texts: What is the difference in performance of a JFET current source to a 741 Op Amp current source?

texts:
It is possible to build a circuit that provides a steady current source via these two methods:

Screenshot of op amp circuit

Screenshot of self-biasing JFET current source

In the circuit using an op amp, the current stays the same because as the resistance is increased, the voltage also increases (likewise for decreases). Thus, a steady current is maintained.

In the circuit using a JFET current source, there is negative feedback that maintains a steady drain current. This is because if the drain current increases, then \$R_S\$ increases, which makes \$V_{GS}\$  incerase and moves the FET closer to pinch-off, which then decreeases \$I_D\$.

What are some of the differences in performance of these two circuits which are intended to ultimately do the same thing (maintain a steady current)?


texts:
I observed something different in LDR (Light Dependent Resistor) today. I made a "magic" LED circuit such that when lights are off, the LED glows, else when the lights are on, LDR creates resistance and the LED stops glowing.
Later when I connected just the LDR and LED (in series) to the battery, LED glowed very dim when there was light in the room, and stops glowing when no light reaches the LDR. Why does this happen?

I know just the basics of electronics. I request you to provide an answer I can understand.


texts: What is an RC time constant and why do I have to wait for the capacitor to carge up before taking samples with ADC?

texts:
I am using LTC6403 in my project. It is used for single-ended to differential conversion, which will be driving LTC2185 ADC.

In the application information of "Interfacing the LTC6403-1 to A/D Converters" on page 19 of the datasheet, it is mentioned to have a discrete RC filter between Differential outputs of the amplifier and ADC input signals.

In the second paragraph, it is mentioned that " 16-bit applications require a minimum of 11 R-C time constants to settle". What is the meaning of this?
I know that 16 bit refers to the number of bits of ADC.


texts: Diode testing: rising voltage in reverse direction?

texts:
I have some AUK diodes (http://www.kodenshi-tk.co.jp/products/power_semi_device/pdf/power_diode_02/14-19_SF10A400HDS.pdf) set in a Samsung X-sustain buffer board for a Plasma TV (PCB number LJ41-08420A). I'm testing with a Klein Tools MM400 multimeter set to diode mode.

Testing with positive on anode, negative on cathode, I get between 0.396 and 0.4v drop between terminals.

Testing with negative on anode, positive on cathode, I get steadily increasing voltage. I let it get as high as 2.8v before stopping.

This happens on all 11 diodes I have tested. A few of these diodes also test as shorted to ground.

I expected to see one of the following: a voltage drop (forward) and OL (reverse) for a working diode; OL in both directions (open circuit); 0v to 0.v4 in both directions (shorted).

Are these diodes faulty? If so, how would I explain the multimeter reverse reading? Is this just a quirk of my multimeter?


texts: How to calculate the transmission ( channel ) bandwidth in a digital communications system?

texts:
Is it the bandwidth ( BW ) of the individual pulse or should I generate a random process and calculate the BW from its PSD.
In my class we considered it the bandwidth of the raised cosine when we were studying the ISI. but then when we came to the modulation techniques we calculated the PSD of the random process ( and we considered that each bit is a rect not a raised cosine ).
What is the difference between the two approaches and which one is the transmission bandwidth?


texts:
Searched a lot and didnt managed to find this smd . Any suggestion , replacement smd ?
Thanks in advance. (SMD code as pic shows PH69 A 918010 )
Here is an other pic


texts: Does the standard termination of 120 ohm really suppress reflections in recessive state in CAN?

texts:
Suppose we have a multi-node CAN network with the ends of transmission line terminated with the standard 120 ohm. When the recessive state is on the transmission line, the voltage on both CAN_H and CAN_L will be 2.5V, so, when this state reaches the termination resistors at the end of the transmission line, the voltage at both ends of the termination resistor is 2.5V(voltage drop is 0V), so no current flows and voltage would see a high impedance state and should reflect back, but is not observed. What is the flaw in my explanation? Please explain in detail.

I don't clearly understand how this standard termination is actually suppressing reflections in recessive state?


texts: Channel to bulk capacitance in inversion

texts:
This lecture (page 11) said that as Vgs increases further, the inversion layer forms and
the channel to bulk capacitance is “shielded”. So the channel to bulk capacitance is 0.

Could anyone explain why? What does "shield" actually mean here?


texts: can anyone point me towards the math behind biquad antennas?

texts: I've looked everywhere for the equations to build a biquad antenna. Calculators are nice, but I want the math. Just point me In the right direction since I've had zero luck on Google.


texts:
Not sure if this should go here or in Super User, but I'm primarily concerned with how safely I can solder an AC power connection with little/no experience.

So what exactly am I doing and why? I am looking to make some minor modifications to a home-theatre PC, one of which is relocating the power supply to inside the chassis. In doing so I would like to create a false PSU "plate" that I can screw into the back of the chassis to make it look as stock as possible and maintain an external AC power connection.

I've already cut out the back of a cheap power supply and all I need to do now is cut an AC power cable and solder it to the female plug so I can connect that to the power supply inside my chassis. But are there wattage/safety limitations with different types of solder? Are their certain types of solder that are better than others for handling AC current or just power in general? I have not purchased a soldering iron/gun or solder or anything yet, so if one thing works better than something else I'd rather know before I spend my money.

I'm not worried about how good/bad the actual soldering work looks once I'm done since it will be inside the case, but should I "finish" it in some way to make it safer/insulated? Like wrap it in electrical tape? Or if that's a stupid idea, heat-shrink tubing or glue or something else?

Any insight/suggestions would be appreciated!

EDIT: One of my concerns is that I would like to be able to draw a few hundred watts over this connection in case a turn this into a little living-room gaming rig in the near future. Not sure if/how that would affect anything.


texts: How to it is only use of kalman filter with accelerometer and magnetometer ?(LSM303C)

texts:
I have LSM303C acc and mag sensor. But my sensor is drifting. i want use kalman filter,but it usually use kalman filter with gyroscope and acc meter.

İs it possible to make with acc and mag ?

this is something i want for example:

https://www.youtube.com/watch?v=fzjEMOOBuFA


texts: Should "get new sensor data" be its own task in an RTOS?

texts:
I am new to RTOS coding practices/architectures, and am specifically learning on RTX.  Should I have a get_new_sensor_data task for each sensor, or is sensor data usually taken care of by some other means, such as in the ISR outside of any particular task?  How do you flag your applications that you have a new piece of data for them?

I don't want to call hardware reading subroutines from the applications that use the sensor data because the data may be blocking several different applications. e.g. temperature may go into a relative humidity calculation task, it may get used by a task that outputs temperature to the user over the UART, and it may get used in another task that is correcting some other sensor that has a temperature-dependent output.


texts: Why do power banks have such a limited amperage vs. 18650 battery packs?

texts:
I ordered an LED light that ships without a power supply and has an USB connector to connect one. I thought I'd just buy some power bank subsequently to power the device, but then I realized that

all the power banks on the market can only provide like 1-max2.4 amps. Why can't one find a single one above this limit? The funny thing is that even power banks having 6-8 pieces of 18650 cells are limited to 1-2 amps and I just don't understand why as the C-rate of some 18560 batteries can be so high that some of them could output 10 or even 20 amps, not to mention if you bind 6 or 8 of them together.

Now it's a pity a cannot buy a good quality power bank to drive my lamp and I have to buy some Chinese 18650 battery pack which I don't know how reliable is (and by far less practical for other purposes).. Oh wait, I have a USB connector, so that's not an option either :/


texts:
I wrote a number of microcontroller GPIO libraries (essentially set pin direction, set pin, read pin, read pin as analog input). I'd like to create an automated test to verify that my library indeed does the correct things with the correct pins. Doing this by hand is tedious and not something I want to do after each change.

Has anyone designed a hardware software combination to automate this? For instance, some resistor DA converter connected to the output pins, output to an A/D pin, seqeunce the output pins and verify that the correct voltage is read from the AD pin. But that leaves the digital inputs untested.


texts:
With no experience in VHDL, I am trying to convert a C++ code for driving a CCD to VHDL based code. This is very likely not the best way to implement it, but it's intuitive to me. So, my counter counts clock cycles and based on the clock cycle number, I assign the specific state to the output. I am able to implement the design successfully:

However, when I run simulation, the ALLOUT does not change, in fact it stays in ST3 state. The warnings from the test bench console:

They repeat every 25ns up to the end of the simulation.
Any suggestions on where I made the mistake?


texts: What Lithium chemistry in phones' (now) 3.8V batteries?

texts: I'm specifically looking for the discharge tolerances...can communicate with the charge controller on the phone and want to increase the discharge depth from 3.5V to say 3.1-3V for longer battery life. The cell won't sleep until at least 3V or something, damage doesn't occur until 2.7V on the standard lithium batteries used in phones a few years ago, and a replacement is only $12.50 so I want to see what I can do.


texts: What happens to a MOSFET if i apply voltage between Drain and Source leaving the Gate floating?

texts:
lately i was analyzing a simple circuit with 2 MOSFET, 1 Nmos and 1 Pmos, where the Nmos was acting as a switch and its drain was connected through a resistance to the Pmos' gate. The pmos had it's source connected to a positive reference voltage and it's drain connected to a load. Between the Pmos' gate and drain a capacitor was placed.
Now, i was trying to get the circuit polarization but to me, when no signal is applied to the Nmos' gate, the Pmos should have its gate floating.
But in reality it seems that that Pmos should actually be turned off and not on.

Am i not considering some aspects of a 'real-life' MOSFET for this?
Thanks in advance.

EDIT - Here's the schematic:


texts: How can one pair of headphones be connected to two audio sources?

texts:
I'd like to connect one pair of headphones to the headphone jack on two audio sources simultaneously. I realize I can't just wire two audio sources in parallel since they'll then be driving each other. Commercial solutions appear to all involve amplification and volume control, which my two sources already have.

How can I combine audio signals from the headphone outputs of two different devices while still presenting just the impedance of the headphones to each device?


texts: Are the instructions fetched from RAM or ROM in an ARM micro-controller?

texts:
In many tutorials regarding ARM CPU registers, the instruction register is mentioned in such way: "Register R15 in ARM micro-controller is the program counter and it points to the next instruction to be fetched from memory."

But I also read that in Harvard architecture, there is instruction memory and data memory. What I understood or misunderstood from this was the instruction codes are stored in flash ROM, and the data is stored in RAM.

But when I read more about it, I get the impression that the instructions also are fetched from RAM instead of ROM.

