texts: Can one of the capacitors in series get negative Voltage when discharging?

texts:
Supppose i have the following circuit. And I complelty discharge all the capacitors by having a load on them for a long time, so there will be 0V overall. Let's assume the one in the middle has a slightly different capacity. My question is will C5 have a negative Voltage because it has less capacity ?

simulate this circuit – Schematic created using CircuitLab

I'm asking this because in my setup i have 3 Supercaps (which have polarity) connected in series and I'm wondering if I can discharge them all the way without giving one of the caps a reverse polarity.

Some thoughts:

This seems like a very basic question, but i've never asked myself this until now. So from a logical point of view it must get negative, because let's say they all start at 3V when discharging . Then the voltage starts to drop , then one of the caps must reach 0V first because it hass less capacity and then the current should still continue to flow because the overall potential on the load is > 0V .

But my first instinct was that it shouldn't get below 0 , although I have no argument for that it's just a feeling. So that's why I'm a bit skeptical what will happen.


texts: Why does this datasheet show an example with an input voltage outside its recommended range?

texts:
I am using the IRS2453 which is an H bridge driver.

The example is page 3 show an input voltage on Vcc of 15V. In page 6 it indicates the recommended Vcc is between Vccuv+ and Vclamp.

On page 7, it indicates the range for Vccuv+ is 10.0V-12.0V, and the range for Vclamp is 14.6V-16.6V. This leaves a guaranteed range of 12.0V to 14.6V for the input.

Why would they show an example with an input of 15V, as this can fall outside of the recommended range if Vclamp were to have a value between 15V and 15.6V?


texts:
I am working on a project to produce high voltage output. Since I supply this circuit directly from mains I have some problems. Here is my representative circuit:

I am controlling transistors from a PWM generator. Duty cycle is %25. I checked for dead time. It is safe.
Now, here I used safety bulb in series with the main (220VAC). When I plug it in Lamp goes fully on after 1-2 second later it goes almost off (just a little bit blinking). I thought first light is because capacitors are charging. So my questions are;

After I start pwm generator, I can see arcs but bulb also goes almost fully on. Is this a sign of a failure or short in the circut ?

I am checking voltage across C3 after I start pwm. Depending on my distance adjustment on flyback's secondary cables to have arc, it shows up to 1800V.

I will later add voltage feedback and current feedback. Other then these additions, what kind of improvements should I do? Or is this a completely ridiculous way?


texts: LinkSwitch-XT2 (LNK3696) with opto feedback

texts:
What's a proper circuit if I want to use a LinkSwitch-XT2 device (from Power Integrations) with an opto coupler in the feedback loop?

This is the typical application circuit of LinkSwitch-XT2 devices.

The datasheet mentions that the current into the feedback pin should be limited to 1.2mA (see page 3 - Chapter: "Feedback Input Circuit"). How can I limit the current into the feedback pin??

Link to the datasheet:
https://ac-dc.power.com/sites/default/files/product_document/data_sheet/linkswitch-xt2_family_datasheet.pdf


texts: Multi phase vs single phase power factors

texts:
Are there any differences between calculating single phase and multi phase power factors?  I'm open to general answers, but more specifically:

If PF1=P/S, does PF3=(Pa+Pb+Pc)/(Sa+Sb+Sc)?

Does averaging work: PF3 = (PFa+PFb+PFc)/3?

Could a reactive load in one phase throw off the power factor of the others, or is power factor pretty well isolated between phases?

I thought I knew the answers to these questions from deriving them mathematically, but some meter readings today are making me question myself.


texts: How to cool electronics when the air is always hot

texts:
I'm in the process of planning an experiment that involves placing some electrical equipment in a mine for a year or more. Where the equipment will be placed in the mine (770m in depth,) the amient temperature will constantly be approximately 45C. I need to check this but I imagine it will also be fairly humid.

Specifically the equipment I will be using includes: a laptop, two high-voltage (up to 2.5kV, low DC current) photo-multiplier tubes (whose power supplies undoubtably generate a significant amount of their own heat), and a low-voltage DAQ board.

The trouble is that in the mine (or equivalently in a desert or some high-temperature industrial setting) the constant heat means the normal method of cooling components - by fanning the ambient air over them - simply wont work. Furthermore, I had considered putting the equipment in a 'mini-fridge' but the heat exchanger on the back also relies on cool ambient air so it would soon break.

The equipment will be housed in a sealed crate so it may be possible to exploit this fact so as to maintain the entire inner-volume at a more processor-friendly temperature. To be honest however, I don't know where to start.


texts:
I have a question about Flyback converter simulation on Altium. I set my reference ground GND.  When I try this schematic with all grounds as  GND like below

Simulation is working good as you can see in Image 2

But I want to make these output grounds different. As in the Image 3.
But simulation gives me error Image 4.

Even if  I try to tie all grounds to reference ground  GND in Image 5. Again I took an error and simulation results like in Image 6.

I only show you OUT1  but it is same with other outputs. I guess my problem is multiple ground. What you advice me?

With my best regards..


texts: Help! Need advice identifying the leads on this transformer

texts:
Hello Guys. I need help identifying which pair of leads can be used for 110V. I tried continuity test with multimeter and got continuity on the following pairs (1&3) and (2&4).

Thanks in advance.
Cheers


texts: Determining if a diode conducts or is cutoff?

texts:
Can somebody please explain to me how you exactly determine whether a diode conducts (shorted) or is cutoff (opened)? I found a couple of posts on this but I wasn't able to justify the answers myself, probably something I'm doing wrong. It was said that the anode should be greater than the cathode for the diode to conduct but it's not making any sense to me in these examples.

The answers are: for (a), D1 is cutoff and D2 is conducting. V = 2V, I = 3.5mA
(b) D1 is conducting, D2 is cutoff. V = 1V, I = 2mA


texts:
What is the meaning of switch failed open or failed closed in electronics?
I did a search but without results.


texts:
I am an engineering student at Oak Ridge High and have started to learn PCB design. I just finished designing my first PCB and had several concerns about it. My main concern is that I'm not sure is the supply rails for the 5V and GND are large enough.  I'm expecting at most peaks of around 15-16 amps to go through this board.

If anyone would be able to take a look at my board design before I have it made and then possibly fail that would be so helpful. Any suggestions on changes are readily welcome. This board is going to be used to drive a 8x8x8 cube of LEDs.

The board and schematic files are in the enclosed link: https://www.dropbox.com/sh/33xup0rf5dw9f36/AABldcXm4Cta2-585d3HQwXLa?dl=0


texts: current spike of a momentary toggle circuit

texts:
The toggle circuit below works well, but I noticed that there will be current spike when the switch is closed, i.e., when switch is closed, the two caps will charge each other without resistor in between, the energy is small, but current will spike.

Is it necessary to add a 1k resistor between the 0.01uF cap and the ground?

Or is the 0.01uF cap redundant and can be removed? (I assumed it is added to ensure the toggle is on OFF state when power on, but seems not really needed).

http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/electronic-circuits/push-button-switch-turn-on/latching-toggle-power-switch


texts: How can STM32 on Maple Mini (leafLabs) be programmed using Keil?

texts:
First of all I am not unfamiliar with embedded systems. Moreover, shame on me, I am an electronics engineer specialized in embedded systems.

The question I am asking is actually a little bit complicated. Thus, I will not ask it directly but explain my intention for your understanding.

Maple Mini, as some of you know, is a little development board based on STM32F10x arm processor. I intent to use it directly in my projects instead of designing a circuit for STM3210x processors.

Since my applications need to be real-time, fast and hardware oriented I do not want to use its own IDE. I need to use Keil uvision. (For instance, I am programming Arduino Pro Mini with Atmel Studio)

Now my question can be a little clearer, which is as follows.

Since the processor on Maple Mini is a standard STM32F10x I need to be able to program it on any platform that is suitable for this MCU, but factors that are not related to STM32 itself prevent this." Can you briefly explain what causes the difference when it comes to programming different boards (but same MCU like STM32F10x) with different IDEs?


texts: Truth table for incrementing and decrementing 4-bit numbers

texts: A3, A2, A1 and A0 are the bits of the number which needs to be incremented/decremented. The first column with F bits is the incremented A number and the second column with F bits is the decremented A number. But I don't understand that second F column, how are those numbers decremented? It looks like they are incremented. And P columns are for bit transfers (if they cannot be put in those 4 bits).


texts: Transfer function of a digital phase frequency detector

texts:
I'm confused about the transfer function of a digital phase frequency detector. Why can we say that the pfd output is proportional to the phase error?

The pfd (with charge pump) generates current pulses of fixed amplitude \$I_{CP}\$ like it is described for example here. For small phase deviations the length of these current pulses is proportional to the phase difference of the input signals. So the pfd output current is clearly not proportional to the phase error.

On the other hand, the transfer function of a digital PFD is said to be \$K(s) = \frac{I_{CP}}{2\pi} = \frac{I_{out}(s)}{\Delta \phi(s)}\$. In this sense the pfd generates a current proportional to the phase error.

Why is this not a contradiction?


texts: Rectifier circuit for ACS712 with 3.3V ADC

texts:
I'm using an ACS712-5A hall effect current sensor that output a voltage roughly between 1.5V to 3.5V. I'm am measuring a main AC power line at 50Hz. I'm using and ESP32 which has a built-in ADC with a reference voltage of 3.3V.  Hence, the signal will be alternating from 1.5V to 3.5V which will then be processed by the MCU accordingly. I understand that I can simply use a voltage divider to step down the voltage but that will lose some precision. I have two solutions which I'm not sure which is better.

Solution 1:
Using a zener diode with a Zener voltage of 3.3V to clip the output voltage. I won't be operating the current sensor at full capacity all the time so it shouldn't be a big problem. Will this work? Do I have to add a resistor in series with the voltage output or anything else?

simulate this circuit – Schematic created using CircuitLab

Solution 2: Using a rectifier circuit recommended in the datasheet of current sensor. However, I don't fully understand this circuit and unsure on how to calculate the values of Rf and C1.


texts: Receiving SMS using GSM and controlling LED using Arduino

texts:
Has someone come up with a solution with the above stated problem?

We are using Arduino Duemilanove and SIM 900 GSM module (http://robokits.co.in/shop/index.php?main_page=product_info&products_id=303)

We've tried to work on the similar problem of lightning Leds from port 9-12 when we send an sms #aibicidi, where i = 0 or 1, 0 =off, 1=on.
Eg. #a1b1c1d1 will switch on all the Led's.

When we upload the code and run it through serial monitor and enter the #a1b1c1d1 in the serial monitor, we can see all the led's lighten up.  But if we send the sms with having content "#a1b1c1d1", we dont see any function of leds.

It would be great if anyone can give some guidance about the same.

 char inchar; //Will hold the incoming character from the Serial Port.

 int led1 = 9;
 int led2 = 10;
 int led3 = 11;
 int led4 = 12;

 void setup()
 {
 // prepare the digital output pins
 pinMode(led1, OUTPUT);
 pinMode(led2, OUTPUT);
 pinMode(led3, OUTPUT);
 pinMode(led4, OUTPUT);
 digitalWrite(led1, LOW);
 digitalWrite(led2, LOW);
 digitalWrite(led3, LOW);
 digitalWrite(led4, LOW);
 //Initialize GSM module serial port for communication.

