texts: Wind-powered fairy lights + battery charger: preliminary help

texts:
I'm new here and asking for help designing a yard-art project. I would like to use a small DC motor as a wind-powered generator to charge a battery (with overcharge prevention) and run some battery operated fairy lights. I'm looking for autonomous function (no manual input). I would like it to be lit any time the wind is blowing or the battery is charged, and continue to be lit from the battery when there is no wind and the battery has remaining charge (obviously not lit when the battery is drained and there is no wind).
I was thinking along the lines of the following. Once I know the basic design, I will look for the correct components, so appreciate any preliminary advice you may have!

simulate this circuit – Schematic created using CircuitLab
My thinking is as follows:
V1 is the DC motor used as a generator
D1 and D2 are the fairy lights (2 small strands if I can)
D3 is meant to prevent battery drain when the wind is not blowing
D4 and D5 are meant to prevent overcharging of the battery
Bat1 is the battery
I probably also need a resistor to regulate current charging the battery, and a whole lot of calculations to 'right-size' the components, but at this stage I am looking for help with the general concept so I can start the process of looking at the components.
Thank you in advance, and apologies if anything (or everything) above doesn't make sense.


texts: Move part to bottom layer without mirroring in Eagle

texts:
How can I move a SMD part in Eagle to the bottom layer without using mirror?
The resulting PCB should have the SMD pads on the bottom layer but mirrored (if you turn the PCB and look on it from top view) so that the SMD part does NOT fit on it.


texts: Clarifying an article on switch debouncing - something about leakage current causing trouble

texts:
I recently read this article on switch debouncing: A Guide to Debouncing - Part 2, or, How to Debounce a Contact in Two Easy Pages, by Jack Ganssle.
The article is on choosing the correct resistor and capacitor for your debounce circuit.
In the article, after calculating a (seemingly good) value of one of the resistor he goes on to say this :

But. the analysis ignores the gate's input leakage current. A CMOS device like the 74AHCT14 dribbles about a microamp from the inputs. That 180K resistor will bias the input up to .18 volts, uncomfortably close to the gate's best-case switching point of 0.5 volt. Change C to 1 µF and R2 is now 18K.

I am only beginning with electronics, so I can only guess what that's supposed to mean. And my best guess is that the leakage current is somehow affecting us in a bad way.
It will be a big help if someone can give me an explanation on what this section. I prefer to know what I am doing, if I am doing it.


texts: Hi, I've built the schematic shown in the picture. It is an ESP-12 module that should communicate via I2C to the MPU6050. However, the communication seems to be disturbed. The clock and data line produce a flat 3.3V (Vcc) output after measuring, instead of a block wave shape signal. Both modules have a working supply and it is excluded that one of these components is broken. Why do I not observe an I2C signal as output?


texts:
Can't find this electrical symbol
What is the name of this device?


texts: NAND gate from BJTs: interfacing +/- 12v op-amp and 5v logic: destroy BJT with excessive Vebo?

texts:
I want to switch on a relay when both a 5v logic input is high and a (LM741 used as a) comparator is around +10v, and the circuit I planned to use is below.

The problem I see with the circuit is when BUF1 output is low, (0v) and OA1 output is low, (-10v) the base of Q1 will be at 0v, but the emitter will be floating. Could this destroy Q1, given that Vebo absolute maximum for BC547A is 6v?

simulate this circuit – Schematic created using CircuitLab


texts: Altium - Changing the libraries for completed schematics and PCB design

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I made a design using a library (say 'All.SchLib' and 'All.PcbLib' where I have everything). Then I made libraries from the project (say 'projectA.Schlib' and 'projectA.Pcblib' which now contain only the parts from the project).

Can I change the libraries in the project from 'All.SchLib' and 'All.PcbLib' to 'projectA.Schlib' and 'projectA.Pcblib' so that 'All' is removed from the project?


texts: advice on a transformer for power-supply

texts:
i know this type of question is common and yes i could just buy a known transformer for $10 on ebay or something. either way :)

i am interested in building my own power supply, something variable around 3-30v dc and maybe with a digital voltmeter built in. i was thinking of recycling some components out of scrap devices that were headed for the recycling depot anyway. So i removed the power boards out of my old printer/scanner and my old cable tuner.

i did some continuity testing and checked resistance levels, my diagram shows the results of those tests. the windings that overlap in my drawing are just to illustrate where the pins actually are in relation to each other.

the original circuit used pins 1-6 as input and 7-10 as output.
So my question is, based on the image i drew up, how should i wire up this transformer to test it's output? can i just wire all three windings in parallel and see what the other two put out?

*edit

this one is out of my old printer. it was indeed run off 110v main. i powered it before butchering and checked voltages across the transformer inputs and was reading 114v. i read 115v before the smaller coil which was between the main and the yellow transformer.

is it strange that the voltage is rectified before the yellow transformer?


texts:
So, you can buy 20mW LEDs and you can buy 10W LEDs. What are the construction differences between these? Is it only the heat dissipation?

If I took a 5mm 20mW LED, ground the plastic down from the back (while keeping the die intact), and mounted the metal inside really well to a super effective heat-removal-system, would I be able to run it at 10W continuously?


texts: Power supply sequencing for low power camera module

texts:
Could you please suggest a simple method how to make power on/off sequence of three different input voltages?

I'm making a board camera using this image sensor.
The sensor requires three different input voltages: 3.3v, 1.8v and 1.2v. Also around the page 101 it says that there exists a power on/off sequence, which means the 1.2v should be applied first and 1.8v, 3.3v later. And the order should be reversed when the image sensor is turned off. But I have no idea how to make it.

Before taking account of the sequence, I planed to use TPS62243(3.3v->1.8v converter) and TPS62242(3.3v->1.2v converter) so that I have 3 different input voltages. (This is their datasheet) Could I use these voltage regulators for making the sequence? The data sheet says you could use EN pin for this. But I couldn't understand clearly how it works.

Or could you please suggest a way to make the power on/off sequence by adding a simple circuit? Because my application requires very small power consumption and price, I'm afraid of using a complex system for it. It would be very helpful, if you could give me suggestions.


texts: How to use the same antenna to receive and transmit on the same frequency with an SDR [Half-Duplex]?

texts:
Considering that the SDR board has one TX/RX output/input and one RX input, I am wondering how could I use one antenna for a half duplex communications on the same frequency.

The idea is to use the TX/RX output for transmitting and the RX input for receiving. The problem is that the required output power is around 47dBm (which is achieved after a HPA) and if I use a fairly good circulator (for joining Rx with TX) as this one, it gives a 20dB isolation and that is not enough as it would burn the whole thing with the reflected power (max. input power of the SDR is -15dBm after the LNA!). Scheme:

As an alternative, I have thought of using a electronically controllable switch that could open one path while closing the other. The problem with this option is that so far I have only found very expensive solutions and my budget is limited.

Can anyone give me some guides on building a PC controllable switch for this purpose (should withstand around 50W of power while offering the typical 50\Ohms of impedance)?

Otherwise, any different ideas/approaches on how could I solve the problem?


texts:
When putting mounting holes for screws on a PCB, should the holes be plated or unplated?

I've read plating the holes provides better support for the screw and helps prevent the PCB from being damaged, but looking at some PCBs I have around (including the extremely popular Arduino UNO), most of them don't seem to have plated mounting holes.


texts:
I want to do the GLS simulation after the RTL simulation. I was asked to add
uut : entity work.eq3(structure)

instead of the one specified below used for RTL
uut : entity work.eq3(struc_arch)

When I run with modified TB it says error finding design .


texts: Advise on developing (by self) in analog circuit design field

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I am a fresh graduate specialized in analog design and would like to work for an industry. For sure, there are opportunities, however, most of the industries look only for the (industry) experienced people in this area. Hence, with the probability of getting low, with fewer openings and requirement of experience, are there any strategies to develop ourselves (after graduation/self) so that we at least get a chance of interview?

I have some techniques:

Doing self projects - however, it is vulnerable to be (not considered) as professional experience.
Investing time in online courses, which are very costly for the analog design field.
Trying to apply for a non-matching role for which we need to depend on luck, which is highly random.

Hence the above techniques seem to be weak for the areas of analog circuit design because for a software/IT role, there are plenty of online certifications/projects, which would be respected because the results are instant. However, for analog circuit design, there are not any certifications to at-least get an interview.

Therefore, I need some guidance on how to develop in this field (after graduation) by self study.


texts: A question about oscilloscope and common mode noise

texts:
To ask this question I needed to simulate two circuits as an example. Imagine we want to measure the voltage across a device output. Call the differential voltage across its terminals Vd. And imagine we couple a usual scope to its terminals to observe the voltage. Call AGND is the scope's own ground. And call the usual triangle reference symbol as the earth ground for this example.

Now on the left side circuit, if the scope is earth grounded and if there is a common mode interference as Vcm the simulation shows the green plot as the difference between Scope and AGND nodes. But if I cut the earth connection of the scope as on the right circuit the simulation shows the blue plot as the difference between Scope1 and AGND1 nodes.

In the simulation above, cutting the earth is hiding the common mode interference information. Is that what happens in reality? Can this be a way to check whether the noise is common mode or differential in nature?


texts:
All books and references I read say that RHP zero gives a negative phase shift.
I can infer that by plot the phase of the function \$w_{z}-s\$ where \$w_{z}>0\$.
With this function, when frequency increases the phase is negative and goes from 0 to -90 degree.

However, with exact the same RHP zero \$s=w_{z}\$ but now I write it in the form \$s-w_{z}\$.
If I plot the phase of that function with frequency, the phase is positive and decreases from 180 to 90 degrees as frequency increases.

So is it correct to say RHP zero give a negative phase shift?
Maybe there is something obvious I am missing here.


texts: Export Modelsim waveforms as image for printing

texts:
I want to export the Modelsim waveforms of my simulated design in a form where they can look decent when printed. To be more specific, without the black background, in a vector format preferably.

