texts: Issues with displaying graph ltspice simulation of CB characteristics

texts: Sometimes when I simulate the CB or CE characteristics of a BJT, for the input and output characteristics I get a graph that is inverted (upside down) rather than looking the way it normally should. The currents are all marked negative instead of positive. Any reasons why it should appear like that?


texts: Capacitor's energy required for a predetermined drop in its voltage - with LDO and constant current elements as load

texts:
I am trying to understand how much energy a circuit (composed by some passives here called analog, and an MCU) will require. The system is powered through a capacitor, and the "passives" are actually some low power op amps attached directly to the capacitor, like the following schematic:

simulate this circuit – Schematic created using CircuitLab

The MCU is powered through an LDO, and has a determined active time while otherwise is in sleep (now for simplicity I consider sleep equal to 0mA), but the active part is always on.

I need to understand how much energy the system requires to have a predermined drop in the capacitor voltage. From such results, I will define the next design steps or various tunings.

The approach was to compare the total energy required, given the capacitance in consideration, with $$ E = \frac{1}{2} C (V_{0ms}^2 - V_{10ms}^2) $$

The MCU activates with a given duty cycle, and I need to calculate the energy balance only in this period of time, with a given MCU duty cycle. Example, the MCU wakes for 1ms every 10ms, so duty is 1ms and period is 10ms. Duty cycle is 10%. I only want to know the power balance over 10ms, because afterwards the capacitor will gets fully recharged before the next cycle.

But here the problem:

I can calculate how much drop in the capacitor voltage I have with a given energy, but because the energy can be rewritten in $$ E = P t = V I t $$, I can use this form to check, in the duty time activity, how much energy is drawn form the MCU, LDO and active components and check it against the capacitor's energy calculated in the initial formula (related to a given drop).
Despite this assumption, because the energy is th eintegration of the power over time, I am not sure if makes sense to calculate the energy of the active part in this way: $$ E = (V_{0ms} - V_{10ms}) I_{active} t_{10ms} + (V_{0ms} - V_{10ms}) I_{MCU} t_{1ms} + (V_{0ms} - V_{10ms}) I_{MCU sleep} t_{9ms}$$  What would be the right approach?


texts: Replace speaker to retrieve audio signal (and isolate galvanically)

texts:
I'd like to capture sound from a speaker output.
The system seems to be running with a small DC current (bias, so voltage across speaker is about 3 V), so the audio AC signal could be (de)coupled from a load resistor via a small capacitor.

The 10 kOhms resistor drops the 6.5 VDC (open circuit) to 5 VDC. The audio signal is in the order of 10 mVpp.

I would then need to amplify this signal and achieve some sort of galvanic isolation. Probably an opamp and a low frequency audio transformer (<1Vpp according to https://en.wikipedia.org/wiki/Line_level).
However, this requires a power supply for the opamp which would be tricky to derive from the system, so I'd need an isolated dc-dc converter.

simulate this circuit – Schematic created using CircuitLab

Audio quality is not a priority - a simple circuit is (one-off build).

If the "primary" circuit could be eliminated using a high impedance transformer directly, it would be even better. The secondary signal then could be brought to line level with a transimpedance amp.

Maybe a mains voltage relay coil with >10 kOhms could be used creatively (but: core? secondary?)? Is a high sensitivity hall-effect sensor a feasability?

Any ideas appreciated!


texts:
I'm trying to understand something about electricity. Is electricity being wasted when you use it?
I mean when you use an electrical appliance, you need to plug it into a socket right? So you create a circle, where electricity goes into your device and returns back into socket... So does any of electricity actually wasted by the device, or does it just go through the device?
Understand what I mean? What the difference between electricity traveling through power cables, or traveling through a TV or a washing machine?


texts: Coilgun capacitor reverse voltage in my schematic?

texts:
I'm going to build a coilgun and have thought about all possible problems, which I solved except the reverse voltage problem. I designed a schematic based on some other schematics I found online. My question is whether the capacitor in my schematic will be able to explode due to reverse voltage or not.

It is a polarized electrolytic capacitor rated for 200v with a capacity of 2400uf (4 x 600uf in parallel). I calculated a graph of the current and the capacitor's voltage, which showed me the voltage of the capacitor will become negative before the current goes through zero, which would deactivate the thyristor which will be used to trigger the circuit. I've added a diode with a resistor next to the coil to absorb the back emf, and a diode with a resistor next to the capacitor to absorb the reversed voltage which could be created across the capacitor.

The 120V DC will be generated using a boost converter with a constant current function that I will be using at around 200mA

Will the capacitor be damaged or not in the following circuit and why? If so, can it be fixed by reducing the resistance of the 2 ohm resistor next to the capacitor?

The graph shows the voltage across the capacitor in red with a peak voltage of 120v and the current through the coil in blue with a peak value of 80A. The total time plotted is 15ms.


texts: is 1.5V accepted tolerance for amplifier power supply

texts: I have A200 Creative speakers with 10.5 V, 1 A transformer which not working, and i can buy 12V-1A transformer only. Is 1.5 V accepted tolerance for the amplifier power supply?


texts: What measures are taken to control inductance in switching stations?

texts: I was thinking about the effect of changing loads on the power grid and I'm curious about the effects of inductance, how much inductance there is, and how to prevent it from causing voltage changes at the outlet. I'm a layman.


texts: I have been trying to implement an assembly routine in MSP430 for division. I already got the code for the division from the Horner Division Algorithm. The problem is that I only got the integer part. How I can get the fractional part from a division? For example: 5/2 = 2.5. How do I get the 0.5 part?


texts:
I am using this buck converter.
Schematic:

Buck Converter Specifications :

Input Voltage - 18V to 32V
Switching Frequency - 300kHz
Output Voltage 9V
Load Current - 0mA to 200mA Maximum.

When measuring the switching frequency using an oscilloscope, I am placing the probe directly on the TP1102 and also measuring the output voltage on the 47uF capacitor pad.
I got the below waveforms :
Input voltage of 14V:

However, with the same input voltage, I am just removing the probe which was placed at the switching frequency node. Now, I didn't observe the ringing.
Input voltage of 14V without probing the switching frequency :

As you can see, the ringing vanished once I disconnected the probe.
Can someone tell me how this ringing at the switching frequency node is happening even though I am probing at the TP1102 and how this is coupling at the other probes also?
Please also provide a solution on how to avoid this ringing while measuring the values.
Below is the ringing frequency:


texts:
After running the design through the Errors Tool and moving a route that had insufficient clearance, I'm left with this blue segment that is overlaying the red route.

Why is it there and how can it be removed?

Another unwanted blue segment.


texts:
I have question about mixer IC (Max2335),

datasheet:
https://datasheets.maximintegrated.com/en/ds/MAX2335.pdf

LNAOUT and MIXIN in pin description (p. 5) have notice:
"Requires an external matching network".
As I understand these external components (like on schematic - p. 9) are part of 50 Ohm matching impedance with LNA output and separately MIXIN input?

Thanks for any answers.


texts: Super Basic Inrush limiting for super capacitors

texts:
I have 6 x 500 farad super caps in series.  I want to use them to smooth voltage dips in a 12v system that is powered by a DC-DC converter.  Currently my application is a water pump (desalination) that builds pressure and releases it through a check valve, cycling like this every 3 or 4 seconds.  As the load increases the voltage drops slightly, which slows the pump slightly, and over many hours would decrease the total output of the pump.
The DC-DC converter says it is "Suitable to buffer-charge a battery"  Which makes me think it has some current limiting built in.  But I have killed one before when I shorted the output, and i'm not keen to
kill another one.
My intention is to put the cap bank in parallel close to the motor, with a 20 amp fuse and a large 0.5 ohm resistor inline with the positive cable coming from the Cap bank.
I will pre charge the caps, so as to limit the inrush anyway, but in a situation when they self discharge for some reason and they are cut off from the DC-DC converter I don't want them to turn the DC-DC converter inside out when I flip the switch.
As I say I REALLY don't want to kill my DC-DC converter, so I want to see what those in the know have to say about my plan.


texts: Self resonant frequency of buck converter

texts:
I know that one can calculate the self-resonant frequency for an LC filter of a simple buck converter(having one inductor and one capacitor at the output) by the formula 0.5*pi*sqrt(LC). My question is if we add another inductor at the output of the converter following the capacitor, forming T type LC filter, will the self resonant frequency for this circuit remain the same ? Or will it change ?
What i mean to ask is that the self resonant frequency of circuit (a) and circuit (b) would be the same ?

The reason for asking this question is that i am supposed to design a current controller for my buck converter. And the controller should be designed in such a way that the controller bandwidth is higher than the circuit's self-oscillation frequency. So initially i had no T type filter, just a simple circuit like (a), and i designed a current controller whose bandwidth is greater than 0.5*pi*sqrt(LC), but later i added another inductor to filter out the current more (which is being supplied to the load). So now i am not sure if my circuit filters self resonating frequency would be same or not (which means my old controller design would work fine or not)

P.S my question may be very basic or stupid, but i dont have detail idea of power electronic components, so i posted the question as i couldnt find anything regarding this on the internet.

Your helpful suggestions and comments would be appreciated.

Thankyou!


texts: What happens if a solder joint cools before all the flux has evaporated?

texts:
Sometimes, when soldering, I see little bubbles come out of the hot joint.  Presumably, this is the flux evaporating and escaping as a gas.

What happens if I remove the iron and let the joint cool before all of those bubbles can make it out?  Can the excess flux weaken the joint electrically or physically?


texts:
I've got an FM25L16 FRAM part in a board design.

For a new part from the manufacturer, what are the initial data values? All 0x00, or all 0xFF, or other? I can't see any documentation of that in the datasheet I've got.


texts: How to cascade multiple look ahead adders

texts:
I know how we can prepare 4 bit look-ahead carry adder (CLAs) to avoid delay involved in rippling of carries in ripple carry adder. We calculate various signal in CLA as follows:

Carry propagate signal $$P_i=A_i\oplus B_i$$
Carry generate signal $$G_i=A_iB_i$$
Sum $$S_i=P_i\oplus C_i$$
Carry $$C_{i+1}=G_i+P_iC_i$$

For 4 bit CLAs,
$$C_4=G_3 + P_3G_2 + P_3P_2G_1 + P_3P_2P_1G_0 + P_3P_2P_1P_0C_0 $$

As you can see, last term above requires 5 input AND gate. As we go one increasing bit count of input operands A and B, we will require AND gates with larger and larger inputs / fan ins. Some sources say, we can avoid this by cascading 4 bit CLAs to get 4n bit CLAs, for n=2,3,4,... However I dont fully get how we can prepare CLA for 4n bits as books / websites rarely explain it well. One good source I found is this pdf.
It gives following diagram:

Diagram 1 (D1)

I didnt get it fully from pdf also, but got some hints. So I tried to figure out the same on my own. I need confirmation of my understanding. Below is what I have thought and figured out.

