texts: Soldering USB contacts - what kind of solder tip and what temp?

texts: I am going to try and make my own mechanical USB cable. For soldering the wires to the usb plug, what is the recommended Solder tip type/size and also what is a good temp to use?


texts: Designing a PD controller for a unity feedback control system

texts:
I am really struggling to see how the constants Kp and Ks can be solved for the closed loop unity feedback system shown in the image below.

This compensator in pink is being designed such that the complex conjugate poles of the system are shifted so that s1 = -4+4j. I understand that the CLCE equation of this system configuration is as follows. $$(s+1)(s+2)+3(K_P+sK_D)=0$$

But then according to my lecture notes the Kp and Kd can be solved directly from this equation but does not elaborate as to how (except with a subscript saying that the complex pole should be substituted in place of s). $$[(s+1)(s+2)+3(K_P+sK_D)=0] (s=-4+4j)$$

I have tried substituting s=1 and getting Kp in terms of Kd and then substituting this value into the compensated CLCE with the pole substituted in place of s  but this is to no avail because every time I get a quadratic in terms of Kd with no solution (after getting rid of the imaginary terms via multiplying by the complex conjugate). Can somebody please show and or tell me how to calculate the proportional and derivative gains in a circumstance like this.

I need to know how this works because I have a homework problem where I have to design a PD compensator for a third order system where the compensated transfer function is as follows: $$\frac{C(s)}{R(s)} = \frac{[K_P+sK_D]21}{s(s+1)(s+3)+[K_P+sK_D]21}$$ and so the CLCE is the denominator of this transfer function set equal to 0. This system has to have a pole at -1+j.

As usual any help is appreciated,

Simon.


texts: Bluetooth Wireless Audio Module (V3.0/V4.0) for us audio interested laymans?

texts:
Hope I'm right asking my question here.
I'm building myself a boombox with wireless audio transmission.

With as of introduction of the iPhone 4S Apple gadgets (and obviously others) nowdays have Bluetooth V4.0. When I've been looking around for a module that I could use in my boombox to allow wireless audio streaming I've not been able to find any that supports Bluetooth V4.0 or even V3.0. Are there any modules out there available for "regular" consumers. I get that the big audio tech companies have special built modules for their purposes. But where can I get my hands on a module that will allow me to use V4.0 with Apt X and the possibility for line out audio and work with Apple devices (iAP/MFi needed? Not so sure what's needed to be honest).

I hope someone can help me out!


texts: How to suppress current spikes in transistor feedback loop

texts:
I am trying to pulse a load with a small constant current pulse (2mA @ 500us). The load does unfortunately have an unknown capacitance in the range 10nF - 1uF, parallel with an unknown resistance varying from 0.5-5kOhm. The current pulse should be constant over a resistor in series with the load, and not deviate more than 2%.

The circuit is powered by a single 3V cell, and will have the L8410 to generate sufficient voltage for the current pulses. An AVR Attiny will control the pulse duration and timing.

I have tested a number of different designs to see if they meet my requirements (current mirror, transistor feedback loops, opamp loops, IC's as LT3092), but they all suffer from large current spikes when pulsing the load.

The circuit design I have found to be best so far is a feedback loop between a MOSFET (M1) and BJT (Q2) transistor, where a second BJT (Q1) is used as a voltage controlled resistor from a LP-filtered PWM input (V5) to adjust the setpoint for Q2. See the LTspice schematics below.

The idea is to use the fast dynamics of the M1-Q2 analog regulation to handle the edges from the switch, while the MCU-Q1 in a loop with an current sensing opamp (not in schematics) will adjust the output to have an average at 2mA in the end. The switch is implemented using Vishay DG4053A (~100ohm ON resistance, ~100ns switch time).

The problem is that I get very large current spikes as in the simulation below (current trough Rtest in lowest pane).

My question is how to suppress/eliminate the spikes in this design. I would also be very grateful for any suggestions for a better design than the one I have proposed if that would help on the problem. The circuit must run on a 3V cell coin, which is the only limitation except the pulse spec and load characteristics.


texts: Competing PCB Crystal layout recommendations

texts:
This is related to this question: How's my crystal oscillator layout?

I'm trying to layout a 12MHz crystal for a micro controller. I've been reading through several recommendations specifically for crystals as well as for high frequency design.

For the most part they seem to agree on a few things:

Keep traces as short as possible.
Keep differential trace pairs as close to the same length as possible.
Isolate the crystal from anything else.
Use ground planes beneath the crystal.
Avoid vias for signal lines.
Avoid right angle bends on traces

Here's the layout of what I currently have for my crystal:

The red represents the top PCB copper and blue is the bottom PCB layer (it's a 2-layer design). The grid is 0.25mm. There's a complete ground plane beneath the crystal (blue layer), and surrounding the crystal is a ground tied to the bottom ground plane using several vias. The trace connecting to the pin next to the clock pins is for the uC's external reset. It should be held at ~5V, and a reset is triggered when it's shorted to ground.

There are still a few questions I had:

I've seen a few recommended layouts which place the load capacitors closer to the IC and others which place them on the far side. What differences can I expect between the two, and which one is recommended (if any)?
Should I remove the ground plane from directly beneath signal traces? It seems like that would be the best way to reduce the parasitic capacitance on the signal lines.
Would you recommend thicker or thinner traces? Currently I have 10mil traces.
When should I bring the two clock signals together? I've seen recommendations where the two lines are directed essentially towards each other before heading to the uC, and other where they are kept apart and brought slowly together like I currently have.

Is this a good layout? How could it be improved?

Sources I've read through so far (hopefully this covers most of them, I might be missing a few):

TI's recommendations for high speed layout guidelines
Atmel's AVR hardware design considerations
Atmel's Best Practices for the PCB layout of oscillators

edit:

Thanks for your suggestions. I've made the following changes to my layout:

The bottom layer beneath the uC is being used as a 5V power plane and the top layer is a local ground plane. The ground plane has a single via to the global ground plane (bottom layer) where the 5V joins together to the source, and there's a 4.7uF ceramic capacitor between the two. Made routing ground and power much easier!
I've removed the top ground elements directly under the crystal to prevent shorting out the crystal casing.
@RussellMcMahon, I'm not sure what exactly you mean by minimize the loop area. I've uploaded a revised layout where I bring the crystal leads together before sending them to the uC. Is this what you meant?
I'm not entirely sure how I can complete my guard ring loop around the crystal (right now it's kind of a hook-shape). Should I run two vias to connect the ends (isolated from the global ground), remove the partial-ring, or just leave it as it is?
Should I remove the global ground from beneath the crystal/cap?


texts: What exactly is "dominant" and "recessive"?

texts:
I am reading data sheets on the LIN bus, but apparently the same terminology is used for CAN.

What does "recessive" and "dominant" stand for, e.g http://hw-server.com/products/rs_optika/prevodniky_optika.html ?

How relate these terms to "low" and "high", or 0 and 1?


texts: Can a capacitor be briefly charged above its voltage rating?

texts:
Lets assume I have a supercapacitor rated for 5v at 200F. That's 2500 joules of energy. My wall socket outputs 120V at a maximum of 15A, which is 1800 watts (or joules per second). If I hook up my capacitor to 120V DC at 15 amps for 1 second, I would expect my capacitor to be charged up to 1800 joules, or about 4.2 volts.

My expectation is that since the voltage across the capacitor is never above 5v, it should be fine.

Will this work in practice, or would my capacitor blow up in my face if I tried this? And if not, why?


texts: Voltage drop across junctions in a bjt transistor

texts:
Above is a npn transistor with a battery connected across emitter and collector.

My textbook and all online resources seem to say this: No current flows in above circuit because the emitter-base junction is not forward biased. The current will flow when another battery is connected across emitter-base junction.

But doesn't the existing battery across emitter-collector already make the emitter-base diode forward biased? Where would all the voltage of that battery appear?

Observations:
If emitter-base junction is not forward biased, then both the junctions will have large but same  resistance.  This means half the battery voltage appears across each junction. This makes the emitter-base junction forward biased.

Where is my error?


texts: What kind of modulation technique and carrier frequency is used for interplanetary communication such as between the Earth and Mars?

texts:
I have just come across this wind sound coming from pressure sensor of Insight lander which is in Mars at the moment.

I know basically that AM, FM, PSK, FSK ect. all have disadvantages and advantages depending on the bandwidth, terrain, distance ect. I'm assuming between the planets or the moon the scenario is more likely pure line of sight with plane waves but have no information on the topic even in a basic level.

What carrier frequency and what type of modulation technique could they be using for such radio transmission?


texts: When does the transformer equation hold?

texts:
The "transformer equation" is as follows, $$\frac{N_s}{N_p}=\frac{V_s}{V_p}$$
What is assumed when this equation is used?

(Primary coil on the left, secondary on the right, in both cases)

Is transformer 1 an ideal transformer, or transformer 2 (I have seen both in books and I'm not sure whether in the first picture, the other field lines are just not shown because they are irrelevant). It would make sense that transformer 1 is ideal and is 100% efficient because no work is done by the magnetic field in the air, but wouldn't a magnetic field through "ideal air" do no work regardless? How does this relate to flux linkage? Surely the flux linkage in both coils must be the same for the equation to hold, so in transformer 2, conceptually, less magnetic field lines go through the secondary coil than the primary coil, therefore the equation would not hold.


texts:
I have a 24V battery and I'm trying to obtain a virtual ground from it. 90% of the circuits I found limit themselves to an opamp, which has very low current sinking. I'm trying to add a pair of transistors in push pull configuration, but my simulations are failing and I have no idea why. I would appreciate very much if someone could help me with this.

So far, so good. I'm simulating the scenario in which I have nothing connected between -V to 0, and a high load connected from 0 to V+. I'm having 10.8V on RL and that's great. But, when I try the scenario in which I have nothing connected from 0 to V+, and my load is between V- and 0, I get 0V on my load resistance.

I thought that, in this second case, the opamp would provide a small base current for the Q1 transistor, which then would drive a higher current from the V+ line and feed the load resistor. It doesn't seem to work this way, however. Please, could anybody enlighten me or give me a few tips?


texts: How does a differential analog to digital converter differ from a regular ADC?


texts: Connect three HC-05 Masters to three HC-05 slaves

texts:
I have 3 Bluetooth modules HC-05 connected to my laptop using an USB-TTL interface and 3 microcontrollers each one has its own HC-05 slave. These devices shall send values to my laptop (each slave sends a value to his own master only). In the laptop side, I have a Python script that manages the communication in this way:

Open COM1 (Master 1)
Send request to the slave
The slave sends a response
Close COM1 (Master 1)
Open COM2 (Master 2)
Send request to the slave
The slave sends a response
Close COM2 (Master 2)
Open COM3 (Master 3)
Send request to the slave
The slave sends a response
Close COM3 (Master 3)

To do so, is it possible to set different baud rates in order to avoid conflicts between them ?