Not something like this:

But instead like this:

The schematics are indicative, but I hope you get the point. Is there any way to achieve that?


texts: How do I get the number of address lines of 12G * 64?

texts:
The example problems I'm seeing in the book gives me nice numbers where the size of the ram can easily fit into a power of 2, but this one doesn't.
The original question:

This is all I have:

I was thinking about splitting twelve into 2^3 and 2^2 then add them but I don't know? or would I just choose which ever ram is higher or lower like 12 is in-between 8 and 16?


texts: Peak to average power ratio reduction by waveform clipping in DSP and digital predistortion

texts:
What comes first in DSP:
Waveform peak to average power ratio (PAPR) reduction by clipping or digital predistortion?


texts: Can anyone provide me the geometric representation of GMSK signal? Also, am I correct in saying that bit energy of GMSK is same as its symbol energy since MSK is a binary modulation scheme with only two signalling frequencies?


texts: Logic gate diagram for JK latch? (Not flip-flop)

texts: What would the logic gate diagram look like for a JK Latch? I know what a JK flip-flop looks like, but how would you build a latch with only J and K inputs, without a clock input?


texts:
I'm facing a little problem with function pointers in a code for the microcontroller Microchip Pic 18 Series.
The code below shows the prototypes of the functions involved in the problem and a call to the function 'insert_task', who should receive the address of the function 'task1' by the parameter 'task'.
However, I'm debugging the code in Proteus Isis and the parameter 'task' doesn't receive the address of the function passed as argument. More specifically, the parameter 'task' doesn't receive anything.
Anyone can see an error in the code?
void insert_task(uint8 priority, type_t type, void (*task)());
void task1();

insert_task(0, 0, task1);

The printscreen below shows the field "value" of the pointer "task" ("tarefa" in portuguese) without a value during the call of "insert_task" ("insere_tarefa" in portuguese).


texts:
Is cyanoacrylate adhesive ("superglue") conductive?

I need to repair some USB housings and I want to be sure any "overdrip" won't short the connection.


texts:
Possible Duplicate:
  Choosing power supply, how to get the voltage and current ratings?

I need to power this fan which is rated at 12 V, 0.95 A, 11.4 W. I am unfortunately without a DC power supply, so I am wondering how I could power this fan using an AC adapter.

I am looking to purchase an AC adapter with variable voltage output, but I can only find ones at my local electronics store that are rated at 0.8 A or 1.2 A.

First question is: since I can't find one of these rated at 1 A, should I go with the 0.8 A or 1.2 A?

Second question is: where do I get Vdd and GND from a tip that looks something like this? I would like to have voltage and ground supplied to a breadboard so that I can supply the fan.

Thanks!


texts:
Okay you might get this a lot around here; I'm trying to figure out the inner workings of this specific potentiometer like component. I want to get my hands on the datasheet or a similar components datasheet.

It is used to change the volume of the device in question. Rolling is infinite in both directions, it has a small click. I tried measuring it's workings with the multi-meter but I'm baffled by its working.

One click in either direction shorts all three pins. The very next click measures a 620ohm between the three pins, along with a 3.2v between pin 3 and 1/2.

I'm a real noob on electrical engineering, never came across something like this.


texts: Compensating for unbalanced via count in DDR3 routing

texts:
I'm working on a DDR3 layout at 533Mhz clock speed in a balanced T configuration. I am  currently unable to route the address/ctrl lines with an equal amount of vias (+1 on a limited number of lines). All the lines have been routed to the same length within 20 mil.

I have calculated my via delay as 68 picoseconds which corresponds to an entire cm difference in the effective length of those lines, board propagation speeds have been calculated as 54ps and 69ps per cm external/internal respectively. At 533Mhz the signal propagates 13.6 cm to 17 cm (depending on internal/external layers) in half a cycle which translates to about a 6-7% skew for those lines.

Can I rely on DQS and write leveling calibration to absorb this difference in effective lengths or should I shave a cm off the lines with the additional vias?


texts: How do I make water tank control circuit?

texts:
I would like to make electronic circuit to control water tank. Its works expected as below:

Once water inside the tank is lower than its minimum level, then the mechanical sensor A will trigger to activate the electronic circuit C to power electric water pump connected to it. Electric water pump would be connected by relay, to make it separate from the electric circuit.
Once the circuit is triggered by sensor A, it have to be REMAIN ON even the mechanical floating sensor no more pulling the trigger. That is required to make sure the pump motor keep working to pump water till the tank is full.
Once the water reaches the maximum or full level, the mechanical sensor B will trigger the circuit to power off the water pump motor (to power of the relay).
If during the filling water to the tank power grid is OFF, then it will be assume as the sensor B as active, the pump is powered off.

My question:

How to make the circuit active (water pump is working) after the mechanical sensor A is no more working as it start float.
How do I make the circuit? Motor is put separate and controlled through relay.

For this purpose, circuit is avoided to use logic gate. Electric power to the circuit could be DC or AC, but preferred is AC.


texts: Ethernet UTP cable test device, protection for PoE and signal voltages

texts:
I’m thinking about designing a device/tool for UTP cable related testing/tracing using an MCU. I just would like to experiment with some ideas involving wire measurements, tone measurements etc. (so not using a PHY, just using my own signaling). But in a live environment (not just having a single cable for yourself) where you could plug-in to a connection that is connected to the network (by accident) I wonder how to protect against voltages present on a live network connection.
So, under normal conditions I would have a cable all to myself (measuring from one side and having some supporting satellite device or resistor network on the other side). But choosing the wrong port by accident in the field is what I’m afraid of (or want to protect against).
As far as I understand the data signals are in the range of -1 to +1 V (2V common mode per pair). And there could be a PoE voltage offset (48V) present.
If a possible PoE power source (PSE) on the line doesn’t detect a magic resistor value (which I will not provide), will it not switch on PoE? So, will I be safe and not have 48V on the line to my device?
Is there also a similar mechanism for the data signal (i.e. if it does not detect a valid communication partner will it not try to put a data signal onto the line)? Or do I have to be prepared to get a signal with an amplitude of 2V?
In other words, do I have to worry about voltages/signals on the wires that could damage my device/MCU and also (!) could I damage other equipment when putting low current, low voltages (or AC signals) on wires when accidentally (not intended) connected to other equipment?
Should I have precautions in place to avoid either of these cases? And if so, is there a simple way to detect that I connected my device to a harmless unconnected cable to do my thing?


texts:
I want to make a small breakout board with Eagle and upload it to OSHPark.

The breakout board needs:

header pins
a BJT transistor
resistors
a LED

Looking at the EAGLE menu, it is hard to map the parts to items in a schematic. How would I:

a) Select a Module or Port for the header connectors?

b) Select the BJT and resistors?

EDIT:

Looking at existing PCBs, I wonder how to find e.g. simple parts like these header pins:

or these LEDs with resistors:


texts: what is a transceiver reconfiguration controller on FPGA

texts: I have come across this on an (Altera) FPGAs that make use of high speed protocols but don't know what it does.


texts:
I was attempting the following problem.

In the question it says there is a non inverting amplifier with a feedback resistor of 100k ohms and a source resistor of 5k ohms. If I use the regular non-inverting op amp formula for the gain I get 21 V/V as the answer.

But in the question itself it also says that the gain of the amplifier is 10 V/V. So which is it?

Also do they mean when they say that the gain is 10V/V, that the gain after removing the output voltage consumed by the input bias current and the off set current.


texts:
I'd like to buy one of those after market Android car head/infotainment units. But I don't think there's a way to reinstall the system software if it gets corrupted, so I'm concerned about how long the data will last on the Flash memory.

I've found old figures like 10 or 20 years, but that's for large, single level cells found in 8-bit microcontrollers, not like the MLC we have today.

According to SanDisk,

  MLC flash data retention is orders of magnitude lower than SLC flash.

According to the JEDEC JESD218A standard, data retention at 25C should be 101 weeks. Another source says, "Flash memory retains the data best if the controller is powered up once in a while to scan and correct any bit errors that creep in."

That means they scrub/refresh just like for DRAM, like proposed here.

46x longer data retention! Incredible, but is this implemented on all Flash memory devices today?

But what is the raw, data retention time without refreshing/scrubbing or ECC for a single cell?
101 weeks * 46 = 89 years sounds too good to be true.

Also, how much improvement comes from error correction?

Obviously, the time to the first error without correction would be very low (following a geometric distribution?) for a gigabyte device and not anywhere near the average time for an individual cell. Does error correction raise the retention time for the collective bits to about the same time as for a single, uncorrected cell? Or does it improve beyond that?


texts:
I couldn't find this information anywhere.
Every tutorial on how to safely handle a capacitor tells you to absolutely avoid touching the capacitors leads, and to grab a capacitor by its insulated sides until you can confirm that the capacitor is properly discharged.
However, nobody ever mentions if the bare metal top of electrolytics capacitors is safe to touch or not. I'm referring to the pressure vents, indicated by the red arrow in the image:

I read a bit about the internal structure of a capacitor, and if I'm not mistaken the vents should be connected with its cathode (as all the capacitor case should be).
My interpretation is that touching the top metal ALONE should be safe, as you are only touching the negative "lead" of the capacitor.
However, touching the top AND the positive lead at the same time will get you shocked.
Is this assumption correct?
Please let me know what's the real situation if my reasoning is incorrect.


texts: Error while reading the BRAM location from PS side zynq interface

texts:
I am trying to write to BRAM from PL and read the written data from the BRAM location using zybo z7 board. But when I read the written data from PS side its not giving the correct output.

The screenshot of the Code for writing to BRAM location  and the corresponding Block diagram file
verilog code

The c code for accessing the written data from BRAM from PS side and the output at the tera term


texts: Reading Basic Diode Circuits Without Connecting Wires Shown

texts: In circuits like the one shown here, I am confused because i’m used to seeing wires connecting everything like in my last 2 circuit analysis classes. Notice the circles at each end. How can I redraw this to better understand how to read these?


texts: is there some sort of paste, grease, spray or similar thing that helps make more contact surface for high-current battery?

texts:
I have terminals attached to a battery, which will conduct high-current (40A to 200A), and these are copper plates. As the plates, and battery terminals are not perfectly even (even if they appear to), just squeezing the contact with a screw won't make the most contact surface as I can get.

Is there some sort of semi-liquid paste, grease, spray or something of similar consistence that I can put between the plates before I squeeze them together to improve the contact area and so improve high-current flow through the contact?

There are thermo-conductive pastes that you put under the fan of the CPU to improve heat flow, as there similar pastes for improving electricity conductivity?

I have been searching to find some, but was unsuccessful, maybe I don't know the right keywords. What kind of pastes I should look for? With copper, silver or graphite? What would be the best?

There are some copper pastes, but they are sold as a lubricant for high temperature applications, for breaks, etc. I am not looking for a lubricant, these plates won't move, I am looking just to improve battery electrical contact. There is also graphite spray, which is said to give electrical conductivity to any surface, meant to be used for applying electrical conductivity to the outside of devices to prevent electrostatic damage, but is that the best thing I could use for my application, considering that none of them listed improving high-current battery contact as a possible application?

