texts: Read 12V input with Arduino/Teensy via PC817 (Optocoupler)

texts:
I have a SPST rocker switch with 3 terminals (Datasheet), which contains a dependent LED which is illuminated via 12V if the switch is on.
I want to read the switch with an Teensy/Arduino.
After some research, I understand that there are many ways to accomplish that, but for me a simple and clean solution would be to use an opto-isolator, like the PC817 (Datasheet).
I'm thinking of a circuit like this:

simulate this circuit – Schematic created using CircuitLab
I thought about separating the switch's current from the microcontroller, because then I can use its native 12V LED and don't have to worry about damaging the board.
Is this correct, would that work? Or do I miss something here? Or are there easier/better solutions?
Thanks!
EDIT 2:

Added the datasheet for the switch: like in the commentaries said: often 12V Buttons comes with separate LED pins. But the switch linked above has an dependent LED.
By the way, in getting my post here
clearer, I found a useful explanation (for me) about SPST or DPST switches are: Whats SPST switches?
Changed schematics: added switch wiring following it's datasheet. And discovered awesome circuitlab feature within stackexchange :)


texts: Measuring small Off state leakage current 10uA or less

texts:
I have a solid state relay an AQZ207 to be exact. I want to be able to measure the off state leakage current of the FET which in the datasheet seems to around 10uA Max. I had some ideas, but not sure what to do. I know the multimeter I have a fluke has a burden voltage and everything that will affect the results.

I remember seeing some kind of resistor placed in parallel with the meter to measure the voltage drop of the resistor that some how scales to current? Anybody know of this method? I'd love to read a white paper or detailed explanation. I'm assuming the resistor acts like a current sensor since if you know the resistance and applied voltage you can calculate current.

However, is this to offset the multimeter's high impedance from the measurement also?

To actually test if the FET is leaking, I'm not sure how to test that in operation there would be a voltage drop across the resistor if the FET was leaking since its being loss in the gate?


texts: Altium problem when components placement

texts: When i try to place the components in the schematic in altium, it looks like it is not allowed and the components became transparent as if it is not active


texts: Expected percentage of collisions for uni-directional wireless transmissions

texts:
I am developing battery-powered sensors to measure different parameters inside my house.

The measurements are taken by simple AVR controllers (no Arduino) at more or less regular intervals and will be be sent wireless to a central Arduino with Ethernet shield that relays them to my server, where they will be stored.

To keep power consumption down and to keep the sensors simple, I planned to use 433MHz transmitters on the sensors and a receiver on the Arduino: no bi-directional communication is expected. The sensors will send the value and a checksum and the receiver will verify them before relaying.

If two transmissions happen at the same time, either

the receiver will be unable to understand them
the checksum will be wrong
one of them will be covered by the other one and lost.

I consider all these three cases "collisions".

I plan to introduce "random" jitter between measurements (and transmissions, they are done always together) by adding to the predefined interval a pseudo-random 8 bit delay. This should reduce the number of collisions. However, there will be some anyway depending on the number of sensors and on the duration of the communication. Moreover, the clocks of the sensors are not tuned, there may be small variations (10% is the tolerance for the integrated oscillator in AVRs).

I can accept some collisions, but I would like to estimate how many they are so that I can lower the bitrate of the transmission (and therefore the transmitting power) and so that I can estimate how many sensors and how frequent readings I can afford.

So, is it possible to estimate the expected collisions according to

duration (in ms) of each transmission
total number of transmissions per second

assuming the transmissions take place more or less homogeneously?

Even if the energy-per-bit can be assumed constant and therefore I should aim to the highest bitrate to save CPU cycles and to go earlier in low-power mode, the question is still valid: know how many collisions should I expect given the frequency of the measurements and the number of sensors?

Thanks

(maybe someone should add "collision" as tag? I cannot)


texts: Can't find the datasheet of cheap Bluetooth audio reciever

texts:
The chip says JL AP24186-26A4, but I can't find datasheet anywhere. Everytime it takes me to dead end. If someone know about it then please help.
Update:
Found that it's Bluetooth 5.0 based audio reciever.
http://dientunguyenkiet.com/module-mp3-fm-bluetooth-5-0qd008-id144.html
[2


texts:
Available speakers all seem to be low impedance like 4 or 8 ohms etc. Philips used to make speakers of 800 ohms for their SRPP valve stereo amplifiers. The speakers weren't that great even in 1958. But the SRPP amplifier is still valid and Audiophiles are designing modern versions today that have very good performance by contemporary standards.

When I would fix a Philips Hi-Z stereo we couldn't get new speakers so we would use an output transformer. The speakers weren't stunningly reliable and they had small magnets by today's standards. My question is would it be feasible to make Hi-Z speakers so the sound of a valve OTL amp could be achieved at reasonable cost?


texts:
I've been wondering about this for a while; I have a Wireless 2.4GHz keyboard that requires a USB reciever to catch the signal.

How great would it be though if I could  use it on my phone, for example, without having to plug a usb in my phone, but rather connect it through bluetooth?

That's pretty much what I'm curious about. Could somebody enlighten me on this?

Thanks.

EDIT

My question is pretty much, is it possible to convert wireless 2.4ghz into bluetooth?


texts:
I want to monitor energy produced by 250W solar panel. But I need some hints. Does anyone knows something? Is it possible using ACS758 chip or better I have to use current transformator?

Finally I plan to log all data and store to create annual report.


texts: How to calculate the effective junction temperature of the FPGA?

texts:
I am using the Xilinx based FPGA. Xilinx datasheet suggest the theta ja value is 7.3 °C/W and power dissipated is nearly 50W and ambient temperature at which it is operated is 85
Junction temperature= ambient temperature + thermal resistance (theta ja)power dissipation
                = 85+ 7.3*50

                = 450°C

Is this junction temperature is expected or some mistake in the consideration. Anybody who worked on thermal analysis can help me out. Xilinx XPE shows the effective theta ja is 1 °C/W. I am not understanding why they have consider 1 in xpe and 7.3 in datasheet. How Theta ja will vary?
Also i want to understand what is the relation between the theta ja, jc, jb
Also as per my understanding,
Materials that are good conductors of heat (metal) have a low thermal resistance
Materials that are poor conductors of heat (plastics) have a high thermal resistance
But i want to understand why we are adding this instead of subtracting to reduce the thermal resistance
Theta ja = Theta Jc + Theta ca
Any insight would be greatly appreciated.


texts: Why do we choose apparent power rating as base in per unit analysis of a power system?

texts: Can you please tell me the reason behind choosing the apparent power as base of power in per unit method. Why don't we choose real power instead.


texts: Why is the output of wien bridge oscillator sinusoidal?

texts: I have been studying Wein Bridge Oscillator for a function generating project. I am curious how output of the oscillator is always sinusoidal. A rigorous mathematical reasoning would be great.


texts: Maximum fuse rating before a MOV (varistor)

texts:
I just watched some scary videos of MOV's catching fire and I've flee'd here to ask you guys for help.

I understand that it's a good idea to put a fuse in front of a MOV, considering it fails short-circuit. However, is there a maximum fuse size that can be used before the MOV?

I'm pondering the possibility of a MOV failing partially short-circuit which then runs away to become a fire hazard. i.e. the short might be enough to blow a 1A fuse but not enough to blow a 13A fuse.

Would it be safe to rely on a varistor to blow a standard, household 13A fuse found in a mains plug?
Would it permit too much power?


texts: Does 12 V DC to +6 VDC and -6VDC with discrete components require conversion to AC?

texts:
I have a 12 volt battery and want to power a 741 Op Amp, but that requires + and - voltage supplies. Is there a more efficient way to give a + and - supply to the op amp from the battery without converting to AC first.

By converting to AC first I mean:

DC Battery->
AC Inverter->
Transformer:Primary Two Tap, Secondary Center Tap:Three Tap with center Tap Grounded->
DC Rectify Top and Bottom Tap
~ +6 V Top and ~ -6V Bottom


texts:
This is from the PCB in a microwave oven. On the right side, there are two symbols with the labels DU and OMIF. They look like inductors. Is that correct?

sidenote: this is found underneath a relay, the DU1PU. I have removed the relay. I'm guessing the components are connected to the relay pins.


texts: Power Transformer: 110V and 220V input, with two 15V outputs 180 degrees out of phase

texts:
I have never designed a power supply before and have a few questions and would appreciate any help.

Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center tap transformer and for 110V put the coils in series and for 220V only use one coil and leave the second open circuited?
Secondly, I need an output of + and - 15, so do I select a transformer with a center tap secondary and wire the two identical outputs to be 180 degrees out of phase?
Lastly, I cannot find any transformers with these specifications. What I've been looking for is a center tap primary and secondary with a ratio of 15:1

Thank you in advance.


texts:
I want to use two LEDs to show send and receive on my max232 RS232 to TTL (5v) converter. I have seen this method as the most conventional way to power an LED for max232:

I tested it and the LED light was very dim and decreasing the resistor value resulted in voltage drop at TTL level.

What is a more intelligent way to do this? Can I use two N-channel MOSFET and connect the gates to RX and TX and use a separate 5v between the Source and Drain? What are the pros and cons of this approach?

I have too many IRF3205 and I can use them. I think they will serve the purpose unless you think the specs are not good.

If it is good what resistor value seems reasonable between Rx/Tx and the gate of the MOSFET?

And one last question. Do you think a pulse stretcher is going to be necessary with this approach? or at least recommended? I am not familiar with them. If it is necessary or recommended I'd be thankful if you could show me a simple way to implement it. I am a tyro at best in electronics so I need a very simple solution... (like LM780x for voltage regulation / max232 for level conversion without too many details and components)

Thank you very much in advance.


texts: If I drive an LED whose forward voltage is 2V with a source that's 3.3V limited to 20ma, will I harm the LED?

texts:
Background: I built a 10x20 LED matrix for use inside a jack-o-lantern. The matrix is driven by 74HC595 shift registers that are connected to an Arduino.

I've attached the Vcc of the shift registers to the 3.3V port of the arduino, so the output pins of the shift registers will be 3.3V when set high.

The datasheet for the shift register says each output pin can source at most 20ma, which is exactly the nominal current of my 3.3mm orange leds.

I know that power supplies can source much more than 20ma, so the use of current limiting resistors are necessary when the voltage is higher than the forward voltage, however is there any harm in exceeding the forward voltage if the current is clamped to the LED's nominal current rating?


texts: How do custom security certificates find their way onto mass manufactured products?

texts:
Amazon and Microsoft both have IoT services that manage message and state brokering. These sort of services generally require machines to have unique security certificates embedded into the firmware so that they can securely authenticate with the service.

How do these sort of security certificates find their way into the firmware of mass manufactured products? Is it the manufacturers job to burn the firmware onto the microcontroller with a unique security certificate installed per machine? Or does a company hire their own workers to accept shipment on microcontrollers, load the firmware, and send them off to the manufacturers pre-loaded?

