texts: Bias-setting on valve amplifier with dual negative bias supplies

texts:
This is a general question, although the immediate purpose is to apply it to a Thorens AZ-25 amplifier from the 1960s. Schematic is here.

Push-pull valve (tube) amplifier output stages are generally either automatically self-biased via a cathode resistor or else have negative grid supplies which are adjustable.
The purpose of adjusting the bias is to set the standing current so as to get the stage just into class B, where the conduction angle of each valve is exactly 180 degrees, to minimize crossover distortion. Increasing the standing current any further takes you into class AB which is no further improvement, and a waste of standing current. (Some people e.g. Bob Cordell call the correct adjustment point Class AB, but in my view they are mistaken.)
In general this is pretty easy to do using a distortion analyzer: set the standing current to zero, or at least too low; feed in a sine wave; observe the output across a dummy load; and increase the standing current until the crossover spikes just disappear.

I've carried out this adjustment many many times on transistor amplifiers and it is easy when there is only one adjustment, typically a bias spreader.
This specific amplifier and others have separate adjustments: one for the upper valve's grid and one for the lower valve's grid. In this case I'm a bit lost for a definitive procedure. The idea is to ensure that the standing currents through each valve are equal, but achieving that seems like an endless back-and-forth procedure to me which may never converge.

My question is really is there a kind of analytic solution to this where you would only have to make two adjustments? or at least be assured of fairly rapid convergence on a setting?


texts: When ESD protection is necessary and where should TVS be placed?

texts:
I'm designing a PCB in which the main ICs are a STM32F0 microcontroller and an INA226. These IC have some IO pins exposed in a header and the device will be handled by people.

Is it likely that an ESD event causes damage to the ICs?
If so, is a TVS IC like this one "SMF05CT1G - https://datasheet.lcsc.com/szlcsc/ON-Semicon-ON-SMF05CT1G_C15879.pdf " enough to prevent such problem?
Which kinds of pins need a TVS and where should it be placed physically in the PCB?


texts: What bandwidth is needed for an arbitrary digital signal?

texts:
I am building a fiber-optic data link, with a laser driver and photodiode receiver.  My goal is to transmit data at 50Mbit/s.  I'm looking for what bandwidth this would take.
Obviously 50MHz would not work, as it would not even begin to approximate a square wave, let alone change in random data periodicity, right?
How many harmonics do I need?  We have designed so that our low frequency cutoff is sufficiently low compared to our data rate (by ~5 orders of magnitude).

Thank you in advance!


texts: Stepper motor phase current driving confusion

texts:
So, I was studying a bit about driving current for Hybrid stepper motors and was faced with some ambiguity related to  the Full Step excitation.
  In this reference, https://www.researchgate.net/publication/3219650_Mixed-Mode_PWM_for_High-Performance_Stepping_Motors, it is stated that the current shape to excite a stepper motor in Full Step must be like as follows:

And measuring the phase current of my stepper motor, controlled by a drive in Full step mode, with my osciloscope, I got that image:

So, all's well that ends well. However.... upon reading a datasheet related to a Toshiba stepper drive chip I've found this:

https://data.emotion-tech.com/ftp/Datasheets_et_sources/Datasheets_electronique/Datasheet_Toshiba_TB6600.pdf

So, what am I missing here? Why Full Step phase currents differs from one reference to another?

Thanks!

Obs:
It's a Hybrid Motor 1.8º per pulse (200 steps/per revolution)


texts:
Brand new member here.

I'm using an AQY211EH PhotoMOS relay to switch guitar pickups via an Arduino, as shown below:

This works great, with one minor exception: even when no power is applied to the Arduino (and, thus, the circuit as a whole), I still get a signal from the pickups to the amplifier. According to the datasheet, the maximum leak current should be 1 micro-amp.

So, two questions, really. One is should less than 1uA should be detectable by my guitar amplifier?

The second, are there ways to eliminate (or reduce) this leakage through additional circuitry on the Guitar-Amp pathway?

My biggest worry here is that the off-state leakage is also present when the other pickup has power, leading to a change in the overall tone from a normally switched guitar (where there is NO off-state leakage).

Thanks. Happy to clarify further if needed.


texts: need to understand the difference in delay for rising and falling reference

texts:
I am rigging up a circuit which needs to generate two signals.

One output signal(R_B) is same as input and the other signal(R_A) is supposed to have a short delay of 5 to 10 ms compared to the input.

The figure below has the waveform and the circuit.

Question:
Why is the delay is different when the input rises and the input falls?
any hints towards matching the delay is appreciated.

Edit: after adding a resistor to the base pin and a little balancing, able to achieve 10 ms.:


texts:
I have built a grain moisture sensor using a 555 timer and an arduino,
 as shown in the figure:

.

The sensor is composed of a two parallel aluminum plates (as in a capacitor):

The output of this circuit is connected to analog arduino pin A0. I have noticed that the higher the moisture of the grain, the lower is the voltage read by the analog pin. From basic phyisics:

\$ C =(ε_0   ε_R   A)/d\$  - in which \$ ε_R\$  is the dielectric of the capacitor, so the higher the moisture the higher the capacitance of the sensor is.

I am having trouble understanding why voltage drops when moisture is higher. Why does the voltage drop when the moisture is higher?


texts: Why does the bandwidth of an OP Amp decrease as temperature decreases??

texts:
From this NASA article on figure 5, you can see that the bandwidth of the operational amplifier drops as temperature decreases.. What is the mechanism that causes the drop on bandwidth because as temperature decreases parasitic capacitance decreases so this seems counter-intuitive?

Figure 5:


texts:
I am trying to implement a small RISC CPU (without branch prediction and register renaming) and I want to give it a fully associatve cache (I and D caches).

Everything is going well, but now I must understand how to decide wich entry to discard. I use a CAM to store tags (page number) and find cache entries. Upon miss i can handle the miss via a MMU unit etc.

I already know how to do direct mapped cache.

But, how to implement a LRU policy on the cache ?

The best solution I found would need N (=number of cache lines) clock cycles to compare each line and find the least recently used entry to be evicted. Thats very slow...

Time to evict the page to external RAM + time to choose the page = too much clock cycles...

Is there any way to decide wich page is the least recently used one in one clock cycle ?


texts: Finding Resonant Frequency in LC circuit using oscilloscope data

texts:
I designed a RLC circuit. I chose L and C such that resonant frequency become 2KHz. L=100mH, C=0.25*10^-6F and I took R to be 100 ohms. Then I generated Bode plot for range 100Hz to 10KHz. Ideally I should look for a phase angle of zero in oscilloscope out for resonant frequency, but there is none.

Now how should I find out experimental resonant frequency? Should I pick up a phase angle nearest to zero and look for corresponding frequency?


texts:
The voltage on capacitor is given by

$$V_c=\dfrac{1}{C} \int i(t)dt$$

and the current is

$$i(t)=0.4 \sin(2t-\frac{\pi}{4})u(t)$$

when u(t) is unit step function. May you show how to integrate the expression, how to find V, how to regard the step function while integrating?


texts: Blog schematics for PNP transistors sometimes connect +5V to the emitter and a voltage divider between the base and an open drain output, and sometimes only connect a base resistor to the low side switch. In the simpler configuration will the current flowing from the emitter to the base pull up the base and turn off the transistor? How long will this take?


texts: Question about the statement "Higher voltage means higher velocity of charge"

texts:
This is the phrasing that I commonly hear when talking about voltage's relationship to charge velocity...something along the lines of:

  In a resistor circuit, raising the voltage will increase the current. Current is the flow of charge and therefore, for a given conductor cross-section, increasing the current must increase the charge velocity.

And this certainly makes sense! However, couldn't the following phenomenon also produce greater current without raising the velocity of the individual charges?:

From what I understand about batteries, mobile electrons moving through the circuit can be derived from either the atoms of wire itself (i.e. external to the battery) or derived from the anode of the battery due to chemical reaction (i.e. internal to the battery). How do I know that as the voltage of a battery increases ...

A) more "external-to-the-battery" electrons are being ripped away from the atoms that comprise the wire and/or

B) more "internal-to-the-battery" electrons are being supplied to the wire?

In either case, you would certainly have a "greater total" of electrons in the circuit as compared to lower voltages...and therefore, assuming these extra electrons are mobile and moving at the same velocity as they were for lower voltages, the current would be higher as well.

So why do we know that this other possible phenomenon is not occurring.

Thanks! Cheers~

Edit: After reading the comments below, I have realized that I can phrase my question more precisely to better capture the essence of my inquiry.

At the moment a circuit is closed, does the wire pick up a net negative charge? It has been brought to my attention that the number of electrons in the wire does not change with time (i.e. whatever enters the wire at the anode exits the wire at the cathode...sort of like conservation of mass for the water-pipe analogies)...but what about at the very instant the circuit is closed?

For example, if at some voltage x, the wire immediately became net negatively charged, and retained this exact net negativity over time (as long as the circuit was closed), it would technically not be changing its number of electrons as a function of time. So does this occur?


texts: LT3680 switcher output doesn't have regulation under no load

texts:
I have a switcher circuit based on LT3680. I implemented the typical circuit shown in the datasheet in a well laid out 4-layer PCB. However, I find that the input voltage is present at the output at no load condition. When I add load of 100ohms and below, I get 5.05 constant output. The typical circuit is meant for 5V, 3.5A load. My loads draw only a few milli amps. So could that be because if the inductor saturating or something. The switcher has feedback and as far as I understand should be able to regulate the output whatsoever. Regulation kicks in only when I add 100 ohm or below. Nothing with 10K, haven't tried with anything in between since I don't have a wide range of resistors available with me. Please have a look at the circuit used.

Datasheet can be found at:

http://cds.linear.com/docs/en/datasheet/3680fb.pdf


texts: How to convert 220 volts AC into 12 volts DC using a transformer?

texts:
I tried to build a circuit that could convert 220 volts AC into 12 volts DC:

My voltage output is as I wanted but the measured current is always blank.
Can anyone explain why this is happening and what should I do to get the (12V / 5A) output (I want to do it with real components.)


texts: I'm trying to make the footprint of a smd resistor. But when I place the resistor on pcb layout and flip it, the pads go on bottom layer but the body remains on top layer, viewing from 3D mode. Instead the standard footprints work properly. Why this happen?


texts:
I’m looking for advice on how close to nominal current draw a fuse should be dimensioned. On the internet I have seen numbers from 125% and to 800% in different applications, which is a rather wide range.

In my system, I have a motor which draws around 1,3 A of DC current and I’m looking to protect the system against short circuit by adding a slow-blow fuse of around 2A (This value can't be changed in my design). Is this reasonable in a motor application? In my case repeatability is not important and other current limiting measures are also acceptable.

