texts: Single shunt with multiple current sense amplifiers vs using multiple shunts

texts:
I would like to turn an Arduino clone into a current meter that allows me to measure the the power draw of a sensor node which has sleep and active modes. The sensor node's supply voltage is in the 4-6V range and during sleep the current I'm trying to measure is in the single-digit microamp range, while during transmission it may draw up to 150mA. Ideally I'd like to stay well below 1% error across the measurement range after calibration.
This type of problem seems to come up occasionally. Here and here are proposals for actively switching circuitry, and I've seen references to a device called uCurrent which also requires manual switching of sensing ranges. Then I came across this question where an answer suggested to use different-value shunts in series to accommodate the different sensing ranges, which struck me as an elegant solution, though I don't know enough to judge the solution compared to what was suggested in this question, namely to use multiple current sense amplifiers to measure voltage drop on a single shunt.
My question is: What are the relative merits of the two designs (multiple shunts + diodes vs single shunt with multiple amplifiers)?
For my use case I found a number of current sense amps that seem to fit the bill:

common-mode input range beyond supply voltage
typical offset voltages in the single-digit μV range
typical gain errors below 0.1%
gains of up to 1000

If I were to use a single shunt, I might use 50/500x gain current sense amplifiers in the INA191 family or 50/1000x in the INA21x family; connecting both a 50x gain and 1000x gain current sense amplifier to a 0.2Ω shunt, I could use two channels of the 14 bit ADC built into my my Arduino clone, measuring over the range 0-2V to sample up to 200mA with 24μA accuracy and up to 10mA with 1.22μA accuracy (assuming 13 usable bits from my 14-bit ADC).
If I were to use two shunts, I might choose two identical current sense amplifiers, perhaps with 100x gain, and appropriate shunts such as 0.1Ω and 10Ω. I'm also wondering if I might want to add a Zener diode to protect the ADC from overvoltages from the higher-resistance shunt.
Would one of the two designs yield better accuracy, or allow me to expand my measurement range noticeably, or be simpler or more reliable to build?
(edit: And would both be usable for high-side current measurement, which I understand is considered good practice and would allow me to re-use my current meter for more projects?)
I apologize in advance if this is not a good comparison for some reason; I'm still trying to understand some of the fundamentals. In that case I would appreciate pointers to relevant material.


texts: Blocking and Nonblocking statements in same procedural block

texts:
Code

module block;
  reg a;
  reg b = 1'b0;
  reg c = 1'b1;

  initial begin
    c  = b;
    a <= c;
  end

endmodule

I simulated the code fragment shown in figure expecting the value of a to be 1'b1 because the statement a <= c; is nonblocking and the RHS of the statement is evaluated at the beginning of time step(i.e before execution of c = b;).

But this is the result I obtained. Why is the output a 1'b0 and not 1'b1?

PS: I know it's not a good practice to mix blocking and nonblocking statements in the same block, but I wanted to know how the IEEE std explains this special case.


texts: I'm powering a project with a 2-cell 7.4V LiPo battery.  What circuit do I add to make the unit stop drawing power when the voltage from the battery drops below 6.4V?  The goal is to protect the LiPo battery from discharging below 3V/cell.


texts: Measure signal from common-source N-MOSFET with ground-referenced oscilloscope

texts:
Update: It was the LED on the load that dropped the voltage.

I have problem measuring the voltage of signal from common-source N-MOSFET switch. Everything including o-scope is grounded and there is no way to decouple them. Obviously I cannot put o-scope between vcc and vout, as it will have constant a 5V one way (Vout connected GND), and fry the circuit the other way (Vcc connected to GND).

So I connected the probe to Vout and grounded to nearest point. It gives a reversed signal when there is a load (1k Ohm), but the amplitude is only 3.4V. The Vcc is accurate 5V from bench PSU at cv mode. MOSFET is IRLZ34N.

simulate this circuit – Schematic created using CircuitLab


texts: Is it ok to put decoupling cap over analog input of amplifier?

texts:
I'm designing a single sided board for a bridge audio amplifier based on TDA2005 (Datasheet). My circuit is the same as the one in Figure 3 in this datasheet. Schematic bellow:

Here is a partial screenshot of my board so far. X1 is the audio input and X3 is the power supply input. C3 is the decoupling cap I'm worried about.

I know from digital circuits that the decoupling caps must be the closest possible to the power pins on the IC. Is this required in (relatively low frequency) analog circuits as well?

I was trying to put the cap "between" the IC and the power supply, but the way it is now seems a bit far away from power pins. Also, the input signal is going under the cap and the power traces going to pins 6 and 9 are surrounding the input traces (and possibly the feedback circuitry in the future). I don't know if that is really a problem. Is it?

Another option I though was to put the cap near the output side, surrounding the output traces, but since they are too thick, I think it would be harder to layout the traces. Also, in this configuration, the cap would not be between the power supply and the IC (but after the IC).

Another question is if it is OK to connect X1's GND the way it is in the picture or is it better to put a separate trace to the GND connection in X3 an avoid sharing the GND trace between them?

I know there is a board example in the datasheet. I'm making this one for learning purposes.

EDIT: Thanks for everyone who answered and commented to this question. I made some changes in the layout and kind of finished the board. Look the high resolution image below:

What I did:

Following the advices of @Vladimir Cravero and @Scott Seidman, I added a 1M ohm resistor in the input and a 1000uF capacitor to the power bus.
Put C3 closer to the Amplifier. Now, the power traces aren't surrounding the input and feedback circuitry. (Well, except by C7, which I didn't find another way to put it).
I routed the GND signal from input to the GND pin in the IC. My intend was to isolate it from the currents going from the supply. Don't know if that is bad or good. I think it is OK to do that. Am I right?

I'm planning to "print" this board by tomorrow, to build the amplifier. Any thoughts or suggestions you want to make before I do that?

Thanks again!


texts: A good way to storage/precharge energy for short bursts of consumption?

texts:
I have a battery powered application that must occasionally use a servo motor (like the ones in model airplanes, e.g. Turnigy TR-1160A). This servo will be used in short bursts of 1~2 seconds at a time, with a resting (inactive) time of at least 10s between usages, but typically hours. The battery is large enough to operate the servo for a couple of hours, but it cannot withstand the instant load (eg. >1A) the servo needs; although it could manage a continuous 200mA load without a problem. I cannot use a different battery, but I could add some circuit to storage (pre-charge) the energy needed for the servo, kind of like the flash system in most cameras. So, my question is: what would be the simplest (less component count) way to achieve this, provided:

Output voltage is 6V; current is between 1A~2A.
Current draw should not exceed 100~200 mA.
It should not be too inefficient.
It should have a very low power draw when not in use (<100µA).
It should provide the output voltage in good enough regulation until depleted (a simple capacitor of course would not be good enough).
It's OK to need a proportional pre-charge time right before each usage.
Battery voltage is between 6 and 14V; a switched 3.5V regulated output is available.

EDIT:

Ideally, the solution would be an existing chip or embeddable module (even better!) with that kind of functionality considered (e.g., switched supply) and that needs minimal external components besides the obvious supercap.


texts: What is standard about standard cells in layout designing?

texts: Why are standard cells called 'standard' cells? Why couldn't it be just cells? What is Standard about them? (I'm talking about the common terminology used in layout designing wherein the standard cells are the building blocks of a bigger circuit.)


texts:
Here are a few things that I thought of or that I'm confused about.

I think I am supposed to simplify the circuit itself to be more easier to work with.
I was confused that there was no current or voltage source and I was guessing that I would have to add one to one of the corners
I'm not sure what the question is even asking, so if someone could try to help me understand what "calculate the resistance of the power grid models" means.
For the first model, I'm not sure what to do in order to simplify the circuit. I was thinking it's just parallel and series connections that I need to combine?
For the second model, I know that I am supposed to use delta to Y conversions, unless someone suggests a better or more efficient way.
I've done some research and came across "infinite resistance grid" (we didn't learn about this in class because it's only an intro to circuits class) and so I was thinking that I should connect a current source coming into Node 1 and a current source coming out of Node 2.

Help would be greatly appreciated. I've been looking at this for hours trying to understand what the correct approach should be but it seems that I'm not understanding the problem itself.


texts: Design of a differential digital signal buffer, 250MHz, 1V output swing

texts:
Primarily for academic interest (so please don't suggest ICs to do this, as they won't help me learn how to deal with this kind of problem) I'm attempting to design a buffer circuit to accept a digital differential signal with input voltage swings between 0.6V and 1.5V frequency up to 250MHz and reproduce the signal with the output voltage swing normalized to 1V.  I'm working with a 3.3V supply, and am aiming to have the signal centred at approximately 2V (although this isn't a hard constraint, so don't mind if this varies by a fair amount).  I'd also like to keep power consumption to a minimum.

What I've got so far is this schematic:

The voltage supply is split so I get 3.3V, 2V and 0V rails (the 2V rail is used as a reference for my inputs and for biasing a current source circuit).  Q1 and Q2 are a differential amplifier, accepting the input signals 'inp' and 'inn'. Their common emitter is referenced to a current source calibrated to sink roughly 0.3mA.  I originally didn't include L1 in this arrangement, but transients during transitions were rather high, and I was seeing quite a bit of overshoot beyond my target rails, and a small inductance seemed to solve these problems.

The outputs of the differential amplifier are then buffered through a pair of transistors that are allowed to draw higher current, and into a load (simulated by a pair of 1K resistors to ground in this schematic).

The 0V voltage sources are used for current measurement; apparently this is the standard way of doing this in ngspice, which I'm using for simulation.

The results of this aren't quite what I was expecting.  The results of a transient simulation are shown below:

With each transition, my output signal hits approximately the 1V swing I was aiming for, but then it rapidly fades back towards the mean output level.  It looks as though some stray capacitance is causing the issue, but I have no idea where it could be coming from.  The transistors I'm using (2SC3356) are designed for high frequency applications (fT = 7GHz) so should be perfectly capable of operating correctly in this application.  I'm at a loss as to what else could be wrong.


texts: How to minimize impedance from capacitor to Gnd and Power planes

texts:
I'm trying to minimize the impedance from my capacitors to the Gnd and Power planes.

1. Via positioning

I've learned from several sources that the best via positioning is close to each other. This way you minimize the loop inductance for currents flowing between the capacitor and the Gnd/Power planes.

The best article I found on this topic is Via configurations for connecting decoupling capacitors from All About Circuits (see https://www.allaboutcircuits.com/technical-articles/different-via-configurations-for-connecting-decoupling-capacitors/). A figure from that page:

2. Via size

I don't know how to choose the ideal via size. I know that small vias have more resistance and higher self-inductance. This is what you can calculate with this online tool:
http://referencedesigner.com/rfcal/cal_13.php

But smaller vias can be positioned closer to each other. The loop inductance is therefore much smaller.

