texts:
I bought a DPS5005 unit in order to setup a cheap power supply. The module seems to be quite popular and has often been described as remarkably good for its low price of about 35 $. However, even under load (2 A flowing through a 0.1 Ohm resistor) I get short 450 mV peaks at a frequency of 35 kHz. These are independent of the power supply that is used as source for the DPS5005.
To smooth the output, I plan to implement an LC-Filter. The formula to compute the cutoff frequency is
$$f=\frac{1}{2 \pi \sqrt{LC}}$$
with the inductance L of the coil and the capacitance C of the capacitor.
As cutoff frequency, I'd like to have something in the range of 10 kHz. According to the formula, I could realize this for example using a 47 uH inductor and a 60 uF capacitor.
Is it sufficient to simply use an electrolytic capacitor? Or should I use a combination of a small ceramic and a big electrolytic capacitor? And since electrolytic capacitors in the mF-range are available, is a bigger capacitance a better choice?
Any tips/hints/empirical values?
Edit: Here are two plots of my measurement:

The first shows an overview. The sample frequency is too low - therefore the variance in the amplitude of the spikes. But I hope it gives an idea of the problem.

The second is a closeup of one of the spikes. I marked the data points by dots.

Edit: According to the post of EE_socal, I have modified the probing setup and indeed, the peaks are much lower. Here is an image of the setup:

And these are the new plots of the signal:

Edit: EE_socal suggested in his answer to add a ferrite bead, bulk capacitor, and small ceramic capacitor. Following this advice, I tested a 80 Ohm @ 10 Mhz, 110 Ohm @ 25 Mhz ferrite bead together with electrolytic 47uF and ceramic 0.1uF capacitors. The peaks have vanished leaving a peak-to-peak amplitude of <0.1 V, which is sufficient for my requirements.
Here is a plot of the filtered supply voltage:


texts:
I am trying to configure UART0 on TM4C123G launchpad. All of my configuration registers are perfect. They've been written with desired values. But somehow, my busy flag is always 1 after first write in data register. I'm using UART0 module on PA0 and PA1 pins. Initialization code is given below.

void UART_Init(void){
  SYSCTL_RCGCUART_R |= 0x01;            // activate UART0
  SYSCTL_RCGCGPIO_R |= 0x01;            // activate port A
  while((SYSCTL_PRGPIO_R&0x01) == 0){};
  UART0_CTL_R &= ~UART_CTL_UARTEN;      // disable UART
  UART0_LCRH_R = (UART_LCRH_WLEN_8|UART_LCRH_FEN); // 8 bit word length (no parity bits, one stop bit, FIFOs)
  UART0_IBRD_R = 43;                    // IBRD = int(80,000,000 / (16 * 115,200)) = int(43.40277)
  UART0_FBRD_R = 26;                     // FBRD = int(0.40277 * 64 + 0.5) = 26
  UART0_CTL_R |= UART_CTL_UARTEN;       // enable UART
  GPIO_PORTA_AFSEL_R |= 0x03;           // enable alt funct on PA1-0
  GPIO_PORTA_DEN_R |= 0x03;             // enable digital I/O on PA1-0
                                        // configure PA1-0 as UART
  GPIO_PORTA_PCTL_R = (GPIO_PORTA_PCTL_R&0xFFFFFF00)+0x00000011;
  GPIO_PORTA_AMSEL_R &= ~0x03;          // disable analog functionality on PA
}

Configuration registers have following values after running above function:

UART0_IBRD = 0x2B        //43
UART0_FBRD = 0x1A        //26
UART0_LCRH = 0x70
UART0_CTL  = 0x301

Only problematic register is UART0_FR. It should have a value of 0x90 at all instances except while transmitting data. But even after transmission, its busy bit remains 1 which hinders any transmission.

I'm writing UART0_DATA register as follows:

  while((UART0_FR_R&UART_FR_TXFF) != 0);       //While transmission FIFO is not full, stay here.
  UART0_DR_R = data;                          // Transmit data to serial.


texts:
I am designing a system with a carrier board that has all of active logic on one board and most connectors on a backplane board. The interface between the two boards is a x16 PCIe board edge connector. Over the edge connector I intend to route USB 3.1 (5 Gbit/s) from the source device (μPD720202) to a USB 3 A receptacle. On the carrier board the SSTX and SSRX lines are at most 30mm and length matched to less than 1mil. The USB traces are routed like PCIe signals would be on the edge connector:

How practical is this?
What issues might I run up against?
How long can I make the traces on the backplane? This document suggests <200mm (https://docs.toradex.com/102492-layout-design-guide.pdf)


texts: RFID tags orientation issue...how to fix?

texts:
We have a product that is a toy bug net. At the bottom of the bug net is a coil that reads bugs with RFID tags in them.

For most of the bugs this seems to work fine and the net is able to identify the bugs.
But for certain bugs, the way that the bug lands in the net seems to affect whether the bug gets read correctly.

I guess this makes sense because the passive RFID tags need to be aligned a certain way in order for it to get energized by the coil's magnetic field.
Is there something that we can do, short of repositioning or remodelling the bugs so that they won't land in the 'bad' orientation?


texts:
I am using a CANUSB adapter connected to my car attempting to read out only CAN messages with 11-bit identifier 0x1D6. I need to do hardware filtering because software filtering is too slow for my application.

The CANUSB protocol description (http://www.can232.com/docs/canusb_manual.pdf) explains how to set up filtering, and refers to the SJA1000 datasheet (http://www.nxp.com/documents/data_sheet/SJA1000.pdf) for a description on the hardware registers involved.

To set up the acceptance code I write "MFFFFF3AC\r" on the serial port. This should be equivalent to setting AC0=FF, AC1=FF, AC2=F3, AC3=AC on a SJA1000 controller. I came up with these values by shifting 1D6 to the left one bit, as the last bit is used for RTR, which I don't care about.

To set up the acceptance mask I write "mFFFFF001\r" on the serial port. From what I understand this should set the SJA1000 controller up to filter only using the 11-bit identifier specified above.

These are the IDs I get with this configuration:

0x0a8 0010101000
0x0aa 0010101010
0x0c0 0011000000
0x0c4 0011000100
0x0c8 0011001000
0x0d7 0011010111
0x2d5 1011010101
0x2fa 1011111010
0x31d 1100011101
0x328 1100101000
0x330 1100110000
0x349 1101001001
0x360 1101100000
0x364 1101100100
0x3b0 1110110000
0x3bd 1110111101

As you can see, no signs of 0x1d6. I do see them if I restart the device without entering filtering commands.

Can anybody familiar with SJA1000 filtering tell me what I'm doing wrong here?


texts:
What is the cheapest/easiest way to switch an AC or DC signal of at least 10 V via TCP/IP?

I have 5 measurement devices which can be triggered over an 0-250 V AC/DC input (switching threshold 10 V). The devices are set up in different power plants which share a common computer network. 230 V AC is available.

For a power quality analysis (one day, about ten trigger signals) I have to trigger all of them more or less at the same time (up to 5 sec difference is acceptable) from my notebook or smartphone.

My idea would be some kind of IP-relay which can be switched over console or a web interface. Because of the different locations I'd need 5 of these devices (1 channel per device would be enough). An arduino or raspberry pi would probably do the job, but buying 5 of these and setting them up may be an overkill. Is there a cheaper device for my one time application?


texts: Make a momentary switch control a toggle

texts:
What are the simplest, cheapest, smallest ways to make a momentary switch produce a 2-state toggling output (latching momentary switch)?

In other words, the output is continuously low, and when you momentarily press the button/tact switch, the output changes to continuously high, and then when you press it again, it switches back to low.


texts: LCD 20x4 Only Show Fist and Third Rows Pixels On

texts:
I have a LCD 20x4 display this display works fine but now it shows first and third rows all pixels On. I am using 4MHz crystal oscillator.

That is happen when Vss, Vdd, Vee, RS, RW, E, A and K pins supply without connect Data pins.

When these pins connected it should show all four rows pixels On right?

Why this happens?

After data pins connect also same things. I am using PIC18F4550 microcontroller. When I use PIC16F887 then it is working fine.

Same pins for both PIC16F887 and PIC18F4550. Protues simulation is working but real LCD not working for PIC18F4550

 // LCD module connections
sbit LCD_RS at RD0_bit;
sbit LCD_EN at RD1_bit;
sbit LCD_D4 at RD4_bit;
sbit LCD_D5 at RD5_bit;
sbit LCD_D6 at RD6_bit;
sbit LCD_D7 at RD7_bit;

sbit LCD_RS_Direction at TRISD0_bit;
sbit LCD_EN_Direction at TRISD1_bit;
sbit LCD_D4_Direction at TRISD4_bit;
sbit LCD_D5_Direction at TRISD5_bit;
sbit LCD_D6_Direction at TRISD6_bit;
sbit LCD_D7_Direction at TRISD7_bit;
// End LCD module connections

void main() {

  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);
  Lcd_Out(1,6,"Welcome !");
  Delay_ms(2000);
  Lcd_Cmd(_LCD_CLEAR);

  while(1){

  }

}


texts:
The WIRED YouTube video Inside Facebook's Quest to Beam the Internet Via Solar Drone and article Inside Facebook’s First Efforts to Rain Internet from the Sky show a dish antenna (starting after 02:00) with what looks like a Cassegrain secondary reflector. The context of the video and article suggests it is for testing E-band  millimeter-wave data up/down link to an aircraft (about 60 to 90 GHz according to the article, or 5 to 3 millimeter wavelength).

I noticed that the secondary mirror is spinning. By watching the wobble and checking individual frames it seems to be turning at at least 4 revolutions per second. It could be much faster and aliasing makes it look this slow.

I can not think of any reason why this would be turning. It's rotating about the optical axis, so it's not switching between primary and secondary horn locations.

Why is the reflector on this millimeter-wave antenna spinning?

above: GIF made from extracted and cropped frames from this WIRED YouTube video.

above: Right-click for larger view; Ground station for millimeter-wave data linking to aircraft, from WIRED. Photo credit Damon Casarez.


texts: Is flash memory in MCU's similar to a hard disk?

texts:
I have taken a Computer Architecture course in the past that focuses on desktop CPU's and I currently work in embedded systems and I am kind of confused as to which memory corresponds to what.

I am trying to create in my head an analogous image of the one of the desktop CPU's and I can't find something that I am really confident in.

For example both microprocessors and MCU's have RAM memory which is fine.
From my understanding this is the immediate memory that the CPU can access
You could use virtual addresses of course and have access to all the data but in effect you would have to move it to cache and memory first in order for it to be accessible by the CPU.

Does this mean then that flash memory inside an MCU is similar to the hard disk of a computer?

And if so then what is the role of an EEPROM?

