texts: How to use the PIC16F628A's PORTA,4-7 as inputs?

texts:
I'm working on a countdown timer and I want to use the MSN of PortA for my switches.
I'm using MPLAB. I can't use C to program the PIC because the collage taught us to program in decimal, and they will think I copied someone else work if I write in C. I've got the rest in order so far, but I'm having a hard time with this part.


texts: Resultant impedance of infinitely continuous circuit of capacitors and inductors

texts: In this kind of question the approach is to assume resultant resistance before and after basic unit and then treat it as a simple circuit, but here i am facing problem because here both inductor and capacitor given (not a single element circuit) which gives really complex result.


texts: How to build an ultra-low power time counter?

texts:
Inspired by this question I would like to know how low power you could go with a counter + 32 kHz oscillator (possibly made by yourself).

I found a nice oscillator circuit on a BJT reportedly drawing less than 1.2 µA from 3V.

Unfortunately the counter and/or prescaler parts are a little more tricky. I do not believe you can make low power flip-flops from discrete transistors but most normal logic ICs are not very efficient either (standard counter ICs all draw around 80 µA at room temperature).

I do not want a counter that is integrated into a microcontroller (PIC or AVR or ARM).


texts:
I want to count how many people every day visits our store. In store has two entrances. Second entrance is not used often. Entrance gate is about 1.5m wide. I plan to attach some device to Raspberry Pi. What is best method to count people flow? I know that i can use laser. Witch is better and precise method?
I also want to make counter electronic stuff myself :), not to buy already made device.
Thanks.

Edit: looks like question is more like: what type of sensor i need to count visitors?


texts: What style of semi-permanent power connector for vibrating environment?

texts:
With the only constraint being that the connection is "easily" removable (e.g. not soldered, but common tools are fine), what style of power connectors work best for vibrating environments?

Specifically, I'm looking at 3D printers. A popular brand has a moving bed with a power connector to attach it. Their warranty stipulates that the connection is regularly checked and tightened. As you can imagine, there are cases of the connection loosening, then shorting and frying the bed. Is this a poor implementation, or is this a standard enough design for the circumstance?

For some context, here is their assembly manual.

There's a question here regarding which is better - screw vs. push in. I'm curious in the general case what style is the most robust to regular movement.


texts:
It's likely ESP8266-01, but when I look better there a bit more differences at its components. Also I think its pinout is different with a ESP8266-01. When I attach it to PCB I made for ESP8266-01 it gets hotter and also there is no LED in that module to know its status.
Do you have an idea what this module is?

Thanks..


texts:
I have a question regarding the design of DC inductors with the book TRANSFORMER AND INDUCTOR DESIGN HANDBOOK. Chapter 9 describes the design of powder cores.  A so-called core geometry constant is defined with

\$ Kg = \dfrac{Energy}{\alpha \cdot Ke} \$

Ke is the electrical constant and is defined with

\$ Ke = 0.145 \cdot Po \cdot Bm^2 \times 10^{-4} \$

Po is the output power and B is the magnetic flux density.

My questions, in case there is somebody here who knows this book or this design process (Kg-Method): What kind of constant (Ke) is this exactly?  Where does 0.145 come from?
Thanks!


texts: Changing Direction of twist in a twisted pair (24V 4A)

texts:
I have two wiring harnesses one going to my power supply (24V at 5A) and the other harness going to my main board, there is a motor controller on the board so it can draw a few amps.  I noticed that the harness coming from the power supply has a left hand twist and the harness going to the main board has a right had twist so at the point when I solder the two wires together the twist will switch direction. The location of the splice is going to be near an arduino board with analog sensor lines going to it.

Is it a reasonable issue to be worried about the noise this creates?  If so it is better to retwist the harness so they go the same direction or apply some shielding over the splice joint?


texts:
I am using a PIC12F1571 which have 3 PWM pins and two alternate PWM pins. What I want to achieve is to use the 3 original PWM pins and the switch to an alternate pin in software in order to get a 4th PWN pin. I am only partly successful since I am able to write to the 4th PWM but at the same time the original PWM is written to out of my control. It is obvious that I am doing something wrong or it may not be possible.

The thing is I don't need the PWM that I switch from at the time, its is idle and won't be active again until I have switched back. The data sheet allows two PWM pins to be switched to alternate pins. The idea is to have individual PWM signals to four different LEDs of which none will be active at the same time.

My question is if anyone know if it is possible to switch to alternate pin controlled by software using the PIC12F1571? The data sheet does not give a clue on this.


texts: Is LED properly implemented in the constant current circuit?

texts:
Consider this simple constant current source. The voltage is 27 V, yet the indicator LED is rated to a much lower reverse breakdown. Is the LED safe?
Will the LED draw current away from the output load? Output would be less than 1.5 mA.
Simulations in LTSPICE proved LED won't lower output current below 1.5 mA but I don't know for sure.


texts:
This is sort of a follow-up on this question: How important is impedance matching in audio applications?

So if impedance matching is not important, why don't we use say 1M inputs for line level inputs?


texts:
I am doing one hobby project, using STM32F103R8T6 Micro controller for my project, now I am using JTAG pins to program the controller. I will keep on modifying the firmware for my project, in this case which terminology is helps me to keep on updating my firmware. I am looking just plug and program kind of solution.
1) USB transceiver
2)Boot loader

Having USB transceiver is easy option or
Having bootloader is easy option


texts: What type of plug is this (looks like mini din 4 pin)

texts:
I'm holding a connector that looks just like a 4-pin mini din male plug, except that the plastic prong is in the wrong place and there is an extra metal strip, wide, thin and too short to be a pin, where the standard mini din plastic prong should be.

It is used to connect the pedals to the main body in my Korg EC310 digital piano.


texts: How does a center tapped transformer work?

texts:
I'm having trouble understanding the electric principles that allow a center tapped transformer to work. Lets say we're working with 240/120V. I understand if you connect a voltmeter across the top and bottom wires, you'll get 240V, and 120V between the center tap and other two wires. This is where I'm having trouble. The center tap is essentially a grounded neutral wire if my understanding is correct.

--------------A
~
~
~
--------------G
~
~
~
--------------B

Here is my secondary transformer. So i measure between A and G and get 120V because A is 120V more than G which is 0. So now when i measure between G and B i still get 120V telling me G is 120V more than B, or B is 120V less than G. This is the part that confuses me. How can my center tapped wire G which is grounded be at a higher voltage than B when it is supposed to be 0? Thinking about it the other way still confuses me as well; how can B be at a 120V less than G, what would that mean? Can someone explain the theory behind why/how this works?


texts:
Sorry if this has been asked before. Could also be a really basic question (new to electrical study).

I am a bit confused about the relationship between electrons and charges. So what I understand is this: (1) One coulomb of charge has 6.24 x 10^18 electrons and (2) an electron always carries one charge. Does that mean that ALWAYS for any given amount of electrons, there will be the same amount of charges? I am confused about this because the definition of coulombs interchange between electrons and charge. Some say it is 6.24x10^18 charge - some say it is electrons.

I am conceptually picturing in my head an electron "soldier". It carries a "charge". A soldier can only carry one charge. 6.24 x 10^18 "soldiers" equals one coulomb which simultaneously means the same number of charges (in essence, an electron is a charge carrier). Each soldier also carries food (stored potential energy) which is measured volts, which gets used up as the soldier goes on his/her journey.

So the question is - am I going in the right direction in terms of conceptually understanding charges, electrons and less importantly, voltage?


texts:
I am taking some off the shelf weighing scales and would like to interface a PIC to them for display and wireless transfer... The scales have four 3-wire load cells, one in each corner, and look very like the ones on the SparkFun web site.  I am guessing but I think the load cells have two resistors in them, one for tension and one for compression.
After the bridge arrangement the output of the bridge goes into a capacitor, resistor arrangement. I am guessing that the next stage is an amplifier of some type but it's inaccessible to me as it's a custom controller covered by a black blob.

Please can someone confirm the picture is about right and also suggest a good, PIC friendly way, to amplify the output either before or after the discrete.


texts:
I am working on a DALI system and I came across this schematic for the DALI power supply in a Microchip app note AN1465:

It says the power line can be 12-20 Volts but the current has to be limited to 250 mA or so. Some power supplies limit to 70 mA or 100 mA as well.

I need some help understanding this circuit.

simulate this circuit – Schematic created using CircuitLab

I made the schematic and ran a DC sweep for various values of R3 (1 ohm, 100 ohm, 1000 ohm) and understood that if I put a heavy load (R3), the voltage at Node1 will go low (mV range). However I need some help understanding what exactly is happening.

Is this schematic better or more efficient than a series resistor to limit the current to whatever I want. For example, I could simply put a 120 ohms resistor to limit the current to 100 mA on a 12 V power supply line.


texts: How can I make a 16x16 led pannel without losing the brightness intensity of each single led?

texts:
So, this is my first question here in this forum and I don't know if I'm doing this right. Then in fisrt place, I'd like to apologize myself if I'm doing something wrong or if my english is a little ununderstandable. I also don't know much about electronics, but even so I want to do this project and because of that I'd be extremely grateful if someone could help me.

What I'm trying to do is a 16x16 (= 256) led panel with 5W leds that need a 700 mA current each. The leds have differents wavelenght and beacuse of that, I want to divide these leds in two differents groups so that I can control the brightness of each group independently with its correspondent dimmer. The main point is, I want that when the dimmers allows the maximal current flows, each led must bright with the full intensity.

So, having said that, I'd like to ask 3 questions:

Would I need to use something else than a heatsink, transformer, the leds, and the dimmers to do this? (of course things like wires and plugs are already implicit).
Wich transformer suld I use ?
How should I set those things to not lose any brightness intensity of each led ?


texts: Send multiple analog signals to PC audio input

texts:
I have 4 signals that I need to send to the PC through the audio jack. Is there a way to do so with minimum data losses? I can't use frequency division multiplexing, so I need a way to get the 4 signals to be sent serially in order to record it using the mic, and extract each separate signal.

Is that doable? If yes how?


texts:
Among the ATmega328 "key parameters" is listed:

  # of Touch Channels: 16

What does this number refer to?


texts: Ensuring that the a circuit breaker in a secondary elec. distribution board will go off before a circuit breaker in the main board

texts:
I want to create a small portable single-phase secondary electrical distribution board to safely power up some lights in my back yard.

The board will be powered from a wall socket, and will contain 3 circuit breakers (perhaps a main breaker too) and three output sockets (to connect chains of lights).

Is there a way to ensure that if I get a "short circuit" (between Live and Neutral) or "leakage" (between Live and ground), the circuit breaker that will trip will always be the one in the secondary board?

I basically would like to avoid tripping breakers in the main board (which would shut down PC, refrigerator etc.).