Thank you @Huisman to point out that my big and small vias (see details in next paragraph) are in fact equally spaced if you measure their distance edge-to-edge: Both have 0.175 mm annular ring size and 0.125 mm clearance.

However, if you rely on the center-points for distance measurement, they are no longer equally spaced. So it depends on how you measure the "via distance".

So what is actually the ideal via size, to maximize the effect of the capacitor? Suppose that the ideal via size is rather big, I'd like to know how much extra impedance I cause by choosing for the small via anyway. In other words, is it worthwile to go for the bigger vias?

3. Some details

3.1 Via details
---------------------

Normal via
 - Via diameter:      0.7 mm [27.56 mil]
 - Finished hole diameter:   0.35 mm [13.78 mil]
 - Annular ring:       0.175 mm [6.89 mil]
 - Minimal clearance:     0.125 mm [4.92 mil]

Small via
 - Via diameter:      0.5 mm [19.67 mil]
 - Finished hole diameter:   0.15 mm [5.91 mil]
 - Annular ring:       0.175 mm [6.89 mil]
 - Minimal clearance:     0.125 mm [4.92 mil]

Please help me to choose which via is best to connect the capacitors to the Gnd/Power planes.

3.2 Capacitor details
------------------------------
I mostly use ceramic capacitors:
 - 100nF Close to chip power pins, also connected to vias for Power/Gnd connection.
 - 1uF Next to the 100nF ones.
 - 10uF dispersed all around the board, connected to Power/Gnd planes.

3.3 Frequency region of interest
-----------------------------------------------
For my current project, I need to get a clean 5V from a step-down converter based on the AP1501-50K5G-13 chip (see https://www.diodes.com/assets/Datasheets/AP1501.pdf).

This DC-DC converter chip operates at approximately 150kHz. However, it generates noise in the MHz range as well, because of the sharp switching edges. Perhaps even in the GHz region - I don't know.

Aside from my current project, I'd like to know the ideal via choice for all kinds of frequencies.

4. Quantify the impact [+50 bonus points]

I read interesting ideas and "rules of thumb" in the provided answers. But nobody calculated/simulated a specific example.
If you've got the right simulation software (I don't), perhaps you could do some simulations to get graphs like this:

I believe we could discover interesting trends from such simulations. I'd be very thankful :-)


texts:
I'm a electronics hobbyist and I have an old computer, a VIC-20, that I like to build hardware peripherals for.  The computer's logic runs on 5V and there's a user port which can supply up to 100mA at 5V on the computer's main VCC line.

I'm designing a 32 pin GPIO board for it. Since the GPIO chips can sink around 30mA per pin, I'm planning to have an optional external supply jack.

However, I'd like it to be able to support projects with smaller amperage requirements which are only powered from the computer's supply.

I've never done an optional external supply and honestly I'm not sure how to approach it.

How can I connect the internal and external supplies together?

Back-feeding 5V into the computer's VCC while it's turned off seems like a bad idea to me.  How can I avoid that?

Is having 5V on TTL input pins bad if the computer is turned off?

Or are there any other pitfalls I may run into that I'm not aware of?

Thanks.


texts:
I'm making a 4 layer board, with ground on one of the inner layers, as usual. I would like to keep the digital and analog grounds logically separate, although they of course connect on the PCB, and the standard solution to this is a net tie component, which allows me to connect the nets exactly where I choose to.

My problem is that while the newer KiCad versions (I'm using 5.1.5) finally officially support net ties, there is no obvious way to place the tie on an inner layer. I wouldn't want to bring my ground to the front via vias (no pun intended [2]) and back again just to satisfy a DRC rule by tying them on an outer layer.

So the question: how can I place a net-tie in KiCad on an inner layer? "Official" solutions are preferred, but workarounds and hacks are also welcome. I would really like for the final solution to pass DRC though, and even better if the net tie itself is not DRC exempt [1].

[1] In earlier KiCad version, the net tie you could make yourself was based on the DRC not noticing graphic polygons, which would make the tie pass DRC. However, as a side effect if you happened to pass another track through the graphic polygon of the tie, that wouldn't get picked up by DRC either, so extra manual checking was needed.

[2]

    pun indented


texts:
When debugging a circuit using a micro-controller and triac to control AC current I ran into an issue (the triac wouldn't switch off) that was only resolved by flipping the polarity of the triac. The circuit design had the triac and optoisolator MT1 connected to hot, I accidentally switched the triac and had the polarity reversed. Since I presumed that triacs where symmetrical devices I thought it was no big deal, but apparently it was.

Since TRIAC's are supposed to be the equivalent of two Thyristors in reverse-parallel, I couldn't think of any reason for this switching asymmetry, maybe someone can shine light on the situation.


texts: Calculating resistor values for a Schmitt Trigger and LDR circuit

texts:
I am trying to make a light sensing circuit which has hysteresis.

I want an op-amp (LM358) to output logic 1 (12v) when the light level rises above 250 lux, and output logic 0 (0v) when the light level drops below 100 lux. The hysteresis should be enough to prevent small, insignificant changes (~1v) in the light level from abruptly flipping the output.

I made a simple potential divider to get my threshold voltages for the LDR I was using:

simulate this circuit – Schematic created using CircuitLab

I measured:

At 250 lux, the voltage is 5.27v.
At 100 lux, the voltage is 3.4v.

I have then created the following Schmitt Trigger circuit schematic:

simulate this circuit

My problem is that I have no idea how to calculate R2 and R3, and I don't know what Vref I should pick! I would much appreciate some guidance on how to create this circuit.

Thank you


texts: LED and photodiode characteristics at very low currents

texts:
I'm trying to understand the coupled characteristic of a classic 4n35 optocoupler, used in reverse biased photodiode mode (I'm only using the B-C junction only).

Over 1mA input forward voltage, the characteristic is nicely linear, which is to be expected since

the led light output is proportionnal to current,
the photodiode's photocurrent is proportionnal to photon influx.

However, under ~1mA input forward current I measured the following coupled characteristic :

Measurement notes : The currents are measured as the voltage at the given points, divided by the corresponding resistance value. The voltage is measured by an arduino that also provides the PWM. I vary If through the PWM duty cycle. I wait about 100ms before measuring a new datapoint so that the ADC S&H circuitry stabilizes ; and I increased the PWM frequency so that ripple is more or less negligible.

Obviously, the characteristic is not linear anymore. What is the reason for this behaviour?

I thought that that might come from the diode or the photodiode side :

On the LED side, the input led forward voltage collapses at a low current. That may imply that the energy of the charge carriers is not enough to emit a photon ; however as I understand it the photon energy comes from the electron+hole energy, not from the forward voltage drop. Or am I mistaken?
Now for the photodiode side. At vanishing photocurrent levels, I'd expect the dark current to be significant. However this dark current should add up to the photocurrent, so that without any input the diode reverse bias current is not zero. We should therefore observe a straight line with a positive offset. This is not what I can see here : it looks like there is the photocurrent plus a negative current that vanishes when some light strikes the junction.

Unfortunately most information I found on the web about leds or optocouplers assume current levels much higher than that. OTOH, information about dark current is plenty but it doesn't seem to apply here.


texts:
We have a 50 pair cable running about 1.5-2 KM with some services running on different pairs. One pair has recently become intermittent and is losing connection for  1-2 seconds at random. It might happen a few times an hour, so I jumped the service onto another pair. There is a modem connected to the pair for communication between two sites.

When resistance tested with a multi meter with a loop in one end it was reading 330 Ohms. When using an oscar meter it was reading -2.4db which is the same readings for other pairs.

I would like to use an Arduino to monitor the line resistance for a few days and see if there are any spikes or breaks in the line.
I was going to use an analog input as a multimeter by using a known resistor and the looped pair as the other resistor.
As seen here.

Does anybody think this will not work?

How else could I go about this?


texts: STM32F107 SPI -> UART maximal transfer rate

texts:
I am designing a board with STM32F107 microcontroller and AD7680 ADC. What I need is to read data from ADC, increment sequence number after reading each sample, and send ADC values via UART or USB OTG (USB CDC device) to a computer. Also I need to catch rising edge on a single GPIO trigger pin and remember the sequence number in the time of triggering.

The main constraint is the speed - I need to make it as fast as possible.
Since I don't have to much experience with Cortex MCUs, I have two questions:

Is it possible to achieve this scenario using DMA (i.e. without some loop which will consume all CPU time)?
I know, it's difficult, but can somebody estimate the maximal achievable sampling rate (5 kHz, 20 kHz, 50 kHz...)?

Thank you in advance, any suggestions are welcomed.

Klasyc


texts: How to count the number of high voltages in Hantek Oscilloscope?

texts:
I have a Hantek 6022BE oscilloscope and I want to know how I can count the time and number of times a certain voltage is reached by the wave. For example, I am measuring the voltage of data being transferred over a USB cable. So since the data is transferred as 1s and 0s, the voltage is approximately either high (around 20mV) or low (0V). I want to know how many high voltage (around 20mV) spikes there are. Obviously since there is a lot of noise, the electrical signal of the waveform is not very clean.

I want to know if there is a way to count for how long the voltage was above a certain, manually set, voltage. Can the Hantek application which I downloaded do this for me in any way?


texts: Transistor Current Ic vs Power Dissipation

texts:
I'm a little confused on Transistors and their power dissipation vs current.

If you look at the 2N2222A datasheet. It claims the max Vce is 40 volts.

And that the Ic max current is 1A.

It also says the power dissipation is 625mW.

So, clearly it can't do BOTH 1A & 40V and stay under 625mW.

Does that mean if I want to drive it at 40 volts, then 0.625/40 = 15.6 milliamps would be the most I could put through it?

Or say at +9V you would only get 0.625/9 = ~70mAmp.

Even at 3.3V you only get like 190milliamps.

To get a full Amp out of the transistor, you have to drive it at LESS than 1V.

What am I misunderstanding. I know I see things all over the place talking about the 2n2222 getting 1 amp out of it. But shouldn't it be burning up all the time then?