  Consider this CLA block diagram:

  Diagram 2 (D2)

  Considering above 4 bit CLA, I prepared block diagram of 16 bit CLAs as follows (please right click image and click "Open image in new tab" in Chrome browser for zooming in):

  Diagram 3 (D3)

  I prepared D3 myself and hence I need confirmation for correctness of explanation I have given in below numbered points, more importantly points 4, 7 and 8:

  In D2, all things which are done outside of carry look ahead block (green and blue gates) is done inside PFAs blocks of D1. (You may have to read the pdf to confirm this.)
  All boxes in top most row of D3 corresponds to green gates in D2. Blue XOR gates calculating sums Si in D2 are not shown / ignored in D3. In D2, carry lookahead block is shown to have P and C as output. In D3, I have shown only C as output of carry lookahead block (CLA blocks in 2nd and 3rd rows), as D3 ignores sums.
  Since PFAs in D1 also contains logic to calculate sum, they also have carry input from Level 1 CLs. This is not the case with blocks in top most row of D3 as they do not contain the logic to do sum, blue XORs in D2, but contains only logic of green gates of D2.
  Following naming in D1 is incorrect:

  It should have been:

  The red colored carry signals in D3 are not generated or are ignored as we dont want rippling carries. Instead green colored carry signals are produced (as per look ahead logic) and used.
  Red colored P and G signals in D3 CLA 2 are also unused / ignored
  Green colored C15 output of D3 CLA 2 is final carry. It is produced by same logic as carry logic specified above: $$C_{15}=G_{12,15}+P_{12,15}G_{8,11}+P_{12,15}P_{8,11}G_{4,7}+P_{12,15}P_{8,11}P_{4,7}G_{0,3}+P_{12,15}P_{8,11}P_{4,7}P_{0,3}C_0$$
  Does OC block in D1 represent above equation only? (I dont think so because there is no such explicit block in D3 accepting G(0,15) and P(0,15) as input.) (You may have to read pdf to confiem this.)
  In D1 and D3, $$G_{x,x+3}=C_{x+3}$$ and $$P_{x,x+3}=P_{x+3}P_{x+2}P_{x+1}P_{x}$$
  that is, they dont follow standard equations of Pi and Gi (repeated below): $$P_i=A_i\oplus B_i$$ $$G_i=A_iB_i$$


texts: Push-pull configuration over single mosfet

texts:
I'm dealing with a simple application in which I need to drive a pure resistive load and to control it by voltage. I control the load through a pwm signal coming from a microcontroller in 5V logic. The pwm frequency can be easily set from a few hertz to several kHz. The supply voltage is 24V and the maximum absorbed current is 15A.
I wonder, what are the advantages in using a more complex push-pull configuration over using a single power mosfet?
I am aware that push-pull configurations are usually considered more efficient, but what about using a single mosfet with extremely low rdson?
In example, a single IRFS7430-7PPBF would be enough? With the current values required this mosfet seems to be dissipating only 0.17 W in worst conditions.
At this point I would prefer the single mosfet configuration over a more complex and costly push-pull configuration.
What about if there is a need of linearizing the output of the driving stage with an inductor and a capacitor? Would the push-pull configuration offer bigger benefits over the single mosfet?


texts: Antenna Coverage Area using H-plane E-plane diagrams

texts:
On many antenna product sheets the H-plane and E-plane angles are given. On some data sheets you can find the diagrams for aformentioned planes.

Are these values the same as where manufacturers define the azimuth and elevation diagrams, so one can figure out the coverage area or are these two definitions unrelated?

I.e. Is H-plane == azimuth? and E-plane == elevation?
Or more accurate, can H-plane and E-plane diagrams be used for coverage computation?

See for e.g this, no info is given regarding azimuth or elevation.

Tnx


texts:
I am using ADM2482, Isolated RS-485 Transceivers. I need to calculate total max power needed to Drive this circuit.

Specs are
1. Logic side voltage is 5V
2. bus side voltage is 3.3V
3. Speed 1 Mbps.
4. RS 485

In datasheet it it given

SO what will be my total power needed to drive this circuits.

= 5V*6mA+3.3V*50mA=195mW ( total power) only  ???

what about the short circuit current shown in attached pics, do I also need to consider this current , if yes that which side Logic side or bus side.

if logic side

=5V*6mA+3.3V*50mA + 5v*250mA=1.4W ( total power)

if bus side
=5V*6mA+3.3V*50mA + 3.3v*250mA=1.02W ( total power)

Does RS485 need this much power (1W/1.4W) to operate ??


texts: Why is my Arduino Ethernet shield getting hot?

texts:
I just got an Ethernet shield, but I'm having some problems. After about a minute of being powered, it gets fairly hot. The PWR light is red, but otherwise, it works fine.

I'm using an Arduino Uno with a HanRun HR911106A 10/49 shield. Is it faulty, or am I not connecting it to power correctly? It heats up both from battery power and from USB power.


texts: Why is an opamp with single corner frequency more stable?

texts:
I read that freq. compensation is done to adjust opamp's corner freq. to single one.

A text mentions:

....

Freq. compensation does that i.e reduces corners to one for stability:

But why is an opamp with single corner frequency more stable than the one with two or more corner frequencies?


texts: Does the resistor divider value used in adjustable linear regulators matter? If so, to what extent

texts:
I will use the adjustable LT3015 as an example. http://cds.linear.com/docs/en/datasheet/3015fb.pdf

You can set the output voltage based on the equation Vout=-1.22(1+R2/R1) + R2*Iadj where Iadj is 30nA nominally.

Now, the datasheet shows nominal R1 values for different output voltages. Most of these nominal R1 values are around 12K, giving us a resistor divider current of ~100uA. It also mentions that the R1 value should be less than 50K to help keep R2 value low enough so as to minimize errors from the adj pin current.

My question is, is there a specific reason they chose the nominal R1 values to have a 100uA divider current? Is there anything stopping me from using much lower values, lets say in the hundreds of ohms?

I understand that will increase the quiescent  current(correct me if I'm wrong), but if I don't care about that, does it matter? Are there any pros and cons regarding transients or efficiency depending on what my resistor divider current is?

In their table of output voltage resistor divider values, for -5V they have R1 as 12.1Kohm and R2 as 37.4Kohm. Why not R1 as 1Kohm and R2 as 3.09Kohm?

Is this something I should contact LT about or is there an actual reasoning. Looking at other regulators, I don't think it specifies either.


texts:
I'm trying to get going with the RPI-1391 sensor but I'm obviously doing something wrong.

I'm connecting it to a Raspberry Pi, where:

Pins 1 and 3 are connected to Pi's ground
Pin 2 is connected to physical pin 2 on the raspberry (5V)
Pin 5 is connected in series to a 270 ohm resistor which is connected to 5V on the raspberry as well
Pin 4 is connected to a GPIO pin set up to listen for changes in voltage configured with an internal pull-down resistor.

I tested my GPIO pin by supplying 3v to it directly from physical pin 1 on the raspberry and my program is successfully reading changes in the state.

With this setup I insert a piece of plastic in the sensor's opening and nothing happens, where I expect to see a changed state on my GPIO pin.

Things to consider:

Previously I connected the sensor's pin 5 directly to 5V before I knew better which should have burned the IR LED, however I tried connecting a white LED in series to pin 3 and then to the raspberry's ground and it very slightly lights up which means current is passing through the IR LED on the sensor which I'm assuming means that it's not burned?
When I measure the voltage after my 270 ohm resistor to raspberry's ground I'm reading 4.5V where I was expecting something along the lines of ~1.5V, since that's kind of the nominal voltage of the IR LED.


texts: Identify unknown disc-shaped component - markings include VF10 0471K

texts: I am trying to identify this piece, which I believe is a varistor, though I'm not sure. It comes from a Samsung rice cooker. I have attempted numerous google searches on the markings, but I have so far come up empty handed. Any help would be much appreciated.


texts: Water detector with a BC547 and help understanding transistors

texts:
I have set up a basic water detection sensor using a BC547 transistor to switch on an LED if there is current between two electrodes (which are spaced about 1 cm apart):

I'm trying to understand more about how transistors work.  I have some questions which I would appreciate help with:

The 4.7k resistor is a failsafe in case the electrodes touch each other and send too much current through the transistor and destroying it. I've made this mistake already. If the electrodes touch, with the 4.7k resistor in place, only 1.9 mA will pass to the base. How do I know how much current is too much for the base? I've looked at this spec but I don't see a specification for this.  Is it the same as the max collector current (100 mA)?

If I replace the 4.7k resistor with 1M ohm then the LED burns very dim. How is this happening? Surely the switch is only on and off.

It seems that my tap water provides a resistance of roughly 500k ohms. This means that as little as 18 uA of current is going to the transistor's base, which does indeed switch it on.  What current would be too small to work and how would I calculate this number?

The BC547 spec says the max emitter-base voltage is 6 V.  Does this mean I need to drop the voltage along this line? Should I plug in a couple of diodes?

Any other points or suggestions would be appreciated!


texts: Stuck with deciding the location and the type of variable declarations for this MCU code

texts:
I'm using ATmega328P with Atmel Studio. In the following code I declare almost all the variables inside the while loop:

#include <Arduino.h>//this is to use the Serial library
#include <util/delay.h>
#include <avr/io.h>
#define F_CPU   16000000UL

const int DATA_PIN = 6;

int main(void) {

    DDRD = B0100000;
    DDRD |= 1<<5;
    Serial.begin(57600);

    while (1) {

        unsigned long data = 0;
        uint8_t val;

        for (int i=0; i<25; i++) {
            data <<= 1;
            PORTD &= ~(1 << 5);
            _delay_us(2);
            PORTD |= (1 << 5);
            _delay_us(2);

            val = 1 & (PIND >> PIND6);

            data |= val;
        }

        PORTD &= ~(1 << 5);
        _delay_us(2);
        PORTD |= (1 << 5);
        _delay_us(2);

        alarm = 1 & (PIND >> PIND6);

        //rest of the code....

        unsigned long angle_count = data & 0x1FFF;
        unsigned long turn_count = data >> 14;
        float angle = (angle_count * 360UL) / 8192.0;

        Serial.print(angle);
        Serial.print(";");
        Serial.print(turn_count);
        Serial.print(";");
        Serial.println(alarm);
    }
}

In terms of speed and efficiency, I cannot be sure where to declare them. There are two more alternative places such as in the main but outside the while loop or right at the very beginning of the code after #define and %include libraries. Also how can we make judgement whether we need to use volatile or not?


texts: How to opto isloate a pin and still use it as either an output or input at will

texts:
I am looking for a clever way to merge the two circuits. I want the freedom to configure the pin as input or output  but still have the isolation. Not sure if this can even be done but I am for suggestions.
Thanks.


texts:
This is my first post here on electronics stackexchange.
I am a hobbyits in electronics, and a professional in programming.