Does ROM have nothing to do with the whole operation besides storing the machine code?

edit: Question assumes no operating system, just a standalone ARM micro-controller.


texts:
The answer to "DC Motor as a Generator Voltage and Current" from
Olin Lathrop included:

"Sometimes these parameters can be inferred from other specs. For example, consider a motor that puts out 100 W of mechanical power at 60 Hz rotation (3600 RPM) speed, at 24 V applied, and is 90% efficient. The electrical input power is (100 W)/90% = 111 W. That means the current is (111 W)/(24 V) = 4.6 A. The winding resistance is then (11 W)/(4.6 A)² = 518 mΩ, which is dropping (11 W)/(4.6 A) = 2.4 V. That means the back EMF at 60 Hz is 21.6 V, or 360 mV/Hz.
If you were to drive this motor mechanically at 40 Hz, it would look like a 14.4 V source with 518 mΩ in series. If you were to put a 1 Ω load on it while still keeping the rotation rate at 40 Hz, you'd get 9.5 V and 90 W."

My question: is there any way to know what current I could get out of this stepper motor at 200/300/400 RPM? 65V 5.1A Bipolar parallel, 176W, 5.1A, 1.8DEG/STEP, not variable reluctance.
thanks


texts: Effectivity of additional external battery hot-plug connecting device

texts:
I have been tinkering with electric last-mile vehicles lately and stumbled upon an interesting device, Rita, which is “Universal adapter for additional external battery hot-plug connecting"
It has additional features for specific e-scooter, but I am more interested in the voltage switching part.
I have read over and over again that 'different types of batteries should not be mixed', so the question is..
Is there any drawbacks to this kind of arrangement?
Or could I simply hook up two batteries and have a transistor switch to the battery with higher voltage and call it a day?
Thank you for your time.


texts: (inverter repairs) Does reverse polarity can kill power MOSFETs in UPS inverters?

texts:
I had an old computer UPS (almost 7 years) and I modified it to use external battery (a 12 Volt motorcycle battery) since the old 12 Volt battery is completely dead and no replacement is available for sale for the same model.

So far, I used the UPS with the new battery for almost 1 year and it worked fine, until I did a maintenance and voltage checks. I disconnected the battery during the process, but this is where things get screwed up.

I accidentally connected the battery backwards (I didn't notice the battery polarity markings because it's just embossed on the black plastic surface and there's no color markings, and I worked in the nighttime lighting.)

There was just a small spark from the battery terminals where I touched the battery cables and nothing more (no smoke, explosions or whatever) Everything works fine except for the inverter part of the UPS is not working and there's no output voltage (there's just one small voltage pulse on the output where the inverter is supposed to turn on, I checked it with a 5 Volt USB LED light connected to a phone charger plugged into the inverter output).

The indicator LEDs and the buzzer works fine. (I tried powering it both from the battery and mains input). The circuit seems doesn't have any reverse polarity protection (Because it seems unnecessary as the battery replacements and repairs have to be "done by professionals" as the manual says) and there's no fuse for the battery side.

There's only one fuse for the mains input but it's still good and it has nothing to do with my problem here. There are possibilities that the reverse polarity killed the power MOSFETs (it has two SW3205 MOSFETs) or the oscillator/controller circuit (it has 3 LM339 comparators and 1 SG3524N possibly for signal generator) There's also a voltage regulator (UTC317) possibly for powering the oscillator and control circuit.

Any chance that one (or more) of them are killed by the reverse polarity? (I don't know about the MOSFETs, whether they can be killed by 12 Volt reverse voltage or they're supposed to take that much power since it's a high power component).

If there's any chance for repairs, I want to give it a shot repairing it but I don't know where to start.


texts:
I was wondering how voltage drop works when using PWM from a Raspberry Pi to generate the data signal for a WS2812 LED strip.

I already have experienced votlage drop when dealing with the 5 V, 300 LED strip, I only manage to get about 15-20 LEDs at pure full white so my current solution is to wire the source (5 V, 20 A switching power supply) in parallel and have it run along the strip powering it at multiple locations.

Right now I am trying to plan forward and I am wondering if I will run into any issues when trying to run more LED's. My goal is to get two 5 m strips, which would be about 600 LEDs. If I connect them in series but with independent sources, will the data line continue to travel at the 5 V needed.

I can easily measure the voltage drop in the strip from one end to the other using my multimeter, but I don't know how to measure the PWM 5 V data signal that is going into the LED strip to see if it is indeed dropping. My main concern of having 600 LED's is the possible fact that the data line might not be strong enough to make it through all 600 of them.

I am currently using a 3.3 V PWM from the RPI, then using a 3.3 up to 5 V level shifter to ensure that the signal entering the LED strip is accurate.

Is there anyway to measure the data line PWM voltage in a LED strip? And is it possible for the 5 V PWM data signal from the Pi to travel 10 meters with timing accuracy?

I originally tried to power the level shifter with the 5 V pin from the Pi but that caused many issues where the data signal wasn't strong enough to send the value along the LED strip.


texts: Why a damaged LED was acting like a weird memory cell?

texts:
I remember playing with signal LEDs and observing what happens when I misuse them, and one particular LED behaved very strangely, as if it were stateful.

Using a drained 9V battery (that can only deliver about 100-200 mA), the (probably green) signal LED and a tester, I remember observing the following cycle:

I apply the current forward, the LED shines dimly, current is rather constant (5-15 mA?)
I apply the current backwards, the LED obviously does not emit any light and the meter showed small, but raising current (beginning under 1mA)
The current keeps raising and suddenly spikes (50-100 mA?), as if the LED is almost short circuited
I reverse the polarity again. The same relatively high current flows in other direction, no light is emitted. But the current slowly decreases.
Suddenly the current drops to about 5-10 mA and the LED starts emitting light again (first dim, then a bit brighter).
The more time the LED is turned on "normally", the more time of reverse 9V needed to trigger the breakthough. The more current flowed backward, the more forward-flowing time needed to "repair" the LED.

It didn't look like as if it were just temperature. If I waited a bit the "state" preserved.

How can this stateful behaviour be explained? What happens when current flows backwards though LED? Why could it be "healed" by forward current?


texts:
it's the first time that I create gerber files for a pcb printing website. I'm looking to the bottom layer with a gerber view, but it doesn't seem to be mirrored...

it's the same view as in eagle, i.e. from the top. Is this ok or not?

thanks


texts: Replacement cap (filter / choke) for oscilloscope power supply

texts:
My dad's poor old Philips PM3070 scope died in a sizzle and a puff of smoke a few days back, after being sat in the garage for a year or so. He donated it to me and it seemed to work at first, but unfortunately it didn't last more than a couple of hours.

Whilst I was taking a photo of my new toy, it started crackling and began exuding some pretty acrid smelling bright-white smoke. The screen remained on whilst this was happening, though I very quickly unplugged it and didn't get to test any functionality. I'm hoping that this indicates a non-fatal fault; it would be a shame to have to commit it to the great electronic beyond.

I've now got it at home and have taken it apart, and pretty quickly discovered the culprit:

Well, no wonder it made such an awful stench! The cap's a bit dead it seems. Since the scale is not immediately obvious: I'd say it's about 22mm across, by 17mm high, by 12mm deep. The traces leading to it are about 2mm wide.

I've got a service manual that shows the circuit diagram as follows. I circled the failed capacitor in red.

(excerpt of circuit used under assumption of fair use allowance)

For clarity, X6014 is a standard Molex connector that brings the 240V mains in from the external plug. S6001 is the main power switch. I don't know a huge amount about power supply design, but I'm going to guess that this is some kind of filter or choke.

I'm looking for a replacement, but don't really know what to look for. I can't tell whether this is a standard cap, or whether it has some special properties specific to its role. I also don't know what current rating I need to look for. Any ideas on what I should be looking for, and how I should come to such a decision?

For example, is this an appropriate replacement? If not, which properties are incorrect?


texts: What are my options for interfacing **30** incremental encoders to an MCU?

texts:
Background: I am familiar with interfacing a few incremental/quadrature encoders to a single MCU chip. My go-to chip STM32F10x can decode 4-5 encoders even in a LQFP64 package (e.g. STM32F100R8T6 has 4), which had always been more than enough for me... until now.

Problem: I want an ATXMEGA128 to effectively poll counts of all 30 encoders at 1kHz (say, by keeping 16-bit counters). I cannot change the ATXMEGA128 to some other MCU, but I can add another MCU to interface with it.

The bottom line is I could slap on a FPGA (e.g. Spartan3E) and make it talk to MCU through SPI or parallel, but I'd like to consider some alternatives before I go down this path (for non-technical reasons). The number can be reduced to 15 if 30 seems too hard without FPGA.


texts: Audio equalizer circuit using multiple feedback bandpass filter for each frequency band

texts:
I have a project to design an audio equalizer circuit with the following specifications.

Bass band, center frequency = 180 hz, quality factor =0.7, range of adjustable gain 0.4-8
Midrange band, center frequency = 1 khz, quality factor =0.7, range of adjustable gain 0.2-4
Treble band, center frequency = 5.5 khz, quality factor =0.7, range of adjustable gain 0.1-2

I did the calculations to satisfy the center frequency and quality factors, but I am not understanding the range of adjustable gain.
I only have 6- LM741 op amps (I understand the 741 is vintage, it is all I have, I'm just a college student. Trying to make it.) I don't understand where to fit my potentiometers.
Initially I thought I could place a variable gain inverting amplifier after each filter, but I then thought I would need a summing amplifier to combine the inverted outputs and that would be one two many op amps.
Any help or advice would be greatly appreciated.


texts: Transformer's Primary and Secondary Voltages

texts: In general, which is the phase relationship between the primary and secondary voltages of an ideal transformer? Does it depends on the dot convention?


texts: Can FTDI Basic Breakout and FTDI XBee Explorer USB be used alternatively?

texts:
I wonder if these two boards from sparkfun can be used alternatively for USB to Serial communication?

The first: (FTDI Basic Breakout)

https://www.sparkfun.com/products/9716

The second: (FTDI XBee Explorer USB )

https://www.sparkfun.com/products/11812

Thank you


texts: How read -8v to +2v using ADC ? which ADC i can use?

texts: input signal is from +2v to -8v whose time stabilization is 3-8 Sec and frequency is varying from 60 Hz to 100 Hz. How i can read that signal, and which ADC i can use ?


texts: Difference footprints of part in Altium Designer

texts:
What is the numerical difference between footprints marked with "* _M", "* _N", "* _V" and "* _L"?

P.S. I was looking any information in google, but as a result nothing.


texts: Why do datasheets include Tape and Reel information?

texts:
Specifically:
 - Does a PCB designer need to be concerned with tape and reel information?
 - Is the information intended for PCB assemblers, pick and place machines, etc?
- Will a pick and place machine mess up if you create your part with an orientation different from the way the part is oriented on the reel?


texts: Build a transimpedance amplifier that does not invert

texts: I want to convert a temperature dependent current from a PT100 into a temperature dependent voltage. I opted for a transimpedance amplifier, but it gives me a negative voltage. How can I construct a circuit that does not give me a negative voltage without using a second opamp?


texts: Toggle two different LEDs with one T Flip flop

texts:
Imagine we have one green LED, one blue LED, power supply and resistors and grounds. We also have a switch.

