texts: Enhance sensivity of my magnetic field measuring setup

texts:
I have the following magnetic field measuring setup:

Picoscope 2204A
16m wounded up bell wire connected to tip and ground clip as search coil antenna

Now I want to enhance the sensivity for 50Hz to 1MHz.
I have thought about the following things:

Picoscope measuring sensivity is near white noise, so an osciloscope amplifier wouldn't have an effect I think.
Maybe replace the bell wire with a litz wire with many strands like in Coaxial cables? RG58?


texts:
Can anyone provide a link for complete list of status codes for AVR TWI?

I am working with DS1307 using TWI, during which at some point I receive a status code of 0x40. However there is no mention of this code in the ATmega8 datasheet.


texts:
When should be clamping diodes preferred over one-directional TVS for input sanitation?  Consider only digital inputs, not power lines. Clamping diodes seem to be recommended so I worry I might be missing something.

Single one-directional TVS can supply operation of both clamping diodes (over/under voltage protection)
Clamping diodes are not faster: small signal Schottky diodes switch in tens of picoseconds (Wikipedia), beefy models can take much longer. Littlefuse's SMBJ series switch in 1.0ps.
With clamping diodes the power supply must be able to absorb the charge coming from the input. This can be fatal for badly designed supplies.
TVS with low BV can have high leakage current but that is problematic with Schottky diodes as well


texts: Laptop keyboard backlight ribbon cable broken

texts:
I've accidentally broke my laptop keyboard backlight ribbon cable when disassembling my laptop. I want to solder it back by patching with copper wires or maybe copper plates.

My question is, it is a 4-pin connector, i exposed the end of the ribbon with sand paper but there is only 2 lanes of copper instead of 4. Do I just need to solder them back or it should be 4 ? I found the diagram of the keyboard light and attached some photos of my cable.


texts: Use a solar battery charging system to power day/night security camera?

texts:
I have in mind a wireless security camera but it still needs an AC adaper for power. I wish to supply this power from a 8 x 1.5v supply of 2,500 mAh batteries that are charged in daytime with 12 volt [near 1 Amp] solar panel.

Can this be done? Limitations? Any way to tell me where I am going wrong with this?

If the Adapter says "12 v @ 700 mAh" shouldn't my "12 v 800 mAh" AA's NiMH be enough, being recharged with solar?

Thank you.


texts: SPI SS line gets raised to ~3.7V on custom PCB

texts:
On a custom PCB design I did recently, I ran into an issue.

The basic concept of the PCB is connecting up to ten NFC sensors (via SPI) through USB-C connections (not using actual USB communication, but simply routing the wiring through USB-C wires).

All SPI lines (MOSI, MISO, SCK) go to an ESP32 mounted on the PCB.

The SS lines for each sensor are connected to an MCP23016 I/O expander (SENS_EXP on the PCB).

On a breadboard prototype, the whole thing works and sensors get recognized via SPI. However, on the PCB, sensors do not get recognized.

I have managed to (most likely) locate the issue: During sensor initialization, instead of staying at 0V, the SS line for each sensor briefly rises to ~3.7V instead of staying at 5V. This most likely causes the sensor to become inactive and thus not be recognized. I assume it occurs at the moment an SPI transaction is initiated, however I'm not 100% sure of that.

From the PCB layout posted below, could you identify any possible cause for this? The problem occurs for all sensors (meaning pins GP0.0 to GP1.1 on the MCP23016). On the breadboard prototype, using the same IO expander and same ESP32, the SS lines behave as expected.

The problem also occurs without any wiring (or sensors) connected to the PCB, so it must be related to something on the PCB itself. We have tested three identical copies of the PCB and the problem exists for all of them. Also, there are no measurable shorts between any of the related pins.

Thank you in advance!


texts: I am trying to create a 6A, 60Hz sinewave. A 50W audio amplifier with the standard 4Ω minimum output resistance is available, but I deduce it is only able to supply an absolute maximum of 3.5A. My idea was to use a transformer on that output and increase current that way. The signal will be applied to a measurement device, meaning minimal load only. Finding the right transformer is getting me headache. What is the right way of creating such low-voltage, high-current, virtually no-load AC signal, what would you do? Cheap & easy preferred.


texts: Expression for currents and potential over a resistor when switch is opened at t = 0

texts:
I am studying a text book and need to come up with time-domain expressions for the current in the resistor \$R\$, the inductor \$L\$ and the potential over the resistor or inductor (which is equivalent).

A switch shorting the current source is opened at t = 0

I have come up with

$$i_R(t) + i_L(t) = I_s = 2A \tag{1}$$

where \$I_s\$ is the source current of \$2A\$.

$$v(t) = L\frac{di_L(t)}{dt} + Ri_R(t) \tag{2}$$

and

$$i_L(t) = K_1e^{\frac{t}{\tau}}, s = \frac{-1}{\tau} \tag{3}$$

which could be written as

$$i_L(t) = K_1e^{st} \tag{4}$$

KVL gives us that the potentials in the resistor-inductor loop sum to zero

$$LsK_1e^{st} = Ri_R(t) \tag{5}$$

and an expression for \$i_R\$ is

$$i_R(t) = 2 - K_1e^{st} \tag{6}$$

I need to solve for \$K_1\$ and \$s\$ to discover \$\tau\$ but I can't seem to solve for either. I substitute 6 into 5 and solve for s to come up with

$$LsK_1e^{st} = R(2 - K_1E^{st}) \tag{7}$$

and

$$s = \frac{R(2 - K_1)}{LK_1} \tag{8}$$

but both \$s\$ and \$K_1\$ remain unknowns.

Conventionally I would solve with initial conditions, at \$t = 0^+\$ I have \$i_R(t) = 2\$ since we know the current in an inductor cannot change instantaneously, and so at the opening of the switch, all the current is delivered to the resistor only.

This gives from equation 6

$$i_R(0^+) = 2 - K_1e^{st} = 2 \tag{9}$$

and so

$$2 = 2 - K_1, K_1 \equiv 0 \tag{10}$$

if I solve for \$t = 0^-\$ I get

$$0 = 2 - K_1, K_1 \equiv 2$$

which is correct but this does not make sense to me as it has derived information from the \$t > 0\$ circuit and solved for the \$t < 0\$ circuit

Where have I gone wrong?


texts: How to measure small AC mains currents from a microcontroller?

texts:
I'd like to build a battery charger control circuit using an Arudino, a relay module, and a current sensor.

I'd use the relay to turn on AC power to a "smart charger" for one or more sets of lithium cells in bike headlights (and other types of battery chargers too. This is just a typical use-case). One of the headlights will draw as much as 2 amps at 5 volts. I suspect the other one only draws 500 mA, or perhaps 1A.

I want to sense the current being drawn by the charger(s), and detect when they switch off and their 5V current use drops from 500-2500 mA to the trivial amount of power used energize the power supply and drive their display LEDs (probably <50 mA at 5V.)

500 mA at 5V, the lowest expected "active" current,  will be a very small amount of current at 125 VAC. (about .02A, by my calculations)

I COULD cut the USB charging cable and put my current sensor on the low voltage side, but I'd like to make this a versatile charger controller that I could hook to just about any smart mains-powered battery charger by just plugging the charger's AC power cable into my controller. (And possibly adjusting the threshold current, although I'm hoping to make it smart enough to measure a baseline charging current and detect the drop in current when charging completes.)

What could I use to measure the AC current and feed that information into the Arduino? Ideally a digital signal would be best. A variable input voltage driven by current would be my second choice, and a logic 1 that drops to a logic zero when the current drops below a set threshold would be my third choice.

I'm interested in either an off-the-shelf current sensing module, or something I can build.

If this is a more appropriate question for the Arduino Stack Exchange, I apologize. It seems like a decent fit for this site.

Some background:

I've built a home-brew passive current sensor myself before that lets me switch my shop-vac on and off when I turn on my drill press or other power tool. I wound bell wire around a ferrous rod (a nail, if memory serves) and then wound the load wires from the drill press around that, creating a crude transformer. I fed the output of that into a full-wave rectifier diode I had lying around, and attached the positive output from the rectifier to an electrolytic capacitor, and tied both negatives to ground. Then I connected the positive lead of the capacitor to the positive input of a solid state relay. Finally, I ran the mains power into through the load side of the solid state relay. When I draw enough current through the power tool load, it generates a stiff enough output to raise the voltage out of the capacitor enough to turn on the solid state relay. However, this rig only detects several amps of current. I want something much more sensitive.

I'm expecting to need to use active components here. I might be able to build an analog circuit using an op-amp, but my electronics knowledge is a bit weak (I'm a software guy) so I would struggle to figure out to configure it. I seem to remember that the ratio of a resistor on the input and a "feedback" resistor lets you adjust the sensitivity of an op-amp circuit, but I'd have to do some serious digging to figure out what type of op-amp to use and what resistor values would be appropriate. I guess I could use a properly sized potentiometer to adjust the current threshold, but again, my preference would be a way to convert the current measurement to digital information that I could then handle through software on the microcontroller.


texts: Change current using PWM, for specific range outside PWM boundaries

texts:
I have a circuit where I use a digital potentiometer (namely MCP41100) to change current, and I use duty between 0 and 255 (thus, I have 256 steps). The current changes from 25 micro to 50 micro. And things are running great for these numbers, but I want a different range.

What I would like to have is a current that goes between 0 and 16 milliampere with very small steps (each step is like 10 to 20 micro, thus I will have over 500 steps (16000/20)).
If you know the right component(s) to make my circuit work, please let me know. Any hint in the right direction is appreciated.


texts:
I'm a beginner in electronics and I found two quartz crystal oscillators, each one has two pins. Their numbers are:

sjc4.000a
ee4.000

Is it possible to know the frequency by knowing the numbers? If not, how can I know the frequency?

How do I use them in a very simple circuit?


texts:
I salved a lot of ICs but this one I couldn't find (and is maybe interesting enough to be play with it, since I never used an FPGA).

It's from a semiconductor chip production machine (high likely) and the PCB was marked 'Rejected' (but hope most ICs work) and was in the electronics garbage bin. So I don't know exactly for what device it was meant for.

It seems to be an Altera EPC3TC32, but where can I find the datasheet? Altera.com forwards to Intel and there I cannot find it.

The package is QFP32.


texts: Pseudobipolar signal example - Analog Devices AD7682

texts:
What is a pseudobipolar signal? I read this word in the datasheet below:

http://www.analog.com/media/en/technical-documentation/data-sheets/AD7682_7689.pdf

Can you show me an example with a plot please?
Online I found only the definition of pseudo-differential unipolar and other definitions:

http://www.analog.com/media/en/technical-documentation/product-selector-card/2PB_sarinputtypesfb.pdf

Thank you in advance.


texts: Do capacitors waste power as heat or whatever on AC?

texts: Capacitors store energy then give it back once required. A perfect capacitor is nearly lossless on DC power because you only fill it once then it keeps energy in it until you discharge it so no power loss to mention, but on AC the capacitors will be charged then discharged all the time which in my theory seems to waste power, is that true? If it is true then how can I measure that loss for a 250V 8000µF capacitor connected to 170V AC power line?


texts: Need help finding an under-voltage protection IC for 2-4 cells

texts:
I've been looking for the last few days but I just can't find one. I've found a ton of single cell protection IC's but I can't find one that does the same for up to 4 cells. A stackable single cell IC would work so that I can set them up in series to monitor multiple cells, if something like that exists. I just need something that can read the voltage and when one of the cells gets to  ~3.3v, output a 3-5v analog or digital signal that I'll use as an input to a microcontroller. I don't have much space so the smaller the better!