I am working on a inductor circuit to heat a workpiece. I have a working setup @12Vac.
In short I have the following elements in the circuit:

Microcontroller to generate pulses with a DC of 50% with its own power supply, sharing ground with the transformer powering the solenoid.
2 MOSFETs (100Amps continues drain current, 150Vds) on the low side to switch the direction of the current, through
a 3570 nH solenoid of 11 turns, ~5cm Diameter, made of copper pipe with 1 cm diameter. (Planning to apply watercooling through the coil some time later on)
a 230Vac to 12Vac transformer that can deliver up to 35 Amps peaks, or 20 Amps for a while.
A MOSFET driver (TC4428A) to drive the gates of the MOSFETs

a 10K resistor on each MOSFETs Gate to Source.
1000pF ceramic capacitor on each MOSFETs Gate to Source (to reduce some ringing on the gates). Vpkpk is ~17Volts on the gates

Now the circuit shorts when I want to apply 48Vac to the circuit, by using a welding machine, which the MOSFETs would be able to handle (48Vac = ~68Vdc * 2 = ~~136Vpkpk).
Nothing explodes, the MOSFETs are in one piece. But the resistance between the pins of the MOSFETS (Gate,Source,Drain <-> Gate,Source,Drain) are all 0 or very low (<20Ohms). So they broke down.

What caused my MOSFETs to break down? Its hard to examine the circuit when components die.

My equipment exists solely of an osscilloscope and a mutlimeter.

Ringing on Gates without C2 and C3, while solenoid was not powered. Sharing common ground with transformer.
The wires from MCU to the TC4428A driver are, say, 5cm. From the driver to the gates, the wires are ~15cm. Does this cause ringing? thich ~2mm wires where used from the TC4428A driver to the gates.

Snubbed ringing on gates with C2 and C3, while solenoid was not powered. Sharing common ground. Looks much better than the first picture.

Ringing on Gates while solenoid was powered. Why is the ringing increased when the solenoid is powered on, and how to prevent/mimize it while maintaining switching speed?

Measurement on Source to Drain with workpiece in solenoid @ ~150Khz. Shown in the last picture, if the signal was clean, it would yield a Vpkpk of ~41 Volt. But due to the spikes it is around ~63 Volts.

Would the latter of 150% over/undershoort Vpkpk be the problem? Would this result in a (48Vac => 68Vmax => 136Vpkpk * 150% = ) ~203Vpkpk? How would I reduce the noise on the waves measured on the Source -> Drain?

EDIT

Here I disconnected one MOSFETs gate from the driver. CH1 is the gate, CH2 is the Drain of the MOSFET that was still connected. Now both waves looks fine. No /minimal current was flowing here.
When I do connect both MOSFETs to the driver, and measure the resistance between the two Gates, it says 24.2K Ohm. Could it be that if one MOSFET is turned of by the TC4428A driver, that somehow it still picks up a signal from the other MOSFETs Gate when it is turned on by the driver? Is it a meaningful idea to put a diode like so Driver --->|---- Gate to make sure there is no noise? Preferably a diode with low voltage drop of course.


texts: Using Reactive vs Real Power to Manage Distribution System Voltages

texts:
This is my first post.  The introduction of photovoltaics (PV) on the electrical distribution system creates changes to real power, resulting in voltage fluctuations.  Those voltage fluctuations can be mitigated in two ways:

a) real power

b) reactive power

My questions are below. I am hoping that somebody can provide the calculations in their responses, and explain those calculations if they are not simple.

1) Why is reactive power generally more effective than real power in returning voltage to system norms?  (Assuming this is correct, please provide the calculation demonstrating this to be true)

2) When and why does this general rule stop being the case?  Why do long feeder with different X/R ratios require more real power for voltage control? (Assuming this is correct, please provide the calculation demonstrating this to be true)


texts: Connect servo and dc motor to raspberry pi

texts:
I'm currently working on a project where I have build a RC car with one DC motor (forward/backward) and one servo motor (steering). I'm a newbie with electronics so I figured out by myself I needed a motorhat shield for my Raspberry pi 3 B model. Problem is, that it only can run DC motors or stepper motors.

My question is: how can I control my servo motor as well as my DC motor at the same time?


texts: What happens when an FPGA is powered on and left unconfigured?

texts:
I am trying to get a general understanding on what happens if you leave an FPGA unprogrammed for a long duration of time.

Suppose you have an FPGA and you leave it unprogrammed for a long period of time (several minutes to hours after power-on), i.e. no bitstream on it, is this bad for the device? Is it recommended to have some bitstream on a powered-on FPGA at all times? What is the general opinion regarding this?

Are the results different on different devices or manufacturers (Xilinx vs. Altera vs. others)?

Additional Info:

I have a custom SoC board which uses a Xilinx Virtex-6 FPGA. I also have a Xilinx ML605 which I use for reference purposes.

Custom board: I power-on the board. I notice that I get a short duration of time to program it using XMD (Xilinx Microprocessor Debugger). If I lose the 20-30 sec window, I have to switch off and switch on the board before trying again. This does not happen with an ML605.

When I try to program the custom board over XMD, I get something like:

Error: Device Reset by JPROGRAM command, failed. INIT_COMPLETE did not go high.

Let me know what you think.


texts: How can I disconnect a Battery Charger from the Battery while not Charging

texts:
I have a LiIon Battery Charger IC which will draw around 50µA when not needed, see circuit 1. This is a lot of current for no work in my opinion. Now I search for a solution how I can disconnect the charger if not needed. There is one open drain status pin from the charger I can use for it (active low).

What I came up with is in circuit 2. If the Charger is loading the battery the #CHG pin is pulled down and opens the PMOS  (controlled by the charger control inside the charger). If the charger is not charging the charger control is giving out a undefined voltage as I understood.

So my Question is: Can this solution do the job of disconnection the charger if not needed and connect it if needed?

Circuit 1:

Circuit 2:


texts: Should cable shields be connected to earth ground, or to power supply negative?

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I'm working on a PLC cabinet, and I'm wondering whether I should hook cable shields to earth ground, or to the power supply negative.

I checked and the power supply DC output is isolated. There's no conductivity between earth ground and the power supply negative.

Would the answer change if the supply were not isolated?

The cables go out to sensors, and they carry 24v power, 4-20ma signals, and 0-10v signals.

Side question: Is there anything wrong with leaving the dc supply isolated? The chassis is grounded to earth.


texts:
LM3478 datasheet

This circuit was designed with the help of Ti webench, I have checked all the connections, everything checks out. When i connect a 24V 2.2A Dc supply the supply voltage drops to 3V but nothing gets heated up. If the circuit is connected to the supply and then i turn on the power the power supply voltage drops to 3v and output is less than 3V. While the power supply is ON if i connect the converter the output voltage is 48V.
Can someone shed some light on this mystery?


texts: NPN trigger voltage & resistor temperature

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I want to trigger the base directly. What must be the voltage needed? This is the datasheet.

http://www.secosgmbh.com/datasheet/products/SSMPTransistor/SOT-23/MMBTA44.pdf

Can I just use DC and separate power supply to trigger it. I don't want any AC if possible.

Also when the base triggered it and Collector has current flowing to Emitter.

How hot do you think can the 1M ohm resistor get (estimate) when it is continuously exposed to 240v ac supply?


texts: Why do we care about voltage and current not power only

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I don't understand why do we care about voltage and current supplied to any components, why not just the power, no matter how much are the current and voltage?

For example: a red LED needs 2V to function, but why? Why don't we say the LED function at - just assuming - 10 W, whatever the combination of voltage and current?


texts: Arduino: Only reads serial input when Serial Monitor is open. Fails when it's closed

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I feel like maybe I'm having a brainfart, but I've been searching around a lot.

Setup:

I have a Python script using pySerial that connects to the device and writes a line to the serial port @ 4800.
I tried using "while (Serial.available())" both in serialEvent and directly in the loop.

What should happen:

When the devices receives any kind of serial input, an LED should light up.

Problem:

When I have the Serial Monitor open, everything works as expected. The LED lights up and I see the content printed out.
When I have the Serial Monitor CLOSED, nothing works. The LED doesn't light up.

Something I recently noticed: When Serial Monitor is open, I get 1 TX blink followed by 1 RX (yellow) blink. But when it's closed, I get 1 TX blink followed by 2 PIN 13 (blue) blinks. Supposedly the PIN 13 blinks mean something about troubleshooting, but I don't know where to look.

The event that happens has been simplified to a very basic LED light which works in every other instance (button press, serial monitor open while receiving data from python, or just sitting in the loop).

So my questions:

Why doesn't the device receive the serial writing when the Serial Monitor is closed?
What are the differences in these RX, TX, PIN13 blinks telling me?
How do I troubleshoot that?


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I am implementing an emulated EEPROM in flash memory on a STM32 microprocessor, mostly based on the Application Note by ST (AN2594 - EEPROM emulation in STM32F10x microcontrollers).

The basics outline there and in the respective Datasheet and Programming manual (PM0075) are quite clear. However, I am unsure regarding the implications of power-out/system reset on flash programming and page erasure operations. The AppNote considers this case, too but does not clarify what exactly happens when a programming (write) operations is interrupted:

Does the address have a arbitrary (random) value? OR
Are only part of the bits written? OR
Does it have the default erase value 0xFF?

Thanks for hints or pointers to the relevant documentation.


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Here is my bandgap,and i want to change the current "I" ,according to the formula:

I=\$\frac{nk\times lnK}{qR}\$, n,k and q are constant

So i can only change \$ lnK \$ and R to adjustment the current,the calculation of  \$ ln\$ is too complicated ,so i choose to change the value of R,after i change it,the voltage before R1 change,but the current does not ,what do i miss for adjusting the current?


texts: Resistors, what do I need for my 3V LEDS?

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I bought some lights off of Amazon in both the "White" and "Warm white" options (Link).
I think they are 3 V and operate at 15 mA, whatever that means. I want to wire the lights in a series/parallel circuit.
Key:

Red: Positive
Yellow: Negative / Ground
Blue: Resistor (Green numbers are for ohms - See below)
Green: Switch
Grey: Lights with back numbers (Lights #3&4 are "White" and Lights 1,2,5,6,7 are "Warm White").
Purple: 9 V battery

The problem:
Only some lights will light up. Some only partially light up, etc. (Note: this is when I had fewer resistors in weird spots, not relevant anymore)
The solution:
Add a resistor (Blue in diagram)
Where I get stuck:
What resistors do I need?
The resistors that come with the lights (Labeled "5.1V-9V use") power one just fine (Like #5), but don't power the pairs well (Every light but #5).
I think I need a 200 Ω (or maybe 180 Ω) resistor on the dual pair. And 390 Ω or 100 Ω on the single one. But I honestly have no clue, and each person I ask says something different.
The ones I'm using now for the lights that work are, I believe, 100 MΩ, but that makes no sense.

Also, I have no clue what side goes first...

