texts:
I'm not sure I know the proper term or how it is in other parts of the world, so I'll just explain in detail:
In my country every house has a "fuse box" - the electrical entry point to the house. This is where the electrical cables first enter the house and split off into the different electrical sockets. This box is also fitted with fuses that protect the cables from excessive loads by tripping/triggering and having to be replaced or switched back on.
Since we are (supposedly) in the 21st century I was wondering if they don't make some kind of "smart" fuse boxes - such that they would report how much energy each circuit is consuming and alert you if you are approaching the fuse tripping load.
I couldn't find anything similar online and, frankly, wouldn't be surprised if such a thing does not exist but I wanted to ask people who are more knowledgeable in the field.


texts:
I have came across a question where it asks if the input to SSB (LSB) modulator is mh(t) (which is the hilbert transform of m(t)),  will the of the modulator be LSB?
What I did :
I did the math and came up with an output of mh(t)cos(wct) - m(t)sin(wct) . Is this the SSB with a carrier of sin instead of cos?
This was my conclusion after trying substituting with diffrent m(t) - is it true?


texts:
This is a 40 pin display connector that was found on a mass promotion video player mailed to a house. I disassembled it and I would like to use the display for a project.

The display has the model numbers JTM 50008W12-A. The flexible circuit board has the part number JTM050N-3047.


texts: Controlling large AC machinery using small DC power

texts:
I am currently working on a water treatment machine where I need to have control over a pump and several solenoid valves. In order to do that, I am provided with a pre made controller bought from alibaba. The only problem is that the controller works with 24VDC while my pump and solenoid valves works with 230VAC..
How should I convert the 24VDC output from the controller so it can power my 230VAC pump and valves?
Is it possible to use a relay in which the 24VDC output from the controller is only used to power the relay's coil while the main circuit is powered by a separate AC power supply?

ps: I don't need to have a sophisticated control over the pump and valves, the only conditions are "on" and "off". There's no need for speed control or position control.


texts: Danger of high voltage in electroadhesion

texts:
I am currently doing my master internship to get a degree in mechatronics. For an experiment I would like to conduct, I am interested in using electroadhesion.
For those who don't know about it, the principle is easy. Get two electrodes (side to side or interlaced), put them on a flat surface and apply a high DC voltage across the electrodes. The forces are developed on a molecular level, so I won't go into details.
The electrodes are usually well separated (by a gap) and embedded in a dielectric material (silicone or overlaid in tape for the cheapest versions).
When I say high voltage, it is around 2-6kV DC, more might cause air ionization between the electrodes.

I know this process was used in old HP plotters to hold the sheet of paper while the tracing pen moves on the paper, and I remembered touching the surface of one and feeling some kind of buzzing in my fingers.
In my experiment, there might be contact between humans and the electroadhesive surface, and I am concerned about safety. The HV DC-DC converters used usually provide several kV at less than 1mA of max output current (Emco produces the C50 that gives 5kV at 0.2mA). I know a DC current around 1mA can give a slight sensation.

The question is: Provided the electrodes are covered by dielectric, will there be this buzzing feeling when touching the surface? If yes, is there any danger?
Provided there are holes or imperfections (due to time damage) in the dielectric, is there a danger, if the person touches both electrodes at the same time (with a finger crossing both electrodes for example)? If yes, what kind? Simply a shock similar to when you rub a balloon and get shocked, or something nastier?

Thanks a lot for your answers!
Sebastien


texts: How to link 3 RF transceivers to 1 antenna

texts:
I'm not an RF designer, so excuse the newbie question:

How would I link three transceivers, say WiFi and two separate bluetooth transceivers, to a single antenna.

I have found a 3-way combiner https://www.minicircuits.com/pdfs/SCN-3-28.pdf

Is this the right circuit?

Is there a better method?

How bad is it that I'm loosing a lot of power - is there a way to mitigate this (amplifier, etc.)?


texts: What's the next logical step in applying input to this FM transmitter circuit?

texts:
Last year, I posted this question about a very simple RF transmitter circuit:
Does this simple RF transmitter circuit actually work?

I built it myself, and actually remade it after I posted an answer to my own question; I applied CA glue to the coil so that it would stay around the same frequency.  Though I think that power and even temperature(or air pressure?) could alter the frequency, it remains stable for a long period of time.

Anyhow, I am curious as to how I can add a microphone or direct AUX input so that I can actually transmit sound instead of silence.

I have achieved this to some degree by connecting an audio source to a secondary coil placed next to the main coil in the circuit.  The second coil acts like an electromagnet and seems to modulate the frequency of the main coil.  This does work, though the volume of the audio is low yet it is still prone to getting distorted at a certain volume.  I'm guessing this has something to do with the frequency being only modulated in one direction(my understanding is that an FM "channel" is the center frequency for the modulation), and maybe the difference between high and low volume needs to be less significant.  I'm unsure how to word it better than that.

I want to stick to the spirit of the circuit and go with something as dirt simple as possible.  Indeed, the coil itself can act as a microphone but I've yet to make this practical or not prone to frequency drift.


texts: Tips for constructing small PCBs with only one SOIC

texts: So I'm going to repackage this breakout module for simple SPI with a bus-powered LED light strip. It seems expensive and unnecessary for advanced SMT assembly equipment and since its a small PCB with only a few SMDs. What techniques should I employ for this simple SMT assembly?


texts: A simple bit-math question on register bit manipulation

texts:
I read in a tutorial such descriptions:

DDRD |= (1 << DDD0);        // sets bit DDD0 to 1 within register DDRD

PORTD |= (1 << PORTD0);     // turn on PD0

I can understand step by step the following example:

SREG |= (1 << 7);

Above means take 1 = 00000001

Shift it to left 7 digits so it becomes 10000000

Now expression becomes SREG | 10000000

So far so good but how about again the following:

DDRD |= (1 << DDD0);

How can we analyse it step by step? If I take DDD0 as zero then 1 becomes again 1 as 00000001 and expression becomes DDRD | 00000001.

Is DDD0 simply the number 0 here?


texts: Driving 7-Segment Displays using a microcontroller

texts:
Before I start out, let me just point out that I'm new to hardware design. In fact, this is just hobby for now, but might turn into something later. Because of this, I don't follow any standards per se, but I like to be as organized and efficient as possible.

I designed a 16-bit microprocessor from the bottom-up, including the architecture and instruction set, as a hobby project. It has been implemented on a Spartan 6 FPGA and is working great. I made a casing for the processor to be used as a panel, which integrates with the DMA capabilities of the design.

One of these is the ability to choose which part of the processor you're currently observing on the data output display. This information about the currently chosen 'entity' is also to be display on a 3-digit 7-segment display, in characters. For example, 'ALU', 'STA' for Stack, 'ADD' for MAR, etc.

This is completely unnecessary, but I'd like to do this anyway, as a visual treat. Since I'm new to circuit design entirely, what I thought of first was to use an array of multiplexers to simply choose the state of the 7-segment displays depending on the input. But this would require some manual IC wiring, which I'm not too keen on doing. I tried to make a PCB, but most of the copper tracks were broken.

What I would like to do is use a microcontroller (something I've never done before) to achieve this. I have never used a microcontroller, and I'm unaware as to which particular one would be useful in the scenario. I'd appreciate it if someone took the time to point me in the right direction.

Ah, and also, the reason I'm not simply using the FPGA to drive these three displays is because I've run out of the 70 GPIOs on the development board.


texts: Op-amp subtractor: problems supplying a fixed base voltage to be subtracted

texts:
The context is that of a simple sound-level meter. An electret mike, pre-amp (transistor), amplify with a 386 op-amp, detect the envelope of the waveform, and the output the level to an ammeter. (Simple reflection of the level, with no need for a logarithmic response.)

After the envelope stage is complete, the quiet signal is at 4.0V, and with sound in the room it jumps to 4.5-5.0V. Up to there, everything seems fine.

But before I show this signal on a meter, I want to subtract the 4.0V of quiet signal, using a 741 op-amp (the photo's a bit fuzzy, but should suffice):

This requires me to provide a fixed 4.0V to R1 on pin 2, but I'm failing to do that. I tried a simple voltage divider (shown on the left), but I see two problems when I connect my voltage divider (point A, above) to the R1 resistor on the inverting pin 2:

the voltage at A drops by 1.5V
the voltage at A is no longer fixed. It reacts to sound level.

What am I missing?

My voltage divider shares the same +9V and ground as the main circuit.

Here is a link to the schematic.


texts: Low latency, high channel period wireless protocols

texts:
I was wondering if anyone can suggest any low latency  high channel period wireless protocols or devices.

I have been using the ANT and xbee chips to sample a digital signal however their channel periods are too long for my application.

The xbee takes at best ~50ms for the data to be received, whilst the ANT takes ~7.5ms at a 256hz channel period.

I would like to know if anyone knows of any device/ protocol that has a channel period of 500khz or higher preferably above 1000khz to be able to receive within 5ms consistently as at worst the ANT takes ~15ms

Cheers


texts: analog linear ramp with external pulse trigger

texts:
I am a hobbyist working on a project that requires a linear ramp generator (0VDC to 5VDC @ 120Hz) that is triggered by an external pulse. The requirement for the external pulse is so that the ramp waveform lines up with the zero crossing of the 60Hz AC power that I am attempting to "dim" with triacs (so it can potentially be used with inductive loads). The output of the ramp generator (Vo) will go to a comparator that will also look at the voltage of a voltage divider controlled by a potentiometer to fire the triacs for the appropriate amount of time during each half cycle of the 60Hz AC. The schematic below shows what I have come up with so far. I am considering referencing Q1 and Q2 to -5VDC instead of ground and using a diode clamp from GND to Vo in order to keep the output waveform in the more linear region of the RC discharge curve. I have narrowed the width of the pulse trigger at the base of Q1 to 420usec (5% of 1/120Hz), which would be acceptable, but would like to see it narrowed to 0.1% of the period if possible (8.33usec). Possibly some sort of high pass filter? Trying to narrow it more by further increasing the value of R3 causes circuit instability. Q1 and Q2 are currently both 2N4401TF (small signal transistor) devices.

Am I on the right track here, or is there a much simpler and cheaper way of going about what I am trying to do?


texts:
I'm trying to figure out the Thevenine resistance of this circuit using loops.

Perhaps loops is the wrong way to go? I've made the circuit using a breadboard and found out that the answer should be \$\frac{3R}{5}\$.
Using loops I get that

\$V_S-IR-i_1R=0\$   (1)

\$i_1R-2i_2R=0 \Leftrightarrow i_1=2i_2\$  (2)

And from looking at the current, I can see that \$I=i_1+i_2=2i_2+i_2=3i_2\$

Then I rewrite the first equation as

\$V_S=(i_1+i_2)R+i_1R=2i_1R+i_2R \Leftrightarrow 2i_1+i_2=\frac{V_S}{R}=2(2i_2)+i_2=5i_2\$

Solving for \$i_2\$, I get \$i_2=\frac{V_S}{5R}\$, and which gives me that

\$I=3i_2=\frac{3V_S}{5R}\$. Then using Ohms law, I get that \$R_{eq}=\frac{5R}{3}\$, which isn't correct.