For example:

Master 1 and Slave 1: 115200 bit/s
Master 2 and Slave 2: 19200  bit/s
Master 3 and Slave 3: 9600  bit/s

Is there another efficient way to make sure that every pair of HC-05 avoid other HC-05 devices ?


texts:
I'm wondering if a switch exists that fits this functionality I imagine:

The user would depress the switch, it would latch and stay depressed. Once the product completes its function, the control circuitry sends a signal to the switch which un-latches it. I imagine the actuator could be spring loaded so it would pop back up, or maybe a solenoid pushes it into the open state.

I wouldn't even mind having to supply current to a solenoid to keep the switch depressed. That is what most toaster actuators do. In fact, what I want is exactly what a toaster does. But I want to avoid investing time in designing a custom mechanical solution for this.

Can anyone confirm that such a product exists in a form factor like a standard panel mount switch?

Some words I can think of to describe this are:
Electrically toggleable switch
Latching switch with electric reset
Switch and latching relay combination
Electrically controlled switch

I've searched around with these and other terms, but haven't found anything.

Here is what I imagine the circuit symbol would look like:

Thanks for your help.


texts: Unwanted capacitance in measurement setup - what to consider?

texts:
I have a current measurement setup (which supposed to measure < 1nA). It has 20 channels and switched using a relay matrix.

Using a LCR meter I measured for one channel (In the schematic below, removing capacitor and putting LCR probes in series), and it happend in open mode, the whole setup capacitance is 6pF and if a chanel is closed (Obviously when taking a measurement, the respective channel is closed) the capacitance is around 50pF

I really would like to know how this capacitance (which I beleive comes accumulated from 22 coaxial cables, roughly 20 meters and count the internal wiring of test setup) can affect/contribute to my measurement? What is the theory behind it (I want to study it further) and possible workarounds?

Here is the schematic of my setup:


texts: What material is comonly used as insulator in laminations?

texts:
I am trying to build a brushless motor for quadcopter use, with a semi-CNC lathe and a CNC mill.

I know I can buy a stator core on gobrushless or maybe other place, but I want to know if I am able to build the stator core also.

There is a place near where I can buy electrical steel (silicon steel). I was thinking to use the mill to make several "stars" (shape of the stator core), and then somehow glue them together.

Then I want to know actually two things:
- What can I use to glue the laminations toghether?
- What material can I use to insulate each of the laminations from one another?

I am also shamefully ignorant in this field, so I don't know if this question is nonsense. Please if it is, explain why.


texts:
I am trying to implement a simple latching circuit that will turn an LED on if the signal from an AND gate is high (LED latches ON if high, and only way to reset is to remove power). I was thinking of using an SR latch, where I reset to the initial state (resulting in an off LED) then when the signal comes in, I switch the state. However, I don't know if 1) this is the right way to do this (seems a bit too complicated, since I don't need 2 outputs or 2 inputs) or 2) how exactly this would even be implemented in a circuit (especially the initial reset, or the power removal feature).
I hope my question is clear, since I am a beginner and am not sure if my descriptions are technically informative. I appreciate any help!
EDIT1: Attempt 1 Using SCR and Transistor:


texts: How to calculate this two transistors Constant Current Source circuit?

texts:
I came across a constant current source calculator at Electronic Product website:enter link description here

For example, for a 13.5V input, 300mA output, it comes out the following parameters:

R1: 4.5 ohm
R2:  45 ohm
R3: 382 ohm

I put the circuti in LTSpice with above values, and set 2N2907 for Q1 and Q2, a Load resistor of 10Ohm then measured current at each node:

I1:     247 mA
Iout:   245 mA
IB-Q1:  1.6 mA

I2:    27.5 mA
I3:    29.1 mA
IB-Q2:  119 uA

How can I calculate current through each component manually?


texts:
I have been trying to read FIFO buffer from LSM6DS3 inertial sensor via i2c. The processor will read LSM6DS3 buffer every 20s so the FIFO will contain approximately 3120 bytes of accelerometer data. The sensor contains 2 registers to read FIFO data which are FIFO_DATA_OUT_L and FIFO_DATA_OUT_H.

In my host, I use read-write system call to communicate with the sensor. And My i2c clock is 400KHz also I have couple of other devices connected on the same bus.

i2c_init()
{
    fd_i2c4=open("/dev/i2c-4",O_RDWR);/*open i2c. fd_i2c4 is global*/
    if(fd_i2c4<0)
    {
        perror("i2c device open : ");
        BLOGV(LOG_TAG "i2c device open error");
        return -1;
    }
    if(ioctl(fd_i2c4,I2C_SLAVE,addr)<0)
    {
        perror("i2c slave error : ");
        BLOGV(LOG_TAG "i2c slave error");
        return -1;
   }
}

This is my i2c read function

static int32_t i2c_read_low_latency(int *file,__u8 reg,__u8 *buff,__u16 len)
{
    buff[0]=reg;
    int temp=write(*file, buff, 1);
    temp=read(*file, buff, len);
    if ( temp!= len) {
        /* ERROR HANDLING: i2c transaction failed */
        printf("i2c read error \n");
      }
    return 0;
}

and FIFO reading function pseudo code,

fifo_read()
{
    int fifo length=get_fifo_data_level()  //to get number of available data in fifo.
    while(length-- >0)
    {
        i2c_read_low_latency(&fd_i2c4,LSM6DS3_FIFO_DATA_OUT_L,ch,2); // x axis data.
        i2c_read_low_latency(&fd_i2c4,LSM6DS3_FIFO_DATA_OUT_L,ch,2); // y axis data.
        i2c_read_low_latency(&fd_i2c4,LSM6DS3_FIFO_DATA_OUT_L,ch,2); // z axis data.
    }
}

The problem is it takes around 2-3 sec to read complete data. this consumes  lot of power. Any idea why this slow reading?.
link to data sheet lsm6ds3


texts:
I am trying to build a circuit that outputs ~180V for a nixie watch using the LT1308A. I'm modifying the following circuit found in the datasheet on page 17:

Now my circuit is essentially the same, only removing the voltage doubler, changing the transformer from a 1:12 to a 1:10, and changing the feedback resistors to output 180V.

Though the output ranges between -50V and 243V, not the 180V I am expecting.

Does anyone know what I'm doing wrong here?


texts: How can S11 component measurement circuit be made on a pcb?

texts:
I have a material whose dielectric properties need to be measured. I have done literature review on the physics & impedance based methods to determine the dielectric component.

It requires S11 to be measured. I can design circuits and PCB's along with embedded system development but dont have a great knowledge about RF, Can anyone suggest on how to proceed further?

I read about VNA's to measure S11, can that be done using a custom miniature circuit for 4.5 GHz (using any relevant IC like AD5933)


texts: Why doesn't this MOSFET driver work when load supply is isolated?

texts:
I need to use a mosfet driver in my next project. For this purpose I made a demo board with this schematics. My aim is to light the led by either applying a logic high level voltage from the control input or by pressing the button.
Schematic Notes:

The components marked with DNP are not fitted.
I didn't solder the bootstrap circuit elements (i.e.; Dbs and Rbs), because the switching frequency will be too low (1Hz at most). In my opinion, the bootstrap circuit can't keep the capacitor Cbs0 filled up at that frequency.
You see two mosfets connected in parallel. One is low power, the other is high power. Only one of them will be soldered in this demo board.
The points where I soldered external wires are marked in the schematics.
Supply voltage is 12V.
Control voltage is 0V/12V.
Isolated supply voltage is 12V.
The voltage the mosfets turn on or off is 12V.

My final PCB is like this:

The leftmost cable pair is for the supply.
The cable pair second from left is for the control signal.
The third cable pair is for the isolated suplly.
The rightmost cable pair for the voltage with the mosfet will turn on or off.

I did a setup like this:

My power supply is HMP4040. Please note that, all of its outputs are isolated.
Every channel is adjusted to 12V and the channels are connected to "supply", "control", "isolated supply" and "voltage controlled by the mosfet" from left to right.
I am trying to turn on the led by changing the voltage at the "control" input (the 2nd channel of the supply).

Now, are we okay until here? I am finally coming to the issue.
In this setup, I can toggle the led for a few times as intended (either by by pressing the button or changing the "control" input). But after a few times, the led stays either turned on or off and it doesn't change anymore. After I turn off then turn on the "supply" input, again I can light the led a few more times and it stays turned on or off forever until I reset the supply voltage again.
In this "stuck" or "uncontrollable" state:

I check the mosfet driver output (the gate and source pins of the mosfet) to see that the IC is trying to turn on and off the mosfets as intended.
The floating high side voltage (measured between Vb and Vs pins of the IC) is correct (12V) all the times. The IC requires it to be between 10V and 18V.
The voltage between "Ground" and the floating high side ground (Vs pin of the IC) doesn't stay fixed regardless of the "control" input value. It random walks between -10V and +10V. I expected it to be fixed (0V when "control" is logic low, 12V when logic-high).

While I was trying different things and struggling the find what was wrong, I discovered something. When I short circuit the "Ground" and "Vout-" as seen in the images below along the hand drawn red line, the problem is solved. By "solved" I mean, I can now turn on and off the led as many times as I want by both pressing the button and changing the control signal. This solution is okay for me, because in my final application, the load ground will not be isolated from the circuit ground.

But I want to understand the reason behind this phenomenon. When the mosfet driver applied enough voltage between the gate and source pins of the mosfet, its channel (between drain and source pins) will have low resistance. Regardless of applying an isolated or non-isolated voltage between the drain and source pins, some current must flow through the led. But it doesn't happen like that when the controlled voltage is isolated.
Can you please explain me what is happening here when the controlled voltage is isolated?


texts:
I am attempting to calculate the noise on the power rail that my ADC is receiving so I can calculate my effective number of bits. But the different units on the datasheets of the regulators are throwing me off. I don't understand the decibel unit in noise suppression. I clearly understand and visualize volt peak to peak and frequency.

So the ADC rail pass thought several regulators and filters.

