texts:
I've been trying to understand EMF, specifically back EMF in electrical motors, such as for example a setup like this:

Say that we apply a voltage to the brushes. I understand that once the rotation gets going, a current will be induced by the changing flux inside the loop, and that this induced current is opposite to the current created by the external voltage. My understanding is that this results in a smaller net current in the loop, and this phenomenon is called back EMF.

However, I don't exactly understand "where" the EMF (which is a voltage?) appears. One explanation I've seen is this:

where the EMF appears as a voltage source in series with the motor resistance. While this may be a good way to explain how the current will behave, it doesn't seem to explain what actually goes on inside the motor. Surely, the EMF doesn't appear "before" the motor, but rather inside it. Should it then somehow be seen as being superimposed on the resistor? Where, in the first figure, would the EMF appear? Does it change the voltage across the brushes? Where does the "extra" voltage drop happen?


texts:
I'm new at coding and need some answers, I doing some mini project and I got caught in some errors I'm not sure,

I'm doing a ''photocopy'' machine and I have to code it in C under the Microchip MPLAB IDE.

so this is the requirement in my machine

Input On and Output does nothing
Input On and Increase(paper)toggle count increase
Input On and Decrease(paper)toggle count decrease
Input On,LED Copy on,and Motor runs.(7 Segment display countdown)

But here the problem, I manage to get all requirement right but for the last requirement
after the thing have countdown and 7 segment shows 00, when I attempt to increase the count,the 7 segment increase count by random eg 00 > 5,00 > 18. what do I add in the coding line to make it increase by 1?

My last current count code is this

for(i=paper;i >=0;i--) //for countdown

   {

    while(SW3==1)

    LED1=1;
    Delay1KTCYx(250);
    LED1=0;
    Delay1KTCYx(250);
    M_On=1;

   }

what do I need to add to make sure the count doesnt jump,eg 00 > 01


texts: How can I connect the MPLAB X software from MicroChip with the mikroICD debugger on my Big Pic 5 board of microElektronics so I can flash and debug my assembler programs? The MPLAB X Software only contains 'ICD 2' and 'ICD 3' under the menu 'Programmers'.. I want to type in a program in assembler in MPLAB X and then be able to set breakpoints and check the registers while it is paused on my Big Pic 5 board.


texts: What actually is the differential gain of an operational amplifier and why does its value change when we consider the common-mode gain?

texts:
Okay, this may be a stupid question, but at the beginning of my Applied Electronics course they taught us that the differential gain \$A_d\$ of an operational amplifier is ideally infinite; however, in real op amps, we get a limited bandwidth. Which is fine, because it's still very high.
My problem raises when I was introduced to common-mode gain and differential-mode gains. In particular, I read that an amplifier subject to common-mode input signals has as a (non-ideal) output a linear combination of its differential mode input voltage mode and its common mode input voltage, i.e., $$A_dv_d + A_{cm}v_{cm}.$$ And for now, everything's fine. But let's consider the practical example in the picture below:

simulate this circuit – Schematic created using CircuitLab

According to what I read, in the schematic above $$V_u=(1+\frac{R_1}{R_2})(v_+-v_-)=\frac{R_1+R_2}{R_2}V_1-\frac{R_1}{R_2}V_2.$$ And since \$\frac{V_1+\frac{R_1}{R_1+R_2}V_2}{2}=v_{cm}\$ and \$v_d=v_+-v_-\$, then \$V_1=v_{cm}+\frac{v_d}{2}\$ and \$V_2=v_{cm}-\frac{v_d}{2}\$.
Moreover: $$V_u=\frac{R_1+R_2}{R_2}(v_{cm}+\frac{v_d}{2})-\frac{R_1}{R_2}(v_{cm}-\frac{v_d}{2})=v_{cm}(\frac{R_1+R_2}{R_2}-\frac{R_1}{R_2})+v_d(\frac{R_1+R_2}{2R_2}+\frac{R_1}{2R_2})=\Big(\frac{1}{2}+\frac{R_1}{R_2}\Big)v_d+v_{cm}=A_dv_d+A_{cm}v_{cm}.$$
How are we even just able to say that \$A_d=\frac{1}{2}+\frac{R_1}{R_2}\$? It's limited, fine, but I would've imagined bigger numbers. I guess I can live with a common gain of 1, but since they called both differential gains \$A_d\$, are they seriously the same?

Already from the beginning, I couldn't even understand why would we use $$V_u=(1+\frac{R_1}{R_2})v_d,$$since \$V_u=A_dv_d\$, with \$A_d\$ a big value and, instead, considering an ideal op-amp, as \$A_d\$ approaches infinity, \$V_u=\frac{1}{\beta}v_+=(1+\frac{R_1}{R_2})v_+.\$ But shouldn't \$(1+\frac{R_1}{R_2})\$ be the gain from the non inverting terminal to the output (i.e., closed loop gain), not of the op-amp, or am I wrong?
What am I missing?
Thank you in advance!

Edit: I am starting to assume that the answer is due to the principle of superposition of effect, i.e., shutting \$V_2\$ off and compute \$Vu\$ due to \$V_1\$, and then shut \$V_1\$ off and compute the overall gain due to \$V_2\$, and adding then the two results together. This could make sense, I suppose, but I can't still figure out why the result is equivalent to \$v_d\frac{R_1+R_2}{R_2}\$, since \$v_d\$ is supposed to be very small and it should therefore be amplified by a high gain \$A_d\$.

Edit 2: fixed typo that made the result wrong, but the question still holds.

Edit 3: fixed the value of \$\beta\$ in the formulas for this schematic. Unfortunately, I chose an unconventional position for \$R_1\$ and \$R_2\$ in the schematic.


texts:
I have two different PCB boards. One is a sensor board and the other is a power board.

I connect a 9V battery to the power board, to a 7805 5V regulator, and through a filtering process of some capacitors.

simulate this circuit – Schematic created using CircuitLab

When I measure the voltage with the two boards separated I get 5V and everything is fine.

However, when I connect the power output via a flat flexible cable to the sensor board, the input drops from 5V to 0.5V on the sensor board and the LED starts dimming, and thus my sensor board does not work!

I checked on a breakout board and the cable can handle up to 30V.

Why is this happening and how can I fix it?

I can add the sensor board if its relevant. But it will take me a while to draw the schematic.


texts: Calculating the core area for a low frequency transformer part 2

texts:
I posted a question a while ago about calculating the core size of a transformer when the frequency is relatively low (<50Hz). Thank you to everyone for the comments and feedback. I have done some more research and would like to post a follow up question outlining my thinking. I would really appreciate any comments.

I am interested in calculating the core size for a 20 Hz transformer. Single phase, step down. This is a theoretical question - I understand that low frequency transformers require core sizes that make them impractical, but I am just trying to understand how the core size would be calculated. For the purpose of understanding this, I have treated the transformer as a “perfect” transformer with no core losses - the thinking being that core losses could be factored in after I understand how the core size is worked out. (if this is a mistake, please let me know)

My primary coil has 400 turns & 8.05429 Voltage.
My secondary coil has 50 turns
The formula
(Voltage in Primary/turns on secondary coil)=(Induced Voltage in Secondary/turns on primary coil)
gives the induced Voltage in the secondary as 1.00678625, with a turns ratio of 400:50=8:1

I wanted to then use the following formula-

induced voltage = 4.44*fNA*B

Where
f= frequency in Hz

N= number of turns in the coil

A= cross section of the core area in Meters

B= flux density in the core in Tesla

(I have done some FEMM simulations that give me a value for flux density in the core)

My questions:

1.
I know the saturation point of the core material, so can I switch the formula

induced voltage = 4.44*fNA*B

to

B=induced voltage/(4.44fNB)

and then play around with plugging in values that deliver a value for B that is safely below the saturation point of the core material(e.g. 1.8T)?

2.
How does the turns ratio of 8:1 influence the values for the Induced Voltage and the Number of Turns that I need to put in to the above formula? At first I thought I should just use the primary coil values, then I thought I should add the primary and secondary together. I have chased my own logic around like a dog chasing it’s tail and now lie in a dizzy heap!
If anyone has any advice here, I surely would appreciate it.
Thanks


texts: What is limiting my BLDC Motor power Output?

texts:
I am using a BLDC 3 phase hub motor and recently installed a motor controller rated for 3000watt (I originally had a 1200Watt controller installed).

The motor is rated for 500w nominal 800w peak but is currently probably producing approx 1000w power at the wheel (with the 3000watt controller installed).

I was wondering what design aspects of my BLDC motor would be the limiting factor (in terms of max useful output wattage).

I think it's one of the following things:

Stator magnetic core is saturated (I need a wider or bigger diameter stator?)**
winding diameter too small *
permanent magnets need to be bigger? (not sure if this would do much) ***
motor needs better cooling *

*(probably not a big factor since motor performance when motor is cold is not far off from the wattage output (useful) I got with 1200watt controller))

**What design changes (for example more layers, other shape of magnetic core) would positively influence the magnetic saturation point (make it so that this point is reached later/at a higher amount of magnetic flux produced)?

*** the permanent magnets (36 pieces if I counted correctly) are approximately 3mm thick, 40mm in height.

I'm running the motor at 72v (84v when battery fully charged), originally was intended for 36v/42v .

The power output/torque produced by the motor did increase after switching to the 3kW controller but not by a lot. It appears most of the extra watts going to the motor are going into heating up the motor.

The motor gets significantly hotter (gets hot in shorter amount of time) than with the previous controller.

The motor is running with hall sensors connected to controller (motor controller supports hall sensors)

Wires from controller to hub motor (3 phase wires) are 16mm2 each so probably not a limiting factor.

The performance appears a tiny bit better when the motor is cold but the output is still quite comparable to the 1200watt controller..

Does the number of windings have any influence on the efficiency of the motor? I'd think longer overall path length of windings within motor would result in more voltage loss thus less efficiency.

The winding wire diameter is approx 1.5-2mm. I'm not sure how many layers of windings there are unfortunately (have not rewound this motor yet).

Stator's magnetic core outer diameter is approx 25cm, stator's magnetic core inner diameter is approx 15cm. See image:

( Note: currently used wires are much thicker than the ones in the photos, it's an old photo )

What changes could I theoretically make to my motor to get more power output at the wheel?
Thank you!


texts: What do I do with the extra "ground chassis" tab on a DC power jack?

texts:
Product Link

Datasheet

I have about fifteen 9v wall warts within specs for the circuit; I'm going to use the one that fits the jack. There are three solder tabs on the jack. One for the positive tip, one for the negative ring/sleeve, and one for the chassis ground. My schematic has Vin and ground specified. I'm relying on the wall wart to appropriately ground the AC end of things. My pos/neg tabs are used for source voltage and ground, respectively, and that leave the third chassis ground tab.