Where do I go wrong? Is this an example where loops can't be used to determine the equivalent resistance?

Thanks in advance


texts:
I have the following problem: I wish to build a microammeter/milliammeter that will interface to an Arduino.  Sparkfun sells an ACS712 breakout board with an op-amp and two pots for calibration.

Suppose I'm running a 5V Arduino UNO or equivalent.  I want, say, 100uA to be full range.  So I need a 100uA constant-current source to use for calibration.  I've read the various answers to other constant-current questions, but they are unsatisfactory.  For example, an answer that explains that the output voltage will double if the load doubles doesn't help much, because the only voltage I have available is 5.0V.  Or perhaps 5.2V or 4.95V.  So I need a reference that will provide me with 100uA, that will allow me to tweak the gain of the breakout so that I get a reading of, say, 1000 units on the 10-bit ADC.  The ACS712 has a resistance of 1.2m ohms (yes, milli, not meg), so unless there is an external current limit, the power supply would self-destruct or the chip would vaporize.  It would be nice if it were independent of the power supply voltage, but I could save the calibration voltage, which I can read, in the EEPROM and adjust according to Ohm's Law, although I'd rather avoid that.

Sparkfun also has a voltage reference chip, the TL431, whose datasheet shows a constant-current sink (see Figure 21 on page 7).  Would this create the constant-current reference I need?

Note: my goal is to have six ranges on my ammeter.  To do this, I am considering the brute-force approach of buying six ACS712 breakouts, calibrating each of them at 10uA, 100uA, 1mA, 10mA, 100mA and 1A, and feeding them into A0..A5.  If I choose 1000 units as my calibration point, then overrange is going to be >1000.  So all I need to do is read analog inputs until I get one that is <=1000 and thus my meter becomes autoranging.  But without a set of six constant-current sources I have no way to calibrate.

Thoughts/suggestions?

TIA
joe


texts: How does this transistor dual LED flasher circuit work?

texts:
I am a beginner in electronics and have been playing around with simple LED circuits and using Ohm's law to determine what size of resistor to use to limit the current to the LED.  I have also been studying how resistors and capacitors work in series and parallel.  I think I have at least a fundamental grasp of these theories.  I have since moved on to diodes and now transistors and how they are used in simple circuits, again using LEDS.  I found the following circuit which uses two transistors, capacitors and resistors to alternately flash two LED’s but I am struggling to understand how it works.

Dual LED Flasher Circuit (CircuitLab)

How I think it works is this:

Voltage is applied to the base of Q1 from capacitor C2 thus switching it “on” which allows charge to flow through to LED1 which lights it.
At the same time, capacitor C1 is charged.
When C1 is charged it begins to discharge into the base of Q2 thus switching it “on” which allows charge to flow through to LED2 which lights it.
At the same time, C2 is fully discharged which switches Q1 “off” causing LED1 to go off.
Eventually, C2 is again fully charged and the cycle repeats.

But I have a few questions which I cannot seem to answer.

I believe that the resistors R1 and R2 are the current limiting resistors for the LEDs, but what are resistors R3 and R4?  Do they control the rate at which the capacitors charge and discharge?  Or do they have some other purpose that I am not grasping?
There seems to be a “chicken and egg” situation here.  When the circuit is unpowered and both capacitors are discharged, what causes either of the transistors to be “switched on”?  Where does the voltage for the base of either of them come from?
And a more general question:  What "triggers" the capacitors to discharge?

I have read articles about how a transistor works at this link:  http://amasci.com/amateur/transis.html and it has helped some, but the simple circuit above is still fuzzy to me.

Can someone help me to understand this so it “clicks” in my head?

I have also looked at the question below but it has not cleared it up for me.

How does this 2 LED flasher circuit work


texts: How to prevent blue oxidation / corrosion from growing back?

texts:
I've got a PCB for an old console. It had some blue corrosion which I cleaned off using some diluted vinegar and isopropyl. Its not the typical brown rust when it has been exposed to water or white drying residu.

I've noticed that after a while the oxidation grows back, without the PCB having been used. How can I prevent this from happening?

Do I need to apply some sealer after cleaning?
Did I not clean the PCB properly?


texts: What kind of generator do i need to run a 1.5 or 2 ton Air Conditioner?

texts:
I am planning to purchase a single AC that would operate on my Diesel generator. My Generator is a 5kVA , 8 HP air cooled one. I want to know that If I have to run only one AC on the generator shall I install a 2 Ton Split AC or a 1.5 Ton Split AC?

Also I Want to know the diesel consumption by the generator per hour.


texts:
The goal
I would like to know how to connect a transistor (MOSFET) to a capacitive load. I would like to rapidly charge and discharge a capacitor.
How do I do it correctly? I basically want the transistor to work as a mechanical switch.

What I have tried so far
I have tried the following circuit, but for some reason, VDS (voltage, drain-source) is always zero. Here VDS = V_cap (Voltage over the capacitor)

Here is a transient analysis:

The issue:
As you can see VDS is always zero. I expect it to be alternating.
Additional Material

Download the TINA simulation here.
I used this MOSFET.

EDIT:
As suggested, putting a small Resistor (here I put 10Ohms) in parallel solves the issue:

... but I don't understand why? Wouldn't we have a floating node if the transistor is open?


texts: Full-bridge output doesn`t work as expected

texts:
I am making a half-bridge amplifier and successfully managed to amplify a sinusoidal wave (simulates a sound signal). When amplified it has almost 100V of amplitude. It has a inductor and a capacitor to create a low-pass filter.

+Sine waveform plot:

After that I duplicated the entire circuit and made some changes to act as the other side of a full-bridge. Basically I just inverted the signal.

It works fine and the -Sine signal has the same amplitude as +Sine but it is inverted.
The following plot displays both outputs.

My plan was to put both outputs into a resistor (simulates a speaker) and it would have a 200V amplitude.
I know those values might not be realistic but at the moment I just want to understand why my assumption doesn`t happen.
When I put both signals into a resistor the amplitudes goes to 120V instead of 200V.

If I plot +Sine and -Sine we can see that they no longer reach 100V.

They now reach 60V each.
Does anyone knows why this happens?
EDIT 1:
I tested a suggestion and deleted the 5ohm resistors. I also change the load resistance to 5ohm.

Unfortunately the voltage at the resistor still has a 120V amplitude.
EDIT 2:
Issue solved and explained by the solution comment from @aconcernedcitizen. I just needed to recalculate my filter values using half of load resistance.


texts:
In the ADC I have 2 bit system and Vref=1V with actual voltage shown as shown bellow.
I have transformed the actual into UNIFORM as shown bellow and i produced INL from it.
Bu when i started to calculate the DNL by the definition i see that the DNL's are far from following the rule of
INL(N)=DNL(0)+DNL(1)..+DNL(N-1)
Where did i go wrong?
Thanks.


texts: Acs712 current sensor ic interfacing with ade7858(energy metering ic)

texts:
I am trying to interface Acs712 current sensor IC with an energy metering Ic(Ade7858),there are two problems am currently facing.

1) The energy metering Ic takes in bipolar input (± 0.5 V) which is designed to use current transformer but the output from Acs712 is uni-polar which is (0-5v).

2)I tried using the schematic above to convert uni-polar (0-5v)  to bipolar(± 0.5 V)  which gives a single ended output but the inputs for the Ade7878(energy metering IC) is differential input as shown in the below diagram from datasheet.

kindly suggest me if I should go with a single ended to differential converter if am not wrong or is there a better cost effective solution.


texts: Having trouble finding LTSpice (or just spice) models

texts:
While looking to run some simulations on LTSpice (or others spice solutions) I cannot seem to find a single source of truth for models and LTSpice lacks some common components like 1N5221 to 1N5267 for example.
While it is true I can pick a basic model and modify it to adjust the parameters I need from the components, I fear my simulation will fall very far from the real thing. And the same happens for various ICs.
I'd like to throw a 2 for 1 question:

What is the best way to find LTSPice models, or working around the lack of them?
Is there a source for the 1N5221 to 1N5267 diodes spice models?

Thanks!


texts: I want to setup a radio transmitter and reciever a few centimeters apart and measure the signal strength i get. There will be a filter in between which absorbs  particles and the idea is that i want to know when the particle-density reach a certain point. I will be using an arduino in the project as well. What would the best approach be to effectively measure the RF power? I'm thinking about using the 433Mhz arduino RF kits.


texts: Looking for the part number of the button

texts:
Installed in the Acer Aspire 2920 notebook. Does not work at all - pushing at any angle has no effect. Second button (left touchpad one) works properly.

Circuit diagram lists SW-TACT-119-GP / 62.40009.671. Can not find anything using these numbers other than various Wistron circuit diagrams.

Dimensions are (approximately) 6 * 6 * 3 (mm).

Update:

After taking the closeup pictures I thought that according to the construction the buttons seem to be maintainable. I disassembled all of them - without desoldering the device (only desoldering the top metallic cover's pin), cleaned, assembled back, and now all the buttons function properly.


texts: What is going on with this piece of equipment?

texts:
I am working to automate a machine to come back on after a power flicker. There are three things it needs to do when it starts up: power up, restart function A, and restart function B. Power up happens when the electricity is restored but functions A and B have to be turned back on by pushing buttons. These are pretty standard normally-closed buttons, so to simulate pressing them I'm using a microcontroller to operate relays that connect the pins of the buttons when appropriate. In order to know whether to start one or both of the functions on power restore, the microcontroller is constantly polling two inputs and recording the state in EEPROM when the state changes.
Function A is controlled by a board inside the machine that has a set of electrical connectors. 0 is ground, 1, 2, and 3 are all ~7v when function A is on, and are either 0 or 15v when it's not (I haven't been able to identify a pattern as to which one(s) are 0 and which are 15). Connector 4 is always 15v. Connectors 5, 6, and 7 are always ~50v when function A is off and ~8v when it's on.
This all seems weird but it's not impossible to work with. Since 5, 6, and 7 are reliably 50-ish volts when off and 8-ish volts when on, I thought ok I will make a voltage divider and take a tenth of the voltage on an input pin for my microcontroller to detect whether function A is on or off. I put a 47kΩ resistor between the microcontroller input pin and the input meant for pin 7 of the control board. I put another 4.7kΩ resistor between the 47kΩ resistor and ground. I tested it with a multimeter and it seems to be successfully dividing voltage to a tenth of the input voltage.
Here's where it gets weird. I went back to the machine I'm trying to modify and connected pin 7 of the control board to my voltage divider. Instead of the expected 4-5v I expected, I was getting 0.4-0.5v. Did I mislabel my resistors? Did I miscalculate something? I tested it with it turned on, expecting 0.8v if the divider is correct. I got 0.8v. I checked the voltage at the connectors. 0 is still ground, 1-3 are still their weird 0 or 15v when off and 7v when on, 4 is still 15v all the time, but now 5, 6, and 7 are ALL only 4-5v when OFF (still 8-ish volts when on). Even though I only connected these resistors to one of the connectors.
So my question is: What might be going on here, and can I make it safe for my microcontroller if I adjust the voltage divider and treat them as a lower voltage input than what they are when nothing is connected to them?


texts:
We have a robot, and it has 32 digital output, fed into a homemade PCB.