Any help would be greatly appreciated!


texts: How does the chassis ground on an automobile protect against lightning

texts: How does the chassis neutralize the excess of electrons from a lightning strike?


texts: How to calculate average power consumption in mAh?

texts:
I'm working on a device that sleeps for most of the time and occasionally wakes up and takes some sensor readings. This device will be battery powered so I'm trying to calculate how long it will run on a 2,000 mAh battery. A typical hour of application looks like this:

It's easy for me to calculate how long each stage would take by itself (for example sleep could run for (2,000 mAh/.05 mA) = 40,000 hours) but I'm confused on how I would calculate every stage together and get an accurate calculation of how long the battery would last.

Thanks!


texts:
Let's say we have this logic function:

g = abc + abc' + a'bc

and let's try to simplify this using laws

= ab(c+c') + a'bc

= ab + a'bc

and there's the point I stuck.

But using the good ol' Karnaugh map it seems that the result should be ab + bc

So, does absorption law apply here?

Or I got it all wrong from the start?


texts:
I am working on a design that needs to operate outside on two AA batteries for at least a year.

I have optimized the design to reduce power and using a spreadsheet analysis I now have an average current consumption. I should be able to verify that is right by monitoring a prototype for a while.

I have the following pieces of information:

Average current consumption in mA \$Cave\$
Supply of Duracell AA batteries in mAh \$Bsupply\$
Starting battery voltage \$Bmax\$
Minimum battery voltage for DC-DC converter \$Bmin\$
Non-linear discharge profile from Duracell website https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2016/03/MN1500_US_CT1.pdf
Climate data

How can I take this to create a realistic estimate?

I think it is perhaps reasonable to use the average environmental temperature \$Tave\$.

Note - I chose Duracell simply as an exemplar of a quality battery. I wouldn't need/want to consider poorer-quality batteries.

Many thanks!

Update - average power consumption is 1.11mW.


texts: Analog remote control signal's threshold voltage, length and delay

texts:
I do not have too much knowledge background of RF knowledge.
Background:
I am using Arduino board to record and interpret RF analog signals. There is an 10-bit analog-to-digital converter.
Questions:

I saw many people use "threshold voltage" to describe the levels of analog signals (convert to digital). In the case of Arduino's 10-bit ADC, it is level 1-1024.
So what this "threshold voltage" actually refer to (e.g. strength of analog signal or something else)?

Continue Q1. If the threshold is low than certain value (e.g. 80), it is defined as LOW signal. Similarly, HIGH signal for threshold higher than 100.
For example, remote control signal (e.g. air-condition) consist of a series of (LOW, HIGH) pairs. This is what I saw from some Arduino projects. Is it a common way to define LOW and HIGH signal?

What means the length of analog signal? Time?

If you convert digital signal back to analog signal, and send them through a transmitter. You need to set certain delay between each (LOW, HIGH) pair. Why there is such delay?


texts: DIY function generator with an operational amplifier

texts:
I am trying to make my own function generator.
I will make it with adjustable frequency and peak voltage but for test reasons I'm simulating a constant frequency one.
My output has distortion which I believe is due to UA741's poor slew rate.
How can I fix that and get a more precise output?
I'm using +12/-12 Volts power supplies. I'm using a Wien bridge oscillator (WBO) to generate the sine wave. There's a filter to get the square and filter it twice to get the triangle wave.
I know using a 555 timer to create square-triangle-sine waves would be easier but as far as I know Wien bridge oscillator creates a very clean sine wave.
Also I want to go with the WBO for educational purposes. The output of WBO is about 750mV/-750mV peak so I used another amp to amplify the sine wave.
The output of the first amp is the yellow trace, the second is blue, the third is pink, and node after R8 is green.
Distortions are clearly visible in third picture, although I think my sine wave is pretty clean.
I want to change the op-amp but can't find a good substitute which also works in simulation. Are there any other improvements you can suggest?
Can I get a sine wave with bigger peak voltage wihtout using the second amplifier?
I don't have a scope so I adjust the frequency about 15 Hz and connect an LED to output to see if there a oscillation or not.


texts: How many capacitors are needed for a step down circuit?

texts:
I'm tyring to build my first step down component using TPS562219 to get 5V output from a 12V input (instead of 1.05V output shown in the example). But as I'm new to this electronic stuff, I have some problems of understanding.

Input capacitors

In this example circuit there are three capacitors. Why should I use three of them and how do I know the values of these. In the text of the datasheet (page 15, section 9.2.1.2.3) they are talking of two capacitors: "A ceramic capacitor over 10 µF is recommended for the decoupling capacitor. An additional 0.1 µF capacitor (C3) from pin 3 to ground is optional to provide additional high frequency filtering."

Output capacitors

For the output capacitors table 2 on page 15 gives a range of 20-68µF. How do I choose the correct value? And why should I use three of them?

In another circuit which is using the same TPS562219 they are using just two input capacitors and one output capacitor - with different values:

So I would be very thankful for some explanation, so I can understand that and build some own things. How many capacitors do I need and which values are recommended?


texts:
I'm designing a boost converter to boost 3.3 V to ~25-30 V. I have successfully simulated it in SPICE, but the current draw for converter is enormous - about 8-9 A. How can I handle this nuisance? This is the boost converter circuit I used.

I used \$R_L = 10 \Omega\$ so it doesn't go into discontinuous mode.

I don't need actually any output current, because all I need is to hold a 25-30V potential over a Numitron tube.

I managed to google some versions of this converter featuring MOSFET driver, but failed to understand how they work. Could you please light it up a bit for me?


texts: How many 200 Watt solar panels do I need to power a 3.5kVa 48DCV inverter for 24 hours if the load on it is 1500 Watts and the batteries are 200Ah, 12DCV each in a country with about 6hrs of sunlight?


texts:
I was wondering if an ADC like this https://www.analog.com/media/en/technical-documentation/data-sheets/ad9883a.pdf would work for making an oscilloscope. Will it work? Is it suitable?

added

I found an ADC that says says it works both for imaging and communications. There is a clamp circuit example on page 13 https://www.analog.com/media/en/technical-documentation/data-sheets/ad9280.pdf . Maybe the AD9883 works similarly? Seems like clamp may even be a good thing? So the real problems may be the hsync/vsync?

PS: Most likely not going to use either, just trying to understand why it's not suitable.


texts: Safe use of high voltage in laboratory environment?

texts:
I'm completing a project in the lab that requires a spark. As such I've acquired an ignition coil and can use the Lab's standard 12V DC power supply that connects to the 240V AC Mains to power the ignition coil. My issue is grounding the spark plug. I'm assuming that a spark plug doesn't offer much resistance (something about the voltage ionising the air and lowering resistance significantly?) and that even if it does the output voltage would be too much for the 12V supply to ground. What are my options?

EDIT (Details):

I don't have a schematic so I've drawn a small diagram showing my configuration:


texts: How can I test a Hall effect sensor at a given distance?

texts:
I have a project that includes an Ablic S-5716ACDL1 omnipolar Hall effect switch. It has a sensing range of about 3 mT (±1.6 mT).

Prior to going down a rabbit hole of magnetism in physics, I confirmed that the sensor works as expected when bringing an axially magnetized neodymium disc magnet (22 mm dia. X 6 mm thick) within approximately 30 mm.

There is about 2 cm of plastic/air between the sensor and magnet, so this establishes the minimum distance I'm able to place a magnet for testing.

Please excuse the crudity of the diagram, I didn't have time to build it to scale or to paint it...

My goal is to automate this particular test by employing an electromagnet instead. I naively purchased a small electromagnet thinking it would be similar in characteristics.

Unfortunately, while it has a reasonable holding force of 5 kg, it is not detected by the hall effect sensor until surprisingly near, about 10 mm (with the plastic cover removed).

I purchased a larger electromagnet (10 kg holding) expecting to increase the detection distance, but without luck.

I suspect that the construction of these electromagnets (with a metal chassis surrounding all but the "business end") lends itself to their holding strength, but also might be limiting the distance at which the magnetic field can be detected. Bringing an energized electromagnet near steel doesn't seem to have any noticeable attraction/effect until roughly the same 10 mm distance that I experienced with the Hall effect sensor.

There's a similar question here, but the answer goes beyond my understanding at this point. For example, I know that 1 mT = 10 gauss, but I don't know how to derive that for a given electromagnet, or more precisely, a given distance from said electromagnet.

I've only found a few electromagnets that are constructed differently, but this is based on my potentially wrong assumption that the construction method is key. I'd like to find a solution with somewhat less trial and error, and without vastly overdoing it with respect to the electromagnet strength.

My design limitations allow for up to 25 watts (up to 24 VDC), and physical space for the electromagnet is up to 80 mm vertically and about half that in depth and width.

I've also considered just mounting a neodymium magnet to a servo arm, but that introduces a mechanical/moving aspect which could be more likely to require service.

Q: What electromagnet specs should I be looking for, knowing that I need to detect 3 mT at 30 mm?


texts:
I am unable to understand the working of the below circuit and how it act as amplifier.

Enable the SAEN signal i.e. turning it high.
Let us assume that we get DL as 1 and DLB as 0. Actually it will be (Vprec+deltaV) and (Vprec-deltaV)
Now the A nMOS is conducting and we will get both pMOS gate as Logic 0.
This will make both nodes at A and B as 'Strong +".

What will be the level at A as the pull up pMOS will pull it up and pull down nMOS will put it down.
And what is the use of the current mirror?
And how does it amplify?


texts: Positive and negative potential via two power supplies with common ground?

texts: I need to use a positive and negative potential on a circuit including an instrumentation amplifier. My lab only has single supply power supplies (only offers positive voltage). I know that I can reverse the polarity and achieve a negative potential, but this means using multiple power supplies. (I am pretty sure that I cannot reverse the polarity on a single rail to fulfill both my negative and positive potential needs as this will cause a short). I do indeed need to tie the grounds for both supplies to one another, correct?


texts:
I'm learning about the Miller capacitance effect when a capacitor is tied to both the output and input of an amplifier. This is specifically about learning to deal with the parasitic capacitances of a transistor amplifier circuit. I understand the derivation to get
$$
C_\mathrm{Mi} = (1-A_v)C_f,
$$
and it makes sense that you will get a positive miller input capacitance when Av is negative (or I guess also when Av is positive but less than 1?)