 Serial.begin(9600);
 delay(3000); // give time for GSM module to register on network etc.
 Serial.println("AT+CMGF=1"); // set SMS mode to text
 delay(200);
 Serial.println("AT+CNMI=3,3,0,0"); // set module to send SMS data to serial out upon receipt
 delay(200);
 }

 void loop()
 {
 //If #a1b1c1d1 comes as sms, all led's should light up.
 if(Serial.available() >0)
 {
 inchar=Serial.read();
 if (inchar=='#')
   {
   delay(10);
   inchar=Serial.read();

 //first led
   if (inchar=='a')
     {
   delay(10);
   inchar=Serial.read();

 if (inchar=='0')
   {
   digitalWrite(led1, LOW);
   }
 else if (inchar=='1')
   {
   digitalWrite(led1, HIGH);
   }
 delay(10);

 //Second led
 inchar=Serial.read();

 if (inchar=='b')
   {
   inchar=Serial.read();
 if (inchar=='0')
 {
 digitalWrite(led2, LOW);
 }

 else if (inchar=='1')
 {
 digitalWrite(led2, HIGH);
 }
 delay(10);

 // Third led
 inchar=Serial.read();
 if (inchar=='c')
 {
 inchar=Serial.read();
 if (inchar=='0')
 {
 digitalWrite(led3, LOW);
 }
 else if (inchar=='1')
 {
 digitalWrite(led3, HIGH);
 }
 delay(10);

 //Fourth led

 inchar=Serial.read();
 if (inchar=='d')
 {
 delay(10);
 inchar=Serial.read();
 if (inchar=='0')
 {
 digitalWrite(led4, LOW);
 }
 else if (inchar=='1')
 {
 digitalWrite(led4, HIGH);
 }
 delay(10);
 }
 }
 Serial.println("AT+CMGD=1,4"); // delete all SMS
 }
 }
 }
 }
 }


texts: Capturing x86 register value changes in hardware i.e. at circuit level

texts:
I need to find a way of observing (on another 'monitor' machine) changes to registers critical to the address translation process on x86 platforms - including IDTR, GDTR, CR3, etc. This monitoring needs to be in real time, in the sense that any malicious changes must be observed.

Have considered hardware debugging, but this may be not feasible. What I would like to know is whether it is possible/feasible to extract information directly from hardware registers via a probe. I want to suggest, in my thesis, probing the instruction register, so that all instructions executed can be analysed on the external monitor, and use this to determine whether the instruction modifies one of these other registers.

Sorry if my question is vague, but can someone explain whether it is possible and if so how to capture values from registers  in hardware (not at the software level) and in real time. All I know is that registers use 'flip flops' for storage of bits. How do I send notifications of changes to the value of these registers/bits to another device - not including any methods involving software on the machine in question?


texts: Can't delete a rigid/flex substack from altium 19

texts:
so I've recently been learning altium and I'm one of those learners who tends to click things to see what they do and then figure out how to undo it afterwards. Unfortunately I've now run into a problem with that method because at some point I clicked the "rigid/flex design" option in the features tab of the layer stack manager and have managed to save the whole project in a state where I can't delete that substack.

I open the layer stack manager, deselect the "rigid/flex" option and it returns to a normal stack up, complete with a bottom solder mask layer (which I'm now trying to add) and save the stack. But when I reopen the layer stack manager, the substack is there, and the rigid/flex option is still active and I can't add a bottom solder mask to the pcb.

I can't find anything on the internet that say's anything other than "just delete the substack" but the problem is I can't delete it at all, the bin icon is greyed out.

Does anyone know of a way to undo that without just recreating the project? I'm worried about misaligning screw holes and connector tabs and the like and I'd rather know what I did so I can undo it in future rather than just nuke the thing and start again.


texts: Digital Counters Counts Sample External Frequency Wrongly

texts:
Hi:
Please see the attached schematic. I am experimenting with a circuit for sampling an external frequency. The counters do not always count correctly.  At first I suspected the breadboard and I replaced it with no success.
I would like to know if anybody understands what mistake I have in my circuit which results in wrong count. It seems to me the only reason could be timing. I also experimented with timbases of  8, 16,  64, 128, 256 and 512 HZ. But it looks like that a timebase with lower frequency produces less sever errors for counting the pulses.
The update pulse (UPD) and reset pulse (RST) are derived from AND gates and inverters fed by the outputs Qk, Qj and Qi of a 4040 counter which divides a 32768 HZ frequency obtained from a crystal controlled timebase. All ICs are bypassed by a capacitor from their VCC to ground.
The 163 counters count during half cycle of the 32 HZ timebase or during 1/64 seconds. The output of the counters is fed to a 373 latch. If, for example, the counter counts the 1 HZ during 1/64 sec, then the output of the latch should be 1000 / 64 = 15.6  as either 15 or 16.
The problem is that the count, which I verify by an oscilloscope at the output of the latch, is not correct and the problem could be metastability which was not resolved with two D flip-flops is series.
Here are some examples:
Clock = I HZ, output of the latch is 00011111 which is double of 00001000.
Clock = 2 KHZ, output is 00111111 which corresponds to 4 KHZ.
Clock = 2.4 KHZ, output is 00100111 which corresponds to 2.96 KHZ.
Clock = 3 KHZ, output is 00101111 which corresponds to 3.008 KHZ and is acceptable.
Clock = 4 KHZ, output is 00111111 which corresponds to 4.032 KHZ .
Clock = 4.6 KHZ, output is 01001010 which corresponds to 4.736 KHZ .
Clock = 5 KHZ, output is 01001111 which corresponds to 5.056 KHZ .
Clock = 8 KHZ, output is 01111111 which corresponds to 8.128 KHZ .
Clock = 9 KHZ, output is 10001111 which corresponds to 9.344 KHZ .
Clock = 10 KHZ, output is 10011010 which corresponds to 9.856 KHZ .
I am particularly concerned with when the error at the output of latch is more than 65 HZ.
I use pulse generator of my oscilloscope for generating the input clock frequency to the 163 counters.
When I use output of Qf (1 KHZ) of the 4040 of the timebase generator as input clock from the 163 counters and the same two AND gates and inverters to generate the update and reset pulses, I do get the correct count at the output of the latch. This reveals the timing issue for getting the right count of an external frequency. So, how can we correctly read (sample) an external clock frequency that comes from a source other than the 4040?
The actual connection of counters and latch is as shown in the original schematics. I included the timebase generator, the gates, part numbers, and a picture of the oscilloscope. I had taken the pictures when I was testing 16 HZ timebase with similar results. I had two probes but unfortunately one of my probes is now defective so I could not show the pulses on one screen when I took the new picture with 32 HZ. I hope this can help. When I used a low pass filter of 100 KHZ all outputs of the latch went high. So I eliminated the filter from the circuit.
Could someone who is well experienced with frequency sampling tell me why the count is wrong specially when the count is double?
I appreciate your response and thank you.


texts: What's the difference between consumer and pro audio equipment?

texts:
There are some diffences between consumer/Hi-Fi and pro music audio equipment, besides that pro audio equipment is bigger and louder, requires cooling fans, etc. eg. Hi-Fi uses a pre-amp, pro audio uses a mixing desk.

What's the difference in terms of the electronics? Can an electric/electronic instrument (eg. electric guitar) be plugged into a domestic Hi-Fi, or an iPod into a guitar practice amp? What are the differences in the I/O line levels and impedances, etc. for each?


texts: Semiconductor Database for damage to electronics

texts:
My colleague, who has experience with EMP (electromagnetic pulse) analysis, mentioned a database for electronics (IC, discrete circuits, semiconductors devices) that contained the information on the "measured" damage level.  These values usually exceeded the maximum ratings which can be found on the part's datasheet.
Is anyone familiar with this database? He does not remember anymore details and I am hoping someone else on here can point me where to find it.


texts:
I have been working on a project to make my own laser tag gins and sensor vests.

I have completed the electrical side of my design but this is the first time I have designed something like this and have a few questions regarding some design decisions I have made. First just some background info. I have attached the layouts for my backpack and the gun. The comms cables between my boards are just running a 10khz bit banging protocol I have created. And the IR sensors and emitter will be running at around 1khz. The leds are ws2812b so are running at around 4mhz on the signal line. All the boards have a ground plane with a ground pour and via stitching on the top layer. The sensor board has 3 isolated ground planes for the motor, led and ir sensor. The diode boards just have a load of IR and normal LEDS and the required transistors and resistors. I also have more 2 strips of sensor boards in the backpack. These are wired the same but not shown in the diagram. In the backpack diagram, the green cables are the led comms, orange is IR output from TSOP sensor and blue is the motor turn on signal.

My questions are:

The battery for the whole system is in the backpack. I have lots of pairs of power cables running to the power board in the backpack to keep various things isolated. Would it be ok to link these all together in the gun, maybe adding a voltage regulator and some caps where they connect, and run a single pair of power cables back to the supply. Or just run less pairs and run a few devices off the same pair. Also, should I do this for my sensors or keep the 3 separate power runs for motor, led and IR sensor.
Have I gone overkill with the amount of separate power cables. For example would it be better to run the power for my IR sensors directly from the PCBs power or is having separate power feeds for them a good idea. The actual main IR emitters have a separate power connection on the main PCB which is linked to the boards main ground plane.
I haven't added return ground cables for anything that is just a low level signal to turn something on/off with a transistor. For example the non PWM leds on the gun diode board or the turning on of the motors. But is it necessary to have the negative return cables for my comms cables between the two boards as they're only running at 10khz.

I think that covers anything. Thanks in advance for any advice.


texts: Is there anyway to detect lowest voltage of a signal like capacitor and diode do for the high one?

texts: Is there any simple (not the best one) way to detect the lowest value of a signal, like a diode and capacitor detect the peak value, I want to do it for detect the lowest value of a signal.


texts:
(https://i.stack.imgur.com/kDEx6.jpg)
ICOM 2300h external speaker

I have a 2" 5 watts 8 ohms ordinary speaker, i wired them and use it as my external speaker of the ICOM 2300h.

What bothers me if I have to put a resistor with it?
If yes, what is the value of the resistor?
And where to connect the resistor from the terminal of the speaker?

Please help, with simple drawing very much appreciated


texts:
How can we get the current \$I\$ if all resistances and current \$I_g\$ are known?

Is there a special name for circuits like this one? Is this some kind of a bridge?