Am I misunderstanding what the power dissipation spec means? I must be.


texts: Turn on LED if certain voltage range is detected

texts: I'm new to circuits and in a side project I'm trying to design a DC circuit without microcontrollers that will turn on an LED if a certain voltage range is detected. For example the LED turns on if there's a voltage over 1.2V on a certain node. I'm not sure what component or setup will be able to trigger at a threshold. I'm not familiar with most EE components beside the very basic ones (resistors, capacitors, inductors), but I would definitely like to know which ones I would need to look into to make this.


texts: question about signals from NPN - 4 -wire proximity switch

texts:
I am testing a float proximity switch not connected to any load. It has 4 wires:

Brown +
Blue -
black  NO
white NC

I connect the proximity switch to 12 V, but why am I getting 12 V between the white and blue (when there is object the + probe on white), also 12 V between black and blue (when there is no object, the positive probe on black).
Reference image:

Shouldn't I get no reading in both cases?


texts:
I'm trying to operate a classic ultrasonic sensor breakout board on my Arduino. I'm aiming for some ultra low power consumption and I have been trying to switch the ultra sonic sensor board via NPN transistor low-side switch. However because the ultra sonic sensor trig Pin is an output set to LOW when not measuring, the breakout board find itself a ground without being switched by the NPN. Any idea how to tackle this ? I was thinking to use a PNP high-side switch circuit, would this be the solution ? Or is there any thing in software side to avoid the trig pin to ground when not in use ?

const int trigPin = D6;
const int echoPin = D7;
const int enPin = DXX;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(enPin,OUTPUT);
  digitalWrite(enPin,LOW);
}

void loop() {
  digitalWrite(enPin,HIGH);
  getDistance();
  digitalWrite(enPin,LOW);
}

Thank you!


texts: How can I view USB traffic on an oscilloscope?

texts:
I'm trying to examine the communication of a USB mouse with an oscilloscope (PicoScope 3204).  When I connect the scope's ground to one of the two data signal lines (Data+ or Data-) the mouse shuts down.  The mouse is the 1995 Microsoft Home device, so it must be using USB 1.1, not some fancy high-speed version.  I also tried the same on a USB memory stick and experienced the same problem.  Is there an simple circuit I can build to overcome this problem?

I'm aware there are sophisticated USB test fixtures for this purpose, but I'm trying this as a demonstration/experiment, so I'm looking for a minimal home-brew solution.


texts: In my project, I am using an Esp32 powered with a LiPo battery of 3.7V. I do not have a battery charger, can I charge the battery by plugging the esp in with USB? Does it handle reverse current in order to be charged?


texts: Solar panel output about 22 - 24V not charging batteries connected in series

texts:
I have an eco worthy 4 solar panels (2 * 12 connected in series and 2 * 24 connected in parallel). I can confirm that on a good sunny day output voltage from panels (measured on the red and black cables is about 22 to 24V) produce the output expected. On the battery side, I have 4 * 12V 30AH batteries (li Ion) connected in series(2) and then parallel to produce output 24V.
Issue When I connect solar panel in series mode across the 4 batteries(I tried even just 2 of them in series) they dont seem to charge since the solar output is just less than 24V.  On the other hand, if I connect the solar output in parallel on directly to one battery it charges fast (like an hour or so) to about > 13.5V. And, then it is able to handle load for a few hours.
My issue I am unable to get the batteries to charge in parallel from a solar array configured to produce 24V.
On the battery side, I have 4 12V 30AH batteries (li Ion) connected in series(2) and then parallel to produce output 24V.
Does anyone have any suggestions if solar panels expected to produce 24V are lesser than 24V expected(Live in a moderate weather not always bright sun)? My issue I am unable to get the batteries to charge in parallel from a solar array configured to produce 24V.


texts: How is a 'ribbon controller' called in electrical terms?

texts:
On some synthesizers, there is a strip called ribbon controller, to wipe your finger over and it detects pressure. It's a bit similar to a mobile phone's LCD touch panel, except that it is one-diagonal (horizontal only) and the accuracy is (probably) less. It's typically around 10cm/4" and the amount of pressure is normally not checked (just pressed or not). Also simultaneous presses are not supported.

It is used for adding an effect to a sound, like vibration (pitch), volume, filter cutoff or other effects.

It looks like the black square in the buttom left (under the joystick).

I have an idea to make something like this myself, but I was wondering how it is called in 'electronic' terms. I tried to search for ribbon controller, but I get some Play Station 4 ribbon 'controller' which I don't think is the same. It is also possible to buy readily made separate ribbon controllers but these cost like 300 euro and normally come with a MIDI box (while I want to create my own functionality, MIDI related or not).

So, what is the name of such a strip/touch/pressure sensor?


texts:
I have asked a similar question but I did not get an answer, as it was too specific. So I will build on it but make it a bit more broad spectrum.

I would like to make a digitally selectable BPF using transistors to select a component in the filter; resulting in the center frequency being changed.

I have used FilterPro to generate quick second order filters and get a rough filter response.

For all the designs, a Multiple-feedback was selected:

In the first picture, a center frequency at 108KHz with a bandwidth @ -3dB of 103K to 113KHz is given.

For the second, a center frequency at 117.5KHz with a bandwidth @ -3dB of 112.8K to 122.2KHz is given.

The only difference between these two circuits is R3.

If I were to implement a circuit as shown below, would it work and what transistor would be recommended? I have selected the TL082ID  as the Opamp in the circuit design as that is what was used for the ST7590 RX gain amplifier.

For the transistors, I was thinking of using the MOSFETs (2N7002) used in the ST7590 design as well.


texts: Why won't "wait until a'active" return when the signal a is assigned the same value as before?

texts:
For a signal a, the attribute a'active is true whenever a is assigned to - even if its value does not change (i. e. the same value as before is assigned).

In the following example, the signal a is assigned its previous value, '0', at 100 ns. a'active should therefore be true, but the wait until a'active statement in process p1 does not return.

The wait statement in process p2 waits for a'transaction'event in addition to a'active (to my understanding, the conditions should be equivalent). This wait statement does return, confirming that a'active is, in fact, true.

So why doesn't the wait statement in p1 return, even though its condition is clearly fulfilled?

MWE:

library ieee;
use ieee.std_logic_1164.all;
library std;

entity vhdl_active_minimal_testbench is
end vhdl_active_minimal_testbench;

architecture rtl of vhdl_active_minimal_testbench is
    signal a  : std_logic := '0';

begin
    p1: process
    begin
        wait until a'active;
        report "p1: a'active";
    end process;

    p2: process
    begin
        wait until a'active and a'transaction'event;
        report "p2: a'active AND a'transaction'event";
    end process;

    stimulus: process
    begin
        wait for 100 ns;
        a <= '0';
        wait for 100 ns;
        std.env.stop;
    end process;

end architecture;

ModelSim 10.5c output:

# Loading generic.vhdl_active_minimal_testbench(rtl)
# ** Note: p2: a'active AND a'transaction'event
#    Time: 100 ns  Iteration: 1  Instance: /vhdl_active_minimal_testbench
# Break in Process stimulus at [...]/test_vhdl_active_minimal.vhd line 29


texts:
I have to find voltage gain $$\frac{v_2}{v_1}$$ as a function of x in the following circuit:

As far as i can see, this xR thing is obviously a potentiometer, usually, i would do this using superposition, i would firstly find gain when negative port of v1 is on the ground with positive one being connected to generator, and then i would do the other way around, sum of those gains would be the total gain.

However, i am not very familiar with potentiometers in circuit analysis, so i cannot progress any further since i don't know how would circuit equivalent to this look like because solving circuit with arrow pointing towards resistor makes no sense to me. Any help is highly appreciated!


texts: ESP8266 Wifi Module - prints “ready” but not responding to AT commands

texts:
Just received my first ESP8266 wifi module with some excitement. However I've been unable to fully communicate with it. I have connected the module to my computer via a usb to serial cable and I'm power the module via a separate power supply (3.3v).

After powering the module up I receive the following information (via PuTTY or and Arduino serial monitor window):

[Vendor:www.ai-thinker.com Version:0.9.2.4]

ready

I have tried sending various AT commands e.g.

AT+RST

But I get no response. Using ctrl+m and ctrl+j in putty didn't help either.

Please see my youtube video if its helpful:
https://www.youtube.com/watch?v=RvasOuHuWDc


texts: I'm looking at different FPGAs for my dissertation project and I keep seeing that the multiplier blocks are 18x18 bit, why is this? Why are they not 16-bit?


texts: Using MAX232 to fix prolific usb to serial voltage levels

texts:
I have a hobby PIC programmer (K8048) that uses rs232 to communicate with PC. My new laptop doesn't have rs232 port so I bought a prolific usb to serial converter to interface with this programmer but it appears as if the usb to serial converter is not fully rs232 compliant with its voltage levels so...

Rather than scrap the board and fork out £30 for the usb version I wondered if any one could see a problem with running the signal into a max232 and feeding that into the K8048? The max232 datasheet shows +- 25ish volts on the TIN/RIN pins... It seems so simple I must be crazy?!


texts: Creating a loud cracking sound to scare cats away forever and ever

texts:
So we have some hardcore cats in our area, recording their glorious conquests with excrement. They don't scare easily. I'll be conducting psychological warfare, they must start associating some form of visual cue with being scared, and I'll have one real and maybe 6 fakes around the garden. Each day I'll move them a bit and switch out the real one. It will probably be a garden gnome or something equivalently horrific.

So I've picked out an arduino board, it will have standard 5v at 40 mA pins. I have a PIR sensor and some red LED's. I'd like to create a loud "crack" noise, like a gunshot or firework. Like an audio version of the flash or strobe. I've tried setting a piezo buzzer to go off when they are close but it just doesn't cut it. Neither does that very high pitched whiny anti-cat noise. In the worst case I will resort to some form of aggressive sprinkler system but that's suboptimal.

I was wondering if there is some sort of component which can make such a noise? Is there a simpler solution than going all out on speakers? I know what a capacitor is but I'm lost beyond, please aid our species against these fluffy faux-cute lawn-soiling horrors.

p.s. I do like cats but my father is allergic and they do relieve themselves all over our (now smelly) lawn a tad too often


texts: Crystal grounds and minimal trace distance to leads

texts:
Some questions have already been asked about crystals but there's a few competing designs and I have a few "obsessive" type questions on layout. Here's a almost completed layout with a PIC16F microcontroller connected to a 32.768kHz (12.5pF). Relevant linked questions are:

Competing PCB Crystal layout recommendations

How far is "too far" when routing traces for crystals, and how asymmetrical is "too much"?

Traces under 32kHz Crystal

C22, C23 are 18pF, that's what I came up with after doing: 12.5 * 2 - 2 * stray.

The snap grid on Eagle is 0.5mm.

