texts: What does a 'full 18×16 barrel shifter' mean?

texts:
My practical textbook asks me to design a full 18×16 barrel shifter on paper.
I have tried looking around but cannot seem to figure out what the A×B convention means when describing a barrel shifter.

Online resources describe a barrel shifter in terms of the total number of input/output bits (n) and sometimes also add a max shift capability (k). In most cases I have seen described, n is a power of 2 (2,4,8,16,...) while k is almost always equal to n - 1.

I could simply treat n = 18, k = 16 here and implement a left shift-only, 4 stages of 18 2:1 MUXs each, but that'd be cumbersome and/or incorrect.


texts:
I want to design a bias-T for satellite application where L band RF (950-2150 MHz),10 MHz, and DC will be multiplexed.
I need help in finalizing/selecting the inductor(choke) through which DC (13V/18V,2 amperes) will be passed.
Also what I understood is the inductor must block both L band RF and 10 MHz signal.
Exactly what parameters I should consider while selecting the inductor?


texts: Total inductance of two Parallel aiding inductors each with an inductor in series

texts: what would be the total inductance of this circuit?


texts:
Suppose I have a circuit like the one below. In simulation, at the point of maximum current draw, I measure the current through R1 to be ~-10mA, R18 to be ~28mA, R19 to be ~28mA, R3 to be ~-25mA, and R5 to be -25mA (where positive currents flow to the right).

If I were considering each of these op amps individually, I would design my power supply to be able to deliver at least 28mA to U1 (neglecting quiescent current draw), |28mA|+|-25mA| to U6 (neglecting the bottom branch), and 25mA to U4. However, using simple junction rules, I can see that at the junction at the output of U6, 25mA flows in from the right while 28mA flows out, so therefore the output current need only be 3mA (this is in the low frequency regime, the capacitors are not conducting). This 28mA flows to the left through R18, and at the junction to the left of R18, 10mA flows out, so the op amp needs to supply (or sink) only ~18mA.

Is this the proper approach? How should I properly analyze the output current requirements of my op amps so that I can choose a proper power supply for circuits like this?


texts: What type of equipment can I use to detect object 3d distance?

texts:
I would use a kinect but that's too cumbersome. I want to ditch the camera and the microphones leaving me with the "3d sensor" but what is this mystery sensor even made of? I would use some sort of radar depth detection but that's too finite, I want to view objects more like a camera would with the additional sense of distance. Is this possible?

** EDIT **

Too add a bit more clarity: What I want is a "3d camera" but I don't know what technology is out there for my using. The closest thing I can think of is what Passerby mentioned as the kinect camera: "The depth sensor consists of an infraredlaser projector combined with a monochromeCMOS sensor, which captures video data in 3D under any ambient light conditions."

My target project is to be able to walk around a room with this "3d camera" and have it collect data about the room which I can then use to create a 3d blueprint in .obj form. Color is irrelevant for the first phase of the project.


texts: How to test a MOV with no visible damage

texts:
As far as i know cumulative degradation occurs in a MOV when multiple surges appears in a circuit, A way to minimize this degradation is having multiple MOVs in parallel.
This kind of damage can be internal and so not detectable by visual inspection.

In this situation i can use a digital multimeter to test the MOV for a short circuit between its terminals.
I'm aware  that this test is not 100% precise since a MOV can be damaged and present a open circuit between its terminals.

Taking  MOV  above its breakdown with a high voltage, to see if it conducts and check the clamp voltage  does not seems very safe or practical.

My question is:

Beyond looking for short circuits between the terminals with a multimeter  is there any practical way of testing a MOV (with no physical damage visible) in a PCB?

Thanks


texts: What is the best way to generate a negative supply rail using a microcontroller?

texts:
I need a ±5V symmetrical voltage to power 5 amps, 4 op amps and 1 in amp (TL081 and INA118). I would like to use only the 5V voltage of the microcontroller (an Arduino this case).

Is it possible to use the 5V Arduino output to power the 5 amplifiers
(symmetrically) and one more IC (with only 5V positive) that I will
use?
What is the best way to do this? (Generate a voltage of + 5V and -5V).
I intend to power the Arduino with a 9V battery. Is that too little
for an application similar to that?
If I choose to use a single TL084, instead of 4x TL081. Would that
make a difference?

If you can not do this, what do you suggest?


texts: How do capacitors maintain their charge?

texts:
If a capacitor is connected to a copper circuit and a battery, electrons would travel to one point of the capacitor plate, then a negative charge will build up because of the presence of excess electrons. The plate used is a conductor, right? When the battery is removed, wouldn't the electrons travel trough the copper until the end of the copper wire (because electrons travel easily through conductors, and they repel each other in the capacitor plate)?

(CLOSED) Thanks to everyone. Now I understand


texts: What benefits we have in reduction in clock cycles

texts:
If I implement a function with multiple algorithms but all providing same functionality and measure total number of clock cycles required to execute the program on a MCU platform, what benefits will reduction in clock cycle count will have?

For example algo A for function my_function() requires 1000 CC and Algo B for the same function requires 500 CC. After the execution my system goes to low power mode.

One obvious benefit is that because I have reduced the execution time by 50%, my system will enter low power mode quickly thus improving. However I want to ask that whether reduction in clock cycles itself will save power of transistor switching etc? and can I safely say that it is also reduced by 50%? it not then please explain this as I cannot grasp this idea. Thanks


texts: Can DC gain be smaller than the very low freq. AC gain in this amplifier?

texts:
An amplifier module has a 10Hz low pass filter.

When I obtain the gain vs frequency graph by applying different freq. signals to the inputs I get a consistent plot for the gain. I use a function generator and between 0.001Hz and 100Hz I get very consistent decrease in Bode plot.

But if I apply a constant DC offset to the amplifier inputs, the gain I obtain is lower than the gain at 1Hz. The difference is around 1dB. The 1Hz gain is 1dB more than the DC gain.

If I also apply 0.001Hz the gain is less  comparing to 1Hz.

But if I apply 25mV DC input, the gain is less comparing to 1Hz and 0.001Hz. I would expect max gain at DC inout but it is not.

When I measure DC gain I even tried to take offsets for input and output and subtract them but still it is lower than the gain at 1Hz.

Is it possible DC gain is less than the gain at 1Hz or this is due to measurement error?


texts:
I recently acquired a bunch of vacuum tubes from ebay and I'm in the process of trying to design a simple tester to check the functionality.

Below is what I'm currently thinking about:

I managed to scrape a transformer that was used to output 6V from various input voltages; so I'm inputting 6VAC to get different HVs on the secondary (from 110 to 240VAC).

This would connect to a full bridge rectifier filter capacitor (the switch to the rectifier tube to be tested is an impromptu idea that I got right now). The rectified voltage then goes through a potentiometer to get 200V (on the picture 220 is wrong), 0V (ground) and -20V for the polarization. The rails that come out of the first potentiometer go through other another potentiometer to set the variable voltages (0 - -20V and 0 - 200V). This latter rails will go to pins to be connected to the D.U.T..

I used the voltage dividers because I would like to have at the same time 200V to have a decent plate voltage, a variable bias voltage for the control grid and a variable voltage for the control grid.

I know that the voltage dividers are not exactly the best option but I would like to keep it as simple as possible and is not essential that the device is power efficient. Would this be a feasible idea?


texts:
I've trying make a very simple 3 LED circuit with a red, blue and green LED.

I know my 3v battery will take the path of least resistance and only flow through the red, so I've added resisters to the green and red at 47 and 56ohms respectively, as instructed by this website:

http://led.linear1.org/led.wiz

I also added a 47 to the blue just to try and help it, because you see the blue is still barely lighting.

I don't know what I can do beyond trying to balance their resistances which I thought I had now done properly.

Thanks in advance for the help.


texts:
I am trying to design, and later implement, a Butterworth high-pass filter with a cut-off frequency of 8kHz and a decay rate of 60dB/decade.

For this filter \$ \omega_c = 50265.4824 rad/s\$ (converting from Hz)

So far i have determined the order of the required filter as:

$$order = \frac{\text{desired roll off}}{20dB/decade}$$
$$=\frac{60dB/decade}{20dB/decade} = 3_{rd} \text{ order filter}$$

I will be using this equation for a normalised low pass third order filter:

$$H_{LN}(sL_n)=\frac{a_0}{b_0 +b1SL_n +b_2SL_n^2 +SL_n^3}$$

and i have obtained \$b_n\$ terms from the following table which comes from G.E Carlson signals and linear system analysis:

so we have \$b_0 = 1, b_1 = 2,b_2 = 2\$

Next i want to frequency transform this transfer function to that of a high pass filter so i will replace $$SL_n$$ by $$\frac{\omega _c}{S}$$

with \$ a_0 = b_0 \times G_{DC} = 1 \times 1 = 1\$

resulting in $$HL_n(\frac{\omega_c}{S}) = \frac{1}{1 + \frac{2\omega_c}{S} + \frac{2{\omega_c}^2}{S^2} +\frac{\omega_c^3}{S^3}} $$

I'm a little lost here as we now have \$S^n\$ terms as 1 over in the denominator. To get the form of the transfer function back to normal i got the lowest common denominator which then gives:

$$HL_n(\frac{\omega_c}{S}) = \frac{S^3}{S^3 +2\omega_c S^2 + 2\omega_c ^2 S + \omega_c ^3}$$

Using the Bode plot function in Matlab:

wc = 50265.4824;
num = [1]
den = [1 2*wc 2*wc^2 wc^3]
opts = bodeoptions('cstprefs');
opts.FreqUnits='Hz';
G = tf(num, den)
bode(G,opts), grid;

This is clearly not correct as what is displayed in the magnitude plot is that of a low pass and not of a high pass so i have gone wrong somewhere. Any help would be greatly appreciated!


texts: Input circuit for GPIO of a 3.3v tolerant microcontroller

texts:
The micro controller I'm using detects Low for 0-1.8v and high from 1.9-3.3v.

The level I need to check is if the input if from 0v-5v stay low, 5v-24v go high on the micro-controller pin( above 1.8v).

I cannot use a Voltage divider here as the high range has to work from 5v till 24 while giving an output of 2v-3.3v.

I tried using a basic comparator circuit but here the output becomes Vcc. I need the output to become 2v-3.3v.

Output State needs to be digital and not analog.
EG:
    0-5v should be LOW and 5v-24v should be HIGH

I have a 3.3v power source for the micocontroller.

How could this be achieved?

Reference attached for comparator.


texts:
I have no skills with electronics, but I can code.
Which kind of hardware I can use to create an electronic scale that runs with Linux? Will Arduino fit this task? Where can I find the sensor to keep track of the weight?

In my application I need to keep track every hours of the weight of a liquid bottle
and store the results into the hardware until I plug an USB pen drive on the board.
I have to detect that and store the data onto the USB pen.