I just find it strange that I couldn't find any product which has listed improving a high-current battery contact electrical connection, and it'd seem that'd be a pretty common and useful application, i.e. car batteries?

There is also silver glue, which is meant to be used for repairing circuit boards, but I don't want to glue this thing together, I just want some paste/grease.


texts: What is the purpose of this transformer winding in the following SMPS schematic?

texts:
I am trying to understand how the following PC switched mode power supply works :

The way it works in general is OK.
What is not clear to me is what is the purpose of the following part in red :

AFAIK :

The main IC (TL494) alternatively open/close Q3 / Q4 transistors.
This, in turn, induce current in T2 windings and alternatively open/close Q01 / Q02 transistors. It will connect one end of primary winding of T1 to positive or negative voltage.

When either Q01 or Q02 transistor close, current is forced to go first to the part I have highlighted in red. Why is it so ? What if the primary side of T1 is connected directly to Q01 emitter (instead of having to pass thought T2 red part) ?


texts: Best materials to prevent reverse engineering of PCBA components?

texts: I have an overmolded PCBA on a cable with passive components only. Some of the components are hard to identify, but I'm still concerned about the possibility of competitors trying to reverse engineer it. What are the best materials I can put on the components to make it extremely hard (expensive, time-consuming, etc.) for anyone to get to those components in-tact? I'm concerned that standard potting materials, conformal coating materials, and epoxies would be too easy to remove with heat, chemicals, sanding, or milling. Essentially I'd like to have something that bonds so strongly to the components that trying to remove the material also destroys the components. Of course if the material is too hard on the hardness scale, or has a high thermal expansion co-efficient, then the board components might get damaged during manufacturing or during use in the field.


texts: New to PCB design - why doesn't auto placing components exist?

texts:
The circuit design software I have seen has the ability to automatically route traces etc. on a PCB.
But why doesn't this software have the ability to automatically place components on a PCB say to minimise total board size?
Is this just too complicated to be automated?


texts:
I am trying to build a custom light setup for my computer desk.  I want to use the scroll lock LED signal to control a pair of 12 volt DC CCFL lights run off the same inverter.  The problem is when I plug in the CCFL's they just turn on and no matter what I run across the signal pins, they don't turn off.

The SSR I have purchased is from Crydom part number CN048D05.  This is a drawing of my circuit:

I am not really an electronics guy, but I have some basic knowledge.  The LED circuit that I am trying to use as a control works.  I verified that.  What am I missing here?


texts: How signficant is leakage inductance in a flyback converter?

texts:
In designing some flyback DC-DC converters (to give us isolation), we have been simulating potential designs in LTSpice, which has gone well. (Isn't LT great at documentation? Pretty much perfect instructions on putting transformers into LTSpice: http://cds.linear.com/docs/en/lt-journal/LTMag-V16N3-23-LTspice_Transformers-MikeEngelhardt.pdf)

The issue comes when we start including leakage inductance in our simulations, either by using a series inductor or a coupling co-eff of less than one. In much of the documentation about simulating transfromers they say "you can include leakage by use of a less than one coupling factor, or by putting in a series inductor, but that's not really important so don't worry about it."

As we want to check the real efficenies of the power supply, we want to include the leakage inductance. If we are using a standard transfromer from WURTH or similar, we can download the SPICE model (which states it includes leakage inductance), put it in the system, and all seems ok. However, if we follow the instructions for either less than 1 coupling factor (which works out to be about 0.97 for our 38uH inductor with 2.5uH leakage), or in series inductor (2.5uH inductor in line with the primary coil), we get a very poor system that doesn't look anything close to as good as one using a standard SPICE model from WURTH, despite the WURTH model including the parasitics.

The question is: how much influence does leakage inductance have in a system? Is 2.5uH leakage really as bad as our simulations show? How signficant is leakage inductance compared to a series DC resitance of 0.07?

NOTE: this is using LT3748, a transformer with a turns ratio of 4:1, primary inductance of 38uH, leakage indutance of 2.5uH, DC resistance of 0.07 primary side and DC resistance of 0.01 on the scondary side


texts: Understanding the 2N2222 transistor, Where is this voltage coming from

texts:
I was using Proteus to simulate NPN transistor then I saw this
Both Switches are open. Why I see 3.12 Volts


texts: Mason's Gain Formula with a not connected loops

texts:
We have the following path.

I tried to create the gain with Mason's formula, which lead me to the following:

Forward Path 1: 1
Loop 1: (1/s)*(2/s)*2
Loop 2: (-1)*(2/s)*2

When I put them together I get:

(1/1 - ((1/s)*(2/s)*2) - ((2/s)*2)) * (-1)*(2/s)*2

If I multiply it with s^2 I get

(-4s)/(s^2+4s+4)

But according to the solution it should be

(s^2 + 4s)/(s^2+4s+4)

So my upper part does not match. Do I use Mason's Gain Formula wrong?


texts: What's this triac-based device that controls the lamp in my ceiling fan?

texts:
I have a Harbor Breeze (Lowes) ceiling fan with a defective light, but with a working fan motor.  (A tree fell on my service drop, cutting the neutral wire but not the ground or 240V line wires to my house, and a number of devices failed.)

I was getting 90VAC (should be 120VAC) in the sockets with no lights connected, but with 3 8W LEDs installed that drooped to 6VAC, and with one 2.4W LED candelabra bulb I get inconsistent voltage and a ~2 Hz flickering, blinking light. I opened the fan to find this device between line in and the light:

It's not the motor speed capacitor, that's in the top part of the fan and seems to work fine.  I get 3 speeds with this device removed. It consists of:

An ST T4 1060 triac, which has a bunch of vias, and a thermal plane with a gray silicone thermal pad and paste beneath that connects to the aluminum heatsink this was mounted to.
A big yellow SR Cap 0.68 uF/280V cap
A smaller yellow SR Cap 0.1 uF/280V cap
A 470 uF/10V electrolytic
A  blue Bourns 240V MOV
An adjacent large (0.5W?) gray through-hole resistor R11, banded black/black/black/brown, with some overheating discoloration. Measures as an open circuit.
A tan 100 ohm resistor, about 0.25W
A TSSOP-10 device with the label (8?)202 937PC, function unknown
4 1206 package 100K resistors, 2 SMD diodes, and one glass zener diode (A rectifier/cheap voltage regulator circuit?)
2 SOT23 devices, one labeled 'D4'
~20 0402 resistors and caps around the TSSOP

The black line in wire connects to the MOV and thence through R11 to the capacitors, and the red light out wire connects to the output pad of the triac. The white neutral wires on the output are shorted together.

What is (was) this module supposed to do? It has no input for the fan state, and I don't see why I'd want my lights to run off a fancy triac setup when there's a pull cord on/off switch downstream of this device.

The lights are 120V candelabra bulbs, there's a pull-cord switch, and I'd rather have lights and no fan than fan and no lights...so I removed this, connected the line in that used to go to this to the light, and the whole system works.  Lights switched by the pull cord, fan goes through 3 speeds with the , lights, reverse switch.  Am I just reducing the Energy Star efficiency/power factor of my fan? ...But how, if this is just in parallel to the motor and in series with the light switch?

I don't think I need to replace it - everything seems to be working fine - but should I? Where do I get one? What did it do?

Edit: Partial schematic:

simulate this circuit – Schematic created using CircuitLab

It's difficult to trace what's going on with all those tiny SMDs in the U1 cluster under all the conformal coating. Some decoupling caps, some 10k, 2k, 1k resistors, and some kind of logic IC...but not really sure.  Really more interested in what purpose it could possibly serve to have some unknown IC modulate a triac between line in and the rotary switch for my lights.

Other writing on the PCB, front side:

2008.02.28
HT-207-07097A-PC-V06
J1 J2 J3 A1 G TR2 D4 D3 D5 ZD1
ZNR1 R11 R22 C11 R24 etc.
WHTITE [sic] N N RED LAMP BLACK LOAD

Back:

CODE QC QC
ICT PbF
ZPMV2
RU E252098
RH-3
94V-0
4309
X1 X2 RST 5V GND

Also, there are a few areas of traces coated in solder (presumably for higher current capacity) and what looks to be a routed grove filled with white epoxy - or maybe just thick silkscreening - for isolation on the reverse.  I also noticed that either they marked the edge under the blue MOV with a sharpie, or the FR4 was blackened (the reverse has thick traces from the black wire to the blue MOV).


texts: Transistor with 2 voltage sources (power supplies)

texts: Is it possible to use a transistor to act as an relay? What I mean by that is using a 3V battery to control the gate so that a separate 12V battery can let its current flow to other parts of the circuit. Or must a transistor use only a single power supply? Some examples would be great.


texts: How to build an usb c to micro usb cable?

texts:
I bougth a new phone, it came with usb type c charger, i mean there's a usb c port on the charger and a usb c to usb c cable. I had a wireless charging base wich i want to use with my new phone, this base can handle wireless fast charging if you provide a charger with 9v output, but it has a micro usb connector.
Tried to make a cable splitting two other cables, usb c to A and a micro usb to A but the charging pad never worked.
Got an adapter from usb c to usb A and a usb A to micro usb cable and it works but only in normal mode of wireless charging not fast charging.
Tried with my wife's charger from another brand, wich has an usb A port and a usb A to micro usb cable and it charges at fast speed as intended.
Can some one tell me how can I build an usb c to micro usb cable that works at fast charge? Of course I could get a cable but must tell, I couldn't find that type of cable in my country, and not so easy to get from US or other countries.


texts: Please help me with this diode identification - i can't find company name and datasheet

texts: I have a problem with this part, can't find the datasheet and company name. The logo is very characteristic and I put it in the left corner. I would appreciate your help.


texts:
I understand the use of diodes as switches or "clamp circuits", however I needed a little clarification in this diagram, taken from the site https://www3.nd.edu/~lemmon/courses/ee224/web-manual/web-manual/lab5/node9.html

I understand that when Vin>5 V, the top diode to the power supply is forward biased, and ~shorted, and when Vin< 5 V the top diode is reverse and open.  However is the bottom diode to R2 and ground not forward biased in both cases?  I don't quite see how that arm is always an open circuit if we don't know Vout. Thanks!


texts: Why is the loaded Q of a critically coupled two-resonator circuit approximately equal to 0.707 times the loaded Q of one of its resonators?

texts:
From RF Circuit Design by Christopher Bowick (page 32 bottom of the page left column):

  The loaded Q of a critically coupled two-resonator circuit is
  approximately equal to 0.707 times the loaded Q of one of its
  resonators.

This isn't clear to me. How can I prove to myself that this is true?