Power plug (5v/3v3)  16 Hz RC Low Pass  16 kHz Low Pass  LP5097  ISOW7841  ADC

That is basically the chain for the power to get to the ADC. I do not know the units of the final answer to look into the data sheet of my ADC to see if it's acceptable.


texts: Differential BJT Class AB amplifier DC analysis

texts:
I have a few questions regarding analysis of the amplifier schematic below. Bear in mind that the resistor values have not been decided yet and are just copy-paste for now. The only requirements of the amp are that it drives an 8 ohm speaker with a supply rail of +16V and a total voltage gain of 1500 minimum (I know I am likely to have to add stages).

How is the best way to work out biasing the current mirror to provide the correct current? Previously we were given equal values of 1mA for each branch off the supply rail (so as not to cause current drive between stages I believe?), with 2mA coming from the current mirror. Should I use this arbitrary 1mA as a starting point to find resistor values?
In the amp's quiescent state, I understand that the voltage at the collector of Q8 should be 8V ideally, to allow for maximum output swing. How can I calculate the voltage at the base of Q8? I feel like I'm missing something obvious related to Q8 itself, and maybe assumptions on its Vbc?.
We have been told previously that as a rule of thumb the load resistance (R3 in this case??) should be a tenth of the circuit's output resistance. Is that true for this configuration? What about R2? That rule was given on a circuit without an R2.

I hope these questions aren't too simple, but we have never studied a circuit quite like this, and I am finding it hard to find a similar example online. Of course I don't want the answers outright, I'm just struggling with where to start. I am not confident enough that the addition of a couple of resistors or removal of negative supply doesn't throw me completely!

Thanks for reading, and for any advice you can give!


texts: Why does this connection not become a low impedance between Positive (Isolated system) and Ground (Earth)?

texts:
I was going through a lecture regarding oscilloscope grounding methods and saw this image.

Assume I have the isolated widget powered by an external battery. Now, I am going to measure the signals using an oscilloscope.
Question : Why does the current not flow between the "Power In" rail in my widget and the "Mains earth ground" when I connect my oscilloscope alligator clip ground to the "Power In" Rail of the widget - as shown in red in my above image?
I believe that the Current follows through the path of least resistance. When the scope ground (which is connected to the earth's main) is connected to the +V in my widget, does the +V not have a least resistance path to ground (Earth in this case - assuming earth is lower potential that +V rail)?
I am having this confusion and not able to understand clearly why the current does not flow. Can someone please explain in simple terms on how to understand this?
I understand the when I connect the scope ground to any point on my widget, that point will be "Earth" referenced. But, I am not getting how the current does not flow between the +V and Earth when the above connection is made?
P.S. the lectures says that since the widget is isolated and has its own +V and negative, "there are no loops formed when the oscilloscope ground is connected to the +V and that's why current does not flow from the +V to the scope ground" - I am still not getting this. Any analogy or illustrations with simple terms explanation will greatly help me understand.


texts: Can anyone please identify this 6 pin SMD A28L integrated circuit or what it does?

texts: I could not find it by the code written on it - A28L.  It is from a headlamp light with lithium battery and I need to replace it.


texts:
I have this LM358 op amp as a non inverting amplifier used for high side current control.

I feed this ic with 5v on pin 8 and ground is pin 4.
Pin 2 and 3 are the inverting and non inverting inputs. I use a pot to change the gain of the op-amp in order to change the current output for the load when it's connected.

I've been searching about what's the best way to ground op-amps used as current controllers in situation like this but I can't found something convincing to me.

What I don't want is to introduce large current peaks on the ic when a load is connected on the output, that's why I use a 0.3mm trace on pin 4 that connects to sense resistor ground. Also I put a ground via near pin 4 in order to connect common ground of the pcb too.

I don't know if this ground connection (trace from pin 4 of the op-amp to ground sense resistor) it's ok from what I want or I have to make some improvements.


texts:
I just recently started trying out on electronics engineering, and have built a OR gate, NOT gate and a AND gate using NPN transistors. When building the XOR gate, this is my design:

However, SW2 will not activate the LED due to the current at the base of Q4 (activated by SW2) activates Q5 to bypass the LED. Thus, the Q3 & Q4's AND gate does not work. Is there any way I can get the between Q4 and Q5 to not flow unless both Q3 and Q4 have been activated?

Thanks in advance! I'm such a newbie.

P.S. The simulation lets the current flow from the positive side to the negative side.


texts: Logarithmically-spaced resistances using switches

texts:
If you want a linearly-spaced set of resistances, you can use a ladder of logarithmically-spaced resistors and short out different combinations, as described here.

Is there a way to get a logarithmically-spaced set of resistances?

Simplest case:

If you have 2 SPST switches, there are 4 different states they can be in (off-off, on-off, off-on, on-on).

Is there a way to connect these switches with (any arrangement of) resistors, such that the total resistance between two nodes of the 4 states is {1, 10, 100, 1000}?  In other words, a digitally-controlled logarithmic rheostat.  The states don't have to be in any particular order.

If this is possible, can it be extended to larger numbers of switches (8 values from 3 switches, 16 from 4, etc.)?


texts: Using piezo sensors to locate vibration position

texts:
I am working on a project where I have to determine the position of vibration or knock using multiple piezo sensors.
I am using simple piezo discs and reading the voltage signals from the discs using Arduino Uno synced with Matlab.
I have 4 such discs arranged at the corners of a square plate.
I have different signals at different time stamps. I tried working with the speed of sound to calculate the position but the results are not what I thought would be.
Can anyone help?


texts: Why use a concave vs. flat mating target for pogo pins?

texts:
I'm doing some research into using spring-loaded pogo pin connectors with a mating target for a project I'm working on. During this research, I discovered that there is a concave mating target, yet, I have only seen flat ones on products. Why would I pick one over the other?

If it makes any difference, in my case the pins would slide into place from the side (lateral), rather than coming from the top (axial).


texts: What are the application difference of the circuit breakers which have difference "Circuit Breaker Characteristic Trip Curves"

texts: I know the difference of different type of "Circuit Breaker Characteristic Trip Curves". However, I don't know what are the application difference. Please help


texts: Why do most USB OTG dual-role devices use micro-B connector instead of micro-AB

texts:
I mean, this is against the rules!

Most USB OTG devices claiming to be host capable (most Android smartphones and tablets) have a simple micro-B connector. Shouldn't they have a micro-AB connectors? Micro-B are supposed to be for devices unable to act as hosts.

It actually leads to a proliferation of USB OTG cables like this one:

Which are forbidden by the USB specs (micro-USB specs chapter 3.4: Compliant Cable Assemblies). We clearly see it is a micro-B, not micro-A plug (there are chamfers), and it is associated with a standard-A receptacle. I wonder how they are even allowed to print the USB logo on this, by the way.

So, why do manufacturers do this (both phone manufacturers and cable manufacturers)? How is it allowed by the USB consortium?

I'm asking this because I am actually designing a USB OTG device. I don't plan to make it certified by USB anyway (given the costs), but I'd like to know whether I should strictly follow the standards, or screw up with them like everyone else (the fact is - because of this - everybody is used to micro-B, not micro-A, and it's true the chamfers help prevent trying to put the connector the other way around).


texts: What happens when current sourced from a switching regulator goes too low

texts:
On the recommendation of an SO-er, I'm looking at using a TPS54295 to power a controller that uses an ATMega 2560. The regulator will be powered by a 3-cell LiPo battery, implying input voltages between 9 and 12.4V. The controller will be in standby mode for a few minutes at a time, waking up periodically to check sensor states and perform various tasks. I expect the controller part of the circuit to draw 15-20mA when active, and 15-20uA when sleeping. Looking at the data sheet for the regulator, I'm seeing two things that concern me:

First off, there seems to be some amount of instability in the regulated voltage when the current draw goes below a hundred mAs or so:

Does this mean I need to consider a different regulator, does it not matter, or is this something that I need to rectify with additional passive components?

The second part is this section of the efficiency curve:

this tells me that when in standby, efficiency will drop into the low 20s or even 10s of %. Again - is this standard for this type of regulator (meaning I don't need to worry about it), or does this mean that I'll be burning it up at those levels?


texts: Can Original Arduino Mega 2560 Work with Google ADK?

texts:
Stupid question fellow Stack users...

Can I use Google's ADK on the original Arduino Mega 2560? From what I can tell, the main difference between the Mega2560 and the Arduino ADK is the addition of the USB host port on the board. I haven't played with ADK yet and cannot seem to find any direct answers via the Tubes.

Your help is greatly appreciated!


texts:
Something I have been thinking that could drastically reduce the cost of powerline devices in a bridge that uses the switching circuit to provide both regulation and data.

Basically you could have a wifi, bluetooth, homeplug 230Vac low voltage bridge.
This would allow a simple 16 device master/slave 12v DC side for sensors and devices with extremely simple low cost powerline data embedded and created by the already existing SMPS circuitry.

The cost saving on end points could be huge as a very simple data line of a strong signal could be used and multiplexed into power usage.

Would be prefect form for LED lighting to home control systems.


texts: Moore machine state diagram and state table

texts:
Is it me not understanding this table and diagram or something?
If in a Moore machine, the output only depends on the current state
Then why does the table for states F and H say the output is independent of the input?
At F, if the input is a 0 the state changes to I and output would be a 1
At F, if the input is a 1 the state stays the same at F and the output would be a 0

The state table does not reflect this?

The state table should show multiple outputs...


texts: I need to get a interrupt when some motion is detected. I tried example state machine from the application notes (wake up), and connected led to int1 for debugging. After setting all registers and shaking a bread board led started to glow. But it glow constantly, I have no oscilloscope unfortunately to check deeply. But in any case it continues to glow without any movements. Do I have some mistake in the state machine description, or do I have to reset it after each interrupt ( sounds weird)?


texts: External signal noise versus ADC resolution

texts:
One of the answers in this question says: “Having an ADC that has better resolution than the external signal noise is a waste of money.”

I want to illustrate and understand what is meant here. So for clarity I tried to ask by using the following figures:

Above in Fig1 random noise in color red imposed on a constant input signal where the peak to peak is 1mV as shown in the figure. And in Fig1 the ADC has a resolution  of 1mV. In Fig2 however the same input now goes to an ADC which has a resolution of 0.3mV.

Does that mean for this input any ADC with resolution Δ<1mV is redundant? What could be the minimum adequate resolution?

Imagine the 1mV peak to peak superimposed random noise is always the case. And the signal is coming from any voltage source with a sensitivity of 0.5mV. So there are two things here. One is the sensitivity of the source like force transducer sensitivity and the other is the random noise I showed in red.

