texts:
(see update at the end)

This is a continuation of my previous question about a relay: Question

What I want is a notification LED for both power and if a switch is on, which controls the relay.

Below is the circuit I have in mind:

simulate this circuit – Schematic created using CircuitLab

Below are my calculations and reasons.

S1: Adapter 9V DC
D1: Voltage reducer, 1N4148, Vfw = 0.7 V
D2:  Power indicator, Blue 3mm, Vfw 2.8-3.2 V. 5 mA is enough for a LED indicator.
R1: Resistor for power voltage indicator LED. V = I*R. R = V / I = (9 – 0.7 – 2.8) / 0.005 = 1,100 R -> 1,000 R … A will be V / R = (9 – 0.7 – 2.8) / 1000 = 5.5 mA.
For minimum: A will be V / R = (9 – 0.7 – 3.2) / 1000 = 5,1 mA.
Relay_vcc will be 9 – 0.7 – 2.8 = 5.5 V, which is in spec (5 V , 120% is 6 V). The minimum value is 9 – 0.7 – 3.2 = 5.1 V
D3: Switch indicator LED. Should be around 5 mA. Green 3mm, VFw = 1.8-2.2 V
R3: Resistor for switch indicator LED. V = I * R.  R = V / I = (9 – 0.7 – 1.8) / 0.005 = 6.5 / 0.005 = 1300 R -> 1200 R, resulting in I = V / R = 6.5 / 1200 = 5.4 mA. In case of Vfw = 2.2 : V / R = (9 – 0.7 – 2.2) / 1200 = 5.1 mA

I'm wondering mostly if I miss something, and if my values are 'ok'.
I hope this is not a too broad question, the reason I ask is since in my previous question I forgot to add the extra diode, so supplying around 6-7 V to the VCC (since I missed the 1N4148 diode).

UPDATE

I found out:

CH1 does not need has requirement regarding current, in examples from Arduino there is not a resistor between a GPIO and CH1 (or IN).
VCC probably uses the nominal current for the coil, which is about 75 mA.

However, my main question is:

Since VCC of the relay needs 75 mA, and D2 will burn when 75 mA is applied, but also D2 is used as voltage limiter, what should I do?

I read in other threads that a resistor divider is not good for relays, and the only other way I can think of is adding 5 or 6 1N4148 diodes, reducing the voltage to 9 - (5 * 0.7) = 5.5 V.

(Btw, the best solution is to use a 9 V relay module, or use 5 V input. Since I don't have the first one, I am going to use a 5V cable and cut it or check for some bracket).


texts: What would be the difference in a coil of wire and just a cylinder of solid copper?

texts: Ok so I am learning about induction and I always see coils of wire with no insulator. So I was wondering, What is the significance of it being a coil of wire rather than just a solid cylinder since there are already many points of contact between each "wrap" of the coil?


texts: 220 VAC Control Transformer "voltage on" indicator light.

texts: I would like to know where to place an indicator light (what voltage, as well) for the incoming 220VAC, after the 2 pole circuit breaker? The IEC Connector will provide 220VAC to the transformer, 120VAC to each leg, then the transformer will supply 120VAC to our equipment. The 120VAC "Power On" indicator light is wired below the transformer.  I am just having some issues with the 220 wiring.  Would a 220 VAC Panel Light illuminate, when wired across the two hot wires? (H1 and H4)  Where would a neutral come from, if it at all needed?


texts: Center-tapped transformer and inductance calculation for transformer driver

texts:
Using a push-pull transformer driver, for example the LT3439 like below with a center-tapped transformer, more precisely this one here

So we there is a center tapped transformer (with 1:1.3 ratio between two "full" windings, without the tap) and a half-bridge rectifier. At each half-cycle of the switching frequency, a current flows through half the primary and half the secondary at all time.

I wonder now:
The linked transformer datasheet says the primary inductor (the whole primary winding if I understand correctly) is 475uH, and the ratio is \$a = V_p/V_s = 1/1.3\$.

So I wonder what is the equivalent inductance at the secondary. Is it \$L_p \cdot 0.5^2 \cdot (1/a^2) = 200uH\$ or I'm I wrong.

Given \$|Z_L| \propto L\omega\$ and the general formula \$|Z_{sec}| = Z_{Lprim}/a^2\$ (load seen at the secondary), and the fact \$L_{coil} \propto N^2\$ (N=# of turns), I would think it's a correct assumption but I'm far from being sure. The 0.5^2 factor thus would be because current flows only in half the transformer coils at all instant.

