texts:
I'm trying to design a supply circuit for a board that should deliver 3.3V using a LiPo battery, the battery should be that charged using a micro USB cable.
here is what I've done so far.

the LM3940 regulates the supply voltage to 3.3V and the MCP73831 is a battery charger. the Target voltage supplies the whole circuit.

after doing some research I figured out that need to take the load sharing in consideration, I found the following schematic for that :

My question is how big is the voltage on the  MCU pin (my target voltage should be 3.3V)
the way I see it , if  **Vin ** is equal to 5V the output voltage is also 5V ?
should I connect the the MCU pin to the voltage regulator ?
thanks for any hint !

UPDATE
made changes based on Andrew answer


texts: What are the major advantages of using a closed-loop over an open-loop and vice versa?

texts: I'm trying to gain a better understanding on the pros and cons using closed-loop or open-loop motor control. Also trying to better learn when it's more sensible to apply each one


texts: How do I transition from one state to another with d-flip-flops? (digital lock)

texts:
I am currently trying to make a digital lock for an assignment, the code in this example is hardcoded 1-2-3.
This is what I have so far:

x0,x1,x2 are the BCD input for the lock. I am trying to make the circuit go from state q0 = 0 and q1 = 0, to state q0 = 1 and q1 = 0, when the input x0 = 1 and x1 = 0 and x2 = 0. I am trying to implement this with dflip flops, but I am having a really hard time, and cannot for the life of me figure out how to do this right. Out is the signal to open the lock. It will only open if q0 = 0, q1 = 1 AND x0 =1 and x1= 1 and x2 = 0.

The circuit behaves like I expect it to, but I can't figure out the memory aspect of it  at all. Any help would be greatly appreciated!


texts: How does battery protection ICs sense current

texts:
I have a hard time grasping a concept when it comes to a particular type of battery protection ICs (which protects from overcharge/under-discharge and over-current). One example is the BQ2973 from TI, although this topology is quite common.

Link: http://www.ti.com/lit/ds/symlink/bq2973.pdf

They all can "sense" the charge/discharge current, through a specific pin (in the case of BQ2973 the pin is called V-). I don't get how the IC can detect and categorize the current going through the battery. I see no way the current through the battery can generate some kind of voltage difference anywhere in the circuit so that the IC can measure anything related to the battery current.

In many cases there seems to be some internal circuitry with some kind of resistor between VSS and V-, but in my opinion no current would flow (at least no current proportional to the battery current) through this resistor once the transistors are fully open, as is the case when charging/discharging.

Does anyone have any experience with these kind of protection circuits?


texts: Best Circuit Design for a 12VDC Wall-Wart > Ouput Voltage of 1.5V (Replacing Alkaline Batteries)

texts:
I have multiple stationary baby items for my son Oliver that require a serious supply of batteries each month. I would like to hook a few of these stationary items up to wall warts to conserve the constant expense of alkaline purchase/recharging of batteries. I currently have two spare wall warts laying around the house: first at 9V/1A and the second at 12V/1A. I am located 15km from a Mouser warehouse in case the garage will not suffice.

Two items I would like to wire up right now include a baby rocker which requires one D battery and a crib which includes a mobile electronic toy rotation device requiring 3 AA batteries.

I was lucky enough to get these from a baby shower and due to my current job situation, I can't upgrade. I would like to build a circuit for both but will discuss the baby rocker at this point.

This circuit would need to accept either voltage from the wall warts and drop it to 1.5V to run the baby rocker's vibrator. I have been looking at the 780x type linear regulators at this point but am not sure if this is the way to go. I wanted to see what you might recommend. I need advice that will not only eliminate batteries, hopefully save electricity, and also be easy to solder as I do not have the skills and equipment for SMD applications.

Thx in advance for your help!


texts: How to measure water heater temperature?

texts:
I'm building a summer cottage and plan to add some sensors for monitoring system health, with a Raspberry Pi and/or Arduino. Specifically, since electricity is not always available there, I'd like to measure the water temperature in a stock water heater (50..100 litres, 13..26 gallons) that doesn't have any extra connectors to use, eg. a Jäspi 30 or 60 litre model (pdf).

What kind of sensor should I get? How do I plug/plumb it securely?

Some notes:

I'm aiming for a "ballpark" accuracy, maybe something like ±5°C..±10°C (±9..±18°F)
I'm not planning to control the water temperature, just for logging
I'd rather not damage the heater or its insulation
I'd prefer a solution that would not void my house insurance (in case of an unrelated water damage)
It doesn't have to look pretty :)


texts:
I've known about the coldboot trick for a while, but have never really considered the physics behind it. I've read the paper, but it doesn't really cover why it works.

How does physically cooling a stick of RAM to a very low temperature cause the data stored in it to be maintained over long periods of time, even without power?

I know that DRAM ICs are essentially a large array of transistor-capacitor storage cells, but I can't work out why the temperature makes any difference.

It also raises further questions:

Are the decay characteristics of the device enough to allow for the "previous" value of a cell to be measured, at normal or lower temperatures?
Is this the same phenomenon that causes bit-rot, i.e. random flipped bits in computer memory?
Does this apply to other scenarios, such as altering the state of microprocessors, or changing how a transistor switches in a discrete circuit?
If extreme cold causes the charge state to decay more slowly, would that imply that heating the RAM would erase any data stored in it?


texts:
I am facing a problem with a voltage source with 0 current through it. Will the power of that source be 0 according to the formula P=V*i? Is there a reason to use such a source if it neither provides nor receives energy ?
Thanks.


texts:
I would like to better understand how a PFC controller works, especially PFC which work in CCM mode. I found the following documentation from International Rectifier: https://www.infineon.com/dgdl/an-1077.pdf?fileId=5546d462533600a40153559563801007
which deals with the mechanism of a PFC converter. The mechanism is described at page 4: "One Cycle Control for PFC".

Here is what is described:

I know that the result duty cycle should look like to this:

What I understood:
The main goal of a PFC is to put the input current in phase with the input voltage. In order to do this, if Vin (rectified) increases, the total variation of Iin (Ioff + Ion) across the inductor during the switching period must be superior to 0 in order to increase. It means that the Ion variation must be superior to Ioff variation. And inversely if Vin (rectified) decrease. Besides, the voltage output must be regulated to an output which is constant! So if Vin increases, we have to reduce the duty cycle in order to transfer less energy to the load and inversely when the input voltage decrease. This is exactly what we see in the above waveforms.

What I did not understand is how the controller works to do what we see on the above waveforms.

Suppose Pout is constant over the time. If Vin decreases, the energy transferred to the load decreases as the variation of the current across the inductor is lower, the the output voltage decreases, so the error amplifier voltage increases, it means that the slope of the integrated error amplifier voltage increase, then if Pout is constant as Vout is lower than previously, Iout  which is proportional to Isense increases. So the slope of "-GdcRsIsense" (there is a minus) will increase, and it will tends to decrease the duty cycle where as we want to transfer more energy to the output in order to have a constant output voltage? Where is my error?

Thank you very much!


texts:
I'm trying to configure the timer3 to have a frequency of 1KHz, without success.

Here's my configurations:

System Clock:

RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 4;
RCC_OscInitStruct.PLL.PLLN = 64;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;

So SYSCLK=64MHz

Timer3:

htim3.Instance = TIM3;
htim3.Init.Prescaler = 480;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 66;
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
{
    Error_Handler();
}

sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
{
    Error_Handler();
}

sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
{
    Error_Handler();
}

if(HAL_TIM_Base_Start_IT(&htim3) != HAL_OK)
{
    /* Starting Error */
    Error_Handler();
}

So APB1 Timer Clock = 32MHz.

So the Timer3 Clock Frequency should be (1/(32MHz/480))*66, which is approximately 1Khz, but for some reason I'm getting 500Hz.

Any help will be greatly appreciated.

EDIT:

My interrupt function:

/*check if interrupt is from TIMER 3*/
    if (htim->Instance!=TIM3)
        return;

    timer_counter++;

    if (timer_counter == 65500)
        timer_counter=0;

    if(timer_counter%1000==0)
    {
        uint16_t test[4];

        Send_CAN(&CanHandle2, 8, test);
    }

I'm receiving the CAN message every 2 seconds instead of every second.


texts: Local voltage regulatıon on large board with 12V - 24V power input - is it a good idea?

texts:
I am designing a board for my Bachelors thesis. The board takes 12V - 24V as an input. The dimensions are 100mmx100mm. It will be a 4 layer board and has an onboard antenna, multiple sensors and a Raspberry Pi compute module 4 as well. I am thinking of reserving 1 layer as a power rail and 1 layer for GND. My question is:

Should I regulate the 24V voltage into 3.3V & 5V near the VCC, use wide track width and then just use low pass filters near the Vin of ICs?

or

Should I feed 24V into the power rail and regulate the voltage locally at multiple points on the board?


texts:
I'm not sure if this is the best place to ask this but I'm not sure where else too

For my graduation I'm trying to embed a Led RGB matrix display connected to a raspberry pi on my cap. Iv seen this done before but I'm trying to figure out the best way to power it.

The documentation says the board needs 5v/4a for full power. The connector is just +- bare wires and I was originally going to splice this onto a USB cable to be powered by a backup battery pack.
(Like the kind you would charge an iPad with)
 This is the way I have seen it done before as well but the best battery I can find are max 5v/2.4 amps on a single port with 5v/4.8a total.
I'm not sure how others have made it work, maybe by using both ports simultaneously or maybe just by not using all the LED on the board at a time.
The raspberry pi is easy to power but the led Matrix it's self is the problem.

Specifically what I'm using is this led board
https://www.adafruit.com/product/1484
With this as the control board
https://www.adafruit.com/product/2345?gclid=CjwKEAjw3KDIBRCz0KvZlJ7k4TgSJABDqOK7cI7D7wwQngD1iQS12nLYY6kadgxEOYFFARfDUHfPChoC4_Dw_wcB

I would be grateful if anyone has any suggestions for me.
Thanks


texts:
Do gas discharge tubes used e.g. for surge protection have a polarity, i.e., do they protect in both directions (i.e., depending which wire is hit, or if it is a positive/negative lightnings?

The symbol (see below, from Wikipedia) has a dot that suggests some asymmetry. Electrons should be able to jump in any direction, but how are the positive/negative electrodes engineered to facilitate/stand the discharges?


texts: PWM created from 16-bit timer and 32-bit timer

texts:
I have a question that does the PWM created from 16-bit timer differ from one created from 32-bit timer.