Considering all these I cannot make reasoning what limits what along with ADC resolution.


texts: Why is a dc voltage of 0.3v is applied in order to check the closedloop1 AC response?

texts:
I have read the article related to current source “ opamp current source in simulation on prototype”. I wanted to know during simulation why a dc voltage of 0.3v is applied in order to check the closedloop1 AC response. Is there  any specific reason to choose 0.3v? I am attaching the link related to this question.
Opamp current source stable in simulation but unstable on prototype

Similarly I have also observed the same dc voltage of 0.3V with ac source to plot the bandwidth in the following thread.
The links are shown below:
<https://electronics.stackexchange.com/questions/392662/current-source-with-unlimited-cap-drive-op-amp-oscillating >


texts: Analog input buffer for an A/D Converter - what op-amp to use?

texts:
For a small audio-recorder project i'm currently working on i will use a Nanopi Neo and an audio chip from Cirrus Logic. I'm pretty stable in my skills as soon as it comes to the digital side of the project, but the analog circuitery somehow bothers me.

For the analog input buffers of the A/D converter an example circuit is being provided. It looks like this:

What Op-Amps should i use for this? Is there any special requirements to them?

edit, additional information:

Offset Voltage should be at 2.5V, with +-1.4V when arriving at the pins of the chip. I'm not quite sure what the input voltage to the circuit is going to be, as the requirement for -10 dBV or +4 dBu are not yet clear. THD should not be an issue, it's just an experiment right now, i would be glad not to have excessive noise though. What would that mean for the choice to make?


texts: Is it necessary to allocate multiple channels to an access point at the same time?

texts:
I need to ask a question about practical issue in channel sharing in wireless communication as follows.

Let we have a set of 4 unlicensed networks with access points denoted as, \$\{N_1, N_2, N_3, N_4\}\$.
Let we have 2 channels (frequency slots) available to allocate to the networks, denoted as \$C_1\$, \$C_2\$.

Let 3 networks' APs, \$\{N_1, N_2, N_3\}\$ demand one channel for a certain time duration to operate while network 4's AP, \$N_4\$ demands two channels to operate for a certain duration.

My channel sharing system properly schedule them in Time-domain.

The system allocates the required number of channels to these APs. However, in order to satisfy some other allocation constraints, my system may schedule the AP \$N_4\$ in different time-window in \$C_1\$ and \$C_2\$.

For example, system may schedule \$N_4\$ on \$C_1\$ in time window \$T_1\$ while on \$C_2\$ in time window \$T_2\$.

Now someone make an objection that

"it is not practical that you schedule a network in different time window." He said, "if a network is allocated multiple channels then it needs all those channels at the same time to operate. We cannot schedule the network in different time window"

I am wondered that, is this objection true in the perspective of any of the network technology like WiFi, WiMax, WRAN etc.? I mean is it necessary that an AP is to be allocated all the desired channels in the same time window?

If there is no such compulsion can you please tell me some reference so that I can use that reference in the argument.

Thanks,


texts: Why do we need orthogonality for FSK carriers?

texts:
I keep on coming across a requirement for FSK carrier separation, \$1/T\$ for non-coherent detection and \$1/2T\$ for coherent detection, where \$T\$ is bit period. I understand where this comes from in the context of an optimal quadrature receiver, such as this: . Now from an electronics standpoint, say I design a filter-envelope detector receiver:
In this scenario where we use bandpass filters why do we need the FSK carriers to be orthogonal? - Why do they need to have a frequency separation of 1/T? Also, if this scheme works then why is it not considered an optimal receiver system, in contrast to the quadrature receiver?


texts: What does the "phase margin" parameter of an opamp imply?

texts: I was reading datasheet of MCP6072. I saw a parameter namely "phase margin" (table 1-2, page 4). As far as I know, "phase margin" is a control engineering term, and implies the phase difference between input and output when the gain is unity. I don't understand the meaning of this term in opamp terminology. The typical phase margin of this opamp is given to be 57o. That what does it mean?


texts: Going from 72V to 5V with multiple switching regulators

texts:
I have a 72V battery which I want to step down to a 5V controller with limited power loss. The problem is that looking on the TI website the biggest range I could find for power regulators is the LMZ36002 which will take a maximum of 60V. How can I use this for my application? Can I put two of these in series? Is there a way I can split the work or some devices Ive missed to do this?
Thank you very much for your help!


texts: What is the structure of a typical 5V-tolerant input?

texts: How do 5V-tolerant inputs work on a (3.3V or lower) device?


texts: what does this number(spacing between pads) in the datasheet mean?

texts:
i am going to design footprint for a devise and i need to know spacing between pads. do you know what does (2-1.27) mean?
the devise is pico oem socket.

thanks


texts: Why does the LM317 generate VOUT of ~1.7V with Adj at ground, instead of 1.25V?

texts:
According to the datasheet equation of the LM317, if R2 is 0, then Vout should always be 1.25V. The Wikipedia page of the LM713 says the same thing.

I have five LM317s, and if I ground the Adjustment pin, they all produce ~1.65 to 1.7V on Vout and not 1.25V. I tested with 1k, 10k and 100k load.

My test schematic is trivial: Vin = +5V (from a fancy power supply), ADj = GND, measure GND to Vout, plus .1uF and 1uF caps.

I'm looking for a temperature and Vin independent way to generate 1.25V reference and I thought since I had some of these they would work...

UPDATE: linear regulators need a load (see answer below). However the min current is 10mA, which is quite a bit for a battery op device. I found an LM385 which is a 1.2V diode shunt that only requires 10uA.


texts:
I have a circuit that is controlling a water valve.

The state of the valve can be controlled via an http request, or a physical rocker switch.

I would like the physical rocker switch to represent the current state of the water valve. ie it is in the "Open" or "Closed" position.

This means that if the valve is closed or opened over the http request, then the switch moves to represent that state.

Does such a switch exist?


texts: PWM Modes: Center Aligned and Left Aligned

texts:
I am using the Atmel AT32UC3C2512C and looking into the datasheet there are two kinds of PWM modes: Center Aligned and Left Aligned.

I would like to know when one is supposed to use each one of these modes, and pros and cons of them.


texts: LEDs in parallel WITHOUT Resistor and Constant Current

texts:
Before I go on, I should stress that I have read many many other forums and scoured all stackexchange recommended 'questions that may already have your answer' things, and none of them answer my question.

Let's say I decide to put 3x 20mA 3v LEDs in parallel.

That equates to a power consumption of 60mA @ 3v = 180mW

But not all LEDs are created equal, and alas, one of the LEDs want 40mA. That should then increase the power consumption to 40+20+20=80mA @ 3v = 240mW and it burns itself out. Let's assume the other 2 LEDs are properly manufactured and draw 20mA

Shouldn't the other 2 LEDs still draw 40mA @ 3v?. It's not like I have a constant current device that forces 60mA.

Here is the scenario everybody talks about:

The power supply is 3v at 60mA (CC/CV)

One of the LEDs is faulty and draws 40mA. The other 2 draw 10mA each (Since there is 20mA left over. Let's assume they split the current evenly)
The faulty LED burns itself out. That leaves 60mA for 2 LEDs. So each of the proper LEDs use 30mA. But oh no!, one of them overheats and dies!
The sole last LED is forced to use all 60mA of the current, and it soon overheats and dies.

My scenario:

3v power supply directly from a battery. There is no current limiting, current control, or anything at all. No resistor.

Again, the faulty LED draws 40mA and dies.
Shouldn't the other two LEDs still draw 20mA each? This means that overall total consumption of the circuit is only 40mA @ 3v.
Boohoo, one LED breaks. That should be all. Why not?

My questions are:

Why would the two LEDs have to use 30mA if one dies? Why would the two LEDs draw the current meant for 3?

My 5 torches I have all have their LEDs arrayed in parallel. THey are high quality torches, most from Arlec. One of the torches have 16 LEDs in parallel. They do not have any resistor or anything. THe LEDs are literally all slapped onto a cheapo PCB, directly connected to the batteries. These torches all run fine, don't have varying levels of brightness, and haven't died on me in years. Why can't I do the same?


texts: What happens to a DC current at the end of a wire?

texts:
This question might be a little more appropriate for the physics stack, but I'd like to test the water here first. I am just getting into electrical engineering, and as I go along, certain aspects grab my curiosity.

When you have a junction, like the letter "T" we could say that the top of the T is a serial bus wire or something, or just a wire carrying DC current. Then the base of the "T" is a connector that some peripheral can connect to, to use some current to power itself, however, it's not always plugged in.

So assuming nothing is plugged in to that wire at the moment, what exactly happens? Is the DC current somehow reflected back? Also this may come across as naive, but when a peripheral is plugged in, do the electrons from one wire actually physically move into the other conductive compound? Or does the electromagnetic energy from the end of the wire induce current into the attached conductor?

Thanks for feeding my curiosity. I've Googled endlessly for this kind of info but I always turn up empty-handed, maybe someone can point me to some good reading material!


texts: How to program a MSP430FR5959 using pogo pads?

texts:
I am laying out/designing a board that will be using a MSP430FR5959 microcontroller and I need to be able to program it as requested with pogo pad/connectors. I will probably be using 2-wire or 4-wire JTAG to do the programming of the microcontroller, but I don't know how I would be able to do this. Can someone point me in the right direction?

Here's the circuit schematic for using JTAG and the microcontroller.


texts: Looking to make some SIP to DIP adapters and I'm trying to find some individual flat pins as per the below image - does anyone know where to get them or what they are called? An alternative is to use 2.54mm header strip (as used with Arduino for example), but these flat ones look a bit more flexible, which may be useful if the pins need to be bent over to enable fitting in tighter spaces. Any ideas?


texts: Writing a driver for a wireless usb dongle for an AVR microcontroller

texts: I have an avr micro-controller which supports USB OTG. I also have a wifi usb dongle which connects to the internet. I need to write the required drivers in order to interface this usb dongle with a wifi module. What books would be the right starting point. Could someone please point me in the direction of some good tutorials for achieving this.


texts: Testing Capacitors - Differing Results Each Time One Is Tested?

texts:
I have a bust LCD TV - I've already ordered a replacement but am interested in using the broken TV to learn a little more about how these are put together and if I'm lucky fix it to have as a spare.  Most of the information I've found for the TV's symptoms (standby light on, but won't power up) points to the capacitors so that's what I've been focusing on.

I've have looked across all of the immediately visible capacitors and none are showing bulging / leaking electrolyte, so I pulled out the power board and have now removed two capacitors to test.

It turned out my trusty old automotive multimeter didn't have a capacitance setting so I went to the local electrics shop and bought a relatively cheap auto-ranging multimeter which they recommended as being quite popular. I'm not use to autoranging meters so this new toy is taking me a little while to get used to anyway.