Thank you very much for your help.


texts:
I have a guide stating that the following diagram represents a DRL AND gate:

Suppose that both A and B have 5-V inputs with a corresponding switch. I tried to simulate it for learning purposes and placed the ammeter right before the LED. The problem is that the current does not change at all. I suspect that the diodes prevent the current from moving through since they are pointing to the left.


texts: Low Pass Filter With Hall Effect and ADC Help

texts:
Background:

I am using the Allegro ACS758KCB-150U hall effect based current sensor, here is the datasheet, I am using it to measure current drawn by 24V motors, between about 20A - 130A.  The reason I need to measure the current is to get a general trend of how hard the motors are working to accomplish there jobs, by measuring their current draw.  I am using this ADC, but I would not be opposed to getting a different ADC or using a different type of sensor to measure the current.  I would like to measure 10+ times a second.

My question:

On the datasheet for the current sensor on page 1 there is a diagram labeled Typical Application, it shows a low pass filter between VIOUT and GND.  There is a resistor Rf which is later defined as greater than 4.7kohm, and a capacitor Cf that is not defined.  How do I assign values to Rf and Cf to work for my application?  If I need a different ADC what should I look for when selecting one?

Here is what I know in relation to my question:

I know the formula to find the cutoff frequency for a low pass filter, I haven't taken any college physics courses as I am only in high school, but I have taken calculus.

Thank you for any help,

Joel


texts: How to suppress a short circuit to prevent fuses from blowing

texts:
I have a circuit that is modular and one of the modules involves interfacing from an external relay.

Now this sub-module has a fuse set to blow a bit below what the main module's max current. (why put a fuse when the main module has over current protection? So that when this sub module fails it wont take the whole system down with it) This sub modules can cater upto 24 external relays and in the image below i will be showing how one channel is setup

What i would like to protect is the fuse from blowing from a false short circuit(not really false, since it is doing its job) in the cenario that the user might incorrectly wire the connection and shorts pin A and pin B. I need a current limiting solution so that the fuse wont blow up and the user of the sub module can rewire and try again.

The circuit is designed to trigger one relay at a time, a signal will be sent by a portexpander(not shown in picture) to the bs138 mosfet to open. the signal typically last around 250ms - 1000ms.

I have considered a polyfuse but it to slow to react the main module protection will trip first. Another is adding a resistor in series with the relay line but it is either a bulky high watt rated resistor or a high value resistor that might not make the relay trigger because of voltage drop.

there is also the problem since there is a short the power to the sub-micro controller will be cut, so this protection circuit i am looking for would probably happen in either series or parallel of the connection for the external relay

I need current limiting solution between pin A and pin B so that when A and B is shorted by the user and the mosfet turns on the fuse wont blow

how do you recommend to solve this problem, Thank you.


texts: Increasing PCB trace current capability by duplicating on other layer

texts:
I just came across this video:
https://www.youtube.com/watch?v=fxC5w3f8FkY
which says that I can duplicate a trace on the bottom layer and then at the end just via it back up to increase the current capability of that trace.

Say for example I want to carry approx 5A ish on a trace. A trace calculator gives me the following

I would require 68mm trace width. Is it possible to just do 34mm on the top layer and 34mm on the bottom layer? I.e each trace would be carrying approx 2.5A each. How would that work if the target device pin is SMD? I would need to via it up to the single 34mm trace, wouldn't that be a bottleneck?


texts:
So I have a LM358 Dual opamp. I only care about the first op amp, the second I just have set to put out 12V to keep it from floating. The the first is reading in feedback from a 1k potentiometer from 10-0 volts. The voltage divider knocks it down to the uC analogue voltage level.  it all works fine, but when the pot is disconnected the output of the op amp rails to 24 volts. Why is that? if you have 0 volts on the non inverting input it should be 0 for the output correct?
EDIT: Maybe this picture is easier to follow


texts: DC-DC boost converters in parallel to run DC motor

texts:
Our aim was to power the motors of our bot (which were selected according to the torque requirement of our bot) using a single AAA Battery but due to limited time and and the difficulties in international shipment we are stuck with boosters only available in our country.
The boost converter cannot provided the required current to our motor at it's boosted state even though we are pretty sure that our battery can provide more current, as a result the output voltage of the convertor across the motor drops from 5v to about 0.8v. So we though of using a bunch of them in parallel to solve the issue. Using 5 such boost convertors we saw that this drops from 5v to about 3.8v. So naturally adding more of thes in parallel should be sufficenint to spin the motor at out desired rate. But this seems very sketchy. We tested all this only a single motor and connecting two across the whole configuration will obviously result in a larger drop. So even if we increse the number of boosters from 5 to say 10 there should be a limit where adding more of them stops giving us results. We are reallly hoping it is not the case.
What can we expect going forward or is there something that we are missing from this equation. This is pretty much our last hope
Battery : 1.2 volt 800mah
Motor : 12v 200 rpm but we are plannig to use it at about 5-6v
Boost Convertors : 0.9V ~ 5V to 5V 600MA
NOTE : I should have mentioned it from the start but using a single AAA is a rule in our problem statement that we have to follow. Also the motors are fixed according to our torque requiements


texts:
i'm coming back from my previous post, to give some futher details: here's my problem:

We're going to supply power to a 4-motors drone with one/several photodiods.
Here are the characteristics:

4-motors drone: 1.8V/1.1A
Photodiode: Vmax: 30.4V and Imax=15mA

So as you can see, the drone needs approximately 2W to fly, whereas my photodiode can supply 378mW max....

So my idea was to amplify the current out of it, by using BJT transistor ( a BJT with a Beta =100 would give me 1.5A output current if the base current is set to 15mA). Is it true to say that?

Is is possible to do what i want to do?
Any other idea? it seems that when you want to amplify the current, you usually use a current-voltage converter...

Thank you for your answers


texts:
I would appreciate any help anyone is able to give me on this.
I live in Spain and I am trying to check the polarity of a wall socket where I plan to plug in a extension block with all the various parts of my hi-fi using an electricians screwdriver (there is an improvement in sound if all the electrical components - amps etc - are the same polarity).
I found to my surprise that both sides seem to be live! When I stick the screwdriver into the holes in the IEC plug on the end of the (removable) cable from the extension block I get a light from both holes. Shouldn't I get a light only from the live hole?
What could be the reason for this?
many thanks in advance.


texts: How do I size the output capacitor for a DC bench power supply?

texts:
I'm designing a DC bench power supply and have come to the matter of choosing
the output capacitor. I've identified a number of related design criteria, but
I'm finding my reasoning still going a bit in circles as I try to sequence
these into a sensible design process.

Here's the working schematic to give you an idea what this will go into. The
constant current circuit is not pictured.

Here are the considerations/relationships I understand so far:

During a fast load step, \$C_{out}\$ moderates the output voltage change undershoot/overshoot) in the interval required for the control loop to respond. In general, a larger capacitor produces a smaller under/overshoot.
\$C_{out}\$ participates in the frequency response of the control loop. It contributes a pole by its interaction with the load resistance and a zero by its interaction with its own effective series resistance (ESR).
In general, a faster (higher bandwidth) control loop reduces the output capacitance required to achieve a given undershoot.
The portion of the under/overshoot produced by the ESR of \$C_{out}\$ (the vertical bit right at the step) cannot be reduced by a faster control loop. It's size is purely a function of the current (step size) and the ESR.
The circuit driven by the supply can and often will contribute additional capacitance, for example, the sum of the power rail bypass capacitors in a connected circuit. This capacitance appears in parallel with \$C_{out}\$. It's not inconceivable these may equal or exceed the value of \$C_{out}\$, causing the \$C_{out}\$ pole to move an octave or more downward. The performance of the power supply should degrade gracefully in this situation and not fall into oscillation, for example.
The energy stored in the output capacitance lies outside the control of the
power supply's current limiting circuitry. While using a large output
capacitor may conceal some sins in the control loop design, it exposes the
connected circuit to the risk of uncontrolled current surges.
When the voltage set-point is turned down, the output capacitor must be
discharged quickly enough to meet the specification for down-programming
speed, even when no load is attached. A discharge path proportional to the
output capacitance and the specified down-programming speed must be present.
In some cases the output voltage sampling circuit (resistive divider) may be
adequate; in other cases a shunt resistor or other circuit feature may be
needed.

So my question is: "How do I approach selecting the output capacitor for my DC
bench power supply design?"

My best guess is this:

Start with a modest \$C_{out}\$ value, say 100µF in this case.
Work backward from the undershoot spec (say 50mV max, 25mv preferred) at the
maximum output voltage (30V) for a full load step (0-300mA), and considering
the ESR of available capacitors, see what kind of bandwidth I would require
to keep the undershoot within spec.
Move to a larger \$C_{out}\$ value either to reduce the required crossover
frequency or reduce the ESR value.

Am I on the right track? Any guidance from more experienced practitioners will
be very gratefully received :)


texts:
I'm hacking my car's locking system, I want to be able to lock/unlock using a MC and ultimately my phone. I've spliced the connector and after a quick inspection I located the 3 pins that do just that, I've labeled them lock, unlock and common. As you probably guessed shorting lock and common locks the car and shorting unlock and common unlocks it. I wish I could go with a simple schematic like this:

The problem is that I measure 12V across Unlock and COM, but it goes the opposite way -3V across Lock and COM, so the schematic turns into this:

Which can't work because COM and Lock are permanently shorted. I thought of adding a third transistor on the red lock path but I'm losing the feeling of knowing what I'm doing at this point.

The next obvious solution is to use relays but I'd like to ask if there's a smarter solution to this problem?

Note: I'm using TIP120s because I have a handful laying around, I'm aware it's probably overkill and also I'm just a hobbyist, please don't give me a hard time if that stuff is too basic.

Update:

As suggested in the comments I measured the voltages of all pins relative to ground and here are the results:

Unlock: 12.6V
COM: 1.09V
Lock: 0.00V

I also measured the resistance of Lock to ground which turned out to be 30.8 Ohms if that is relevant in any way.


texts: For 12X8 LED array with any 1 LED glowing at a time, should we charlieplex or use 74HC595n?

texts:
Apologies in advance for probably missing a lot of things. I'm pretty new to electronics.

I'm building a 96(12X8) led (monochrome ultra bright, white) multiplexed array, driven by an Arduino nano. Any one of the leds can be on at a given time.

I tested one of the LED's and when configured and ran though Arduino's blink program and it works fine and the LED is lit bright.
Next i had to try out the same LED with a 595, so i used this tutorial for reference.
I accordingly hook up the LED and it's working fine, but the brightness is significantly low.

And that brings me to the question, whether i should charlieplex and build the whole network, or is there a way to improve the LED brightness while using 595's?

Thanks for your comments and suggestions.


texts:
Possible Duplicate:
  Determine 4p4c wiring

This might sound highly trivial, but search in google for it, you won't find a circuitry.