Edit:

Edit2:


texts: methods for servo or stepper synchronized multi-axis control

texts:
I have designed a 6 axis robot. The main requirement of the robot is that all axes must be highly synchronized in order to create precise (sub-millimeter, sub-degree) 6DOF (x, y, z, yaw, pitch, roll) trajectories in space. I implemented this robot using:

Hardware:  NI PCI-7358 controller, NI MID-7604 amplifiers, steppers

Software: NI Labview

However, I would like to move away from NI products to something more compact so that I don't have to lug around a computer cart. One example I found on github is a robot where the creator used the following:

Hardware: Arduino, A4988 stepper drives, steppers

Software: python

However, with such a setup I am worried that synchronized multi-axis control will not be maintained due to Arduino processing lag. Can anyone recommend if the Arduino solution is suitable or present alternative solutions (please list your specific hardware and software)?


texts: Amplitude Spectral Density from a Fast Fourier Transformation

texts:
I want to calculate the Noise-equivalent Power (NEP) of a photodetector.
Hereto, I have to measure the Amplitude Spectral Density (ASD) of the detector and divide the result by the Responsivity:

The response of my detector is shown in the figure below: I measure the current as a function of time. Hereby, a pulsed illumination is applied between 0.0 s and 0.5 s.

The Responsivity calculation is straightforward: I integrate the current between 0.0 s and 0.5 s and divide the result by the duration of 0.5 s. I then divide the result by the incoming illumination power to obtain the responsivity in units of [A/W].
Next, I have to determine the Amplitude Spectral Density without any optical input. Hereto, I perform a Fast Fourier Transform on the detector output in the range between -0.7 s and - 0.2 s. The result is shown below. I have already scaled the data to be consistent with Parsval's theorem.

I do not understand how the calculate the Amplitude Spectrum Density in Units of A/sqrt(Hz) that I need for the NEP calculation from this graph.
My plan was to integrate the Amplitude Spectrum over the frequency range and then take the average, but this approach does not end up with units of A/sqrt(Hz). Where is my mistake and where does the sqrt(Hz) term come from?


texts: What is the function of Vm (Voltage max) in this closed-loop feedback?

texts: Attached is the image of my project's closed-loop system. I need to describe each of the function based on the diagram. However I am unclear about the function of Vm in the closed-loop system and why it has to be divided by one? Can anyone clarify this? Thank you.


texts: Are Faston tabs safe for earth grounding?

texts:
I am having a discussion with coworkers about sufficient grounding to a chassis... my opinion is that a toothed ring terminal in contact with bare metal is required, e.g. Molex 19074-0025, so that the teeth will scrape through any oxidation layer:

(Alternatively a regular ring terminal with a toothed lock washer.)

Someone else suggested a Faston tab like the ones in the picture below:

https://www.flickr.com/photos/mouser-nerdbot/4676010617

I am uncomfortable advising use of these terminals, or any other connectorization of earth grounding.

Any suggestions?


texts: The things affecting operation of a transformer

texts:
While using transformers, is it only the winding ratio that matters?

I cannot understand one point that the voltage between primary cables of a transformer is very low when I measure. It is logical because it is just cables. But then how do we refer primary voltage for example 220 Volts ? And also how does the frequency of the signal affects the working of the transformer? I tried like a frequency sweep between almos 0.5 Hz to 150kHz (i hope did not harm the transformer) by hand but could not catch a pattern.

The thing is actually are the transformers as simple as Vs = Ns/Np * Vp ?


texts: Can VHDL read binary files i.e non text files?

texts:
I have a binary file which represents memory contents of a memory device. I want to load these into my testbench. The hex file obviously is not text file thus no concept of line break and carriage return exists in it.

The problem is that as far as I can see, VHDL only reads text files aka ASCII files. I cannot find a way to read binary files.

The file has no structure as such, all contents in it are to be loaded into std_logic_vector array which shall obviously require parsing.


texts: what is meaning of infinite bandwidth of an amplifier

texts: I have just learned about amplifier but the term infinite bandwidth confuses me a lot.plesse explain with some example.


texts: Current spikes on rising and falling edge of NPN BJT switch

texts:
I am simulating a simple NPN BJT switch for PWM in LTspice, and I observe some current transients on the rising and falling edges that I do not understand. The circuit is here:

Picture of the falling edge:

Picture of the rising edge:

On the falling edge, why does the current through base resistor R3 go negative by ~1 mA? Is there a way to eliminate this such that the PWM voltage source does not have to sink this current?

On the rising edge, why does the load (R6) current go negative by ~1 mA? Is there a way to eliminate this such that the voltage source V3 does not have to sink this current?

EDIT: I put D1 there to prevent Q1 from entering saturation (Baker clamp with a single Schottky diode). The current through D1 on the falling edge mimics the current through R3, but slightly smaller in magnitude. On the rising edge, the current through D1 is plotted in the following picture:

Edit 2: Removing D1 only serves to increase the turn-off delay, as expected. With D1, adding a 22 pF capacitor across ce junction of Q1 has no effect. Why the value of 22 pF anyways? Adding 100pF or more across R6 appears to help reduce the negative current draw on the rising edge.


texts: Driving hard drive voice coil actuator with PWM

texts:
I have been trying to control a voice coil actuator with PWM input, but i have the following problems and would like you to correct or point me in new directions.
I have an arduino which outputs PWM voltage. As i only have a single power supply and PWM is always positive to ground i figured i would just use a voltage divider op amp(12v->+6v;-6v) to feed the TL062(which i happen to have in handy and has nice rail2rail swing, i think).The impedance of the coil is 12 ohm.
The op amp voltage divider is done with only 2 equal resistors in inverter mode.
Regarding the driver op amp TL062,I am planning it as inverter dc coupled but i am not sure. I am also not sure what is Vs in the equation but i assumed 5 because of the max PWM voltage(i really don't know if this is right).
The problem is i can't get my circuit to work with the parameters i have set. Which are

Gain=(-6-6)/(5-0) = 2.4 which makes that R2=2.4*R1
Vbias = (Vout + GVin)/(1 + G) (+6 +2.4*0)/(1+2.4) = 1.76V
Vbias = R4/(R3+R4)*Vs <=> R3 = 1.84 * R4

I have taken the equations and theory from Link to Google PDF viewer the section about DC coupled inverted amplifier.
I am sorry for the length of the question but it is so everything is stated as clearly possible at the first time


texts:
here's my schematic.

I've got this circuit hooked up to those pins. Q1 is P-channel MOSFET (AO3401A), I've also got an ATmega328P not pictured, and POWER_BUTTON is connected to PC4 of the ATmega328P, POWER_HOLD_UP is connected to PC5 of the ATmega328P, VBAT_SWITCHED is connected the input of a linear voltage regulator (NCP603SN280T1G) and a 10uF capacitor. I expected in the default state that this circuit would pull the transistor gate (i.e. both POWER_BUTTON and POWER_HOLD_UP nets) up to VBAT, but as you can probably guess that's not what I'm observing through measurement.

With everything in circuit, and VBAT = 4.84V, I measure 0V at the POWER_HOLD_UP net, 3.37V at the POWER_BUTTON net. The regulator is on and regulating (not what I expected, but predictable based on the measured voltages).

With the FET removed from the board, I get 1.41V at the POWER_HOLD_UP net, and 1.49V at the POWER_BUTTON net. The regulator is not regulating (as I would expect), measured output is however 0.9V, despite there being no clear path between VBAT and the input to it.

With the FET removed from the board, and the source-drain junction bypassed with a 0-ohm resistor, I get 0V at the POWER_HOLD_UP net, and 1.2V at the POWER_BUTTON net. The regulator is on and regulating (as I would expect it to).

This last test is perhaps the most telling and most puzzling to me, leading directly back to to wonder if this is somehow related to input impedance of the microcontroller pins when they are configured as inputs with internal pull-ups disabled, but I'm grasping.

Anyone got any theories about why both POWER_BUTTON and POWER_HOLD_UP are not at VBAT in this scenario?

I was thinking about knocking those two resistors down to 3.3k and 1.0k respectively, as well as trying to lift PC4 and PC5 pins off the board and retaking measurements, but I figured I'd see what people here thought first. I've spent some time chatting with an FAE from the FET manufacturer, and I'm pretty convinced at this point that's not where my problem is originating (again based on the last experiment).

I know there are imperfections in the circuit, and I'm more than happy to try bodging fixes in. I've thought about putting in a bleeder resister (like 10k) to GND on the VBAT_SWITCHED net for example, but that had no impact. I'm just about out of inspiration, hopefully I can acquire some here.


texts: Friend used a 12V power adapter instead of a 9V adapter without looking. Is my guitar effect pedal wrecked?

texts:
Pretty much what the title says.

Later I tried a 9V adapter which I brought from home and the pedal isn't releasing any sound. On/off lights are saying it's off.

Cables and the 9V adapter from home shouldn't be the cause (tried them with another pedal and that worked).

The problem definitely lies within the pedal I lent the friend.

Also, I have no idea about electricity-related stuff. Just thought I might mention that.


texts: Amplifing the output of a current transformer sensor

texts:
I have to make a current transformer sensor from scratch for one of my projects this semester. I bought a torroid ferrite core and wrapped a copper wire around it. Plan was to thread a wire as the primary through the core and get the output.

When we did that the output voltage through the ends of the winding was very low (0.2 uV). How can I amplify this value at least up to about the mV range?


texts: How to receive data via SPI Interface with No Master Command but Multiple Slave Commands?

texts:
I am using
STM32f401rct6 microcontroller - master (No Commands)
and LTC6811 battery Monitoring IC- Slave (Multiple Commands)
I have developed full firmware perfectly including drivers. But i have a small doubt in SPI Interface between Stm32f401rct6 microcontroller. I have understood the concept of SPI also perfectly.i understood that SPI interface is all about transmitting data Through Shift registers
SPI Specs:
Full Duplex
Master mode
1 Mhz of Clock
CPOL High
CPHA High
hardware Slave management
But my doubt is i would like to receive data from the slave (LTC6811) but I have No Command for master To Send. But i have Multiple command for slave as mentioned Below,
Slave Commands:
LTC6811_adcv();   // For Measuring each Cell voltges from 10 cell battery pack.
LTC6811_rdcv();   // Reads and parses the LTC6811 cell voltage registers.
LTC6811_adax();   // for Measureing GPIO of Slave IC LTC6811
LTC6811_rdaux();  // Reads and parses the LTC6811 GPIO registers.
LTC6811_clear_discharge()   // Discharges the Cell voltages which reaches the threshold voltages.
I want to receive Cell Voltage Measurement and GPIO Measurement .By using Cell Voltage Measurement data i need to discharge the cell voltages which is reaching more than threshold voltage.
Since there is No Command to send from master i am sending a Dummy byte to receive the data . But my Doubt is i Have multiple Slave command So Should i send seperate Dummy byte for cell voltage measurement command and seperate Dummy Byte for GPIO Measurement command and seperate dummy bytes for other commands to receive all the datas in the loop or How should i receive data Kindly Suggest Me a Solution Since iam a beginner kindly help me.
I havent Implemented the SPI Receive or Dummy Byte Code  Based on the suggestions  i will Implement.
main.c Code:
#define DATALOG_DISABLED 0