When testing the capacitors which I have removed I get a range of different values. The multimeter is quite slow to respond (I believe this is from the meter charging the capacitor before making the reading?) and will switch it's range which has confused me a few times.

My method of testing is to have the meter on capacitance setting. It will usually show a reading of 0.04nF with the leads not touching anything. Once touching the probes to the capacitor (taking care with polarity), I get my results after 2-3 seconds.

The capacitors I'm testing are a 35v 1000uF and 35v 450uF. The readings I'm getting will be have ranged around ~1.4nF, once or twice around ~30nF and a few times OL.

I don't know how to interpret this.

I'm not sure if this is:
1) Indicative of bad capacitors
2) Cause by me incorrectly measuring
3) The new multimeter is a lemon

My plan is to go and buy a new capacitor or two tomorrow and test them with the meter to see what the results are to try to eliminate a few options but I'd like to hear your thoughts.


texts: Need Help With A Component(Octal D Flip Flop)

texts:
I'm analyzing the following component:

http://www.futurlec.com/74HC/74HC574.shtml

It says that this flip-flop has a high impedance state when the output control bit is raised high.  Does this allow the flip flop to be connected directly to a bus, without a buffer chip?  If the chip is switched into high impedance mode would it lose the data locked into it?

I'm wanting to use this chip as a home brewed cpu register.  I was looking at An octal buffer(54AC541) between this and the bus; however, I no longer think this is necessary.


texts: Possible to buy Atmega328p with programmed Flash and EEPROM?

texts:
I've recently upgraded my old project that goes to mass production (a pair of thousand pieces, pretty niche). Previously I used DIP atmega328p, which were manually programmed in China. I sent them a detailed instruction, HEX of Flash and HEX of EEPROM, all was OK, I made the process as quick as I could, given limits.
But I've decided to switch to SMD version of the MCU (hardware/spacing related reasons). So it will make assembly process quicker and easier. So I thought why not to optimize MCU programming step as well, now that I have a little more experience and knowledge (the original project was one of my very first projects ever). So if I can also get rid of manual programming, it's a double win. I'm aware of zif sockets for qfn-32 which can be used to program the MCUs manually, it's a backup option. I want pick-and-place machine to solder the MCU onto the board and be done with it. Manual programming means manual soldering of the MCU, which, in case of QFN-32, sounds like a really bad idea.
Unfortunately, fierce and fingerbreaking googling didn't yield expected (or desired) results. The best I saw was purchasing Atmegas with a bootloader, which doesn't really solve the problem of course.
So is there a way to buy Atmega328p SMD with Flash and EEPROM programmed? The rest of the PCB will be assembled in China, so if there is any way to do that in China too (LCSC?), that would be great, but I just want to find out if/how this works in general, who could I contact? Should I contact, say, LCSC? Or someone else? It's critical to have BOTH FLASH and EEPROM.
In case it somehow matters: in my project the Atmega328p runs from the internal 8mhz oscillator


texts: A heat sensor that powers an LED with no controller

texts:
I'm a programmer, and I can wrap my head around having a controller board which monitors a temperature sensor llike this http://www.digikey.com/scripts/dksearch/dksus.dll?pv469=113&FV=fff4001e%2Cfff80137&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 , and then tells an led how bright to glow based on the temperature.

Is it possible to do this with just a breadboard and a powersource?  Pipe the output of the sensor reading into some series of components to regulate how bright the LED would glow ?


texts:
I am using this MCP4922 12-bit DAC, and the range of voltage to convert is from 0-5 volts, what is the recommended voltage on its external Vref pin?!
Thanks


texts: Help Identifying Radio Component and Replacement Part

texts:
My girlfriend picked up an old Philco tabletop AM radio. If I had to guess, I'd say it was manufactured around 1960. I couldn't find any model number or year stamp. It's encased in plastic. It powered up, but didn't really pick up any signal. I told her that I'd open it up, clean it up and inspect for any bad parts.

The tubes looked in good shape, but there was a cap that is blown. I'd like some reassurance that it is indeed a capacitor and that my reading of the color code is correct.

I read it as yellow, violet, orange, black, yellow. According to an online calculator, that gives me a \$4.7 \mu F, \pm 20\%, 400V\$ cap. Does that seem correct? If so, what is a suitable replacement? Searching Mouser or Digikey yields many results. I'm not sure which part is best to go with.


texts: If mobile phones have to go through such extensive FCC/CE/EMI testing, why do they interfere with my radio?

texts: It seems that to sell a GSM mobile phone, companies like Apple, Motorola, Sony Ericsson and many others invest a considerable amount of money in EMI testing them. Yet they still interfere with my stereo, radio, computer speakers, and other devices. Why?


texts:
So I'm trying to make a small Maglev train for a science fair project. I understand how to make the train levitate, but not how to make it move forward. When I look online, everyone explains how you can have magnets on the sides of the track and magnets on the sides of the train:

To make the train continuously move forward, you must constantly alternate the polarity of the electromagnets, but I don't know how to do that. Is there some kind of tool that can automatically convert the polarity of the magnet?
Last thing: is there a reason why the magnets on the sides of the train are not in the same position?

Please help.


texts: What would cause a power meter to report negative vars?

texts: I have some digital power meters at work that we installed due to previous concerns of voltage instability.  The voltage instability has been corrected and these are now primarily used for monitoring of energy usage.  I have noticed some strange reactive power measurements.  These meters report a lagging power factor as positive vars (inductive) and a leading power factor as negative vars (capacitive).  At no load, or very little load, when we have many idle VFDs, large transformers and voltage regulators online but without any load, the meters report a lagging power factor or positive vars for the most part, which I believe.  When we start bringing loads online, motor loads to be exact, the vars start to go negative and the meters report a capacitive load.  This seems to be the opposite of what would be expected.  Wouldn’t you expect the power factor to be lagging even more as motor loads are brought online?  What would cause these meters to report a capacitive load as inductive loads are brought online?  Thanks!


texts:
I am confused about the action of a spark gap. I realize the gap is breached when the voltage reaches a critical point. But what happens to the remainder of the voltage?

In the attached circuit the power supply has 2000VAC 10mA 30KHz. The breakdown voltage on the neons is 90V. The capacitor is 874nF and L1 is 40microH.

Without the neons the full 2,000V (rectified DC) would appear accross C and L1 (L1 before C). With the neons would that be reduced to 90V? Would the neons fire at the same time? Will L1 resonate with C? It's a bit different to a tesla coil in that a tesla coil has just one spark gap between L1 and C and C is pumped up to the breakdown voltage of the spark gap. I don't think that would happen in this case as the neons would break down at the same time.


texts: Voltage DAC, overcome settling time in a corner case

texts:
I need a (relatively) cheap DAC to produce a ramp voltage with a update rate of ~1uS per step. Since fully specified 1uS settling voltage DACs are quite expensive, I investigate  the possibility to use a little slower device, like ~5uS as DACx0501.

In addition REF and BUFF are included.

http://www.ti.com/lit/gpn/DAC60501

This is based on the fact that:

Settling time is specified from 1/4 to 3/4 full scale. I need to settle from one LSB to another (up or down) and according this fig. of datasheet (glitch impulse), I should be fine, about 1uS

SPI interface is specified to 50 MHz. However, there is a parameter in datasheet that isn't appearing in timing diagram, nor specified anywhere

tDACWAIT Sequential DAC update wait time  min. 1uS

According to my calculations (assuming 50 Mhz), timing diagram should be as follows

I have 1.65uS and I need 1uS :))

The question is about that tDACWAIT parameter, why to wait for?

Wait because of DAC analog circuitry needs to settle and in this case, I can ignore a little. While DAC settle, I can write a new value over SPI.
Wait because DAC analog still reads from digital section, faster will put other data and confuse output.
No idea, combination of above?

Thanks a lot for clarifications!

EDIT 1

To be more clear, this is how I plan to use it, not necessarily violate parameters, depends how I understand that tDACWAIT


texts:
I am trying to figure out if there's a way to calculate the prescaler value for Timer 0 on the PIC16F877. I've looked at both parts of Microchip's tutorial on timer 0 and some other tutorials:

PIC Timer Calculation
Timer and Prescaler - Calculate Elapsed Time
Picmicro: The Timer0 and the prescaler

These tutorials just mention that it's using a certain prescaler but don't specify why. I know what the prescaler is and how to calculate everything else since I just always used the maximum prescaler available. However, for my current studies I need to know how to calculate it or justify the choice of prescaler.


texts:
As a continuation of the previously asked question and accepted answer Analog 0...10V signal splitting, I have a new question.
We implemented two analog buffers with LF353P and the rails are connected to 24V and 0V. We inserted the analog buffer between source and sink since the sink has capacitance on its input which affects our measurement. (Second analog buffer is redundant, but it can also be inserted between source and monitor)
The accepted answer works as intended with a slight problem. Signal coming out of the sink can reach 0V, and when the op-amp input signal is near 0V, the output from op-amp is at 22.#V which results in an error state in the sink.
My understanding is that this is because the input voltage is near the lower rail voltage of op-amp. If my reasoning is correct, the following circuit will be able to output 0V..10V (with both 0V and 10V being possible outputs):

Those batteries should be able to drive op-amp for a long time since the current needed by op-amp and sink is measured in mA. Is my reasoning and approach to the solution correct?


texts: Getting the wrong voltage while simulating a 555 timer

texts:
I'm designing a circuit based on the 555 timer. I'm using EasyEda as simulator.
The problem I'm having is that, with a voltage supply of 5V, I'm getting 3.3V in the output, while I was expecting 4.4V minimum.
I'm expecting the mentioned value because the VOH stated for 5V supply in the LMC555 datasheet (see 6.5) is that. However, since the voltage I'm getting is lower, I suspect that my confusion comes from the 555 my simulator is using. Let me explain:
As far as I understand, the 555 timer is kind of a standard part. Many manufacturers make it, but they all should match some pre-established specification. However, there might be different families of 555 timers depending on the technology they use (CMOS, TTL...). Is this correct?
If so, my guess is that the simulator I'm using is simulating a TTL 555 timer, while the datasheet I was reading (the one above) speaks about a CMOS 555 timer. That would explain the voltage drop I'm seeing (it makes sense that BJTs drop more voltage than CMOS, right?). Is this correct?
To verify this I have done the following, I'm not sure if I have understood it correctly though:
I have noticed that the 555 timer that is available in the simulator is called 555_BJT_EE. That BJT part makes me thing that it is simulating a 555 based on BJTs, that is, TTL technology. Next, I have searched a datasheet that corresponds to a TTL 555 timer and I have found this: LM555 timer datasheet.
In the part 6.5 I can read in the table that the output voltage drop (high) for 5V is between 2.75V and 3.3V.
I think that output voltage drop means the voltage you need to substract to your Vcc to get Vout. Is this correct?
If it is, is my above reasoning correct? (namely, I was looking at the wrong datasheet because it was describing a CMOS 555 timer, while I'm using a TTL (BJT) one. Thus, I need to stick to a datasheet which corresponds to a TTL 555, which happens to be the one my simulator has)
EDIT
I have no load for now, just an oscilloscope to measure the output frequency.
Here is the schematics (555 in astable mode to generate a sqare wave signal at 2 Hz):


texts:
I understand an Encoder is 2^n input lines and n output lines`.