The circuit that describes a critically coupled two-resonator circuit is basically a signal generator with a source resistance Rs feeding a parallel LC filter which is then coupled to another parallel LC filter through a coupling capacitor. The first LC filter is made up of L1 and C1 and the second LC filter is made up of L2 and C2. There is a coupling capacitor C12 between the two LC filters. The output of this two-resonator circuit feeds a load resistor RL.

This is schematically shown as:


texts: 3.3V SMD transistor to switch HF152F relay

texts:
I am an Electronics Hobbyist. I have always been using TIP120 to switch relays.

Now for a project, I want to switch a HF152F relay using a 3.3V signal. The transistor has to be SMD and switch using a 3.3V signal which rules out TIP120 family. I also don't want to use ULN2803 because I just want to trigger 1 relay and the rest of the channels would be wasted.

I have been searching a lot to find a suitable transistor. Can someone suggest me any other NPN darlington pair transistor which comes in SMD packaging and capable of switching through 3.3V?Should I look at using a low threshold logic level mosfet ?

I have to switch the relay on using 12V through the transistor. One small question there also is how to determine how much current will flow through the transistor when this relay is turned on? The datasheet mentions the coil resistance at 12V to be 400 ohms. Do I just simply apply Ohm's law to determine the current or do I have to keep in mind some other factors as well?


texts: What are the rules to make different drill pairs for VIAs in PCB layers?

texts:
Considering a 6-Layer PCB with the layer sequence as below:

1-Signal

2-GND_Plane

3-Signal

4-Signal

5-VCC_Plane

6-Signal

-What are the considerations that I should take care of when making drill pairs for VIAs?

-Is it possible to make a VIA starting from 1st layer to 3rd layer and also from 1st to 4th without any consideration? If not possible, what is the best way to connect these layers?

Generally, is there any suggestion for multilayer PCB drill pairs that is practically possible to fabricate and has the minimum limits for traveling between layers and also has the minimum impact on price increment?

I'm using Altium Designer and have BGA devices such as LPDDR3 RAM (if is important!).


texts: How to supply a microphone with plug-in-power via TRS or TRRS plug?

texts:
I would like to use a Rode VideoMicro microphone requiring low-voltage phantom power, or plug-in power, on a device which does not supply plug-in-power. There seem to be commercial options, though I would like to DIY a tiny, cheap version for my use-case.
What circuit is needed to supply the microphone with the needed 1.5-5v? Does either of these circuits below work?


texts:
I've come across the following problem:
I need to figure out what the voltage is over every element. I already know that only diode 3 is on and that diode 2 and 4 are off. But how do I determine the voltage? Do I need to use KVL? And how?


texts:
I am using STM32F4 microcontroller and 24AA512 EEPROM, which uses I2C to communicate with MCU. Like many EEPROMs it has W(rite) P(rotection) pin and I want to use it because why not. But there is one problem I can think of:
In documentation it says "The WP pin is sampled at the Stop bit for every Write command". That means it will sample the pin here

TM_I2C_Start(I2Cx, address, I2C_TRANSMITTER_MODE, I2C_ACK_DISABLE);
TM_I2C_WriteData(I2Cx, HIGH_BYTE(reg));
TM_I2C_WriteData(I2Cx, LOW_BYTE(reg));
TM_I2C_WriteData(I2Cx, data);
TM_I2C_Stop(I2Cx); // <-------------------------------------------HERE
GPIO_SetBits(GPIOC, GPIO_Pin_13); // Set WP pin high (PC13 connected to WP)

or better when it receives that stop bit over I2C bus. With 168MHz I'm pretty sure MCU can switch WP ON faster than EEPROM can sample it, because I2C might still be transmitting when MCU continues executing.

My question is:
Is this really a problem or am I imagining it and if it is a real problem, do I add a delay before turning on write protection again or is there some other solution?

Thank you!


texts: making sense of HCT ACT cmos "addional supply current"

texts:
I'm trying to make a low-current level shifter from low voltage (~2V) CMOS up to 5V CMOS.

I had the idea to use TTL-compatible CMOS gates in the HCT or ACT families.

But this line in the 74HCT04 datasheet that concerns me, the "additional supply current" line.  This is not in the HC version.

Is this a static current drain?  Or only when the input is high?  Or what?


texts:
I doing a bit of research into the concept of using webcams to watch crab and fish traps to solve the problem of hauling up empty traps.

Depth 100 fathoms = 600 feet.  Obviously wireless won't work. It also has to be cheap because the fishing gods like holding onto your gear at regular intervals - and seemingly the more expensive your gear the more they like holding onto it.

Q1: Is there a standard that is intended for this scenario?

Failing an applicable standard I am thinking a couple of DSL line drivers - essentially a home made DSL modem on either end of twisted pair with power provided by an AC signal down the same line that I rectify back to DC.

Essentially it would look like a 600ft telephone line that I can map to USB at each end allowing cheap off the shelf USB cameras to be used.

Q2: Is there some obvious concept I am missing with the latter?


texts: The motor gets slower and continues to decrease in speed when using 6+ transistors in the circuit, why does this happen?

texts:
Using a simple light circuit to power a motor, when using 5 transistors, the motor spins fast increasing in speed and amps as each transistor is added.

However, when I added a 6th transistor, the speed (and amps?) decreased, and continued to decrease as I added more transistors.

I was using 6V, with a 6V motor and bc548 npn transistors - the transistors where connected from emitter to base, and the collectors all connected in series with the motor.


texts: Question about trace length matching patterns for high speed signals

texts:
A colleague and I had a discussion and a disagreement about the different ways high speed signals can be length-matched. We were going with an example of a DDR3 layout.

All the signals in the picture below are DDR3 data signals, so they are very fast. To give you a sense of the scale, the entire X axis of the picture is 5.3mm and the Y axis is 5.8mm.

My argument was that, length matching done as in the middle trace in the picture can be detrimental to signal integrity, although this is just based on an intuition, I have no data to back this up. The traces in the top and bottom sides of the picture should have better signal quality, I thought, but again, I have no data to back this claim.

I would like to hear your opinions and especially experiences about this. Is there a rule of thumb for length matching high speed traces?

Unfortunately, I could not simulate this in our SI tool because it is having a difficulty in importing the IBIS model for the FPGA that we're using. If I can do that, I'll report back.


texts:
Help me identify the burnt out SMD located on M801 position in the attached photographs.

It belongs to a Philips Bodygroom BG2024/15 PCB.

I intended to replace the two rechargeable batteries, but somehow it got burnt out when touching inverted polarity from new batteries.
I`ve got to see the code 20 inverted written + letter t with 10x magnification and a PCB support stand. So then I attach another little big zoomed out photo. I hope it helps to identify and may be find an equivalent one.

As a clue to guess what else could be damaged, I´ve tried to connect the batteries with correct polarity and the motor keeps running even while switching on/off the pushbutton. Also the Diode beside looks a little bit damaged and might be a Schottky because of the 4 White stripes cathode marking and BAt2d. But I don't know which Brand it is or any other info about the SMD package type.
In the end I removed the wrecked SMD from M801 location (see attached photo), also a little bit of the PCB circuit on the 5th contact got broken.


texts:
I'm currently building a robot, and as part of its spec it must connect to a wifi network. I have a Belkin wireless router, which I have taken out of its case to expose the PCB.

My question is:

Is it dangerous to run the wireless router when its out of its case, as the case provided some sort of shielding? I am only 16 and studying electronics, so I am not really sure if the plastic router case actually sheilds anything, or is only there to house the electronics...


texts: My friend and I are currently working on a robotic vehicle project, and he had some spare steppers lying around from a previous project. Instead of using DC motors or servo motors, is it viably to use steppers to drive a small vehicle?


texts: Is there a standard that specifies the polarity when using an SMA connector (or similar) to connect a DC power source?

texts:
For regular DC power adapters I will see a polarity indicator like the following:

However I have seen some RF circuits that indicate a DC power connection to the circuit over an SMA connector but do not specify a polarity. Is there a standard for the polarity of the center connection?

I was originally going to assume the center connection as positive but then I came across a BNC to post adapter and it had the center connection as negative.


texts: Loop compensation design of buck converter

texts:
I am trying to design loop compensation with type-3 error amplifier for a buck converter. I'm a student and very inexperienced in this subject. Please bear with me.

Here is the general procedure that I've gathered from reading many many application notes:

Derive an averaged small-signal model. Analyze the open loop gain of the converter(which would include gain of pulse width modulator and output filter) without compensator.
Select the unity gain crossover frequency to be 1/10th or 1/5th of switching frequency. Measure the required gain shift and phase boost required at that frequency.
Place a pole at origin (integrator) to provide high DC gain (obtaining zero steady-state error)
Place two zeroes near LC resonant frequency. One of these would compensate for the gain roll -off due to pole at origin and other would cancel one of the complex LC poles, making the magnitude to roll-off at a rate of 20 db/decade instead of 40 db/decade.
Place two more poles near ESR zero frequency to attenuate high frequency noise.

Depending on these, I have designed my compensator and I can't for the life of me figure out if what I've done is right.

Here is the schematic of output filter model:

LC resonant frequency is 20.86 kHz
ESR zero frequency is 15.91 Mhz

To find out the required gain shift and phase boost, I have set the gain of VCVS (error amplifier) as 1.

The height of sawtooth signal is 2V and the maximum supply is 3.3V. The small signal gain of modulator would be 1.65 V/V which is 4.34 dB. The resistor divider contributes to an attenuation of 1.2 V/ 1.8 V =0.66 = 3.42 dB. The open loop magnitude response consisting of Filter, PWM modulator and resistor divider hence starts with at 827 mdB.

Desired crossover frequency is 200kHz(1/5th of fs). I've marked the required gain and phase boost that compensator has to provide at 200kHz. So I have designed the type-3 error amplifier with above points in mind:

Resonant frequency of filter:
$$
f0 = 25.16 kHz
$$

Placing two zeroes slightly below f0:

$$
fz1 = fz2 = 25 kHz
$$

With R1 = 1M, the value of C3 to placea zero at 25kHz is calculated as:

$$
C3 = \frac{1}{2 \pi R1 fz1} = 1.06 pF
$$

Placing a pole near ESR zero frequency

$$
fESR = 15.91 MHz
$$
$$
fp1 = fp2 = 16 MHz
$$

Value of R3 to place a pole at 16 MHz is calculated as:

$$
R3 = \frac{1}{2 \pi C3 fp2} = 9.9k  \Omega
$$
For a gain of 35.04 dB at crossover frequency:
Evaluating magnitude response at 200 kHz, with R1 = 6M

$$
R2 = 19.47 M  \Omega
$$

$$
C2 = \frac{1}{2 \pi R2 fp2} = 0.0005 pF
$$
$$
C1 = \frac{1}{2 \pi R2 fz2} = 0.327 pF
$$
Here is the schematic and response of the compensator with above values:

Now when I run the AC analysis for the entire loop, the results appear to be more than fine:

The shape of curves looks fine but the stability margins don't seem right. A gain margin of 292 dB? Is there anything wrong in my results?

