texts: Need help with timing circuit for ballistic sensor

texts:
I built a project using an Arduino microcontroller to manage high speed photography of an air rifle shooting targets like balloons.

I have a contact switch on the trigger. When that feeds a logic 1 into my Arduino program, I tell the camera to fire it's shutter, turn off the LED room lights, and start looking for the pellet from the air rifle to break a beam of LED light that's placed in front of the barrel of the gun. When that happens, my program times the amount of time the pellet takes to break a second beam that is exactly 2 inches past the first. My program uses the delay between the 2 events to calculate the speed of the pellet, and multiplies the by the distance to the target that I've entered into the Arduino.

At the calculated time my rig uses a solid state optio-isolator to close the contact on a flash.

Everything works well, to a point. I wrote Arduino code that deals with the i/o ports directly rather than using the Arduino functions to minimize the latency of inputs.

However, the Arduino is relatively slow, and it takes several instruction cycles to respond to a triggering event. That means that my calculated time is limited to multiples of the response time, meaning that my timing for firing the flash is often off by a small but important amount.

What I'd like to do is have a microsecond precise programmable realtime clock chip that I could trigger on a rising edge signal, have it measure the delay to the second sensor, calculate the projectile speed and the required delay until the projectile reaches the designated distance to target, and then trigger a logic 1 at that moment with microsecond accuracy.

Most real time clock chips I've seen output the time over a serial line, which would be way, way too slow for this application. Even for my air rifle application the pellet would be stuck in the "bullet trap" at the end of the target before the first time value has finished being sent to my microcontroller.

I'm currently working with air rifles, but hope to switch to .22 caliber bullets, which can move at faster than the speed of sound.

Is there some high precision programmable realtime clock chip I could use for this application? Or perhaps a circuit I could build with a quartz crystal, a digital counter, and a programmable gate array?

P.S. Here is a link to some of the results from my current setup. When it works, the results are very cool looking:

High speed photography


texts: How does a two input transistor AND gate work?

texts:
I'm trying to self study electronics. I started reading a book on digital electronics and I got stuck on the first chapter. It's about the logic gate circuit. There is a two input AND gate circuit and it uses three transistors.
Although, in my physics book, the circuit for AND gate shown is pretty clear. It used two transistors and I get that theory. But I don't get this.
In this image, why is it that when either A or B or both  are at 0 V, X=0 V? I know that in these cases, at least one of the transistors is off, so current from 5V passes through R and to the base of transistor T3, making it on. The current should also flow through the resistor across R... why X has an output 0?


texts: Performance analysis of embedded firmware

texts:
I'm working on a project where I want to make the software the most power efficient it can be on the system.
What ways can I do performance analysis of my system?

I'd like to run the system off AAA batteries but would like to estimate how long between the batteries needing to be changed.

My system mainly consists of a MSP430G2553 with a nordic nRF24L01+.

Are there any commercially available devices that I can hook up that'll monitor the power performance so then I can relate this to the firmware and work out how to redevelop the software to become more power efficient?


texts: Is there a component like terminal block that would allow you to create a power rail?

texts: I'm after supplying 5v to a bunch (5) devices from a single 5v power supply (with sufficient power output). I'm wondering, is there something like a terminal block, but instead of being  pairs of connections, all of one side would be connected and all of the other, so you could wire in your +5v and GND to the end and effectively have a power rail that you could wire in to.


texts:
I'm creating a simple circuit simulator application. Is there somewhere a csv/xml/... database of diode and transistor characteristics?
It would be a great help for me.
Thanks in advance


texts:
My GSM module is in such a place that antenna should be at least 100ft away from it to get signal(2g.) I searched for SMA coaxial antenna extension cables but they are only available in 25ft.
Is there a limit such that this long extension will degrade the network quality?
If I connect regular 100ft wire to helical antenna, will it work?


texts:
is there a simple way to connect the 5V pins of the Arduino and the raspberry pi in series to get 10V ?
Thanks


texts:
I'm an electrician and my work is to maintain boats.

I have a problem.  On the boats are sailing lights, and for each sailing light is another light inside the boat that tells you if the sailing light is working or not.

This was no problem with the old 40W incandescent light bulb but now all the lights are LED and the trick doesn't work any more.

This is the sailing light I'm using:

Hella marine. NAVILED PRO TOP. 2LT 959 908-5.
Operating Voltage 9 to 33V DC
Power Consumption Less than 2W (0.14A@12V / 0.08A@24V)

So this is what a have on the drawing on picture 1:

H1 is the sailing light.
D1 is the indicator light and will only shine if the sailing light is okay.
D2 is only to drop the voltage be 0.7V.

Picture/designs 1 and 2:

Picture/design 3:

EDITS:
And here is how I ended up doing it, and it seems to be working :)
Thanks for all your help!


texts: I want to create a wien bridge oscillator to use in my later projects so I tried to simulate a schematic I found online. Its stated that R1 = R2 and C1 = C2 should be true in order to circuit to oscillate. Ironically, thats the only situation that my circuit does not oscillate. I chose C1 = 1uF and C2 = 1.1uF and that is the closest I can get to a clear sine wave. While C1 = C2 my circuit does not oscillate. I tried C = 1n which is useless too. I even tried charging one of the capacitors beforehand to kickstart the sim but it doesnt work either, the wave just flattens in time. If I remove C2 I get square wave which is more interesting. Later on I decided to try the working one (C1 = 1uF/1nF, C2 = 1.1uF/nF) on my bread board which didnt oscillate, but created a steady voltage. I formed a voltage divider and powered it with my dc power supply, used the middle node as my virtual ground. Im lost and I need help.


texts: Arduino Uno Doesn't show up under Serial Ports, but it does show up in Device Manager

texts:
My Arduino Uno doesn't show up under Serial Ports in the Arduino IDE, but it does show up in Device Manager.

I have a I2C Sainsmart LCD connected to the Arduino.

Do you have any idea why it would do this?


texts:
I was looking more into the GPIO pins of the ATmega328p and came across the simplified schematic of a I/O pin. The schematic includes two reversed biased diodes, one to the ground and one to the VCC.

I could identify the use of the reversed biased diodes on the I/O pin.
What is the use of these diodes?


texts: Is there current flowing through this capacitor?

texts: Let's say \$ V_s \$ is some time-varying voltage source. Is it necessarily true that the current going through \$ C_1 \$ is zero? I would think that the answer is yes, because the current flowing through R_1 must be equal to the current flowing through \$ R_2 \$ (as these are the current out and in of the voltage source). I think the op-amp should be in negative feedback and shouldn't contribute any current through its terminals.


texts: How to choose and design a waveform generator such that it generates signals of mentioned rms voltage, Vi and of frequency f given below?


texts: Is there any possible low-frequency electrical resonance can be caused in a power grid?

texts:
I am wondering if any potential damage or fault can be caused by low-frequency electrical resonance/oscillation in a power grid/system due to its internal & external/parasitic inductive and capacitive components.

If so, what are some good examples to prove and show this point?

We know at the resonant frequency, a system can output much higher output in magnitude which might exceed the power rating of the circuit, which can potentially damage the circuit or the load that's connected to the circuit. I am wondering if this situation can be applied to power systems/grids, more specifically in the low-frequency range, like 1Hz to 20Hz.

Many thanks in advance!


texts: Choosing a large, reliable input capacitor for switching regulator

texts:
A project I am designing has to be reliable for many years. I have a switching  power supply using a LM2596S-5.0/TR

I am having trouble deciding on the capacitors. I have placed a tantalum 10v 220 uF on the output but on the input I am having trouble.

The datasheet says:

  A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground pin.

The example application lists a 660uF.

Looking on LCSC, I can only find a couple of SMD capacitors at 50V, 660 uF and they don't mention their ESR.
It doesn't help that the datasheets are in Chinese.

I can't seem to find tantalums of this size and voltage either.

Can anyone recommend the types I could use here? Favouring reliability if possible.


texts: Does not the wire signal affect in sequencial logic?

texts:
I want to make 1 delay signal with an wire signal.
Let's here my case.

wire done;
reg done_d0;

always @(posedge clk or negedge rst)
begin
if(!rst) done_d0 <= 0;
else done_d0 <= done;
end

But done_d0 does not have a delay when done is high.
Both are triggered at the same time.

What am I missing ?


texts:
I'm trying to add the following function on my Simulink model.

where C, B, and N are already variables in my file. Is the correct way to multiply omega by the gains 3N and N/2 an input that into the sine (as shown)

or should I change the value of the frequency? If so, what would be the right value?

Thanks


texts: How can pin states be altered by using JTAG Instruction Codes?

texts: There are several mandatory JTAG instructions to use for boundary scan. I have learned, we can change pin states of MCU or CPU by using that instructions. However, I could not find any detailed information about it. How can I change pin states with JTAG? Which instructions should I use? I want to program an external flash by using that property.


texts: High pass filter that locks voltage at certain amount until frequency is reached

texts:
I have a sine wave that is biased at about 1.5V DC. I want to create a high pass filter that allows any frequency through greater than 4000Hz.
Want I want my high pass filter to do is to be at 1.5V default with no fluctuation. Then when the frequency is greater than 4kHz, it lets it through.
A long while ago I found this high pass filter online:

I cant remember where I found it (I think it was just on Google images) but it does almost what I want. Here's the LTspice simulation:

Green is my biased sine wave which has an amplitude of 0.1 and a freq of 4kHz. Blue is the output of the high pass filter.
The output does exactly what I want. I stays at a constant voltage and then only increases after the frequency reaches the is greater than a certain amount.
The main issue with this is that the constant voltage is 0 whereas I would like it at 1.5V. I could (and I did last time) add a voltage divider on the output but I feel like it's a bit of a bodge and there must be a better way of doing it.
I also don't know the equations for the different resistors and capacitors so I don't know what the real cut-off frequency is.
How can I achieve my goal without a voltage divider on the output?


texts:
I am considering a project involving a fair share of digital signal processing. As far as I know, the best type of IC suited for this are the Digital Signal Processors. I have never worked with them before - can you recommend me any model that is simple enough for beginners? The project involves filtering hi-fi digital audio (44100Hz, 16 bit stereo) in several ways.

Also, do I need an additional uC to for example control an UI with an LCD panel and some buttons, or can the DSP handle this along its signal processing task?


texts: Help with using a tunnel diode in LTspice

texts:
I want to use a tunnel diode to implement a simple van der pol oscillator
circuit. So far I found a SPICE code for 1N4393 from this reference.