I want to construct an Encoder from scratch so I can understand how it works, so that I can construct any other Encoder in the future.

I believe that the Input lines are an address to the output lines. So for a 4 by 2 encoder we would first construct a truth table. My biggest problem is I can't construct the output part of the truth table for an encoder. I don't know how to get the output, if I knew the logic I could build it.

Encoder Truth table with what I think the output is.
http://www.flickr.com/photos/76226081@N08/8931456484/

Every time the input lines are x x 0 0 I put a 1 for O0.
Every time the input lines are x x 0 1 I put a 1 for O1


texts: I set up a clearance of 0.256 mm, however, this distance is only applied between the ground and traces. When it comes to ground and pads, this distance is small. I am wondering will be the copper removed from that purple area, between the pads and the ground (see image), and what is the purpose  of that purple layer in manufacturing process?


texts: Books for an introduction into higher level electronics

texts: I’m looking for a book that will introduce me to higher level mathematics in electrical networks. Specifically calculus/multivariate calculus/vector calculus/Fourier transform. I’ve read many books on circuits but all fail to define the fundamental mathematics involved in the concepts they attempt to explain. I wish to understand the concepts at a (mathematical level) fundamental level.


texts:
I'm building a MOSFET+LiPo battery driven multi stage coilgun as a hobby.
My question is:

How much does MOSFET gate-> Driver circuit distance matter in my case?(very low frequency)

I've read many articles stating the importance of minimizing the distance to avoid stray capacitance/inductance. However these articles all focus on using MOSFETs for high frequency applications on tiny PCBs, where super fast switching times are paramount. In my case there is no real hurry from the coilguns point of view. The coils are "ON" for at least a millisecond at a time, followed by tens of ms of "OFF" time. So I've gone with the assumption that distance doesn't really concern me.

This was further encouraged by my first serious test setup where i had ~15cm between a gate driver mounted on a solderless breadboard and the MOSFET. The test went perfectly, it operated at ~10cycles/second (9ms ON, 91ms OFF) in 30cycle bursts, with no apparent trouble (no broken MOSFET). I lack the expertise and equipment to really measure things like turn on speed or such, so I have no idea if the MOSFET was operating well, or if a shorter better circuit would really pay off in the long run.

I would be fine with what i have, but the full-scale coilgun will be ~80cm long. If i place all the drive circuits on one board at the spot where i would want to have it, the longest distance would be ~60cm. Would this matter? I would prefer not placing individual gate drivers next to each mosfet (which must be under the coils due to space issues).

I use:

MOSFET:IXTN660N04T4
Driver:MCP1407
LiPo: 6S = 25 Volts
Coil: ~70mOhm, ~10-100microHenry

Thank you in advance!


texts: Is it dangerous if I do not connect the ATX shield to ground?

texts:
I'm living in an Asian country and there isn't a ground connection provided on sockets here. There is only L (live) and N (neutral) so I need to use a 3-to-2 converter. It means that the ATX case does not connect to ground like in other countries and when I touch the case I feel hurt by electricity.

When using a volt meter to measure, it tells me that the computer case reaches ~80v AC between me and the computer (Ground ---> Me ---> Computer).

I found an ATX power supply circuit and I found that the ATX shield is connected to the ATX AC input circuit between the L and N lines and there are two capacitors in the middle.

I'm very new to electronics and I don't know why they connect the shield like that and I think it may be dangerous in my case? As I see the shield is connected directly to the L line so it's very dangerous if I don't connect the case to ground?

See the circuit here :


texts: How to build a copy of the Franklin's bell

texts:
I read that Benjamin Franklin built the Franklin's bell using a long vertical rod connected to one bell, and another one connected to another bell and then going in the ground.

I did build a Franklin's bells machine and works nicely, but I have to create the electrostatic potential.

How did Franklin build his own machine at that time? How high was that rod in the sky? What are the dangers in doing this (I guess it is potentially dangerous using it during a storm with lightings in case I catch one and I touch the rod).


texts: What types of signals can a dynamic microphone generate?

texts:
And what design generates what type of signal property?

For example there are dynamic mics with or without output transformers. Do they differ in the type of signal outputted?

Do most dynamics generate a balanced differential signal where pin 3 is polarity reversed?

Also where and how is the pin 3 signal polarity inverted? At the voice coil? At the output transformer?

Thanks for any help!


texts: Single Opamp with "Isolated" positive input pin or method to invert the feedback loop ? (SOT-23-5 or other package)

texts:
To improve isolation between the input and the other pins of the circuit, I used MCP6001R SOT-23-5 Opamp which has a pinning like this:

I am interested by the fact that there is quite some space around pin 4 to do guarding experiments.

However, when I designed the board I made a mistake an I thought took the "-" pin as the "+" pin.

I looked for an opamp that would have the "+"-pin on pin 4, but I could not find any.

As I really want to keep the signal input "isolated" on pin 4, I should either find the appropriate opamp or introduce an inversion in the feedback loop.

Fortunately, I know that I can't do this, but unfortunately I can't think of another simple solution:

The above schematic is for showing the principle of applying negative feedback on the "+"-pin  - it does not show the OPAMP that is currently selected. Source of the schematic: Stability problem in unity-gain opAmp .

Questions:

Is there an Opamp out there that has the + input on pin4?  Idealy in a SOT-23-5 package, but other suggestions are also welcome.
Or a high impédance analog follower/buffer (<1pA input current) at a reasonable cost?
How would I introduce a simple inversion in the feedback loop on the positive pin without breaking the stability?

It does not have to be a follower, inverting is fine too and the amplification does not have to be 1 - it can be smaller.

My input signal is a low frequency, high impedance source.


texts: Connecting signalling lines of the multiple devices with different power sources

texts:
I started to develop a simple device and this question arose. I need to make some uC device that will be connected to the PCI-E bus via M.2 socket. And I need this device to be working even during computer sleep. Since computer (as probably mostly any other) has only 5v standby power, I decided to power it using 5v standby power. To to that, I've put some 5v to 3v3 converter to my device. Then I started to worry, is it safe at all? Of course, all ground planes are connected to the single ground circuit.
To make my question more common: assume, there are 2 devices powered by the same voltage but different power sources, each with its own power source. These devices have some data lane to exchange data. Is it safe to connect data lanes, as long as they have common ground? It's unlikely that both power sources will be completely identical, for example, for 3v3 one could be 3v20 and second 3v33, so logical "1" levels will differ. What is the solution for such a case - for both particular PCI-E case, and for common case with multiple uCs, powered from different sources with common ground exchanging data? Is it safe to connect them directly?
Update: for example, XIO1100 chip defines levels tolerance as "+0.5v" Is it standard? Cannot find any references to that.


texts: Op amp follower not actually following in LTspice simulation

texts:
I have a simple non-inverting follower circuit that I'm simulating in LTspice, but the simulation shows the output is 1.6 volts when it should be 1 volt. Any thoughts on why this may be? Here is a picture of the simulation.

Here is a description of the circuit:

2V in
Divide in half to 1V
Output of the op am is 1.6V ??? which does not make sense to me. This should be 1 V

Also I tried with several other op amps with similar results.


texts: Logisim Evolution Oscillation Apparent With RAM

texts:
NOTE: I am using Logisim Evolution, not the original Logisim

I created a simple subcircuit for a RAM chip in Logisim Evolution. It works perfectly fine unless I write to more than 1 at a time. It only happens if the chips being written have different values to write. If I do, it says both the subcircuits have oscillation apparent, and when I view any of them, the only place with oscillation is the output point of the RAM. What about this is oscillating in any way?

Here is the subcircuit:

The RAM piece itself has an address and data bit width of 4, triggers on High level, and separate databus for read and write.
It works perfectly writing any values in here, even if I copy and paste so I have two in the same subcircuit. Writing new values to this still works.

Here's the main circuit with 2 RAM subcircuits being written to at the same time:

It results in an oscillation error if I am writing to 2 chips at the same time with different values. If they are the same value or are being written separately, they write perfectly fine.

As you can see the only point of oscillation is the single output point. I have no idea why it would be oscillating or even how. Yes, I could make an 8-Bit subcircuit, but I'm trying to replicate my breadboard computer as accurately as possible to be able to plan new pieces easily.


texts:
I am a bit in trouble with finding a double insulated 10k NTC sensor and
I am questioning what double insulation really means.

Does double insulation mean, that there are really two different isolation materials on top of each other or is it enough, that the insulation material has double the thickness and so double the insulation resistance that is necessary for single insulation?

I contacted several manufacturers and the answere is mostly, that there is no breakdown at a specific voltage, for example 1500V.