Can anyone help me figure out what resistor (and 5-band color) would be needed for both the 1 and 2 light combinations?
I am not sure if the ones that came with the lights are the best or not.
Thanks!
I'm also brand new at this, so sorry if the answer is obvious.


texts: I am having trouble trying to get my head around using safety relays in PLC controlled machinery. I want to install a PLC into a machine that needs upgrading, it is straight forward enough, well i thought so until i ran into two safety relays im just not sure how or if i should tie them in to the PLC. The relays are controlling 4 estops and 12 guard door sensors, which i thought the PLC would be capable of doing. So how do i keep the two seperate or do they get hardwired to each other? The net seems to be very scarce on this info


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So for some MOSFETs, specially with Power MOSFETs, the body diode is a flyback diode that (as far as aI can tell) can be conveniently added to the MOSFET's bulk as there already PN junctions (correct me if I'm wrong).

I've looked at the datasheet of a Power P-MOSFET and it has parameters like "Internal Source Inductance" and "Internal Drain Inductance". So, is the build up of reverse voltage on the source and drain sides, when said MOSFET is suddenly turned off, a behavior intrinsic to (at least some) MOSFETs? Or are these from the rest of the circuit, say inductive loads?


texts: Is this capacitor suitable for boost converter (low ESR)?

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I am about to build voltage booster (1.5V battery to 3.3V) with NCP1402.
Datasheet recommends 68μF tantalum or two 22μF capacitors for output.
Schematic looks like this:

Output capacitor should have low ESR (page 16):

  The output capacitor is used for sustaining the output
  voltage when the internal MOSFET is switched on and
  smoothing the ripple voltage. Low ESR capacitor should be
  used to reduce output ripple voltage. In general, a 47 μF to
  68 μF low ESR (0.15 Ω to 0.30 Ω) Tantalum capacitor
  should be appropriate. For applications where space is
  a critical factor, two parallel 22 μF low profile SMD ceramic
  capacitors can be used.

I have smd ceramic 22μF caps, but I do not know whether they are suitable or not.
I measured ESR of those caps with LCR meter:

8.30Ω @100Hz
0.63Ω @1kHz
0.04Ω @10kHz
0.04Ω @100kHz

ESR is fine for frequencies over 10kHz. But it is larger than recommended value at 1kHz and lower.

Is this capacitor suitable? Is it possible to ignore higher ESR at lower frequencies? Should I buy different/better caps?


texts: STM32F3 - diffrence between PWM1 and PWM2

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Can anyone explain to me wht is the difference between PWM1 and PWM2 in STM32F3 timer configuration? It is mentioned frequently in documentation, however I can't find the difference between these two settings. Code example for setting PWM1 OC mode for timer 8:

Tim_InitStruct.TIM_OCMode = TIM_OCMode_PWM1;
Tim_InitStruct.TIM_OutputState = TIM_OutputState_Enable;
Tim_InitStruct.TIM_Pulse = 512 / 2; // 50%
Tim_InitStruct.TIM_OCPolarity = TIM_OCPolarity_Low;


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The task is to measure the voltage of individual cells in a 48-cell battery pack of AA cells in series.
The measurements serve to log performance statistics, warn the user if/when a cell dies, or that a cell is otherwise unbalanced compared to the whole pack. I'm thinking about how to wire this up to the MCU. My current design idea is as follows: connect the minus of the battery pack to GND, and then place a voltage divider from each tap of the pack towards ground, so that the voltages of the taps are brought within the 0..5V range. After that, place 6 analog multiplexers of 16:1 configuration, so that any two taps can be addressed individually. These two selected channels are amplified with an opamp in differential fashion, and fed to a PIC. The analog muxes, the opamps and the PIC are powered by a battery/LDO combo.

It isn't hard, it just seems overly complicated, so I wonder if I miss a simpler solution?


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I've bought an USB to UART CP2102 and I want to connect it to a router to see the booting process. However, although I can see five pins in the router, I don't know which one is TX, RX and GND.

Could I test each router's pin one by one to find out which one is TX, RX and GND? or if I do this I could break the router?

--------Edit--------

This is the router/ont -> ONT I-240G-T. It works like this:

Thanks, best regards.


texts: RS485 vs RS232 similarity vs differences

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I have used UART RS232 communication between MCUs extensively. Now I need to interface my STM32F407 MCU over RS485 bus with with devices. I have understood few things about RS485 but not-clear about some points. Please correct me if I am wrong in my understanding:

From MCU firmware point of view both are same since we use same pins for RS232 or RS485.
The main difference is in their signal voltage levels and point-to-point (RS232) or multipoint (RS485).


texts: MOSFET drives high voltage and high current load with PWM

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If I adopt this circuit if there is a problem,Do I need to further improve or add components？

If I were looking to drive a FET at:
Logic voltage drive (5V)
Duty cycle is 0-100%
20A load
48V
How would I determine an appropriate MOSFET and how would I determine the driving requirements?

MIC5018 datasheet


texts: How to handle 2nd USB and Audio ground in a project powered from isolated 5V Wall Wart

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I've read a dozen questions that are similar to mine, but have not found any responses that provides the specific guidance I am seeking. Here are some that I've read:

Ground Connection When Using AC Wall Wart Supply
When using USB and external power, how should I isolate the grounds?
How to safely connect the Arduino 5V Pin with a 5V wall wart and USB TTL converter for data transfer?
USB port and bench power supply ground difference
Common ground : Computer A and USB powered Arduino ( MCU ) from Computer B

Here is my situation: I've built an embedded device project that is powered from an FDA-compliant 5.4V floating wall wart. It connects to an earth-ground referenced laptop through a primary (isolated) USB serial emulator. In that scenario, all is well.
The problem, as expected, occurs when I introduce an earth-ground reference into the circuit. This can happen in several ways.
In the first case, I need to connect an FTDI serial emulation cable for out-of-band debugging output. The FTDI cable may go to the same laptop or to a different laptop, but the FTDI ground will always be connected to USB ground somewhere near the level of earth ground. The FTDI power pin is left disconnected since the device is self-powered, but the ground is required for D+ and D- signals to be transmitted.
In the second case an unbalanced audio connection may sometimes get plugged into a grounded mixer.
Finally, I need to be able to put an oscilloscope on the board, and the scope ground is at wall-ground.
By design, power and ground from the wall wart float WRT ground, and my scope shows that both positive and negative carry a 60 Hz AC potential of ~150 volts P-P relative to earth ground. My Fluke multimeter reads this as 48V (I assume this is RMS of the alternating voltage, which isn't really very sinusoidal). At first I thought there was something wrong with my wall wart, but I've tested a number of different models of 5.4V 2A wall warts from different manufacturers, and they all look about the same on the scope.
Within my project, the (floating) ground of the wall wart and the ground reference from the FTDI cable and/or the audio mixer are all connected via the ground plane of the PCB, but I am seeing some real problems with this.
When I connect the FTDI serial emulator ground, the I2C bus on my board runs inconsistently and eventually locks up.
When I connect the audio output of my floating PCB to one channel of a mixer, even a channel that's turned all the way down, 60Hz hum affects every channel of the mixer.
When I connect scope ground, the PC sometimes drops and reconnects its USB device and the embedded system may reset
These problems can be made to go away by tying the floating wall wart power supply ground directly to another physical ground (e.g. my scope ground).  However, this introduces a huge amount of digital noise on the ground lines. This (and ground loop issues) originally led me to an isolated power supply and isolated USB signal path, and a lot of things got better after I installed isolation, so I'm not sure I really want to undo that if there's an alternative.
Can anybody point me towards an optimal approach to this problem? It would be possible (though expensive) to require that the FTDI connection also go through a USB signal isolator, and presumably something similar can be done for the audio signal. But is there a better way?


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Hobbyist developing first PCB. Only caught this on my PCB/Schematic design after I had received them, was too focused on functionality of other components.
Resonator designed like crystal, resonator GND pins not going to GND. How it's designed.

How it should be designed according to datasheet.

Edit: Ignore schematic title, its obviously a resonator.
Edit+: https://datasheet.lcsc.com/szlcsc/1811141821_Yangxing-Tech-X322516MLB4SI_C13738.pdf - Apologies, thought resonators all wired the same.

**Have I ruined my PCB? **
Thanks :)


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I have a couple of active PA monitors with only unbalanced inputs. I want to be able to use the balanced monitor outputs from my mixer, so I am planning to build in a balanced to unbalanced converter in each monitor. I have build the boards using NE5532s. These works fine, then my next step should be to make a power supply taking power from the power lines for the amplifier and regulating it to approx +/- 15V using LM317 / LM337.

When I measured the power supply of the amplifier, it turned out to run on +/- 58V. As the NE5532s are rated to run at up to +/-22 V (recommended up to +/-15)  and the LM317 / LM 337 can take a voltage drop of 40V, this should just work, but I do not like it - it is a bit too close to the limits. As I measured the voltage of the amplifier across the filter caps without any signal, the voltage will probably be slightly lower under normal use, but anyhow...

At the moment think I have these possibilities:

Run it as planned, since the circuit is not pulling much current (< 100mA), it will probably work fine.
Try to find other power lines in the amplifier with lower voltage. This may be more difficult and a bigger risk of somehow creating problems for the amplifier.
Running two sets of LM317 / 337s in tandem, i.e. using the first stage to get from 58 to 30V then the next from 30 to 15. - I have never seen this been done, a slight waste of components, but I cannot see any reason why it should not work.
Use some other voltage regulators, integrated or discrete, that can take a higher voltage drop. The only reason to use the LM317/LM337 is that I have a few of them in storage. But are there any recommended voltage regulators that can take a voltage drop in the order of 40V? The monitors are old Laneys, so I do not think I want to put a switched voltage regulator too close to the active circuits.

What would you recommend? Maybe I even have overlooked some possibilities...


texts: Is it easy to siphon power from a powered antenna?

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I have a property which is in a bit of a hole.  My driveway goes up to an elevation above my house where semi-local TV signals are present.  When they were still in local business, I bought a powered antenna from Radio Shack and mounted it on a pole at the top of that driveway.  It has an internal amplifier which is powered from a small (200 mA) DC source down at the house, and which is "injected" on the same coax line the signals it picks up are returned on (there is no separate power line needed to run to it).
I imagine this is simply a matter of "AC riding on DC", and that at the antenna, there is some kind of circuitry to pull off the DC without impacting the signals (I know I would likely be aghast if I opened it, since it may be something as small as 2 or 3 capacitors, when it cost around $70, but it was the SuperBowl, and I was having people over).
Fast forward to today.  This driveway is wide enough for 1 car, and is semi-long and has a small curve.  I'm a bit of a train signal system fan, I thought it would be neat to to put something the railroad calls a "dwarf signal" next to the road to let cars at the bottom know when a car is coming down from the top that they can't yet see so they can stop and back down.  Since we're talking approx 600 feet, I'd rather not run another cable up there to power this light and any associated sensor(s).
THE QUESTION:
In such AC+DC amplified antennas, can I reasonably expect to draw off DC current for this signal system without interfering with the TV signals present?  Broadcast TV uses such a wide swath of frequencies that it might be hard to interface with this antenna without creating interference or attenuation.  I'm guessing I would likely need a very wide bandwidth bandstop filter.
Can anyone point me to any circuit examples for circuits like this?


texts:
Wave soldering

I am trying to understand how wave soldering works. Unfortunately the Wikipedia article has has left me unsure about the process:

Is the entire board with its components quasi-immersed in liquid solder while it passes through the wave? (If not, the following question probably make no sense.)
If the board cuts into the wave, how is the wave maintained?
Why does this not leave superflous solder residue on the board?