Are there any rules of thumb when it comes to choosing fuse size?


texts: How do I implement an SPDT switch in Logisim? I need it for connecting 2 pins to ground but not at the same time.


texts: USB-C Connector: How to properly route on EAGLE CAD to supply power to PCB

texts:
So basically, I am needing to power my PCB using an additional USB 2.0 Type-C connector, but was having trouble understanding the pinout on eagle versus a typical USB Type-A where I could use VCC and GND and neglect the other pins.

Looking at this footprint pinout below, if anyone could explain to me how I should properly route or use these pins, I would definetely appreciate it, thanks in advance!

Component Model : USB4085-GF-A


texts: LED drive circuit (PFET) turning ON by itself

texts:
I thought 10k pull-up would prevent LED from turning on, but when I connect +VBAT (4V) and have D_LED_S_W floating the LED turns on slowly (in few seconds). When this happens the gate voltage starts decreasing from 3.2V and at about 2.8V LED is fully on.

What is happening here? I want to drive the LED with MCU GPIO. How can fix it?


texts:
I am now occouring a FPGA pin damage problem.

One of my pin is hardware connected to a 1.8V signal that will be switched on/off occasionally, while the port is not connected to any other logic gate in my FPGA, so the input pad is FPGA internal folating.

And this structure seems to damage my FPGA input port, the input resistance decreased from infinite to hundreds Ohm after some time.

I also have another test that the input pin directly feeds the signal to a FPGA otput pin, in this case, it seems to work perfactly so far.

So, I was wondering, will an internal floating input port damaged by external signal easier than those connected ones?

When I searched "pin" "floating", it always came out with external floating related results, plus an "internal" key word does not really help, so I am here to ask you for help.

Thanks.


texts:
This is the method for calculating the State of Charge (SOC) of the 12V lead acid vehicle battery. Based on the formula for battery capacity (C) formula

$$C = (\text{Current}) \cdot (\text{Time of Discharge})$$

and my approximation that under loaded conditions (even 1 amp) if the battery voltage reaches 10.5 the SOC is 0%.

So, if the present battery voltage is say \$V_1\$ and on applying a load of say \$I_1\$ the voltage has fallen to \$V_2\$ and the present SOC is \$\text{SOC}_{\text{present}}\$. Then the formula for the new SOC is

$$\text{SOC}_{\text{new}} = (V_1 - V_2) \cdot \dfrac{\text{SOC}_{\text{present}}}{V_1 - 10.5} $$

This is the final equation I derived after intermediate calculations. But my main concern is when you crank the vehicle the voltage falls sometimes below 10.5 and hence my SOC is 0% in fact less than 0% which is not practical and returns back to normal SOC after vehicle starts though.

So, my question is can I omit that one condition and still say the formula is valid? If required I can show the intermediate calculations. For simplification I made lot of approximations like neglecting peukart equation, temperature affects which in fact will be reflected in the voltage is my assumption.


texts: Relationship between order of filter and impulse response?

texts:
I see that the slope of the frequency response of a filter (such as the Elliptic, Butterworth...) becomes steeper as its order increases; for instance, a low pass Elliptic filter with an order of N=3 has a much slower rate of change in the frequency response than one with N=6.

How does the order of a filter affect the impulse response of the system, however? Plotting the impulse responses of systems with certain orders suggests that the decay of the sinusoidals takes place much more slowly as the order increases, but I don't understand why. I've attached some examples. Thanks!


texts: stability of negative feedback amplifier

texts:
https://en.wikipedia.org/wiki/Negative_feedback

Wikipedia says the O/I =A/(1+βA)
When I set A=1 β=10, then O/I becomes 1/11
But when I put 1mv sin wave as input, the magnitude of signal after passing β is 10mv and (1mv-10mv) sin wave becomes input and the magnitude of signal after passing β is -90mv and input becomes again 1-(-90)=91mv.
When I calculate this again and again, the magnitude of absolute value of output seems to go infinite and the system seems to be unstable. But above calculation shows the O/I is finite. What's wrong to my thinking?


texts: Input protection circuit with P MOSFETs and SPDT for ON-OFF switch

texts:
I am making a circuit which may draw up to 3-4 Amps, so I am avoiding using a Schottky diode as fool-proofing it from incorrect polarity on the battery (12V, automotive style) input.

I have used P channel MOSFETs, one as an input polarity protection, and another after a fuse for ON/OFF by way of using a PCB mounted slide switch, which is a Single Pole Double Throw switch. This allows me to either pull the gate high of the second MOSFET shown below as Q11,  into an "OFF" mode, or pull the gate to ground into an "ON" mode.

I have used a PFET instead of the physical switch in series due to the size of switch needed to have the proper current ratings. This way seems like a better way to handle current for a PCB mounted ON/OFF switch with more than a few hundred milliamps going through it.

Should I bother with the 10K resistors, or will it be okay without them?

I am thinking of putting an ~18V zener clamp/TVS diode to protect it from inductive spikes from connecting long cables to the input, and perhaps some 10uF ceramic capacitors very close to the drain of Q11 to also help reduce spikes on connection.

Here is my possible improvements. Have you guys got any better ways to do this, which is cheaper/will get the job done and be robust enough for 12-14V input, 5A fuse in-line as shown, and loads being in the range of 2A-3A maximum (usually will be more like 1A).

In the second version I also moved the fuse up to be the first thing from the input connector, because it's possible for the first PMOS to die and short in strange ways, so the fuse will blow if ANYTHING weird happens. I think this is better.


texts:
Is there a way to make a speciffic routing rule applicable only for selected components (or component class)?

I want to define some "routing width" rules that will start routing the same net (e.g. GND) with a wide tracks from components with wide pads and use thiner tracks for smaller components.

Is there a way to do that without defining some extra rooms around components?


texts: What kind of hardware multiplier do modern processors use?

texts: I was wondering what kind of multiplier implementations modern processors use. Is it some derived variant of booth Wallace tree algorithm? Are these kinds of micro-architectural details publicized nowadays? What about back in the late 90's or early 2000's? Would a booth Wallace tree perform well on an FPGA? I'd imagine the Wallace tree aspect would cause some problems.


texts: Question Pertaining to Equivalent Resistance

texts:
I've got another question which pertains to Thevenins and Nortons Theorem. This time is about disabling all independent sources to find the Rn or Rth. I have the circuit attached below, and once disabling the independent sources I can't tell which resistors are in parallel or in series. I've also attached an attempt of mine where I coloured all the nodes to try and visualize which are in series or parallel but It was incorrect, on the right side is a redrawn circuit with the 8kOhm and 1kOhm in series and other notes. Is there a good way of thinking about this or a rule which makes visualizing which resistors are in parallel or series easier?

Thank you.


texts: dsPIC33 Code Protection, how does it work?

texts:
I have a dsPIC33 series micro that I believe is "code protected" because when I try to read back the data on the micro, I get all zeros using a PICKit2 programmer.  The PICKit2 programmer is one I purchased from Microchip and I know it works as I've programmed other micros with it.

I'm fairly new to the field of embedded and micro and I'm trying to learn.  So various devices I have in my possession, I've successfully tapped the micro and read it's code but the dsPICs I'm not able to get anything but zeros.

I have two questions:

If the micro is, in fact, code protected then is there a way to unprotect and extract the image?  According to Microchip's web site it states it might be possible but such methods involve subjecting their products beyond their normal operating limits.  I'm guessing they are referring to messing with the voltage levels and what not.
What is actually going on when I code protect a micro?

As an interesting side note, this particular dsPIC33 I have is programmed in the clear over the USB bus.  I could, theoretically, sniff the output of the FTDI chip that sits in front of the Micro and get the code that way but I'm more interested in knowing if reading back all zeros means the chip is code protected and, if so, if it's possible to break the protection, and how this protection is accomplished.

I plan on working on a small gaget as a proof of concept and I would like to ensure the code I write and flash in my own device is protected and so I'm trying to understand how secure this really is.

And for the purist out there, I do realize anything can be broken into -- I'm just trying to see what kind of effort is involved in this particular case.

The exact part number is dsPIC33FJ256GP710A from Microchip.

Thanks for reading!


texts:
I'm designing a 4-layer board with BGA components. The BGA part I'm working with, the SensL MicroFJ-60035 TSV, is a BGA SiPM with its pads in a 6mm by 6mm square layout. Most of the pads are no-connect, and SensL recommends that I solder these no-connects to a ground plane for heat dissipation. My design requires the SiPMs to be put close together, and there's enough spacing between the individual pads to put small 0.508 mm through-hole vias (with the drill being 0.254 mm) with enough room for soldermask to surround the via. It seems like this is a common practice, especially for complex components like FPGAs, but I was wondering what should be taken into consideration when performing this practice?

Here's a link to the product description below:

https://sensl.com/products/j-series/

EDIT: I'm going to post more information about the part here. First off, here is a link to the PCB solder footprint guideline for my SiPM, so you can see the pin out here: http://www.sensl.com/downloads/ds/CAD_MicroFJ-60035-TSV-A2.pdf

Please note how the anode pins are next together in the edge of the center two rows (with the fast output pins on the opposite side of the anode pins), and the cathode pins are at corners across from each other at the top rows.

In my setup, the round pad size is 0.27 mm with a copper clearance of 0.2 mm around the pad. The pads are spaced out 1 mm from each other in all directions, and there are 36 pads total. The SiPM might be a 6 mm square, but the pads underneath the part form a 5 mm square from the pad centers. Hope this helps.

My cathode layer is the second layer of my board, so that the SiPMs on the top layer can quickly reach it through vias. My trace widths for the SiPMs are 0.9 mm, mainly all on the top layer, and my layer clearance is 0.2 mm for all non-cathode vias and traces. This is just for my cathode inner layer. The other three layers of my board are all ground planes.

EDIT: To showcase my intentions, here's my schematic:

simulate this circuit – Schematic created using CircuitLab

It's a simple circuit. I'm using a filter to bias 16 SiPMs at the anode (though I only show four of them here), and their cathodes are all connected together through a resistor which goes to a connector for the output. Now, I plan for this to have the SiPMs on the top layer and the rest of the components on the other side of the 4-layer board. I was thinking of having the top and bottom layers be ground and the inner layers be the anode and cathode, respectively.  Since I have to wire sixteen of them in parallel, I figured that using planes would be the best way to go.


texts: What would be the options to supply a 3-phase motor without using the power lines?

texts:
If we have a 3-phase 600A, 400V AC induction motor with a VFD.
Are there any techniques to supply it with a huge acu/battery or a generator.
This is to use when electricity is gone or no power network grid around.
Any ideas or examples from industry?


texts: Calculate minimum voltage to turn off/on solid state relay

texts:
I have an AQZ204 AC/DC type solid state relay AQZA204 datasheet

Basically I want to calculate the minimum supply voltage required to turn the relay on

and the minimum supply voltage required to turn the relay off. These are similar to Pick/Drop voltages of mechanical relays or must be on voltage, must be off voltage..