R23 is a resistor I'm undecided about because I see designs with 100k or so and designs without it. That's question 1!
I've added a ground fill under the crystal (pins 2 and 3 are unconnected on that particular part) and connected it to local ground only. Olin has mentioned doing that about 100 times so I believe that is the right thing to do. But other designs do a ground ring around the crystal on top layer. Is that only necessary on a single layer board?
Pin 6 on the PIC is an digital assert line. I'm hesistant - how close can I bring that trace to the crystal before upsetting the high impedence crystal oscillation? The distance between pins 3 and 4 is 0.7mm approx so it stands to reason (?) that I can be that close?
the crystal traces are not equal. Should I make an attempt to make them more equal?


texts: differences between photelectric amplifier and optical amplifier?

texts: i'm researching about fiber optic sensor and stumbled upon a question regarding about the amplifier. I've read in the internet that optical amplififer contained many type such as EDFA,semi-conductor and raman. While, on the other hand, photoelectric amplifier has scarce information about them. Both of them are related to fiber optic but to me it seems like there are two category where the optical amplifier is for telecommunication while photoelectric amplifier is for industrial sensor. Maybe someone can give me a clear explanation whether these two are the same or not and what are their working principle?


texts:
For an outdoor system I'm designing, I'm looking for a sensor able to detect a signal light from a distance of 50-150 metres and provide an output to a low-end microcontroller (i.e. not enough processing power to deploy CV). Cost might be high if reliability also is. Key features of the setup are:

-the signal light is diffused inside a cube whose side is approx. 12-15cm long. I will measure light intensity on a side of that cube;

-the diffused light is not significantly stronger than ambient daylight and the system will operate during the day;

-the light is colored and I can choose the color as long as it's in the visible spectrum;

-the light works in an on-off fashion and I have all the time in the world to determine any threshold values if the system needs them;

-response times of 0,1s or less are acceptable;

-it's ok if the sensor will have to be stationary.

A ready-made sensor is a luxury I can ditch easily - I investigated collimators and other optical components and I think I could devise a custom solution myself, but my knowledge of optics is limited. I think what I need might be compared to a single-pixel camera; if I'm correct, the sensor in a custom solution would probably be a simple photoelectric one, but the optics would be the most complex part, the one I need most pointers for.

My creative instincts seem to have died down when investigating this issue, so I'll be most grateful for any advice. Thanks!


texts: Super Capacitor battery replacement, Lead Acid vs Capacitor explosion

texts:
I'm considering replacing my lead acid starting batteries on my boat with something like this. 500F @ 16v Starting battery module
https://www.maxwell.com/images/documents/ESM_Manual_Install_4_15.pdf

I understand the high current risks associated with capacitors vs batteries. I had an older 12v 8d battery explode on the boat, my guess is that it was off gassing due to age and condition and the off gassing ignited.

I have seen what happens when a lead acid battery explodes, and the gas / acid is bad. What kind of gases/explosion/fire from a capacitor?


texts:
This circuit is a DC bus capacitor soft charge from a 3phase inverter.
I've seen a lot of similar products but this one is a little strange and I'm curious how it works.
I want to know why the transformer's output is rectified(I assume) knowing that the contactor works with AC.


texts: Generator supply not working on Automatic changeover

texts:
I am using Havells Changeover for switching between generator and main supply. There are three slots.

Main
Gen
Load

Main has two Neutral wire, Gen has one, but Load has no Neutral wire.

When system is on Main power, it works fine. but when Generator is started i don't get electricity in house.

Lights blinks a little whole time.

Is it due to missing neutral wire in Load?

Should i remove one wire from Main and put in the Load? are all neutral wires same, or there is some difference


texts:
I am currently working on optical isolation of the i2c bus in order to remove the risk of damaging the PI from outside noise.

I am using Si8400 optical isolator but I was so far unable to make it work, so I would like to check with you if I am doing it all ok (and the reason for it not working is that I destroyed the part during soldering or something like that.)

I have a separate 5V usb power supply for the B side of the Si8400 and I am testing connection of an i2c thermometer TC74A5.

When the thermometer has power and i2c bus connected to the pi, I can see it using i2cdetect on its proper address (and all other i2c devices I have connected).

Then I tried connecting the the TC74A5 to the B side of the isolator, and I simply cannot see it using i2cdetect (all the other devices are still there).

Originally, I did not have a 3k pullup-resistor connected to the B side lines, which resulted in the i2cdetect not finding anything at all. After that I have connected two 3k 0.5W resistors between the +5V and the data + clock lines (one at each line). This has resulted in i2cdetect now reporting the devices connected straight to the PI but still no sign of the TC74A5 on the B side.

Am I doing something wrong with the connection?

To summarise the connections of the Si8400:

1 - AVDD - connected directly to Pi's 5V
2 - ASDA - connected directly to Pi's SDA
3 - ASCL - connected directly to Pi's SCL
4 - AGND - connected directly to Pi's GND

8 - BVDD - connected to another 5V power supply
7 - BSDA - connected to +5V using 3k resistor and to SDA of the TC745A
6 - BSCL - connected to +5V using 3k resistor and to SCL of the TC745A
5 - BGND - connected to the ground of the other PS

Links:
Si8400 data sheet
TC74 data sheet


texts: Is it a good practice to use resistors for MCU inputs for this case?

texts:
I want to use Arduino Uno or a Nano which uses ATMEGA328P as micro-controller.

D2 is now set as INPUT. During the start up I want the MCU to detect whether pin D2 is HIGH or LOW depending on the setting set by the user. The setting will be done by an SPDT switch as shown below:

So if the switch pole is coupled to the +5V the state of D2 will be HIGH and if coupled to the GND the state will be LOW. Depending on this state in void main(), the program will perform a specific task.

I'm just not 100% sure whether it is very fine to connect pins that way. Is there any need for a pull-down resistor between the switch and the GND or between the switch and the +5V pin?

(What if the worst case D2 is accidentally set as OUTPUT pin?)


texts: Solve setup time violation when CLK is same as data input in shift resistor

texts:
DSTM7 is same as push button 1 and DSTM8 is same as push button 0. I want shift resister shift when either button is pushed. For example, when push button 1 is pushed and DSTM7 has a pulse and shift resister shift with first element 1 and when push button 0 is pushed and DSTM8 has a pulse and shift resister shift with first element 0.

In this circuit in the picture, I input 100101. (DSTM7 indicate 1 and DSTM8 indicate 0). And when new input come, I want to change QA, QB, QC, QD which is LLLL in initial state to become HLLL, LHLL, LLHL, HLLH, LHLL, HLHL in a sequence.

This circuit works well in pspice but I know this cause setup time violation because input SR and CLK is same in 74194 ic. How can I solve this problem without delay ic?

This is sample output. This is my first question so please forgive me even if I violate community guide. (Just notice me and I will change my question)


texts: Noise due to stray voltages in a data acquisition system

texts:
A single ended earth grounded data-acq. board on the left in the below illustration has inputs coupled by BNC cables coming from force transducer amplifiers A1, A2, A3, A4 as shown on the right:

If no BNC is hooked up, when I measure the voltage between any BNC connector terminal to earth I read around 100VAC by a multimeter. But by using low impedance setting of the multimeter  I verified that this is stray voltage aka ghost voltage.

Since I measure this stray voltage between BNC inner pin to earth and BNC outer pin to earth, I guess this stray voltage is in phase both terminals of the BNC.

There is no direct ground loops in the system i.e the amplifiers'/sources' grounds are not earthed. During data acquisition sometimes I see noise coming and going for some seconds sometimes, and I was suspicious of capacitive coupling.

My questions are:

1-) The data-acquisition max input voltage is +-10VDC. Would this stray voltage be problem in this case? Is it exceeding maximum common mode range? Because the moment I hook up the reading are okay. But Im not sure is this stray voltage still have side effects.

2-) Is this configuration is more susceptible to error in readings than in differential ended inputs? How would diff ended. connection eliminate the noise caused by stray voltages?


texts: What is the difference between smart antennas and phased arrays?

texts:
Wikipedia defines smart antennas as follows

  Smart antennas (also known as adaptive array antennas, multiple
  antennas and, recently, MIMO) are antenna arrays with smart signal
  processing algorithms used to identify spatial signal signature such
  as the direction of arrival (DOA) of the signal, and use it to
  calculate beamforming vectors, to track and locate the antenna beam on
  the mobile/target.

And phased arrays as follows

  In antenna theory, a phased array is an array of antennas in which the
  relative phases of the respective signals feeding the antennas are set
  in such a way that the effective radiation pattern of the array is
  reinforced in a desired direction and suppressed in undesired
  directions.

From these definitions it seems that two terms define similar things. And yet the article on smart antennas do not reference (in the text) phased arrays and vice versa. To contribute to my confusion, there is a book Adaptive Antennas and Phased Arrays
for Radar and Communications by Alan J. Fenn, which has two major parts: one on adaptive antennas and one on phased arrays. These parts address different problems: smart antennas for nulling out interference sources and phased arrays to scan an antenna field of view. And again the core structure looks the same to me.

So what exactly is the difference between smart antennas and phased arrays?


texts: Are RC circuits suitable for use as power sequencers?

texts:
Are RC circuits suitable for use as power sequencers with EN pins on LDOs?

I know that there may be a problem with reverse sequence on power off, but some devices allow that on power down all power supplies must go down together or in reverse order, so cutting out power would solve power off problems related to RC circuits.


texts:
On page 3 of Hierarchical Timing Analysis: Pros, Cons,and a New Approach , how is set_output_delay related to set_multicycle_path here in this case ?
and how to re-code the path exceptions ? Any examples ?
Why need to duplicate the ports for that MCP ?
Someone told me that another way to set path exception is by using set_case_analysis ?

Path exceptions modeling
In certain situations, path exceptions must be re-coded for ETMs,
e.g., when there are multiple output delays on a port and one of the
output delays has a multi-cycle path (MCP) through one pin internal to
the block. Unless one successfully preserves that internal pin (which
increases the size of the model) or duplicates the ports for that MCP,
design teams must create and manage exceptions to achieve the same
timing result as flat analysis.


texts: Will a parallel capacitor placed before a series inductor be capable of self-resonance?

texts:
If a parallel capacitor is placed in a circuit before a series inductor or ferrite bead (CL instead of an LC), will this combination be capable of any self-resonance? Or does the inductor have to be first in order? This will be in a DC circuit but dealing with potential unwanted self-resonance from noise and 60Hz wall power / switching PS / data transmission line frequencies and harmonics. Thanks in advance.

simulate this circuit – Schematic created using CircuitLab


texts:
I've read in the Make magazine that LEDs can sense darkness. How should I use it in a breadboard circuit?
Is it possible to read the ambient light level and send it to the computer?
How does this work? Does that mean a speaker can be a microphone? In that case, how would you do that?


texts: What are class E amplifier RF choke guidelines?

texts:
I am designing a novel circuit that I beleive has not been constructed yet! No -- I'm just using an exotic switching device for a class E amplifier.

My operating frequency is close to the 160 ham band (my target is between 1 and 2 megahertz).