Personally, I deem that they are the same, since by taking the fourier series of the PWM signal I see that the dc level of PWM signal solely depends on the duty cycle.

Thanks!


texts: Identification of bipolar transistors on die (pnp or npn?)

texts:
is it possible to tell from this photograph whether the transistors are npn or pnp? And if so, what is the line of reasoning? How to sort that out?

This photo I took is from a Sharp GP1FAV51RK0F Toslink reveiver and shows two bipolar transistors (at least I guess so).

Edit:
Some more photos of other transistors on that die:


texts:
I'm trying to understand the schematic of the Apple 1 computer power supply.

Nothing surprising at first sight. Two power transformers (117 VAC -> 10 VAC / 117 VAC -> 28 VAC), two diode bridges, and four voltage regulators (+5V / -5V / +12V / -12V).

But looking closely, I can't understand the logic here.

While the +5 volts output uses the first power transformer, through rectification and regulation, the -5 volts output uses the regulated -12 volts output.

So basically, why is that? Why doesn't it use the rectified output of the 10 VAC transformer, as does the -12 volts output with the second transformer?

Or maybe why is there two power transformers? If the -5 volts uses the regulated -12 volts, why can't the +5 volts use the regulated +12 volts?

And if I may ask another question here, what about the capacitor values? Looking at the datasheets for the voltage regulators, capacitor values look really huge.

For instance, typical application schematic of the LM323 uses 1uf and 0.1uf capacitors. So what's the benefit of using such high capacitance in the Apple 1 power supply?


texts: Can a power MOSFET for switching application be used as a linear amplifier?

texts:
Power MOSFETs nowadays are ubiquitous and fairly cheap also at retail. In most datasheet I saw power MOSFETs are rated for switching, without mentioning any kind of linear applications.

I'd like to know whether these kinds of MOSFETs can be used also as linear amplifier (i.e. in their saturation region).

Please note that I know the basic principles on which MOSFETs work and their basic models (AC and DC), so I know that a "generic" MOSFET can be used both as a switch and as an amplifier (with "generic" I mean the sort of semi-ideal device one uses for didactic purposes).

Here I'm interested in actual possible caveats for practical devices which might be skipped over in basic EE university textbooks.

Of course I suspect that using such parts will be suboptimal (noisier? less gain? worse linearity?), since they are optimized for switching, but are there subtle problems that can arise by using them as linear amplifiers that can compromise simple amplifier circuits (at low frequency) from the start?

To give more context: as a teacher in a high school I'm tempted to use such cheap parts to design very simple didactic amplifier circuits (e.g. class A audio amps - a couple of watts max) which can be breadboarded (and possibly built on matrix PCB by the best students). Some parts I have (or I could have) available cheaply, for example, include BUK9535-55A and BS170, but I don't need specific advice for those two, just a general answer about possible problems wrt what I said before.

I just want to avoid some sort of "Hey! Didn't you know that switching power mos could do this and this thing when used as linear amps?!?" situation standing in front of a dead (fried, oscillating, latched,... or whatever) circuit!


texts: Help understanding the SPICE input impedance - why does it seem lower than I expect?

texts:
I am attempting to model a very simple common emitter amplifier for 144Mhz (2 meter HAM band). I found a LTSpice model for a nice RF transistor (MPSH10, 650mhz Ft) since jellybean transistors like the 2N4401 can't really give much gain at this frequency. I thought with this model I should be a more successful at simulating a circuit at higher frequencies.
I wanted to simulate and check the input impedance, and try to set things so the input will match without any matching network (by modifying emitter resistor and current). This is where I'm having trouble understanding something.
To measure input impedance I used the LTSpice current source set to a AC value of 1, so I can just look at the level directly as ohms. I then performed an AC analysis from 120Mhz to 150Mhz
My problem is even with the MPSH10 transistor, for some reason this circuit gives me an input impedance of only 13 ohms.  Why?

My emitter current is around 10ma. My Collector voltage is about 7volts.
I'm confused. Because my emitter resistor is bypassed with a capacitor I should only have to take into account little re for emitter resistance -The "conventional" way I've seen the impedance calculated by hand for a Common Emitter circuit is to take the transistor emitter little (re) and do: 25(mv)/Ie to get little re, that would give me 2.5, then multiply by beta to get the base impedance (and then of course put that in parallel with the base resistor bias network). According to LTSpice, if my input impedance is only like 13 ohms that means my beta would only be around 7 or 8. That doesn't make sense at all given this is an RF transistor, the beta should at least be around 50ish, if not higher,  at this frequency I would think.
Can you help me understand what I might be doing incorrectly?
This is the model for that transistor, it has exteremely low Base-Collector and Base-Emitter capacitance:

I want to understand how to find the input impedance, and have it makes sense to me as to how it's "normally" calculated in common emitter circuits.
I realize a real circuit will have parasitics too and I am greatly simplifying things here.


texts: Opto switch for detecting translucent polypropylene

texts:
I am building a liquid handler (a CNC machine that pipettes small quantities of liquids). The machine switches polypropylene "tips" between pipetting different fluids. Positional accuracy within 0.5mm of the pipette tips is key. However, I have sourced tips from several different manufactures and in each batch there are some tips that are slightly bent/warped. I would like to find the position of the bottom of the pipette tip to calculate any offset into the g-code if the pipette tip is bent. (Note: The diameter of the bottom of the pipette tip is 0.75mm.) These tips are very fragile, so I would prefer not to bump them into mechanical switches. I wanted to use optical switches, but polypropylene has a high transmission of IR wavelengths, and thus do not trigger optical switches.

So my question: is there a way to optically detect polypropylene? Polypropylene has a low transmission at 3250 nm. This is my first post to StackExchange let me know if detail/formatting is lacking. Thank you for your time.


texts: What will happen if I connected 3amps adapter to motor that's need only 2.1amps are that will burning the motor?

texts: I have 3amps power supply and the motor just need 2.1amps so if I connected they together are that will destroying the motor ?


texts: Current mirror LED circuit with constant current source

texts:
I am trying to temporarily fix a current mirror circuit for driving 40 LEDs. Each LED in the circuit represents a custom LED strip that has a forward voltage of roughly 145V and a forward current of 60mA. the problem with the circuit is that the transistors used have a low gain of about 50, which causes the reference string to draw lots of current, about 130mA. This overdrives the reference LED quite significantly. My goal is to reduce the current in the reference string while maintaining the current mirror function.

simulate this circuit – Schematic created using CircuitLab
I have done multiple experiments to figure this out, among which are:

Increasing the reference resistor, R1

This does reduce the reference current but it increases the voltage supply. This then increases the Vce voltage of each transistor causing the transistor to dissipate lots of heat.

Increasing the emitter resistor of the reference string, R2

This reduces the reference current string to roughly 100mA, as it reduces the emitter current of the transistor in the reference string. However, this causes the total base current to increase by about 25mA. Is there a reason for this increase? The higher I increase the emitter resistor, the drop in current seems to be less significant, is there an ideal value I should use?

Unfortunately, the PCB for this circuit has already been manufactured and assembled. Hence, the only modifications I can make are by replacing components and not adding anything.
Any help will be much appreciated. Thank you in advance.


texts:
I‘m new here and have the following problem. I have developed a module in vhdl which scales the frequency of an input clk by the input prescaling value (0-255) s.t. the frequency of the output signal is f_out=f_in/(1+prescale).

My design works fine in simulation but from past uni courses and eyperience I know this is still far from working in hardware.

What I believe might cause a problem is the following: I have an internal signal that switches level when a rising edge for clk_out should occur and one which switches level when a falling edge for clk_out should occur. clk_out is then simply an XOR of both...so behind these two buffered internal signals I have a small combinatorial part that generates clk_out. My design keeps the duty cycle at 50% so a falling edge can be generated at a falling edge of clk_in, thus I cant simply flop clk_out.

So my questions are:

Will the combinatorial part cause problems in an fpga design? Afterall...clk_out will be used as a cloxk signal.
Is there perhaps a better way to approach this? I really only need the rising edge of clk_out so the duty cycle is not too crutial, however how will.I realize the clk_in=clk_out case?


texts: Will a LDO regulator with a proper output capacitor be destabilized by the addition of a high-ESR capacitor?

texts:
I am interested in using a LDO linear regulator, e.g. the On Semi NCP5501DT50RKG, to step down a voltage from 6-9 V to 5 V. It specifies that it is stable with output capacitors between 1 and 10 μF with an ESR of less than 4 Ω:

However, I'm intending on using it to power an IC which suggests the use of a >47 μF bypass capacitor.

With a low-ESR ceramic capacitor (perhaps 2.2 μF) at the output of the regulator, would the addition of a high-ESR electrolytic bypass capacitor cause any instabilities? Is this answer true in general for all LDO regulators which are stable with low-ESR output capacitors?


texts:
I suspect this component to be a SMD microphone made by ST. Unfortunately I could not map the writings on the device to any SMD microphone datasheet issued by ST.

Do you have a clue?


texts:
Hello I am a beginner trying to use the L6203 motor driver.
I am working while looking at the L6203 data sheet, and I am trying to make a circuit as shown in the picture below. However, I am curious about the type and exact capacity of the capacitor used in the picture below. Thank you very much.


texts: How to select most efficient motor for generator?

texts:
First post. Please forgive me if this is a stupid question. This post can be broken down into two questions.

I am building a bicycle generator, but am new to the field of EE. I am trying to select the most efficient means of generating electricity, but have only been able to find suggestions in terms of selection (as opposed to a numbers-based approach). The goal for this phase of the project is to output the highest wattage possible (ultimately in the form of DC power).

1) What numbers and criteria should I use for deciding whether to use a motor or alternator for this project? I understand that alternators generate AC, and (many) motors generate DC.

2) Once I have decided on which approach to use, how I can select the most efficient component?

When searching online for the answer to this question, I came across some helpful links (examples here and here), but I did not see any quantitative methods for finding the most efficient solution.

Thanks.

EDIT:

I am building a generator designed to output 3-phase power for industrial applications. I am not sure whether to create AC (and use a variable frequency drive to convert it to 3-phase power) or use DC, and then convert it to 3-phase power. The idea is a ride a stationary bike (probably just a bike on a stand) to turn the generator shaft.


texts: AC steady state circuit analysis using mesh

texts:
I have attempted multiple tries into this circuit problem and I am getting no where. For this question I have to use mesh analysis to find \$V_x\$. \$V_x\$ is across the right branch containing the 3 ohm resistor and \$-2j\$ ohm capacitor. Everything is in impedances.

simulate this circuit – Schematic created using CircuitLab

After I setup my three loop equations, I got three unknowns, which seemed right because I setup three equations, but after substitution, I realise the final equation had two unknowns in it. However, I noticed since the straight branch of wire the \$4j\$ inductor and 10 volt source are in is in parallel with the right most branch containing the 3 ohm resistor and \$-2j\$ inductor, then both branches should have the same voltage. So that's what I did and set up another equation,

$$I_3(3-2j)=(I_3-I_1)(4j)+10$$

So when I tried to find \$V_x\$, where \$V_x = (I_3)(3-2j)\$, I get a value of 10, which is not correct because the answer is \$V_x = 17.4(-21.625^{\circ})\$ in phasors.