Can we toggle between the two different LEDs when the switch is pushed? If the blue LED is ON and we push the switch, the green LED is ON and blue is now OFF.

The same situation when the green LED is ON, if we push the switch, the green turns OFF and the blue turns ON.

Is it possible?


texts: I'm designing a device which has a DM3CS-SF microSD connector and in the recommended land-pattern for the datasheet they have areas labeled as "Non-conducting traces". What am I suppose to do with these areas? Are these keep-out areas where I shouldn't route anything on the same layer, or do I need to provide a trace with solder mask on them (so that they can't get soldered/electrically connected to the connector)?


texts: Doubt regarding a simple electromechanical system

texts:
My book describes a simple electromechanical system.

Here O corresponds to unstretched spring.It is assumed that magnetic material is highly permeable and clearence at point M is negligible. The book states that in A when the extension in spring is x the movable member experiences a force in such a direction that the energy stored in the field tends to increase so it reaches B with an additional displacement dx.

I couldn't get why the force experienced is such that to increase the energy stored and how decrease in air gap leads to this.In fact decrease in air gap should lead to increase in permeance so that energy stored should decrease.


texts: L293/L293D/TB6612FNG current limitation for Motor Driving operation

texts:
For driving a linear motor, i wanted to use some motor driver IC among L293 or L293D or TB6612FNG. And motor which I am using, has a voltage rating of 12V and current rating is unknown. And according to datasheets, maximum current that can handle by each channel in driver IC seems to be 600mA/1A/1.2A.
My query is, can I use these driver ICs for driving my linear motor and how I can determine the current consumed by the motor.??
Regards
Akhil


texts:
In my project, the current budget is very tight.
With less than 1mA, I have to isolate sensor's signal voltage and be able to measure it with ADC on the other side of the isolation barrier.
What I have thought of is that using VF conversion and send the digital signal via photocoupler.

I have looked for commercially available VF converters. But they all consume a few mA's.

Can Anyone suggest a good way to isolate an analog voltage signal with limited current budget and board space?


texts: Can you turn on / off LEDs from a webpage (javascript) via a microcontroller (arduino)?

texts: I would like to use an Arduino microcontroller (with whatever shield necessary) to control LEDs.  My challenge is how to get users to interact with a javascript-driven webpage to send a signal to the microcontroller to blink an LED.


texts:
I have a 10nF capacitor who's datasheet gives 10% tolerance, and 15% total tolerance over temperature (-55 to 125C). It does not give it in ppm, for simulation purposes, how would I calculate it's ppm value?
Thanks in advanced.


texts: Recomendation for a digital inverter made of discrete components

texts: I have a digital circuit in which I need only one logic inverter, and both PCB size and power consumption are serious constrains. So I thought about using a pair of complementary SMD MOSFETs (the classic coupled gate configuration) instead of an IC with many ready-made inverters. Which MOSFET would be more recommended in this case (both for small size and low gate-drain current)?


texts: Is the 555 necessary here, or can I just use an op-amp?

texts:
Context: The circuit's main input is a line-level audio signal from a computer. Every time that something loud happens in the audio, I need the solenoid to activate for about 100 ms.

The first circuit is below. I derived much of it from this answer. The voltage source is 12V. I biased the MOSFET so that when the audio line went above a certain voltage (adjustable with the potentiometer), the MOSFET would turn on. Unfortunately, it hardly stayed on long enough to make the solenoid move. (The circle and 400 in parallel with the inductor and diode is an LED.)

Next, I tried using an op-amp instead for voltage detection and a combination of a diode, a capacitor, and a resistor to keep the MOSFET on longer. When the audio line voltage goes above a certain voltage, the op-amp charges the capacitor, and the MOSFET turns on until the capacitor discharges. I plan to connect the op-amp's positive rail to 12V and the negative rail to ground.

This worked well, except for a few concerns:

In the simulation, the inductor's current seems to climb higher and higher every time that the MOSFET is turned on, and it never goes back down. I fixed this by adding a 100 ohm resistor (not shown) in series with the inductor. Is that safe, and are there any potential pitfalls to that approach?
I thought of using a 555 chip to control the MOSFET, with the op-amp output wired to the trigger. However, according to this page, the 555's trigger is active low. Could I simply flip the + and - on the op-amp to make the output off when the audio line voltage rises above the certain value? Is there an advantage to using a 555 instead of the diode, capacitor, and resistor?
How can I tell whether an op-amp will accept 0 V as the negative rail?
Have I committed any electrical no-no's?

This is what the circuit would look like with a 555:

EDIT: Thanks to Andy aka's answer below, I was able to create the next circuit. Q1 is acting like a NOT gate, and it controls Q2. Peaks in the audio input now cause C3 to be charged up, which holds the voltage high for Q3, which is still a MOSFET. The sensitivity is adjustable via R1, and I suppose that the duration of the solenoid activation could be adjustable if R7 were a pot.


texts:
I want to replicate this structure in LTspice where the components 1, 3 et 4 are resistors with the same resistance R and  2 et 5 are two capacitors and opamp LT1356

this is the schema I made

this is the bode plot:

I think it's wrong because the max value of the gain  is -50 dB while I need to find the frequency at -3 dB


texts: Include TVS in low current battery powered circuit?

texts:
I'm designing a circuit powered by two alkaline cells in series with a voltage of 2-3.2V. After being fused this is going through the boost converter MCP1640B with constant 3V3 output.

The maximum load on the boost converter is about 300mA pulsed to a SIM7000A chip transmitting an LTE message.

Is it worthwhile to include a TVS across the battery rails to protect against transients? Or would it just be a waste of money/space on the PCB? I saw a source which said to include a TVS in an automotive battery-powered circuit, but that was because the load of the motors is inductive and is known to create transients.


texts: How to mount component perpendiculary to PCB

texts:
I'm designing small PCB(20mm*20mm) where I'm also limited by height of whole project that can't exceed 20mm. I have to place few sensors on the edge of the PCB but not facing up but facing out of the PCB so pads of sensors are perpendicular to the PCB.

Not the real design I haven't designed this part yet but describes what I'd like to do.

My question:
What is the usual way this is done?


texts: lwIP - Best way to send data from microcontroller

texts:
Currently, I am using Server Side Includes to transfer data from my microcontroller to my webpage. The issue with this approach is that if I want to graph the data I have to store the SSI value in a javascript variable, which gets messy (currently I am continuously refreshing a hidden iframe on the page that has an element whose value attribute is being modified with new data from the microcontroller, then my javascript variable reads that elements value to update a graph). Is there a better way to send/receive data?

Thanks!


texts: Convert and shift voltage from DAC using opamp

texts:
I have a signal coming out of a basic DAC (resistor and capacitor) as follows:

1.4V min
4.8V max
~2.8V pp

I have a bipolar supply that is -12V - 0 - +12V

What is the best way to shift this signal to +-5V (10V pp)

As I understand this can be done with a single non-inverting opamp. However being a real electronics newbie I have no idea where to start figuring this out.

Alternately maybe it would be easier (and more beneficial in terms of learning) to shift the signal to ground (-1.4V - +1.4V) and then amplify.

Not looking for an exact answer would just like to be pointed in the right direction. As in what type of non inverting opamp circuit is used to shift the voltage?


texts: Techniques for analyzing Comparator circuits?

texts:
I'm looking for some general guidelines/equations I can use to analyze circuits which use comparators. In particular, I'm interested in hysteresis.

For example, take the following open collector/drain comparator circuit with hysteresis:

How did they derive the equations for calculating hysteresis? I tried doing some analysis assuming op-amp like behavior (assumed that input terminals source/sink negligible current, did not assume that the input terminals have equal voltages, clamped output voltage to [Vee, Vcc]), but I wasn't able to get the desired output results.


texts: Does a gyro need to be placed at the center of rotation?

texts:
When using a gyro chip to measure angular velocity, does it matter whether it is located at the center of rotation?

I've seen it mentioned online without much explanation that it should be placed at the center, but in my introductory physics courses I learned that the angular velocity is the same at every point on a rigid body.  Wikipedia seems to confirm this in the last section of Angular velocity, but I'm not sure I'm interpreting it correctly.

I expect that there is normally some non-ideal coupling of the acceleration terms into the gyro measurement -- is that the main problem?

Is there something obvious that I am missing?


texts: Three series LED arrays in parallel, resistor value?

texts:
i know this is possible but not sure how to work out the resistor value needed... I should point out that I am re-using a PCB that has had all the components removed.

I need 15 LEDs in 3 parallel circuits, each circuit having 5 LEDs in series.
The 3 parallel circuits share 1 current limiting resistor between them.

    |-->-->-->-->-->--|
    |                 |
+ --|-->-->-->-->-->--|--/\/\/---
    |                 |
    |-->-->-->-->-->--|

Assuming 12v 2v forward voltage and 30mA, I know the resistor required would be 68 ohm.
Am I correct in assuming the resistor I need would still be 68 ohm?


texts:
This is a homework question where i am stuck. Please help me out in this:

  Three similar impedances are connected in star across 2000 V, 50 Hz three phase
  supply. Power absorbed is 300 kW. Current taken is 100 A lagging. Find the values of circuit parameters in each phase.

I have found out the power factor to be 0.866.

I found out the impedance Z to be |Vph| / |Iph| = 11.243 ohms.

But now how do we find the inductance of the circuit?


texts: Designing Startup Network for Flyback Controller

texts:
I'm trying to design a startup network for this flyback controller, see the picture at the end. I want the controller to start within 10 ms at most. This is what I'm doing:

Due to the wide input voltage, I'm connecting the startup network to a tapping point from the capacitors in series.  This allows me to choose a lower Vds depletion MOSFET like this: CPC3980ZTR

1) Would this cause some imbalance in the caps?

Now, during startup a current flows from inputs caps C14 & C15 through the depletion MOSFET Q5 (normally on). This current will charge the Vcc capacitor C16. The gate of Q5 is connected in the middle of the resistor divider formed by R29 and R30. As the voltage over C16 increases, the gate voltage of Q5 becomes negative with respect to its source voltage. When threshold voltage of Q5 is achieved, it turns off.

Resistors R29 & R30, and Zener diode D16 are dimensioned so that Vcc achieves the minimum value UVLO for the controller to start. From this point, controller will be fed by the auxiliary winding, and Q5 will stay off until the next start-up.

According to the datasheet, the threshold voltage for Q5 has minimum and maximum levels of -3.1 and -1.4, respectively. The minimum Vcc voltage for the controller to start is UVLO = 21V, and the max Vcc is 35V. I will allow a max voltage of 27.5V for overvoltage protection.
During startup, the voltage over resistor R29 is the voltage between gate and source of Q5.

By setting R29 = 10K
R29*i_R29 < 1.4V only if V_C16 > 19.5V --> i_R29 < 0.140 mA for V_C16
= 19.5V
R29*i_R29 > 3.1V only if V_C16 < 27.5V --> i_R36 > 0.310 mA for V_C16
= 27.5V

By using a 20V Zener diode as D16, the first condition is met.

