texts: Transitioning to lead-free reflow and soldering

texts:
I have recently been thinking about moving to a lead-free process for my production and though I've been reading up, I was hoping someone more knowledgable than me would be able to point me in the right direction. I have an option to choose between the following solder pastes and I was hoping to know which of these would be the easiest to transition to from a SnPb process that I currently have. I don't have any specialised equipment and my reflow equipment is a home-brewn oven that can reach a temp of about 245 deg C.

Solder pastes:

Sn/Ag3/Cu0.5 (SAC305) NC Solder Paste
Sn/Ag0.3/Cu0.7 (SAC0307) NC Solder Paste
Sn/Ag3.0/Cu0.5/Ni0.06/Ge0.01 (SAC305+Ni+Ge) NC Solder Paste

Solder wires:

Sn/Ag0.3/Cu0.7 (SAC0307) Solder Wire
Sn99.3/Cu0.7 Solder Wire
Sn/Ag3.0/Cu0.5/Ni0.06/Ge0.01 (SAC305) Solder Wire

Edit: I went ahead and bought the SAC0307 solder wire and paste. Both were really easy to use. The wire proved a little tough for my 25W iron but it was just as easy as leaded wire with a 50W iron. For the paste, I set the oven max temp to 240 deg C and that did a great job. Thank you again for all the great suggestions.


texts: Is it possible to connect a UPS in parallel with the mains?

texts:
Short version:
When a UPS is plugged in to the mains, is it possible to plug the UPS output back to the same mains?
Will that work as an emergency power backup for the mains circuit?

Longer version:
The question makes no sense at first, since a UPS is supposed to do that by itself. No need to connect it in paralel. But here is my issue.
I need to plug in high consumption devices occasionally to the same circuit that the UPS is supplying to. Devices like a vacuum cleaner or an air heater which surpass the UPS's output power.
So what if I put the UPS in parallel with the mains so that I get emergency power and I can still plug in high power devices??

Full version:
Where I live there are frequent power outages for short periods of time. And I have too many electronic devices that are reset with every outage and they lose any configuration they had.
It's not just my PC, it's also my router, cable TV decoder, stereo system, TV set, clock radio and so on.
I can't afford buying several UPSs to put in each room. Plus, it would be too messy with all those cords and cables going from the UPS to every device.
So it occurred to me if I could power the entire mains circuit (the one that goes to the bedrooms' plugs) with one UPS so all the devices would have emergency power when an outage happens.
And when I need to use the vacuum cleaner or some other high load, it would bypass the UPS and get the power directly from the mains.
Would this idea work?
If not, is there a way I can achieve this in an inexpensive way?


texts: How to convert 48V to 5V in this system?

texts:
I have built a prototype for monitoring the battery voltage of my off-grid PV system. The prototype is as shown in the clumsy schematic drawing below, and it uses 24 V battery. I use an OKI-78SR-5 to get 5 V for an Arduino board with a GSM shield.

To save the battery, the whole circuit is only switched on once per day (with an external system). So it wakes up just to measure and send the data. This should enable me to run the monitor through the winter. I'm aware that this approach is inaccurate due to eg. temperature change, but I hope to get at least some idea of the conditions in a remote location.

The prototype seems to work, but now I've deviced that my battery system will use 48 V (4 x 12 V) instead of 24 V. The OKI-78SR-5 only goes up to 36 V.

To convert the system to use 48 V, what should I do?

a) connect another OKI-78SR-5 in series? Is it possible?

b) buy a 48V to 5V converter, eg. http://www2.mouser.com/ProductDetail/Mean-Well/SD-15C-05/ (or would a cheaper one suffice?)

c) only monitor two of the batteries? Pointless, even harmful?

d) just add a resistor? Bad for efficiency!

e) something else?

simulate this circuit – Schematic created using CircuitLab


texts: What type of electrical sensing element is used in Water Quality Monitoring Meters?

texts:
What type of electrical sensing element is used in Water Quality Monitoring meters such as those pictured below? I might not be using the correct search terms.

Some of these meters monitor Total Dissolved Solids (TDS) or pH levels in water.

I suspect there is an electro-chemical sensor. I have not been able to locate any information on the electrical sensing element or the mechanism. I intend to build a simple water quality meter using a simple microprocessor and respective sensing element.

Note: I posted this question on Engineering. I am looking for type of electrodes and possible sensing circuitry use in such a device.


texts: Why two inverters cascaded in multiplexer control signal terminals?

texts: Why cascaded inverters are used in the multiplexer when it is possible to realize the circuit using a single inverter.


texts: I got a quick question! Is the circuit depicted in the link indeed a voltage doubler or is it just a bridge rectifier with smoothing capacitors?


texts:
Ill try to be as brief as possible. TL;DR: How to use my 3A 5V USB-C charger to power a dumb device that needs 5V 3A to run.

My goal: I want to have a nightstand, that can charge 3 devices at the same time. Doesn't matter how fast.

What I have done so far is, made a board, set out 3 pairs of + and - , to each port that will have a wire connecting to the phone I'll need to charge.

I have a USB-C receptacle (which I am going to attach to my wires) and a USB-C cable. I am going to use an Anker charger (5V 3A output).

I did some research on USB-C and it's very complicated, CC pins and 5.1k ohms resistance and what not.

I am used to old USB cables in which I would just connect VCC and GND and it would supply power.

My question is: Can I just connect wires from the USB-C receptacle VBus and GND pins and it will work and provide the 5V 3A output just like those old cables? Or do I need those pull up and pull down resistors and all that complex stuff which I have no idea what they are.

Please go easy on me as I am new to the world of using USB-C and I want to use it.


texts: Best tools to debug simple digital circuits?

texts:
I am a professional software developer who is used to the luxuries of integrated debuggers.  For a while now, I have been experimenting with the Arduino platform.  However, I find that attempting to interface with components like a Dallas DS1820 digital temperature sensor is like fumbling around in the dark.

Assuming a loose budget of $200 or so, what kind of tools are there to help me visualize what's going on?  I have looked at the Link Instruments MSO-19, but I honestly don't know a whole lot about the difference between an oscilloscope and a logic analyzer.

How do I know that the device I buy will be capable of measuring the types of (simple) components I am using?


texts:
simulate this circuit – Schematic created using CircuitLab

In my book, this diagram is used to explain how a bridge rectifier works, in positive and negative half cycles. But it does not explain the significance and necessity of the ground in the circuit. What is the significance of the ground here?

If we consider ground's voltage as zero voltage (generally what I do in circuit analysis) and for any half cycle (just say positive half cycle), there will be 0.7V voltage drop across D1. Doesn't it make positive half cycle start from -0.7 volt? It seems odd to me.


texts: View RTL/netlist/schematic with Icarus Verilog

texts: I am learning Verilog and using Icarus Verilog for compilation and simulation. Is it possible to visualizate result somehow as a schematic, RTL etc?


texts: Is my understanding correct in selecting ADC resolution? (Noise analysis)

texts:
I have posted a similar question before: ADC resolution, considering DSP. And finally I think I know the answer. Could you please have a check on it?

Here is the set up:

The input signal of the ADC has a noise floor with noise density of \$ 5\times10^{-4} V/ \sqrt{Hz}\$ already.
The input signal has been amplified to full scale of ADC.
The ADC has a range of 3V with 12 bits.
The sampling rate will be 10,000Hz.

Is it correct to say that:

The quantization noise RMS of the ADC will be \$ {q\over\sqrt{12}
   }={3V \over {2^{12} \times \sqrt{12}} } ={2.11 \times 10^{-4} V}\$
The noise density created by ADC quantization will be \${{2.11\times 10^{-4}}V\over \sqrt{5,000Hz}} = {{2.984\times 10^{-6}}V/\sqrt{Hz}} \$
The noise density is dominated by ADC input signal noise, instead of ADC quantization noise. Therefore, 12 bit ADC is sufficient in this application.

Edit: What I want to know

Sorry for the confusion. I will try to put "what I really want to know" here:

Lets assume that ADC is perfect and the only enemy will be analog noises.
Under this condition, we are employing very high Q band pass filters in DSP, with bandwidth around 0.01Hz. Therefore the \$ 0.5mV/ \sqrt{Hz} \$ noise becomes 0.05mV rms here and is acceptable for us.
The measurement precision will corresponds to \$ 3V/0.05mV = 2^{16} \$, which has 16 bit resolution.
Now let us come back to the real case. When a 12-bit ADC is to be employed, could the 12-bit resolution be simply treated as quantization noise? If this is the case, 12 bit ADC can also lead to a 16 bit resolution result.
What bothers me is "Can I really get a more precised result than ADC resolution WITHOUT oversampling?"

Thank you very much.


texts: PICs for beginners using MPLAB Compatible Mini USB PIC Programmer

texts:
I wrote a program to turn on LEDs on PORTB. The programmer erased, programmed, verified, so far so good. But then nothing happened. No lights. My programmer is a MPLAB Compatible Mini USB PIC Programmer.

What are some things that novices miss?

Below is my code:

#include <p18f4550.h>
#pragma config WDT = OFF
void delay (void)
{
  unsigned int i;
  for (i = 0; i < 65535 ; i++) ;
}

void main (void)
{
  TRISB = 0;
  while (1)
  {
    PORTB = 0;
    delay ();
    PORTB = 0xFF;
    delay ();
  }
}


texts:
I was reading the atmega328p datasheet, and suddenly, i saw that a register is mentioned called "OCRA", on page 108 and page 160, which normally, should be register "OCR0A", which is widely mentioned on this datasheet. "OCRA" is only mentioned on those two pages, inside tables, which is suspicious.

OCR0A is normally responsible for the TOP value of compare register for the timer interrups.

Is this a mistake of the datasheet?


texts: Op-amp voltage follower not working as expected

texts:
I previously asked about a circuit to scale my analog value before MCU ADC.
Based on the answers I got from that post I decided to change my op-amp from a TL072 to a CA3130.
The following pictures show my circuit schematic and PCB.

I just tried the circuit and it is not working as I expected it to.
When the input is left unconnected the op-amp output is about 8V. When I connect a voltage source of 1V to input the output voltage of op-amp is 7V. For a 6V input, the op-amp output is 9.6.
I couldn't figure out how it is working. When I read about a voltage-follower circuit I thought how easy it is, but in practice, I learned it is not that easy.


texts:
From the following diagram:

Lorentz force can be calculated from the following formula: F = IL×B What about this wire in the following diagram?