So can someone please help me see where I went wrong?


texts: Voltage doubler 0.7V to 1.4V DC output from air flow sensor

texts: I need to double the DC output of an airflow sensor from 0.7V DC to 1.4V DC. There seem to be numerous options, which just confuse me, and I thought I would ask to see what you would recommend. 12V DC available.


texts:
I am working on how to use ultrasonic devices to inspect some products.

I am completly new to this.

After searching around the Internet and reading the specifications of this transducer, I only know it is an angle beam transducer.

But what type of transducer is it: single element, dual element, or delay line transducer?

By the way, what is the meaning of "delay line" transducer, how is it different from other transducers?


texts: What is the correct name for the ACTION you do when installing a jumper?

texts:
While writing an instruction document for configuring an evaluation board's firmware, involving the repeated installation and removal of jumpers, I used the terms "install", "connect" and "reconnect" to describe putting a jumper in place. I used the term "remove" for taking it out.

One of the reviewers thinks that "connect" is a wrong term, as it may confuse the user, as in "connect to what?".

So I was wondering, are there correct terms to describe these two actions?


texts: General suggestion about how can I cancel the noise

texts:
I have designed a board and I have six relays on it, so I am scared that maybe when relays want to switch, my micro-controller (ATMEGA32) will stop working.

I have used  a diode and also a ferrite bead but if any of you have some kind of suggestion about it, it will be great help to me.


texts: How can such an equation for the temperature of a *black body* be valid in this case?

texts:
I am currently studying The Art of Electronics, third edition, by Horowitz and Hill. Exercise 1.6 says the following:

C. Power in resistors
The power dissipated by a resistor (or any other device) is \$P = IV\$. Using Ohm’s law, you can get the equivalent forms \$P = I^2 R\$ and \$P = V^2 / R\$.
Exercise 1.6. Optional exercise: New York City requires about  \$10^{10}\$ watts of electrical power, at 115 volts (this is plausible:  10 million people averaging 1 kilowatt each). A heavy power cable might be an inch in diameter. Let’s calculate what will happen  if we try to supply the power through a cable 1 foot in diameter  made of pure copper. Its resistance is \$0.05 \ \mu \Omega\$ (\$5 \times 10^{−8}\$ ohms)  per foot. Calculate (a) the power lost per foot from “\$I^2R\$ losses," (b) the length of cable over which you will lose all \$ 10^{10} \$ watts, and (c) how hot the cable will get, if you know the physics involved (\$ \omega = 6 \times 10^{-12} \text{W}/\text{K}^4 \text{cm}^2 \$). If you have done your computations correctly, the result should seem preposterous. What is the solution to this puzzle.

We managed to get the answer to (a) here as \$ 3.8 \times 10^8 \ \text{W}/\text{ft} \$. I then get \$ \dfrac{10^{10} \text{W}}{3.8 \times 10^8 \ \text{W}/\text{ft}} = 26.32 \ \text{ft} \$ for (b).
Now, I'm trying to solve (c). I'm referring to this document, which claims that, to calculate the heat dissipated by the cable, we can use the Stefan-Boltzmann equation. However, according to the Wikipedia article, this equation describes the power radiated from a black body in terms of its temperature. How can such an equation for the temperature of a black body be valid in this case?

EDIT


texts: Trying to obtain a voltage gain equal to 3 without an op-amp

texts:
I'm a beginner in electronics and currently, I am trying to design a Wien bridge oscillator. I've read documents about oscillators. For now I am stuck at trying to design the amplifier, without using op-amps. I'm trying to obtain a voltage gain equal to 3, to respect the Barkhausen condition.
Can you give me some ideas or advice about what I'm doing wrong? The Wien Bridge is disconnected so that I can verify the gain of the amplifier.


texts: What is the difference between these two SSB phasing method block diagram?

texts:
I was searching the block diagram of SSB phase shifting method. I found these two different block diagram:

I thought the second one is wrong but this one is used many times in different websites. I tried to find the output signal by using trigonometric functions (The first equation is for first diagram, the second one is for second diagram):

Are my equations mathematically wrong? And do these diagrams generate exactly same SSB waveform?


texts: Can I replace MC33204P with one of these other op amps?

texts:
I'm working to make this schematic
and I was wondering if it is possible to swap out the MC33204p with either LM348N or LM339AN. And if you could let me know why swapping them would still work I'd be greatful.


texts:
So I have some old dynamo, and I want it to power my GPS navigator.

But first of all I want to calculate its maximum power it can deliver.

Setup: two wires are soldered to dynamo on one end, on other end they are soldered to 5 Ohm resistor. True RMS multimeter is measuring AC voltage across the resistor.

Results: on my normal speed it showed 3 V. On my maximum speed 3.15 V.

3*3/5 = 1.8 W

Dynamo is labeled 3 W, measured resistance 33 Ohm.

The copper wires are near 0 Ohm. All joints are soldered. There cannot be any losses.

Question 1: Did I do right to calculate maximum dynamo's power?

Question 2: Where is 1 W lost?


texts:
The LT3757 datasheet includes the following schematic:

The resistor in the bottom left corner is annotated with a frequency (100kHz).  What is the significance of that annotation?


texts: "Proper" way to wire an unbalanced TRS-to-TRS cable

texts:
I was about to wire up a short 3.5mm TRS lead when I realised that I actually don't know how -- at least, I don't fully remember a non-conflicting set of best practices.

This is the standard stereo audio configuration, so we have two independent signal conductors (left and right) and a common return, no shield (or return is shield).

A lot of the pre-builts I have kicking around have a shotgun coaxial configuration, with the return as a shield around each signal conductor.  I was going to build it that way but then I realised that that means the shield conductor splits in two and rejoins at the other end.

That's not ideal, right?  I faintly remember something about RF passing through the loop -- like it would form a gateway to the Demon World or whatever.

The next most obvious approach (being the next most readily-available piece of cable) is a common screen/return, and two signal conductors inside.  That also seems less than ideal.  I think it could encourage some kind of inappropriate coupling behind the screen.

So... Three unscreened conductors?  Twisted?  An elaborate braid that creates two loops within the same conductor, encapsulating one signal in each?

I'm pretty sure it doesn't matter (audio frequency, short runs, etc.), and there's no need to point that out; but a lot of best practices don't really matter, but they're still best practices and we do them anyway.


texts: Understanding the circuit diagrams for white noise generators

texts:
I'm a huge neophyte when it comes to electronics, and I'm trying to work out how to create a white noise generator for a project. I've been looking at some to base my examples off of. One of which is below from this site.

I see that Vin starts at the +14V. 1N759 must be the diode that is reverse-biased to produce noise. It is then amplified by two MAX2650 low noise amplifiers and then that amplified noise is outputted. Here are some questions I have about this circuit, pretty much entirely due to my lack of knowledge of electronics (of which I'm looking to better understand here):

What is the purpose of R1 and its connection to ground?
What is the purpose of the 5V output?
What is the purpose of the capacitors here at all? What are they serving to do? Especially C3. It doesn't even look like outputted noise goes near C3.

My complete lack of knowledge is clearly showing. Anything you could recommend that I can read to quickly figure out stuff like this would be greatly appreciated as well.


texts: Imagine an ADC unit with a sampling rate fs is not used with an anti-aliasing filter and the sampled data is logged. If in FFT of this logged file one sees a suspicious frequency component call it fx, what can we say about the value of the down sampled high frequency component fh which appears as a false fx? Mathematically speaking.


texts:
I have a four layered PCB with two major high frequency component placed on the top layer. One is JN5169 and other is SE2431l (front end module), both operate in GHz. While evaluating the circuit (with the help of gerber file) I noticed a long trace and I have studied that long traces would add to EMI.
Will it be a good practice if the SE2431l was placed on bottom layer and JN5169 on top and both connected through vias? But I have also read that when dealing with high frequency components vias should be avoided as it would lead to impedance mismatch and hence
would lead to EMI.
So my question is what to prefer? My ultimate aim is to reduce the EMI on the board.


texts:
I'm trying to design an small but effective heatsink (DIY type), the design that I came up with so far is a 4x4x9cm aluminum square tube with a 12V fan under it blowing up:

poor designing skill...

The size of the heatsink is choosen based on the box space limit and I only have access to one side of the heatsink to install the regulators. I want to install 4 inefficient linear regulators on it, which in worst case will waste 20 watts of power in total.

Does vertical heatsinks have any advantages over horizontal heatsinks?
How can I calculate the cooling capability of this heatsink?
That regulator which is going to dissipate more heat, should be at the bottom side of heatsink or top?
Where should I install the temperature sensor to monitor the temperature and change the fan speed?


texts: Two-port network Current Characterization

texts: I was trying to solve this two-pole exercise in which I had to found the z-parameters but I haven't find any clue in the textbook. How should I solve it?


texts: What is the problem with my differential equation solver I made using an op-amp in PSpice?

texts: I designed a differential equation solver using an op-amp in PSpice, but the output is not what I expected. According to the equation, its transfer function poles are (-3,-2) with no complex part. So, its output should be overdamped but it is not. What could be the problem?


texts: Can a lower voltage overheat a magnetron?

texts:
Background
I am working on a microwave oven that starts to emit an odor after 2 minutes of full heating despite otherwise working correctly.  The smell is the same as that "sweet", overheated coil varnish smell that anyone with much electronics experience knows well.  It seems to be coming from the magnetron (inside the area where all the electronics are mounted, not the cooking cavity).
Question
When I measured what seemed to be low voltage going to the magnetron, it dawned on me: Since magnetrons are somewhat mystical in their operation to me, is it possible that a lower voltage could cause them to overheat?  Would it matter if the electrons took a different path inside the tube?
Details
To assuage responders' questions about my methods, the following details are presented.
The magnetron's wave-guide looks clean via a bore-scope and the cooling fan spins.
With a multi-meter, I tested the magnetron, high voltage (HV) transformer, HV diode and HV capacitor while each was disconnected; all test fine that way.
I swapped, one at a time, the HV capacitor and the wave-guide cover, but the smell recurs after the 2 minutes.  I replaced the magentron, too, and the smell changed slightly but was still present.
I can't see the HV diode causing such an issue, but I may try swapping it next.
I have an old, 30 kV, analog, DC voltmeter that I used to test the HV circuitry (I don't know of its accuracy).  According to the oven's service manual for the oven, approximately 2400 volts should come from the HV transformer which is then "doubled" to about 4000 V and then fed to the magnetron.  When disconnected, I measured 3000 V (maybe less) on the lead that is normally connected to the magnetron.
A new, replacement HV transformer is not available and a good used one may be hard to come by.
(If relevant, I remember replacing the HV capacitor years ago and noticed that that capacitor is rated for only 2100 V [what the appliance parts shop ordered for me back then]--I do not recall the original working voltage of that capacitor and it is not in the manual.)