#define DATALOG_ENABLED 1

#define N_IC 1

uint8_t count=1;

cell_asic bms_ic[N_IC];

const uint8_t TOTAL_IC = N_IC;

int main(void)
{
const uint16_t UV=UV_THRESHOLD;
const uint16_t OV=OV_THRESHOLD;
// initialize the SPI2 GPIO
GPIO_Inits();
// initialize the SPI2 GPIO
SPI2_GPIO_Inits();
// initialize the SPI2
SPI2_Inits();
//  This Function sets the SSOE bit to 1 Which helps  the Chip select Pin to automatically  sets Low
SPI_SSOEConfig(SPI2, ENABLE);

// initialising LTC6811
LTC6811_init_cfg(TOTAL_IC,bms_ic);
for(uint8_t current_ic = 0 ; current_ic<TOTAL_IC ; current_ic++)
{
LTC6811_set_cfgr(current_ic,bms_ic,REFON,ADCOPT,gpioBits_a,dccBits_a,dctoBits,UV,OV);
}
LTC6811_reset_crc_count(TOTAL_IC,bms_ic);
LTC6811_init_reg_limits(TOTAL_IC,bms_ic);
//Loop for all the LTC6811 Commands to run

while(1)
{
uint8_t error = 0;
wakeup_sleep(TOTAL_IC); // Enabling Slave ( battery monitoring IC)

// Slave Commands

//  Cell voltage measurement
LTC6811_adcv(ADC_CONVERSION_MODE,ADC_DCP,CELL_CH_ALL);
error = LTC6811_rdcv(REG_ALL,TOTAL_IC,bms_ic);
check_error(error);
print_cells(DATALOG_DISABLED);

//  AUX(GPIO) measurement
LTC6811_adax(ADC_CONV_MODE,AUX_CH_GPIO5);
error = LTC6811_rdaux(NO_OF_REG,TOTAL_IC,bms_ic);
check_error(error);
print_aux(DATALOG_DISABLED);

// Get Cell Max Min Function for Passive cell balancing

get_cell_max_min();

//Passive Cell Balancing code for each cells.

//   This clears all the DCC Bits before or after Discharge process by setting the counter
if(count >=1 && count < 13)
{
LTC6811_clear_discharge(TOTAL_IC,bms_ic);
}
count = 0;
}
}


texts: Unwanted noise/oscillations on op amp output

texts:
I am working on a piezo vibration voltage amplifier circuit. The working schematic is attached below. From a 9V battery I am using a 7805 to provide 5V to both my single supply op amp and the 5V power connection on my contact-mic style piezo.

I have tried this circuit with several different high impedance JFET op amps. The current setup in question uses a an LMC660CN. It can be used from a single supply, swing rail-to-rail, has 126 dB gain (I believe this to be well over 100,000 V/V gain), 6mV input offset voltage, and input bias current 2pA.

When I power the circuit, Vout initially goes low. When I turn the Rf pot up to about 100k, and the gain is about 1000, the circuit is fairly sensitive, and responds as expected to vibrations I make on my table. I need a high gain to pick up some very, very small vibrations.

If I let the circuit sit for about 30 sec, oscillations will start to occur on the output, between about 0 and 800mV, and sometimes a DC bias appears, and it oscillates in this range about ~400mV.

I have read a lot about oscillating op amps, and I have consulted the datasheet on this chip which proposes adding a 10 pF cap and 100 ohm series R in parallel with Rf. In practice, I found a slightly different setup to work better, as pictured on my schematic. I found that placing an 0.01uF ceramic cap in parallel reduced noise on the output significantly.

In one experiment, I have found:

Gain: 1000 (Rf = 100000, R1 = 100)
Without attempting to make vibrations, U3 Piezo signal node has noise on it, peaking at about +/-16mV
v+ and v- inputs on the op amp have about +/-32mV
The +5V node is a very steady 5V, but the ground has about +/- 38mV noise on it; its noise peaks appear to be random, from what I can tell on my oscilloscope
If I ground the v+ input, the output of the op amp is 1.32V, and changes with adjustments to Rf

Two questions:

how can I further reduce the oscillations or noise on the op ampoutput?
how can I avoid Rf adding DC bias to the output?

Maybe the issue to question #1 is simply the input offset voltage -- the datasheet says that input offset voltage is 6mV. If I always have a minimum of 6mV on the v+ input, a gain of 1000 will output 6V. But then, how could this op amp be usable at high gains? (Or any op amp for that matter, since it seems that 6mV is a low value for input offset voltage.)

Thank you for your thoughts.

I have also read this forum, and found the discussion useful about power supplies creating oscillations on the op amp output. I am going to continue to think about some of th
Op amp picks up power rail oscillations from boost conveter


texts:
Rth = (10+10)||5+16=20 ohms.
I think the Thevenin's equivalent voltage is across the 5 ohms resistor which was found to be 11.2 volts Applying nodal analysis but the answer is supposed to be -16.4 volts.
Can you help me find Eth(Thevenin's equivalent voltage)?


texts: What rating should a spade electrical connector have to power an eTopxizu 12v Dc 30a 360w Regulated Switching Power Supply from a US wall outlet?

texts:
I'm looking to power a Prusia i3 3D printer with RAMPS 1.4 from an eTopxizu Dc 30A 360 W Regulated Switching Power Supply, at the moment I'm looking at how to connect it (safely) to a United States wall outlet.

I've seen that you can cut off the female end of a standard power cable for a PC and strip the insulation to reveal three insulated: wires, ground, positive and minus respectively.

And then those would be connected to a spade electrical connector which has a rating for a particular kind of wire.

(And yes, I know this would likely be the last step in the process after wiring everything up before plugging it in, and safety dictates that I NEVER NEVER touch the leads when it is plugged in; I plan to cover the back end of the device with a 3D printed cover and a switch so nobody touches the leads.)

But my question is, that given the type of wire I intend to use to connect it to the US outlet, what sort of rating should the spade connectors have?


texts:
The Arduino DUE runs at 3v3 and almost everything in the world runs at 5v.
When driving for example an h-bridge chip that needs at least 5v to operate, can I use an opto isolator with the diode being driven by the 3v3 from the DUE and the other side switching a 5v supply?
I need the superior speed and resources that a DUE has so using an UNO or MEGA will not work - simply not enough processing power to do all the kinematic calculations for a 6 axis arm.
I also like the idea of isolating my DUE from the side that will probably be making blue smoke ;>}
(32 PIC MCU's fried in my last attempt at this project)
Thanks people.


texts: Reason of using diode between common mode choke legs

texts:
I'm investigating SMPS circuits. And I couldn't understand why there is a diode beetween common mode choke legs (I don't know exactly but it seems like signal diode) What is the main reason of using diode on there ?

Circuit guess

Bottom side

Full photo


texts:
I am doing aging of my product by placing to a chamber for 2hrs 50degrees 95% humidity and 2 hours 0degrees 24/7, I have finished 1 week and the product is still okay. I am wondering what does this 1 week of under a cycle of hot and cold temperature translate to in terms of aging or normal product cycle? Presume that the consumer use it for 8hrs a day under room temp.

Thanks,

Jasp


texts: Ground loop? Switch mode power supply noise

texts:
I have a single 12V supply powering a 12V class D audio amplifier (Tripath TA2020 based, model 'SMSL SA-36') (C) and a very cheap 12V to 5V 2A rated switch mode converter (A). The 5V is used to power a small computer that generates audio (B). The 12V and 5V grounds are tied together at the 12V input socket. The total 12V current draw is 0.5A-1.0A.

When I connect the audio from computer (B) to amp (C) (stereo mini-jack on the computer side, unbalanced RCA inputs on the amp side) I hear a tonne of switching noise (sounds like CPU/RAM/etc activity) on the speakers connected to the amp. If I connect a pair of headphones (D, only one channel shown) in parallel with the amp inputs, I hear switching noise on the headphones; if I disconnect the amp on one channel, then in the headphones (still connected to the computer) the switching noise goes away on that channel.

What's going on here? Do I have a ground loop? How do I get rid of it? Cut the ground wire to the RCA connectors? Use isolating transformers on the audio? Filter something? Throw out the 12V to 5V convertor and get a better one?

edit added amp details, unbalanced input, description of switching noise, diagram.


texts: Connectors in high volume manufacturing?

texts:
How are connectors such as USB handled in high volume manufacture?

Would the panelized board leave room to place these connectors or would the panel be cut apart and the connectors added later. Is there equipment to automate adding these or is hand soldering the only way?


texts: How to partition a combinational circuit into parts with equal delay?

texts: I have a huge combinational circuit with a large delay. I like to partition this design (based on delay) into smaller parts and later, convert it to a sequential pipelined circuit. Are any of the existing tools, such as Design Compiler, Quartus, Yosys, ABC, etc., capable of such partitioning?


texts: What should be assumed regarding the upper frequency of sma connectors

texts:
There are infinitely many sellers of sma connectors of various kind in ebay or other stores. This one is an example.
But they very seldom specify what is the maximum frequency at which the device can be used. Is there something generally assumed here? perhaps some rule of thumb (in particular if it is said that the connector is made of brass and gold plated)?


texts:
I have been looking for 16-bit ICs for a project i`m working on. The project is to build a 16-bit computer from scratch, therefor i decided i nedded cgips that could handle high clock-frequensies. Durring my serch for an optimal IC type i decided that the FAST Advanced Schottky TTL. The problem is that the size of the connectors are to small to fit on a normal breadboard (1 in or 2.54mm).

Are there bigger versions of the same chip sets?
If not, are there other IC that fit while still fulfilling the requirements i need for high frequencies?

eks: http://cache.nxp.com/documents/data_sheet/74AVC16374.pdf?pspll=1


texts: How to feed an SPI TFT display a signal from a composite video source

texts:
Here is the module I am looking at: 1.8" Serial 128X160 SPI TFT LCD Module Display + PCB Adapter with SD Socket

So my question is, is there any way I could convert a video signal from a composite source (i.e. DVD player, game console, etc.) to something which this module could process and display correctly?

Or if you have any other suggestions for a similar sized display which can easily interface (or be made to interface) with a composite video source, please let me know.

Thank you.


texts:
In EveryCircuit, they have a component called a "Current Source". For example, here is a circuit I've created with a 2A current source:

Is there a such thing as a 'current source' in the real world, or is this an abstract component that helps one regulate current (for example, without having to do a voltage source + resistor).


texts: Best humidity/temperature sensor for a nappy?

texts:
Special needs kids have big troubles with potty training. A 'wee-wee' alarm would be of a lot of help.

What would be a good way of detecting 'it' without electrocuting anybody? A possibility would be to detect humidity or temperature but it really has to be a sturdy sensor. Any ideas?


texts: How to achieve this logic function simply?

texts:
I need logic gate that behaves like this:

A=1, B=1, Y=1

A=0, B=0, Y=1

A=0, B=1, Y=1

A=1, B=0, Y=0

The tricky part is (A=1, B=0, Y=0) while (A=0, B=1, Y=1), AFAIK no logic gate distinquish between A or B inputs so dont think its possible with normal gate, is it possible at all?


texts: Best wavelength for IR LEDs to be used with a hacked up IR camera?

texts:
So, I recently saw this question and thought it looked simple enough. Instead of a webcam  though i used an actual (but old, 3MP) digital camera. The camera was a bit broken anyway(always exposed with weird colors and too dark usually). Well, I've confirmed the IR works now by holding my TV remote up to it. I don't actually have any IR LEDs on hand though.