In the case that you DO have a positive gain amplifier, and you calculate a negative miller capacitance, how should I interpret this for the transistor frequency analysis? Would a negative capacitance result in a low-pass break frequency like a positive capacitor? Do you just pretend the feedback capacitor isn't there?


texts: Design a 100 watt inverter, but why when the circuit is connected to the power supply sparks out?

texts:
I'm making an inverter with 100 Watt power, 220 volt output voltage. The input voltage source of the inverter is from solar panels with a maximum voltage of 18 volts and a maximum current of 5.56 Amperes.

This inverter circuit consists of a 150 Watt boost converter to increase the DC voltage of the solar panel to 24 Volts.
Then the inverter circuit uses the P-channel IRF9540 and N-channel IRF540 mosfets, 4N35 mosfet drivers and BD139 transistors to amplify the frequency.
To generate signals I use the Arduino SPWM program.
The 24 VAC voltage will be raised to 220 volts with a 5A transformer and a 12-12 Volt voltage tap. The load for this inverter is the lamp and charger.

Before I connect directly to the solar panel. I first tested my circuit with a 16 Volt battery source, when I connected my circuit to the battery, sparks came out so that the input voltage decreased. Then I test by removing the Arduino pin from the circuit and still sparks come out. Is there something wrong with my circuit and what are the suggestions for this series? Is my circuit experiencing a short circuit? Thank you


texts:
So from what I've understood, the KV rating for a motor gives us the rotor speed based on the voltage applied at the phase of the motor.
Having looked a bit deeper in ESC / inverters, I've come up with the conclusion that it's rather the frequency of phase commuting that sets the motor's speed.

But I guess there is some electromagnetic force (lorentz / laplace?) that defines the force exerted on a body knowing the voltage flowing through it.

What I'm thinking is that the frequency commuting defines speed, but the current/volts going through each coil defines the maximum force/acceleration the rotor can be pulled with. And since commuting is done one zero-crossing of the floating phase, this max acceleration (thus time it gets to do the zero-xing) limits the commuting freq.

Could anyone help me to figure this out ?


texts: Interfacing with Low-Voltage ICM-20948 IMU chip

texts:
I am working with an ESP8266 and an ICM-20948 IMU chip. According to the datasheet, the IMU chip works on up to 3.6V VDD, but I/O voltage only goes up to 1.95V.
I thought about using resistors for stepping down 3.3V->1.8V for one way. However the ESP only recognizes a HIGH voltage level after 2.5V, so I cannot directly connect the other way and I need some sort of level shifter.
The connection is a 400 kHz I²C bus. I've heard that at this frequency, resistors should not be used for level shifting. Is this true, should I rather use a 1.8V regulator, and MOSFETs for the level shifting? The final PCB will be in a small handheld device, so I want to keep component count low for a small footprint.


texts:
I am designing an FM modulator circuit using Colpitts topology. Unfortunately I encountered difficulties and do not know how to solve them as I am new in electronics.
Firstly I don't get a clean sine wave on ouput. Also, the FFT of the output differs from what is being expected - I get only one frequency for the whole input sine wave. So the circuit "shifts" the frequency but doesn't really modulate it.
I might be wrong but thanks for your help anyway.


texts: What's the difference between polarization ratio ρ_C and ρ_L?

texts:
I have the following 2 equations in my textbook:

ρ_L = E_Φ/E_θ

ρ_C = E_R/E_L = (1 + jρ_L)/(1 - jρ_L)

Both ρ_L and ρ_C are called polarization ratio. However, what's the difference between the two?


texts:
I am planning on building a device that will perform a frequency conversion of a band of RF in approximately the region of 650 MHz down to 520 MHz. The bandwidth will need to be approximately 50 MHz.

It is a "repeater" style device, where the device will receive 650 MHz and then re-transmit on 520 MHz.

What are the likely issues with this? I am assuming that there will be filtering challenges and I will likely need to use a much higher Intermediate Frequency, i.e.

650 MHz -> 900 MHz
900 MHz -> 520 MHz

In order to overcome filtering challenges that I assume I would run into if attempting to do a direct conversion.

This will be the first time I have attempted something like this - are there any other issues I might need to consider before planning my design?


texts:
I was wondering if anyone can confirm if this is right or not or if I am even on the right track

The ON State:

Node VL: \$ -\int\frac{V_{IN}}{L}=0\$
Node VC: \$C\dot V_C+\frac{V_C}{R}=0\$

Node VC:\$\frac{V_C-V_{IN}}{L}+C\ddot V_C+\frac{\dot V_C}{R}=0\$
SSA MODEL:
\$\frac{V_C}{L}-\frac{V_C*d}{L}\frac{-V_{IN}}{L}+C\dot V_C*d+C\ddot V_C-C\ddot V_C*d+\frac{\dot V_C}{R}-\frac{\dot V_C*d}{R}+\frac{V_C*d}{R}=0\$

where (variables)

\$V_c = Capacitor\ Voltage \$
\$ D = Duty \ Cycle\$

Assuming its right, I need to linearize it due to \$V_C*d\$ isn't linear.

*\$V_{CE}\$ as in Voltage of capacitor at equilibrium , not VCE of BJT.

Finding Equilibrium points, I want to linearize it around \$V_{CE} = 5V\$ so finding De and assuming all initial conditions are = 0

Where
\$C = 0.000272F\$
\$L = 0.000047242H\$
\$R = 2\Omega\$

\$\frac{5}{0.000047242}-\frac{5*d_e}{0.000047242}-\frac{3.3}{0.000047242}+\frac{5*d_e}{2}=0\$

Solving \$D_e = 0.34\$

Equilibrium Points
\$V_{CE} = 5V\$
\$D_E = 0.34\$

Linearization:

\$(\frac{\partial \frac{V_C}{L}}{\partial V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial \frac{V_C}{L}}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})-
(\frac{\partial \frac{V_C*d}{L}}{\partial V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial \frac{V_C*d}{L}}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})-
(\frac{\partial \frac{V_{IN}}{L}}{\partial V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial \frac{V_{IN}}{L}}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})+
(\frac{\partial C\dot V_C*d}{\partial \dot V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial C\dot V_C*d}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})+
(\frac{\partial C\ddot V_C}{\partial \ddot V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial C\ddot V_C}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})-
(\frac{\partial C\ddot V_C*d}{\partial \ddot V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial C\ddot V_C*d}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})+
(\frac{\partial \frac{\dot V_C}{R}}{\partial \dot V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial \frac{\dot V_C}{R}}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})-
(\frac{\partial \frac{\dot V_C*d}{R}}{\partial \dot V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial \frac{\dot V_C*d}{R}}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}})+
(\frac{\partial \frac{V_C*d}{R}}{\partial \dot V_c}*\sigma V_C\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}+\frac{\partial \frac{V_C*d}{R}}{\partial d}*\sigma d\Bigr|_{\substack{V_{CE}=5V\\D_E=0.34}}=0
\$


texts: power HD44780-based LCD with 3.3V by using a negative contrast voltage?

texts:
I have a circuit that runs on 3.3V and want to use an HD44780-based LCD with it (which normally requires 5V). The LCD logic and backlight works fine with 3.3V, but the contrast doesn't, so nothing can be seen on it.

As the circuit runs on batteries, using a 5V voltage regulator won't work well. I read somewhere that few people got the LCD to work by supplying a negative voltage (mostly 1V) to the contrast pin.

Unfortunately I didn't find any explanation why this works, and how my circuit could benefit from it. The only solution I found made use of a PWM to generate the voltage, but I don't have any micro controller pin available.

My idea would be to use an ICL7660 charge pump to generate -3.3V from my 3.3V input, and supply this directly to the contrast pin. The IC seems to be efficient enough to work on a battery-powered device.

Can you tell me if this will work or if there is a better way?


texts: Noisy record for STMicroelectronics MP45DT02 digital mems microphone

texts:
I bought STM32F4DISCOVERY board and I developed a software that records .wav file using MP45DT02 MEMS microphone on this board. .wav files that I record are really good (almost no noise).

I designed a board based on the schematics of this evaluation board. When I used the same software, I have high noise at the background. I also can't record my voice unless I shout or scream. You can listen the record by this link.

I have 3.3 volts on the board and the capacitors are appropriate in terms of value and closeness to the microphone.

I have two boards and I have the same problem on both boards so it seems to me that the problem is systematic.

Could it be a problem of soldering or PCB cleaning after production of the board? Could it be a problem of noisy power supply? What could be the reason?

Edit: Below is the spectrum analysis of the two records. (Green: Eval board | Blue: My board)

Edit 2: Below is the channel meter of the two records. (Top: Eval board | Bottom: My board)


texts: Do I need FCC certification to sell if my device uses ISM bands?

texts:
I have made a portable xbee-like transceiver. The system will be operating at 2.44000GHz (RX) and 2.46000GHz (TX). The TX power to the antenna is well underneath +30dBm; the EIRP is also less than +36dBm. My understanding is that even though my device is unlicensed and uncertified, and I am legally able to operate under these frequencies in the ISM band.

However, if I want to sell this device, do I need to have this device certified by the FCC? If so, what does it mean to be certified by the FCC for ISM bands?

P.S.
I only care about FCC certification, as I will be getting Intertek certification soon... and I don't really care about UL, cUL, or CE.


texts:
I recently bought Belkin Ultimate Surge Protector for protecting my modem, router and PC. I have a broadband connection from Cable provider (through modem via coaxial cable).
Now I wish to connect modem via Belkin Surge protector.

The above connector is used to connect to my modem.

Now I wish to connect this cable to my Belkin Surge protector. Which comes with the following connectors:

I don't know name of any connectors. Please help me to find out the names so that I can buy appropriate converters for that.


texts: Bluetooth4.0 vs WiFi in a Android to arduino connection

texts:
I've read this article
http://gtms1313.wordpress.com/2013/04/01/bluetooth4-0-vs-wi-fi-direct/

which is a good summary of latest Wifi vs Bluetooth technologies, but the actual hardware being used needs to be taken into account. I need to hack an Android which will also connect wirelessly to an arduino. Will the communication be easier with Bluetooth from a coding and serial access point of view?


texts:
What does typ stand for in this table?

It's in a IC datasheet.


texts:
I'm having some difficulty getting LTSpice to like a TRIAC model.

The specific error it throws is "Missing model definition for VGT-0.65". The trouble is that VGT is a subcircuit parameter, not a model.

The thyristor library is one I found while googling for a SPICE model for the MAC97 (MAC97A8 specifically). It's located here and looks like a decent, well-built thyristor library. It abstracts a single SCR and single Triac subcircuit, and then lists dozens of models of various thyristors which call up one of these two models.

The subcircuit line that is throwing the error is this one:

Rseries  gate    gate1   {(Vgt-0.65)/Igt}

Now I've tried putting Vgt in parentheses all by itself (to try to separate the "-0.65" from the "Vgt", but then the LTSpice error just says it's got a missing model for VGT.