On the PCB we have optocouplers, which have a forward voltage around 1.2-1.3V.

So I need to drop the voltage a lot. That's why I use resistors.  See the following schematic.

The output of the optocoupler is connected to an I/O expanderm and when the 24V circuit is closed the pin of the I/O expander is pulled to ground. It works great.

One problem: R2 needs to dissipate 0.25W, times 32 outputs is 8W in heat.

And that is a bit too much. So I'm looking for other ways to make the same schematic but a bit more efficient.

I came up with the following idea:

The 24 V will switch the transistor and turn on led2.

In total the circuits pulls 135.46 mW, that is 80% better than the first idea.

Is there even a better way do this?


texts: What's the difference between metal and normal high wattage resistors?


texts: Wireless telecom system (cellular with Erlang and spectral efficiency)

texts:
We have a spectrum of 20MHz that we will use on a wireless cellular system, which requires 50kHz per channel. The system is using cluster size K = 4 and the radius of every cell is R = 1 km.

  a) Find the distance between two cells that use the same kind of channels.

My ans: We can use the formula: \$D = R\sqrt{3K} = 3.4 km\$

  b) Calculate the max number of calls that could be served simultaneously from the system per km2.

My ans: From given, \$\dfrac{20000 kHz}{50 kHz} = 400\$ channels, we have though K = 4, so we have 100 channel per cell. So I believe that 100 is the max calls per km2, because from given it says that cell radius is 1 km.

  c) If the system becomes duplex, the users of the system during the peak hour, they do on average 1.5 calls/hour with average duration 120sec. We have Erlang-B and the GoS is 1%. Calculate the average number of calls per hour for every cell and the spectral efficiency.

My ans: Duplex: \$\dfrac{20000 kHz}{100 kHz} = 200\$ channels per cluster, so we have 50 channels per cell. Gos = 1% and cell got 50c, so from Erlang-b table we find that A = 37.90 or just 37.

Though \$A = \lambda H\$, so \$\lambda\$ = 37 calls / 1.5 calls per hour = 26 calls/hour.

Now this is what I tried so far but I am not sure if any of this is correct, so I just want a second opinion.

The last part, wants to find the spectral efficiency. But I really can't find how to do this. I searched a bit, and found this formula:

$$SE = \frac{A_c}{B_T\;C\;M\;S_u}$$

Though I am not sure how to use it exactly.


texts: How do I eliminate voltage spikes at edges of a pulse?

texts:
I am making a Negative edge triggered T flip flop using I2L.
Here is a photo of the circuit

Its working fine and the output waveform is correct, but there is an undesirable voltage spike at each negative edge when it it triggers.

How do I eliminate this voltage spike ??
Could it be just the simulator ? (I am using Multisim 14.2)


texts: Making flip-flops using logic gates in Proteus - I'm getting gray (unknown) signals

texts: for my school project i have to use Proteus to design my circuit. My professor told us that we cannot use any flip-flops and if we had to use them we should make them by using logic gates. I'm trying to make JK flip flops but I'm getting gray signals in the areas shown in picture. Can someone help me how can I get this flip-flop to work?


texts:
What is the working principle of high frequency transformer??
Does it steps voltage or frequency and how it is different from ordinary transformers found in market?
P.S. I could not find proper definition about H.F. transformers on web except for the calculations which made me more confused. So please tell me in lay man's words.
Thank you


texts: What determines the maximum size of a cpu cache?

texts:
Looking at a list of the very latest CPUs, I see several of them with a cache size of 12MB or 8MB - pretty small, when compared to the ever-increasing size of hard drives and ram. It seems to be taken for granted that a cpu cache will always be small, but, why is that? Is it just economicaly unfeasible, or are there engineering reasons why it has to stay small?

I'm thinking of some cryptocurrencies (i.e. ethereum), that are designed to be memory-hard, so the speed of the algorithm is limited by the IO bandwidth of the memory, with the idea that this makes it impossible to design a custom chip specifically to solve that algorithm as was done for bitcoin. But, if someone was making a custom chip anyway, couldn't they just cram a gigabyte into the cache and do away with the IO bottleneck?


texts: Transfer Function: State Space for DC motor

texts:
General question on making state space equations for a DC motor.
In the link below, why are both the electrical and dynamics equations 3 and 4 used to make a state space eqn.8, instead of combining them together into a single? You could combine them by setting one of the equations to theta_dot, and inserting into the theta_dot the other equation.

http://ctms.engin.umich.edu/CTMS/index.php?example=MotorSpeed&section=SystemModeling


texts: Voltage stabilizer without a transformer

texts: I have to design a voltage stabilizer,and I made the circuit from the picture,but I have to do it without the transformer. I have to have an input voltage of 19V and an output voltage that varies between 14V and 9V and the protection current of 3A. How can I modify the circuit to do the same thing


texts: Convert a Dusk-to-dawn outlet device to Dawn-To-Dusk?

texts:
I recently purchased a Dusk-to-dawn outlet sensor (https://www.amazon.com/dp/B00002NB2X?ref_=pe_2640190_261118450_302_E_DDE_dt_1), but I'm wanting to convert this thing into a Dawn-to-Dusk device instead! Why you ask? I bought a plant light for our living room that I want to only be on when the sun is up, because the room all of our houseplants in is north facing, so there is very little light in there.
Seems like it should be a fairly easy 'mod'. Tinkering with it, it looks like this thing is using a Photocell Resistor to control the SPDT relay. When resistence is low, the relay 'opens', when it is high, it 'closes'. Someone on another forum said that you may want to replace the photocell resistor with a photocell transistor or photodiode? Does this sound like the right way to go?


texts: My 3-node serial crossover bus works but I don't understand why

texts:
I have a three-node serial bus, wired into what I thought would be a master/slave configuration, but nodes that I didn't think would be able to receive data are receiving data. In other words, it's working better than I thought it should, and I don't understand why.

First, the setup: I have three Raspberry Pis, each with one of these USB-Serial Adapters:
https://www.amazon.com/Serial-Converter-Adapter-Supports-Windows/dp/B0195ZD3P4/

It claims to have an FTDI chip. I am not using any special drivers - whatever kernel driver that was in Raspbian is what I'm using. I'm testing with minicom, just to send data from between nodes. I think it's in RS485 mode, but I'm not sure how to tell.

I started out with just two nodes. I decided to connect them as a "crossover", because I wanted to test as though it was a Modbus network with one node as a Master and the other node as a slave device. So, I wired the Tx pairs on one dongle to the Rx pairs on the other dongle.

Here are pictures - sorry, don't have enough karma to post them as separate images yet:

For node one (the master) - white/green and green are connected to TR+ and TR-, and white/blue and blue are connected to RD+ and RD-. Brown connects to Gnd.

Then, on node two, I crossed them over: white/blue and blue are connected to TR+ and TR-, and then white/green and green connect to RD+ and RD-. Brown again goes to Gnd.

I set minicom to read from /dev/ttyUSB0 on both of them to be 115200/8/N/1, and success! I could type on node 1 and see it show up on node 2, and vice versa. Typing on node one lit up the Tx light on the Node 1 dongle and the Rx light on the node 2 dongle, and again vice versa.

This is where things get weird. I wired in node 3, exactly like node 2 (white/blue and blue are connected to TR+ and TR-, and then white/green and green connect to RD+ and RD-). Node 2 had each pin connected to two pairs of wires (shown above) and node 3 was wired with only one pair of wires.

And still success! I could type on node 1, and see it on both nodes 2 and 3.

But then something unexpected happened: if I typed on node 2, I saw it on node 1 - but I also saw it on node 3! This was unexpected: node 2 and 3 share the Tx pair, but somehow node 3 is reading from the Tx pair as though it was Rx, without the same crossover that happens at node 1. The full combo turns out to work - if I type at node 3, node 1 and node 2 both see it as well.

So, my question is: how is this happening? Is the USB dongle doing some kind of magic where if it sees data on Tx but it knows it is not the one transmitting, it switches it to Rx? Do "T/R-, T/R+, RXD-, RXD+, Gnd" not mean what I think they mean? I do not have a resistor on either end, in part because I'm not sure of where it would go, so is there some kind of reflection going on?

My worry is that I'm going to get into something undebuggable when I switch between protocols - Modbus wants a 'Master/Slave' setup, with Tx going to multiple Rx of the slave devices, but BACnet appears to want everything on a completely shared bus - all the Tx goes to the Tx of all devices. I thought I was in Modbus configuration, but I'm just not sure anymore.


texts: System of multiple conductors: image method

texts:
The problem statement, all variables and given/known data
  The following figure represents the traversal cut of a system with two cylindrical equal conductors of radius r0 length l at a distance d from one another and at the same distance h of a plane conductor (conductor zero). The dielectric that surrounds the conductors is the air which maximum electric field 20 kV/cm. Consider the approximation of thin conductors. By applying the image method determine the capacitance matrix of the system

  Relevant equations
  The attempt at a solution

So I have no idea where to start...

I now how to apply the image method to a single cylindrical conductor and a plane which would leave us to obtain:

$$ \frac{2 \pi \epsilon_0 l}{\ln (\frac{h}{r_0} + \sqrt{(\frac{h}{r_0})^2 -1})} =\frac{2 \pi \epsilon_0 l}{\ln (\frac{2h}{r_0})} $$

Where I applied the fact that the conductor is thin in the last equality.
Now how do I relate this with the second conductor?
I read that this is the solution for the capacitance between each conductor and the ground plane (so the main diagonal of the matrix). But how is it valid that we "ignore" the second conductor when we calculate the capacitance between one conductor and the ground plane? Is it because the conductors are thin?

Now, what about the conductance between conductor 1 and conductor 2 (C12 and C21 on the matrix)? How do we apply the image method? Do I need to consider 4 conductors? What is the form of the equipotentials? Are they still circumference as in the case of a single conductor and a plane?