How do I get started with this?


texts: Micron MT25QL512ABB8ESF-0SIT not working after Non Volatile Configuration register setting

texts:
I'm using the STM32H7 Evaluation board. There is an on-chip QSPI DUAL NOR CHIP MT25QL512ABB8ESF-0SIT. After setting up the Non-volatile configurations Register value to 0x89D6 and power cycle, FLASH is not working as expected.
Now When I read Volatile or Non Volatile configuration register, the values are:
NonVolatile Register Value read : 0x5555
Volatile Register value read : 0x55
Expected Values are:
NonVolatile Register Value read : 0x89D6
Volatile Register value read : 0xFF
As per This document, We can make flash in sync by performing a reset operation.
I have tried Hardware RESET and Software RESET, both are not working.
Also, there is mention of XIP reset and Protocol Reset, but not more info on how to perform these Reset
How to perform XIP Reset? Protocol Reset?


texts: How can I emit a (loud) 25 kHz sound wave from a Raspberry Pi?

texts:
I am attempting to emit a 25 kHz ultrasonic square sound wave from my Raspberry Pi. I have used two different kinds of ultrasonic speakers:
https://www.amazon.com/gp/prod uct/B00M2GHG66/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
and
https://www.amazon.com/gp/product/B07RW7ZNB4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I use the standard GPIO library with pulse width modulation, set to 25000 Hz, 50% duty (I have also tried 90% duty). The speakers were plugged directly into the Pi on ground and the PWM output pin 12.
My result: Output is very quiet and distorted. It sounds like someone is screaming.
How can I get a louder, cleaner tone at 25 kHz?


texts: What determines how much current can flow through a 2N2222 A?

texts:
I've been fiddling around with a brushed DC motor, a 2N2222 and an arduino's PWM to get different speeds out of my motor. Now, based on a video tutorial I watched on youtube, It was recommended to put a 1k Ohm resitor between the PWM pin and the base, apparently to protect the arduino in case the transistor screwed up. I did what I was told to do, following this schematic (My power supply is 1.5V and R1 is 1K, not 220)

But the motor would not turn when the microcontroller pin would output 5V ( full duty). So I figured, ights, let me not mess around with my arduino in case that was the problem, so I connected the base, throught the 1k resistor, to the same 1.5V powering the motor...still nothing...put a new 1k resistor...still nothing...so I romoved the 1k Ohm resistor and plugged my base straight to the 1.5v source and the motor started turning.

Can someone please explain to me why that is? From what I've been reading, isn't the voltage at the base what determines the current flowing from the collector to the emmiter? -_- <-- Confused face


texts: Calculating LED current flow in a parallel circuit

texts:
I've created the following circuit for educational purposes. It's basically 2 LEDs in parallel. I've used my multimeter to measure the current and voltage of the various components and noted everything down. The idea was to come up with the formula to calculate the current flowing through the 2 LEDs. I know that the total current will be divided between the 2 LEDs but I'm having trouble calculating everything.

I'm able to use Ohms law for a simple 1 resistor/LED circuit but I'm having trouble understanding how to calculate the current flowing through the 2 LEDs in this circuit. Here's what I did :

Current for the green LED :

Here I attempted to use the basic formula to calculate the current through the green LED, but that obviously doesn't take into account that there is a another LED in parallel.

I = V/R = (5V - 2,065V drop green LED) / 270 = 10.9mA

So this is obviously wrong. I don't know what I calculated here. I guess this would have been valid if only the green LED was present, and the voltage drop would have been 2,065V.

Current for the red LED :

Here I tried to visualize the current flow, so I asssumed that the current flowing through the red LED would have to pass the 2 resistors in series (270 + 100) and used Ohms law again

I = V/R = (5V - 1.863V drop red LED) / 370 = 8,47mA

This is again incorrect but seems to correspond to the current flowing through the green LED. Don't know if this is coincidence.

I've chosen the resistor values randomly just to ensure that the 2 LEDs would be lit. This circuit is just for educational purposes.

The logic behind calculating the current is something I'm currently missing. Any help would be great.


texts: Estimate current produced by an IR photodiode on a typical sunny day

texts: How can I estimate or calculate the current which would be generated by an infra-red photodiode (eg. Osram BPW 34 FAS) on a typical sunny day ?


texts: develop webcamera with battery and memory to SELF RECORDING (Disc Processing System)

texts:
In my studies projects I want to make an camera with

SD memory card or USB mass storage (which is simple)

micro-controller to translate commands (start recording, dump JPEG to SD card to make video, or many JPEG files )

battery supply compatible with camera module and the micro-controller and the SD card supply

please is there any one who can help me with exact details about the schematics and the components list or redirect me to an existing succeeded projects like that
because I am new in electronics and this is in my project studies what I have selected.


texts:
I am working with an STM32 and I am a bit confused about interrupts, specifically the Nested Vectored Interrupts (NVI). As I understand there is a NVI vector (called NVIC) where each interrupt has a priority (sometimes settable), and an address (see page 157 of the ARM reference manual here).

Now I am assuming that for each type of interrupt it is possible to attach a callback function, and I suspect that the attached address to each interrupt is related to the address of the callback.

What exactly is the address attached to a given interrupt? How can I define (in C, say) the callback function for a given interrupt?


texts: DC circuit theory: Equivalent resistance help

texts:
In the given DC circuit, I need to calculate resistance \$R_{2}\$:

if the equivalent resistance between nodes 1 and 2 is \$R_{e}=100 ohm\$

I get the value \$R_{2}=36.36ohm\$

\$R_{1}\$ and \$R_{3}\$ are parallel, \$R_{2}\$ and \$R_{4}\$ are parallel.

Sum of \$R_{1,3}\$ and \$R_{2,4}\$ gives \$R{e}\$.

Is this right?


texts: Two audio amplifiers in series (IKEA symfonisk into powered speakers)

texts:
I am hacking an IKEA symfonisk into being a cheap, Sonos connected amp, but the speakers I would like to wire it into are not passive, but active.

I am just wondering if the fact that there is an amplifier in the sonos speaker, which is sending amplified signal to the amplifier in the powered speaker, will cause issues for the speaker and potentially result in damage.

Each Sonos speaker actually has two channels (high and low frequencies) so I would also like to sum those into one signal for each speaker.

Would something like the diagram below work?


texts: I2C slave device address bouncing around


texts: ESD protection for power lines using capacitors

texts:
I heard that a capacitor can protect a DC power line from a transient voltages by ESD event. Unfortunately I don't understand how it works in detail. It would be appreciated if someone could answer the following questions.

For the questions I selected an example product whose specs are 0.01uF, 25V.

(1) basic principle
The transient voltage is bypassed by the capacitor. This protection works for either positive or negative transient. A negative transient voltage is bypassed from GND to VCC through the capacitor so that the potential difference between VCC and GND remains small. Am I correct?

(2) maximum voltage that a capacitor withstands
The example product has a voltage rating of 25V. This would mean that the capacitor can withstand up to 25V. Then is it possible for the product to protect power lines from a 8kV voltage peak?

(3) resulting voltage on the power line
TVS diodes have a rating called clamping voltage. For a capacitor can you assume that the clamping voltage is just the DC power voltage?

(4) Would such capacitor protect 3.3V DC power line successfully against any kind of ESD events that include human body model, charged device model?


texts: interference proof voltage regulated current source

texts:
I want to dim some LEDs, using the PWM output from a microcontroller. There are some more LEDs than in the schematic, already wired, so that they need nearly 12 V to give maximum light at about 50 mA.

The power adapter will give 12 V so I needed to minimize the voltage drop in the reference resistor R22. This is done with the voltage divider R24,R25. The 0 .. 5 V control voltage, generated by the uC's PWM is set down to approximately 0 .. 120 mV on R25.

Problem 1:
For lower voltages, the LED's brightness won't be stable. When e.g. switching a devices with larger power consumptions near the circuit, the LEDs will flash very bright. I think this is a current induced somewhere in the regulation circuit and I will have to think about some filter.

Problem 2:
When e.g. switching the status LED15 on, the brightness of the LED array is reduced for the whole time LED15 is on. This is a problem, I don't understand. The 5 V supply is a power supply for laboratory use. It shows a bigger current consumption when the status LED is on, but the displayed voltage does not change up to the digit for 0.1 µV. I don't think, there is no voltage glitch, but it should be stable at the same voltage as before after some time. But the LEDs are constantly darker when the status LED is on.

The question(s): (1) Does anyone find an explanation for the brightness change, when the status LED is on? And (2) do you know of approaches to make such a regulation circuit more EMI resistant?

Edit: I uploaded an erroneous schematic. The voltage divider is connected wrong. Added the correct schematic.

The correct schematic:


texts: Am I measuring the Op-amp MCP6004 IC output voltage correctly using Arduino

texts:
Right now I am testing an MCP6004 Op-amp IC. A sensor in my main circuit going to give me a signal in the range 0-0.5 V max. So, I want to amplify this in the 0-5V range so that my Arduino reads it accurately.
Now I want to test my op-amp, Arduino measurement accuracy, etc. so I did a trial test.
In this, I generated a low voltage test signal (generated from Arduino PWM) reading 0.5 V. The op-amp receives this signal and amplifies this in the 0-5V range so that my Arduino able to measure this signal.
The voltage gain circuit I have used is:

Case1:

R1 = 90k, R2 = 220
IC supply: Vdd = 4.97 V
Output: Vin = 0.5 V, Vop = 3.54 V

Scope: blue is input, yellow is output

Case2:

R1 = 90k, R2 = 10k
IC supply: Vdd = 4.97 V
Output: Vin = 0.5 V, Vop = 0.56 V

Scope: blue is input, yellow is output

My basic questions:

My actual voltage is totally different and very little compared to the theoretical gain.
Am I measuring the output signal correctly? That is, taking the average value?
How do I measure such a signal in the Arduino? I mean, it is a PWM signal and we need to consider the signal frequency. I did 100 samples average approach, and as expected, it gives way different value.
Am I doing something wrong?

Update: based on below-accepted answer,
Case3:

R1 = 100k, R2 = 10k
IC supply: Vdd = 4.97 V
Output: Vin = constant 0.2 V from a potention bridge, Vop = 2.72 V


texts:
From the schematic provided for DS3234:

It can be seen that the RESET pin is active low, and is connected to unit that provides Vcc. However, if power is disconnected and only Vbat is left, this would mean that RESET pin would be left floating? Wouldn't this configuration render the Vbat useless, as it might not even keep the time?

Furthermore, if I do not plan to do hardware reset, would it be wise to connect RESET pin just to Vbat, to ensure that it is always high until battery drains?


texts: Oversampling, additional bits and a thermistor

texts:
Say we have a ten bit ADC (MSP430G2433) and a thermistor. We have the problem that two temperature measurements are too far apart, whilst the temperature has barely changed. So, we take more measurements in rapid succession, average them and we get closer values. So far, so good.

Now, take the following paper:
https://www.silabs.com/documents/public/application-notes/an118.pdf

This paper explains that if we first sampled at one 1 Hz, and then increase to 256 Hz, we get four additional bits, assuming that the noise is white noise.