So what does a handset's circuitry look like?

And: What's the wiring for german 4P4C connectors? This is - you might not believe it - not in google.


texts: Reversing direction of an AC universal motor

texts:
The problem: I have a table saw motor I am trying to use in a jointer and need it to spin in the opposite direction (permanently). I have had trouble finding an answer that I am reasonably sure applies. Most of the answers I have found regarding this seem to be for more complicated or different types of motors (or very vague on what kind of motor is being discussed). The closest answer I have found is this one:
Reversing direction of a 115v ac motor using Arduino

The motor specs

110/115V AC
15 amp
2.5 HP
5000 RPM
Wiring diagram below (which I think looks like it is lacking some details, but am not sure if the motor can really be that simple)
The part referenced in the diagram as "motor" is referenced elsewhere as "field assembly" and there is an armature assembly that goes inside of it. Unfortunately, there don't appear to be any clearer diagrams than the one below.

Desired Outcome: To be able to spin at 5000 RPM in the opposite direction so I can power a separate shaft (jointer cutter head) connected via a belt/pulley in a 1:2 ratio for a total output of 10,000 RPM.

I would like the opinion of someone more skilled and knowledgable than myself on if it is possible and safe to reverse this motor. Some of the other answers I have found eluded to the motor not being safe to run or running at significantly reduced power. Alternatively, if there are some tests that I could run to evaluate these for myself, any information on what tests and how to conduct them would be much appreciated.

I like doing things without asking questions, but I also want to be safe when trying to rotate metal blades at around 10,000 RPM. Any insight and resources would be much appreciated!


texts: I'm was able to successfully connect ATMEGA328P-PU to my USB port and using avrdude write a simple code (C language) to it. Everything is working, but the problem is that I want to attach a sensor, but am completely lost how can I 'log' the output to my computer. I could do this with Arduino tools. do I need a special bootloader? Thanks


texts: Circuit design - usage of BOOT0 and a Hall effect sensor on STM32G431CBT6

texts:
I am working on motor project with STM32G431xxx, with their stock B-431B-ESC1 Discovery board. I was able to generate code with the  motor workbench and change and debug it on CUBEIDE.
This week I would like to change the MCU from STM32G431CBU to STM32G431CBT because I prefer the LQFP footprint.
The motor-workbench has no option to for STM32G431CBT so that I stayed with STM32G431CUB because both look like identical. Is that OK?
Today I have soldered my new board with STM32G431CB and debugged it, but it hangs once the Hall sensor pin (TIMER 4 CH 3) is started, because it's shared with BOOT0 Pins PB8. See the enclosed schematic the BOOT0/Hall pin has pull up to 3.3V, not sure if it caused the problem (but on STM32G431CB PB8 / BOOT0 is also pulled up to 3.3V without any issues.)
If I remove the DHALL03 diode and RHALL05 resistor which make PB8 / BOOT0 pin floating (not high), code can run without hanging.

Can I use BOOT0 as interrupt (or pull it high)?
What makes the STM32G431CBU and STM32G431CBT different? (I have checked on STM32G321CBU's BOOT0 pin as Hall sensor also pull up to 3.3V without any issue)


texts: Use STM32 BOOT0 to boot custom bootloader instead of ST bootlaoder

texts: I have read AN2606 about the native ST bootloader, but for various reasons decided to write my own bootloader to update the firmware on my application running on a STM32F412. My bootloader is able to program the firmware successfully. Now I want to be able to start the micro in my bootloader using the BOOT0 pin. Is it possible to disable the native bootloader in some way or isolate the BOOT0 pin from the native bootloader to do this or will I need to pick a different pin?


texts: Best way to measure 0-5V with uController running on 3.3V

texts:
What is best way to accurately measure 0-5V with uController running on 3.3V?

It will work in environment with quite a big delta temp (from -20 °C to 80 °C).

I use stm32F4 12 bit ADC.

precise resistor divider 5-25 ppm/K, ADC from uC
some kind of op amp
external ADC running at 5V + 5V ref voltage
other?


texts:
I am trying to find the specific current needed to heat up a wire to a specific temperature. The wire material is kanthal. With a thermal conducitivty of 22 W/mK. I've calculated the resistance, from the resistivty and the dimensions of the wire.

If I want the wire temperature to be, say 1000 degrees. How do I find how much current I need? How’s the relationship between the effect and temperature?


texts:
Do I need to use a diode with the following setup ? What i want to do is activate a relay which then closes the positive side of a nema 5-15 portable receptacle and allows electricity to flow. When a switch is pressed . My aim is to avoid having to  come into contact with the AC and  use relay do it .

The  receptacle I'm using is similar to  the
leviton Snap-In Single Receptacle Outlet Black 1374-1.  My setup consists of  using a 12 volt battery to drive an Inverter and then using the  Leviton 1374-1 as  as the receptacle.

I want to use the following wireless relay to act as the  AC switch :
OrangeTag Wireless relay . This will be used between the Leviton 1374-1 and the inverter .
I've read about issues concerning relays damaging  connected devices due to voltage spikes when the power source is removed and want to know if I need a diode to protect against this issue ?
  if so where do I connect the diode  on the relay ?  The diagrams Ive seen appear to to connect the diode across  the pos/ neg points   of the relay which in my mind means a short circuit  What am I missing ?


texts: Find the Q-factor for coils and understand weak power transfer

texts:
I built coils for wireless power transfer. Found inductance with a LRC meter. Put capacitors, hoping for a resonant frequency at 300kHz. Student assisted me with a NVA machine where a resonant frequency 800kHz was found. It plots power transfer over frequency. My capacitor values were pretty off. Needed a .9micro farad and used a 1micro farad. Still a large shift from 300 to 800kHz. It had like 80% transfer over 2cm distance. The yellow line is S21 at 800kHz.
I also purchased wurht coils https://www.we-online.de/katalog/datasheet/760308111.pdf. Saw a high Q factor around 200-300kHz. Placed capacitors for 270kHz resonance. And they worked best at 303kHz. It lit an led from centimeters away!.
When I place a led on my coil design it doesn't light at all. My coils show power transfer on the NVA machine yet can't light up a led. Wurth coils work great wirelessly lighting up a led.
Could it be the Q facotr? Never payed attention to Q until I bought the wurth coils which inside their data sheet show high Q as a function of frequency.
Looked up the equitation for Q and got Q series = 2 pi f L / R. This graph should look liner with frequency. The Q data graph  looks more complicated(maybe R changes with f). I'm lost. Why don't my coils light up a led, even with them almost touching(NVA says 95 power transfer). Also how would I calculate Q and better understand Q for my coils. I believe either the NVA machine was wrong or my S21 has a power sent so week, that my coils could not light a led. Maybe if I run my design at resonance and high Q value. Any tips or resources would help.


texts: Can a photodiode tolerate a reverse bias beyond its specification

texts: While searching a literature related to my experiment I come across this paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4424026/pdf/PP_PP201500119.pdf . On the page 27 under the section SRS microscopy they have described the set up. The detector used is a thorlabs si-photodiode https://www.thorlabs.com/drawings/5192555af7db78e1-C0DBB61A-E594-6195-A9756D77D1A106F9/FDS1010-SpecSheet.pdf, whose spec says that max reverse bias is 25V. However, in the paper they have said to have it operated under 70 V bias. Am I missing something ?              P.S: Question was initially posted on beta engineering but deleted.


texts:
I designed a Constant K (I don't remember the constant K) LC band Pass filter with lower cut off frequency 1 KHz and upper 5 KHz. Using the value of K, I deduced the values of L and C and made the following circuit:

I've used R1 = 999999G to show infinite resistance.

I carried out the AC sweep (frequency response) in PSpice and got something like this:

Is the graph correct?

Also one more thing I want to ask is that, can we get Vout (output voltage, the green probe in the circuit diagram) more than 5V i.e. the input voltage?


texts: What is the name of this kind of DC power connection?

texts:
This connector is going to an LED grow light and is the output of the pictured LED Driver.  The output of the driver is 20-30VDC 900mA.

First of all, I didn't know that DC power could even use a third pin?

Second, the cable is too short and I need an extension cable but don't know what to search for and "3-pin DC power cable" turns up nothing useful.

Note too that there's a flat ridge on the top so orientation seems to matter...


texts:
I was trying to solve this question but I got stuck when I tried to use AND gate with clock and some output. I want to ask whether value of rising edge of a clock is taken as 1 or value preceding it and same for falling edge does it is taken to be 0 or value preceding it while gating clocks ?

What I think rising edge=1 and falling edge=0.

Question:

Also, have a look at solution provided. Is that correct ? It's not mine solution.

Solution:

Ignore flip flop delays.


texts: 3-dB Frequency of second order transfer function

texts:
How can i obtain the 3db frequency of the each transfer function ?

My attempt:

My guess is both transfer functions have the same 3db frequency.But equating the magnitude to 0.707 gives a fourth order equation which can be reduced to second order to obtain square of 3db frequency.

However, i am not able to simplify it.The exact expression however is as follows:

Is there any approximate approach for obtaining the same?


texts:
If I have a power supply that outputs 32V,7A and I need to power an LED that requires 24V-2.8A, can i use this step-down module to power up the LED?

Module Properties: non-isolated constant current and voltage module
**Rectification: non-synchronous rectification**
Input voltage: 5V-32V
Output voltage: 0.8V-30V
Output current: adjustable maximum 5A
**Switching frequency: 300KHz**
Output ripple: 50mV (max) 20M bandwidth
Load Regulation: ± 0.5%
Voltage Regulation: ± 2.5%

Is the switching frequency and/or the rectification a problem?


texts: Schmitt trigger, what does the voltage divider at the base of the second transistor do?

texts:
The following Schmitt trigger has a low threshold of about 3V and a hight threshold of about 7V:

simulate this circuit – Schematic created using CircuitLab

As far as I understand Q1 is setting the low threshold and Q2 is setting the high threshold through the resistors RC1,RE and RC2,RE respectively (the transistors work as a voltage divider according to this). However I don't undersand what does the R1, R2 voltage divider do at the base of Q2, I tried to remove it and connect the base of Q2 directly to the collector of RC1 and didn't notice much effect on the low threshold, the high threshold on the other hand jumped to 8.6V then I tried to change RC2 value but it didn't change the high threshold significantly.

I thought that the voltage divider could be setting the base voltage of Q2 and that would also set the voltage of Q2 emitter (as in emitter follower) but shouldn't RC1 be setting the base voltage to be equal to \$V_{BE} + \frac{R_E}{R_{C2}+R_E} Vcc\$? What's going on in this circuit and how do you calculate the resistors values without using a simulator?


texts: Easiest way to check if uln2003a is working

texts:
Ok, here's the schematic I'm trying to use to test if my uln2003a chip is working. While checking the pinout with my multimeter, I couldn't find that pin out1 was connected in some ways to the com pin. When I short the input with 1.5v the led doesn't light up and the led never light up.