Double-Sided SMT soldering

How are double sided boards with SMT components soldered? How is it prevented that the components on one side fall off?


texts: Programming an AVR microcontroller with multiple SPI channels

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I am trying to design a PCB which will make use of the ATmega324PB microcontroller [Datasheet here]. I have previously worked with smaller AVR chips such as the ATmega168PB, and programmed them through the ISP pins using an AVR Pocket Programmer.

This is the first microcontroller I've used with multiple SPI channels (MOSI0 and MOSI1 etc.). The datasheet makes no mention of how to approach this when performing In-System Programming, am I right in assuming that channel 0 (i.e SCK0, MISO0, MOSI0) should be used for this? The only real differential I can find between them is in the block diagram in Figure 4-1 (pg 13 of the datasheet).

The AVRDUDE tool used by the Pocket Programmer has not been updated in some time and does not list this this specific IC as supported (though it has the 324P and 324PA listed). I'm considering upgrading to an STK500 as Atmel Studio 7 lists it as a supported device for the micro, are there any issues here?


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I am self-studying on how 802.11b bandwidth and data rates are calculated, primarily those of 1 and 2 Mbps. These are my understandings, please correct them if they are wrong. Please keep in mind I am not an electrical engineer.

At 1 and 2 Mbps, DSSS performs signal spreading resulting with 11 and 22 mega bits (chips) per second for BPSK and QPSK, respectively. In both cases, this stream has to be modulated with mentioned modulations and equal symbol rates of 1 Mbaud per second.

Bandwith equals 2 times bits_per_second/number_of_bits_per_symbol (1 or 2 depending on modulation scheme). This "2" at the begining is because of null-to-null bandwidth of a modulated signal. For both cases, the bandwidth is 22 MHz.

The data rates are equal symbol_rates times bits_per_symbol, resulting with 1 and 2 Mbps.


texts: Zero crossing detection and Light dimmer

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I am confused by zero crossing detection of opto-triac. I know what is the zero crossing detection or switch. (ZCS)

Zero crossing detects what is the point that wave is going to positive to negative or negative to positive.

But, I cant explain function of below circuit with help of zero crossing.

Can it control the load using PWM signal at terminal named signal?
And explain How can dim the light bulb using PWM signal.


texts: Why logic low Inputs to a logic gate need to be grounded

texts: For example if we take a 2 input AND gate . And want to apply 0 and 1 to the input terminals ..one terminal will be connected to a voltage source . But the other terminal where logic 0 is to be given , why do we ground it . Logic 0 means low voltage than logic 1 . Why can't we just let the other terminal hang freely in air ....not connected  to anything ..Will it not have zero voltage when in contact with air ?


texts: Circuit to adjust -30V to +30V input to 0 to 3.3V for ADC?

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Currently working on an oscilloscope design that would require each channel to be able to take in between 30VPP, -30V to +30V, which will go to an ADC which has a maximum input of 3.3V.

What types of designs or specific circuits could I implement to offset the voltage where 0 is -30V and 3.3V is +30V ?

ALSO - Yes, I will also be implementing a voltage divider, but the ADC cannot take in negative voltage.


texts: LT3663-5 with 5V and 3.3V output, can RTN be connected to common ground on circuit board?

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I'm making an automotive circuit where both 5V and 3.3V is needed. I'm planning to use LT3663-5 and 1761ES5-3.3 to create those voltages.
Now my question is, whether it is safe to connect RTN on 3v3 output to common ground?
(See example at: https://www.arrow.com/en/reference-designs/typical-application-for-lt3663ems8e-5-5v-step-down-regulator-with-isolated-33v-output/4c40a44cc9a9bb46946efb3da9dc5c84)
I'm using those voltages to feed micro controller board (5V (but 3V3 logic)), CAN controller (3V3)(MCP2515) and CAN Bus interface (5V) (TJA1050)
I believe that those all need the same ground level in order to work together.

Thank you for your answers, they were very helpful. Based on ideas presented here, I came up with the following circuit:

Image source - OneDrive
I added also reverse polarity protection to the circuit. How does it look?


texts: Software package for interfacing Arduino with MAX MSP?

texts: What is a good software package for interfacing Arduino's input pins to MAX/MSP?


texts: Is eMMC really a good choice for a low-volume long-product-life design?

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We're looking for a flash device for a low-volume (batches size < 100) industrial product, in the 2/4/8 GByte range.

In applications like this we've previously used SD card, which is an obvious choice.  For better mechanical robustness and device consistency, we'd really like to use a fixed IC in this product.   It feels like eMMC is absolutely the obvious choice for this - avoid both the NAND management hassle and the downsides of SD-cards.

However, there is something about the supply of eMMC devices which makes me suspicious about whether they're a sensible choice.  Supply from the usual catalogue companies (Mouser,DK and Farnell for us) is really patchy, with few parts listed, those that are listed not on manufacturers' websites and many with 1000-level MOQs.   This is not just 'difficult' manufacturers (Samsung, etc), people like Micron who have DRAM parts widely available seem to be different for eMMC.

Obviously the Arrows & Avnets of the world list everything, but this doesn't mean I could actually have 50 parts tomorrow from them.

Is there something odd about eMMC (licensing, whatever) which I'm missing, which means that it's not being carried in the normal way?  Are there people here with any experience of using eMMC in real, low-volume, production?


texts: How to reach ~50nA p-p current noise in ~200mA current source?

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Target application is driving single-frequency laser diodes (@2.5V) which are sensitive to current noise. Current is constant, with no modulation.
Strightforward solutions that first comes to mind is low-noise LDO (for example LT1963) that can reach ~40µV RMS which would give us around 4µA RMS of current noise. TPS7A4700 is better at 4µV RMS, which will give us ~400nA of RMS noise. But that is still far away from 50nA p-p.
Could the rest of the gap be covered by filtering / capacitance multipliers? Or there are specific solutions to low-noise current sources that are significantly better than high-end LDO?


texts:
what is the max value of the Repetition Counter register?
Because i am trying to use a TIM1 as PWM output.
Period = 50kHz
Clock = 72Mhz
72Mhz/50kHz = 1440Hz  -> PWM freq

So if I set Repetition Counter to 1440 is should generate an interrput one every sec. But it doesnt work that way?

Could you explain me why?
Greets


texts: Can I take DC directly from W1209 Thermostat board?

texts: I want to make an incubator. So I am using W1209 thermostat. I want to control AC and DC. I can control AC (220v AC) by the relay output. Can I control DC by connecting DC directly from the relay input (12v DC)


texts: DC Motor giving poor output waveform - how do I fix?

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I am trying to make a DC motor controller with an H-bridge and PWM powered. The circuit diagram for the motor controller is:

The inputs can obviously only be on 1 at a time to prevent short circuit. I am connecting the motor across where the two open circuit nodes, and if I measure the voltage across these two nodes without any motor connected the output is basically just the 5V PWM signal amplified to 12V - which is what I want. The problem arises when I connect the motor across:

Yellow curve is the input, blue curve is the motor output. As it can be seen, it is somewhat okay when the input is HIGH, but when the input is LOW, the voltage across the motor is zero for a little while, and after a bit of time it is then non-zero, even though the input is 0. Should be noted that the other input is grounded. Does anyone have any idea on how to mitigate or remove this non-zero period where it should be zero? Thanks


texts: Calculating power received and V (rms) given powr loss

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The transmission line cable below is 10m long and has a power loss of 1 dB/m at the frequency of the source. What is the power received at the receiver (in dBm), and the voltage (RMS) of the signal at the receiver in \$dB\mu V\$?

Here's what I have:

\$P_{in} - P_{out}\$ = Power loss

Power received at receiver = -30dBm - (10)(1) = -40dBm

-40dBm = \$10^{-4}\$ mW = \$10^{-7}\$ W

\$P = \frac{V_{RMS}^2}{R} = 10^{-7}\$

\$V_{RMS} = \sqrt{10^{-7} (300)} = 0.005477 V = 5477\mu V\$

\$V_{RMS} = 20log_{10}(5477) = 74.77\:dB\mu V\$

Are my calculations correct?


texts: A question about splitting a regulated power supply by resistors vs discrete components

texts:
Assuming the source voltage Vs is regulated in below diagrams, is there any advantage of using this rail-splitter topology:

instead of this simple one?:

Is there any good reason or scenario which makes the first topology superior to the second one if the power supply Vs is a regulated supply?


texts:
Typical CPU instruction set: the CPU has several functional units, and when each instruction is read, some bits specify which functional unit is to be activated, while others specify the details of the operation.

Today's CPUs tend to spend some of their large transistor budgets on out of order execution, where they have a bunch of instructions in flight at once, trying to keep multiple functional units busy all while creating the illusion that it's still a serial instruction stream for backward compatibility. For the purposes of this question, to keep it simple, say we are talking about 90s technology with no more than a few million transistors.

VLIW: let's save time and transistors on decoding, and keep all the functional units busy, by having an instruction word that has a group of bits for each functional unit, specifying work for them all at the same time.

One problem with VLIW is it exposes more hardware details, making it difficult to keep backward compatibility with subsequent CPU generations without losing the advantages. Let's say we get around that problem with byte code and a JIT compiler.

Another problem is that not all workloads want to use all the functional units, and that's what I'm looking at now.

Let's say we're designing a CPU for an early 90s workstation, in the era of the 486 and i860. Roughly speaking, there will be two kinds of workloads, number
crunching (e.g. CAD, simulations and of course 3D games) that uses the floating point units, and other stuff (e.g. word processing, compiling) that doesn't; this roughly corresponds to SPECfp vs SPECint.

For number crunching workloads, we could design a straight VLIW, maybe with a 64-bit instruction word that specifies integer and floating point operations, control flow etc all at once, and that will give great performance. But for integer workloads it will have poor code density because the bits specifying floating point operations will always be saying 'no FP ops this clock cycle'.

Would it make sense for the CPU to have a mode bit to switch between the two kinds of workloads? In FP mode, it works like the above, but in integer mode, maybe each 64-bit word just supplies a pair of 32-bit integer instructions? Would that give most of the simplicity and performance advantages of VLIW without the potential code density disadvantage?


texts: How to add components using loop in Eagle PCB script?

texts: Eagle command language contains the ADD function but not loops. Eagle ULP contains loops but no function to add a component. Under these circumstances, how does one add components e.g a lot of LEDs into a schematic using a loop?


texts: High current low voltage transformer not working

texts:
I have rewound a microwave oven transformer to produce a low voltage on the secondary. I'm not sure what the ampere rating of the transformer is but its about 4mm thick wire on the primary.
I wound the transformer to be 93:3 turns, yielding about 3 volts on the secondary. If the input max is 20A, that gives me around 600A on the secondary. Still about 2200W. Trouble is, the secondary appears to have very little current running through it. Why is this?