I have seen multiple designs for bands closer to 80 meters (a few megahertz) that use a 47 uH RF choke on the drain of a mosfet. I will be winding this inductor myself so I would like to optimize this value and determine its effect on the output matching circuit.

I have an LCR meter and I am operating this amplifier at a bandwidth not exceeding 10kHz.

Have a schematic (I see this is for 160m and has a larger inductor):

Do I have to know my load impedance before selecting the RF choke or is that load independent? (as a side note I am using Cree SiC power mosfets because I have a source...)


texts: Connecting grounds of a disconnected power source?

texts:
Background: I'm designing a portable appliance (24 DC, ~30 amps, air conditioner) and need to have a switchable power source between vehicle-supplied power (alternator) and a separate dedicated battery (LiFePO4).  Both are 24v.  This battery is NOT connected to the vehicle in any way, it is dedicated to powering only the unit when selected.

Can I simply leave the ground terminals of both vehicle and battery connected at a common grounding point, and only switch the positive line via a single relay? From my limited knowledge and reading other power supply/ground related questions I would tentatively think the answer would be "yes" but would feel much better if someone would confirm for me. :-)


texts: Looking for criticisms for a VNA-like meter I am designing

texts:
I would like some help from anyone who could let me know any flaws or improvements in my design they can find and help me reconsider any last minute design fixes before I send my new project off to be mass produced. This is the second version of the design but the changes I made were extensive.
So basically I'm building an Arduino shield where the primary use case is to be a SWR meter with an LCD display (not depicted here as that is a seperate shield). But it provides all the functions of a Vector Network Analyzer (VNA) and as such goes well beyond your typical SWR meter.
Because the primary use case here is to act as an inline meter on a transmission line with an existing transmitter its not designed as a typical VNA would be using mixers. The only thing it doesn't have that a VNA would have is a function generator, as it relies on the transmitter to do that, and the directional coupler would be external. However I have designed it in a modular way so not only can the directional coupler be swapped out for one the user prefers or more suited for their setup, but it can also be configured to work more like a traditional VNA as well. With the additional of an additional shield with an in-built low power directional coupler and a sine wave generator it would be possible to also pop on this other shield and effectively have a handheld VNA instead. Being modular there are also several other possibilities for how this device can be configured including as a remote SWR meter so you can have a meter at both the transmitter and the antenna to properly calculate feedline loss, or to understand how the complex impedance of your antenna changes with frequency.
Because of its role as an in-line meter in an existing antenna system it also provides functions a traditional VNA would not, specifically the ability to analyze properties of the transmitter such as accurately determining the true RMS under modulation or precisely determining the frequency the transmitter is transmitting on. Perhaps in the future I may add other features as well either in software of hardware.
Some specifications:

Operates 1 MHz to 500 MHz

Can measure input signals from -52dBm to 0dBm (adjust external directional coupler and attenuator to handle any power transmitter).

Inputs are 50 ohm matched but if building yourself you can switch out different resistors to match different impedances

Note: This is an open-source project and free for anyone else to replicate my work. At some point I may sell kits and/or the printed PCB to people to make it cheaper than needing to pay to get your own PCB printed. So I'd like to make sure if I provide PCBs they have been scrutinized and tested first.
The link to the projects source can be found here for anyone who wants to access the actual files.
https://git.qoto.org/roes/roes-hardware/
Here is a picture of the schematic:

Here is an older picture of the UI in demo mode. The data on the screen is intentionally bogus, and the glitches in the rendering have since been fixed.

This is a four layer board so youll have to see the GIT repo if you want to pick apart my layout in detail. But for now I will share the front side and back side so you can at least get a sense of my placement of the chips and my use of shielding.
Front:

Back:


texts: Altium Polygon Pour gap - minimum feature clearance rule?

texts:
Didn't find anyone covering this.
On this image I'm showing a GND Polygon pour artifact that I cannot seem Altium to detect that gap is too narrow.
Polygons are:
Remove Islands less than 0.2 sq.mms area
Arc approx: 0.025mm
Remove necks width less than: 0.2mm
Signal clearance rules make the pour bleed away 0.15mm.
That particular pour gap is 0.015mm wide - manufacturer cannot produce such feature!

Ok, for a) manufacturer will ignore this (somehow) and provides no guarantee how much the copper will bleed away from that particular place.
b)
Sure, easy fix for that particular spot is to move the via and allow polygon to fill
BUT
I must look and Find them manually - If I get lucky I find them.
Anyone has experience on How to make Altium find such pouring artefacts and report them ?


texts: Why does the Slipring Motor speed increase with a decrease in resistance?

texts:
With induction motors, we know that the speed depends on the number of poles and also the supply frequency.
Now, the slipring motor is also an induction motor and should follow the same principles, but it doesn't and that confuses me.

Consider a slipring motor with resistor banks that are cut out of the rotor circuit in stages.  At  starting, the torque is much higher and gradually decreases as the resistance is lowered. But at the same time, the speed increases as the resistors are cut out of the rotor circuit.

How does this happen and why does it happen? Also, does this mean that the resistance of the rotor circuit affects the speed of the motor?


texts: STM32 Series Microcontroller - Calculations of Timer Variables

texts:
This is a subject that seems to have a lot of confusion (I do not fully understand). How to calculate the Variables:

Period
Prescaler
Duration

if only a few other variables are known. At higher frequencies, for example 1000000Hz simple rules work. At lower Frequencies like 1281Hz things get a little more complicated.

As an example: if we aim for an output frequency of 1281Hz, we need to set the ARR Register to: 32785. We need to set the PSC Register to: 3 and if we want a 50% DutyCycle, we need to set the CCRx Register to: 16393. Where the x in CCRx is the specified Channel one is going to use. 1, 2, 3 or 4.

The Registers need to see values of 16 BITs, Integer Values(65535 or less).

Equations exist so calculations can be made, for example:

\$TIM_{Update Frequency(Hz)} = \frac{Clock}{(PSC - 1) * (Period - 1)}\$

\$1281.11273792094 = \frac{84000000}{3 * 32785} \$

now, the problem becomes more complicated, for a desired frequency of 840Hz:

\$425.946209078739 = \frac{84000000}{167 * 1189}\$

Here in lies the problem, how does one find the value of PSC when one knows only the values for "Clock" and "Period"? The value "TIM_Update_Frequency(Hz)" is not always the actual Desired Frequency.

Other equations must exist so as to calculate the "PSC" Value, or to calculate the "TIM_Update_Frequency(Hz)" so as to deduce the other values.

Guess work is just not a logical approach here.

Can anyone help with more equations for solving for the other variables?

Thank you

Chris


texts: Does a synchronous shift register put out its result at the same time as it gets its input, or does it output it at the next rising edge?


texts: Determine location using IR transmitters and receiver

texts: Let's say I have multiple IR transmitters with known relative locations. Each transmitter emits a unique frequency. I also have an IR receiver in an unknown location surrounded by the transmitters. How can I determine the location of the receiver?


texts: Spartan-6 LVCMOS33 input pin: can it take 5V without damage?

texts:
My Spartan-6 device has an input pin with IOSTANDARD = LVCOMS33 as constraint.
If I accidentally or otherwise connect it to a 5 V signal, will the FPGA get damaged?
There is no current draw to this connection, it is just a voltage input.


texts: Using multiple power supplies to increase current

texts: I need 1300mA at 3.5V, but the highest power AC-DC wall adaptor I have is 1A 12V. Is it possible to use two of these to get ~2A? I'm thinking that diodes would be needed from the positive pins of the supplies?


texts:
I am trying to understand the parameters in an ADC datasheet. The precise parameter being the INL(integral non linearity). Now, I was going through this website INL website.

.
Now, there is another website that shows the ADC error of a 12 bit ADC as 0.00024.
The other website.

.

In the former it is in terms of percentage so I understand. But why a factor of 0.5 or 1/2 is present ?

The ADC I am using is the ADS62P15. In page 5 of the datasheet I see the INL defined (typical) as +/-1 (LSB). Now, is this a percentage value ?


texts:
I programmed UART3 peripheral on LPC4088 to send a single unsigned character posiljka over Tx line. This is done by continuously copying this character into the Transmitter Holding Register (THR) which is the top of the transmitter FIFO.

So I connected my oscilloscope to the Tx line and tried to sent these characters over while recording their oscilloscope images:

0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x25, 0x26.

Oscilloscope images looked fine at the beginning, but once I reached values 0x20, 0x21, 0x22, 0x23, 0x25, 0x26 I noticed that oscilloscope images for these characters look the same than those for images 0x00, 0x01, 0x02, 0x03, 0x04, 0x05. How is this possible? Here is the compressed folder with all the images (please don't pay attention to measured frequency which is wrong as oscilloscope takes wrong edges to measure it).

My C program was supposed to set UART3 communication to be 9600 8N1 which means 9600 baud rate, 8-bit character length, no parity and 1 stop bit but width of the sent character looks two times shorter to me from the beginning.

Here is the program:

#define IOCON_P0_0      (*((volatile unsigned int *) 0x4002C000))
#define IOCON_P0_1      (*((volatile unsigned int *) 0x4002C004))

#define PCONP           (*((volatile unsigned int *) 0x400FC0C4))

#define THR             (*((volatile unsigned int *) 0x4009C000))
#define DLL             (*((volatile unsigned int *) 0x4009C000))
#define DLM             (*((volatile unsigned int *) 0x4009C004))
#define LCR             (*((volatile unsigned int *) 0x4009C00C))
#define LSR             (*((volatile unsigned int *) 0x4009C014))
#define FDR             (*((volatile unsigned int *) 0x4009C028))

int main(){

    //we use UART3 on pins P0.0 and P0.1 with on-chip and external pullup-resistors
    //we set P0.0 and P0.1 as U3_TXD and U3_RXD, no-pullup, no-hysteresis, no-inversion, standard-mode, open-drain (0b0100000xx00xx...)
    IOCON_P0_0 &= !(0x67F);
    IOCON_P0_0 |= (1<<1);
    IOCON_P0_1 &= !(0x67F);
    IOCON_P0_1 |= (1<<1);

    //we turn on UART3
    PCONP |= (1<<25);

    //we set 8N1 communication in LCR (we only have to set first 2 bits because rest is already set properly by default)
    //we also set LCR.DLAB = 1 so that we can aces DLL and DLM in next paragraph
    LCR |= (0b11);
    LCR &= !(0b0011111);
    LCR |= (1<<7);

    //we set DLL[0-7] = 96 and DLM[0-7] = 0 which sets baud rate to 9600 - check referenced user manual, page 510.
    //we don't need to manipulate FDR register as DIVADDVAL=0 and MULVAL=1 are already set ok by default - check referenced user manual, page 510.
    DLL |= 0x96;
    DLM |= 0x0;

    //we set LCR.DLAB = 0 back to original value and can now acess THR
    LCR &= !(1<<7);

    //we enable Rx and Tx FIFO
    FCR |= 0b1;

    while(1){

        //here is where we set the character to be sent
        unsigned char posiljka = (0x25);

        //we input character "posiljka" into THR and send it.
        THR = posiljka;

    }
}

Am I missing anything?


texts:
Today I was reading the datasheet and reference manual of STM32.
Here are the datasheet and reference manual of STM32:
Datasheet & refrence manual.
We should consider two aspects of thevADC to have an accurate ADC - hardware and software.
Ok, let's take a look at datasheet. I think we just should read the datasheet because it appears there is nothing about having an accurate ADC.(Am I right?)
Hardware
There is a figure (fig 58) that tells us many things. At first we have two components out of MCU. "Rain" and "Cparasitic".