Do I ignore it? Connect it to the negative side ground? To the chassis? What should I do when there's no specification about what to do with the extra tab?


texts: Signed or unsigned distance in electric potential due to point charge(s)

texts:
I am reading about the electric potential:
from wikipedia:

The electric potential (...) is the amount of work energy needed to move a unit of electric charge (a Coulomb) from a reference point to the specific point in an electric field ...

Consider then an electric potential due to a point-charge \$Q\$:
I would assume that the potential should be positive whenever our (unit)test-charge and the point-charge repel each other, and negative when they attract each other. Since our test-charge is fixed to be \$1C\$, we only need to consider the charge \$Q\$, and our electric potential will be proportional to this charge.
Let's say we consider the potential \$ \varphi_0 \$ at the origin. Whether \$Q\$ lies at \$\left(1,0,0 \right)\$, or at \$\left(-1,0,0\right)\$ shouldn't matter since we only consider attraction or repulsion. Also I see many formulas just considering \$r\$ which to me doesn't look like there is a sign involved.
Now here is where my problem starts:
Consider now two point charges \$Q_1\$ at \$\left(-1,0,0 \right)\$ and \$Q_2\$ at \$\left(1,0,0 \right)\$.
Let \$Q_1 = Q_2\$
Wikipedia also explains how to calculate the potential due to multiple point-charges, namely by just adding up the individual potentials due to one point charge.
Now if we consider again the potential \$\varphi_0\$ at the origin, we would have:
$$ \varphi_0 = \frac{1}{4\pi\epsilon_0} \left(\frac{Q}{1} + \frac{Q}{1} \right) = \frac{2Q}{4\pi\epsilon_0} $$
Thus we have double the potential.
Now this is not what I expect.
Since the point-charges lie on opposite sides of the origin, I would very much expect them to cancel each other out when calculating the potential at the origin. Thus I would assume using a signed distance (\$1\$ and \$-1\$ in this case) to be the correct approach, but then the previous logic of the sign of the potential signaling repulsion or attraction would not work anymore.
Where has my reasoning gone astray? Where am I making wrong assumptions? Where am I misreading/misunderstanding the wikipedia-explanations?


texts: Taking Quizbowl buzzers and connecting to a computer

texts:
Recently I Bought quizbowl buzzers from buzzersystems.com and the buzzers i received use an rca cable.

If you did not know basically, when you click a button, it sends a signal to a box which receives it and lights up/makes a sound.

Is there anyway that I can somehow connect this to my computer so that every time I click the button, it sends the signal of the enter key on my keyboard? Preferentially something that uses usb to reconfigure the signal.

Sepcs
22AWG, uL2464#22x2c cord
Normally open, momentary push-to-close switch
0.050 ohm (max when new, measured at button)
* AC specs (current and voltage): 3A @ 125 VAC 1.5A @ 250 VAC (250VAC is max AC voltage)
* DC specs (current and voltage): 24 VDC (max),10A (max) Note: LOW DC VOLTAGE!

Anyone know if this is equivalant to what type of normal rca cable? Audio, video,mono or dual channel etc.


texts:
I made a project with Arduino using a breadboard. Everything is working, but nothing is soldered in place. So, for example, I cannot put it outside, otherwise after the first wind, everything will break :-)

I would like to pack it in a box and actually used as a gadget. Can anyone suggest ways to do this? For example, are there any breadboard + screws that I could use, without having to solder my Arduino?


texts: Is it better to use USB A or USB B or RS232 to communicate over long distances?

texts:
Similar post
As per the previous post (which was 5 years ago), I have a device that has three forms of serial communication. One is an RS232, the other is USB A and finally a USB B. So I have three options to connect my PC to this device. The device sends the scanned RFID tags through this serial connection to my PC.
I want to place the reader 60 meters away from my PC. Which type of serial communication should I use?


texts:
Is creating an electric heater really as simple as creating a resistor and connecting a power source? I feel like it shouldn't be that simple.

Part of the reason is what values of resistors to use. My guess is you want them to be a few kilo-ohms as if they are to small you have the equivalent effect of shorting a battery (or power source). Then you can use the voltage to control the rate (P = V^2\R).

Thanks for any help.


texts: electronic scheme "R1=2500M" how many ohm?

texts:
I have an electonic scheme of a Sony microphone that indicate R1 as 2500M. But how many ohm is "2500M" ?

thanks a lot


texts: Connecting more than one serial device to PIC16f877a

texts: In my project i need to interface a gps receiver and a gsm modem to pic16f877a, But there is only one set of UART lines in this Microcontroller. Is  it possible to multiplex these two devices using software without the use of additional hardware?


texts: Output two different voltages at the same times

texts:
First I'd like to excuse myself for my English, especially when talking about electronics, because I don't always know the correct translations.

I plan to use this Deal Extreme portable 12 volt battery

YSD-12450 12V 4500mAh Rechargeable Lithium Battery

to power my 3"5 HDD when I'm travelling.

However, to power a 3"5 HDD, I need 12v AND 5v at the same time. How could I achieve that ?
Is the only choice using two different batteries, or would even that be a total fail, due to the mains not being the same ?

Thanks, and sorry for the mistakes


texts:
I'm new to signal processing and have a specific question about a PCB design by TI. (TDC7200EVM User’s Guide ) (TDC7200EVM)

Could anyone explain why they place the series terminating resistors on the receiver side?

Is it not better to use parallel termination in this case?

Or am I completely wrong and these aren't terminating resistors?


texts: How to get a CMOS transistor SPICE model?

texts:
So far in order to simulate CMOS circuits I relied on a library that I had to randomly download from Internet such as this one:

http://ecee.colorado.edu/~ecen4827/spice/ltspice/5827_035.lib

Inside the library the PMOS and NMOS model is defined using the BSIM3v3 model and I only have to create an instance of these transistors and wire them together and  run the simulator.

My first question is that from where the professor of that class got this BSIM3v3 CMOS SPICE model?

Second question is: "Can I create my own transistors and extract such parameters and put them in my own library file?"

The only thing that comes to my mind is to use IC layout editors such as Cadence virtuoso or Microwind (I don't even know if they are the right software for this task, I just HEARD they can be used for IC design) to layout my transistor and then extract the SPICE parameter from them.

My ultimate goal is to design a simple standard CMOS digital cell library and use it for my more complex VLSI designs.


texts: How to calculate resistor values for certain filters?

texts:
Hello i am having trouble understanding how to calculate the resistance for the low pass filter. Mainly since i dont understand if i have to take in the other ressitors. When calculating can i just analyse them separately is the red lines show and break them up into sections? Also for the high pass, to calculate R do i have to take in the resistor 3 value or can i ignore that and focus on R1+R2 for Req? I need the 2 reistors so that the input voltage is dropped so that the output voltage 1 is less than a certain voltage as this voltage then feeds into an amp.

Is there a better way to implement the low pass after the highpass or not? Need the highpass to block dcbias and the voltage divider is used to keep voltage under a certain amount due to vout1 requiring a certain value.

Basically:Can i just find the values for the high pass as one section and ignore R3 for Req for that 1st section, then find the low pass filter components so that the output voltage of that can be fed to an amp.

For the low pass filter can i calculate it from using R1 and R2 or not. If so please show how you did this.


texts:
We are using an old electrical system in industry. My task is to digitalise it. As i saw, PLC is too expensive and large scale for our operation. Also, microcontroller needs programming which makes operation only depending on me. I am considering simple logic by using logic gates of TI. I would like to ask whether it is possible to use these ICs without microcontroller and also what alternatives can I use? It may be also possible with TTL, DTL logic but combinational circuit becomes too complicated with them.

System works at 24V normally but not necessarily.


texts: Is the flow of current in this RL circuit ambiguously defined?

texts:
TL,DR: Why does i_L in this point down instead of up? I get two different answers for the current i_2 when I imagine them in these different ways. Or am I (likely) making a mistake or missing some finer point here?

This is an image from an example question in my Introduction to Circuits textbook. For the sake of helping other users find this, I'll quote the text here.

  8.5 At t = 0.15 s in the circuit of Fig. 8.21, find the value of (a) i L ;
  (b) i 1 ; (c) i 2 .

  Ans: 0.756 A; 0; 1.244 A

As I picture it,

The current coming from the 2 A current source at t > 0 flows upwards, to the right, and then immediately downwards and back to the source again.
i_L flows downwards, bypasses the 8 ohm resistor, and then upwards "against the stream" of the 2 A source, and then returns to the inductor through the 2 ohm resistor.

But I'm unclear as to why i_L has to flow downwards in this case. It seems to me it would be just as correct to have i_L start upwards, flow through the 2 ohm resistor first, and then downwards through the short circuit instead. It's the same path, after all.

Is there a reason my textbook wrote that i_2 should be the difference between 2 A and i_L?

Thank you very much for your time.


texts: Question on PID for speed control of DC motor in treadmill application

texts: In treadmill applications with DC motor, you can't go from 0.5 mph to 1 mph instantly. The speed should be gradually increasing. If I want to design a PID for speed control, my setpoint should be a ramp instead of steps, right? Or, I can give the setpoint in steps and the P gain adjust the time response of the system? Which one is the right approach? I think that once the final setpoint is reached as ramp, the PID controller should compensate the output for changes in the load. My feedback is a speed sensor that will tell the controller the actual speed. If I said my setpoint is 0.5 mph, the PID doesn't care if gave the setpoint as a ramp or step. Am I right?


texts: What means voltage range in this LED driver?

texts:
Many types of LED drivers has output Voltage range and not exactly regulated voltage, i asked the seller and he say that means it suitable for all power LEDs that works with voltage range between 60 to 90 V, but i am wondering how can this LED driver understand how much voltage your LED need?
Already i test the open circuit voltage and it was even more than 100 V.


texts: ac load control using a microcontroller via relay

texts: when i switching ac induction motor  by micro controller via a relay it some times hanging up or restart the controller while I'm using optical couple r for isolation between 12v supply of relay and 5v supply of micro-controller. I'm trying to use large capacitors on supply but in vain


texts: how to measure mosfet impedance in LTspice?

texts: I am trying to design a 13.56MHz 20W class E amplifier based on a TI app note this. On page 5, it say "FET(IRF510)’s gate impedance is 14-j26", which I should match impedance to my driver output. However, I am confused how to measure IRF510's gate input impedance, for example, in LTspice. Should I use either of the two test circuit in below picture? The first one gives 8.7-j34.9, and the second one gives 3.8-j28.8. None of them the same with the value mentioned in TI's doc(14-j26). Is the spice model in LTspice is different, or my test circuit is wrong?


texts: Power switch (backup battery voltage is higher than main line voltage)

texts:
The main power is USB charger 5V.
The backup power is battery 12V.
Output should be 3.6V
Current goes to DC-DC LM2596 that gives 3.6V output.

So, I cannot use simple schematics with zenner diodes or MOSFET cause to fact: voltage on backup battery is higher than that on main line.

The ideal switch is relay. But it is so slow.