Here is also an example from an NTC datasheet I found. Can one say from there if this NTC is double insulated?


texts: Moving Data, Bss and heap memory to external SRAM Atmega2560

texts:
This is my first question here, sorry if I miss something.
I’m using an Atmega2560 as main processor for my project but I’m running out of ram so I have connected an external 64 KB (64 x 8) SRAM to it. I searched around and found couple of projects and libraries that use the external sram:
http://andybrown.me.uk/wk/2011/08/28/512kb-sram-expansion-for-the-arduino-mega-design/
https://hackaday.io/project/21561-arduino-mega-2560-32kb-ram-shield
But all of these use the external SRAM as heap memory.
I would like to use the external memory as data, bss, and heap memory leaving the entire SRAM for stack.
I found this in the avr-libc manual:
https://www.nongnu.org/avr-libc/user-manual/malloc.html
Using the information from the manual, I changed the makefile for Arduino Mega bootloader here:
C:\Program Files (x86)\Arduino\hardware\arduino\avr\bootloaders\stk500v2
Link to original makefile:
https://github.com/arduino/ArduinoCore-avr/blob/master/bootloaders/stk500v2/Makefile
I changed “EXTMEMOPTS =“ to this:
EXTMEMOPTS = -Wl,--section-start,.data=0x802200,--defsym=__heap_end=0x80ffff
0x800000 is the offset for Harvard architecture, 0x802200 is the first address for the external memory.
I’m recompiling the bootloader with the new make file but I get the following error:

I believe it’s complaining because the address is outside the internal SRAM, I couldn’t find any way to fix it.
I’m not sure what’s wrong, what am I missing ?
Also if this gets solved Is it okay to initialise the external memory hardware (by setting XMCRA and XMCRB registers) in bootloader’s main function? If not where should I do it ?
Update: Here is the linker script: https://codeshare.io/aJom3K
Update 2: The first problem is solved now; I was editing the wrong ld file and after changing the correct file to the following It worked:
DATA_REGION_ORIGIN = 0x802200;
The next problem is where to initialize the hardware for external SRAM ?
I'm currently doing this in __jumpMain function of the bootloader which also sets the stack pointer register. Is this fine or should I do it somewhere else ?
bootloader: https://codeshare.io/5zNr1b
Update 3: As mentioned by @Brian Drummond in the partial answer, I changed the linker args to this:
EXTMEMOPTS = -Wl,--section-start,.data=0x802200,--defsym=__heap_end=0x80ffff,--defsym=DATA_REGION_ORIGIN=0x802200
and reverted the changes to the build script to avoid problems in the future.
For anyone doing something similar:
You also need to add args for changing the DATA_REGION_LENGTH to the new length otherwise, it will only use the old length which in my case is: 0xfe00.
Update 4: After some testing, apparently the MC is not using the external SRAM; after programming it with the new script I can disconnect the SRAM and it will continue to work fine. Also I checked the data and address lines to the SRAM and nothing is being written or read.
So I'm back at the beginning, Any ideas what's wrong ?


texts: Moving the magnetic field around a fixed conductor?

texts:
From this figure:

And many others related to electromagnetic induction, the main component of motion would be the conductor perpendicular to a magnetic field.

I know it's possible to have it the other way around, fixed conductor and move the magnetic field source(e.g magnets, electromagnets), but I'm curious of the type of force the magnet/electromagnet would experience when current flows to the stationary conductor.

In a typical generator(where the wire rotates around a fixed magnet(s)) there is an induced EMF(vBL) and current will flow to the load, and due to the induced EMF is opposing the change in magnetic field flux, the Lorentz force acting on the wire will oppose the applied motion(v), what about the case when the magnet rotates around a fixed conductor? Will it experience a form of force opposing it's motion(besides eddy currents)? When the conductor has current flowing?


texts: Dual Fuel Senders - Shared Fuel Gauge Circuit Help

texts:
Just planning should I ever convert a car to run dual fuel i.e. Petrol and LPG/Autogas and decided I don't much like the way the gauges are done in most installations, so I decided I wanted to find a solution I prefered.

Currently most LPG conversion come with a small square gauge thats just stuck on the dash somewhere and looks awful aesthetically (pic 1), I came to the conclusion that using the standard car fuel gauge would probabally look best.

I decided I would use Yenka to try and create a solution and using a few transistors (PNP & NPN) I thought I had come up with the answer. I have 3 LEDs in the diagram, 2 to indicate the fuel source and 1 to indicate the gauge getting the feed. The diagram (pic 2) should make it fairly clear what I was attempting to achieve, but I overlooked one thing that I think would cause major issues.

Fuel gauges/fuel senders work on resistance and I've added and used LEDs, resistors and transistors which I assume will all help to give a false reading.

How could I switch between two separate fuel sender feeds without affecting the resistance values and therefore have a false reading on the gauge?


texts: Designing footprint for LFCSP CP-8-13 what should be the pad size

texts:
I am scratching my head to create a footprint for ADA4817 which comes in LFCSP CP-8-13 package. I reckon this package is only used by Analog Devices.

The main problem is I do not know what should be the pad size for the pins. The pins are stated to be 0.25mm in width and 0.40mm in height with a semi-circle ending:

So these are my concerns:

What should be the pad size be (copper) for each pin
What should be the glue size be (for stencil)
The copper shape should be a rectangle, or I should care for that round ending on the pads?
My other concern is the distance between pins and the exposed pad. Can I get away by making the exposed pad footprint smaller than the actual exposed pad size? e.g. going with a 1x1mm square instead of 1.4x1.4mm?


texts:
I'm designing a PCB to host an Applanix APX15 GPS/inertial navigation device. The hardware integration manual (which seems not to be publicly available) shows that a 10/100 BaseT Ethernet is supported via four pins on the board and explains that the magnetics are on the APX15, but little else.

Is it really just as simple as connecting these four lines to the RJ45 jack? Are other components required? How about trace widths/lengths and impedance? Grounding? Are there any gotchas with respect to e.g., routing TD to RD and vice versa? (I'm having difficulty finding schematics or explanations of this topic suitable to a novice like me.)
Note: I have tried naively connecting these pins to an RJ45 jack with no magnetics, but it doesn't work. Ethernet works fine with the test board (which has its own magnetics identical to those on the APX15) that came with the device.
Edit: There is a Pulse HX1188FNL chip (magnetics) on the board. Link goes to a datasheet with a schematic that reflects the APX documentation, with the addition of connections of the remaining pins to chassis ground via a resistor and capacitor.
Edit 2: Found layout guidelines for the magnetics on the APX. For now I'll assume that this 4-lead connection will work, but my impedances are messed up.
Edit 3: It has been suggested that this is an MDI-MDIX problem. If I'm connecting a straight-through (not cross-over) ethernet cable from my computer to the device (which works on the test board), the device should behave as the Hub MDI-X device in this image:

I had connected pin 1 to TD+ but perhaps I should be connecting pin 1 to RD+, etc.
Edit 4: It turns out the four leads do have to be reversed, which is equivalent to using a cross-over cable. So RD+ goes to TD+, and RD- to TD-, etc. Then, everything works as expected.


texts: What are the limits & capabilities of Op Amps with AC signals?

texts:
I have learned about op-amps from Practical Electronics for Inventors and The Art of Electronics, but they do not talk much about op-amps with AC input and output. Maybe I missed it and it was "hidden" in the textbook, but to my comprehension, they did not talk much about it.
I know about DC op-amps, but I want to know how op-amps work with AC.
So my question is, what are the capabilities/limits of op-amps for AC applications?

Some things I would like to know (but not limited to):

What is the maximum frequency an op-amp can amplify?
Does an op-amp amplify the RMS value of the AC signal or the peak value? Does this apply to both voltage and current?
When the op-amp receives a negative swing of the signal, does it make it more negative?

And if there is anything else that is important to know, please post it in your comment or answer.
Thank you.


texts: Voltage of capacitors after long time (RC Circuit)

texts:
I'm currently taking a course in electromagnetism, and I got stuck with this problem:
The Problem:
All of the resistors and capacitors have the same values, R and C respectively. The circuit is analyzed after a very long time. What is the voltage on the capacitors?
My Reasoning:
After a long time, the capacitors charge up and every loop that contains a capacitor has no current flowing.
C1 was charging through current I, I then was split and the rest of the capacitors where charging with current I1.
So the moment the current stopped flowing in the circuit, C1 built up Q1 charge and the other capacitors built up the same amount of charge Q2 (Same current flow through them for the same amount of time)
For some reason I get weird results, I would really appreciate it if someone could point to my mistake


texts: Assumptions for an op-amp and when they do and don't hold?

texts:
Correct me if I am wrong but the following is what I think the assumptions we make for an ideal op-amp:

Negative feedback (output connected to the inverting input):

No current goes into either of the inputs
The voltage at each of the inputs is the same
We assume that \$A\$ in the formula \$V_{out}=A(V_+-V_-)\$ is equal to \$\infty\$. (Does this need to be infinity or can it just be very large?)

Positive feedback (output connected to the non-inverting input):

No current flows into either of the inputs
The output will always be at saturation (or heading there) (it is bistable) (This  does however follow from the other assumptions, namely the one below)
We assume that \$A\$ in the formula \$V_{out}=A(V_+-V_-)\$ is very large. In this case however I don't think we have to assume that it is \$\infty\$.

In all other cases we assume that no current flows into the op amp.

If we have positive and negative feedback, all we can assume is that no current flows into the op-amp and the voltages depend on the circuit in question. In the specific case of the astable multivariate it happens that the output voltage changes between its two saturation values.

So here are my questions:

Firstly, is the above correct and is there any further assumptions that I can add?
Are there any exceptions to the above rules (staying of course with ideal op amps)? I was thinking about e.g. a capacitor in the negative feedback situation, like in an op amp integrator circuit, could the rule about the voltage across a capacitor not been allowed to change instantaneously mean that the assumption that the voltages at the inputs are the same does not hold?

Is it possible to have a circuit with positive and negative feedback that does not go to one of its saturation points?

If you want me to expand on any point, just ask. Thanks.


texts: Digital signal controller with GNU toolchain?

texts:
Does any manufacturer offer a digital signal controller (which basically means a microcontroller with some DSP functionality like a MAC instruction and other stuff) to which I could compile software with GCC? dsPIC apparently use Microchips own C30 compiler which is a GCC spin-off but it is not free (as in free source code).

I'd just need a few ADC channels, two DAC channels and an FPU so nothing too special.

I'd like to try to stay away from single manufacturer toolchains if possible.


texts: Which aluminium extrusion for LED strips has better cooling?

texts:
I have a choice of two aluminium extrusions for LED strips. They have identical dimensions, except the one on the left has "wings" on both sides.

They will be installed in free air, suspended 10-20cm away from the ceiling for good convection cooling, LEDs pointing down (ie, upside down from the illustration).
Question: which one will have better cooling? Will the extra surface area of the "wings" help ? Or will they push the airflow away from the sides and back, making it less efficient?


texts:
What are the principles of implementing Ethernet over power lines ?
Is it reasonable/possible to create an Arduino shield which will provide both power & network ? (properly isolate the "dangerous parts")
Mains is 220V 50Hz where I live.


texts:
How can I convert the binary data to voltage: where each sample stored as 2-bytes(16-bit signed integer); and the resolution of the ADC is 14-bit with -10V to 10V range?

I tried the following which didnt work:

voltage= (20/2^14)*data - 10; (where data is a signed 16-bit integer per sample)


texts: Opamp output on loaded and unloaded cases

texts:
I have a design project to rotate a motor. In order to do that, I have designed a very simple but smart circuit. However, in signal comparison stage, if it is unloaded, i.e. not connected with the next stage of the design, it gives the output as expected. However, if connects two stages, if gives unexpected outputs. I could not express this situation. Design and test results are given as attached.