Curious how this is actually done in practice.


texts: wien bridge oscillator transfer function

texts:
I am trying to calculate the transfer function of a wien bridge oscillator but there is something wrong in my calculations.

In the picture below there are my results from this calcultation. I am using signal flow graphs

results from maxim


texts:
Ok so I am looking to regulate a 6v power supply down to 3v

Constraints are:
Extremely limited board space (no room for any IC)
Must be power efficient as the module is powered by 2x button cell batteries. (IE as close to 0 drain when off as possible)

my first thought was to use 2x resistors of equal value in series and pull the power from between them to regulate to 3v, but my only concern here is that in this scenario there is a constant connection between Vcc and Vdd (through 2 resistors) which would cause a constant drain on the battery.

If using a high resistor value it will limit the constant draining but will also limit current to the only IC used. Low value and the opposite is true.

So i'm just wondering my options here, would a schottky diode be appropriate?

Oh yeah this is supplying power to a simple 3v PIC microprocessor, which is driving a 3v SMD RGB LED so it must have enough current to drive both.

Thanks in advance for the help

Best regards,
-J


texts:
Recently i bough an Arduino Uno, along with a breadboard starters kit (those two were bough separate) and i am trying to configure my first project. Looking to the breadboard instructions, if i am not mistaken, i am supposed to remove the ATmega328 from the Arduino and use the other one (the one included in the kit).

Question is: 'Can i leave it as is and then tell the program which one to use?'

I am a bit confused in that part since i am not really experienced in electronic engineering.


texts:
I'm trying figure out what connector this is? The pitch is 2mm. I believe it may be a type of JST connector.

connector:

mate:

pitch:


texts:
I have two definitions for antenna efficiency:

\$ \varepsilon = \dfrac{P_{rad}}{P_{in}}\$

and

\$ \varepsilon = \dfrac{R_{rad}}{R_{rad} + R_{ohm}}\$

Coming from physics, I was wondering if there is always a clear distinction between the active power P, reactive power Q, and complex power \$S = P + jQ\$, or if P is interchangeably used for active and complex power.

My problem is this: if P in the first equation is the active power, then it doesn't account for all the power in the antenna. If P in the first equation is actually the complex power S, then the two definitions are not equivalent.


texts: Is there any technique which can detect and correct all error bits. To my knowledge 100% error correction is not possible but is there any technique that possibly exists? And can hamming code correct only 1 bit error or more? what is the simplest error detection coding technique based on hardware complexity?


texts: Safe to rely on individual 18650 cell protection in a 4S4P configuration?

texts:
I'd like to build a power bank with hot-swappable 18650 cells. A "retirement home for salvaged cells" device.
It would be expected to keep providing power on cell failure and replacement (similar charge level first assured)

The cells have different capacities and resistances, and possibly slightly different chemistries.

The answer here explains much re: mismatched cells in parallel.

I wonder if the combination of multiple protection circuits and PTCs in a 4x4 array doesn't perhaps lead to some dangerous feedback loops, deadlocks, etc - e.g. reaching a level where components cause each other to repeatedly swith on and off, or require special circumstances to reset.

Is that a noteworthy danger?


texts: Why do alkaline batteries seem to leak (corrode) more frequently when installed in a device?

texts:
I know that dead batteries can leak and the alkaline ones are specially corrosive.

Alkaline batteries self discharge even when not installed in any device.

I've already opened a four battery pack with one battery leaking, but this situation is by far more uncommon than finding leaking batteries in forgotten devices.

Nowadays some appliances have standby power that possibly in a long time can drain the batteries and consequently provoke a leakage.

But why alkaline batteries with the same age, brand and charge installed in simple flashlights with a mechanical switch seem to leak even when the  switch is off  and the flashlight is not used by a long time?

(This is a suspicion i have. I don't have  enough data so i may be wrong)


texts: LTspice transformer voltage course problems at low duty cycle

texts:
I am trying to simulate full bridge SMPS in LTspice where I can change the input voltage to the voltage regulator (LT317) by changing the pulse width of the PWM signal at the MOSFETs.

Everything works as expected at higher duty cycles (>20%), so the voltage on the transformer is positive when the 1st pair of MOSFETs is conducting and the voltage is negative when the 2nd pair of MOSFETs is conducting. Here is the schematic and plot for 80% duty cycle:

But when I change the duty cycle to the lower value the transformer seems to be "working" even if the transistors arent conducting.

Notice that the time base is the same.

And the same plot but enlarged:

Questions: Why is the transformer working when all of the transistors are not conducting?

How can I make the transformer work only when the MOSFETs are conducing?

This problem makes the voltage on the C2 condensator always the same (independent from the duty cycle).

Thanks in advance.

UPDATE(27.11.2019)

I've tried to solve this problem byt trying few things:

I thought that because of the MOSFET capacitance, inductance of the transformer and the resitance there was an RLC resonant circuit. I changed the values of the capactiances in the IRF740 model that I applied to the schematic.

.MODEL IRF740 VDMOS(KP=3.1089 RS=0.0048 RD=0.4166 RG=0.91 VTO=4.5
+LAMBDA=0.001 CGDMAX=1218p CGDMIN=15p CGS=1300p TT=533n
+IS=2.41E-09 N=1.401 RB=0.013053 m=0.452 Vj=0.36 Cjo=1424.39pF)
+mfg=STmicro Qg=35n Ron=0.48 Vds=400)

Changing the values didn't solve the problem.

I changed the circuit by removing the MOSFETs and replacing them with voltage controlled switches pararelled with diodes. That erased all the capacitance but there was no result that try either. In fact there were much more oscillations after switching.

So I returned to the MOSFETs.

After reading (this article)(http://ltwiki.org/index.php?title=Transformers) I've decided to change some of the inductors parameters (pararell capacitance, resistance and series resistance). It did change the voltage course on the transformer but still I am not satisfied with the results.

3.1. For values of the inductor: R_series = 10m; R_pararell = 2; C_pararell = 10p (for the primary winding I've set the secondary winding parameters 100 times lower - 10:1 ratio); the oscilations where gone, but the peak voltage on the primary side of the transformer decreased from ~325 V to ~150 V.

Green is the transformer voltage, red and blue PWM to the mosfets.

3.2 When I changed the parameter values to more be "realistic" (R_pararell to 200 ohms on the primary winding, 2 ohm on the secondary) the peak voltage transformer went up to ~325 V, but there appeared one overvoltage, oscilation (I dont know how to call this). This time I think it looks "real" and the opposite polarized voltage peak is just because the energy stored in the inductance has to unload somehow (is that correct?).

I've applied the inductor (L = 200 uH) before the C2 (C2 = 100uF) capacitor. However the voltage on the capacitor never stopped rising.

The plots are for 10% duty cycle.

Is that because the way im driving MOSFETs is wrong due to what @Big6 wrote?

Where my approaches at least somehow correct?

@Big6 why only the lower transistors capacitances will be charged? Also according to Kirchoff's law even if they would be charged one would be charged to +Vp and the second one to -Vp so the voltage on the primary winding should be 0 V.

(here is the .asc file, I uploaded it to the google drive)[https://drive.google.com/file/d/1amOW-eyB5OYwljlaeMHK7lGp6Er8rYW8/view?usp=sharing]


texts: Problem with understanding the circuit related to stable matching security

texts:
I am trying to understand a circuit used for stable matching. The paper title is:
MPCircuits: Optimized Circuit Generation for Secure Multi-Party Computation and is available :
here
I am attaching the image:

I have following questions:

why Preference of group1 starts from L_0 where as preference list from group2 starts with L_(n/2+1)?
Any reason why they used the priority encoder?
What is the technique for the security of preference list?

Somebody please guide me.


texts:
I am doing a reverse engineer project but I can't find what these components are.  Can someone help me?

The components have the folowing text on it:

IC #1 = 7HUH
7HUH

IC #2 = AAPQ
AAPQ

Here you can see the 7HUH and AAPQ + external components.


texts: NgSpice transient analysis on BJT Colpitts oscillator

texts:
Can you tell me how can I run a transient analysis on it? What I am curious about is the startup process.
I'd use a simple textbook example BJT circuit, the point is on the simulation setup/commands.
I'd measure the voltages in certain points in ~1000 time points.
Thanks in advance!
ps.: I've seen the topics with similar title, but this isn't a duplicate.


texts: Measuring 400V three phase large consumer power

texts:
I need to measure the power consumption of a large (11kW) electrical motor during various stages of operation. I have a few interlinked questions:

I'm interested in the power the operator of that motor would be charged for. I'm not sure if that is real, apparent, both?
Can I use a clamp on ammeter and measure the current of just one phase, or do I need to measure all three?
Given I cannot measure the 400V supply, is it reasonable to trust that it is in fact 400V, or what voltage do I need to use for a three phase power supply? Or do I need to hire a qualified electrician (Health ans Safety...)?

A certain scientific rigour for this is required as I intend to model the power consumption of the motor, but with a linearized system, to be presented at a civil engineering conference. (So accurate, but I and the audience are not interested in the details too much)

I intend to use a clamp on ammeter, preferably with logging (PC hookup), capability. Any recommendations (I'm UK based)?


texts: type of capacitor (0.01uf) for this circuit?

texts:
I'm having difficulty sourcing the correct/safe capacitor for this circuit (despite my research).

I know it should be 0.01uf and is being used in a 120v AC (upto 10amp) circuit. Schematic below. Also attached: Photo of the creator's circuit.

Are typical disk capacitors ok? (ie capacitors @ local store)


texts: Is it detrimental to an SMPS to turn it on and off frequently?

texts:
I've got a 5V SMPS powering two separate servos:

and

The smps is a tps562200

The application is an autonomous sail boat (3 feet long). One's a winch, the other a rudder. I have code that scans various sensors and when appropriate makes adjustments, anywhere between every 2 seconds and every 30 seconds (depending on how stable things are). The two servos never need to be active at the same time. To not waste power on the switcher's quiescent current, I pull its EN line low whenever not in use.

I'm looking at two possible options:

disable the switcher in between each servo access
be a little smarter about it, and keep it enabled during the autopilot cycle

From an power savings standpoint, turning off the switcher more than makes up for the energy lost in recharging the caps on the servos, but does this much cycling do any damage to the switcher / associated circuitry?


texts: Difference between __asm__ volatile("jmp 0x0000") and ((void(*)(void))0x0000)()?

texts: Is there anything slightly different between the two calls? Which is the "better" version?


texts: what is the EEPROM (28C64) output behavior between address change?

texts:
I wrote all "1"s into a 28C64 EEPROM from address 0 to 15 (the rest address lines tied to GND).