Assuming that all the variables are the same(I,L,B). However, the diameter(range) of the magnetic field is much smaller. Would both conductors/wires experience the same Lorentz force? My assumption is the second diagram would have a much smaller FL than the one that has the magnetic field incompletely covering it.


texts: Help selecting a Mosfet/driver for 300vdc 3amp continuous on Arduino

texts:
The title spells it out mostly. Actual voltage will be from 15-240vdc max, load will be 1-3amp max, the mosfet will connect a resistive load. The circuit may be on for 10-30 hours at a time, 6-8 times per year.

The Arduino will want a 5v logic level gate. I am not sure, but I think it needs to be oversized to 300-400v 5amp rating? to reduce overheating. I can run a fan/heatsink/compound if needed.

The project I want to do has been done by many people in a manual archaic scenario, and a few commercial companies have automated using a complex circuit.

I have looked on Digikey, but honestly I am fuzzy on Mosfet ratings and 240vdc is extremely dangerous so I want to get it right the first time.

I also need suggestions as to driver selection, or need for diodes or protective addons between the driver/fet.

I have done a lot of preliminary research on this project, and it is probably above my current experience level, but this will be a learning experience that I embrace to take me to the next level.

My experience: I have 20 years of constant basic experience in electronics, I have a few occasional intermediate projects I have done, building or repairing things using high level guidance I find online. I am not very good on circuit design, I carry a few resistors and diodes around in my tool bag, I have replaced CAPs/FETs on a few stereo amps before, but it is easy to match a part number and suck some solder. I understand ohms law, and can read simple circuit diagrams. My profession is in the IT field, and I was taught to build houses and pull engines by the time I was 12- jack of a few trades.

I humbly offer my thanks to anyone that is willing to give me instruction.


texts: Can electronics be damaged by under-currenting it?

texts: Someone just asked Can electronics be damaged by undervolting it?, so now I am going to ask under-current. Let's say something requires 10A, 12V, if I limit the current to 5A, could anything go wrong?


texts:
I'm currently trying to connect a Macronix MX25L6406E SPI flash memory chip to a Raspberry Pi so that I can (hopefully) dump it's memory.

I am using a small Python script to bit-bang the commands and read data from the chip, an approach the worked for a previously used Winbond chip. My problem, is that the chip seems to be holding the MISO line high which is causing the Raspberry Pi to read in 1's (0xFF bytes).

I have confirmed that the pins of the chip are all connected to the correct GPIO pins on the Pi, and that the Vcc voltage to the chip is correct (3.3V).

Also, if it helps, the Pi isn't holding the MISO line high, as the LED I've attached to the line remains illuminated after disconnecting the Pi, but reconfiguring the corresponding GPIO pin as an output and setting it LOW seems to cause the MISO line to drop LOW.

The pin states during the transactions are as follows: MOSI: 1 0 0 1, MISO: 1 1 1 1, CS: 0 0 0 0. That's the first nybble of the Read ID commands (0x9F). Then, this is the first nybble of the response: MOSI: 1 1 1 1, MISO: 1 1 1 1, CS: 0 0 0 0.


texts:
I'm just starting to learn SystemVerilog and work with FPGAs, and so far I haven't found a satisfactory way to test my code.  I'm coming from a software background, and I have always been writing  thorough automated tests for my code.  I have been using JUnit-style frameworks (with lots of domain-specific wrapping on top, to reduce boilerplate), as well as QuickCheck-style frameworks, and found ways to use these frameworks to write concise test code that nevertheless provides me with high confidence in the product I'm developing.  I haven't yet found anything equivalent for hardware description languages.

Introductory Verilog texts typically present testbenches that are just driving the input signals.  These testbenches are unreadable repetitive walls of code (signal assignments) without assertions; these tests are not even automatic.  Some texts try to incorporate machine-checkable assertions into the testbench code so that one does not have to look at waveforms to determine whether the test passed or failed.  Still, the "wall of repetitive text" problem remains.

I researched  the issue further, and found that the current industry standard for RTL verification is UVM.  The idea does look better to me, I haven't looked in detail into it, but for me the big disadvantage of UVM is that UVM testbenches are not synthesizable.

If I can't run my tests on the actual FPGA, how can I be confident that my synthesized design works correctly?  I understand that there is a high chance that it will work after the simulation tests have passed, but there are a lot of assumptions involved (that my code is not racy, that my code meets timing requirements, that the synthesis tool is correct etc.)

A parallel in the software world would be developing a program in C, compiling with gcc and testing it on x86 on Windows, and then compiling it with Clang and running it in production on ARM on Linux.  The program should work, assuming that it does not have undefined behavior, does not have non-portable assumptions about the execution environment, both compilers don't have bugs affecting the program.  This is a lot of assumptions that most software engineers would not make and instead would just run their tests on the production configuration.

Am I fundamentally misunderstanding something about real-world hardware design process?  How are designs verified once synthesized into FPGAs and actual silicon?  How to run existing test cases on designs in FPGAs and silicon?

Are there any industry-standard practices for synthesizable testbenches?  Do people actually write synthesizable testbenches?


texts: What does a beginner need to know to build an inductive heater?

texts:
I'm a programmer by profession and building skills in metalworking and my goal is to build certain types of chemical reactors. As a learning project, I want to construct a programmable deep fryer. One of the missing pieces in my concept so far is the heating system, and during my research I have kind of fallen in love with inductive heating.

Now, my knowledge in electronics is basic at best, but I'm quite used to study stuff on demand, and I'm not in a hurry. Besides Wikipedia, I found this page to be a good primer on the subject. I'm currently working through the words I didn't understand, such as 'impedance'.

What are good resources to learn, and what are good beginner design choices for things like operating frequency of the work coil etc? What are essential safety guidelines that a more experienced person would already know by heart? Are there complications in design or construction that I can avoid by making some tradeoffs, like reducing heating power, or efficiency? Is there some equivalent of a Hello World program in RLC circuit design?


texts: Can I add a resistor to a 120V-24V power source to convert the amperage from 2.9 to 1.8?

texts: I have an old Kodak printer dock for an Easyshare camera but I'm missing the power source for it. The dock requires 24V 1.8A power so I bought a power supply marked 24V (24.2 measured) and 70W but the printer only powers up and then shuts down after a few seconds. If the problem is the supply amperage is too high can I use a resistor inline somewhere to lower the amperage? As you may have guessed, I've done some research but I'm new to this kind of thing.


texts: Where are the losses in an inverter-type portable generator?

texts:
I have an inverter-type portable gasoline generator that is rated at 3kW / 3.3kW surge.
In the service manual, the engine's power output is said to be 4kW. (The engine's displacement is 269cc).
I am curious as to where do the power losses happen in an inverter-type generator.
In the rotor/stator assembly, as heat? In the inverter electronics?


texts: Is this symbol for common-mode choke or usual inductor?

texts:
In the below circuit from this datasheet, I think L1 represents common-mode choke; but what does L2 represent?

And in this datasheet for a similar filter, I don't see any difference between the symbols:

Which one in these circuits is common-mode choke and which one is usual inductor? Which one has inductance?


texts:
I am going through the circuit as shown above.
In such LED drive design (constant current), I am not sure about the role of R16 (2 ohm) resistor.
Is it for transistor to have less power dissipation since as current flows R16 will have some voltage across it, reducing Vce drop?

Thank you.


texts: Capacitor voltage of Buck converter with LC input filter

texts: What will be the voltages across capacitor C1 and inductor L1 in terms of Vg,D,R? From the amp charge balance equation, i1=-io *D because i2=io.From my observation, Vc1= Vg for 0<T<DTs and Vc1= Vg-vL1 for DTs<T<Ts. But I can't reach the equation of VL1 and Vc1 using Vg,D,R. Please help me to express the equations.


texts:
Please find the attached image showing amaron quanta 12 V 100 Ah VRLA battery discharge chart at constant current rating.
I am bit confused that how should I calculate the battery capacity based on that.

In the table they shown end cut off voltage like 1.3 V, 1.55 V, 1.6 V, 1.7 V, 1.75 V and 1.8 V and corresponding ampere in table like 5 min, 10 min, ....5 hr, 10 hr, 20 hr etc.

If I simple take 10 hr reading then
1.6 V = 9.72 amp
1.7 V = 9.49 amp
1.75 V = 9.31 amp
1.8 V = 9.26 amp

Out of all this what parameter to be consider in discharge test. Most searches says that it should be 1.75X6=10.5 V is the cut off voltage and related to that constant current to be passed. but if that is the case why manufacturer is giving 1.3 V, 1.55 V, 1.6 V, 1.7 V, 1.75 V, and 1.8 V etc. and current parameter for that. If I take 1.6 V and related to that 9.72 amp as discharge current does it will show different capacity of battery or it will be the same regardless of the cut off voltage and current rating.


texts: Establishing a physically enforced unidirectional Ethernet link with 1000BASE-X, fiber optic PHY

texts:
I have a use case where I am attempting to establish a unidirectional Ethernet link where a singular fiber is used to transmit data to the receiver. The Rx of the transmit side and the Tx of the receive side are not physically connected.

The proposed configuration is as follows:

•The PHY is a fiber optic 1000BASE-X (LX or SX)

•Autonegotiation and any link monitoring protocols are disabled

•Full duplex configuration

•A second transceiver on the low (transmitting) side is used to provide a connection to the Rx port on the transceiver attempting to transmit unidirectionally (Ethernet spoofing) to set the signal_detect variable in the PCS

•UDP is the transport protocol and ARP is statically configured

So the question is will this configuration allow for successful synchronization at the PHY level for the transmitting side, i.e. will this "Ethernet spoofing" allow the second transceiver to provide the /Comma and /Idle code groups to the first that are required to achieve synchronization? Does synchronization need to be established on the high (receiving) side to successfully receive data?

Alternatively, will COTS SFP transceivers support IEEE 802.3 Clause 66, i.e. setting the mr_unidirectional_enable PCS variable, if the PHY is not of the passive optical network type and an OAM sublayer is not present?

I'm aware of security appliance data diodes however am trying to avoid that implementation.


texts: Switching circuit using a MOSFET to not destroy the power supply

texts:
I am designing a temperature control system with arduino and PID , and i am using a Mosfet to switch the PwM from the arduino and allow 2A 5V heater to heat up.

Can you tell me a good switching circuit, i can use in additional with the MOSFET , since i assume that the switching will destroy the Power supply on the Heater. because to the temperature is oscillating between (37deg and 36 deg) so the Mosfet keeps putting in betweeen On and Off.
The Pwm is oscillating between 0 and 255 no (in  betweens)
Thanks


texts:
I measure in common source connected mosfet (19N10L) Vds about 2.4V in on state. The current is 2A.