The two prevalent kinds I see seem to be 950nm and 850nm. For the purposes of making a night vision camera, which one would be more bright? I would think 950nm because it's closer to the visible spectrum, but everyone else seems to say 850nm is brighter. So which one works better? Or should I just buy one of each and see for myself which one is brighter?(as in, it depends on the camera)


texts: Transformer VA Ratings, Power factor, and Pulsed current

texts:
What exactly goes into a transformer's VA rating? At a fundamental level it seems that there has to be a limit to what the VA rating can represent.

For example if I draw 2 Amps-RMS from the secondary of a 30VA rated transformer at 15 Vrms this makes sense as the maximum Complex Power I can draw. Still, at a power factor of 1 my maximum current in the transformer would be sqrt(2) * 2 Amps.

But what if my power factor is abysmally low (ie in a DC rectifier) due to harmonic distortion and while I still draw 2A-RMS I have brief current spikes of 15 Amps? Surely the transformer's magnetics couldn't handle these spikes as I'd expect the core would saturate.

My question is what is the practical limit for VA ratings of transformers? Would brief current spikes that reduce to only 2A-RMS in this case be fine? Obviously the secondary/primary copper losses play a part in the rating but how do the magnetics factor in?

I ask this because I am designing a simple bench power supply using a 125VA transformer with a 24Vrms secondary and am trying to figure out how much power I can draw before the current spikes into the inductor are too much for the transformer. I also don't want to have to resort to active PFC as I don't want to risk messing up any HVAC PCB design.

Thank you


texts:
I will drive a load low side with IGBT. IGBT gate-emiter (Threshold) voltage will be 12 V. This voltage level is enough for my load current.
I will use a gate driver. When ı search gate driver for low side Igbt always I saw current rating. What is it? I will use only voltage on gate of IGBT and any current will not be on gate of IGBT but I see sink or source current always.

Question two: I will use IR4426 (Infineon) for gate driver. Typical application was attached.
According to this product, if I use microcontroller voltage level on input pin, I will to take 12 volt on output? Is that true?

Question three: Can I use this gate driver for this IGBT? IGBT will carry about 500 V and 5 A for 1-2 seconds.

Link: https://www.infineon.com/dgdl/ir4426.pdf?fileId=5546d462533600a4015355d60b491822

Sorry for my basic questions. I'm a new hardware design engineer.


texts: compare base current of different transistors

texts:
Can you please compare the base current of 2 transistors:

T1 has Vbe = 0.7 V and Vce= 0.7 V
T2 has Vbe = 0.7 V and Vce= 0.1 V

i believe that T1 is in active mode while T2 is in Saturation mode, so the only comparison i am noticing is that Ib(T2) > Ib(T1), if you have any other comments please tell me.

thanks in advance


texts: Calibrating RTL-SDR Power with 50 Ohm Load and Thermal/LNA Noise

texts:
Ultimately I'm generating some spectrum plots in L-Band (1200-1800 MHz) and I need to get calibrated flux units (dBm/Hz) for my y-axis. I need a little assistance on creating this memo.
I've been tasked to use simply a 50 ohm matched load followed by the 2 LNAs and RTL-SDR v3 and use the difference between the front end ON vs front end OFF to arrive at a value I can use for my reference. I realize there are a few assumptions going on here (input impedance vs. gain, RTL tuner noise lower than thermal noise, etc.), but they can be ignored for this (unless of course the tuner noise is indeed higher than thermal noise).
I'm having trouble putting the equations together to arrive at what I ultimately want (the ratio of the two?). I know Sin = kT (assume B = 1 Hz?). So Sin = 4.045 x 10^-21 W/Hz or -173.9 dBm/Hz. I will use GQRX for observing the noise floor in dBf. Do I solve for Teq2 which I can use kTB to give me the total estimated noise floor?


texts: Error while simulating the speed control of a brushed DC motor using a 555 timer and a high boost convertor using Multisim simulator

texts:
Reference paper: https://ieeexplore.ieee.org/document/6183251
I'm trying to simulate the speed control for a brushed DC motor using a 555 timer (astable multivibrator) and a high boost convertor using the multisim software.

It simulates for a while before giving me a simulation error. Any tips on how I can fix this would be highly appreciated.


texts: Should you plug your device in more frequently and wear out the MicroUSB port, or let the Li-Ion battery drain more and wear out the cells?

texts:
I would like to know what advice to give the consumer about how often they should charge the device.

I read in this answer (and various other places on the net) that MicroUSB ports are rated for about 10,000 unplug cycles.

I also read in this article and this answer that Lithium Ion batteries will last longer when you "avoid full discharges and charge the battery more often between uses."

So running the battery down is bad, but there's a limited number of times that the user can put it on the charger to keep it charged up.

How much of a charge would you need in order to justify the wear on the MicroUSB port that happens when you plug it in or unplug it.

Let's assume that neither the Li-Ion battery, nor the MicroUSB port is serviceable by the end-user/consumer, and when either one fails, the device must be sent in for repair.

The device I have in mind in this case is a cell phone, however (I would assume that) this concept should apply to any device that uses a MicroUSB port and a Li-Ion battery. If this assumption is wrong, please help me (and others) to understand why.

As @Asmyldof points out, for very light usage, it can be fine to plug the device in once or twice a day and never run out of "plug cycles," but as smartphones begin to fill roles that once were reserved for dedicated hardware devices, this can quickly change.

Think about a delivery driver who gets in and our of their car 20+ times a day, and has to keep their phone both charged and on their person so they can be reachable by the dispatcher (and maybe they need to use the GPS or listen to Pandora too.)

At 20 cycles a day, that gives you only 1.3 years of life for the port. That even assumes that each of those 10,000 cycles includes a plug-in, and an un-plug.

Then there are those who like to set their phone on a non-wireless cradle charger to prop it up and keep the screen on, then take it off each time they need to answer a call or reply to a text. The consumer may not even know that they are drastically reducing the life of the device itself in their good-faith efforts to preserve the battery.

There must be a "happy medium" somewhere inbetween where both of these components will wear uniformly, and neither one causes premature failure of the entire device.


texts: High power voltage controlled bidirectional current source circuit

texts:
I have tested various amplifiers and motor drivers and none of them are capable of driving my 20Ohm 100mH load at 0-> +/-2Adc (max 0 -> +/-100Vdc) in function of a control voltage (from a 16 bits DAC) with a closed-loop bandwidth of 5kHz. The bias and noise must be <= 1mA. I can give away 10V on the output for sensing.

Honestly I can't see any particular challenge for manufacturers of such equipment to make a product with these sorts of specs and yet I have found nothing suitable - so I am trying to make my own.

I'm looking for a very simple circuit topology that I can design in details - again, I was not able to find anything online after much research other than an application in the LT1990 datasheet that unfortunately can't go beyond 36V. I have two 4-quadrant +/- 100Vdc 2Adc lab supplies with voltage+current limiters so I thought about a simple opamp controlling the gate voltage of a MOSFET push pull based on the readings of a low-side sense resistor, but maybe there is something better?

Space, cost, dissipation are not an issue - I am solely interested in the high-speed performance.


texts: How to convert a Boolean expression from POS form to SOP form?

texts:
POS equation is given as F=pi(3,8,12).
By converting POS to SOP form directly I get F=sigma(0,1,2,4,5,6,7,9,10,11,13,14,15)
But according to the process given in the above picture F is given as F=sigma(0,1,2,4,5,6,8,9,10,11,13,14,15)
Now, I'm confused as to which one of these equations are correct?
Or does it depend on the implementation technique? Like Kmap and others
This SOP conversion is for implementing Boolean expressions using Multiplexer. Does the equation change if it is implemented for Multiplexer?


texts:
I have a problem interpretting the temperature reading of a DS18B20 chip. There is a certain situation I am not abble to resolve. This is the example temp table for the chip from the datasheet:

an example for reading of -0.5*C is shown as FFF8. Cutting off the 4 LSBits we get 0x0FFF. In signed data structure that is equal to -1, not 0. How am I abble to resolve the difference between 2 readings: -0.5*C and -1.5*C? If 0xFFF8 = -0.5 then what is the form of -1.5?

The table then shows an example for -10.125*C. Cutting off the 4 LSBits gives 0x0FF5 which really is -10, then there is no reason to think that there is some kind of a shift for reading negative values...


texts: H-bridge with optocouplers input not smooth

texts:
With commonly used bridge schematics, the operation with optocouplers are like on and off, like without smooth transitions under PWM. If opto with additional 10-12volts to gates via them, are excluded, and 5v logic are given to gates only, it works as it is required. As I get it, it works like in linear mode. But what can be done to eleminate the on'off operaton of the h-bridge with optos?
The second schematics gives the full power constantly.
With the first, if opto are changed to 2n2222 it makes it weaker.
Mosfets P-channel - IRF4905, and N-channel -IRF3205


texts:
I have been given a question and tasked with identifying the various components. However, this circuit doesn't really seem to make sense to me.

Error: RC RE inverted

simulate this circuit – Schematic created using CircuitLab

It is given that the input signal is a sin wave that goes from 12v to 8v (4v PP). I understand that for modulation, you essentially have to generate a carrier wave that is mixed in with the input. Op amps won't work for such a high frequency so we have BJT's instead.

For a sin carrier wave to be generated, we need a band pass filter at the output of the amplifier fed back to the inpit? But from what I see, that seems to be a butterworth low pass filter
I assume the LC network is going to cause some drop in gain. So assuming I calculate it, must I set the gain for the BJT amplifier to match the drop of the LC network?


texts: DS1822 1-Wire Sensor, Parasitic Power, and Strong Pull-Up Circuit

texts:
This question would be common to any parasitic 1-Wire devices from Maxim/Dallas Semiconductor. I have a functioning 1-Wire circuit to a DS1822. The 1-Wire protocol has been bit-banged on a 3.3v MCU (mbed lpc1768). I believe this question would be pertinent to any microcontroller used in the same manner.

As reference, I have used the DS1822 datasheet http://datasheets.maximintegrated.com/en/ds/DS1822.pdf.

My 1-Wire circuit uses a single digital pin on the MCU as an open drain pin connected to the 1-Wire bus and the DS1822's DQ pin. (Open drain is managed by setting the pin to output and setting it to low in order to pull the 1-Wire bus low, or setting the digital pin to an input in order to allow a 2.2k resistor to pull the bus high).

Up until now I have powered the DS1822. I would like to implement the 'Strong Pull-Up' circuit defined in the datasheet above as specified in the circuit in 'POWERING THE DS1822'. The strong pull up circuit calls for a MOSFET driven by a second digital pin (SPU) on the MCU that can pull the 1-wire bus straight to the 3.3v rail during operations that require additional current and a sustained voltage level.