The specific model for the MAC97A8 also looks fine, and defines Vgt:

.subckt MAC97A8         MT2 gate MT1
* Min and Max parameters
X1 MT2 gate MT1 Triac params:
+ Vdrm=600v  Idrm=10u     Ih=10ma      dVdt=25e6   Ton=2u
+ Igt=5ma    Vgt=2.0v     Vtm=1.9v     Itm=.85
* 90-5-18    Motorola     DL137, Rev 2, 3/89
.ends
*$

I've tried a few other TRIAC models to see if there was something specifically goofy about this one but that does not appear to be the case. At this point I'm starting to wonder if there is something odd about LTSpice's handling of the Triac subcircuit, but LTSpice is a pretty decent SPICE program so I'm hesitant to blame it, especially with a thyristor library found out on the random 'net.

Has anyone simulated TRIAC circuits with LTSpice before? Is there something specific that I am missing?


texts: Fit a switch to rectifier input or output?

texts: I have a set of LED fairy lights. The cable has an AC/DC rectifier between the mains plug and the LEDs. I want to fit a single pole switch so I can turn the lights on or off without having to use the switch on the mains socket. Should I switch the rectifier input (i.e. fit the switch between the mains plug and the rectifier) or switch the rectifier output (i.e. fit the switch between the rectifier and the LEDs)? If it makes no difference, is there a convention to follow? Thanks for the advice!


texts: Terminating a 50 Ohm source into 1M Ohm oscilloscope input

texts:
Due to buying some equipment several months apart I am now faced with the task of connecting a high speed ,up to 1GHz, light detector that requires a 50\$\Omega\$ load impedance, but my oscilloscope only offers a 1M\$\Omega\$ input impedance.

Can I connect via a tee piece and a 50\$\Omega\$ terminator?  Are there other options to connect the detector to the oscilloscope?


texts: Can I use these normal IR Photo-Diodes for long range laser communications?

texts:
This is my first time working with lasers, I made a data transmission system with a laser using normal components, and now I would like to change It to a very long range system (~2-3 KM).

My question is, would I be able to use these cheap IR photodiodes: Link

if I use a very powerful laser Such as > 5-watt laser? If not do you have any recommendations for a photodiode for the range I specified?


texts: Simple low pass digital filter implementation for non-uniform sampling?

texts:
I have a system sampling an analog input and I want to filter that value using a simple, first order filter.  EG something of the form:

Yn = A*Xn + B*Yn-1

However I have no control over the underlying process and the sampling period is non-uniform, and varies (randomlyish) somewhere between 25ms and 29ms. In addition I want to use a 30 minute time constant, and can't keep a running buffer of 72,000 sample values.
Given that a typical filter implementation requires a uniform sampling period, is there any simple algorithm that takes into account the time difference between Yn-1 and Xn? (which I guess really means a time varying version of my "constants" A and B)

Note that I'm inclined to simply take the average sample time over an extended period and using that to calculate my constants, however there is also the possibility of the final system not running at the same average rate as my test system, so I want to come up with a solution that is  somewhat adaptable.

answering questions

The filtered signal is being used as a part of a vibration monitoring system in some industrial equipment.  It will be used for more of as a qualitative than quantitative purpose.
The customer requirements are 30 minute rolling average for the data.
I have zero control over the sample rate.
And the sample rate varies every second
And the sample rate defines the speed at which my code runs
The final system should run at about the same speed as my test system, however it could be somewhat slower, maybe down to a 35ms rate


texts: Are unaligned LDRH/STRH supported on Cortex M3/M0?

texts:
Can all Cortex M0/M3 cores do this?

LDRH r0, [0x8001]

This would suggest yes but I don't see anything specific about Cortex-M cores.


texts: What would be the easiest way to use an Arduino to control a 24AC solenoid, when I only have access to 220VAC mains?

texts:
I do also have the Arduino power supply and output pins at 5 or 3 volts to control, for example, a mosfet gate voltage.

Sorry if this is a nooby question - I am an electronics noob


texts: Question about connector, or how to connect

texts:
I bought force sensing resistors and they have a flat connector at the end.
I tried to connect them to jumper cables but the fit isn't good.
https://www.interlinkelectronics.com/fsr-400

On the image labeled connector options I have the bottom one the one they call solder tabs. Does that mean you can solder on these?
Looking at the user guide it says:

  Do not solder directly to the exposed silver traces. With flexible
  substrates, the solder joint will not hold and the substrate can
  easily melt and distort during the soldering. Use Interlink
  Electronics’ standard connection techniques, such as solderable tabs,
  housed female contacts, Z-axis conductive tapes, or ZIF (zero
  insertion force) style connectors.

I have no previous experience of any of those techniques (I think), Googling on them gives me some clues but not enough to say "That's what I'm going to do!".
So what is a good method to get a wire on these resistors?


texts: How do I find Vab and Vcb in this series circuit?

texts: In, general, I dont understand double and single voltage notations. How do I find Vab, and Vcb? Steps would really help.


texts: How can I determine the capacitance required for an oscillator (NOT A CRYSTAL!)?

texts:
In a typical clocking circuit configuration, where a crystal is tied at the input to an amplifier such as is shown below:

The capacitance required for \$C_1\$ and \$C_2\$ would be based on the load capacitance equation (sorry, not sure how to format equations on SE):

$$C_L = \frac{C_{1}\times C_{2}}{C_{1}+C_{2}}+C_S$$

However, what happens when you use an oscillator... such as the ACH-25.000MHZ-EK?

There is nothing in the application notes about needing a capacitor, so do I actually need one? (and for oscillators in general?) I am thinking that because this is still an oscillating circuit, similar to the crystal (clock configuration circuit)... That I will still need some sort of capacitor to keep the oscillator stable. Or am I wrong, and do I not need to attach any capacitor(s) to either the output or GND pins?


texts: How to find Voltage based on reference nodes?

texts:
I came across this problem and I'm trying to really understand it.

  VB is the voltage drop across a particular element, it is the change in voltage from node a to node b. Find the value of VB in volts
  and enter it in the box below.
  The expression Vab indicates the voltage referenced from node b to node a. In other words, imagine Vab being identified in the diagram as
  having a "-" at node b and a "+" at node a. For the circuit above,
  find Vab and enter it into the space below without units.
  For the same circuit above, find VC and enter it into the space below without units. (VC is the voltage across the top element, not
  the voltage at the point c in the circuit.)

  The answers are:

  1)  3
  2) -3
  3) -2

Now, I know that since VA is 3V so do VB because they are in parallel.
but why is not VC + VD= 3V since they are also in parallel to VA

what is throwing me off is that if VA=3V that means the voltage at node b is 3V
now the voltage at node a is 1V, that would mean that the voltage at node b minus the voltage at node a is equal to 2, (i.e. Vb-Va=3V-1V=2V=VB) but it is 3 instead.

The way I solved for VC is just intuitive, subtracted VA-VD and then multiplied by a negative sign because the negative sign is first (assuming that my current flows clockwise through the whole circuit), why can I do this fro VB?

Also why is Vab negative if voltage is dropping and not raising?


texts:
Given this circuit, we want to find V(t) or the equivalent D node circled.

I set up the nodal analysis equations in the phasor domain as follows, with a super  node at the dependent source.

However, Wolfram Alpha shows no solutions. There is something wrong with the set up of my equations I believe, but I am having trouble figuring out where.

https://www.wolframalpha.com/input/?i=solve+(5-a)%2F2%2B(5-c)%2F4%3D0,2*i%3Db-a,(a-5)%2F2%2B(b-c)%2F2%3D0,(c-b)%2F2%2B(c-5)%2F4%2B(c-d)%2F3%3D0,+(d-c)%2F3%2Bd%2F(0.5*10*root(-1))%3D0,(c-d)%2F3%3Di&rawformassumption=%22i%22+-%3E+%22Variable%22


texts: How to replace a green LED with a red one in a simple transistor switch?

texts:
I am designing four traffic lights that I can control with a single digital switch. When the signal is 1, two traffic lights should be green, and the other two red, and they should reverse when the digital signal is 0. I'm using a simple transistor switch to achieve this:

This one works in the simulation, but I tried it on the breadboard, and it won't work properly unless I swap the green LED with the red one and vice versa.
Otherwise, the red LED stays on regardless of the applied base voltage, while the green one stays off.

Moreover, the whole implementation doesn't work in the simulation. Only the first and the third gates switch properly. The second and the fourth ones have the above-mentioned issue:

Now, I'm aware that the red and green LEDs have different forward voltages (1.7V for red and 2.2V for green), but I don't know how to fix this problem.


texts: Different decoupling capacitors in parallel

texts:
Page 29 of this DAC datasheet gives a typical operating circuit. I notice the power supplies have two decoupling capacitors in parallel: 100nF and 10μF.

What caught my eye is that there is a different symbol for each. (One has a curved edge, the other not.) As I understand, one is a "polarised" capacitor, and the other is not.

What is the qualitative difference between the two capacitors? Why are the types mixed in this application?


texts: Power supply capacitors in an amplifier circuit

texts:
What is the role of each of these capacitors?
What is the difference between the  1uF capacitors and the capacitors marked in red, and why are they placed at the level of the \$V_{sp}\$ power supply and not at the level of the other power supplies?


texts: How does the wired Tado smart thermostat operate without a neutral connection?

texts:
I’ve been studying the wiring diagrams for the Tado smart thermostat and noticed that it only uses a live ‘common’ and a switched live to operate.
Given the smart thermostat has electronics which are, for want of a better term ‘always on’ and connected to home Wi-Fi etc, how can this be the case without a neutral wire?
I assumed there would be a built-in battery, but I see no mention of how to replace this on their site.
Can anyone explain how this might work?
Tado wired thermostat installation manual


texts: Can I use the transfer function of a servo DC motor as a close approximation to the transfer function of a stepper motor?

texts:
I have been trying (just spent many hours on this) to find/calculate/derive the transfer function of a hybrid stepper motor. I don't need an exact transfer function (the electrical and mechanical equations are very complex! at least, in my opinion). I just need a good estimate or simpler equation that i can use to model the motor in Matlab/Simulink.

Here are the equations for a hybrid stepper motor: https://se.mathworks.com/help/physmod/sps/ref/steppermotor.html

During my search for some answers, I came across the dynamical equations for a servo DC motor and I managed to figure out the transfer function calculations.