In datasheet is defined Rds 0.1ohm. Why is Vds in this mosfet so high (2.4V)?
Shouldnt be Vds = 0.1 x 2A = 0.2V?

Vcc is 18V.


texts: Maximize output signal swing in digital circuit design

texts:
Please help me understand the following paragraph in chapter CMOS Digital Logic Circuit from book"Sedra/Smith micro electronics circuit 6e".

  An ideal VTC is one that maximizes the OUTPUT signal swing and the noise margins. For an inverter operated from a power supply VDD, maximum signal swing is obtained when VOL = 0 V, and VOH = VDD. Where VOL and VOH is the Output Low level and Output High level respectively.

But I thought the amplitude of OUTPUT signal swing is determined by the Bias point Q in the VTC transitional region (the linear section). and in my opinion what the above statement does is maximizing the INPUT signal swing (rather than output) because when VOL = 0 V, and VOH = VDD, the Noise Margin for both Low input and High input are maximized as Noise Margin is defined VOH - VIH = VDD - VIH for Logic High input signal, and VIL - VOL = VIL - 0 for Logic Low input signal. And a wider Noise Margin indicates better tolerance to noise signal at the input, therefor a greater headroom and legroom allowed for the input signal instead of the output signal.

What did I misunderstand here? How does conditions like VOL = 0 V, and VOH = VDD maximized the output signal swing?

thank you so much everyone.

Zheng


texts: LED light bulbs flicker when switched off - where does the energy come from?

texts:
Outside my house, at the front, I have a set-up of 3 lights attached to the wall. These lights can be switched on using a switch inside the house. Furtermore, they are attached to an infra-red sensor which can switch the lights on for 2 minutes at night time, when someone passes by. I have this same set-up at the back of my house. So far, so good.

I recently changed the light bulbs from incandescent to LED. At the back of my house, this worked fine. The set-up at the front of my house resulted in the LED lights flickering when switched off. If I place back 1 incandescent light bulb, leaving the other two lights LED, this problem does not occur. Following the post Mains LED light bulb flickers when switched off, I understand how LED lights work and why they can flicker. My remaining questions are:

Where does the energy come from leading to the flickering?
Can I
change something in the switch or the sensor to make it stop?
Why does the addition of an incandescent light bulb stop the LED lights from flickering?
Is a set-up with all incandescent light bulbs using up the same amount of energy, without me noticing as easily?


texts: Resistor that can be placed like a jumper

texts:
I want to make a relay output to be configurable by the client as NO/NC or guarded by resistors (10k opened, 1k closed).
A solution I have been thinking about uses resistors that can be placed like a jumper on a pin header, like this:

A quick search for existence of this jumper type yielded nothing. Does anyone know if this is an actually available component? Any other (albeit simple for untrained end users) solutions are welcomed.


texts:
I am using the a hall effect sensor - model 480-5198-ND. I have tested this simple circuit using a LED and it is working. However, it is "ON" by default. Only when the magnet is near the hall effect sensor , it will be "OFF".

How do I make it such that it is OFF by default and ON only when the magnet is near the hall effect sensor?


texts: determine necessary current to drive a stepper motor?

texts: I am trying to drive a stepper motor. It is a 12V unipolar motor. But it is not moving. I tried with L293D , ULN2003 etc. I think it is not getting sufficient current. But how do I determine how much current is necessary, so that I can chose a driver IC? In the datasheet there is no current mentioned.


texts:
I am working with an existing design and seeing a 200Ω, 2W resistor becoming discolored in the field (customer questioned its condition), but not appearing to fail. I measure resistance and is 203Ω, maximum measured voltage across this resistor 3.5V. That’s .06W, this is a 2W resistor. The resistor is not hot to the touch at all. My thinking was possibly moisture, but there are many other resistors on the board and none look like this.

The purpose for this resistor in the circuit is to prevent the input voltage to the +5VDC liner voltage regulator from exceeding its maximum allowable (35VDC).
There is one relay powered off of V+. So drop across said does vary from 2VDC (relay off) to 3.5VDC (relay on).

Has anyone seen this or have any input as to why this is occurring?


texts: Inductor waveform not increasing when supply is increased

texts:
I am building and testing the transmitter side of a wireless charger.

The image below is a rough representation of what I am doing, U1 is powered by an IR2110 driver at 5kHz off a 555.
V1 is 30VDC and the flyback diode is a 10 amp ultra fast recovery diode( cant remember exact model)

When measuring across the load on a scope I get a just the positive cycle of a sine wave ( so what a sine wave looks like after a rectifier), its voltage however, comes solely from the mosfet and if I am to increase and reduce the supply it does not effect the wave. I can't for the life of me figure out why?

Could this be to do with the internal diode inside the MOSFET? Would an H-bridge configuration work better in this situation?

Why does this not work? Because in my head the voltage across L1 should be drain signal plus V1 shouldn't it?


texts:
I am currently in a computer engineering class and I have been asked to design a product that can guide blind people. In my fictitious product I am going to implement a module to detect distances (a simple laser range finder that consumes 10 mA when Idle and 100 mA when it shoots a beam), a speech recognition module (which consumes 1 micro Ampere when idle), and also a GPS system. This means my device will be constantly processing input from the distance sensor and the GPS system. It will also output instructions like "turn left" based on the destination address the user entered via a voice command, and it will also tells the user observations like "There is an obstacle directly ahead".

I have been asked to estimate the processing power required by this device, and also the amount of volatile and non volatile memory required. It is all of course based on estimations, and the components used can range from 2014 to 3 years into the future (2017). Are there any estimation methods to define the processing power required? And more specifically, how is processing power quantified? In terms of non volatile memory I believe the only information I need to store are addresses the user inputs, and the commands the system can enter and the commands the system can output. Thank you for any advice!


texts: Arduino Uno + Ethernet Shield : 16x2 LCD Not Initializing

texts:
I have a 16x2 LCD shield that I have tested to be working fine when connected to arduino uno using the following pin connections:

3: RW
5: EN
6,7,8,9: DATA(4 bit mode)

The contrast is nice and dark and the text gets displayed properly.

However when I make the same connections to a UNO + Ethernet Shield two things happen
1. The contrast goes all light
2. LCD does not get initialized (row of black boxes)

As per the page here the ethernet shield uses the pin D2, D4, D10-D13, hence i chose the pin assignment above.

Now this has stumped me, why would adding the shield make a difference? Any ideas ??


texts:
I'm trying to use a RPi3 to output/control a lamp using this relay module.

I also want to be able to read from a push button and a switch.

The problem I'm having is that it looks like switching the relay is introducing noise in to the GPIO input and creating false positives.

The RPi and relay module are in a outdoor enclosure 190mm x 145mm x 140mm. They are right to each other.

I tried using a solid state relay and that solved the problem of the interference, but I would prefer to use a conventional relay because of size and pricing.

I have tried to see the noise picked up by the GPIO using a cheap Hantek digital USB oscilloscope, but unfortunately wasn't able to see anything. Still waiting to check with my analog oscilloscope. In addition, I'm thinking about trying shielded cable from the pushbutton and switch to the GPIO and also wrapping the relay module in grounded metal mesh to create a Faraday cage.

Till now I've tried putting a low-pass filter for each inputs.

The first circuit I tried was: C1 - 10n and 100n

simulate this circuit – Schematic created using CircuitLab

Then I tried a low-pass filter:
R1 - 100 and 1k
C1 - 1u, 10n, 100n

simulate this circuit

Also I tried with GPIO pull-up on and off

In any case none of them improve the result.

On the software side of things I'm using Python, RPi.GPIO event_detect; I tried increasing the bounce time and inserting a delay after event-detect to "filter" human generated events, but this would only work for the push button case, not switch.

Any advice would be appreciated.

UPDATE: This Relay Module insert a lot of noise, I tried with the RPI HAT slice of realy and tha same code worked fine, could detect any false positives on a quick test run.

this is the code:

#!/usr/bin/python

import RPi.GPIO as GPIO
import time

GPIO.setwarnings(False)

GPIO.setmode(GPIO.BCM)
GPIO.setup(24, GPIO.OUT)
GPIO.setup(26, GPIO.IN, pull_up_down=GPIO.PUD_UP)

GPIO.setup(20, GPIO.IN, pull_up_down=GPIO.PUD_UP)

GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def read2(channel):
    print "GPIO 2"

def read20(channel):
    print "Button"

def read23(channel):
    print "Switch"

if __name__ == '__main__':

    GPIO.add_event_detect(26, GPIO.BOTH, callback=read2, bouncetime=300)
    GPIO.add_event_detect(20, GPIO.BOTH, callback=read20, bouncetime=300)
    GPIO.add_event_detect(23, GPIO.BOTH, callback=read23, bouncetime=300)

    while True:
        pass

Regardless I'm still looking for how to be able to use that board.


texts: Do I need to control trace impedance for DDR2 memory?

texts:
I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-)

3) What is up with controlled impedance of PCB traces? Why it's important? What will happen if I would just have usual non-controlled 0.15mm traces? (distance between FPGA & DDR2 chips is 5cm).

Aligning trace length (especially on data & clock lines) is pretty clear, shouldn't be a problem as distances & frequency is low. As far as I understand there is still some 5-20cm length difference tolerance on DQ, but no harm making it equal.


texts: Using Arduino/Processing to print text on screen when an LED light up

texts:
I have a question regarding the programming of printing text on the screen after an LED lights up on a breadboard. Should we plug in the LED into the Arduino board or a regular breadboard? How do I get the Arduino to recognize that the LED has lit up? I am doing a physical game where if you touch the wire with a wand, a buzzer and a LED lights up, which is currently connected as a parallel circuit.

Thank you very much in advance!


texts:
I'm implementing the NXP TDA19988 HDMI transmitter IC in one of my projects and I am currently in the PCB design stage. I am building my component library and when I came across this part I wasn't sure how to proceed. I am familiar with standard 64-pin QFNs. However, this one seems to have additional "pads" on the bottom, besides the normal electrical connections:

Unless I overlooked it, they do not seem to be mentioned in the datasheet. Are these simply extensions of the ground plane/pad on the bottom of the IC? My suspicion is that they are acting as a reference plane for the internal bond wires leading to the electrical pads to provide controlled-impedance, in which case I assume I need to have them connected to ground. Is there a specific land pattern that I should follow for these sorts of packages? The land pattern I have is the SOT804-2 (vs. the SOT804-4 I'm really looking for) and can be found on page 3 of this document:

https://www.nxp.com/docs/en/package-information/SOT804-2.pdf

EDIT:

Since apparently I wasn't being clear enough with my question, here it is in a concise, readable format:

Where can I find the recommended land pattern for the SOT802-4 64-pin HVQFN package used for this device?


texts:
I made a 4wd mobile robot with an 4 DoF robotic arm on it and currently in process of designing a power board for my robot. I would like get a detailed road map on designing a power board for the robot. Here is a brief overview of my hardware:

The robot has 8 joints which each of the motor runs with 12V (stall current: 800mA, nominal run: ~200mA),
The control board works with 5V (nominal current draw: 500mA, max: 1.5A),
Overall(averge) energy consumption of the robot is around 6 Watts (max 18Watts).