For the second condition, the current through R29 can be calculated as

I_R29 = (V_C16 + V_D17 – V_D16)/(R29+R30)
R30 < (27.5 + 0.3 – 20)/(0.4mA) – 10K
R30 < 15.2K
R30 = 10K

2) How do I calculate a proper value for C16? And the time this circuit will actually take to start the controller?

EDIT: Below there is a potential way of doing it with a known current


texts: How can I at least estimate the optical power that an RGB LED radiates given the typical parameters?

texts: How can I at least estimate the optical power that an RGB LED radiates given the typical parameters - say luminous intensity in Candela or Luminous efficiency - from a data sheet? Assume this is a narrow-band LED and can be characterized by a single wavelength for each color, λ, to keep the solution from getting too complicated.


texts: Is it a bug in the design of a low side UCC27524A, and 2EDN7424 gate driver if it doesn't use VDD capacitor?

texts:
I am using low-side TI and Infineon gate drivers.
If I don't use a VDD capacitor, then there is a glitch in the output waveform as shown in the figures. It seems it's the designer's or layout problem but I'm not sure about it.
Can anybody give me a suggestion on what kind of problem it could be a and how to correct it?


texts: Loud hum emitting from output stage of Raspberry Pi guitar pedal

texts:
I've been trying to implement the electrosmash Pedal Pi project using a Raspberry Pi 4 Model B, breadboards, and parts purchased from DigiKey.
For reference, here is the overall schematic of the build:

So far, I've built the input stage, and the power supply stage which seem to work fine. My struggle currently is with the output stage. When I plug in the output jack into my amplifier, there is an incredibly loud hum emitting.
Here is what I have tried:

I disconnected PWM0 and PWM 1 from the raspberry pi. When I do that, there is still a loud noise, which leads me to believe that the noise isn't coming from the PWM pins.
I have plugged in my 1/4 inch jack into my amp and disconnected the other end. The amp did not create any hum at this point which leads me to believe that the issue is not with the amp.
I have tried changing out the op amp for a spare one I have, and the humming persists.
I have tried changing the C6 capacitor to an arbitrarily higher capacitor (I believe 0.1uF) and that did not change the humming.

I'm not quite sure how to debug this, and it's been quite a roadblock since I can't distinguish the output from the PWM pins through all the noise.
Further details:
The parts I am using for the circuit are:

R6, R9, R10: RES 4.7K OHM 1/4W 1% AXIAL (DigiKey Link)
C6, C7, C8: CAP CER 6800PF 50V X7R RADIAL (DigiKey Link)
R7: RES 300K OHM 1/4W 1% AXIAL (DigiKey Link)
MCP6002: MCP6002-E/P-ND (DigiKey Link)
C9: CAP ALUM 4.7UF 20% 25V RADIAL (DigiKey Link)

My breadboard layout for the output stage looks like:

where the output jack is on a separate PCB, following the schematic.


texts: Is a 2A transformer too much for a power supply that outputs 13V to 15V DC

texts: For a class project (basic electronics class 1st year) I have to build a basic power supply. The proffesor told the class that the power supply must output 13V to 15V. He said use a 20VAC to 25VAC transformer that outputs 1A to 1.5A. The problem is I can't find any transformer with that current rating. I don't have time to buy online because I have to build it in class monday (the project was given yesterday). I have to buy from a local store like radio shack. The problem is the only transformers that they have are 25V 2A or 12V 450mA. I'm still not knowledgable in electronics so I'm wondering if 2A is too much. As far as I understand current is not pushed is only pulled by a component, or am I wrong? Some info. I'm using a full bridge rectifier, I still haven't calculated the capacitor value. I'm also going to be using an IC 15V regulator.


texts: Input and Output pin voltage specs on a datasheet

texts:
I'm a bit confused about input pin voltage tolerances and output pin voltage values of ICs.

I would think that datasheets for ICs that involve signal inputs/outputs would list two values:

The maximum voltage for a signal HIGH that it can tolerate at an input pin.
The minimum voltage for a signal HIGH that it will set at an output pin .

But many datasheets don't appear to list them for all pins. For example, I'm experimenting with STM6600, and its datasheet doesn't provide them; see below:

Above, "PB" is an input; "EN" and "INT" are outputs. Notice that only EN's minimum HIGH output is provided, but neither INT's minimum HIGH output nor PB's maximum HIGH input is provided.

Thus, I'm unsure about what to do in this situation.

Let's say I set VCC = 3.0V on this IC.

Then how do I determine:

Will this IC (STM6600) tolerate a given input signal HIGH from a different IC running at, e.g., a higher VCC = 3.3V?
And correspondingly, will a given output signal HIGH from this IC (STM6600) cause damage to a different IC running at, e.g., a lower VCC = 2.7V?

Even if the answer to these questions is No, I would still be interested in knowing the actual numerical values that I should expect, hence my problem with the datasheet.


texts: What if there are an odd number of twists in a twisted pair cable?

texts:
I am not an electrician, or a student of the field. I am a Network Engineer with a curiosity bug and that has recently taken me to exploring cabling and Twisted Pair specifically. I say this to plead that the answers be 'dumbed down' so that I can understand it ^_^.

I have just finally understood the reason why 100BASE-TX and 10BASE-T uses two wires (one pair) for TX and another two wires (another pair) for RX. I understand that across each pair, one wire transmits the original signal, and the other wire transmits the exact inverse.

I also just finally understood why the wires are twisted within the pair. Effectively, to allow ambient sources of Electromagnetic Interference (EMI) to affect both wire pairs equally, rather than one disproportionately to the other.

What lead me to understand it was this image, posted on ResearchGate.net on this Post by Dr. Ismat Aldmour:

I'll post his explination here as well, to avoid the risk of link rot:

  I had to explain this to my students in networking once by drawing
  something similar to the attached Figure. In Figure 1, for the case of
  parallel pair, the interference causes the red wire (the closer to
  interference source) more pick-up voltage (induced) per unit length (1
  mV as example) while less induced (0,5mV) in the blue wire. Total
  difference at the destination is 3mV. While in the twisted pair case
  (Figure 2), total difference is 0V at destination because parts
  (twists) of red and blue wires alternatively subjected to same level
  of interference and thereby total difference at destination is 0V. I
  drew this figure for this question hoping to use it in lecturing as
  well. This is especially useful when teaching networking to
  non-electrical engineering students who don't recognize terms of
  impedance, differential mode noise terms, ...etc . By the way,
  interference in twisted pairs comes mainly from signaling on other
  pairs running together within the same cable which can have many of
  them. Thanks. @AlDmour.

With the image and explination, I understand how the six, even twists cause for both wires in the pair to be equally affected by ambient EMI, and the net delta interference to end up at +0.  My question is, What happens if there is an odd number of twists in the wire?

For instance, if one more half twist is added to the Figure 2 image above, the interference delta on the Red wire would be +1mV, and the interference delta on the Blue wire would be +0.5mV.

How does the receiving end compensate for that, and/or detect the EMI and determine what mV on each pair it can ignore?


texts:
Is there a way to set Altium to select only COMPONENT and not anything else like pads, nearby text or polygons?

I'm used to OrCAD where click simply selects the components required to be moved.


texts: How to do circuit analysis using Matlab?

texts:
I often hear of people using Matlab for circuit analysis, but I never actually figured out how it is done. I assume that there is something more to it than just setting up equations by hand and solving them in Matlab.

I'm looking for a good starting point.


texts:
I have: 11-12 meters of RGB 5050 LED strip, which consumes 14.4W per meter, seller says I should use 12V DC 180W 15A power supply, to power the whole thing up. I also have 3x MOSFET-N (IRLZ34N) I want to connect the strip to my digispark (as an alternative for arduino) to control its colors.
Will it be safe to connect them as pictured below?


texts: Configuring the Ports of an AVR Microcontroller for SPI Use

texts:
I am trying to configure the an ATtiny84A for use with SPI, but I have some confusion with what Is being said in the datasheet for configuring the ports. The ATtiny84A has, what the datasheet calls, "alternate port functions", so each port can have multiple functions. In my case with SPI, the pin that serves the SPI Clock also serves the ports GPIO functionality, an ADC, the clock for I2C, among others (as seen on page 64 of the datasheet: Port A, Bit 4).
What I understand from what its saying in the datasheet, is that it somehow automatically configures the port when a functionality is set. So what happens if I try to configure multiple of these port functions at a time? For example, what if I configure the ADC on port A4 and SPI which has its clock source on port A4? I can't find a table which explicitly states how to configure the port which enables or disables other functionalities, so I imagine that some sort of function priority is taken?
Furthermore, where is the information on setting the direction register to allow the SPI clock through? This confuses me, because like I said, the datasheet seems to say that the port is configured automatically; however, for me to pipe the clock through port A4, I must write a 1 to the direction register (set it as an output) for the clock source to come out, but I cannot find any information in the datasheet to back up this behaviour.
Here is some sample code for getting a continuous clock to come out of the SPI clock port:
USICR   |=  (1 << USIWM0);  // Set Bit 4 (USIWM0) of the USICR register
USICR   &=~ (1 << USIWM1);  // Clear Bit 5 (USIWM1) of the USICR register

USICR   &=~ (1 << USICS0);
USICR   |=  (1 << USICS1);
USICR   |=  (1 << USICLK);  //Sets USITC as the clock source for the 4 bit counter.

DDRA |= (1 << DDA4); // Configure PortA4 as an output?

while(1)
{
    USICR |= (1 << USITC); // Toggle the SPI clock output.
}

EDIT: I'll summarize the information which I am specifically confused about/don't know what to do with from the datsheet:
Table 10-2, page 60: I am unsure what the purpose of these overriding signals are when configuring alternate port functions.
Table 10-5, page 64: I see the USI clock in this table, but I don't know what the rest of the information that it contains is telling me. I see that USCK is in the DI row, but I don't know what that is telling me for the configuration of the port.


texts: Meaning of diamond with four triangles in schematic?

texts:
What is the meaning of a symbol consisting of a diamond with four boundary triangles in a schematic?

Re. the following from the Atmega328 datasheet:


texts: How to design a common source amplifier with inductive load?

texts:
If I want to design a common source amplifier with inductive load (L as the RF choke), how can I choose the values L, C, and W of the transistor? Given the following parameters:
Vdd = 1V
Vout peak swing = 2V
R = 50 ohm
Vin 1GHz, 0.1V peak
Vth = 0.5V
Power delivered to the load = 1W
Why Vx can be larger than Vdd?

Thanks.


texts: Difference between current equations of enhancement and depletion mode MOSFET

texts:
1)Are the equations and operating region conditions the same for both enhancement and depletion type MOSFET? Are these equations and operating conditions valid for both enhancement and depletion type MOSFET?