The circuit breaker of the wall socket is 16Amps, and I was planning to install 10Amp circuit breakers in the secondary board (perhaps, if you think it wise, I'll add a "main" circuit breaker of 16 amps in the 2nd board, too). But will this suffice? If not, is there another way to go about doing this?

The "path" would look like:

main board (c.b. 16A) ->
wall socket ->
schuko plug ->
secondary board ->
main c.b. 16A (optional) ->
3x c.b 10A ->
3x output female schuko plugs

Note that the secondary box will be located inside the house (and not outside which would render it a hazard on its own!)


texts: CMOS Inverter DC charecteristics steepness

texts:
I was trying to solve the following multiple choice question(only one option is correct).

I simulated the inverter for varying W with L constant. What I found is the absolute value of dVout/dVin increases when W decreases.

Can anyone explain this?
I went through this question where I found the small signal gain increases with decreasing W.
But here we are looking at large signal behavior.
Also please mention the solution of the above question.


texts: Addressable simple serial bus for medium distances using PIC microcontrollers?

texts:
I am looking for serial bus, that could have addressable nodes, with maybe max. 30 nodes. I don't need multi-master, and the speed is not an issue.
The distance between the nodes could be something like 20 meters. The easier it is to implement with Microchip PIC microcontrollers, the better. I2c seems otherwise nice, but it isn't designed to work at such distances.

I have looked at RS485, CAN, LIN, and so on...
Atleast for CAN and LIN there are integrated peripherals in some of the higher series PICs.

What are the advantages and disadvantages of these, and how do they compare to each other?


texts:
Can someone explain to me how this (as advertised) full bridge load cell works?

I'm aiming for good temperature stability and I understood a full bridge load cell configuration should reject error from temperature variation based on the fact that you're measuring the difference between two elements.

This particular load cell varies by about 1% per 1°C.

I'm struggling to see how this configuration is an improvement over a single, 2-wire resistive element at all.


texts: Direct current measurement without circuit breaking

texts: Is it possible to measure direct current without breaking the circuit? For AC parameters its no problem using current clamp. I would like to know if something like this is possible with direct current with sufficient precision (say 0.1%). Range of current lets say is 10 mA - 10 A.


texts: Possible cons of excessively long microphone cable (XLR)

texts:
I'm very new to this page and anything electrical in general. I considered putting this on the music SE page but I thought this site may prove more helpful.

I have a small personal "studio" (put very lightly) for recording my own music as a personal hobby. I have a mic hooked up through to a vocoder synth through 2 XLR cables, as my mic uses a phantom power supply. The total distance from the mic to the synth is about 6 feet, but the smallest XLR cables I have are 25 feet and 10 feet, respectively.

My question(s) are thus:

If I coil up the excess slack in my XLR cable, will I experience unwanted interference (either from the loops or the unneccesary length of the cable)? Does this apply to any audio-carrying cable?

Would buying 2 shorter XLR cables give me a cleaner signal than keeping my current ones?


texts: How does this current monitor circuit works?

texts:
Can you please explain how can I analyze and equate its feedback?

I have simulated it in LTspice as follows:

I have tried for 0.5A and Vout is precisely 2, half of above, so it is working, despite not according to the 5V/A expected. (Where is that missing volt?)

Vout and Vdrain are overlapped, and obviously Id = Is.

Also, I have noticed that in any case, Vgate (op amp output) is always saturated to Vsupply, so how is there any feedback? I thought from Vout equation that gain is R1/R2, then Vgate over R3 dictates sensitivity, but it doesn't seem like that.

Can you analyze it step by step to eq.: Vout = (R1/R2) * R3*Il?

EDIT: new simulation:

Values:

V(v+)-V(v-) = 550.4 mV

V+ = 4.55 V

V(vout) = 4.597 V

V(gate) = 5.191 V

V(gate)-V(vout) = 593.77 mV

I(R1) = 5.40 mA

I(R2) = 919.44542 µA

Ix(U2:OUT) = -6.323833 mA

4:


texts: Detecting a threshold position in movement

texts:
I am raising an object/platform up and down using a DC motor connected to a threaded rod.
I wish to know exactly when the top of the object reaches a certain threshold point during its movement, sort of like a limit/end-stop. See drawing below.

What would be the best way to do this such that my microcontroller can be notified with low latency (< 50 ms) and good positional accuracy (< 1 mm)? Would mounting a simple reflective optical sensor at my desired height do the job?

Note: I understand a stepper motor + driver would have been an acceptable solution but I'm going with a DC motor for lower cost, and because I only need to "know" one position along the movement.


texts: What is the fixed-on interval with regards to stepper motors?

texts:
I am using a stepper drive board to control a stepper motor. It has settings for for fixed-on time when using the open-loop PWM control method.

According to the API description:

The fixed-on time is the amount of time that the winding will be left
turned on at the beginning of the step, in order to let the current
rise as fast as possible. At the end of the fixed-on time, the control
signal switches to PWM.

Can someone please expand on this explanation as to why it is required?

I have set current limits for the motor, does this mean that it waits for the fixed-on time to let the current reach this level or is it something else. What would happen if I raise or lower this value, and how do I get the optimal value for this parameter?


texts: Difference between virtual and ground plane

texts:
Ive created two PCBs, a power board to output a +-5V supply and a midway voltage reference (using the TLE2426) at 0V. This PCB powers a biosignal acquistion board shown in the spice diagram below.

The amplifier is an INA129 and the rest of the op amps are AD822ARZ. The power board does exactly as its meant to do, it supplies the board with +-5V and a midway reference voltage for the INA129, however there is almost a 1.3V difference between my floating virtual ground outputted from my power board and my ground plane on my biosignal board.

The V- and V+ are -+5V with reference to the Vref but are +1.3V and -8.7V when measured from the ground plane in my biosignal board, is there anyway to correct/explain this?


texts:
How would I go about finding the equation of the solid black line exponential/logarithm graph?

The two data points are:

(x,y)

(9,-14)

(20,-21)


texts: Trouble deriving/understanding time constant

texts:
I have the following problem:

Consider the circuit below:

The component values are: \$R_1 =5000 \Omega\$, \$R_2 =1000 \Omega\$, \$V_z = 5 \text{V} \$.
When \$i_1\$ jumps from \$12 \text{mA} \$ to \$0 \text{mA}\$, what is the time constant for discharging the inductor immediately after?

\$ \tau = L/R_1\$

\$ \tau = L/R_2\$

\$ \tau = L/(R_1+R_2)\$

\$ \tau = L/(R_1||R_2)\$

Here are my thoughts.
Since current through an inductor can't change momentarily, \$i_L=12 \text{mA}\$. The current will run through the zener-diode, when \$V_z=5 \text{V}\$.
The zener-diode allows a current of \$i = \frac{5 \text{V}}{5000 \Omega}=1 \text{mA}\$ to run through \$R_1\$, while there flows \$11 \text{mA}\$ through the zener-diode. These two currents meet at the middle node, and causes \$ 12 \text{mA}\$ to flow through \$R_2\$.
So as far as I see it, the current flows through bots \$R_1\$ and \$R_2\$ back into the inductor. \$R_1\$ and \$R_2\$ are in parallel, so my guess it that the time constant is expressed as: \$ \tau = L/(R_1||R_2)\$.
HOWEVER, it turns out the correct answer is \$ \tau = L/R_2\$ which I don't quite understand.
Can someone explain to me why this is the case?


texts: Does the bandwidth at the receiver really affects the noise in digital modulations?

texts:
I know that, in a telecommunicacion system, the AWGN power after going through the receiver filter is
$$
P_z = KTB
$$
where B is the bandwidth of the filter, T is the operating temperature of the receiver and K is Boltzmann's constant.
One of my professors has used this fact to show that a bigger bandwidth implies worse SNR in the received signal, but I'm still confused about what are the implications this has. As far I know, in a digital communication system, when a matched filter is used at the receiver, under AWGN conditions the received symbol distribution will be
$$
b/A=a_i \sim N(a_i, \frac{KT}{2})
$$
where b is the received symbol, A is random variable for the sent symbols and a_i is a particular realization of A.
Looking this distribution, it is that variance of the received symbol $$\frac{KT}{2}$$ what affects the probability of symbol error and it is independent of the bandwidth of the receiver matched filter.
For that reason, I would like to ask: Is there any reason why a bigger bandwidth could affect the BER in digital communication system?


texts: ADC signal long trace voltage drop compensation using amp and return trace

texts:
I'm running a signal for an ADC a pretty good distance and through a connector.  The voltage drops are not unsubstantial.

The concept is to run an identical return trace and compare the post-loss voltage to the orignal output voltage right at the source. That goes through a fully differential amp, boosting the signal so that the halfway point is exactly what originaly came out of the source amp.

Is this common?  Is there a better way to do it?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm using an Arduino MEGA 2560 to control some mini dc vibration motors that work with around 3V and I'm using 16 digital outputs (I'm creating the PWM wave myself).

The Arduino Mega provides 5V and therefore, when I have a dutycyle of 70% or more I go over the 3V allowed in the motors, and thus bad things can happen.

I wanted to use some transistor driver to reduce the output voltage, and so I thought on using a MOSFET Gate Driver.

simulate this circuit – Schematic created using CircuitLab

I wanted to use something like that î.

However, since I have 16 motors I wanted to use a driver that has more than one mosfet, and when I went to look for it I realized that I don't really know what to look for, since most of the drivers I found say that they need a supply voltage of at least 4.5V (which I dont have unless my dutycycle is ~80%) and that the output voltage is ~45V.
They also mention something like inverting and non inverting, but I cant find anything about it (does it have the same meaning as in the OpAmps?).

Example:Mosfet example store

What I wanted to know is if you think the mosfet driver is the best option, and what is the difference between inverting and non inverting, and also, how can I control my output voltage if the voltage said by the manufacturer is different of what I want?

I'm sorry if I wasnt very clear but I'm very confused myself.

Thank you in advance!


texts:
I'm having a problem with a H-bridge, that drives a motor.

Schematic
This is the schematic for the H-bridge.
Signals H[4:1] are generated by a microcontroller.
mX and mY are the outputs for a DC motor.

How it works
The microcontroller receives an external message via UART.
When the message is received, the microcontroller switches de H-bridge, reversing the motor direction.
This messages are received around once at every 4 seconds. So, in practice, the motor should be changing its rotation direction at every 4 seconds.