Here is what I have done so far for powering the robot:

I am using 2 ncr18650b battery in series with a cheap of-the-shelf battery management system (BMS), so I do not kill the batteries while over-running the robot,
Nominal voltages of these two batteries are 7.2V where I use one boost converter for driving the motors with 12V and a buck converter for driving the controller board with 5V,
I have to unplug the batteries when ever I need to charge them (since I do not have a charging circuit for the batteries yet).

Since I was working with the rest of the robot, I just built this battery setup in two days and it was working and enough. Now I would like to focus on developing a professional power management module. Here is simply what I need (need to understand) for designing the power circuit board:

I would like to power the robot with 2 18650 batteries in series,
the batteries (in series) should be charged without unplugging (from a 12V DC input port),
the robot can also be powered on while charging the batteries,
I would also like to monitor the batteries,
I would both want to supply 5V for controller board and 12V for the motors from the same battery unit. I encounted a problem with my cheap dump setup which; if motors draw much current from boost converter (12V), buck converters 5V drops. So, I would also like to prevent this happening.

As I am going to through the ICs and datasheet, I assume I need:

a 2S battery charging IC with a power path management (eg: bq24075) to also power the robot while charging the batteries,
a 2S battery management IC for balancing/protecting/monitoring the batteries (which are in series),
a boost converter for 12V,
a buck converter for 5V,

I am fairly experience with designing circuits but never worked on a power management circuit for batteries. I will appreciate if you give me detailed road map or resources for reading (schematics/articles etc.).

EDIT

A conceptual block diagram


texts: What is the peculiarity partial discharge?

texts:
I'm studying partial discharge, and it's not yet clear to me what the difference is between an electrical breakdown and a partial discharge.

Is partial discharge just a "small" electrical breakdown?

Wikipedia states that

  In electrical engineering, partial discharge (PD) is a localized dielectric breakdown (DB) of a small portion of a solid or fluid electrical insulation (EI) system under high voltage (HV) stress, which does not bridge the space between two conductors

"which does not bridge the space between two conductors"  is really unclear to me and an explanation of it might help me to understand the whole concept of partial discharge better.


texts: Which method is better for liquid crystal overdriving?

texts:
Recently, I started to design a LC (Liquid Crystal) shutter glass. The question is which component should I use. This is the LC shutter I might use: PolarSpeed®-S

However, there are a few more shutters to test so this shutter is not the only option. Anyway, we need fast switching response (below 100us) and to do that overdriving is essential.

Coming back to the question, this is the usual way to implement overdrive:

you see, applying higher voltage for enough time of period then returning to nominal voltage level makes LC switching faster.

And this is the overdriving method of PolarSpeed®-S:

PolarSpeed®-S uses two cells and this way it achieves below 50 uS rise and fall time.

So I was thinking there must be several ways to apply those voltage levels to LC cells.

1- An analog switch + Linear regulator(3 outputs)

simulate this circuit – Schematic created using CircuitLab

I couldn't find a deMUX in schematic so think those switches as 1:3 deMUX, everything is digital.

the other options are similar also:

2- Several Linear Transistor Driver

3- Several Voltage references + Swicthes

Or, can I:

4- Just use a few Op-Amps + resistors + switch

simulate this circuit

4- is the easiest and most flexible one because I already have 28V supply and all I will need are 3 Op-Amps, a voltage conterter to < -15V and switch. Also, this might be a good fit because I am allowed to change the gain of the opAmps so I can change the applied voltage to cells via changing resistors that way I can use the same pcb to test several shutters.

But I can not think of anything about pros and cons of those 4 options. So would you help me through this? What is the finest way for LCD overdriving? There may be other options I missed so if you know other options please share. Thanks per advance.

edit: a new idea by ChrisR is added below:

simulate this circuit

in the schematic GD(Gate driver) supplies are different in tme mean of overdrive purpose. GD1 supply is 14V - 0V, GD2 supply is 8V - 0V and GD3 is 14V - 8V. And just to simplify, diodes forward voltages are 1 V. So if I use this configuration, output will be like:

this I think, but I am not sure. Is this configuration safe to use?

edit(2): I decided to go with gate driver IX4428N and boost reg MIC2288YD5-TR.

simulate this circuit


texts: 4 iPad Air charging circuit indicator led not working

texts:
I developed this circuit in order for it to be connected to 4 ipads at the same time  the current they use to charge when they are on low battery goes around  1.8Amps, That its working as intended, however the part that has the led indicator for a blown fuse indicator doesnt seem to be working

the female headers are connected to a dual SUB female port which are used to connect the lighthing connector, however after removing the fuse the current should flow through the led and 470 ohm resistance , and yes i have a voltage of 3.5v in each led but it doesnt seem to be enough current for it to turn on , i would like any advice about this topic

Pins 1 and 2 carry the 5volts to each usb female port


texts:
I've a 5v 2200mAH battery and a 12v solar panel and charge controller.

Is there any danger in charger my battery from the 12v panel/controller? The batter will then power my raspberry pi zero micro-controller.

What would be the recommended/ safest way to do this?

Many thanks,

Paul


texts: What's the purpose of such weird wiring inside this smart card?

texts:
Here's a scan of a stripped MIFARE Ultralight smart card

That's some plastic film with (I assume aluminum) foil wiring acting as the antenna for both powering the chip and providing radio communications.

Two things look suspicious.

First, there's a wide stripe on the right (pointed to by the arrow) - a wide carefully engineered stripe of metal not connected to anything.

Second, note what happens between points A and B which I connected with a dotted line. There's a metal stripe going from B leftwards to the card perimeter, then downwards to the end of the "tunnel" crossing the wires and that end of the tunnel is also connected to the stripe that goes to point A. So it looks like the stripe from the "tunnel" end to point B can be eliminated by simply connecting points A and B and thus saving some metal.

Why are these two seemingly useless elements of wiring present in the circuit?


texts: Maximum signal transmission from OPAMP output

texts:
I generate an analog voltage from PIC microcontroller output. I want to transmit this analog signal to maximum distance as much as possible using single wire.  I have non-inverting OPAMP at the output of PIC pin.

Which configuration best for this maximum driving purpose?

Without OPAMP, direct driving from PIC
Unity gain OPAMP, R45=open, R46=0ohm
With some values of R45 and R46. Noninverting topology.


texts: Basic microcontroller + RF transmitter/receiver plausibility

texts:
I am a complete beginner (I have only gone through the beginners book to Arduino + done a few small projects). I want to know if it's possible to connect a very basic/cheap microcontroller like the MSP430 to a RF transmitter (for example this one) and another microcontroller to a RF receiver, add power supplies, some code and have them communicate (I am going to add a buzzer later). I also only need the receiver to acknowledge that it is receiving a signal. Data is not very important (i.e. 1 bit is enough).

Am I being naive/leaving something out/making a mistake? I understand resistors, diodes, etc. and c++, but have no idea of the rest of the world of electronics...

(By the way, the reason I chose the cheap parts is because I'll eventually need loads of them).
(Also, is there a cheap RF transmitter/receiver built onto/into a microcontroller?)


texts: How do I model a digital out in a circuit simulation?

texts:
I have a PIR: Panasonic NaPiOn AMN34112 that has a digital output.
When it detects motion it outputs 4V and 100 uA max.
I want to connect this output to a LED using one or more transistor amplifier stages. Before I do that I want to model what happens in the circuit simulator Every Circuit. How do I model a digital output? I want to make sure I am not sourcing more than 100 uA from the PIR. I was thinking modelling the PIR as a 4V battery. Is this wrong?

EDIT: after reading your answers I understand that this is very wrong.
Instead I will try this:

I used the default mosfet in the circuit simulator. In this circuit it has a voltage drop of V_SD = 1.4 V whereas I_DS is 281 uA => R_DS(on) = 1.4/2.8 E-4 = 5K Ohm which is the same as you mentioned.


texts: Measuring current transducer output - differential or single ended?

texts:
I'm designing a front-end for an ADC that will be measuring the voltage of a hall effect current transducer.

I have been reading up on differential vs single-ended measurement, and have become a bit confused as to how differential measurements work in a case like this.

I need to filter out noise that will be imposed onto the signal from the transducer because the wiring is passing through an electrical distribution box that has AC.

What I don't understand is this: if I want to reject this noise by using a differential amplifier, do I need to have an isolated power supply powering the current transducer?  If not, then where do I make the ground connection in the differential measurement schematic, below?

Also, do I run all the wiring to the current transducer as a double twisted pair (i.e. all 4 wires?)

simulate this circuit – Schematic created using CircuitLab

EDIT:

The hall effect transducer that I'm thinking of using is CSLT6B100, which has a ratiometric voltage output of 2.5V ±1500mV over the range -100 to 100 A

It's block diagram is as follows:

and transfer function:


texts: Can wireless communciation be synchronous?

texts: I understand that in synchronous communication, the sender and receiver need a common clock. Is it possible that wireless communication be synchronous? Can some common clocking element be there for such purpose?


texts: What happens to output if OPAMP its supply is tweaked?

texts:
Say the above OPAMP is normally operated with supply of +15V and -15V and output is said to swing from +15V to -15V. But I changed -15V power supply {of OPAMP} to -14V and Vi to:

(a)1V

(b)-15V

(c)1/2V

What should be the output and regions at which the OPAMP operate in each case?

Actually in Sergio Franco's book it was written that if we do so we will have to change the reference voltage of the circuit to average of supply and I am a bit confused about it.It is not meant as practical implementation I am just trying to learn.
Also consider below examples (they are not homework just trying to be exhaustive)

simulate this circuit – Schematic created using CircuitLab


texts: Is post fit simulation using timing netlists necessary although design meets setup-hold time requirements?

texts: In a purely synchronous design, if the design has positive slack for setup and hold times, it means that it meets timing. Therefore, provided that we have carried out static timing analysis and are happy with the slack at our targetted frequency, is there any point in carrying out post fit simulation with timing netlist anymore?


texts:
I have a circuit with a rotary switch (1 pole, 6 positions).