Then we should put these between MCU and the line that we are supposed to measure. Am I right,or did I interpret this figure incorrectly and these two are because of impedance and capacitance of line and this figure tells us another thing that we don't know.
If my first suppostion is correct, so we must find out what resistor and capacitor we should choice.
-Rain
First off let's check out the datasheet more. From table 59 we see that this resistor have a maximum value. It's 50kOhm. Why? How they say it? In the next page there is an equation named "Equation 1: Rain maximum formula". Ok, as the discription tells us, we can determine the maximum external impedance(Rain). The equation:

There are five parameters we should find and put in this equation to calculate the maximum value.
Radc: To determine this, we can use table 59. The maximum value for Radc is 1kOhm and I think we can use this value for every case.
Fadc: We determine this when we are configuring the clock for ADC and it's pre-determined.
Cadc: Just like Radc, we can use table 59 to determine the maximum value for this parameter. It's 8pF.
N: Is it bit resolution? Should we always take it to be 12?
Ts: Again, we should use table 59. Its range is 1.5 to 239.5 Am I right?
Ok, let's use this equation and do an example:
Assumptions:

Ts: 1.5
Radc: 1
Fadc: 14
Cadc: 8
N: 12

After calculation,  I get = -0.9986
A negTive number? Why? There is a table below the discription of this equation. Table 60. Rain maximum for Fadc=14MHz . For Ts=1.5 Rain is 0.4kOhm and I expected to get a value close to this but what I get so far is a negative value.
-Cparasitic
I still don't know, if we should put a capacitor as Cparasitic between the pin of MCU and the line that we must measure, or if is the capacitance between the source of our line and our MCU and it just affects on the measurment and we should reduce Fadc. indeed it's a question to me.
Software
Okay, let's talk about this part. If you take a look at figure 57 (ADC accuracy characteristics) you can see there are five errors that I think we can remove in software:

How can I remove them? I've an idea to remove EO and EG errors. This is my approach:
If we take a look at the graph accurately, we know that there are two curves. An ideal and an actual. All we must do is to coincide the actual curve on the ideal one. Assume that the both curves are linear. Then we have a function X=EG*x+EO
To find EO we can connect iuput pin to ground to find the value of EO and put it in the function.
To find EG, after adding EO to x, we must find the slope of the actual curve. Then we take two samples and use this relation to find the slope. S=(Y2-Y1)/(X2-X1) and then EG=1-S
Now using X=EG*x+EO we removed these two error.
What's your opinion about my approach? Is it correct? Do you have any idea to remove ET and ED and EL?
Also please answer to the question that I asked in the above passage.


texts: Can the M590E's boot pin be used to reduce power consumption?

texts: What does the boot pin actually do? Can it be used to reduce the module's power consumption when the module is not required? All recommendations are to pull it low to boot. Can it go hi again to turn off the module? Perhaps there are serial commands I should use to shut the module down when not required.


texts: Hand contacting op amp photodiode circuit causes interference - what ist the physic behind it?

texts:
I am new to analogue electronics and I am still learning about op-amps.
I use the most common circuit for amplifying a photodiode's signal to measure it with an ADC:

Amplification gain is 1M, the 22pF cap in parallel is for damping oscillating noise when the impulse comes in. I got some 50Hz noise in the signal due to the diode's cable is a .5 meters long flat ribbon cable, that's a problem, but not for this thread (if anyone knows how to filter that I will listen ;) ).

Now, when I touch the solder joint on the output of the diode (1), the 50Hz noise gets massively amplified. I don't want this to be gone, it will be isolated later, but I want to know why.

My guesses:

a) I'm a big resistor, adding additional resistance to R1 (1M) and so increasing the gain of the amplifier (keyword biopotential)

b) I'm a big antenna, receiving 50Hz noise of my surroundings and the op-amp amplifies that, so the signals do have different sources.

Thanks for any information!

Some background: I'm a computer science master student writing my thesis about hand gesture detection with infrared measurements through the skin, therefore the measured signals are rather small and need amplification.

[edit]

I was able to measure my own body's 50Hz signal with my oscilloscope, thank you all!


texts: 11.1v Lipo battery thick to thin wire connection heating up

texts:
I have a lipo battery, 11.1v, 2200mah, 20C. I needed to connect to to a smaller wire because the thing I am connecting it to has a little jst connector.

So I bodgily just wired the thick wire to the thin wire and plugged it in - All works perfectly fine.

The problem is, when using it continuously the thin wire gets warm and after about a minute it gets hot.

Now I wouldnt be running it continuously like that anyway out of testing, only in bursts. But I am worried because you know, lipos are fire hazards and hot wires just arent something I am comfortable having going on.

My question is what can I do to stop the heat problem?

I thought of just rewiring the gel ball blaster with thicker wires, but that seems like the longest way to fix this.

I thought about unsoldering the thick wires from the battery and soldering the thin ones to it, but would they get hot that way? (Im new to electronics xD) I dont want to do it and the battery catches fire in my hands haha.

The other thing I was thinking, maybe someone knows of some sort of connector that is made for connecting thick wires with thin ones and restricting the current or whatever happens so the small wire doesnt get hot.

One thing I should have done before asking is check if the wires on the original smaller battery get hot with extended use. I doubt it but you never know with chinese engineering xD

Anyways I look forward to your answers and welcome myself to this community : D

P.S I tried to upload photos but I am using my phone and it says they are too large for the forum. I will try to find a way to resize then upload afterward.


texts: What is the difference between a general comparator and a differential comparator?

texts:
I notice that the LM339 quad comparator comes in 2 different varietys: general-purpose and differential.  Besides a big difference in price, what is the difference between the two?

Specifically, I want to use it in a slow-changing (as in whole minutes before crossings) single-supply (12v) circuit that needs to output very close to 0 for Vsat-.


texts: Can we implement physical DIP switches to route different differential signals?

texts:
I want to route two different CAN BUS signals (differential) to a CAN controller. Since the controller has only one CAN interface, I can not connect both differential CAN signals to the input of the controller at the same time. I was thinking about using a physical dip switch and then route the signals to the controller by opening on CAN signal line and closing the other signal line and vice versa.

Since CAN implements differential signaling scheme, is it possible to use DIP switches? Does the signal get distorted? Or is there any alternative where I could control the switches with a micro-controller instead?


texts: Turning off the LM3914 dot/bar display driver per the datasheet

texts:
I'm designing a circuit with an LM3914 dot/bar display driver and want to shut off the entire bank of LEDs based on conditions in the circuit. I'm having some difficulty turning off the driver from the information in the datasheet.

The LM3914 doesn't have an "enable" pin, but the datasheet (PDF here) states the following on page 19:

Perhaps I'm misunderstanding the text, but I take this to mean that the internal current sources (e.g., for the LEDs) can be turned off by supplying 100 µA through the REF_OUT pin. I tried this on a breadboard by connecting pin 7 to +5V through a 47 kOhm resistor, but the LEDs remained illuminated (I also verified the current draw with a multimeter). Am I missing something?


texts: How to use this BLDC and know more about it?

texts:
I have this BLDC I removed from a CD Drive.
I want to use it. Just for playful reasons. But I don't know what to make of it. Where to get started with on the Internet. Any help will be appreciated.


texts: Pulse sensor: Choosing the right resistor for the phototransistor

texts:
I want to use specifically the SFH 309 NPN phototransistor in order to create a pulse sensor that works as seen below:

The IR diode emits IR light to the fingertip from the one side and on the other side the phototransistor is picking up the light "converting" it to voltage values. When there is a pulse, the excess blood "blurs" further the fingertip and the transistor is picking a weaker light beam.

The problem statement here is:
How do I find the right resistor to get the best result? (interested more in the procedure of what to look for in the data sheet and how to calculate it)

This is the kind of signal that I am looking for (here the diff is 50mV, and I am hoping for something better than this).

The VCC is 5V.


texts:
I am performing electrical validation of EMMC interface using oscilloscope per JEDEC spec. One of the test is to validate setup and hold time for CMD and DATA signal both way (R&W).On scope,I can't tell the difference between data read/write. I was wondering if anyone knows how to tell the difference. Same goes for CMD in vs CMD out.

Many thanks'


texts: PIC:how can we operate PIC24FJ256GB106 controller to 32MHz internal frequency?

texts:
I am using below configuration bits for 32MHz internal frequency.

_CONFIG2(IESO_OFF & FCKSM_CSECME  & OSCIOFNC_ON  & POSCMOD_NONE  & FNOSC_FRCPLL)

I know that FNOSC_FRCPLL give me 32MHz frequency but I am getting only 8MHz frequency.

Is that any configuration which am i missing ?


texts:
I am using Atmega328P to read temperature from LM35 and display it on the LCD (along with few several things it does).

I want to understand the capacitor and connections for the AVR itself and AVcc.

I read stuff online, about decoupling, bursts, under-power and such, but I did not understand what I should connect to do it right.

Some said I need to connect 10uF electrolytic cap to Vcc and ground, and to AVcc and ground.

Others said I need to connect ceramic 0.1uF to Vcc and GND and AVcc and GND. Some said both.

I am confused, really confused :)

Also, I am starting to think I need to recheck my LM1117 3.3V regulator caps, I am using 2 10uF caps (Input V and GND, and 3.3V and GND).