I'm using 31.5 volt DC supply, with a series 4.7k Ohm Resistor to the input LED of the relay.

The data sheet is a little confusing to me, it saids the LED max dropout voltage is 1.5V so I calculated around 6.38mA forward current for the LED:

31.5VDC - 1.5Leddrop = 30VDC/4700 = 6.38mA

I'm confused by the IFon current being 3mA max?

So I can test the relays to see if they are in spec.


texts: How (or what is the best way) to raise and / or separate an LED from the PCB?

texts:
I'm designing a PCB where I have to locate two super flux LEDs like this one.

The problem is that it has to be elevated, approximately, 8 mm from the PCB. What is the best way to do this? What type of socket, spacers, standoff... is usually used in this case?


texts: Symbolic logic operator "implication" to logical gates

texts:
I need to translate a symbolic operator to a logical gates circuit.

Following the table that the symbolic operator has:

P Q    Result
1 1    1
1 0    0
0 1    1
0 0    1

Any idea how can I make it?

This is a draft of solution


texts: Is this the proper way to fuse a DC/DC Converter?

texts:
I am designing a solar power system for camping. I'll use a couple different DC/DC converters to provide DC voltages for the specific items I want to power. I want to properly fuse the various components to avoid damage or to limit the impact of defective or faulty parts.

I'm unclear on how to fuse the DC/DC converter. If the converter is rated for 20A and the load it will drive should only pull 7A do I use a 7A fuse for F2 to protect the load or do I use a 20A fuse for F2 to protect the DC/DC converter?

My next question is given the above demo circuit, how do I determine what size fuse to use for F1? If a DC/DC converter says it's rating for 20A, does that mean it can supply 20A at the converted voltage or that it can pull 20A from the input source? If the former, do I calculate the supply current using Ohm's law:

I = (Iout / (Vin/Vout)) * (1/.9)   (assuming 90% efficiency)
I = (20 / (24/12)) * 1.1111
I = (20 / 2) * 1.1111
I = 10 * 1.1111
I = 11A

Obviously I'm not an electronics engineer :) Hopefully my questions are clear enough you understand what I'm after.


texts: Low voltage drop current limiter for charging supercaps with a MOSFET

texts:
I have an RPi that I want to give enough juice to auto shutdown when the power goes down. For this I'll use 2 supercaps of 6F (2.7V) in series, giving me plenty of time. Now, I was wondering if I could charge these supercaps on the same 5V source that I connect to the RPi. The powersupply gives maximum 2.4A, but I want to limit the current into the supercaps so there is enough for the RPi and have a low voltage drop of around 0.1-0.2V. I thought something around 100-150mA, charged in 7-10 minutes, so there is a good 2A left and the eventual voltage drop would be low.

I could use an LDO with a fixed voltage and current output, analog to question 3V Current source with low voltage drop. For this I found the MIC5205-5.0YM5-TR (http://www.farnell.com/datasheets/29605.pdf) but in the datasheet it says under 'Electrical Characteristics' Vout = Vin + 1V so I guess that I can't use this one.

Other than an LDO I thought of a current limiting circuit with an MOSFET.

The circuit has 3 parts, first the voltage source of 5V with a maximum current of 2.4A.
Secondly, the current limiting part with the pMOSFET and the sense resistor, for this I thought of the PMN50EPE (http://www.farnell.com/datasheets/2621318.pdf) with Vth = -2V typically. And lastly the supercaps in series with their internal series resistance and a voltage divider to keep the voltage across both supercaps equal.

So,

Vin = 5V
Id,max = 0,15A
Vth = -2V

Rsens = 1 Ohm

Vgs = Rsens * Id - Vr1
Vth = -2V = Vgs,max = Id,max - Vr1
Vr1 = 2.15V
R2/R1 = 2.15

The datasheet of the MOSFET says that Rds(on),max = 0.07 Ohm, but in with lower current I guess this will be more? Is Rds = 0.2 Ohm a more realistic estimate? Then the voltage drop would be (Rsens + Rds) * Id,max = 1.3 Ohm * 0,15A = 0.2V.
I suppose this would drop as the supercaps are getting charged and R3 and R4 are taking over.

Is this a good design? Can it improve? Like decreasing Rsens and playing with the ratio of R2/R1, replace with/add in parallel to R3 and 'R4' 2 2.5V zener diodes. Will it fail completely as I oversaw something?

The datasheets of pMOSFET's give broad ranges for Vth how do I know I have a 'good' one?

Some calculations to verify the mode of Q1.

Id = 0.05A
-> Vsens = 0.05V
-> Vgs = Vsens - Vr1 = 0.05V - 2.15V = -2.1V

Vds = Id * Rds = -0.15A * 0.2 Ohm = -0.3V

Vgs < Vth
Vds > Vgs and Vds < Vgs - Vth = -0.1
-> saturation mode?

and

Id = 0.2A
-> Vsens = 0.2V
-> Vgs = -1.95V

Vgs > Vth
-> cutoff


texts: Non-contact voltage tester beeping near anything metal in my house?

texts:
Ok this is my first post so apologies if this is inappropriate but I need some solid opinions from guys who know about house earthing
So me and my dad just moved into an old house and I was walking around with my multimeter in NCV setting and it starts beeping when I hold the meter up in the air.
Now I'm not talking a stray beep every now and then like a false reading, this thing beeps continuously until I bring it back down close to my body and immediately beeps again when I raise it up, I'm familiar with inductance and body capacitance and all that but this is spooky

It beeps when I put it close to the kitchen bench (which has a metal strip along the perimeter), as soon as I touch the metal it stops beeping

It beeps near his ACOUSTIC guitar strings which is sitting on a stand and stops once I touch the strings

It beeps near any metal plate such as a small metal poster or piece of metal rod I have laying around and again, stops once I touch them

It beeps near some of the door hinges too

Is my house not grounded properly or something because both our phones act weird and slow in the kitchen and in some spots around the house
Now I'm an electrical engineer so please don't tell me I'm using my meter wrong or that it's broken because it beeps everywhere it's supposed to (near mains plugs, lights, appliances) but I've never seen the NCV go this crazy around random things and I'm worried the house may need some attention
Thank you to anyone who reads this and chips in, all advice is appreciated.


texts:
I am calculating The SAR anlysis on a human head of a wearable antenna that i have made . I have added a waveguide port and after simulation it does not show the radiation pattern
using the HFSS software 19 version this is the file that i have been working on
and  this the paper i am following


texts:
I designed an RF amplifier that should amplify signals in the FM band of 88 to 108MHz. The circuit is as shown below:

The input to the circuit is connected to an USRP through an SMA cable. The output is connected to an half-wavelength (1.5m) dipole antenna. The input power is in the order of 50 to 100mW. The output which is close to 2W in my simulations is about the same power as the input in the real world. What is causing this?

Edit: I am actually using RD06HVF1 transistor. I am using the spice model for RD06HHF1 as the specs are identical.


texts: How to generate 5- 20 Hz mechanical vibrations?

texts:
My project deals with simulating a fixed frequency tremor and process it. The  required tremor range is 5-20Hz. I have been trying to generate this vibration motion with a vibration motor, but all i get is a frequency greater than 30Hz ( measured using accelerometer).

Is there any other way in which i can generate a 5-20Hz mechanical vibration?

OR Is there a way of reducing this frequency generated by the motor?


texts: Integrated Circuit Chip number AUT1020218-A. Does anyone know what this is or where to get one?

texts: A chip number in this device is AUT1020218-A. Does anyone know what it is? I am trying to repair a timer device.


texts: Part number / manufacturer of microSD connector of Raspberry PI zero

texts:
Do somebody know what is the part number / manufacturer of microSD card of Raspberry PI zero?
I would like to include it on my Digikey cart if possible.
Schematics does not show the part number...

Regards.


texts:
I have been trying a lot to get my circuit work. I want the led to light up when the LDR receives no light and vice versa. I have found that the LDR offers the resistance of approximately 6k ohms when light is exposed on it and 66k ohms when light is not exposed to it. So I have used the resistors with those value. But I am not being able to achieve it in the simulator. Also there is glowing of the led in which lesser current is flowing but there is no glowing when more current is flowing. Please point out my mistakes and suggest me to get my circuit work.
I want the current to flow through the transistor "only" when there is light exposed to the LDR (possibly by keeping the low resistance for this path compared to the closed path of the LED). And when there is darkness, the current should not flow through the transistor leaving only a single path for the current to pass i.e. through the LED. Thanks for the help.

edit:  The source in the collector circuit needs a ground return. Why is it so?


texts: Am I using this LM393A comparator incorrectly?

texts:
I've read about comparators and from my understanding, you've got 2 voltage inputs: reference voltage usually connected at the inverting input and Vin i.e. voltage you want measured usually connected at the non-inverting input. The output voltage will depend on your V+ and V- values and whether it's Vin>Vref (V+ is the output) or Vin<Vref (V- is the output).
My goal was to use a comparator (LM393A) that will output either a HIGH (5V) or LOW (0V) signal depending on the value of the Vin I've used as the input for the non-inverting input, but here is what happened instead:

I was expecting the output to be at 5v once V7 has surpassed V6 (V7 > 3.7V) but instead, Vout looks like this (graph fitted for your convenience):

Is there something I did wrong?


texts: No response from 2 working spi devices when they are stacked

texts:
I have two identical SPI devices but each off them is on a separate board, they are connected via a header that allows the board to be "stacked" on top of the master controller. the signal will pass through two ICs before it reaches the slave device, a signal mux  SN74CBTLV3257 and a digital isolator ISO7741. Here is the schematic.