Instead of turning this switch by hand, I would like to control it via a computer.
Are there any components that can do this? They would receive commands and then switch their relay between several positions accordingly? If so, what are they called?


texts:
I am routing Ethernet traces from a Colibri iMX6ULL computer-on-module to RJ45 Ethernet connector (In-build Transformer). The layout design guide says that Ethernet should have 95 ohm differential and 50 ohm single-ended impedance.

I have following connecions:

Ethernet TX+
Ethernet TX-
Ethernet RX+
Ethernet RX-
Ground

I am confused how to achieve a particular single-ended impedance and differential impedance at the same time for Ethernet. My PCB fabricator has shared an impedance sheet with me which lists trace width and spacing to achieve particular impedance.

They have mentioned 7.5 mil trace width for differential impedance of 95 ohm and 9.18 mil trace width for Single-ended impedance of 50 ohm. I need to maintain differential impedance of 95 ohm and single ended impedance of 50 ohm for Ethernet connections as specified in the above layout design guide (Page 34). How can I select an appropriate trace width and spacing for Ethernet connections?


texts:
I need guidance in the explanation of utilizing LED light bars for a different function then designed. I do stage production, sound and lights for concerts and would like to adapt these LED light bars to "blind" to crowd.

My issue is that each light bar operates 12-30 Volts DC @ 300 Watts. In order to power and control with our DMX software (standard lighting control language/interface for stage production) I would need to build a more complicated device for each light bar. Meaning I would need DMX control PC board, relay to handle high wattage, power source, XLR in/out jack for communication, IEC jack, fuses, housing etc...
Multiply by 4 costs add up FAST.

My thoughts include:

A single high wattage (24volt @1500watt) DC power supply to power all.

Then I thought, can I wire in series to 120AC, this would put me at 30volts AC for each fixture. This would make controlling ALOT easier and cheaper because I could use an off the shelf DMX relay switch to control the bars.

I hope I explained well...

I am looking for any suggestions.


texts: Where do I find USB controlled digital potentiometers sampling a wide array of values?

texts:
I am looking for a set of digitally usb-controllable potentiometers sample a range of resistances from 1 kilo-ohm up to 1 mega-ohm in ideally both linear and audio (logarithmic) taper.  Here are some sample values:

Linear: 1K, 5K,  10K, 25K, 50K, 100K, 250K, 500K, 1 Meg
Audio: 10K, 25K, 50K, 100K, 250K, 500K, 1 Meg

I have found this link but they only have 10K, 50K, and 100K values:

http://www.controlanything.com/Relay/Relay/DPOTS

Does anybody know of a good source or solution to the problem?  Thanks in advance for your help.


texts:
I have been working on a project that uses an ESP32 board to drive a HUB75E RGB matrix (using the library from mrfaptastic ) . And as an extra challenge, I decided to try and design my own PCB for it.
The final PCB looks like this:

First of all, feel free to point out any mistakes I might have made with the design. Just remember that this is literally my very first attempt at PCB design, so please be gentle :)
Secondly... something is wrong. As soon as I connect the matrix to the assembled PCB, nothing happens. The ESP32 keeps the onboard LED (GPIO2) lit, and it looks like it never boots. When measuring the GPIO2 voltage, I am getting around 2.5V - which could mean that the ESP32 is continually resetting, and/or outputting a PWM signal on that pin.
Unfortunately, I am unable to troubleshoot this behavior - as soon as I connect a USB cable to the ESP32 board (so that I can see the serial output), the device boots just fine. And as far as I can tell, it really boots (going through the initial setup steps), so it does look like it was not booting before.
What I have tried in order to troubleshoot the behavior:

I assumed a power issue (the onboard trace for the 5V power supply to the ESP32 is 6mil), so I soldered an additional wire between the external 5V and the ESP32 5V pin. Same result.
I started tracing the HUB75 connector pins, and noticed that I had reversed two of them ( LAT and OE pins on the matrix side). Instead of LAT going to ESP32 GPIO4 and OE to GPIO15, I had LAT-15, OE-4. So I tried reversing them on the PCB as well. Same result.
I tried connecting the HUB75 connector pins one by one - the problem appears when I connect pin 15 (matrix OE, going to GPIO15 on the ESP32 board. So I tried moving that pin (GPIO15 happens to be a bootstrap pin for ESP32) somewhere else - I connected OE to GPIO33. Same result.

In the end, my PCB looks like this, and I am still facing the same issue.

Before I give up and restart the design from scratch, I was hoping maybe someone can point out something obvious that I missed?
If you need additional information, I would be glad to provide it. Also, you can find the complete Eagle files for this project (including a photo of the schematic and some images of the boards as "seen" by Gerber viewers) here - just note that they might not match this board 100% (I did make some changes to the design after submitting it to the PCB factory).
As per the comments, I am adding the schematic:


texts: I Googled this, but didn't find anything that could put it in layman's terms for me to understand. I know it has to do with signals/ pulse compression, but I am not grasping what exactly it is. If anyone could help, it would be appreciated.


texts:
I'm looking for a microphone that will record the vibrations of different textures and then with some signal processing I will get frequency as output. However, I don't know which microphone which suits best for this kind of application. Does anyone have any suggestions? Should I look for MEMS or ECM? Is it important to choose a digital or analog microphone? I only want the microphone to record the texture of a surface and not the background noise.
hopefully a clearer description:
Sorry for the lack of description, but yes, the point is to use a microphone and drag it over a surface with different textures to record the friction-induced vibrations. A previous study used microphones to pick up the friction-induced vibrations so the user can "hear the texture" through headphones and it works pretty well. They used an electret condenser microphone. And I have to use microphones as well for this project, I'm just not sure if there are other microphones that would work better for this type of application.
My thoughts so far (which I'm not sure if it's correct, so please let me know if I'm wrong). Since I'll be recording noise (friction-induced vibration from different surfaces/textures), an analog microphone would be a better choice since it captures the signal as is. I also guess that ECM would be preferable and not MEMS since MEMS reduces the mechanical vibrations, and I'm guessing the kind of friction vibrations you get from dragging the microphone on surfaces is kind of mechanical vibrations, or am I wrong?


texts: Practical considerations using Ethernet bus for a large number of sensors?

texts:
I understand that an Ethernet bus design with hubs has largely been superseded by star topologies with switches and that is largely due to the issues of collisions. However, I am interested in networking a large number (say up to 1000 for now, possible 10 times more in the future) soil moisture sensors and latching solenoids that have very low bandwidth needs. These would be located along rows in an orchard.

Currently, people are generally using LoRaWan or other radio networks, and fewer sensor locations, but these have disadvantages such as of lack of handshaking to ensure message delivery, the need for lots of batteries, and regulatory limits on transmission volumes.

What are the practical considerations for using a PoE Ethernet bus design or are there reasons this would not be a good idea? Is the hardware available to link multiple controllers together this way?


texts: Has LTspice been extended to support the modified-Chan, non-linear hysteretic model for coupled inductors (transformers)

texts:
I'd like to figure out how to simulate coupled, non-linear cores using the included modified Chan model in LTspice and I'm specifically interested to know if LTspice has ever been extended to support transformers, using the modified-Chan hysteretic core model that Mike Engelhardt announced back in 2004 for LTspice. (I have already searched the LTspice archives on Yahoo Groups and found nothing much since about 2004, when it was announced.) Mike Engelhardt, writing on April 24th, 2004, explicitly said that this new (then) hysteretic model wasn't supported for coupled inductors.

I'd like to know if anyone here is aware if LTspice has since been extended to support coupled inductors using the above-mentioned model, and if so, if they may have attempted to use it to validate a transformer design.

For those otherwise just curious about this arcane part of LTspice, it allows an inductor to use "a model first proposed in by John Chan et la. in IEEE Transactions On Computer-Aided Design, Vol. 10. No. 4, April 1991 but extended with the methods in United States Patent 7,502,723."

In the schematic entry process, it achieves this by using a strangely attributed inductor, where the symbol attributes to use are: Value, Value2, and SpiceLine, as shown in this extraction from a schematic file:

SYMATTR Value2 A=0.0000251 Lm=0.0198
SYMATTR SpiceLine Lg=0.0006858 N=1000
SYMATTR SpiceLine2 Rser=0.
SYMATTR InstName L1
SYMATTR Value Hc=16. Bs=.44 Br=.10

And I believe it supports it with a specialized "L" Spice model line in the spice netlist deck.

I've already done the usual search on this site. I have examined the following obvious links: transformer with hysteresis in ltspice and
modeling transformer in ltspice and also ltspice how to make a time variant mutual inductance coefficient in transformer. I also did a search for the specific parameters of "Lg=", "Lm=", "Bs=", and "Br=", as well as it may relate to transformers and LTspice. I'm coming up a bit short.

It's probable that LTspice still doesn't support coupled non-linear inductors using this hysteretic model. I'm hoping that someone may know better than this, though.


texts: Will this circuit behave as I am expecting it to?

texts:
I'm an almost total newbie at electronics, but keen to learn more. As a first "serious" project, I wanted to build a device with 4 half-bytes of addressable NOR memory. As a first step to that I've drafted a schematic for the "data entry" block of the circuit, this has:

Four flipflips
A (momentary) button and LED per flipflop to set and display the state. Push button, corresponding LED turns on.
A "global" (momentary) reset button that will set all 4 to 0 (I.E. all the LEDs turn off).
A "write" button which will transmit the current state of each flipflop out of this 'block' by setting the output of the corresponding AND gate to the value of the flipflop

The fourth element will be the "write" button that drops whatever value is set in these 4 bits to the storage, after going through a 2-4 addresser.

The NOR gates are provided by 2x 74HC02. I'm supplying 5v to VCC, which is well within the acceptable range defined in that datasheet. The LEDs have forward voltage 1.9v and 20mA max forward current, which I worked out as needing roughly a 155-ohm resistor.
My question I guess is, have I made any design errors that will stop this circuit from functioning as I expect? I've simulated it in software (components not arrived yet) but the simulations don't seem particularly robust (ignoring VCC and GND connections entirely for example, and AFAICT no "you're gonna blow this component mate" calculations...though perhaps I'm using the wrong software.)


texts: Voltage drop on motor controlled by arduino via transistor

texts:
I am using a transistor (TIP 122) to control a dc motor using arduino. Although the power source I use is measured at 6V, I only get 5V at DC motor(M1) when I use the transistor. Here is the schematic:

Is this voltage drop normal or do I miss something?


texts:
I am trying to use a solenoid valve in order to switch on tap water using a switch on the live supply to the solenoid, but every time I switch on the first time, the solenoid activates and burns immediately, leaving the valve in a normally open state.