Is it possible to simulate 1N4393 to convert and use the following SPICE code for LTspice?:

* JFET n-type, analog switch; 40V 50 mA, low Ron resistance
.MODEL 1N4393 NJF (VTO=-1.50 BETA=4m LAMBDA=.035 RD=14 RS=15 IS=2E-15
+ CGS=7p CGD=9p KF=1.5E-16


texts: Integral only control (as opposed to PI or PID)

texts: I am familiar with PI and PID control but I've recently been reviewing code that seems to use I (Integral) only control. What are the benefits of I control over PI control, and when should it be used / not be used?


texts: Microcontroller working voltage + brownout circuit

texts:
I'm working with LPC1769, but this applies to any MCU.

The datasheet states that the power supply range is from 2.4V to 3.6V.
The included brownout detection circuit triggers a warning interrupt below 2.2V and  asserts the Reset below 1.85V.

What happens when the supply voltage is between 1.85V and 2.4V ?
Why the BO circuit was not designed to reset the MCU below 2.4V ?

I know that the operation is guaranteed down to 2.4V and that the MCU might work very well even at 1.85V, but this is a grey/risky area.

Thank you.


texts: Can mobile reception 4G/5G signal reception be affected by atmospheric changes?

texts:
For example, if it rains or there is smog in the air can this atmospheric change affect the signal quality of mobile phone devices such as 4G and 5G?

I have been noticing changes in the reception here in Australia when it is cloudy and when it is smoggy also.


texts: Comparing sine wave and triangular for spwm using comparator

texts:
i am trying to generate sinusoidal PWM by comparing sine and triangular wave.

First i just tried to compare sine wave with reference voltage in order to check the working of op-amp. I get a problem in using op-amp(741) as a comparator at high frequency, so i used comparator by the suggestions from electronics stack exchange.
enter link description here

Which work great for comparing sine with reference voltage.
Later i noticed that there is a offset problem. Input waveform having an offset of 0 volt, but when i connect my input (both sine or triangular wave) to a comparator. The input waveform get changes by it dc offset to 6 volt.

Input waveform before connecting to a comparator

Offset voltage = 0 volt

Input waveform after connecting to a comparator

Offset voltage = 6 volt

How to compensate the offset voltage to zero volt after connecting with comparator.

Circuit..
Triangular Waveform...

Comparing triangular wave reference voltage...

Without connecting with comparator

How to compensate the offset voltage to zero volt after connecting with comparator.


texts: Trying to get that tube sound from a gainclone amp

texts:
A Gainclone amplifier makes for a nice simple benchmark/monitor amp. It is a class AB linear amplifier capable of 20 W - 120 W of power, and is based on a monolithic amplifier chip such as the LM1875, LM3875, LM3886, or LM4780.

What different ways are there to add controllable even order harmonic distortion to its sound?


texts: Self Contained Temperature Display in Very High Temp Environment

texts:
I want to build a temperature sensor + display that will operate in a high temperature environment (routinely 120C, but periodically spiking to 175C, and might be exposed to 350C where it would be required to survive for very long--ie it could fail after a short time) that would also function at lower temperatures (e.g. 15C).  Can it be done?  How?
Challenges/Questions:
1)  Is there a way to generate power from the heat that would drive the electronics?
2)  Is there a battery that would survive the heat?
3)  Is there a way to keep the electronics cool enough to function?

OR:
Is there another (non-electronic) way to display the temperature where the sensor and display are while in the high-temp environment (obviously not a EE question here...but open to idea).


texts:
Well, I've recently started reading about thyristors and I have been stuck by something my instructor said about the turn-on process.

During the forward-biased state of the thyristor the junctions J2 is reverse-biased, which is essentially responsible for the forward "blocking" mode. However, after the break-over voltage, J2 starts conducting magically.

How does this change come about? Is this due to the breakdown or avalanche process?
If so, how can a device recover from it and turn-off?
I mean, we say diodes are destroyed if the reverse voltage exceeds the breakdown voltage but how come the same process not destroy the thyristor junction?


texts: Why are batteries measured in ampere-hours but electricity usage measured in kilowatt-hours?

texts: I was reading about energy usage in batteries and don't quite understand why it is measured in different units than home electrical usage.  An ampere-hour does not include a measure of volts.  But my understanding though is that a battery has a constant voltage (1.5V, 9V, ...) just as much as home electrical usage (120V, 220V, ...).  So I don't see why they have different units by which they are measured.


texts:
I have question regarding the pull-up resistors when UART/I2C lines are running on 2.5V and GND. Is it OK if pull up resistors are used on these lines which are connected to 3.3V
or Vice versa when bus is on 3.3V and pull-ups are connected to 2.5V.


texts: What do the values on the back of an encoder mean?

texts:
I have an encoder (at first I thought it was a potentiometer!) and on the back it has B1 03 (separated).

Research thus far has shown that an encoder can have anywhere from 100 to 6000 steps. I imagine those numbers are related to that value, but I do not know how it reads.

Do they have meaning? (This came with my Arduino)


texts: How does current flow in unbalanced antennas?

texts:
I have been researching and learning more about antennas recently however I am a bit stuck on understanding how balanced and unbalanced lines / antennas function.
My understanding is that a balanced transmission line is balanced simply because the current in must equal the current out on both lines (ie. on a ladder line). An unbalanced transmission line is unbalanced because the current in does not need to equal the current out (ie. a coaxial cable). Maybe there is a better definition than this, having to do with the fact that the outside of coax grounded and the twin lead carries a differential signal but I am not sure.
When a balanced line drives a balanced antenna ie. a dipole, the same current has to flow out of each end of the balanced line and the same current must flow into the dipole, thus keeping the dipole balanced even in the case of a small difference in impedance between the transmission line and the antenna.
With a coaxial cable things are more complicated. From my understanding within the coaxial cable the currents must be balanced due to the internal H field inducing equal and opposite currents on the inner and outer shield of the cable. When attached to a balanced antenna such as a dipole, the current in the centre conductor must flow through one arm of the dipole (or reflect if there's a mismatch) since there's nowhere else for that current to go. However the inner shield's current has the choice now to either flow into the second arm of the dipole or over the outer side of the shield: in the case of a small mismatch between the dipole arms the second arm of the dipole may "want" less current than the inner shield is carrying and so some "common mode" current will flow over the outside of the coaxial cable, causing more issues than there would normally be with a small load mismatch on a balanced line.
To fix this one needs a balun to make it so that equal currents will flow in both arms of the dipole.
Up to here things feel fairly sensible. However things get confusing when I start looking at unbalanced antennas for example monopoles and whips.
With monopole antennas, the shield is connected to a plane and the vertical radiator is connected to the coax centre. I have heard that because this an unbalanced antenna, it can (or even must?) be directly fed with an unbalanced line such as coax. However, it seems to me to have a similar problem as before: the current flowing into the vertical section is well defined and the current flowing out of the inner shield must be equal to the current flowing out of the center conductor which is equal to the current flowing into the vertical section. Thus there must be some current flowing from the inner shield onto the ground plane OR onto the outside of the coax, since these two are in parallel. Again, it seems like we should need a balun to force all the current from the inner shield to flow onto the ground plane but I've heard people say other wise. This confuses me.
This gets more confusing with whip antennas, which appear to not have anything connected to the inner shield of the coax whatsoever. In this configuration, I think the current on the center conductor should be equal (but opposite in phase) to the current on inner shield, but since the current out of the inner shield has nowhere to go it should either reflect causing atrocious things to happen to the transmission line or flow along the outside of the cable, radiating and probably also causing other issues. I assume these things do not happen or else this would be a poor antenna design to use, thus I think I am misunderstanding something.
So my question is, how do unbalanced antennas such as monopoles and whips prevent current from flowing along the outside of a coaxial cable, and what does the current flow in these antennas actually look like?


texts: Operational Amplifier gain bandwidth product

texts: If the gain bandwidth product of an operational amplifier is a constant and |Vout/Vin| is also a constant does that mean that the operational amplifier will not function for all but 1 frequency? Please explain.


texts:
I have to give audio Line Out in my project. I don't know which connector I have to give this out. I have found that in PC, 3.5mm Jack is used for line in and line out. Also found that RCA jacks have been used for line out in other equipment. I want to know what is the standard connector for LINe out interface.
Also please suggest whether 3.5mm headphone jacks can be used for Line Out?


texts: VHDL define range as previously defined range + offset

texts:
Is there some way in VHDL to define a range as a previously defined range plus some offset? Below is an example of what I would like to do but I can't figure out the correct way of going about it. In this example the FIFO's din/dout are 47 downto 0.

constant X_DEPTH        :   integer := 8;
constant Y_DEPTH        :   integer := 8;
-- Expected range 7 downto 0
subtype X_MAX_RANGE is natural range (X_DEPTH-1 downto 0);
-- Expected range 15 downto 8
subtype X_MIN_RANGE is natural range X_MAX_RANGE + X_DEPTH;
-- Expected range 23 downto 16
subtype Y_MAX_RANGE is natural range X_MIN_RANGE + Y_DEPTH;
-- Expected range 31 downto 24
subtype Y_MIN_RANGE is natural range Y_MAX_RANGE + Y_DEPTH;
-- Remaining bits (Expected 47 downto 32)
subtype REMAINDER is natural range 47 downto ???; -- Y_MIN_RANGE max + 1
signal dummy1,dummy2    :   std_logic_vector(REMAINDER);

begin

    FIFO_inst : entity work.FIFO
    PORT MAP
    (
        clk     => CLK,
        srst    => RESET,
        din(REMAINDER)          => dummy1,
        din(Y_MIN_RANGE)        => y_min,
        din(Y_MAX_RANGE)        => y_max,
        din(X_MIN_RANGE)        => x_min,
        din(X_MAX_RANGE)        => x_max,
        wr_en   => wr_en,
        rd_en   => rd_en,
        dout(REMAINDER)         => dummy2,
        dout(Y_MIN_RANGE)       => y_min_out,
        dout(Y_MAX_RANGE)       => y_max_out,
        dout(X_MIN_RANGE)       => x_min_out,
        dout(X_MAX_RANGE)       => x_max_out,
        full    => full,
        empty   => empty,
        valid   => valid
    );


texts: USB signal routing - Swap data lines using vias?

texts:
I'm making my second USB design, but the D+/D- pins on the MCU (atemga16u2) aren't in the right order for the micro B connector. What's the best practice for routing these to go the right way? My current idea is to rotate the atmega 180 degrees and route them under, but it feels like the traces are fairly long.
I could also drop one of the lines under the other, but I'm sure that would mess with the lengths for the differential pair.
This device won't go over Full Speed, so I can get away with less than perfect routing.


texts: Obtaining P(w) expression from figure for zero ISI

texts:
I have a practice test which asks to find P(t) and verify that it have no ISI

I know that zero ISI means that the function will have a value 1 at t = 0 and 0 at multiples of T (sampling intervals)

My confusion to the question is how they obtain the expression P(w) from the figure below

P(w)= (w2/w2-w1)T(tri(w/2w2))-(w1/w2-w1)T(tri(w/2w1))
where T= 2pi/w1+w2 (the T was obtained in the first part of the problem)


texts: How to switch between accurate current sources

texts:
I would like to switch between two resistor loads in order to change a current source value.  The current way that I am doing it is with something like this:

simulate this circuit – Schematic created using CircuitLab

Where M1 and M4 are low (< 10mΩ) Rds(on) MOSFETs at 8.5V Vgs.