Microcontroller firmware
while(TRUE) {
    if(receivedCmd == 0x01) {   //direction1
        GPIO_WriteLow(GPIOD, (GPIO_Pin_TypeDef) (GPIO_PIN_2 | GPIO_PIN_3));    //H1-H4
        GPIO_WriteHigh(GPIOC, (GPIO_Pin_TypeDef) (GPIO_PIN_3 | GPIO_PIN_4));   //H2-H3
    }
    else if(receivedCmd == 0x02) {  //direction2
        GPIO_WriteLow(GPIOC, (GPIO_Pin_TypeDef) (GPIO_PIN_3 | GPIO_PIN_4));    //H2-H3
        GPIO_WriteHigh(GPIOD, (GPIO_Pin_TypeDef) (GPIO_PIN_2 | GPIO_PIN_3));   //H1-H4
    }
    else {    //do not activate
        GPIO_WriteLow(GPIOC, (GPIO_Pin_TypeDef) (GPIO_PIN_3 | GPIO_PIN_4));    //H2-H3
        GPIO_WriteLow(GPIOD, (GPIO_Pin_TypeDef) (GPIO_PIN_2 | GPIO_PIN_3));    //H1-H4
    }
}

The problem
At first, the circuit is working as expected, but after working for 1 minute or so, the mosfets Q3 and Q4 will endup burning.

Questions
I only have 2 spare mosfets left with me right now, so I decided to ask for help here before trying to implement some changes.

I did not add flyback diodes in parallel with the mosfets. Are they really necessary? Should I add them? Could this be the problem with my circuit?
Is there something wrong with my firmware? Should I add a deadtime before reversing the motor direction?
Could breaking the motor (activating Q1 and Q3, and deactivating Q2 and Q4) before reversing it be a solution?
Any other ideas on what may be happening?


texts: A question about Transistor in forward-active biasing?

texts:
I have question about transistor biasing.
Between picture 1 and 2, what's difference, why we add the resistor RE in pic 2 ? what's it effect to circuit ?
Similarity for pics 3 and 4, instead of connecting RB to Vcc, why do they connect RB to the collector of BJT ?
And which is the better way to bias a BJT among 4 pics ?
thanks very much :)


texts:
I would like to design a 3D printed enclosure for my project.

I am using these perfboards from amazon. I could not find online the dimensions for the mounting holes. I know I can use a calliper, but I was wondering if there is some kind of standard for hole size, distance from edge, etc.

EDIT
Based on the comments I decided to test the measurements with a calliper. I have designed a simple model to do this that should use very little material.


texts: Verilog project - Binary to BCD - 0-49 2 digit display

texts:
I have an end of the year project where I must create an 4 operation ALU that outputs its result onto 7 segment displays in Verilog.
2 of those operations are multiplication and addition. Considering each input is 3 bits, I can achieve a max number of 49 (7x7).
I originally created a binary to BCD converter, using the double dabble algorithm with the iterations being triggered by the clock cycle. My project was running and I got into the report and ran into a major issue.
Our project must show from the top level blocks all the way down to the gate level
I spoke to my professor about this and he informed me that my method of using the double dabble algorithm is too complex for this project as we need to show the gate level of our design.
I'm somewhat stumped on where to go from here. A majority of other students are using a case statement with 49 options for each display (0-49, where the ones column shows 0,1,2,3,4,5,6,7,8,9,0,1,2,3... and the tens column shows 0,0,0,0,0,0,0,0,0,1,1,1....) I don't see how this would simplify things in terms of design using logic gates, however, maybe I'm wrong?
Can someone shed some light onto a possible route I could take with this?


texts: DC bus correction for inverter VFD via PWM modulation

texts:
This is a question concerning an inverter circuit without PFC.

Single phase AC is rectified and pooled on DC bus capacitors.
From there the DC voltage is modulated at 5kHz on 6 IGBTs, emulating sinusoidal waves of the required frequency, using an open loop V/F scheme.

Now assume the requested frequency is steady.
Due to fluctuations on the AC input, DC bus voltage may vary from 280Vdc to 330Vdc. Which is the best way to modify the PWM signal in order to drive the load at the same power?

At the moment I'm adjusting the PWM duty cycle proportionately to the nominal DC BUS voltage (limiting the maximum adjustment up or downwards).

DutyAdjusted = DutyNominal * (DCBusNominal / DCBusMeasured)

Is that enough? Is the approach dependant on the type of load?


texts:
I am learning computer architecture and organization I am stuck in the following question.

Consider a hard disk with sector size 1024 bytes, 5000 tracks per surface,
64 sectors per track, and 8 surfaces. If the disk platter rotates at 10,000
rpm, and one track of data can be transferred per revolution, the average
data transfer rate is ……………. Mbytes/sec.

Correct answer is 10.66 Mbytes/sec.
1 track = 64 x 1024 = 64 Kbytes.
Time for one revolution = 6 msec.
So, in 6 msec the data transferred is 64 Kbytes
Thus, in 1 sec the data transferred is 64 / 6 Mbytes = 10.6 Mbytes/sec
The solution was given along with the question which I think is wrong as the correct answer should be (64 * 1000) / (6 * 1024) = 10.41 Mbytes/sec.


texts: PWM photodiode bias circuit control voltage

texts: Cant the photodiode bias regulator described here, Fig 6 be controlled with a PWM input? The RC loop right at the control input seems to filter PWM frequencies, but I am not sure if there are any more implications as the control signal would be placed directly at the FB input.


texts: Any help identifying these parts and their purpose

texts:
Short: I'd like a manufacturer identified.
Long; I've been tearing apart old electronics and looking at them to see how they work and getting caps, op amps, transistors, small logic circuits and the such off, but I've come across a chip on the board that has me stumped. It's off of an old hughesnet modem board that I was going to strip for the Ethernet jack. I've seen this manufacturer's logo several times in multiple power bricks while I was hunting for toroidal rings, so I think it may be some sort of power company. I was just wondering if anyone has seen this logo before and if so, what company it belongs to. I tried googling sti, 691, 6pi, s9i, etc. No hits. Any help? I'm posting this from my phone so I'll link to the pics. http://imgur.com/a/3o4aY


texts: Is it possible to bi-directionally route a 4G signal using a connected set of antennas only?

texts:
Is it possible to route a 4G signal from inside a room to just outside the room without using a powered booster if the signal right outside the room is good?
I'm assuming there is lot of interference within the apartment itself (too many walls?) and the cell closest tower is located somewhere far to the left hand side (refer to room layout in images) of my room.
Room config and current situation:

I don't get any better 4G signals in the other rooms either.
Would the following antenna setup work?

Yagi antenna & inner patch panel antenna reference
Note: The inner patch panel antenna doesn't look suitable for higher (~2k) 4G frequencies since the description reads 698 to 700 MHz. Please correct me if I'm wrong.


texts: Connecting AC and DC Voltage Sources in Parallel

texts:
I am still having trouble understanding how voltage sources combine when they are connected in parallel. Consider the following circuit below:

If we assume that the wires connecting the resistor to the two voltage sources are perfect (zero resistance), then we get what appears to be a paradox since the voltage at node 1 needs to be both 1V and 2V at the same time. In reality, this situation is resolved by the finite resistance that real wires possess.
My misunderstandings occur when one of the voltage sources is an AC source such as below. In this case, is the voltage at node 1 really just a sum of the AC and DC sources? In this scenario, does this mean that the DC source outputs an AC current in order to maintain a constant voltage? Would this AC current coming from the DC source be in-phase with the current from the AC source in order to cancel out the AC source's effects on the DC source?
Also, for real world applications, does this type of connection lead to any negative effects that would damage the AC or DC source? I've seen suggestions that using a capacitor or transformer would be better to add AC and DC voltages rather than connecting them directly.


texts: Solution for different Wire sizes in one circuit

texts: I have two ac voltage sources in series. the connection between the sources is a 13 gauge wire. the rest of the circuit uses a 16 gauge wire. for safety i dont want to exceed 20 amps. is there a ac current limiter that i can place between the 2 voltage source?


texts: Modelling this differential ended system for SPICE simulations and grounds

texts:
Considering above illustration, imagine a voltage measurement by a voltmeter where the voltage is coming from a differential output device i.e a device which sends mirrored voltages according to its own ground. Lets say at this moment the orange device above outputs +1V and -1V differential signals. Now this is coupled to the voltmeter terminals and it will show us 2V i.e the potential difference.

And as you see only the + and - signals are coupled to the voltmeter. Not the grounds.

My confusion is Voltmeter has its own ground. And the diff. out device has also its own ground. But as you see their grounds are not connected to each other.

1-) How is it possible to model/draw this above system for a SPICE simulation? How to model a very simple diff output device and very simple diff. amplifier(representing the voltmeter)? I need a very simple educational model.

2-) In reality their circuit analog grounds are not connected. In simulations should they inevitability be connected ?


texts:
So I'm given a parametric formula for current measured across an ideal basic circuit element. It is \$i = 0 A\$ at \$t < 0\$ and \$ i = 20e^{-5000t} A\$ at \$ t\ge0\$ (t being time, in seconds). I'm then asked to calculate the total charge at the higher potential terminal.

The book lists the answer as \$4000\mu C\$. When I integrate the current equation, though, I use U-substitution (\$u=-5000t\$) and come out with \$ (-\frac {20}{5000}e^{-5000t}) + (\frac {20}{5000}) \$.

What step am I missing?


texts: Choose the resistence with voltage divider sensor

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I'm on voltage dividers circuits for reading some sensors that changes their resistance (force sentive resistor).

With my tester (with input scale set on 200K ohms) I read 23 if sensor is not touched and 65 if the sensor is touched at maximum.

Now, I'm trying to read it with a microcontroller and with a 220 ohms resistor (red red brown) i read values from 7 (not touched) to 1 (touched). With a 1000 ohms (brown black red) i read values from 40 (not touched) to 15 ( touched).

I would like to get the best from this sensor and this microcontroller (it could read analog values from 0 to 1023) and I want to calculate the best resistor for get the best result and the biggest range of values i can.

Can someone point me out?


texts: Under what conditions is the star-mesh transform invertible?

texts:
We all know and love the Δ-Y (delta-wye) and Y-Δ (wye-delta) transforms for simplifying three-resistor networks:

Image from Creative Commons

The Δ-Y and Y-Δ transforms have the nice property that a Δ can always be turned into a Y, and a Y can always be turned into a Δ, no matter the value of the resistances involved.

There's a generalised version of the Y-Δ transform called the star-mesh transform. This converts a "star" of \$ N \$ resistors into a "mesh" of \$ ^{N}C_{2} \$resistors.

Image from Creative Commons

Wikipedia suggests that the star-to-mesh transform will always exist - but that the inverse transform, mesh-to-star, may not exist. To wit:

  The transform replaces N resistors with \$^{N}C_{2}\$ resistors. For N > 3, the result is an increase in the number of resistors, so the transform has no general inverse without additional constraints.

What are the constraints that must be satisfied in order for the inverse to exist?