This simulation uses VCVS with a high gain of 200k. But the error amplifier (two-stage CMOS opamp) I have designed provides a gain of just 1000. When I use an amplifier with a gain of 1000, the response of compensation network is not like the one shown above. Because of the pole at the origin, the gain should start rolling-off from very low frequencies (which happens when gain is 200k). But with a gain of 1000, the pole appears at a frequency near to 100 Hz.

I understand that I don't have a very clear idea of what is actually expected. But I want to know if the little that I've understood and worked on is correct or not. Any help is appreciated.


texts: How to choose a cut-off frequency by interpreting FFT

texts:
I have a question concerning low pass filtering of IMU acceleration and gyro data. To choose a reasonable cut-off frequency, I thought about making some observations in the spectrum.

Now I have some interpretation problems. In my original thoughts, I assumed there'd be some major peaks. E.g. one peak where the frequency of a rotational movement lies. There wouldn't be much high frequencies and I could clearly see a place, where I could cut it off.

That was wrong... Since the FFT is taken over a complete measurement of about 30 seconds, the plot had nothing to do with what I had in mind.

How do I have to interpret the FFT over a complete measurement? I see now, that it isn't like watching a music live through a spectrum analyzer.

Is it even a good solution, to take the FFT for choosing a cut-off frequency?
If not, which are better ways to do that?

Edit 1:

After a few good inputs I add some more information.

The idea was to kill some noise generated by the IMU. Since the IMU is mounted on a vehicle or on moving parts in the vehicle (e.g. the steering wheel), I assumed the fastest reasonable movement should be known.

The used filter function was this one:

function Hd = lp_equiripple2
%LP_EQUIRIPPLE2 Returns a discrete-time filter object.

% MATLAB Code
% Generated by MATLAB(R) 9.2 and the Signal Processing Toolbox 7.4.
% Generated on: 29-Mar-2018 11:37:08

% Equiripple Lowpass filter designed using the FIRPM function.

% All frequency values are in Hz.
Fs = 100;  % Sampling Frequency

Fpass = 10;               % Passband Frequency
Fstop = 20;               % Stopband Frequency
Dpass = 0.0057563991496;  % Passband Ripple
Dstop = 0.0001;           % Stopband Attenuation
dens  = 20;               % Density Factor

% Calculate the order from the parameters using FIRPMORD.
[N, Fo, Ao, W] = firpmord([Fpass, Fstop]/(Fs/2), [1 0], [Dpass, Dstop]);

% Calculate the coefficients using the FIRPM function.
b  = firpm(N, Fo, Ao, W, {dens});
Hd = dfilt.dffir(b);

% [EOF]

The FFT was received and displayed this way:

plot( ( 0:length(acc) - 1) / length(acc) * 100, abs( fft( gyr(:,:) ) ) )

which I know, is indeed a bit of spaghetti code.

As an example I'll attach this image received by this plot. Blue red yellow equals rotation around x, y and z axis.

The whole image is zoomed in since DC is about 2.5e5

Edit 2:

I've just seen that there is no huge DC. If I zoom in, it's a really huge peak at 3 Hz which makes a lot of sense. In the gyro plot this frequency is clearly visible:

The spectrogram was a good visualization too. Although, I still can't see a good place to cut off. Not sure if I even should anymore...

Edit 3:

As asked, I'll show you some spectrogram plot. For now I have decided to leave the data unfiltered, since it's not completely clear what's really noise. The bias of the IMU data is of course the much greater problem.

On the left you can see the gyro data of the y-axis, whilst on the right side the rotation on the z-axis is shown.

If someone's coming up with a good idea of filtering it tell me, I'll try it out :)

Otherwise I'd say this one is closed.


texts:
In below  picture there are two graphs representing the function \$H(s) = s-z_1\$ (assume \$z_1=2\$ is a constant).

The left graph has \$\omega\$ on x axis and \$\|H(j\omega)\|\$ on y axis.
The right graph has \$\log\dfrac{\omega}{\|z_1\|}\$ on x axis and \$\log\dfrac{\| H(j\omega)\| }{\|z_1\|}\$ on y axis.

I completely understand the left graph. I don't understand how they got the right graph. I get why \$\|H(j\omega)\|\$ approaches \$\|z_1\|\$ as \$\omega \to 0\$, and I get why \$\|H(j\omega)\|\$ approaches \$\omega\$ as \$\omega \to \infty\$. But what happened to the graph for \$\omega \lt 0\$ ? I don't see it in the right graph ?

EDIT :  Kindly bear with the poor quality screenshot. Looks MIT folks have compressed too much these videos...  Here is the video from which I took this screenshot


texts: Is it ok to connect a CMOS logic output to a power-on-reset circuit like this?

texts:
I am trying to make a power-on reset circuit that can also be manually reset. The reset is active-low.
When the capacitor is charging, I'm assuming 5v will be present on pin 10. Would this damage the IC?


texts:
I have a task in which I have two sensors, each reading a voltage value. I want a circuit to output 1 if the difference between the two readings is smaller than 10% and 0 otherwise.

I can solve it both analogic or digitally.
Since I have more experience dealing with digital circuits than analogic ones, I thought about doing the following:
Convert the readings to binary and build a circuit which basically uses the formula  | (V1 - V2) | / ((V1 + V2)/2) ) and compares it with 0.1. I think there is an easier way of solving this and wanted some help to find it.

Any help will be greatly appreciated.


texts: Am I creating this LTSpice Symbol Correctly?

texts:
I am trying to create a symbol for LM358 for use in LTSpice. Here's the SPICE File.

The beginning of the SPICE file looks as follows:

* LM358 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT
* CREATED USING PARTS RELEASE 4.01 ON 09/08/89 AT 10:54
* (REV N/A)      SUPPLY VOLTAGE: +/-5V
* CONNECTIONS:   NON-INVERTING INPUT
*                | INVERTING INPUT
*                | | POSITIVE POWER SUPPLY
*                | | | NEGATIVE POWER SUPPLY
*                | | | | OUTPUT
*                | | | | |
.SUBCKT LM358    1 2 3 4 5

The symbol I see in the datasheet is:

My Question is:

The pin numbers / assignments do not match between the SPICE model and the schematic symbol. For example: Pin 1 in Schematic symbol is OUTPUT A but in the SPICE model it is 'NON-INVERTING INPUT`.

Is this kind of discrepancy normal?


texts: How can electricity be positive when electrons are negative?

texts: I don't understand how can a for example a battery be positive charged when the electrons are negative charged? I've read that protons are positive but they can't move so are all electricity negative?


texts:
I have led string lights outside (6 sets) that each have their own 3.6v power supply.  The power supply's are not weatherproof and are failing.   In addition the 6 separate power supply's are not ideal required a few extension cords.  I would like to directly connect these lights to my 12v low voltage outside lighting system.  How would i drop the voltage?  Would i connect them in parallel or serial?

Thanks for any help.


texts:
As known most of modern Intel CPU has contact pads instead of contact legs (pin). This makes it impossible to solder them onto the motherboard.

But are there any Intel CPUs which have contact legs (pin) and how to find them here http://ark.intel.com/ ?

Are there any embedded Intel CPUs that can be soldered?


texts: What should be on a DVT (Design Verification Test) checklist?

texts:
Despite doing a Google search and finding this from Avanthon Engineering (link now dead, see archive.org), I haven't found a good checklist.  Theirs is more for board bring up than making sure a design really works before it goes to production.  I'm thinking of checks such as

Check at high/low voltage
Check at high/low temperature
Check more than one unit
Check signal integrity on clocks and other critical signals

In this case the design is an analog one.  But since I mainly do digital designs, suggestions there are welcome.  I have a mental checklist, but I'm sure I could use a written one.


texts: How do I use a transformer as an inductor?

texts:
Lp: Self inductance of the primary winding.
Ls: Self inductance of the secondary winding.
Lm: Mutual inductance between the primary and secondary windings.

Assume that I need an iron core inductor with large inductance to use under 50Hz or 60Hz.

How do I obtain an inductor from the given transformer in the image? I don't want to use any other circuit elements unless it is absolutely required. The dot convention of the transformer is given in the image; terminal connections must be done so that the inductance of the resulting inductor must be maximum (I think that happens when the fluxes generated by the primary and secondary windings happen to be in the same direction inside the transformer core).

I'm expecting an answer like "Connect \$ P_2 \$ and \$ S_2 \$ to together, \$ P_1 \$ will be \$ L_1 \$ and \$ S_1 \$ will be \$ L_2 \$ of the resulting inductor.".
I understand that I can use the primary and secondary windings separately by making the unused winding open, but I'm looking for a smart way of connecting the windings so that the resulting inductance will maximize.

What will be the inductance of the inducter in terms of \$ L_p \$, \$ L_s \$ and \$ L_m \$ ?
What will be the frequency behavior of the resulting inductor? Will it have a good performance at frequencies other than the original transformer was rated to run in.


texts: Designing high bandwidth current sensors for inductor current sensing

texts:
I am designing a high-frequency current sensor, suitable for sensing +/- 20 Amps at frequencies of 200kHz. This is being used in average current mode control application in an isolated forward converter I'm designing. Do you have any suggestions?
I need to just get you suggestion on the analog front end amplifier that can take a +/- 50 mV signal from a shunt resistor and amplify it to +/- 10 v while preserving the bandwidth of 250 kHz or more. Do you have any suggestions in this regard? I considered an INA828 analog front end instrumentation amplifier at a gain of 200 for achieving this, but, under such circumstances, the bandwidth is less than 260 kHz (the datasheet gives 260kHz bandwidth at a gain of 100, so I'm guessing it is less than 200kHz at 200 gain)
I also found this OPAx354 250-MHz, Rail-to-Rail I/O, CMOS Operational Amplifiers that can have a gain-bandwidth product of 100 MHz, so at a gain of 200 I get a bandwidth of 500kHz., so are these better choices? I have never designed current sensors before. Am I thinking about these in the right way?


texts: Measurement of high voltage with low voltage circuit

texts:
Is it possible to make a high-impedance, precision measurement of a 10V DC signal (dynamic range requirement is only ±1V with a DC-1kHz BW) using amplifiers and an Sigma-Delta ADC supplied only by +3.3V (or +5V)?