Now, we sample once per minute and we used to take 8 samples. Say now, that we increase the sample rate so that we have 64 samples, but we take those samples within a second (ADC lies dormant for 59 seconds, then takes 64 samples, etcetera).

Can we now say that we have gained 3 bits?


texts: Routing Differential Lines vs PCB Fabrication Constraints

texts:
I'm in front of a big question. I need to route 90 Ohms differential lines for a USB 2.0 Project.
I understand how to use tools like Saturn PCB Design to give me the correct spacing and lines width.

But it seems difficult to achieve fabrication constraints, for example with Eurocircuits :

I can't route these lines with basic technology settings (0.15mm) ? Although i can route larger lines, i can't use >1mm widths on some integrated circuits.
Thank's to help me to understand how to achieve the best compromise between pcb layout constraints and signal integrity requirements.
Adrien


texts: Is this a reasonable setup for terminating and protecting an RS-485 transciever?

texts:
I'm working on a design where an RS-485 transceiver IC is connected to a Cat5e cable, hopefully at 96k baud at a distance of up to 150m. I'd like to offer some protection in the design, but I've never really worked with RS-485 or TVS diodes, so I'm looking for some reassurance and advice around the protection implementation.

I'm using a MaxLinear SP485EEN-L/TR RS-485 transceiver. The TPD1E1B04 TVS diodes have a VBRF of 6.4V and VRWM of ±3.6V.

The data is sent over one of the twisted pairs. Another pin on the RJ45 will provide a ground reference to the other side, and the shield will be grounded.

My thoughts in the design above are as follows:

The receiving end will have a matching protection and termination design, the only difference being that IC1 will be configured as a receiver (RE and DE tied to ground, RO outputting data).
The termination resistor values (R3, R4, R5) were chosen fairly arbitrarily based on the five or six different conflicting examples I found online.
R6 and R7 are intended to offer some minimal current limitation in the case of a short, and act as fuses for high voltage shorts (e.g. short to mains in a catastrophic failure scenario). With 10R on each side, I devalued the usually-specified value of R3 by 20R.
R6 and R7 plus the others on the receiving side might help resolve the impedance mismatch between the RS-485 driver (expecting 120R) and the Cat5e cable (which I understand is 100R). Probably won't matter too much at 96k baud though.
The positive and negative TLP curves of the TVS diodes show no significant conduction until around 6.3V, which should be sufficient to protect IC1 but shouldn't trigger until there's an actual overvoltage.
I wasn't sure whether to leave the RO pin on the SP485 IC floating, since it's unused on this side of the circuit. Same for DI on the receiving side. I couldn't see anything in the datasheet that specified this, or showed what the IO circuitry looked like. I'll likely include pads for resistors on both, but mark them as DNP, unless someone has more info to offer.

Does this design seem sensible? Any major mistakes? Are there any improvements that can be made?


texts: Relay Driver with 24VDC Relay.... Zener diode?

texts:
I am part of a physics project group, and we are trying to design a relay driver.

Our Relay is rated at 24VDC (it is a Tyco Electronics 1432826-1). What zener diode (or regular diode if that would work better) would work best as a flywheel diode and why? Our Vin is also variable.

We are basing the setup off of this picture

Although, of course the zener diode and 9V are incorrect.


texts: Superheterodyne and intermodulation products: understanding f_RF-f_LO Graph

texts:
While studying superheterodyne-based spectrum analyzers I ran into the concept of intermodulation products explained through a \$f_{RF}-f_{LO}\$ graph.

If it's not clear enough, the dashed lines are simply references \$f_{RF}=kf_{LO}\$ (\$k=1,2\$), while the others are \$f_{RF}=nf_{LO}\pm f_{IF}\$. \$f_{IF}\$ is the intermediate frequency of the system, at which the output of the mixer is filtered; \$f_{RF}\$ is the frequency of the input radio frequency signal; \$f_{LO}\$ is the variable frequency of the local oscillator.\$f_{LO}\$ is chosen in such a way that \$f_{LO} - f_{RF} = f_{IF}\$, so \$f_{RF,max} < f_{LO,min}\$ must hold: in the example, \$f_{RF} \in [0, 3]\, GHz\$ and \$f_{LO} \in [3, 6]\, GHz\$. No problem so far.

Then my lecturer said "if we set a fixed \$f_{LO}\$, then we have more than one curve at \$f_{IF}\$ output". That is true, of course, because \$f_{RF}=nf_{LO}\pm f_{IF}\$ holds and we get \$f_{IF}=\pm (f_{RF} - nf_{LO})\$. What I don't understand is the fact that to me the only segment that matters is the one that projects \$f_{LO}\$ in the range \$f_{RF} \in [0, 3]\, GHz\$ (so, the one marked as \$1-\$ in the picture), since we can suppose to provide a 3 GHz bandwidth spectrum analyzer with a signal that resides in that frequency range (I guess...). That would make more sense to me if we considered not only \$f_{RF}\$, but also the \$mf_{RF}\$ components of the mixer output, so that we could obtain \$f_{RF}=\frac{1}{m}(nf_{LO}\pm f_{IF})\$ in the spectrum analyzer range.

Of course, that doesn't make much sense, otherwise there would be no intermodulation products affecting the measurement. Where am I wrong?


texts:
I have no background in electrical engineering so please bear with me.

I want to create a random number generator/displayer using a resistor. My idea is to wire a resistor to an amplifier of some sort and display the signal on an oscilloscope. The idea I have is based on these:

Diagram:

Actual generator:

Closeup of amplifier setup:

Closeup of resistor setup:

Questions

First of all, I am wondering if I over simplified the setup. As stated above, I believe I can simply flow power through the resistor, amplify, and use. Also, the setup of the amplifier confuses me. I've tried Amazon searches for "amplifiers," "signal amplifiers," and "op amp," a term I've heard on vaguely similar questions, but none of them return something similar to the gold box. Furthermore, what are the use and names the three wires and the gray machine connected to the amplifier? In addition, what is the device the resistor is sandwiched between? I assume its the power source but that looks a bit odd. If it is, what is it called or are there any simpler methods to power the variable resistor? Lastly, is the  connecting the amplifier to the oscilloscope a coaxial cable?


texts: Could I replace a diode with a BJT in a pinch?

texts: I'm trying to learn the device physics of these transistors. If I were out of diodes and really needed one to complete my circuit, could I just replace the diode with the emitter and base of a BJT? Or is the idea that BJTs are made of diode junctions just an analogy.


texts: How many hardware PWM pins and ADC on the ATxmega128A1?

texts:
As I mention in another post I am trying to find a microcontroller that can handle a Lynxmotion hexapod. Unfortunately I am stuck with hobby servos so I would like a controller with 18 ADC pins and to generate 18 PWM signals (in hardware as opposed to bit banging). Looking through the datasheet for the ATxmega128A1 it would seem to have what I need but I'm not confident I am interpreting the document correctly.

The way I read it the chip has 8 16-bit timers. Each of 4 of the timers have 4 comparators and each of the other 4 have two for a total of 24 total pins that can generate PWM. It also appears to have 2 ADC with 4 result registers each and 4 way muxing for a total of 32 pins with ADC. The pins for the timers and ADC all appear to be on different ports so there is no clashing amongst them. My question to you is, is this interpretation correct?


texts: Watertight enclosures - what production steps are required to ensure no condensation on the insides?

texts:
Background

We want to waterproof an electronic device and the specifications call for IP-65 protection. To this end, we have selected a sealed polycarbonate box to put the electronics in. The external connectors are reduced to a minimum and we use automotive IP-67 connectors. We tested a few prototypes and they cope with submersion. I'm closing on any remaining issues that may cause water damage in operation.

I'm worried that atmospheric air that gets trapped inside when the device is fully assembled might condense if cooled significantly. Especially if assembly is in mid-summer.

It seems that this problem is tackled in the industry by displacing ("backfilling") the air in the enclosure with nitrogen, helium and/or clean dry air. I don't have any experience with these, but they seem to be expensive operations that only make sense for medium- to large-scale production, when you have the equipment required.

Question

What production technique can be used for small-scale production (10-100s/month) to keep the humidity of the air low enough so that it doesn't condense?

Non-solutions

The device has a display which needs to be visible through the transparent box, so condensation-resistance is a must. Conformal coating alone won't suffice.

The device is battery-powered, so keeping the innards at elevated temperatures is also not an option.

I've read the excellent question about waterproof enclosures and unfortunately the "leaks more on the bottom than the top" strategy cannot be used here. Moreover, its answer specifically assumes "this is not meant for production" :)


texts: What is the thevenin voltage and resistance of the following circuit?

texts: What is the Thevenin voltage and resistance at terminals a,b? Specifically, how do you go about finding these? I tried this problem and I get a Thevenin voltage of 57.6 V and a Thevenin resistance of 6 Ohms.


texts: Operational amplifiers and virtual ground

texts:
Could you physically clarify why we use virtual ground in op amps?
I have seen the argument that since A(open loop gain) tends to infinity, we need the difference in inputs to tend to zero(to maintain a finite output.) Now, this is confusing because aren't the inputs under our control? What would happen if I gave one very large positive and one very large negative input to the op amp?


texts:
I am trying to build my own RGB + WW + CW led with 5050 leds and to make a prototype I bought some leds.
I have RGB leds and regular white ones, the RGB are kind of dimmed at the voltage from the next datasheet, but the white ones are really bright. I use my lab power supply and when i power the white leds at 2.9V, it draws 80mA, if i use 3.2V like the datasheet suggests, it draws around 150mA and at 3.6V (maximum from datasheet), it draws about 500mA
I connect all 3 pins to have the 3 leds together.
Am i doing something wrong because i can't understand why it uses this much power
Datasheet:
https://www.iled.com/class/INNOVAEditor/assets/YeniDatasheets/4050-4055-4057.pdf


texts: How does a GFCI breaker protect me if my device has no connection to ground?

texts: I use a hairdryer with a 2-prong US plug (no ground).  Suppose I plug it into a GFCI-protected outlet and drop it into a sink full of water.  Will the GFCI still trip even though my hairdryer doesn't have a 3-prong (with ground) plug?


texts:
My light switches at home are connected to a circuit board. The light switches themselves are push buttons connected to it. The circuit board is in turn connected with 3 wires (black, yellow, red) leading to another circuit board controlling an array of relays which switch the mains power to the lights. All circuit boards are connected to eachother with those 3 wires.

With a multimeter I found black to be GND, yellow around 13.3 VDC (it dips to 13 when push button is pressed), and red a steady 13V.

I couldn't find any serial protocols with 3 wires and those voltages. I thought I could search the correct adapter or circuit board needed, to ultimately hook up a raspberry pi / arduino to those 3 wires and send whatever serial data to control my lights.

I've looked into logic analyzers, osciloscopes, icsp, avr's, ... I need a little guidance in what the next step should be.