I am particularly interested in converting a 4-node mesh network into a 4-resistor star network.

Motivation for the question: I have an industrial power systems model (really just a very large network of constant-voltage sources and impedances) containing ~ 2,000 nodes. I am attempting to reduce it to just four nodes of interest.

Edit:

There are some published papers on this topic.

Versfeld, L., "Remarks on star-mesh transformation of electrical networks," Electronics Letters , vol.6, no.19, pp.597,599, September 17 1970

Two new aspects of the well known star-mesh transformation are studied: (a) the necessary and sufficient conditions for the transformation of a given general mesh network into an equivalent star network; (b) an extension to networks containing sources.
Bapeswara Rao, V.V.; Aatre, V.K., "Mesh-star transformation," Electronics Letters , vol.10, no.6, pp.73,74, March 21 1974

An equivalent star network exists for a given mesh network if the latter satisfies the Wheatstone relaflonship. Using this fact, it is shown that all the offdiagonal cofactors of the datum-node admittance matrix of such a mesh network are equal. From this property, a simple relationship between the elements of the two networks is derived.

I don't have IEEE Xplore access so I can't read them.


texts:
I'm about to install a voltage sensitive relay which will be in between my car battery and my auxiliary battery in my van. When doing research for this, I find diagrams like this:

What confuses me here, is ground, and if I should be grounding my aux battery to the chassis, and what would be the purpose of this?
In this schema, does ground just mean that the negative poles should be connected? I understood it like just a shortcut, instead of having to close the circuit in the schema, you can just use the ground symbol, which means the negative poles should be connected to each other. Or does it actually mean grounding to the chassis?
Sorry if this is a duplicate. I've done research for this but I haven't been able to grasp it yet...
Thank you.


texts: How do I create a fiducial with gEDA pcb?

texts:
I'd like to know how I can create fiducials with gEDA. Some PCB manufacturers, such as Eurocircuits proscribe zero-aperture drill holes so I can't just whack in a via or pad and set its diameter to zero. BTW I tried that and gEDA PCB doesn't even allow a null-diameter for a via.

I also tried clearing a round-sized track but the solder mask doesn't clear. Hence my question: how am I supposed to create fiducials with gEDA?


texts: How long can I run my camera off this battery?

texts:
I have Ultramax NP7-12 12v 7ah specifications here: http://www.batterymasters.co.uk/ProductDocs/SLAUMXNP7-12-TECH.pdf

My camera consumes 1.25 watts per hour and runs at 7.8 volts but can run between 7.4-8.1 volts.

I have used a  LM2596S DC-DC Buck Converter Adjustable Power Supply Step Down Module to go from 12v to 7.8 volts. Housed inside the black shrink-wrapped as seen in the photo.

A picture of the set-up if that helps?
https://www.dropbox.com/s/at40cnb773gk7ia/Photo%2010-09-2014%2010%2017%2006.jpg?dl=0

The Turnigy is a watts monitor from the RC world.

If it runs 24 hours per day how long will it last and if you have time can you show me your workings so I can learn how to do it myself in future please?


texts: What happens if the signal frequency exceeds the sampling rate?

texts:
As the title states, I was wondering what happens to the frequency contents of the sampled signal of a pure sinusoidal signal that exceeds the sampling rate.
I am familiar with the shannon theorem and the effect that a signal of say 0.75 times the sampling frequency would be mirrored at the nyquist frequency to turn out as a sampled signal of 0.25 times the sampling frequency, like shown here: https://www.youtube.com/watch?v=eYzrcbnZqaE
But what would happen if I turned up the signal frequency further than the sampling frequency, so that the "mirrored frequency" would exceed zero? Would the frequency of the signal "Bounce back" from the y axis once more and in effect bounce back an forth between the nyquist frequency and zero when increasing the signal frequency indefinitely?


texts: ATX PSU as bench power supply. Voltage dropping issue

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I am trying to use a PC ATX PSU as a bench power supply in order to achieve a high current 5V and 12V supply. The PSU is 550W and I am using a single SATA power connector (to connect to the device to be powered). I also have the PSU on signal tied to ground permanently so the switch on the back of the PSU is the main method of turning it on and off.

When connecting a load to either the 12V rail or the 5V rail, the voltage drops to outside the tolerance of the PSU. The load does not exceed the current rating of the PSU. For example, when I connect a 1 ohm load across 5V and 0V, the supply voltage drops to 3.7V. The wiring used to power the device from the SATA connector is suitable enough to handle the required current.

Is it possible that the wiring from the PSU PCB to the SATA connector is causing the voltage drop (too small to handle the current I require)? If this is not likely, can anyone offer some insight into what I am seeing? Also, different load values have been put across both the 12V and 5V rails (10 ohms to 1.8k ohms) to try and force the PSU into thinking a motherboard is attached (this has not changed anything).


texts: Is constant current achievable with a dc/dc converter?

texts:
I'm an electronics novice and part of a rocketry club. During the 4th of July we try to do a mass launch of rockets. Doesn't always work. I thought about building a capacitive discharge circuit to launch about 50 rockets and wow the spectators. The line of rockets would span about 100 feet using 22 gauge copper wire. I'd probably be another 100 feet away. For this much resistance I'm thinking I need a good amount of voltage.

So, each rocket requires an "electric match" to electrically fire. The electric match basically looks like a matchbook match head with wire leads. Each match requires 1 amp to pop and produce flame, per specs.

I purchased some photoflash capacitors, a toggle switch, a 12v battery and started to think about how I would charge the capacitor and looked into dc/dc converters. But most produced low watts. A 12v to 100v converter had a 1.5w spec. To my understanding that would only produce .015 amps. Somewhat expensive as well.

I need some insight on how I can get this to work. Would I need a dc/dc booster with a constant current of 1 amp?


texts:
The default outline selection of a component is rectangular:

Is there a way to set it to follow the real outline?:

I'd like to do it to be able to place components in the middle without adding a rule that ignores that component's clearance.


texts:
Quoted from the ebook Introduction to Microcontroller by Gunther Gridling (pg. 43):

The class width of most classes corresponds to 1 lsb, with the
exceptions of the first class (0.5 lsb) and the last class (1.5 lsb).
This asymmetry stems from the requirement that the representative of
the code word 0 should correspond to 0 V, so the first class has only
half the width of the other classes, whereas the representative of the
code word 2r − 1 should be Vref − 1 lsb to allow easy and compatible
expansion to more bits. To avoid the asymmetry, we could for example
use the lower bound of the class as its representative. But in this
case, the worst case error made by digitization would be +1 lsb. If we
use the midpoint, it is only ± 0.5 lsb

I understand that lowering Vref or using a higher bit ADC can increase the resolution of conversion or make each quantized step of 1 lsb smaller to associate with more digital/binary states. Each lsb or level is named a "class" (I don't understand why there are multiple terms to represent the same abstraction).
But why is there a 0.5 lsb or 1.5 lsb class? There is no binary state between 000 and 001 to associate with 0.5 lsb, and the digital output signal can only be integral value of lsb.  So why is it there and what does it mean? If there is a 0.5 lsb class/level at the start and another 1.5 lsb class/level at the end, does that make "this" symmetric instead of of asymmetric?


texts: I'm looking for an PCB FFC connector to replace the FH26-24S-0.3SHW(05), which I cannot find stocked anywhere. I've looked for replacements with .3mm pitch, .2mm flex thickness, and 24 contacts, but cannot find any via either DigiKey or Mouser. I can, however, find connectors with 25 pins. Would having one extra unused contact on the PCB FFC connector cause problems when using a 24-contact cable, assuming the cable was seated such that contacts 1-24 were aligned properly?


texts:
I have an Octopus Soil Moisture Sensor connected to a Rasberry Pi through an MCP3008 ADC chip.  The sensor is working correctly, but I have no idea what the reading values mean.

I say its working correctly because when I place the sensor in known dry soil and take a reading, I get a 'dry' result.  When placed in known wet soil, I get a 'wet' result.  These delineations I was able to find in this datasheet.

However, that is the only datasheet I can find, and in the Specification section we are given this table:

My ultimate goal is to turn on either a valve or pump when the moisture content in the soil drops below a certain percentage of either weight or volume (SI units of either grams / gram or inches / inch, which are the units mostly used in the industry).  I have found scholarly articles which contain easy to use equations for converting between different units of measurement, including going from a dielectric constant measurement to % Moisture Content.

I believe the output value is either somehow related to the drop in voltage observed or an indirect measurement of resistance, but I cannot be sure. Without some kind of units I cannot perform any calculations to obtain the result in the units I desire. According to this, correct values of the dielectric constant should not be above ~80 or so for water.

I tried emailing the company I purchased the sensor from but without a response after 2 weeks.

The datasheet I linked above does state this:

  This sensor uses the two probes to pass current through the soil, and then it reads that resistance to get the
  moisture level

Can I take that as meaning that the output units the sensor is giving me is in Ohm meters? If so, I find it odd that the same document doesn't also list that as the units in the specifications. Does anyone here have any experience with this sensor, or know where I can find a datasheet that provides the units it is measuring in?


texts: Why do I get terrible static in my phone mic / recording when my phone is charging from the mains?

texts:
I live in an apartment block in the UK. When I record my voice into my phone's voice app when the phone is charging from the mains, I get a terrible constant static sound that is not present when the phone is not plugged in. I suspect that the static gets much worse when my neighbour is using their washing machine.

Is there anything I can do about this? Is it harmful to my phone or to any other appliance like a laptop?

Thanks!


texts:
I started working with the LT1990 Differentiel amplifier.
In the datasheet, it's stated that it needs a 1.25V voltage reference.
I made some research and I found the TLVH431 Low-voltage adjustable precision shunt regulators but I didn't understand how it works and how from an input voltage I can have 1.25V voltage reference ?
Can someone explain to me how it works


texts:
I know there are similar questions on the site, but I wanted to ask it from a somewhat different perspective.

I've got a 5V device (Device A) that can operate at 3.3V.
I've got a 3.3V device (Device B) that does not have 5V tolerant inputs.
I want to connect these two devices together to communicate over an SPI interface.
I want to be able to operate Device A selectively at 5V or 3.3V.
Device B is independently powered and always runs at 3.3V.

I know I can use (and have successfully used) a buffer (e.g. 74HCT125) powered by the same voltage as Device A to boost Device B's signals up to 5V. I'm not as sure of the best approach for the other direction though (i.e. dropping Device A's outputs to an appropriate level for Device B).