Then I use a 4-bit counter (10HZ clock) to drive the address lines from 0 to 15 to read the 28C64. I noticed that there is a short voltage drop (output goes from high to nearly zero and back up to high, last about 160ns) when the address changes.

It happens somewhat randomly: the voltage drops may happen when address changes from 1 to 2, or from 5 to 6, etc. Then I tried two another same 28C64 chips, one does not have this voltage drop, and one does.

The data sheet used cross marks during address change.  http://www.jameco.com/Jameco/Products/ProdDS/74827.pdf

I am quite confused, it is normal for the output to drop during address transition? thanks!

Here is the scope captured the voltage drop. The total time is about 240ns, the chip is -25.


texts: What's the difference between a Zener Diode and a Switching Diode? I.e: 1N4148 (switching) vs 1N5225 (zener).


texts: Examples of current-controlled negative feedback?

texts:
I'm learning negative feedback topologies and am stuck on current-series and current-shunt.  I can't find examples of simple circuits to help me understand their function.  All I can find is block diagrams but I'm looking for simple op-amp or BJT circuits that I can learn from (like when I used inverting and non-inverting opamps to learn voltage-controlled feedback).
What is the simplest circuit using current-controlled negative feedback possible?
I read somewhere (apologies, can't find it now!) that a common emitter can show both these topologies.  A resistor from collector to base can show current-shunt and the emitter resistor can show current-series.  But how do these circuits match up with the block diagrams?  What parts of the circuit get included in the amplifier and feedback network boxes in block diagrams?


texts:
I have a precision application where I am demodulating two sine waves using an analog mux (ADG613) and then Low pass filter to measure it's amplitude.
The ADG613 is a 1:4 MUX made into a DPDT (chosen because of its low charge injection) by connecting S2 and S1 together and S3 and S4. Then the inputs are D1 & D2 and D3 & D4
I think that in between break before make, where the output is connected to nothing I get some 'leakage spikes'

here is the SPICE simulation. I can't exactly see where the spike is in the simulation but a clue is the current going into the MUX.

zoomed in:

With 300 ohm pull downs, the current is certainly higher but the spike looks 20mV smaller:

Zoomed in:

I am wondering if I can put a pull down resistor on the output of the Demodulated signals (input of LPFs) to prevent these types of spikes/glitches but not lose precision or signal integrity on the output of the LPF. above are pictures of using a 300 ohm pull down on the de-modulated signal output.  I think the glitches are happening during that break before make period where only leakage currents are rushing to the output.

If using a pullup resistor I will be wasting some power, maybe there is a better way to clamp down that make before break error?

The MUX inputs have some Ron resistance about 85 ohms to 115 ohms, a max of 40 ohm flatness, and a max of 4 ohm matching. The error between Demodulated output and inputs is not going to be precise because of that voltage drop. Should that be anything to worry about on the output of the LPF?

Thanks in advance


texts:
I am trying to measure battery's voltage and current but with a very high accuracy. So i've selected a 12 bit ADC to be interfaced (via I2C) with my micro-controller. My micro-controller will receive these values form the ADC and send them to the PC via the USB.

Now my question is, can we interface a 12bit ADC with an 8bit MCU like this one ?

Being new to microcontrollers i did a research over the internet and got the concept of 8bit Micro-controllers. But i couldn't find any where if i am able to interface it with a 12 bit ADC.

Also IF i am able to interface it, would it be more easy to use for eg a 32 bit MCU like this one instead of using the 8bit micro-controller, and interfacing it with the 12 bit ADC ? P.S by 'more easy' i mean simplicity of coding.

Looking forward for your suggestions.

Thankyou.


texts:
I have some tamiya motors and would like to use them on a project, the problem is when i looked up the data sheet of my motor (Tamiya plasma dash 4WD). the motors are at 3volts , 4-5amps. this is quite difficult since common drivers (L293d) only drives motor above 4.5 volts at 1A. I have read that MOSFETS are good, but i don't have a lot of experience using MOSFETS. But i think i can learn, question is there a MOSFET that can carry it though.

Does anyone know a common IC that does the Job?

If there is none, a workaround to drive the motors is also greatly appreciated.

PS. i will be an arduino Microcontroller , with either a LiPo or Eneloops batteries.

EDIT : I would like for it to be bi directional, Electronic Braking would be great.

Thank you.


texts: Connecting the voltage sense screws of a power supply (wire gauge to use?)

texts:
Very often I see high wire gauges (i.e., very thin cables) used for the wires that connect a test circuit's voltage input terminals to the sense screws of a power supply. I would have thought that you would want to use very thick low resistence cables to get an accurate read at the sense screws of the actual voltage that the circuit is getting.

It seems to me that by using thin wires of any length you are introducing parasitic resistence into the equation and skewing the voltage that the sense screws are receiving. Yet this seems to be common practice, thick cables for the power cables coming out of the supply and much thinner cables for the two sense connections.

What is the reasoning behind this?


texts: Does a lithium battery make a good ground plane?

texts:
A patch antenna I'm using calls for a 50mm x 50mm ground plane under it, mostly to cut multipath reflections in the bottom lobe. Naturally, the closer to the antenna and the more conductive the ground plane is, the better. Ideally, it would be the top layer on the PCB on which the antenna sits.

For unrelated constraints, I may have to make the PCB smaller than ideal, but the board may end up sitting directly on top of a flat lithium cell that powers the circuit. The cell is slightly larger than the ground plane requirements.

How well, if at all, can a lithium cell act as a ground plane?


texts:
I want to do RS-232 communication with a PC terminal using interrupt on the receiving for the STM32F11RE.
I've done polling using

HAL_UART_Receive(&huart2,&data1,sizeof(data1),HAL_MAX_DELAY);

in a while loop, echoing back upon completion lie this:

HAL_UART_Transmit(&huart2,"OK",sizeof("OK"),HAL_MAX_DELAY);

Now I want to do the same but without polling, but I don't know how to proceed.
The manual says "Enable the NVIC USART IRQ handle.", but there is no reference to NVIC in STM324fxx_hal_uart.c
There is a function

void HAL_UART_IRQHandler(UART_HandleTypeDef *huart);

Since it has an input argument, I guess this is not called by an interrupt vector somewhere. It must be the case that I will have to call it from main.
Should I somehow create a highpriority task and call the IRQ-handler?
Currently I have disbaled FreeRTOS.
There is a global interrupt flag that I checked in the CubMx.

I've add this now

void USART2_IRQHandler(void)
{

HAL_UART_IRQHandler(&huart2);

uint8_t data1;

 HAL_UART_Receive_IT(&huart2,&data1,sizeof(data1));
      if(data1 > 0)
      {
          HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin,GPIO_PIN_SET);
          HAL_UART_Transmit_IT(&huart2,"OK",sizeof("OK"));
      }
}

It works with this in main:

void MX_USART2_UART_Init(void)
{

 huart2.Instance = USART2;
 huart2.Init.BaudRate = 115200;
 huart2.Init.WordLength = UART_WORDLENGTH_8B;
 huart2.Init.StopBits = UART_STOPBITS_1;
 huart2.Init.Parity = UART_PARITY_NONE;
 huart2.Init.Mode = UART_MODE_TX_RX;
 huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
 huart2.Init.OverSampling = UART_OVERSAMPLING_16;
 HAL_UART_Init(&huart2);
 HAL_NVIC_SetPriority(USART2_IRQn,14,0);
__HAL_UART_ENABLE_IT(&huart2,UART_IT_RXNE);
}


texts: Is wire-wrap for components, or just special boards and pins?

texts:
Are common components suitable for wire-wrap connections?  Or is wire wrap designed for a special type of pin?

I just checked some resistors and diodes and found them ranging from .5-.7mm, and the legs on a MOSFET are rectangular, ranging from .65-1.65mm.

I was looking at one hand-wrap tool for 22-24AWG wrap wire and it specifies a "wrap post size" of 1.14mm.  How precise must the size of the wrapped conductor be to the tool's specification?

Also, is it important that wrap wire be plated in tin or silver?


texts: Slow solution of LTSPICE electric-magnetic model for transformers

texts:
I am trying to model a transformer using coupled electrical and magnetic circuits. SPICE has many advantages in assembling these circuits. I was able to model properly for an transformer with no load, although the solution is a little slow.
When I try to add a secondary to the transformer, the simulation is prohibitively slow.
Does anyone have any clue as to what the problem might be?


texts: Governor Droop Response (Demand Balancing)

texts:
I am having trouble figuring out how to solve the governor droop response question in a textbook I am studying for a certification.
This is the question:

A 100 MW generator at 50 MW output that has 5% governor droop response will respond how much to a -.15 HZ frequency deviation (Actual frequency = 59.85 HZ)?
A) -10 MW
B) -5 MW
C) +5 MW
D)  +10 MW

I do know that because the frequency deviation is below zero, that the governor droop response will be greater than zero, thus eliminating choices A and B. I looked at the answer pool in the back of the book and the answer is C.
I did this to see if I could figure out the problem by working backwards, but I cant seem to wrap my head around it. I am not an Electrical Engineering student, and I have been out of school for some time now.
How would I approach this kind of question, and is there any base formula I could use to solve for the droop response?


texts: How to provide power to a micro controller in a high voltage (180V DC) circuit?

texts:
I have a 230V AC to ~180V DC circuit to drive a DC motor and need to power a micro controller board with 5V DC in order to provide a PWM signal.

Originally I thought of simply recycling a USB mains adapter but since most/all of those are isolated from the mains and the motors power supply is not I assume there zero reference is going to be incompatible.

Whats the simplest way to provide a compatible (needs to control MOSFET gate in high voltage circuit) low voltage DC?


texts: How to convert a metal work table surface for electronic work?

texts:
I have a 23" x 60" metal work table...the kind that restaurants use for prep work. I'm using it as my computer table & electronics workstation.

I want to make the surface non-conductive in the cheapest way.

I've seen cheap neoprene mats and more expensive mats with grounding wires.
An expensive example out there:
Static Control Work surface mat

What are some cheap alternatives to cover a large area? Can I get something from the hardware store? Rubber shelf liners?


texts: What usb-class for a device intended to be as future proof as possible?

texts:
I am writing specifications for a product and need help to minimize its future need of maintenance.

In order to be able to be (optionally) monitored from the Internet the device is supposed to have a USB port to connect it to a computer (I am now developing it as a python script on raspberry) able to poll data from it (less than 10 byte a minute, speed is not the problem here) and generate a nice webpage.

My concern is to minimize the need for future work on this communication capability feature: we decided to make it as a pr stunt but we expect to be used by a minority of our customers, spending days every year maintaining and fixing the code is not an option.

Computer-side we decided to open source the code and, of course, also the AT command for the device.
Device side, what worries me is the need for drivers.