Is there a better way to do this?  Changing Vref changes the compliance of the current source, so it would be better to change the resistor.  Unfortunately, the resistors value (the dominant error term here) is known to .1%, so M1 needs to be < .1% of R1 (or <10mΩ), and these MOSFETs are a little on the expensive side.


texts:
So I came up with the following filter to analyze:

My first thought was that this reminded me of a Sallen & Key biquadratic section. However I'm having trouble identifying each component. Taking the general Sallen & Key structure:

Let's start with the obvious ones:
$$Y_3=sC_3$$
$$Y_4=sC_2$$
$$Y_5=\frac{1}{R_4}$$
Now comes the troublesome part.
I would guess that
$$Y_1=\frac{1}{R_1}$$
And we can make Y2=0? What about the R5+R6 series resistors (assuming ideal OpAmp)? How do I fit them here to work with the equations?


texts:
I need to detect and count a number of metal plates coming by my sensor. I need to do it cheap as possible. There are around 1-2 centimeters between the plates, and they are 3 centimers thick. The sensor can get pretty close to the plates: ~1cm.

What do you see as my options?

I have tried an IR distance sensor, which works OK. Problem is that the plates are black, so I need to use a lot of power in my emitter LED to light up the black. Besides day light and other light sources might interfere.

I've looked into inductive proximity sensors, but I haven't found any IC's are reference designs for this. The ones that you can buy for automation are to expensive.

Any other ideas? :)

EDIT:

To clarify. Actually it is a stack of weight plates that is moved up and down (like in a gym machine):

I need to count how many plates passed a curtain point. I was thinking if it is possible to do something electromagnetic? Create a long coil (the blue line in the drawing) or something similar?


texts: Converting analog CRT adjustments to digital

texts:
Many CRTs use analog controls (potentiometers) to adjust various picture settings such as brightness, contrast, geometry, etc. My objective is to replace these analog controls with digital ones.

Preface

I only know the basics of CRTs. I have some experience with programming microcontrolers like the Arduino and Raspberry Pi, but little EE experience. I know CRTs are dangerous and I will only be messing with the detached control board.

I am working on building an arcade cabinet that can play multiple games (MAME). Many games run at various resolutions including CGA, EGA, and VGA. In order to run these games at their original/native resolutions, a CRT that supports 15kHz, 24kHz and 31kHz horizontal frequencies is needed. These are called multisync/tri-sync/tri-mode monitors. 10 years ago there were digial multisync CRTs available, but now only analog multisyncs are available. Specifically, this Makvision M3129DS-LG CRT.

The difference is important as picture adjustments are necessary when switching between horizontal frequencies. A digital multisync stores adjustments for each frequency and automatically switches between them. An analog requires manual adjustment after each switch. I want to avoid having to manually adjust the picture when switching between games.

My solution is to convert the analog adjustments to digital ones using a microcontroller. I would simply replace the mechanical potentiometers on the control board with digital potentiometers controlled by a microcontroller. However, after doing some reading on digital potentiometers (digipots) vs normal/mechanical potentiometers (pots), I have come up with this list of considerations:

Noise: Do digipots produce enough noise that it would affect the picture? I would assume not.
Zero crossing: This was frequently mentioned regarding preventing popping noises in audio when using digipots as a gain/volume control. Do I need to worry about this? You can get digipots with zero-crossing detectors built in.
Maximum operating frequency: Does this refer to the frequency of the signal the digipot is providing resistance on? Do I need to worry about this?
Power-up/default resistance value and off-state resistance value: If the monitor receives power before the digipot receives power or before the digipot is set, the resistance provided by the digipot is undefined and could be at the ends of the resistance range (turned all the way up/down). You can get nonvolatile digipots that retain their resistance value without power and on power up.

My biggest question is: How at risk is the CRT while I play around with this? Again, I will only be messing with the detached control board. Does the monitor have safe guards in place to prevent damage? For example, what if you were to turn the existing pots all the way up or down? What if the existing pots were removed (infinite resistance) or shorted (0 resistance)? I assume I can use resistors in series and in parallel to ensure the resistance is always in a "safe" range. I don't want to fry an expensive CRT.

I have not purchased the CRT yet. I want to know if this is a feasible idea or not.


texts: Read self battery voltage using PIC microcontroller

texts: I'm working on a battery powered project where I have to constantly monitor the remaining battery level of the battery that is powering the mcu. I know it can be done using arduino and its internal vref. Now, The PIC18F26J50 I'm using also consists of a Band Gap Reference(vref). But I Don't know how to proceed or it's even possible using PIC. Is there a way to monitor the battery level in PIC using this method (or another method)?


texts:
I am trying to build an EEG circuit based on the description here: https://www.instructables.com/id/DIY-EEG-and-ECG-Circuit/. I would like to simulate the behavior of certain sections of the circuit to help me to understand the circuit and to facilitate testing.

I am stuck on the 60 Hz notch filter. I have pasted my LTspice schematic below. By the way, I am using "UniversalOpamp2".

While I expected that probing Vout in the AC analysis would show attenuation of frequencies centered on 60Hz, I am seeing only high-pass behavior at Vout.

On the other hand, I am seeing notch filter behavior when I probe between R2 and C5.

What am I doing incorrectly?

Thanks!


texts: Rheostat power rating vs. current rating

texts:
I have a 1k ohm rheostat that has a 25W power rating, and a current rating of 0.15 amps.

I got it because I was running a 12v/24v circuit at 1amp draw. I just looked at the power rating of 25W and thought it would be OK in my circuit. However, that's a low current rating (which I did not notice till just now). I have not used the rheostat yet, but I am guessing it will not handle the 1amp current even though it would be within the power rating.

Please confirm. Thank you.


texts: Phase noise improvement after gain compression

texts:
The very curious question/observation is about the improvement in phase noise for input power levels greater than P1dB.
I am designing a cascode 3 stage distributed amplifier in 65nm CMOS technology. My input referred P1dB is -4.5 with -152dBc/Hz phase noise and I am getting -170dBc/Hz phase noise at P1dB=28. I am not sure what is going wrong at large power levels. After P1dB=28, the phase noise degrades again.
I think the phase noise should degrade as the amplifier becomes non-linear i.e. in my case P1dB is -4.5. So I expect degradation in noise beyond P1dB but it seems getting better.
I'm not able to find any particular reference for this case to understand the reason behind it.


texts: Analysing interleaved DC-DC boost converter

texts:
I don’t know why the current does not pass through NP2 (I think the current through Lm2 would have magnetised the primary winding Np2 already) and if someone could help on analysing this circuit it would be of great.Thank you
Source: https://jit.yuntech.edu.tw/2021/JIT-V03N01-06.pdf


texts: I've watched every video on youtube to create an electro magnet for my school project. I think I'm doing everything normal but it's still not working.


texts: What is the practical benefit from very sharp probe tip and fast continuity test of DMM?

texts:
What is the practical benefit from very sharp probe tip and fast continuity test of multimeter?
I was searching for a while with google and in ee.se but results contain mainly a dmm seling ads with featuring sharp tip probes or similar. Maybe can't find correct search keywords, but can't find this question answered here too.
In EEVblog, Dave Jones mention quite few times importance of fast continuity test, but only once give the example with faster and more convenient way to test multiple pins on a IC. Fair and square, but only applying in electronics. That disperse the fog a little but I remember a friend of my father talking something similar and I am quite sure he was in electrician. On top of that IC weren't that prolific at that time at all.
Sharpness of the tip, I can rationalize that albeit having smaller area of contact, probably give you better mechanical contact in practice, specially if probe make miniature dents in softer metals. Easier to penetrate very tin layers of oxidation or other impurities. Electrical current like to flow from sharp pointy surfaces better and flat, but not sure how that translate into practice with much more less that kV range (U<30V) and no arcs.
Is there more than just psychological point of view mine is better because is (bigger, faster, sharper, stronger etc.)? How blunt is blunt and how sharp is sharp actually? If there is practical difference is it noticeable? Is it possible to be quantified?


texts:
What does the phase discriminator portion of the Costas Receiver do mathematically?

The output of the I-channel is \$ \frac{1}{2}A_C \cos \phi m(t) \$. Which means for small deviation of phase \$ \phi \$ , \$ \frac{1}{2}A_C \cos \phi m(t) \approx \frac{1}{2}A_C m(t) \$. Or it can be said that \$  \frac{1}{2}A_C m(t) \$ would be attenuated by a small amount. However, we have to keep in mind as the text says (as it not might be as innocuous as it seems):

The output of the Q-channel is \$ \frac{1}{2}A_C \sin \phi m(t) \$. Which means for small deviation of phase \$ \phi \$ , \$ \frac{1}{2}A_C \sin \phi m(t) \approx \frac{1}{2}A_C \phi  m(t)\$.
As per the text, the phase discriminator consists of a multiplier followed by a low pass filter.
Which means multiplication of \$ \frac{1}{2}A_C \cos \phi m(t) \$ and
\$ \frac{1}{2}A_C \phi  m(t) \$ would yield:

\$ g(t)=\frac{1}{2}A_C \cos \phi m(t) * \frac{1}{2}A_C \phi  m(t) \$

\$ g(t)= \frac{1}{4}A^2_C \phi \cos \phi  m^2(t)\$

Now, let's say \$ m(t) \$ is band limited to \$ M \$. then the term \$ m^2(t) \$ in the frequency domain would spread across  \$ -2M \$ to \$ +2M \$ centered around \$ f=0 \$ and the term \$ \frac{1}{4}A^2_C \phi \cos \phi \$ is a constant.
Now, if \$ g(t) \$ is subjected to a LPF, then the term \$ \frac{1}{4}A^2_C \phi \cos \phi  m^2(t) \$ would be retained as it is(if the cutoff frequency of the LPF is slightly > \$ 2M \$).
So, what does phase discriminator in Costas receiver do mathematically?