Can anyone confirm? The reason I'd like to know the inductance at the secondary is to calculate some RLC filter with it (to match the output filtering to my desire), taking directly the L of the transformer into my calculations. I'm also interested at the answer for the sake of theory.

Thanks!


texts: Is there an implicit "unit of time" involved in electricity measurement? (e.g. miles per hour, kb per second, amps per ???)

texts:
I'm very new to electronics and I am going through what must be a common difficulty in grasping voltage, current, and resistance. I'll restrict my question to current as I suspect understanding that piece may shed light on voltage and resistance.

I've read a few questions here:

Help with understanding Current, Voltage and Resistance
Understanding voltage and current

And they helped a bit but I'm still struggling. One specific part that's difficult for me to resolve mentally is that I am reading about the basic units of measurement, but I'm not entirely sure what is being measured. For example, a pound is measuring the force of gravity pulling on a collection of atoms. A gallon is the amount of liquid that can occupy a fixed amount of space. Electricity... I get lost on the details of what's being observed.

Many units of measurement are a fixed quantity of something that does not change (unless acted upon). For example:

1 Gallon of milk
16 ounces of beef
30 cubic liters of air

That doesn't seem to make sense with something like current that is measuring electrons constantly in motion. Alternatively we perform measurements of something as it changes over time:

35 miles per hour
128 kilobits per second
5,000 gallons per minute

When it comes to current, we just say "amps", not "amps per something". Well, I get that "amps" measure the flow of electrons, but what exactly does that "flow" mean? Is it the number of electrons (or the number of something else) passing through a location on a circuit in a second (or some other unit) of time? When I touch the leads of my multimeter to a wire, what exactly is it "looking at"?

I've read that volts are a measure of potential energy related to joules and coulombs (http://www.allaboutcircuits.com/vol_1/chpt_2/1.html) (more confusion but that's fine) and I believe that coulombs are measured per second. Does the per-second carry over to amps as well?

The only other thing I can think of is that amps might be more like pressure where you're measuring pounds per square inch.

I know electricity is electricity and no analogy is perfect.  I'm trying to understand electricity for what it is, I'm just not sure how these measurements are actually made.  Perhaps I'm overthinking, but any deeper insight would be great.

(If this has already been explained to death I apologize, I may not know the best search term to use.)

Man, as someone new to this site I'm so blown away that so many people took so much time to help me understand this. Like a lot of things I think it's going to take time and a lot more reading / experience to "sink in" but all of the answers were so helpful.  I'm marking the "amps include time" answer as the one that helped me the most because it answered the core of my question "amps per what?". I'm picturing "amps" kind of like "knots" in the sense that the quantities are part of the definition of the word as opposed to being explicitly stated as they would be in another unit like "miles per hour". Not a perfect analogy but at least it helps me understand where all the hard numbers went.


texts: Dual GPS Antenna Connection to Positioning Module

texts:
I am using a Positioning module that has a SMA port to hot plug an SMA antenna. It also has pins available through its footprint to connect a GPS Antenna.

The module name is SIM908. I was not able to spot a place in its data sheet that describes if both antennas can be connected at once.

I want to solder a passive chip antenna about 5-10cm away from the GPS module to be used in case should the external SMA antenna is broken or disconnected. At least with a longer fix time, I would still have some fix, without having no fix at all.

Would having two antennas connected, one through PCB trace and other through direct SMA cable be a problem for the performance of the device?


texts: Similar LED, higher voltage drop, less bright

texts:
I was measuring voltages in my circuit, and noticed something strange.
I have an array of 8 LEDs. Each of them is in series with a 220 Ohms resistor. The circuit has a 5v source.

simulate this circuit – Schematic created using CircuitLab

The LEDs are all the same model. They all have ~1.90v across them. All but one, which has ~2.1v. At the same time, that LED has an inferior brightness. I can interchange this LED with another anywhere in the circuit, and it still behaves the same.

Is it normal / usual ? Does it mean I burnt it somehow or made a mistake in my circuit ? What's with the inferior brightness when it drops a higher voltage ?


texts: Why is DMA Continuous Requests not selectable as enable for STM32F446RE?

texts:
I have an Nucleo STM32F446RE and I'm used to enable DMA Continuous Requests with ADC. But in this case, I can only select disable. Why?
If it's not possible to use DMA Continuous Requests with ADC. How can I use my multi-scan ADC?

I can anyway create a DMA Stream and connect it to the ADC inside the DMA tab.