The led works when connected to the battery directly.

Is there a better way to test if my uln2003a chip actually works. I'm worried I might have damaged it while soldering it (it's a SMD part). Looking at the schematic if I check for resistance between any of the output and com, there should be no or little resistance but in my case my multimeter always shows 1 (infinite).

simulate this circuit – Schematic created using CircuitLab

Edit:

Ok since leds are a bit worrying I decided to move a bit further on this without leds.

I uploaded a stepper program on an arduino board. I connected the pinout to a digital analyser and can confirm that the arduino program is fine.

I connected my inputs to the uln2003 and checked with my analyzer the output. The uln2003 is powered with a 5v power supply.

When I check the output pin with the digital analyzer, I can see that I have spikes of less than 1ms from times to times but not similar to the input.

Now things get weird when I connect only one input, then I can see the 10ms up and down of the stepper motor on all four output but only 1 input is connected.

When I measure the resistance between all input pins, I can sense around 18kohm. That said, the digital analyser will raise up even if it sense really little amount of energy passing through.

Then I tried it without actually pluggin the power supply and if only one input is connected I can still see some output on all four connected output.

Then I configured the program on the arduino to make really long step so I could measure the voltage on output pins when they're up. But it looks like it's sinking only a few mv.

I measured the resistance between inputs on a chip I didn't solder yet and can still sense around 18k ohm between inputs.


texts:
I understand the basics behind the concept of common mode voltage and CMRR and friends, in the context of differential amplification.

What I don't understand is the determining if the whole concept of "common mode voltage" actually applies to a given circuit. That is, sometimes the signal being measured (i.e., the V+ and V-) doesn't have any particular relationship to the supply voltage. In that case, how can a common more voltage even be determined? The V+ and V- might be 1001V and 1000V or 1V and 0V - since voltage is relative I can't see how the amp would even know the difference.

For example, consider the case of a handheld multimeter - it's seems pretty clear that there the concept of common mode voltage wouldn't apply here. The voltmeter should perform identically in the 1001 V- and 1000 V+ case as the 1 V+ and 0 V- case (indeed, they aren't really distinguishable, are they)?

So if a dirty cheap voltmeter can simply avoid the whole question of staying inside the supply rails, and have a "perfect" CMRR, why is it such an issue for most components? I.e., components with very high CMRR are expensive, and require special designs, etc.


texts: How do devices with different external clock communicate between each other on a motherboard?

texts:
I don't have any pratical knowledge about eletronic circuit. Actually I am a high level software programer and I've just begin to learning about computer hardware and eletronics.

Basically, I understand that every device has its own internal frequecy but they use an external frequency to communicate to other devices such as the CPU vice versa through a ''bus''.

And I know the motherboard has its own clock also.

What I cannot realize is how these devices can communicate each other if they have different clock and how exactly happens this communication? What is a clock cycle and what the ''motherboard's clock'' has to do with it? What happens if i use one 1000Mhz CPU with one 1333Mhz memory?

All internet explanations vary and are not very clear. I know that when I start to study electrical engineering from the beginning all this will automatically clear, but for now, I need to have an accurate sense of how everything works.


texts: Is there any relation between LJU (Line Jack Unit) and broadband speed?

texts:
My question is about LJU (Line Jack Unit) aka Rosette.

I am having BSNL (service provider company) copper line broadband in India.
In spite of having wired broadband, I get speeds of 6Mbps(download) / 0.75Mbps(upload). Upon raising the issue with officials, they checked & did not find any abnormality at their end. There are no cuts in wire running from DP.

What I did notice is -- there is no LJU (Line Jack Unit) to connect incoming copper line with telephone cable which goes to splitter.
What I wish to know is "Whether not having LJU can affect the internet speed?"
Thanks.

EDIT:- I am using ASUS DSL N10 E modem.
The first image shows incoming copper wire on left side, which is twisted with phone-wire for making connection, tape applied; phone wire (right side) has RJ11 jack on other end which goes to splitter. I have attached images.


texts: linear regulator with high current capacity

texts: Recently I have seen that adding 7805 in parallel is not really a good idea as the load on each regulator may NOT share equal load, is there a regulator whose output voltage is 5V and can supply at least 2A of current under full load ?


texts: Is there a tool to generate .svf file for XMEGA programming?

texts: There is a tool called avrsvf that can be used to convert .hex file to .svf for JTAG programming of AVR devices. The tool, however, does not support XMEGA devices. Is there a similar tool for XMEGAs?


texts: How do we know that current doesn't get "stuck" in junctions?

texts:
I know the question might sound slighly basic, but stay with me here.

Kirchoff's Current Law states that

  "The algebraic sum of currents in a network of conductors meeting at a
  point is zero."

But how do we know that no charge gets "stuck" in the junction? Usually, I see people justifying KCL by pointing to the law of conservation of charge, but that doesn't mean that those charges couldn't get more or less concentrated in a region of a circuit. I understand physically that the electrons would want to spread out as far as possible, so of course they physically shouldn't get stuck in a junction - but how do we know that happens every time, and can we prove it in the lumped element model?


texts: Why kicad schematics pin electrical type is always power input?

texts:
I was designing new schematics and decided to inspect another library downloaded from kicad official sources on Github. The one thing that cought my eye instantly was that Electrical type for both GND and VCC was POWER INPUT.

Is it meant to be that way or just a workaround for an existing problem, eg. failing DRC?


texts: How do logic chips (74LS, HC, ...) provide output=Vcc/0V when all standalone diodes and transistors suffer voltage drops?

texts:
If you use a transistor to pull signal to high from a Vcc of 5V, signal only goes to 4.5V or so because of voltage drop over the transistor.

Likewise if you use a transistor to pull signal to ground, signal is still stuck at 0.5V because of the voltage drop...

But logic chips, though they consist of transistors, act differently. How?


texts:
I don't have a formal education in Electronic Engineering, and after some reading, I learned that a resistor could have different roles in a circuit. The roles I've learned so far are the following:

Current Limiting Resistor
Pull Up Resistor
Pull Down Resistor
Voltage Divider Resistors

What are the rest of a resistor roles categories? Is the term "Role" correct for this context? Where canI read more aboy resistir roles in circuits?


texts: Relay being switched on even though voltage not applied?

texts:
Introduction
Firstly, I was not sure if the Home Improvement SE was appropriate for this or here, so if in wrong place I can post there instead.  So, what I am trying to do should be very simple to achieve. I have a series of stair lights that use motion sensors to turn them on. There are two sensors at the top of the stairs. Since the eye of one sensor "sees" too much (turns stairs on when I pass by the top), I want to wire it up so that the stairs will not turn on unless BOTH sensors at the top of the stairs see me.
My attempt
Below is the circuit I have created:

simulate this circuit – Schematic created using CircuitLab

The power supply, motion sensors, relay that I have used. The way I understand it, I provide the + to all lights, both + and - to turn the sensors themselves on, and then when either is tripped, they provide -. The relay in my mind should only turn on if sensor 1 is tripped.
The Problem
The problem is that when sensor 2 is tripped, it somehow turns the lights on. I am not sure how this is possible since the relay should not close the switch. I even verified with a multimeter and indeed the two output terminals are continuous even if nothing is hooked up to the relay input. How is this being tripped with no input??? How can I fix my circuit to get the desired effect I am after?


texts: finding angular frequency when current is maximum in circuit

texts:
A series of ac circuit consist of an inductor and capacitor. The inductance and capacitance are  1 henry and 25μf. The current is maximum in circuit, then what will be the angular frequency?

The answer is 200. Could somone explain how???


texts: How long does developer solution last within its bottle

texts: Originally I was going to just use UV exposure method but the boards tend to be expensive. Now that I've invested in a laser printer I can do toner transfer which I find much much easier/ more convenient to do. So will the developing solution (the stuff to remove the uv coating) go off any time soon? I don't want to waste it. I'm keeping it in the original bottle in came in. Would uv exposure work better for boards with really thin traces?


texts: 5v to 3.3v and 1.8v power regulator incorrect voltage output

texts: I have designed 5v to 3.3v and 1.8v power regulator using PAM2306AYPKE and implemented on a PCB. I've prototyped 3 boards and on all 3 of them the voltage on the 3.3V rail is 2.6v-2.8v. The regulator produces 1.8v on output 2 as expected. Since it's the same problem on 3 PCBs I've ruled out that this could be caused by a soldering issue.


texts:
I'm doing a project here. I'm designing my own generator using genset and motor to produce 12V of electricity.
The main objective of my project is to produce a 12V from the generator. This 12V is used to charge LiPo battery ( 3 cells ). The cable from the motor which produce 12V will be connected to the battery charger then the battery charge will be connected to LiPo battery. So when the LiPo battery is drain to certain voltage, there will be a sensor that detects the draining of the battery and automatically charge back the battery. The power or electricity is obtained from the generator. What kind of sensor should I used to detect the voltage of the LiPo battery ? I can't over charge the battery as it damages the battery.
So, I need to figure out a suitable sensor to prevent it from over charge also.


texts: Standard for electrical schematics in the UK

texts:
I'm trying to find out whether there is an accepted standard for electrical schematics in the UK. From my research so far, I've come across IEC 60617 however this appears to have been withdrawn. I also found this post on the IET website (https://communities.theiet.org/discussions/viewtopic/348/20012) which states the following but I'm not clear what is meant by "the database".

IEC 60617 contains graphical symbols for use in electrotechnical diagrams. All the parts (Ed. 2 or 3) of the previously published IEC 60617 have been incorporated into this database that currently includes some 1900 symbols. The database is the official source of IEC 60617.

Is IEC 60617 the de facto standard for electrical schematics in the UK or is there another standard? The area I'm specifically interested in is schematics for industrial control panels.


texts:
I would like to design a circuit around the W7002 antenna (Dataheet) and the NXP PN532 NFC Reader Chip. Since I never worked with antenna design before I do not have a VNA and I also don't have experience in antenna matching. The goal is to get an antenna which is able to read desfire tags through a plastic cover at around 7cm distance. Even a shorter distance like 4cm would be fine, but generally a longer distance is better. Fortunately for the antenna I want to use there are many values already provided in the datasheet so it shouldn't be that difficult to calculate the necessary values. I tried to use Adafruit's circuit as a "template" and I understand that I need to adjust C1, C2, C7 and C8. The damping resistors R3 and R4 might need to be changed aswell and lowered a little (to 1 Ohm each). What would be a good starting point to get the correct values for those Capacitors? I assume once I have a general idea I can try increasing/decrasing the values on a prototype and see if that increases or decreases the range? Also I am not sure what the purpose of C5, C6, C9 and C10 is, those are labeled "NC" so are these non-existent in this case?
Would I contact the antenna manufacturer or NXP as the chip manufacturer in this case for further assistance?


texts: How does this electronic wall switch work with only a 2 wire circuit.

texts:
This is an RF wall switch

but it uses only LIVE + LOAD1 cables like in the wall lamp switch
(2 wires wall switch, load and live)

If you short LIVE and LOAD the lamp turns on

LIVE 220V------[SWITCH]-----LAMP----GROUND

This RF switch replace the mechanical switch and toggles by touch the lamp with relay, and can do it by rf 433mhz.