( )


texts: What will be the steady state Charge distribution of given configuration- battery vs capacitor

texts:
I was try to figure it out what should be the charge distribution over the spherical conductor of radius R (in figure below) in following two configurations-
Assumptions
length of wire (l) connecting battery (capacitor) to spherical conductor is very very long , wire and battery are ideal and initially charge on spherical conductor is zero(before closing of switch)
1.in first case ,only  one end of charged capacitor is connected to the spherical conductor
2.in second case, only one plate of battery is connected to spherical conductor
In first case(capacitor)
as soon as switch closes  distribution of charges started until (sphere + plate of capacitor ) becomes equipotential and this distribution causes a New potential difference between the plates!
But when we apply same logic for second case (battery) - similar to above there would be a new potential difference between the plates but it contradict the fact that potential difference between the plates of an ideal battery is constant
On the other hand  if we keep voltage difference between the plates of battery constant then it implies that there would be no charge distribution even if we closed the switch , but isn't it again contradict the fact that conductor connected to same wire should be at constant potential (if current is Zero)?
Can anyone suggest how would distribution takes place in both cases at steady State?


texts: Battery voltage increasing while measuring (NiMH)

texts:
I was going through conditioning for a NiMH battery pack (12 x 1.2V, 1500mAh cell) and decided to check the cell voltages. I noticed that the measured voltage, with a multimeter, increased over time. 0.001V change noticeable over periods of about 10-15s. Nothing serious, it was a minor voltage increase, I'm just curious as to the mechanism (maybe also use this phenomena?).
   Here are the voltage numbers per cell; I measured it three times and the voltage seemed to peak about 1.557V.
  So, any thoughts?


texts: Polar pattern of typical speakers and microphones found in smartphones

texts:
I'm interested in knowing how is the directivity of the typical microphones and loudspeakers found in smartphones and tablets affected as they operate in the near ultrasound region (18-21 kHz). Near ultrasound region smartphone's transducers compliance has been recently added to android OS so that manufacturers can rate their devices according to whether they have this feature or not (see). I've been doing some research and I've found that nowadays most used microphones are MEMS. I would like to know:

How does the directivity behaves in these transducers even though the only available data belong to transducers not yet inside the smartphone case?
What is the manufacturing technology of smartphones' speakers?
What is the diameter of the microphone's and speakers diaphragm ?


texts:
I've got an older Tektronix 2430 100MHz oscilloscope. The older probes are "coded" and according to the manual are supposed to automatically select the proper scale based on the probe type. My last original probe just broke, so I ordered some inexpensive generic replacements. These have a 1x/10x switch on them to select the attenuation built into the probe. Obviously, the 'scope doesn't know anything about the generic probes and always defaults to 1x mode.

Thus, when trying to use the 400mV P-P 1 MHz square wave for calibration it shows up on the display as 40mV P-P (10% of actual value).

Normally, there is an attenuation setting on the 'scope itself to get the scaling right for display, but this this one is either automatic-only or there is a really cryptic setting that I can't find... Sure, I could always do the 1:10 conversion in my head, but it would be more fun to build something that fakes the 'scope out.

Question: Does anybody know how this "coding" works so I can fake it out and make the 'scope think that the probe is a 10x probe all of the time?

Images below for your reference. Thanks for your help!

Connection on 'scope:

Genuine Tek probe (P6131)

Generic replacement probe


texts:
I have been reading and watching TI's material on EMI input filter design, and I have a few questions.
My basic question is "How do you select the component values for your EMI input filter?" The specific application I am designing a filter for is a 24V, 120W flyback converter in the consumer electronics market.
Next, I will detail what I have learned.
The input EMI filter has 4 main components: Common-Mode choke, X-Cap, Y-Cap, and Filter Inductor.
The CM Choke and Y-Caps are in charge of attenuating the common-mode noise, while the Y-cap and Filter inductor are in charge of attenuating the differential-mode noise.
I believe that the common-mode choke is first selected based on its attenuation curve and what you think the the trouble frequencies will be. You then verify this choice experimentally.
I believe the X-Cap choice is based on power consumption and power factor (according to post linked below)?
X capacitor selection for SMPS power supply
I will admit that I am not sure how to calculate the power consumption of a capacitor in this context.
TI's application notes on the filter inductor put it in the context of a CLC filter, which is confusing because I thought we chose the input/smoothing capacitor value based on the input power and not the required attenuation.
My design (and the reference designs I am using) does not feature any Y-Caps because the line cord does not have an earth-ground connection prong.
Best,
Basically, I just need some help on how to initially determine the values for these components.


texts: Displaying image on Tianma LCD + Controller Board

texts:
I want to wire up this board but I don't think I have the proper equipment for it. It's a Tianma LCD with a controller board that is displayed below. It's TM035KDH03.

Here's what it comes with:

Need help powering this up. If anyone has any separate documentation, that'll also be helpful.


texts: What are the various 'properties' of a diode?

texts:
I have come across various properties of a diode, phrased differently in different places (product sheet, everycircuit, etc.). For example:

The wavelength is the simplest and that is the color of light for the LED. What about the others though:

Voltage: 2V --> Is this the same thing as the "Forward voltage"? Does this mean if the Voltage is under 2V then current will not flow through this component? Does this also mean, that the voltage drop across this component will be 2V?
Current 20 mA --> Is this the same thing as "Forward current"? Is this the minimum amount of current required to flow through the LED to make it 'turn on' (and is that 'fully powered', or just slightly 'turned on'?)
What does the junction capacitance mean?
What does the ohmic resistance mean?
What does the emissions coefficient mean?
What does the saturation current mean?
Finally, are there any additional 'properties' of a diode component that isn't mentioned here?


texts: Recently I am studying about Phase Locked Loop. My professor said that it is an amazing device with a variety of application. I understood the basic working of a PLL. But I couldn't appreciate his statement. Can anybody make me understand it's operation by giving a practical example..?


texts:
I have a 30A 5-30V Single Brushed DC motor driver that will be used with a 12V 30A gear motor.

I have a MegaWatt 36 Amp 12 Volt 13.8V DC Regulated Power Supply that I wanted to use for the driver pwr source. But, I just realized the driver docs say to ALWAYS use a battery as a power source if an inductive load is used.

The docs say that a battery must be used in parallel with the power supply to protect the driver against possible flowback when the motor is stopped.

My question is: can I use a 12V car battery, and simply wire the power supply and motor driver to it, then set pwr supply output to 13.5V? The pwr supply would always remain ON.


texts: Using Multiple Taps on Transformer with Shared 0V

texts:
I have a multiple winding / multiple tap transformer and I need to know if I can use the 0V tap for the taps on the same winding. So the transformer is 320-0-60-320, and I need to combine the 320-0-320 into a full wave restive load to get around 430V DC, but then I also need to get the 60-0 to provide the 60V AC + Ground.

So basically, what I am asking is will the proposed connections in the image below work.


texts:
TL074 or TL072 VOL (output voltage swing low)?

I can't find it in any datasheet.

I want to know how low the output can get if Vdd=9V and Vss=ground (0V).

If I read the datasheet right, VOH (output swing high) should be at least 6V. Am I correct?

Another really annoying thing is that I can't find a maximum output current.

Can you help? Thank you very much.


texts: Function of diode in the following circuit schematic?

texts: I feel that I have a semi-solid understanding of op-amps (and the circuit above) after reading quite a few explanations online. Where I'm starting to get quite lost is the function of the two diodes in the schematic above. My understanding is that diodes are meant to inhibit the flow of current into one particular direction. If op-amps have (ideally) infinite impedance at the inputs and outputs, what are the diodes doing below? Why is the output of IC1-B (right side of image) connected to the voltage divider at the positive input of IC1-A?


texts: 60V 200mA LED strip powered with step up converter

texts:
I've got a strip of LED lights that requires a 60V supply with 200mA of draw (15w).  I am curious what would be required to get this to run off a significantly smaller voltage source (i.e. USB)  I don't believe a traditional USB charger would work as they are 5V/1A and there is no way to turn that into 15W but if I had a USB C battery pack that was able to deliver >15W is it possible to use a step up converter to power this strip?  Or a couple of 18650 batteries?

I've looked at TI's simple switcher site and it is suggesting the LM2587/LM2588 as a way of turning ~5V into 60V at 200mA.   Are there more gotchas that I am missing?

The LED strip is from something like this.  Our office recently got an upgrade and a few fell off a truck for experimentation.


texts: Why anode attracts Anions if anode is positively charged and anions are negatively charged

texts: Why does anode attract anions if anode is positively charged while anions are negatively charged ? Same is with cathode ...cathode is negatively charged and attract positively charged cations ..why is it so?


texts: The memory regions I can write and cannot write to, ARM Cortex-M architecture

texts:
I hope my title is correct terminologicaly. I am working(learning) with STM32F4 discovery board, which has an STM32F407VGTx microcontroller on it. I really try to find the answers in the reference manual, but sometimes it is really hard to find even where to look. Maybe because of the fact that it is 1700+ pages long...
So, here the situation, during my tests(C code, compiler is arm-none-eabi-size), I realized that, I can write any value to peripheral registers, for example to GPIOD registers. But using same code (to write to an address), I am not able to write to, for example, 0x58(0x00000058 indeed) address. In case of peripheral registers, document clearly states which registers/bits are write enabled, which ones read-only with notations like 'r', 'rw'. However, for the address 0x58, I couldn't find the reason why I cannot write to it.
Any guidance, or explanation would be appreciated, thanks.

update:

Counter-question: Why should you be able to write to that address? Is something mapped to that? – Marcus Müller

OK, it is a bit interesting. I was just started to learn about external interrupts, and I want to do everything(thus including external interrupts) at register level, during my learning. So, that's why I did not use any functions from HAL, SPL, or CMSIS and also none of those files are present in the project directory. I kind of managed it, so I had EXTI pending register firing up correctly, but I could not manage to find a way to link a callback function to the interrupt which will define the process I want to be executed in case of the interrupt. Inspecting NVIC table(page 372) from the reference manual, revealed that each interrupt is related with a memory address on the last column. So, I thought, maybe, just an idea, those locations will contain the memory address(pointer) to the interrupt handler functions. So, I then thought to define a function and then write the address of that function into the 0x58 memory location. So that, when the interrupt comes, the microcontroller will look at 0x58, which will redirect it to location of the function of interest.
Yes, this update could have been a whole another question by itself. Sorry for the mess. I think the question can be answered without this story, but, a comment made me to also append this...


texts: Is there a way to extract out just the Carrier signal from an AM signal?

texts: I have a AM signal with 13.56MHz carrier and 125KHz data signal. I was wondering if there is a way to extract out just the pure carrier signal out of this AM signal. I was thinking about passing it through a high pass filter, instead of a low pass filter, as used for its demodulation. But I am not sure if this will work.


texts:
I recently ordered two Bluetooth dongles for my Arduinos so I can have them communicate over long range.  The dongles that I ordered have pin labeled CTS-I and a pin labeled RTS-0.  I did a little bit of googling and found that they have something to do with "flow control," what is that?