Is one more scheme based on 2 DC-DC LM2596 with inverted OE pin.

The next solution is LTC4412, but its hard to find.

Advise me solution, please. I know how to solder SMD and have a lot of different fets, transistors, zenner, etc.

What about https://electronics.stackexchange.com/a/131048/97927 ?


texts:
Is possible to obtain a resistor controlled by RMS of a voltage in LTSpice? The syntax \$R=V(n001)\$ works, whereas \$R=rms(V(n001))\$ does not work.
Thank you for your time.


texts: Why did my oscilloscope hookup trip my RCD?

texts:
I was attempting to investigate an SPI interface on a power line meter (typical model that measures Voltage, Frequency, Amps, Watts).

I opened the module and found the SPI pins broken out. So I plugged in the meter and the oscilloscope, and connected the oscilliscope probe to the CLK pin, and the probe ground to the GND pin.

A second or two after connecting the GND pin, the device IC caps blew off, and the RCD for the property blew and had to be reset.

What did I do wrong? How did this blow the RCD?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm experimenting with transmitters and receivers. I have a long piece of wire hanging from my ceiling, that has its lower end connected to a function generator. This is my transmitter. I'm using frequencies around 1-3 megahertz.

I hung another piece of wire a few meters away and connected an oscilloscope to the lower end of the wire. When I turn on the transmitter, I see a clear sine wave on the scope output on the same frequency as I transmit. Next I tried a magnetic loop antenna: I simply took some wire insulated and made a loop of 7 turns, approximately 30cm in diameter. I connect the scope to the ends and I again see a clear sine wave. I understand that this works by using the magnetic part of the EM wave to induce a voltage across the loop.

Now I want to amplify this signal. Above I have a schematic of a simplistic common base amplifier I built on my breadboard. I tested it with my function generator and it works very well. Even as I set the input voltage very low I see a nicely amplified output. I wanted the amplifier to be as simple as possible so I do not care about any offsets on the output (no capacitor on the output).

Then I connected this amplifier to the loop antenna. One end to the input, other close to the negative terminal of the battery. I turn on my transmitter but now I see nothing on the output except the biased DC voltage. I simultaneously measure the voltage on the output terminals of the antenna as well as between the output and ground of the amplifier, and both show no sine wave (the antenna shows 0 volts always between its terminals, the amplifier shows just the DC bias). I now test again without the amplifier by connecting the scope over the antenna terminals and now again I see the sine!

So this is strange: The amplifier and the antenna work very well separately, but not together! I tried tweaking the values of the bit, and I also tried putting a capacitor (tried many values between a few nanofarads to several microfarads) at the input; nothing worked.

Can somebody perhaps point the flaws in my experiment? Again I'm not trying to build anything practical, I just want to see an amplified voltage at the output. I've checked my setup many times and I don't think I've made any mistake in the wiring.

EDIT: I added the input capacitor to the schematic. I did mention in the text that I tried using one but alot of answers mentioned this. I should have added it in the first place.

EDIT: Below is a schematic of a common emitter amp that I tried. Like the previous common base type, this one works well when using a function generator, but not when I transmit to the antenna. I even tried simulating the impedance of the loop antenna By using a resistor (tried 500-1000 ohms) at the input, and it still works great. But with the antenna I get nothing on the output except some weird ripples when I tap the function generator output lead against my transmitting antenna. Picture of these ripples are below.


texts: When do we prefer isolator over optocoupler?

texts:
Today I have learned that a device called "isolator" exists (eg: SI8712CC-B-IS). Its function is very similar to the optocoupler's. On the good side, it is much much faster. While it is very hard to find an optocoupler with propagation delay less than 1\$\mu\$s, almost all isolators have less than 100ns delay. On the other hand, they are slightly expensive though.

If such a device exists, why do we keep using optocouplers? Is the price the main factor of choice? Can we always use an isolator instead of an optocoupler? How do they differ in general?


texts: How to measure/show MIPI-DSI 4 lane signals on DSO/oscilloscope?

texts:
I want to measure/show the MIPI-DSI 4 lane signals on an oscilloscope. There is MIPI type display has been connected with LVDS-to-MIPI converter. I want to measure the signals at the output side of LVDS-to-MIPI converter, i.e. MIPI signal.

I don't know how can I measure the signals on an oscilloscope. Is there any other special device needed apart from an oscilloscope?


texts: Why can't a first-order block have an oscillatory step response?

texts:
From what I understand, multiple-order blocks can have step responses that oscillate.

It's apparent that a first-order block cannot have an oscillatory step response.

How come?

Is it due to the mathematics revolving around it?


texts: practical concideration for op-amp differential amplifier

texts:
i'm trying to make a current sensor based on an op-amp differential amplifier with a unity gain (all resistors are equal so to have the best CMRR.)

The output of the op-amp differential amplifier will be linked to an ADC so that I can capture the voltage drop across a shunt resistor and make some processing .

the design i'm planning to implement is this one as published on EETIMES:

My questions are :

1)-Are there any practical consideration that I might be missing for this this circuit to work well .(i see in a lot of practical designs (for other circuits) some additional capacitors that are linked to terminals , diodes ... )

2)-I now know that this design has a draw back which is low input impedance ,can any one explain to me the impact of that on the design .

3)- for solving this problem of input impedance , can we consider increasing the values of the resistors R1,R2,R3,R4 .

Thankyou


texts: Input impedance of Arduino Uno analog pins?

texts:
I'm using the ACS712 hall-effect based current sensing chip on some small robotic arm motors, and reading in the analog voltage with an Arduino Uno.  I've had reasonably good results, but only after putting in an RC filter on the output.  However, in the application note on the datasheet, it says not to do that:

"the addition of an RC filter to the output of a sensor IC can result in undesirable
device output attenuation — even for DC signals."

Then it gives a formula to calculate attenuation, but it depends on knowing the input impedance of whatever is reading the signal, so that's what I'm after here.


texts: During dead time of any DC-DC converter both the switches are turned off to avoid any shoot-through current. But in a synchronous Buck converter that would mean sudden zero current through inductor. Wouldn't that cause any problem?


texts: Does an inexpensive screw terminal "expansion strip" exist?

texts:
I've got a messy security panel that needs cleaning up badly, as I need to connect another PCB for remote access and can't get the wires to reliably stay in place:

If you look at the black, red, green, and yellow terminals, they already have three separate wire (pairs) connected!

So far, a terminal strip like this is the only solution I can come up with.  However, I'd have to add an additional bus bar across the terminals that need to share a signal, which just adds to the size of the bar needed and is a little inconvenient:

There's always Phoenix Contact terminal blocks like the following:

However, at over $10 each from Digikey, it's a pretty expensive (though elegant looking) solution.

I guess I'm looking for something like the following photochopped image?

Note that I'd like a bus bar that connects the columns of terminals...

Can anyone suggest other options?


texts: The 7-segment LED display is too dark when connect to a auto dimming circuit

texts: I'm using the below circuit to build a auto dimming circuit. I was fine when I only use one 7-segment led, but when I connect more 7-segment led (parallel to L1) the light intensity is very low. How to make it brighter and function properly? Thank you.


texts: Schematic Infrared Break Line Alarm Receiver

texts:
Can anyone help me with the attached schematic, I don't really understand were the line of " VREF" connects to , maybe I can not see the trees for the forest!

9v

cheers

spike
Hi

Thank you all , for all your replies, I have tried to do a schematic that I can understand from the schematic I first put on here, would anyone be able to have the time and patience to check it out!

Cheers and again thanks, what a great site, and nice people willing to help people like me that are very new to electronics.

spike


texts:
I have a two stage op amp. I was able to find the TF if it was just one stage, which would be:
$$\frac{V_o}{V_i}=\frac{R_2C_2s}{(R_1C_1s+1)(R_2C_2s+1)}$$
Can I apply the same procedure to the second half (after the second node) then end up with the final TF as the one right here, or do they change when the circuits are cascaded?
$$TF=TF_1*TF_2$$
Hope someone can give me some insight!


texts: Why does my RTC generate interrupts faster than once per second?

texts:
I have configured an RTC module on a uC to generate interrupts every second (~32 kHz module clock with a 0x7FFF prescaler in between the counter and the clock - I hope so, seems like ~32k is the default value, and it would be a shame if the error arises from an incorrect clock being connected to the module). However, it seems like seconds counter register is incremented every time a single assembly instruction is carried out (sometimes every two assembly instructions), thus generating interrupts at an astonishingly fast rate. What could be the cause of this behaviour? And if you were to troubleshoot it without being able to ask this question on forums like I am doing, how would you go about finding the issue?

In response to comments - RTC clock indeed may only be connected to either an internal or an external oscillators, both oscillating at ~32 kHz. The uC is an Infineon XMC series with Cortex M-4 processor. I can hardly think of any section of my code that I can post, as it's simple register configuration that (a) Enables periodic RTC events, (b) Enables SCU (System Control Unit - in charge of clocks, hibernation domain and power/reset domains, etc.) RTC periodic interrupts, (c) Configure NVIC properties. As I've noted in one of the comments; the part that confuses me the most about this problem is that the 'seconds' value seems to be correct when passed to a hyperterminal, yet the refresh rate (putty terminal is refreshed every time an interrupt is handled) is very fast - yet the seconds count seems to increment every second, meaning that the timekeeping is correct.

One more small update on the issue. Seems like the RTC timer is working correctly and even manages to keep up with real life for at least an hour when I leave it running in the background. However, what happens is the interrupt sequence gets stuck in a while loop for no particular reason - if I set up the interrupts to trigger every minute instead of every second, then the program will issue an interrupt one minute after I start running it, and then execute that interrupt over and over again, flickering the terminal very fast.


texts: What exactly is the definition of an operating point in the context of Bipolar junction transistors. What is their physical significance? I was going through few books on electronics and found that a load line is drawn (Linear relation between collector emitter voltage and collector current) and the point of intersection  with the output characteristics provides us with the operating points. Why is it necessary  to  fix the operating point in the linear part of the output characteristics so as to operate the transistor as a D.C. amplifier?


texts: Is this DSP sinewave inverter a marketing hype?

texts:
There are some companies in my country(India) which try to sell inverters for home
marketing in the name of DSP Sinewave Inverter and claim are
superior to normal sinewave inverters.

I am trying to buy one but confused with this term.

What is DSP used in inverter for?
Does it have a edge over normal sinewave inverter or just a marketing hype?


texts: Deciphering datasheet descriptions: "normalized series 54/74 load"

texts:
I was reading something when I came across a project using the SN74180 parity checker IC. I begin looking at the datasheet when I came across this description:

  The SN54180/SN74180 are fully compatible with other TTL or DTL circuits. Input buffers are provided so that each data input represents only one normalized series 54/74 load. A full fan-out to 10 normalized series 54/74 loads is available from each of the outputs at a low logic level. A fan-out to 20 normalized loads is provided at a high logic level to facilitate the connection of unused inputs to used inputs. Typical power dissipation is 170 mW.