I am really confused. Can someone give me some hints on how to attack the problem?


texts: Panel-mount Solderless Connection for Prototyping Station?

texts:
I built a convenient prototyping station with a bipolar and 5V power supply in an enclosure, exposing binding posts for the supply and with a solderless breadboard stuck on with the adhesive backing. I would like to install some 1/4" phone jacks and DIN connectors, etc. What kind of panel-mount solderless fixtures are available that I could install to connect to the jacks?

Clarification: I want to install phone jacks and din jacks onto the enclosure. Those are terminated inside the enclosure. Then, I want to bring the contacts to the front of the enclosure into something I can easily wire to the breadboard as needed. My solution for the power supply was binding posts that I can secure wires to. I am looking for something more convenient than binding posts to wire the new connectors.


texts: What happens if I reduce the air flow for an exhaust fan?

texts:
I'm not very familiar with 220V AC circuits and motors that run on them, so let me explain my question.

I'm building a soldering fume extractor for my workbench similar to what is shown in this  video. It basically uses a simple ceiling exhaust fan along with some hose pipe to suck the fumes away from the desk to the window. He uses an exhaust fan which comes with a metal box enclosure and an outlet to attach the hose.

Unfortunately, where I live, I couldn't find the same type. So I settled for a simple exhaust and used the cardboard box it came in as the enclosure. I then connected 2 hose pipes which direct the air flow out to the window.

So this works all nice and dandy, but I noticed that when I close the box so that air only flows through the hoses, the fan speed slows down. I guess that's expected when the air flow reduces.

I'm sort of worried that this may put the fan motor under some additional stress and may cause it burn if I let it run for too long. Will this turn out to be some sort of safety hazard?

EDIT: I considered putting a fan regulator to the fan to control the speed, but I read online that adding a regulator to a single speed fan may lead to it getting burnt :(. So I guess that's not an option.

EDIT2: I also guess another option is to increase the dia of the hose or add more of them, but the ones I have are about 1 inch in dia and I'm not too keen on having more than 2 of them since it'll become unwieldy.


texts:
I made a simulation for a simple output buffer to use more current for an operational amplifier. The goal is to achieve a precise output voltage at moderate speed (This is considerd a DC application) but a maximum current of 1.1A. The amplifier is controlled by V3 which is a DAC in the real application. The DAC provides voltages from 0 to 2.5V.
I decided to use a current mirror (Q4, Q5, Q3, Q6) to provide the current for controlling the output transistors (Q7, Q9, Q1, Q8, Q10, Q2). Some negative feedback resistors are used to prevent asymmetric current through the output transistors.
At this point the circuits works in the DC simulation but the output voltage can't get any higher than 15V. This is where I need help because it would be nice to use the full output range if possible which not much more parts.

Edit 1:
Thanks for all the Answers so far. I modified the design to use a much simpler one with less transistors (See the picture below). This is from the LT application note where I modified the input to structure to map positive inputs to positive outputs and shift the input by (Explained above why).

I can get DC analysis to work in ngspice but not transient analysis. Here is the DC analysis result for the output voltage over the input voltage V1.

DC Analysis looks good and the power dissipation for the resistors is as expected to shared over them. In the real circuit a tweaking of the feedback resistors might be needed. Transient analysis looks like this and I have no clue why.

I think that is a simulator problem because in theory the circuit should work when prototyping. Maybe you guys have some ideas. I tried simulating much longer but that doesn't change the result.
Edit 2:
Now I measured the open loop gain to get the phase of the output. The output is in phase with the input at around 535 kHz.


texts: What is the simplest way to attach an external USART to SAM3x8e (Arduino Due)?

texts:
I need an extra USART on Arduino Due having ability to operate with 9 bits data characters. I have poor knowledge in schematics. I've been searching web for hours but still have no conclusion for the subject.

I know that I2C can be used for this purpose as well as SPI. Also there is possibility to map the USART to external memory bus. (May be I'm wrong)

So what is the simplest option? It would be great to get comprehensive answer, please.


texts: 4066N analogue switch rapidly switching ON/OFF when should be OFF

texts:
I have the following circuit that should light up two LEDs at the exact same time:

(Edit: Removed incorrect 1.64V enable input because, though I now understand it's on the low side, it is not a part of the question that I need an answer to -- it's when the input is 0V that I get the flicker.)

I am using this analogue switch.

When I have 0V on 1E/4E, the 1Z/Y and 4Z/Y switches rapidly close and open -- I took a video with a 1200fps camera and they appear to flicker on and off every 2ms-5ms or so. The LEDs do not flicker identically, but are both flickering rapidly nonetheless.

Is there something wrong with my wiring? Or did I maybe fry this analogue switch somehow?


texts: how to draw a timing diagram for a logic circuit

texts:
Hello does anybody have a guide to drawing timelines for logic circuits? For flip flops like this

Basically I want to draw corresponding timeline for any circuit like this:


texts: Diode for 200v charging of ev battery module

texts:
Im attempting to use a DC power supply to charge a 200v battery module.

I realise the power supply is not "smart" and I do not plan on fully charging the module. Long story short, I just need to raise the charge level a bit so that another smart charger can take over.

My power supply puts out up to 300v, 6 amps.

Upon connecting the battery to the power supply (still turned off), two 250v/10A fuses that I had on + and - blew.

I think in order to proceed, I need a diode on the positive? I ordered these (https://smile.amazon.com/gp/product/B079KBP5CN/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1), and while the specs seem to line up, I could use some reassurance as this is new territory for me.

Will one of these diodes on the positive do the job? Should I be looking for a different type? Thanks.


texts: Is a resistor compulsory in a NOT gate made from an NPN transistor?

texts:
I am making a NOT gate using a BC337/BC547A transistor (tried both) and I have made this circuit (image shown below) using a simulator:

This is working properly. However when I remove the resistor R1, as shown below, it is not working.

Can you please explain what the importance of the resistor is here?


texts:
Forgive me if this is not the proper question format.  Please critique it if not.  I am new to this site.  I am reading "The Art of Electronics" and cannot understand the jump made in equation 1.35 to go to from \$V_{out} = \frac{R}{[(R^2 + (1/\omega^2C^2))]^{1/2}}V_{in}\$ to
\$V_{out} = \frac{2\pi fRC}{[1 + (2\pi fRC)^2]^{1/2}}V_{in}\$ for the magnitude of the Voltage output in a generalized voltage divider.

Thank you!


texts: Can I wire the ouput and Vcc of an electret condenser microphone amplifier and get the same signal out?

texts:
So I am using MAX9812 amplifier to build a microphone module, but from the pic you can see it requires 3 wires, vcc, ground and output.

I was thinking to wire Vcc with output to get rid of one wire, making it a 2 wire system, is this possible without losing the amplification?

Thanks for any help.


texts: Why would ALU Output be Asynchronous with Input Change?

texts:
Wikipedia states "An ALU is a combinational logic circuit, meaning that its outputs will change asynchronously in response to input changes."

But, the definition of a combinational logic circuit is: "combinational logic ... where the output is a pure function of the present input only."

If the output of a combinational logic circuit is purely determined by present input, is Wikipedia stating that it's asynchronous because of the time it takes for an electrical signal to travel through the circuit?  If so, why is it stating it as with "this means" as if combinational logic implies a delay (as this would be the case with any circuit)?


texts: How was the first overseas phone call possible back in 1927?

texts:
I was watching the Peaky Blinders TV Series when something triggered my curiosity: If there were no satellites, nor underseas cables, how come the characters were making overseas phone calls?
After some research, I learnt that those phone calls were made via radio. But due to Earth's curvature, how is it possible that a radio wave from the U.S could reach an antenna in England, and vice versa?


texts: GB cart with Ram, Rom, no MBC. How do they work?

texts:
Gameboy cartridges, without memory banking, have 32KB of ROM and no RAM. To have more, carts tend to use a MBC (Memory Bank Controller) IC to add RAM and ROM, among other things.

However, two cartridge types, 8 & 9 (08h  ROM+RAM 09h ROM+RAM+BATTERY) don't seem to have an MBC.

How do types 8 & 9 work?


texts: Practical considerations while designing simple boost converter

texts:
I understand the step-up DC/DC converter theoretically but there're some questions in my mind about practical design.

Assuming that \$V_{in} = 5V \$ and I would like to create a variable output voltage. Arduino UNO is controlling the duty cycle \$ D\$. The frequency is 500 Hz.

Is there any practical limitations (restrictions) for the output equation equation: \$ V_{out} = V_{in} * \frac{1}{1-D} \$

If \$ D = 95 \$%. Will \$V_{out} = 100V\$ in real life?

What if I applied a DC signal to the gate (\$ D = 100\$%)?
I don't think this will lead to a very high voltage. I think the inductor will just form a short circuit and the load will not receive any voltage. This could damage the inductor as well, Am I right?

What type of inductor should I use? Air cored or axial inductor or anything else?

Is the ohmic resistance of the inductor make a significant effect? Should I put it in consideration?

Selecting a very very large inductor and a capacitor will greatly decrease ripples. But will this lead to any negative effect (side effect)?

Thank you,


texts: My take on an automatic source selector between USB and wall supply

texts:
This is my take on an automatic source selector between USB and a 12Vdc wall supply. There is something similiar in this post. The problem I have is the Voltage drop across the diode on the USB 5V.

In my version below, the idea is that the FET will keep the VUSB off while the 12V is present and the body diode of the FET will act as blocking diode. If the 12V is disconnected, the 47k pull down resistor will switch the FET on and this will also result in a lower V drop across the FET.

Anybody have any suggestions? Will this work?


texts:
I am having difficulties understanding sections \$j-m\$ in the following question. What's meant by \$R_o,R_i\$? Input and output resistances or rather input/output resistances of feedback unit? If standard input/output resistances, then what's \$R_{in}\$, in section \$k\$?

First, assuming that \$V_A=50V\$ (despite that all other parameters have changed), in section \$e\$ I found that:

\$A=i_o/i_{sig}=-g_{m1} \cdot \frac{R_{sig}||R_{11}}{R_{sig}||R_{11}+r_{\pi 1}} \cdot r_{\pi 1} \cdot \frac{r_{o1}(\beta+1)}{r_{\pi 2}+r_{o1}+R_E(\beta+1)}=-396.08A/A\$, where \$R_E=2K+R_{22}=3K\Omega,r_{o1}=r_{o2}=V_A/(g_m V_T)=100K\Omega\$

Is that correct?

Next, I'd truly appreciate some help with sections \$j-m\$, at least fully understanding what's asked of me.


texts: Choosing correct relay for LED power supply rating

texts:
I have a 500W 24V power supply for running 24V LED strips.  The power supply says it's rated for ~21 amps (500W / 24V).  Assume input is US 120V household power.

I want to control the 120V supply with a relay driven by 5V Arduino logic signal.

I'll be driving 4x 24V 96W LED strips.