Edit: Repair
For those who are curious about the end result of the repair, I fixed the magnetron overheating smell with an exact replacement, HV diode change.  I didn't expect this.  Again, the old diode behaves normally on a meter, forward-biased vs. reversed (though it measured 1/3 lower resistance in the conducting direction than did the new diode--I assume it has gone out of spec.).  But I now measure 1 kV DC with the magnetron connected (versus 1.5 kV DC with the old diode), 2 kV DC when it's disconnected (versus 3 kV DC with the old diode) and there is no smell even after several minutes of full-power use.  Thank you all for your helpful comments.


texts: How can current be in different phases in the same wire at the same time?

texts:
We know that either in ideal or practical transformer in no-load condition, the exciting current has two components Ic(core loss component) and Im(magnetizing component). Now since the same current will flow through the winding, how can the two current be out of phase as we learned the current goes out phase when the current is divided into paths, and there is the same voltage between two distinct terminals. You can explain this in an equivalent circuit but in the actual circuit the current division is not possible as there is just single wire winding.

Also, the same case is with the compensation current that appears in the full load condition. The two currents are out of phase in the same wire.

How is this possible? Is it just a theoretical concept just to make it easy for understanding, or am I missing something here?


texts:
Question

Will this switch spark when it is switched?

Intro

I am currently working on a electric longboard and I came across this problem.
I have a  LiPo battery providing power to the motor through the ESC (electronic speed controller). Now, when the batteries would run out of juice I'll have to charge them and in doing so I'll have to connect those leads to the charger. Most E-board builders use a loop-key to cut the circuit between the battery and the ESC. This is a good and working solution but the only problem is that if you were to forget to remove the loop-key you would potentially harm the ESC. An anti-spark on/off switch is more elegant solution, but still has the same problem.

My question: would an SPDT switch with the following specifications suffice?

Rated Voltage @ 15A 250VAC, 20A 125VAC

Schematic

simulate this circuit – Schematic created using CircuitLab


texts: Operational amplifier output is asymmetrically clipped

texts:
Why would an amplifier output be clipped asymmetrically?

I am building a small headphone amplifier using the Texas Instruments TPA6100A2. I have built up the circuit just as in the TPA61002 Evaluation Board User's Guide:

The opamp is designed for single supply, single ended use. The only difference is that I added 100uF electrolytic capacitors at ROUT and LOUT with 20 Kohm discharging resistors on the headphone side.

I am powering the 6100 from a 3.3v regulator and it works very well and looks like will meet my needs. I will add that the datasheet references driving 16 or 32 ohm headsets. However in my case I will be using it to drive an aviation headset with impedance around 300 ohms. The tests with said headset are very promising.

Below there are two screen captures of the amplifier output (yellow trace) being fed a 500Hz sine wave from a cell phone (blue trace).

I will note that at the level of output on the top picture with my headset the volume is too loud. Withing the listening level there is no clipping (at least for my use), meaning I don't expect to spend any time at all in this region of the performance domain.

Just to find out where the limits are I pushed it into full overdrive (bottom picture).

So it is not rail-to-rail (I knew that) but gets fairly close to the full 3.3v in the supply (not shown but the oscilloscope was displaying 3 volts as the amplitude). It is still clear that the wave is clipped in an asymmetrical manner.

Why would this be? I've double checked the wiring and setup, all that seems correct as per the schematic referenced above. Is it possible I have a bad opamp? Unfortunately I do not have another on hand to compare against.

Adding information:
The datasheet provides this insight:

"For
maximum
signal
swing
and
output
power
at
low
supply
voltages
like
1.6
V
to
3.3 V,
BYPASS
is
biased
to
VDD/4.
However,
to
allow
the
output
to
be biased
at VDD/2, a resistor, R, equal to
RF
must
be
placed
from
the
negative
input
to
ground."

Also, this setup is on a breadboard with jumper wires and 5% through-hole resistors and capacitors, not like the EVM with it's fancy SMD 1% components.


texts: Will there be a problem if I stay almost in the border in trace spacing when dealing with line voltages?

texts:
The IPC-2221 standard shows that 1.25mm will be enough at less than 3050m at 250V (220V is the line voltage here in Turkey), even if the coating gets damaged. However, people generally recommend 5mm even 10mm. Why is this precaution taken? What is going to happen if I stand in the border and make the trace spacing 1.25mm or 1.5mm or 1.75mm or 2mm?  That is a lot of options :)

Here is the table for IPC-2221. (I just saw IPC-2221 in the first line in Google that's why I've chosen that. My question is not standard specific meaning it could be other standards too.)

1.25 mm =  50 th
1.5  mm ~= 60 th
1.75 mm ~= 70 th
2    mm ~= 80 th
5    mm ~= 200 th
10   mm ~= 400 th


texts:
I just started to use PSpice. I created a rectifier in PSpice 9.10, but somewhere I'm making a mistake and I don't know where.

The output:


texts: Measure distance using an ultrasonic sensor in a pipe

texts:
I am trying to find the distance of an object in a pipe, but I am getting wrong values using the ultrasonic sensor with an Arduino as the sound is bounced back from the surface of the pipe.
What do I need to do to get the right values?
This is the picture of what I am trying to do.


texts: Why are there current and voltage limits in a DC bench power supply?

texts:
I have a few questions about bench power supplies.

Why does a DC PSU have a low output voltage limit, usually in the range of 18V-24V?
Why is there a current limit built into the PSU? My understanding is that the PSU should only supply voltage (i.e. energy to the electrons in the circuit wires) and the supplied current should only depend on the resistance of the wire or the internal resistance of supply or component attached, i.e. a resistor or LED?
When we short the terminals of the power supply, why does the output voltage on the supply approach zero? If there is no component attached, shouldn't there be zero voltage drop across the terminals, leaving the output voltage the same as if the output was not shorted?


texts:
I've a dimmer in the wall (I assume it is a TRIAC) and I would like to get the "signal" or the dimming position into a MCU as a number 0..1024 (for 0..100%). The TRIAC will never be connected to a lighting load, I just want to gather the information to a MCU. What I will do with the signal (LED, PWM, aso) is not relevant for my question.

I assume that I have to attach some type of load that waste as little as possible power <<1W.

I suspect that this is not even possible since my goggling has given me no result, but perhaps I miss the right concept/words.

EDIT The lighting (probably LED) will be controlled both from the dimmer in the wall and from other sources (probably android app or home wep app), and as soon as the other source says "light on" the light should work even if the dimmer is completely off. The idea with the pot (thank you @Transistor) is very good, the only point is the model of my dimmer is part of a model/line and every piece is very expansive.


texts:
I am planning on powering 10 white LEDs (LUXEON 3014) from a single AA rechargeable battery with Vin min=0.9V, Vin max=1.4v
VLed=2.8v @ 23mA so total Vout for 10 LEDs Vout=28v, iout=23mA
I found this boost driver from Diodes ZXSC310. The issue is the app notes doesn't tell you how to calculate key parameters like the inductor.
This is the schematic I will be using. Instead of D1 I will have 10 LEDs.

Now as far as values I used this calculator to find the inductor value

Does L1=7.2uH ipeak=0.665A and a duty cycle D=0.975 sounds about right?

Would you recommend having the LEDs in parallel instead? if that's the case then Vout becomes Vout=2.8V, Iout=23ma*10=230mA. The downside is the inductor will have to be bigger and the LEDs will need a balast resistor to even their light output.
I would appreciate your input.

****Updated Design**
I am changing the design to 2 x AAA cell instead of a single AAA. This way it will improve the efficiency of the circuit.
LEDS are now configured to 5 in parallel and 2 in series.

Attached is the new Bootstraped Boost converter to help achieve the higher drive current to the BJT.
The Transistor was also changed to NSS40201LT1G, this has a higher max VCE of 40v and cheaper than the FMMT617.
Below is my calculation of the circuit variables

LED Driver Input voltage vs BJT drive current.
  6:


texts: Can we attach LED to VGA port and make it light up, the same way we do in Parallel Port?

texts:
I just connected an LED to a parallel port in my PC and controlled it successfully through inpout32.dll

I was wondering, if it was possible to do the same with the VGA port. Where can I find information about the functions and layout of the pins of a VGA port and how to use it to light up an LED?

Tried to search myself but was really tough - any Google search using the terms "VGA" and "LED" is only resulting in the TV and Monitor related websites.


texts: ASDA-A2 RS-485 Communication Configuration

texts:
First of all, I know that my question is very specific for those who have hands on experience with the ASDA-A2 Servo Drive from Delta-Electronics. But I hope that someone will guide me through the solution of my problem.

I have a Delta ASDA-A2 Servo Drive and I want to send control commands from my PC through the COM port, so I have used a USB-RS485 converter from the same manufacturer of my drive which is called (Converter) IFD6500.
The problem is when connecting the Servo Drive through the converter to the configuration software (ASDA-SOFT) I find that it's not working except under the 9600 baud-rate, and it gives me a lot of timeout failures and wrong communication messages. When changing the communication speed from the parameter P3-01 to any other higher baud-rate it gives me an error of device not found.
I though that may be the problem is from the wiring of RS-485+ and RS-485- signal pins so I have replaced their position and I got a total communication failure.
I want to solve this problem and get a successful communication with different baud-rates between my Servo Drive and PC
Here are the pin-out diagrams of my devices:

IFD6500

RS-485 Port on Servo Drive(ASD-CNIE0B06)


texts: One particular part number not showing up on Eagle board layout

texts:
I finikshing up the silkscreen for a board about to be sent out for fab, and for some reason, I have two diodes whose part numbers are not showing up on the board layout, while all my other parts numbers are displayed just fine.