What is meant by a "normalized series load" and why would you need an input buffer?

It seems like this description is alluding to the fact that this device supports up to 10 fan-out loads for each output at logic LOW, and 20 at logic HIGH.

How can this number be different for each type of logic level?

It would seem that the fact that it can support 20 fan-out at logic HIGH would be moot since the 10 fan-out at LOW would be a bottle-neck anyway. Surely I am misunderstanding this characteristic.

What is meant by ".. facilitate the connection of unused inputs to used inputs"?


texts:
I need an embedded micro controller to detect some 120V AC signals, I decided it would be safest and most likely the best to use an opto-isolator. Below is my circuit, I rectify the incoming 120V and limit the max current. My question is, even with the blocking diode, could the LED still be exposed to a high enough reverse voltage to ruin it? The LED is only rated for a 5V reverse voltage, but would the blocking diodes D3 and D4 take the line voltage or would it be split in some manner by the LED also, I'm thinking it would be split based on the leakage current of the diodes. I was going to add diodes in reverse of the LED, or a Zener could be used also.

So, are Diodes "D5" and D6" needed? And do people agree this is a good or best method of detecting 120VAC? Note that "R3" and "R4" will be rated for > 300V.

Edit: I did examine this post, but it does not touch on this question.

Update:
After searching more, I found this post and based on what  Spehro Pefhany said below, AC isolators exist with LED's in both directions on the input. That seems to be the correct direction to go, it reduces the parts needed to a single resistor on the input to limit current.


texts: Adjustable LDO output became unregulated

texts:
I designed a simple LDO circuit using LM1084 (circuit A as in the picture) to power a small MCU board (circuit B) and the two circuits are connected with a 40cm wire because of installation constraint.

When the circuit B is not connected, circuit A can output 7V as expected. However, after circuit B is connected, the circuit A output dropped to about 2.4V.

I understand that R45 should be as close to ADJ pin as possible, and the PCB picture below shows the actual layout. Is this considered close enough?

I understand that the wire resistance could deteriorate the output as explained in the LM1084 datasheet, but it seems that would happens only when R45 is close to the load side, which I thought was not the case here.

So would anyone please advise how the voltage drop happened and how I can solve the problem?


texts:
I have following situation in Altium Designer:

Now, AUDIO_INPUT_SELECT[0..3] are connections to Bus, made using Wire command. However, after researching Altium, I've stumbled upon Bus Entry command and the question is, do I have to change these Wire entities to Bus Entry entities or not and if I must, how do I transform Wires to Bus Entries in most elegant way? I know I can delete Wire and place instead of it Bus Entry, but I have several such connections and I want to know the most elegant path of executing such task.


texts: What is the real purpose of analysing an amplifier with resistive or a current source load? How does its behaivor change?

texts: We're analysing in class common source, common gate and common drain amplifiers and the analysis of resistive load and current load is being done but I don't get the purpose of doing this... how does it help us to get the behaviour of the amplifier.


texts: I would like to know if there's a negative implication of using non-inverting op amps with sensors, for example a pressure sensor? Would it be a better option to use an inverter, and if it is, why?


texts: What's the use of tantalum resistors in audio circuits?

texts:
I've been looking at some "pro audio" sites and saw that tantalum resistors are often mentioned with claim that they somehow improve sound quality, but I've been unable to find any reasonable descriptions for discrete component operation that don't trip my audiophoolery alarm.

So is there any real need for them?


texts: Choosing a connector for a 12-wire keyboard scan matrix

texts:
This is my first real electronics project, so please do let me know if I’m doing something stupid here. :)

I’m wiring up an old set of organ pedals to a Teensy LC for use as a MIDI controller, so I’m planning for each of the 32 pedals to have an individual magnetic reed switch, and then to connect all 32 switches to a keyboard scan matrix (12 wires, either 6×6 or 8×4). Ideally I’d like to use something like this construction, where the switches are on a separate board beneath the pedals (edit: and the Teensy will probably be in an enclosure on top of the unit). In order not to have lots of loose wires running all over the place, I’m thinking that I should use a cable to connect the board with switches to the Teensy.

But...what kind of cable? The page I linked to mentioned a Centronics connector, but that seems like overkill if I only need 12 pins. For the moment, I’m leaning toward a DE-15 connector, since it’s the same as used for VGA, so I won’t have to make my own cable. Or maybe a DA-15, for which I could use IDCs and ribbon cable... but ribbon cable is unshielded, right? So would it be appropriate to use it outside of an enclosure?

Or am I going about this engineering process all wrong?

I think I’m looking for something that satisfies the following criteria:

At least 12 pins.
Connectors readily available.
Connectors rated for a reasonable number of mating cycles.
Cables readily available (e.g. VGA) or easy to make cheaply (e.g. ribbon/IDC).
Cables suitable for use outside an enclosure.

Any of these are up for debate. :)


texts: How is a high avalanche ruggedness physically achieved for a MOSFET and what are the trade-offs in other parameters to get a high avalanche rating.  Also, how should one interpret the avalanche energy listed in the datasheet?  Another way to state this may be, for a given design, how do you know how high a rating you will need?  Thanks.


texts: What would be the simpliest buffer amplifier design in this situation?

texts:
Take a look at this schematic:

It is important to assume that we have the following constrains:

1) Load is connected to ground, therefore it requires a positive potential to activate

2) The voltage potential to the load is at 5V regulated supplied lets say by a voltage regulator L7805CV that can supply the appropriate current (i know the load on the schematic is 380 omhs but please don't mind that)

3) Signal comes from an external low current 5V source, and we want logic 0v=off 5v=on

For this logic normally an N-channel mosfet would do the job but since the load would have to be connected to its source the mosfet will not fully saturate therefore the voltage going to the load will be a lot less than 5V.

Using a p-channel mosfet is ideal the way the load is connected but the logic will be inverted. So the simplest thing in my mind is to basically invert the input to its gate. But how do i do that with minimal components/lowest cost/simplicity?

Also is there a better way to do this than what i am thinking?

edit: In addition, is there any way i could employ a specific N-channel mosfet as my main buffer into my design while keeping the same constrains? i.e. Allow the mosfet to fully activate keeping the load connected to its source?

Kind regards!


texts: How does the internal circuit of the 555 works in terms of transistors

texts: I saw many explanations of 555 internal design based on block diagrams. It's good for basic understanding, but I want to understand how those internal transistor circuits make those blocks. I can see (https://en.wikipedia.org/wiki/File:NE555_Internal_Circuit.svg) some current mirrors there, but they looks different from examples in books.


texts: Debugging implementation of low current battery monitor

texts:
I have tried to implement the circuit in this answer in order to measure the voltage of an external battery using an Arduino. However, I am not sure if I have wired it correctly. Here is the diagram:

And here is my implementation:

I have redrawn the circuit to match the layout above:

simulate this circuit – Schematic created using CircuitLab

The voltage divider should in theory drop the voltage of the battery from 4.2v to 3.22V. When I measure the voltage with the multimeter as shown, the voltage measured is 3.64V. When I measure the voltage between the middle of the divider and the Arduino's GND I get -0.37V. In both cases measurements are made when PIN 8 is set to HIGH. With the pin set to LOW, the voltage across the divider drops to 0.

First question: does it make sense to use this kind of circuit to measure the voltage of a battery that is not actually powering the Arduino itself?

Second question: Assuming I eventually power my MCU with the battery, will this circuit work correctly?


texts:
I was just trying to get port IO working with this code:

#include "p24Fxxxx.h" // This header will choose the right device header

#define FCY 16000000UL // Running at 16 MIPS = Fosc/2

#include <PIC24F_plib.h>
#include <libpic30.h>

// Configuration setup
_CONFIG1( FWDTEN_OFF & GWRP_OFF & GCP_OFF & JTAGEN_OFF & ICS_PGx3 )
_CONFIG2( FCKSM_CSDCMD & OSCIOFNC_ON & POSCMOD_HS & FNOSC_FRCPLL & I2C1SEL_PRI & PLL96MHZ_ON & PLLDIV_NODIV & IESO_OFF & IOL1WAY_OFF );
_CONFIG3( SOSCSEL_IO );

int main() {
    TRISB = 0;
    PORTB = 0;

    PORTBbits.RB0 = 1;
    PORTBbits.RB4 = 1;

    while(1) {
        __delay_ms( 200 );
    }
}

So I breakpoint on the __delay_ms instruction, and take a peek at the LATB registers:

(As pictured, only LATB4 is switched on - confirmed with a multimeter)

Also, if I comment out the PORTBbits.RB4 = 1; line, LATB0 is turned on (but not LATB4)

Is the second call overwriting it somehow? Maybe, because PORTB = 0b10001; alone works.

I'm using a PIC24FJ64GB002, MPLAB X, C30 and a PICkit 3. I realise that MPLAB X isn't 100% stable - but something this simple should work.

If some PIC guru could point me in the right direction, that'd be awesome.


texts: RS-232 control for Advance Energy Pinnacle power supply

texts:
I am inspired to post this question and answer by this meta post.  This problem caused me a lot of problems and took a while to figure out.  I have a partial answer.  Perhaps others can elaborate based on their experiences.

I work for a small business and we have several Pinnacle power supplies made by Advanced Energy.  We have recently been making a push to automate a number of our processes.  The hope is to control the power supplies from a computer via RS-232.  Are there any caveats to be aware of?


texts:
I'm working on a hobby Arduino project to create an audio visualizer using an LED strip. I'm using the MSGEQ7 to separate the signal into 7 bands, then send it to a Wemos D1 Mini. I started by constructing the following schematic based on the typical application diagram as found on the last page of the MSGEQ7 datasheet here

Assembled on a breadboard, it works as expected with a few noise spikes here and there that can probably be filtered out on the software side. Where do these voltage spikes come from? Originally, I wanted to forego the DC jack and power the MSGEQ7 from the 5V pin on the Wemos (with the Wemos powered via USB), however, if I remember correctly, powering it via a DC jack/12V wall-wart + 7805 5V regulator resulted in less of these voltage spikes.

I want to protect the A0 input that's rated at 3.3V max, and research online has led me to what I believe is called a Zener clipper pictured below.

Should I protect the analog input or does this seem like over engineering? How do I decide on the value of R1?

Here's the final schematic after working in the clipper.

The frequency of the noise spikes increased a bit after adding this clipper (I arbitrarily used a 56 ohm resistor for R1), it still seems like it could be filtered out software side, but am I somehow able to reduce these spikes by redesigning the circuit?


texts:
I am a little confused, shouldn't I take into account the maximum battery voltage when trying to add-up batteries in order to achieve certain voltage?

For instance if I want to drive a 48V 1000W DC Motor with li-ions, I need 11 li-ions to approximate 48V (46.2) with probably a voltage regulator or a step up module. If I make my calculations with 3.6V I will need 3-4 more batteries and a step-down module.