What USB class should I put my device into for it to be recognized as a COM port without the need of distributing drivers? I.E. if I make it adhere to Communication Devices Class specification can I have it recognized as a com port thru "standard, omni-present" drivers?


texts: Solid-state version of a uniselector (rotary relay)

texts:
What would be the circuit equivalent be of a uniselector, aka rotary relay, aka stepping relay?

Uniselectors were commonly used for phone switch boards (and thus why we used to hear individual pulses). The uniselector:

has high-voltage galvanic isolation between inputs (easily hundreds if not thousands of volts)
carries bi-directional, high current at low resistance
incrementally steps between inputs, guaranteeing input pairs stay exclusive
has a floating ground (it really has no ground at all)

Potential equivalents

An array of bistable relays, controlled by a decade counter and an overlap protection circuit, is the closest I can come up with. However, this feels very unsatisfactory as its needlessly complex in part count.

Transistors and FETs do not provide isolation, so are not a replacement.

Analog switches are not an equivalent as they have relatively high internal impedance (>1ohm), and thus cannot carry much more than signal current.


texts: Can super amplified line-level audio (e.g. 60Hz sine) signal be used as an AC power source?

texts:
However inefficient (or bizarre) this may sound— can a line-level 60Hz sine (originating from a sound card, oscillator, etc) amplified by a heavy duty 1000W+ RMS monoblock be used as a substitute for a high voltage AC power source?

If the square root of (1000W * 4 ohms) gets us 63V, AND supposing we use a step up transformer on that signal to bring us into the 120V range, theoretically, would we end up with a usable 126V 7.9A (from amps = watts / volts) power source?


texts: Digital oscilloscope maximum input voltage

texts:
I recently bought a new GDS-1052-U oscilloscope. I read a few pages from the oscilloscope manual and I found that the maximum input voltage is 300Vpeak.

I have a question regarding the maximum input voltage: Is 300V peak the maximum voltage input for 10V/div or for 2mV/div using a 1x probe and AC coupling?

Will the oscilloscope be damaged if I set the vertical voltage to 2mV/div and connect the 1x probe to 200V peak? I know that the 200V peak voltage cannot be displayed on the screen if the vertical voltage is 2mV/div, but I want to know what can happen?

The last question: What is the maximum DC input voltage, using a 1x probe and DC coupling?


texts: Why do laptop batteries have so many terminals?

texts:
Why do laptop batteries require so many terminals (upwards of 10 or more!)? Why not just a positive, negative, and a data pin?

All the phones I've used only have three terminals, and I would think these these are more or less comparable devices, separated by scale. All other devices I can think of using or taking apart only use two to three connections/terminals. Likewise, you remove the laptop battery, it runs fine with just the positive + negative of the power adapter, and maybe a data pin.

It seems as if the number of terminals has been growing, too. Is there a reason for the terminal-wagging competition amongst laptop makers?


texts:
I've got an old barcode scanner that I've decided that I want to connect to an Arduino Uno(for the purposes of wireless transmission).  After poking around I've found some information that states that basically it should act like an old AT Keyboard.  I haven't even gotten to the coding part of it, but my findings with a scope are providing me what I think are garbage waveforms.  This uses the old DIN5 connector, which has clock and data lines.

I have:
Vcc - 5V
Gnd - gnd
clock - 2(on attached scope waveform)
data - 1

This is the waveform I get on scanning.  Otherwise they both hold at 5V.

From my understanding, the clock line is supposed to, well, be a clock!

I have looked at the following resources trying to figure this out.
http://www.hardwarebook.info/AT_Keyboard/Mouse_protocol
http://retired.beyondlogic.org/keyboard/keybrd.htm
I can't seem to find anything for the particular model of scanner I have (Unitech MS283).  There exist no manuals online that I can find.

I guess the question here is; is there any sort of circuit that I'd need, or some control from the PC that's missing in my testing?  And if this does turn out to be the actual signal, where should I look for programming for this?

Thanks in advance for the help.


texts: Gathering accelerometer data over I2C not updating every 1 ms

texts:
I am using an STM microchip to communicate with an IMU over I2C. I am requesting 3 axis of acceleration information from the IMU (x,y,z). I have the ODR Selection frequency set at 1.66 kHz. Currently the acceleration values don't always update every  1 ms (I have a timer set to send the acceleration data out over UART every 1 ms). The I2C baud rate is set as fast as it can go. Currently about 1 every 3 data points does not update. Any thoughts on initially where I can start looking for a solution?

I can add some of the code that I'm using. However, I don't think would be helpful to just lay it all in here. I am more looking for a trouble shooting starting point, or maybe some common mistake I might be making.


texts: I am building an embedded gaming system to... well to play games. I looked up to the gameboy advance cpu manual and saw that it had some sort of gpu. Where can I find a gpu to use with an arm cpu? I need it on a chip, I don't want to stick a whole gpu inside my device. What is the term for those?


texts: Current consumption of PWM controlled MOSFET

texts:
I'm trying to design an application in which a DC/DC converter with limited output current capabilities drives the gate of one or more transistors in PWM mode. My question is, how can I estimate the average current consumption of the switching process itself (not that of the controlled current) if I know the switching frequency, the gate on voltage as well as all the common parameters given in a transistor datasheet?

Can I calculate this current via Switching Energy * frequency / Von?

And can I design the DC/DC converter with this current in mind or do I have to consider other factors as well, e.g. that the switching current isn't steady but instead consists of lots of peaks which have higher amplitudes than the average current value? Do typcial DC/DC converters like buck / boost provide those spike currents even if they exceed their max currents as long as they are short enough?

Concrete case which inspired my question was the control of a BLDC motor with 3 half bridges. There I needed a DC/DC for the gate voltage and my question was what max current should I choose for that DC/DC? Does switching current event matter at all? Do the high amp spikes of MOSFET switching matter or only their average due to the huge output capacitors in DC/DC converters?

Know that there are a lot of questions, don't mind to search intensively / open another question about that DC/DC converter spike current behaviour part if you think it's wiser. Couldn't find a question about switching current consumption though.

Hope to get help!


texts:
I’m fairly well versed in component labels like C1, R12, U72, etc but while taking apart a small external hard drive I found a component which looks to be made of ceramic labelled SK1.

Now, crystals should be marked as Yx (where x is a number) and both ends seem to terminate at a chip, but is this a standard part label? Other oscillators on the board are labelled as you’d expect.


texts: Can someone explain me that when we sample that sinusoid with a frequency below the Nyquist frequency (below half the sampling frequency), why we end up taking two samples per cycle of the sinusoid?


texts: Construct a post-equalizing circuit to compensate imperfect of the DAC

texts:
The post equalizing circuit is shown on above. How do I determine the value of the capacitance? I couldn't find any equation to determine it.

It have been advised to use LT6202 to construct it, data sheet here.

The data sheet didn't show any post equalizing circuit, so how do I determine the connection of resistor and capacitance to the IC?

The frequency response of DAC.

Pinout for LT6202:


texts:
Here is the link to the sensor I am talking about.
Now the problem is that according to the label it has as shown, it says that Brown wire goes to V+, Blue wire to V- and the Black wire goes to Signal. THe output depends n the input and the signal will be in operating voltages of 6 to 36 Volts DC. I am working on these sensors for the past 5 days. No datasheet, No information online, (Company name is Omdhon, not omron) and I can't seem to get a change in its output if I get a magnet either normal or rare earth strong magnets into its proximity (8mm).
If anybody knows what should I do to make it work, it would be a great contribution and will save me.
1. Whether Pull up is requires or not.
2. What should be the configuration to make it work. Seriously I am going mad.


texts:
In: 21-32V

Out: 12V, 3A

Working Frequency: 300 KHz

Controller IC: FP5138 from Feeling Technology

MOSFET: IXTP44N100T from IXYS

Schottky Diode: MBR20100CT from ON Semi

The MOSFET and the diode are going to be isolated from the heatsink. Should I connect the heatsink to the ground via two screws that are shown below?

Should I connect four mounting screws in the corners of the PCB to ground?

I tried to minimize the length of the critical traces but the heatsink didn't allow me too much. In addition to that, I kept the area of these critical traces that can act as an antenna to a minimum -only as big as to carry the currents. Also, I tried to keep output capacitors away from the heatsink as they are electrolytic and they should be away from the heatsink.

It would be great if you can draw the main current loops!


texts: How can this circuit read a value for amps at 0 volts

texts:
I made a simple circuit using this:

It can tell you the voltage and current along a wire if you mouse over it. The wire down the bottom reads 4.55mA and 0V (the little yellow dots actually move to show current, and the green colouring is voltage).

I don't get how that can be. If there is no voltage how can anything possibly be moving? And if nothing can move, that implies no current. Where does 4.55mA come from? If I remove the 1k resistor, it goes up to 50mA and still 0V. It doesn't make sense to me.


texts: How to achieve Better power consumption (operation of automatic chicken coop door)

texts:
Newbie to electronics and am looking for help with a project I'm working on.
I have a 12 v light detecting relay module which I'm using to drive a 12v motor in h bridge relay figuration, taking the + signal from the n.c or n.o contacts of the light sensor relay to drive the motor in one direction or the other until reaching a switch cutting the power to the motor driver.here are my issues.

Power consumption.. As the relay of the light sensor is activated the whole time during daylight hours the battery(12v 2.3ah)is not lasting very long.
The light sensor keeps flicking from on and off at the switching point.is there a way of latching the relay(or by using other components)once the trigger point is reached then resetting once the light sensor deactivated

Can I some how use the signal which switches the light sensor transistor, to operate an ic or some other arrangement of components to achieve the function I require-being

To drive a 12v motor (using a 12v 2.3ah battery)forwards and backwards which open/closes a door with relation to if it's light or dark?

As i said i am very new to electronics so have no idea where to even start looking for the info to solve my problem so any help would be much  appreciated


texts: Where does energy go when not enough voltage is applied to charge a battery?

texts:
Currently I am working on creating a DC motor that when manually cranked, or spun, will charge a rechargeable battery. Through some research I found the only way to charge a rechargeable battery is by supplying more voltage than the battery currently has to the battery.

My question is, if I spun a DC motor to create a current that is 2.0V into a battery that is 1.2V what happens to the energy (spinning DC motor) when the voltage slows down to below 1.2V?


texts: KiCAD: Adding a label to schematic produces error in Pcbnew

texts:
I had a schematic, then I went to do layout work in Pcbnew.
I layed out the parts and then proceeded to draw the easy traces, the low hanging fruit.
This is the PCB at this point:

I had created a GND layer in the bottom side copper.
However, since I had 3 ICs that all used 5V power, I decided to duplicate the bottom layer to the front side copper and have it at 5V, instead of GND.
To give them the proper value, I wanted to have a label, so it is easy to find it.
I went ahead in the schematic editor and added the label Vdd.