2)If they are the same then what things(difference) should I take into account while evaluating enhancement and depletion mode MOSFET circuits.


texts: Can I2S tdm interface send more channels with less sampling frequency?

texts:
We have a arm SoC(system on chip) connected with I2S to a DSP (digital signal processor). SoC and DSP both support 48khz, 8 channel and 16bits in TDM mode.

Is it possible to use this interface to send 24channel, 16khz and 16bits as DSP is able to encode the data and SoC can decode this encoded data?


texts: FPGA firmware design: How big is too big?

texts:
I have a particularly large signal processing transform that needs to be ported from matlab to VHDL. It definitely requires some kind of resource sharing. A bit of calculation gave me the following:

512 ffts of 64-points
41210 multiply-add operations

Considering the largest Virtex 6 FPGA has ~2000 DSP48E blocks, I know that I can resource-share in order to re-use the resources multiple times. Execution time isn't really an issue, the processing time can take relatively long in FPGA terms.

Looking at resource usage, using radix-2 lite architecture gets me 4dsp blocks/FFT operation = 2048 DSP blocks, a total of ~43k. biggest Virtex FPGA has 2k blocks, or 20 operations/mux.

Obviously including such large muxes into the fabric is also going to take up slices. Where do I find the upper end of this limit? I can't infinitely share the FPGA resources. Is 41210 multipliers too big? How do I calculate what is too big?

I've also looked at other resources (Slices, Brams, etc). Radix-2 Lite also gives 4 x 18k brams/fft = 2048 brams biggest Xilinx FPGA contains 2128 Brams. very borderline. I'm concerned that my design is just too big.

UPDATE:

Some more info on the design itself. I can't go into detail, but here is what I can give:

Initial conditions -> 512 ffts -> 40k multipliers ---------|----> output data to host

                 ^------re-calculate initial conditions----|

output datarate spec: "faster than the matlab simulation"

calculations wise, this is where I am:

FFT stage: easy. I can implement 1/2/4/8 FFTs, store the results in SDRAM and access later. Relatively small, even if it takes long, it's ok. using radix-2 lite I can get 2 DSP48Es and 2 18k BRAMS/FFT. streaming gives 6 DSP48Es 0BRAMS/FFT. in either case, 64 point FFT is small in FPGA resource terms.

Multipliers: this is my problem. The multiplication inputs are taken from either lookup tables or FFT data. It really is just a whole bunch of multiply-adds. There isn't much to optimise. Not a filter, but has characteristics similar to a filter.

Considering resource sharing on the FPGA, maths works out as follows:
One LUT-6 can be used as a 4-way mux. The formula for an N-way, M bit mux is as follows:

N*M/3 = number of luts, or N*M/12 = slices (4 LUTS/slice).

crunching the numbers for my implementation does not give good results. 90% of the virtix-6 family doesn't have enough slices to resource-share their DSPs in order to perform 40k operations.


texts: Troubleshooting an op-amp for amplifying a low voltage AC input

texts:
I am trying to amplify a low voltage AC input with a gain close to 5. It has a 0 DC offset and about 300 mV of AC amplitude, at 250 kHz. This is my first venture into electrical engineering and I’m having a good time, but alas, my first circuit does not work.

After doing some research on op-amps, I bought a NJM072D because it has enough gain bandwidth product & slew rate. But for some reason, after placing it in a non-inverting configuration with a 0-5 V supply, I’m getting a constant 3.4 V at the output.

I saw this post, so I decided to put a capacitor & resistor at the input, but the problem still persists.

So then I went back to you guys and found this post. And I think I’m having a similar problem?

The common mode voltage is +/- 10V on the data sheet and it was supplied +/-15V, so am I correct in saying that this op-amp will only accept inputs within 5 V of either side of the power supply? Why  does this requirement exist? I have a 0-30 V power supply, so can I simply use that to power then op-amp and then offset the input to be above +5V and below +25V?

Here is my schematic:


texts: What is difference? The name of IC's are punched or printed or stickered on top of it

texts: I've seen in some IC's the name of it is 'printed' on the top side. But in some IC's the names are 'punched',they have impressions on the IC. And in some cases, a 'Sticker or a Label' has been 'pasted' on the IC. What is the difference between these types of Naming methods? does these 3 types differs in quality? or somewhat...


texts: Using linear and switching regulators in parallel for servos and microcontroller

texts:
I'm just wanting to confirm that this circuit would be safe/reliable to implement. I'm hoping to run two servos - one 6V one 7.4V - in parallel with an ESP32 dev board with built-in linear regulator, from an already regulated 7.4V source. Each regulator is a store-bought module with all surrounding circuitry.
The first switching regulator is pretty tolerant to current draw so I'm not too concerned about voltage sag under load (also servos using maximum stall current will be unlikely). Am also not too worried about voltage ripple to each servo from the switching regs. I've heard that sharing current can be an issue between linear voltage regs in parallel, so am hoping a switching reg doesn't have the same problem and have used it in place.
I'm pretty sure I should also have Schottkey diodes on each separate voltage line but wanted to confirm if any other problems may arise. Appreciate any feedback, thank you.


texts: What exactly makes ICs have different operating temperature maximums?

texts:
What exactly happens to an IC that is (for example) specified at maximum 85 degrees C? Also, being made from I assume similar materials, how is it possible for another chip to have a higher rating like 105 or 125 degrees C?

Edit: my question title was originally "What happens when an IC goes over it's maximum operating temperature specification?" but I have changed it to reflect the text of my question


texts: Turning an inductor into transformer and leaving the secondary open

texts:
Let's say I have an inductor of whatever type (ferrite core, air core). This inductor is a part of a circuit, an oscillator for example. Now I wind some magnet wire around it and I leave the ends unconnected so that this new winding is an open circuit.

Now the inductor is essentially turned into a transformer with the primary coil acting as an inductor in the bigger circuit and with the secondary open. I have learned that the product of voltage and current across the primary and secondary windings must equal to have conservation of energy. But as the "secondary" is now open, it has zero current, so the primary should have zero current too! If the "transformer" was previously an inductor in another circuit, does it mean that the inductor (and therefore the circuit) stops working (stops conducting, except for maybe some small magnetizing current)? This does not sound logical, I would assume that the new winding makes no real difference to the circuit, but how do we get around the fact that the inductor is now essentially a transformer?


texts: Is there a connection between Drain-Source voltage and Gate voltage?

texts:
I have an IRF530 n-channel MOSFET with me which I intend to use to control speed of a 450mA motor from my AVR controller. The controller can either be  that can either run at 5V or 3.3V. I intend to PWM the voltage at the gate of MOSFET to see how the speed of motor reacts to that.

But before doing that just to do a sanity check I hooked up the power supply module to my breadboard that supplies both 5V and 3.3V. I checked the current rating of the power supply module and it said it can deliver up to 700mA of current. So the power from rail (5V) goes to motor, from there it goes to my multimeter and then at the drain of the MOSFET. The source of the MOSFET was connected to Ground. I then gave a stable 5V to the gate of the MOSFET. The current flow stabilized at around 280mA. I then changed the voltage at the gate to 3.3V (drain to source voltage stayed at 5V). The current flow stabilized at 240mA this time. If I remove the MOSFET and just directly connect the motor to the power supply, the current flow stabilized somewhere around 360mA.

Now I have this question:
1. When the supply is capable of delivering up to 700mA why just ~300mA flow through? The power supply module is fed by a wall wart adapter which says maximum current of 500mA. But still it could go higher but it didn't? IRL530 datasheet says it can deliver up to 22A of current so the limiting factor shouldn't be the MOSFET. The graph in the IRL530 datasheet says that at 5V gate voltage and 5V drain-source voltage close to 22A should be able to flow through. But I am new to MOSFETs. Is there a connection between the gate voltage and drain-source voltage? What is limiting the current flow here?


texts:
I would like to create an inverter because I would like to have an inverse switch, that is: my circuit should only work when some signal current does NOT flow. This is even mechanic: When a certain switch is NOT set, I want no current to flow at all.

The only idea that I have right now is using an NPN transistor in parallel with my circuit, while the circuit has a higher resistance than the collector-emitter part of the transistor. I could then connect the switch to the base of the transistor. If closed, the main current flows through the emitter-collector. But the down sides clearly are that:

1) current flows, nonetheless

2) a certain current will flow, according to the resistance, through my circuit anyways

My circuit is battery-powered and I would like to not have the battery be consumed at all. I have a 3V coin cell and, without use, it should last weeks or months.

I do not need an electronic inverter, it could also be mechanically triggered (my application is that I have a box and I want to have LEDs glow when it is opened... when the box is closed, I can have contacts closed, i.e., a closed switch; but I cannot close a switch when the box is opened)

Any ideas welcome!


texts:
This is a circuit for a remote control toy receiver. Can someone help me understand this. Connecting the antennae to the collector makes no sense to me. RF is my weakness.

Datasheet where this came from is here, page 617.
http://www.bitsavers.org/components/samsung/1990_Samsung_Linear_IC_Vol_1_Audio_CDP.pdf

simulate this circuit – Schematic created using CircuitLab


texts:
Considering 74AUP1G07, I was wondering why this design, which I recently came across, supposed to be correct.
since I'm not allowed to share the schematic, I will describe it:

on separate part of the schematic we have a signal "DDR_VTT_CTRL" that starts from an off-page connector, and passes through 0 Ohm resistor and ends with a wire named VDDQ_VTT_MEM_EN
on another separate part, we have "DDR_VTT_CTRL" coming from an off-page connector, going through "A" input in 74AUP1G07. while from the Y input we have a pull up resistor where its node is connected to 0 Ohm resistor and ends with a wire called VDDQ_VTT_MEM_EN.
Note: 74AUP1G07 is marked as EMPTY.

looks like DDR_VTT_CTRL and VDDQ_VTT_MEM_EN edges are shorting the whole device (while R10501 is 0 Ohm). what I am missing here?


texts: What does it mean to "swamp" a radio signal?

texts:
Context: It frequently happens that when a particular brand of RC transmitter and receiver are too close (within a meter) the two units lose connection.  The recommended fix (which works) is to move the two units farther apart, and the explanation usually given is that the signal is "swamped".

What is "swamping" in this context? Is this a commonly observed phenomenon in radio communications?


texts: Adding Raspberry Pi Hat edge-cuts and holes in Kicad (after schematic capture)

texts: I'm looking for a way (in KiCad 5x) to build a Raspberry Pi HAT around a design that has already been completed.  That is, I did not start with a Pi Hat TEMPLATE ... I hope to find a way to add it after the (schematic capture) phase. I need edge cuts , hole placement and connector alignment that is known to be correct. I see its easy if you start with a Pi HAT TEMPLATE but I need to get the dimensions right AFTER the design is completed. How could I do this in KiCAd?


texts: Predict channel strength through Hidden markov model

texts: I have to provide noise variance,channel bandwidth ,channel bandwidth’s average power received and fast fading observed as my input to hidden markov model how can this be done


texts:
This SPST switch is labelled on the box as "Rated 10A at 125VAC or 6A at 250VAC".