So what should I watch when making such calculations, maximum or nominal voltage or it doesn't matter?


texts: How does the voltage doubler work at the startup?

texts:
I have no particular interest in power electronics but I am always impressed by such clever circuit solutions as the Greinacher voltage doubler. The idea behind it is so clear and intuitive that it can be explained in a very simple way as I have done in my answer to a similar question.

There are many sources dedicated to this circuit but they (including my answer) consider its operation in steady state (during one cycle of the mains AC voltage). But how does the circuit get to this state after startup? This is the question that concerns me now...


texts: How to use negative voltage feedback to make output voltage constant?

texts:
I have the circuit below, which generates 1.5kV from a transformer. The primary is driven by a MCU oscillator, mosfet driver and a pair of n-channel mosfets. It works very well as it is:

But now I need to make it stabilized: output voltage must be constant with a varying load.

The best approach, in my opinion, would be to take advantage of the LM350 adjustable regulator I use to feed Vcc to the circuit: if I could get a sample of the output voltage, using a simple voltage divider, and use it as a negative feedback to the LM350, I could make it react to any change in load. The primary voltage would change compensating changes in load, making a closed loop that would create constant voltage at the output.

The problem is: I have no idea on how to do it. I know how to adjust LM350 output using a potentiometer, but can't figure a way to use my divider voltage as a negative feedback. An additional detail to note is that the feedback voltage is negative in relation to ground (which may help, since the feedback is negative, or it may make things more complicated). And more than that: is this approach good? Is there a better way to do it?

Another concern is to prevent the regulator from going over a given voltage (18V for example) if the load is excessively high. From this point on, the load voltage would not be stabilized anymore, to protect the circuit.

Thanks!


texts:
I'm building a wireless project using a RFM12B RF transceiver. As I understand it I have to make an antenna myself, and its length has to match the frequency (in this case 165mm).

BUT, can I use anything as an antenna? I have this hook-up wire, can I use it?


texts: What does %FS (Full Scale) represent in load cell?

texts:
Lets say that a load cell has these specifications:

Rated Load = 500 g
Rated output = 1 mV/V
Excitation voltage = 12 V
Creep = 0.02 %FS / min

Then the output range should be 0--12 mV.
Does %FS mean out of the maximum of the output voltage range? That is FS = 12 mV
Then the creep could be converted to 0.0002 * 12 mV/min = 2.4 μV/min?
EDIT: Of course it should be 0.0002 * 12 mV/min and not 0.02 * 12 mV/min. But then I got the original question answered, FS stands for the maximum rated output voltage.


texts:
How can I reduce the delay happening between writes to the DAC (as shown below)?

The yellow represents how long the DAC writes last for which is 232.9us The green represents the output from the DAC, if zoomed in you will see a 16.30kHz sine wave.

After the first DAC write (0 - 1024) there's a 15.4ms delay until the second write occurs which is also shown below.

It takes ~232.9us to write 1024 values into the DAC. How do I close this 15.4ms gap and make it transition to the second write much cleaner? I was thinking using perhaps timers?

The way I have the DMA set up is as follows:

When the ADC detects an incoming signal DMA starts sampling
The DMA will first sample 1024 values this takes 15.7ms
Once done it will request a half complete interrupt where then I start my first DAC writes
the DMA will sample the other 1024 values as this takes 15.7ms as well
Once done will request a complete interrupt then I start my second DAC writes

Code:

void DMA2_Channel3_IRQHandler(void){

    if (((DMA2->ISR) & (1<<10)) != 0){ // Check to see if the Half Complete Flag is set
        halfTransferComplete = 1;
        DMA2->IFCR |= (1<<10);
    } else if (((DMA2->ISR) & (1<<9)) != 0){ // Check to see if the Complete Flag is set
        transferComplete = 1;
        DMA2->IFCR |= (1<<9);
    }
}

int main(void) {

    while (1) {

        if (halfTransferComplete == 1){ //Stays in this block of code for 15.7mS
            GPIOA->BSRR = 1<<0;
            for (int i = 0; i < 1024; i++){
                DAC1->DHR12R1 = adcValue[i];
            }

            GPIOA->BSRR = 1<<16;
            halfTransferComplete = 0;
        }

        if (transferComplete == 1){ //Stays in this block of code for 15.7mS
            GPIOA->BSRR = 1<<0;
            for (int i = 1024; i < 2048; i++){
                DAC1->DHR12R1 = adcValue[i];
            }

            GPIOA->BSRR = 1<<16;
            transferComplete = 0;
        }
      }
}


texts: Problem in circuit that charges tablet/cell phone via Micro-USB port

texts:
I am trying to design a circuit that can charge tablet/cell phone via micro-usb port. Attached is the circuit I put together. The basic idea is, take 6 ~ 12V DC from an AC-adapter, then step the voltage down to 5V with a buck converter (AP5002, datasheet)and feed it to VBUS on USB port. Somehow this design doesn't work. It doesn't charge either tablets/cell phones. In one case, an old nook color, it was able to charge to battery to ~65% then stopped. In other cases, the tablets just don't recognize the charging circuit.

What  could be the problem? My thoughts are:

1) When this circuit is attached to the micro-usb port of a tablet, there is usually a 5.1V voltage on VBUS, which is higher than 5V, the output of the step-down IC AP5002. So I put a diode in the place of L2, this doesn't do the trick.

2) USB charger is more than simply applying a 5V voltage on VBUS. There should be some controller IC.

What else I am missing here? Please advise, and thanks in advance.


texts:
I would appreciate any advice how to improve PCB design to achieve the highest sensitivity for the GPS signal. The design is based on S76G chip. The tracker will be sewn or encapsulated in plastic into cat collar together with two dipole wire antennas (GPS 9.04 cm, LORA 8.20 cm, lambda/2 & lambda/4 - 5%) and fine tuned by NanoVNA.
I am not sure if I should include GND pads for both antennas to signal via shielding (GPS & LORA) and make separate grounds for digital, GPS and LORA signals, connected in one place only. The PCB is 27 x 12 mm four layers: VF signal/GND, VF GND, Power lines, Digital signals/GND. The CPWG is designed to 50 Ohms (189/90/100/4.05 w/space/height [um]/er).
X1 is MEMS LSE 32.768kHz oscillator, X2 TCVCXO 26MHz and U2 is LDO 1.8V


texts: Use a DC Signal to govern another circuit using AC

texts:
this is my first post and I am working on a small project where I have two circuits A and B. A is controlled a micro-controller which sends and output of 0V and 5V depending on the conditions. This signal is sent to circuit B.

Suppose B works has a filament lamp connected to it. It turns on when A sends 5V and remains inactive when it sends 0V.

So how do I bridge these two circuits? I have an idea of bridging with a transistor or something. If it's possible do provide the simple circuit diagram.

Thank you.


texts: Plotting bode plot, how the starting gain is in negative?

texts:
For function;

\$H(jw)=10jw/((1+jw/2)*(1+jw/10)\$

To find starting gain, i did, \$20log(10)\$ which equals 20, but in matlab, it shows -40 ? how ?
Bode plot for the function is given below,


texts: is a higher voltage battery a more efficient energy deliverer than a lower voltage battery?

texts: a DC electric motor moving a car. will it experience the same torque with current provided from a 4V battery with a capacity of 1000 Ah as with current provided from a 400V battery with a capacity of 100 Ah? according to math, P=V x A it should be the same, but would 4V be enough to move that car, even though it is supposedly moving so much more current (same C rates)? i have read about "energy efficiency" where higher voltage batteries are more efficient deliverers of energy as opposed to higher capacity ones, but don't understand why.


texts: What are the little brown things on the back of a Pentium 4?

texts:
The other day, I removed a Pentium 4 from an old PC that I was dismantling. I was intrigued by the little brown components on its backside (sorry about the picture quality):

A closeup:

Here, there is a grid of gold contacts (in groups of 8). Some of the groups of 8 contacts have a tiny brown IC soldered1. Most don't. To me, it looks like those empty pads are for soldering on more brown things. (A lot of other boards have such spots where you can add "expansion packs"--for example, an avr development board I've worked with has spots for extra EEPROM, some LEDs, and a motor driver chip).

But I couldn't think of any use of an "expansion pack" on a microprocessor. The most I could think of was "something or the other to make branch prediction more efficient", but that's probably not it.

I found a pic of another Pentium (this one's LGA though), with brown thingies in all spots:

So, my question is, what is the function of these brown ICs, and what do I get by adding more to my Pentium, if it is possible to do so?

1. I know that "soldered" probably isn't the right word here -- but basically there is an IC attached to the group, with one IC pin per pad


texts:
Converting an ATX PSU to a bench supply i found out how to start it by shorting the green wire to ground with a Push-button, and that I have to place a minimum load (preferably on the rail with highest amp rating) to keep it running.

What I want is another Push-button to shut it down again.
(I don´t want to use a on/off switch between green and ground, I also dont want to use the on/off switch on the back of the PSU)

How does a mainboard turn off the PSU? does it simply disconnect all loads? if so, how can I achieve this for all rails (3.3, 5, -5, 12, -12) with a single Push-button?


texts: Lightning/surge protection for a Arduino monitored thermistor circuit

texts:
I am considering whether to replace the commercial differential temperature controller on my solar water heater with a Arduino based controller of my own design.  I know just enough to be dangerous about such things.

First question: will the classic 5V/10Kohm thermistor voltage splitter circuit blow something during a lightning storm?  The thermistor is located 60 ft away on the roof mounted solar panel.  The cable is shielded and grounded.  What's needed - surge protector on the thermistor circuit, some RC connection to the thermistor leads, reduce the base resistor for more current flow to the thermistor ....

Second question: does the Arduino Atmega microprocessor auto-reboot and resume software execution after a loss of power?  Put another way, does the reset button have to be pressed after a loss of power?


texts: Capacitor leakage and design for low energy battery powered devices

texts:
For the design of a portable battery operated device, I have some power circuitry which requires a DC-DC converter and some other regulators, battery charger IC etc.

While in the process of selecting capacitors for the power system design, I noticed some leakage currents which were quite high, such as 220 micro Amps. If my battery is exposed to this kind of leakage current constantly, I'm sure there will be storage/long term usage issues.

What capacitor chemistry/types do you guys use for battery operated devices, but still for use in power filtering/supply roles? The battery charger IC has reverse blocking diodes/FETs built it, so I can assume that on the input side (external power input) it's okay for leaky capacitors. What do I do about the battery-side of the system? Rely on ceramic capacitors?