Also, if the phase error is significant(that is we have no idea at all about the probable phase of the carrier), then how does the analysis change? Because this is a possibility that we might have no idea about the phase of the carrier.

Text Used: Communication Systems By Simon Haykin


texts: Negative 5 volt logic: is this a real thing?

texts: I was onsite with a technician working on an outdated industrial control panel.  He stated offhand that the panel used "negative 5 volt logic".  I had not heard of this previously.  Is this a "standard" similar to 5V TTL? or is this more likely a proprietary design?  If it's a standard, is -5V a digital 1 or zero? and what are some common gate chips analogous to the 74xx series?


texts: Stop mask error upon running DRC in Eagle 7.3.0

texts:
I'm working on my first board layout using Eagle (7.3.0). I've got the layout done, but when I run DRC, I get a number of Stop Mask errors:

These seem to be due to small rectangles on the tStop layer (layer 29). If I hide the tStop layer, the errors go away, but I don't understand them in the first place. It appears as if there are two rectangles for each capacitor pad on the tStop layer, and the smaller of the two (highlighted in the screenshot) is provoking the error.

I'm using capacitors that use the C0402 package from Eagle's builtin resistor.lbr library. I don't see those additional small rectangles when I open the C0402 package directly in the library editor. They're on a few other pads (e.g. the pad at the top of the screenshot), but only for devices from Eagle's built in library. Footprints that I created myself don't show them, nor do they cause DRC errors.

Has anyone run into this before? Is there a solution? Are they something to worry about?

For what it's worth, I'm using SeeedStudio's DRC file as I intend to possibly have them make these boards for me.


texts:
I am trying to convert a number I get from a keyboard to the IEEE-753 standard using VHDL or a logic implementation, I don't want the complete answer only a guide about how I should encourage this.

I read a keyboard and store in memory every digit from the entire and decimal part and the user also has the option to enter the exponent which is also saved in another memory position.

I read in this website about how to convert a decimal number to the IEEE standard. Suppose now that I have a number represented in scientific notation, for example:

  22.523 x 10^20

I read this number in BCD from my memory so I need to convert it to binary to then process it, my idea is:

Convert entire part to binary.
Take binary entire part and multiply by 10 times indicated by the exponent in this case, 22 x 10^20.
Convert decimal part to binary.
Take binary decimal part and multiply by 10 times indicated by the [exponent]-[number of decimal digits] in this case, 523 x 10^17.
Add the two binary numbers.

So now I have my number in binary and I can apply the method indicated in the website.

To represent this number I will need two registers, one for every part of the number the first one will need: log2(22 x 10^20) bits which is 71 bits  and the second part will need log2(523 x 10^17) bits which is 66 bits so I will need 71+66 = 137 bits to store the result and then convert it to IEEE-753.

Is this normal? Is any other way to do it? Or is it accomplished on this way?


texts: Is it true that frequency deviation over 2*pi is the phase deviation of an FM/PM signal?

texts:
for ∆f frequency deviation if for FM only and PM has Phase deviation. and
Kf= ∆f (Hz) of FM? Kf = ∆f (rad/s) for PM?
and for th rules:

∆f=(kfmp)/(2p) for FM where mp = mp max-mp min
∆f=(kfmp)/(2p) for PM where mp' =mp'max-mp'min

does this rule apply for frequency deviation of the carrier and the former of Kf and Kp is for the frequency deviation of the message signal?

and do if it is correct that PM has frequency deviation, does FM has phase deviation?

I am so confused and some one clarify me this concept.


texts: Resonant frequency of a three phase thyristor rectifier

texts:
I am trying to inspect how my circuit behaves at operating points around resonant frequency. Is resonant frequency simple equal to 1/(2Pisqrt(LC)) = 1/(2pisqrt(590uH240uF)) = 423 Hz (see the circuit diagram)? Or I have to consider all generator inductances ?
Thanks in advance


texts: How do I design a device to automatically switch to the backup battery?

texts:
I've been told that many kinds of batteries work best if they are used until they are completely drained, and then recharged.

(Edit: The "memory effect myth" is quite widespread. Batteries work just as well if they are "topped up" every time.)

Right now I design devices the standard way: try to use the battery power as long as possible, and then when there is no power left it doesn't work at all.

If there was some simple way of implementing the following, I might use it from now on:

Two independent batteries (or more)
Once you start using one battery, continue to use it until it is completely drained reaches the manufacturer-recommended minimum voltage.
When the "in use" battery is completely dead, switch to using the next battery. Presumably you use some technique similar to the "Switch between 5V power supplies?" question.
Once you switch to the last battery, go into some sort of low-power mode so it can still do the important things in "limp mode", but the user is notified to plug it into a charger as soon as possible.
After plugging into the charger, go back to standard mode -- but if disconnected from the charger before the batteries are fully charged, go back to limp mode.
(optional) When plugged into the charger, only charge the drained battery (or batteries) and keep them topped off; leave the one "in use" battery alone.
(optional) keep track of precisely how much total energy could be extracted from each particular battery the most recent time it was fully drained. Use that number (perhaps modified using Peukert's law) to give extremely accurate estimates of future run-time.

Why don't all devices do this?

cell phones: first battery: talk like crazy. last battery: only emergency calls.
laptops: last battery: throttle back to a slow speed that is adequate for looking up static documents
handheld GPS: last battery: try to reduce energy by updating the screen less often, dimming the backlight, etc.


texts: Series resistor or flat clamping for Analog input protection

texts:
I have an ADC whose analog input i would like to protect. I have found two papers from Texas Instruments which details on how to do so.

Series Resistor Protection

This is basically adding a series resistor to the ADC input and the input node,

Applying the methods above if my Analog pin limit is 3v and would like to protect until 30v

R = (30 - 3)/ 0.001
R = 27k Ohms

And just by adding a series resistor to the analog pin of the adc it is protected upto 30v. Very simple and very easy to implement.

Thats on paper though, I would like to know if this method is really effective in application. For the experienced please do tell me your experience if this alone can protect you adcs

Flat Clamp Diode Protection

This involves placing a surge protection diode on the ADC input lines shunt the extra current away from the adc.

Using something like TVS0500 as a added layer giving a larger over voltage protection. This how ever is not as easy to implement because its not only that you need 6 (do you even need that many?) of them per differential channel, but a slightly meticulous part selection.

Is it worth the extra way to implement this on actual implementation?


texts: How can I make a motorcycle CDI (capacitor discharge ignition) using a power MOSFET?

texts:
Is there any way to make a CDI using only power mosfets.

I've searched everywhere on the internet but couldn`t find any circuit.


texts: A circuit question using multiple MOSFETs with PWM control

texts:
I need to PWM control two electromagnet groups where each group has four electromagnets. Emagnets have nominal 24V 0.33A current ratings. Here is the only datasheet I could find. To supply all the magnets I want to use this 24V 4A single power supply. To model these, I drew the schematics in my mind and simulated it as follows:

(left-click to view/enlarge)

To model emagnets each drawing 0.33A current, I used 72Ohm and 1u inductor. I also added 1N4148 as a flywheel diode to each magnet.

The idea is two PWM outputs of a micro-controller like Arduino's will control(by two potentiometers as analog inputs of the uC) each two groups's PWM input hence the magnet current. Since the uC does not have 8 separate PWM outputs, each PWM is triggering four gates of the MOSFETs as shown in the diagram above.

In simulation I obtain the following power plot for this MOSFET I plan to use:

I have the following questions as concerns before I start soldering:

1-) Is it fine as in my diagram to connect all the gates at a point and trigger four MOSFETs from a single input?

2-) Are the gate resistors values for R_g1, Rx_1, R_g2, Rx_2 correct/sufficient?

3-) It seems I wouldn't need heat sink by looking at average power dissipation. But I wonder if I should change the PWM frequancy. Currently it is 490Hz. Would it make sense to increase it to 30KHz for instance to prevent ringing sound or another issue?

edit:

Using a non-inverting driver TL427:

edit2:

I reduced MOSFETs(one for each group) and diodes(I used 1N4007)

Here is the power plot for one transistor in between 1.15ms and 1.2ms:


texts:
Hello, I'm new to this topic as it is my school works, I try to simulate the diagram below by using Proteus which I follow accordingly with the labsheet given from my school.
The problem is the parameters for the Carrier Wave & Audio Signal is unknown while VCC=15V. There's no output when I run the simulation. Can someone suggest me to solve this problem?
The parameters for R & C were already given in the labsheet which I just follow it and should not be changed.
Updates : I try to run the same circuit by using Multisim and it does generates waveform. But now the question is, what parameters should I change to get the best AM modulation ?


texts: Electrical specifications for a microphone as good as human ear?

texts: I need to buy a microphone to dectect sounds with at least the sensitivity of the human ear. It is for a Raspberry Pi that detects neighbours voices (late at night and loud conversations throughout the day) from 10 to 20m away. A speaker would play white noise to drown out their voices. I had a look at mic sensitivity (https://www.dpamicrophones.com/mic-university/how-to-read-microphone-specifications) but couldnt find how to choose a mic that is approx. as good as the human ear.


texts: subharmonic instability in average current mode control

texts:
The Control Loop Cookbook from TI explained about sub-harmonic oscillation as below.

I am really confused by the part "cross over each other at their points of intersection".

This is probably due to my English language. If two waveforms cross over then they should cross at their intersection points, don't they?


texts: Finding frequency of a three-phase generator from phase voltages

texts:
I'm trying to find frequency (i.e.; rotations per second) of a balanced three phase generator. Output peak voltage of the generator goes up to 150V.

One solution I found is to attenuate rectified and filtered versions of this AC by voltage divider resistor network (Ra, Rb, Rc and Rd), so that the rectified one swings over the filtered one, and then input them to a comparator to find the frequency data.

I would like to know if there is a better way of doing this.

Note: There is already a bridge rectifier in my circuit for other purposes, and the GND is taken from it as it is seen in the image below. I can't afford changing GND position at this design level.


texts: Will this inverted switching circuit to drive 4 Ohm heater work?

texts:
I want to switch a heater, and learn to build some electronics while doing so). The heater is a heated print bed, from the Ultimaker original heated print bed kit (no longer sold I think). The problem is that the PSU that comes with the printer is underrated to provide the current. I've got a spare PSU that I wish to add to power the bed.

The original signal to drive the heater is 24vdc high when the heater is off, and 0Vdc when the heater is on. I hope to be able to drive it using the circuit below. The heaters resistance is 4 ohm, displayed as R5. Q1 (datasheet) is ment to invert the signal, so Q2 (datasheet) should be on when the original signal is low (coming from the 24Vdc + pin in the circuit). Q1 and Q2 are both N-channel MOSFETs.

