voltage multiplier

texts:
I have a push-pull converter driving a Villard-type voltage multiplier. The converter is built as naive as it could be: Two stacked MOSFETs with free wheeling diodes for the push-pull half opposing two stacked capacitors for the voltage divider that creates the center.
In between there is the step up transformer that drives the Villard rectifier.

Now what I am experiencing is that at low to medium loads the current in the transformer's primary winding looks like one would expect: Triangular increasing (in magnitude) slopes during the corresponding on-times of the MOSFETs and decreasing (towards zero) slopes during the free wheeling. That is, it is operating in discontinuous mode.

When load is increased, however, at a certain load level the winding current does not increase further but starts to decrease during the on-times of the MOSFETs. Depending on the on-time the current (in either direction/in either half of the switching cycle) can be monitored to decrease down to zero.

I have checked the following:

Input voltage stays constant.
Center voltage (capacitive divider) stays constant, i.e. the current is not collapsing due to the voltage rail coming down.
The active MOSFETs actually stays switched on as it should.
The other one stays off.
There is no excessive heat dissipated in the MOSFETs, so the switching should be somewhat correct.
The winding current is actually there. I assumed a measuring artifact, so I verified with a current probe.

I am aware that at this state my question is rather vague. Yet I hope it may ring a bell for someone and I will add further details and especially oscilloscope snapshots soon.

Thank you & Best regards


texts: increasing range of photo-diode detector with little voltage

texts:
These are the two circuits I made. The one on the left is the transmitter and the one on the right is a receiver. R4 is set to 180 ohms, R3 is set to 220 ohms, R1 is set to 9.4M and R2 is set to 4.7M. Transistor is 2N3904 and the opamp is LM324. I understand the opamp chip is an overkill for now, but I will be making multiple detectors in the future.

What I'm trying to do is make a long range transmitter/receiver. I don't know if I can optimize my circuit further or if I should just get new batteries even though they hardly have been used, or if the photo-led equipment is unsuitable.

The emitters and detectors I used are the following:

http://futurlec.com/LED/INFD5940.shtml
http://futurlec.com/LED/INF5940.shtml

Also, my receiver is powered with 4 AA cells and the transmitter is powered with a 9V cell. In the future, I want to use regulated 5V for both the transmitter and the receiver and still achieve excellent range.

What can I do to increase the range other than trying new batteries and without increasing source voltage?


texts:
i have a DC signal from some kind of measurement, that changes from 1.75V to 5V. I need to process it, so that it changes from -5V to 1.5V. See table:

So basically I need to subtract from input 4.25V (or add -4.25 offset) and then multiply it by 2.

A have two power supplies: -15V and +15V.

I'd also like to be able to make some adjustments to offset adding (+- 0.5V) by some kind of trimmer.

Is it possible to do in using only one op-amp? What is the easiest way to accomplish this?

Thanks,


texts: Is there any reason for not finding an inverter that only converts from DC to AC maintaining the same output voltage, e.g. a 220V DC to 220V AC inverter?


texts: How does the NAND Gate work using Transistors

texts:
I recently learned about the NAND gate circuit with transistors in my circuits class as shown below.

Unfortunately I'm having a very difficult time comprehending as to why the output is 1 when A or B is turned on. It seems to me that if a voltage source is connected to A or B and is turned with sufficient voltage to produce a current V_{out} will not be V_{cc}.


texts:
The NTE912 contains three standalone BJT transistors and two configured as a differential pair. The datasheet can be found at

http://www.nteinc.com/specs/900to999/pdf/nte912.pdf

and gives a pin configuration that looks like

Short of hooking the chip up and using trial-and-error to see what is the base/emitter/collector, does anyone know how to decipher this pinout?


texts:
This question is continuation of this question: High Frequency Square Wave Generator
I am trying to drive a 400V supply and 50ohm load with an RF MOSFET which has a rise time of 3-4 ns and fall time of 10 ns.
I need to have fall and rise time no more than 2ns (2ns fall 2ns rise).
Since the voltage is high I couldn't find any MOSFET that fast.
Is there a MOSFET which is capable of reaching this speed, or should I seek another solution for this?
Thanks to comments I am looking for Vacuum Tubes right now. It would be nice if someone suggest me resource about how to select fast rise time vacuum tube.
Duty cycle and frequency are not very important. 50 kHz might be enough. I just need fast rise and fall time.


texts:
As I know, with field oriented control of a PMSM it is possible to control a constant torque via the dq-axis currents.