Here is one of the parts; it is a diode which should have a label "D2":

The part is from the SparkFun DiscreteSemi library (SparkFun-DiscreteSemi.lbr), and has a >NAME label defined in the appropriate layer (95 Names):

When display the properties for the part on the layout, everything seems ok including the name:

Any idea why the label for this one part isn't showing up, while all my others are?


texts: Best way to switch between multiple power rails based on whether they're present or not

texts:
I've come across this issue multiple times already and never really figured out the best way to do it.

I'm designing a controller PCB for a drone and I would like to have a few different ways of powering it. USB power just for the control electronics, a battery connector (2-4S, not really sure yet) for the ESCs/motors and another regular connector for development 12V supply so I don't have to rely on batteries.

Now, I'd love to have a circuit that would automagically switch between these and make sure only one of them is active at any time to protect other supplies from reverse current and what not if multiple are plugged in at the same time. For instance, I would probably have USB and the 12V supply or battery plugged in at the same time during development because USB would just be used for debugging and the 12V supply or the battery to power all of the electronics and motors. Priorities would be 12V supply > battery > USB.

I could probably figure out the rest out myself but I just don't know where to start with this.


texts: Why is the DC motor receives higher voltage from the PWM than what is given?

texts:
While I was trying to find the gain (K constant) of a motor, I gave different voltages to see if I will have the same gain constant in each of them.

While doing it, I come through an issue. When I vary the voltage directly from the power supply the motor rotates at the right speed, for example: if I change the voltage from 24V to 12V, the motor speed drops exactly to the half. However, if I do the same thing with the PWM (ie: give PWM = 50% ) the motor rotates at a higher speed than the half value.

Has anyone have an explanation for this? this is crucial as the PWM will be used to control the motor speed and position.

Thank you for your help.


texts: Common emitter amplifier gives an amplified inverted output. So if I fed the inverted output to a speaker, would it sound fine ? If not, how do I get an amplified but non inverted output from a common emitter biased transistor ?


texts: Can I get away with multiplexing an array mechanical Relays via Mosfets?

texts:
I want to use an Ardiuno to drive a Matrix of TO-220 Mosfets triggering mechanical relays instead of LEDS.

I am making an array of glow-tubes (read: flickery, purple lightbulbs) as a dramatic screen interface for an art installation. I would prefer to use mechanical relays for aesthetic appeal (clickity clack!).
I will build a 4*4 prototype, then a 16*16 or larger according to funding etc.

I want it to be an expandable design, so im considering multiplexed control rather than dot matrix.

1: At multiplexing speeds, will a mechanical relay coil hold?

I am switching at full coil voltage, so when multiplexed the current might be alright for holding.
Are there any tricks like putting in a capacitor somewhere that might fill up the tiny delay?

2: I will have a diode across the relay coil, but will jamming coils on and off at high rates create any kind of EM noise or current spikes I should be wary of?

3: Am I on the right track? I basically want a controllable lamp array, im using standard LED multiplexing designs because its readily available for arduino so I dont have to code it all aswell :D

Found an interesting discussion here on a technique using i2c and TPIC6B595 serial latches,


texts:
I am using PCA9685 in a project. 3 are on the same i2c bus and thus I need to change the address of individual ICs. It has 5 selectable address bits as shown in the figure below:

The address will change depending on whether A0...A5 are tied to GND or VCC.

Datasheet says that:

  To conserve power, no internal pull-up resistors are incorporated on
  the hardware selectable address pins and they must be pulled HIGH or
  LOW.

Does it mean I need to use external resistors for pull up or pull down or am I allowed to directly connect the address pins to GND or VCC as per my requirement?


texts: Confusion about currents in switching circuit using flyback diode

texts:
I have a basic switching circuit question. I'm confused about the currents. I'm trying to understand how does the current loop through the diode in the below circuit:

I get the following plots from simulation:

(Blue plot is diode current, red plot is MOSFET current)

Can someone explain in detail(step by step in slow motion) what happens during the pulse_in goes ON from OFF state?

It looks like in the plots, the moment the pulse_in goes ON(MOSFET should start turning on), the diode and MOSFET current both makes a short huge peak. But when the MOSFET is ON how come the diode conducts here? The plots confuses my understanding.

Another thing is where does the diode peak current(during flyback operation) flows into(from and through where)?


texts:
Consider we have equal power divider, So when we have 100 watts in port 1, this power split to two 50 watts in port2 and port 3.
for calculating how much temperature Rising in each transmission line, I should know how much power incident from each transmission line a. Temperature rise per RF Power is will be obtained with Microwave Impedance Calculator Software.
So, how should I know how much power incident from each line of gysel power divider?


texts: Should I use separate grounds for these voltage regulators?

texts:
I am a bit confused right now.
I have 2 voltage regulation modules:

24V->12V
24V->5V

The 24V-12V has Vin+, Vin-, Vout+, Vout- while the 24V->5V only has Vin, Vout, GND.
Do I have to use a different ground for the Vin- than for the Vout- and if, which one should I choose for the second regulator? If not, why are there different Vin-/Vout- in the first place?


texts: Why are telephone/internet lines less susceptible to surges than power lines?

texts:
(I know nothing about electronics, so excuse my ignorance.)

I understand surge protection for power outlets are necessary, or at least recommended, for expensive electronics. But are telephone lines susceptible to the same voltage spikes as power lines?

I am guessing the answer to this question is "No," since I've never actually seen anyone using surge protectors for phone/fax/modem lines. But why are phone lines less susceptible than power lines? What about them makes them more resistant to these spikes?


texts: How to remove Noise/Voltage in TX pin of PIC16F877?

texts:
I wanna connect an existing device to PC using RS485/RS232. I have programmed the microcontroller correctly and it works when I haven't switch on the power of device. I mean after programming by PIC kit 2, I have tested it by connecting the related cable from TX pin to PC and have received the test messages of microcontroller by hyperterminal. but when I turn on the device I can not receive. I tested the output voltage of the TX pin, It shows 4.3v voltage. I used 1k pull-down resistor in this pin. the voltage removed but still I can not receive any message.

Suddenly one day, after programming the microcontroller and without disconnecting the in-circuit programming cable, I saw that the device is sending message. after checking all pins of PICKIt 2 programmer, I saw the pin GND of programmer is affecting the device and removes the voltage in pin Tx. I mean if I connect the GND pin of microcontroller to an external GND, It sends correctly the message but sometimes with a bit changes in some characters randomly like a noise.

briefly, there is a noise in Pin Tx of PIC microcontroller. How can I remove this noise when the device is connected to mains. I should mention that this device has some parallel boards: power supply board, MCU board and IO boards beside each other. the power supply board is very close to MCU board which including out microcontroller (around 2cm).

Should I use a bigger pull down resistor? Should I use capacitor in parallel with pull down resistor? which capacitor?
Please guide me. I'm a EEE student working on a summer project.
I appreciate a lot in advance.


texts:
Question:

The problem is I always stuck at this kind of problems can you tell me how to solve this problem ?

I think about using Thevenin or Norton but circuit seems to confusing.


texts: Request for guidance on sources to help me figure out how to do simple thing

texts:
I have 9 3w leds (white) and 2 1w leds (blue).  I have one led driver with sufficient output to drive only the white leds (either in series or parallel.)  Therefore, I figured I will get a separate driver for the blues(which have a much lower total power requirement than the whites.)  With a 3 position switch, i would like to have:

Position 1 - both white and blue leds on.

Position 2 - all lights off.

Position 3 - blue lights only on.

This seems like it should be simple.  Any direction on learning how to do this would be welcomed.

Thank you.


texts: Effect of antenna position indoor and influence of multipath

texts:
for my current project I do research regarding indoor-localization and I try to use
the RSSI from my wifi to calculate the distance between smartphone and access point.

I heared that:

) this procedure depends on the orientation and position of the receiving antenna.
) On the other hand multipath effects are not relevant.

Because I do not know much about antennas I would like to ask if these 2 statements are correct or where can I read more about them.


texts: How can I identify specifications for this possible passive speaker with subwoofer? And what are each wirings on that cable for?

texts:
From Reddit https://www.reddit.com/r/techsupport/comments/g5aynj/can_someone_help_me_identify_the_specifications/ I tried to get specifications of a speaker. This one here is specifically for ASUS ROG GL752VW, a gaming laptop.

What was found out is that it is possibly a passive speaker, so the speakers don't have any power in it, analogue audio, apperantly. Unsure if it gets sent in digital or analogue.

Here are some images of the speaker from the Google search: https://imgur.com/a/fbIxV9D

and here is a picture of the, that was found from the Reddit post and the image is from here https://www.ebay.com/itm/ASUS-ROG-GL752V-Internal-Speaker-MT2920b/114108584582?hash=item1a9166d286:g:mQoAAOSwfiNeQgK3

From the image of the cable you can see that is uses 2x black, 1x red and 1x white wiring colors. This cable is from the speaker and later gets connected somewhere on the mainboard.

What I could also find out is that the speaker might was made from a company called VECO if, I compare the logo on the casing http://www.veco.com.cn/.

Now my question is, what do each of these colors here mean? And how do the speakers work, do they need power or not? And is it possible to determine what their specifications are, as example "2W x Stereo" or something like that.


texts: I am trying to make a JK flip flop circuit in proteus but 2 of the nand gates does not seem to be working. There are no errors provided. Two of the 2-input nand gates does not seem to show output when one of the signal is neither red or blue.


texts:
I was trying to implement Inductor using capacitor in Lt spice. But the circuit waveform is not steady.

Also the impedance is not exactly proportional to frequency. please explain this deviation.


texts:
Working with microchip MCP73831T chip to charge a single LiPo cell.  We are producing by the 1000 unit and getting significant failure of the charger IC.  I suspect we need ESD protection on the 5V for hotswap events, or maybe backfeed somehow from the L1 inductor hurting the IC?    Does anyone have any clue what could be wrong with my circuit below?

Not sure what that guy meant by non legible.

Product is failing on customers, after 1-3 months of repeated usage. Maybe 5-10% unit failure rate.

USB plug/unplug to charge an 18650 LiIon cell, 2000mAH, at 500mAH per the charger spec sheet. Symptom would be charger IC no longer lights up status LED and does not charge battery or output voltage. Replace IC and works OK again.