I have the Arduinos communicating properly without these pins in use.  What are these two pins intended to be used for? Should I want to use them? How can I use them?


texts: What is the relationship between a 10:5 Gearbox and a 5:1 OSERDES2?

texts:
I'm trying to understand the HDMI implementation in Xilinx application note XAPP495.
In especially,  I don't understand the diagram below where there are connections between gearboxes and oserdes2.

As you can see the above diagram, there are 10:5 Gear Boxes and 5:1 OSERDES2 modules.
Now I'm stuck on: why are the 10:5 Gear box and 5:1 OSERDES2 used in implementing a TMDS video interface in the Spartan-6 FPGA? Would you please let me know?
Additionally, why doesn't it use different types of modules such as 10:1 Gear box and 10:1 Oserdes2?


texts: 24V to optocopler (voltage drop of 22.8V)

texts:
I have to detect a signal of 24V. The lenght of the signal is 1 second. So I use an optocopler. The led inside the optocopler must receive 1.2V.

First I use a resistor (4k7) but the resistor heat too much for the environment of my prototype (50 degres).

I made some research and I thought use a 2V zener diode like in this scheme:

simulate this circuit – Schematic created using CircuitLab

Is that a good solution? Will it heat a lot?

Thanks in advance!

EDIT:

I want to add that this circuit will be part of a PCB. So can I use cms resistor and diode?

EDIT 2:

As asked in the comments and answer, the optocopler LED need 20 mA to work


texts: Designing a power supply (zener) to achieve steady 6V (\$\pm\$ 0.01)

texts:
UPDATE: My target is to obtain 6V as the voltage output. As you can see, it is 5.94 V. I've tried adjusting my variables, yet it varies from 5.6 to 5.94V, never having reached 6V. What would be the best way to make it real close to 6V \$\pm\$ 0.01?

I have designed a DC power supply which has a zener diode acting as the regulator. I've included the capacitor to filter it and to make some smoothing action and to lessen the ripple. Now, what would be the effect of adding more capacitors in a zener regulator? Also, in further designing it, is it worth maxing out the capacitor to some max value, like 10,000 uF?

EDIT: zener is 6V, input voltage would be a 220 V AC (I'll be using a 6V bridge transformer), load will be anything between 500Ω to 20kΩ. The load will vary, by replacing it in 500 ohm increments, meaning one at a time.

I can only use zener regulator, plus some caps and resistors.


texts: Circuit to tell Microcontroller when Voltage is Low

texts: I would like to trip an input, similar to a button input to an microcontroller if the input voltage to the circuit/microcontroller is below a certain threshold. I have transistors and some zener diodes of different voltages but I am not sure how to connect them in order for the microcontroller to get an input when the voltage is below "x" volts.


texts: Differential op amp inputs beyond supply rail?

texts:
I want to measure multi-cell LiPO batteries. I started off building this circuit found in many low-end hobby-grade 1-6S lipo battery chargers. In practice works well enough.

(image from this question, link to full charger schematic also there)

I have built close to this exact circuit and it works too.

But now that I know more about op amps, I don't see how it works properly.

The input voltage to the op amp inputs is beyond the 5V power supply. Everything I have read (like this question which specifically mentions the lm324) says the common mode voltage needs to be within the supply rails. Here, for the 6th cell, the op amp input voltage could be up to (4.2V per cell * 6 cells * (1/3) voltage divider) = 8.4V

How are the input voltages not clamped by ESD diodes to the supply rails? (are there just not any?)
What kinds of op amps and what specs do I need to look for to make this or an equivalent circuit out of more modern op amps with a 5V supply?
EDIT: Is it perhaps possible that the schematic is wrong and the lm324 is actually being powered from the power supply input (which is at least 10V)?

Edit2: Results are in

Looks like #3 is the answer. I disassembled my charger (an older accucel6 50W from hobbyking) and found that the LM324 is powered from the input voltage (11-17V official rating) through a 10Ω resistor, not the 5V like in the base schematic.

Also, I realized that in my earlier construction of this circuit, I was actually using an 8V supply and only measuring 3 cells so I wasn't exceeding any limits then either.

For my project, I will just use the 12V supply that will be available and select an op amp with >12v ratings.


texts: How to achieve better power supply regulation for this remote scenario?

texts:
I need to power a 0-5VDC output ratiometric-sensor from 75 meters far away.

But because the sensor output signal depends on the stability and/or the accuracy of the power supply voltage(because of being ratiometric), I'm recommended to set up a local, well-regulated supply closer to the sensor. But I will not have access to AC mains on the sensor side, so I cannot set up a local supply.

How about using an isolated DC-DC power supply at the sensor end as shown in Figure 2 below?(Figure 1 shows powering directly from far away):

Does Figure 2 provide a better regulation and accuracy for the sensor excitation? If not, what could be a adequate way to achieve this? Does anybody have experience with such scenario?


texts: How to understand the functions of a Therm-O-Disc 12S20 H24V?

texts:
I am an electrical novice and have a Therm-O-Disc 12S20 H24V (original image) relay that I'm attempting to understand.

The only meaningful documentation I've been able to find is this, 12S, 14S, 15S Series Time Delay Relays and Sequencers. Page 3 of the PDF (recorded as page 7 in the footer) of the documentation shows a table which indicates on and off timings in seconds. Could someone explain what this means?

Also, how would I determine what the control voltage is to activate the relay?


texts: Where does my negative input voltage come from?

texts:
I'm a bit confused about the concept of an input ground for an op Amp. Let's say I'm amplifying the output from a 555 timer ic. I assume the output pin from the 555 is my positive input but what is a negative input? Is it just a reference voltage that can wire to a common ground?

Sorry for a very basic question but I appreciate any input, or simply being pointed in the right direction.

Thanks!


texts: In 802.11 (CSMA/CA), does a higher data rate imply more number of collisions?

texts:
In a wireless environment working with the 802.11 protocol suite, where the MAC protocol is based on CSMA-CA (collision avoidance), a higher data rate would mean that data is sent more quickly, which in turn implies that more number of packets are sent successively.

Wouldn't a greater number of packets being sent mean a greater chance of collision? Note that even if powerful error correcting codes or higher modulation schemes are used, collision can't be prevented, as that entirely depends on how many packets are being transmitted 'over-the-air' at any point of time.

Overall, I'm confused how high data rates would work well in a wireless environment, if it resulted in more number of collisions (which would be counter-productive).


texts: Can I use an optocoupler to switch an analog signal?

texts:
I have this setup to select 1 of 4 signals, pass it through a sensor, then output it to its own output line. It must also maintain all the signals at the output at all times, using optocouplers as switches for the signals that are not passing through the sensor.

I have three questions:

Is the configuration of a mux-demux the best way to select one signal from multiple signals, pass it through a current sensor, and then select where to output it?
Is there significant noise or voltage drop that can alter the original signal, when using this mux-demux configuration?
The optocouplers are acting as signal switches. Are they the best option for this operation?


texts: Trying to get 2 Amps out of 3 Amp Regulator (MIC29302WU)

texts:
I am trying to get 5V,2A out of the MIC29302WU (TO-263 package) with an input voltage of 12V. The voltage drops to around 2.2V when trying to supply even 1.3A. Blowing canned air over the regulator helps so I'm assuming it's a temperature issue. This is on a 4 layer pcb without using a heat sink.

Would moving from 3A to 5A help?

Can I achieve 2A without a heat sink?


texts: How do you generate a reference voltage in a circuit?

texts:
Hi Im very new to electronics and had a pretty basic question about voltage reference.

So Ive finally understood that in order to check a voltage in most circuits, a voltage reference is used. The way i visualize this is a chip having 5 wires; the first 2 go to the battery which the voltage needs to be measured, another 2 go to a steady power source(the voltage from the first battery gets compared to this steady source and a voltage reading is obtained) and the last wire is an analog wire(ex. to use on arduino for displaying the voltage read).

I know that if i use only 1 battery for both the voltage readings and to power the voltage reference chip, i will always get a value of 1023, because the voltage measured is always compared to that same value giving a max voltage all the time.

With this in mind my question is: How do i use only 1 power source(in this case the battery, without the steady power source) to power the whole circuit and read the voltage of that same battery? Im basically asking how for example phones are able to measure their battery voltage even without a mini battery powering the voltage reference circuit. Thanks in advance.


texts: Why do my LED lights require a different voltage when they are hardwired?

texts:
I have a cheap set of LED string lights. There are 20 lights, all wired in parallel connected to a small battery bank. There are 2, 3V batteries wired in series, providing 6V of power to the string.
This is a little confusing, since I know LEDs run on 2-3V, but I verified my physics with a voltage meter, and two 3V batteries in series is really 6V. If I try putting the batteries in parallel, they produce 3V and the lights do not come on.

For a small DIY project, I would like to hardwire these lights. That is, I would like to connect them to the 120V system in my house. I found an old 12v DC converter and I have a buck step down converter. Wiring the two units together, I can easily create a DC power supply, supplying 6v.
But should I?

It turns out the answer is NO, they will burn out very quickly. In fact, I can power the lights just fine with 2.3V when they are hardwired.
Why can I power the lights with 2.3V of power when they are hardwired, but I require 6V when using a battery pack?
A follow-up (safety) question. Just because I can do this, should I? Is there a safety concern with the LEDs when hardwired using a DC and step down converter?


texts: Buck regulator frequency requirements (transient response)

texts:
Looking at the frequency choices for buck regulators, is there a defined "good" range for a particular context?

Looking at datasheets, manufacturers extoll the virtues of "better transient response". But it's difficult for me to know what minimal transient reponse is actually required in any given situation.

In front of me I have an LM2596 regulator I bought off eBay for US$3. It's a nice simple design at 150 kHz. It's not particularly small mind you, but that's OK in many scenarios.

Going higher frequency results in smaller inductors and faster transient response. You pay a price for this in low ESR ceramic capacitors, more expensive magnetics and a more critical layout. Plus lower efficiency.

So, size aside, what is 150 kHz good for and what is it not good for? I assume I could drive, say, LEDs with this, even if they had to pulse... If it was something like a Raspberry Pi, would it be a bad idea to power it from this module? How do I know?!

Looking at something like the PandaBoard, they use a TPS54320 at 500 kHz. I have another board with an FPGA (400 MHz) that uses a TPS5430 at 550 kHz. So, generally speaking, can I assume 500 kHz is enough response for anyone?


texts:
I'm trying to interface to a type-K thermocouple with an ATXMEGA128A4U and have been experiencing some difficulty and I'm hoping someone can confirm the process I am using.

Details..
1. TC is connected to standard A/D input via an AD8223 instrumentation AMP with a gain of 106 and an offset of half my A/D reference voltage of 1.25V offset.  My A/D reference voltage is 2.5V
2. I am using a standard 10K NTC for the cold junction reference.  It's soldered directly to the TC socket and I have calibrated it in an incubator and am confident that my cold junction temperatures are being converted and processed correctly by the processor.