The sort of parameters I was looking for were 16-20V rated (for the input side) and 6.3V rated for the DC-DC converter output, and ripple current ratings up to 1A


texts: How to generate a high energy electromagnetic wave? Using high voltage or high current?

texts: I am about generating an electromagnetic wave which should be powerful enough. So I should manipulate its electric field and magnetic field simultaneously. As far as I know E amplitude depends on the voltage in the circuit and B amplitude depends on current intensity. I do not have any idea to generate EM wave. Which method is infeasible and efficient? (high voltage or high current)


texts: What is this strange artifcact on my inductive element?

texts:
I was looking at the Voltage/Current on an old inductive element, without any other components in the loop, and I got this weird artifact. Sadly, the xml file I saved was corrupted, so i had to reconstruct it by hand, but it looked pretty much like the sketch I drew.

All I know about the inductive element is that it's salvaged from some kind of old lamp and there was a little capacitor-symbol printed on it's one end, and a switch-like symbol on the other.

Has anyone seen something like this before, or any good guesses what could cause this?

The source is a 12Vpp AC Source plugged straight into the inductor in series with a 1kOhm resistor. The yellow line is current (measured as voltage over the resistor), the blue line is voltage. This is a reconstruction of a two-channel oscilloscope picture, please excuse the lack of labels.


texts: Why is a DC to AC inverter called "inverter"?

texts:
A device to convert direct current to grid level alternating current seems to be called "inverter".

It's typically called like that when used in a solar power system.

Why is it called inverter? Does it invert anything?

Is a small DC to AC converter in the range of 1 W also called inverter? And if not: why?


texts:
I am about to make a pcb footprint for this package:
http://www.ti.com/lit/ml/mpds049b/mpds049b.pdf

But I am not sure what the two numbers mean, for example at pin 5 that 0,30/0,15.
Are these maximum/minimum values in milimeters? Is that possible they have this huge difference between them?


texts: Driving a LED Matrix with a N-channel MOSFET (2N3819) using an AVR

texts:
I am trying to wire up a LED matrix using a FET transistor as a switch.

The AVR will be connected to the gate. To turn the LEDs on I have drive the pin connected to the transistor gate low, right?


texts:
1 led strip = 3a, 36w, 12v, 16.5ft ..............6 strips= 18a, 216w, 12v, 99ft

Will this transformer/ power supply (20A, 240w) be capable of handling the 6 strips with the specs mentioned above? Each strip has on its end an external female power adapter that can be plugged with any 3a male power adapter.

1- Which gauge of wire would be sufficient to use for power supply to the female adapter, I have 100ft of 12AWG and will option 1 of having the transformer in middle and run 50ft to left and right be best or with a 30A, if that.

2- Will running two 20a transformers linked to that ONE power feed cause issues?

// Each strip are connected to one another and power on but dim thus the need for external power.  I think of it more like a water hose being pushed by two outlets from each end to maintain pressure :-D


texts: Heat problems for STM32F103C8T6 in enclosure

texts:
For my hobby project, I'm intending to add a STM32F103C8T6 (and later STM32F407VET6 or ZET6) into an enclosure.

For worst case case, let's take the 407, the datasheet can be found here.

On page 80, there are stated some power dissipations (between 435 and 543 mW).
Also some temperatures are shown on the page.

What I want to use in them (maybe spread over two devices, but let's assume I put everything in one STM32):

Reset button
Maximum 10 small LEDS (3mm, some bicolor). if these will cause too much power/heat I want to use smaller ones or less. Also the LEDs will be very sparsely on probably (at least most of them). They are for notification only. I would assume a total power consumption of 100 mA (assuming some are one more than others, so assuming 20 mA per LED, on average 5 are on).
A few dozen ferrite beads
4 or 5 6N137 or similar optocouplers
CAN bus driver (MCP2551 breakout board)
One or two (2.4 GHz transceivers)

Used peripherals:

6-8 UARTs
CAN
Some timers
One or two SPI ports (for the nRF24L01s)
CAN

Environment/Boundaries

No low power mode
Maximum CPU frequency (168 MHz for STM32F407)
Enclosure !

Would I get in trouble putting these STM32 in an enclosure ... I assume I need to add some holes possibly? What other measurements should I take to prevent them frying in their enclosure?

(note: I know I can probably calculate the exact power consumption, but I want to have a general idea about what I can expect, since I never have built a real project, and the only time I put an Arduino in an enclosure it got fried, but it was connected with a 12V adapter).


texts: Where did my thought go wrong (electrical circuit )

texts:
The circuit on the right has two identical diodes, D1
and D2. These diodes have a scale factor n = 2 and a
value of saturation current IS = 9nA. The currents in
the diodes are as shown.

Use the ideal diode equation to calculate the diode
voltages V1 and V2 and hence V3.
Using the above results, calculate the diode voltage drop with a current of I = 0.1mA without
solving the ideal diode equation again. Explain what relationship you used

This was my steps to try to solve the question but my tutor thinks my answer was extremely wrong.


texts: Current specifications for parallel circuit from two cross connected power supplies

texts:
I have two 24 volt DC power supplies (that each look like this - according to documentation).

                 _______
PS + AC in ---->|       |-----   + 24 volt out
                |       |
PS - AC in ---->|       |
                |_______|-----   - 24 volt out

I have been instructed to cross connect to form a common return (apologies if bad nomenclature/vocabulary is being used)

                   _______
PS 1 + AC in ---->|       |-----   + 24 volt out
                  |       |
PS 1 - AC in ---->|       |
                  |_______|-----   - 24 volt out  (return)
                              /
                             / (PS1 - out is cross connected to PS2 + out)
                   _______  /
PS 2 + AC in ---->|       |-----   + 24 volt out (return)
                  |       |
PS 2 - AC in ---->|       |
                  |_______|-----   - volt out

The device driver card I am plugging into requires me to pin together each of these 4 outputs and the specifications says provide 11 Amps for routine use, with a possible maximum of 22 Amps.

An existing setup in the lab is using 4.5 - 6.2 Amp power supplies configured in a similar configuration and it works perfectly.

I am assuming that the 4.8 Amp currents of these power supplies additive (i.e. nearly 10A provided)? But I don't have a good idea of the consequence of saturating the signal request by under powering the driver card.  In general, since I can't provide information about the card itself, what kind of risks are there in this kind of signal saturation, and power plateauing?


texts: Consistent failure of THAT 1646 line driver IC. What could be the cause?

texts:
I work with audio electronics in the touring concert realm and I've been seeing a gross failure of a certain balanced line driver IC, the THAT 1646. Main symptom is no output and most common failure mode is the OUTPUT pins latching to the supply rails (-15V or +15V). I've seen both outputs at +, both at -, or one at each. Usually all other pins look ok but at times I have seen full rail voltage on the SENSE pins or a <10V on the INPUT pin. Most of the time the chip looks ok and shows no sign of heat but I have had a few that were giving off lots of heat.

It's not my business to know what's causing these failures but I am left wondering; whether it be inherent to the chip itself or the circuit surrounding it. Often the equipment is simply the THAT 1646 feeding a passive filter and suppression diode into XLR jack. Are these chips prone to fail on their own? Do they need extra "outside" suppresion and protection from the abuse of plugging an XLR plug in? In addition to the clamping diodes already present.


texts: Dividing output voltage from a buck boost converter

texts:
I am a student in high school and have been working with buck boost converters. I currently have a buck boost converter that steps up 5V to about 58V. I created 3 voltage dividers that should step the output voltage from the buck boost converter to 30V, 35V, and 40V. I then wired the voltage dividers to a 3 way DIP switch. This should allow you to choose which voltage to use (30V, 35V, or 40V via the switch.) However, the voltages I am getting as an output are nowhere near the predicted voltage (given \$V_{out}=V_{in}(R_2/R_1+R_2)\$.)

For example, I am getting an output of 12V with two 1k resistors. I then tried using a voltage dropping resistor to get the 3 voltages. This worked initially, with 10k ohms getting 30V, 15k ohms getting 35V and 23k ohms getting 40V. However, when I turned the converter off and back on, all of these voltages were different (i.e the 10k resistor was giving a \$V_{out}\$ of 40V instead of 30V.) Also, the converter does not give the same \$V_{out}\$ each time it is turned on. The output usually ranges from 52V to 62V but is mostly a steady .939A. The power supply is a 5v usb plugged into an iPhone charger port.

Here is the schematic to the buck boost converter.

Here is the link to the datasheet for the LM2588.

If anyone can offer an explanation to why \$V_{out}\$ is so inconsistent, or offer an alternative method for creating 30V, 35V, and 40V that would be fantastic. I am happy to provide any other information if necessary.


texts: trouble with arduino standalone circuit and xbee

texts:
I have an application that sends data from 1 XBee connected to a computer to another Xbee connected to a microprocessor(ATMEGA328P-PU). I programmed the program into the microprocessor using a arduino board and everything work as programmed on the board itself. However, when brought over to connect everything on the breadboard, it is not working as programmed. I tried loading the microprocessor with a simple blink led program and it works on the breadboard. What is wrong?

What I've connected to the microprocessor on the breadboard: pull up resistor between pin 1 and vcc DataOut and DataIn to rx and tx of microprocessor VCC to pin 7,20 and 21. Gnd to 8 and 22 20Mhz crystal with 2 22pF capacitors to pin 9 and 10.

Thanks in advance for your help!


texts: Difference between capacity and output current rating

texts:
I'm linking to this example, but all battery packs i see on Ebay and Aliexpress are like this.
https://www.ebay.com/itm/4800-20000mAh-Rechargeable-Portable-Power-Li-ion-Battery-DC-12V-For-Camera-PVD/174315363467?hash=item2896015c8b:g:0SsAAOSw4tVd6gIE
Capacity is rated 20Ah yet output current is 1-2A. No where do they mention time rate. Are we to assume they mean 20Ah / 10h, that is, 2A for 10h?
Shouldn't such battery pack be able to provide more than 1-2A?? I mean, even tiny AAA can provide 0.5-1A for an hour, and this massive battery pack can do no more?
They even put discharge protection so it can definitely output only few amps, this one for example, has discharge protection set at 4.5A, yet capacity is 12.4Ah.
https://www.ebay.com/itm/3-7V-12400mAh-Rechargeable-Battery-Pack-Fishing-Lights-Dedicated-Standby-Power/323837413020?hash=item4b6636c69c:g:bS0AAOSw6fVdCJnh
What's the catch.
And what about individual batteries like this, are these really 2.2Ah or is that too false. Aren't battery packs made of batteries like this. They are. So if each can output 1 or 2 A in parallel they should give much more.
https://www.ebay.com/itm/20X-Batteria-ricaricabile-al-litio-li-ion-3-6V-3-7V-2200mAh-a-saldare-tabs/324218214429?hash=item4b7ce9581d:g:YMwAAOSwQpJe~uWl


texts: mc34063 boost converter - low performance and noise on avr interrupt

texts:
I have some problem with my nixie project.

1 - my mc34063 boost converter have poor performance. While i use active pull down D3 and Q2 for driving my mosfet then its enough for only one nixie tube (z566m - ~2-3mA). But when i remove D3,Q2 and use 330ohm for R12 then efficient increase but for only 4 nixies. It should have at least 20mA (with D3,Q2) but now its less than 15mA efficient.