Only reason I can think of is the inductance of the primary being high enough to limit the current to less than 20A or something. 93 turns, 80 mm loop diameter, 4mm wire diameter, and relative permeability of 4000 (transformer steel) yields 5.35 H, which is huge. I'll bet if I plugged that into the impedance formula of 2 x pi x f x H (60Hz) it would be a huge resistance. Yeah, its 2kOhm, which makes the current max on the primary 54 mA @ 110V I'm guessing?
One thing I may have confused is the reactance for a air core coil vs an iron core coil.

Anyways question is, what's wrong with my transformer? Why isn't the secondary high current? What can I do to get high current? I realize I'm probably using the wrong wire size for 600A, yes.


texts: Logic minimization guarantees of arbitrary subcircuits?

texts: I'm trying to better understand logic circuit minimization. Say you try and minimize the number of gates in some simple logic circuit. After minimization is completed, I choose an arbitrary sub-circuit (some group of connected gates). Is that sub-circuit always guaranteed to be as small as possible, or at least as small as possible given whatever particular algorithm is being used?


texts:
I'm trying to model a portion of the Electric Grid (yes, I have looked through the MATLAB forums already and came across the load flow solution), but this is more of a modelling problem for State Estimation.

I have a set of differential equations, non linear, which represent a 5 bus structure (3 generators and 2 loads). I have a state vector which stacks together all my state variables of interest.

Trying to research on the forums, what is the appropriate way to model this system? Is it simply to declare a system of equations which can then be solved by ODE45? Please see some example code at the bottom

A subquestion must also be asked. Is it possible to model a non linear system in MATLAB? Or do we have to use simulink.

Another subquestion. Am i confusing modelling the system with solving the differential equations? Is there a difference? I would really appreciate some guidance with this bit of theory.

Example Code (for just one of the 12 equations):

function [dx_dt] = statevector (t,x)

%This function contains the systems of DE describe the state vector

%State Vector x(t) = (Xg(t), Xl(t))

%x(t)=[V1(t),ω1(t),θ2(t),V2(t),ω2(t),θ3(t),V3(t),ω3(t)},θ4(t),V4(t),θ5(t),V5(t}) %x(1) = V1

%x(2) = ω1

%x(3) = θ2

%x(4) = V2

%...and so on

%Generators are busses 1 - 3, Load are busses 4 - 5

%Define Constants J = 1.26; % Inertia Constant D = 2; % Damping Coefficient Tdo = 0.25; % Time Constant Xd = 1.05; Xdp = 0.185; Pmi = 1; % Mechanical Input Power Ef = 1; % Electromagnetic Field

dx_dt = zeros(12,1); %initializing column vector which will contain eqns

%do i need to transpose dx_DT?

dx_dt(1) = 4 * Ef - 4 * x(1) + 3.46 * (2*x(4)*sin(x(3)) + 4*x(4)*cos(x(3)) + x(10)*sin(x(9)) + 4*x(10)* cos(x(4)));


texts: How to draw SPL curve for a parametric equalizer?

texts:
I want to show (graphically) the Gain/Attenuation vs frequency of a parametric equalizer.
This is my circuit:
https://sound-au.com/project28.htm
The same schematicas as a screenshot:

I want to show the effect of VR1 thru VR7 in the same way as it's shown in the Winamp:

I have tried to decipher this page: https://www.andyc.diy-audio-engineering.org/parametric-eq-parameters-1.html
I don't know how to interpret the formulas to derive the Gain/Attenuation, given the frequency, Q and center frequency of each equalizer band. Can anybody please explain in simple terms?


texts: Why are loudspeakers manufactured in various impedance values?

texts:
I'm acquainted with the concept of impedance matching in audio applications, but there's something that eludes me. First, a snippet from a home theater site:

  Loudspeakers have impedances of 8 ohms, 6 ohms or 4 ohms (those are "nominal" or approximate values, because the impedance of a speaker changes all the time with the different frequencies of music). A 4-ohm speaker draws more electric current through your AV receiver's output transistors, and since more current equals greater power, 4-ohm speakers tend to have greater dynamic range and play louder more easily than 8-ohm speakers.

If a lower impedance loudspeaker generally has better dynamic range and can achieve louder volumes, why do we still see 6, 8 or even 16 ohm speakers? Shouldn't we be "progressing" toward more efficient speakers with lower impedance? Are higher impedance speakers merely a product of backward-compatibility?


texts: Stm32F103 DMA TIM1 - Load 50% of period.

texts:
I wrote a code using DMA with TIM1. In DMA buffer i load diffrent periods and send to ARR Register. How Can I change a Pulse of PWM to 50% from Dma buffer ?

int i = 0;
volatile u16 PWM_Buf[20];
void TIMInit(void);
void GPIOInit(void);
void DMAInit(void);
void PWMInit(void);

int main(void) {
    GPIOInit();
    TIMInit();
    DMAInit();
    PWMInit();

    for (i = 0; i < 20; i++) {
        PWM_Buf[i] = i*100+300; //TU ŁADUJE WARTOSCI DO DMA ALE OKRES TIMERA SIE NIE ZMIENAI
    }

    while (1) {
    }
}
void TIMInit(void) {
    TIM_TimeBaseInitTypeDef TIMInit;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);

    //TIMInit.TIM_Period = 1000 - 1;
    TIMInit.TIM_Prescaler = 64000 - 1;
    TIMInit.TIM_ClockDivision = TIM_CKD_DIV1;
    TIMInit.TIM_CounterMode = TIM_CounterMode_Up;
    TIMInit.TIM_RepetitionCounter = 0;

    TIM_TimeBaseInit(TIM1, &TIMInit);
}

void GPIOInit(void) {
    GPIO_InitTypeDef GPIOInit;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

    GPIOInit.GPIO_Pin = GPIO_Pin_8;
    GPIOInit.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIOInit.GPIO_Speed = GPIO_Speed_50MHz;

    GPIO_Init(GPIOA, &GPIOInit);
}

void DMAInit(void) {

    DMA_InitTypeDef DMAInit;
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
    DMA_DeInit(DMA1_Channel5);
    DMAInit.DMA_PeripheralBaseAddr = (u32)&TIM1 -> ARR && (u32)&TIM1 -> CCR1;
    DMAInit.DMA_MemoryBaseAddr = (u32) PWM_Buf;
    DMAInit.DMA_DIR = DMA_DIR_PeripheralDST;
    DMAInit.DMA_BufferSize = 20;
    DMAInit.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMAInit.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMAInit.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
    DMAInit.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMAInit.DMA_Mode = DMA_Mode_Circular;
    DMAInit.DMA_Priority = DMA_Priority_High;
    DMAInit.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel5, &DMAInit);

    DMA_Cmd(DMA1_Channel5, ENABLE);
}

void PWMInit(void) {
    TIM_OCInitTypeDef PWMInit;

    PWMInit.TIM_OCMode = TIM_OCMode_PWM1;
    PWMInit.TIM_OutputState = TIM_OutputState_Enable;
    PWMInit.TIM_Pulse = 5;
    PWMInit.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM1, &PWMInit);
    //TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);
    //TIM_ARRPreloadConfig(TIM1, ENABLE);
    TIM_DMACmd(TIM1, TIM_DMA_Update, ENABLE);
    TIM_Cmd(TIM1, ENABLE);
    TIM_CtrlPWMOutputs(TIM1, ENABLE);
}


texts: How does the network card determine the cable length?

texts:
I have an older Gigabyte Technology GA-MA770T-UD3P motherboard with an on-board network card described like this:
Model: "Gigabyte Onboard Ethernet"
Vendor: pci 0x10ec "Realtek Semiconductor Co., Ltd."
Device: pci 0x8168 "RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller"
SubVendor: pci 0x1458 "Gigabyte Technology Co., Ltd"
SubDevice: pci 0xe000 "Onboard Ethernet"

The BIOS of that board is described like this:
Vendor: "Award Software International, Inc."
Version: "F12"
Date: "03/22/2011"

However that BIOS has an interesting feature: It can determine the length of the wires of a network cable being plugged into the network card (if the other end is "open" (i.e..: not plugged into a switch), and I wonder how that works.

I've seen no other motherboard/networks card/BIOS combination that offers a similar feature, while I wonder:
If one network card can do it, aren't all the others able, too?


texts:
I'm in the process building a linear lab PSU, the fan which is supposed to cool the heatsink is causing 6 mV peak to peak noise at the output of PSU. It's a 4x4 cm brushless chinese fan with unknown brand.

I tested adding a wide range of capacitors from 0.1uF to 100uF, close to the fan circuit or on the supply and it didn't make any difference. also tried adding an LC filter (47uH with 220uF) with no luck.

Adding an overkill LC filter on the fan input smooths the output though, 100mH inductor with a 100uF capacitor is causing a huge drop in the current (fan voltage drops to ~4.5V).

PCB trace:

The fan is being supplied from a different secondary than the main secondary:

simulate this circuit – Schematic created using CircuitLab

The secondary that is supplying the fan is also used to supply the op amps in the PSU circuit and has a common ground with the main supply.

How do I eliminate the fan noise?


texts: Programming stepper motors to smoothly show value that is refreshed at certain intervals

texts:
I am making analog speedo and rpm gauge for both a bike and a car using x27.168 stepper motors and AX1201728SG motor driver. I have encountered quite a problem with showing data that is not constantly updated (or at least as often as would be needed for stepper movement to be smooth).
Because data is coming at intervals that are quite long, steppers rush to next value, then they have to wait for next value to come in when they start moving again. That makes movement look jerky. The library I am using for this (SwitecX12 by Guy Carpenter) supports acceleration/decelleration table, but tweaking this to be too slow would make the needle less responsive when it has to travel larger distance. Its also not practical as I cant hope to cover all cases. I need to somehow take into consideration when next value is expected to arrive and time the movement of stepper to this, so that it reaches its goal at about the time next value is available. But here's when complicated part comes in: if next value is further down, then stepper must not stop at current value as that would again look as a jerk but must continue, adjusting speed only slightly over period of time unnoticeable to human eye
I need some advice on how this is usually done. If I try displaying my data on real car gauges its exactly as I want it to be, so there must be some kind of algorithm behind it. Is there any known algorithm/way of doing this, any implementation, anything that would help me with making this?
Help is much appreciated!
Thanks!


texts: Can this H-Bridge circuit be used with 12V?

texts:
I plan on building the following circuit with TIP142 and TIP147.

Source: Circuits Gallery.

Can you use 12V for the Vcc terminals? Thanks.


texts: Make a symmetrical power supply with a single power source

texts:
I need to read a strain gauge with some opamps. To keep the project simple, I wanted to power it with a single battery. I need to power the strain gauge with 10V, so my battery is going to be more than that (probably regulated by some sort of linear regulator) to avoid ripples in strain gauge measurement.