I have already confirmed that each of the circuit works perfectly fine when it is alone. The problem lies when both of them are stacked, i can confirm that each slave device has received my spi transaction as i can visually see that it is doing what im telling it to. Supposedly the slave will send a response back but i am not getting any.
With a bit of tinkering around the circuit i have concluded that the signal from the slave device is not making it back to the controller. In the schematic above i tried probing testpoint A and testpoint B with my logic analyzer and this is what i got.

at point B the correct signal is still there ( i checked that it is indeed the correct response to what i sent), at point A the signal seems very noisy, an lastly at MISO (directly on the master controller pin) it doesnt see anything.
The only explination i can think of is something between the two ICs are interfering with each other preventing the signal to be pulled high/low. But i could not make out why it is interfering with each other. The mux is able to handle bi directional signal so it should be it, It might be the isolator, when the other isolator pulls low the two muxes somewhat forms a voltage divider with isolator 1 Dout outputing 3.3v and isolator 2 Dout trying to pull it to 0v, and assuming both muxes has same resistance the controller would essentially be seeing 1/2 of 3.3v. I have no idea if that sounds correct though but it would be hard to test without an oscilloscope.
Can anybody help me with what might be happening and how to resolve it?


texts: Is there as way to verify a spectrum analyzer setup?

texts:
I just finished setting up my spectrum analyzer and I would like to ensure that everything is as accurate as possible. I was thinking of getting some kind of RF transmitter that transmits at a frequency between 30MHz-1GHz with a known dB level. If it helps the test is against CISPR 11 and I am going to test my unit at 3 Meters. My antenna is 30MHz-1GHz.
Anyone know of something that could fit this need?


texts: 3phase generator from signle reference signal

texts:
I need a 3phase (0-120-240deg) signal from one sine wave reference. I want control reference signal frequency in 5hz-50khz range with constant output phase shift in all frequency range.
What would be the best way to implement such circuit? Simple RC shifter won't work because it's phase shift changes with frequency


texts: Pseudo Random Number Generator and Propagation delay

texts:
I've recently just implemented a pseudo random number generator. This one to be more precise: http://www.cr31.co.uk/stagecast/trains/tt9_rng.html.
Of course, for the sake of my experiment, it's random enough. I use it to "randomly" assign 0 / 1 to an output.
The issue is that, due to the propagation delay that comes with the setup, I can't properly count the times when output is 1 or output is 0. Theoretically it should be 50/50.
With this pseudo rn generator, because it has 31 states, the occurrence of 1 is 16 and of 0 is 15.

I have to specify that I need a way to generate the random variable using only logic gates.

The question is: Can I determine the propagation delay of the setup presented above?
Is there an alternative to pseudo generate using only logic gates? with or without delay?


texts: How could this GPIO-controlled LED status blinker be improved?

texts:
I'm building a simple circuit to drive an LED status indicator in a project built around a RPi. The circuit takes its power from the same source as the RPi and is connected to one of the RPi GPIO pins. The aim is that the LED should start blinking when the system is powered on and continue to blink until the RPi system has finished booting, at which a process is launched to set the GPIO high, causing the LED to stop blinking and stay latched on.

I started with this circuit

(source: wild-bohemian.com)

Which I modified like so:

I've implemented a few circuits as designed by other people but this is the first I've attempted to design myself (ok, only a tiny part is mine, but hey). It does seem to work but I'm not confident that it is robust and I would appreciate any advice on how to do it better, or more simply.

One thing I've noticed when setting up on a breadboard is that if I just hold the wire that goes to the GPIO pin between my fingers - without attaching it - the LED latches on. I don't understand why. I'm not planning to put the circuit somewhere people can stick their fingers in but I would like to understand why it does this and if it is a symptom of a design flaw.


texts: Split 5V 3A into 1A in 2A to make USB charging device

texts:
Overall goal: make a couple USB phone & tablet charging ports from a 12V deep cycle battery.

Steps taken so far: I've read that using a resistor based system to step down from 12V to 5V leads to a lot of heat inefficiency so I purchased a SMAKN 12V to 5V 3A voltage regulator. I can simply solder the + & - terminals of a female USB port to this regulator but I thought it would be more efficient to split the 5V 3A output into 5V 1A and 5V 2A to charge a phone AND tablet at their desired wattages.

Confused part: Googling this leads to surprisingly few results, most of which discuss using PSUs where the answers generally revolve around picking a more specific PSU.. [Edit]: While other answers do discuss the underlying solution, they are specific to choosing a PSU and don't get into the details of how to construct a multi-device USB charging circuit.

Using Ohm & Kirchoff's laws, if I build a parallel circuit with a 5 ohm and a 2.5 ohm resistor, this will give me my 1A (5V / 5 ohm = 1A) and my 2.5A (5V / 2.5 ohm = 2 A).

simulate this circuit – Schematic created using CircuitLab

Jump back on google to find a 5 ohm and 2.5 ohm resistor and...I see a number of results some of which say to operate at 1/4 Watt which is clearly way too low.

I called local electronic shops - they all seemed surprised that I needed such a low resistance resistor with such high wattage.

All of which adds up to me thinking I'm going about this incorrectly or am violating some basic principle? Are my resistors (R1 = 5 ohm, R2 = 2.5 ohm) correct? Are there such resistors for 5V circuits? Is this design going to lead to power loss if only of the two USB ports are in use?


texts: Controlling a single lightbulb from multiple switches

texts:
It is quite common to have a single lightbulb in the home that has two switches to control it. It works so that whichever way the light is (on/off) you can change the state of either switch and it will change the state of the bulb.
For this you could use something like an XNOR gate circuit. (Is this how it is done in practice?).
Is it possible to do the same thing with three switches? So that if any of the three switches changes state it will toggle the state of the light?


texts:
I've got a logical design that uses roughly 3000 NAND gates. So far it's only on simulation, but I would like to physically implement it. The circuit is already simplified.
What are my options to do that? Buy 750 TTL 7400 does not seem to be a good one.


texts:
I'm currently looking into securing my RS-485 connections against ESD. My current understanding is that a TVS diode is put between the data line and GND, so that any discharge will be shorted to ground immediately, without going through other devices (sometimes also against +5V [>USB], not yet sure how that is supposed to work out or where to look it up).

Now I've found some sources that also put a TVS diode between the two data lines
(Protecting RS-485 by TI), some that don't and one even omits the ground TVS completely (TI again).

So apparently I don't completely understand how that's supposed to work and what the TVS between the two data lines tries to accomplish and I seek enlightenment so that I may not fry my circuit by accident. The first document explains it in a way I don't completely understand and the second one doesn't explain the reason at all (or I'm too blind to find it).


texts: How to decode a two bit signal into one-hot encoding, with 7400 series ICs?

texts:
Is there a single 7400 series IC which does this directly?

(I know can do this with 4*NOT + 4*AND gates, but that will be 2 ICs.)

Truth table:

 in | out
h l | 3 2 1 0
----+--------
0 0 | 0 0 0 1
0 1 | 0 0 1 0
1 0 | 0 1 0 0
1 1 | 1 0 0 0

(I'm not looking to mux/demux a signal.)


texts: How can i add an LED for identify working status?

texts:
I have a  GPS module, it's working well.
I integrated it with a STM32, getting latitude and longitude values through UART.

How can I connect an LED for indicating the connection status for this module?
Is any pin in this module capable for this purpose?

Thanks..

DATASHEET


texts: Are Fiber Media Converters Technically Modems?

texts:
Fiber media converters are devices used to convert fiber optic signals to other types of (digital) network data.

I'm curious as to whether these devices technically fit the definition of a Modem? If not, why?


texts: Can A Coil (1000 Turns) of 32 AWG Wire Stand 220V AC Mains

texts:
I am really new to Electronics. I spend time on it as a hobby. I have recently grown my interest on inductors but most of the calculation seems pretty hard to me. Little unsure if what I made can stand 220V AC Mains Current. I have made a Coil of 1000 turns of 32 AWG Annealed Copper Wire whose DC resistance measures 25.5 Ohm. My simple understanding suggests 220V across 25.5 Ohm, approx 8.627 Amps will flow, which seems way too high for this poor coil (I know, since it's inductor, it's not simple a resistive load). I calculated the length of the conductor to be 247.093 foot.

I am basically trying to make a transformer with it. Can I use it as Primary side of my coil?

If yes, then I am expecting the output to be 6V. I have used a 2" X 1" plastic former to wind it. If I expect the transformer to supply 4 Amps at 6V from secondary, which AWG wire (37 Turns Approx) will be suitable?

Please pardon me if the question is too simple. I am kind of stuck, because I still have lot of doubts on these calculations


texts: position of brushes on the commutator in a dc generator

texts: i am having a hard time understanding why do we place the brushes on the Magnetic neutral axis, the textbook simply says, because this is where the current reversal takes place, is the point where emf from different meet is the same as the point of current reversal?


texts: What does 'passband phase' and 'stopband phase' mean?

texts:
I've been provided with a Bode plot for an RC filter circuit with a cutoff frequency of 10kHz. Im asked to find the stopband and passband phase from the graph. I'm confused how these can be just a single number, since stopband and passband represent a range of frequencies. (All the frequencies that can pass through the filter and all the frequencies that would be attenuated).

So when giving the stopband or passband phase, should it be the first value of phase in each band? The last value? Maybe a range of values? Or possibly the difference between the first and last values (i.e. how long the band lasts in phase)?

If anyone can help me clear this up I'd appreciate it


texts:
I have 2 NiMh batteries 3500mAh 7.2V. However, first one have 7.58V(it increases each time Im measuring it) and second one have 8.37V.

Can this be the reason why 5x servos are doing unexpected movements and squeaky noises without even sending pulses to them(Im using arduino)?
Arduino Uno is powered by 9V battery and servos with that 7.2V battery.
Servos are HK15298 with volatge range 4.8~7.4V.

Are these 2 batteries already damaged and I should stop using them? Or how could I discharge them without damageing servos? To charge them I use charger with Delta Peak, but I dont think its working.


texts:
In my book I've seen many assumption done for to analyse BJT circuit. Like; Thumbs rule (when we assume Vce~ Vcc/3, Ic*Rc ~ Vcc/3) or assumed Ve is one tenth of supply voltage in another analysis (where it says that it is in the range from one fourth to one tenth ). This assumption are taken in the process of circuit design where Rc and Re along with other many values are to be determined. Again in this example one answer is given using assumption that under quiescent condition collector current voltage will be half of Vcc.

Q1: how do I know When I do which kind of assumption? Is there any rules?

Q2: My friend said that I can make assumption during circuit design but when I'm solving one I can't do assumption. Is it write?


texts: Detect string plucking in electric bass guitar?

texts:
Anyone knows any idea of how can I detect plucking in a string of a guitar with an arduino (possibly using the pickup signal)?

Thanks in advance ! ;)


texts: How can I light up 3 LEDs in sequence but only one at a time?

texts:
I have 3 LEDs in a row on a breadboard. I want to simulate a visual depiction of a current pulse by lighting up LED #1, then turning that off and lighting up LED #2, then turning that off and lighting up LED #3 then turning that off. How can I achieve this effect? To keep things simple, assume that it is irrelevant whether this process repeats endlessly or if it is activated based on some event. Also assume that only simple components are available, i.e. I probably can't use any component that a PhD in Electrical Engineering would consider "the most optimal component to use in this situation", as that would probably be too complex. The "most complex" components I have available are things along the lines of op amp, transistors (bipolar, FET), comparators, MUX's, and DAC/ADC.