Can I use a servo DC motor transfer function for a pretty close modelling/simulation of a stepper motor?


texts: modbus register address vs. register number; absolute address vs. offset

texts:
I'm developing a Modbus Slave device, and I'm having a little trouble understanding how to name/address my registers.
Let's say I have 2 Discrete Inputs and 2 Input registers. From Modicon standard, the Discrete Inputs will have register number 10001 and 10002, while the Input registers have 30001 and 30002.
Reading here and there, it looks like these will translate to register addresses 10000, 10001 and 30000, 30001.
Now, how to access these registers? What will be passed in the Modbus message starting address field? This is my firmware and can do whatever I want, but what is the standard? (this is what I don't understand)
I see 2 options:

absolute address approach: if the user wants to read the first Input register he'll send 30000 in the starting address field; from firmware side, I know it is an Input register both from the function code and from the register address itself, and I know it's the first one since I received exactly the address of the first one
offset approach: if the user wants to read the first Input register he'll send 0 as starting register; from firmware side, I know it is an Input register from the function code, and I will look for the first Input register since I received a 0 offset

The first approach seems more reasonable for me, since it avoids registers access errors;

absolute address approach: if the user sends a read Input register function code for address 10000 I will answer with an error code; maybe the user wanted to read an Input register, but sent the wrong address, or maybe he wanted to read a Discrete Input but sent the wrong function code; better notify him with an error than send a data that he'll probably misuse
offset approach: if the user sends a read Input register function code for address 0 I will answer with the data; but what if he wanted to read a Discrete Input but sent the wrong function code? Dumb him, ok. But since the same starting address can refer to 2 data types (or more, if there are Coils and holding Registers, too), I'll also feel a little guilty

Besides my preferences, I have a "real case scenario" that support the offset approach. I've interfaced my device with a gateway that translate the Modbus to another fieldbus protocol. To configure this gateway I need to define the Modbus addresses that will be periodically read/write. I need to use 6-digits addresses. So, in the example above, the 2 Input registers will be 300001 and 300002, and the 2 Discrete Inputs will be 100001 and 100002. From firmware side, for both data types I receive 0 and 1 as starting addresses, so the second approach (starting address indicates the offset) is used.
Again, is there any standard way to approach the Modbus addressing?


texts: Oscilloscope V_rms vs V_avg for effective voltage across an LED?

texts: I'm using a PWM signal to vary the effective voltage seen by the high side of an LED.  When probing this signal on an oscilloscope, I can read the RMS voltage or the average voltage, which vary dramatically at about 20 KHz.  What voltage should I use to estimate the current flowing through the LED?


texts:
The picture below is named as headphone amplifier on the internet. My goal is not to do "headphone amplifier". I want to design an analog frontend with a bandwidth of 10 MHz for ADC input. This circuit will form the amplifier part.

What is the detailed analysis of the circuit in this picture?

Let me explain the circuit as far as I understand. I would be glad if you correct both the points I do not understand and my mistakes.

Input voltage is adjusted with the original RP1.1 potentiometer.
The C1 capacitor required for AC coupling and together with the ground resistance (R1 47k) creates a "high pass filter". The purpose here is to prevent noise frequencies (0.33 Hz) from passing. From there it was connected to the noninverting pin of the opamp.
R3 and R2 resistors that determine the gain were connected to the inverting pin.

What I don't understand here is the C2 (47uF) capacitor. I don't know what this capacitor does.

Also, R4 and C3 components are circuit elements that need to be explained for me.


texts: Measuring the Internal Resistance of an Electrolytic Capacitor

texts:
I was wondering if its possible to measure internal resistance of a capacitor from a DC circuit using the below formula and method.

\$\ V=V_0e^{\frac{-t}{\tau}}\$

\$\ lnV=-1/\tau\ *t + ln V_0\$

Using a graph to determine the gradient can I then solve for \$\tau\\\$?

From there I was thinking of using total resistance R and subtracting the resistance of the resistors to find internal resistance.

\$\ R= \frac{\tau}{C}\$

\$\ \frac{1}{R}= \frac{1}{R_{resistor}}+\frac{1}{R_{Internal}}\$

Will this method give me valid results?


texts: Source synchronous interfacing. How to sample serial data

texts:
I'm stuck with a sampling issue. I'm trying to sample a serial data line coming from a sensor.
Basically, I send clk (max. 5Mhz) from the FPGA to the sensor, and then I receive the data bits from the sensor (1 bit per clock cycle).

I have written (in Verilog) a module to send a 5Mhz clk to the sensor, but I don't know how to sample a 5Mhz serial data line with a 50Mhz FPGA.

Any ideas?


texts: How can I drive an LC tank circuit to get a nice and clean sine wave?

texts:
As advised by Andy in this post, I constructed single loop transmit and receive coils:

I use this circuit to transmit a powerful field:

The Tx signal has a large spike that is reflected in the Rx signal, too:

How can I drive the Tx tank circuit to get a nice and clean sine wave?


texts: Is a DVD sensor a photodiode or an array of them?

texts:
Is a DVD sensor just a photodiode or an array of them?

I need to know if it is a CMOS with an array of them or just a single sensor.


texts: Shift left followed by round for performing: y=x+cz in hardware

texts:
I wan't to implement a simple arithmetic, given the following (say 8 bits) integers x,y,z
$$y = x + c z$$
where 'c' is a fraction of a power of 2: 2^-1, 2^-2, 2^-3,...

I was adviced to perform the following:

1) shift left x by the power of c (if c=2^-3, then shift left 3 times)

2) add z

3) shift right the result c times again to obtain the final answer

Why is it better than simply performing shift right to z according to c and then adding x?

Thanks


texts: Best way to switch electronically between different voltage sources for measurement

texts:
I am trying to make a circuit that can measure voltage between three different terminals. The Voltage under measurement can range upto 0 to 1500V.
As you can see in the circuit, I want to Measure the Voltage across Terminal 1 and Gnd (Terminal 3), Terminal 1 and terminal 2 and also switch and measure the Voltage across Terminal 2 and Gnd (Terminal 3). I found reed relays but they are way too expensive for the rated voltage. Any other Cheaper suggestion for this application? is it also possible to do with mosfets?
EDIT: This is the circuit diagram of the measuring setup


texts: Increasing cache line size when cache and RAM don't work asynchrounsly

texts:
I want to improve a processor design. It has a simple directly mapped cache, and I want to improve the hit rate. I've been working on increasing the cache line size from one data word to four, but since all accesses to the cache and RAM are currently blocking (I mean that the operation of the whole CPU is blocked when it's waiting for a data read or write), I think that I am merely shifting the delay that is needed to access the RAM to the moment that any data in the same cacheline is needed. If I am correct, this won't make the processor execute any faster (and probably only slower, since more data is transferred between cache and RAM).

Is this the case or am I overlooking something?


texts: Can I replace p6ke110a with 1N4148 in my smps circuit

texts: I am building an smps circuit using TNY280. I would like to know if I can use 1N4148 in place of p6ke110a to protect TNY280 from flyback voltage from transformer as they both have almost same specs


texts: Replace potentiometer with digital version (Speakers)

texts:
I am trying to get my PC speakers to be controlled by my arduino. I've taken apart the control and it seems very straight forward, just need a few questions about subbing the manual pots for digital ones.

Volume circuit looks like this (R/L for right and left channels)

    R Aux -> Pot Leg 1 -> Out Pot Leg 3 -> R Audio Out
    L Aux -> Pot Leg 2 -> Out Pot Leg 4 -> L Audio Out

All other POT contacts are grounded and it's a B10K pot.

Why are these split by channel? Isn't a standard 3 terminal pot the same? Or is it to keep the audio in R and L channel's seperate?

Is there any weird issue I'll run into subbing out this pot for a digital one? Or would another 4/6 contact digital 10K pot do just fine? Are their power requirements (voltage/heat dissipation) i need to watch out for?

Thank you! Just learning speaker wiring.


texts: 74193 stops working after compilation on another PC (QUARTUS)

texts:
I got a Quartus project with a mod 22 counter using 74193 from a friend. It works just fine when I run a simulation before a compilation on my PC, but after I compile it on my PC, it stops working correctly. Is it possible to check what settings are different during compilation?

Before compilation

After compilation on my PC


texts: Why linearise around an equilibrium point?

texts:
In the control theory dealt in class I was taught to always linearise a nonlinear system around an equilibrium point, i.e., where $$\dot x = 0$$

However, linearization is a Taylor series expansion, so why the equilibrium point in particular? What happens if you don't use it?

I know that if the system is at the equilibrium states then the system is 'unperturbed' and will continue to stay in unperturbed state unless given an external disturbance / excitation / input. If you give an example please use non-zero equilibrium states.


texts:
I want to generate a 10ms timer using ATMEGA32. The crystal used is 8MHz.
Is this calculation correct TCNT0 value is correct.The prescaler value i used is 1024.

is the calculation and the value 78 for TCNT0 is correct?


texts: Discrete time decimation bandwidth expansion

texts:
I have been reading about discrete time decimation in Signal and Systems by A.Oppenheim. The decimation process expands/scales the bandwidth of the original non-decimated signal by N, I have a hard time visualizing/reconciling this because of the relationship X[e^jw]= X[e^jw/N]. It seems as though if you divide w by N the bandwidth would be getting more compacted, not spread out. Can someone please point me in the error of my ways,
Appreciated.


texts: Why do we use a DB9 connector for serial com?

texts: We only use 4 wires (pwr, common, and two data), so why does rs232 use such a big connector?


texts: Prevent current backfeed without power loss

texts:
I have a solar panel and an external power source feeding into a DC converter (U10) that are both used to feed a battery charger (U2):

In a previous design I used 2 schottki diodes to prevent back feeding from solar to U10 and from U10 to solar.

But as the schottky has a voltage drop I would like to use a different solution with as little power loss as possible.

Any tip on how to design this?

Thx!


texts: How to find the peak current and Vswce of this IC - NCV3063

texts:
I need to design a boost converter using this IC. From (7.5V to 16.5V) to 23V. Load current max is 255mA.

I am having some difficulty in understanding some of the design calculation.

How will I calculate the peak current, Ipk and the Vswce parameter?
And moreover, how does the SWC and SWE pin work? Please explain.

  NCV3063


texts: Most common cause of fire in gadget chargers

texts:
Can someone explain some scenarios where laptop/phone chargers causes fire hazards and what circuitry parts actually fails/heats up that much to cause the dangerous and potentially fatal results?

I am curious to what parts of the electronics inside a compact transformer-based charger is most likely to make it dangerous and why.

I am soon done with the first year of electrical engineering in college, and this still perplexes me. We only calculate and design things that works, not the opposite. And it is frustrating not being able to explain why these things can actually cause fires.


texts: How does the shunt mmf in a long-shunt compound DC motor remain the same?

texts: In a circuit model like this, the textbook says that the shunt mmf is the same for no-load and fully loaded conditions of the motor. How is this possible when the armature current (Ia) changes?


texts: ESP 01: Sketch uploading but not running

texts:
I have this ESP8266 I've been trying to get to work with a USB to TTL converter. I can flash the code through the Arduino IDE to the ESP8266 and it supposedly succeeds, but the ESP8266 isn't running the code. If I try to make a Wi-Fi network (to create a webserver), it won't appear, and if I try to print something to the serial log, it won't appear. Here is a Fritzing model of my circuit:

(Note: The pins of my TTL converter are actually GND, CTS, 3V3, TX, RX, and DTR. I wish I could change the text of the Fritzing part I downloaded, but it is what it is.)