I've read the Sparkfun Tutorial on the subject. They offer a few ways to approach the "downward" level shifting. What is the preferred way of handling this aspect? Since I'm using SPI here, the classic MOSFET solution for I2C seems like overkill to me since I don't need bidirectionality. I like the Inline Resistor approach for its simplicity, but I am uncertain how to size the resistor. The CLK and MOSI pins of Device B are specified with V_IH_min = 0.7 * V_cc = 2.31V, V_IH_max = V_cc + 0.3 = 3.6V and with Input leakage current of max 0.5 uA.

By my math this means I need to drop between 1.4V and 2.6V in the case (1) where Device A is operating at 5V and no more than 1V in the case (2) where Device A is operating at 3.3V. If I assume the 0.5 uA leakage current is responsible for the voltage drop then case (1) calls for a resistor between a 1.4/0.5e-6 = 2.8 MegOhm and a 2.6 / 0.5e-6 = 5.2 MegOhm resistor(!). And case (2) calls for a resistor no smaller than 2 MegOhm. Therefore case (2) is dominated by case (1), and I should pick a resistor somewhere in between the calculated range, like 3.3 MegOhm for example.

That value seems ginormous to me (especially when the SF tutorial is showing values like 10 kOhm) ... and that is just for the max input leakage current (no min or typical is specified) is there a flaw in my reasoning or calculations, or is this not the preferred way to interface the devices (e.g. the Diode method)?

If it matters, one case of Device B I'm thinking of is a 23K256 SRAM, but I'm trying to account for a variety of devices.


texts: Flashing program into microcontroller, usb-ttl, idea behind?

texts:
I have limited knowledge on this topic(MCUs, communication protocols, etc.). I back then worked with an STM32 MCU and did some UART(or USART, can't remember) communication between a PC and the MCU. While I was doing that, I was using on-board ST-LINK programmer/debugger to load my programs into the MCU(F4 Discovery board, to be specific).

Now, while I was doing U(S)ART, I had to configure corresponding pins as U(S)ART alternate function along with configuring U(S)ART peripheral registers.

I recently, looking for programming so called Blue Pill board based on STM32F103Cxx MCU. The point I did not understand is, they(the tutorial owners) don't do a configuration for U(S)ART or so. Generally, they just replace a jumper from one location to another and be able to load programs via USB to TTL converters.

So, what is the exact working behind this, why don't they need to set some pins as U(S)ART Rx or Tx for example?

Another little question, I see some products sold as "FTDI programmer". Now, I do have a Prolific USB to TTL/Serial converter. Will there be a difference in functionality, can I use any USB to TTL converter for programming the MCU? I mean, does that "programmer" have a meaning, or just a naming?

Thanks.


texts: How to get into Freescale 32-bit MicroControllers?

texts:
Which websites/blogs/tools/books/manuals would you recommend for getting into the Freescale microcontrollers, especially the 32-bit models?

What are the best development tools (IDEs, compilers) for this environment.  There is so much out there for the AVRs, ARMs, PICs but not too much for Freescale.  I admit, I need to spend more time with Google on this and just thought I'd save myself plenty of time by asking the "experts".

Thanks


texts: How to use 2 power supplies in my scheme?

texts:
I am building a device to send a signal from Raspberry Pi GPIO to a vibration motor. Here is how it should work: the RPI outputs 0v or 3.3v, and when it outputs 3.3v, the vibration motor should vibrate. I figured out that RPi GPIO current is too small for this vibration motor, so I decided to use some external power supply (in my case, 9v battery), so 9v should be sent to vibration motor when GPIO outputs 3.3v. The problem is I don't understand how to connect it properly.

I guess I should use the transistor key with base connected to the RPi GPIO output and base and emitter connected to the 9v. But it somehow doesn't work the way I want it.

Can you help me with it? I'm completely lost.


texts: How to find voltage gain of below analog circuit without using Nodal analysis?

texts:
This is a theoretical circuit just made to see that if I can find voltage gain of circuit and it took me much calculations then anticipated to get voltage gain.I just want to find if there is better way then nodal analysis to solve this question.

This is an arbitrarily made circuit where Q point is already found using using DC analysis so I didn't mention power supply.The transistor is operating in active region and the value of collector current at Q point is mentioned in description of BJT.


texts: Why do some PCB antennas have a return path to ground?

texts:
I'm finding it hard to find an answer for the question, as I'm asking about the circuit's GND, where searching for an answer online or in stack-exchange is coming up with Earth GND for large Antennas such as VHF.

As an example from this application note from Cypress, one antenna has a node connected to system GND like so:

Where as another antenna in the same doc has no connection to system GND:

I don't understand how the antenna can work when it's output is just shorted to GND. Can someone help? Thanks!


texts: Connect VGA cooling fan (12vdc - 0.1A) to constant current driver (120Vac to 12- 22vdc @ 0.3A)

texts:
I have an AC driven COB LED which can be connected directly to the AC main in house (120v). I would like to attach a cooling fan to the COB which requires 12vdc @ 0.1A. I have a constant current driver which converts 120VAC to 12- 22Vdc @ 0.3amp.
Is it possible to use this driver to power the cooling fan at the 0.1A rating by using a resistor?
I am assuming the power supply would increase the voltage to get the current to 0.3a, therefore I do not know if this is possible, or what voltage value to use to calculate resistance needed.


texts: Two isolated circuits (different ground) detecting contact with each other

texts:
EDITED:

Two arduinos, each one powered by a battery. Each arduino is connected to a piece of metal. When pieces of metal from both arduinos touch each other, the arduinos have to realise the event.

The problem: by having a different ground, they cannot detect each other electrical signals. Is it there any workaround for this?

I've take a second guess: each arduino uses the piece of metal it is connected to as a capacitive sensor. This way, both arduinos are able to "detect" that the pieces of metal have come together. But, this has the problem that if a human grabs both pieces of metal at the same time, the arduinos will believe that both pieces of metal have make contact.

The problem is: how to make the arduinos able to detect their respective pieces of metal touch each other, without giving a false positive when a human grabs both metals at the same time.

Any ideas about how to resolve this problem?

Edited:
About the strength of the signals each arduino takes when the metals as capacitive sensors touch each other, it is of the same intensity and as such non-differentiable from the signal the arduino gets when the human touches the metal.


texts: Simulating graphene-based antenna using HFSS

texts:
Recently, I am learning to simulate the graphene-based antenna using HFSS software. There are some issues I did not figure out.

According to my understanding, since there is no graphene material defined in the HFSS software, we need to define the material ourselves in the HFSS software. From the Kubo formula or Drude model, the complex conductivity of the graphene can be calculated, which is frequency dependent. However, in HFSS, the properties to define material only allows real values for all the items as shown below, so may I know how to map the complex conductivity to the items in the bellowing HFSS table. Or are there other ways to define the graphene material in HFSS?

Thank you guys in advance.


texts:
I just bought a solar powered LED light that has a motion sensor and a light sensor.
When it is dark, it turns on but very dim. When it detects motion, it turns on full power (not very much...) for 20 seconds, then returns very dim.

What I want to remove is the "very dim" state. I'd prefer it to be off when no motion is detected, so it will save power.
Someone on Amazon (Italy) suggested to remove the R6 resistor, but I discovered I have a newer printed circuit board, so I'm not sure if it is the right resistor (I am no expert in electronics).

Here is the picture of my circuit. Can you tell me if my R6 resistor is the right one to remove?

EDIT

I do not have enough reputation to answer my own question, anyway it worked.

I remove R6 and it worked, now there is bright light for 20 seconds and then nothing. Probably U1 gives a timed output that controls Q2 as suggested by brhans, so R6 is bypassed and the bright light is achieved by the R5.

Thanks!


texts: What is the physical/electrical limit of audio quality?

texts:
A few days ago I was in a class about electronics on my study. The first lesson was an introduction into the main subject, bits, analog signals, conversion, etc. An example was asked by the teacher: What is the maximum feasible amount of bits to store audio information in?

Some of the answers that were thrown through the class included "64bit, 32bit, 16bit, 8bit (yeah I know..)...".

then the teacher said it's about 18,19 bits, then you are reaching the upper limit because distortions, noise, etc begin to play a big role for audio recordings.

I do know the typical DVD/Studio quality is 24bit audio.

However this led me thinking: What is the maximum physical/real/electronic bitsize in which a piece of audio can be stored? would 32bit audio be overkill/contain too much noise?

Any explanation/sources on this?


texts: The base resistor of the transistor with speed-up capacitor

texts:
I've designed a relay driving cuicuit like this

Under DC the current is limited by R1. R2 is added to limit the current flow through C1 and the base of the BJT when the Q from 0 to 1. Is resistor R2 neccessary? And how to calculate its value?


texts:
I am trying to work with attiny85 to give a delay of 5 sec when a signal from IR sensor, before giving it to 8051. I am quite not getting the code work for it as it should. Actually I am programming it in mikroC IDE and not sure about syntax.
Here is the code that I tried:

void main()
{
 DDRB = 0b000111;       // set LED at pin B0,B1,B2 as output.
 while(1)
{ if ((PORTB3 & 1) !=0) // check B3 and delay if 1
   {Delay_ms(2000);
   PORTB = 0b000001;
   if ((PORTB4 & 3) !=0) // check B4 and delay if 1 while B3 is 1
   Delay_ms(2000);
   PORTB = 0b000011;
   }
   else
   PORTB = 0b000100;   //else LED at b2 is high
 }
}

I tried using arduino ide but then I am not able to simulate it in proteus.
Please help me with this.
Thanks!


texts: Index of frequency larger than power spectrum length

texts:
I am new in this community. So excuse me if it seems easy.

I want to calculate the amplitude of a specific frequency in a signal.
The frequency precision is (relevant question)
$$
df = \frac{fs}{NP}
$$
$$ fs=1/dt$$
NP is the number of points in the signal time seri.
The index of the frequency in the signal is
$$
ind = \frac{f}{df}
$$
the length of power spectrum array of signal is length(pxx) = NP/2-1

Example 1: for small frequencies

frequency = 1.0/128.0
dt=0.4
df = 0.001
NP = fs/df=2500
index of the signal = 8

lenght of pxx is 1249 so no problem.

Example 2: for large frequencies

freq = 2.0
dt=0.4
NP = fs/df=2500
index of the signal = 2000

The index of the frequency is larger than the number of points in pxx.
If I double the number of points in the signal, the frequency precision halves and the index of frequency also doubles.
Is there a frequency limit or I am doing something wrong?

Thanks for any guide.


texts: Simple circuit with transistor using Raspberry Pi

texts:
I'm trying to use a Raspberry Pi to control a set of 4 LEDs. I'd like to control the LEDs in software by using a GPIO pin. Here is the schematic I've come up with... (please ignore the wire in the top right corner of the diagram, the transistor should make or break the circuit)

I'll be using a 9V battery to power 4 LEDs in series. Each LED has a voltage drop of 2V and a current rating of 20mA. Therefore my resistor should have the value of 50 Ohms (1V / 20 x 10^-3A). The diagram has an incorrect resistor value shown.