Summary of requirements:

LEDs must only light up one at a time in sequence
Must have a way to adjust the speed at which they light up
Cannot do this by mechanical methods


texts: Is it Possible to Produce Any Color Temperature?

texts:
I see it is possible to purchase many different color temperatures in light bulbs from 3500K (in the red spectrum) to 6500K (in blue spectrum) all the way to 10,000K and even 20,000K or higher.

All bulbs available for purchase however comes in specific ranges. For example, you will not find a bulb that produces light in 5400 Kelvin or exactly 5200 Kelvin and so on. In other words, while there are many ranges available they are still limited to certain numbers.

My question is - how is the color temperature determined? In other words, does a given material always produce the same color temperature? Or is it possible to tweak a substance to produce any color desired? If yes, how would this be done?

FYI, I am interested in producing specific temperatures for a scientific experiment.

Thanks


texts:
I recently read something about the latch-up effect in CMOS-Structures but I don't understand why are MOSFETs affected by this effect. I understand that high currents through the source-drain path cause this effect because there are npn-pnp structures in the substrate which form transistors.

But I often read that "high" voltages (VDD + 0.7 V) on the input also causes latch-ups which is a problem if the device of the input is powered of. A logical one (active) would cause a latch up because 3.3V > 0 V + 0.7 V.

Why does this cause a latch-up? I thought latch-ups are caused by high currents. But the gates are isolated which does not permit any flow through the source-drain path, especially if the device is powered off. I see only a problem through the powering on phase where the operational voltage clamps up.

So my question is: Why do "high voltages" on the input cause latch-ups too and why is the condition VDD+0.7 V (VDD + Diode drop)? How can I protect CMOS inputs against latch-ups through signals which occur even if the device is powered off?

I would by very happy about answers :)


texts: Interfacing a GPRS chip (WISMO218) with an RF antenna. Calculating line width for the right impedance

texts:
I want to interface the WISMO218 GPRS chip with an antenna. The antenna lines on the PCB board have to be very specific, otherwise the system won't work. I have uploaded the part of the datasheet that refers to the antenna.

I am going to use an antenna and and a coaxial jack as seen at the links below:

http://dk.farnell.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=15001&langId=45&productId=64957755&storeId=10157

http://dk.farnell.com/johnson/142-0701-841/rf-coaxial-sma-straight-jack-50ohm/dp/1019324?MER=i-9b10-00001460

My PCB board is of the type "FR-4", Copper thickness: 35um, Height of the board: 1.6mm

I would like to interface the antenna on the same way as seen at the datasheet.

How can I calculate the line width, and the distance from the ground planes in order to achieve the 50 ohms impedance? Only the top layer is going to used for the antenna.

Remember that this operates in high frequencies.

Thanks in advance

The data sheet states the following:


texts:
I am developing applications for energy automation for power generation and distribution utilities but i dont have much electrical engineering background.

I always have confusion when it comes to terms like phase angles lag,lead,import and export
and four quadrants.

Can someone please explain a Four quadrant system considering the power systems?

I want to know what happens when a phase angle falls into a quadrant (such as import/export,lag/lead,inductive/capacitive  etc.)


texts: Overvoltage at input causes small jump at IC input pins

texts:
I have a PCB with voltage regulator (5V), op-amps, 2 multiplexers, 1
  counter, several pots, caps, and resistors.

  I supply 9V. The voltage regulator converts it to 5V. Without
  connecting any TTL signal through the function generator, I probe the
  input and output pins of the counter and I see a jump from 0V to about
  2V in ~4ms. Then when I turn the power supply off, I see another jump
  from 0V to about 1.44V in the 10ms range.

  I notice this behavior when I turn on and off the power supply. I
  removed the counter and op-amps, and I still see the spike in voltage
  but in the ps range and only when I turn the power supply off.

  There is an overshoot from the power supply where it jumps to about
  10V then back to 9V. There is also a tiny transient voltage but it is
  very small and I have the necessary passive components at the voltage
  regulator to control this.

  I do not know what is causing this issue. Tried different things, I
  breadboarded the voltage regulator by itself and I do not see any
  issues at the 5V output, I added just the counter, and I saw this
  issue, it seems like whenever an active component or IC is added this
  issue occurs. Can this be a PCB manufacturing issue? Any suggestions?

I see, I was not clear enough.Lets forget what I said in the block above. I made something to make this clear, see below. I also wrote my questions there.

I kept the recommended design set up for the regulator and I'm only powering the counter as seen below. I'm not providing any input signal or anything else. All of this is done on a breadboard. I have a more complex circuit on a PCB but I still see similar issues. That jump at the output pins is an issue for me.

Data input is grounded on the counter.


texts: Digital DC DC Converter for Power Control

texts:
I want to find a way to control a power device from a microcontroller. I must control a power device from the microcontroller, making the voltage to vary betwen 0 and 28 VDC, knowing that the power device could need up to 10A.

So the "module" should have the following specifications :

Vout : from 0 to 28 VDC (adjustable)
Iout : 10A max
I2C Digital interface to set Vout. Could also be just PWM input but i2c preferred
Vin : from 28 to 36 VDC (open to other specs for Vin, not the most important)

So I was looking to a digital programmable buck, flyback converter or programmable switching regulator fitting the exposed needs.

The main contrainst is that the module should ideally be COTS as I do not have access to full PCB design. (Yes, that is awful)

After having dissected a lot of electronics components constructors, as Ti, Analog Device, MaximIntegrated, MPS, and others electronics components suppliers,  I am not finding the ideal component/COTS... That's should be so straight-forward in my opinion ! Since it's just a flycback/buck converter with I2C PWM controller above ! I was suprised to not find quickly a module fitting the need.

Some power management modules exist, but the output voltage is set with analogic potentiometer (soldered in the board) or with a jumper to select Vout among others choices...

Any ideas ? Power electronics is not my main field so maybe I am not searching in a appropriate way.

Please let me know if the question looks unclear.


texts: Selecting the power source for load using MOSFETs only?

texts:
I'm looking for the circuit to automatically switch the load (< 0.5 A) between the main power source (USB) and back-up (battery) without a specialized IC and without the functionality of charging the battery.
I found two options:

with 2 diodes
diode from the main source and switchable P-MOSFET from the battery

I wonder if a similar solution can be implemented with MOSFETs only and came up with the following circuit:

Where VDC is the external power source, +BATT is voltage from battery, and VCC is the output voltage (automatically switched).
To my understanding (I'm not an EE) this should work as follows:

if VDC is connected:

the top P-MOSFET connects the VDC to VCC since the lower N-MOSFET shortens the gate of top P-MOSFET to GND and opens it
other P-MOSFETs are closed.
VDC = VCC

if VDC is not connected:

the VDC is pulled to GND, it opens the left bottom P-MOSFET, which pulls the top P-MOSFET to the VCC and closes it to prevent the back-flow from VCC to VDD
P-MOSFET connected to battery is open and connects the battery to load
VCC = +BATT

My questionas are:

Is it going to work? In case if VDC is USB and +BATT is 3xAAA batteries? Or if +BATT is a LiIon battery?
Is this solution any better in terms of saving energy than option with 2 diodes and/ one diode and mosfet? Are the voltage drops lower in such schematic?
Are there any other problems in this schematics except the hustle to find P-mosfers which can be open from small batteries voltage?
This circuit is going to work only if VDC > (+BATT +  body voltage drop on right bottom P-MOSFET)?


texts: Altium: board cutouts and multiple flex-regions

texts:
I am currently trying to create a rigid-flex PCB in Altium according to the following picture:

Purple: this should be the mechanical bard shape ;
Red: flex regions

basically i want to have a foldable PCB with two sections that are connected by multiple flex regions.

What I know/am familiar with:

Layer Stack Manager: I have created a rigid and a flex layer stack
Board Planning Mode: Assigning Layer stacks to board regions and define bending line/angle/radius for flex parts
create board cutouts using tools - convert - board cutout

What i dont know:

The board cutout seems to be ignored in board planning mode, so i cannot create flex regions in the red areas whle keeping the inner sections of the purple cutout rigid.


texts: Inductive reactance: frequency vs current. Why current goes to zero as frequency increases?

texts:
Suppose I have the circuit below with the frequency of the voltage source as a free parameter. Assuming the inductance is constant, the current flowing through the circuit shoud equal

$$I(f) = \frac{V}{j2\pi fL + R}$$

(I'm using phasors). Then by increasing the frequency up to infinity the current goes to zero. Why is this happening? I mean it is probably clear to me from a mathematical point of view and by using the frequency response I guess the absolute value of the trasfer function is going down as f tends to infinity, but what is the physical explanation behind this effect of a high frequency?

simulate this circuit – Schematic created using CircuitLab


texts:
I have a 12V signal which by the nature on how the sensor is mounted it generates a lot of unwanted noise, i created a filter which a microcontroller so that if the state changes 15 seconds then the output changes to that new state, and the same way the other way around.

I was wondering is there an easier/cheaper way into creating this, so that no micro is needed? with some passive components?


texts: Why is my relay oscillating for over a half-second?

texts:
I'm building a circuit that can turn on a relay when the variable resistor cools down.

Its operating principle is cooling down the variable resistor increases its resistance, causing the voltage at Node 1 to increase until BJT 2 turns on, driving BJT 1, driving the relay. The LED is there as a visual indicator.

simulate this circuit – Schematic created using CircuitLab

However, when I built, I observed some strange behavior: upon cooling the variable resistor, after about 2 seconds the LED begins to glow and over the next second increases in brightness. Then, when the relay turns on, instead of a single "click", over the next second I hear a buzzing sound as the relay oscillates on and off before staying turned on.

When turning off (letting the variable resistor warm up), first the LED begins to grow dim, and then the relay, instead of cleanly turning off, oscillates for a second before remaining open. Moreover, when the relay is bouncing, the LED grows very slightly brighter (I don't think this is just my imagination).

My current understanding of the circuit is that as the resistance of the Variable Resistor increases, the current is amplified by the two transistors and gradually increases the current flowing through the relay until it turns on. While I know that relays can experience contact bounce, especially when run at less than rated voltage, I have no idea why it should oscillate for so long, or why the LED should grow brighter.

What circuit effect is responsible for the relay bouncing for so long?

EDIT: I'm not looking for how to fix my problem - I did that simply by making the relay a latching relay. What I want to know is the why - the reason it was bouncing for so long.