Here are the options in the Arduino IDE I used:

Note: I saw this question, but the answer only made it worse (wouldn't upload at all), so I am asking this question.


texts: Multiple transformer windings vs a single winding with a buck converter for dual output power supply?

texts:
I have to create a power supply that has both a 5V output at 1A and a 3.3V output at 0.4A. I was wondering if I should add another winding to my transformer or just make a 5V 1.5A power supply, and then use a small buck converter to drop down the voltage to 3.3V.
I would think using a buck converter is both cheaper and easier, however I am a little worried about the noise adding a high frequency switching component will induce to the circuit.
So I would like to know, which option is cheaper, and will noise become a significant issue if I go with a buck converter?
Additional information: Flyback topology, switched mode power supply.


texts: What is a comprehensive document from STM for PCB design using their STM32F302C8 MCU?

texts:
I have to design a STM32 based PCB and connect it to peripheral sensors that will communicate using 3 Analogue Pins and 5 digital.
I have found documents from STM on oscillator placement and EMC design considerations.
Will these documents contain all that I need or are there any more which will make my job faster?
I am mostly just concerned about this thing blowing up in my face due to the lack of a pull-up or pull-down resistor.


texts: How can I control voltage level on a specific pin in PIC18F? Let's say then I want to send about 0.6V to transistor base. But I cannot use a voltage divider. I need to control output voltage by my PIC18F (PIC18F2525).


texts:
I'm a beginner in electronics, read a few books, have solid understanding of the basics.

I would like to make an LED Screen Project I need some quick advice for.

I want my RGB LED Matrixes to be able to join for bigger size screen and have the same controller sending all the signals for each matrix module.

Processor was between FPGA and Xcore by Xmos. I chose the xCore for the C-like programming ability out of box.

How can I put this matrix together for them to be addressable (rgbs) LEDs?

Is there a library for processing video, images to this LED Matrix even if it's separated in modules to still be able to send information from one controller to each matrix/module?

I'm having a hard time beginning, because I mostly find Raspberry Pi and Ardunio controlling a few LEDs, some claims thousand. I don't think they control stadium LED screens with Ardunio module, nor with LED strips, I would like a real guide for a professional, scalable LED screen?


texts: Drive P channel MOSFET with Arduino, unable to get desired behaviour (LOW pin, MOSFET ON)

texts:
After hours of building a circuit on a perfboard, I discovered that Vgs is not easy with P-MOSFETs.
After searching I figured out that I need to use either a N-MOSFET or a BJT (NPN) to bring the source voltage to the gate in order to turn the MOSFET OFF.

It is very important to me that when the Arduino pin is LOW, the MOSFET stays ON. This is to provide current to the Arduino itself if the system behind has no power left (not relevant to the circuit here).

Because of this limitation, circuits like this:

will turn off the MOSFET when arduino input is LOW. (To my understanding)
I have tried to provide the voltage to the gate using an N-MOSFET on the HIGH side, see this screenshot (apologies for not using a proper circuit software):

Despite having the N-MOSFET shown as in saturation, only 3.32V gets on it's source, not enough to trigger fully the P-MOSFET's gate.

My short knowledge of electronics has been beaten, as I cannot wrap my head around this. It would be logical to me that the N-MOSFET would apply the full drain voltage on it's source, given that the gate voltage is high.

While primary interested in a solution for this circuit here, tired of spending time on this, an explanation on to why my knowledge is flawed would be welcome.

Thanks for your time, I'll update the post if I am missing something


texts:
I want to use a PMIC chip in my project. As any PMIC, it has a couple of outputs: buck Vout, and an LDO out. The PMIC is operated over the I2C bus. The MCU acts as the host device and runs on Vout, so I have the I2C lines from my MCU pulled up to Vout.
The LDO output is controllable, in the interest of saving power and not losing quiescent current, I would like to use the LDO output to power another slave device. Here is a block diagram of how I would like to connect the MCU and slave device:

This slave device also operates over I2C. I only have one I2C bus, so I can  only connect the device on that bus. Assuming the voltage levels are the same on Vout and VLDO, I am not sure the configuration I have will completely turn off the device, since the lines are still remain pulled up to Vout. Is this the right way to implement it? If not, how can I correctly configure it? In case my LDO and Buck outputs are not the same, how can this be connected?


texts:
My Raspberryπ has a serial console in its GPIOs. My logic level UART converter has four pins: GND, RXD, TXD and 3V3. It works without connecting 3V3.

Why should I want to connect the 3V3 pin to the Raspberryπ?


texts: How can I actively provoke data rot on a storage unit?

texts:
For a project, I am looking to deliberately provoke data rot on a storage unit (e.g., a hard drive or a flash drive). I understand that most modern OSes and filesystems as well as hardware have countermeasures in place to prevent data corruption. How could I set up a simple system such that one could see visible corruption on, e.g., image files within a week?
I am trying to provoke actual physical data rot.


texts:
These small LGA16 parts needed replacing:

Desoldered them with heat gun, cleaned with acetone, put new parts into place, fixed them with this sticky aluminum tape, applied flux and put them to the oven:

upped the temperature a bit on the soaking part of the profile and baked them. They all came out bad (brand new parts used). Tried doing them manually with the heat gun as usual in an attempt to fix any non contacting pads without any luck.
What would the main culprit be here, upping the temp a bit from a 204 deg C max to 212 max, with the max reached some 10-15 seconds faster, or that aluminum foil ?
------------------EDIT-----------------
In response to the comments - I should have mentioned that all else besides the two changes are my standard procedures / tools that I have been using, mostly successfully. A third culprit comes to mind: the bag with parts got unsealed some 30 hours before I did the work. I did not left it open but neither did I reseal it. The humidity indicators inside looked fine after those 30h, parts being of MSL 3.
--------------------EDIT2----------------

What do you mean by "they all came out bad"? – Justin 20 hours ago

Actually, this particular batch of 5 do not respond on I2C.
Usually when they turn bad it means their sensing capability is diminished
--------------------EDIT3----------------
After many more hours of frustration I have (likely) discovered some more subtleties of reworking; have not used the oven but just the hot air gun
It seems when I only do 185 - 190 deg C just so the solder melts I am getting opens like @Chris Stratton suggested As soon as I go 200+ no mor eopens, but the sensitivity is badly impacted... I am, how should I say, in despair...


texts: why two pair of terminals are used in a shunt?

texts: The working principle of two pair of terminals of a shunt is required here.


texts: Why not use actual switches instead of Relays

texts:
Relays are expensive and have limited lifetime. Choosing a proper relay for a particular application is also important. In other words relays require a bit more of everything when compared to a simple electric switch. So why not instead of using relays, manufacturers somehow couple a small servo to a simple electric switch. Then use it for switching, by controlling the servo. We too can do it (though not perfectly) . What's the reason that relays are so popular and so common for power switching? What's the flaw in using a switch as suggested?

Edit: Using switch can be a one time investment instead of using relays which requires replacement. Also, the cheapest servo motor(premade) can do the work for us. Main idea is lifetime, which I think, may be a reason enough! Also, if this setup is fabricated there may be less chances of individual part failures.


texts: Opinion on design changes for Latch circuit

texts:
So just to give some background I've designed a circuit to suit the following task.

12V DC Motor moving a carriage up and down a column
2 'End stop' magnets, active-low hall effect sensor attached to carriage
Motor must move continuously to one end stop, change direction etc.

The physical motor/end stop construction cannot be changed in anyway, the motor and hall effect sensor are part of a pre-existing product

This is just a one off test rig but as I'm relatively inexperienced in circuit design I can almost guarantee I've done it the most awkward/overly complex way. I was hoping that people could provide maybe some insight into design changes

Personally I don't like my 'momentary to latch' circuit using the PNP, relay and inverters but was unsure of another way of doing so and this is the area I'd like critique on mostly. I got some input from another more experienced colleague who mentioned analogue switches or potentially using optocouplers.

Any input is appreciated, thanks.


texts: I am trying to Identify this SMD component, Pin 1 GND , 2-VCC, 3-? Out I can identify top letter is C , Bottom is G11, I think it might be a transistor but it odd being connected to the main power rail. Part is from bremshey bike monitor. Unfortunately  other identification is blocked out because it's burned out.


texts: Range of RF module (and antennae) given then "sensitivity" in dBm?

texts:
Is there some simple (maybe somewhat rough, i.e. not very accurate) way to determine the farthest distance that an RF module pair (i.e. an RX-TX, or pair of TRX's) can communicate reliably, given the "sensitivity" (in dBm) ratings of the modules ?

Also, can someone explain the difference & significance of --

sensitivity of the module itself
sensitivity of the antenna
and how the RX + TX RF properties interact.

Edited:
Here are the Sparkful RX/TX module pair which we could use as reference.

transmitter and receiver

While I might end up using different modules, I wanted to know how to figure out the distance for which they work, in clear-line-of-sight.

Manufacturers or vendors (especially hobby electronics vendors) sometimes do provide the information on max. distance, but I've rarely found it to be true. Even in clear-line-of-sight.

Also, is there some rough yard-stick by which one could estimate the drop in effective communication distance, with introduction of obstructions, s.a. concrete walls ? Something like, for every concrete wall, reduce the power by 50% !


texts: Apparent lack of rigor in Phasor domain analysis of steady state AC circuits

texts:
so I have encountered a hitch in my understanding of analyzing steady state AC circuits. I have looked everywhere for the answer to my question and I can find nothing. Usually when we analyze ss AC circ. we convert everything into the "Phasor domain." Now I have heard people call it Phasor domain and Frequency domain. Well I used the Fourier transform to derive the inductive and capacitive reactances just by simply taking the transform of:

\$I = C\frac{dv}{dt}\$ and \$V = L\frac{di}{dt}\$.