I can't use an instrumentation amplifier without at least a +12V/-2V supply. A voltage divider would be a trade-off between input impedance and Johnson noise.

Is there another way to do this that I am missing? A way to subtract the 10V bias without needing higher voltages in my circuit?


texts: Step up transformer for low frequency AC with DC offset

texts:
What is the best way to step-up a low frequency voltage with a DC offset?

I have the following signal coming from a function generator:

\begin{equation}
V_f(t)=8  Sin(2\pi f t+\phi) + 4
\end{equation}

Where:

$$(5 \leq f \leq 100) Hz$$

The desired output is:

\begin{equation}
V_f(t)=80  Sin(2\pi f t+\phi) + 40
\end{equation}


texts:
I am using the Falstad simulator.
I do not understand why am I getting a DC current through a capacitor in simulation.

This must be an error from the simulator. Please, let me know if I am sane, I don't get why there is current flowing.


texts: Headphone volume control works for one speaker only

texts:
I have just completed my first ever electronic creation, a pair of headphones.
It composes of a TRS stereo jack joined to four leads (left, right and two for common ground) braided nicely along the way to a 1k potentiometer along the two common ground leads. The braid then carries on to the right speaker (connected by the right lead and one of the ground leads), from there two leads (left and the other ground lead) go over the head band to the left speaker.

The gadget works almost perfectly, almost as it has one problem that I cannot fix.
When the potentiometer is set to minimum resistance, the sound is perfect and I'm happy. However, trying to decrease the volume using the potentiometer results in only one of the speakers go quiet plus the overall sound quality seems off.

I hypothesized a couple of causes but I have no idea what the actual fault may be. The most likely cause in my opinion is putting the potentiometer on the ground leads instead of connecting a double gang (or maybe double pole single throw(?)) potentiometer to control simultaneously through right and left leads. On the other hand, putting potentiometer on common ground should affect both speakers equally nevertheless.

I don't know what to do so I'm asking the experts to give a helping hand.

EDIT: For those who requested a schematic, I hope I displayed the situation clearly in this one.

simulate this circuit – Schematic created using CircuitLab

The reason for the double ground wire between potentiometer and the TRS plug is just so the braid look uniform plus to hopefully reduce resistance along the wire (increased cross-sectional area).


texts:
I have to program a combinational circuit which sorts a 32 bit array like this: 10011011010101101010101010110010 ==> 00000000000000011111111111111111

The input must be parallel and 32 bit.
The output must serial and 32 tacts.

I hope it's clear what the problem wants.
I'm not doing very well with verilog so i need help with a project. I don't even know how to start.


texts: Why does a BJT act as an amplifier in the linear region?

texts:
I'm covering BJT's in my semiconductor class and in lecture, the professor said that BJTs are used as amplifiers in the linear region. I'm confused because I thought the gain was proportional to the base current.

By that logic wouldn't the highest gain be in the saturation region?

Can someone clear up this confusion?


texts:
I found in a book the air gap area is \$Ag= (W+l_g)*(d+l_g)\$  However, I know therectangular prism is \$A=2*(w*d+d*lg+w*lg)\$. Could any one please help me what they  have air gap equals \$Ag= (W+l_g)*(d+l_g)\$

The refereance book for \$ Ag =(W+lg)(d+lg) \$ is Electric Machines and Drive: A First Course.Mohan, Ned


texts: Multiple SPI devices using single select line?

texts:
I wish to send data back-and-forth between a Master and one of a few dozen slaves within a mesh-network style arrangement.

Assume that all units are (identical) microcontrollers within my control, i.e., can be programmed. In the interest of maximizing data throughput to several hundred kb/s, I am considering SPI.

Are there any strategies or existing implementations to achieve such a topology while using only 1 or 2 pins/signal-lines in total, aside from MOSI, MISO, and CLOCK?

These 1 or 2 pins could be for a custom handshaking or slave-selection method, however what I don't want to do is spend one pin per EACH slave (or use multiplexing) due to some constraints, including the wiring arrangement and limited physical space on the hardware of each master and slave.

I see I2C raising its hand here, but would like to maintain the advantages of SPI (e.g., simplicity and much faster data transfer). I expect throughput would decrease somewhat in this kind of bus implementation especially if I use software-addressing/polling, but perhaps there is some smarter solution to not drag it down too much?


texts:
I want to design 3-Bit 2's Complement Circuit but saw too many ways of it.
Also many of them were not described with detailed gate drawings.

So what is the best way to design 3-Bit 2's Complement Circuit with minimum gates?


texts:
What is the principle of the difference between a supply which provides 0-18V and +9V and -9V?

If I am using a circuit which takes a +/-9V power supply, and instead start powering it with 2 9v batteries, is there a fundamental difference in the supply, or is it just a verbal one?


texts: What is the terminology of, and relationship between, these two characteristics of gimbal motors?

texts: I am currently tinkering with robotics projects to help me learn electronics, and I just started learning about motorized gimbals. After observing various gimbal motors, I've noticed two interesting, and seemingly related, characteristics: (1) how "smoothly" the gimbal motor moves (including how smoothly it is able to move whatever is attached to it), avoiding "jumps" or "rough"/sudden movements, and (2) how "finely" it can move (call it "precision"). I would like to do further research on this, but I don't know what the terminology for this is. What is the terminology for such characteristics/factors of gimbal motors? Furthermore, what is the relationship, if any, between these two characteristics?


texts:
We are currently designing a system which will use a relay, a MCU and a sensor (powered in 3.3V with 100mA max current consumption) + a few LED (2.2V type). it will be powered by a 9V battery

After inspecting a similar product we find out they use MSP 430 from TI which use 3.3V, and a relay HK4100F-DC5V which supposedly work with 5V DC (datasheet http://img.ozdisan.com/ETicaret_Dosya/445413_4369639.pdf/) . I read in this datasheet that coil voltage can also be 3V.

I need to choose the PMU which is going to be used to power this system.

1./ Do i really need to use 3 LDO/ DC-Dc to power 3.3V,, 5V and 2.2V or can I group all of those under a 3.3V power rail ? I was thinking to use TPS563200

2./ How do I determinate the current required by the coil of the relay ? Do I just take the voltage applied to it and divide by its resistance?


texts: STM32 Unwanted Bootloader on first power-up

texts:
According to this, seems like stm32 boot process is as follows:

Check if FLASH is blank. if yes, goto bootloader mode
Check if BOOT0 pin is asserted. if yes, goto bootloader mode
goto Program mode

My problem is the first condition on first boot.
when i buy some MCUs fresh and blank, and i solder them to my product boards that i plan on programming them in-system via SWD protocol later ( so i don't need bootloader anyways ) I tie BOOT0 pin low in pcb. but seems like its being ignored on the first boot when the flash is blank and the bootloader code gets executed anyways.
Lets say i planed to use a GPIO pin as input, which happens to be the same pin that bootloader uses as USART_TX (or USB or anything else) so if the code gets executed, it becomes a PUSH_PULL OUTPUT, whereas its also externally driven by something else on the PCB because it was considered an input in product design.
thats quiet a short there.
Do i have to consider these? is this even true?
Seems like there is some unclear variation between different series too...


texts: DALI Communication: Is DALI protocol a byte transfer mechanism or packet layer mechanism?

texts:
As per the DALI light-control standard protocol, DALI bus communication uses Asynchronous half-duplex(two-wire) serial communication. It uses Manchester coding at 1200 bits per second(baud). A DALI bus can have up to 64 slave devices in the network.

I am trying to implement DALI protocol on STM32E407 (as Master) and STM32F3Discovery board (as Slave). I am looking for some practical advice on implementing DALI communication.

I have a few basic questions about DALI communication:

Is DALI protocol itself is a byte transfer mechanism or is it a software level packet layer (like CAN)?

If DALI is a packet layer mechanism, which byte-level transfer mechanism will better suits for it?

If it is the popular asynchronous communication protocol UART(or USART), how good is UART(or USART) for multi-processor communication (for around 64 slave devices)?? and at micro-controller level, how much faster the serial interface (UART or USART) should be to "DALI 1200 baud rate" for efficient execution Manchester coding?

Thanks in advance!


texts:
I am having this configuration set in my arduino uno: Programming ATtiny84 / ATTiny44 with Arduino Uno

I have even uploaded the blink LED program(using arduino sketchbook) and it works great at 8 MHz. Now I am trying to add an external 12 MHz crystal. I tried burning my internal crystal by using the command mentioned below but stuck with this error.

D:\software\avrdude>avrdude -c arduino -p t44 -P COM7 -U lfuse:w:0x60:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0xe0

*update: I'm using arduino as ISP as my programmer


texts: What would be state diagram of robot controller?

texts:
Robot Controller Problem

A computer needs to control a robot, where the computer sends the following commands:

Do nothing 00
Turn right 01
Turn left 10
Move forward 11

You have to design a circuit that accepts these commands and sends the robot the following signals

Do nothing 000
Turn right 001 010 011
Turn left 101 110 111
Move forward 100 100

So they respectively take 1,3,3 and 2 clock cycles. Until the current command is completed, don’t take a look at the next input from the computer.

Input

Clock Pulse CP
Input Available IA
Input Command C0, C1

Output

Output Available OA
Output Signal S0...S2

Is the state Diagram correct. What would be output values? Or Output is not needed? And What Information is helpful to know in advance for building this project?


texts:
I have 10A lab PSUs at work of which most don't support sinking current (they shut down on overvoltage). The sinking time I need is typically very short: a few A for less than 1 second, the time it takes to dissipate energy stored in inductive parts of the circuit I'm supplying.
I know I can preload a PSU with the worst-case sinking current, but at 10-20V even a couple of A of preload becomes problematic due to heat dissipation. Another approach I have seen is a big cap on the PSU output capable of absorbing the complete overvoltage peak. The downside is that the cap itself stores quite a lot of energy which makes any shorts in the load much more destructive in spite of the current limitation feature of the PSU.
I came up with the following external add-on for the PSU which seems to do what I want, except that I lose about 0.7V on the diode.

Aside from power dissipation (7W at 10A), the user must keep this voltage drop in mind at all times when setting the output voltage. It wouldn't be a problem for PSUs which support remote sensing, but most basic supplies don't.
Is there a better way of absorbing overvoltage peaks on PSU output?


texts: ATMega328P - minimal programming circuit?

texts:
I am used to using an AVR ISP programmer to update the firmware on my project. My project is open hardware, and I'd like to offer pre-programmed controllers for sale to save others having to buy a programmer (if they're that stingy).