I try to understand the behavior of a permanent Magnet synchronous machine when the frequency of the energizing current is not aligned with the rotor speed, i.e., the corresponding fields are not synchronous.

Would in this case the torque varying in time, in other words, the torque cannot be constant? When I simulate a PMSM with sinusoidal coil voltages of fixed frequency, would it be possible at all to create a constant torque, unless the rotor is rotating with the same frequency?


texts: Why is the air gap between the stator and rotor on a motor kept as small as it is?

texts: Between the stator windings and rotor is a small air gap. What would happen if this gap were larger than it is? Surely the magnetic field set up by energizing the stator windings would still cut the rotor and induce an emf across it. So what effect does this air gap have on the performance of the motor?


texts:
I have this asynchronous generator Plot (please see below)

where n = efficiency, P1 = mechanical power, P2 = power to the network, cos phi2 = power coefficient, and I2 = current.
I guess as the current increases (due to charge) the others increase as well, the only exception being the efficiency that declines due to increase of variable losses.
Mechanical power influences the network power (being directly proportional), so as mechanical power increases, so does the network power.
What do you guys think that generate that behaviour of the plot?


texts:
I am looking for a way to add a relay-based safety feature to my BLDC controller.
In case of an emergency the user must be able to push an e-stop (probably consisting of an NC contacts) completely disconnecting the power to the motor.
After the E-stop is pushed, the relay(s) may not close until the E-stop is reset and the RESET button is pressed.
Basically I want to mimic the workings of a safety relay with an E-stop and reset. What type of IC and/or circuit can I use here?
Thanks!


texts: Design/Purchase a Filter for Data Acquisition System

texts:
We have several types of data acquisition devices where I work. They're used primarily to measure low frequency voltages (<100HZ, +/-10V). One device has a built in filter that does an excellent job. I asked the manufacturer for details about the filter. They would not elaborate on the specific design of the filter, or where to purchase one. Here's the way they describe the filter in an email:

"the filter before the ADC is a 2nd order RC filter with 90dB at approximately 128kHz"

The user manual describes it simply as a 50/60 Hz filter.

To my surprise I'm having difficulty finding such a filter using Google. Can anyone tell me how to construct such a filter or where to purchase them? Ideally it would be a module with BNC connectors so I could simply attach it inline with the signal cable to our other data acquisition devices.

As a mechanical engineer I have little knowledge about filters. However I did try connecting a 2000uF capacitor across the test leads. To my surprise this actually helps a lot to remove noise. It is an electrolytic type which I understand is polarized and only to be used with positive signals. I haven't found any non-polarized types of capacitors with that much capacitance. But 20000uF seems like way too much. I want to find a more appropriate solution.

How do I design an appropriate filter for my application?


texts: Altium Remove Component Overlay but Leave Part Designator?

texts:
I'm working on a board using someone elses footprint library for passives, and the part outlines for some reason are really close to the pads.

I see how to use PCB list to hide part designators, but is there an easy way to hide the footprint outlines and keep the part designators?

I want to keep the part outlines in Altium but hand off gerbers to the PCB fabricator that just have the component designator.

Any ideas?


texts: I am currently trying to build a PWM H-bridge, it has a power line of 12 V and the arduino uno provides the PWM. The MOSFETS I have are: IRLZ44S (N-channel) and FQD11P06TM (P-channel). Basically, the p-type MOSFETS go in the upper side of the circuit and the n-channel go at the bottom. I would be building 6 of these circuits to run 6 motors in an ROV. At the moment I am using this circuit (see image below) but I have been told that it might have problems due to problems of straight through currents which could burn the MOSFETS so I would have to add some capacitors. I honestly don't know which resistor values I should use and where to place the capacitors (or their values). Any help will be appreciated. I am more than welcome to accept a different H-bridge circuit which is simpler than the other one as it uses BJTs and, ideally, I would only like to use a simple circuit with only 4 transistors (the MOSFETS). Thank you for your support.


texts: Need help identifying some sort of "wire"

texts:
I just disassembled my Android Galaxy S in attempt to create something like the iPhones physical sound on\off switch. This is how the unplugged speaker looks like:

Until now I have learned the speaker is connected directly to the phone like shown in this picture (The bump in the green zone indicates the wire that's popping out of the speaker. that goes right into the blue "receiver").
What I want to do is "plant" a micro-switch between the phone and the speaker.