Then I pressed "Update PCB from schematic."

Unfortunately, I now get two errors about two of the button's pads.
I don't understand why I get those errors because I did not mess around with the button at all.

How come there was no error the first time, and now I have an error about the button, while I changed nothing on the button?
I cannot debug this at all and unfortunately, I cannot procceed with my design.
EDIT:
Here is my schematic picture of the switch I used (4 pins.):


texts: How easily can a microcontroller be damaged by mishandling?

texts:
I bought my first microcontroller and a few shields for it, and they arrived yesterday. I was so excited about tinkering with them that I completely forgot about all safety precautions and think that I might have broken them.

The microcontroller is the Wemos D1 Mini and the shields are:

OLED display
SHT30 temp/humidity sensor
TFT display

I downloaded the Arduino IDE and installed the related libraries for ESP-8266 support and the shield specific libraries, and then compiled and uploaded sample code for operating the OLED and the SHT30, but nothing seemed to happen.

Serial out was just printing "Error" from the sample code, indicating that the sensor didn't respond on I2C, and the OLED display was just black. I then tried moving the shields a bit and disconnecting and reconnecting them while still powered. I'm quite sure that I connected the shields the correct way, but I can't be completely sure.

I then tested only the OLED shield, only the SHT30 shield and only the TFT shield, but I couldn't manage to get any of them to work. I managed to get about 10 readings from the SHT30, but after that it started erroring again. The TFT screen also displays white only when trying its example code.

So here are the main questions:

If I accidentally placed some shield upside down or rotated it, so that the pins were incorrectly, could this have killed the pins for example from the 5V pin touching something it shouldn't?
Could I have shorted some pins with my fingers by touching them while powered?
Could I have damaged the shields/microcontroller by disconnecting/reconnecting them while powered?
Is it possible that the components have been damaged from the start before I touched them?

I will probably have to buy new components and be more careful this time.


texts: Number between square brackets on FPGA schematic

texts:
I'm studying the schematics of an FPGA dev board. I have noticed that many pins have a number between square brackets. I attach a screenshot of a part of the schematics, with these number circled in green. Furthermore, on the right of the green circle, there is one pin with [2,5] before the name.

I would like to ask if you know what do they mean.


texts: X Ray Transformer with Full Wave Rectifier Design

texts:
I current am in possession of a center tapped X-ray transformer that can supply 80 kV and 10 mA. However, I need this transformer to supply approximately 0 to -37 kV DC at around 8 mA. In order to achieve this, I am planning to use a full wave rectifier, specifically, the one that I have designed below.

Sadly, I only know what the output of the transformer is as well as the input voltage (120 V AC) and input frequency (50-60 Hz) is. Beyond that, I am only certain of a center tap being present.

All 12 diodes below are rated to have 30 kV and 100 mA go across them. The current rating is so high because I am expecting a ~100 mA surge to be present for about 2 seconds max. Since the diodes are also rated at that exact current, should I be looking to find diodes rated for a higher current, or is this acceptable? Also, is the 30 kV rating for the diodes acceptable as well?

By the ammeter (which is a Southwire 10030S Multimeter rated for 6,000 volts at 200 mA), there is a set of 5 resistors linked in series, each having a resistance of 20 ohms, a power rating of 1 watt, and a voltage rating of 20 kV. These will serve as the meter shunt and shall go directly between the probes of the meter. All of this is attached to the center tap line. Will this provide proper protection for the multimeter/ammeter, which would otherwise be rated for 6,000 V?

As a side question, would the type of resistor matter for this set up? I was considering either using carbon composite or metal film resistors due to their lower cost.

After the ammeter, I have a Fluke 80k-40 meter connected to an Innova 3300 multimeter. This will allow me to safely detect the voltage going through the circuit.

The 60 k Ohm resistor serves as a ballast resistor to dissipate energy in the case of a significant current draw by the source. It (also with the rest of the system) will be submersed in mineral oil and transformer oil.

Thank you.

simulate this circuit – Schematic created using CircuitLab

EDIT:


texts: Where is the location of display buffer on a computer board?

texts:
On an OS development text by Nick Blundel, at chapter 4.1 titled Adapting to Life Without BIOS, it is explained that while graphics
hardware is in text-mode, we can write ASCII characters on screen by writing them directly to display buffer starting at address 0xb8000.

Therefore I can do something like this with NASM assembler:

VIDEO_MEMORY equ 0x000b8000

mov edx, VIDEO_MEMORY

mov [edx], ax    ; "al" register already contains character itself
                 ; "ah" register already contains character attributes

My assembly code works fine, but I have a question about the location of display buffer: where is it? Does display buffer reside inside computer main RAM or does it reside inside graphics card memory?

Maybe the following image clarifies my question:


texts: While reading a datasheet for an IC I came across the pin voltages being presented as 3V3 or 1V8. What does this representation stand for?


texts: Understanding Power Good Signal in TPS54719

texts:
I'm using TI TPS54719 DC-DC and I'm trying to understand the PWRGD signal functionality.
Definition of PWRGD pin in datasheet: An open drain output, asserts low if output voltage is low due to thermal shutdown, overcurrent, over/undervoltage or EN shut down.
This is an illustration from datasheet that demonstrates sequencing of two TPS54719 devices:

Also, according to the datasheet:
The PWRGD pin output is an open drain MOSFET. The output is pulled low when the VSENSE voltage enters the fault condition by falling below 91% or rising above 110% of the nominal internal reference voltage. There is a 2% hysteresis on the threshold voltage, so when the VSENSE voltage rises to the good condition above 93% or falls below 108% of the internal voltage reference the PWRGD output MOSFET is turned off. It is recommended to use a pull-up resistor between the values of 1kΩ and 100kΩ to a voltage source that is 6 V or less. The PWRGD is in a valid state once the VIN input voltage is greater than 0.8 V, typically.
I didn't understand why we need the Pull-Up resistor for the PWRGD signal, and why for example in the picture above they didn't use this Pull-Up resistor.
when I tried to do a simulation in https://webench.ti.com/power-designer, the PWRGD signal was automatically connected to VIN through 86K Pull-Up resistor. how in this case I should use this signal for sequencing?
what I expect from PWRGD is to go from LOW (0V) to HIGH (some value above EN threshold) when VOUT is above 91% of it's final value.
so first, I'm confused with the fact that PWRGD signal changes according to VSENSE and not VOUT. and second, according to the explanation above, I understand that if we want to sequence two devices (like in the image below) the signal between PWRGD1 and EN2 should be connected to VDD through a pull up resistor.
why it's not connected?
here is an image of the internal circuitry:


texts:
I decided to rip apart a cheap super Nintendo and wire it to a small screen. I am using it to learn more about electronics, practice soldering, using an oscilloscope etc.

One of the challenges I have is how it would be battery powered. I have wired the screen and Nintendo into a breadboard and plugged in my bench supply. Nothing will turn on below 7v and with a game playing, I see about .565A. Both devices came with 12v power supplies. In order to run the two devices off of battery, what is the most effective way of going about it? When I look for videos and tutorials on this stuff I find a lot of RC hobbyist stuff.

Can I get a 3.7v LiPo battery and boost that, is that unwise? Or do I get a pair of 3.7v LiPo batteries and put them in series and boost that?


texts: Converting a DeWalt charger from 110V to 220V, rational of component selection from the guide

texts:
I'm going to convert my DeWalt charger from 110V to 240V as I got sick of lugging a step converter around.
I have found two guides which use the exact model of charger I have but they have partly different solution. I would like to know more of what could be the reason that they did what they did.
It is clear that the transformer that powers the charging circuit can handle 240V. Both of the guides replaced the 200V 220uF which I totally understand - that capacitor would pop under 240 VAC and should be replaced with a value above the peak 400V + should be fine.
Now the similarities end, the first guide changed the capacitor and added 2  0.33Ohm  5W resistors.

The second guide did not speak in english so I did not understand what he was saying but basically I think he add a varistor on the main input and instead of using a resistor I'm not sure what that black thing is (ceramic capacitor?) but why would he add a capacitor? If you closely look on either of the videos you might notice that that slot is labeled "R" so I assume a resistor is supposed to be placed there (instead of a jumper.)

Can someone help explain to me what could they possibly be doing? Sadly I don't currently have my charger so I can't take more detailed pictures of the circuit. But maybe someone may have an idea based on past experience.


texts:
I needed an LM565 to simulate, but unfortunately, the software did not have that LM565, and I accidentally saw this code on the Internet!
But I do not know how to give this code to the software! The code is available in the following file
PDF: PHASE LOCKED LOOP BEHAVIORAL MODELING

I spent a whole day understanding this PDF file and the code inside it and I was confused.
Because I do not know how to use this code! But in order for you to better understand my question, I ask in a different way so that your time and mine are not wasted.
I use this software:

When I put the LM565 chip on the schematic from the library, I realized that it could not be simulated with this chip, or in other words, it did not have a file PSpice! Well, I searched the internet for this piece, but I did not find it, but I managed to find a PDF that has a code in it, and I have no familiarity with this code! And I do not know how to use it. How do I copy the code inside this PDF file? I mean, in some places this code went to the next line and I was confused, I do not know how to copy this code! That I do not have a problem in simulation! Because I am not familiar with the format of this code and I always use the graphical interface to simulate the circuit.

when I copied the code I said to myself, is this + now for addition, or does it have another use ?!
Because I saw this example in a document. And well, I'm not familiar with this code either, I just want my circuit to work, that's it!

I came across this text in an educational document and realized that this program is a subcircuit netlist. But I still do not know how to use this code snippet ?!

Now I had to go and design this IC (lm565) in the software, I guessed to myself that maybe this code was given to the schematic of that chip! But I came across this page and got stuck here!

So what is the best way or the fastest way that I can use this code and be able to deliver this circuit to our college teacher! I just want this circuit to answer! I will do whatever you say so that this circuit will respond.


texts:
For timing analysers, FPGA operating conditions are sometimes know as "PVT", which stands for "Process, Voltage and Temperature".

While voltage and temperature are self explanatory, what does process mean in the context of FPGA operating conditions?


texts: Can I use a PET capacitor in a power supply? What's the difference?

texts:
I've noticed that certain types of capacitors seem to be used more commonly in certain applications. I've got a few over-sized 1uf PET caps that are a little too large for the application I originally got them for, and I should have enough spares to build this power supply design:

simulate this circuit – Schematic created using CircuitLab

On the other hand, I've never seen anyone use anything but electrolytic caps in power supplies (and in general nothing but PET and other plastic capacitors for audio use, other than a handful of tantalum capacitors). Would it be OK? I'm feeding it off a switch mode power supply, and I'd like to get as clean an output as possible.


texts: Help understanding open collector comparator

texts: I am working on a simple circuit based on the LM311 comparator. It has an open collector, which is not something that I've used before, and I have a few questions. First, my understanding of the open collector model is that the internal comparator switches between open and connected to ground, requiring a source at the output to create a current. If that is the case, what is the purpose of the VCC rail voltages? Finally, I've tried modeling the circuit in multisim but I keep getting 5v at the output regardless of what the + and - inputs are. I assume that is due to my pull-up resistor, but I think I am just misunderstanding somewhat how this comparator is meant to be setup. My circuit is below, I've tried tying pin 4 (VCC-) to ground, and pin 8 (VCC+) to my 5v VCC, but I get the same result regardless.


texts: Installation of an AC Drive on a Plastic Extruder

texts:
We operate a Plastic Extruder for reprocessing plastic waste.