Can you help please?


texts:
I'm implementing a systolic array for a project, every Processing Element (PE) contains many multiplexers in cascade due to absolute value subtraction and conditional operator, the code looks like something like this:

reg[1:0] direction;

localparam [1:0] DIAG  = 2'b00;
localparam [1:0] WEST = 2'b01;
localparam [1:0] NORTH = 2'b10;

assign pixel_up_1   = (pixel_down[23:16]>pixel_up[23:16]) ? pixel_down[23:16] : pixel_up[23:16];
assign pixel_down_1 = (pixel_down[23:16]>pixel_up[23:16]) ? pixel_up[23:16] : pixel_down[23:16];
 ...
assign match = 255 - ( pixel_up_1 - pixel_down_1 );
 ...
assign selector =  (match >= n_wire ? (match >= w_wire ? DIAG : NORTH) : WEST)

always@(posedge CLK) begin
    direction <= selector;
end

The problem arise instantiating many PE in the Systolic Array, the routing in the synthesizer is very high and few Flip Flop are used.

I have tried to use pipelined logic for the PEs, more FF are used but the routing doesn't decrease, how can i reduce the combinatory part of the design?

Someone says me to use chip-select logic to avoid mux, but i don't know what it means, any hint?


texts: Electrical Induction, what are the cable limits before it becomes a problem

texts:
I have a little hobby that has 3 power cables coming and going (each cable is 12V DC, 7.55 amp max).
Now these cables are ridiculously long (approx 5m+) and the equipment having to be mobile is small 0.5mx0.5x0.5.
Been looking at solutions to better cable management but nothing has stood out yet, most invovle having cables stretched out, which doesn't help me.
Now i am considering of creating 3 small spools that i can wrap each of the power cables on and then attach the spools to each other.
This is where i been advised to be careful of induction and to look into it.

Now considering the low power of these cables (the equipment is sensitive so doesn't consume large amounts of power) would my solution of creating 3 spools if power cables then attaching them together next to each other cause induction and thus problems or am I within safe limits to do this?


texts: Interfacing thousands of RGB LEDs in a matrix

texts:
So I have 3072 RGB LEDs I need to connect in a matrix.

I have decided to split the project into smaller matrices and all LEDs are common Anode.

Datasheet for LEDs is here:
http://docs-europe.electrocomponents.com/webdocs/13dd/0900766b813dd0f4.pdf

Im thinking about splitting it into 4x 16x48 matrices which would be 48 Anode pins and 48 Cathode Pins (16 for each colour).

Im struggling to work out which ICs to use to drive the LEDs.

What LED drivers would be suitable for driving a 48x16(x3) matrix?

Is there any suitable LED drivers ideally with 48outputs that would drive a matrix of this size directly or will I need a current sink/source as well as the driver / expander chip?


texts: Can I parallel two constant-current power supplies to drive 1 bulb?

texts:
I have a piece of historic equipment that HAS to have an incandescent bulb.*  The preferred-voltage bulb (64V) is no longer available, so I'm forced to use 32V bulbs. This one wants 8.4 amps at full brightness/spec, and about 4 to 5 amps at "dim" setting.

This is giving me two big problems.  The second one I'll cover right now, which is that the power supply (nominally 75V) is sagging as low as 60V, and that's dimming the light.  I'm hoping to eliminate that problem.

Originally, this used a dropping resistor to produce bright and dim brightness, which made sense for a 64V bulb and 75V supply. But we had to re-factor the resistor to make it work on 32V, and it's positively enormous, is overloading the supply, and you can cook eggs on the panel :)

So I want to install the original/historic resistor, and behind it conceal an electronic switching power supply of some kind.  I'm hoping the bucking nature of a switching power supply will take care of the voltage dip problem.

However, the LED revolution has had a very distorting influence on the supply chain. Given my oddball voltages (on both sides), the most procurable way** I've found to do this is actually using constant-current power supplies.  And I'm super comfortable with driving an incandescent light constant-current.

What's readily available in appropriate input voltages and output currents (and voltages) is a 4-amp CC power supply (driver).

4 amps is very workable for the "dim" setting.
8 amps is acceptable for the "bright" setting - it's 9% below target brightness, but that's better than the voltage dips are doing already.

So my hope is to have one such supply/driver be turned on at "dim" setting, and both of them turned on at "bright" setting.  This will mean paralleling two CC supplies/drivers.

Is this a very foolish idea, or does this make sense?    If we were in a constant-voltage world, I'd be skittish, but these supplies will inherently current-limit.  What could go wrong?

-

* So this is not an XY problem in that sense, I'm not asking "how do I get over my fear of LED" - LED is off the table.

** This is also not a "Shop-for-me" question; I'm not looking for someone to locate a 75 to 35V 300W constant-voltage power supply, though I wouldn't mind lol... I just haven't found any at non-nosebleed prices.


texts:
I have a transformer found on my old computer ups.
I dont understand its pin out. It has black and red lead one side. And on adjacent side it has four wires connected with a female connector.
I want to make a bench power supply for my lab with it.


texts: Finding values of LRC circuit when frequency is given

texts:
I am trying to solve the following question. The original question is:

  The given impedances of the series LRC circuit are established at an
  angular frequency of 2000 rad/s.

  Calculate the resonance angular frequency from the given circuit and
  calculate the current I through the inductor at resonance, given the
  voltage across the capacitor is 4j mV at resonance.

This is my approach:

First, I think that the given impedances are when the frequency is 2000 rad/s , so I tried to find their values when the frequency is 2000 rad/s. Is the approach correct?

Then I remember the formula for finding the critical frequency was as how I wrote it in part 2 of answer. Any ideas if this is correct?

Also, I have no idea how to find the current across L at resonance. What I remember is that in resonance the impedance of C and L are canceling eachother so the given voltage should be the voltage same across the resistor. Can you check please?


texts: How do I use Circuit Lab to show me Voltage and current information on this circuit?

texts:
I have a bunch of red LEDs, I don't have their data sheet and I am trying to figure out a safe resistor to use to lower the current across them safely.

My current setup is as follows:

simulate this circuit – Schematic created using CircuitLab

I figured a 100 Ohm resistor and 68 ohm resistor in series because, assuming a forward voltage of the led of 3 volts, and a desired current of 20mA (which I assume is ok?) I get:

R=V/I
R=3.3/0.02
R=165 Ohms.

So, I pop that into the circuit lab as shown below, click run, then click DC simulation, but then it just throws an error saying : "unable to get solution"

How do I use this tool to allow me to inspect various values at various points in the circuit? Have I got this wrong somehow?!


texts: DC block capacitor choosing with 50 Ohms input impedance

texts:
I need block DC in a 50 Ohms terninated system. The passband will go from 100Hz to 100MHz, so the needed capacitance is around hundreds of uFs. For normal chip capacitors, I think I must take the ESL into consideration.

Are there any good methods to achieve a flat passband as wide as this? Or there are some special capacitors can handle this? Any suggestions are appreciated.


texts:
I was looking through an STM32 development board schematic and found a circuit I don't understand.

The circuit is a ferrite bead (120 Ohms at 100MHz) in parallel with 4 100nF capacitors. This is between the USB connector's ground and shield, and the circuit ground:

I assume the ferrite bead is to keep noise from entering/leaving the USB cable, but I'm not sure what the capacitors are for. I'd assume whatever noise the ferrite bead blocks would just go straight through the capacitors.

My only thought is that it's some sort of notch filter, but I'm not sure why you'd want that on a USB port ground.

Pictures of the board seem to show all components are fitted:


texts: No Output From LM2596-5T from TI. Any Ideas Why?

texts:
So I built a board with LM2596-5T as the voltage regulator. Below are my schematics.Just as described in the datasheet.

And the layout is as below:

After assembling, the output is at 0V. Vpin12 is 24V (VIN=24V). But nothing on the output pin at all. I would have thought I should get at least 1.23V (VREF). Can anyone spot anything I might be getting wrong?

Here is my BoM:

C9: 680uF, 63V Electrolytic Cap.
U5: LM2596-5T
D1: SB530
L1: 33470C
C12: 220uF, 25V Electrolytic Cap.


texts: Can a transformer have no secondary stages?

texts:
While disassembling the power for the spindle of my hobby CNC mill, I came across something peculiar which I think warrants a question on this site.

The input is standard 220V AC.

Phase 1 (brown) from source is fed directly to spindle phase 1.
Neutral (blue) from source is fed to transformer primary coil in.
Transformer primary coil out is fed to spindle neutral.

Please see photos below.

Gray cable to right is source
Black cable to left is spindle
Bottom gray cable is transformer

Only connectors for primary stage on this side
Name of this transformer is "drossel", which according to google means "throttle"

No connectors here (or anywhere else for that matter)

So it appears that the transformer has only a primary coil and no secondary. In other words, it is functionally equivalent to a giant coil.

My question is, what purpose does this transformer serve?

My naive guess as a novice is that it is used as some kind of filter or storage, like a capacitor.

Any hints are welcome!


texts: A few questions about flyback dc-dc converters

texts:
I have a few questions regarding this flyback converter simulated in LTspice. 9V was stepped up to 27V using the transformer. My questions are:

Why didn't the output voltage change with the change in load? I have seen the use of feedback loop in buck/boost converters just to keep output voltage constant with changing load. But here no feedback is presumably needed.
Why are there negative spikes in the pulse generator? The spikes occur when transitioning from 5V to 0V. There are no spikes while going from 0V to 5V. How can the spikes be eliminated?


texts: Closed form expression for a resistor ladder network

texts: Is it possible to find a closed form expression for the resistance between A and B for the general n-section ladder network, below, where all resistors are \$\small 1\Omega\$? An iterative expression is quite easy to derive (\$\small R_n =2 + 1//R_{n-1})\$


texts: Measure the power consumption of a circuit with Arduino

texts:
I need to measure the power consumption of a circuit I have built.
The components are as follow:

Lipo battery 500mAh
Accelerometer
RTC
RedBear Nano 2

Usually I measure the consumption using an Arduino and its analogical pin. The level of accuracy is enough. In this case my idea is to attach to every component a relatively small resistor and see which is the voltage of this resistors. Comparing this values to the battery voltage I should get an idea of how much power consumption I have. Is that correct, am I missing something?

The picture shows the configuration I wanna make, the green annotation represents the measures I will take with an Arduino.

The Arduino code I am using for a single analog pin is the following:

int Re = 1000;

void setup() {
Serial.begin(9600);
}
void loop() {
int sensorValue = analogRead(A0);
float voltage = sensorValue * (5.0 / 1023.0);
float current = voltage / Re;
Serial.print(millis());
Serial.print(",");
Serial.print(voltage, 10);
Serial.print(",");
Serial.println(current, 10);
delay(500);
}

EDIT:
What I am trying to measure is basically how much time my circuit can be on. Thus, let say that 2 or 3 days of variance in the result can be manageable.


texts: BLDC 3phase motor. The resistor 5W 0.1 ohm to ground very hot when motor working at 250Hz

texts:
Any one help me on this my issuse.
I have a BLDC 3 phase motor controler similar to this Schem here encloses. When the motor working at 150Hz everything is ok. But if it is works at 250Hz then the Resistor 5W 0.1 ohm ( Red mark) very hot. Any one can tell me what happen?
Thank you.