To do so, I need to find out the type of connection of the speaker shown in the first picture, and then get:

A few wires of this sort.
A microswitch that goes with it, or some kind of adapter to transfer the wires' signal to and from thicker wires. that way I can plug those wires to a microswitch and then back to the speaker.

As you can see I'm quite a noob in this area, but I'd really appreciate any help given. To sum up, my questions are:

What kind of wire is this?
Where can I get more of this type?
Where can I get a microswitch to fit with it, or maybe, like mentioned before, somekind of adapter from and to thicker wires?


texts: DC Motor driver interfacing problem Atmega32 Board

texts:
simulate this circuit – Schematic created using CircuitLab

I want to drive 24V/5A DC motor with Atmega32. So bought motor driver having 24V/20A rating. But i am facing some issues :

When i connected Atmega Board with Motor driver and connected 24V supply to driver input, motor worked fine. But after that when i turned off power supply to Atmega Board, I observed that Power indication LED on board was still glowing as well as motor was rotating.
Is it due to Back EMF ?
To solve this, I connected diodes in series to the connection between Board to driver, to avoid Back EMF. It was a success. But after few seconds driver was blown with fumes coming out.

(Note : I maintained proper input to drive, i.e 24V. Didn't cross that mark.)

So my question is how to stop Back EMF as well as save the driver ?

Thanks.


texts: Resistors too hot - possible due to transistor type?

texts:
I am new to electronics.

I am trying to control RGB Led Strip (5050) 5m using arduino. In doing so, tutorials recommended using TIP31 mosfets along with resistors. However, I switched them with BC547 transistors along with resistors.

Now, using a 10k resistor decreases the luminosity of the LED strip too much and when I use very low value resistors like 33Ohms, I get the desired brightness, but the resistors become way too hot and have even started blackening.

Is this due to replacement of TIP31 with BC547?
Or something else is causing this?

Update:

Here is the tutorial I used
Here is the schematic:

Note that, I am using BC547 instead of TIP120 in that schematic, without any heat sinks.


texts: Using Analog potentiometer as a digital one to SW control

texts:
I try to read an analog potentiometer that will control specific software functions.
That means that I want 0 fluctuations in its reading.

For this reason, moving average and other techniques do not work. What I want to do is to use this pot as a digital potentiometer with values from 0 to 63 (6bits) even though I am reading a 8bits value.

What is the best technique to achieve this?


texts: Reading and writing CAN messages through ELM327

texts:
I have an OBD-II cable, and an UART-to-OBD-II board which has the ELM327 IC in it. I want to communicate with my ECU by sending-receiving CAN messages. Is it possible to communicate through ELM 327?

I've been able to diagnose the ECU to fetch basic information through the UART board (ELM327) using HyperTerminal and Raspberry Pi.


texts: Capacitive Touch and implementation with BeagleBone Black

texts:
How might I make a basic capacitive touch sensor for the Beaglebone Black that is capable of sitting behind an insulating material? I would like to make it as basic as possible, and without any sort of "breakout board", or specialized IC, using only the Beaglebone to interpret data received as might the specialized IC would.
The Beaglebone has digital IO pins, a 12-bit ADC, and PWMs (for reference), and is very similar to the Raspberry Pi. Is it do-able? (With only the Beaglebone, breadboard, jumper cables, copper tape, and resistors of any value)

Answer to that: It is doable. Same as in the circuit schematic, it would seem! Can be done with the digital pins. You put a large-value resistor between the send pin and the receive pin, set the send pin to high, and time how long it takes for the receive pin to be brought up. The sensor acts as a capacitor, storing charge, so that the receive pin takes a longer amount of time to be brought up.