EDIT 2: The relay is driven by a 5V switching step-down regulator that draws power from a 8.4V battery. It turns on a 30W heating coil (driven by the same battery).


texts:
I am pretty new with this stuff, just learning. I wanted to make a simple PCB, and as this was my first project, I decided to go with astable multivibrator circuit, to oscillate 2 LED's using transistors and capacitors. Unfortunately when built (and sadly I didn't bother to breadboard this first for some reason) only one of LED's (white) was lighting up and just staying like that. Because I am new to this, I am not sure how to approach the concept of "troubleshooting" and debugging the problem. So any advice is appreciated. I am attaching schematic, PCB, and the photos, with some data to make things clearer.

Several places I might have got this wrong are - maybe wrong resistor values? if so what are the correct ones?
Also I think I am not seing a difference between 10nF and 10mF (the myu letter for m) maybe I put wrong capacitors in?
Maybe wrong transistor? I just had this one.
Lastly ignore the LED values on the schematic, I just used some led's I had at home, and there is no values written on them, so I don't know. It's just regular LED I suppose.

Thanks!

Update 1: it appears I had wrong resistors for collectors, I had 2.2k instead of 220, so that is fixed now, and white led is brighter. Oscilation still not happening.

Update 2: It also appears I had polarity of capacitors wrong, that is fixed with no effect.

Update 3: Tried some messing around, like shortening transistor CE on the red led side. This causes a short blink (white off, red on) then in a milisecond white comes back, and red still remains (so both on). if shortening is removed, red turns off, and white remains. Not sure if this can hint a problem or not.

Update 4 As it was suggested apparently I got the C and E of transistor swapped somehow o_O. So got this fixed. Blinked for a second, and red was much deemer then the white.

Update 5 Changed LED's to both be the same green, as well as changed Capacitors to 100uF, and base resistors to 4.7k. (As it was suggested by many my current resistance for base was too high, and capacitor change was to keep same frequency of oscilation. Didn't work as well.

Update 6 After examining each part of board, I found a small part that was not connected. Self made PCB's are not reliable as someone from comments suggested :) This did make thing finally work, nice and steady green blinking led's. Yay!

At the end funny thing is that EVERYTHING was wrong with this board. and Everyone who commented had found something important :D Thanks! I hope I get better at this, currently I beter retreat into my embarassement cave.


texts:
Imagine you want to produce 1k pcs of hardware(mixed signal) per month and you would like to have tester in order to load firmware, calibrate sensors etc.

How do you approach that problem? I see many of people are talking about in-circuit tester using pogo pins.

Is that something you buy and "just" write firmware and position the pins correctly? Do I need to develop test hardware and then just use pogo pins to connect it with the pcb in testing?

EDIT: Ok, I intendedly asked general question, but I will specify it more.

There is a request to design 4 layer PCB with MCU, external memory, display, eeprom, CAN and Bluetooth Smart. PCB will be produced in 1000 pcs. per month.

Obvious fact is that I must design/buy piece of hardware which I will give to technician in order to test production items before attaching QC marks on it.

Is that kind of hardware something you buy from i.e. NI and use LabView to program the test procedure
Do I need to design PCB with MCU and bunch of analog and digital I/O, program it with production firmware and use it to flash the code to production PCB's. If yes, are the pogo pins and box shown on picture below right way to do it?

I agree that the question is too broad but I couldn't find any relevant information regarding the topic online.

Thank you all for your help!


texts: Cascade Wheatstone bridge sensor to increase sensitivity

texts:
This question is applicable to any generic sensor in a Wheatstone Bridge configuration.Let us assume it is the following pressure sensor.

http://www.aztronic.cn/thermistors/ntc/design-support-tool/four-arm-wheatstone-bridge/

Is it possible for me to connect two of these full-bridge wheatstone sensors in series or parallel and get double the output voltage as compared to a single wheatstone bridge.

Thank you.

@Henry and @Wouter. Thank you for your answers. I tried to run a quick experiment by connecting two resistive W-bridges in series, but did not get a double output voltage.

The following image shows what I am trying to do. Here, the output differential voltage (V1-V2) will not be different from a single W-bridge. The individual voltage at these nodes will always be the same voltage divider of the bias voltage irrespective of how many W-bridges are cascaded in series.

Please let me know if I am missing anything here.


texts:
I am a newbie to freeRTOS and I was trying to learn about semaphores,I am using ATmega32a microcontroller, the plan was to create 3 tasks each is blinking the same led for some time with different frequencies the result was the led is just on forever.
so I canceled 2 tasks and kept only one task to catch the problem and the led is just on forever again.
I used the debugger and what happens is that it never continue the loop of for loop it toggles the bit and then delay and then toggle again and then go out to check the semaphore and repeat, this is very strange behavior.
but that's in the debugger, in reality, it never toggles it's on forever.
can you help me?
#include <avr/io.h>
/* FreeRTOS files. */
#include "FreeRTOS.h"
#include "task.h"
#include "croutine.h"
#include "FreeRTOSConfig.h"
#include "semphr.h"
#include <avr/interrupt.h>

/* Define all the tasks */
static void ledBlinkingtask1(void* pvParameters);

xSemaphoreHandle  MySemaphore = 0;

int main(void) {
    DDRB=0xff;

    /* Call FreeRTOS APIs to create tasks, all tasks has the same priority "1" with the
    same stack size*/
    xTaskCreate(ledBlinkingtask1,"LED1",
    configMINIMAL_STACK_SIZE, NULL, 1, NULL );

    // Start the RTOS kernel
    vTaskStartScheduler();

    return 0;
}

static void ledBlinkingtask1(void* pvParameters){

    const uint16_t blinkDelay = 500;
    while (1)
    {
        if (xSemaphoreTake(MySemaphore,2000))
        {
            for (int i =0;i<9;i++)
            {
                PORTB ^= (1<<0); //toggle PB0 //PB0
                vTaskDelay(blinkDelay); //wait some time
            }
            xSemaphoreGive(MySemaphore);

        }
    }
}


texts: Short circuit between Vdd and Vss after high current through microcontroller clamping diode

texts:
When hotplugging a connector on my PCB, my microcontroller gets hot and a short circuit is formed between Vss and Vdd. One pin of the connector is the power supply ground, another is connected to an IO pin, but is driven at ground potential. When this IO pin makes contact before power supply ground, a high current flows trough internal clamping diode D1, destroying it. Is it possible that this shorts the other clamping diode D2, causing a short between Vdd and Vss?

I have already found a way to prevent this from happening, but I am interested to find out how the short circuit is formed.


texts: No driver IC on net in Hyperlynx problem

texts:
I am getting the 'no driver IC on net' problem in Hyperlynx signal integrity software. Does anyone have any idea bout it?
This is my PCB:

It has an SMD connector and an AD9767 DAC. I have added the IBIs model to the pins of the DAC. Then I added stimulus to the pin of the connector on the net I want to simulate like this:

After saving this, I tried to run the simulation on the oscilloscope but I get a mistake like this:

Also i'm not able to add SLM (single line model) for the connector in BoardSim but the net can be exported to LineSim where transmission lines can be added to trace and described as a connector where SLM models can be added like this:

But even after doing this I dont get simulations on the oscilloscope. I get the same error there too.
What am I doing wrong?


texts: Does it matter if I shield the antenna wire or the interference source

texts: I have a problem. My car radio is picking up interference when ever I plug a device into the power outlet/ cig lighter. I know that the solution would be to put shielding around the antenna wire, but the shielding wont fit over the antenna plug. So I thought I might put the shielding around the power wire (source of the interference). Provided the shield is properly grounded, does it make a difference which one I shield?


texts:
I am researching studies for common source MOSFET amplifier and I found two different terms for voltage gain - overall and partial.

What is the difference between overall and partial gain when talking about MOSFETs?
What do each one of them mean?
Are both used in practice when applying equations to real circuits?

Where partial voltage gain is defined as

And overall voltage as

Circuit schematic

Equivalent small signal circuit


texts: Thermocouple amplifier - single-ended vs differential?

texts: When connecting a thermocouple to an amplifier, what are the advantages of the differential versus the single-ended configuration?


texts: Automatic Baud rate selection in STN2120 logic, i would like to implement in TMS470. So, can someone help for Algorithm

texts:
I would like to implement set auto baud rate in TMS470 as like STN2120 or ELM327.

ELM327 have a algorithm to select a auto baud rate by itself. can we implement in TMS470MF06607 controller?

I want an algorithm for that.


texts: How to improve the accuracy of measured ADC voltage in a circuit connected to Vcc

texts:
The question is based on the following setup.
As depicted there is an IC to measure the real value of the 3.3V supply voltage accurately. The measured value of the 3.3V source is transferred via SPI to the microcontroller. This microcontroller is measuring the voltage divider between 3.3V and GND and has a reference voltage for its ADC.

simulate this circuit – Schematic created using CircuitLab
Problem: If the 3.3V supply voltage is changing the ADC measurement from the microcontroller is influenced.
Question: Can I compensate a changing 3.3V source with the measurement of the IC if the accuracy if this chip is within my limits.


texts:
I'm working on a legacy product, so I can't adjust the crystal or board in any way. It was originally written in PicBasicPro and I'm moving things over to Hi-Tech C.

It's a Pic18F4525 and has a 20Mhz crystal. According to the datasheet, the PLL just multiplies the frequency by 4.

So, this would give me a frequency of 20Mhz

__CONFIG(1, HS & IESOEN & FCMEN);

This would give me a frequency of 80Mhz

__CONFIG(1, HSPLL & IESOEN & FCMEN);

Surprisingly, by enabling HSPLL, the serial port outputs correctly, lcd still outputs, other than delay times I didn't see anything break.

So, my question is, what frequency is the clock running? Is it really running 80Mhz with PLL? or does the Hi-Tech C compiler know the max clock speed is 40Mhz and limit it there?

I will probably just stay safe and leave it at 20Mhz, but I would have expected serious problems clocking a 40Mhz chip to 80Mhz and didn't see any.


texts: Textbook confusion with CMRR and transconductance mismatch

texts:
I am just looking for an explanation on how a 2% mismatch in aspect ratio (W/L) results in a 1% error in transconductance paramater g_m (I can't figure out latex right now). The textbook conveniently skips over how they arrived at this value.
I have been struggling over this solution for most of the day and to no avail. When I looked up a similar solution online for a textbook question in the back of the book, the author also skipped explanation of this. So now I am here, as a last resort.

As Brian pointed out in the comments, my main question is essentially: Why does using this specific equation work (9.89 in picture), but using $$g_{m}=\mu _{n}C_{ox}\frac{W}{L}V_{OV}$$ does not.


texts: How can I know a signal's bandwidth before sampling?

texts:
Shannon's theorem tells us the minimum sampling frequency based on the bandwidth of the signal which has to be sampled.