Is there a calculation as to the amperage it will handle at 12V DC?

(update) As JYelton points out, a naive assumption would be that the switch capacity would be a simple function of current flow, implying that the switch would handle 100A or so.  Why is this not the case?


texts:
Why people choose to buy Arduino when they can get a cheaper and better dev board?

For example, Arduino Uno with ATmega328 has only 16Mhz clock speed, 32KB Flash and 16 IOs costing 20£.

Where as for 10£ you can get STM32F4 DISCOVERY with 32bit ARM Cortex-M4 having 168Mhz clock, 1MB Flash and 100 IOs?


texts:
What are the F-parameters, how are they computed in CST and what is the relationship between S- and F-parameters?
In CST, they can be obtained, when running the integral solver and having a farfield-source imported. However, because I have no other active port, I cannot see the S-parameters. Those F-parameters are also having a real and an imaginary part, being dimensionless, like the S-parameters.
I suspect that the reference signal might be somehow normalized, but it is just a guess.
Thank you!


texts: Processor design: turning blocks on/off dynamically to save power?

texts:
I was wondering if this is possible and if it is done in current designs. Seemed like an interesting enough idea to me. Here's a little diagram I made to help try and explain:

So let's say I'm clever and I build a bit of hardware that tracks the number of floating point operations I've done lately. It tells me, hey, you haven't done any FP operations in the last 2000 instructions! And then decides to "power down" the whole floating point pipeline hardware. Of course when a FP op does come up in the instruction queue, it needs to turn that power back on, maybe with a delay.

Does this make any sense? Can you "power down" specific parts of your chip and extract real power savings? How (physically speaking in terms of circuits) can you power down parts of hardware? And how hard is it to power them back up?

Sorry if this isn't a good traditional question! I know it's not very specific.

Cheers


texts: Error while running linker am using TIVA C TM4C123G and IAR

texts:
I am trying to change and read my TM4C123G launchpad clock frequency to 80 MHZ using TIVAWARE libraries so here is my code:

#include <lm4f120h5qr.h>
#include <stdbool.h>
#include <stdint.h>
#include "driverlib/sysctl.c"
#include "driverlib/pin_map.h"

void main()
{
SysCtlClockSet(SYSCTL_SYSDIV_2_5|SYSCTL_USE_PLL|SYSCTL_OSC_MAIN|SYSCTL_XTAL_16MHZ);
int x= SysCtlClockGet();
while(1){  }
}

I am facing two problems the first problem there is an error while compiling this code the error is:

  Error[Li005]: no definition for "SysCtlDelay" [referenced from C:\Users\ZMK\Documents\TIVA C\IAR\TM4C FREQUENCY\Debug\Obj\main.o]

where SysCtlDelay() is a function and its definition is in the driverlib/sysctl.c included in the top. so I don't know why this is happening!!

the second problem is while debugging the code the local variable X doesn't show a value it only shows an unknown value, I tried to make it volatile but nothing changed too!!

thanks in advance.


texts:
What would be the main advantages of constructing an astable multivibrator with two
CMOS inverters? Can these semiconductor
devices be declared to introduce small parasitic capacitances to the circuit?


texts: single-capacitor oscillator choice for digital theremin

texts:
Intro

One of the pupils puzzled me with a question of building a theremin - a basic musical instrument which has a pitch manipulated by moving the hand around the vertical antenna.

Due to specifics of our course (and skills of our pupils) I proposed to create a digital solution, like this:

we have an oscillator with antenna attached to one of its capacitors
the oscillations are fed to counter input of arduino, which generates sound from the preprogrammed waveform, with the frequency depending on the values from the counter

Well, the part with arduino works right now. We also have tested ultrasonic distance sensor (instead of antenna+oscillator), but it is not very handy.

Oscillator - what I'm trying

But what oscillator to use? The simplest thing I've taught my pupils is the 555-based generator, so I've tried to plug one with a very small capacitor first - like this:

Here C = 5pF   R1 = 400k   R2 = 1k, the output from 3 goes directly to arduino counter input.

This works, giving the frequency of about 200 kHz (decreasing by about 3% when hand is about 1 cm from antenna). It should be higher (judging by R1*C, though there is also capacitance of antenna) and I want it be higher (for more accurate count) - however I could not increase it by changing R1. With 100k it is only about 250 kHz. With 21k it is only marginally higher and seemingly stops to react to waving around antenna.

This is puzzling. I think I'm either doing something wrong, or can't get more frequency due to some limitation of the chip (probably it may work better at higher VCC).

The question

So I'm seeking for either advice to improve this design, or suggestion of some transistor based oscillator. The most familiar thing is a symmetric multivibrator, but I'd rather prefer something with a frequency depending on a single capacitor (either in LC or RC setup).


texts:
I have a questions regarding a simple schematic.
I would like to calculate the total angle (φ) and power factor (cos φ) of this circuit and the total impedance (Z).

-- Not using the complex-method (jω)

Values are as follows:

\$ R_{L} = 120 Ω  \$

\$  L  = 800 mH => X_{L} = 251 Ω \$

\$ R_{C} =  40 Ω  \$

\$ C  =  16 µF => X_{C} = 199 Ω \$

\$ f  =  50 Hz  \$

My initial thoughts were to do a normal calculation for parallel connections, where I would only take the length of the vectors.

\$Z = {\frac{Z_{1}*Z_{2}}{Z_{1}+Z_{2}}} \$

Where \$ Z_{1} = \sqrt{R_{L}² + (X_{L})²} \$ ;
\$ Z_{2} = \sqrt{R_{C}² + (X_{C})²} \$

Which gives me a total of \$ Z = 117 Ω \$

And then calculating the angle as \$ arcsin(\frac{X_{L}-X_{C}}{Z}) => φ = 26.4° => cosφ
 = 0.89\$

Which is WRONG. The correct effect factor should be \$cosφ = 0.85\$.

Could you please explain what parts I've misunderstood and give me any ideas to solve it. Im able to solve the circuit using the jω-method but by using that I feel like I'm missing fundamental parts that I would be better off learning and applying with the regular vector calculations.

simulate this circuit – Schematic created using CircuitLab

EDIT:
I think I could do something like
\$Z = {\frac{\sqrt{X_{L}² + R_{L}²}*\sqrt{X_{C}² + R_{C}²}}{\sqrt{(X_{L}+X_{C})²+(R_{L}+R_{C})²}}} \$

In that way, I'm splitting the real and imaginary parts and taking them seperatly. And then for the angle, I'm thinking something along the lines of \$ arg(Z_{1}) - arg(Z_{2}) + arg(\frac{\sqrt{(X_{L} - X_{C})²}}{\sqrt{(R_{L} + R_{C})²}})  \$ but unfortunately with that I get a degree of φ = 56.25° => cosφ = 0.55.
How should I do to calculate the correct effect factor, angle and impedance? What am I missing?


texts: Finding Wilson Current Mirror Output impedance

texts:
I am trying to confirm my output resistance calculations with my simulation.

How can I measure the output resistance seen by Q4 in order to confirm my calculations?

How I measured \$r_{o2}\$ (image 1)

How I measured \$r_{o4}\$ (image 2)

My total output impedance as seen by Q4 can be calculated using the follow formula:
$$
\begin{split}
g_{m4} &= 0.02267\mho\\
r_{o2} &= 42\mathrm{G}\Omega\\
r_{o4} &= 2.95\mathrm{G}\Omega
\end{split}
\Rightarrow
\begin{split}
R_o &= r_{o4}(1 + g_{m4} \cdot r_{o2})\\
  &= 2.95\mathrm{G}\Omega(1 + 0.02267\mho \cdot 42\mathrm{G}\Omega)
\end{split}
\Rightarrow
R_o = 2.7258\cdot e^{18}\Omega
$$


texts: Industrial contactor frequency influence

texts:
I'm thinking of using industrial motor contactors at the output of a 3-phase electrical generator.
An example here : CONTACTOR DATASHEET

The only difference /  problem is that the electrical frequency of that generator is in the kHz (1-3) range (high-speed generator).

All the infos available for these industrial contactors are given for 50 or 60Hz but no mention of a maximum (or minimum...) frequency.

Would it have no influence at all as long there's a zero voltage crossing every now and then?
Should I derate the current given for 50/60Hz somewhat? If so, what would be the physical explanation behind that?

Thanks for the feedback,

Marc


texts: Battery Pack Design: Charging Parallel 18650s Through a Step Up Converter and BMS

texts:
I taken the necessary precautions in creating my own custom battery pack: I bought two 18650s from the same shipment and will attach a diode from each positive end of the 18650s before attaching the positive ends into one wire.

However, I am confused on how to charge the batteries when the eventually deplete, all in one circuit.

I am trying to power an item that takes a constant 5V input in order to run.

Here is my design:

More Specifically,

I am going to connect the batteries in parallel, with diodes on the positive terminals of the batteries/wires. Connect the positive wires with diodes and negative wires to form a parallel battery.
Connect the positive and negative "double wires" to the BMS B+ and B-
Connect the BMS P+ and P- output to the 5V Step Up Conveter Input
Connect the Output of the 5V Step up to a Switch so I can turn the whole system off or on.

Question:

How do I charge the parallel batteries in this circuit?

All of this circuitry is to make 5V output from a two 18650 batteries in parallel, so how do I get power in? Would I make a Y Split at the P+ and P- of the BMS output, maybe?, not sure if that even makes sense?
Do I need diodes, wouldn't I not be able to charge the batteries if I put in diodes, blocking current from coming in?
Is the switch in the right place?


texts: Before storage why should a Lithium Polymer battery be charged up to only 40-60%

texts:
While storing a Lithium Polymer battery cell or a device with a Lithium Polymer battery why should we make sure to discharge the battery to 40-60% (and only then put it to storage)?

What happens if you store a Lithium Polymer battery with 100% charge and WHY DOES IT HAPPEN?

I am more interested in "WHY DOES IT HAPPEN" part and if someone can explain to me in terms of Chemistry and Electrical Engineering involved I will be very glad.


texts: Sequence of evaluation in the following non blocking code?

texts:
I have the following verilog code that I came across and trying to find the sequence of evaluation. What value does 'A' have at the end of a cycle and after 5 cycles, when the value of A is 'x' at cycle 0.

always @ (posedge clk)

A <= 1;
A <= A+1;
B <= A+1;

I understand that the evaluation of RHS is done on the posedge and the assignment happens at the end of the cycle. What value would A have after the assignment? Is it '1' or 'X'?

Also does adding the delay to the statements act as blocking for the following code?

always @ (posedge clk)
begin
#5 A<=1;
#5 A<=A+1;
B <=A+1;
end


texts: STM32 - How to run the USB DFU In application programming, in Linux command line

texts:
I'm using the STM32CubeProgrammer application in Ubuntu 16.04, running the "STM32_Programmer_CLI" in USB DFU mode, to flash STM32H743 device, with BOOT0 connected to 3V3.
Example for flashing command: sudo ./STM32_Programmer_CLI -c port=USB1 -w /FilePathHere.hex -v -s
It works well when the hardware is in bootloader-ready mode, get flashed then it runs the core and open's cdc usb: /dev/ttyACM0.