Other questions

How does such a sensor operate, and how does the sensor itself affect this circuit? (shown below, representing a touch sensor)

  There is only one source of charge, through the resistor. So if you increase the room for storage of charge by adding the capacitance of the finger it will take longer to fill.

(and thus the differences in time indicate whether or not the finger is there)

simulate this circuit – Schematic created using CircuitLab

Thanks!


texts: Ultralow power reed switch signal reading with mcu

texts:
I'm a newbie in electronics.
I need to build an ultra low power (nA) reed switch signal reading for an mcu.
I'm using the following schematic diagram.

The Vo output goes on a mcu input pin that is a Schmitt Trigger.
Is there any chance this to work ?


texts: What is the difference between the substitution principle and Thevenin theorem?

texts:
The substitution principle (as seen in this book; in italian, sorry)

  Let A and B be any two part of an electrical network with voltage and current sources and  only resistances, connected by
  ideal conductors. Suppose the voltage between the conductors is v.
  Then, in order to study A, B can be replaced with an ideal generator
  of voltage v.

Thévenin's theorem

  Any linear electrical network with voltage and current sources and
  only resistances can be replaced at terminals A-B by an equivalent
  voltage source Vth in series connection with an equivalent resistance
  Rth.

There must be something I do not understand.

It seems to me that these statements cannot be both true (or at least, the first one would imply the equivalent resistance in Thevenin's theorem to be zero, and so the theorem loses any meaning.)

Thank you all in advance for the answers!


texts: digital control of voltage step up to 100W LED

texts:
I am trying to control the voltage going to a 100W high CRI LED, which requires 3A in and a voltage between 20 and 40 V. Normally, a 12V power source could be used with a voltage step up  board to current limit at 3A and use a potentiometer to have manual analog control over the voltage going to the LED, and thus the brightness.

I would like to have digital control over the voltage on the voltage step up board, eg via arduino. A digital potentiometer wouldn't be able to handle the 3A post step up; it would have an higher current pre step up.

What solutions are there for digital control of the range of voltage out from a booster board?


texts: System Generator: How to make a buffer implementation

texts:
I would like to make a buffer in system generator to use it with a FFT block.
I want to charge 16 values to a FFT block from another system I´ve designed and I need a temporary memory system. Could anyone tell me what xilinx blocks I have to use to get a buffer?
Thank you so much.


texts: Is there a technical reason why most touch screens use glass rather than plastic?

texts:
Most modern touch screens in portable devices are made of glass.

This glass often breaks if accidentally dropped. Also, it is very reflective, making it difficult to use in strong light.

I know that touch screens without glass exist. For example, the multi-touch screen on my e-ink e-reader has a plastic front. I remember many other examples, such as the personal in-flight entertainment systems on many airplanes.

What are the reasons that most modern portable touch devices come with a glass panel on their fronts, rather than plastic or something else?

The cracking of glass seems to be a pretty big problem.

Edit: I've seen a lot of cracked touch devices, and it's nearly always only the front panel that's cracked. The actual display is usually fine underneath. Even the digitizer usually works perfectly.


texts: Oscillations in Precision Voltage to Current Converter Design

texts:
I am trying to re-design the TI Precision Design - Low Level (5uA) V-to-I Converter. My design goals are:

Increase bandwidth from around 1kHz to 100kHz (ideally 1MHz in the future)
Increase output range from 0-5uA to 0-50uA

To increase the output range I simply decreased Rset by a factor of 10 down to 10kOhm. To increase the bandwidth I needed to select a new op amp and instrumentation amp; while selecting these amplifiers I prioritized GBWP > input offset voltage > offset drift. My reason for this is the TI app note says that the key design specifications for the amplifiers are offset voltage and drift, but with my goal of increasing bandwidth I moved GBWP to the top.

I settled on replacing the OPA333 with the OPA277 and the INA326 with the INA118. Note, I switched from singled ended to +/- 15V power, this was necessary to find amplifiers with the bandwidth that I wanted. My schematic of the entire redesigned setup is at the very end of this post.