Basically, I am not getting the output that I would expect across a fairly narrow temperature range of 0-80C.  I'm not 100% sure that I'm processing properly.  If we ignore the calculations I am using for the conversions for now, am I correct to think that I can take the TC output in mV and use the NIST lookup table to convert that mV to a temperature and then subtract my cold junction temperature (which will always be close to Ambient 20C) to get my tip temperature or is there more to it?

To illustrate my problem, I just placed the ThermoCouple in a mug of 76.4C water (confirmed with Fluke 51II ThermoCouple Meter) and Im getting an output of 5.151mV with my NTC reading the Cold Junction at 18.4C.  According to the NIST table, 5.151mV equates to 125.5C.  When I subtract the 18.4C cold junction I'm left with 107.1C.  Clearly not correct.  I'm actually using rational polynomials for the conversions in code but I thought I would refer to the look-up chart analogy to keep things simple for the sake of this post.  I'm hoping that someone might be able to confirm my logic before I go any deeper.

Perhaps I'm thinking about this the wrong way.  Feedback is greatly appreciated.


texts: What happens to current transducer if the line it is attached to short circuits?

texts:
I am using a SCT013-30 current transducer to measure current to an AC line. I hook it up to an ADS1115 16bit Analog Digital Converter. I would like to know what happens to the signal when the AC line that I am measuring lets say get shorted out for a duration of 1-3 seconds (by this time the breaker should have tripped.)

will the transducer generate a very high voltage that might kill itself?

will the ADS1115 get blown up too?

How can I protect my ADS so it wont get damaged?


texts: I don't understand the working principle of this metal detector circuit?

texts: The circuit below is a metal detector circuit. The inductor serves as a "sensor" to detect metal. The tone of the speaker changes when a metal is detected. However, I don't know anything about how the circuit works internally. I can only do the circuit connection. Please can someone explain how how the internal circuit of the 555 time makes this possible? What mode is the IC operating? How does each passive component (resistors, inductors and capacitors) in the circuit functions? I need it urgently!


texts: Does DisplayPort support scaling natively?

texts:
In the DisplayPort Wikipedia page, in advantages section it is stated that "Can drive display panels directly, eliminating scaling and control circuits and allowing for cheaper and slimmer displays".

In the DisplayPort 1.2 specification, it is stated in external connection objectives that " Support external display configurations that do not include scaling, a discrete display controller, or on screen display (OSD) functions, enabling low cost, digital monitors. "

DisplayPort 1.2 specification - https://www.google.com/url?sa=t&source=web&rct=j&url=https://glenwing.github.io/docs/DP-1.2.pdf&ved=2ahUKEwjkq-_xgrDmAhVsxTgGHaCjCB0QFjAAegQIAxAB&usg=AOvVaw1P2cs_sDfKQF4AX6NoqNMa

Does this mean DisplayPort will upscale or downscale according to display panel connected without a scaling unit in between ?


texts: Circuit with both current and voltage source

texts: I am preparing for an upcoming exam. Can someone explain the procedure to solve this kind of problems in detail, please?


texts: Should I short these ground pins together?

texts:
I'm trying to design a PCB breakout board for an IC - the MAX86150.
This IC requires three separate power supplies, and it also has three corresponding GND pins. My question is, is there any reason not to simply short the three separate ground pins together and send one common ground for all three power supplies into the breakout board?
I see that Note 4 indicates they should have zero resistance between them, which I think means they should be shorted to each other, but the circuit diagram does not show them connected by a wire, which makes me worry there's something I don't understand about "common design practices". Are "common design practices" fancier than...connecting them with a trace?


texts: J1708 (open collector RS485) at higher baud rates than 9600 bps?

texts: I have here a PCB which has a kind of "open collector" RS-485, known as J1708 (schematic attached). The default baud rate is 9600 bps and there is no terminators, J1708-TX is a 3.3V signal. I would like to know if I can get higher baud rates like 38400, 57600 and maybe 115200 bps with the same schematic but changing (reducing...) the values of resistors R1 and R2 and capacitors C1 and C2...


texts:
I power a DAC from SMPS. After the SMPS I use a LDO

My problem is that most LDOs only have a good PSSR around 100Khz or lower, while my SMPS has a switching frequency of about 1Mhz (thus noise)

1Mhz noise is not in the audio band....but my question is should I use a low pass filter (lpf) before the LDO to filter that high frequency noise ?
 IS it possible to have high frequency noise pollute the audio-band ?


texts: Why does current flow into the transistor in a current shunt monitor?

texts:
I'm looking at the basic operation of a current shunt monitor*, but I don't quite understand the 'operation' description given by it's manufacturer.

  Figure 1 shows the basic circuit diagram for both the INA139 and the INA169. Load current, IS, is drawn from the supply, VS, through the shunt resistor, RS. The voltage drop in the shunt resistor, VS, is forced across RG1 by the internal op amp, causing current to flow into the collector of Q1. The external resistor, RL, converts the output current to a voltage, VOUT, at the OUT pin.

Why does the voltage forced over RG1 cause a current to flow through Q1, and what is the purpose of RG2?

* Texas Instruments INA169


texts:
I found out this driving circuit of LED somewhere as in the below picture, and I just can't figure it out what its design purpose is.

There are two kinds of VDD input, 9 V and 6.5 V. I guess maybe this driving circuit is making sure that no matter which these two input voltages (9 V and 6.5 V), it will keep the same brightness.

So, my questions are, 1). What is its design purpose? 2). What is its theory?


texts:
I have some boards with Xilinx Spartan 3 FPGAs, I would like to upload new bitstreams over JTAG. I was planning on using UrJTAG.

I already have a couple of FTDI based JTAG adapters for ARM targets - can these be used?

They run at 3V3, I read that the Xilinx JTAG is at 2V5 will this be a problem?

Alternatively, I have a few FTDI FT232s, is there a simple cable I could build?


texts: Won't the ferrite bead (L3) will restrict sudden power requirement of bluetooth module (U4)

texts:
I know the circuit is well tested by STm but, I think, C15 should not be able to provide enough instantaneous power.
Does noise suppress by this ferrite bead (cross-over frequency 12MHz) will be same for other circuits if U4 is used?


texts: Arduino Uno R3: Controlling Tx and Rx LEDs

texts:
I am currently attempting to control the Arduino Uno's Tx and Rx LEDs.

These are connected to digital pins 0 and 1 respectively, which are AFAIK, PD4 and PD5.

They are held at +5V, so I assumed that they would switch on when PD4,5 were driven low, however this has not proven to be the case.

I would be immensely grateful if anybody could offer a solution.

The schematic I referred to is here: http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf


texts: VCD files - flatten busses to individual nodes

texts:
I was wondering if its possible to flatten all of the busses in a VCD file such that there will be a separate value change recorded for each bit - rather than a cumulative recording of the following syntax: b<value> <identifier>

My goal is to count the number of transitions that occur after each timestamp recorded.  If all busses were flattened, this would be straight-forward since it would simply be the number of value changes listed.

However, these vector changes instead of bit changes complicate the issue.  You would need to keep a record of the previous state of the vector in order to determine exactly how many bits in the vector transitioned.

Any other suggestions to fix the problem are welcome, any help is appreciated!

-k


texts: Why couldn't the following circuit have an active transistor?

texts:
I've designed the following circuit as a means of increasing a 1.8V PWM signal to 5V PWM. Currently, I see no operation problems based on the diagram below.

When the signal is HIGH, \$V_{c}(+5V) > V_{b}(+1.796V) > V_{e}(0V)\$, which means it should be in Forward active mode, Until it hits Cut-off mode, because \$V_{c} = V_{e}\$, where current should stop, until the drain capacitor (R2) lowers the voltage enough to turn it back on (very quick).
When the signal is LOW, \$V_{c}(+5V) > V_{b}(0V) = V_{e}(0V)\$ thus it should teeter between Reverse Active and Cut-off.

In my mind, this circuit should work, but a user has pointed out to me that the transistor will never turn off, however, if everything is drained properly, how can this be? As far as I know, \$V_{b}\$ and \$V_{e}\$ should both be zero while the PWM signal is low. The same user then pointed out to me that the transistor can never be active. At first I thought it was because 1.79V may not be enough to overcome forward voltage, but there are many transistors that have operation ranges around one volt. It appears I'm stumped.
Why will this never turn off?
why will this never turn on?
Is said user wrong somehow?

I see people using Higher voltages and doing something like this:

simulate this circuit – Schematic created using CircuitLab

and it works very well, with no voltage drop of \$V_{ec}\$ whatsoever! But this circuit only reduces the voltage. Why is this?


texts:
Given
$$x[n] = \cos\left(\frac{\pi}{3} n\right)$$
That was obtained by sampling
$$x_c(t) = \cos(4000\pi t)$$

At \$T\$ samples per second, find \$T\$. Is \$T\$ unique? Why or why not?

$$x[n] = x_c(nT)$$
$$\cos\left(\frac{\pi}{3} n\right) = \cos(4000\pi nT)$$
$$\frac{\pi}{3} n = 4000\pi nT$$
$$T = \frac{1}{12000}$$

So far so good. Is \$T\$ unique? No, because either of these periodic signals can be phase shifted by \$2\pi\$ and remain essentially unchanged. E.g.

$$x[n] = \cos\left(\frac{\pi}{3} n + 2\pi\right)$$

EDIT TO SHOW STEPS
$$\cos\left(\frac{\pi}{3} n\right) = \cos\left(\frac{\pi}{3} n + 2\pi\right)$$
So,
$$\cos\left(\frac{\pi}{3} n + 2\pi\right) = \cos(4000\pi nT)$$
$$\frac{\pi}{3} n + 2\pi = 4000\pi nT$$
$$\frac{1}{3} + 2 = 4000 T$$
$$T = \frac{7}{12000}$$
END EDIT

Using this new \$x[n]\$, which is equivalent to the original, and the same relationship as defined above, we find that \$T = \frac{7}{12000}\$. While the math checks out (unless I've seriously screwed up), intuitively this makes no sense to me.

How would lowering the sample rate simply shift the resulting discrete time signal? By this logic, lowering the sample rate won't change the output, which is fundamentally wrong (isn't it??)

I must be missing something here, please enlighten me!


texts:
So I bought a transformer VC 18/1/16 and when I plugged 240V to from the mains to the primary winding. I then plugged into my voltmeter and it is suppose to show 18V . Does this seem correct on my meter?

Does it mean I need to connect the two tops together and the two bottoms together to get out 18V?

This seems to work

So I have done this connection and it seems reasonable. I guess I would get 18V if the AC was at 230. Since it is 240V it is showing 21. This seems correct.


texts:
I am trying to understand an explanation written here: http://people.ucalgary.ca/~aknigh/vsd/ssim/vsi/co.html

As far as I understand:

voltage V(A) is line 1 voltage
voltage V(B) is line 2 voltage

... but what/where is voltage V(X) ... or V(X) at time t? I would like to understand the equation "Once phase B voltage is high enough for its diode to conduct:".


texts: How to check whether an IC has gone bad or not?

texts:
My Question
I have unfortunately, had an incident with my the 74LS08 (And Gate) IC. When I accidentally powered it incorrectly, the IC started to heat, very quickly. I was powering it using an adapter from a wall socket (5V of input power).
I cannot remember exactly the wire up, however the IC was getting hot very quickly. I unplugged it from the mains and from the connection onto the breadboard. There seems to be no visible damage to the IC, however the area of the breadboard below it seems to have widened a bit (I was bridging it over the middle channel of the breadboard). There was also no smoke, or anything else apart from the IC heating and the breadboard damage.