To make life easier on me, I am going to build a little board with an ISP programming header wired up to a ZIF socket so that I can do this all assembly-line like.

The fuses are going to be set during programming as they would for an Arduino Uno - so they'll be set for a 16 MHz external crystal oscillator.

While programming is taking place, must the crystal be present?

Again, I don't need to actually have the controller run - all of the I/O pins are going to be NC (apart from the ISP ones).

Is it enough to have a 10K resistor between reset and Vcc, a single decoupling cap and nothing else other than the ISP lines wired up?


texts: What determines the current in the circuit realizing the voltage-controlled current source?

texts: What determines the current in the circuit with Ideal operation amplifier realizing the voltage-controlled current source?


texts:
I am looking into writing data onto some Flash memory serially, the requirement is to replace the old parallel programmer with a serial based programmer example Cheetah SPI Host Adapter. The Flash memory has 19 address lines, and 8 data lines, meaning they will need to be converted to serial most likely with 3 shift registers for the address, and 1 for the data.

The current proposal is to use an use a programmer to communicate with an SPI chip then to shift the serial data and store onto the Flash. I know with this the difficulty will be with the timing parameters of all the hardware.

My question is how is this proposal possible or is there something else more suitable.

Thanks for the help.


texts:
Could someone have a look at this scope trace?

Video

This is a signal from an internal clock in a piece of gear I have no schematics for.

What I THINK I'm seeing is the duty cycle going from ~80% to 100%?

I need to be able to use that short 100% pulse to flash an LED, but I'm honestly not sure where to start. Is it something that could be done w/ logic gates, 555, etc?  Or is a micro-controller the better choice?  Any solution has to be near zero latency, this is a music application, the "pulses" superimposed on that signal are 1/4 notes.
Thanks kindly for any insight on this.

EDIT 09/08/16-  I want to thank all who provided feedback/advice below.  I've been at this hard for a week or so.  Upon further experimentation, I've realized that this is not simply a duty-cycle modulation.  This particular digital signal is apparently used by multiple functions within the unit I wanted to modify.  The signal changes in too many different ways when other functions are enabled, to simply isolate that one "event" I describe above.  Without a schematic and source code for the mcu that is generating the signal, I don't see any way to interpret that signal, even w/ another mcu.  The gentleman who designed the hardware is not longer alive, so I don't hold out much hope for obtaining a schematic/source code.  Thanks again for your help.


texts: Should I cycle my Li-ion from 100% to 80% or from 60% to 40% to maximise life?

texts:
Reading a few other answers including:
this detailed answer,
this one and this one on apple discussions

The evidence in those answers focusses on the 100% start point in the discharge cycle.

Generally there is agreement that the net amount of usage (total current in and out) increases with lower depth of discharge, or at least lower cycle range. I wonder if the word 'depth' isn't a little erroneous. Apparently Li-ion degrades fastest at the highest state of charge.

Many of my devices have design lives of 1000 cycles.  If I want to increase this by reducing the depth of discharge cycles I might say reduce the cycles to 20% rather than 80% cycles.  If I do that is it best to start at 100% and go down to 80% or start at a lower value and go down from there? What is the most optimal point?

I presume starting at 20% and draining to 0% is a bad idea.

The use case I'm most interested in is my laptop, and mobile phone.


texts: Why usb3.1 Type-C has two Dbus, RXbus and TXbus?

texts:
So I am using a camera and making it connect to a hub. The hub only has 9 pins(single Dbus, RXbus and TXbus) while camera has usb3.1 which has double if all these buses (D,RX and TX). So to connect it to a hub can I just short these two buses. What should I do?
USB ports:

Hub ports:


texts:
We need to get some kind of a simple sensor, that can sense someone is standing close to a product . But, it has to be behind plastic, and not seen at all .
We only need to  detect someone 1 meter away from the product .

Using PIR sensors is a problem because its covered.(is it possible somehow?)
using any lights resistors/sensors also a problem when it covered .
ultrasonic is a problem because its too big and battery eating .
infra is no brainer because its covered .

Is there a simple yet powerful sensing method that i am missing here, that takes no energy and detects a small distance human body ?


texts: What hypothesis are needed to support the following argument on a three phase system?

texts:
Given the following three-phase system:

simulate this circuit – Schematic created using CircuitLab

Suppose to set 2 wattmeters as follows:

\$P_{21}\$ which measures current \$I_2\$ and voltage \$V_{21}\$
\$P_{23}\$ which measures current \$I_2\$ and voltage \$V_{23}\$

Show that
$$P_{21} + P_{23} = 3 P_2 = 3V_{20}*I_2$$ holds true.

Here is the proof with the necessary assumptions:

$$V_{21}*I_2+V_{23}*I_2 = (V_{20}-V_{10})*I_2 + (V_{20} - V_{30})*I_2
= 2V_{20}*I_2 -(V_{10}+V_{30})*I_2$$

Now, assuming that $$V_{10}+V_{20}+V_{30} = 0$$ (from here named assumption 1)

The above equation yelds $$P_{21} + P_{23} = 3V_{20}*I_2 = 3P_2 $$

My question is: what assumptions on the three phase system should hold true in order for the above assumption 1 and, consequently, the proof, to be true? For instance, should it be symmetrical? Should it be balanced? Or both?

My reasoning is that since assumption 1 should hold true, the system should be symmetrical since the vector sum of phase voltages in a symmetrical system is always equal to zero (check the triangle of voltages below where in my case N=o and E1 = V10 and so on...)

I guess the real question boils down to this: since the o point is the centroid of the triangle of line voltage phasors, and the phase voltages is a half median, is there a property of a generic triangle that states that the sum of half of each median (the half closer to the median's angle) is always zero for each triangle?

I hope I made my question clear. If not please let me know in the comments, I'll try to explain better.

Note 1: * is used to express the dot product.

Note 2: All the voltages and currents are phasors.


texts:
The question is to calculate the voltage gain, V_out / V_in in terms of small signal parameters and R_C.
(Ignore Early effect)
First I made a small signal circuit for it, and found voltage gain. But it's different from the solution... I can't found any wrong step from my calculation. What's the problem?


texts: Why are laptop/smarthpone chargers not smarter while MCs are dirt cheap and the demand is there?

texts:
This question might be a better fit for superuser.SE
Assumptions:

some microcontrollers are dirt cheap
Lithium-Ion batteries love being charged to to 50-60% of maximum (== degrade the slowest)
there exist various rules of thumb about maximum charging current but none about minimum
Fast Charging is a thing and people need it

Question:
Why don't smartphone/laptop/all_others chargers ask the user what mode of operation do they require? At the higher end I can imagine voice recognition and soft reasoning. At the lower end there's a 3-state selector switch: (fast, normal, tickle). The demand is there, why does the device not exist?


texts: Create a rolling code garage door opener

texts:
I've been tinkering with my Raspberry Pi lately and I've been looking at opening garage doors. A majority of garage doors have the ability to "learn" a new remote. Is it possible to program a Pi with a 315MHz transmitter to "sync up" with a garage door receiver using the learn button?

I've been looking online and I haven't come across anything that can tell me what frequencies garage doors run on and what data the transmitter needs to send.

Long story short, I want to create a garage remote exclusively with the Pi and accessories.


texts:
I've tried researching this extensively, checking existing threads, but I suppose with any uncertainties in this subject, they are hard to convey properly and therefore hard to find answers to.

So I understand static electricity (I think) and don't need to be convinced about the merits of taking precautions to protect electronic components from getting fried. But I fear there are gaps in my knowledge and/or don't understand things correctly. So I'll ask questions as I try to convey my understanding.

My basic problem is: I need the right setup for working on small electronic components. Let's say a RAM chip.

For working on internal PC components, most places I've come across suggest use of an anti static wrist strap hooked to the metal chassis of the computer and that's it.

Question 1: The internal components are all eventually connected to the conductive metal, so won't they absorb the static discharge from your body?

Then there are places which suggest connecting yourself to an ESD mat using an anti static wrist strap.

Question 2: Wouldn't this just create an open circuit to ground?

Question 3: The mat is high resistance so electrons from you would flow very slowly through it. I know electricity still moves really fast but my mind doesn't and I'm seeing discrete intervals of time. So I'm thinking that if you touch the sensitive component straight after connecting to the mat, you might still discharge to the component.
So how quickly does your body take to achieve neutral charge?

Question 4: Can there be a state where you and the mat achieve equilibrium but your body still has a charge that can damage the component if touched?

Question 5: Can there be a charge in the mat that can transfer to the component once the component is rested on it?

Finally, some have suggested connecting yourself using a wrist strap to an ESD mat and then connecting the ESD mat to mains ground with the outlet switch off.

Question 6: If the switch comes on by accident or there's a fault somewhere on the circuit, will the high resistance of the mat stop the current from flowing through you freely and hence stop you from getting fried?

Question 7: Even after you've discharged, wouldn't you, the mat, and the strap be on a different (and possibly higher) potential than the component (which currently sits outside this circuit) you will now touch and therefore damage?

Now let's say with the previous setup, you are working away on the component that is resting on the mat and it's still fine. Then you rub your feet on the carpet subconsciously and gather static.

Question 8: Will there be a constant discharge through the mat while you gather charge? If so...

Question 9: Wouldn't the discharge cause current flow through the mat where the component is resting? and if so...

Question 10: Could that current damage the component?


texts: Distributed Transmission Line, Characteristic Impedance in AWR Microwave Office

texts:
I am trying to design a distributed amplifier in which the parasitic capacitances of a small-signal FET model are linked to inductors to form a distributed line across the drains and gates and I'm frustrated because nothing is matching what I expect from theory.

I know the characteristic impedance of my two lines should be sqrt(L/C) and I've chosen my values as such.. however I am still getting a ringing in my input impedances even when I just simulate a simple LC distributed circuit cell for a transmission line, and there is no real part as can be seen in the graph.

So my questions are - does the characteristic impedance calculation not work in AWR for a distributed element model of a transmission line?

If I measure the S(5,5) or S(1,1) it is resonant at DC, which makes sense because an inductor is a short at DC frequencies, but then what does the resonant frequency wc=1/sqrt(LC) mean and what is its significance in the AWR simulations?

Thanks for your time!

--
edit:

so the ultimate goal is the distributed amplifier as it appears below where this cell is repeated five times. The inductors add in series, so at the end there is another L/2 value inductor while between each cell the inductors are value L. The four ports are all terminated in a 50Ohm impedance. I simplified by taking out the fet small-signal model to inspect the input impedance.