I'm far from experienced with electronics. I hope that someone will shed some light on whether this will work, and if not, what I should correct. And of course, why it should be corrected, because the learning is an important aspect of doing this for me.

And of course, if there is something wrong with the drawing. Like unusual choice of components or symbols, I like to hear that to.

Will this circuit work to drive the heater?

EDIT

As Chris Stratton pointed out, there are test points on the circuit that is driving the heater, as shown here (or in the image below).

TP15 shows 8.2volts, steady line (measured with oscilloscope), when the heater is powered, and 0 when it is not. The 075N15N MOSFET shows the following figure, which seems an acceptable RdsOn with 8.2v on the gate. I do not understand why it is 8.2v and not the seemingly more optimal 10v as it is seems to me to be simply a matter of picking different resistors for the voltage divider R29/R30. I did not dare to put the probe on pin 4 of Q2. But I assume the voltage is probably the same there. Anyway, I can use the signal coming from TP15 to switch a low side N-channel MOSFET to drive the heater using an external PSU that shares GND.


texts: How does a transistor behave when the gate is disconnected?

texts:
On an n-type transistor, if a voltage above a certain threshold is applied to the gate, current can flow from source to drain.

On a p-type transistor, if a voltage below a certain threshold is applied to the gate, current can flow from source to drain.

But what about when the gate is disconnected?  Every point on earth has some voltage -- 0V in a circuit diagram is merely a convenient reference rather than a point with zero voltage.

Thus, my disconnected gate much have some voltage -- it's just not readily known.

So is the answer that my disconnected gate might activate an n-type transistor, or it may activate a p-type transistor, but the answer is unknown and the behavior of the circuit is undefined?


texts:
The question is purely academic, as normal sound dampening solutions seem to work fine.

I understand how electronic circuits make sound as per this answer:

How can "purely" electrical circuits emit sound?

My question is, a cheap 2 AA battery (3 volt) inverter makes as much sound as the cathode ray moving on an old tube television.

What part in it is "moving" that creates that much noise?
How much amplitude is created? and how? The sound can be heard from across quiet room.
Normally high frequency sounds are very easy to locate the direction. However, in this instance, why does the sound appear directionless, like a low frequency sound?
Is it possible to invert DC to AC without audible noise? Or is this a mechanical feature?


texts: how to handle GND reference in Arduino connected to separate electronics?

texts:
I am building a system that consists of an Arduino-type device, connected to a host computer via USB, which interfaces with some additional electronics which are driven off an isolated switching DC power supply (https://www.mouser.com/ds/2/260/lrs-100-spec-752931.pdf).  I believe the GND node of the Arduino is connected to the GND pin of the USB.  Can I assume that the GND pin of the USB is at the same potential as the EGC of the AC mains ?   Thus if I connect the negative terminal of the power supply to EGC, then it'd be at the same potential as the Arduino's GND, and I can tie the Arduino's GND to the additional electronics' GND ?

If not, how can I best interface the Arduino to the separate electronics ?


texts: How to get the desired signal from a photodiode and phototransistor multisim?

texts:
The above is a visualization of an IR transmitter and receiver circuit I'm building. Sending a 2v and 1khz sine wave through a photodiode to a phototransistor.

The figure above shows the outputs I get from running the simulation. I send in a sine wave(blue) and a squarewave(yellow) is what I get at the phototransistor output. At the amplifier's output, I get also a squarewave(green) on the negative side of the vertical axis.
My question is how do I get a better approximate signal of the input signal from the photodiode and the phototransistor?


texts:
I have just started programming on ARM, I had some experience on AVR but not that much. The question is probably too trivial but the material about ARM is too little on the net... sorry anyways.

I know for implementing delays in ARM we can use timers or busy-loops. I tried those methods out. But one of my friends suggests there is a "delay.h" headerfile for arm that contains all the necessary delay functions just like avr, delay_ms and ... .

First of all, as stupid as this question may sound, is there really a built-in delay function in ARM programming. Is it in delay.h?

If so, why is the use of timers for implementing delays so popular? Why don't they just use the built-in function?

I'm studying LPC17xx series.


texts: How does a multimeter sense whether it is measuring single or 3 phase voltages?

texts: How does a multimeter sense whether the voltage we are measuring is single phase or three phase? It might be simple but I have no idea so please help me.


texts: Converting small AC output voltage of a piezo element to DC without IC

texts:
I've been trying to find a AC to DC converting circuit that will take a piezoelectric crystal as its input.  I have the piezo to a bridge rectifier but all the diagrams I am finding have some kind of an IC to help smooth out and regulate the voltage(3-5v output is what i'm looking for).

I'm trying specifically without an IC as I am using circuit simulating software that does not have the IC models i'm finding referenced.

ideally i can build this circuit in software before I buy parts.

Thanks!


texts: SPDT mechanical relay: do NO and NC pins short between each other as pole switches

texts:
I have a mechanical SPDT relay (Digi-Key PN 281-6348-ND, I am only using one of the two channels).  I also have a sensitive circuit downstream of the relay.

(Image source)
While a mechanical relay is switching, is there a chance that the NC and NO pins can make contact of any kind?  Or is this something one should never have to worry about?

Bonus: is there a "relay speak" term associated with potential shorting?


texts: How do I resolve the following error "Verify failed. [ Pgm ] at 0x0, expected 0x00002805, got 0x00002807" in MPLAB X IDE

texts:
I recently decided to get into learning how to develop embedded systems, using MPLAB X IDE and literature available on microcontrollers. The vast majority of which referenced the PIC16F84 and as such I decided to invest in the hardware to build and test out the programs, once I had gotten familiar with coding using the PIC16F84.
Unfortunately, the specific ICSP programmer used for this MCU is no longer available & a lot of the online commentary were suggesting that PICKit 4 was essentially the same, but much better & faster. Therefore, I bought the PICKit 4 assuming that it would be backwards compatible with the PIC16F84.
To cut a long story short, it is not backwards compatible without making a slight modification to the circuit, which I found after doing some research on the internet. It simply involves putting a 100ohm resisor in series between the PICKit progamming pin and the progarmming pin on the PIC16F84.
However, although the PICKit 4 is able to communicate with the PIC16F84, I keep on getting this error "Verify failed.  [ Pgm ] at 0x0, expected 0x00002805, got 0x00002807".

Despite my best efforts, I am unable to find a resolution to this problem, as of yet. However, any insight that anyone can provide will be very much appreciated.
Before, I forget I am using MPLAB X v5.05! :)
Another thing. I have also tried to slow down the program, using the device properties menu!


texts: Time Auto-correlation function for a polar reutrn-to-zero waveform

texts:
I used matlab to calculate the time Auto-correlation function for a polar return-to-zero waveform
to make sure that it has an ergodic property . I implemented the following formula as a function in matlab

I then got the following output Rxx(m) plotted versus the time shift (m or lags).
I expected the output to be A^2 at n=0 according to analysis of polar RZ data shown here in page #10:
https://homepages.wmich.edu/~bazuinb/ECE3800CMcG/Notes7_2.pdf

but in matlab it showed me the following output (with Rxx(m) = A^2/2 = 8 ).
Notice that the vector has 100 bits ,each bit is sampled 8 times(Tb=8ms) , that is 1x800 vector . I plotted it vs lags in ms but it may not be clear in the graph below .

so Can anyone explain this ?


texts:
Is there a safe way to dispose of lead solder waste?

Like used sponges, PCBs, tips, etc.

Should I place it in a bag, label it and throw it to a battery disposal boxes I see here and there?


texts: Where do input bias currents flow and what voltage drops do they create?

texts:
I have asked this question (and answered it below) mainly as a continuation of the question, How does the compensation resistor in an inverting amplifier compensate for the input bias current?... but I have seen that this topic is the subject of many other similar issues in SE EE (I found 26 and stopped looking for more):
Input bias current existing even when no input is given
In an AC coupled Op-Amp circuit where do input bias currents flow from?
Input bias current compensation
Negative feedback output question
Resistance between non-inverting input of op-amp and voltage source
Operational amplifier parameters: Input bias current, Input offset current, input offset voltage
Do I need to make a DC path at the input of an op amp?
Does an op amp needs an Input Bias Current to operate?
Input Bias Current in an OP-AMP and its value in a datasheet
Input Biased Compensated Op Amps
How does the compensating resistor act in op amp?
What is the purpose of a resistor in the feedback path of a unity gain buffer?
What's input bias current in opamps?
Where does an op amp's input bias current come from if capacitor is used?
Op-amp's input bias current
Opamp input bias current and current sources
Why 2 input bias currents are equal for OpAmp?
The direction of the bias current of LM311
Understanding balancing resistor in bipolar op amp
Calculating the input current that can be taken by an Operational amplifier
Input Biased Compensated Op Amps
effect non- inverting resistor in the integrator op amp
Reason behind choosing the compensating resistor for input bias current in op amps
How to select resistance to cancel offset output voltage due to bias current?
Basic understanding of op amp circuit
Why is non-inverting op-amp input resistance on a tee to ground?
Digging through them, I wondered, "What is it that makes it difficult for beginners and makes them ask all these questions?" It is a great challenge to find and explain it...
It is my belief that these questions can only be fully answered by drawing power supplies and input bias current paths... but it will be interesting for me to see how you would explain it...


texts:
I am able to see following specs on my laptop adaptor.

65 W
Input AC: 100 - 240 V, ~1.5 A, 50 - 60 Hz
Output DC: 19.5 V,  3.34 A
My HP laptop:

I am bit unclear about, the conversion of AC to DC. While this conversion takes place, Voltage gets reduced, by a significant no. of times, while current increases marginally. Why is it so ?

I am Software Engineer and knows very little about electrical engineering. Sorry for such a silly question.

Thanks in advance.


texts: Charging circuit for Lithium Iron Phosphate batteries

texts:
This question is regarding charging circuit for Lithium Iron Phosphate batteries.

I have a pack of Lithium Iron Phosphate batteries rated 3.2 V / 7.5Ah which will drive a circuit. According to the data sheet provided by the vendors, they have told me to just keep voltage under 3.6 V and maximum current of 1000 milli Amperes while charging and I should be fine.

My charging source is a solar panel of rated 5.5 V and 500 mA. Since they have a protection circuit which will take care of Constant Current & Constant Voltage , short-circuit and over charge/ undercharge, can I just use a 3.6V Zener Diode and a forward biased pn junction Diode in the circuit to ensure the voltage does not shoot above 3.6V and if the panel's voltage is below 3.6V, the diode is going to protect it.