The question is how should I flash it while the application is already running. I understand this feature should ne implemented in the GUI version, but it's not mentioned how to use it in linux command line.


texts: I am trying to build a circuit that has wheels rotating that are connected to a motor. This motor will then generate 5 Volts to a battery which then charges lets say a cell phone. I have two wheels that have motors on both, that are connected in series which is then hooked up to a portable charger and a multimeter. I got an open circuit voltage of 5 Volts but when i connect it to the load (the portable charger), i am only getting about 1 Volt. How many motors, or of what kind, do I need to get the output to be 5 Volts under load?


texts:
Can anyone tell me if this is ok and it is just a drawing issue or I have a real problem when ordering my pcbs?

My understanding of solder mask expansion is the minimum distance between a track/pad... and the next one (Isn't it?) So, I wanted to have avery wide track and put instead of a small distance to the next one, a bigger one. But I see the bone white line inside of the copper track...

How can I make this distance bigger? I want to create a gnd plane and the distance seems to small for me (Big track is AC current)


texts: At what resistance do I not see a voltage drop across a resistor?

texts:
If I have a circuit like this and measure the voltage drop across the resistor I get a value, regardless of what resistor I use:

However, if I stick a piece of wood in there instead of the resistor I get nothing. My intuition says there must be some resistance value between wood and conductor where the voltmeter switches from reading the voltage source to reading zero. Is that how this works? Is there some high resistance value where the voltmeter reads a fraction of the source voltage? Is my understanding of electronics terribly wrong?

EDIT: I suspect the answer has to do with current and the voltmeter not being an ideal, infinite resistance machine, but I can't get from there to the answer.


texts: When wiring a European (Schuko) plug, what thing should I focus on not to mess up?

texts: I know this might be a dumb question, as wiring a plug isn't some rocket science, but I am wondering if there is something not so obvious that can go wrong, or any tip at all for me to care when doing a cable assembly for a custom power extender cable?


texts:
I want to measure temperature of an oven using a thermocouple. The maximum change in the temperature will be 1oC/s. The amplifier section will already contain a low pass filter, but I want to put an extra passive RC filter very close to the ADC input pin of PIC32MX270F256B. However, I can't decide a suitable resistance value (R) because I can't find the input impedance of the ADC pin neither in the datasheet nor in the family reference manual. What range of resistance value can I use here?

simulate this circuit – Schematic created using CircuitLab


texts: Is there a spice directive to export waveform data in LTspice?

texts:
http://www.linear.com/solutions/1815

The above web-page explains how to export the waveform data to a text file. You basically run the LTspice simulation, clicking on the waveform window, go to File>>Export, chose the variable to be exported and then specify the filename (usually a .txt is convenient). I am looking for a spice directive (or any other command) to automate this process.

I can run the spice file through LTspice using the command line. However, to export the waveform data, I still need to access the GUI. This is botching up my plan to use a python script to simulate the circuit for varying parameters. Any insights are appreciated.


texts: How can you handle noise in multi-level pulse amplitude modulation?

texts:
When using multi-level Pulse Amplitude Modulation to transmit a message, how should the receiver handle noise?

For example, suppose there are 5 levels (0,1,2,3,or 4) and the following message is transmitted: {2,5,1,4,0,0,0,2,3,2,3,2,3}

On the receiving end you get:

{2,5,1,4,0,0,0,2,2,3,3,2,2}, which is clearly incorrect.

So the amplitudes that are a distance of 2 or more get received correctly, but amplitudes with a distance of 1 from each other are more difficult.

What are some techniques used to handle this kind of noise?


texts: Constant low charge in PCB even when disconnected

texts:
I have a very strange issue that I can't explain but maybe someone can shed light.

I cut a homemade PCB on my CNC that basically just connects a couple Arduinos to a Raspberry Pi using i2c. It's mostly breakout board stuff. I actually have two variants of it that connect via a board connector. Both PCB's have the same issue:

There is a small voltage of exactly 0.37V on the circuit - EVEN when disconnected. But what even spookier is that the +5v voltage line for the Arduinos pull 2.7V even when there is no direct connection between the Raspberry Pi voltage powerline.

I thought first that I soldered a short circuit or something like that but I couldn't find anything - all traces are clean. I have a feeling that somehow there is some flux under the connectors for the Arduino and they short circuit some of the stuff.

But the 0.37V on both boards makes no sense... I tested with 3x different multi readers and they all show the same.

I know it's Halloween pretty soon but that's spooky.

How can be there Ba constant charge without electricity?


texts: Will this Optocoupler and MOSFET be able to deliver 5V +2A?

texts:
I'm working on controlling the supply of an amplifier board with 5V 2.4A power in a manner which tries to eliminate noise from the speaker. I asked a few professors at my university and they said that an optocoupler would be the best way. Since I need a higher amperage, I also need a MOSFET or transistor or some sort.

The following circuit is the result of my research and testing in Livewire. The idea is that this will then be my first custom PCB which we'll etch in the lab and then incorporate into my refurbishing of an old vintage radio.

Q1: IRL520 (or similar) MOSFET

Q2: 4N35 Optocoupler

CN1: Line to 5V 2.4A power supply

CN2: Cables to On/Off switch

CN3: Power line to amplifier, needs at least 5V 2A

CN4: Control lines to 3.3V microcontroller, (Rasp0W or Arduino)

R1: 1k Ohms to make sure the gate isn't triggered unless microcontroller is HIGH

R2: ~250 Ohms to make sure the optocoupler's LED (Vf~=1.5V) only gets 10mA off a 3.3V line.

When I simulate the circuit by:

adding a 5V source at CN1
shorting the terminals in CN2
adding a lamp/led at CN3
adding a 3.3V source at CN4

The circuit remains closed when the microcontroller is LOW, and when it is pulled high, the voltage to the gate of the MOSFET reads 3.3V (wire marked with purple). However, it doesn't indicate that the light bulb at CN3 lights up.

My line of thinking is that Livewire doesn't know that I'm using a logic-level MOSFET, therefore thinks that I need at least 5V to trigger the gate.

Will this circuit be able to deliver 5V 2.4A to the amplifer at CN3? Are the parts adequate or are there better options out there? Thanks!


texts: Identification of a very strange SMD component

texts:
Could anyone help me identify what component this is? It is the white component with a black stripe.

What ever it is, it appears to be a open circuit. I couldn't measure any resistance (or capacitance). One pin of the connection has DC voltage while the second pin has 0 DC voltage.

(Also the backside of the component is plain white, not sure if it helps but just in case)

Thank you in advance


texts: Could this white paste be the cause of intermittent power in a Dell LCD board?

texts: I took apart my Dell 17" to try to repair it. I expected a burned out capacitor or something else obvious but the only thing I found was this white paste touching several components. Could this be the cause of the problems or is it generally non-conducting?


texts:
The first image shows the circuit we start with. The second image shows the circuit in which I had the load removed (as I know from Thevenin's theorem).

After that I'm getting confused because of the 2 voltage sources not knowing what to do. I tried finding videos on You-Tube but it's difficult to find a decent one that I can understand.

As you can see I'm in a rather terrible predicament and am clueless as to what I should do next that's why I would like to ask if there is someone to just tell me how to proceed.

If there is something missing I am willing to provide any additional details if needed.

Also it is important to note that I'm trying to find the current,power and voltage across the resistor R3.

Thank you!


texts:
Suppose I am trying to solve the following circuit, where \$V_i\$ is the potential seen from the top branch to the bottom branch (which is 'grounded') and \$V_o\$ is the potential across \$C_2\$:

If I want to find the transfer function \$\frac{V_o(t)}{V_i(t)}\$, I can of course go through the laborious method of obtaining the voltage drop across the top branch and calling it \$V(s)\$ and then substituting this into an equation in terms of \$V_i\$ and \$V_o\$, respective of the whole circuit, finally obtaining the Laplacian transfer function:

$$\frac{V_o[s]}{V_i[s]}=\frac{RC_1s+1}{RC_2s + RC_1s + 1}\ \ \ \ \ (\text{Eq 1})$$

I have been told that I can also do this by considering impedances though?

How would I do this?

I guess I would consider the top branch parallel combination of R and C as:

$$Z_\text{total} = (1/R+1/X_c)^{-1} \equiv (1/R + j\omega C_1)^{-1} = \frac{R}{1+j\omega RC_1}$$
And then consider this in series with the second capacitor?

Further work:

The voltage drop of the top branch must be:
$$V_s(t)=i(t) \times \frac{R}{1+j\omega RC_1}$$
Laplace transform gives:
$$V_s(s)=I(s) \times \frac{R}{1+j\omega RC_1}$$

\$V_i(s)=V_s(s)+V_o(s)\$, just by KVL. We know that \$V_o(t)=i(t)\times1/j\omega C_2\$ and Laplace transforming natürlich gives: \$V_o(s)=I(s)\times1/j\omega C_2\$. Therefore, the transfer function is something like:

$$\frac{V_o}{V_i}(s)=\frac{\frac{I(s)}{j\omega C_2}}{\frac{I(s)R}{1+j\omega R C_1}+\frac{I(s)}{j \omega C_2}}$$

Is this somewhere along the right lines? I don't think it can be, because to me, there is no way to now cancel out \$j\$ and leave myself with \$\text{Eq 1}\$?


texts: Measuring an analogue voltage with isolated ground

texts:
I am working with a solar EV (car), and I need to measure the throttle pedal signal. The throttle peddle is essentially a 10k ohm pot between 5v and gnd on the motor controller. (0-5V signal).

As per the rules, the high voltage and low voltage circuits in the EV must be isolated. The exact spec is 100 V ohm resistance isolation from both terminals of the high voltage battery bank to the low voltage circuit, where V is the nominal voltage of the bank.
The bank nominal is about 110V so afaik I need to have at least 11k ohm resistance to the HV side. The low voltage circuit (which runs my electronics) is powered from an isolated DC-DC converter.

As such, the problem as it stands is that the HV gnd and LV gnd are isolated, so I cannot feed the throttle signal directly to my MCU. I can see a couple of solutions but I'm not sure what is the best/easiest/quickest(in terms of implementation and signal delay)/most reliable solution. I think I would prefer an optically isolated solution if possible.
My ideas:

Isolated op-amp (TI ISO124 http://www.ti.com/lit/ds/symlink/iso124.pdf ? Problem: expensive, don't have part on hand, never used before.. simple solution though)
Linear opto-coupler (IL300 , no part on hand, complicated, never used before)
ADC - opto - DAC (use small MCU on HV side to do ADC and send over opto-coupler serially. Easy but complex, potential signal delay?, will take time..)
Volt to Freq -> opto -> MCU(LM331 : Dont have part on hand, never done before, have to write freq conversion code for MCU. Simple however)

Or non isolated:

Differential instrumentation amp, tie HV gnd to LV gnd at amp with high value resistor (INA128 : Have part on hand, simple solution with minimal parts. Disadvantage of no isolation but maybe not a problem because it complies with the rules AFAIK. Potential noise issues? Potential for fault through high value resistor? Potential for damage to amp if HV gnd rises with respect to LV gnd?)
Option B ?