By ringing I mean that the impedance value is purely imaginary and oscillates. I guess I'm not surprised that a few LC circuits are not giving an input impedance of sqrt(L/C) but I just can't justify to myself why they disobey this relationship because it should scale with length and number of cells.

I really apologize for the horrible screenshots, I have a cap on how many images I can post.

--edit
So I realized I was plotting Z(1,1) instead of ZIN in AWR, which solves a lot of my issue understanding what I'm doing wrong. But thank you for your time and thoughts I really appreciate it!


texts: I found some articles talking about transformerless power supplies, and I have uploaded the schematic of such a circuit. Does anybody have an idea about the pros and cons of such a power supply? Also how to calculate the value of this capacitor "C1" ?


texts:
I am fooling around with a solar panel and I am trying to make a circuit, which would monitor its voltage and eventually switch the load on and off.
The thing is, I don't have a good "reference" voltage to compare with. The solar panel can produce anywhere from 0 to ~20V. If it is high enough I can use zener or even voltage regulator, but when it is (almost) dark both of these options will drop in voltage.
So, I was wondering if it is a good practice to use a battery (like a coin cell or something) just to feed one input of a comparator. It doesn't need to be precise, and I think there will be virtually no drain from the battery, so it will last very long.
Another option is to stick with the zener and abuse the gate threshold voltage of the NMOS (whos gate is connected to the comparator output). I mean, if the comparator outputs either ~0V or the zener voltage and that zener voltage drops low enough, the MOSFET won't turn on anyway.
I will probably ask a separate question with more details of what I am trying to do and whether it makes sense at all, but right now I am just asking whether using a battery as a reference voltage for a comparator (and nothing else) is something common, does it make any sense, etc.


texts: How can I match phase voltage between a transformer primary and secondary?

texts:
I am trying to make a circuit to transform 240VAC, split-phase to a 0 to 5V waveform for an Arduino ADC so I can measure the mains voltage. I have read this question (How to measure line voltage (220V) with an arduino?), which describes very well how to use a transformer to isolate the circuit from mains voltage and bias the transformer secondary voltage so it's always positive (relative to ground).

Simulating this circuit, however, I found that the transformer causes the line voltage and current to be out of phase (as expected for an inductor). I am trying to ensure that my measurement system has a minimal impact on the mains voltage and current, so I wanted to correct the transformer primary power factor so voltage and current are in phase. To do this, I created the following circuit:

This circuit assumes the primary inductance is 4H, but with the transformer I'd like to use, I can't find its inductance in the datasheet.

However, when I add the remainder of the secondary side, there is a 90° phase shift in the voltage.

Here, the second scope is the voltage across the 100kΩ resistor (representing the ADC input). The third scope is an XY-plot with the mains voltage on the x-axis and the ADC input voltage on the y-axis.

I attempted to fix this with another capacitor to induce a 90° phase shift, but I run into a problem where the larger the capacitor is, the closer to output phase is to the input phase, but the gain decreased. Conversely, a smaller capacitor increases my gain, but corrects the phase shift less.

It make sense that the gain decreases since the capacitor changes the impedance of the voltage divider, but also changes the impedance of the entire secondary side.

Because of this, I thought about adding an op amp to buffer the stages, but now this is getting more complicated than I can easily design. Ultimately, I need to do three things to the secondary side in order to have the correct input to the ADC:

Scale the peak-to-peak voltage to ~5V
Add a DC offset of ~2.5V so the output voltage swings from 0 to 5V
Phase correct the output voltage so its voltage is no longer leading the mains voltage.

I can use the op amp to both scale the voltage swing and add a DC offset, but I wasn't able to decouple the gain/scaling from the phase correction. I even tried a circuit that buffered the output twice, but still had problems.

How can I accomplish my three goals for conditioning the ADC signal?


texts: parameter that limits data rate in communication

texts:
In communication, the maximum data rate that can be achieved is given by Shannon as

C=B*log2(1+SNR) bits/sec. Supposing that I've a very high SNR and an infinite bandwidth, then
can data be transmitted at infinite rate? If no, then what are the conditions that limit my system to operate at a fixed rate.

thanks in advance
phani tej


texts: Can be lead-acid battery charged using NiMH or NiCd charger?

texts:
I would like to check total capacity of 64Ah lead "car battery" ^ by fully charging it and currently I have only older intelligent charger (Robbe Power Peak 8467). It directly supports charging modes for NiMH and NiCd batteries (not naming Li-Po mode) and I plan to:

Discharge the battery. (already done)
Switch to mode for charging NiCd batteries.
Set charging current to 2 A.
Start charging and wait until finished. :)

I am not sure whether NiCd mode is more suitable than NiMH mode for the task. Or should I forget the entire idea of using such a charger?


texts: Timer/counter overflow and TIFR register

texts:
I recently planned to use AVR timer/counter for my projects. I have studied a number of documents about how to set it up. I use ATTiny2313A to test it out and learn about its features. I came across a problem when tried to toggle a pin for every few seconds.

According to the datasheet the TIFR has the following bit arrangement:

As you see the first bit is assigned to TOV0. When a counter overflow occurs this bit is set to 1. I used this fact and developed a code as following:

#include <avr/io.h>

int main(void)
{
uint16_t count=0, M=500;
uint8_t n=0x02;
DDRB=0xff;
TCNT0=0x00;
TCCR0B=(1<<CS00) | (1<<CS02); //use prescaler 1024

   while (1)
   {
       while ((TIFR & n) == 0); // control passes this loop after TIFR sets to n,
                                   // which is when counter overflows

       TCNT0 = 0x00;
       TIFR=n; // clear TIFR
       count++;

       if (count>=M)
       {
           PORTB ^= (1 << PB0);
           count=0;
       }

return (0);
   }

The code works as expected. I expect that when an overflow occurs TIFR changes to 0x02 as TOV0 sets to one. But that seems not to be the only scenario. If I change the variable n to something like n=0x04 and build the program I see the same behavior, meaning that the LED connected to PB0 still toggles with the same frequency as it did previously. The second bit in TIFR corresponds to OCF0B. So if the code wants to work as before this bit must change to 1 when an overflow happens. But does it? I don't think the output compare flag is enabled so OCF0B can't change.


texts:
I have read about Series RC Circuit and have understood the Time constant concept.
Wikipedia states - "It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to approximately 63.2% of the value of an applied DC voltage, or to discharge the capacitor through the same resistor to approximately 36.8% of its initial charge voltage. "
Since Capacitor is charged through this resistor, the concept of time constant is valid.
But assume a parallel RC Circuit. I was not able to find the formula for time constant of a parallel RC circuit and also not sure whether the concept of time constant in a parallel RC circuit would mean something?
Can someone provide me the formula for Parallel RC Circuit during charging and discharging?
My question is based on the below circuit :

Once the voltage across the sense resistors cross 0.7V, the Transistor Q2203 will turn ON. What role does the C2202 play in combination with the sense resistors?
I have checked and reduced the value of C2202 in simulation and saw that if I decreased the value of C2202, the transistor turns ON quickly for a certain load resistance. If C2202 value is increased, the time taken for the Q2203 to turn ON increases? So, I thought of researching on charging of a parallel RC Circuit and its formulas which I couldn't find?
Please help me to solve my queries in the question.


texts:
I am in the process of reading through the above mentioned doc from here.

In page-21, second paragraph in section 8.5 I/O Memory, line 6 is given as below:

  When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used.

However, in page-224, row 1 of table, first column, Assembly Code Example has the last line as follows:

out TWCR, r16

But as per page-21 statment, above instruction is wrong as TWCR has memory address 0xBC as given in page-396 row 6.

Is there something wrong here, or am I understanding it wrong?

Please help.

Edit: definitions file


texts: Using potentiometer in two separate circuits

texts:
I am building a circuit with Arduino to control the motion of a stepper motor.

I want to use my guitar amp potentiometers to feed voltages back into the Arduino without disassembling the original amp circuit.

Is this possible? How can it be achieved?


texts:
I am making the "Pocket Laser Engraver" on instructables, but I need to find a replacement for the DVD drive's laser diode. (Already broke both of mine)

Online I might want to get the 12x20mm 5mW 650nm Laser diode and casing from AixiZ.

However, I need to know the rating of the laser diode in a 5.25 in DVD IDE drive so I can get one just like it. I've looked quite a bit for an accurate answer, with no luck so far. I'm sure somebody knows what the actual answer is, though!


texts: How many ESP32 WiFi devices can transfer data to an android phone same time?

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I need to connect multiple ESP32 wifi clients to a single android phone,
the android phone will be a wifi server,

I need to transfer 3Mbps of data from each ESP32 to the android phone simultaneously via wifi

I could not find a maximum number of ESP32 clients that can be connected to the server (android phone)

In general, I know the maximum no is anyway defined by the bandwidth usage as well.

How many ESP32 devices can connect and transfer data to an android phone same time?


texts: How is it possible to have high voltage and low current? It seems to contradict the relationship between current and voltage in E=IR

texts: I have read different forums and watched a few youtubes (in addition to my textbook readings) and the explanations seem to fall short.  The issue seems to be how we are first taught about a direct relationship between voltage and current (that is, an increase in voltage renders an increase in current if resistance remains the same) and then we're taught about power lines that have high voltage and low current (because other wise we would need thick wires that carry high current [which would run the risk of overheating due to the joule effect or something or another..). So please don't explain to me the infrastructural reasons why high voltage, low current is necessary for power lines.  I just need to know how high voltage, low current is even possible.  I've only been studying DC so far so maybe AC has rules that would enlighten me...but I thought the E=IR formula was universal.


texts: Why does my atmega32's malloc function returning me the pointer address in multiple of 4?

texts:
I am in a learing phase so I am no pro when it comes to understanding the memory and hence I am having a little trouble in understanding few things

The datasheet of atmega32 says that it comes with 2K of SRAM

How does this make 2k?

When I ran the following code in an infinite loop until it returns 0, the malloc function returned me with addresses in multiples of 4 for Atmega32.

p = (char*)malloc(sizeof(char));

From what I am understanding , the char is of 1 Byte hence it should be giving me the adjacent addrresses instead?


texts: I have been building a robotic arm for a while now and finally got onto the actual coding side of things. I have been looking around the internet and I’m trying to build some AI code for the arm. Everyone says to use python but is that possible to put on an AVR chip? How do you guys go about implementing AI on circuits? Any tips and tricks would be great.