Is this approach okay? Or is it complex than this? Thanks.


texts: Expected values for \$V_{BE}\$ in darlingtons

texts:
In this answer @stevenvh points out that \$V_{BE}\$ for a TIP110 darlington may be as high as 2.8V. This looks extremely high to me, even for a double junction.
In normal use you don't need to drive a darlington with more than a few mA, and I expect \$V_{BE}\$ for the first transistor to be less than 800mV. Then the voltage drop for the second transistor would be 2V! Even when the 2.8V is equally shared that's 1.4V per junction. A 1N4001 needs 20A to get this high voltage drop! I doubt that a transistor will survive 20A of base current.
How can this high \$V_{BE}\$ be explained?


texts: How does increasing the capacitance affect the output voltage for a buck converter and boost converter?

texts:
From the formula of charge relating capacitance and voltage,
$$ Q = CV $$
Capacitance is inversely proportional to voltage.
This is how I got the idea that possibly when increasing the capacitance, the output voltage would decrease for both buck and boost converters.
But I think that idea is invalid because I'm just grasping at straws for the formula because it has a voltage. I have a feeling that the behavior of increasing capacitance might result differently for buck converters and boost converter.
I would like to ask what the answer to this is with an explanation of how it works. I just can't understand what would happen in the given situation of the question.
Thank you.


texts:
I am currently designing a device that is intended to be used outside the car and supplied by car 12V socket (also during the drive).

The question is: Are there any specific requirements for example international standards related to this kind of devices?
Is there any EMC certification required before allowing the device to be sold?

Usually in case of devices designed for automotive market, OEMs define this kind of requirements, it's a little bit different story since the device could be used in any car/truck and is not an actual car part.

I am aware that the device should be both protected against potential supply line disturbances [cold cranking, over-voltage etc.] and also not generate any disturbances/conducted emission backwards. But how to define actual limits?

I believe most of modern cars 12V sockets are filtered and protected against potential short circuit / conducted emission, but this cannot be guaranteed right?


texts: What's the easy way to measure a DC hobby motor's inductance?

texts:
When using simulations(SPICE), I need to model a DC motor or an electromagnet, relay ect. as an RL in series.

I can measure the R resistance by an ohmmeter. But I couldn't find an easy way to find out L value. Should I use a sinusoidal AC signal and measure the impedance from the phasor equations for that? But then I would need other equipment.

Any ideas?


texts: Is it possible to refurbish a depleted battery?

texts:
It's common knowledge that batteries deteriorate and lose storage capacity over time. Once this happens, it seems like the only solution is to discard or recycle them, which means stripping them down to retrieve the raw materials.
Are there any battery technologies for which the degradation can be reversed? Say, by disassembling the battery and subjecting the plates to some electrical or chemical treatment? Or are all batteries bound to degrade in a way such that reversing the degradation is not possible, or extremely complex?


texts: How to make a digital comparator with multiple inputs?

texts:
I have been attempting to make a digital comparator but I am struggling to get in more than one input. The idea is that I have 2 sets of 2 numbers (4 inputs total) and I want to have the output take all 4 numbers into account rather than just 2. Here is what I roughly have so far:

What I want the circuit to do is have the two inputs in the two sets treated as separately. Any ideas on how to achieve this would be very welcome.


texts: What is the name of this connector / board?

texts: I'm trying to make a custom HID, and would like to include a joystick, it has this carbon 6 wire ribbon cable, but I can't for the life of me find this kind of breakout board or even the connector name if I wanted to make a custom PCB, could anyone help me out?


texts:
i'm new in electronic, I made a simple circuit to control a pump it's working, but i'm really not happy of the result.

I have to plug 2 power sources because if I have only one for the pump and the board, it fail (I think it's because the pump get too mutch power to start so the sensor dont like it).
The circuit is too big (due to the relay size and because of the 1st point).

I think i should use a transistor for replacing the relay ? but i really don't know what kind of transistor I should use...
And may be a capacitor to handle the problem of the pump draining too much power when it start ?
I'm really new and I didn't really understood the usage of capacitors for now ...

This is what my circuit looks like for now, The little thing in the middle with QRD1114 wirten on it it's actually not a "QRD1114", it's a soil moisture sensor like this one, it's just here to illustrate.

Thanks a lot for your help.


texts: How would you search for this type of screen?

texts:
I have this cooking thermometer with a very small screen. For my DIY projects I'd like to buy some of these screens in bulk (say 10 or 20) and use them with arduino but I can't find a proper name to search them with. It seems to be something between a 7-segments display and an LCD screen, probably designed specifically for this application. How would you go about searching something similar on the marketplace?

EDIT: I'm adding that I'm specifically interested in these very small screens. The one in the picture is 10mm X 25mm


texts: How do I solve the input resistance of this BJT and MOSFET in series?

texts: This is a sedra-smith microelectronics excercise question for which I can not find the answer and I hoped for perhaps a solution here?


texts: Extracting a sub array from an array of switches with Verilog?

texts:
I am working with a Cyclone board. A basic code to assign every switch to the red leds is:

module part2 (SW, LEDR, LEDG);

    input [17:0] SW;
    output [17:0] LEDR;

    assign LEDR = SW;

endmodule

But I need the value of SW[17] to do some output operations, I don't understand how to store it in an subarray... (I also need the inputs of SW[7:0] and SW[15:8] ). How can I achieve this?

I just started with Verilog today and I am confused.


texts:
[![Why doesn't this work?
I can adjust pot and relay will energize. 4-20mA will not energize relay. ]2


texts:
This "742 PG" seems found to be nowhere in any place.  What is the best SMD diode that can replace it?
It is from Lenze PCB for the 8211E variable frequency drive.
Please show me the way to replace it with an equivalent one.


texts: Why dimension of antenna's elements can be 1/2 and 1/4 or wave length and what about 1/3 or 1/8?

texts:
I'm an amateur and looked to the calculators of TV/3G/WiFi antennas.
All articles state I can get away with all sizes divided by 2 or 4 (for biquad antenna & the range 400MHz - 2.1GHz dividing by 4 makes antennas compact enough to keep it indoor without ruining room aesthetic).
Why are fractions 1/2 or 1/4 of a wave length allowed and 1/3 or 1/8 are not suitable?
Following answers have related but not exact discussions:

Why does 1/4 wavelength have a ground plane and 1/2 wavelength needs none?


texts:
I am coming from Eagle background where there is a common library file that you use across all projects. Taking an example of a capacitor - I design one generic capacitor symbol, add multiple packages (0402, 0603, 0805 etc) to it and make it a device. One project might need 10 values of capacitors. I insert the same capacitor device and just select the correct package and enter the value.

I signed up for an online Altium course recently and I observed that the library is being created inside the project. For every value of capacitor, a new symbol and a new package is being created. This looks like a lot of work but I see a value in the sense that each component has a part number and complete manufacturer and pricing info.  Is there any other advantage to it?

Besides, if I have created 20 parts during a project, I might need the same in other future projects. For ex - almost every project needs capacitors. How do I manage my library from the very beginning so that I can conveniently re-use the components?

Edit: I did some more research and found out that it's not necessary to make libraries inside projects. I can add components from a central source. However I see a value in including the libraries inside the project because this allows me to send the PCB files to a different team without worrying about missing component library.

As such, I want to know how to deal with this? Do I need to make a central library, then duplicate it into every project I make?


texts:
How can I solve this circuit for \$\beta = 100 \$ , \$V_D = 0.7V \$ and \$V_{BE}= 0.7V\$ and arrows go to power \$V_{DD}=9V\$

simulate this circuit – Schematic created using CircuitLab

general procedure with explanation is appreciating.


texts:
I am totally lost in a question, how can be derived the friction losses of a induction machine  based on this equation (It wasn’t given explication about these nor the bibliography/source of this equation and I don’t find it in the Chapman,Stevenson,Sen, Beaty among others)

\$T_{e}=J(\frac{2}{P})\frac{d\omega_r}{dt}+T_{L}\$
Im guessing that

\$T_{e}\$ is the motor torque

\$J\$ is work in Joules

\$\frac{2}{P}\$ 2 divided by the nominal power

\$\frac{d\omega_r}{dt}\$ the instant angular speed

\$T_{L}\$ The torque of the load
But I dont have a  idea how to justify the friction losses of a induction machine based on these equation


texts: I'm pretty certain that RF jammers work by overpowering the target signal with their own higher powered signal at the same frequency.  So the question is, how does anti-jammer technology negate the effects of a jammer?


texts: i wonder about scott connection's phase shift like a 90 degrees

texts:
first of all it is necessary to refer this link.
https://circuitglobe.com/scott-t-transformer-connection.html
In this link u can know scott connection and i wonder about V2t and V2m's phase difference.

something like wye-delta and delta-wye connection.

we can originally know wye-delta connection is step-down transformer and second side voltage phase is being to -30 degree. And also delta-wye connection is step-up transformer and second side voltage phase is being to +30 degree.

But the other side, we also can make wye-delta connection is step-up transformer if it get turn ratio like 1:2. So in this case maybe will be become +30 degree in second side voltage.

apply this principle in scott connection, how can work it?

case1) turn ration 1:2 - step up second side voltage's angle +90 degree?

case2) turn ration 2:1 - step down second side voltage's angle -90 degree?

if you have any information or homepage link, can you leave it for me?

As a result in this question's key point is this one.
https://circuitglobe.com/scott-t-transformer-connection.html
In this web site, u can see scott connection and then i wonder about this phase shift. V2t and V2m have a phase difference of 90 degrees. And V2t is leading of V2m. But if we give another turn ratio like a step up or step down, is it possible to replace the position like V2t is lagging of V2m?


texts:
In system-verilog I am trying to build a small ALU unit which takes a and calculates the negative value of it (-1) in a CPU.
I wrote:
 // Secondary ALU
 logic [31:0] negation_result;
 always_comb
    negation_result = 1'b0 - alu_a;

But the result saved in memory in hex is 00000000
I changed negation_result = 1'b0 - alu_a; to negation_result = 32'b1; and now in memory I can see 00000001
Any idea of what is causing this problem?
For example I have this ALU which works perfect:
logic [31:0] alu_result;
 always_comb
     case (alusel)
         ALU_ADD: alu_result = alu_a + alu_b;
         ALU_SUB: alu_result = alu_a - alu_b;
         ALU_SLL: alu_result = alu_a << alu_b;
         ALU_SLT: alu_result = (alu_as < alu_bs) ? 1 : 0;
         ALU_SLTU:alu_result = (alu_a < alu_b) ? 1 : 0;
         ALU_XOR: alu_result = alu_a ^ alu_b;
         ALU_SRL: alu_result = alu_a >> alu_b;
         ALU_SRA: alu_result = alu_a >>> alu_b;
         ALU_OR : alu_result = alu_a | alu_b;
         ALU_AND: alu_result = alu_a & alu_b;
         default: alu_result = alu_a + alu_b;
     endcase


texts:
!
How does this circuit work? why do you get different threshold voltages for increasing and decreasing Vin?


texts:
I would like to use a single pin (tri-state buffer, 3.3V logic in case this matters) to drive two P-channel MOSFETs as high-side switches. Only one of them will be 'on' at any time. When the pin is in the high-impedance state (hi-Z), I would like both turned off.