The Extruder is powered by a 40hp 1,440rpm AC Motor.
Motor Pulley: 8"
Machine Pulley: 16"
Gearbox's Gear Ratio: 14:1

Currently, the motor is started by a "Star Delta" Starter and provides a screw rpm of 51.42.

Currently, when we start the motor, the motor consumes approximately 60-70amps in the "Star" phase.
Upon entering the "Delta" phase, the motor's current consumption varies between 17 to 25 amps.

Considering that the motor is barely taking enough load and that our extruder fails to meet its target throughput, we are contemplating the introduction of an AC Drive to enable us to increase the screw rpm.

We intend to alter the pulley ratio, such that at 70% speed, the screw runs at 51.42rpm. Thereby giving us the ability to increase the screw rpm gradually, taking it up to 90-100% speed, depending upon the type of material being processed.

Although I believe that I have an elementary understanding, several attributes such as "Low Overload" and "High Overload" on commercially available AC drives confuse me. Furthermore, I'm on a very tight budget which limits my options tremendously.

The most cost effective AC drive that I could find in my local market is the Siemens V20. The drive's rating can be found in the table below:

Considering that our motor is not taking enough load, would the above Siemens AC Drive that is not high overload at 40hp (see above table) work for it?

Secondly, what happens happens if the overload exceeds the cycle time stated. Example, I find AC Drive stating an overload capacity of 110%/150% of output current for 300s. What happens if the overload lasts for more than 300s?

Please note that Siemens V20 supports V/f, V2/f, FCC and V/f multipoint control methods.

Other data that may be useful:
V: 440V
F: 50Hz

Motor Data:
Max FLA: 51amps

Thank you for your time and assistance.


texts:
I am looking into AVR chips (big fan) for a personal project. I need capabilities similar to Arduino Uno, so I recently compared Atmega 328p and Atmega 324p.

To my surprise the 324p has significantly more features and on-board hardware than the 328p. To me, higher model number == more powerful/more features product, so discovering this slightly confusing me.

Could anyone explain to me why Atmel chose such weird convention for naming their chips? I know this is not a big deal, but for the future reference I would like to know how to choose AVR MCU's for my needs properly (their buyers guide is not very helpful).

edit: the 328p consumes twice less amount of power, so is it all down to smaller, less power hungry product?


texts: Limiting the current into Raspberry Pi GPIO pin

texts: I have a dc dc regulator which can output .35A Current at 3.3V. I just need to check that the voltage it is producing is 3.3V by connecting it's output into one of the GPIO pins of Pi. So i was wondering what is the easiest way to do it, will a series resistor do the job. And what would be the value of it.


texts: Overdischarged 18650s and a TP4056 module

texts:
I disassembled an old laptop battery and found 6 Sanyo K29B 18650s.
All of them have a voltage of <= 2.5V.
When I tried to charge them with a TP4056 module, while measuring the current, the module provided 500-700 mA and got the battery to 3V in under 15 seconds.
Are these batteries still good to use?


texts: Driving Servo Motor with Raspberry PI 4 and ServoBlaster

texts:
I'm trying to drive this DS3225 servo motor with a Raspberry Pi 4 using the ServoBlaster software.
After installing ServoBlaster, I run the following commands:
sudo ./servod
echo 3=30% > /dev/servoblaster

I also tried to drive it with a python script using RPi.GPIO but nothing works. I hear a subtle clicking in the motor but it doesn't move at all.
I tried with other servos, and they work fine. Also, this servo works on other MCUs so it's not defective.
I tried to play with the frequency and the duty cycle duration but haven't managed to make it work.
Any suggestion?


texts: Is there a motor design where a rotor gradually moves into a stater?

texts: I was wondering if there is a motor/generator design where the rotor moves gradually in and out of the stator along the axis of rotation, or the stator over the rotor, but the primary motion is rotary, and this rotary motion is moved into, or out of a stator slowly to a fixed position so that more or less electricity is generated by the rotation. If so, I'd like some resource(s) to read more about it. The application I have in mind is for a wildly variable load like a wind turbine. If this is a bad design, pleas briefly explain why. Thanks in advance.


texts: Minimum time of stable input address on read cycle of a flash chip

texts:
While reading the specifications for the SST39SF010A flash memory chip (here), and looking at diagram 5 and the general specifications, there is no minimum stable address input time.

Looking again at diagram 5, we can see that the output data can be ready before the end of the cycle. But then, if a noisy non stabilized input address comes in, must I fear of triggering a read cycle ?

Again, given the diagram it doesn't seem, but the specifications don't list that, and so I am afraid of triggering a write cycle before the input address is fully stabilized, and "wasting" 55/70 ns before creating a new. Is there a general guideline or implicit rule I'm not informed about in this case ?

I am looking forward to your answers, any help or tip is greatly appreciated


texts: Random Access Memory Modelling in Verilog

texts:
Is there a better/alternative way of modelling RAM Memory in Verilog other than declaring it as an array of registers? Most of the sources I referred to have memories coded in the following manner.

output reg [WIDTH-1:0] word_out;
input [WIDTH-1:0] word_in, cpu_addr;
input reset, we, clk;
reg [WIDTH-1:0] chip [0:DEPTH-1];

always @ (posedge clk)
begin
  if (!reset)
    begin
      if (we)
        begin
          chip[word_addr] <= word_in;
          word_out <= word_in;
        end

      else
        word_out <= chip[word_addr];
      end
    end

Is there an alternative to this, probably using flipflops or something?


texts:
im new to memory cells.
I have taken the below image from a video, i wanted to ask in the video he explains that the MUX can select 8 bits, but how is this even possible?
The output of a MUX is always 1 value isnt it?
Does he mean a series of MUX's to select 8 bits from 16bits?
He's using 1 bit to select 8bits through a MUX


texts:
I am designing a big digital circuit in Proteus and I need to create my own components because I am going to reuse them lots of times for example 32 bit adders, big buffers, etc). I read this but he got no answer so I created a sub-circuit instead:

The problem is that when I create multiple sub-circuits bus names enter in conflict because they have the same name, and I want to duplicate them so I will need to create a sub-circuit changing the bus name (with the labels inside each sub-circuit) for every new sub-circuit I add.

How can I solve this problem? Is any workaround for this? Aren't big designs possible in Proteus?


texts:
I am reading an application note entitled Using MOSFETs in Load Switch Applications

This part says that Q1 is a small signal NMOS transistor. Could you explain what does it mean by "small signal transistor" here?
I am familiar with small signal but it is strange to talk about it in switching application.


texts: Series RLC measurement result different with theory

texts:
I am measuring the current and voltage in simple RLC circuit:

However,the result that I measured show big difference with the simulation result using Multisim.

Why is there are a big difference between 5k-7k measurement value?

For your information I set the function generator output load to high-z. Is it due to this setting?


texts: Sometimes i think why the heck this ohms law created to make troubles for us, as nowadays i am deeply working on Basic Electronics so there Ohms law actually sucks... I was studying transistor configurations, where in (CB) amplifier where he have no current gain but there voltage gain is whooping ?? How is that possible inverse relation between current and voltage, similarly in (CC) Amplifier where the current gain is touching the skies while voltage gets attenuates.. I mean where does this Ohms Law fall there again now i am studying DC bias of BJT where in Emitter bias a emitter current increases then voltage across base decreases i am confused...


texts: Norton's equivalent circuit with independent sources

texts:
I need to find the current flowing through \$R_{5}\$ by using Norton's theorem.

What I tried to do was:

Open-circuit the part of the circuit where there is \$R_{5}\$.
Calculate \$R_{n}\$ by open-circuiting the independent current sources (that is, \$I_{1}\$) and short-circuiting the voltage sources (\$V_{1}\$).
Calculate \$I_{n}\$ by short-circuiting the part where there is \$R_{5}\$.

So,

 2.

$$R_{n}=R_{4}+\frac{R_{2}R_{3}}{R_{2}+R_{3}}=7.5ohms$$

3.

I used KCL to find \$V_{C}\$:

$$\frac{V_{1}-V_{C}}{R_{3}}+\frac{0-V_{C}}{R_{2}}+\frac{0-V_{C}}{R_{1}}-I_{1}=0$$

$$V_{C}=4.18V$$

Then,

$$I_{n}=\frac{V_{C}}{R_{4}}=\frac{4.18}{6}=0.696A$$

Apparently, \$I_{n}\$ is wrong, but I can't find any mistake in my reasoning. Any idea?


texts: How to identify/measure a power transformer using signal generator and scope

texts:
I have a power transformer that I pulled out of a UPS a couple of years ago and I'd like to re use it in a linear power supply.

It has 2 wires on one side and 3 on the other. Currently, I don't know which side is primary and which one is secondary but I suspect, maybe wrongly, that the side with 2 wires is primary. The side with the two wires has screw terminals (a ring to put a screw through) and the other side has plug terminals that if I remember well used to plug to the board.

Now, since I'm not sure about a lot of things about this transformer, I don't want to just wire it up and measure it while connected in the mains, especially since I'm not very experienced with mains voltages. (I do work servicing 3-phase dimmers but it's different when you have the safety measures we have at work).

My thought was to connect it to a signal generator and scope (I have a USB combo) and see if the other side is of higher or lower voltage in order to identify the primary and secondary sides. Since this was part of the power supply of a UPS, in theory the primary should take in 230V and the secondary should give out a voltage that when rectified would be sufficient to charge 12V batteries + maybe a second secondary for +5V logic(?). So I estimate that I expect a 20something:1 drop in voltage on one secondary and a 50ish:1 on the other.

To formalize this question a bit:

How do I safely measure a power transformer using a signal generator and scope without damaging my equipment?

Is a 1V (peak to peak), 50Hz sine wave signal sufficient/suitable for the measurement?

I suspect I need to measure the secondaries across a load. Will a resistor around 1MΩ (1/4W) be sufficient (or necessary)?