Okay so that makes sense we want to analyze the circuit in the frequency domain so we use the Fourier transform to do that. But what I never see justified is how you can take a time domain source such as cos(w0t+phi) and suddenly just write it as a Phasor such as He^(jphi), where H is the magnitude. I always see the argument that you can write cosine as the real part of a complex exponential and since the frequency does not change you can just ignore it and then you get a phasor. That is not very rigorous and it bothers me. I feel like I should be able to take a Fourier transform of the source and get a phasor from that when I plug in the condition that w=w0. So I found the Fourier Transform of a phase shifted cosine and when plugging in the above condition I get pie^(jphi). Here is the derivation here,https://imgur.com/a/QNU8lt4. In the image they used a minus phi but if you use a plus phi then you get pie^(jphi). The problem is this almost works but there is a factor of PI in there which as we know when we write the phasor form of a cosine there is no pi in the mag unless we put one there on purpose. Does anyone know where my thinking is going a miss? This has been driving me insane. Also sorry for the lack of TEX use, I am not familiar and its late and I needed to get this question out there. Thank you!


texts: What is the use of the transistor in this circuit?

texts: This is an LED driver circuit, but what is the use of the transistor in it?


texts: No debug information in Keil when I try to simulate a STM32F103C6 in proteus ISIS

texts:
how are you?. I need to simulate a project I what I'm working made with keil in proteus, Labcenter's people enfasizes in that those simulations needs both the .elf file and the dwarf2 file, in Keil with the option --dwarf2 the compiler can generate the dwarf file and giving the extension in the C/C++ and output tab respectively but when I run the simulation in proteus then the proteus log shows the following messages:
[ELF] Loading ARM ELF file '..\..\..\..\Desktop\Proyecto\Objects\Luz.elf'. [U61_CM3CORE]

[ELF] No ".debug_line" section, cannot associate addresses to source lines [U61_CM3CORE]

[ELF] No ".debug_info" or ".debug_abbrev" or ".debug_str" section, cannot extract variable location &
`type data [U61_CM3CORE]

So the problem is keil, Can anyone tell me how to generate both files in keil?.
Thanks in advance for the help.


texts: why maximum value at middle of pn junction is negative?

texts: Why the slope of the electric field of N side of the junction is positive and p side is negative.Also, why can't be maximum value be positive i.e on the Positive axis of the Electric field?Please explain.Thanks in advance.


texts:
I'm trying to make use of an Adafruit PCB with an LM3671 on it. Note on the PCB layout how the EN pin is connected to Vin via a 100Ω resistor.

On the 3.3V output, I've connected a 100Ω resistor and then a 1.8V Red LED to provide a load and show that it's working.

When I apply 5V, the LED blinks once and goes off and my power supply starts making a buzzing sound. Testing the LED after shows that it still functional.

Where have I gone wrong?


texts:
I am currently working with ATTiny1634, executing the following code

After executing break statement the program is not exiting from the inner while loop to outer while loop; instead, it jumps to main function.

To test, I removed all the USART functions uart_init, writecommand, transmit, after removing all these function code is working perfectly.

The code works with ATMega16A, but getting problem in ATTiny1634. Why?

int main()
{
    DDRC=1<<DDRC0;
    DDRA|= 1<<PORTA3;
    uart_init();
    sei();
    writecommand("AT");

    writecommand("ATE0");
while (1)

  {
    int8_t t;
    PORTA=1<<PORTA3;
    // controller sleep mode
        if(MCUSR & (1<<WDRF))
        {
            MCUSR&= ~(1<<WDRF);
            WDTCSR|= 1<<WDE;
            WDTCSR= 0x00;
        }
        PORTA=0<<PORTA3;
        set_sleep_mode(SLEEP_MODE_PWR_DOWN); // sleep mode selected
            //PRR=0X75;
            wdt_reset();
            WDTCSR |= 1<<WDE;
            WDTCSR |= (1<<WDIE|1<<WDP3 |1<<WDP0); // ENABLE WATCH DOG TIMER INTERRUPT WITH 8S TIME OUT
        sleep_enable();  //set SE bit
        sei();
        sleep_cpu(); //sleep mode activated

      while (1)
        {
         if(count >=2) // 80S DELAY
           {
            count=0;
            sleep_disable();   // SE bit reset
            WDTCSR|=0<<WDE|0<<WDIE; // disable watch dog timer
            transmit("AT+CFUN=1\r\n");
            _delay_ms(2000);
            clearbuffer(buff);
            clearbuffer(temp_buff);
            _delay_ms(2000);
            break;
           }
         else
          {
            WDTCSR|=1<<WDIE;
            sleep_cpu();
          }
        }

    }

}

The code for writecommand:
    void writecommand(char *q)
    {

    char str[3]="OK";
    char str1[50];
    do
    {
        clearbuffer(str1);
        strcpy(str1,q);

        i=0;
        _delay_ms(10);
        clearbuffer(buff);
        clearbuffer(temp_buff);
        transmit(str1);
        transmit("\r\n");
        _delay_ms(200);
        for(j=10;j>0;j--)
        _delay_ms(10);
        logic();   // my me
        clearbuffer(buff);

    }while(strcmp(str3,str)!=0);

I am using the 8 MHz internal osc and the baud rate in USART is 9600. Other functions are:

void uart_init()
{
    UCSR0B=(1<<TXEN0)|(1<<RXEN0)|(1<<RXCIE0); //transmitter enable,receiver enable,receive complete interrupt enable
    UCSR0C=(1<<UCSZ01)|(1<<UCSZ00);//8 bit data bits
    UBRR0L=51; // baud rate 9600
}
void uart_send(unsigned char ch)
{
    while(!(UCSR0A &(1<<UDRE0)));
    UDR0=ch;
}
void transmit(char *p)
{
    i=0;
    while(*p!='\0')
    {
        uart_send(*p);
        p++;
    }
}
void clearbuffer(char *p)
{
    while(*p!=0)
    {
        *p=' ';
        p++;
    }
}


texts: do the voltage and amperage applied to a motor matter as long as the wattage stays at what its rated for?

texts: I have an electric 180w motor from an electric go cart which currently runs on lead acid batteries but I want to convert it to have a 18650 battery pack for a power supply but I cant find the rated voltage and amperage for the motor I only know that it runs at 180w so can I use whatever voltage and amperage I to power it as long as it is running on 180w?


texts:
Background

I am working on a school project where I have designed a prototype PCB with the core being a STM32F042K6T6 microcontroller. I am using the ST-Link from a Nucleo STM32F401RE card to program it.

Problem

When programming the device with some simple code to light an LED, the LED wouldn't light up. While troubleshooting, I accidentally realized that the LED would light up after a fresh "power on" (without changing code or reprogramming the MCU), simply pulling the power supply and then reconnecting it.

This lead me to believe something was wrong with the reseting of the device after the programming. To test this I started from a shining LED after power-on, and then pressing the reset button for a hardware reset. As suspected the LED would go dark and then not light up again. Then when I disconnect the power and reconnect it again it lights up.

Further observations I reckon might get asked.

The voltage levels of the device seems good, decoupling is placed according to data sheet.
Reset is implemented with external pull up with a 10k resistor to 3.3V and then a button for shorting to ground on reset and a parallel cap of 100 nF down to ground. (This is connected to the NRST pin on the MCU as well as the NRST pin on the programming connector).
The LED is a simple SMD led with a 180 ohms series resistance put on GPIO PB5. (Actually have 3 different status LEDs on the board, and can start them all in code

I have probed the "analog" signal of the reset pin, and to me the signal seems fine, dropping low when I click/hold the reset button. And as the LED turns off when clicking the reset button, I believe it starts to restart the program. However it doesn't seem to fully reinitialize and start executing code from the start of 'main()`? As the code actually works to light the LED after a power-on reset. Therefore the correct instructions seems to have been uploaded to the program memory, but the resets (both while programming and on clicking the reset button) seems to somehow fail to reinitialize the .

Any assistance would be greatly appreciated.


texts: Do AC inverter H bridges ever get driven this way?

texts:
There's a google competition going on at the moment called the little box challenge. It's to design a very efficient AC inverter. Basically the inverter is fed a DC voltage of a few hundred volts and the winning design will be chosen by its ability to produce a 2kW (or 2kVA) output in the most electrically efficient manner. There are a few other criteria to be met but that's the basic challenge and the organizers state that an efficiency greater than 95% is a must.

That's a tall order and it got me thinking about it just as an exercise. I've seen plenty of inverter H bridge designs but they all drive PWM to all four MOSFETs meaning there are 4 transistors contributing to switching losses all the time: -

The top diagram is as I normally read about inverter designs but the lower diagram struck me as a means of cutting switching losses by virtually 2.

I've never seen it before so I thought I'd aske here if anyone else had - maybe there's a "problem" that I don't recognize. Anyway, I decided not to enter the competition if anybody wonders why I'm posting this.

EDIT - just to explain how I think it should work - Q1 and Q2 (using PWM) can generate (after filtering) a "smoothed" voltage that can vary between 0V and +V. To produce the first half cycle of a power AC waveform, Q4 turns on (Q3 off) and Q1/Q2 produced the PWM switching waveforms to make a sinewave from 0degrees to 180. For the 2nd half cycle, Q3 turns on (Q4 off) and Q1/Q2 produces an inverted sinewave voltage using the appropriate PWM timings.

Question:

Is there a problem that I'm unaware of in this type of design - maybe EMC emissions or "it just won't work stupid!"


texts:
I read the Christophe Basso APEC 2011 seminar, about this figure I have one question.
1.) Why RLED,max need to below this equation(Red line), what happen if RLED above this equation(Red line)


texts: Range for raw analog import in PulseView (SigRok)?

texts:
Apologies in advance if I chose the wrong forum - this is mostly a software question; however, I thought it would be irrelevant to most on StackOverflow that don't do electrical engineering, so I hoped I could get an answer here. If not, please advise a more appropriate place where this question can be moved.

I'm using PulseView (sigrok) on Windows 10 installed via:

https://sigrok.org/download/binary/pulseview/pulseview-0.4.1-64bit-static-release-installer.exe

I want to analyse multichannel raw analog (binary) data in PulseView. First problem I had, was not knowing how PulseView interprets multi-channel data - interleaved, or not (that is, channel 1 in its entirety, followed by channel 2 in its entirety).

Eventually, I've made this simple test in Python:

import struct

with open('binfile', 'wb') as f:
  for ix in range(256):
    f.write(struct.pack("=B", ix))

Then, I imported this via Open icon in PulseView/"Import Raw analog data without header..." (remember to set the file filter to "All files", otherwise binfile will not be listed, as only .raw or .bin file extensions are shown by default), and used:

Data format: U8 (8-bit unsigned int)
Number of analog channels: 10
Sample rate (Hz): 0

This imports, and gives this plot (after manually setting all "Vertical Resolution" to 1V/DIV, accessed when you left-click the CH1 etc labels which sit at the left of the tracks):

As it can be seen, when the cursor is over the leftmost sample in the multitrack, the values we get are: -500 mV, -496 mV, -492 mV, -488 mV, -484 mV, -480 mV, -476 mV -- which for me, means that PulseView interpreted the data in binfile, to be interleaved, as in:

byte1|byte2|byte3|...|byte10|byt11|byt12|byt13|.....
  ==
ch1s1|ch2s1|ch3s1|...|ch10s1|ch1s2|ch2s2|ch3s2|.....

So that question is solved (hopefully, unless I interpreted it wrongly)

What I still don't get, is:

Why did PulseView decide to map byte value 0x00 to -500 mV, and byte value 0xFF to 500 mV? In other words, how did it decide on this default range - is this documented anywhere, and can I change the interpreted analog range (in volts)?
When I use Sample rate (Hz): 0, PulseView seemingly choses 10 ms as sample period by default. Why is this number chosen, and is this documented anywhere? (I expect if I enter a proper sampling rate, then I'll get the corresponding sampling period instead).


texts: Do I use a 5V 2A or 3A DC adapter to power my 2m (6.5ft) WS2801 LED strip?

texts:
(Please excuse me if my English is bad)

I recently purchased a 5m LED strip, but I only need to power approximately 2m (6.5ft) of the 5050 RGB LED WS2801 strip, but I'm afraid that a DC power adapter with 2A may not provide enough current, or a 3A or more may damage the LEDs, what do you think I should go for?