The solution I came up with is to pull-up the hi-Z state (to 0.2*Vcc, see comments) and use two comparators (open collector type) to drive the FETs when the pin is in either the Lo or High state:

simulate this circuit – Schematic created using CircuitLab

I wonder: is there a better, easier or more elegant approach to this? Is this solution suitable for fast switching?


texts:
I have made a pcb .
A part of the circuit is  the  Schmitt trigger   comparator seen above .
The  positive feedback resistors are chosen to give the noniverting input  values from zero to 0.5 volts .
 The inverting input will receive pulses of around 300mV amplitude and 20 ns width , but   while the amplifier isn't connected anywhere (yet)   a voltage of 1.1 volt appears on the pin  . Any ideas why that happens ?


texts: Asking about old russian amplifier internal circuit

texts:
I worked with an old russian machine in my lab, which contains an input from a photodiode with amplification circuit.

The amplification is composed into 2 stages , the first with a JFET transistor and the other with an amplifier IC (123ун1б) where the internal circuit in the figure below :

In the datasheet the only interesting Information that the gain is between 100 and 350 , and nothing either.

The amplifier ic with external components are showed in this figure :

where the correction capacitor is 120 pF, the resistor between 4 and 5 is 3.9K
and the load resistor is 5.1K

My goal is to know how we can choose the gain of this circuit which given approximetly 100??
what are the value that should be changed?
What are your opinion and what's the way to know the solution ?


texts: Voltage spike in pump/fan combination killing fan

texts:
I built a simple swamp cooler that consists of a 12v DC pump and a fan connected in parallel to a power source.

When I repeatedly connect and disconnect the power source, eventually the fan dies. I lost multiple fans this way already. I'm not sure if it happens on the connect or disconnect. When the first fan died I thought that water might have killed it, but it happened twice more with a different, waterproof fan. Once there was a burning smell.

I thought that maybe an inductor in the pump produces a voltage spike when the power gets disconnected, burning out the fan in the process, and that the addition of a flyback diode might prevent that.

When I measure the voltage across the pump in isolation while disconnecting the power, I see the voltage spike shown in the screenshot below. I expected a negative spike but I see a positive one, and it seems a flyback diode won't help with that.

What could be the reason for this spike?
Could it be responsible for burning out a 12v fan (or should the fan be able to tolerate this duration and/or level of spike?)
how could I fix it?

Update: One commenter recommended a 10000uF capacitor but the largest I had around was a 470uF one rated at 50V. I tried that, and it fixed the problem, no more voltage spikes.

Out of interest I also checked if the fan produced any spikes that might damage the pump. It did produce some small negative spikes on power down but the magnitude seemed harmless. I quickly checked if a flyback diode would help and it did, but I ended up not adding that to keep it simple.


texts:
I am a beginner with FPGAs and EE in general, so please bear with me!

It is my understanding that many modern FPGAs are SRAM-based, and for good reason: SRAM can handle higher clock speeds and has lower standby current than DRAM. However, it is MUCH larger than DRAM.

So, say you had some kind of logic circuit that was absolutely enormous and you didn't care about speed at all. In this case, could it be plausible to use a DRAM-based FPGA (assuming you find a way to fix DRAM's parasitic reads)? Does such an FPGA even exist?

Additionally, how much smaller would a design on a DRAM-based FPGA be than on an SRAM-based FPGA?


texts:
I need to drive several indicator LEDs at <2mA.  Each LED has a nominal Vf between 3.2V and 3.3V (Vf max up to 4V).

In the past I've had the luxury of (a) current-limiting resistors or (b) constant-current power supplies.

But what do I do when my entire circuit has to run off a single 3.3V SMPS, and the microprocessor outputs are limited to 25mA?
Here solution A isn't applicable, and the budget doesn't allow solution B (unless maybe all the LEDs can share a single current-limited supply--they don't all have to be on at the same time--and yet I still get to control the LEDs from a microprocessor directly, without external transistors.)

Background:

I have a microprocessor with a few PWM outputs, but not enough
for every LEDs.  (yes, multiplexing is possible)
This is an ultra-low-power, portable application.
BOM cost has to be low, low, low.


texts:
I'd like to construct a device which can control a servo in one of two modes - passthrough the original signal, or override with own values.

Am I correct in thinking that I can just smooth out the original signal with the right resistor and capacitor and treat it as an analog input?

More context:

I've already got a typical RC model receiver connected to the servo itself. I'm planning to insert maestro mini in between, with original signal attached as an analog input.

Now, according to the datasheet, that servo controller reads the analog input at 20kHz, which seems like it wouldn't catch the expected level, but rather a single point from the PWM signal. Is my capacitor idea enough here?


texts:
I have an LED.  The LED is listed as 3 Watt with a Forward Voltage of 3.2-3.4V and a Forward Current of 700mA.

Wouldn't this make it a \$3.4V*0.7A=2.38W\$ LED?  If so is it common practice for a 3W LED to be closer to 2W.
Thanks

EDIT: This was a purchase from ebay.  There is no 'complete' data sheet available.  The one I have is composed mostly of product dimensions, with the only relevant numbers being the ones already provided.

http://www.ebay.com/itm/122469513514?_trksid=p2057872.m2749.l2649&var=422924889580&ssPageName=STRK%3AMEBIDX%3AIT


texts: add LED indicator and fan to power supply

texts:
just a Grade 4 Filipino student asking for help.
I'm kinda new to this and I'm not good at math..

Corrections and add-ons:
1. input is 220V AC
2. transformer is multi output(3v,4.5v,6v,9v,12v)(but I used the 12v output only), and is 750mA
3. 1uF EC is 10v
4. DC fan is 12v and 0.14A

is my circuit safe and functional? which part of the circuit should I put my LED indicator and fan?


texts: How can I read the graph of a low pass filter

texts:
Given information
I have the following circuit, and frequency graph. The capacitor is connected to ground at the bottom. Unfortunately the graph is in dutch, but it won't matter much. Just understand "Passief laagdoorlaatfilter" means passive low pass filter and \$U_{uit}\$ means \$U_{out}\$.

I understand the following

Hz means the amount of periods per second. The frequency spectrum is on the x-axis.
The low pass filter attenuates/mitigates the higher frequency's, so without the filter the signal in the graph would be constant (like the dashes indicate)
\$f_k\$ is the cutoff frequency

My confusion/question
I am having difficulty understanding how to read this graph. What's happening here? My teacher calls the thing on the y-axis the "transfer (function)". I don't understand what transfer means, and when I try to do some research on it, the pages are filled with way too difficult math and terminology etc. for me to handle.
Things that confuse me:

What does transfer or \$V_{out}/V_{in}\$ mean, and why is it on the y-axis? Because I don't understand this, I can't understand the graph either...
Why the y-axis also has to do with decibel. I've done some research on decibel, and apparently it's a ratio between an output and input voltage. It's still very confusing to me... I'm going to do some more research on this as soon as I posted this question.
How can an analog signal be graphed like this? An analog signal has only one frequency unless it changes periods. So if the frequency of \$V_{in}\$ would be 100 Hz, wouldn't there just be a single discrete value when frequency = 100? But instead this graph looks like a continous curve. So what is it showing the frequency of?

This is very challenging for someone who knows very little about physics...


texts: Two port network z parameter determination

texts: I would like to know how it is solved in book as I found that it is way quicker than the way I solved. Any detailed explanation will be appreciated.


texts: Determine whether chassis is a suitable heatsink?

texts:
I picked up a sweet little aluminium box for a small USB powered DAC project...

...and while putting it together I noticed the side panels of the box were very cool to the touch, and made of thick aluminium with a promising looking design:

I've got a couple of potential ICs that might need cooling, depending on where the design/schematic takes me, and I was wondering how it might be determined whether or not the panels would be at all useful as heatsinks? I don't expect them to function nearly as well as an actual heatsink, but for smaller ICs (voltage regulators and the like) it would be handy to know the option is there.

Is there a way to mathematically calculate the thermal resistance of a panel like this, or is the best way to just run some temperature tests?


texts: Can I use a RN2483 to make a LoraWAN gateway?

texts: I have a Microchip RN2483 LoRaWAN module and I would like to use it for making a LoraWAN Gateway. Is it possible? If it is, how can I do it? Or if it is not, why?


texts: I need to take a 0-5V signal and scale it to a 0-1.5V signal. How can I do this? I've seen posts using op-amps, but I'm not sure how to approach this with my voltage ranges.


texts: How to handle moving time window event in an embedded software

texts:
Edit3: As requested I'm going to be more specific about my issue, previous description is still below

A motor must not be activate more than MAX_TIME hours (20hours - consecutive or not) during a sliding time window of WINDOW_TIME hours (72hours).
Every SAMPLE_TIME minutes (1minute), the software check if the motor must be ON or OFF.
My idea was to create timestamp on rising/falling event of the motor state and store them in a buffer. This buffer will be evaluated every SAMPLE_TIME to check if the sum of the timestamp is not greater than MAX_TIME. Because of the sliding window, the buffer must also be updated to remove timestamp that are too old and add new ones.

I have limited memory (around 60bytes). I'm looking for somekind of algorithm that could be use to handle this problem (with an embedded approach if possible, at least for the memory footprint)

According to comments I should:

reduce the SAMPLE_TIME period to reduce the memory footprint of my buffers. If I evaluate the state of the motor every 10 minutes which is the maximum time for my application, I still have (72*60)/10 = 432 data to store if it's the worst case scenario and the motor is toggled ON and OFF every 10 minutes. It can be stored as bits (ON or OFF), so that's 54 bytes. Problem with this solution is that when the software check if the motor is ON, it might be the case, even if the last 9minutes it was OFF, and this will still count as 10minutes of motor activation

Previous description:

  I have an embedded software project where I need to check if a motor
  was not activated too often during a time window. Every minute the
  program acquire data that tells if the motor must or must not be
  activated. During a 72hours time window, the motor should not be
  activated more than 20hours in total (it doesn't need to be 20hours
  consecutive), that's why I need to get a warning when this happens.

  I'm using a microcontroler from Renesas (RL78) and I don't have any
  OS.