If unable to figure out, maybe just dump microchip brand charger for a comparable texas instruments...


texts: Low pas filter time constant for a square input

texts:
I am trying to plan a low pass filter as in the picture:

I use it to create an ON/OFF lag (Is this the correct term?)
I have calculated the time constant τ of the system:

My question is:

How do I calculate the time constant for the same circuit, but with a square (not sine) input?


texts: What would be the best type of cover/front panel for a circuit board that has an IR proximity sensor consisting of an IR LED and an IR photdiode? Would regular plastic/plexiglass work or would that reflect the emitted IR too much and screw up the proximity detection?


texts: Isolation of the transformerless power supply

texts:
One of the disadvantages of transformerless power supply is the isolation problem because of the absence of the transformer. My question here is : Doesn't the capacitor in series at the input do the trick? the capacitor is 2 parallel plates isolated from each other and the current flows through them by the electric field.
isn't that enough?


texts: What is this Circuit's function? Does it involve Isolation?

texts:
My question is: Does this circuit isolate the "X Volts" lines from ground (1) If not, how should I implement an opto-coupler to provide isolation between the data lines ("X Volts") and ground? (Question 1 - Main question)

I briefly looked up the datasheets for both the BAW56 and the GL05T

The BAW56 is a high-speed switching diode? Is this for when one line is in use it will close the other line? (Question 2)

and the GL05T is for ESD/groundloop protection is this correct? (Question 3) It looks like Unidirectional Clamping as shown in the datasheet. So this means no current can pass FROM ground, and only current can pass TOWARD ground once the zener is satisfied?

It doesn't seem to be isolated because I don't see any opto-couplers involved.

Further information:

"X Volts" lines are data lines pulled up (with resistors) to 3.3v


texts: Does forward current of diode has any affect on forward voltage?

texts:
In datasheet I observed that forward voltage of diode given as between two values (min and max). In my application the current though the diode is not constant it switches every 15 min(may be more or less).

Is it that the forward voltage remains constant even if the forward current changes ? Does current has any affect on forward voltage?


texts: Solar panel voltage drops when connected with load

texts:
I have a 100 watt solar panel with the specifications:

Optimum operating voltage = 18.1 V
Optimum operating current = 5.52 A
Voc = 22.1 V
Isc = 5.86 A.

I connected this solar panel directly to a 100 watt microinverter and connected a 33 watt lamp to the inverter.
The voltage from the solar panels dropped from 19 volts to 8 volts.
Did something go wrong with the solar panels?


texts: What is the proper and up to date method for multiplexing digital inputs?

texts:
So Im following the diagram here for wiring up a MC14067BCP:
http://fluidforms.eu/docs/MultiplexedArduinoWiringDiagram.pdf

The only difference being that I am doing one set of 16 sensors and not four. Additionally, my sensors are 5k - 250k LDRs (light sensitive resistors) that I have connected to ground on the end opposite of those connected to the connections shown in the diagram above.

When I run my sketch, the serial line shows output that is similar to what would be shown if no wires were connected to my analog in at all. (see the question here to see what I mean by that: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1238854387)  This is really stressing me out and it would be amazing if someone could enlighten me as to what is going on.

Here is my code:

int CONTROLpin1 = 2;
int CONTROLpin2 = 3;
int CONTROLpin3 = 4;
int CONTROLpin4 = 5;
int analogPin = 0;

// Variables:
int actualSensorValue = 0;             // value from the analog input

void sendCommand(int value) {
  Serial.println(value);
}

void setup() {
  //  set the states of the I/O pins:
  pinMode(CONTROLpin1, OUTPUT);
  pinMode(CONTROLpin2, OUTPUT);
  pinMode(CONTROLpin3, OUTPUT);
  pinMode(CONTROLpin4, OUTPUT);
  pinMode(analogPin, INPUT);

  Serial.begin(9600);
}

void loop() {
  int i;
  for (i=0; i <16; i++) {

    // set control pins on the multiplexers
    digitalWrite(CONTROLpin1, bitRead(i,0));//bit4
    digitalWrite(CONTROLpin2, bitRead(i,1));//bit3
    digitalWrite(CONTROLpin3, bitRead(i,2));//bit2
    digitalWrite(CONTROLpin4, bitRead(i,3));//bit1

    Serial.println(i); // print which pin we are on
    actualSensorValue = analogRead(analogPin);
    sendCommand(actualSensorValue);

    delay(1000);
  }
}

Additionally, I have tried cutting it down to the bare minimum and only wiring up a single sensor. When looking at the output, there appears to be no change.
Here is a picture of the bare bones wiring:

(but to be clear my end goal is still the diagram at the top of this post).


texts: Getting rid of ripple from an LCD backlight

texts: I have built a circuit which contains an integrated power supply stepping down mains voltage to 5v through a transformer, rectifier circuit and a voltage regulator. With a couple of smoothing caps the ripple is (virtually) non existent. I'm using this power supply to power an ATMega168 and a 16x2 LCD display, with a minimal amount of other small components, mainly a voltage divider with 2 x equal value resistors. All works fine, but when I connect the LCD backlight to my power supply, a large amount (1.3v) of ripple appears all over my DC supply which is obviously upsetting my voltage divider. I have searched on StackExchange and also other places to see if there is an easy solution to what I imagine is a common problem, but haven't found anything, so was wondering if you guys could help? What's the simplest way to get rid of this ripple?


texts:
I'm trying to build my own relay board to use with a 3.3V controller. I found the schematic of the board, so I'll try to replicate it. I'm only having trouble understanding what's the purpose of the LL4148 diode parallel to the coils.

Here is the schematic:

Here is a simulation of the circuit. Removing the diode seens to make no difference.

http://bit.do/fgPsz


texts: What determines the operating point of an op-amp?

texts:
Let's say I have the following 2-stage op-amp:

The DC transfer is as such:

I would like the slope to be steeper and the center point to be at 0mV input. What should I be changing? In other words, what are the factors affecting the DC operating point?


texts: Using a variable as array index - Optimization Bug?

texts:
I discovered a bug in my code which only turns up if avr-gcc optimization is used.

Can somebody explain whats the problem here?

I'm aware that there are several smart ways to achieve some PWM, but that is not the point here.

Background Information

I play around with an LED and dimming it with PWM. To do some simple gamma correction I use a predefined array with the right values.

Code

This is the code I use, Main contains just the interrupt init and an empty while(1) loop:

volatile size_t fade;
volatile uint16_t counter = 0;

const uint16_t PROGMEM pwmtable_10[64] = {
    0, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 7, 8, 9, 10,
    11, 12, 13, 15, 17, 19, 21, 23, 26, 29, 32, 36, 40, 44, 49, 55,
    61, 68, 76, 85, 94, 105, 117, 131, 146, 162, 181, 202, 225, 250,
    279, 311, 346, 386, 430, 479, 534, 595, 663, 739, 824, 918, 1023
};

ISR(TIMER0_OVF_vect) {
 // fade is set in the main loop or somewhere else
    if(counter < pwmtable_10[fade]) {
        counter=counter+1;
        PORTB = 0;
    } else {
        counter=0;
        PORTB |= RED;
    }
}

A value of 1 gives a very bright light, a value of 1023 gives a very dimmed light. The value 1023 is accessible through the array index 63.

The Problem

It doesn't matter which value I set fade to, the LED is always bright, if I compile my code with avr-gcc -Os.
By using avr-gcc -O0 the code works.

Changing to code doesn't work even by setting fade to 63 inside the interrupt:

ISR(TIMER0_OVF_vect) {
    fade=63;
    if(counter < pwmtable_10[fade]) {
    //[..]

This is what works:

Replacing pwmtable_10[fade] with 1023.
Replacing pwmtable_10[fade] with pwmtable_10[63]
Replacing fade with a new variable directly declared before the compare

Additional Info

Platform: Atmega 168

% avr-gcc --version
avr-gcc (GCC) 4.8.2

Commands to build and flash the code:

avr-gcc -Wall -Wextra -Os -mmcu=atmega168 -DF_CPU=16000000 -o moody.elf moody.c
avr-objcopy -j .text -j .data -O ihex moody.elf moody.hex
avrdude -b4 -c usbasp -v -p m168 -P usb -U flash:w:moody.hex


texts: Understanding s-domain poles, negative frequencies and bode plots

texts:
The transfer function of a low-pass filter, \$H(s)=\frac{1}{s+1}\$ has a pole at \$s=-1\$. Setting the real part of s to 0, we have a pole at \$jw=-1\$. In the bode plot of this transfer function, at \$\omega=1\$ the gain has dropped to -3db.

What I don't understand is why the effect of the pole \$jw=-1\$ appears on the bode plot at \$\omega=1\$.

I guess I am confused about the significance and relationship between the s-domain, the jw axis, and real frequencies, and how a pole in the s-domain affects the other domains.


texts: Can anyone tell me the value of this resistor

texts:
I put the colors into fields on a webpage but when I get to the 3rd color reading it in both directions the color is not there????????????????

No larger space between bands so I know I'm reading it in the correct direction....

Here is the pic-


texts: Strange trend for ECG gold electrodes impedance at DC

texts:
I’m trying to characterize two electrodes for ECG which are made as a classic PCB with a rounded shape and with the copper covered by a thin layer of gold (ENIG process). My first attempt was to put these electrodes in a 1% NaCl saline solution and connect them to a known load to create a voltage divider (in the picture Z represent the electrodes/solution). Then I applied a DC voltage to calculate the electrodes/solution impedance. In the schematic, Vin is the DC voltage aplied and R is the known resistance from the electrodes/solution to ground with a value of about 22.6 Kohm. The resulting value of Vout is then used to calculate the Z impedance.

The result is the following graph which shows 5 minutes of constant voltage application (every sample represent one second).

Why I obtain this trend? I really don’t understand why there are these kind of steps during time. And on top of that, for every test I perform I have different results which means that not always the trend reach an almost stable value (like in the case shown in the picture) but sometimes, even after two hours, it continues to grow.

In the test illustrated, the "distance" between steps are successively (ohm)

2056 - 2151 - 2293 - 2347 - 2526 - 2637 - 2821 - 2969 - 3163 - 3352 - 3558

In the following picture a particular of the last step where the impedance rises about 3 Kohm in ten seconds and then stops.

Can anyone explain me the reason of this behaviour?


texts: Are toroid chokes lossy? Are they good for winding inductors?

texts:
I am going to try using a QX5252 to drive 300ma led. The specs imply a 30uH inductor in the 'boost' circuit would do the trick, which I would wind on a small ferrite ring I have, the kind used to suppress rfi by running ribbon cables through it.

But those rings are not 'meant' for hi Q inductors. Are they maybe specially made to be lossy for rfi suppression, and hence not a good choice for a switch mode power application?

A previous question on SE advised about ferrite properties here, and, later, here.