Here's a few specs about the 5m LED strip:

Input voltage: DC5V
Current: 3.2A
LED Qty: 32 per meter
Power(W/M):7.68W/M


texts: Minimum components for BJT (edit: or FET) H-Bridge applied to a small 3-6V motor controlled by Arduino

texts:
First, why did he put R3 high--alone: H-Bridge Transistor Smoking?

My real question is about the minimum number of parts. I believe the minimum components for a BJT H-Bridge applied to a small 3-6V motor, controlled by an Arduino, are four of each: transistors, diodes and resistors.

I plan to use two 2N906 (PNP), two 2N3904 (NPN) and four 1kΩ resistors. I chose BJTs because they seem cheaper than MOSFETs.

http://everycircuit.com/circuit/4696275458195456

Edit: Since this question has been downvoted, I recede the BJT constraint.

Can it be done with less components?

I found many poor designs with less parts. For example, this one and this one are missing flyback diodes among other things.


texts:
First conceptually:

Assume you placed two metal electrodes/tags on a fencer's body: one on the torso (large, the lamé), one in the hand (small, the guard).
Equipped with a Capacitive Sensor located at the tip of the attacking fencer, you contact each of the target areas (electrodes/tags) in sequence and measure/calculate the capacitance obtained.
Your goal is to identify which of the parts/electrodes have been touched from differing capacitances. You expect to read different values because both targets feature very different areas/sizes, shapes, locations, and physical characteristics. Indeed you can see a clear difference between touching the lame versus, for example, an area covered with clothing, or indeed direct contact with skin.

Figure 1.

simulate this circuit – Schematic created using CircuitLab

BUT... you obtain very similar values for the Lamé and the Guard: you were expecting larger values for the large electrode, and (slightly) lower values for the small electrode. This is confirmed with a DMM.

Q1- Is this due to parasitic capacitance coupling?

Q2- What are my options to mitigate the effect of coupling? (Connect one or both electrodes to GND, send some Signal DC/AC, through them, etc...).

Q3- I read that placing a capacitor between the lines will prevent DC but will allow AC to pass. Would adding this Cap solve this problem?

Figure 2.

[legend: Capacitance measurements in pF]

More background:

The full circuit (Figure 1.) is composed of a Target fencer and an Attacking fencer. Both fencers carry a weapon. A weapon has a guard and a blade. Both have three identified target areas (tags or electrodes, as above):

1) the target areas are:

i) target 1: the "Lame", (a conductive metal jacket),
ii) target 2: the weapon "Guard" (also metal, a metal shield protecting the hand from direct hits),
iii) any other areas other than i) and ii) (i.e. clothing).

2) Each weapon is linked to a capacitive sensor (Oscillator, MCU) at the end of its tip. When the weapon tip is depressed (outside the scope of this post) the signal sensed at the end of the attacking weapon tip is conveyed to the MCU via the blade line, the capacitance is calculated and the system detects if a target area has been touched.

3) Power sources and Grounds of the two fencers systems are separated (critical). Both fencers stand on the ground. No particular return path to earth is set: target areas/electrodes are connected to their circuit (MCU, bluetooth, etc.). The circuits are DC powered and can be considered isolated from earth.

4) The purpose for sampling numerical capacitance values is only to differentiate between the three target areas: electrode1, electrode2, no electrode/clothing.

5) Figure 2 (above) shows the capacitance readings from contacting four separated target areas: Lame, guard, clothing, non-fencer (ground). Observe the very small difference in average deviation between touch 1 and 2: very similar capacitance levels are obtained suggesting capacitance coupling.

Since very little can be done at the signal level to increase the contrast between the two states, the option envisaged is to further differentiate the signal at inception.

(Note: Amplification via signal processing has been considered, yet amplifying two very similar signals barely solves the issue, notwithstanding the time consumption aspects which make this kind of solution unaffordable in this context).


texts:
I have encountered a few references to Ni-Cr batteries, such as a Charger for NiMH and Ni-Cr batteries. I think it may be a synonym for NiCd. If you can shed any light on this, it would be most welcome. If it is just a synonym for NiCd, how did it come about?

I also found several alibaba listings for "NiCr" batteries. They appeared to just be NiCd, but I am not sure.


texts: Do you have to set the TRIS register when using open collector outputs on Microchip microcontrollers?

texts:
I'm using a dsPIC33FJ series microcontroller from Microchip. It has dedicated open-collector outputs/registers.

I've read the documentation and it is extremely brief. Does setting the ODCx register have precedence over the TRISx registers? Or do I need to configure the TRISx registers to some setting as well when I am in open-collector mode? I don't have the hardware to test this right now.

Thanks,


texts:
It is known that GPS satellites transmit information in the  frequency 1575.42MHz MHz while GLONASS satellites transmit information at the some other 1602.0 MHz.

How come most GNSS module makers say their modules receiving frequency is 1575.42MHz in the specification sheet?

In that case, even though their module supports GLONASS how could it view/read from those satellites when the antenna cannot pick up info sent by GLONASS Satellites?

For examples check these leading manufacturers

http://www.linxtechnologies.com/en/products/gps-modules/tm-gnss-receiver
This module claims to support GLONASS but its suported frequency is 1575.42MHz. So in that case how do we know even by inserting a GLONASS supported antenna, this module will fully make use of it?

Dont we have to use antennas that capture both GLONASS and GPS frequencies with such modules?

Im sorry if the answer is too obvious but these vendors are really confusing us, beginners.


texts:
Given a microcontroller that is running the following code:

volatile bool has_flag = false;

void interrupt(void) //called when an interrupt is received
{
    clear_interrupt_flag(); //clear interrupt flag
    has_flag = true; //signal that we have an interrupt to process
}

int main()
{
    while(1)
    {
        if(has_flag) //if we had an interrupt
        {
            has_flag = false; //clear the interrupt flag
            process(); //process the interrupt
        }
        else
            sleep(); //place the micro to sleep
    }
}

Suppose the if(has_flag) condition evaluates to false and we are about to execute the sleep instruction.  Right before we execute the sleep instruction, we receive an interrupt.  After we leave the interrupt, we execute the sleep instruction.

This execution sequence is not desirable because:

The microcontroller went to sleep instead of waking up and calling process().
The microcontroller may never wake up if no interrupt are thereafter received.
The call to process() is postponed until the next interrupt.

How can the code be written to prevent this race condition from occurring?

Edit

Some microcontrollers, such at the ATMega, have a Sleep enable bit which prevents this condition from occurring (thank you Kvegaoro for pointing this out).  JRoberts offers an example implementation that exemplifies this behavior.

Other micros, such at PIC18s, do not have this bit, and the problem still occurs.  However, these micros are designed such that interrupts can still wake up the core irrespective of whether the global interrupt enable bit is set (thank you supercat for pointing this out).  For such architectures, the solution is to disable global interrupts right before going to sleep.  If an interrupt fires right before executing the sleep instruction, the interrupt handler will not be executed, the core will wake up, and once global interrupts are re-enabled, the interrupt handler will be executed.  In pseudo-code, the implementation would look like this:

int main()
{
    while(1)
    {
        //clear global interrupt enable bit.
        //if the flag tested below is not set, then we enter
        //sleep with the global interrupt bit cleared, which is
        //the intended behavior.
        disable_global_interrupts();

        if(has_flag) //if we had an interrupt
        {
            has_flag = false; //clear the interrupt flag
            enable_global_interrupts();  //set global interrupt enable bit.

            process(); //process the interrupt
        }
        else
            sleep(); //place the micro to sleep
    }
}


texts: Charging Batteries from DC Bike Generator

texts:
I have salvaged a motor from a treadmill to make a stationary bike generator.

Motor Specs:
180 VDC -4500 Rpm 1.3 Hp 6 amp

I mocked up a bike trainer and using the rollers from treadmill and was able to output 100-160 VDC unloaded, and using a 50 cm piece of Nichrome wire I was measuring 20-30 VDC @ 2-3 amps. But the current fluctuates.

I am trying to work out what I would need to safely charge a deep cycle battery which I understand I will need a controller or circuit to reduce voltage and manage battery charging, but not sure what that would look like.

The generator will be placed in a communal space for people to help power the campsite, so it would need to be idiot proof.

Thanks

Edit: 1: Battery hasn't been finalized most probably a 120 Ah 12v AGM Deepcycle Marine battery

2: Disregard what load will be coming off the battery as it should not interfere with what can be put into the battery


texts:
I was checking out my Moulinex electric sandwich maker recently and a question popped into my head. On the reverse side of the maker it says that it takes as input 220-240 volts at 50-60 Hz and it's power consumption is 700 watts. From what I know about electricity this tells me that the current flowing through this device is 700/~220 = 3.18 amperes.
Now this is kind of surprising, since the way I understand sandwich makers work, is they take a current and essentially drive it through a piece of high resistance alloy. Now shouldn't this  high resistance material drop the current in the whole circuit? It certainly can't be as high as 3.18 amperes.


texts: RLC receiver - problem dealing with signal

texts:
Hello I have just build colpitts oscillator, which gave me perfect 500Hz sinusoidal wave. So far so good. Now I would like to receive this wave in second circuit "receiver" and here problems start.
I try to employ parallel RLC oscilator hopping that incoming wave wil resonate and produce output voltage across R. Here is the schematic of receiver:

Values were taken to receive 500Hz according to this formula:

So the resonant frequency is equal to 503 Hz
Scope Output ( Yellow - oscilator output | Blue - received output):

Problems:

On the scope I monitor the received signal and the good news is, there is some small amplitude, noisy sinusoid. Is it the one I wish to receive? I think it is but I am not 100% sure. The freq on scope jumps back and forth from houdrends of hertz to kilohertz. On the flip side hovewer when I turn of osilator the received sin is also gone. So to summarise how to be sure that I received intened signal?
As you can see received signal is small in amplitude and quite noisy. My goal is to clean it and amplify. Any suggestion in this regard, so I can drive a speak for example?
The received signal (blue one on scope) seems to be a little bit out of phase. Is that normal?
Assuming everything is fine and I receive correct signal, how can I calculate what is the range of my oscillator/transmitter. Any reference, text will be appreciated.

UPDATE:
Input impedance calculations for 500hz input signal:
Resistor -> 10k Ohm
Capacitor -> \$\ \frac{-j}{\omega c} = 7*10^-4j\$
Inductor -> \$\ j \omega c = 314 j\$
So the total inpedance -> \$\ \frac{1}{\frac{1}{R} + \frac{1}{Xc} + \frac{1}{Xl}} = 4,89 * 10^{-10} + 7*10^{-4}i\$
Thanks for help :)