2 - when i set voltage above 180V then my avr very often hangs (it probably hang because noise on I2C line, it also hang more often when i connect my 4x20 I2C lcd using 20cm wires), and it also count very high interrupts form RTC - im not sure is it weak pullup or noise on supply line. Currently i do not have osciloskope so its very hard to guess.
Also when voltage is above 180V then very often I'm unable to send new hex to my avr (failed connection, mishmash or something else). I already burn 2 avr during programming form unknown reason (i cant rescue them even with avrdoctor - HVPP)

3 - any objections to HV layout? i never project this kind projects so here may be some mistakes in routing.

Thans for any help


texts:
I understand that using a ferrite bead attenuates high frequency currents and can help reduce EMI. However, I'm confused about how to select the frequency range that should be attenuated. For example, is this a function of the frequency range of currents that the load IC will draw from the supply? If so, how does one go about determining this frequency band?
Or is the bead more about suppressing currents that are picked up from interference from other devices? Again, if this is the case, how does one determine what frequency band requires attenuation?


texts:
I saw this material for making capacitors (http://www.capacitorfilm.com/web/enproduct.aspx?ch=64).

It said capacitor with the material is very safe, does anyone know what is the principle under which this safety is achieved?

It is metallic film.


texts: Can it be said "transistor open/closed" and what does it mean?

texts:
I some other language literature I used to read it is common to find a text that translates directly into English as "transistor open" or "diode open". This means that transistor is conducting notable current between collector and emitter, for diode this means that forward voltage is applied and notable current is flowing through it. The same way, "transistor closed" means that there is no notable current between emitter and collector, for diode this means that reverse voltage is being applied (no notable current).
I have recently received some criticism on this terminology, saying that "closed" should mean conducting, and "open" should mean no current. Indeed, this is true for the switch or relay contact: the literature I used to read also uses the opposite terminology for these devices.
However also in English it is possible to say "the door is closed", "the gate is closed", "the bridge is closed" or "the road is closed". This means you cannot pass through, not the opposite.
Is it appropriate to say in English "the transistor is closed" in the case like in the diagram below? If this is not the right wording to use, that wording should be used instead?

simulate this circuit – Schematic created using CircuitLab


texts: Oscilloscope not visible in PROTEUS simulation

texts: I tried simulating astable multivibrator using OPAMP. At one instant i got the oscilloscope but wasn't able view the waveform. I tried running again but this time there was no oscilloscope visible. Can anyone tell me the problem. If not, can you suggest me a better simulator to simulate analog circuits . Most of them include OPAMP and some logic gates, comparators. I want to view the analog output waveforms in most of the cases.


texts: Why can I have the positive and negative at the base of a transistor at the same time?

texts:
I am reading/doing the make electronics book and I am having a hard time in understanding how is it possible to have the positive and negative poles connected (even with a resistor) to the base of a transistor.

1) Wouldn't it be a short circuit?

2) Why not just the positive?

Below is the example circuit from the book:

Edit: Adding a schematic with a more conventional layout that aids understanding. Current flow generally top-to-bottom, and signals (such as they are in this circuit) generally left-to-right.


texts: DC to DC converter: How do I convert 110 Vdc to 5 Vdc with 2.5 Amps current?

texts: I am new in circuit designing and want to design a circuit for a DC to DC converter.  Input voltage is \$V_i\$=110 VDC ,wheras output dc volatage is \$V_o\$=5 V with \$I_o\$=2.5 Amps current . So can anybody tell me how can I do it?


texts: 10-bit ADC resolution doubt - 1023 or 1024? ESP8266

texts:
I am working with ESP8266 which has a single ADC channel with 10bits and 1V reference.
What is the correct resolution in mV/ADC result? 1000mV/1023 or 1000mV/1024?
Also, I wonder if the reference of the ADC of ESP8266 is really 1V or 1.024V.


texts: Any idea on any device which track multiple mobile phones

texts:
I'm currently ask to work on a project which I have never worked before.

And I have no freaking idea or its not even in my area of expertice.
Ususally I Google as everyone does. But what is the use if you don't know what you ar looking for?

Now the task is to track everyone in a mall.
I came up with two ideas:
Heat maps and Tracking Mobile as every one has one.

But due to some reason, heat maps didn't lead me anywhere.
Hence, now I have to shift on the Mobile tracking technology which gave me some idea after looking at some video and after reading stuff.

For mobile I can use "Cell Phone Detector"

  DIY Cell Phone Detector

Now the QUESTION IS
How will it defferincate between different mobile phone egWhich technology is this?

Please help me out. You can forward me to links or anywhere or even EBOOKS. or just give me what it is called. I will google it and study it


texts: How can I make an amplifier such that its gain increase proportional to the input difference

texts:
I want to make an amplifier that has a gain which increase with the difference between the inputs. For example:

If I have 2 volt difference between two input of the amplifier will have gain factor as 2.
If I have 5 volt difference between two input of the amplifier the gain factor will increase to 5.
Is there such amplifier? What is its name? What is the key word to find such circuit?


texts:
I am designing a circuit that receives a signal from a motion sensor, and then turns on a light for 15 seconds. I have a rough idea on how to make the circuit, but I am also curious what are the different options to implement the circuit.

I think this circuit would do what I am thinking of. Can I or should I use a thyristor instead of a relay?
And is there a way to keep the light on for 15 seconds without a microcontroller?
I have never used a microcontroller before, so is there any recommendations to what controller to use and what relay/triac to use? (Vdd=7.8V)


texts: Transformer powering an alarm system heating up

texts:
I have an alarm board from Paradox, model SP6000. I power it with 16Vac/2.2A from a 40VA transformer which is connected to the electrical circuit from my house(230V 50Hz). The board has an AUX power line where I can connect multiple consumers(eg. keyboards, motion sensors, exterior siren). In the manual it says that the typical current consumption on the AUX line is 600mA, maximum 700mA and fuseless shutdown at 1.1A.

I connected 2 keyboards(power consumption at max of 250mA based on the manual), 10 motion sensors(8mA idle - 10mA max power consumption for each sensor), external siren(35mA idle + whatever power is needed to charge a 12v/7A battery attached to it) and a communication module which has a max power consumption of 100mA. Based on my calculations the max power consumption on the AUX terminals is 735mA. The alarm board has a separate circuit where used to charging a second battery with 350mA. According to the manual the max power consumtion for the entire board is 1.7A.

The transformer was heating up a lot after 1h of running so I turn it off.

Any advice on what to do? Could it be cause I had too many consumers?

Thank you.


texts:
If we had a group of n resistors connected in a parallel combination, and one of the resistors burns out, what is the effective resistance? I had a question based on this in my exam recently and I want to make sure I was right. I assumed a resistor burning out would result in an open circuit.

I assumed that a resistor results in an open circuit when it burns out.


texts:
I've made this simple AM transmitter:

http://makerf.com/posts/fun_with_crystal_oscillators_part_3

The author of this circuit, claims that would be possible to extend the range of this transmitter by attaching a longer antenna and  a better plane ground: i'm using a 10 feet of wire as antenna and a plane ground, but this transmitter is still barely able to transmit to a max distance of few inches. Why? Maybe there would be a way to amplify a little bit more the output signal, maybe using a small transistor?

Thank you.


texts:
I'm trying to refresh my knowledge on RLC filters, and I'm using MATLAB to model it. Given an RLC circuit with the elements in series, taking the output at the capacitor should result in a 2nd-order low pass filter. You can see the circuit I'm trying to replicate here.

simulate this circuit – Schematic created using CircuitLab

However, the results don't seem to match up with what is expected. I'm using this Filter Design Tool as a check to see if my work matches up with the same values, but the results that I got, when plotted, doesn't make sense. Rather than getting the low pass filter, I seem to have gotten a Notch Filter, which doesn't make sense. I'm sure I got my transfer function right, but what in my code is causing this outcome? Could it be my component values are impractical that's causing this?

EDIT: To better show what I'm talking about, I cleaned up my code a bit, and below is an image of what I'm getting for the bode plot with the exact code. As you can see, it is definitely not a low pass filter as what I expected:

clc; clear all; close all; clc;
omega=-1.*(10.^6):100:1.*(10.^6);    log_omega = log10(omega);
%Limits
nzero=zeros(size(omega));

L = 0.005;     R = 1200;      C =  (10.^-3) ;

%Terms    %Solutions
alpha = (R./(2.*L));        omega_z = 1./sqrt(L.*C);
s1 = (-1.*alpha.*alpha) + sqrt((alpha.^2)-(omega_z.^2));
s2 = (-1.*alpha.*alpha) - sqrt((alpha.^2)-(omega_z.^2));
f1 = s1./(2.*pi);    f2 = s2./(2.*pi);

%Denominator Impedances
ZR = R;
ZL = j.*omega.*L;
ZC = 1./(j.*omega.*C);
denom = ZR + ZL + ZC;

%Function
HC = (ZC)./ denom;
magHC=abs(HC);
logHC=log10(magHC);

subplot(2,1,1);
plot(omega,magHC);title('Log Freq. vs. Magnitude RLC-C, magHC');
xlabel('Freq.'); ylabel('Mag.');      hold on;

subplot(2,1,2);
plot(omega,logHC,'r');
title('Log Freq. vs. Log RLC-C, logHC'); xlabel('Freq.'); ylabel('Log.');
hold on;


texts:
I'm developing my bootloader based on AN1388. My bootloader is working pretty well.

I'm having problem with my app code. When I try to generate the hex code, seems there isn't "C startup code". My .map file says kseg0_boot_mem used is 0.

So I've tried to compile the demo app that came together with AN1388 "as is". It happens the same. But the pre-compiled hex in this example is correct. It has the kseg0_boot_mem in the hex.

So, anyone knows what I'm doing wrong?

Edit:

I'm using C32 v2.00 and the AN1388 was compiled with C32 v1.11.


texts:
I've always thought that the absolute maximum ratings on a part are the limits that thou shalt not violate.  Period.  End of story.

However, another engineer is making the case that it's okay to exceed the absolute max rating for the input voltage on a microcontroller I/O pin.  Specifically, he wants to apply 5v, current limited to 30uA, to a micro with an absolute max voltage of 3.8v (Vdd + 0.3V <= 3.9V).  The argument being the clamp diodes will take care of the excess voltage.

I couldn't find anything in the datasheet about the I/O hardware on the micro.

When is it okay to exceed the absolute maximum rating on a part?