Not sure which path to take from here. Short on time and need a reliable solution. Feel like there is a super simple solution I'm just missing? Perhaps the diff amp solution is fine and I'm just being paranoid? Any suggestions or resources would be appreciated!


texts: I have a farm with solar panels. Right now, it is powering the house, and excess gets sold to the electric company. I was thinking that instead I could have the excess power bitcoin mining equipment. Is there a way to essentially turn off a specific line when the house is drawing over a certain number of watts? I am thinking some sort of relay. I am not an electrical engineer, and this may not be the right place to ask this, but I would appreciate any insight. The actual problem is more complex than I described, because it also depends on how much is being generated at that moment. But, basically, I want to turn the equipment on when solar power > bitcoin mining power ( a constant value ) + house power.


texts: What is the difference between wavelength and period?

texts:
Currently I have some problems with basic terms and need some help please.
I'd like to know:

What difference exists between wavelength and period ?  When should I use the name wavelength and when period ?


texts: How to control voltage and current output for flyback converter with varying load

texts:
I managed to design a working flyback converter with a feedback. I have one last obstacle and I hope a kind soul is able to help me out.
I placed a dummy load, for instance, I dictate it as 1 ohm. The waveforms are as attached.

Output 1: 12V, 12A
Output 2: 5V, 5A

Apart from connecting an additional resistor, how do I reduce the current for output 1 from 12A to 9A?
Is there a way to maintain the values as the load increases. I observed that an increase in load reduces the current.
How would I do an additional current control feedback. A hint would be great for me to get started

Below are some info that could be of help,

Np1: 100, Np2: 20, Ns1: 28, Ns2: 12, Lm: 788 micro F, Vs = 230V, Freq = 50hz, Switching Freq = approx 100Khz, Vref @ TL431: 2.5v
Dmax: 0.33,


texts:
This feels like a silly question, but after taking apart some of our 6W 12V DC power supplies I've noticed that none of them are fused.

Out of curiosity more than anything else, I'm wondering why a fuse isn't required for these power supplies - for the record these PSUs are:

Input: 100-240V~50/60Hz
Output: 12V DC 500 mA
CE compliant (tested by a UK test house rather than just relying on
manufactures word)

UPDATE:

Thanks for the responses, so on closer inspection (and based off comments and answers) I think I have found the fuse like component on each board.

My confusion came in that I was expecting a removable fuse as found in a standard 3-pin plug socket.

If someone were to ask me what these were fused to though what would I say? Whatever the input current is stated as? 0.18A?


texts:
I want to build a toy. The initial build will be a prototype but if the idea 'sells,' I want to build en-masse.

For the prototype, as I do not have (beyond what I learnt at Uni) industry experience, I want to make use of freelancers for designing and programming the board.

The toy basically will play sounds based on which button is pressed. The sounds are recorded sound/music. I am currently working with a freelancer who is designing a PCB for this but we are stuck on how to store the sounds. At the moment, SD card is the recommendation but I know that this is not an option due to cost (if one is producing en-masse.)

Can someone please recommend a possible solution? The freelancer has also mentioned possibility of using a semiconductor memory but says that the programming for this will be difficult. Are there other options?


texts: triac controlled voltage preregulator (mains)

texts:
At present I am rebuilding an 1990 Elektor powersupply with a triac controlled preregulator able to handle inductive loads. My intention is to modernise the design but first I want it to be operational. The preregulator does not work as intented resulting in an hot transformer.

With the DUT connected to a safety transformer 1500W I hooked up a resistive load in the form of a 230V 250W halogen lamp.
I was able to look at the some signals and found that the triggering in the quadrants 1 and 2 look ok. Triggering in the quadrants 3 and 4 behave differently.

Accros R33 the quadrant 1 and 2 pulse train is visible but appart from a few blibs no action in the quadrants 3 and 4.

Looking at the discharge slope of C1 I have have the feeling that Tri2 is not firing well in quadrant 3 and 4 . But I can not find the reason.

The information from the datasheets for the BTA41-800 the TIC206D and the DB3 did not gave me any clue.

The Elektor design appears to have originated from an SGS THOMSON design found in http://www.datelec.fr/secteur/ST%20AN308.pdf

The image on the ocilloscope is measured accros C1 ( in the bridge)


texts: I'm looking to power 5 Arduino Nano devices and an Uno. I'm wondering if I can power the devices with one power supply. I know that I'll need to use the VIN pin with 7-12v since the 5v will be used for another device. Is it possible to power the 5 Nanos with one single power supply?


texts: Circuit's Load Falling Below Voltage Regulator's Quiescent Current

texts: I have a MCU that can be put into a sleep mode that pulls only 5uA, but my voltage regulator has a quiescent current of 50uA datasheet Normally the MCU pulls 300mA or so, but I am wondering what will happen to the voltage regulator if the MCU goes to sleep.  Will it cease to produce any current on its output?


texts:
I'm trying to solve a transistor problem, but I'm stuck on the I2. Is I2 equal to I0 ? The question is: The transistor circuit in Fig. 3.45 has β = 80 and VBE = 0.7 Find V0 and I0 . Answers : 12V, 600 mA.

My equations:

For \$I_1\$,

\$-1+120 \mathrm{k} \cdot I_1 + V_{BE} = 0\$.

Therefore, \$I_1=2.5μA\$.

For \$I_3\$,

\$10\mathrm{k} \cdot I_3+20+10\mathrm{k} \cdot I_3 - 10\mathrm{k} \cdot I_2=0\$.

\$2\left(I_3\right )-I_2=-2\mathrm{mA}\$

If \$I_C=I_B \cdot \beta \$, \$I_B\$ is equal to \$I_1\$, isn't it ?

However, I get \$I_2=\$ 0.8μA


texts: Using Electric Motor/Generator Instead of Inverter to Deliver AC Mains from Batteries / Solar

texts:
I am exploring/researching Solar PV systems and the possibility of setting up a solar installation company. DC/AC inverters are very expensive and I am trying to find a cheaper solution.

Question: How feasible is it to remove the Inverter from the solar setup and instead use the battery bank to power a motor that is directly coupled to an AC generator to deliver AC mains power to a house?


texts: Nodal Analysis Current Direction Matters

texts:
simulate this circuit – Schematic created using CircuitLab
I'm currently doing a question and it appears to me that the direction of the current matters.
For both the batteries I've assigned a current direction that goes from the - to + terminal. So both batteries push the current into node V1 and the only exit is via (V1-0)/5.
However, I keep on getting it wrong. It appears to me that the current direction matters! But everyone online states that is not the case!
Can someone please explain what I'm doing wrong. I'm totally lost.


texts: how does ceiling fan remote implement reverse function?

texts:
Most ceiling fans come with a remote control transmitter/receiver pair.  The transmitter is hand-held or wall-mounted, and the receiver is installed in the ceiling box.   Input to the receiver is a 2-wire circuit from the house wiring (neutral & hot, white & black) and output is white/black/blue, that is, neutral plus hot for the fan and hot for an optional light.

My question is, how does the receiver work, specifically the reverse function ?   The light control is probably just a triac like an ordinary light dimmer, and the fan speed is likely controlled using switched capacitors (as described in How do ceiling fan controllers work?).   The mystery to me is, how does reversing the fan direction work ?   (Some fans include a reverse switch on the fan motor itself, but many do not, so the remote receiver must somehow accomplish this).  I doubt it reverses the neutral and hot connections to the fan motor (I don't see how this would work, and it may violate code).   Does it somehow send a code to some logic in the fan motor ?

Note (as pointed out below), this question really boils down to: how do you reverse a ceiling fan motor using only the two wires going to it ?


texts: Using stop mode in freeRTOS on a STM32L0 and waking up using EXTI interrupt

texts:
I want to make a low power device, running freeRTOS.
There are 3 threads, which I planned to suspend normally into stop mode and resume execution depending on an EXTI interrupts.

I intended doing so by this Idle hook

void vApplicationIdleHook(){
    trace_printf("Enter Idle \n");
    HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
}

Which should be woked up by this Interrupt

void initInterrupts(){
    HAL_NVIC_EnableIRQ(EXTI0_1_IRQn);
}

void EXTI0_1_IRQHandler(void) {
     __HAL_GPIO_EXTI_CLEAR_IT(BTN_PIN);
     trace_printf("interrupt\n");
     xTaskResumeFromISR(thread_handle);
}

It's working so far, as my power consumption drops from 1.7mA to 1.5mA somehow I suppose, but I encounter two problems:

that the RTOS doesn't seem to kick in anymore
the debugger loses it's connection to the board

I do not know, what I am missing. Which are the general steps for enableing RTOS after entering the stop mode?

Concerning the debbuger connection, the print statement reaches it's way somehow to the PC, but openOCD complains by

Info : Previous state query failed, trying to reconnect
Error: jtag status contains invalid mode value - communication failure
Polling target stm32l0.cpu failed, trying to reexamine

I have set debbuging register as this, but it does not seem enough. Can I even hold the debugging bridge in stop mode? I mean the DBGMCU_CR_DBG_STOP bit makes me suppose yes, but what options have to be set therfore?

__DBGMCU_CLK_ENABLE();
DBGMCU->CR |= DBGMCU_CR_DBG_SLEEP_Msk | DBGMCU_CR_DBG_STOP_Msk | DBGMCU_CR_DBG_STANDBY_Msk;

For me it is very confusing, that the MCU still can send to the PC, but the openOCD fails resuming or holding the connection.

Thank you all to much for any hint.


texts:
I have a small question. I was doing a lab with MOSFET 2N7000. The circuit is something like the one below:

There was a question asking if the gain should change if the resistor R1 was changed to 10K? The teacher said the gain should change (slightly) but I did not see any change on the Oscilloscope.

Can someone please advice whether the gain would change if R1 is increased?


texts: What is the formula for finding temprature from resistance? I want to use it with PT 100 / 500 / 1000 .


texts: Why is this MOSFET Differential Pair On on the Right-Hand Side?

texts:
Could someone please explain to me both the qualitative and quantitative analysis of the following MOSFET differential amp circuit, to explain why Vs = -0.5 V and the Right-Hand MOSFET is "on"?

EDIT - a little more detail

The goal of the circuit is to have M2 ( left-hand side ) MOSFET turn on at Vg=~0.25V instead of Vg=~0.7V with point S tied to ground. The current source was the only method I could think of to achieve this.