My Question
So what is the best way to test whether the it is usable? I currently don't have a spare, so I don't really want to be throwing it away unless I can be sure that it is definitely dead.

Other Notes
I have checked out both other questions on whether an IC is fried, however I have seen no smoke or the like to make it obvious that it is definitely useless.

Datasheet
https://www.bitsbox.co.uk/data/7400/74HC08.pdf


texts: Basic TIE HIGH and TIE LOW circuits in Digital VLSI Design

texts:
I am trying to understand how a basic TIE HIGH and TIE LOW circuit that are based on diode connected MOSFETs followed by a PMOS pullup or NMOS pull down for TIEHI/TIELO accordingly work ?

How does the pull up PMOS transistor turn on in TIE HI ?
How does the pull down NMOS transistor turn on in TIE LO ?

I could not find this anywhere in this forum. If not please redirect me to that..Thanks

I have attached the circuit schematic for TIE HI..I understand that diode connected NMOS is always in saturation region and that it can act as diode. But how does the PMOS turn ON ?.


texts: Why put 158K resistor between the input signals and negative input signal and ground?

texts: In the istrumentation amplifier circuit below, why would someone put a 158K resistor between the input signals? Also, how about the 165K signal between the negtive input and ground?


texts: Crossover distortion returns when load is applied

texts:
I built a small audio amplifier using a OPA2134PA as a pre-amp to drive a complementary pair of Mosfets (IRF9540NPBF and IRF540NPBF). I've biased my Mosfets using two 10k resistors and 6 diodes. I've also fed some of my combined Mosfet output back into the inverting input of the OpAmp. The output looks great all across the audible range of 20Hz to 20,000Hz until I place a low impedance (8-10 Ohm) load on it.

My question is: Is the return of crossover distortion expected when a load is applied and is there a way to mitigate it?

Yellow: Input signal from generator
Blue  : Combined output signal from Mosfets.

Without load, the output looks good:

With a 10 ohm load, the distortion returns:

Pretty accurate representation of my output stage:

simulate this circuit – Schematic created using CircuitLab


texts: Prevent loss of Large Signal Voltage Gain at low Rload

texts:
Operational Amplifiers (opamps) have the tendency to drop their Large Signal Voltage Gain when the load is too low. This behaviour is usually described in the datasheet. Loads of 500 ohm and lower usually result in very low gain.

How can I prevent this loss of gain?

I've tried using another opamp as a unity buffer, but the top of the signal gets clipped. I've tried a transistor, but the signal got distorted. My target load is 50 ohm and the signal is a triangle in 50 - 10000 Hz range, 0 - 10 V. The opamps in use are LT1077.

EDIT: I'm aware of the trouble the LT1077 has at low loads. I'd hoped there would be a buffer solution like I tried with the transistor (as far as I know though, Class A are used when the load gets too heavy, not when too low).

When trying the transistor, the top of the signal got clipped. I made sure there was enough voltage available, so I'm not sure how that happened.


texts:
Following is the problem:

A sinusoidal signal $$A_c\cos(2πf_ct + φ)$$, where φ is uniformly distributed over $$[−π, π]$$, is quantized by a 1-bit quantizer. Assume that the signal utilizes all the representation levels of the quantizer. What will be the signal-to-quantization noise ratio?

I have done some basic problems on quantization but I am not sure how to proceed when a probability distribution is given.

Any help is appreciated. Thanks!


texts: Figuring out how much torque dc motor will need to run at a certain speed. (E-skateboard project)

texts:
Suppose I want to purchase a DC motor online, how can i determine how much torque my motor will need to run at a certain speed? I.e. 15mph

This is for my electric skateboard project and the load on top of the board will be 140 lbs.

Really having a hard time figuring this out and was hoping someone can share their knowledge.


texts:
I need to be able to reverse the direction of a RS-360SH motor

The operating voltage is 7.2 volt
Current is around 5 A on normal running and
around 8 A during stalling.

I tried to use a 2-pole 3-position changeover switch. Is it suitable?

I found that most H-bridges have less current carrying capacity.

What should I do.?


texts: Energy Harvesting application capacitor selection

texts:
I have an energy harvesting application and I want to use a capacitor to store energy. Due to the application being very low power, a capacitor of around 50uF might be enough. What is really important though, is to have the lowest discharge possible, since the charging of the capacitor might be happening over a long period.
What type of capacitor is best suited for this case?


texts: Electrical symbols, what does a dot before a triangle mean?

texts:
Good day.

Trying to recreate a circuit, but I'm not sure what the dot BEFORE the triangle means. I know after it means invertor, does before just mean it's inverted BEFORE, instead of after? Rather confused, and not having luck searching.

Really appreciate the help.


texts: GPS Antenna Selector: How to electronically select one antenna from multiple available antennas?

texts:
I want to connect multiple GPS antennas to a single GPS module and select one of them based on some logic. Basically, I want the module to receive signals from only the selected antenna.

Is there an inexpensive/generic/common IC that can act as a Demultiplexer for GPS RF signal (without distorting it too much)?


texts: Communication failure using PCA9615 Differential I2C Bus Extender

texts:
I have used PCA9615 differential I2C bus driver in one design to extend the I2C bus over CAT5 cable.
(datasheet https://www.nxp.com/docs/en/data-sheet/PCA9615.pdf)
The design has been done according to the datasheet recommendation and with the help of a reference design of a popular open-source board manufactured by Sparkfun which I used as a demo board, before starting the design.
Unfortunately, the design didn't work well in my case, as the communication doesn't establish when connecting a pair of PCA9615 using CAT5 cable.
I have attached my schematic and layout of the board, and the connection topology I used.
Here are some observations:

It seems when connecting the PCA9615 boards over the ethernet cable (tested it using 1 m long cable), both SDA and SCL lines get pulled low, so there is no connection over I2C.
The termination resistors have been calculated according to the datasheet recommendations (yielding 88.5Ohm parallel resistance close to the 100Ohm indicated in the datasheet, it should work since SparkFun's module uses the same values as I)
I tested it for the pin-to-pin continuity for one board to another and it's correct.
Every board designed with three I2C inputs, if I connected to two I2C devices on the same board without connecting the second board, then it works fine, which means no problem from the I2C side.
I have tested the voltage levels on both boards and they indicate correct voltage levels (5V in my case)

I would appreciate any help or suggestion regarding this problem.


texts:
For a project I'm working on, I've to calculate a function for the output voltage of this filter:

The things I calculate:

The input voltage:
$$\text{U}_{\text{in}}\left(t\right)=\hat{\text{u}}\sin\left(\omega t+\theta\right)$$
The voltage after the rectifier: $$\text{U}_{\text{C1}}\left(t\right)=\left|\text{U}_{\text{in}}\left(t\right)\right|=\left|\hat{\text{u}}\sin\left(\omega t+\theta\right)\right|$$
Using Laplace transform, I got for the output voltage:
$$\frac{\text{U}_{\text{C2}}\left(\text{s}\right)}{\mathcal{L}_t\left[\left|\text{U}_{\text{in}}\left(t\right)\right|\right]_{\left(\text{s}\right)}}=\frac{1}{1+\text{L}\cdot\text{C}_2\cdot\text{s}^2}$$

Where \$\omega=2\pi\text{f}\$

  Questions: 1. Why does the output voltage not depend on the value of \$\text{C}_1\$? 2.Is the amplitude of the voltage after the (not ideal) rectifier equal to: \$\hat{\text{u}}-\text{V}_{\text{d}}\approx\hat{\text{u}}-0.7\$


texts:
I'm still trying to get used to some of the quirks of VHDL and I'm having a bit of an issue. First off, I understand that shift operators like rol, ror, ssl, srl, etc. are not synthesizeable. The purpose of this lab is to use a golden model to check against a synthesizeable version of the same thing in a testbench.

Now, the purpose of this program is to convert thermometer code into a 3-bit binary number. So, in other words, thermometer code "00000001" = "001", "00000011" = "010", "00000111" = "011", etc. I'm basically trying to count the number of 1's in the string from right to left. There will be no case where a '0' is placed between the string of 1's, so the vector "00011101" is invalid and will never occur.

I've devised a non-synthesizeable (and so far, non-compile-able) algorithm that I can't figure out how to get working. Basically, the idea is to read the thermometer code, shift it right and increment a counter until the thermometer code equals zero, and then assign the counter value to the 3-bit std_logic_vector. Below is the code I've done so-far.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity therm2bin_g is
    port(therm : inout std_logic_vector(6 downto 0); -- thermometer code
         bin : out std_logic_vector(2 downto 0); -- binary code
         i : integer range 0 to 7);
end therm2bin_g;

architecture behavioral_g of therm2bin_g is
begin

golden : process(therm)
begin

    while(therm /= "00000000") loop
        therm <= therm srl 1;
        i = i + 1;
    end loop;

    bin <= std_logic'(to_unsigned(i,3));

end process golden;
behavioral_g;


texts: In a circuit schema, why the voltage at the battery anode is conventionally 0V while the voltage at cathode is usually the voltage of the battery?

texts:
I will try to explain where my question is coming from.
Knowing that voltage is the electric potential energy per unit of charge at a given point.
And knowing that electrons are pushed from - to go to +
To me that means that the electrons won't have potential energy when arrived at +
And they have the most when starting from -
They should have more potential energy where they are leaving from and less where they are arriving.
That would mean that electrons have more potential energy at - than at +
So in an AA battery (1.5V) I would expect that the voltage at the anode (-) is 1.5V and the voltage at the cathode (+) is 0V
But I am learning the opposite from my course and I do not understand why it is so.


texts: Problem with a solar power bank indicator LEDs

texts:
I bought a 10000mAh (actual 4000mAh) solar power bank from Victsing few days ago. After having solved a short-circuit problem that affected the solar panel, I noticed that it took an extremely long time to charge from direct sunlight: in six very sunny days just about one quarter. The device presents four blue indicator LEDs that sequentially turn on when the power bank is charging (both from sun or microUSB). The problem is that the LEDs are very brights and seems to consume a lot of energy. From some calculations and measurements, it seems that they consume about 10-30% of the energy harvested by the solar panel, a lot in my opinion. The four LEDs are controlled by an unidentified microcontroller. The question is: is it possible to reduce in someway the consumption of the LEDs, by modifying the circuit, the microcontroller or the LEDs?

Thanks a lot.

Alessio


texts: Resistor for indicator LED on higher voltage (70V) DC

texts:
I'm driving an N-channel MOSFET on a 70Vdc supply (to power a pinball machine's solenoid), and I want to add an indicator LED to the circuit after the MOSFET, to see whether the MOSFET responds as expected.