The question I have specifically surrounds the possibility of a short circuit. If I implement the circuit as shown in the diagram, it would seem that as long as my digital pin (DQ) is set to an input while the second digital pin (SPU) enables the 'Strong Pull-Up', then a short circuit would not occur.

However, should my digital pin (DQ) be set to an output and driven low while the second digital pin (SPU) has enabled the 'Strong Pull-Up', it seems that this would create a short circuit through the DQ pin.

As I am only surface level versed in circuits, I'm seeking the expertise of this group to confirm that this is indeed a danger. Additionally, I'd like to understand what could be done to protect the input pin under this scenario. Would the addition of a resistor between the 3.3V rail and the MOSFET ensure that the level of current sunk by the digital pin stays within the MCUs' parameters enough?

Additionally, how would one determine the 'right' MOSFET for the job. What characteristics should I look for?

The circuit is driven by a 3.3v MCU and the 1-Wire bus uses a 2.2k pull-up resistor.

Thank you,
Karl


texts: I was trying to use S8050 in a schematic and thus was checking the datasheet. The datasheet says Vbe Sat. is 1.2V. Is it correct? As a learner I have seen most of the transistors have Vbe 0.7, I am little confused in calculating the base resistor.. Please help ... here is the datasheet..


texts:
I have a circuit with split ground planes one for analog, and one for microcontroller/DC-DC etc. The microcontroller will be using its ADC to sample from the analog circuitry.

Ideally I would like to connect the microcontroller to analog ground, so that the ADC voltage measurement is correctly referenced to the analog ground, and not digital ground. However, as the microcontroller is inherently noisy, this is likely to create return current thought the analog ground, which is not something I want. (Previous versions of the circuit have had significant problems with noise).

What is the best practise here?


texts: Arduino Boost Converter. Connecting load makes converter non functional

texts:
I am trying to build a DC-DC Buck-Boost Converter using this basic schematic and an Arduino with the analogWrite() function as my PWM generator. I only want to step up 2.4-3V to ~5V. If it's just the capacitor and no load, the converter works so good that I have to switch it off after a few seconds since the voltage I measure on my capacitor is exceeding the capacitor limit. However, when I connect any load to the capacitor(for example a motor or a resistor) my voltage drops to a really low value(0.1-2v) and stays that way no matter what frequency PWM signal I send to the transistor using Arduino. I really tried but couldn't find the cause of the problem. Is it because I have two grounds, the battery pack one and the Arduino one? Is it because of the inductor(I tried using a smaller, 45uH, torroidal one but couldn't get any better results)? So what am I doing wrong?

I only expect to draw 500mA of current at 5 volts at the output side, and according to this calculator my inductor and transistor should be fine.

Components: 100uF 35V electrolytic capacitor, 200uH inductor, BYW29 rectifier diode, TIP 120 power transistor, 1k resistor

A schematic of the circuit or at least how it is supposed to look. Maybe I miswired something? The resistor is to represent  the load, the value doesn't matter since my problem persists at any value but the multimeters "infinite" resistance.

This is how my circuit looks

I used one coil of an old transformer as my inductor

However I also tried this inductor


texts:
I am looking for a way how to detect the rotation of an object that is hanging from ceiling, attached with a rope. Since the object can freely rotate for many revolutions (until the rope is too twisted), there is no way to provide power to any sensors and/or microcontrollers if they are attached to the hanging object. Batteries are not an option since they would have to be replaced regularly. So I thought maybe I could pass the rope through a pipe, attach magnet to the rope, and sense the position of the magnet by a magnetic sensor that is fixed on the pipe (see the diagram).

For context: this is an installation in art exhibition. The object is freely hanging in the rope and is expected to be manually spinned by the visitors. When it spins, sound effects are played on several speakers that are placed around the object. Object is firmly attached to the rope and thus pulls the rope along with it. The rotation would go several revolutions on one direction, and when the rope has aggregated enough resistance, the rotation would get slower until it starts going in the other direction. The plate with magnets would be attached as close as possible to the object so that it could be assumed that the rotation of the plate reflects the actual rotation of the object.

Since the pipe is fixed, there is no problem powering the sensor and microcontroller to read it.
I found this magnetometer - HMC5883L and would like to know if that could be used to read the position of the magnet. Or maybe there is much better way to achieve what I'm looking for, with of without magnets.


texts: How to find area under the curve of a signal?

texts:
I am using a Wheatstone Bridge circuit with one pressure sensor. I want to find the area under the curve as the signal goes from 0 to maximum to 0 again. I have tried to use ADC of Arduino and then use the counter to count++ as long as the signal is not zero.

simulate this circuit – Schematic created using CircuitLab

The above values are not exact.

What I want to ask is how can I find the area under the curve of this signal. If I simply add all the signals then the variable which is storing the result might get overflowed. I want to find the area and print it on a display or something like that. Is there any better way of doing it?


texts: Understanding the Verilog Stratified Event Queue

texts:
I'm trying to understand how the Verilog scheduling algorithm works. The below example outputs 0, xxxx and not 1010. I'm not clear why. If I do put a delay before $display, it would output 1010.

module test;
  reg [3:0] t_var;
  initial begin
    t_var <= 4'b1010;
    $display("%0t, %b", $realtime, t_var);
  end
endmodule

Same output, 0, xxxx, for the below example:

module test;
  reg [3:0] t_var;
  wire [3:0] y;
  assign y = ~t_var;
  initial begin
    t_var = 4'b1010;
    $display("%0t, %b, %b", $realtime, t_var, y);
  end
endmodule

Based on the examples, it looks like that both nonblocking assignment and continuous assignment are two-step processes where the RHS is evaluated at the current time step and the LHS is scheduled to happen at the next time step (if no delay is specified) or at a later time step (if a delay is specified).

Can someone please confirm or explain to me a step-by-step flow of the algorithm below (from Clifford Cummings) as it applies to the examples above?

Thanks!


texts: How to analyitically optimize an RLC "circuit" to reduce overshoot?

texts:
I have a "circuit," that's not really an electrical circuit but rather a physical process that follows the same functional form as an RLC circuit with regards to how it responds to excitations--basically, it's a second-order linear differential system.  However, I have no real way of measuring "R," "L," or "C" except by looking at how the "circuit" responds to stimulus.  I can, however, modify R, L, or C in a relative way (i.e., make whatever C is 1.5x bigger) by making changes to the system design.

Every day, the system is excited by a step function.  It responds in a manner very similar to an "under-damped" RLC circuit--that is, it greatly over-shoots, then oscillates around the step around once and hour, slowly settling down after about a day.  I know this, because I measure the fluctuations in the levels of my system over time.

My question is: Given that it isn't possible or practical to measure R, L, or C (and hence I can't calculate damping factor), but it is possible to make modifications to the relative ratios R, L, and C to each other, is there any way for me to analytically determine how to modify my system to make it critically damped, based on the measurements I can make on the system as it exists now?


texts: What is the smallest and simplest seed for a random number generator?

texts:
A small microcontroller (8-bit Atmel) controls a number of lights in order to present a light show with many fancy randomized light sequences.

A suitable pseudo-RNG does its job nicely, but I'm looking for a good seed for it. A seed will be necessary because if someone turns multiple such devices on at the same time, it won't look good if they all generated the same sequences of effects until they slowly drift apart due to the tiny differences in their individual clock sources.

A very good method to seed a pseudo-RNG, which I often used, is possible in case of a device which has to be started with the press of a button or flip of a switch. As soon as the µc is powered on, a very fast timer can be started, and the value of this timer seeds the RNG as soon as the button is pressed for the first time.

The problem is, in this scenario, there are no buttons. The program has to start as soon as the device is powered on.

The place on the PCB is extremely limited (nothing more than a few of the very smallest SMD parts might fit), so I'm looking for the smallest and simplest possible solution. Therefore I'll rule out fancy solutions like true RNG hardware, radio receivers, etc.

All I have is a 16 bit timer-counter in the CPU, and an unused portpin which has access to an ADC.

My current solution is to just use a resistor (as inaccurate as possible) to provide approximately half the supply voltage to the ADC pin, and seed the RNG with the first AD conversion value. However, nowadays most 10% resistors have an inaccuracy well under 1% (it would be fun to imagine the face of a supplier when I tell them we want the worst quality SMD resistors they can find), so there is a very high chance of multiple units starting with the same seed.

A better alternative would be to make multiple conversions and build a value out of the least significant bits of these measurements. However, I used the ADC of this µc type before and I know it's very accurate. Running the ADC at the fastest possible speed might help here.

Does anyone have a better suggestion? The seed is not required to be perfectly uniformly distributed, but the more uniform the distribution is, the better. A 16 bit seed with a perfectly uniform distribution would be a dream too good to be true, but I think a halfway decent distribution over 5 or 6 bits might be sufficient.


texts:
I'm using this ESP8266 board, which has a Vin pin.

This link - says specifically that Vin get a direct 5V from USB's DC. But when measuring it using a voltmeter, I get 0.1V (2 boards were checked and got the same result).

Can someone explain what is true? (My goal is exactly to get a direct 5V from external USB).


texts:
I have a colleague who is off work for the next 2 weeks and has asked me to finish off one of his schematic designs. I have a list of operations it needs to be able to perform, seems simple enough.

I got round to making a start on it today, and after having a browse through what he has already done, I notice something that I haven't seen before.

Here is the basics of what it looks like:

simulate this circuit – Schematic created using CircuitLab

I have not seen an op amp circuit which uses a diode in the feedback circuit in this way. I recognise it is a window comparator, and this part of the circuit is used to detect a voltage level and turn on an LED if it goes above or below a threshold. I just can't work out what the point of the resistor and diode is in the feedback.

My go-to op amp configuration PDF is one from texas instruments (LINK) and I couldn't find one like this. So can anyone tell me what the function is of this feedback circuit?

NOTE: I have labelled things as V1, V2, OUT etc as they should be irrelevant to the circuit, V1 and V2 are measuring the input voltage, Vref is the threshold, and the output toggles LEDs

EDIT: I have updated the schematic to include the resistors that Andy aka mentioned, the values of resistance are what was on the schematic at the time, they may be incorrect, I am unsure, as the schematic is not finished.


texts:
I have a cheap IR remote control from Ebay (like this one) and I´m straggling with the modulation of the IR signal. I use an BPV11F photo transistor as receiver and I get this signal with my scope

But this signal looks very identical to the signal which comes from my TSOP38238:

So I would expect to see some kind of modulation (the 38 kHz carrier signal) when I receive this signal over the photo transistor, like in this image.

My guess is that this cheap remote doesn´t use a modulation (is this possible?). Or do I have some misunderstanding?


texts: Effect of parasitic capacitance on an ideal signal?

texts:
How does parasitic capacitance affect an ideal signal?