My problem is that I'm not sure of what will happen when I connect the Pi's pin to the base of the transistor. Will it mean that the pin becomes connected to the 9V circuit and will draw 20mA after I set the pin to high? Or does the pins voltage have its own influence? (the pin operates at 3.3V).

There is probably a better way to do this but I'm trying to learn about transistors so I don't want to remove the transistor.


texts: NPN or PNP transistor for common-cathode seven segment display LEDs?

texts:
I've read a bit about this but there seems to be much ambiguity.
When using common cathode seven segment display LEDs would you use NPN or PNP? Or can you use either?


texts: Reading a rotary encoder using a microcontroller and converting to Serial TTL?

texts:
I have an incremental rotary encoder (Bournes-EMS22Q) that I would like to have available on a wired network via RJ45 or via serial TTL (we have a serial-to-ethernet converter we can use Netburner SBL2E). This seems like a fairly simple problem however the more I look into it the more complex it gets, there doesn't seem to be an off-the-shelf solution and it looks like I'll have to make something myself.

Has anyone come across this problem before? How can I get from the encoder output (5 pin) to serial/ethernet?

I'm now looking at a chip-level solution using this 32-bit Quaderature Counter which gives me an SPI output but how do I go from SPI in this case to serial TTL/Ethernet? Will I need to use a microcontroller?

Is there a magical hardware component that I'm missing? Any recommendations on how to solve this problem greatly appreciated.


texts: May I connect 3.6v Li-pol accumulator to 3.3v dc supply?

texts:
I have an old Bosch electric owen which has clock and timer on-board. The problem is: on each electricity fail (even milliseconds) this clock resets to the time edit mode and zummer starts to make sound. To stop this I have to press Edit Mode button twice. It's boring.
I have disassembled the clock module and found no battery there. Only the 470 uF capacitor in the 3.3v DC which powers the IC. But as I guess, this capacitor does not help on AC failures.
I have tried to replace the cap, no success.
My idea is to add the small Li-pol accumulator in parallel to this capacitor. Those accums usually installed in car electronics and have some schematics on-board (I guess stabilizer). Is it a normal mode for these accumulators? Will it work? Thanks.


texts: How can I find out which leads are +, - and video signal on this miniature camera?

texts:
I have this miniature camera but lost the cable connector.  How can I find out which of the leads are positive, negative and video signals?

back http://accentual.com/images/back.jpg
back http://accentual.com/images/front.jpg


texts: an/prm-10 grid dip question - how the voltage can be negative at the grid?

texts:
I am trying to repair a recently bought AN/PRM-10 grid dip. I have replaced some electron tubes by new ones and (almost?) everything seems to be OK regarding the voltages at the pins of the electron tubes, according to the one-to-last page of the manual that can be downloaded here (bottom of the page). For the convenience of the readers, I've attached here a copy of this page, and of the schematic of the grid dip.

As everything is OK for all the other electron tubes, I am interested only in the V-201 acorn electron tube. According to the document, the voltage at pin 3 should be -10V AC (this is of course a mistake and should read -10V DC). If I measure this voltage with an electronic tester, it gives me -11V DC (so far so good). If I invert the ground and positive terminal of the tester, surprise ! it gives me +4V DC (and not the expected +11V DC). The same occurs if I measure the voltage with an analogue voltmeter. I have two questions:

why is not the voltage +11V when I exchange the terminals of the tester ?
I don't understand how can the voltage at pin 3 be negative with respect to the ground, as according to the schematic, I see no voltage source that can bring this potential below ground.


texts:
This image is of a DC/AC converter (inverter), but with the addition of a "C S" block to the left. What is the meaning of this additional block?

The wire at 9 o'clock is from an AC supply. This is from a UPS-type system


texts: What electrical symbol where it looks like two resistors in parallel and connected on one end

texts:
I am trying to copy a circuit from a schematic but i stumbled upon a symbol that im not familiar of and the part label does not yield any relevant result from google

What is it and what does it do in the circuit?


texts: USB A 2.0 +5V bus interfering with Vsys?

texts: I want to have a USB connector on my PCB that will act only as host for joysticks. It will be a USB2.0  A connector. The voltage supplied for this is from +5V_Vsys. My question is what happens when a user will plug in this connector  a PC port wich will have also a +5V voltage across is right? The input voltage will not mess my Vsys? should i have some diodes on my line? i dont want to implement an OTG function because my PCB dont need to be slave by USB A 2.0.


texts:
I took apart an old Huawei 3G wifi modem, hoping to leave the radio stuff, and find an off the shelf MCU in there.

Aside from an Atheros wifi chip, and a Hynix memory chip, the only other ones not to do with RF are:

Hi 6755RBC / 120 / HP0221122

And:

Hi 6331RBC / 381 / CP0051127

However, I can find nothing about them. Can't even establish which company this is.

The modem exposes an admin web page, so I'm sure one of those must be doing the business!


texts: What is the difference between input and output offset voltage for an opamp?

texts:
Looking at many OpAmp (and InAmp) datasheets, I find the info either confusing or lacking. For example, in one datasheet they just call something Offset Voltage where in others they have two, separated as input and output offset voltages, respectively.

What is going on?

UPDATE

I must apologize from not paying full enough attention to the entire datasheets. The tricky part is that sometimes the data, as stated, are put under a header (a page above) as input), whereas when written in the summary, the offset is to be understood as input offset. However, occasionally the output offset is omitted. Either way I appreciate knowing the difference between the two terms.


texts:
I am designing a SIM900 schematic so before going further I thought of verifying the schematic first. I will using SIM900 with PIC18F2520. So to power the SIM900 and Microcontroller, I am using LM7805 for MCU and LM2576 for SIM900. Following is the circuit:

LM2576 o/p 4.1v is for SIM900 & LM7805 o/p 5v is for MCU

SIM900 Circuit:

Explanation:

PWRKEY: PWRKEY is connected with a push button which when pressed will connect this pin to ground, in order to start the power on scenario of module.

UART: TX RX lines are connected to RX TX of the MCU.

NRESET: connected to a push button to reset the module.

VRTC: I am not using any RTC function so just connected a 4.7uF cap.

NET & STATUS: Connected led's to these pins to show the status and network of the module.

Apart from the above schematic, is there any recommended circuit which I am missing in the circuit.?

Do I need a voltage level shifter between TX RX of SIM900 and TX RX of MCU.? I initially used a breakout board of SIM900 and tested it with the MCU, it was working fine without any external circuitry for voltage level shifter.

Is there anything which I am missing in the circuit. Any suggestions would be very helpful.

Breakout board:


texts: Does the internal 8Mhz oscillator in an ATTINY run even if no clocks are connected to it?

texts:
If I set up the fuses on an ATTINY so that the system clock uses the internal 128Khz oscillator (sometimes called the "Watchdog oscillator"), does the internal 8Mhz oscillator still run?

It does not seem to say either way in the data sheet, but I would guess that the primary motivation for running off the 128KHz oscillator would be power savings - in which case it would make sense to shut down the unused 8Mhz oscillator.

Can you think of a way you could even tell? Maybe a super-sensitive antenna coil near the chip looking for a tiny 8Mhz signal while the chip is running?


texts:
I've got this phone I'm doing some range testing with...Namely, a Samsung S5 with the latest firmware and I'm testing the WLAN/Bluetooth radio.

This phone has unbelievable range...but, when I replace the phone with a similar homemade class 1 device (20dBm) with this Molex antenna, my range is just about half of the Samsung.  The reciever is the same and I think that the power is the same (I can only guess that Samsung will output max power that the class of the device will allow when needed), so the only thing that's different is the antenna and the matching network.

I thought of a LNA, but LNAs that I have seen are unidirectional, and since Bluetooth communications need to be bidirectional (an acknowledgement after each packet), having only one device with a higher transmit power would only solve half the problem.

Am I correct in thinking this?  Can I do as well as a cell phones WLAN/Bluetooth RF transmitter circuitry by impedance matching that antenna or is there a common topology with LNA's or something that I'm not aware of?


texts:
I read that PLL are used in CPU to generate the clock, but I can't understand why.

I don't really have any guess of why this is.


texts: Why operations on float variable are performed on a double? STM32F401RE, MDK-ARM v5

texts:
I am debugging a simple line of code:
float temp_f;
...
...
temp_f= temperature[0] +(temperature[1] >> 5)*0.125;

that is assembled into
316:                 temp_f= temperature[0] +(temperature[1] >> 5)*0.125;
0x080018CE 4C1C      LDR           r4,[pc,#112]  ; @0x08001940
0x080018D0 7860      LDRB          r0,[r4,#0x01]
0x080018D2 0940      LSRS          r0,r0,#5
0x080018D4 F7FEFDD6  BL.W          __aeabi_ui2d (0x08000484)
0x080018D8 ED9F1B1A  VLDR          d1,[pc,#0x68]
0x080018DC EC532B11  VMOV          r2,r3,d1
0x080018E0 F7FEFD5E  BL.W          __aeabi_dmul (0x080003A0)
0x080018E4 EC410B18  VMOV          d8,r0,r1
0x080018E8 7820      LDRB          r0,[r4,#0x00]
0x080018EA F7FEFDCB  BL.W          __aeabi_ui2d (0x08000484)
0x080018EE EC532B18  VMOV          r2,r3,d8
0x080018F2 F7FEFCAE  BL.W          __aeabi_dadd (0x08000252)
0x080018F6 F7FEFDE5  BL.W          __aeabi_d2f (0x080004C4)
0x080018FA 4621      MOV           r1,r4

Since the ARM Cortex-M4 FPU is specifically for single precision floating point operations, I cannot understand why the compilation process links everything to double precision instructions like __aeabi_dadd (from what I understand being an external run-time ABI for ARM that runs in software) and only then converting back to float, instead of doing everything directly in single precision floating point format, maybe even in hardware?
This operation is performed inside a timer interrupt routine but I don't have anything related to float in my main process.
I'm using HAL, with cubeMX and Keil.
EDIT: solved by suggestion of @nanofarad writing 0.125f instead of 0.125.
Apparently the default x.y notation in C is for double values.


texts:
I am working on designing a theoretical microgrid for a school building, but before I can even select theoretical components, I need to select what the structure of my microgrid will be.