  Since I have limited ressources and the time window is huge, I though
  of using somekind of timestamp. When the system activate the motor a
  timestamp is saved, and it's deactivated another timestamp is saved
  and it goes on. Once i reached the first 72 hours i can compute how
  long the motor was activated thanks to the multiple timestamps. The
  timestamps are erased when there are out of the window (since it's
  'moving').

  I guess there is something easier but I don't know where to start.

  Edit1: I need to check if the 20hours period is reached within the
  72hours, and if it's the case, set a flag.

  Edit2: I have a really limited RAM size, around 60bytes available


texts:
For me there is no doubt that one of the most time consuming tasks when it comes to produce a new board is going from a ratsnest to the final layout.
I must admit I am not an expert, but to me it takes days, and I would never ever be able to do it without the aid of Kicad, even for circuits of modest complexity.
It would be very interesting for me to know how it was at the beginning, when EDA (electronic design automation) software didn't exist at all. Which was the technique, which were the tools? I'm convinced one should learn how to do math with paper and pencil before using a calculator, this is why I'm asking.


texts:
I recently found my way onto a Datum x72 rubidium standard and had half a mind to turn it into a homebrew atomic clock, since I'm not exactly using it for a garage-based satellite business.

It seems there are plentiful examples of building atomic clocks using AVRs and PICs online, but most of these appear to feed one of the source-derived inputs (for example, the 1pps signal) into a timer that counts. On the interrupt, there is software action that drives the clock.

I suppose the main question is - is there a better, more direct way to do this? I haven't found any RTC modules that would accept a 10MHz signal (seeing as that would drive power draw up, voiding the concept of an RTC), but is there any sort of clocking device or IC out there that could reference the rubidium signal?

The software clock-timer system tends to feel like a bit of a hack to me, so if someone could break the components of this project down for me a little better it'd be much appreciated.


texts:
In a data acquisition system absolute accuracy is defined as measure of all error sources as following:

Abs. accuracy = error from Gain(Span error) + error from Offset + (error from Noise + Quantization)

Here in the following data sheet at page 30:

http://www.mccdaq.com/pdfs/manuals/PCI-DAS6034-35-36.pdf

for analog inputs the absoulte accuracy for +-10V range is defined as 10.2*LSB where I calculate absoulte accuracy as:

10.2 * (20/2^16 = 0.00030517578125V) = 3.11mV

And at page 31 there are absolute accuracy components at table 2:

Offset err: 531µV

Noise + Quantization err: 180µV

Absolute accuracy at Fs: 3.1mV (This must be the gain error)

When I add up these three it makes 3.81mV instead of 3.11 expected.

What am I doing wrong here?


texts:
In the process of a project I decided to try my hand and the skill of schematic design. I tried my best to follow the "make it clear and readable" advice from this link:

Rules and guidelines for drawing good schematics

I won't turn away advice on the circuit itself, but what I'm really looking for is constructive criticism on the layout/design aspects of the schematic itself. I was just hoping you all could help me to make it better. Here's the design, what would you change to improve it?

Here is an updated attempt, based on the advice here:

v3 with inputs to the left(mostly) and new component layouts:


texts: How to estimate the magnetizing inductance in transformer?

texts:
I did a lab a month ago, one part just said that to set the signal generator to 5Vpp and connect it to primary coil in a transformer, and record the voltage at different frequency. Finally, estimate the magnetizing inductance.
However, is it possible to measure the inductance in primary coil if we don't connect any load (such as an inductor) to the primary circuit? Or, the coil winded part in the transformer can be a kind of inductor?


texts:
The DS1307 has two power sources: the main VCC source and the backup battery. The latter will power the DS1307 when the main power goes down so the clock can keep ticking.

I am facing a problem with the RTC DS1307 when the main power suddenly goes down and then return back the time on the LCD just freezes. Sometimes when that happens (power off) the RTC keeps running (it seems that the DS is stuck when the main power off).

This is the exact circuit I used and the battery gives 3.0V:

The code I used is exactly in blog post: DS1307 Real Time Clock Working.

What could the problem be?


texts: Im using one BTS7960 driver to control a motor. The motor i have is  24V 500watt. If i use a 12V psu will it draw more current?


texts: Circuit for another circuit proximity detection

texts: I just want to ask for some ideas, are there any known low-current circuits to detect direct proximity (max 1-3 cm) of another specially designed device? Must be difficult to "trick" by any other common-world influence, if possible. My goal is to design two PCBs which are only activated by close presence of each other (maybe by some EM/inductive means), both battery-powered.


texts: How much current should a car draw from a battery when it is off?

texts:
My SUV died last night, and it draws 540mA now, when the car is off, and nothing (that I know of) is on. How much does a car typically draw from the battery when it is off?

EDIT 1:
I think you've already answered my question (half an amp is an unreasonable amount of power draw with the car off), but I would like to give you more information anyway.  I narrowed it down to one fuse, which has a bunch of stuff on it:
BCM, Auto Light & Photo Sensor, Room Lamp, Driver/Passenger Vanity Lamp Switch, Date Link Connector, Door warning Switch, RF Receiver, A/C Control Module, Luggage Lamp, IPS Control Module, Instrument Cluster (IND.), Map Lamp, Electro Chromic Mirror
I am going to assume that "Date Link Connector" is really "Data Link Connector".
"IPS Control Module" is also listed under multiple other fuses, and I don't know what that means.  Tried to find out what IPS means, but there is no glossary or abbreviations table, and I'm not sure.
"A/C Control Module" is also listed under multiple other fuses as well.  Not sure what this means either.

EDIT 2:
This fuse is part of a two part special assembly called the "Memory Fuse" which apparently is a collection of devices, some having non-volatile memory that gets lost if it is unpowered.  Also, that's where the half amp of power is being drawn from (the second of the two fuses).
Here are some pictures of the assembly (which has two 10-amp fuses) and relevant sections from the manual:

The following portion of the manual explains that some things will not operate if you pull this fuse assembly, namely "warning chime, audio, clock and interior lamps, etc." I like the "etc" part.
It also states that "Some items must be reset after replacement" indicating the non-volatile memory will be lost. I'm assuming audio (radio presets), but don't yet know what else that may mean (perhaps the A/V, which we don't have).

Here is what the "Memory Fuse" protects, the first fuse for the first section, and the second fuse for the second section (the second fuse is the one drawing the half amp):


texts: Where did I go wrong in formulating my mesh equations?

texts:
I think I've got my mesh equation right for mesh 1,3,4, and 5. But I'm dumbfounded at mesh 2 since the 20 mA current source is included in the mesh, when I write it all and place all the unknown currents in the left side, and the voltage at right side, there exist a 20 mA and 6 V. Hence, I cannot readily apply system of equation to solve for the unknown currents.
Edit:
Here are my mesh equations:
Mesh (1) $$300(i1)-100(i3) = 12V$$
Mesh (2) $$5000(i2)-2000(i3)-1000(i5) = 0.02 A - 6 V$$
Mesh (3) $$-100(i1)-2000(i2)+2100(i3)+1x10^5i(5)=0$$
Mesh (4) $$-1x10^5(i5)-4(i2) = -0.02A$$
Mesh (5) $$-996(i2)+(11000)i5 = 0$$


texts: What makes a particular platform suitable or unsuitable for production use?

texts:
Let's assume that the cost of goods is an insignificant factor.  If a company lacks a team to produce a custom board for a particular product, but has success with an off-the shelf development platform like Arduino / Netduino / mbed, what sorts of things should be considered before going forward?

If I'm not mistaken, Arduino was originally targeting university students because of its low price and ease of use.  It naturally became a popular platform for artists and makers.  I see the Netduino as a logical extension of Arduino -- it allows people to use a robust and rich IDE (Visual Studio 2010) and get things done quickly via the .NET Micro Framework.  mbed is another nice hobbyist platform because of its ease of use, free tools (online compiler), and hardware peripherals.

So my question is, why shouldn't companies adopt these development platforms for production usage?  In other words, is it a bad idea to just buy several boards from Sparkfun, program each of them with the code, and then deploy the product to customers?

I'm specifically interested in Netduino, but arguments for / against Arduino and mbed are also welcome.  On the flip side, would you, or have you done this before?

I personally look at the Netduino development as a "core module" that other processor manufacturers sell for product integrations, but maybe I'm missing something important here.


texts:
I'm planning an energy harvesting circuit using LTC3105 (400mA Step-Up DC/DC Converter with Maximum Power Point Control and 250mV Start-Up).

The problem is that my energy source is bipolar, although polarity switch is a matter of seconds (very low frequency). I very much like the 250 mV startup voltage of this chip and such low voltage is required by my application.

The obvious solution would be to use bridge rectifier, but it introduces voltage drop that is significant compared to 250 mV startup voltage. Is it possible to solve it in another way? It is allowed to use two LTC3105 chips.

EDIT: LTC3105 supports only positive voltage with regard to GND. The problem is that I'm using small motor with gearbox as a dynamo which will be turned by hand in both directions. If connected directly and turned in one direction it will produce positive voltage, if turned in opposite direction it will produce negative voltage. The slower you turn the motor the lower voltage you get and the goal is to produce energy from smallest turn speed as possible.

So maybe instead of rectifying the motor input and losing some voltage, there is a method to route each motor polarity to separate LTC3105.


texts: Super Duper Vdd stiffening required on 555 timer, what is the best way?

texts:
I am using a 555 timer for a (16bit) frequency sensor/counter.

It works by counting the number of pulses read in the 125ms sample time set by a 555 timer; resets & repeats...

I am using the timer in astable operation.

TH (time pulse high) is the sampling ON signal.

This time is set and trimmed (+/- 5% adjustment range) with a high quality POT.
TL (time pulse
low) falling edge initiates a data-latch read --> then a counter reset operation

Right now I have it on a bread board. I am making a PCB for the final design and I want to iron out the following problem for the PCB design.

Here is the problem:

The measured frequency is not super stable (+/- ~3Hz @ 25kHz) and it takes a while to settle.

I think it is because the sample time is getting affected by the noise on the Vdd rail. I have decoupling caps on all the IC's but it is on a bread board so this can be expected.
For the PCB layout I want to insure the 555 timer is on a solid 5v and the DCDC converter output is steady.

Here are some ideas I have on how to do this.

Use a rail-rail opamp and 4v7 reference to regulate the Timer Vdd @ 4v7
Use ferrite beads to further decouple the Timer and all the other ICs from each other.
Use a seperate DCDC converter for the timer.
Use a linear regulator IC for the Timer Vdd.

Which of these would be the best practice for insuring a constant timer Vdd value?