From A = W / V:

A = (4 * 96W) / 24V = 16

Does this mean I need a relay rated for 16 Amps or 21 amps listed on the power supply specs?

OR

Do I work back to Watts from the relay's specs?

Example relay is rated at 5A / 220V AC:

W = 5A * 220V = 1100

Though I've read choosing a 16A or above relay is a good idea since it shouldn't be the first thing that fails in a power surge.

More info:
Here's the power supply I have:
https://www.amazon.com/gp/product/B01IU8QBCO/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

And will be purchasing one of these for 12V landscape lighting:
https://www.amazon.com/gp/product/B06XR3ZLSG/ref=ox_sc_saved_title_8?smid=A3S4SVMWTDK1H2&psc=1

Looking at a relay like this to be on the safe side:
https://www.amazon.com/AC100V-250V-2-Channel-High-low-Trigger-Arduino/dp/B077W1NVLM/ref=pd_ybh_a_15?_encoding=UTF8&psc=1&refRID=RAE8FR66XX0GN9YQANXR

EDIT: Suggested alternative:
 Though I'm confident wiring mains I like to avoid it. I'd suggest anyone not confident to go buy one of these (I'll be getting one for my project):
https://www.adafruit.com/product/2935

https://www.amazon.com/Iot-Relay-Enclosed-High-Power-Raspberry/dp/B00WV7GMA2/ref=sr_1_1?s=wireless&ie=UTF8&qid=1542226953&sr=1-1&keywords=Controllable+Four+Outlet+Power+Relay#customerReviews


texts: Linked grounds produce "noise" on Arduino's 5V lines

texts:
I'm using an Arduino to realize two "simple" tasks. The Arduino shall receive messages by an 433MHz receiver and send them via ESP8266/ESP-01 to a server. The schematic/wiring plan is attached below.

As you will see, there is a connection between ESP8266's and Arduino's GND. This ist necessary, because otherwise I couldn't get a proper serial connection between them both.

But this connection also "kills" the functionalty of my 433MHz receiver. Once the grounds are linked, I get a "noise" on the 433MHz receiver's data line.

I watched the receivers data line with the poor man's oscilloscope and could see that the receiver starts to output strange signals when the grounds are linked together. I also hooked up the Arduino 5V line on oscilloscope and could that once the grounds are linked, the 5V line isn't "stable" any longer. (It drops one ore more times per seconds from 5V to ~4.7V).

What am I doing wrong? How can I get a proper serial connection between Arduino and ESP8266 without "disturbing" my 433Mhz receiver?


texts: How to calculate electrical power needed to produce a given electromagnetic RF field?

texts: What Electrical Power (watts) needed to produce the electromagnetic RF field intensity (strength) ≈ 60V/m? How to calculate electrical power needed for a given electromagnetic field strength value? RF field within frequency range 80MHz - 2000MHz, and when RF field is concentrated within the area of approx. 20x20 cm.


texts: How does this reverse polarity circuit work?

texts:
The circuit in question uses the LT4356:

So, I'm trying to get a grip on how this circuit works precisely.  I've prototyped the pictured schematic minus everything to the left of D2.  So, essentially, no reverse polarity protection... it's just the main IC controlling Q1 to allow power through.  That part I understand just fine.

When adding the reverse polarity protection via all that extra stuff before D2, everything get super fuzzy for me.  I know Q1 and Q2, based on their datasheet, have body diodes.  Thus, I know that when everything is hooked up correctly, Q2 will let power flow and everything past it should work normally.  Conversely, I know when polarity is reversed, the body diode will block power flow.

After that, I'm pretty confused.  I can roughly reason the operation of D1, Q3, R7 and D3 as a group, but together with the rest of the circuit.... I'm confused on how they work / help the circuit in either a normal or reverse polarity situation.

Anybody able to shed a little light on this for me? :)

EDIT: I realized, after some more graph paper and highlighter action, that when there is normal polarity that Vbase will be the same as Vemitter, so Q3 should effectively be off.

I'm still sort of unclear, though... when Q3 starts conducting during a reverse polarity situation... is all it's doing is pulling the gate for Q1/Q2 to ground to stop them from turning on?  If so, why even bother with Q3?  Q1 would have its body diode to allow enough current to pass to turn things on normally, and otherwise, it would block reverse polarity.  Confused on the benefit of Q3 still. :(


texts: What could be the reason SPICE is outputting very different CTR curve for this optocoupler?

texts:
For a 4N25/26 I tried to plot the CTR vs LED Current graph by simulating the following circuit. To obtain results similar to the one in the datasheet I keep Vce constant at 10V and sweep the forward LED current between 0.1mA upto around 50mA.

As you see the peak CTR occurs when the LED current is around 1.8mA.

But in the datasheet here, at Fig. 2 or Fig. 3 the graph looks very different and the peak CTR occurs at 10mA LED current:

CTR plot is basically Ic/If when Vce is kept constant. But I obtain very different plot. Am I interpreting something wrong?


texts:
I am reading about CRC algorithms. And have a few basic doubts

Referred Link

I have 3 questions :

Suppose, I have a Microcontroller and an EEPROM. I have read that CRC employs different algorithms. So, my question, how to check if the data sent by the Microcontroller with Checksum will be decoded by the EEPROM correctly, if the Microcontroller employs a different protocol and the EEPROM employs a different protocol to code and decode a checksum? Is the checksum coding and decoding algorithm the same or how to check?
Is checksum done for all data transactions or only specific data transactions? Is it a mandatory thing to do for each data transfer?
Last question, Is checksum only done for data values or address values too?


texts: What does this power designation/rating mean, and do I need to custom-build a power supply to provide it?

texts:
I'll start by saying that I'm a relative self-taught newbie in the electronics world. I recently bought a tube amp kit off of eBay. There were no assembly instructions included, but a very self-explanatory screen on the PCB made it easy to put together.

Power supplies are a gap in my knowledge; I usually just trust the product specs. But this fails my reasonability check, so I was hoping someone else could share their knowledge with me. According to the auction listing, "Power requirement is 60VAC ~ 70VAC 0.2A & 0 - 9VAC 1 ~ 2A."

First, I'd expect it to be an OR, not an AND for the two voltages. Second, when I try to google the power supply specs, I get overrun with results that match 60Hz...not VAC...and sifting through the results for something relevant is challenging at best.

If this isn't a type, I suspect that I may need to create SOMETHING that takes 120VAC in and uses two transformers to output 9VAC and 60VAC. If that's the case, I'd like some references to sites that have examples of "splitting" the power like that so I can research the circuit. I understand how to use a transformer to change 120VAC to X-VAC, but not sure if there are other considerations to get X-VAC and Y-VAC from a single 120VAC source.

If nothing else, it's a great time for me to start learning about power supplies. :)


texts: Do I need a resistor on the base of a transistor?

texts:
When I am connecting an IO pin of a microcontroller to the base of a transistor, do I need a current-limiting resistor between the IO pin and the base? Or can I just directly connect the pin?

My thinking is that I can just omit the resistor because the microcontroller (attiny85 in my case) has an absolute maximum rating of 40mA sink/source for the IO pins, so it won't supply any more than 40mA to the base of the transistor.

Do I need a current-limiting resistor between base of transistor and IO pin on microcontroller?


texts: DC-DC buck regulator MP2359 sometimes damaged when input voltage is high

texts:
I use MP2359 (datasheet pdf) to convert high voltage into 3.3V. The input range of voltage is from 4.5V to 24V.

At low input voltages, things seem to be OK. However when I input a voltage of 21V (MP2359 allows 24V max), it sometimes failed to work when start up, the internal MOSFET seem to be punctured, and the output voltage goes to 21V as the same as the input voltage terribly, parts at the output side burned.

Here is my circuit:

The output current requirement is low, about 20mA.

The input capacitor is MLCC 50V 10uF, and the output capacitor is 100uF 6.3V MLCC, they are from Samsung in 1206 package.

1N5819 is in SOD323 (0805) package, and L1 is in 0805 package.

Here is my layout:

So what's going on?


texts:
I am designing a 2 layer PCB. I have a question about trace connection to through hole.
Which of these is correct way of connecting a trace to through hole via?
a)

b)

Thanks!


texts: Choosing between a darlington array, H-bridge, and solid state relay

texts:
I'd like to use an arduino to switch four separate lamps independently, each of which requires 12VDC and 200mA. It seems to me that this could be done with an H-bridge, a darlington array, or solid state relays, and I'd like to know what are the comparative advantages of each.

H-bridge, like the L293D.
Datasheet: http://users.ece.utexas.edu/~valvano/Datasheets/L293d.pdf

Looks like I could independently set each of the 4 input channels and hook up the lamps to the 4 output channels. I'm concerned though, because I know that H-bridges are usually used for bidirectional current flow through a stepper motor. Is it okay to use for multiple unidirectional loads?

In fact the Wikipedia page says that enabling two channels at the same time will lead to shoot-through and damage. Maybe this is only the case for a simplistic implementation of an H-bridge.

Darlington array, like the ULN2803A
https://www.sparkfun.com/datasheets/IC/uln2803a.pdf

This one allows me to control 8 separate channels.

Solid-state relay, like the ASSR-1611
http://www.avagotech.com/products/optocouplers/industrial-plastic/other/solid-state-relay/assr-1611-001e

I would need a separate relay for each device.

My guess is that the SSR would mainly be useful for applications with much higher current or voltage that would burn out the other devices, or when you want to use optical coupling to avoid noise problems. And that the H-bridge would work okay for this application even though this is not really what it is designed to do. But I'm not sure even after having read through the data sheets.


texts: Are pick & place machines allergic to bags of parts

texts:
I am designing a circuit board and replaced some through hole headers with surface mount ones to try and reduce a board house price which uses a pick & place machine.  The rational is that through hole components require extra steps.
I sorted DigiKey to get the surface mount headers which I wanted and made a mental note that some of the headers had plastic hats on them while some do not.

Not paying attention I selected a component and when copying the sourcing information into kicad I noticed that the only packaging option this component has is being delivered in a "bag".  This sounds all jumbly.  I then noticed that this component doesn't have the plastic hat that some of them have and am wondering if I just inadvertently picked a component which isn't pick & place friendly.  So I was wondering if this is a thing that people know to watch out for.


texts: CCP PWM Strange behavior - Brief failing

texts:
I am trying generate a PWM using CCP and change its frequency on the fly, going from 1.15KHz to 3.28kHz in 180ms.

I am using:

PIC: 16F887

Frequency: 4MHz (internal)

Compiler: CCS PCM C Compiler, Version 5.008

My problem is: My code is generating the PWM and going from 1.15KHz to 3.28kHz (50% duty) in 180ms as I wish to active, but it is also generating "holes", gaps, where nothing happens for some time.