Could you help me to express what is wrong?


texts: Can somebody give me a technique to power a laptop with AC to DC supply with connection to laptop battery pins

texts:
It's my first question here please bare my language and long paragraphs.
I have this lenovo R400 it was running without battery for 7 years. All of a sudden it turned off and didn't show any activity.
I tried all the possible ways to connect with DC plug. Checked the plug,  wire and voltage; and everything is alright. Then I took it to a repairing guy, whom I trust, to check it thoroughly.  He came up with repairing strategy but gave me 0% guarantee that it would be successful (and there's 99.99% of it becoming dead).
I can't lose this computer. So, I bought new battery and it's running with it, but problem now is that it doesn't charge. It has lost the ability to charge as it does not detect DC plug.
I connected 12v 2.5A DC pins directly to battery junctions but it charges very slowly.  It takes 10 hours to charge for 36% and then it gets stable at 36%. However, the laptop consumes more power and the battery drains in 2 hours even with the DC input still connected.
The battery output voltage is 11.1v and its 49Wh with 6 cells. I attached a picture of outputs from battery. I don't know if its series terminal outputs or resistance varied voltage or resistance.

If there's anybody who can suggest battery terminal outputs and resistance so that I can mock a battery it'll be helpful.

There is no concern of data or anything like that, i just want it to run so i can donate it to needy students. I already mentioned about charger and plug its alright. I just need to know if this hypothesis works or not. Consider it as experiment. We need to find a way I'll update if i got succeed please enlighten me with  your knowledge so that it becomes handy of there's any way to mock a battery. That's all!

The dock station also use same charging ic so it's not working anymore.
i left it connected for another 8-10 hours with a 7.2Ah Pb acid battery+ 16v DC supply in parallel circuit and it acheived 90% of battery backup.


texts: Would there be a magnetic null point of a flat coil when pulsed dc is passed through it?

texts:
Flat coil is only of a few turns and does not go upto the center and also has a consistent pulsed dc passing though it.

Shouldnt the electromagnetic radiation cancel out each other and have null effect in the center of the coil ? I understand that energy cannot be destroyed but shouldnt magnetic effect be nullified?


texts: Are there any open design files for an NXP LPC1* breakout board?

texts: I would like to build a board for an LPC1* processor. Are there published Eagle layouts for these?


texts: What is meant by the Sending end and Receiving end in 3 phase electrical circuits?

texts:
I do not understand the what sending or receiving end means in 3 phase circuit analysis.

Aside:
Also I am struggling to understand 3-phase just in general with respect to circuit analysis so if there are any links to helpful sites, please add them.

Thank you


texts:
I have made a four bit adder with carry-in & -out that contains an unsigned and signed architecture:

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

entity four_bit_adder_w_carry is
    Port ( A    : in  std_logic_vector(3 downto 0);
           B    : in  std_logic_vector(3 downto 0);
           Cin  : in  std_logic;
           Sum  : out std_logic_vector (3 downto 0);
           Cout : out std_logic );
end four_bit_adder_w_carry;

architecture signed_impl of four_bit_adder_w_carry is
    signal total : std_logic_vector(4 downto 0);
begin

    total <= std_logic_vector(resize(signed(A),5) + resize(signed(B),5) + signed'('0'&Cin));
    Sum   <= total(3 downto 0);
    Cout  <= total(4);

end signed_impl;

architecture unsigned_impl of four_bit_adder_w_carry is
    signal total : std_logic_vector(4 downto 0);
begin

    total <= std_logic_vector(resize(unsigned(A),5) + resize(unsigned(B),5) + unsigned'('0'&Cin));
    Sum   <= total(3 downto 0);
    Cout  <= total(4);

end unsigned_impl;

When I am testing the two different architectures I do not notice a difference in the output that I am getting.
What is really the difference between these two and what inputs should I choose to show that there is a difference between them?


texts: Ideal diode using PMOS and two PNP transistors not behaving as expected

texts:
I'm using the circuit given in the example here:
Understanding an 'ideal' diode made from a p-channel MOSFET and PNP transistors
[a]

Basically there are two issues.

In the forward direction [Vin = 15V on IN] it appears as if the gate voltage is only just below the positive rail, it is not being pulled to ground, which may have implications for higher currents. Purple is the gate voltage, also indicated by cursor A which reads 11.6V.

[b]

The ideal diode works below 13.4V in the reverse direction [VIN 10V applied to OUT] but as soon as the voltage rises above this current flows to the input side.

[c]

[d]

From these c and d you can see that the mosfet gate is kept at VIN and at 10V there is no voltage rise at the input, but at 15V there is 2.7V at the input.  If the mosfet is off it where is the current leakage coming from?  The IRLML9301 is rated to 30V Vds and 20V Vgs so it should be fine.  It blocks 20V in the reverse direction just fine when the gate is pulled high.
I have tried a few resistor combinations with no change and my simulation in iCircuit does not reproduce this behaviour.


texts: Can a Zener diode be used in place of a Schottky?

texts:
I want to use a LM226677 Voltage reagulator to achieve a step-down converter from 12V to 10V. However, in  a Schottky diode is used reversely polarized at the output of the LM22677, and the datasheet claims "A Schottky type power diode is required for all LM22677 applications. [...] The reverse breakdown rating of the diode should be  selected for the maximum V_IN, plus some safety margin. A good rule of thumb is to select a diode with a reverse voltage rating of 1.3 times the maximum input voltage." datasheet

Not being able to find/get hold of Schottky diodes with a reverse breakdown voltage of 12V~15.6V (lowest I can find is 20V), I was wondering if it is possible to use 20V reverse breakdown Schottky diode or replace it with a zener diode?


texts:
How to calculate check practically POWER of SMPS required for desktop computers

I have  10 desktop pc in one PC i have a high end gaming  gigabyte motherboard with AMD processor graphic card and cooler master  premium extreme cabinet with 5 big cooling fans. I have  600w corsiar true power smps installed in it but still fans and PC works slow

In other desktop PC  I have another medium end gigabyte  motherboard with  normal cabinet with 1 cabinet normal small fan and have 450w normal zebronics smps

Both PC was lagging and slow   and 450wat smps was overheating and just shorted or blasted  then I changed it with corsair true power 600watts smps in medium end desktop pc and founded drastic change in speed of PC with no HDD or other lagging problems and speed and performance was great and I  came to know the difference and need of smps true power

So I decided to purchase true power smps for all my desktop machines but all of them have different boards low level medium and high level

Now my question is that

As motherboards ram hdd graphic cards cpu cabinets fans dont specify the power they need to operate in.
How can I monitor or check through software app or device that how much  watts will they required for optimum performance
As in market 450 550 600 800 1000 watts smps  are available which one will be good which pc
Is there any reading available in BIOS windows of any power consumption
If I give more wattage to lower end  will it damage the board or components
Many companies write 600 880 watts how to check before purchasing if they are true power or nor

Waiting for precious and professional advice suggestions and thanks a lot in advance for your help and advice in advance


texts:
I am sorry guys if I didnt make myself clear. So here is an another attempt.

I am trying to view the output of MPU6050 (gyrometer + acclerometer) in Processing IDE. I added the FreeIMU library in arduino and then executed the FreeIMU quaternion code from the examples. I was able to see the change in data values in the serial monitor of arduino.
Now I wanted to see a graphical output using Processing IDE using FreeIMU Cube example.
I am just not able to proceed furthur from here.
Kindly provide me with the steps from here onwards. See video:
https://www.youtube.com/watch?v=gU9vM0UE3Ug


texts:
I'm trying to make a PSU for a Zero88 Juggler lighting desk (as ours has been misplaced and a new one is £70) and am struggling to find a transformer to be able to power it. The pin out on the back of the desk (picture attached) shows 5V 12V -12V 0V and ground. I was wondering whether anyone could help with how I would be able to craft a PSU for this?

Thanks in advance


texts:
I would like to match the output impedance of amplifier IC (1.5 + j1.7) with an antenna of impedance (50 or 75 Ohms) at around 950 MHz.
I thought of using a balun so that I could avoid the inductor and capacitor.There are 1:1 or 1:4 or 1:10 or 1:16 impedance conversion baluns. But here I have complex impedance at the source.
Could any one recommend how to deal with this ?


texts: Strange noise at peaks of measured sine waves STM32F103

texts:
Please look at this picture:

I'm using STM32F103, a popular Blue Pill module. What you can see in the picture are three signals, from bottom:

green - AC voltage of 14V RMS, measured with step down transformer (400/6 ratio), then amplified, filtered and then applied to ADC by resistor divider.
red - AC current of 60mA RMS, measured with ACS712 5A Hall effect current sensor. Then by resistor divider it is applied to ADC.
blue - the same AC current as above, but amplified three times with LM321 (with exact values from documentation's example).

Details about STM32 program:

sample rate was set to "ADC_SMPR_55_5" in circular mode - ADC was constantly measuring and buffer was updated every 55 cycles with an averaged value (but changing this setting did not improve anything as it works way faster than 50 Hz),
in the above picture you can see 500 samples taken with distance of 50us, not averaged,
ADC of this uC has resolution of 3.3V/4095

As you can see the noise appears at peaks of measured sine waves and I have no idea about its source. I ask you to help me identify it. I know I can simply average it but it will introduce phase delay which is not acceptable (especially in the current signal, as my control loop in the final project will be oriented on the current signal).

What I tried so far:

Since both sensors are close to each other I thought that maybe the transformer interferes with the hall sensor, so I removed one sensor and checked the value from the other, but the noise was still apparent.
Initially both sensors and microcontroller were supplied from SMPS but changed it to linear ones, noise still there.

Edit:
I did an oscilloscope measurements and here is what I got:

Edit2:
About load - the load that was measured is 220 ohm 5W resistor. Also the voltage across the resistor is pure, non-deformed sine wave so there's no source of any distortion in the load circuit.

Edit3: setup photo

schematic1:

schematic2:

edit, last one:

So, I changed resitor dividers at the output of the sensors from 33k/68k to 3k3/6k8. It helped a little bit. Unfortunately don't have space to add voltage follower. The noise was still apparent when I supplied the sensor from battery. I guess high impedance output and long wires picked up noise from the air.

One thing worth to mention is that ACS712 5A chip according to datasheet has its output noise up to 21mV, that means with accuracy of 185mV/A, any measurement below 100mA can't be reliable. I connected a small 12W lamp to the output and it doesn't look that bad at higher amperage (about 1A of current).

Anyway, thanks you guys for help! Lesson for me was that the next time I will be doing any signal measurements I will convert them to digital before passing them to the wires.