Here's what I know:

That MPPT charge controllers work by finding the maximum power points on your solar panels to ensure you get the most bang from your solar panel (and charge your battery safely and quickly)
MPPT CC's can work with hybrid inverters to invert however much you need to power your AC loads while the rest gets sent to batteries (refer to the diagram at the bottom)
DC coupled systems are much more efficient at charging batteries than AC coupled systems
About 160 [kW] of PV panels would be used
Unlike hybrid inverters, grid-tie inverters sync with the grid frequency and therefore scale infinitely
A purely grid-tied system with no batteries is the most economical, but my project involves looking into a system with batteries anyway as a "what-if" scenario
A DC busbar would be used to connect the batteries, hybrid inverter, and output of the MPPT CC's for the model. The higher the voltage, the less losses in the lines but there are safety considerations and component selection limitations to consider as well.

Here's what I don't know (these are my questions):

How to make a system that uses MPPT CC's, hybrid inverters, and grid-tie inverters (to "sell back" excess generation when the batteries are full). A picture of what I was thinking is shown below. Otherwise, I feel as if I would need to have some of my PV panels only connected to a MPPT and a grid-tie inverter. Then the rest connected to the MPPT CC, battery bank, hybrid inverter, and loads. The problem with that is that there will be times when the batteries are full so the part of the PV panels that is connected to the batteries and hybrid inverter would be wasted.
How AC combiner boxes work. Are they manufacturer specific where they only work with a specified inverter model (and number of inverters) or are they more of a stand-alone product like an inverter can be?

Current idea:

So what I was thinking was having a switch that just switches the PV panels to the grid-tie inverter when the batteries are full. As you can see, DC-coupled system. The problem with this idea is then the school building will start draining the batteries unnecessarily (batteries cost money and using them when you don't need to lowers their lifespan).

Another possibility I was thinking was just to leave however much the building will ever need at a given time always connected to the hybrid inverter and then just switching the rest of the PV panels either to the hybrid inverter or grid-tie inverter based on need (batteries need charged or batteries are full and I need to sell the excess).

I'm not an EE, so I wanted to see what your thoughts on this was (and info on AC combiner boxes).


texts:
I've searched for this until I'm starting to get sick.  I decided to just ask for help.  My friend has a CCTV camera with the typical BNC/Power cable, but he doesn't have a DVR.  I have zero interest in buying any adapters or anything for that matter.

If possible, I would like to simply chop off the BNC end that goes to the DVR and splice either an F-connector or an RCA connector - allowing the camera to hook directly to a TV.  From my Google searches, nobody has appeared to have ever done this.

Is this possible without buying any extra junk and if so, how would one go about doing it? I have tons of coax/F-connector cables and RCA cables, but there's only the single BNC cable to work with.

Thanks for any help.


texts: Atmel SPI Serial EEPROM Writing Error - Page Write?

texts:
I'm using this EEPROM: Atmel AT25640B SPI EEPROM DATASHEET

It seems pretty straight forward to operate and I've followed the datasheet closely when coding my driver. I seemed to have some success without too much trouble. Now, I'm having some issue with writing bytes and they're not sticking. For example, I write 10 bytes, but when I immediately read them back(to verify they've been written, I get all 10 bytes back at 0. Is there possibly something fundamental that I'm missing with how to operate this EEPROM?

As I understand Page Write, I can write up to 32 bytes sequentially and then it will roll over to the start address? Are the "pages" physically set 0-31, 32-63, etc or are they determined by where you start writing? ex: If I write 8 bytes at address 29, will it roll over to 0 or will it continue as expected and finish writing at 36? The datasheet is not clear.

The basic steps seem to be to send a WRITE ENABLE Command(1). Then separately, send a WRITE Command followed by address and the bytes to write.

I'm running the at 5v. I've tried to slow down the SPI clock to 1khz from 10mhz with no difference in behavior.

What else can I try?


texts: Transfer Function: Trying to understand the Laplace analysis of this circuit

texts:
I am trying to do the transfer function of this circuit and also trying to understand the frequency domain thing of the Laplace transform.

I want to do a transfer function of VA/V1, considering B to be ground.

After doing the node analysis and if my equations are correct, I have ended with this transfer function on the s domain.

A calculator online gave these answers for the cubic equation on the denominator

x1 = -915.52763
x2 = -42.23618 + i * 3304.67537
x3 = -42.23618 - i * 3304.67537

These are my problems:

what do these numbers represent?
the equation is on the denominator, what about the s100 on the nominator?
how do I find the frequency performance of this circuit as the frequency changes?
what does this function say about the circuit?


texts: Issue in CP2102 Breakout module interface with PIC16F877a microcontroller

texts:
How to make pin connection between PIC16F877a and CP2102 Breakout module?

below is what i am using now with many pins(confusing).

what are the pins should connect with the PIC microcontroller for data transfer?
I want to transfer data using UART protocol from my PIC to laptop. I didnt find any answers from google also


texts: Calculating the Thevenin Voltage of this circuit

texts:
What I did was apply kirchoff's voltage law to the closed network with the 2 resistors and the voltage source to calculate the voltage of the resistors.
I got U - 2*Uresistor =0 <=> Uresistor =5V

Then, did the same to the closed network with a, b and the one resistor and got that UThevenin=5V

However, the answer is 10V. What did I do wrong?

Also, is there a way to do this by calculating the current first, and then applying the formula U=RI?


texts: How do I measure differential signals (like RS-485 or DMX) on an oscilloscope?

texts:
I've encountered differential signals in a few places, such as a differential output audio amplifier and now in a project working with DMX which is similar to RS-485. (Here's a similar question about RS-485.)

Looking at a waveform from a DMX lighting controller for example, I connected the channel 1 probe to D+, channel 2 probe to D-, and both ground leads to ground.

It produces this display:

While this is usable, I know it's still not the correct way to look at differential signals.

What is the correct way? I've heard of "differential probes;" does that mean I need to purchase new probes?


texts: Is there any special kind of DC motor with no mechanical resistance if unpowered?

texts: Im trying to find a dc motor that does not have any significant mechanical resistance if unpowered. So if i were to spin one up with my finger it would keep spinning. Im not looking for a specific motor just wondering about what kinds of motors there are and which of these would fit best into my question


texts: Assembly XMEGA program creating a longer than expected pin toggle?

texts:
I'm trying to do the fastest pin toggle possible on an XMEGA32E5 running at 32MHz. My code is as follows:

.include "ATxmega32E5def.inc"

.ORG 0x0000     ;Code starts running from address 0x0000.
rjmp MAIN       ;Relative jump to start of program.
.ORG 0x0100     ;Start program at 0x0100 so we don't overwrite vectors that are at 0x0000-0x00FD

MAIN:
    ldi R17, 0x3            ;set R17 to 11
    sts PORTA_DIRSET, R17   ;set all the GPIO's in the four bit PORTA as outputs

LOOP:
   sts PORTA_OUTTGL, R17    ;toggle the state of all the pins in PORTA

rjmp LOOP                   ;repeat forever!

According to Atmel, the instructions that are looped, sts and rjmp, should take two cycles each. However, when I probe either of the two pins that are being toggled, the wavelength is 2 microseconds, or half a MHz. This is way lower than the 32MHz clock. What am I missing? Is there a better way to do this?


texts: Amplified electret mic gives a lot of low frequency noise

texts:
I am trying to build a circuit that amplifies an electret microphone. I have made it based of a youtube video.

The microphone sort of works at this point, however there is huge amounts of noise around 0 to 100 Hz.

I have connected the mic to my PC and with some software analysed the frequencies and it gives the following graph:

The graph is what the microphone puts out when it is in a mute environment.

I have used capacitors to remove any noise from the power supply, and I have tries using a high pass filter but that doesn't seem to really solve anything as I would need to use a very high cutoff frequency.

I should also note that when I increase the gain, the noise also increases, so I assume the noise comes before the signal is amplified.

This is the circuit as shown in the video, I have made mine exactly alike, also using the same op-amp.


texts: In qelectrotech how can I draw a busbar?


texts:
I've beenstudying Real(True), Active and Apparent power in AC circuit.

I have understood all the concepts including phasor diagram, lagged sinusoidal waveform,the relationship between those three power.

However, I'm stuck on a this one concept at the moment and I feel really stupid.
The definition for real power is "Real/True power is power dissipated by a load (resistor) and it is the actual power transferred to the consumer".

But doesn't dissipated power due to load mean that it has lost that amount of power because of the resistance and the power is wasted as heat?


texts:
I would like to know how could I know the current consumed from a battery using this sensor, or other similar, using a microcontroller.

What I would like to know is shown in this video, where you can see the current consumption.


texts: What is the number of decaps used in each power pin?

texts:
The preferred decaps for the power pins in the Ic is one smaller value, say 0.1uF and one bulk value like 10uF. But for FPGA there are several power pins in one IC, if I have to provide decap for those power pins:
1. weather one smaller and one higher value capacitor is enough for all the power pins? or
2. Should i have to give two value(smaller and bulk) capacitor for each power pins?
3. weather i can give smaller value to each pin and single higher value decaps as shown in attached image?


texts: DC Analysis of Transistor Circuits - Double vertical line symbol

texts:
I have stumbled twice across this symbol || being used in the analysis of transistor circuits.

An example can be seen at this address: http://www.learningaboutelectronics.com/Articles/Dc-analysis-of-a-bipolar-junction-transistor-circuit

I can understand it: x||y = (xy)/(x+y)

But what is it called and why is it used? Because I do not know the name, I was unable to find anything with a search. "Double vertical line transistor circuit analysis" didn't return any results.


texts:
I got this 200KG Load Cell, it has 4 wires:

Red:   +EXC  12V
Black: -EXC  0V

Green: +IN
White: -IN

Sens. 2.000mV/V

According to tech support I have on Green/White:

200Kg  -> 2.4V
100Kg  -> 1.2V

I want to connect it to the arduino to measure, for example, 3Kg, but the signal is too low for the Analog in.
Can somebody post what parts and schematic I need to have it done?

I saw mentions to these parts:

AD 620
INA 125P
MAX4208
OP07

but also:

ADS1234

I am confused and where I live there are none of those parts, so I need some assured part list to buy over internet and wait then arrive by mail.

Will be happy for some light.


texts: Maximum Average Power Transfer and Efficiency

texts:
I've got this simple exercise about maximum power transfer.

simulate this circuit – Schematic created using CircuitLab

Where \$E_{th}=100\angle 0º \$ [V] and \$Z_{th}=100\angle 20º \$.

Then I completed this table with values I obtained after solving the equations on \$Mathematica\$.

I know that the theorem states that the maximum power transfer on the load will be when \$R_{L}=R_{eq}\$ and  \$X_{L}=-X_{eq}\$ .
This agrees with the values of  \$P_L\$ .

The efficiency is bugging me. How is it the same efficiency with the first 2 values? and is it true that the efficiency isn't the best at the maximum power transfer load values?

Are my calculations wrong or is it something else?