From my calculations I found that if I use a low-current LED (such as this green 5mm LED at 2mA 1.9V) I should be able to do it with a 70Vdc supply voltage.

For the resistor I calculated:

\$ R = (V_{in} - V_{LED}) / I \$

\$ (70V - 1.9V) / 0.002A = 34k\Omega \$

And then the resistor would dissipate:

\$ P = (V_{in} - V_{LED}) \times I \$

\$ (70V - 1.9V) \times 0.002A = 0.14W \$

This seems reasonable, and any 1/4W resistor should do the job.

However, all online LED calculators that I could find tell me they they don't do LEDs with a supply voltage higher than approximately 35V. Are my calculations correct? Is there a better way to have an indicator LED on a 70Vdc supply?


texts:
I have my MSP on Com8. Here is my code:
#include <msp430.h>
void Uart_SendChar(char c);
int main(void)
{
    WDTCTL = WDTPW + WDTHOLD;

    P4SEL |= BIT4+BIT5;                       // P3.3,4 = USCI_A0 TXD/RXD
    UCA1CTL1 |= UCSWRST;                      // **Put state machine in reset**
    UCA1CTL1 |= UCSSEL_2;                     // SMCLK
    UCA1BR0 = 9;                              // 1MHz 115200
    UCA1BR1 = 0;                              // 1MHz 115200
    UCA1MCTL |= UCBRS_1 + UCBRF_0;            // Modulation UCBRSx=1, UCBRFx=0
    UCA1CTL1 &= ~UCSWRST;

    while(1)
    {
        Uart_SendChar('k');
        __delay_cycles(3000000); //3sn Bekleme suresi
    }
}

void Uart_SendChar(char c)
{
    UCA1TXBUF=c;
    while(UCA1STAT&UCBUSY);
}

But I'm not getting any output. What might be the reason why?


texts: Designing audio player - low-pass filter, DAC

texts:
I'm building audio (wave) player on some microcontroller.

I will have external 16-bit DAC and I wonder if that's enough?
I mean, is low-pass filter really needed? (I know what it does and why you use it after DAC, but will it be hearable if there is no LPF?)

So my question is: do I need anything more then just DAC? If I set DAC value and put its output (without any additional buffer/oamp) to speakers (from my PC, with built-in amp), will it work? (I'm planning to use DAC8531E as DAC).


texts: My son and I are working on building a snake habitat.  We have a Current Orbit Marine LED light (https://x4u6a9v7.stackpathcdn.com/wp-content/uploads/2018/06/Orbit-Marine-LED-Manual-V5.pdf). The light hub can connect via a micro USB cable to a pump hub (https://x4u6a9v7.stackpathcdn.com/wp-content/uploads/2018/06/Orbit-IC-with-eFlux-Wave-Pump-Web-Quick-Start-Guide-2.pdf). We don't want to control Current's wave pump, but would like to control a small USB  powered pump (https://smile.amazon.com/gp/product/B01CG2YE6K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1) in order to make it rain in the habitat. What do I need to do to accomplish this?  Do I need a USB controlled relay such as (https://smile.amazon.com/dp/B01CN7E0RQ/?coliid=I28EQTP5KRNHLO&colid=3HFYILRHYY33E&psc=1&ref_=lv_ov_lig_dp_it)?


texts: What to do with internally unused pins on a non-programmable device?

texts:
I'm designing a board for using the FLIR Lepton 2.0 LWIF camera (datasheet at https://www.flir.com/globalassets/imported-assets/document/lepton-engineering-datasheet---without-radiometry.pdf), and several of the pins are marked as unused. One is labeled as "No Connection" and four others as "RESERVED" (which is due to the fact that the Lepton 2.5, which uses the same case, has additional I/O pins). Given that I cannot set (and therefore do not know) the input/output state of these pins, and that they are likely disconnected internally, what should I do with them? My instinct is to connect them to ground through a pull-down resistor, but this may not be correct.

(As a side note, I'm using the Molex 105028-1001 socket for mounting this component.)


texts: What are the important specs for inductor in passive tone control?

texts:
I'm pretty much an electronics newbie. I'm working through some circuits in "Electronic Projects for Musicians". It has a "Passive Tone Control" which seemed like an easy start. Unsure if I can reproduce the circuit here (if that's allowed, I mean). But anyway it has a rotary switch that connects one of 5 capacitors (0.01uF to 0.22uF in range) to an inductor.

It lists the inductor as 5 or 6H center tapped. Then references a part (Mouser 42TM019) with primary impedance 10k ohm at 1Hz, secondary impedance 600 ohm. Primary resistance 600 ohm, secondary 100 ohm.

I've not been able to find that part in stock. Mouser has some others, but I don't know what specs are important to keep and what are not. For example 42TL021-RC where secondary impedance is 600 ohm but primary is 4k ohm instead of 10k.

Could someone explain what might be the important bits of an inductor in this case?


texts: How to measure correctly efficiency at high load with LT8646

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i'm trying to measure efficiency of a LT Part LT8646 at high load with the attached schematic.

i'm using a dynamic load and a power supply to give 12V. I'm using a digital multimeter to read the input current and find the efficiency. What i'm experiencing is a drop of the output voltage when the current is greater than 3A. I know this is due to the measurement setup, is there a method to avoid this and doing a correct measurement? Thanks


texts: Calculating voltage output from a circuit with capacitors

texts: The question is outlined in the image below. I am having trouble solving this problem. If at all possible would one of you please provide the solution. Thank you


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I am currently learning about mosfets and was looking to get some intuitive guidance on the load line on a typical MOSFET curve.
I am using this very helpful and intuitive lecture slides from http://aries.ucsd.edu/NAJMABADI/CLASS/ECE102/11-F/NOTES/ECE102_F11-LecSet-2.pdf . However I am little confused by what happens if you increase VGS above VDD. The line continues into an area that is not bounded by the load line.

Does the MOSFET break?
or is there some equation that governs it's Vds and iD at these given values for Vgs?
Is there an equation for this behaviour?


texts: A question regarding sizing some resistors in a circuit

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I have the following circuit's old version soldered which works fine in real. The updated circuit in the below diagram exists only in simulation. Recently I will in real add a zener with a series resistor and a Schottky to the positive rail for reverse polarity protection as you can see in the below schematic. And mainly I will add  a new output Vout2.

The reason for the zener is I want to limit the Vout1 voltage to around 8V if the supply rail exceeds 8V. The supply rail Vcc can be between from 5V upto 24V.

I want the circuit to have two outputs Vout1 and Vout2. Vout1 will be an Low-High pulse train with 0-5V or 0-8V amplitude(low can be between zero and one volt).

I want Vout2 to swing between around 0V(or a bit more) to around 15V. Vx and Rx is known which are 15V and 2.1k.

But for a good saturation I couldnt figure out an optimum value for Rb since Vout can be from 5V to 8V as I explained.

In simulation I get what I want to see, but I'm not sure about the values for Rz and the base resistor Rb. What should be a good value for Rx and Rb and how do you conclude that? Thanks.


texts: Alternative name for overhead line, typically for data link between buildings

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What is the term I should use to describe an overhead cable link that typically connects two buildings across a gap, eg a road?

For the life of me, I can't remember the word I'm looking for.  I think it may sound like the words stanchion or catamaran, but I can't place the actual word I have heard used to describe this type of link.

Apologies if this question is better suited to another SE site.


texts: Voltage Regulator and Resistors for LED Circuit

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I'm trying to design a circuit to power 17 LEDs. The LEDs I'm using are AA2810AQBS/D Blue SMD LEDs with 3.3v Forward Voltage at 20mA.

I would like to power this using EITHER 2xAA Alkaline batteries OR a 5V USB battery pack.

I was looking at the AAT1217-3.3, 3.3V Step Up Converter but I'm not sure if 3.3V is enough and it's unclear to me if this can accept the voltage range that I need for 2xAA's or 5V battery pack (potential battery voltage range of 2.4V to 6V?)

Can I power these LEDs with 3.3V and 1 ohm current limiting resistors?

Any suggestions on a low cost regulator and LED current limiting resistors for my needs?


texts: I am trying to get an IC to generate a 100kHz sinusoidal waveform for my circuit. However when I google, all I can find are retired products which make me very hard to find (I stay in Singapore) so anyone know any active IC that can help me generate 100kHz signal? Thanks in advance.


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I'm controlling a P-Ch MOSFET on a circuit,

VIN is 8-30V
TTL_IN is a 0-5V signal generated by a MCU, which can source/sink currents up to 15mA
Zener Izt 5mA (BZT52C15)
MOSFET Vgs limit 25V

I'm currently using this circuit:

I find many different implementations for this situation; I see voltage dividers at gate, emitter resistors for current limiting, replace NPN with a small N-ch FET, gate driver IC's etc.

My questions are:

Is my circuit is valid and safely usable? (I actually use it with no obvious effects (heating etc.) but I want to be sure)
For relatively fast (5KHz) switching speeds, what should I need to change?

I previously used 10K for R12 and it cannot charge the gate fast enough, leading slow turn off times. 1k is much better for regarding speed but I'm not sure R9 limits the current enough.

Thanks.


texts: Are the resistance values (R1 and R2) in this circuit reasonable?

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This simplified circuit is intended to sense two limit switches (which can never be closed simultaneously-- at least in theory). The voltmeter shown is a place-holder for a connection to an analog input pin of an Arduino. When both switches are open as shown in the diagram, the pin should sense 3V31. Closing SW1 gives 5V and closing SW2 gives 0V.

This works great in simulation, but I am wondering about the total current as shown by the GND probe… My vague newby intuition tells me that there must be some minimum amount of current in order to be sensed by the A/D converter in the Arduino, but I haven't been able to find (or recognize) a spec for this minimum anywhere. (In contrast, the specs for the maximum current that a pin can sink are widely discussed.)


texts: Which kind of AA battery should I use to power up my ESP-32

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Disclaimer : I have few knowledge in electronics

I have an ESP-32 device that use 3.3V to run perfectly.
The 3.3V and the Ground of the device is directly connected to an AA battery container with 2 slots.

The device is a homemade sensor that use an ESP-WROOM-32 and some additional component like water detection, humidity, temperature sensors. I don't have the tools to change it. (Datasheet of ESP-WROOM-32)

Until now, I powered up my ESP-32 with 2 Alkaline Battery at 1.5V each. I was able to run it but it didn't last long (Near 20 minutes, not including deep sleep periods).

What kind of battery should I use to power up my ESP-32 and last more than 20 minutes ?


texts: How to calculate the max transfers per frame and the remaining bytes in USB protocol?

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Could someone explain the attached table and how the values are calculated? (the table is taken from the official usb 2.0 specification page 42).

What I could understand is just the relation between the bytes/frame and bytes/second (as in Full Speed the second consists of 1000 frames). But how is the max transfers, the bytes remaining, frame bandwidth per transfer, and the bytes/frame calculated?