Finally, please let me know if I'm moving in totally the wrong direction.


texts: About a 50 ohm stripline: freq range 0 to 18 GHz

texts:
I have a shielded box stripline as shown below:

|-------------------------|
|         ___W___         |
|        |_______|t       |
|                         |
|-------------------------|

box dimension: 4.3cm x 1 cm x 6 cm. Y x Z x X

Now, the coax(the 50 ohm SMA) is touching the end of the stripline. the dimension of the stripline is width: 1.44cm, thickness: 0.048 and length is 6 cm.

We did 20* cut both side so that 50 ohm is uniformly on each side.

However, we didn't find any good result as expected. From theory we find the stripline should behave as 50 ohm line but it is not as shown below:

the result:

S11 maximum is -5 dB where we are expected it should be below -30 dB. It is not.

Now, anyone if encountered or made any 50 ohm stripline and also tested in VNA, please help me. What is the problem with the structure? The experiment and the simulation is same, S11 is maximum is -5 dB which means impedance mismatch. Please help. I can upload the S11 if necessary. BTW, the frequency range is 0 to 18 GHz.

thanks in advance.

material: copper as strpline and AL shielded box.


texts: How does a "speed up capacitor" work in Schmitt trigger?

texts:
Hello I'm trying to understand how adding a capacitor across R2 in below circuit increases the switching speed. I don't see how C2 supplies charge to C1.

With the additional capacitor C2, it seems the output voltage has to charge one additional capacitor. Hmm.. Or, does the speed increase because capacitors in series reduce the capacitance ? I'm very much clueless and my textbook doesn't explain it well.. Appreciate any help. Thanks!


texts: Are IOT wireless network protocol right for high throughput point to point communication?

texts:
I am trying to build a "professional" 2 way point to point radio system (like this) to control a RC 1/10 scale car (like this ) using UART, the challenge I am currently facing is finding the right radio modules for the application.

Requirements :

Frequency 100-950Mhz.
Power 27dbm (0.5w) to 30dbm (1w).
Modulation is FSK or OFDM or QAM or PSK or **SK etc. (encryption
is nice option not a must)
Multiple units up to 10 point to point units can be operated at
the place with interferance ( i think this is called number of
channels )
High throughput 10 to 100 packets per second ( packet about 6
bytes)
Two way communication (High speed switching between send and
receive)

I have been investigating several IOT wireless Modules ( LoraWan , SigFox , M-Bus ) and can't find one that works for my application, since most of them don't allow high throughput and are designed to transmit at approximately 1 packet/second which is enough for remote sensing applications. BLE and WIFI lack in power, range and frequency.

The only option I have found so far is Xbee ( maybe i am still reading about ) and TinyMesh

So my questions are :

Is my observation regarding IOT wireless protocols correct?
Can some one guide me to the right protocol for low latency communication I require?

PS: Hopefully this will not be marked as shopping question, I want to understand the protocol or type of network that fits an application :)

EDIT:
After Tony's comment about missing specs: cost should be <100$ per Transceiver. Weight and battery power is not an issue as long as it is doesn't consume more than 5W DC (ex: 5v 1A). error correction & detection is a bonus not a requirement. Range is left intentionally Since i mentioned the RF power and frequency.


texts:
I'm trying to get my PIC24FJ64GA002 running at 32 Mhz. I measure the frequency on OSCO pin, and it's only 4 Mhz. Here's my code:

config  __FOSCSEL, FNOSC_FRCPLL & IESO_OFF
config  __FOSC, FCKSM_CSECMD & OSCIOFNC_ON

                mov        #0x1182,        W0                    ; OSCCON
                mov        #0x0000,        W1                    ; CLKDIV
                mov        #0x0000,        W3                    ;OSCTUN

                mov        W0,                OSCCON
                mov        W3,                OSCTUN
                mov        W1,                CLKDIV


texts:
So I have two PWM outputs configured in my PIC32, with PWM2 duty cycle 100-PWM1 Duty Cycle, where the objective was that when PWM1=0 PWM2 would fill the rest of the cycle so an 180º phase shift I guess.
How do i implement this to work correctly?The problem is that  PWM2 generates the HLevel at 0Seconds and not when PWM1 is going L.
How do i implement this shift when I can't "read" the output ports and delays aren't viable for a variable pwm implementation.


texts: Design ALU with 2 Select lines, 2 Inputs ( n bits )

texts:
I want to design ALU with 2 select lines , 2 inputs ( n bits ) that do the following:

this is a homework and I want to know what to do, writ to me the steps for design it.
the first thing I thought to do is to build a table with S0,S1,C, then I have 8 rows, and the output will be F. its ok? now what should I do?
thanks!
EDIT

S0 S1 C  |  operation
0  0  0  |  S = A+B
0  0  1  |  S = A+B+1
0  1  0  |  S = A transfer?
0  1  1  |  S = A+1(inc)
1  0  0  |  S = B`
1  0  1  |  S = B`+1
1  1  0  |  s = A+B`(negate)
1  1  1  |  S = A+B`+1


texts:
I’m working on a problem where I have to build a speed detector using a hardware circuit with a microcontroller. I will be using a radar motion detector module to do this. I have contacted the manufacturer B+B sensors for information regarding the application circuits with no reply as yet (https://shop.bb-sensors.com/out/media/Datasheet_RADAR-IPM-165_DBE_Rev01.pdf)

I’m looking for some advice to determine which filter to implement to ‘clean’ the received frequency. Does anyone have any ideas on how I could go about this? The received frequency will be in the GHz range I imagine due to the operating frequency being 24GHz.


texts: Thevenin Equivalent Circuit with Sinusoidal Current Source (Vth)

texts:
In a practice test we are asked to find the Thevenin equivalent by finding the Thevenin voltage and Norton current within the following circuit.

We were given the following answer for Vth:

I feel like I'm making a simple mistake but I'm coming up with
Vth=  which is equal to  as I see he wrote down. So why does it wind up as 7+7j?


texts:
I am building a circuit that allows me to control a set of light (more specifically Christmas lights you see in supermarkets) with relays (AQH 2223). My idea is to have the controller input on one side and the light on the opposite side. An example would be something like this.

My problem is that I don't know the exact trace dimension I need to the light circuits such that I don't melt the board over a long period of use (around 30 minutes). What are some typical trace dimension values for household appliances? Also, are there libraries for AC outlets? I am planning on using something like this.

I want to mount AC outlets on the PCB but so far I haven't find any libraries for eagle yet and I am quite sure that people have done this before. I am fairly new to Eagle so sorry if this kind of question has been asked before. Thanks!


texts: Can I use a capacitor which has 275v +-10% tolerance in a 9V circuit?

texts:
I am trying to get parts for a circuit i want to make and I'm very new at making circuits. As a result i'm unsure if i can use a 150nF capacitor with 275v+-10% tolerance in the following circuit or whether i need a different tolerance or anything. As far as I know the 9V in will be DC.

Any help would be greatly appreciated, thank you.


texts: Let me try and explain my project as best as I can. I am making a DIY battery bank that can be powered off of tool batteries. I can put two separate batteries in my system so that I can have a backup if one or the other runs out of juice. Currently, I just have the positive terminals hooked up to a 3 position switch so I can manually choose the battery, but I want to add more functionality by automatically switching outputs when one battery gets too low and also displaying a level of charge. Here's the problem. How do I appropriately choose the initial power supply? These batteries have the potential of being the same voltage and also having a battery in the "1 slot" only or "2 slot" only and maybe even both are installed. I've drawn out a couple of circuits that end up being either too complicated and can cause severe power loss or end up causing more problems. Any ideas on how this can be achieved?


texts:
i have a problem with this code, because in the RTL simulation, the output Cookie appears as StX. I don't know why this is happening since i don't know verilog well.

Can someone help me?

module dispenser(
CLOCK, SReset,
SBCD, Cookie, valor,
reciba
);

//Port declaration
input CLOCK;
input SReset;
input [3:0] valor;

output reg reciba;
output reg [3:0] SBCD;
output reg Cookie = 0;

always @(*)
        if( valor >= 4'b1000)
          begin
            Cookie = 1;
             SBCD = valor - 4'b1000;
             reciba = 1;
          end
        else
          begin
            Cookie = 0;
            SBCD = valor;
            reciba =0 ;
          end
endmodule

and this is my testbench

`timescale 1 ns/ 1 ns
module vendingMachine_tst();

   //Parameters

   parameter TCK = 20; // clock period in ns
    parameter CLK_FREQ = 1000000000 / TCK; // Frequenzy in HZ

   //general purpose register
    reg eachvec;

    //Internal wire and reg declaration
    reg [3:0] TB_Un_US;
    reg [3:0] TB_Dos_US;
    reg [3:0] TB_Cinco_US;
    reg TB_Clock;

    wire [3:0] TB_SBDC;
    wire TB_Cookie;

    vendingMachine vM1(

      .Un_US(TB_Un_US),
      .Dos_US(TB_Dos_US),
      .Cinco_US(TB_Cinco_US),
      .SBCD(TB_SBDC),
      .Cookie(TB_Cookie),
      .CLOCK(TB_Clock)

    );

initial
begin
// code that executes only once
// insert code here --> begin
   TB_Clock <= 0;
// --> end
$display("Running testbench");
end
always
// optional sensitivity list
// @(event1 or event2 or .... eventn)
   #(TCK/2) TB_Clock <= ~ TB_Clock;
initial begin
// code executes for every event on sensitivity list

//Caso 1: El cliente entrega justo el precio de la galleta
    #0     TB_Un_US <= 4'b0001;
   #6000  TB_Dos_US <= 4'b0010;
   #60000 TB_Cinco_US <= 4'b0101;

//El cliente supera el precio de la galleta
 // #0   TB_Un_US <= 4'b0001;
//  #60   TB_Un_US <= 4'b0001;
//  #600  TB_Cinco_US <= 4'b0101;
//  #6000 TB_Dos_US <= 4'b0010;
//
//
////El cliente no completa el precio de la galleta
//
//   #0   TB_Dos_US <= 4'b0010;
//  #6000  TB_Un_US <= 4'b0001;
//  #600000 TB_Un_US <= 4'b0001;

 #(TCK*300000) $finish ;
#(TCK*300000) $finish ;
@eachvec;
// --> end
end
endmodule


texts:
I have a small problem figuring out how to properly solve that. I could use help.

Say a system with a transfer function \$ H(s) = \frac{100}{0.4s + 1} \$ is excited with an excitation \$u(t) = 8V\$ since very long (steady state). At time \$t_1\$, \$u(t)\$ is abruptly set to 0V. What is the value of y(t) at time \$t_1\$ + 0.1?