Actually I have no detail schematic but have 2 PCB exactly same and connected whit same motor. but one of them works fine with both 150Hz and 250Hz. The rest only works normal at 150Hz. But for 250Hz the Resistor too hot. 150Hz - 220mA. 250Hz - 350mA (when motor works stable)
(https://i.stack.imgur.com/ezhBQ.jpg)


texts: PSIM: thyristor acting as a diode in a full bridge rectifier with C filter

texts:
We were asked to simulate a controlled bridge rectifier with C filter for class.
Whatever I change the firing angle into, the output stays the same (Same Vdc).
I thought that a capacitor filter couldn't force a thyrsitor to stay on and that was only an inductor.
pictures included:
alpha 60:

alpha 0:


texts:
I have bought a phono-preamp stage from Audio Technica, and the output is quite low. (Using a MM cartridge.) I managed to retrieve a data-sheet which shows how the circuit is laid out.

I'm not entirely sure how to proceed. The setup seems to be a fairly standard non-inverting OP-Amp setup. The Equalization appears to happen in the feeback. I initially thought R28/R18 were responsible for the gain but that doesn't seem to be the case.

I'm a bit stumped and would love to know if anyone knows if what I'm attempting to do is even possible.

Thanks!


texts: Any deleterious effect from very strong, close magnets on NiMH cells over time?

texts:
This question probably isn't a perfect fit for this SE, but I did find this question: Will placing a strong magnet near my electric skateboard Li-Ion Battery pack damage or discharge it?

This is a different situation, though: I would like to attach some small, powerful magnets to the outside of the thin aluminum casing of a single-AA-cell flashlight. These would only be at a distance of about 1-2mm from the side of the cell itself. Does anyone with strong physics/chemistry side-skills know if this would be likely to affect the battery over the course of sustained use (or sooner)? I'll probably victimize an old cell to test empircally, but it would be great if I could get some information in the short term.


texts: Building a Vintage Car Microprocessor Controlled Climate Control System

texts:
First, let me just say that it has been over 50 years since I worked much in electronics and that was mainly using vacuum tubes so my question here is not so much to get any details but just to find out IF what I want to do is feasible. I hope I can explain this without boring everyone and if there is a more suitable group to post it in, please advise.
I am trying to re-create and modernize an A/C system for a specific make of vintage car to replicate the original factory installed unit but which can also be retrofit into a car that did not original have A/C.
There is a spacious trunk-mounted unit which is the heart of the A/C system and a relatively large dash control panel, in a zinc alloy casting, which has three knobs. The devices that these knobs turn in the original are massive '50s-era ceramic rheostats and switches which I want to replace using modern electronics both for the controls and for what they do in the trunk unit to adjust fan speed, to direct the inlet air source, etc.
The first caveat is that I want to do all this using the original wiring which has only four wires leading to the rear unit and possibly only two of those actually come from the control panel. That is, I am expecting that one will be for power to the trunk unit's processor and through it, the fans and servos, and the other wire will be what is left for sending any control signals to the back.
The other caveat is that it must be able to run on either 6v positive ground or 12v negative ground.
Ultimately I'll have to hire an engineer to assist in designing the controls (I hope it can be someone who loves old cars and can work on a budget - yes, I know I'm dreaming) so what I am asking here is, is doing something like this even possible whether on a budget or even otherwise?


texts: Circuit to limit a set of outputs so that only one is on

texts:
Background:

I have a set of irrigation control valve solenoids (24V ac) that I control via a set of mechanical relays with the GPIO pins of a microcontroller (ESP32). The power supply does not have a large enough current to operate two valves at once, which is fine because the system also does not have enough water pressure to run two zones at once.

In theory, I should be able to limit the system to one valve at a time strictly in software, but I keep finding corner cases where I have not ensured that, and when I mess up the supply voltage to the IC drops below 3v and the system reboots, so debugging is a pain.

Question:

Is there a reasonably simple circuit I could construct that would prevent a second pin from going high if another one is already on?

Bonus points if there is an output that I can use to trigger an interrupt when this happens.

UPDATE:

Several people have asked about a software solution.

Yes, I did refactor my code so that pins were set in exactly one place.  I missed one piece of code in the refactor. sigh I also had an interesting bug where an internal process still wrote to an external pin when writing to flash memory.  The ESP32's GPIO matrix makes it pretty hard to ensure that a library never accidentally takes over a pin.

So while I agree that the software solution is ideal, my lived experence is that I would benefit from some hardware fault protection here.


texts:
So if I  build up a lot of static and put on my headphones, it creates this loop in the circuit or whatever and produces constant static until i somehow ground it out. It has even shocked me on the head sometimes. Any idea how to fix this issue? How can I troubleshoot it? I've tried plugging my headphones into just integrated audio with the mobo and there's no static. No static on the front port either.

edit so it seems like if I turn off my computer... flip then switch on the power supply, and then turn it on... it grounds out the sound card.


texts: How can I reduce the power consumed with wall warts?

texts:
I have been designing a project that requires a 5V for some components and 12V for others. I am planning to leave this plugged in 24/7 so I want it pretty efficient. I know they don't waste that much energy, but I still want to make it as energy efficient as possible even if I don't notice a difference in my energy bill.

[A.K.A. This is for a friend that read somewhere wall warts waste tons of energy, but if it makes them happy, I might as well do it. I have seen this: How much power is really wasted by a wall wart? but my friend isn't happy with that. I just want a power efficient source. Also, this isn't related to How can I reduce power consumption of my device? because that is saving energy in theory.]

I have a couple of options to use:

Buy a 5V and a 12V adapter. Connect the grounds.
Buy a 12V adapter and use a voltage regulator and a cap.

Which one is better? Do some adapters/adapter types waste less energy?

Another problem is I might need 1/2A for the 12V circuit which is only going to be used 5% of the time. Does the higher amp converters use more energy when idle? Suggestions? I don't want to use relays because they would be dangerous. I would need less than .5A for the 5V one. Do I need to pick out adapters?

Thanks!


texts:
Find the stability where:
Find the stability:
\$ G(s)= \frac{(s+3)(s+5)}{(s-2)(s-4)}; \$
\$ H(s)= 1; \$
I run this code in matlab:

clc;close all;clear all;
G = tf([1 8 15],[1 -6 8]);
H = 1;
Cloop = feedback(G,H)
nyquist(Cloop);
figure(2)
step(Cloop)

Output is:

From the two Graph What I understand is:
\$ N= 0 \$ as \$ -1 \$ is not encircled
and \$ P=2 \$ as there are two right-hand side poles.
So, \$ Z=N+P=2 \$
From this, the system is Unstable as there are two zeros in the Right-hand side.
But from the step response, it is obvious that it is stable.
So what's the problem here; Which is correct??


texts:
I have 4 Tower Pro MicroServo 9g SG90 I want to power with a battery. This is the datasheet I found online: http://abc-rc.pl/templates/images/files/995/1428085018-sg-90-tower.pdf

I have a small breadboard and some resistors laying around (220, 1k, 10k), and a 9v battery.

I hooked up the battery leads on the power rail of the breadboard, and added my 4 servos in there, and they turned on and rotated properly when I issued commands from my Arduino board. The thing is that AFAIK it operates on 4.8v-6v from what I have read.

I did a voltage divider using some of the resistors I had and I could output 5v when tested with my multimeter, but the servos didn't work (probably because low current).

So my question is, can I power my 4 servos with a 9v battery? Should I add some resistors before? Bear in mind I am new to electronics.


texts:
I made this circuit inspired by this website: http://www.electroboom.com/

It seemed to work for a few seconds but the mosfets got really hot, they started to smoke and eventually one of them died. I suspect my DC switching power supply might not have a clean voltage signal and this is what is causing the excessive heating.
I'm waiting for a new mosfet and I'm going to try with a battery next time. In the meanwhile, do you have any observations or do you see any other problems that might be causing this? I'm using heat dissipators with thermal grease, but no ventilation.


texts:
I have to detect a small radiation from this tags and I´m looking for some ideas how I can do this with some kind of small electronic circuit (or lecture to read how to do it) - not with a Geiger-Müller counter!

My current idea is to use an array of PIN diodes (see here) to detect the tags. But I don´t know if this solution works for my problem or if I can use some better solution (maybe an IC?).

So I´m looking for some other ideas of how I can do this.


texts: What electrical processes are behind RECCO system?

texts:
According to Wikipedia, RECCO system for finding people buried under snow uses reflectors each of which contains a pair of foil aerials, joined by a diode. The text further says the size of the aerials makes the unit a tuned circuit resonating at one specific frequency.

AFAIK any piece of metal will reflect electromagnetic waves and will resonate when irradiated with waves of length matching the piece size.

How does connecting two pieces of metal through a diode form a resonating circuit? What is the diode doing in that circuit?


texts: What are the freeware SPICE simulators available?

texts:
Does anyone know of a freeware SPICE / circuit simulator?

  SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose, open source analog electronic circuit simulator. It is a powerful program that is used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior. Wikipedia


texts:
I only have one power supply and I only have the LF353N opamp. Is it possible to design a non-inverting amplifier circuit for this op-amp with only a single power supply?

Otherwise, what are some single power supply op-amp alternatives could I use? I'm using a non-inverting amplifier to amplify a 1V pk-pk 10kHz sine wave to 5V pk-pk.


texts:
I have these LEDs for which the max current was not specified. However I know that the voltage is 3.2V-3.6V and the power is 1W.
Is it correct to assume that the maximum current is therefore 0.27A ?

i=p/u=1W/3.6V


texts: Why do Flyback Transformers have C-I cores?

texts: Usual transformer cores are either E-I or E-E. What's the reason for Flyback's being only C-I? Does it simply cut the cost?? I want to know if it would perform less if it were an E-I.


texts: I'm working on a rudimentary flight stabilization system for an airplane, which reads in 4 PWM inputs from an R/C receiver. The problem is, the pulseIn command is taking far too long to execute, so I need an alternative method of reading the four inputs. With all the code running except the PWM, my entire cycle takes ~ 45ms, however adding the four pulseIn(pin, HIGH) calls leads to ~250ms cycle times, which isn't working out for me. Is there an alternative, perhaps an interrupt-driven, way to read the duty cycle time of the PWM lines?


texts: Explanation of capacitor usage in this N-MOS application

texts:
I'd like to understand why capacitor is used in this circuit instead of connecting PWM pin directly to N-MOS.

How does Q3 have HIGH reference with no direct connection?
What kind of advantage I have using a C between PWM and gate?