I need a symmetrical power supply for the strain gauge because the output can be negative. Are there any "known to work, tested, and reliable" circuits?

EDIT:

The datasheet:


texts: \$R_e\$ when using a common collector amplifier

texts:
For the DC biasing of a common collector BJT amplifier, how to choose \$ R_e\$ to get a proper DC biasing? (see image attached).
Furthermore, is it possible to control \$V_{ce}\$? I am confused. Thanks!


texts: Controlling speed of motor through L293D using TLC5940NT

texts:
I am trying to control a DC motor through an L293D. Ultimately I am controlling it with an Arduino, but I am trying to use a TLC5940NT chip as an intermediary to increase the number of outputs that I have.

I have hooked up three of the pins on the TLC5940 to the input 1, input 2 and enable pins of the L293D, using 2.2k ohm pull-up resistors on the two input pins (I've tried to diagram it below - apologies if it isn't clear. Full-size version):

Diagram of TLC5940NT hooked up to L293D:

When I hook the enable pin up to +5v, the motor works and I can control the direction using In 1 and In 2. However, I want to control the speed by PWM. When I hook the Enable pin up to the TLC5940 (as in the diagram) I can't get the motor to spin at all. I tried using a pull-up resistor as well on the enable pin, but it still didn't spin - and when I connect it to +5v DC using just a 2.2k ohm or 560 ohm resistor nothing happens. The only thing that has made it spin so far is constant 5v DC with no resistor.

Can anyone explain what's wrong and how I can get it working?

Edit: I've tried to add a more complete schematic


texts: how to measure RBG values of a color using phototransistor

texts: I am developing a circuit which can measure RGB values of a given color. I have used LED to transmit light and reflected light is filtered by 3 R, G, B filter papers. Earlier I used LDR and found that the accuracy of the result was low even though I managed to minimize background light. I want an accuracy about 1%. Can I use photo-transistors or photo-diodes? If so how can I use them increasing the accuracy?


texts: How to wire 0.91/0.86 inch display to i2c?

texts: I have a 0.91 inch display with a 4 pin I2C connection. I then realised that I needed to use a 0.86 inch display with the connector in the above image. I have searched on google on this but nothing has come up. Are there any suggestions on how to connect this? Below is a part of the datasheet if that helps.


texts: Why a double fuse is used in some applications?

texts: In some DC applications in an isolated system (i.e. no grounding), sometimes two fuses are used: one is positioned on the positive (Vcc) line while the other is located on the negative (return path or ground). What are the advantages of having two fuses (aside from redundancy)?


texts: Strange problem with differential amplifier for current sensing with TL084

texts:
I have a problem with the circuit below:

I'm using the op-amp as differential amplifier for low-side current sensing with gain of 100. All resistors are 0.1% and the load is just a variable resistor for testing the circuit.
The problem is no matter what load I have and how much current is going through the sense resistor the output of the op-amp is around 23 - 24 volts. I tried switching all of the components checked all the connections and even rebuilt the circuit on a bread board with no avail. I feel like there is something obvious that I'm missing.
I have the same circuit in simulator and it works just fine.
Update: As I mentioned I did miss something obvious and didn't check the datasheet fully.


texts: Solid state switch with Terra-Ohm off-impedance

texts:
I am looking for a way to create an ultra-high impedance switch without mechanical components. The off-resistance should be around one Terra ohm for a signal range of 10V DC max. On the other hand, the on resistance could be as high as one Mega ohm.

Is an impedance in this order of magnitude possible without using a relay?


texts:
I would like to make a siren on an UPS backup. I used this board with an 18650 embedded battery: https://www.aliexpress.com/item/32911096857.html?spm=a2g0s.9042311.0.0.24db4c4dn31JsH

And this siren: https://www.aliexpress.com/item/4000049267294.html

The UPS has an 5V output, and I use a DCDC step-up converter to drive the siren with 12V.

When the UPS is connected to the USB power supply, and the siren triggered, the system is working fine! When the siren is ON, and I remove the USB power supply, everything is still working fine.

However, when I try to trigger the alarm when the USB power plug is disconnected, the UPS goes in security and the siren never start.

I think that it is because of the inrush current of the siren.

I bought a 33 Ohm EPCOS NTC (Ref. B57153S330M51) to add it in series with the siren.

It is working now on the UPS only; however, the siren is not loud as without the NTC. It seems that the resistor value goes too slowly to 0 Ohms.

The consumed current of the siren is about 300-400 mA. How can I choose the right NTC in order to have the loudest sound of my siren after only 1s ?

Thanks for your help!

Aditionnal informations :

I have made some voltage measurement on the DCDC output.

DCDC Output, on USB plug

DCDC Output, on battery

My project only use chinese modules, so I have no real datasheets... My schematic :

Siren consumption under 12 V : between 0,25 and 0,35A

Edit 2 : Voltage on the 5V UPS output (yellow curve)


texts: Is there current flowing out of an Operational Amplifier output?

texts:
I came across the following self-study problem, taken from The Analysis and Design of Linear Circuits (8th edition).

I was not intending to solve the problem, since I am just looking over all problems in the book. Something caught my attention, however.
I was looking at node c, the one labeled with \$v_c\$ in the Figure. If I were to apply Kirchhoff's Current Law to then perform node-voltage analysis, I would not know what currents to write down. I know the current flowing into the positive input of the second OpAmp is zero, so that means there is either current going into/coming out of the output of the first OpAmp, and current through the 150K resistor; or else, no current goes through the 150K or out of/into the first OpAmp output. Then, what is the point of cascading two OpAmps?


texts: Cable selection and wiring for RS485 communication

texts:
I'm designing a sensor system where each sensor communicates via RS485 MODBUS in a high-density environment. Each line consists of 18 sensors which then goes to a gateway (Elfin EE11) that converts RS485 into ethernet which then goes into a server. Each line has a maximum distance of 30m from the last sensor to the gateway. Each slave uses a RS485 to TTL module to communicate with a MCU. Each slave operates at 5V and consumes up to 1A.
Cable Selection
 I intent to use the same cable to provide power to each sensor. This cable will also be running parallel to some power cables that are carrying 240VAC 30A. My current selection is to go with CAT5e cables that will carry 48V similar to a PoE system. Due to the power cables running in parallel, should I use STP cables instead of UTP? If I were to use STP, how do I ground the cable properly?
Cable Wiring
The standard CAT5e cable has 4 twisted pairs in it. I intend to use 2 twisted pairs for power. Another twisted pair to RS485 A and B respectively and the other as a spare. Is there anything wrong with this wiring? Do I need to put a termination resistor on each sensor device?

Any help will be much appreciated. Thank you in advance.


texts: Understanding this comparator circuit for AC voltage protection

texts: The circuit shown below is taken from this whole design. I understand the main idea. They want to measure some voltage condition and trigger something else with the comparator. R39 and C38 form a low pass filter. R37 is the pull-up resistor as the comparator's output is open collector. D19 and D20 are protection diodes as the input goes positive and negative. What I don't understand is the arrangement of the resistors R36, R38, R35, and R40. Why are R36 and R38 referenced to ground in the midpoint? How is the comparison process achieved? According to the reference design, the input AC voltage is 230 VAC 50/60 Hz.


texts: Why is current controlled feedback faster than voltage controlled feedback in PWM controllers?

texts:
Looking at modern ICs, we prefer current control feedback over voltage control feedback, due to the speed of the feedback. Current control will react faster than voltage control. Here are 2 images, first of voltage control PWM feedback and secondly of current control PWM feedback

But why is current control fundamentaly faster?

Both images come from the RECOM DC/DC book of knowledge


texts:
I would like to know why pH electrodes are always with BNC type connectors (or DIN, S7, etc.), but never with "simple" wires.

Can we put a BNC adapter to 2 wires and read the tensions with a multimeter?

Thanks.


texts:
I am currently looking over a PCB and performing a spike check on the device of interest.  The device itself has a 7V maximum rating on a pin and I am seeing a strange behavior resulting in a 17-18V spike/switching noise.  The scope shot is shown below:

At first glance, it appeared to be a spike when I look at the full spectrum (shown below), but it is not a spike since it is approximately 150us burst width.  A regular spike would appear to be much shorter in time.  Since there is relays and capacitors between the power supplies, could it be a relay sticking and having a hard time switching off?  Have anyone seen behaviors like this before?


texts: Can I use a 12MHz for NTSC video generation

texts:
I want to use a shift-register to generate video signal directly from SRAM. And researching I found that the pixel rate of NTSC is 12.272MHz and I can't find any crystal closer to that speed than 12MHz. That also makes easy to generate the memory addresses on the memory.

I want to know if modern TV sets can compensate for the offset. I won't be using the color subcarrier. Only grayscale.


texts: Any ideas to make IR LEDs identifiable during position-tracking?

texts:
Background

Johnny Lee demonstrated various interesting ideas (detailed, e.g., in this video as well as this page) that take advantage of the Infrared camera from a Wii-Remote. The IR camera has 1024X768 resolution, and is designed to position-track the 4 brightest infrared-lit points in its view, at 100 Hz. Each of these 4 "points" could be a moving marker in the form of, e.g., an infrared LED -- the LED's emission is detected by the camera, which in turn outputs at 100 Hz, the position data of the IR "blob" observed. Which allows a fast and inexpensive DIY position-tracking system.

Problem

In the above setup, if each IR LED is not just powered on but also somehow made uniquely IDENTIFIABLE, it would give rise to many interesting possibilities. For example, this would allow continuously position-tracking each marker in space uniquely (i.e., with knowledge of which blob is which). In addition, having each IR LED marker being unique also means the setup could be extended to any number of points (say 50 markers) instead of just the 4 brightest points.

The question is: Assuming you start by connecting each IR LED marker to a microcontroller, what would be the most effective way to extend the above setup so that each IR LED marker is uniquely IDENTIFIED? I roughly describe one approach below -- is there some more versatile or simpler approach than it, or perhaps can improvements be made to it?

First, a method that is NOT promising: Since each infrared MarkerLED is connected to a microcontroller, you could have each MarkerLED blink in a unique pattern. But the IR camera has only 100 Hz refresh rate so if there were 50 LEDs, it would be difficult to fit in a unique pattern for each, without the camera's effective position tracking of the points becoming really slow.