But how does it get power and keep the lamp off, if it disconnect the LOAD cable it will shut it's own power off.

I believe it keep some kind of always connected LIVE+LOAD with low resistance when "OFF" so the IC will keep geting his power, but the lamp will say off because the current is too low or something like that.
 Can anyone shade some light on this? :)

Does anyone has any schematics that will allow me to replicate this device to operate a 5v micro-controller with relay on 220v live line & load.

I have a 220v to 5v power supply.. IC and relay lke that:

LIVE 220V + -------- [ 220V-5V + IC + relay ]--------LAMP -----GROUND

Try to keep the micro-controller on 247, and the relay to toggle the lamp,

how can it be done?
what part do i need?
anyone done that before?

thanks allot...

EDIT: adding my draw :)

so what do i need to put instead of the "?" compnent?
is it a current limiter? does anyone can give me a schematics of current limiter that will lower the amps to low as 50mA-150mA but keep it 220v?
technically i need a "constant" lamp dimmer on his lowest setting but not off, right?

thanks


texts:
simulate this circuit – Schematic created using CircuitLab

I use D1 to visually indicate the active transistor.
However, gate pin acts as if it were floating.
What is wrong with my gate-grouding mechanism?

Obviously, small current originates somewhere, even with MCU's gate-facing pin = LOW.
Replacing the MCU with the battery doesn't resolve the problem - weak noise comes out of the speaker. If, i.e. LED is introduced instead - if flashes slightly.
If 5V RAIL is replaced with i.e. 12V, in OFF mode I can still see 10V on the output.

Removing D1 solves everything.

How can D1 cause M1 gate to float?


texts: How does an LM7805 voltage regulator work?

texts: How do most voltage regulator ICs work? Are they the same as hooking up a variable resistor and a voltmeter and turning the knob until you get the desired voltage?


texts: "switching box" with microcontroller and relays

texts:
I need to build a switching box, which switch between 4 pairs of the contacts, and give one of the pairs to the output (to read one of the 4 signals).
I am going to do that as follows:
For each pair of contacts I would have a DPST relay. Each of the relay I would connect to the output pins of the microcontroller (if the relay needs 5V, and microcontroller has 5V operating voltage, it should be possible directly. Otherwise, if operating voltage is lower, I would use operational amplifier or transistor-based one). A 4-buttons keyboard array would be connected to the input of the microcontroller, so that only signal between respective contacts go to the output of my circuit, since only circuit with this contacts would be closed by relay.
However, I don't have so much experience so far, and need advice/comments if this plan should work or something looks wrong, bad (if I miss or overcomplicate something).

I also consider possibility of using circuit without any microcontroller, but just mechanic switch, operating DPST relays. My understanding of the 2 options illustrated at the images below. Only 1 pair of contacts shown, because the others would look the same.

I also would appreciate comments if choice of such relay would be ok. It has DPST modification which I need, and also provided already with protecting diode.

Voltage and currents through the contacts will be low (less than 10V voltage, less than 1mA current), and the main requirement is that my switching box shouldn't affect those currents, which I am going to measure at the "out" contacts.


texts:
I'm working on customized ignition system and want to implement the final stage as robust as possible.
The ECU (Engine Control Unit) provides TTL level control signal to drive ignition system. The duty cycle of that signal depends on engine's speed (RPM).
Ignition coil must be energized in order to provide spark. After it is energized it starts heating and can be broken.

The ECU can't control the current and different coils can be used in amateur autosport engines.
So ignition driver should control the current. Firstly I wanted to use MC33812 IGBT ignition driver. In case of overcurrent it closes IGBT. This produces early spark as the coil discharges. It can broke the engine at high RPM. And I found no ignition driver that can work as Pick'n'Hold driver.
So I selected IRGB14C40 IGBT with TTL gate level. I decided to use ACS712 current sense IC. It has proportional voltage output. Add Voltage-to-PWM IC, like TL494 and drive IGBT's gate in case of overcurrent.
And of course PWM should work inversely and keep current steady.
Or may be I should use inverted op-amp comparator and compare ACS712 output with voltage source. When it close gate current drops, and if op-amp and ACS712 are fast - current flow starts again and prevent the coil from discarge. This will works like PWM may be

simplified block-scheme

Input frequency is about 20kHz at max. I'm sorry for my bad english


texts:
I got a field report of a product which is sealed in an IP66 aluminum die cast body. it was observed that water/moisture had condensed inside the enclosure over and over and creating some white marks inside (see attached). The product was installed in a US region about a year ago.

It was reported the top cover was screwed on properly, and there is no way water can get in. However one question in my mind is: we install this product on a street light pole, and the top cover is screwed on in the field only after the power cable gets in. So what if the atmosphere is already full of moisture during installation? That moisture will be trapped in the enclosure and sealed after covering the top. And due to the weather changing over and over that moisture gets condensed over and over and creates the problem. How can I get out of this? One way I think would be to use some kind of silica bag to absorb moisture. Any advice?


texts: Should negative and positive wires be of same length?

texts:
Do positive and negative wires need to be of same length all the time for a circuit to run smoothly? Of course same gauge but only different lengths.
What would be its effect on the system if we say my negative wire is like 5x longer than the positive wire or the other way around? Or it does not really matter?


texts: SPI interface on Xilinx FPGA, clock domains and timing constraints

texts:
I am interfacing a Raspberry Pi board to a dev board with a Spartan 6. I want to do this using SPI. Because of the way the dev board is designed, I need to connect SPI CLK and DATA to standard IO pins.

I am aware of the need to cross clock domains with double-buffering to guard against metastability. The RPi and the SPI CLK are obviously in a separate domain to the internal FPGA fabric. I don't see too much problem : only one 8 bit register and the signal that says when a byte is ready need to be synchronised to the internal fabric clock. I am not trying to get high data rates. A byte will only get written about every 25us (this is because the RPi is slow to read a GPIO, but no problem for this project). I am thinking to clock the SPI at 15MHz, and even could reduce this if necessary.

This is my verilog. It simulates and bench tests fine.

module my_spi_in (
  // RPI clock domain
  input i_RPI_spi_data,
  input i_RPI_spi_clk,
  input i_RPI_reset,
  // internal 64MHz domain
  input i_sys_clk,
  output [7:0] o_data,
  output o_fifo_write
);

  // registers in RPI clock domain
  reg [7:0] r_RPI_shift_in = 8'b0;
  reg [2:0] r_RPI_ctr = 3'b0;
  reg r_RPI_word_done = 1'b0;

  // synchronisation registers
  reg [7:0]r_data_sync_1 = 8'b0;
  reg [7:0]r_data_sync_2 = 8'b0;
  reg [2:0] r_word_done_sync = 3'b0;

  // RPI clock domain : input shift register logic
  always @ (posedge i_RPI_spi_clk, posedge i_RPI_reset) begin
    if (i_RPI_reset == 1'b1) begin
      r_RPI_shift_in <= 8'b0;
      r_RPI_ctr <= 3'b0;
    end else begin
      r_RPI_ctr <= r_RPI_ctr + 1'b1;
      r_RPI_shift_in <= {i_RPI_spi_data, r_RPI_shift_in[7:1]};
    end
  end

  // RPI clock domain : word done
  always @ (negedge i_RPI_spi_clk) begin
    if (~i_RPI_reset && r_RPI_ctr == 3'b000) r_RPI_word_done <= 1'b1;
    else r_RPI_word_done <= 1'b0;
  end

  // sync registers
  always @ (posedge i_sys_clk) begin
    r_data_sync_1 <= r_RPI_shift_in;
    r_data_sync_2 <= r_data_sync_1;
    r_word_done_sync[0] <= r_RPI_word_done;
    r_word_done_sync[1] <= r_word_done_sync[0];
    r_word_done_sync[2] <= r_word_done_sync[1];
  end

  assign o_data = r_data_sync_2;
  assign o_fifo_write = r_word_done_sync[1] && ~r_word_done_sync[2];
endmodule

In my .ucf file I only have the following, to tell ISE that this is not a "real"clock (it won't build without this):

NET "i_RPI_spi_clk" CLOCK_DEDICATED_ROUTE = FALSE;
NET "i_RPI_reset" CLOCK_DEDICATED_ROUTE = FALSE;

My question : is this the best approach? Do I need to do anything else? (Ideally it would be good to also set some timing constraints for the SPI clock and data, to make the tools aware of the SPI interface speed.)

Thanks in advance of your advice.

EDIT:
I should maker clear that the RPi is only transferring a single byte before checking a GPIO pin. This turns out to be slow (takes around 25us), so there are never two bytes back to back on the SPI bus. There is SPI activity for about 0.5us (one byte at 15MHz), then nothing happens for about 24us until the RPi has read the GPIO. This is obviously far slower than SPI is capable of - the RPi read time is slowing the transfer quite a bit - but this is quite acceptable for this system.


texts:
I did a search on "ultraviolet sensors" in this forum, and came up with only three results, so, it appears, that this has not been asked before.

I have a hand-held ultraviolet light sensor from Extech (Extech UV505) to measure power density from a 300 nm UV LED.

http://www.extech.com/UV505/

The UV LED is collimated with a lens at NA=0.9, and produces a good spot about 10 mm in diam. The output of the LED is listed as 30 mW at 6V, and yet the sensor reads 3 mW. The sensor is bigger than the spot. For another LED emitting at 365 nm, the sensor shows the expected value (or ballpark). Even though I mostly use the sensor for relative values, I need to have an idea of the power density to compare to published values. E.g. in the past people used UV lamps, and I am trying to replace the expensive 100W $5K lamp with a $200 LED.

Even though the specs of the sensitivity state "290-400nm", I suspect that the response is very much non-flat, and that the sensitivity in the 300/10 nm range is much smaller than at 365. The datasheet does say "peak at 365", that's as much of the spectrum as is available from the manual. I asked for the response curve from Extech, and their answer was "we do not have it", literally (facepalm).