But I wonder, how can I know the signal's bandwidth before sampling it?

It is generally assumed that one knows in advance the continuous time dependence of the signal (that is, f(t)), but I don't understand how this information can be available without a measurement, which in turn requires a sampling rate to be chosen.


texts:
To preface this I am a complete beginner with verilog and FPGAs in general. But I recently purchased a MAX1000 board to start learning things on and one of the first programs that I made was this:
module top (
    input CLK12M,
    output TEST
);

    assign TEST = CLK12M;
    endmodule

I then configured the pins so that I could look at TEST on my oscilliscope. I expected to see a 12MHz clock as that is what the device has and how it is configured but instead I am seeing a ~320Hz clock signal. For reference this is what the .sdc file looks like.
create_clock -name  CLK12M -period 83.333 [get_ports {CLK12M}]
derive_clock_uncertainty

Does anyone know what I need to do to see the 12Mhz clock signal?


texts:
Is it possible to swap two nets in Eagle schemtaic editor. For example, I have two LCD connectors and PCB is very badly routed, so I need to swap some nets on second LCD connector. Is this possible with single command or I have to do following:

Memorize name of first and second net
Delete both nets
Create new net and assign to it second net name
Create new net and assign to it first net name

Here is a screenshot of situation:


texts: Easy way to protect a battery from charging

texts:
I am looking for an easy way to protect a battery from charging.
I have a one cell li/ion that should supply the electronic of a board with a connector usb c (one connector from the battery, one on the other PCB). The one cell battery 3V will be removed every time we want to charge the battery with a battery charger.
As you know usb C as the same connector on each ends, what I don't want is that we can connect a usb C 5V directly to the battery.
If I put just a diode do you think it's gonna be enough to provide only one way for the current?
Thank you


texts: How do I perform logical operations without a micro-controller?

texts:
I would like to build some (hopefully) simple logic circuits without the use of a microcontroller. I'm a software engineer primarily so I think of things slightly differently. To implement this with a microcontroller would be simple but I want to learn how to do it without.

Take the following image. Imagine four photoresistors separated by some baffles. As a light travels around this, each photoresistor would change it's resistance in response to the light, obviously.

If I had this mounted on a two-axis pan-tilt mount, I could track the light with the following simple pseudocode:

# primary axis
if (A+C > B+D) rotateRight()
else if (A+C < B+D) rotateLeft()

# secondary axis
if (A+B > C+D) tiltUp()
else if (A+B < C+D) tiltDown()

Now say I have four LEDs, I want to light them up depending on where the light is. I essentially have four inputs and would like to electronically do this:

LED 1 = A+C > B+D
LED 2 = A+C < B+D
LED 3 = A+B > C+D
LED 4 = A+B < C+D

How would you go about that? Is it possible (/viable) with standard transistors or would you need specific chips? Is there a simple way of doing this?

I look forward to hearing back from everyone!

Thanks


texts: Is keeping HDD ON the anti static paper likely to damage it?

texts:
I bought a new HDD which came packed in a gray antistatic bag.
So while i was removing the HDD inside the laptop, i kept this new one on the anti static bag, after i unpacked it.
I took care not to touch the green circuit board. I held it by its sides.
Is keeping the HDD ON THE BAG likely to cause electrostatic damage?


texts: Why don't we have an instruction called LDAX H in 8085 microprocessor?

texts: Whereas we have instructions such as LDAX B , LDAX D !!!


texts:
I was wondering if it is possible to tap into the signal either on the low power side (between motion controller and the stepper motor driver) or on the high power side (between the stepper motor driver and the step motor itself).

I have a 4 axis motion controller, from which I am trying to take the signal off of the Z axis and use it to drive a optocoupler that would be in Darlington configuration with a bigger transistor to drive a relay.

Stepper motor is a big one Leadshine 86HS120 High Performance 2-Phase NEMA 34 Hybrid Stepper Motor, 70 V / 5-7 A.

Is this "tap" going to degrade the signal in any way, and if not - what should be required (I was thinking about some rectification and smoothing circuit to drive the optocoupler LED).

Excuse for my lack of knowledge in this field and please share your thoughts. Any word of advice is appreciated. Thank you.

Update #1:

Before anything, thank you everyone for engaging. Secondly, I see your point - so I am including the details for easier understanding.

This is a commercially made industrial laser cutting machine. It uses two axes (X, Y) for laser cutting head and Z axis for moving the belt "bed" underneath the material (textile material that is fed from a spool on the right side of the machine, goes trough the machine and out the left side).

There is an additional table to the left side of the machine, that needs to rotate its belt when the belt inside the machine rotates, so the cut material flows out without wrinkling.

This side table is the issue. It has its relay that is connected to PIN 6 of the general purposes "OUT" port of the controller, and should get a command to start the side table belt when Z axis is engaged. But it does not - and the manufacturer is unable to debug it for a long time.

Thus a need for alternative solution arised from. To make a circuit that would take Z axis signal and trigger a relay, bypassing the port "OUT6".

Controller model is AMC6340, and the driver model is DM856.


texts:
My teenage son has been building Cockcroft-Walton multipliers in his spare time lately, and I'm potentially a little concerned in case he electrocutes himself. His circuit is powered by 4 AA cells in series (6V), and judging by the spark gap he's managed to get to around 6kV using an oscillator and transformer followed by the Cockcroft-Walton cascade. Since he's building this on a simple breadboard there is no insulation between him and parts of the circuit, and he's already told me that he's had a few shocks.

I'm a physicist working in a university, so I looked up the regulations regarding home appliances in Europe and I think it should be ok (we use the same regulations to assess Van der Graaf generator demos). The total capacitance of the cascade circuit ends up at around 1nF, so at 6000V the total charge should be 6uC which I believe should be safe (EN-60335-1) but as I'm not an engineer I can't say for sure.

My question is: should I stop my son from building these? I have always encouraged creativity, and his love for electronics but I don't want him getting injured or worse.


texts: I need to get some sort of ESD/safety mat (2 actually) for working at home to protect myself and equipment. I was wondering what to look for/avoid if I were to purchase a rubber mat from a rubber supplier.


texts:
I'm building a new battery pack for an electric drill. One of the cells went dead, but I'm replacing all three to make sure they match.

The new battery pack will have 3 AA NiCd cells in series. Each one will have 1000 mAh and 1.2V. The original charger has an output of 4.2V AC ~ 100mA. Will this be sufficient to charge the new pack? Also, how long should I charge?

I've read tons of info on charging single batteries, but I can't seem to find any info on charging them in series.

update:
I appreciate the responses and thought I'd let you all know how it turned out.
I ended up leaving out the diode from the old battery pack, and swapping out the proprietary charger connector with a more standard one. Rather than reusing the original charger, I have it on a smart hobby charger. This new charger can be set for multiple configurations, including 3s NiCd, and charges them up accordingly. So the cells charged up happy at 100mA, and the drill now works perfectly again!


texts: DIY Bluetooth speaker - Some power related questions

texts:
I'm new to electronics and I'm making a DIY Bluetooth speaker. The problem I have is with powering the circuit. I plan to use 2 18650 2200mAh 3.7V lithium-ion batteries in series and use an XL6009 step-up converter to boost the 8.4 volts to 12V needed by the TDA7266 Amplifier Board. Also, I'll be using an LM2596 step-down converter for the 5V needed to power the VHM-314 Bluetooth Audio Receiver Board. To charge the 2 18650's, I'm using the HX-2S-A2 BMS module and TP5100 Lithium Battery Charger.
1: Am I doing it right?
2: What kind of adaptor should I use to charge the batteries?
3: Can I use an MDY-03-AF Xiaomi Adaptor to power the circuit and charge the batteries?
4: Do I need any type of Relay in this circuit?
5: How can I automatically stop using the batteries when the adaptor is connected?
And here we have my crappy schematics (Sorry!):

Information for the MDY-03-AF Adaptor:

Model : MDY-03-AF
Quick Charger 2.0
Output : DC5V-2A / 9V-1.2A / 12V-1A
Input : AC 100-240V, 50/60Hz, 0.5A


texts: What does the pill-shaped 'X' mean in electrical schematics?

texts:
I'm not familiar with this symbol.
Does it have a name?  What does it imply when reading an electrical schematic?


texts: I need to calculate bias current Ic1 and Ic2. I understand that both currents are the same and, because of beta being infinity, there is no base current (Ic1 = Ic2 = Ie1 = Ie2) and Ic3 = 2 * Ic1. I am confused of Q3 being there, because I can't split the circuit into 2 single ended stages and calculated the current to 1 single ended stage, or can I? I would be happy if you could help me to understand the schematic.


texts:
I have got few analog and digital signal that needs to be galvanically isolated. I am thinking to use H11F1M for analog signals. I am not sure how to rig-up the circuit using this device. Specifically bias resistors to be connected on LED and FET side.

And can the same device be used for digital signals also. And what precautions shall I take while using it for analog signals or digital signal.

EDIT1:
I want to isolate RSSI generated from AD8367. RSSI vs Voltage graph on Page 10.

Apart from HCNR200 from Avago as a solution.

I got a application note from Silabs which claims to use Si8660 for isolation of analog signal as it has internal RF Modulator and Demodulator based on OOK. But I am not sure whether analog signal can directly be fed to this chip of I need to use some extrnal opamps as shown in the Evaluation Board of Si866x.


texts:
So I thought I knew what I was doing but, this 3rd voltage source is totally throwing me off. Any explanation is very much welcome.

simulate this circuit – Schematic created using CircuitLab

So I have

I1 = I2 + I3 ------------------- (1)

-I1(3) - 30 - I1(2) = 0 -------- (2)

-I2(4) - 10 - I2(5) + 30 = 0 --- (3)

Solve for I1 in (2), we get:
-(5)I1 - 30 = 0
I1 = -6

Sub I1 = - 6 into (1) and then that into (3)

(I2 + 6)(4) - 10 + (I2 + 6)(5) + 30
(9)I2 + 74 = 0
I2 = - 8.2

Therefore I1 = -(-8.2) - 6 = 2.2

Does this look right? I want to be able to double check my answer using power but am unsure what voltage to use for each resistor. Any help/explanation is greatly appreciated.


texts: Solar panels sharing two controllers on two separate batteries

texts: Installed a system for a client but it's not working well.two panels each 175watts have 2 bringing in 350watts to a controller of 10amps to charge two different batteries of 100Ahr each total of 200Ahr so if I get another charge controller of 15amps and connect to this system but each controller charging a battery of 100Ahr but using one powerful solar panels bringing in 350watts will the system work well?


texts: How can I diagnose possible problems with my breadboards?

texts:
I am an EE professor, and in my digital lab my students had issues with breadboards this week (somewhat along the lines of this question). Components seemed to work when moved to a different area on the board, and I helped troubleshoot, so I don't think it's a case of student error.