I am using a solenoid valve from CKD corporation:
Serial: 4Z13
Model: AB41038.
Operating specifications:
-220 V
-50 Hz
I am supplying 199 V to it through the switch.

What could be cause of my problem?


texts: Can a machine be powered with food energy?

texts: Would it be possible, in principle, to create a machine that digests food in a similar way as humans do, extracts energy from the food, and stores it as electrical energy in a battery to power its own function? I understand this might be impractical or inefficient compared to other technologies, but I am just curious to know if it's something that can be done. (Not sure if I should ask here or on Chemistry Stack Exchange, really...)


texts: Can I write to an I2C EEPROM with an arduino if it is powered by a different circuit?

texts:
That is to say, can I just connect the SCL and SDA lines from an externally powered EEPROM to an arduino to write to it? The EEPROM in question is AT24C16A.

I am trying to make a circuit which relies on EEPROM data that I might have to change later and I was wondering if I could get away with just a 2 wire header instead of four.


texts: Memory Selection and NOT Gate in Embedded System

texts:
I'm currently studying Embedded Systems and in the topic of drawing a schematic for the address of a microprocessor (16bits address x 8 bit data (64Kbytes)) with 1 ROM 32Kx8 and 1 RAM 32Kx8, I simply cannot understand why A15 is the address for memory selection and why there's a NOT gate in A15 preceding the RAM memory.
I attached a picture with the schematics from what I refered.
Thanks for all the help!
PS: I've might not used the correct words for the right terms since I'm not learning this topic in english!


texts: How to calculate phase shift of a low-pass filter's output?

texts:
I'm simulating a basic low-pass RC filter in Proteus, and I need to find the phase shift of the output at varying frequencies. I've plotted a frequency response graph which shows the phase against frequency, but it doesn't show specific values. I can get rough values by just looking at the graph, but I need a precise answer.
Can anyone show me a way to actually calculate the phase shift of the output? (Using Proteus, MATLAB, or just a calculation if possible)

Edit: I've tried a couple of calculations that I've seen while researching this, but I believe that the phase should be 0 at 10Hz, and neither calculation gives me that.
I tried: arctan(fRC) and -arctan(f/20)


texts: TEM Propagation in Infinite Ferrit Medium

texts:
I have realised a question on Collin's Foundations of Microwave Engineering book which is related to TEM propagation in infinite ferrit medium.

I could not find a way to establish to relate positive and negative admittances with propagation direction.

This is a link for question.


texts: Low battery detection circuit that can tell if temporary voltage dip or actual low battery

texts:
I am currently using a schmitt trigger to turn off power to non essential circuits when the battery voltage dips below a certain threshold.

The problem with this circuit is that it is dumb, i.e., it cannot tell the difference between a temporary voltage drop across the battery due to a high current load being switched on, and when the battery is actually low.

What kind of analog circuit can I add to differentiate between these two events?

Edit: I have a 12V LA battery that dips to around 8V for approx. 1 sec when I turn on a high current load.


texts: what should be the aspect ratio for 32nm and 45nm technology?

texts: i am designing a combinational circuit and circuit worked well too. but i want to know if i directly write a net list rather than generating it through some schematic what should be the concept behind selecting w/l ratio?


texts: Adding voltage divider to output of power amp concerns

texts:
I have a load box I use to test and burn in analog audio power amplifiers. Each load box is tailored for a specific amplifier circuit and for one of the load boxes I would like to add an LED that starts to illuminate when a certain output voltage is reached and get brighter as the output signal gets larger. The amplifier in question can produce signals as high as 200V peak to peak and drive loads as low as 4 ohms. I am running into an issue:

The output signal needs to be stepped down so that I can use an opamp based LED driver circuit running on +/-15V. The problem is.. a resistive voltage divider would alter the impedance seen by the amplifier output as it would be in parallel with the load resistor.

Is there any way to implement this LED without altering the overall load impedance?


texts: So, i want to make a timer that will turn on/off a circuit. I want to turn on the connected device at 08:00 and stop it at 20:00, so the interval is 12 hours. Correct me if i'm wrong but i can't use IC 555(or another IC), i'll need some huge resistors/capacitors. Is there another way to build that other than using a microcontroller?


texts:
There is a electric motor butterfly valve that opens and closes by putting 12v on the motor to open the valve. Reverse the polarity and it closes.

This is the motor and valve in question

I can see as the valve opens and closes i can see applying voltage for too long will overload the motor because when its closed or open it cant move anymore as the valve hits the side and cant move no more. So if you dont time it right the motor will overload meaning increase in current ? Am i correct?

I see in the picture they are using a simply DPDT toggle switch (ON OFF ON)
SWITCH
They are way over charging for this switch so i would like to build one myself as im sure its very simple.

Could i add two 3A resettable Fuses one on the negative side of the motor and one on the positive. so when the motor closes and cant close no more the current increases and the fuse kicks in and turns voltage off till i let go of the  switch. then again polarity is reversed when i flick the switch the other way  and as valve opens and cant no more the other fuse does the same ?

It takes 3 seconds for the valve to open/close but holding the switch down every time counting is not desirable. also the website mentions the motor has a Bumpstop. I cannot find any information on this on google.


texts: Need help to determine whether PWM frequency is suitable

texts:
I am using a solar panel as the power source for making a simple DC motor based fan

Parameters of panel:

Voltage at max power point:8.2V

Nominal output voltage:6V

Max output current :0.62A

Max power=5W

My DC motor is rated at 3V. So i am planning to use a DC-DC Buck regulator with switching frequency of 200KHz for stepping down to 3V.The motor is of permanent magnet brushed type. It looks like this:

DC motor parameters at 3V:

1A consumption at max efficiency

Stall current :~2A

I am planning to use MIC2177 buck regulator(of Microchip) at 3V output with conversion efficiency of >85%  at 3V output.

My questions are:
1) Is the switching frequency too high or low for this application?
Are there any problems which i might encounter during operation?
(Or , am i misunderstanding things here?)
2) Which  flyback diode should i connect  in parallel to the motor?


texts: How do I switch between primary battery and backup battery, if the primary battery drops below operating voltage or get disconnected?

texts:
I have low power system which requires dual batteries to overcome the loop holes in the current system. Currently I have two batteries: Primary Battery Li-Ion 3.7V 1800mAh and a secondary battery Li-Ion 3.7V 560mAh. Both these batteries are connected to a load sharing circuit wich uses LTC4413 IC to control the switching between batteries. Basically what LTC4413 does is it constantly compares the voltage of the two batteries and keeps switching them ensuring both batteries discharge at the same rate.

But my application need is different. I am trying to design a circuit that only switches to back up battery under two conditions: 1)If primary battery is disconnected OR 2)If the voltage of Primary Battery is lower than 3.3V. Ideally I would like to have a STATUS pin which can transmit information (Low/High) to the uC regarding the which battery (Primary or Secondary) it is connected too.

During my research on internet, I have come across several circuits that can switch from battery 1 to battery 2 in absence of battery 1 but the 3.3V condition is vital and challenging. I am also trying to implement without a uC to control the switching. However if a uC is present with very low power characteristics in order of uA, I might use it as a last resort.

I would be obliged if somebody can suggest an IC that can do the job or circuit with low power loss.

Thanks.


texts: Absolute cheapest, (easy) way of starting programming on ARM microcontrollers

texts:
I want to start using ARM processors, migrating from PICs which I've been using for too long. 8 bit models were available for under $1, programmers for under $10, and I have been spoilt by the ease and low cost of getting started. But seeing that their power is dwarfed by some ARM chips at the same price, and being fed up with closed-source software, I want to make the switch.

I would rather avoid getting any development boards, and instead get straight into it with a cheap generic break-out pcb ($1), and on a breadboard using whatever external components are essential to get it going.

What are my options for programming ARM chips in this way? Are there programmers such as the PICKit2 which use USB to connect to a PC, programming via a simple serial connection (like ICSP) with the chip? How much of a difference in setups is required for different ARM manufacturs, ARM versions and individual chips? (ST, Atmel...)  E.g. does each manufacturer need their own compilers, programmers, IDE etc? Or are there common tools for all?

EDIT: Alright so after more research I believe I have come up with a relatively cheap solution, an stm32 dev board can be flashed with DAPLINK firmware, but I dont believe that the official github firmware will work natively(all of this is speculation until I get my stm32 dev board in the mail). But I found that the daplink_usb board included with the readbear mk20 is running an stm32 chip, they have released the firmware, which needs to have a line changed to make it compatible with the 8mhz crystal(Detailed in forum post linked below). Otherwise change out the crystal with a 16 mhz one. Ill update once I've confirmed this when my dev kit arrives.

GITHUB REPO

Good Forum Resource here.

Redbear Github fork


texts: I have a DC motor rated 24VDC@200mA driving at 40% DC and 20% DC(PWM) should run at what speed? Is there any formula to calculate the motor speed based on duty cycle


texts: I was just perusing the Microchip ENC28J60 Ethernet Controller datasheet and saw that the operating current can be as high as 180mA while transmitting and 120 mA typical while active but not transmitting. At 3.3V we're talking 400 to 600 mW of power. What is all that power being used for? Is it possible to implement 'low power' Ethernet somehow?


texts: Low Voltage DC Automatic Transfer Switch

texts:
I am new to circuits and have a very basic knowledge, and am currently interested in building a simple circuit that would take 2 DC inputs each of 12V 1.5A and output 1 x 12V 1.5A input even if 1 of the inputs fails.

I believe the inputs will have to be regulated and stabilized such that the output is always 12V and 1.5A. The aim of the circuit will server as an automatic transfer switch between the the sources for use with a computer modem.

Would appreciate your help in guiding me where to look at and start with.


texts:
I'm involved with a project that is using these neat bluetooth modules from sparkfun. However, right now there are two problems with our design. The first is that its using a little too much power. The second is that we actually only want the bluetooth to transmit in a smaller range and a smaller scale of directions(i.e. be directional).
The hackish but seemingly obvious way to fix the directional problem would be to put the device in a not perfect faraday cage (I believe they call them cantennas) which directs the waves. We could also probably weaken the signal in this manner. So that solves 2/3 problems.
The last problem is about saving power. Would it be feasible to design an antenna for this system (probably an etched one?) that could meet my directional/smaller range requirements and save power?
Any ideas welcome.


texts: Can we calculate the baud rate of RS232 communication from the TX output signal?

texts:
Can we calculate the baud rate or communication speed of RS232 communication from the X output signal?

The below image is from an RS232 communication output signal. I took this picture with 0xaa, and the time period between highs is 100.us.