What type of a sensor might this be, so I can look up the curve online? This must be an old technology, since the meter shows a similar number at 365 as an old UVP meter I borrowed from a colleague (the meter says 1991 on it). Interestingly, the UVP unit is still sold, and the design and the pricing both look as if it was still 1991:

https://www.coleparmer.ca/i/uvp-97-0015-02-uvx-digital-ultraviolet-intensity-meter-radiometer-without-sensor/9765110

Another puzzling feature about the Extech unit is that the sensor looks covered with a translucent plastic window which does not seem to be removable.


texts: Connect ALU to CPU in Logism Circuit Design and output to 7-segment Display?

texts:
I've been playing around in Logisim to get some experience in designing basic electrical circuits. While I'm sure not the best, I was able to put together a functional ALU:

1-Bit:

This ALU is capable of the operations AND, OR, XOR, NOR, ADD/SUB.
[A] & [B] are separately 8-bit inputs.
The [Sub] input designates whether adding (0) or subtracting (1).
The [Operation Setter] designates what operation is being performed.
[R] is the result of the designated operation, with the [Zero Flag] alerting us
to a ‘0’ output, such as when a number is subtracted from itself.

Using the 1-Bit ALU I pieced together an 8-bit ALU (this image directly below performing an ADD operation):

(SUB operation):

I'm now attempting to take my ALU and combine it with some form of CPU (for now mainly focusing on adding/subtraction & outputting to a few 7-segment displays). I've got a 7-segment Display put together (also have another for alhpa characters AbcdEfG):

I can't quite figure out a good way to take what I have for an ALU and place the output into my 7-Segment Display (ultimately I want to have the result display via 3 to display all possible 255 values from my 8-bit addition):

The following is what my circuit does for each different operation:

AND Operation - 1.1 = 1:

OR Operation - 1+0 = 1:

XOR Operation - 1 XOR 0 = 1:

NOR Operation - 1 NOR 0 = 6:

ADD/SUB Operationg - 1+1 = ERROR (Sub Flag is errored out for all OP's??):

I'm not quite sure:

Why my Sub Flag isn't selectable.
Why my Zero Flag errors out on an Add/Sub Operation.
How to fix my result from my ALU to properly go into and display in my 7-segment Display (currently outputting 8-bit into an 8-bit splitter and then placing the first 4 as my input for the 7-segment Display).

Does anyone have any input for how I can correct the issues in my design and make this work? Thanks in advance!

EDIT:

Sub flag issue fixed. Somehow when I brought the circuit over for use in my main one, it had the properties of being an Output, and being 3-state (which I don't believe I ever set). In any case, that minor issue is fixed.

Seems the Zero Flag was also set as 3-state for some reason.

Any advice on fixing the Add/Sub issue?


texts: Why do I get such high values when calculating the power dissipation of MOSFET in boost-converter circuit?

texts:
I'm a hobbist interested in electronics so I don't have any "professional" training on that.
Currently I'm trying to design a boost converter and now I'm stuck at some calculations.
I wonder if it's possible to calculate how much the mosfet is going to heat up. I'm using two inductors in series which add up to 134uH and an IRFP460 as the mosfet. The converter runs on 12v and is driven at 4.7KHz with 78.38% duty cycle.

simulate this circuit – Schematic created using CircuitLab
My first idea was to calculate the mean resistance of the inductor which I did by calculating the ripple current through the inductor and dividing it by two:
$$\Delta I_{L} = \frac{V_{In} * D}{f_{s} * L} = \frac{12v * 0.7838}{4700 * 0.000134H} = 14.93A$$
$$I_{mean} = \frac{\Delta I_{L}}{2} = \frac{14.93A}{2} = 7.465A$$
$$R_{mean} = \frac{V_{in}}{I_{mean}} = \frac{12v}{7.465A} = 1.608Ohms$$
Then I proceeded to look up the RDS(on) of the mosfet which is 0.27Ohms so when the mosfet is on the total resistance is: 0.27Ohms + 1.608Ohms = 1.878Ohms
So there should be 6.39A flowing through the mosfet and thus 76.68W right? (I = 12v/1.878Ohms and P = 12v*6.39A)
The RthJA (Max. junction to Ambient) of the IRFP460 is 40°C/W so at 76.68W it is 40°C/W * 76.68W = 3067C°!!! This can't be correct that's why I'm asking what I'm doing wrong...


texts: Simple SPST Switch Circuit - Pull-down Resistor VS. Current Limiting Resistor

texts:
Super Noob EE question:
Here is my quick draw-up of my SPST switch circuit schematic.
I know I probably did not do this right, but if it gets the idea across, then thats good enough for me atm.

simulate this circuit – Schematic created using CircuitLab

The right boxed section is a connector where I showed the power pin (V1 @ 12V), trigger pin, and ground pin (chassis).

The left side is a (hopefully correctly drawn) pull-down resistor setup with SPST switch (SW1) and standard 10k resistor (R1).
Does this 10k resistor (R1) act as a current limiter in this circuit?
On the top of that, I added a 1k resistor (R2A OR R2B OR R2C) in series with the SPST switch (SW1) because i was wondering if it could be used as a "current limiting resistor".
I was also wondering if it matters where the resistor goes, whether its before or after the switch, shown by R2A & R2B & R2C.
What are the differences (if any) between positions R2B and R2C?

Also, I think this becomes a voltage divider right? where the voltage will be 10/11 * 12V at the trigger pin when the switch is closed?
If I didnt have resistor R2, then what voltage would the trigger pin see with the switch closed? 12V?

Can it "make sense" at all to put in this R2 resistor in this circuit? What uses can it have?


texts:
for the following convolution integral

$$ \int_{-\infty }^{\infty}\sigma (\tau)\tau A\sigma(t-\tau)\sin(t-\tau)d\tau \text,$$ where \$\sigma(t)\$ denotes the step function

We'll only get results for \$t>0\$, since thats when \$\sigma(t)\$ will have the value 1, which means that the integral will be evaluated for \$\tau\$ from \$0\$ to \$t\$.

I get the rest of the math in the given solution (partial integration, integration by substitution etc...).
What I don't get is the following:

\begin{align}
\int_{-\infty }^{\infty}\sigma (\tau)\tau A\sigma(t-\tau)\sin(t-\tau)d\tau &=  \int_{0 }^{t}\sigma (\tau)\tau A\sigma(t-\tau)\sin(t-\tau)d\tau\\
&= A\sigma (t)\int_{0 }^{t}\tau \sin(t-\tau)d\tau
\end{align}

Why can \$\sigma(t)\$ be taken out of the integral just like that? Isn't the integral of the step function \$\sigma(t)\$ the ramp function?

I have another, somewhat related question: Why is the stability in a bode plot evaluated at the cutoff frequency? The solution to a given problem in my script says that if the gain at the cutoff is \$< 0\$, then it's stable, if it's \$> 0\$ it is not. Intuitively that makes sense, but why at the cutoff frequency?


texts:
I had to store a computer motherboard were the cardboard box was lost. The motherboard is in the original antistatic bag still closed with tape. I decided to put it inside a regular plastic bag thinking the motherboard would be protected from ESD by the antistatic bag. However, now I have second thoughts if this was a good idea.

Could my motherboard get damaged from ESD by the plastic bag, when it's still in the original antistatic bag?


texts: Can switching between two unsynchronized sources cause problems for an average office building?

texts:
We have a 100kW 3Φ 208V generator and ATS operating in North America.  The system as installed does not allow for a test where the load can be placed on generated power when utility is available.  We have solicited quotes to modify the system to allow such testing.
The suggestion from two licensed electricians who have bid the project has been to interrupt the sense circuit which the generator uses to detect utility power.  The ATS contactor is two-position three-pole (single coil). I asked if the lack of "dead time" where the load is disconnected from either supply would cause problems, and got what I would best describe as a shrug.
Since the generator is not phase synchronized with utility power, I imagine this would cause... interesting things to occur.  I'm not so concerned about lighting or electronics - but synchronous motors (HVAC / Elevator) do seem like they would have quite a bit of stored energy.  On the other hand, I can envisage this to be equivalent to starting from a stopped state or slip as one would see from a VFD.
Should a rapid (~50ms) loaded cut between two unsynchronized sources be expected to cause problems other than the brief outage for an average office building?


texts:
From my experience so far I am aware of the following to pay attention to when working with ISRs:

An ISR should complete quickly
Variables shared between an ISR and the main execution path should be declared volatile to avoid accesses to it being optimized away
Access to shared variables with 16 bit and more should be accessed in an ATOMIC_BLOCK because the 8 bit CPU cannot access such variables in a single cycle

But I am wondering about functions called from an ISR:

Does calling a function from an ISR add any particular overhead? Looking at the disassembly, code in a function and the same code directly in the ISR yield the same instructions
I suppose everything that applies to an ISR also applies to a function called from an ISR since it is the same execution path?
If a function called from userspace contains an ATOMIC_BLOCK, is it valid to also call it from an ISR?


texts: What is the overall transfer function for this sensor considering its datasheet specs?

texts:
I want to read this sensor(MPX4115AP) data accurately but I am not sure about using the given transfer function and the datasheet information good enough. The device is ratio-metric and temperature dependent.
Nominal transfer function is given as:

Above the sensor supply voltage Vcc is 5.1V but in my case it is less than 5V and it might vary so I also monitor it.
I have wired the the sensor as follows and reading the output via a micro-controller:

The micro-controller also reads the ambient temperature T and supply the voltage Vcc simultaneously.
So I have the ambient temperature data T, and the sensor's supply voltage data Vcc as well as the equation given in the datasheet. By using these, I need to write a single formula in C which can output the pressure data. I am afraid to make a mistake and measure the pressure wrong.
I am a bit lost in the datasheet to obtain a correct accurate equation.
How can we obtain the transfer function considering the ambient temperature T and the sensor's supply voltage Vcc?


texts: Fully understanding LM386 datasheet minimum parts example

texts:
I'd like to fully understand the circuit marked as "Minimum Parts" at page 5 in LM386's datasheet:

Is there any reason for 10k resistance at the input potentiometer or is it just an arbitrary value?
For an audio application, should that be a logarithmic pot?
There is a resistor and a capacitor connected in series to ground right after the output. It looks like a low-pass filter to me, but I've usually seen those with the load connected between R and C, not parallel to both. What's going on?
Why is there a 250uF polarized capacitor right before the speaker? Is it just a DC blocking cap? Why 250uF and not other value? Perhaps just a high value so that the resulting high-pass filter cutoff is low enough?


texts: Half Bridge Bootstrap configuration using IR2184 Gate Driver

texts:
I am planning on building a half bridge inverter for use as a tesla coil driver, using a couple of IGBTs, with gates driven by an IR2184 half bridge gate driver. According to the data-sheet, the typical connection is as follows:

However simplified half-bridge schematics all across the internet have a different configuration with the  source of the high-side switch connected to the drain of the low-side switch, accompanied by a couple of capacitors across the load as follows:

I understand how the second configuration works, but I'm lost as to how the 'Typical Connection' as provided by the IR2184 datasheet would create an AC voltage across the load.

I've made this schematic which blends the two above, but I wanted to check if this would work, or is there some function of the IR2184 that I'm missing that allows it to work in the first connection.