Below is a rough idea I'm currently considering (tracks & identifies 50 IR LED markers):

Start by tagging on a simple IR-Detector next to the IR-Camera, both of whose ouputs are read/tracked in sync by a common microcontroller or computer.
Now, let's say there are 50 Markers. For each MarkerLED/Microcontroller circuit, you also add on a second IR LED, called the IdentifierLED, thus there is a pair of IR LEDs for each marker, both controlled by the microcontroller.
For a given marker, so that its position can be tracked, the MarkerLED is only turned ON for exactly a specific 20-millisecond-window out of each second (each marker has its own 20-msec window). During that same particular 20-msec-window, the corresponding IdentifierLED is pulsed in a specific manner by the microcontroller at a high frequency (e.g., 38 kHz), setting up a unique pattern/ID for that specific marker.
And the same for the remaining 49 Markers consecutively, each with its own different 20-millisecond-window and its own high-frequency identifying-pattern. That takes care of the markers' side of things.
Now, on the sensing side of things: For each consecutive 20-millisecond-window during a second, the IR-Camera detects the position of one specific marker (whose 20-millisecond-window it is) via the corresponding MarkerLed. At the same time, the IR-Detector identifies WHICH marker it is, from the detected pattern of the corresponding IdentifierLED.
And this position- and identification-tracking continues for all fifty of the 20-millisecond-windows within each second.
Thus, all 50 markers are tracked, with the tracking-side microcontroller able to update each marker's data once per second.


texts: Whats the difference between Soft IP and Hard IP in FPGA? I dont know whats the main difference. Can anybody help.


texts: Reverse polarity diode, which diode is better: SB140 or 1N5819

texts:
I want to add reverse voltage polarity protection into my circuit to protect the components in my Arduino robot. But i want to know which diode has the edge on the other: SB140 or 1N5819? Or is there another even better diode for this application?

Here are the datasheets for both mentioned diodes.

SB140: https://www.diodes.com/assets/Datasheets/ds23022.pdf

1N5819: https://www.onsemi.com/pub/Collateral/1N5817-D.PDF

From my understanding, i would need to use a diode that has a very low forward voltage drop, but from the datasheets, it seems that both diodes have about the same Vf and both have a Peak Repetitive Reverse Voltage of 40 V which i think should be enough for my battery-powered robot with 12 V. Are there any other characteristics that i should be considering to justify the choice of diode?


texts: Getting high current pulses from a low current source?

texts:
I need to switch on/off a coil draining a high current (close to 1A) during intermittent small intervals (500 ms). Unfortunately, my source is only capable of 100mA in small bursts (say 100 ms).

So, I thought of using a big tank capacitor which I would first charge (either with one pulse, or several pulses). Then, once charged, it could be used to supply the high current that my coil needs.  Does this idea make sense? If not, what could I do there?


texts:
I'm currently trying to re-use some hw from an old project which happens to have the correct ICs I need for a prototype, but the engineer that designed it has left, so i'm essentially now reverse engineering it...

I'm writing PIC24F code from scratch for it, and I can get the I2C bus running (verified with scope and logic analyzer) but have strange ACK/NACK behaviour from the other ICs on the board.

I have devices at 0x68 and 0x40, and both ACK to an initial address write. I thought I was winning, until testing other addresses.. and they all ACK too.

If I continue to try to write to the bus after the first ACK, all I get is NACK for the data frames I write.

My question is, in what scenarios would this occur? I've been debugging this for 2 days and a little haggard now.

Brief description of hw/sw -

PIC24FJ256GB106
Analog Devices DSP
Should be 400kHz I2C, with 2.2K pullups. Voltages all check out.
All start/stop/restart traces are fine. The bus appears to be working.
Baud rate on PIC seems fine. I've recalculated according to datasheet.
Analog scope trace shows 0v and 3.3v acheived, analyzer gives correct logic for various tests (using I2C decoder)
Using Microchip PIC24 periph. library
Addresses of ICs confirmed, but none accept data frames, only initial ACK from slave address

It's quite vague not providing traces, I'll try to later when I'm back with the HW. It's infuriating as this HW definitely works and is currently in mass production, so it can't be a hardware problem.

Edit - trace added and datasheets linked above!

Scope trace -

(Analog trace of SDA for reference)

SDA seems to be being released correctly by the slave, but I'm confused as to what is pulling it low for ACK on other addresses. The scope trace shows a write to 0x68 with 0x08 then 0x1C.

I get an ACK for the address but NACK for everythign else, this is the same on all addresses though...

I2C Library setup call -

c1 = (I2C_ON | I2C_GCALL_DIS | I2C_IDLE_STOP | I2C_IPMI_DIS | I2C_7BIT_ADD | I2C_SLW_DIS | I2C_STR_DIS);
c2 = 4.2;    /* Baud rate */

OpenI2C2(c1,c2);

Everything else is done as the Microchip example shows in the xc16 docs. I might resort to porting some old bit banged i2c just to be sure their functions aren't being weird with me... I know the old engineer used some Renesas lib from another project, this is why I'm rewriting it.


texts: How do I amplify the difference between two voltages?

texts:
Starting at the beginning: I have a shunt that carries DC current, and the voltage drop is very slight. I want to amplify it in order to see it better on oscilloscope, and to have it scaled correctly for e.g. an Arduino ADC. This to measure the current.

So one side of the shunt has voltage V (~12V), the other side has V minus epsilon. I have a pile of NPN and PNP transistors, capacitors, resistors, diodes, etc…

It would be more obvious to me as a newbie if I were trying to scale up a signal around 0V, but since I'm trying to measure "epsilon". I would like to power the whole thing (transistors, arduino, etc…) off of the same circuit, so I'm guessing I'd need a common ground. This means I don't think I can use "V-epsilon" as ground.

So, how do I amplify, and/or "re-base" this voltage drop across the shunt?

Edit:
Ideally not with a ready component dedicated for this (though thank you for the pointer to that), since this is also part for me to understand how to build circuits with transistors, and I have transistors on hand and stores are not exactly open and convenient at the moment.

(oops, obviously buck converter also has access to grund. And "magic happens here" can also have access to both ground and 5V from buck converter)


texts:
I'm trying to connect this to this. From another question I asked (I can't find it anymore) the cable is a flexible flat cable, and I should pull out the black plastic piece at the bottom right of the picture in the first link, insert the cable, then push the black piece back in. Unfortunately, the black piece isn't going fully back in like it started, and it keeps wiggling out, and the screen doesn't display properly. I know the problem is in the screen because the raspberry pi works fine when connected to a TV.

The screen:

The connection:


texts: Causes of over-voltage at the gate when a MOSFET is being switched

texts: For a circuit such as this, people have suggested on this site, to add a zener diode to prevent the MOSFET from blowing up by protecting against gate overvoltage. I want to know that: if the voltage at the gate is 12V or 0V, then what could be the possible reasons of overvoltage?


texts: Can we generate electricity efficiently from a peltier device by supplying heat?

texts:
Is it possible to generate electricity from a Peltier device by only supplying heat (not ice)(something above 343 K )?

How efficient can it be?

Which is more efficient?- Using Peltier device or using the heat to convert the water to steam and then to electricity(heat is obviously not 343K in this case, it's something above 373 K)?


texts: How does this transistor (pre-)amplifier work?

texts:
The following circuit is part of a larger circuit and processes analog audio. The input comes from the top-right and the output is the rightmost terminal of the pot, which then feeds into a straightforward audio amp chip (LM386N to be precise) before finally going to a headphone jack.

My basic read is that the signal comes in and

gets high-pass filtered by C10/R10
something ampey involving R11, Q1 and its base components, and C12
gets low-pass filtered by R13/C13
goes through the pot

What I really don't understand is what is going on with #2 (though a friend suggested the entire thing may be a single amplifier and the 4 parts can't functionally be separated).

Is this a single circuit or is my breakdown more or less accurate?
In either case what is #2 doing?
How does a transistor work when the signal is at the collector and not the base? In looking at amplifiers I've been unable to find a single example of this.
What is the function of the diode in all this?
What is the function of the pot? Is this related to volume, or is it related to the beta of the transistor as friend suggested?

Keywords that can readily be googled or links will suffice for answers if you don't want to type it out.


texts: VHDL: Does VHDL allow enum to be passed to generic?

texts:
Is it true that one can pass boolean, integer and its subtypes as well as std_logic_vectors as generic to a VHDL entity?

Does this list also include enum types, which is user defined i.e describe an enum in package and then include it in the entity declaration and then declare a generic of that enum type?


texts: How can I control the route to analyse with HyperLynx in a switch?

texts:
Good day to everyone.

I recently started using HyperLynx from Mentor and I'm having difficulties in analyzing the signal-integrity of the signals due to having switches in the circuit.
When I load the IBIS of the switch, it detect correctly the different routes, but when I select the input route, it also selects all possible outputs.

In this case, the idea is to analyze the route from:

1) CLVTH16245 (bi-directional transceiver)  <- 2) SN74CBT16390DGGR (switch) <- 3) SN74CBT16214CDL (switch)

I select the line using right button and include in Analisys but it selects all the possible routes as you can see at the next image:

Moreover, when I try to modify the assigned model it doesn’t allow me to select only one route and select all three routes as you can see on second image.

Can anyone tell me how can I select only one route at a time to analyze?

Best regards.


texts: Transistor saw-tooth oscillator. Saturation issue using LTSpice

texts:
I'm currently designing a saw-tooth oscillator that should be frequency adjustable, I don't want to use potentiometers, so it has to be voltage controlled. The frequency is controllable in the circuit shown, although it has not a very wide range, but has problems when the control voltage (VC) exceeds a perticular value.

At the moment I have trouble understanding this Sawtooth Oscillator fully. These kind of oscillator are always a bit tricky to me to understand, most of the time there is too much going down. Which gives some problems at certain voltages.

My current understanding:

The first part concerning Q1 is a current source for C1, which integrates voltage VC, which is 11V in this example. We choose VC to be adjustable for frequency control of the oscillator
The last part is a voltage divider for static voltage VA. It ensures a static voltage at Vbase if it isn't pulled to ground.
The middle part:
If the integrated voltage of C1 (Vout) gets higher than Vbase + Vbe of Q2, current can flow through Q1 from emitter to collector, which saturates Q3 and pulls Vbase and C1 to ground. C1 gets discharged, Q3 isn't saturated anymore, Vbase isn't pulled down and C1 (Vout) can't make the Vbe jump of Q2 and VC gets again integrated by the current source.
And the cycle continues.

Seems to work:

Bigger
Green: Vout, Blue: Vbase

As expected the output voltage rises to Vbase + ~0.6V (Vbe), then gets quickly discharged. The blue line also shows that the divider voltage gets quickly pulled to ground.

There is only one problem. What if I increase the voltage VC to 12V?

Bigger
Green: Vout, Blue: Vbase

The first cycle everything is going right, but the cycle doesn't continue. Q3 stays saturated and pulls Vbase to ground. Vout stays at +Vbe.

I'm fairly certain I'm missing something in understanding this circuit. Can someone explain me why the cycle doesn't continue, although it does for lower voltages, and maybe a way to fix this to increase the frequency range.

Here is a Pastebin link to the schematic file for LTSpice, if anyone needs a different file/output please give me a comment! http://pastebin.com/VMVLEJkv

Thanks!


texts: I am making a wheel encoder out of a Hall Effect sensor with magnets in a concentric circle on the wheel. The Hall effect sensor is on a 2-layer 9x5mm pcb. I usually fill in the layers by drawing a ground shape and then deleting the islands. My question is: should I not add the ground shape because the magnets will induce currents in it- making my circuit unstable? or to put it another way, with magnets passing the pcb, is the less copper the better?