I tried to tag this with 'Q' or quality factor, but it wasn't there.


texts: VCTCXO control voltage circuit recommendations?

texts:
I'm building a frequency calibration rig. Right now, I've got a fixed TCXO and it has an uncalibrated drift versus GPS of around 0.185 ppm ±50 ppb. I'm prepared to simply subtract 0.2 ppm from the observed measurement either in the firmware or by hand/eye and call it a day.

But academically, I've considered what I would do if I required the ability to tune out the drift. My trepidation is that the control voltage must be exceedingly stable, possibly in the face of changing environmental conditions. Just sticking a multi-turn pot between Vcc and ground doesn't seem like the best answer... does it?

Connor Winfield has an application note with a schematic for supplying the control voltage, but their source is an SPI D/A converter. I'd want to make it a manual adjustment - the multi-turn pot. But is it just as simple as replacing their D/A converter with that pot? If so, then what am I getting out of the precision OP amp immediately following it?


texts: CC1 and CC2 when connecting USB C to USB 3.0, is this pulldown network correct?

texts:
I have a USB C port on my computer and a USB C male-to-male cable, as well as USB C female and USB A 3.0 female breakout boards.

I have connected my computer to the breakout via USB C cable and wired the USB C breakout to the USB A breakout. So, I can connect devices to the USB A breakout to connect to my computer. The connections I used are below.

My problem is the CC1 and CC2 logic. I read about the pullup and pulldown networks needed for UFPs and DFPs for USB C. Some sources: (1), (2). So, I connected CC1 to a 5.1k resistor and connected that to ground. I did the same for CC2. This works when I plug in a USB 2.0 mouse (it uses D+ and D-) but this does not work for my USB 3.0 drive (even when I flip the cable).

USB A USB C
1 -> A4,A9,B4,B9
2 -> A7
3 -> A6
4,7 -> A1,A12,B1,B12
5 -> B10
6 -> B11
8 -> A3
9 -> A2

Do I need a different resistor pullup/pulldown network in order for my design to work with USB 3.0?


texts: TP4056 - Micro USB 5V 1A - Output pins Current supply

texts:
I have "TP4056 - Micro USB 5V 1A Lithium Battery Charger with Protection" as below

I have a Li-Ion 3000mAH battery like below

Connected them as below

Questions:

What is the maximum current that I can get out of Output + , Output - pins.
If I use the battery directly to my load I guess I can get up to 3Amps as battery has 1C capacity. Will it be the same from Output +- pins. In other words , are these pins just an extension of my battery (or) do they limit the current to 1 A ?
Can I charge the battery ( as depicted above) and also connect to the load to it at the same time.

My requirement: I am trying to power on my SIM800a module that needs 3.7 - 4.2 V and 2 A current max at some times. So I want the module to be powered using this battery , but just like we use phone, want to use it when the battery is being charged as well. I would also connect nodeMCU( D4,D3) to the SIM 800 ( Rx, Tx) to send and receive data for further implementation. At the moment I am powering my nodeMCU with another 3.3V/5V power supply, but I would want to use the same battery to it too.

Question 3: To power both of them ( sim 800a, nodeMCU) using the same battery , how should I connect them to Output pins.?


texts: Current monitor output doesn't respond to load changes

texts:
When I physically build this circuit the output voltage doesn't response to load variation.
The voltage across the sense resistor is definitely increasing when decrease the load resistance, the voltage difference between the opamp input pins varies accordingly, and there is a voltage at the output which means the NPN is turning on.

What am I missing?


texts: current amplification on common emitter mode of bjt transistor

texts: what actually amplifies the current in CE mode of a transistor(npn here)? When the input is applied betn emitter and base, the forward biasing causes the electrons to move from source to the emitter say 100 electons. The same 100 electrons move towards the base where very few no. of electrons combine with holes say 2. they move out of the base towards source. so remaining electrons are 98 which move to the collector and out to the output circuit. So where is the current amplification? i have considered the Veb as 0.7 and Vce to be 1.


texts:
I have looked through several documents, but I haven't find found a clear answer which pins on ESP32 support I2C communication.

Can the I2C be routed to almost any I/O pins?

Are there certain pins which support I2C?


texts: ULN2003 IC , should I stack it or should I divide the load?

texts:
I am trying to drive 7 led strips.
I saw in the datasheet that the ULN2003 IC can supply 500mA per channel. In reality this would be limited due to heat dissipation by the IC.
Should I drive 3 led strips on 1 IC and 4 on the other, or should I stack it to increase overall current and divide the heat dissipation?
Each strip takes around 400mA at 12 volts.


texts:
I have just seen the comparator as figure 1 below and I am wondering why don't we use a simplified version as figure 2?

Hope anyone could make it clear.
Thanks.

Figure 1:

Figure 2: simplified version


texts:
What does limp mode mean in this sentence below?

  Make sure the PLL is not running in limp mode.


texts:
I am attempting to put a switch between the Data + and the ground wires in a USB cable. Now that I have cut open the USB cable, it does not seem to match any of the pinout diagrams I can find online.

The next few statements are based on doing continuity tests on each wire with one probe connected to bare wire in the middle of the cable and the other probe in contact with the terminals on the USB connector. I am also using this pinout diagram to determine which terminal serves which function. http://pinouts.ru/visual/USB.jpg

So far, I have two separate red wires that each pass cont tests with the Vcc terminal, a white wire that passes cont with the Data+ terminal, a green wire that passes cont test with the Data- terminal. The 5th cable is not insulated, and passes cont test with the ground terminal.

My question is, is my ground wire useless now that I've cut open the braided insulation and foil sleeve that contained all 5 internal wires? Alternatively, is any of my methodology for testing this cable incorrect or do I seem to be missing a key bit of understanding?

Thanks


texts:
Rise time and Fall time of both SDA and SCL signals are given as 20 + 0.1Cb ns in I2C bus fast mode electrical specifications version 2.1.  Cb is bus capacitance and units in picofarad.  How do the units match when Cb is in pF and time in ns?

From page no-32 in the specification.


texts:
What would be the best way to generate a triangle wave that can operate at 250kHz @ 4V peak-to-peak? I have tried the following circuit:

However, the best I could obtain was a 4mV peak to peak voltage at 160kHz despite mathematically calculating resistor and capacitor values, and trial and error.


texts: Will a start capacitor be damaged by an overloaded motor?

texts:
Background: A few days ago, the air conditioning unit at work began failing to start. Fans would turn, lights would be on, but no compressor start. I called a technician and he said the start capacitor was damaged (open).

So, I said, please replace said start capacitor (not expensive, excluding workmanship), and he replied that the compressor should be checked because if the compressor is being overloaded the capacitor would blow again.

Knowing that start/run capacitor, when used in monophasic applications, have only the purpose of creating a phase shift allowing for increased starting torque, and after started it effectively is disconnected from the circuit I suspect there is no sense in that.

That said, I ask you if the load profile of a motor, for example, if overloaded, have any influence in the longevity or failure rate of start/run capacitors.

Do not take into consideration ambient temperature, line voltage fluctuations and other factors not related to the motor and the capacitor.

Thanks


texts:
I am learning digital logic design with FPGA's, and I am using the Xilinx Spartan6 FPGA. I am able to successfully able to simulate my design correctly, but the design does not work properly, when I download it on my FPGA.

For this reason, I am trying to understand how my design is actually synthesised in order to understand what mistakes/assumptions I am making. But, I am having some problems understanding the schematics generated by the RTL Viewer

What does each component do (Simple ones like Mmux and Madd are easy to understand, but some like LDE, are not). Is there a guide which explains what all the components actually do (I tried googling, but could not find one).
Is there some definitive guide somewhere which explains how exactly to read and interpret these schematics ?
What do the component names mean? (i.e I have a multiplexer named Mmux_n00341, why Mmux? why n00341? ...)

Also, is looking at the RTL schematic the best way of understanding what is happening during synthesis ?


texts: Headphones wiring issue jack (ground loop?)

texts:
I replaced my 3.5mm jack 4 pole but it had 5 wires shown in the image below. I connected the mic ground and stereo sound ground and soldered together in the same slot on the 3.5mm jack.
BUT my friends can here the videos I watch and the sounds from my game almost perfectly. What should I do? I have a jack splitter, should I cut the green and pink heads and wire them directly? Any tips?
The wires are represented below


texts: Scale and expand an analog signal voltage

texts:
I have an absolute pressure sensor: MPXA4115A that give me an analogical signal between 4.307 and 4.846 V. To get an altitude measurement I give it in input to an Arduino Due board which admits a maximum of 3.3 V. I am thinking to employ a voltage divider in order to scale the signal between 2.843 and 3.198 V. Now, I would like to gain resolution expanding this signal range on the entire Arduino Due's voltage range that is between 0 and 3.3 V. I am new in this matter and reading around other questions I think that what I need is a differential amplifier or an instrumentation amplifier but I am not able to do the correct choice. Before writing this question I tried to make an electrical scheme using the software LTSpice. I have imported the model of the inamp MCP6N11 but the analysis does not work and the following error message occurs:

Analysis: Time step too small; initial timepoint: trouble with node "u1:_u1:21"

More in detail I replicated the standard circuit showed in the MCP6N11 data sheet (page 27):

Here is the circuit:

I don't know if the error in the analysis is due to the fact that in the imported .txt file for the MCP6N11 is recommended to use PSPICE (other simulators may require translation).

So my question is: what kind of amplifier I have to choose?

Thank you for any suggestion.


texts:
I'm working on getting an ATMega168 to talk to my GPS that I ripped out of the casing from Microsoft Streets and Trips. I know it talks RS232 @ 5v (according to this post) and I just need to listen on pin 3 and apply 5v to pin 5 and ground to pin 2. I'm having a hard time finding good info on how to use the MAX232 and I just followed a diagram from somewhere but I omitted all capacitors as I need to get some. I'm using the FTDI from an Arduino to forward any TTL to my computer and I get a special "y" symbol coming in when I unplug the data out from the GPS and I get the initial "Hello World" serial message I have in there, so I think the MCU side is all good. Do I really need these caps that I ommitted on the MAX232 chip? Why? Is there some other issue? How do I troubleshoot? I've got no scope.

Here's my pinout for the MAX232:

2 -> +5v
6 -> GND
8 -> GPS RX (pin 3)
9 -> MCU Digital in (software UART)
15 -> GND
16 -> +5v


texts:
I'm learning about the ideal diode.

The relation is pretty clear for V <= 0.

If V < 0, the diode blocks the current.