I heard that the external oscillator's frequency is 8Mhz. Can we calculate the baud rate from that?


texts:
What's the difference between an Analogue and Digital Voltage Rail?
Why their grounds have to be different?


texts: Why do I need a transistor to control a relay with an arduino, and which one should I get for this circuit?

texts:
I need to control a coffee machine plugged into a wall outlet using a relay connected to an arduino. Apparently I need to connect a transistor to the relay. Why? Is it because the arduino can't supply enough current to trigger the coil in the relay?

So the info on the packaging of this relay says "R46-5D12-12 ROHS SPDT 12A-12VDC". How do I go about choosing a transistor? Will I need anything else other than a diode?

edit: The relay will need to be triggered for about 0.5 - 1 seconds every once in a while. The load is definitely not big. It'll simply replace the power button on the coffee machine with an arduino.


texts:
How to determine the maximum RPM that a stepper motor can run at?
(2.6V, 1.2A stepper for example)


texts:
I have been facing an issue that has been a mystery to me for quite some time, and I wanted to see if someone here can potentially give me more insights on this so I can understand why it is happening. Please bear with me since electrical engineering is not my specialty and I am doing my best to understand this phenomenon.

The issue I am facing is as follows:

I have two laptop chargers. One aftermarket charger from China and an official one from HP. Whenever I use the aftermarket charger from China, my KZ earphones (which are fairly low impedance) connected to the laptop would make electrical buzzing noises. The more power than the laptop draws, the more buzzing can be heard over the earphones. This issue does not happen with lower quality or higher impedance earphones.

As a reference, this was the sound that was heard over the earphones when the device was in use:
https://drive.google.com/open?id=1OXwNHcq476hf_FxVr9n_bPVIcNwdNnzm

The Chinese charger is a Class II power supply which lacks a grounding pin. If I shunt 0V on the DC side to AC ground, I get a reading of 59.8V @ 78uA AC on my multimeter. As soon as the shunt is connected, the noise stops. Likewise, the noise stops if I laid my hand on the laptop external chassis (which I suppose had a similar grounding effect).

Thinking that the problem could be due to some kind of leaking AC current, I repeated the test on my HP power supply which was grounded. However, this time I also have lifted the ground prong using a cheater plug so that the leakage current cannot escape. There was no noise on the earphones line with this setup. That said, I was still able to measure 54.1V @ 54.1 uA AC from the ground pin to ground if a shunt was connected in that manner.

To see if the manufacturer would know something about this, I contacted them about the issue and they suggested that I remove the two Y capacitors on CY1 and CY2, or downsize them from 400V 100PF to 47PF to possibly mitigate the noise issue.

Not specifically knowing how this works, here are my questions:

a) What creates the 60V AC voltage on the isolated DC side? Is this caused by the safety capacitors used in the power supply? Why is it specifically half the line voltage?

b) What noise am I specifically hearing over the earphones? I know that it has something to do with the impressed AC voltage on the DC side since the noise is gone as soon as I shunt the 0V side to AC ground but wasn't sure specifically what I was hearing? I am guessing that the AC current is trying to find its way through the ground and parts of that current are flowing through my low impedance earphones and be interpreted as sound...

c) From what the manufacturer is suggesting, it sounds like that they may be shunting the parasitic capacitance from the transformer to the 0V output side and using it as ground. I am assuming the rationale would be that a smaller capacitor would result in smaller leakage current and hence less noise being picked up by the earphones (and perhaps less EMI compliant). Would that be a good assumption? Why did they need 2 capacitors? Is it due to polarity?

d) Would the placement of the Y capacitors matter in this setup? Would it be better to simply place them between L-N and 0V-N so the noise can be diverted from the connected device (laptop)?

e) Why did the HP charger not create this same noise even when it was ungrounded? Could it be due to the positioning of such capacitors or some kind of circuitry design difference? If so, is there a way I can confirm without cracking the charger open?

e) Without knowing anything about the schematic, would there be a better setup than using Y capacitors in reducing EMI? Would the capacitor values suggested by the Chinese manufacturer be a good value to prevent EMI emissions?

f) If I were to view this under an oscilloscope, which two points should I be using to confirm this issue and visualize my findings?

Thank you for your time!


texts:
I was going through the standards related to motor testing that are IS 12615, IS 15999-1, IS 15999-2-1 while reviewing a motor with requirements of 3phase induction motor, 1500rpm, 120hp, 415V and delta connected.
I observed that there are requirements specified for

Insulation resistance (less than 30 Mohm)
HV test (1000+2*rated voltage for 1min)
Reduced voltage test (Apply 1/sqrt3 of rated value and check ability to run at rated speed)

But there are no requirements specified for

Stator resistance
Speed (The rated speed is 1500rpm but I am getting a motor with speed 1460rpm, is it acceptable?)
No load test
Locked rotor test.

I would really appreciate if you could clarify what I am missing here.


texts:
I am studying the Input Bias Current compensation technique by connecting the resistor to non inverting terminal of opamp. why the reistor of bias compensation should be parallel value of Rf & Ri ? the other end of Rf and Ri is not same and voltage produced by bias current in Rf and Ri does not add up together ..

Kindly help me understand with this bias compensation idea.


texts: How do you control relay using two different methods?

texts:
I would like to control a relay using an esp8266 module sending the signal. However, I want to also have an optional push button in case my internet is down.

Is this possible? If yes, how can I do this? Eg. Schematic etc.

This is the relay i'm using:

This is my attempt at a block diagram:


texts: Finding AC equivalent seen between two nodes of a BJT Amplifier

texts:
In the textbook, Electronic Devices and Circuit Theory, 11th Edition by Boylestead and Nashelsky, on page 566, the lower cutoff frequency is derived for a voltage divider BJT circuit. The circuit used is shown below.

The lower cutoff frequency of \$C_E\$ is to be found. For this, they first find the equivalent AC circuit as seen from \$C_E\$.

My question is, how did the obtain this expression?: $$\dfrac{R_1||R_2}{\beta}+r_e$$

I understand that they applied Thevenin's thorem, but I'm stil not sure how this expression comes out. Also, doesn't \$R_C\$ play a role here?


texts: Is AC coming from a DC powersupply normal?

texts:
I recently bought a Oubel Laboratory Power Supply 60V/5A, that I'd like to use for hardware diagnosis.
When measuring the - and + outlets, the oscilloscope picks up ac voltage, that propagates through the pcb with Buckconverters. Is this ac current normal and/or dangerous to lets say a GPU?
The ac in the following image can be measured on both outlets, the bottom graph is the fft of the signal


texts: Circuit Breakers in Low Voltage Chemistry Projects?

texts:
I'm currently using a circuit breaker for low voltage (6V) but high current (60A) electrochemistry projects. My bridge rectifier is rated at 60A max. I'm aware that circuit breakers work in counter intuitive ways (they don't trip at exactly their rated amperage and instead are the Thermal - Magnetic type) and have read the NEC regarding their use and have the trip curve for my breaker.

In my applications, the amperage never exceeds 40A due to the resistance of the solution. The real problems are with:

The current circuit breaker I've selected is designed to trip immediately at over 50A (Thus saving the bridge in the event of a short of the electrodes), but trips intermittently during use due to its low rating.

I've been playing around with an idea, but I'm not sure if it will fry the bridge or not. In the trip curve it says that the breaker will trip in half a cycle or so above a certain amperage (lets say 200A) due to the magnetic force generated. If I have a circuit breaker rated at 50A and the transformer will put out 300A on a dead short will this protect the bridge if the solution's resistance prohibits such currents from flowing typically, aside for a short of the transformer secondary?

EDIT 0:
The transformer secondary is connected to the breaker in series (before) the bridge (for clarity, the bridge is a full bridge rectifier with the typical 2 AC input, DC+  and DC- output model), then the DC current is used for electrochemistry and passed thorough a solution and back into the bridge and into the transformer secondary.


texts: Carry-lookahead adder in VLSI, Static VS Dynamic?

texts:
I study one course about VLSI. in adder lecture my profesor talk about Adders. in Carry-lookahead adder first talk about static version, as follows:

at next we start about dynamic version of CLA and says:

1) we remove kill carry and propagate 0 transistor and add phi transistor as footer and clock.

  my question is

  I) what is different between Static and Dynamic
  version, and

  II) What is the benefit?

  III) what is the role of Footer
  and clock?


texts: I get the same value, when read via i2c - stm32 + hih6030

texts:
I want to use my HIH6030 humidity and temperature sensor with my STM32F4 board, but I have the following problem:

I turn my board on and start debugging. The first time when I try to read out it's ok. It seems I got good values, but next time I read data from the sensor I get exactly the same values as before. All the times I get the same values, until I restart my board.

I can't see what could be the problem. I hope you guys can help me.

My code:

#define HIH_ADDRESS 0x27

typedef struct {
    double temperature;
    double humidity;
} HIH_readout;

void initI2C() {
    __HAL_RCC_I2C2_CLK_ENABLE();
    hi2c2.Instance = I2C2;
    hi2c2.Init.ClockSpeed = 400000;
    hi2c2.Init.DutyCycle = I2C_DUTYCYCLE_2;
    hi2c2.Init.OwnAddress1 = 0;
    hi2c2.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
    hi2c2.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
    hi2c2.Init.OwnAddress2 = 0;
    hi2c2.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
    hi2c2.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
    if (HAL_I2C_Init(&hi2c2) != HAL_OK)
    {
        initStatus = ERROR_I2C_INIT;
    }
}

int HIH_read(HIH_readout* buffer) {
    uint8_t data[4];
    uint16_t temp_humidity;
    uint16_t temp_temperature;

    if(HAL_I2C_Master_Receive(&hi2c2, HIH_ADDRESS << 1,data, 4, 10) != HAL_OK){
        buffer->humidity = 0;
        buffer->temperature = 0;
        return HIH_FAIL;
    }
    uint8_t status = (data[0] & (uint8_t)0xC0U);
    //Masking MSB (status) bits
    temp_humidity = ((data[0] & ((uint8_t)0x3FU)) << 8) | data[1];
    //Masking LSB (don't care) bits
    temp_temperature = (data[2] << 8) | (data[3] & ((uint8_t)0xFCU));
    //The last two bits -> don't care
    temp_temperature = temp_temperature >> 2;

    //SCALE AND CAST
    buffer->humidity = (double)(temp_humidity * 100 / (pow(2,14) - 1));
    buffer->temperature = (double)(temp_temperature / (pow(2, 14) - 1) * 165 - 40);

    return HIH_OK;

}

When my main begins I call HAL_Init(); initI2C(); and after in while(1), I call HIH_read; I used Cubemx to generate initialzation code, so hopefully it works well.