This gaps goes from 3,7ms to 4,07ms, as shown by this image I could get from my oscilloscope:

I am doing this using the following code:

main.h

#include <16F887.h>
#device adc=8

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES HS                       //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPUT                    //No Power Up Timer
#FUSES NOMCLR                   //Master Clear pin used for I/O
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOCPD                    //No EE protection
#FUSES NOBROWNOUT               //No brownout reset
#FUSES IESO                     //Internal External Switch Over mode enabled
#FUSES FCMEN                    //Fail-safe clock monitor enabled
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NODEBUG                  //No Debug mode for ICD
#FUSES NOWRT                    //Program memory not write protected
#FUSES BORV40                   //Brownout reset at 4.0V
#FUSES RESERVED                 //Used to set the reserved FUSE bits

#use delay(clock=4000000)

main.c

/*
   Effect vars
*/
short STATE = 1;
int PR_VALUE = 33;
short CHANGED = 0;
int16 counter = 0;

#int_RDA
void  RDA_isr(void)
{
   //TO-DO
}

/*
   Runs every 256us
*/
#int_RTCC
void  RTCC_isr(void)
{
   counter++;
}

/*
   Performs a step every 20x256us = 5.12ms
   Goes from 53 (1.15KHz) to 18 (3.28Khz)
*/
void EFFECT(){
   if(counter >= 20){
      CHANGED = 1;
      if(STATE){
         PR_VALUE++;
         if(PR_VALUE >= 53) STATE = 0;
      }else{
         PR_VALUE--;
         if(PR_VALUE <= 18) STATE = 1;
      }

      counter = 0;
   }

   if(CHANGED){
      CHANGED = 0;

      setup_timer_2(T2_DIV_BY_16, PR_VALUE, 1);
      set_pwm1_duty(PR_VALUE/2);
      set_pwm2_duty(PR_VALUE/2);
   }
}

void main()
{

   setup_comparator(NC_NC_NC_NC);
   setup_adc_ports(NO_ANALOGS|VSS_VDD);
   setup_adc(ADC_CLOCK_DIV_2);
   setup_spi(SPI_SS_DISABLED);

   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);

   setup_timer_1(T1_DISABLED);

   setup_oscillator(OSC_4MHZ);

   enable_interrupts(INT_RTCC);

   enable_interrupts(INT_RDA);

   enable_interrupts(GLOBAL);

   setup_ccp1(CCP_PWM_L_H);
   setup_ccp2(CCP_PWM_H_L);

   while(1){
      EFFECT();
   }
}

Things I have done trying to fix this problem:

Removed the counter and added a push button and for every push I incremented the PR value, I went from 18 1.15KHz to 3.28Khz without this "holes" appearing
Attached an square wave frequency generator to the input where the push button was and noticed that the fasted I changed the PR more "holes" appeared

Any ideas how I am able to remove this weird errors?


texts: tvs diode for push button switch section

texts:
Do push button switch signal requires TVS diode in its path ?
I have seen TVS diode for push button switch signal in many circuits along with pull resistor , capacitor (RC for debouncing) as in below image,

In this image what is the exact purpose of TS6 TVS diode. As per my understanding , TVS diodes are used to suppress high voltage spikes. What is the condition to occur high voltage spikes in the button signal in above image?
Also even when the switch is pressed , C2 discharges through 1.5K resistor which  avoids sudden discharge through low resistance load. I understood it like, high voltage spikes occur only when capacitor suddenly discharges through low resistance load. But there is 1.5K resistor present in discharging path. So what is the exact need of TVS diode here. Please correct me if my understanding is wrong.
Thanks in advance.


texts: Is there altitude limit for GSM(SIM908)?

texts: I'm using GSM(SIM908) in the machine. I need to know whether there is an altitude limit for gsm to operate. Does GSM just stops working after reaching certain height? I will use SIM908 or SIM808.


texts: Can a device be damaged by water even if there is no power supplied?

texts:
For example, say I submerged a computer mouse entirely. Assuming that I ensured that all traces of the water were gone, would the device suffer any issues?

It is my understanding currently that provided that there is no power being supplied to a device, and assuming that non-electronic damage like rust etc. hasn't taken place, then once the device is completely dry, it can be used without issue. Is this correct?


texts:
In the AD7173-8 ADC,
the default gain value is said to depend on the IC type. In the datasheet, the value is mentioned as 0x5XXXX0. But I couldn't find the exact value in the datasheet anywhere.

should I consider it as 0x5FFFF0 or?
I am a newbie to the circuitry. Sorry if this is a noob question.
Thanks for any help


texts: Struggling with patch gps smd antennas connections

texts:
I'm struggling with antenna connections to GPS module in my PCB design.

My antenna is a smd passive patch antenna, "SGGP.25.4.A.02 from Taoglas". The antenna shape and recommended footprint is in the first two pictures. I'll be adding an antenna ground plane directly underneath the antenna.

I'm confused about the digital GND pads (1 to 9 in second picture) of the antenna connections.  I'm guessing they need to be connected into the digital gnd layer I have on layer 2 through lots of vias with copper keepout regions between the ground pads and surrounding the feedline.

Is that correct?

The third picture is the only patch antenna layout I've managed to find from Abracon patch antenna application note but it's for an active antenna.

Their design is confusing me greatly and it doesn't seem right to me.  They don't have an antenna gnd plane underneath the antenna.

I'm guessing the yellow region is a digital ground (separated from the ground of other components) and they're connecting the ground pads of the antenna to the ground of the GPS receiver through traces.

If I connect the gnd pads this way I'll have an interrupted antenna ground plane.


texts:
I have simulated an open loop boost converter using LM3481 average model, given by texas instruments and I got a very strange bode plot (More precisely, strage phase response), please can you tell me why I did not get the general forme response?

Here is the circuit simulated in TINA TI simulator:

Expected forme of the phase response


texts: How to calculate Tesla coil secondary inductance with spacing between the wire.

texts:
I have built a secondary coil for a tesla coil, and I used 24 gauge wire spaced with fishing line the same diameter as the wire.

I have found formulas for no spacing, but not encountered how to figure out inductance with spacing between the wire.

How can I calculate the inductance of the tesla coil if the secondary winding is spaced out instead of being right next to each other?


texts: Everywhere I see slip explained it says that is the percentage difference between the speed, or frequency of the rotor and the magnetic field. However the only way I can imagine magnetic field and rotor having different speeds is if the angle between the two is constantly increasing. Is this what is actually happening?


texts: Xilinx System Generator: A summary of frequent errors during the Simulink - modelling stage

texts:
I wonder if there is a kind of guide or summary about tipical errors at modelling design stage that users tend to do.

Thank you so much for your help.

By the way. Some people ask me why I don´t use the official site to ask these kinds of questions. Besides I do, the reason I use this site is because is faster in getting answers to me than the official site of Xilinx


texts: Is there a formula to determine heat output of a wire with current applied?

texts: I want to try and make a heating pad for starting seedling plants. I know you can buy those but I think it would be a fun learning experience to try and make one. What I don't know is how to determine the size wire I need and size power supply I need. Is there a formula or equation that lets you determine how hot a wire gets when a current is applied? Like if I have a 20 gauge wire and I apply 5 volts and 20 milliamps to it then it gets this hot. That is just an example. I would have to go backwards on that. I want a heating pad that is between 70 to 90 degrees Fahrenheit.


texts: Picking Supervisors for a battery with correct Hysteresis

texts:
I am trying to find a Supervisors ic that will detect low voltage(5V) on 6v lead acid battery so I can disconnect the battery from the circuit using MOSFET or load driver.

how do you calculate hysteresis, since battery voltage will fluctuate when you disconnect the battery? (there is small pump 150ma max and circuit which use 50ma)


texts: Connecting loads to an MCP23S17 GPIO outputs

texts:
I would like to connect various MCP23S17 datasheet devices to the Raspberry Pi3 MB SPI port. But first I would like to start making some test with a single connection: only one chip. After this I will add more than one expanser to the SPI net. First I will try to connect a LED to the output pins (aprox 20mA).

I have some questions regardless electrical characteristics of this device. About outputs there are two instructions:

1."output current sourced by any output pin.. 25mA"

2.and "output clamp current, IOK...20mA".

What is the difference between 2 both expressions? If 20mA is a damaging value how is it possible that they could give until 25mA?
Could I connect a load to these output pins when current load requirements are closer or bigger than 20mA?
If not, How could I do it? Things I was thinking as a solution for this:

using current drivers
single transistors working in active zone

Have you any other option suggestion?


texts:
I am planning to buy a small solar panel where it is specified that it produces 6V and 100mAh. So does this means that the solar panel will produce 100mA in 1 hour or will it produce 100mA straight away as the sunlight hit the panel.
The panel size is 7 * 7 * 0.3 cm and it is made of polycrystalline.


texts: How to connect a diy audio signal to my "expensive" audio interface

texts:
I'm a hobbyist and after some experimentation (around 4 years) I want to connect my signals I create on the breadboard to my expensive audio interface. Until now I was using the "mic" input on my laptop to connect the signals and I haven't damaged it. I'm using a 40k resistor in series with each of my 2 signal(s).

I create my signals with a "modular synthesizer" running on an arduino due, DACs and with low-voltage op-amps (mcp6002-4) and I power my circuit with the due's power supply (3.3V).

Now my "expensive audio interface, a DSP platform that costs around 4k euros, has two mic/DI inputs (located at the same plug) with just these specifications:

"2 x MC (switchable phantom power), 2 x instrument input with impedance transformer, adjustable input level
2 x Mic, Hi-Z or Line
    XLR/jack
phantom power
    48 V (switchable)"

So I would appreciate some info about the power of the mic/line inputs in general.

Should I take any precautions electrically so to avoid damage the line inputs of my audio interface and the low voltage signals of my audio experimentation circuit? (will activating phantom power accidentally, destroy my circuit and Arduino? Does it pass through the unbalanced 1/4 jack?)

Are the 40k resistors a good value?

Can you point me to an article that discusses line connections, levels, impedance, phantom power, direct boxes etc.

EDIT:
The mic input (the physical) takes an XLR cable but at the center there is a hole that takes a jack input.
It is labeled as MIC/DI. The signals appear at the same hardware source module in the software.
So to make it clear: I don't want to connect to "mic" input but at "DI" line instrument input (which is located at the center of the MIC XLR cable.
I suspect phantom power only goes via the XLR cable (3 pins)

The hardware also has balanced line inputs but I'm using these to connect a secondary audio interface.

Lastly: Should I measure the voltage at the audio interface inputs with my multimeter?