Datasheet

User Guide


texts:
What kind of 4-pin power connector is this, displayed in this (exemplary) image? Are there any specs of the maximum current and voltage it is designed to provide?
(Unfortunately this was the best image I could find.)


texts: I just got started with PIC32MZ curiosity development board with MRF24WN0MA Wi-Fi Module and MPLAB Harmony v3. I am unable to find drivers for wi-fi module (including ATWIN1500c) in harmony v3. Attached is an image of driver layer options which only includes Ethernet support. Harmony v2 used to support wi-fi. How do I use Wi-fi in Harmony v3 ?


texts: What is the part name / description for these test points?

texts:
What is the name/description for the test point pins on this board?
I've tried Digikey for all combination of binding post, test pins et, but no luck.

These are through hole parts, height ~6mm, pin dia 1mm.


texts: TMS320 Floating Point (Texas Instruments DSP from '98)

texts:
Background

Is there anybody here who is an EE with programming experience who has worked with the Texas Instruments TMS320 C3X-series DSP? I am currently doing some work with the C3X for a project. My goal here is to convert C3X-formatted floating point hexadecimal values into IEEE 754 format. The code that I have works properly for:

Where x is the input single floating-point C3X hex number (represented as a UInt32).

The issue, is when I attempt to use a number such as 0.123. It seems that I always get a NaN value as a result. I am currently using this code snippet from the University of Florida that I have ported over to C#.

Procedure

Swap the sign and exponent fields to go from C3X to IEEE. I will not show this code (unless asked) as I believe it is very straightforward for anyone who has worked with this DSP.
Perform the University of Florida algorithm (linked above), that I believe I do not fully understand.
Combine the sign, exponent, and mantissa into single-precision IEEE 754 floating point.

C# Implementation

Here is the code used to implement the algorithm for when the C3X float-number happens to be between 0 and 1 (where the issue is happening). The c30 object, represents the C3X floating point number. The ieee object represents the IEEE 754 floating point number.

EDIT: Upon popular request, here is a code sample that isn't awful. This sample is the properly working version where we dump in 15,913.35... (as C3X hexadecimal).

C30Float c30 = null;
UInt32 bias = 127;
Int32 mantissa = 0;
Int32 digit = 0;
double fraction = 0;
double exponent = 0;
double fpValue = 0;
double sign = 0;

// 1. Declare the new C3X floating point value.
c30 = new C30Float(0x0D78A56B);

// 2. Get the sign bit value.
sign = c30.GetSign();

// 3. Decide whether or not to do the flip.
if (sign == 1)
{
    // flip
    mantissa = c30.GetMantissa();
    mantissa = mantissa + 1;
    mantissa = (~mantissa) & 0x007FFFFF; // the first 9 bits have nothing to do with the mantissa
}
else
{
    mantissa = c30.GetMantissa();
}

// 4. Obtain part of the fraction (do the swim!).
for (int i = -1; i > -24; i--)
{
    // mantissa index
    int currentDigit = i + 23; // n = -23 + 23 => n = 0

    // shift forward (get the digit)
    digit = mantissa;
    digit = digit & (1 << currentDigit);

    // shift back (get the digit into the lowest place)
    digit = digit >> currentDigit;

    // apply the digit to the fraction
    fraction += digit * Math.Pow(2, i);
}

// 5. Obtain the exponential part of the number.
exponent = c30.GetExponent() + 0x7F;

// 6. Get the floating point number.
fpValue = Math.Pow(-1, sign);
fpValue *= (1 + fraction) * Math.Pow(2, exponent - bias);

I know that I have not provided the implementation details for the following:

GetMantissa()
GetExponent()
GetSign()

or...

SetMantissa()
SetExponent()
SetSign()

The reason for this is that all these are doing is entering/pulling the numbers to/from their respective fields as specified in the TMS320 C3X User's Guide. Who knows, maybe that is where I'm going wrong, but for now I'd like to start at where I think the scope of the problem begins. If any of you believe that the issue is not here then feel free to ask about this implementation and I will provide more detail as warranted.

Question

My issue is apparently with numbers between 0 and 1. So if anyone has known C3X hex values and their known counter-part floats/reals that I can plug-and-chug that would be great so I can troubleshoot this algorithm.

Note: We don't have the DSP in front of us for what we're doing and can't just get the numbers out.


texts: Problem interfacing with an lcd with an arduino

texts: My lcd arrived today and i saw that when i connect the backlight pins (A and K) to GND and +5V, the backlight turns on, but i cannot control it with the potentiometer. The wiring seems fine (ive checked and rechecked). Also, the 'hello world' sketch from the arduino website does not seem to be working at all. Any suggestions?


texts:
I'm trying to answer the question that has been given here.
I think I understand which transistors are on and which are not under the two different logic states i and ii.
However, what I really struggle with is understanding the voltages at the nodes.

For instance, for condition (i) :

T1:ON(forward), T2:ON, T3:ON, T4:ON(cut-in), T5:OFF, T6:OFF

I'm not completely certain about these states of the transistors, particularly T4. I think it might be in cut-in because it appears to be in a similar question I have looked at, but I'm not sure why -

And so the diagram can be re-drawn without the transistors that are off.

like:

From looking at a similar example in a book I can see that

N1 = V BE Sat (of T1), N2 = V CE Sat (of T5) and N3 = 0V

But I'm not exactly sure why this is and how I would go about calculating the voltage at the remaining nodes.

Any insights or help would be greatly appreciated. Many thanks in advance


texts:
I know what you are thinking, but hear me out. Let's do KVL in this loop:

simulate this circuit – Schematic created using CircuitLab

We get:

$$
-V_{PD}+I(R_s+R_L)-V_1 = 0
$$

Now we solve for the current:

$$
I = \frac{V_1+V_{PD}}{R_s+R_L}
$$

If we remember that in Photodiodes \$I=P\phi(\lambda)\$ where \$P\$ is the intensity of light and \$\phi(\lambda)\$ is the photosensitivity of the photodiode at that wavelength then we get:

$$
P = \frac{V_1+V_{PD}}{(R_s+R_L)\phi(\lambda)}
$$

Which is exactly the formula for the Saturation Intensity of a photodiode! (Source look at equation 3).

So what's the problem?, that it is exactly the Saturation Intensity, and nothing else, but photodiodes are not always saturated.

What happens if the photodiode is not in saturation?, I can't for the life of me figure it out, the circuit must be different but I don't know how and I can't find a mention to this anywhere, please help


texts: Need Circuit advise to drive high current loads

texts:
I need some advice on the circuit I plan on building.

This circuit is to run any high current (Max. 100amps) device in my car. I want to use a high side MOSFET to supply power to any field device. An Arduino will be used to provide a PWM signal (PWM_Out1). The Arduino will also be used to read the current through the shunt R23. INA169 is used to amplify the shunt signal and provide it to the Arduino via AI1. DI1 is also run back to the Arduino and it provides the status of the fuse F1.
D4 is just used as an indicator if the fet is on.
D10 id my flyback diode.
TP1 Jumper is used just to trigger the fet in the field for testing purposes.
I used two NPN transistors to have the same logic from the fet that the Arduino provides.
D7 is used to limit Vgs voltage to 12v
The 24v supply is being provided by a buck/boost circuit (still working on that).

I am definitely not an engineer but I have done a lot of reading over the last few days.

Any comments are welcome.

OK, I changed the circuit to fix some of the issues. Now it seems like there is an issue when the fuses blow, current id drawn through the Vgs zener. In the case below, if the fet is being told to conduct and the fuse blows, my blown fuse indicator still remains high. Any idea how to resolve this?
My blown fuse indicator would get connected between the 1k resistor and the 5.1v zener diode.

Here is the revised circuit now. Just trying to figure out the feedback through the fet when its told to conduct and the fuse is blown. My blown fuse indicator @D1 still remains high in this condition.


texts: How to switch positive/negative voltage to positive voltage

texts:
I have DIY telephone line powered flashlight (similar to this post, but I have used LED strip). The positive & negative leads seems to get updated frequently. Since I soldered the leads to LED strip, it doesn't work if the +ve /-ve leads are swapped.

Is there a way to swap the +ve and -ve if they are in wrong order with simple circuit/component?


texts:
So today I opened up my Senseo because I wanted to attach an arduino with a Bluetooth module to the 3 buttons (for some coffee when my alarm goes off). I wanted to measure the voltage but after the most idiotic move I made I shorted out the circuit. Now except from the black stuff in the left bottom corner I can't really determine any damaged components (nothing blown, nothing molten, diodes still work).

Now my question is, is it wise to keep on using this PCB or how do I test if the PCB still works?

Thanks in advance!

[UPDATE]

I cleaned the PCB and it looks good to me. The leftover burnt places are contactpoints of 2 resistors which are still working.


texts: Reducing ripple from switching regulator

texts:
I'm assembling a PCB and have only the power supply section installed, shown below. The input (VIN) is 9V from bench power supply and output (VCC) is 5V. During testing I measure 4.86V on the output and am seeing a ripple of ~140mV with a light load of 15mA through the LED.

I'm using an Oki 78SR switching regulator. Its datasheet says the output ripple at full load is under 20mV. What could cause increased ripple in my circuit?

simulate this circuit – Schematic created using CircuitLab

The Oki datasheet recommends the input and output capacitors should be 10uF or larger where I used 1uF accidentally. However the part doesn't require these to operate. I will replace them when the new parts arrive.

What's not shown are decoupling capacitors for approximately 30 more ICs on the board, mostly 0.01uF to 1uF ceramic and then six tantalum 15uF capacitors. This total is within the maximum capacitive load the Oki part can handle which is 300uF so I hope that isn't an issue. To be clear the ICs are not populated, but their decoupling capacitors are.


texts: I'm wanting to build this circuit. Here is a link https://www.youtube.com/watch?v=__FRCSvEYdE which talks about it 6 minutes in. If I have a 6 volt dc battery what farad capacitor should I look for? How do I decide what ignition coil to use?  And how do I ground this circuit? I read that when you ground a circuit you use a metal chassis, but do not know how to do so and do not want to get shocked.


texts:
I need to calculate CMRR error for the current sense circuit. From Texas Instruments I have the following formula to calculate the CMRR error:

Schematic of my device looks like this:

There are two boards, one have only network of resistor to measure current, voltage for multiple channels (schematic is simplified), and 2nd board has microcontroller with sensing circuits.
I am not sure which value I should take, as V_CM_SYS from above formula. Should it be 12V, as on the microcontroller board, or 50V, that is max value that can flow through the 1st board.


texts: Most commercial headphones are advertised to have sensitivity greater than 90 dB/mW. But to my understanding, even with 100% efficiency that's not possible (if we use 10 log (I/I0) where I = 1 mW, we get 90 dB). So, is this an exaggeration or am I missing something?


texts: Expressing output voltage in a circuit with zener diodes without any value given

texts: I have this circuit and I need to find \$u_{o}(u_{i})\$ if \$ZD_{2}\$ and \$ZD_{1}\$ are ideal zener diodes with \$U_{z}\$ zener voltage and the op-amp is also ideal. My problem is that I have no values, I just need to find the expression for \$u_{o}\$, but how do I know if a diode is on or off or reverse-biased? I don't know where to start.