texts: Why Does a Shunt Cap Help For Deglitching Digital Signals?

texts:
In some of my projects I have digital pulse signals that are sent over fairly long wires (~12in). For example tachometer readings or stepper signals.
I've tried various things to reduce glitches in these signals (for example causing erroneous stepper motor steps). I've determined experimentally that adding a small shunt capacitor ~1nF near the receive end of the signal dramatically reduces the glitches in almost every case.
What I'm wondering is why that is? My naive understanding is that very short, sharp RF pulses are shunted to ground through the cap. However the shunt cap seems to be much more effective than a low pass filter, so I assume there's more to it than that. For example maybe the cap is spoiling the wires ability to function as an antenna?
Related question I asked about a year ago: What's a good method for filtering out glitches from stepper motor step signal?
Edit: Here's a diagram of what I mean by "shunt capacitor"


texts:
I'm designing an active bandpass filter (using only BJTs, voltage sources, resistors and capacitors) with the following properties:

Corner frequencies \$8 ~ \text{kHz}\$ and \$800 ~ \text{kHz}\$ (bandwidth of about \$790 ~ \text{kHz}\$)

\$40 ~ \mathrm{dB/dec}\$ roll-off of the LPF (second order filter)

\$20 ~ \mathrm{dB/dec}\$ roll-off of the HPF (first order filter)

Gain of about \$42 ~ \text{dB}\$

Low input impedance: \$\sim 60 ~ \Omega\$ (over a wide range of frequencies \$80 ~ \text{Hz} - 80 ~ \text{MHz}\$)

High output impedance: \$\sim 50 ~ \text{k}\Omega\$ (over a wide range of frequencies \$80 ~ \text{Hz} - 80 ~ \text{MHz}\$)

I thought about the following simple input stage: let the input be applied across a resistor (\$R'\$) with the desired input impedance followed by a unity-gain buffer (which has a high impedance and therefore wouldn't affect much the input impedance). Then, take the output of the buffer and process it through an HPF filter (and later through LPF). However when I tried to implement the buffer using emitter-follower I quickly ran into some problems.

In order to establish a proper biasing of the transistor we have to have the resistors \$R_1\$ and \$R_2\$. Crucially, a coupling capacitor \$C_{in}\$ is required (otherwise the circuit just does't work properly - SPICE simulation yields extreme attenuation in the frequency response). But the introduction of this capacitor creates two serious problems:

It affects the input impedance. The input impedance now changes with frequency, and it's hard to maintain a constant low input impedance over such a wide range of frequencies

It acts as an HPF filter and therefore adds another pole. In other words, if I want to have \$20 ~ \mathrm{dB/dec}\$ roll-off I must remove the HPF filtering of the buffer output (which in turn completely changes the design of the circuit).

What are some possible ways to alleviate these issues without over-complicating the circuit?


texts: Is there a pushbutton that does what a latching relay can do?

texts:
Is there a small (around 1 cubic inch) pushbutton that does the same function as an NVR (No Voltage Release) switch or a latching relay?
Functions needed:
-Must press button when circuit loses electricity to prevent automatic starting
-Preferably a normally-open momentary


texts: Storing the charge from a MOSFET Bridge Rectifier

texts:
I am using the following MOSFET Bridge to harvest AC bursts, that come from an electromagnetic transducer.

In front of this circuit is a supercapacitor I have added.

I read the following on a webpage that talks about this design:

  One caveat of the FET bridge circuit: do not use it as the rectifier in front of a capacitor-input power supply!  In a conventional rectifier bridge, the diodes prevent the backflow of current from the power supply input capacitor as the applied voltage drops below the voltage on the capacitor.  With this design, the MOSFETs act like switches rather than one-way valves for current flow.  They don’t care which way current flows, hence the input capacitor of the power supply will be discharged to near zero volts with each half-cycle of the applied AC power!  This limits the power supply applications for this circuit to inductive- or resistive-input designs.

I would like know a successful method I can use, to store the charge coming from the electromagnetic harvester into a supercapacitor, using this FET-based rectifier.  This temporary charge in the capacitor is used by an energy harvesting IC, to store into a LiPo battery. The bottom line is that I want to overcome this problem of losing charge in the capacitor in the reverse direction.


texts: Precision Shunt Regulator Increasing Voltage overtime

texts:
I want to have a stable voltage of 2.47V using TLV431AC which is a precision voltage-adjustable shunt regulator. http://www.ti.com/lit/ds/symlink/tlv431b.pdf
I am able to get it by putting a 5k potentiometer and a 500 ohm resistor in series connected to the REF pin of the regulator. Since the cathode current limit is 15mA, I have used a 500 ohm resistor between the source and the CATHODE pin to limit the current to about 10mA.

On choosing the right load capacitor for stability, I have referred to the table to the datasheet and it looks like 10uF is outside the unstable range of values so I chose that one as my load capacitor.

My problem is while the time goes by, my output is slightly increasing by a few millivolts and would not stop which I think is bad because I am planning to use the output of this circuit as a voltage reference. What could be the problem? Is there anything wrong with my circuit?


texts: Why do we not use both E and B fields for a receiving antenna?

texts:
An antenna is an electrical device which converts electric power into radio waves and vice versa we all know this.

In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). The electromagnetic wave has an E and B field which are perpendicular to each other; but in antenna reception we only use the E field of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.

Why do we not use both E and B fields for reception? Can we produce more voltage by using both E and B fields?


texts: To avoid oscilloscope ground short, why not simply unground the scope?

texts:
We all know what happens when we ground a regular oscilloscope probe at the wrong place: a short. There are two main points to consider:

1) All channels share the same ground plane, so we can't take 2 or more simultaneous measurements referenced to different "grounds".

2) The scope's ground plane is directly connected to the center pin on oscilloscope's AC power cord, which is probably connected to the ground of the equipment we are probing, preventing us from using any other reference than the "official" ground itself, otherwise we will have shorts and possibly fireworks, in more severe cases.

There's nothing to be done about point 1, but about point 2, why not simply disconnect the center ground pin on scope's AC cord and leave it floating? I personally do that with my older scope. When using channel 1 only, I can freely move my ground hook everywhere in my circuit, and I never had any problems, apart from some 60Hz noise, but this is expected, I guess, since the whole scope is floating and subject of all kinds of noise.

So, apart from the increased noise, is that harmful to leave the scope ground floating? What else am I loosing doing things that way? In which situations my practice will bring me serious trouble? Does that damage the scope in the long term?


texts: Does the resistance of a coil increase if it gets burnt?

texts:
If a coil gets burnt, does its resistance necessarily increase? The reason I'm asking this is that I have a vape, and burnt coils are common in vaping. The vape has an LCD that shows the resistance of the coil in real-time. So my question has two parts:

A. Same resistance as before --> not burnt?

B. Burnt --> increased resistance?


texts:
I'm working on a little project(an infrared jammer) and I'm having a few issues.
Why (and how) exactly do circuits like the one below use electrolytic capacitors? Wouldn't ceramic capacitors be suitable for this?
Also in the NPN configuration, why are the LEDs placed with the collector and not the emitter?
If I were to make the frequency variable by using a potentiometer in place of the 39K resistor would the duty cycle change as well as the frequency?

(source: reprise.com)
I'd appreciate any help! Thanks.


texts: How to fix a 'PCB' without mounting holes inside a case (or on a PCB)?

texts:
I want to use several of the 'filled PCBs' below, or other ones, but the question does not change.

How can I fix such thing in a case, or on a proto/veroboard PCB (like the picture below)?

I thought about:

Glueing: but since the case (including the components) will be moved a lot, it doesn't seem a good way.
Using tie wraps, in this case it might work because it can be put around the yellow component, but what if I want to use another component that does not have a nice yellow box?
Using one of the above methods with spacers to prevent contacts with the protoboard.

I don't need a professional solution, but I want a solution that doesn't break or getting loose after being 100 times moved neither.

Update

I asked a similar earlier question. However, this was about a temporary solution, in which I expected components need to be changed/added. However, in this case it's about a fixed/known setup. So I hope that a more professional (or at least 'better') solutions exist.


texts: Measuring temperature with ±0.01°C accuracy

texts:
What is the most accurate way to measure temperature to ±0.01 °C? I have looked into using a Wheatstone bridge (with a minipot for minor calibrations) and an RTD for its precision and range. I need a range of -85 °C to 55 °C. Ideally this would be a low voltage operation (6 VDC). The output needs to be a digital signal and currently will be sent to Arduino, however in the future I would like to include a datalogging system alongside this device before connecting to Arduino. Powersource is also from the Arduino so stability is currently dependent on the hardware of the Arduino, however the unit will be plugged into a 115 V outlet so a ground reference can be used.

The ultimate goal is have multiple temperature units like this logging data and sending to a mC that can graph the data. I've found various platinum RTDs that are precise enough to measure but I want to know how I will need to lay the circuit out, how to convert the analog signal to digital accurately and any voltage stabilizers that will be necessary for the power supply.


texts: I need a help to design rectfier circtuit for 5v

texts:
I have 230v ac to 9v ac step down transformer. I started doing the mini project with Arduino and Raspberry Pi.I need help for designing the rectifier circuit by own. Plz, help me to understand the concept of the rectifier.

My actual question is, how should I select the capacitors?


texts:
Edit:
I did a dumb-dumb. I got the emitter and collector mixed up on both transistors. Now it works.
What I'm trying to accomplish:
I'm planning to run a ESP8266 microcontroller in my car. The ESP runs off a 3V converter. I want it to turn on when turning the ignition on, but when ignition is turned off I want the ESP to decide when to turn off the curcuit. (I want to save some data etc. before shutdown)
I want as little power draw as possible (or none) when it is shut down.
Current sollution attempt:

After some suggestions from others, I attempted to set up the circuit as shown in the schematic, using two transistors. The NPN transistor is a BC547 and the PNP is a BC557. The 3V converter with everything connected draws about 25mA at 12V. With the transistors in place the numbers are roughly 11.5V 30mA.To keep the circuit on the ESP outputs 3V on the D5 pin.
However, there are problems:

When the circuit is supposed to be off there is still 4V on the PNP transistor emitter pin.
When powered through the transistors the ESP does not turn on. I should measure what I'm getting out of the 3V converter, but I'm currently not at home so can't do that right now.

Help?

Is the attempted sollution the best way to go or would it be simpler/better using a relay or any other sollution instead?
My knowledge of transistors is limited even after trying to read up a bit. I must be doing something wrong, but what? I am trying to learn, so just giving me pointers and letting me do some of the work is fine. (Also, I'm as lazy as anyone, so no complaints about complete sollutions either ;) )

Thank you!