Ie. We have an ideal signal shown below, what would it look like with parasitic capacitance accounted for?


texts: Boost power losses - What is "Voltage drop of MOSFET"?

texts: I'm following this tutorial on calculating boost converter efficiency and I'm a bit confused on the "Voltage drop of MOSFET" variable. Is this just the voltage drop of the FET when it's on? Meaning it would just be the sum of Vout and the forward drop of the diode? If thats the case, then the equation for the duty cycle "D" would result in a denominator of VD + Vout - VS, which would equal zero. What am I missing?


texts: Finding the unknowns of a current equation leads to non-sense

texts:
Suppose a series RLC circuit that is critically damped.

Circuit is RLC in series with a DC voltage source \$ V_S \$ and a switch initially open. Capacitor and inductor are both discharged.

at t=0 the switch is closed.

I am trying to analyze what happens during the transient phase.

The circuit equation is

\$ i(t) = (At + B)e^{-\alpha t} \$

I want to find A and B.

So I apply the initial conditions.

The first condition is current when t=0. We know that the inductor will resist the initial current, so i(0) = 0.

If this is true and I apply that to the equation, to find A/B, I get

\$ i(t) = (At + B)e^{-\alpha t} \$

\$ 0 = (At + B)e^{-\alpha t} \$

at t=0

\$ 0 = (0 + B)e^{0} \$

\$ B = 0 \$

The other condition, di/dt at t=0.

We know that current will be zero, because the inductor will guarantee that, so

\$ \frac{di}{dt} = \frac{V}{L} = 0 \$

so,

\$ i(t) = (At + B)e^{-\alpha t} \$

\$ \frac{di}{dt} = 0 = -\alpha A t e^{-\alpha t}  -\alpha B e^{-\alpha t}  \$

when t= 0

\$ \frac{di}{dt} = 0 =  -\alpha B  \$

\$ B = 0 \$

again... I don't get it.

What am I doing wrong?


texts: Working out what happens to the brightness of a bulb in a simple circuit

texts:
I have been going through some past questions for my exam that is coming up this summer. I have come across this question which I originally deemed to be easy however the more I have looked over it the more I believe I am confusing myself and over complicating things!

This is the question I am looking at:

My current thought process is that the voltage across Bulb A will not change when Bulb B is removed, however the current which previously was split between the two branches of the circuit (Kirchoff's Current Law?) will now all flow through Bulb A and its resistor.

This lead me to believe that if the current effectively doubles and the voltage stays the same then P = IV will mean that the power dissapated in Bulb A will also increase. This means that Bulb A is now brighter? and the answer would therefore be C.

I am asking if this thought process is correct? or if I have simply confused myself and gotten it wrong! If that is the case I would love for someone to explain the answer to me so I can understand it and attempt other questions like this.

Many thanks!


texts: CN3722 solar charging IC not working properly

texts:
I'm currently working on a custom PCB where I have a microcontroller hooked up to 3 LiIon batteries which are meant to get charged by a CN3722 IC. However, when I connect a solar panel to the circuit the batteries are not getting charged. The datasheet of the CN3722 can be found here.
Some more information:

All three LiIon batteries have a voltage of 4V so they should be getting charged.
One has to specify what the battery regulation voltage is supposed to be. This is done with a resistor divider. The formula is Vreg = 2.416 * (1 + (R22 / R23)), in my case this equals to roughly 12.6V.
You also have to specify the MPPT voltage (since its not real MPPT). The formula for this is Vmppt = 1.04 * (1 + (R17 / R18)). I wanted to be able to adjust this in the finished PCB so R17 is an adjustable resistor in my case. At the moment I have set it to 150k Ohm in order to have the MPPT voltage set to roughly 16V.
A charging cycle should basically start, if...

Vin rises above the battery voltage and
Vin is no less than the MPPT voltage set by the resistor divider.

My problem is that it doesn't charge. I have measured the current draw from the solar panel and I only measure ~6mA under pretty much full sunlight. This is due to the "CHARGE" LED being lit. However it is not charging.
I don't know why though. I designed everything like it is described in the datasheet and tried to take all PCB layout considerations into account.
This is my schematic: (typical application circuit can be found on page 2 in the datasheet)

The Vsolar net is connected to an INA219 IC, which basically just measures the charging current so I can monitor it.
This is the rather small INA219 circuit:

As you can see its simply measuring current/voltage. I don't think this might cause any problems, can it? The VCC net is directly connected to the positive of the battery.
Finally I will attach a few images of my PCB. Even though I don't think I made huge layout mistakes I could miss something. This is the complete PCB, which contains some circuits I haven't mentioned (like a 3.3V buck converter.), because they are not related to this problem.

This is the CN3722 circuit on the PCB:

I know this is a rather extensive question, but I would really appreciate any help.


texts: Is it dangerous to connect an IC output directly to GND?

texts:
Is it dangerous to connect an IC output directly to GND while there is a risk this output can be high?
BUF1 is the 74LVC2G125DC dual buffer. datasheet here. But my question could also apply more generally to "any commonly used ic". Answer concerning this ic specifically or more general answer are appreciated.

The goal of the MOSFET is to pull Q (DATA OUT) to GND as soon as OE is high and Q turns High Impedance (Z). If I don't put this MOSFET, the High Z output on Q will likely show a logic "1" or be unstable. It needs to be a "0". If I put a pull down resistor, Q falls to zero volt way too slowly. I tried with a 22K resistor and I don't want to go lower. The MOSFET (M1) offers the ideal solution and theoricaly there shouldn't be any problem as both M1 and OE turn on instantly.
But what could happen if at the time M1 turns on, the Q pin of the buffer is high and OE reacts more slowly than than M1?

What happens,  (this is not planned in the design but I would like to know), if OE is not pulled high and data keeps flowing, with constant "high" output out of Q while the MOSFET connects Q directly to GND without practically any impedance?

For safety, for the moment, I put a 1K resistor (R2). What is the lowest value you would put for this resistor to be safe keeping in mind that it has to be pulled low as fast as possible?
(Ideally it should be zero ohm.)

simulate this circuit – Schematic created using CircuitLab


texts:
I am developing an UART protocol to ensure communication between two boards (Master board and Slave board). Slave board includes many sensors and actuators and Master board shall command this board by a set of commands like GET_SENSOR_VALUE and SET_MOTOR_SPEED etc ... Many functions shall be executed in my project and a permanent control of sensors values shall be done (Example: Master board shall get temperature value each 5 seconds, it shall get Battery's level each 5 seconds, it shall enable ventilation when temperature is high ...). All equipment are connected to Slave board (sensors and actuators) and the main role of Master board is monitoring.

I've been reading some articles about specifications and embedded systems design and figured out that the first thing to do before starting is to choose the kernel: RTOS or GPOS (Bare metal).

My question is: In my case, if I choose RTOS (in Master board), Should I implement my needs as separate tasks/functions?

temperature_task
humidity_task
battery_task
motor_task
ventilation_task

If yes, does UART support high speed context switch time? example:

00:00 temperature_task : GET_TEMPERATURE
    if temp>threshhold send START_VENTILATION
  00:01 battery_task: GET_LEVEL if level < threshhold send TURN_OFF_SYSTEM
  00:02 humidity_task: GET_HUMIDITY if level < threshhold send DO_SOMETHING
00:03 temperature_task : GET_TEMPERATURE
    if temp>threshhold send START_VENTILATION
  00:04 battery_task: GET_LEVEL if level < threshhold send TURN_OFF_SYSTEM
  00:05 humidity_task: GET_HUMIDITY if level < threshhold send DO_SOMETHING


texts:
What is a convergence problem? My circuit code is below and when I simulate it is saying that the NMOS transistors MPDA and MPDB are not converging. See the following screenshot:

Here's the netlist:

V1 1 0 DC 5V
V2 2 0 PULSE(0 5 3ns 3ns 3ns 20ns 40ns)
V3 3 0 PULSE(0 5 6ns 3ns 3ns 20ns 40ns)
CL 4 0 0.15PF
MPUA 4 2 1 1 IRF150
MPUB 4 3 1 1 IRF150
MPDA 4 2 5 0 IRF250
MPDB 5 3 0 0 IRF250
.MODEL IRF250 NMOS (level=3 w=4u l=3u vto=1.0 tox=470e-10 nsub=38e14 cj=160e-6
+cjsw=430e-12 mj=0.5 mjsw=0.33 kp=30e-6)
.MODEL IRF150 PMOS (level=3 w=10u l=3u vto=-1.0 tox=470e-10 nsub=8.7e14 cj=100e-6
+cjsw=180e-12 mj=0.5 mjsw=0.33 kp=12e-6)
.TRAN 1ns 80ns
.PROBE V(2,0) V(3,0) V(CL) ID(MPDA) ID(MPUA)
.END


texts:
I have a project in which I have to "close a digital switch" using either a 5V or a 3.3V supply. The load will be at 12V, with a required current of around 200mA.

As a newbie I thought to use an N-channel MOSFET such as the FQP30N06L datasheet.

While the transistor will actually provide me more than enough current, according to the datasheet, either at 3.3V or 5V, I will be in the saturation region and not in the ohmic region.

I thought I was fine with that, but reading around I found out you should be in the ohmic region to use the MOSFET as a switch.

Why so? Also: What are the downsides of my configuration (i.e. switching in saturation region)?


texts: Current measurement USB to serial UART converter or Arduino

texts:
I want to perform a current measurement of an electronic module with the help of a multimeter with log function.
Can I just couple the module to a USB to TTL serial UART converter and perform the current measurement or do I need to connect it to an Arduino where it will be used later to get more accurate results?


texts: How exactly does getting 7V by connecting both terminals to the 12V and 5V sources work?

texts:
When I Googled MOLEX pinouts and checked some questions on Stack Exchange. I saw interesting images where if you were to connect both the 5V and 12V ends of the PSU connector to a device, you would get 7V power.
How does this work? Doesn't DC work by forming a loop from positive to the negative? I don't know much about the electronics other than reading MAKE books back in the day so I am curious.


texts:
can someone help me out with using the MC34063 ic, i have a 12V battery and need to have 15V to power 7 LEDs in series (many LEDs altogether).

Ive used a couple of online calculators and an offline one (mc34063 universal calculator) but its not specific.

Is the calculator correct and what values components do i need?

For instance ive found a couple of 39uH inductors but i don't know which ones i need, 2A, 0.8A or 150mA

Inductors from here


texts:
So i ordered this cheap 100 ohm ten turn pot from ebay: Potentiometer

The problem is that it doesn't work as a normal pot (or it is broken).

When i check resistance from pin 2 to pin 3, everything is working fine, i can turn the wiper and the resistance is changing, however, if i check from pin 2 to pin 1, it shows 100 Ohms resistance all the time, no matter how much i turn the wiper. Is it supposed to do that or have i wired it wrong? Thanks!


texts: Why doesn't this capacitor voltage rise when the current does flow into it

texts:
I use a capacitor and a resistor to be a battery,the simulation show me the current does flow into it(charge it).The reason that i believe the current does flow into the capacitor is because that the current is positive for flowing into the component,and negative is for flowing out off the component in this software(virtuoso cadence).However,the capacitor voltage did't rise up ,why?it does't make any sense.