I calculate steady state value (before time \$t_1\$) using laplace final value theorem:
$$
U_0(s) = 8V \\
Y_0(s) = H(s) \cdot U_0(s) = \frac{800}{s(0.4s + 1)} \\
y_0 = \lim_{s \to 0} sY_0(s) = 800
$$

I have a first order linear system, so the form is (including initial conditions):
$$
Y(s) =  H(s)U(s) + C(s) = \frac{K}{\tau s + 1}U(s) + \frac{\tau y_0}{\tau s + 1}
$$

Since at time \$ t_1 \$, u(t) goes from 8V to 0V abruptly, I conclude the excitation at this instant is a negative step of 8V, i.e. \$U_1(s) = -\frac{8}{s} \$. So I guess I have to calculate the response at time 0.1 of a negative step of -8V with initial condition \$y_0 = 800V\$ to obtain the correct answer.

So the general response \$Y_1(s)\$ at \$t = t_1\$ will be:
$$
Y_1(s) = H(s)U_1(s) + C(s) = \frac{-800}{s(0.4s + 1)} + \frac{320}{0.4s + 1}
$$

Doing the inverse Laplace of this expression I get:
$$
y_1(t) = 1600 e^{- 2.5t} - 800
$$

Knowing this, finding y(t) at \$ t = t_1 + 0.1 \$ would correspond to \$ y_1(0.1) \$, which gives 446.08.

Well the answer should be 623.04. Could someone explain me what I'm doing wrong?
I feel I did everything correctly.


texts:
In my neighbourhood, a 220 kiloVolt high voltage line is being renovated. It seems that they are replacing the cables, and they also may do some other maintenance. This, however, gave rise to some (possibly) noob questions.

What sort of maintenance is required for high voltage lines?
Which parts need replacement?
What are the life-time determining factors for high voltage transmission lines?


texts: What factors should I consider when choosing a high amperage power supply?

texts:
I've searched around, but I haven't found an answer to this particular question yet.

I'm building an elecromechanical project which requires somewhere around 60 Amps at 12 Volts. While this may not really be high amperage, it's more than the <10A supplies I've worked with before. I've been trying to understand how to pick the right power supply for my needs, but I'm not sure I understand everything that factors into the decision.

I'm fairly certain I want a regulated switching power supply, but I'm not really sure what differentiates the many available on the market.

For example,  I see this 750 watt power supply from
jameco: https://www.jameco.com/z/SP-750-12-MEAN-WELL-AC-to-DC-Switching-Enclosed-Power-Supply-12-Volts-62-5-Amps-750-Watts_319944.html

What makes it so different (and more expensive) than this EVGA PC power supply: https://www.evga.com/products/product.aspx?pn=220-G2-0750-XR

They both give me 62 amps on the 12V rail, and in fact, the EVGA is more efficient. So what other discriminating factors should I be looking at?


texts: I've heard fuse fatigue mentioned as a possible cause for unexpected fuse failure. I've seen some documents claim fuse fatigue isn't an issue on certain modern fuses, but I'm not clear on exactly the details. In what circumstances, or with what fuses, is fuse fatigue a possibility?


texts: How to choose resistance and capacitance value in active bandpass filter?

texts:
I am trying to make a bandpass filter around 300Hz using this circuit. I have calculated the values of the components using the equations shown in this website assuming low frequency cutoff 160Hz and high frequency cutoff 480Hz.

With the equations you get values of RC. So I thought I could select the resistance and capacitance as I wish as long as RC gets the right value.

But when I choose R1=1k, R2=330, C1=C2=1u and simulate it with Proteus the frequency response is nothing like a bandpass filter.

But when I choose R2=3300 and C2=0.1u frequency response is fine.

Why does one work and the other does not?

PS: I am using a LM358 operational amplifier.


texts: What is the rule of the Vdc regulation in a shunt active filter

texts:
I understood very well the principals of harmonics identification in an shunt active filter ( PQ theory : Akagi & al for example), but what i don't understand is why do we care about regulating and maintaining the DC link capacitor voltage ?

In a paper they quoted :

  the active power flowing into the active filter needs to be
  controlled. If the active power flowing into the filter can be con-
  trolled equal to the losses inside the filter, the DC link voltage can
  be maintained at the desired value. The quality and perfor- mance of
  the SAF depend mainly on the method implemented to generate the
  compensating reference currents.

If someone can help me understand that, i will be thankful.


texts:
I was rather curious about why many buck converters and linear regulators were rated up to 42V, or close to it. It's a rather strange voltage to stop at, after all - why not 40V or 45V?

I read that it was due to an idea in the late 90's to early 2000's where every car was going to use a 36V lead acid battery (which would have a peak charging voltage of 42V.) A higher voltage means smaller wires. And cheaper high-end stereo systems as 36V can drive loudspeakers louder and they can have higher impedances. And smaller, cheaper motors. And a few other things.

However, the idea died down because a lot of car manufacturers already had a large inventory of 12V parts and accessories and didn't want to change them. Additional issues were found with making relays compatible with 42V due to arcing and contact wear.

Yet I still see parts being made with 42V ratings. Why? Just a throwback to the old days? Is there another industry that uses 42V?


texts:
I had never really thought of resistors causing a voltage drop, I have only used them to limit current to say an LED.

Using something such as E = IR I can use a single resistor as an example:

5v / 100ohm = 0.05A * 100Ohm = 5V

Now I can maybe assume that is 5 volt drop, leaving 0 after it. How does this allow an LED that requires, say, 1.8 volts that it drops if it leaves 0V at the other side of the resistor?

Using a simple circuit simulator..

5v ------- 220Ohm resistor resistor -----1.8v-----led-------0v

Why is 1.8V "left" that is required by the 1.8 drop led?

It is apparent that the resistor just "consumes" 5 - 1.8 volts magically.

I am confused by this, as you can calculate voltage dividers much more simply. Although, does a voltage divider "split" some of the voltage to ground? it is parallel however, so I am unsure why one branch (with resistor) affects the second branch (the output)


texts: HSPICE - Measuring a series of values in transient simulation

texts:
I'm doing a transient simulation in HSPICE with an input vector file of N values (N>100).

I would like to get at each rising edge of the clock (i.e. timing of the shape kT, T period, k integer)  a measure of a value of the current. My goal is then to process those values through a script.

Does anyone know how to do that please?
I can't use N times the .MEAS statements as N is really huge...


texts: Total thermal noise of a photodetector connected to a spectrum analyzer

texts:
I connected a photodetector to a spectrum analyzer (SA) and observed the signal (i.e. noise) on the SA when there is no light hitting the detector.

I noticed that when I set a low spectral resolution on the SA (e.g. 10 Hz), I can see the photodetector noise. That is, when I turn on the photodetector, the noise level shifts to a higher value.

However, when I set a higher spectral resolution (e.g. 1 MHz), I can no longer measure the photodetector noise. That is, when the photodetector is switched on or switched off, the noise level displayed on the SA is exactly the same.

This is contrary to what I expect. I expect that both the photodetector and SA have white thermal noise and if I can distinguish the photodetector noise in a 10 Hz bandwidth, I should also be able to distinguish it for a 1 MHz bandwidth. As the bandwidth increased by a factor 100'000, I expect that both photodetector and SA noises should increase by this factor and the photodetector noise should remain the dominant one.

So why isn't it the case ? Is there additional noise in the SA ?

I used a Keysight N9000B SA and a NewFocus 1607 photodetector.


texts: If an inductor is in series with each of the upper and lower MOSFETs of a half-bridge, will the switches experience zero current turn on?

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simulate this circuit – Schematic created using CircuitLab

I am imagining of a half-bridge converter feeding a normal resistive load.  In series with each of its switches is an inductor.  During the switch "on" instance, there should be zero/negligible current flowing through the switch.  Does this mean there will be relatively lossless turn on?

EDIT: Here is a schmatic of what I mean.  I forgot the anti-parallel diodes, but they're there.


texts: Can I apply fixed DC voltage to cluster of LiPO batteries to charge them?

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I know the "proper" way to arrange LiPo batteries (18650's) is to isolate them as single cells.  But for now I'm retro-fitting a cluster of 6 batteries (2 groups in series, each group having 3 cells wired in parallel) that give a combined 8.4 volts (I guess).  This is to replace a 6-cell NiMH (1.2 v per cell, all wired in series) battery pack for a cordless sweeper (shark I think).  The LiPo batteries came bonded as 3 groups of 3 wired in series from an old laptop battery.
I'm going to take a 9V 1-amp wall wart and maybe add a diode to drop the voltage to 8 and simply wire that directly to the LiPo pack.  There will be no charge indicator, and charging sessions would be limited to 1 or 2 hours when the pack runs low.  The only thing I think I need to worry about is overcharging (over-voltage) but if the output is limited to 8 volts I don't see that as a problem.  Anyone see a problem with this?


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I am looking at a small board in a paper shredder (it does not work). If I apply AC power and measure AC voltage across the X2 capacitor (I think it acts as a voltage dropper for the low voltage circuit), I read 240 V (line voltage). My conclusion is that the capacitor has failed open.

Is that the correct conclusion, or am I missing something?


texts: Ethernet trace layout and passive placement

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I'm designing a board (with KiCAD 5.1.0) besides other I need to properly route two ethernet ports and the whole board should be kept as small as possible (50x82mm). The guidelines of components (magnetics) give some hint about trace layout but the main component (where the two ports originate) is not very well documented... anyway I looked around and did my best.
The final result lead me to some question:

On this port I had to reverse the magnetics ports to avoid vias and complex traces to connect the main component with magnetic IC itself:

Please note that the ethernet connector is not an RJ45 since I have very big space constraints and RJ45 should not fit in the assembly.

In the first port I needed to reverse the polarity of the magnetic input for the same reasons as above:

The effect of these workarounds are negligible on the overall performance?
Take into account that both ethernet ports will be connected to a very near device (around 20cm of cable length or less) and that the overall troughput on such ports will never exceed 10Mbits.

Differential pairs have been setup to have 100ohm impedance (the board will have a standard 4 layer FR4 stackup).

To keep everything small and avoid complex traces I placed some of the passive components on the top layer and some other on the bottom side:

Of course I needed to place some vias on the forbidden zone below the magnetic IC... is it soooo wrong?

Magnetics IC = Wurth 749010310.

Any comment will be appreciated. Of course I can share the whole design if someome wish/need to investigate further.


texts: Dual AC Power Input on Audio Amplifier Board

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I'm confused as to what kind of transformer I should use to power this board. The manufacturer states the operating voltage as follows: AC12X2 to AC22X2.

Should I assume a phase shift of 180 degrees?


texts: I need a circuit that allows current to flow in both directions through a load, and I came up with this. Is it good or is there a better way?

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this is one of my first circuit "designs" (quotes on since it's simply switches). I need current to be able to flow in both directions through a certain load, and the direction of travel should be electronicaly commanded. This is what I thought of:

simulate this circuit – Schematic created using CircuitLab

Sorry if it's too messy. This way, making pins 1/2 high (but never both at the same time) makes current flow in each direction. Is this a good way or is there a simpler one?