I was having troubles simulating with various SPICE tools (I couldn't for the life of me get the TI models to work in OrCad PSPICE and TI's TINA kept freezing on me) so I did a quick turn PCB with the circuit after getting some vaguely similar simulations running. What I found in the lab is that my circuit oscillates at around 25kHz and is just flat out unusable. I am positive that it is my compensation network, as I didn't change any of the values from the TI design so it makes perfect sense that my bandwidth isn't my desired 100kHz. I am struggling to understand how the compensation network values are picked and how I can design something that is stable. Can anyone point me in the right direction or offer some advice?

I should note I'll be attempting to drive this current in to a capacitive load (approximately 10uF after several feet of cabling). For the first level bench top testing I was attempting to drive the current in to a 50kOhm load (no large capacitance yet).


texts:
I want to produce a discharge of a capacitor against a test cell, as part of a study on high energy states of materials.
I'm using a standard microwave oven transformer as the power supply that I convert to DC with a 4 diode briege.
The capacitor that I use is from the same microwave oven.
Spec: CH85
1*10-6 F+-3% , 2100V
I'm looking for an electronic switch that will allow me to fully discharge a matching capacitor to the test cell with minimal losses of potential.


texts: CRC/Parity/Hamming Protect 16-bit parallel bus

texts:
I've got a Cortex-M4 based MCU linked to a FPGA via a 16-bit parallel memory bus interface. In essence the FPGA behaves like an external memory mapped to the memory space of the MCU: the MCU presents an address followed by either a data word (write) or reading the word presented by the FPGA (read).

I want to protect both read and write against transmission errors both during addressing and data write/read. However, I don't expect many bit errors since the distance between both parts is short.

I can easily implement checking and generating of either parity, hamming codes or CRC inside the FPGA. However, doing the same (checking and generating) in the uC seems comparatively harder since I don't want to cripple the throughput. Without error detection, reading and writing of 16-bit words takes around 4-6 processor cycles and is thus rather fast. Consequently I don't want to spend hundred of cycles on protective measures.

In the end I am looking for a moderately efficient error detection method for 16-bit data that is implemented in a uC in as few cycles as possible.

I've posted the same on Stackoverflow. If you know how to properly link the two questions, let me know.


texts:
I am trying to integrate a dual h-bridge design in to my custom PCB (Arduino Nano with integrated motor driver) using the L9110s IC. However, I am struggling to get it working properly. The h-bridge does not provide enough voltage to drive my motors.

The input to the motor driver is a PWM signal from an Arduino (on the same PCB) which I can confirm works correctly when checking with my scope. The output of the motor driver is faulty though. Instead of outputting the full supply / battery (7.2V LiPo) voltage it sags to 3V and does not "respond" to the variations of the PWM input signal.

Even weirder, when I first install a new L9110s IC in my PCB and measure it without load it correctly supplies the full VBat voltage at the outputs. But after one or two input pulses from the Arduino, the IC seems to get damaged (?) and will only output 3V.

I have replaced the IC a few times now, and every time it will work for 1-2 seconds before it starts outputting the weird 3V signal. The IC did not get hot to the touch and I didn't smell anything funny.

I have double checked the L9110s Datasheet and the provide input voltage for the signals (5V) and the VCC (7.2V) should both be fine. I did my testing without any load so ampere shouldn't be the issue.

I have bought an extra dual motor driver with the same IC and schematic and it works fine with the same Arduino, input signal, battery etc.

I have used the following schematic (updated):

My complete PCB is available online here but this is the layouting of the motor driver part:

I am at wit's end and don't know what else to replace and measure. I appreciate any help and pointers in the right direction. Thank you.


texts: How to use a flyback diode on a +/-12V motor

texts: I've got a motor hooked up to +12V on one side and -12V on the other, being driven in both directions by a Motor controller (link). We were getting voltage spikes in the common ground after sending big impulses to the motor, so we put a flyback diode from the negative cable to the positive cable. However, this caused the motor to be less responsive in the reverse direction. How do we correctly prevent voltage spikes in the ground from this type of motor?


texts: What is the difference between capacity use factor (CUF) of solar power plant and plant load factor (PLF) of coal based power plant? Can we compare both since they seem analogous?


texts: Radio Frequency Regulations for continuous low-power single-frequency signal

texts:
I am somewhat confused about the regulations on the radio frequencies.