Not new to electronics, but very new to gate drivers, half-bridges etc, so any help on this would be much appreciated.


texts:
In the begining of section 17.2 (chapter 17) of Digital Integrated Circuits: Analysis and Design the auther says:

  There are positive and negative resists. The use of a positive resist
  for pattern transfer is illustrated in Figure 17.1. First, a fresh
  layer of silicon dioxide is grown over the entire wafer. Then, the
  wafer is coated with a thin layer of positive photoresist. This
  photoresist is spun on and then baked to the desired hardness.

I understand most of the text, but I cant't understand the meaning of "spun on".


texts: Issues with Latching switch using push button

texts:
I'm trying to make a latching power switch based off this schematic (source: EDN)

I emulated the circuit in Falstad and everything works like it should (link to simulation).

However, it doesn't work when assembled on a PCB. When I click the button, I see a sudden spike at Vout from 0 to 0.2V and then it quickly settles back to zero. I'm seeing no behavior that is similar to the simulation. I'm now starting to think I selected the wrong MOSFET/Transistor for the job, but I'm not sure which property would effect the circuit.

Here are some more details about my imlementation:

Vs - LiPo Battery (3.9 to 4.2 V Nominal)
Desired Vout - mirrors +Vs
Mosfet - FDN352AP
Transistor - MMBT2222A

Any thoughts? This is the first analog circuit I've built (simulated a few), so not really sure where to start looking.


texts: Possible ways to represent a circuit schematic

texts:
I have the following circuit with a 9V battery and two resistors, R1, R2, in parallel. Here is how it looks:

Are the following three ways all valid ways to represent this circuit?

Explanation:

In the schematic, current flow is shown, which is always positive to negative.
In #2 I've basically removed the negative terminal of the battery and put it at the bottom of the schematic.
In #3, I've moved the negative side to the right of the diagram and smoothed out the lines, so it looks more like a graph/loop and less like a schematic.

If #3 is a valid way to depict circuits (which for me is the simplest to understand intuitively), what are some resources that show how to decompose a circuit into that?


texts: Oscilloscope Bandwidth, what's it all about?

texts:
This question popped up to me a few moments ago.
I was measuring what is intended to be a 50Mhz square wave of level 0 to 2.5, however what I saw on the screen is a sine wave that was centered around 1.2V and level of 0.5 to 2.0V, the frequency was 4MHz.

I checked up my oscilloscopes datasheet and it showed that the bandwidth was 10MHz with a sampling rate of 50 MS/s.

I'm wondering what these figures are all about.

Are they a measure of the upper
frequency limit an oscilloscope can
measure?
Is this oscilloscope capable
of measuring 50Mhz at all?


texts: What is the best way to measure the following DC motor parameters?

texts:
I appreciate if somebody could help me to resolve this. I bought a geared DC motor from a store. I would like to obtain the following information: Resistance, Inductance, Back EMF constant, torque constant, and the voltage caused by Back EMF when the motor is supplied by a voltage input higher than the recommended one. What is the best method to measure these parameters? Do I need fancy equipment to get these values by experiments?

Even I asked the company, they can only provide the following information (at the recommended voltage): torque constant, Back EMF constant, Dynamic Resistance and Motor Regulation. The guy asked the manufacturer. He said that these are all he can get and he has no idea what they mean. if I supply 4V higher than the recommended input voltage, will these provided values change a lot? Which parameter(s) stay the same?

Thank you


texts: ST-link doesnt run the MCU after programming and reset in KEIL 5.33

texts:
I have updated my KEIL from 5.15 to 5.33. In KEIL 5.15 I set Reset and Run option in Flash->Configure Flash Tools->Debug( Selecting St-link) Settings->flash download and after programming my MCU start working. However, after updating KEIL to 5.33 it just program my MCU and I should power off/on my MCU to start working.
I need to know what it the problem with this new version of KEIL.


texts:
I have the following circuit:

What the circuit should do:

When switch SW1 is open, D1 is OFF and D2 is ON
When switch SW1 is closed, D1 is ON and D2 is OFF

The circuit works almost well. The only problem is, when switch is open, D1 instead of being completely off, it's slightly lit. At some point, I've remove Q1 and D2 completely, but D1 was still slightly lit.

What can be the problem ? Any ideas on how can I fix it ?


texts:
Hello I'm new with VHDL and I'm trying to implement a JK latch in VHDL using this RTL schema:

Where the "latch_rs" is written as follow:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity latch_rs is
    Generic (delay: time);
    Port ( R  : in  STD_LOGIC;
           S  : in  STD_LOGIC;
              Preset : in STD_LOGIC;
              Clear : in STD_LOGIC;
           Q  : out  STD_LOGIC;
           nQ : out  STD_LOGIC);
end latch_rs;

architecture behavioral of latch_rs is

signal Q1 : std_logic;
signal Q2 : std_logic;

begin

proc : process (Preset, Clear, R, S)
    begin
        if (R='1') or (Clear='0') then
            Q1 <= '0' after delay;
            Q2 <= '1' after delay;
        elsif (S='1') or (Preset='1') then
            Q1 <= '1' after delay;
            Q2 <= '0' after delay;
        end if;
    end process;

Q <= Q1;
nQ <= Q2;

end behavioral;

The problem is that during Post-Map simulation the feedback signals (Q and nQ) seems to be consumed by the and port: is this possible? And if so, how can I avoid this to happen? (the clear 0 sets nq to 1)

EDIT: During the Behavioral simulation the circuit is working fine.


texts: How does a traditional CC/CV circuit work?

texts:
I went through an application note from Texas Instruments referenced as snva829 ( the link http://www.ti.com/lit/an/snva829/snva829.pdf  page 2 and 3) where they have discussed superficially the traditional CC/CV circuit.
Below is the circuit from TI application report SNVA829 How to Design a Simple Constant Current/Constant Voltage Buck Converter:

  The converter requires a sense
  resistor (R_SENSE), an amplifier and a voltage regulation circuit (V_z). The current flowing through R_SENSE sets
  the voltage across R_FB , which is the feedback voltage of a controller. In this way, the current is regulated.
  As R_OUT increases, the voltage on the output rises to a point where the Zener diode conducts, and the
  device transitions from a CC converter to a CV converter.

My questions are:

I understand that the Zener diode limits (clamps) the output voltage, but I did
not understand how does this circuit limits the output current ?
What is the role of the PNP transistor in the circuit ?
What is the relationship between Isense and Ifb ?
How does the output of OPAMP drives the base of the PNP transistor ?


texts:
An old question running through my mind:

Displays, camera, speakers, microphones: why after more than 50 years of development do they still need calibration?

Whatever cheap or high-end material I come across in the reviews I read from time to time, none seams to be properly calibrated.

There is enough research and commercial competition over these transducer categories for a time long enough to make this intriguing...


texts: What is the rs-485 protocol for controlling old flipdot displays?

texts:
I have an old Luminator flipdot 16x112 pixel bus destination sign I'd like to hack.  There are numerous resources on the internet for controlling the flipdot display panels with new circuitry, ignoring the existing circuitry, but I would like to get it working with custom messaging in less time than it would take to design, or even build, a custom hardware solution.

The display I have already includes a power supply and control board, and it communicates with the master controller via RS-485.

This particular design is early 90's, with 8051 processors, EEPROMs, and lots of off the shelf logic chips and ULN2xxx series drivers. A middle ground would probably be to remove the 8051, figure out the schematic, and drive the relevant lines with a microcontroller of my own.

Before I give up and go the hard or middle route, does anyone have knowledge of the protocol that is used for these displays?

I do have the master controller and the Luminator control panel, so a path for custom messaging using these elements would be acceptable in the short term.


texts: How do I limit voltage from two power sources?

texts:
I am designing a system to mist my outdoor air conditioning units during the summer.  I will be powering a low voltage irrigation value using the low voltage from the AC controls - 24 VAC.  I have 2 air conditioning units that work independently of each other. However, there will be times that both units come on at the same time.

How do ensure when both units come on at the same time that electricity is sent to the power power supply without shorting out the solenoid or shorting out the air conditioner power supplies?


texts: Create SPDT relay from two SPST solid state relays

texts:
I'm trying to use two solid state SPST relays (P/N SAI4003D) to act like an SPDT relay.  Ideally both will be controlled by the same signal wire.  The relays state that they are "on" at 0 volts, so my idea was to use the arduino io to set them either input/output at low or input/output at high to turn them on.

I'm a little unsure if this will work since the relays are rated 3-30v so I don't know how much voltage will go to the other relay.

simulate this circuit – Schematic created using CircuitLab

For reference, It should act like this:

simulate this circuit


texts: How to propose/work on a project for work

texts:
They keep me fairly busy at work, and I've got a number of cool projects.  We don't have a Google 20% time to work on our own ideas, and we have process improvement engineers and R&D engineers who spend their entire careers working on and thinking up new ideas.  I'm not a process engineer, an R&D engineer, or a senior engineer with the freedom to choose or invent my own projects, but I've come up with some projects that I'd like to explore.

How should I pursue this?  I don't want to appear arrogant to my superiors, I don't want to tell R&D what they should be working on, and I definitely can't just put off my assigned projects to work on what I want to work on.  I would like to get payment and/or attribution for the ideas, but that's not as important as seeing it happen.  I'd also like new ideas to happen with the support groups that we already have (I don't want to do someone else's job.)

As far as I can tell, my options are:

Submit the project to my superiors/R&D.
Make time in my schedule or work more hours to do the project at work.
Work on the project at home.

None of these seem to be ideal.

I can submit the project to someone higher on the decision chain, but my ideas generally aren't necessary to the business or safe bets, like the ones that they are constantly receiving.  I discuss many of them with my boss, and he generally thinks they're good ideas.  Sometimes I have a solution for a pie-in-the-sky feature request that gets put off as too hard.  I just don't want to go to the gurus and say "Look, why didn't you try this?  You should spend the next couple weeks implementing it." I'm just an hourly intern.

Working ahead isn't really an option because they keep a list of projects in my queue.  When I get one done, I'm supposed to move onto the next highest priority, and I really can't just ignore that for my ideas.

Working on it at home is possible, but then I lack the support chain that the rest of the group provides, have lesser tools, and might get into some issues with not being able to take stuff home.  Additionally, I don't get paid for it this way, and this method also guarantees that it will take more time than if it was implemented at work.

Has anyone else had similar struggles?  I'm sure that most every engineer has ideas, and I'd like to hear about what you did to submit them to your company.

Edit:  We have about 5,000 employees at my company.  However, I work in the testing department with about 15 other people; it really doesn't feel very big.  I personally know most of the people who have developed the projects that I want to work on.