Battery model

Resistor and capacitor current and capacitor voltage

After changing the capacitor from 1 to 1p,the wave become like a square wave.


texts: Coplanar waveguide - Calculator question

texts:
I was looking for information on coplanar waveguides (curiosity prompted by another question here) and found this calculator.

In the description of use, it mentions that the units for the dimensions do not matter as long as the same units are used for all dimensions.

  Note: Units do not matter for this calculation as long as they are consistent.

That seems to imply to me that scaling all the dimensions by the same factor would still leave you with the same impedance.

So, if I enter dimensions and get an impedance of 50 Ohms, then I could multiply all dimensions by, say, 137.52 and still have a waveguide with an impedance of 50 Ohms.

That also implies that I could make a waveguide out of meter thick copper bars, as long as everything is proportional to the same wave guide using .1mm copper traces (as long as I also have a substrate of the same proportions with the same permitivity.)

Is waveguide impedance really governed by the proportions rather than the absolute size?

This bugs me because it seems to me that the absolute size determines which frequencies the waveguide can work at.  It doesn't seem reasonable to me that a wave guide 5mm across would have the same impedance as one that is 5M across.


texts:
I am building a memory module:

32 bits wide,
parallel, and,
byte-addressable.

I did a research and i could not find an memory IC that will suit my needs.

It must be able to:

StoreWord,
StoreHalf and,
StoreByte (RISC-V), with or without an offset.

One suggestion was to build it from four 8bits RAMs. I simulated it in Logisim-Evolution, as suggested masking out unwanted data, but even in the uncomplete state, it seems a little too large.
I plan to build it in real life, so it must have as little components as possible, but i just cannot think of a way how to build it, or how is it made in industry?

Thanks for any help


texts: LED driver internal circuitry understanding

texts:
Whenever we talk about LED driver we always think of driving a transistor by keeping a LED in at its collector along with a series resistor.

But I wish to understand what actually these LED driver ICs do? What all the internal circuitry does?

From example datasheet


texts: Would you prefer a voltmeter or a scope when measuring average voltage precisely?

texts:
As far as I understood the DC setting of a voltmeter or a multimeter is measuring the average value of a periodic voltage signal(not rms but the average value).

On the other hand, an oscilloscope as well in DC coupling mode also measures the average value of the signal.

Which one in general measures more precise? Why?


texts:
What does the x that's wired to pin 3 and 6 mean?

Does it mean it should be wired to gnd?


texts: Does swapping the inputs cause increase in the common mode noise in this scenario?

texts:
This is a question I wanted to ask after I have observed much more noise when I swap a filtered traducer's output to a single ended data acquisition board. A transducer outputs Vs1 signal. The transducer is basically a strain gauge with an amplifier and powered by an SMPS supply.

So in Figure1, Vs1 is the transducer output signal, Vdn1 is the differential noise and Vcm1 is the common mode noise. R1 and C1 forms a low pass filter. Rin is the input impedance of the data acquisition input.

In Figure2 everything remains the same but the inputs to the DAQ are swapped.

When I simulate this, I get much more common mode originated noise in Figure2.

Is that correct to say for such circuit setup in Figure2, if we swap the inputs common mode noise component will increase. Am I modelling the issue and interpreting what happens correct?

Edit:


texts: I'm very new to hardware logic (and this site) but I'm trying to understand the exact use and duration of the asynchronous inputs clear (CLR) and preset (PRE) on flip-flop timing diagrams.  They seem to typically both be active-low triggered.  I know that CLR sends the Q outputs to 0, while PRE sends them to 1, both regardless of what edge the clock is on (if any).  What I'm not sure about, is the duration after the initial clear or preset.  In other words, does Q just go to 0 on clear but only when clear is first low, then can be dependent on the inputs (JK, T, D, SR) again?  Or does Q stay low for the entire duration of time that CLR is low?  Similarly for PRE, would PRE send Q outputs high for the entire time that PRE is high, or is it only initially when PRE first goes high? Thanks for your patience as I'm learning.


texts: NPN BJT in saturation, base voltage irrelevant?

texts:
I'm trying to build as simple a circuit as possible that will pull a logic line low every time an automotive ignition coil 'fires'.  My first inclination is to simply attach the 'negative' terminal of the coil to the base of of an NPN BJT through a current-limiting resistor, with the emitter tied directly to ground.  So there would be 5V on the collector and roughly 300V on the base resistor when being triggered.  Somehow, though, I feel like I'm missing something fundamental that won't let this work.  Perhaps it's just me being spooked by the 'high' voltage.  I suppose I could use a voltage divider at the base, but I still feel like I'm missing something.  Looking for confirmation regarding the proposed functionality, or of my idiocy.  Thanks.

Edit:  I don't intend to pass any current through the transistor, besides what little is required by the device itself.  The idea is that the transistor will go into saturation when the ground is removed from the coil (when the counter-EMF brings the coil's 'negative' terminal up to around 300 volts).  Here's a (rather amateurish) schematic of what I'm thinking:

Switch 'S1' in that schematic is just a placeholder for the IGBT/Points triggering the ignition coil.  Sorry again for the confusion, and thank you, everyone, for all the replies!


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I am looking for a USB protocol analyzer and was wondering if anyone had any experience with one.  So far, I am looking at an Internal Test Instruments and a Beagle USB 12.  I only need to watch the full speed (12 Mbs).  I need some low-level protocol information so I'm looking at hardware solutions.

Any input is greatly appreciated.


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Can you critique my design?

After finishing my 5v part, I've added the 35V part, too.

10-32V to 5V 1.2A SMPS Buck Regulator, the IC is IFX91041 from Infineon.

10-32V to 35V  4A SMPS Boost Regulator, the IC is LTC3786 from Linear Technology.

Here are the schematics and layouts in their original filetypes, in this case Proteus .DSN and .LYT files: MediaFire Server

Sorry for the big sized pictures, I wanted to be clear.
For the partitioning of the layout, I have to say that when I use bitmap out-putter of Proteus ARES, it cannot output vias on the top layer, so I had to take a screenshot.

Also, sorry about the mess in schematics, just use it for designators, parts are not as they are, for example Q1 and Q2 are not IRFx.

SMPS PCB Design Critic 2

Schematics:

Top Layer Part 1:

Top Layer Part 2:

Bottom Layer:


texts: Is zero cross control acceptable for small motors? I know it is bad to have voltage and current out of phase for inductive loads but wanted to know if it would not be harmful to small motors (< 500 W).


texts: PNP Transistor to switch between Voltage Regulation and Battery Charging

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I am relatively new to circuit design and would appreciate your feedback on this :)

I am designing a power supply circuit that uses the TI TPS61030 voltage regulator. It features a 4A internal switch connected to ENBL. The regulator is ON if ENBL is high (+BATT) and OFF if ENBL is low (GND).

The power circuit also features a Li-Po charger (MCP73871), which uses USB power to charge the battery. It also has allows simultaneous battery charging and system power output, which is a feature I want to bypass.

Essentially, I want the system to power down as soon as the battery starts charging – when the USB is plugged in. The flow chart below summarizes the desired behaviour.

I chose a PNP transistor with an R1 of 4K7 and and R2 of 47K. I then worked out the logic, shown in the table & equations below. When VBUS is GND, the circuit between the base and emitter acts as a voltage divider. Otherwise, I used Kirchoff's law.

So here are my questions:

Will this work as illustrated in the flow chart?
When the usb is not plugged in, will VBUS be at 0V? and thus a voltage divider circuit exists between the base and emitter?

P.S. J4 is to bypass the transistor in case I wanted to charge and power the system simultaneously. VE < VB > VC (USB ON) -> Cut-off  VE > VB < VC (USB OFF) -> Saturation.

Thank you in advance!


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When using a high voltage IC like the HV509, are there any design constraints with regard to the HVGND (pin27) and the logic GND (pin15).
By design constraints I mean any isolation from the main ground plane in any way.
My thoughts are that both grounds are at the same potential and should be the same, am I wrong?
Any tips would be helpful.

Datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/hv509.pdf


texts: PCBWay sent me this image while trying to troubleshoot my circuit board file content not showing up. I want to know if this program is available so I can download/buy it to troubleshoot my output gerber files without waiting for them to do it for me. Does anyone recognise this program, or can at least identify what it is built on? If not, I suppose the program is proprietary...


texts: DRC check for Silkscreen clearance in Eagle Autodesk 9.5

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Is there a way I can check silkscreen clearance with respect to Pads and vias in Eagle 9.5? I don't want to manually check all legends.
Thanks


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I'm working on a ISM (868Mhz) weather station for my home and i'm trying to implement a Ceramic antenna directly on PCB.
After reading the guidelines, i have questions again.

One of then is what about 4layers circuits...
Chip antenna reference : M620720 from AVX (link)

Actually, my pcb stackUp is like that :
1. Top (Signal).
2. internal_plane_1 (GND).
3. internal_plane_2 (different VCC).
4. Bot (signal).

On page 5, the constructor propose that :

My question, We see a big gnd copper planar (Top + internal_1 OR Top+Bot)(with correct impedance). if i use the first solution (Top+internal_1), what about internal_plane_2. i have to remove it or not ?

tell me more if you have opinion


texts: What are the limitations of the Ebers-Moll model of the BJT

texts: The Ebers-Moll model is considered simple yet effective model of the BJT. What makes it special and when does it break down i.e is not applicable?


texts: How much of an extra cost premium is paid for assembly in the USA or UK?

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Okay, here's the situation: Currently, I am making a small batch of 100 boards of my project. This is a small order, so start up costs are about 10% of the final cost, and the factory charges $50/hour (they say I can get it done in one or two hours.) These will be made in China. Places in the UK or USA won't even talk to me for an order of 100, or if they do, they provide me with outrageous prices (5-10x as much as China.)

Now I know China is cheaper, but to many people, seeing "Made in China" cheapens a product. If I were to make, say 1000 or 2000 boards, would the cost to make them in the USA or UK, or even any European country be competitive with China, even if it was slightly more expensive? I know the Arduino is "Made in Italy", and the low price point of it makes me consider the possibility that I too could get mine made in a country with higher wages. What are other people's experience with this issue?


texts: \$ V_o \$ in this simple circuit with 2 diodes and 3 batteries

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Take \$V_{d (on)}\$ to be 0.6V for simplicity.

What's \$V_o\$? Is it voltage across 1K Resistor?

So... what's the direction of current flow in the 1k resistor? Is it away from BAT3 towards \$V_o\$?

How do two diodes and two batteries (BAT1 and BAT2) being in parallel would affect \$V_o? \$

...

I think \$V_o\$ is voltage across R1 which is \$10V - i \cdot 1K - V_d - 9V = 0\$

\$ i_{R1} \cdot 1K = V_{R1} = 10V - V_d - 9V = 10 - 0.6 - 9 = 0.3V \$

KVL loop.

But if BAT3 was 5V, then what would be \$ V_o \$?

I know that in this case, current has to go from diodes towards BAT3, right?

Do I just look at one "branch" to calculate \$ V_o \$? For instance, the branch with upper diode, D1.

KVL loop 1:

So Vo = 9V + 0.6V - 5V ??