I am designing a system using an antenna, which is not used for communications. It is used for sensing based on the reflection coefficient of the antenna; therefore, there are no modulations used.
The system operates on a single frequency around the range of 500MHz to 800MHz. It will be working continuously on that frequency (or can be designed to be turned on and off in short periods of milliseconds to preserve power or reduce exposure).
It might periodically readjust to select another frequency from the same range around every 15 to 30 seconds.

In a nutshell, it will be a continuous signal on a single frequency that might hop to a new frequency in 15-30sec periods.
According to these specifications, do I have to stay in ISM bands?
If yes, can I reduce my signal power to an adequately low level to be able to use any frequency in my desired 500-800MHz range? And if yes, how much is the maximum power that can an antenna have while operating outside the ISM bands? (specifically in terms of frequency regulations, not to be confused with SAR.)
North American regulations are the immediate priority, but I also wish to know about European Union regulations.


texts: Does some current return to the power company through ground?

texts:
I've come across this diagram:

Notice the connection between ground and neutral at the distribution box. Is that indeed how things are usually wired? If so, why does all current return to the distribution transformer and not into ground?


texts: Why doesn't AC motor slow down when connected in parallel to a capacitor?

texts:
Why doesn't a motor slow down when a capacitor is connected to it in parallel? Here is my understanding. During the first half cycle, the capacitor charges up while the load is getting power. During the zero point, no power from the source goes to the load and the capacitor is holding a charge, but not charging. During the second half of the cycle, the load gets power in reverse and the capacitor starts to discharge in the opposite direction. So there should be two overlapping waves one wgoing go the motor and the other leaving it.
Essentially, the motor would slow down or stall because it is getting negative voltage, but it doesn't. Very confused and please no MATH in your answers. It will only frustrate me further.


texts:
I am looking for a MOSFET that is capable of dealing of a max pulsing voltage of 60A(between drain and source) and came across these 2 MOSFETS
https://www.onsemi.com/pub/Collateral/NDPL070N10B-D.PDF
https://pdf1.alldatasheet.com/datasheet-pdf/view/257362/SUNTAC/IRFZ44N.html
both are capable of dealing with the Amperage and voltage I require
but the only thing I don't understand is that the Vgs is +,-20V .   Excuse me if I am incorrect but that would mean I would have to provide +20V at the gate to turn the MOSFET on (enhancement N type)?
and for it to turn off -20V or just down to 0V.
Is this correct?
Thankyou


texts: How to Design a combinational circuit using a suitable decoder and OR gate

texts:
I need to construct a combinational circuit for the below truth table using a decoder and a OR gate. I'm familiar with the normal procedure of drawing combinational circuit diagrams but got confused when I saw "using a decoder" part.

According to the truth table it should be a 4X16 decoder. But How Can I mark the 16 outputs of the decoder with respective to the truth table's sum of production ??? I know how to use OR gate in this question, but implementing the outputs of the decoder is the problem.


texts:
I need to create a varying capacitor, so I'm trying to make a varicap in ADS. However, there are only diodes, and I don't know how to make a varicap. Can you point me to some resources or walk me through this? I'm also fairly new to ADS.

Thanks


texts: I want to get voltage gain in BJT by using LTspice

texts:
This is the task that I want to solve using LTspice:

I solved the problem like this:

But when I did this in LTspice, something`s different:

Please, someone tell me what the problem is and share a solution. I want to get '-100' voltage gain.


texts: Altera Cyclone IV FPGA and jtag debugging

texts:
G'day All,
Is there a method comparable to jtag debugging on a microcontroller (ATMEGA32) for the Cyclone IV family of FPGA?
I am trying to debug my Verilog code so ideally I just want to be able to step through cycles and be able to read the value of a particular "register"(Not the correct term I am sure).
I have looked at the docs and they describe many different options like "system console" and RTL etc and I have heard of "test benches" but not really got my head around how they work.
I'm not expecting any help with the Verilog code (yet....) just confused about what (if any) option should I be investigating.