Thank you!


texts: Using and maintaining lower end soldering iron tips without destroying them

texts:
I bought a low end soldering iron of eBay - it was advertised as a "15 in 1 Soldering Iron Kit", and was advertised as temperature adjustable. It has a dial to adjust the temperature with numbers in degrees Celsius.
I put a new chisel tip from the kit in it, turned it up to 350 degrees Celsius, tinned the iron, and successfully soldered a couple of joints with lead-free electronics flux-core solder. Then I cleaned it on the damp sponge that came with the kit, and waited for it to heat to a temperature where it would melt the solder again. But by the time it reached that temperature, it had already gone black and the solder just balled and rolled off the tip. Wiping it on the sponge again cooled it, and the same problem was there when it heated back up.
I tried adding no-clean electronics flux from a flux pen to some balls of solder, and melted them into a blob, and it stuck to a tiny part of the tip. I tried letting the tip sit in the ball for a little while, and it still kept rolling off and not tinning. I wiped it on the damp sponge again, and repeated the flux treatment a couple of times, but the tip has developed some kind of yellow mineral-like crusty coating that isn't coming off with the sponge or the flux (and I'm wondering if it is possibly even from the sponge) - and now I can also see a reddish colour that I think might be the copper core.
This is a magnified view of what the tip looks like now (it is cool - red is not glowing metal):

I'm assuming that this one day old tip is completely wrecked now? It was a cheap iron / tip, but I'm getting a more expensive soldering station soon, and I want to make sure I don't ruin the tips the same way. I never used the soldering iron above 350 degrees Celsius, I had the tip on the iron while it was on for less than an hour total, I never scratched it on anything or used much pressure, and I don't think it was exposed to any contaminant (unless it was the flux), and I tried to keep it tinned as soon as it reached a temperature where that was possible - what else could I be doing wrong? Or is it just that the cheap iron is reaching temperatures that are higher than my selection (it does only have two wires from the PCB inside it to the element, despite being sold as temperature adjustable - so I assume it doesn't have a true thermostat and only adjusts the power / current / voltage based on the dial)? Or is it a poor quality tip that was always going to fail after a use or two?


texts:
I am trying to use a high torque dc motor with gears to drive a low torque dc motor but with higher rpm.

Is there a relationship between the current draw of a DC motor with the torque? I have seen a lot of dc motors with currents around 80mA.. I am wondering if a higher torque dc motor will draw more current.

Do you think the dc generator(High RPM fixed with gears around the armature of the dc motor) will stop the high torque dc motor (High torque low RPM) from turning?

Thanks!


texts: How to use MOSFET for load switch applications

texts:
I would like to do something like this application note:
http://www.onsemi.com/pub/Collateral/AND9093-D.PDF

And I'm using this transistor:
https://www.fairchildsemi.com/datasheets/FD/FDS5670.pdf

For me Vin = 20 V, and I apply 5 V on the gate.
Load = 22k

But it's like the MOS is always open. That's I don't understand, Vgs > Vth, so why is it always open?
And what I should do for make it work?

Thanks
edit: Add schematic, sorry I forgot it


texts:
I am trying to make a sheet entry to use ports to connect devices in different sheets as explained in this image:

But I am getting an error from Altium saying:

Sheet Entry RB[0...7]
Warning: Nets whit multiple names
Error: Nets whit possible connection problems

Of course, nets are not being connected on the PCB. It is my sheet entry:

As you can see there is a red line below RB[0...7]. I want to connect a bus between the two sheets. If I put a simple pin instead of a bus I get the same error so I suppose the problem is in the sheet entry and not on the other sheets. My project looks like:

Thank you for your help :)

EDIT:

Esquema PIC.SchDoc:

Entrada Analizador Logico.SchDoc:

Settings:

PCB

I can't see any differences between your examples and my sheets

SOLUTION
@Fake Name answer was ok, you have to name ports and net labels as RB[..] not RB[...] (2 points instead on three) and you have no put a Port in each bus AND a net label also whit the same name in order to connect them.


texts: Confusion about the use of AIGND in a differential amplifier

texts:
Above is a differential amplifier used to measure differential ended signals.
Here is what I understand:
The amplifier subtracts two input voltages with respect to its measurement ground(AIGND in the figure).
But this AIGND should also be connected to the signal source’s ground right?  Otherwise current cannot loop from amplifier’s inputs back to the source and cannot create a potential difference(?)

So I have the following questions:

1-) Must the AIGND be connected to the source’s ground? If so assuming the source is a differential signaling device does that mean AIGND will be connected to the source’s DC power GND?

2-)If AIGND must be connected all the way to the source’s GND, should that be done by using an extra wire or using the building earth as connection?

EDIT:

Here is more on the confusing part. Below is another illustration of differential ended system.

But how will the current loop above from the source back to the source? In this case the AIGND is not wired back to the source's ground.

EDIT2:

I made the above drawing to make my confusion more clear.
Above two 2V battery creates a differential signals which goes to the inputs of the differential amplifier.
Here the batteries' common point is X which is not connected to anywhere else than battery terminals.
So here V_AX = +2V  and  V_BX = -2V.
Now what is the voltage V_AG and V_BG here? (G is the amplifier's measurement ground which is AIGND). X is not connected to AIGND here. Does this make sense?


texts: Use current from SMD LED to switch larger current

texts:
I've got a bluetooth receiver with blue SMD LED's on that flash to indicate connection status. I would like to take that status LED and replace it with the white LED that's in a switch I have.

The switch is designed for 12-24V circuits and has a series resistor (not sure the value), and I have a 25.2V 6S lipo powering the rest of my system, including a similar switch with LED.

I tried to attach the switch and LED to the receiver with flying leads, I piggybacked the DPST switch just fine and removed the blue LED and wired up the switch LED, it didn't light. So I removed the series resistor in the switch, the LED now lights up but is very dim. See below.

simulate this circuit – Schematic created using CircuitLab

So I thought about using a transistor switch to activate a higher voltage circuit. The problem I have is that the blue LED appears to be switched on the cathode after a series resistor, I don't know where to attach the base of a transistor which would see the right voltage drop. Obviously there's a lot of stuff going on on that PCB I don't know about, or don't understand illustrated as the box around the switch.

I've updated the schematic to show how I thought it could possibly work, but I don't think it will.

I can't figure out what this means for what I want to do, does it sound possible?

Thanks.

simulate this circuit


texts:
We want to implement USB on our PIC24 based embedded system.

Hardware:  All done
Firmware:  USB part is currently Non-existent
My role:   Make it all work
Questions: The protocols are very complex

Please point me to relevant sources of info.

The specific chip is: PIC24FJ256GB210.
It will be a "device", and I don't think it will ever be a host, even a host-to-go
I have previously spent time at these places...

A tutorial, here: http://www.usbmadesimple.co.uk/ums_5.htm

Microchip's forums, here: http://www.microchip.com/forums/

The USB Implementers Forum, here:  http://www.usb.org/developers/docs/

Jan Axelson's site, here: http://www.lvr.com/usbc.htm  and purchased her book "USB Coomplete"

The firmwware in the embedded device is what I need to write. The protocol is what I need to research the most. Pointers invited and welcome.

Protocol, Protocol, Protocol; that is what nobody can explain.


texts: What's that two-bracket or pair of slopes like schematic symbol next to a data line?

texts:
I found this symbol in some datasheet. But I have no idea what is it? Can anyone tell me?

The symbol is mirrored and points towards a data signal line
It looks like an icon for a clock signal or a rising and falling slope or like two closing brackets


texts: Why does the output voltage of this bridge rectifier drop by 2VD?

texts: Why does the output voltage drop by 2VD? Whats troubling me is the ground placed after the load resistor. If we were to remove that ground and measure Vout as shown in fig 4.25a, i understand that there would be a 2VD drop. Like this though, it seems like there should only be a drop of 1VD, no?


texts: Wrong Reading output bits of node MCU output in arduino

texts:
I am trying to read output on 3 pins of nodeMPU in my Arduino board. If value of all three pins are same then Arduino is reading wrong values.
For example:-

if pins have values 001, 010, 011, 100, 101, 110 then Arduino is reading correctly.
If pins have values 000 or 111 then Arduino is sometimes reading inverted values. Like if value is 000 then it is reading 111 and if value is 111 then it is reading 000.

How can I fix this?


texts:
I'm tired of having to resort to Google to find every single oscillator design. I would usually just try to search for a circuit using the same frequency crystal, and try to build that.

Right now, I want to be able to design a circuit around the crystal, specifically, 1 MHz. The problem is that I have no clue how to design it. I know that I need some sort of a feedback loop, but nothing really makes sense. Diagrams just show a buffer, so if, for example, the output is high, the it feeds that back to input of the amplifier, which keeps the output high. Shouldn't there be some kind of an inverting device?

I need assistance in designing a oscillator circuit, and determining the correct values for the other components.


texts: What will be case if buck regulator (TPS62067) load current increases the rated current?

texts:
This is buck regulator I am using for 1.8 V output: TPS62067.

Input Voltage = 3.3 V

Maximum rated current = 2 A.

How the regulator will behaving if the load current increases more than 2 A ?

My understanding from the datasheet is,  there will be thermal shut down when the junction temperature exceeds more than 150 C. Also module will be in shut down mode for EN pin is at logic low.

Basically I am looking for a case of over current shut-down of the module and how much time (of course in micro seconds range) it will take the module to shut down.

Edit:
Added the circuit diagram,

From the datasheet, I could not find anything as over current shutdown. Please let me know if there any further information required.


texts: How can I calculate the internal resistance of an alternator?

texts:
I have a 12V, 90A alternator. I wanted to know how can I calculate its internal resistance.
The specifications sheet I received from the manufacturer is a simple image, as shown below:
I
This alternator is going to be installed on a tractor for farm work. Its internal resistance is important as my add on modules (a GPS tracking and motor control device) protection devices are affected by it.
My circuit has a SLD33 TVS diode by LittelFuse that can withstand load dump pulses from alternators that have Ri (internal resistance) >= 1 ohm.
Since this alternator is capable of delivering such high currents (upto 90A), I suspect it might have an internal resistance Ri much less than 1ohm. I will need to update my electronics circuitry with two SLD33 instead of one in that case.
With the help of above image, can anyone tell me how can I find the internal resistance of this alternator? Or if you are aware of any other method, then can you please share the details of the same?


texts:
Some customers ask me about the response time of a relay, But inside the catalogue,two different delays are mentioned: the switch-on and the switch-off delays of the relay. which of these two delays are determinative of the relay response time?

you can check switch-on and switch-off delay in output section:
http://catalog.weidmueller.com/procat/Product.jsp;jsessionid=BCE8FA0695A52E7BE6D7EC63694D5B03?productId=(%5b1381900000%5d)&page=Productue