The physical input is like this:


texts: All Silicon transistors appear to have a reverse base  emitter breakdown voltage rating of no more than about 8 VDC  .It would be extremely useful to have a much higher volt rating . Some OLD germanium transistors are a bit better like say 12V           but probably not worth the hassle.WHY don't they make SI transistors with a higher VEB ?


texts: I’m trying to develop an application where I use an stm32f405rgt6 microcontroller ic to drive a radar that operates in multiple ism bands (433.92 MHz, 915 MHz, 2.4 GHz and 5.8 GHz). The overall idea is to generate a waveform that I want to send using python-based or matlab-based tools, then send it to the stm32 via a usb connection, get the stm32’s inbuilt DACs (one DAC for I signal, other for Q signal) to send the I and Q signals to an LTC5588-1 iq modulator chip (LO signal provided by TI2572 frequency synthesizer). Then the reflected signal will be picked up and demodulated by either an adl5380 or ltc5586, which sends the baseband waveforms to the stm32’s ADCs (again, 2 ADCs, one for I and the other for Q). The thing is, the stm32f405rgt6 only has two DMA controllers. Since i want to be transmitting and receiving at the same time (my radar targets are going to be within a few meters), are these two DMA controllers enough? I was originally thinking that I assign one DMA to transmit and the other to receive, but apparently each DMA can only handle one peripheral at a time. What is a workaround if you know any?


texts: Match impedance from 600 ohm/2kW tube amp to 8 ohm/25W speakers

texts:
Would you please help me to think how to choose an approximate transformer with the least losses for my application? No exact transformer available at market.

Is it best, say, taking a 2600/8 ohms or a 600/4 ohms transformer?


texts:
Can someone please explain, provide a link or cite a book where the properties of the zeros for continuous and discrete time systems are explained? I know that the zeros are the frequencies where the numerator of a transfer function becomes zero.

$$
H(s) = \frac{A(s)}{B(s)}
$$

But I would like to know what role the location plays in the pole-zero plot?
All I can find are pole-zero plots and that basically the poles define the system stability and time response.
However, what are the zeros "doing"?
What happens if the zeros are in the right or left half plane?
Are the zeros describing the damping or also stability?

Here is a link to a pdf of MIT explaining the pole zeros. However, I am missing details about zeros.


texts: Does LT Spice have any way of creating a 4-bit Comparator with outputs A=B, A>B, A


texts: USB microphone power, device connect simulation

texts:
My mic is Samson Meteor. It has aux output on the back, but it is the USB mic.
Data (voice) and power are transfered via USB, but data can be transfered via aux also. (it still needs to be connected via usb for power)
When connected to PC via USB, there is buzzing sound in the backgroud. If I plug USB into laptop, aux output has no buzzing.
I want to connect the USB at the wall charger, to eliminate buzzing which is caused by the power supply and only connect aux into PC.
Problem is, mic isn't turned on (LED not on) when it's into wall charger. Can I simulate the connection to device by for example shortening some USB wires. Any help would be appreciated.


texts: What are the advantages of low-voltage light bulbs?

texts: In DC systems, what could be an advantage of lower-voltage (higher-current) light bulb over a higher-voltage one, assuming the input power is the same? What could be a higher-voltage (lower-current) light bulb's disadvantage? Would the low volt high current lamp have a longer life because its filament has thicker wire that would take longer to evaporate ? Would the low volt bulb be less likely to fail when vibration is an issue ? Would the low volt lamp be able to run a higher filament temp leading to more lumens per watt?


texts: What does the "In-line" in SIMM and DIMM memory mean?

texts: I've been searching for what exactly  the "in-line" part means but I don't get it. Is it the way the chips are positioned, as in a line? If it is, is there another possible configuration?


texts: Considerations for mismatched 18650's in series

texts: I'm building a large battery pack. I'm in the planning stage, collecting parts and such, but my goal is to have something like a 4s9p or 4s10p arrangement. The cells I have vary though. Not by a ton, but a hundred or so mAh here and there. All of the parallel sets would be identical cells that were all originally used together, but each set in series would have slightly different capacities. What considerations do I need to keep in mind with this sort of setup? I know it's not advised to use mismatched cells, but I might not have a lot of choice in the matter. I know I'll at least have to have good balancing, anything else to keep in mind?


texts: Current carrying conductor axially through a copper ring

texts:
What effect would a copper ring around a current carrying conductor have on the current in the conductor? How can I go about mathematically modelling the current in the conductor?

Details : The conductor in question is a electrode roughly 2 meters in diameter. It slides into the copper ring roughly the same diameter but very small in length compared to the electrode and is therefore a ring as you stated and not a tube. By half efficiency I mean the current in the electrode is much less than what it normally runs at. The ring was originally stainless steel and was then replaced by this copper version. After this and some other changes the decrease in current was noticed. It was suspected that the copper is having some form of coupling effect or transformer action with the electrode thus limiting the current. The ring was then divided into 6 parts and rejoined this time insulted from one another inhibiting current flow in this ring. The reduced current was still observed in the electrode. This to me is a pretty clear indication that the copper ring in fact has no effect and I merely want to confirm this hypothesis. I'm assuming capacitive effects are not of a concern either as the ring is small compared to the conductor and the AC power supplied to the electrode is of low frequency. Another observation that is convincing me that the copper is having no effect is that if a transformer action or some form of coupling was occurring between the electrode and the copper, the current induced in the copper would definitely be visible in the form of temperature because at such high currents, even with low resistance, the heat in the copper should be very high.(I2R). Would you agree with this?


texts: Why are circuitboards traditionally green?

texts:
Green is the most common circuit-board color because it has become an industry standard.

What I'm interested in is How the traditional "PCB Green" become a standard in the first place?

Were there any interesting historical reasons for the initial choice, or was it just a product of what one particularly successful company was doing that became the de-facto standard?


texts: Check for 12V with Arduino (Two resistors and a diode)

texts:
I need to read the presence of 12V on one of the lines of the board. I want to read using Arduino UNO.

I found the following scheme:

Is this scheme correct?


texts: Power transistor identification: Philips ON503

texts:
I'm trying to find information on a power transistor used on a 1978 automotive ECU. Having reverse-engineered the circuit, I'm fairly certain that it's a NPN transistor, but I've found some references mentioning a Darlington transistor was used on the ECU.

The markings on the case are:

Philips
ON503
F8131

It's used to drive 4 injectors simultaneously, in this configuration:

simulate this circuit – Schematic created using CircuitLab

Here's what the case looks like from the front:

And here's what the pins look from the other side (they're the long metal tabs that come from the case, around the middle of the picture):

Would someone have information on the device's characteristics, or a pointer to the datasheet?


texts: The datasheet for the ATtiny861a states that "If the ADC is used AVCC should be connected to VCC through a low-pass filter". The datasheet doesn't specify what values I should use or what style of low-pass filter I should use. The ATMega datasheets on the otherhand state that the low-pass filter should be a 10uH inductor connecting AVcc to Vcc with a 100nF capacitor connected to ground. Is this the same style of low-pass filter I should be using for my ATtiny or is there something better?


texts: What's going to be more efficient, buck from series or boost from parallel?

texts: I've found many similar questions, and hate to ask something so similar, but my goal is to get usb power (4A continuous) from 4 18650 Li-Ion cells. I'm debating putting them in parallel and using a simple boost circuit to get them up from 2-4.2 volts to the required 5 volts, or putting them in series and using a simple car charger to bring it down. What would give me better performance/battery life, and also, be easier on the batteries?


texts: Unable to activate an Nmosfet gate with raspberry pi

texts:
So I've been trying to control a motor using a MOSFET transistor, where the gate is controlled by a raspberry pi.

My circuit is wired as follow:

The diodes represent the raspberry pi ground and gpio pin 17

The problem is that when the pin #17 is set to high, the motor should stop, or at least drastically slow down, but nothing happens. Help would be greatly appreciated, thanks.

The transistor model is the IRF730

Edit :

Ok, first sorry for the mess of my first post; second here is the transistor data sheet: http://www.vishay.com/docs/91047/91047.pdf

and the proper schematic I've done to the best of my knowledge:

simulate this circuit – Schematic created using CircuitLab


texts: Scaling of magnetic field strength and flux density measurements and shape of hysteresis loop

texts:
Note: this is part of a larger question which I was asked to separate into subquestions.
Other subquestions: 1 and 2

I'm using the method outlined here to measure the induced magnetic flux density in a toroidal transformer made of Nanoperm (additional datasheets here and here). I have adapted the method to use a passive integrator rather than the op-amp integrator described in the tutorial. (I tried building the active one but it was giving me issues.)

The diagram of my circuit is given below:

simulate this circuit – Schematic created using CircuitLab

The signal generator is connected to an audio amplifier capable of driving large currents.

The first subplot in the two figures below show hysteresis loops measured at an input frequency of 50 Hz and 380 Hz for R2 = 37 kOhm. (I tried additional input frequencies and values of R2, and details of my complete experiment can be found in my original question.) Additionally, the raw voltages VM1 (V(R1)) and VM2 (V(C2)) are plotted in the second and third subplots, and the Fourier transform of V(C2) is plotted in the fourth subplot.

To make my hysteresis loop comparable to those in the datasheets linked above, I converted the raw voltages measured by my probes to magnetic field strength H (units of A/m) and magnetic flux density (units of T) using the equations given in the tutorial linked above:
$$H \equiv \frac{V_R(t)\cdot N}{R\cdot l_c}$$
where \$V_R\$ is the voltage across the resistor, \$N=6\$ is the number of turns, \$R = 400 \mbox{m}\Omega\$ is the shunt resistor connected to the audio amplifier, and \$l_c = 10.03 \mbox{ cm}\$ is the magnetic path length given here; and
$$B(t) \equiv \int_{0}^t{\frac{E(t)}{-N\cdot A_c} dt}$$
where \$E\$ is the electromotive force (EMF) induced in the secondary winding, \$N=6\$ is the number of turns, and \$A_c = 0.88 \mbox{ cm}^2\$ is the cross-sectional area of the core given here. The raw voltages are plotted in the second and third subplots of each figure.

The MATLAB code used to generate H and B from the measurements is shown below:

R = 0.4; % ohms
N = 6; % number of turns
LFe = 10.03E-2; % m
AFe = 8.8E-5; % m^2

H = (V(:, 1)/R)*N/LFe;
B = V(:, 2)/(AFe*N);

figure (1); clf; subplot(2, 2, 1); scatter(H, B, 'k.')
xlabel('Magnetic field strength - H (A/m)')
ylabel('Magnetic flux density - B (T)')

where V(:, 1) and V(:, 2) correspond to the most recent 100 ms of data acquired by the differential probes VM1 and VM2 in the circuit diagram above. (Q1) I'm not sure why, but I am orders of magnitude off in both my calculations of H and B. I think V(:, 2) already accounts for the integration since it is the voltage across the capacitor on the measurement side, but I may be missing a multiplication by time in my calculation for B since the units for B are Teslas, which expressed in more fundamental units are \$\frac{V\cdot s}{m^2}\$. It would be great if someone could confirm this / correct me and let me know where my setup / calculation / code may be going wrong. (Q2) Might it have anything to do with the fact that the integrator has a gain of much less than 1 for the frequencies I'm looking at?