Thx Ben.


texts: I am trying to understand mosfet drivers in general, no specific part. And I am encountering low side and high side drivers. My question is that if for example: I have a N channel mosfet as a high side switch and another identical N channel mosfet as a low side switch. Why do I need a different driver for each? Ultimately you want to charge gate capacitance quicklyand since they are both N channel what is the difference of how I need to charge it if its high side or low side?


texts: Using BJT NPN to drive relay coil sometimes work sometimes not

texts:
I am just a hobbyist and I have a typical schematic I've always used to switch on/off relay coils.

This has always worked the last 3-4 times I've used it (without R1 and C1)

But this time, I can't turn the relay on at all (the transistor collector doesn't drop to GND (~200mV).

If I measure the collector voltage, it starts at 5V then after some seconds it drops to 3.5V-4.5V. I'm pretty sure the few times I've used this in the past (without R1 and C1, the base is connected to a GPIO pin instead) it managed to switch the relay on when transistor is on.

The only things I have changed (I think) is the introduction of R1 and C1 and Vcc 3V instead of just sending GPIO HIGH/LOW to the 1K base. I've also tried various values for R1 and C1 that I have with me.

I'd like to stop guessing what R1 and C1 values I should have. Ideally I would like the relay to switch 5-10 seconds after I connect R1 to Vcc. Currently, R1 & C1 are set to 100Kohm & 220uF to give about 5 seconds.

Note:
Transistor is S9011 I think. Or 9013.
Relay is an 8 pin 5V relay (2 for coil, 3 one side and 3 another side) - come to think of it, I've never used this kind of relay before - I've always used the 5 pin one, but this 8 pin one is the only one I have around this house. So this is also another thing has changed from my prior experience.

Thanks for reading.


texts:
I'm an electronics and communications engineering student undertaking a project regarding the occurrence of Electromagnetic Interference (EMI) in power line communications (PLC).

I would like to ask if anyone has any suggestions on how to do a performance analysis of a PLC modem that makes use of Orthogonal frequency-division multiplexing (OFDM). Specifically, how to measure its signal strength against the noise present in the system.

Your responses are greatly appreciated.


texts: Is there a way to fix a unsoldered SMD decoupling capacitor?

texts:
I'm rather a newbie regarding electronics but I came here to seek for a simple response.

I realized that a electronic appliance I have doesn't work anymore. I tried to investigate the issue and found that a SMD component was missing.

Starting from this I searched for the schematic and found the missing piece, which is a SMD 33pf 5% 25V 0201 capacitor as shown here:

Now, I don't have a replacement part and in any case I wouldn't know how to solder a SMD component (I have a rather old and standard soldering iron) so I was wondering if short-circuiting the connection could do anything useful or tragic.

The missing piece is evidenced here:


texts: I want to use This module\minicircuit Power splitter. I am working on the 2.4GHz to 6GHz band. The isolation parameter on the stated for these frequencies in the "Typical Performance Data" table is in the range of ~20dB. Is there a way to increase the isolation to 70dB? Any other solution will be most welcome.


texts:
I am making a gate driver circuit for SCT3160KL using this isolated gate driver IC from Texas Instruments - UCC21750-Q1.
The problem I'm facing is the selection of external gate resistance. I require a 2.5 A peak source current and 5 A peak sink current. According to the formula on the datasheet, my resistance turns out to be negative. (Formula in Section 9.2.2.5 of UCC21750-q1 I suspect this is because of the SiC MOSFET's gate input resistance which I approximated as 9 ohms for 500 kHz frequency. I chose Vcc = 15 V and Vee = 0 V, to be connected by an isolated power supply (Murata).
I tried some other gate driver ICs too like UCC5350-Q1 Section 9.2.2.2

Is my approximation of gate input resistance off by a wide margin? I don't have an impedance analyzer.
Have I chosen wrong gate driver ics ?
Is the solution to my problem reducing source current?

I intend to use it at 500kHz switching frequency, and as per the datasheet page-11 the maximum frequency is 1MHz. What's the problem?


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I have a layout that was done out of house and the pitch of a IC is listed on the datasheet as 1.27mm. The layout service constructed the IC in imperial and when Altium converted the imperial to metric, the pitch became 1.3mm instead of 1.27mm

The component in question is a CSD16325Q5  http://www.ti.com/product/CSD16325Q5

Should I do a waiver and run the PCB?