What are the problems that can plague a breadboard, and how can I diagnose them? Is it as simple as unscrewing each board off of the platform and checking out the terminal strips? Do I need to remove the strips? Is there a tool I can use to check pin-by-pin?


texts: How to control high power (~5kW) heating element using MCU? I need a very simple application that shuts down the element, when it reaches set temperature. Maybe I can do it using SCR? F.e. Т161-160 (https://www.pentod.com/userfiles/product_files_shared/T161-160.pdf). And what should I pay attention to?


texts: (how) can I use 250v fuse in a 9v circuit?

texts:
I bought a nice big assorted set of fuses ranging .1A to 20A. All of them have 250V on them.

The question is can I use them in circuits with 3, 6 9 or 12 V?

If yes, does lower voltage changes the rating amp of the fuse?


texts: Can batteries be charged and discharged at the same time? And do they wear down faster when doing so?

texts:
Imagine batteries connected to a charge controller and a load at the same time. When the load asks for power, and the charge controller delivers power, there are three possible situations:

P_in > P_out: there is netto power going into the battery: charging
P_in < P_out: there is netto power going out of the battery: discharging
P_in = P_out: battery keeps unchanged

The power that the battery loses/gains is |P_in - P_out|, but in the system as a whole there's flowing a lot more current than that. Does all the current go through the batteries in this system? Or is there no current flow through the battery in situation 3 (such that the current is flowing directly from the charge controller to the load).

Do the batteries wear down in situation 3? Or are they just completely unused then?

EDIT: I think my question is different than the so-called duplicate, since it's more about the physical working of the battery. I made a basic diagram about my question as asked by Olin Lathrop:

So the question boils down to: are the light green and pink currents present (comparable to a dynamic equilibrium state in a PN-junction at rest due to drift and diffusion, when there's also a lot of electrical current flowing throught the component but no net measurable current), which would make the battery wear down? And if they're not, why? Is "path of least resistance" a sufficient reasoning to state this?

Also I am not completely satisfied with the answer given in the other topic, since he tells it depends on the kind of charge controller. If the charge controller delivers e.g. 24W at 24V (so 1A) and the load asks 12W, why wouldn't that current go to the load? Or would the charge controller then deliver only .5A due to the applied resistance (the load), and neglegt the battery? And what will happen with the rest of the energy that the charge controller receives from its source (which is thus 24W-12W=12W)? Will it be dissipated somewhere?

I am talking about a system where charge controller, battery and load are always connected (a stand-alone solar electric system).


texts:
Hey guys i'm on a project in which I have to use Safety Modules.

I'm confused with the pin-out diagram of the safety modules. They reference L and N lines of an AC source. I'm leaving you the data-sheets of two different Safety Modules, both make reference to L and N lines.

http://www.pizzato.com/PizzatoWeb/UserFiles/File/pdf/ZE_GCS01A15/ZE_GCS01A15-ENG_183-206.pdf (page 2)

https://cache.industry.siemens.com/dl/files/885/67585885/att_857967/v1/manual_safety_relay_3SK1_es-MX.pdf (page 50)

The safety Modules should go inside a machine in which the polarity (hot-neutral/L-N) is unknown. What does this mean, or what should I do to use them if I don't know what L and N are?


texts: Does the conjugate symmetry property of the Fourier series coefficients only hold for purely real input signals?

texts: I'm learning out the Fourier series and trying to price conjugate symmetry for a genetic input signal but I'm finding that this property only holds for a purely real signal signal. Is this right?


texts: Cursor (waveform) reading not the same with transcript window

texts:
I have run a simulation of a Verilog code testbench. I ran it in ModelSim, but why the reading I got from just using the cursor on the waveform is different from the one in transcript window.

While in the cursor, the WDIG_OUT values is offset 1 step backwards, making the 111 wDIG_OUT to match with 2181 rANALOG_IN. (just like in the case of "a" here).

I cannot proceed to self-checking because there is an offset. Please help.


texts: Preparing solder paste for syringe-style dispenser

texts:
I've been hand soldering SMD components for years and recently decided to buy a cheap solder paste dispenser hooked up to an air compressor. One of these with a 30cc syringe:

I don't know much about about solder paste, so I picked up a syringe of paste from my local electronics shop. I quickly figured out that adding a little isopropyl alcohol helps soften it enough to work "good enough" with this system. However, I have a few questions for people who have worked with these syringe-style solder paste dispensers for far longer than me:

Do manufacturers make different types of paste for syringe application vs stencil-and-squeegee application? The paste I bought from the local shop is by MG Chemicals, Sn63/Pb37, and comes in a syringe, so I assume it's the right kind for my needs.

What's a good ratio of alcohol to paste (assuming Sn63/Pb37)?

Once I mix the paste and alcohol in a separate container, what's a good technique to get the paste into one of the syringes without smearing it all over the inside wall? I've thought about pouring all of the paste into the dispensing syringe and adding alcohol on top of that, but I'm afraid stirring within the syringe won't mix the mixture homogeneously.

What's a good tip to use on the syringe? The dispenser I bought came with a large sample pack of various types (metal and plastic), but none worked great. The paste is too thick to fit through the metal ones and I find the opening of the plastic ones to be a little too large to be precise.


texts:
I came across this when I was browsing through the data sheets for a current sense amplifier such as the LT6100.

It reads:
"Fixed gains of 10, 12.5, 20, 25, 40, 50V/V are obtained by simply strapping or floating two gain select pins"

Does it really mean, for example 10V per V (10V/V)?

PS. Hmm it kind'a make sense. if 10V/V means that I get out 10 times higher volt (10 times amplification). Please confirm...


texts: Is a usable Laplace function possible with a time shifted resistor, e.g. r = R + Re^-2s? For instance what is the Z(s) of a series RC circuit:  1/Cs + R + Re^-2s. (???)


texts: Open a circuit when voltage exceeds a certain value?

texts:
General question

I would like to protect a load against overvoltage by cutting one of its power lines when the voltage exceeds a set value.

All the examples I have seen online present a way to short circuit the supply but not open it. I can't short circuit the supply nor use a Zener for regulation as the current drawn would be too high (and would limit it under normal conditions).

How can I drive a series transistor to cut one of the lines when a control voltage (from a comparator) is driven high (or low)?
How can I make sure that this protection is unengaged (i.e. supply is on) when the protection unpowered?
How can I make sure it can automatically disengage itself when the voltage goes back within allowed range?

Application

In my case, an alternator generates a voltage which is rectified and fed in a big capacitor before supplying a voltage regulator. I am designing the circuit for a certain alternator rate, but I want to protect it in case it goes faster.
2) comes from the fact that the protection circuit will be powered by the regulator past it... Which means, if it's engaged when unpowered the entire system will never power on!


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I am using a PC2002LRU-BWB-H-Q LCD with a STM32F4 micro and is powered through a TMP10424. There is also some 3V3 and 5V modules to. The problem is that the LCD is displayed fine for over days and then suddenly it stops to display. This may be down to power surges and thought the MCU was hanging. I added a watchdog to reset the MCU if it did hang.

The MCU seems to be fine because there is data coming from the UART and some Led's are toggling as they should but noting on the LCD. There is Light on it just no characters.

Also, I did notice that if I was probing the UART that it stopped displaying characters so it could be some sort of grounding issue, but the micro which is probably more sensitive is fine. I have 2 units set up so its not this particular LCD, the other one also stops displaying characters.

Is this a common problem with anyone?

LCD Interface:

Thanks.


texts: I need to design a second order active filter low-pass Rauch structure of Bessel. Design data: f-cut = 15 Hz; C1 = 50 pF. More info in img

texts: How can I find the values requierd? I tried using the formulas my teacher gave me but c2 is 0 when i use them. Am i doing something wrong? should i use other formulas? I tried to ask the teacher but he is no willing to help at all. I need to give it in monday so please help


texts: Is it possible to drive a stepper motor greater than 1000 rpm?

texts:
How could I achieve this?
What are the stepper motor facts
and principless that I have to
keep in mind to design a circuit
to achive this goal?
Are there any readymade/open source
alternatives and circuits available
to achieve this task?
Do I have to    approach design for
geared and    non-geared stepper
motors?


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I am using a PCIe x16 conn. It has 2 types of PRSNT# pins. My question is :-

What is the purpose of PRSNT#1 pin.
We have four PRSNT#2 pins in x16. (PRSNT#2_1/2/3/4). The purpose of these pins is hot plug detect or to tell the host about width of the card plugged(as I can plug any card x1/x2/x4/x8/x16 in x16 conn). How do I connect all the PRSNT#2 pins.


texts: High power (but low frequency) arbitrary waveform generator

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At least a few times I wished I had a "soundcard on steroids", so that I can replicate a specific waveform I'm getting from a generator, transformer or other devices I'm dealing with (e.g., see this question).

I read this is called an arbitrary waveform generator.

The twist is that I need a high-voltage one and high-power one, reproducing amplitudes to about 250V. On the other hand I don't need high frequency (or frequency precision/stability), so a soundcard followed by ×200 voltage amplification will do the job.

Example specifications:

Frequency: up to 1 kHz, arbitrary waveform, may have DC offset;
Voltage output: ±250V;
Current capability: 3A or 300W, whichever is lower (e.g. 100V@3A or 250V@1A);
Output impedance: < 5Ω .

How can I make such a device? I'm all for buying off-the-shelf parts to reduce work.
E.g. the DDS could really be a soundcard (or a computer-controlled DAC).

For the power amplifier I thought about using a big audio amp, but I'm worried about two problems: they are generally lower output voltage (designed to drive 2Ω or 4Ω loads), and probably cannot tolerate DC offset (I think most, if not all, audio amps use capacitive coupling at the input).

I also found the LME49830 which can be used to build the device I want (albeit "only" ±200V output). It too worries me that it is shown as capacitively-coupled.

What would you recommend?


texts: sim card sizes. Why start with the big one

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Sim cards come in various sizes standard(1ff), mini(2ff), micro(3ff) and nano(4ff).

Many questions I see tend to say there are many advantages to using the smaller size such as placement within the phone itself allowing for easier layout of components. So why did we start with sim cards the size of credit cards then slowly move down is size instead of simply starting at nano which has no waste material and can be positioned as easily as possible.

Was this addition plastic used simply as a shielded way to hold the card with old electronics or is there another reason I'm missing.