Edit2: I've proposed my ideas to my boss, and he's been interested.  I'd rather not just submit them to R&D, as the devices and systems I want to work on would be familiar to myself and my department, but new to the R&D guys.


texts: Serbia, Kosovo power grid row delays European clocks. Why?

texts:
According to this article (and a lot more published today on the same topic), Kosovo electricity net production balance has decreased during the last weeks.
This has led to a small deviation of the European network’s frequency (from 50Hz to 49.996Hz).
In turn, this frequency deviation led to some electric clocks (like ones in ovens) being out of sync (up to 6 min since January).

How can a decrease in electricity production lead to a decrease of the frequency on the grid on the long term? Isn't the frequency a parameter controlled by the power plant at the end of the day?
If the loss of power from some countries causes a frequency deviation, shouldn't we also observe other impacts, like a drop of the output voltage? Does this mean that we've also been experiencing a drop of voltage for weeks here in Europe?
Why do some electric devices directly use the network frequency to sync their clocks, instead of a quartz crystal technology? This means the same oven needs two different firmwares for countries with different electric network frequencies, while, with a crystal (that should be needed anyway to run all the embedded circuits), the same device would run unmodified everywhere.


texts:
Question asks me the voltage of \$V_{AB}\$ and \$V_{CD}\$,

\$V_{AB}=A-B\$ and \$V_{CD}=C-D\$, the solution tells me \$V_{AB}=A-B=10-20=-10\$,\$V_{CD}=30+10-20=20\$

I want to ask

Why is \$A=10V\$, not \$-30V ?\$
Why is \$V_{CD}=30+10-20=20\$, not \$V_{CD}=30+10+20=60\$?

simulate this circuit – Schematic created using CircuitLab


texts: What is a way to figure the pads from a datasheet where the part diagram leaves out dimensions?

texts:
I am trying to draw a footprint in Eagle (datasheet PDF).
This isn't the first time I had to draw a part without enough dimensions, but I'm wondering if there is an easier or more precise method. Previously, I assumed the drawing was to scale and used Microsoft Publisher:

File > Options > Advanced. Then under Display, next to Show measurement in units of, select Centimeters.
Paste the drawing into Publisher, draw a line, left click, Format AutoShape, Size and set a large border dimension (e.g., 3.8 cm).

This somewhat works for basic linear dimensions. For uniquely shaped pads (not in this example) I imported a bitmap from Paint. Is there a less complicated way if the pad diagram is not available?

Also, any idea what the two different connectors are for that part? The larger connector appears to be a MOLEX 43650-0413. The white/yellow connector I do not know. It has four SMT pads (similar to a squirrel track with wide front legs).


texts: Transformer turns and effect on frquency

texts:
What is the relation between transformer turns and frequency of input?

I hear there is a transformer coupling in stratix 2 FPGA. I went through the data sheet and found the lower cut-off input is 400 Khz. Why is there a lower cut off for a transformer?

Also what would happen if I replace 1000:100 transformer with a 10:1 transformer? Answer this not from EMF or flux point of view, but from input frequency point of view or input current point of view.


texts: Regarding PMDC motors attached to two different gear boxes

texts:
Can some one help me on this??

We are using two different make PMDC motors with different gear ratios(motor to gear box to lead screw to load) in one of our application.Below are the details.
Application:Solar Tracking systems.
Load:Around 1 ton solar structure.

***At No load condition:***
Motor 1:                               Motor 2:
current: 0.2A                          current: 0.6A
speed:2100 rpm                         speed:3515 rpm
input voltage: 24V                     input voltage: 24V
Gear Ratio:67                          Gear Ratio:57.
Gear working:smooth                    Gear Working:smooth to hard.
Max current rating: 6A                 Max current rating: 12A
Load current: 1.2 to 2.3A(max)         Load current: 2.5 to 7A(max).

We are using the both motors for same application.

We have used motor 1 and it's working fine.But we  have chosen motor 2 by thinking it has high no load and full current rating so that it can produce high torque.is it correct??
For lifting the same load motor 2 taking high current. Why? and How to reduce load current??
We need to reduce the load current around 3A when we are using motor2.How to achieve this for same load?
is there any possibility to increase the load torque and reduce the load current when we are using motor 2??
And finally where we have done wrong?and what are the changes need to do to get same performance as motor 1 connected to load???

Thanks


texts: Why are ionization smoke detectors bad at detecting smoldering fires?

texts:
I have been doing some research on the differences between ionization and photoelectric smoke detectors, and main differences in their capabilities, seems to be their ability to detect different kinds of smoke. I read that ionization detectors are better at sensing fast-flaming fires while photoelectric detectors are better at detecting smoldering fires.

I can understand why the first detects fast-flaming fires better: because those fires have less smoke, and the ionization detectors are more sensitive (more smoke is necessary to scatter the light in photoelectric ones). However, I do not understand why an ionization detector is less sensitive to smoldering fires. Shouldn't it be equally sensitive to a large amount of smoke too?


texts: Can I use Timer Input capture interrupt and GPIO interrupt on same line?

texts: I use Timer Input Capture of STM32L476RG.Is it possible if a timer capture based on interrupt will disable normal EXTI interrupt on the same line? For example TIM2_CH1 can be input capture on PA0. Does it mean I cant use PB0 as a normal external interrupt?


texts: Need 120A current limiter for 200A source

texts:
I would like an inexpensive circuit while noting wider tolerances are acceptable.   I have a 200A automotive alternator which I anticipate 50-80A will be called upon from the vehicle accessories over time.  I would like to tap off at up to a 120A load to charge some lithium batteries.   The output would simply be limited to never go over 120A and 10-20A drift would be acceptable in most cases.   I'd also like a pot in the circuit if possible to fine tune that maximum say for instance if there was another load on the regular auto that mean perhaps only 100A was available.   I am guessing that I will need a group of mosfets wired in parallel on a good heat sink to accomplish this but I wonder if this is a simple circuit because I don't see much online regarding these heavier current loads that can be varied using mosfets.
Now with this I would not be looking to anything fancy like found in a regulated power supply but simply a few components that guarantee not much more than 120A is going to be seen as available on the output side of the circuit.   Thanks in advance.


texts:
I'm working on a project to wire up a pipe organ's windchest using an Arduino as the backing system.

I'm looking to wire up about 400 outputs worth of solenoids that draw about 100mA of current at 14V each. I have a power supply that can handle this.

What I'd like to do is to create a system with an Arduino and something like a MAX7221 to be able to drive a lot of outputs with only a single Arduino. Obviously with those current requirements I'll need to use MOSFETs or something similar if I'm going to know with a MAX7221.

Besides spinning my own board with a MAX7221s and a diode matrix of MOSFETs are there any other good solutions to help keep costs and complexity down?


texts: controlling a sinking current with a positive voltage

texts:
I have found current mirrors like the basic one below often very useful.

obtained from https://www.electronicsnotes.com/articles/analogue_circuits/transistor/current-mirror-circuit.php

However, recently I needed a circuit where I sink current from a ground node to the negative supply.
The current level ( the impedance) needs to be controlled.
The challenge is that I need to control this current with a positive control voltage.
I was able to solve it with a op-amp and p-channel in  typical current sink type of circuit like the conceptual circuit shown below.

The circuit was changed to accommodate the negative supply.
So the circuit below shows a positive supply variant of what I used.

However, I am curious to see if there is a discrete solution, using MOSFET and BJT's, similar to a current mirror kind of solution.
To summarize:

Available: positive and negative supply (+-10V)
Control voltage is positive, output of MCU.
Restriction : not allowed to use digital pots and op-amps.
Current range: 100uA to a few mA
Accuracy not important, I am more interested in the concept.

http://www.learningaboutelectronics.com/Articles/Current-source-circuit.php


texts:
I would like to build the potentiostatic circuit in Application Note AN-1798 (Figure 2):

However, I cannot determine what parts to use for Q1 and R6.


texts: Replacing resistors with active load in active filter

texts:
I am building a low pass filter IC in 0.25 micron CMOS. My design requires 14 Mega-Ohm resistors. I want to replace them with an active load in order to save space. If possible I would like to use a current source as a resistor.

What would be the most simple and compact design?

I've already tried switched capacitors but had various difficulties, including NOC generation.

A simple floating gate MOSFET would require a transistor length of 2000 microns. If worst comes to worst I'll work on balancing transistor size with capacitor size.

Thanks a lot.

Edit: Topology is Shallen key. Output should be a decent sine wave of frequency 20kHz.

R1 =R2=14MOhm and C1 = C2= 0.56pF.


texts: How to decouple the grounds for two different switching regulators?

texts: I've a single DC 24V battery supply, which I use as the input for generating separate 12V and 5V supplies. Two separate LM2576T ICs are used to regulate the voltage to the lower levels. However, the problem is that I'll be using this to power an STM32 based circuit that drives some relays, the relays being driven by the 12V supply and if the ground for both the 12V and 5V are same then that would defeat the point of using an optocoupler in front of the relays (In fact, for some reason two of the optocouplers on my board got burned which is when I realized that this could be a problem). I want the circuits to be isolated. So the question is, how do I generate two separate ground planes from a single battery supply? Right now both the regulator ICs have the battery negative as the ground.


texts: Hacking an AC power unit with a transformer

texts:
I have some mini speakers whose power pack has died.  I can't find any suitable looking replacement power unit as the spec is unusual - 12V AC output 2.9A.  Nothing on Amazon or eBay looks suitable.

Sounds like it's essentially a step-down transformer I need.  Lots of these available - e.g. this 220-12V 30W example.  But would such a unit be theoretically sound or would it need any additional elements to be safe, other than a 3A fuse?


texts: I am trying to send a solar input into the LT8390 in LTspice. I am having trouble finding example circuits in LTspice that I can implement. Any direction or LTspice model files would be very helpful.


texts: Sensing the higest reading from an array of NTC sensors

texts:
I have almost the opposite of this question: Multiple Parallel LED Drivers with Single Thermal Derating NTC Thermistor

I have an array of devices which depending on operating condidion may run hot or not. I will have an NTC sensor for each, but I'm not concerned about sensing them individually, whichever runs the hottest will be used as feedback for thermal throttling and fan speed. Most likley case say 15 out of 16 will be close to room temperature and one is running hot and I want that temperature to control my system.

Planed operating range is 0-60 degrees, nominal is 20 degrees, warning/fan increase at say 40, thermal throttling at 50 and trip the system at 60.

In the off chance that say 10 of 16 is running at 39 degrees but due to some summing effect the system sees 45 and runs the fan unessesarily high, that's ok. Accuracy is not that important, but it can't be a straight sum of temperatures either.

What methods are there to cheat on this? Cost is a factor so no 1-Wire digital sensors and MCUs. Bias each NTC individually and OR them with diodes and apply some compensation factor? Is there a standard solution for this problem I can't seem to find? My google-fu is usually good, but this week it's not working for me.

simulate this circuit – Schematic created using CircuitLab