If V = 0, the current applied is the current out, and it needs to be controlled with a resistance to make sure the diode doesn't break.

However, I cannot find a clear explanation about what happens when V > 0? In most document I find, they don't even mention it! Would it be impossible?


texts:
Personally I'm having trouble with eagle's bgaAutoRouter when I use it, it's not doing the bga tracks and routes and I'm wasting a lot of time looking for how to make it work. my settings in image.

DRILL = 0.05MM
ALT   = 0.125MM

layer = (1+2*15+16)

eagle version = 9.2.2

BGA STATUS = 0.0% do not leave that percentage

datasheet bga

where I'm wrong that I can not solve this puzzle ?


texts:
I have just recently designed and manufactured my very first PCB with the goal of it being a dedicated circuit to my project. I developed an ESP8266 WiFi Mood Light, but the problems I currently face with VERSION 1 is that is makes a sort of hissing noise when I change colors via Blynk, and the transistors used in the project get very hot very fast. I know this has something to do with the current throughout the circuit being to high, but I don't know how to go about it.

I am open to further suggestions as well.

Thanks

UPDATE: Thanks for the telling me the solution to the problem, but unfortunately after implementing it on a breadboard, the circuit didn't the way I wanted it too. After swapping the emitter with the collector, the RGB led strip would not change color via Blynk. I have no idea how to fix it now. (LED strip uses 3 Amps)

]3
[]4

UPDATE 2: I have changed the BJT type transistors to MOSFETS now. The system works without overheating, however the hissing noise still persists, I have researched about the idea of a low pass RC filter, but I am not sure if it would be suitable.

UPDATE 3: Thank you all for helping me troubleshoot this circuit. It now works without overheating, and hissing. It turns out the hissing was related to the MP1584EN, so I changed it.


texts: Need help designing an airplane legal battery pack

texts:
I know this is not really a technical question but it might also help other people like me who design products with batteries. If it doesn't fit here, then please tell me where I can ask to find a solution, but I think that people who are experienced in electronics are the best to find an answer for this.

I know about the limit of 100Wh per battery pack that you can take on plane without approval of airlines. Recently I have noticed this being written on a Dewalt FlexVolt battery pack. It is a battery pack of variable voltage because its circuitry connects the cells as needed for the application.

It says, that is has capacity of 120Wh and next to it is says shipping 3x40Wh.
So does it means that if you divide the batteries electrically and not mechanically then it is fine to take it on a plane?

Thank you very much for any help


texts: Need Help Turning Circuit Off When Current / battery Gets Too Low

texts:
Big newbie here.... I had a quick question on where I should look if I want to design a switch that reacts to current / battery level? i.e. current above a certain level, circuit on, current below that level, circuit off.

I have a raspberry pi attached to a roomba for automated control. The raspberry pi is connected to the battery with a 5V regulator going to a USB. It works fine, but if it doesn't get back to the base in time the pi ends up draining the battery completely. I would like to make a circuit that turns a switch off when the voltage gets too low.

Any ideas on where I should start? Or is the whole thing dumb to begin with? lol

Thanks in advance!


texts: Measuring multiple analogue signals on 1 analogue Input?

texts:
Is it possible to detect multiple analogue signals from different analogue sources onto 1 analogue input pin on a micro controller.
Another way of asking this question is that we can detect multiple digital signals from a single analogue input by attaching different values of resistors to each digital input source and then when a digital source is activated the specific voltage can be detected using an analogue input, so similarly would it be possible to detect multiple analogue voltages using a single analogue input pin on a micro controller?


texts:
STM32F2: Makefile, linker script and start-up file combination without commercial IDE is a simple but brilliant explanation of what happens when we start a system based on a Cortex-M series processor.

Will be grateful if a similar simple information is provided for Cortex-A series processors too. Since Cortex-A processors use MMU, and conventional embedded-linuxes run ONLY on Cortex-A, so I am presuming that the bootup process would be significantly different.

Thanks in advance.

Thanks and Regards,
Ajay


texts: Convolution perfomed by an analog circuit

texts:
As a Electronic Engineering student I have a fair knowledge about convolution and DSP. But, I was wondering if it is possible to perform a convolution only using analog circuit (without memory)? And if it is possible, what would be the restrictions?

In short, I would like to project this using only an analog circuit:

$$
y(t) = (x * h)(t) = \int^{b}_{a}x(\tau)h(t-\tau)d\tau
$$

Clarifications:

Both signals would be an arbitrary input (x and h in the above formula).
I am willing to make simplifications of all kinds, since it is doing what I am asking.


texts:
I would like to know what is the best way of sending a signal to a smartphone, would it be via Bluetooth? The range needed would not be more than 2 meters, and the device sending the signal should be a very simple device with e.g. two buttons, each sending a different signal or ID. The logic of what needs to happen once the signal is received would be embedded in the software running on the smartphone. Also which microchip would be needed and what type of pricing am I looking at(looking for a fairly cheap cost)? The device should be as small as possible e.g. matchbox size and would need to be able to work under rough conditions, but I am assuming that will just depend on the type of mold/casing the chip and buttons will be built into. I am happy to only support IOS and Android phones released in the last +-12 months and any going forward.

Hope that provides enough information, and sorry for the limited electronic based technical info, but I do not know a lot about electronics and sit more on the software side of things.

Thanks in advance.


texts:
I'm routing some traces which carry high speed UART at 1.8432 Mbaud. The traces will be routed on the same layer as a power or ground plane (because it's a 2-layer design.) This will introduce capacitance.

My questions are:

How much capacitance on average will a 6 mil trace with 6 mil spacing on each edge have? If there isn't a general rule, is there a way to calculate it?
How much capacitance is too much capacitance?


texts: FIFO-related data transmission problems between microcontroller and PC

texts:
I have a situation in which a microcontroller is to perform a large number of ADC conversions and format the results into commands (or data packages) and send these to a PC using the UART. In order to measure continuously while sending data, I created a circular buffer (queue/FIFO-buffer) to store the pending packages, and the microcontroller will then (ideally) empty this queue as fast as the PC will allow.

The microcontroller automatically sends the next command (if any) after an ACK-character (in this case a ‘!’) has been received. The UART Interrupt Handler is like this:

if (ch == '!') // ch is the received character
{
    cmd_rx_ack = '!';
    cmd_tx_pop_cmd();
}

The function cmd_tx_pop_cmd() is taking one package out of the circular buffer and putting the bytes int a cmd_tx[] array and the length of the package in cmd_tx_length.

In the main loop:

if (cmd_rx_ack == ‘!’)
{
    cmd_rx_ack = 0; // Reset ack status

    // Transmit the command
    if (cmd_tx_length > 0)
    {
        cmd_tx_transmit();
    }
}

The function cmd_tx_transmit() is simply transmitting the bytes in cmd_tx[] one by one (this is done in the main loop since it takes too long time to be done in the UART-handler).

This works fine, if the consumer of the queue (in this case the UART-handler) has higher priority than the producer (a timer that periodically makes the ADC convert and push a data package with the result onto the queue). Earlier I had concurrency problems (see Concurrency issues with circular buffer in embedded program) but now I have another problem:

I want the microcontroller to send the next package in the queue not only when an ACK has been received, but also in the situations listed below:

The first package to be transmitted
If the measurements are performed at a speed slower than the time it takes to send a package.

In the first situation, the package is never transmitted since no ACK is received after the package is pushed onto the queue.

In the second situation, the packages are never popped out of the queue for the same reason as in the first situation. (Assume the first package is ACKed and the UART-handler wants to transmit the next one, but the queue is empty at this point in time). In this case, the queue is just getting bigger and bigger and no packages are transmitted.

I can solve the first one by transmitting the first package manually (without the use of the queue) and put the remaining onto the queue. Not a pretty solution, though - but it works... I still need to solve the second problem.

So, I think that the UART-handler is not the right place to do the queue-popping since it cannot take account for the two situations I just mentioned. But I cannot put it in the main loop since it has lowest priority and then concurrency issues become a problem.

What would be a good way to implement this?

Thanks in advance :-)

BTW 1: An ACK is transmitted to the microcontroller if the PC accepted the transmitted package. I have made a special encoding of the packages so their length can be determined. This works just fine and cmd_tx_pop_cmd() will only pop the first package available in the queue. I have tested all this many, many times and it works perfectly, so please do not focus on this part as it is not the problem.

BTW 2: The microcontroller is a Tiva C series TM4C123GH6 as found on the Tiva C Series Launchpad. I am using gcc-arm-none-eabi.


texts: 1000Z in the power circuit, is it a Ferrite Bead？

texts: is 1000Z a ferrite bead, and does it mean 1000Ω at 100MHz? OR something else? please help?


texts: Saturation on characteristic curves of BJT

texts:
how come there is saturation region when \$V_{CE}<0.3 V\$?

I know that:

$$V_{CE}=V_{BE}-V_{BC}$$

thus I can decrease \$V_{CE}\$ also decreasing \$V_{BE}\$. In this case, when \$V_{BE}<0.7 V\$, the base-emitter junction is reverse biased and the base-collector junction remains reverse biased like in active mode. Maybe, if I impose the \$V_{BE}\$, the only way to decrease \$V_{CE}\$ is to increase \$V_{BC}\$?

Thank you for your help.


texts:
I've used an H4155 on and off for about a decade now and every two years or so the backup battery begins to increase in standby voltage and fail.  I prefer to replace it just for the sake of it running optimally (though it is not required for normal operation; just battery swaps) but over the last few years trying to source both the battery (Varta V20HR) and premade replacements has been difficult.  I'm tempted to forgo it completely since I rarely use WiFi on it.

I can't tell if this is a sort of Molex connector or something proprietary as I've not seen anything like it and only have seen it in my iPAQs.  It is also the same type of plug used for the microphone and the H4355's speaker.  What makes it different is that the plug is perfectly rectangular.  The underside (not pictured) is simply the two wires as it doesn't have the protrusion I've seen in CMOS/RTC batteries for my ThinkPads.

As most of the batteries have corroded I want to either source new connectors or replace the wiring as the negative wire I believe is the one the corrosion travels through and onto the connector.  Curious as to which is easier or where to look for wire that thin.


texts: Is the energy loss in a voltage drop equal to heat/mechanical work/light emitted?

texts:
I am wondering if the energy loss in a voltage drop over an entire circuit is equal to the energy transferred from the circuit (e.g. light/sound/mechanical energy/heat).

If this is true, wouldn't that make it so that the voltage drop in a short circuit (with the power supply being a battery) would be 100% since all of the electrical energy must be converted into something else?

What is voltage drop with explanation of the example given?