Additionally, for the 50 Hz case, (Q3) the shape of my hysteresis loop looks nowhere that of the hysteresis loop given in either of the datasheets here (page 3) or here even though both report measuring the hysteresis at 50 Hz. Does anyone why this is the case?


texts: Method for inductance measurement of iron core vacuum tube audio output transformers

texts: I am involved in the direct measurement of inductance of vacuum tube audio output transformers. Inductance levels vary from around 1 H to 50 H for the primary and down to just a few mH on the secondary. In this measurement method, I would like to be able to include copper and iron losses (copper losses are series R and iron losses are modeled as parallel R across the transformer windings). The purpose of these measurements are to help accurately model, using LTSpice, the vintage Acrosound output transformers that are so popular in Williamson type amplifiers. Any and all thoughts would be appreciated including LTSpice models of other transformers. Best regards, David.


texts: I'd like to have 3ph 208 in my house for general use (not a motor). If I run the output of a single phase to 3 phase VFD through inductors or a 1:1 transformer will it smooth the SPWM .output into an accurate sine wave?.


texts:
On ESP8266 the default pins for I2S are:
Data bits (SD) = GPIO3/RX0,
Data bit-clock (SCK) = GPIO15,
Word select (WS) = GPIO2/TX1
However in my application Im using these pins for another purpose. Is there a way how to set I2S pins to different GPIOs?


texts:
how to compute power?, energy expended in joule?

the battery is 3.6V, the device has a voltage reference  which keeps voltage flowing through the circuit constant at 2.5 V, average current is 0.005 A for time period of 10 seconds.

Is it  power = 3.6V * 0.005A? or 2.5V *0.005A?
Energy = 3.6V * 0.005A * 10 seconds ? or 2.5V 0.005A 10 seconds?

Note: i have no knowledge in electrical engineering.


texts: Transmitting data in a house which strongly attenuates RF signals

texts:
Is there a way to transmit data throughout my house without RF?

My application: I want to spread sensors and actuators in my home. Due to the nature of these things I do not need high data rates, a dozen bits per second might be well enough.

My house is very massive with concrete walls and ceilings, so RF has mostly just a one-room-range.

I thought about using the existing water pipes as acoustic audio couplers, but is there a better way?


texts:
I went through the application notes of infineon and TI. In the datasheet on the MOSFET, there is a junction to case Thermal Resistance given.
Can we use these values to calculate the power dissipation in the MOSFET? Since I read that the Thermal resistances given in the datasheet are measured assuming maximum temperature?
Pd= (Tj(max)-Ta)/(Rthjc-Rthca)(°C/W)
Tjmax=maximum junction temperature
Ta=Ambient temperature
Rthjc=Junction to case thermal resistance
Rthca=Case to ambient thermal resistance (Heat Sink assumed?)
It is also said the cooling method used will be forced-air cooling which is bulky and not very easy to achieve.
How do I calculate the heat sink parameter required for the temperature rise I calculate? Do I assume the value of Rthca (Heat Sink thermal resistance)? Is it possible to make a calculated assumption for the Rthca value?
Is it possible to know what extreme test conditions were used to measure the thermal resistances in the datasheet? How do they find these thermal resistance values Rthjc?
How will I be able to calculate the power dissipation due to thermal resistance? Do we assume a Junction temperature of approximately 110 degrees?
Is 25 degrees a good assumption for Ambient temperature or we use some standard temperature according to the application (40 degrees)?
also, how do we use Rthja (Junction-Ambient Thermal Resistance) in our calculation depending on the cooling area given in the datasheet?


texts: What is the collector current of this transistor circuit?

texts:
Knowing that:

$$V_{BE(on)}=0.7V, β=100, V_A=100V$$

I'd like to find the collector current of the following circuit:

It seems I will have to use the fact that the base emitter voltage is 0.7 volts but I have no idea how to do this. Using the equations for the collector current in the forward active region, saturation current Is is required, which we don't have in this case.

Another idea, is to try and find the voltage around the 1KΩ resistor which can be found easily if we know the voltage around the 15KΩ resistor. If we assume that the base current is very small,the two resistors on the left branch form a voltage divider and calculations become very easy. However, I want precise numbers so I can't make this assumption.

Maybe I could find the input resistance seen from the base and that would allow me to calculate the base voltage precisely. I know the Rin seen from the base but only for small signal models. I don't think I'm allowed to use it here, since we don't have "small signals".

$$R_{inB}=rπ+(β+1)R_E$$


texts: Finding source voltage, v1, and I1 in a circuit with a current source

texts:
simulate this circuit – Schematic created using CircuitLab

*Can anyone tell me why this circuit would be considered parallel instead of series?


texts: Am I missing something?  It is my understanding that if Vgs is less than Vtn than the n-mos should be in cutoff with no current flowing from the source.  I have drain hooked up to 12v in series with a 3k resistor and source to ground.  When I send 0V to the gate I get 0mA flowing from the source.  As soon as I increase the gate voltage to even .03V I start getting current from the source!?!? The data sheets for the mosfets I am using all have Vtn anywhere from 1-2V. I have tried this with several different logic level n-mos transistors and get the same result.  Is this normal?


texts: How are conflicts between voltage sources or signals resolved?

texts:
I am trying to understand what happens when 2 supplies or voltage signals are tied to together as I come across similar situations where a Totem-pole output is also being pulled-up by a weak pull-up. In these cases I am wondering if the signal would conflict and result in an unknown final voltage level. Also, wouldn't the voltage difference between the signals cause unwanted current to flow between them which could be undesirable?

I did a simple simulation in LTSpice where I have 2 DC voltage sources connect in parallel across a load. On the right side are the current measurement results.

The simulation result showed that the voltage across the load is 1.8v. On checking the current in the simulator, I observe that DC supply V1 provides the 0.18mA to the load, but DC supply V2 doesn't. I am wondering - how does the simulator decide which voltage sources provides the 0.18mA to the load (in this case V1 is providing 0.18mA and V2 is 0mA)? Also, shouldn't the current be provided equally by both supplies (V1 providing 0.09mA and V2 providing 0.09mA)?

Thanks for any help in developing a better understanding.


texts: Hall Effect Current Sensor for a DC Mosa Welder - Only info is 250A, it reads the + welding cable current output - ideas on make?

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I wish to test/replace this sensor with the same or similar spec. if possible. Its worn inside due to the positive cable rubbing against it for years. All there is for a description from the Italian manual is, "250A". The diameters are 22 mm I.D. & 43 mm O.D. There are four connectors (blue, yellow, white, red)  and a ground.
With the red probe on the red connector, (there's continuity on the white & blue),   (- red probe on the white connector, there's nothing),   (- red probe on the yellow connector, there's nothing), (- red probe on the blue connector, there's white & red)
With the black probe on the red connector, (there's continuity on only the blue), (- white connector, there's red and blue), (- yellow connector, there's nothing), (- blue connector, there's just red)
There is no continuity to ground. The yellow connector does not relate to the other connectors. The polarity matters when in communication with other wires. That's all I have to offer here.
There is a picture of the bottom of the hall sensor (black base), and the positive welding cable before the main terminal, (it has been rubbing/vibrating against the inside wall of that sensor for years).

Fig. 1 - bottom of sensor, note the wear inside

Fig. 2 - Here is the wiring diagram and W6 is the sensor position

Fig 3. - A close up of the connector and ground
That's all I have to guide me in replacing this sensor. Has anyone seen this model before and what might I do to replace it? Someone smarter than me might be able to figure out the internals of the sensor re:  the voltages & connections etc., Thank you in advance.


texts: Conditional analog sample and hold (analog override?) - circuit suggestion request

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Preamble: I have a LED driven by an opamp-based constant current source (CCS). It works fine, I can set up current required and it is reasonably stable. The problem is, that LED forward voltage drops over first 5-10 minutes due to internal heating, optical output power drops with it. To compensate for this, I would like to use a photodiode (PD) as an optical feedback, which adjusts current through the LED to keep optical output stable (increase drive current as Vfwd drops).
Request:
A circuit idea, which would allow to set initial output level as a function of CCS setpoint, which is measured by PD and then used for driving the CCS (in theory setpoint input shouldn't matter after initial setup). The sequence I envision could be:
1. power up
2. set current limit (turn the LED on)
3. photodiode gets connected in feedback (perhaps with a small delay)
4. photodiode feedback controls output power, initial setpoint can be ignored, since no changes in levels are planned

EDIT:
Per Andy's request CCS circuit, borrowed from another question:

EDIT2:
Essentially I'm looking for a way to override one analog signal with another.


texts: How can I build a circuit to convert sine waves to square waves at up to 1MHz?

texts:
May I ask how do I convert sine waves to square waves at a frequency up to 1MHz?
New to digital electronics. Have done some research but not sure which circuit to use/ which is suitable. Appreciate your help. Thanks!

Components I have:

74LS14 Hex Schmitt trigger inverter

74HC132 Quad 2-input Schmitt trigger NAND gate


texts:
Can we change op amp of a circuit and still work?
I am testing AD822 op amp with a simple inverting

Rin I use 10K Rf I use 20K, Vin is square wave of 5v, Vout I am getting a flat signal.

Is correct Vout should be a square wave of 10v if my V+ is more than 10v from a power supply?

My Vin signal 0v is connected to power supply v--, which is also connected to v-- pin of op amp.

My +pin of op amp is connected to ground terminal of power supply


texts:
What is the maximum input frequency that can be applied to a dual slope integrating type analog to digital converter?
Is it \$f_{clk}/2^{n+1}\$? or \$f_{clk}/2^n\$?

And does the time required to convert an analog signal to digital by it depend on the input voltage?


texts: Would this information storing circuit work

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So I tried to make a information circuit which when switch is pressed, and thus turning the led on, it maintains that true state even after switch is opened but I am not entirely sure if I built it correctly.Does the led need a resister?

simulate this circuit – Schematic created using CircuitLab

Sorry for the confusion guys. Edited the diagram and description. Dont worry about the value of the capacitor


texts:
Which is the best way to attenuate a video signal?

I need to reduce the Vpp (Peak-to-Peak Voltage) from 2V of a PAL video signal to 0.75V. I am familiar with filters and amplifiers (like Op-Amp circuits) but are they the best way to do reduce the signal's amplitude or is the quality going to suffer?

The best solution would be if there was a chip especially designed for these sort of attenuations with very little noise.

Thanks in advance.


texts:
I'm designing a device that plugs into a base and am looking for clip-like part that will take a metal tab and transfer a small current (5V) to an LED in the device. The user should be able to pull the device off easily, but still have good enough contact to supply power.

Please see my very rough mockup:

What design consideration should I have in mind?