Here is some print screens.

Here I cannot select "Enable"

But according to data sheet, I can select Enable

https://www.st.com/content/ccc/resource/technical/document/reference_manual/4d/ed/bc/89/b5/70/40/dc/DM00135183.pdf/files/DM00135183.pdf/jcr:content/translations/en.DM00135183.pdf

Should I just change DISBALE to ENABLE here?

static void MX_ADC1_Init(void)
{

  /* USER CODE BEGIN ADC1_Init 0 */

  /* USER CODE END ADC1_Init 0 */

  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC1_Init 1 */

  /* USER CODE END ADC1_Init 1 */
  /** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = ENABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;
  hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T8_TRGO;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 6;
  hadc1.Init.DMAContinuousRequests = DISABLE; // <---- HERE!?
  hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }


texts: I found an FPGA board that I liked. It uses a Xilinx Spartan 6 LX45. When I went to the datasheet for the Spartan 6 series, it only said that there were 43,661 logic cells. How many gates does that equate to? Or rther, how would I figure out the number of total gates from the number of logic cells?


texts: Interface netduino with Iphone via audio jack

texts: I am interested in making the netduino establish a BUS connection to the IPhone via the audio jack. Does anyone have any experience doing this? I have read a few things online...but I am somewhat lost.


texts: Op-amp can add more than two voltages, while discrete transistors can't?

texts:
One of the application circuits for the op-amp is the summing amplifier which can add as many input signals as you need.
It was mentioned that this is one of the advantages of the op-amp over discrete transistors, as the only circuit with discrete transistors that can add two signals is the differential amplifier with the second input signal reversed before passed to the differential amplifier.
My question is, how does the op-amp add more than two input signals when it is actually made of discrete transistors circuits?
Am I missing something here?


texts: Understanding LiPo battery gas gauge circuit

texts:
I want to build a 3-cell battery charger for LiPo batteries using gas-gauge-bq20z65-r1 and bq24753A battery charger IC. But I am having problem understanding how the bq20z65-r1 operates.
http://i.stack.imgur.com/wZbaF.png
If the adaptor is connected, current should flow from Pack+ to BAT+. If not connected, current should flow from BAT+ to Pack+ via the FETs. Pack+ and Pack- are connected to bq24753A IC which is connected to the adapter and the system.

How is bq20z65-r1 getting powered on? The IC gets power from either battery or Pack+, via Vcc. But since Q2 and Q4 are n-channel FETs, Vgs is low and FETs are off. So the IC cannot be powered on. And to switch on the FETs the IC needs to be on.
Could you also explain me how does the current flows through the FETs. Because Q2 and Q4 are in opposite direction. And as I have understood the FETs allow current to flow in only one direction, don't they?


texts: Power supply with switched battery backup

texts:
first of allI'm sorry for my english.

I'm starting with electrical circuits (this is my first circuit) and I'm trying to create a Power Supply for an Arduino with battery backup.

Searching I've found three ways:

A diode on every source to switch to the higher voltage source.
Using a relay to switch when the main fails
Using a Mosfet and a Transistor to swith when main fails

The first works while the main Power Supply has an higher voltage, but both circuits has similar voltages and maybe sometimes the backup circuit will have higher voltage.

The second works perfect, but the relay uses an high power (about 4 times the arduino comsumption) and I want to create a low power circuit.

The third seems to work but for now I don't have materials to test the circuit and I want to ask if is OK and/or can be better, before buy all the things i need.

Searching I've found some info and I've done a prototype on a program that looks like this:

I've done some tests with the program and seems to work, but are not truly real (even the stabilizer has it's own power on that program...).

With this circuit I want to avoid the stabilizer comsumption while is on battery to last as log as possible, then I need to separate both circuits (D2).

This prototype is OK or I've to change something?. Someone knows a better way to do it?.

I take this opportunity to ask for a program to make better tests before build a circuit. I'm using LiveWire now.

Thanks!!


texts: Are there software tools to draw high level block diagrams for chips?

texts:
If one has a chip in mind where the chip has analog and digital functions and sub systems, before designing the chip there is always a functional block diagram as the following one:

I'm wondering how are they drawn? I used some SPICE simulators and board level design tools as hobbyist. But didn't encounter a tool which involves specific shapes for drawing such functional diagrams for electronics as in the above example. Is there standard for such symbols or people draw these things by hand?


texts: Servo not working on PLC's PWM(and no issue on arduino)

texts:
I am using Mitsubishi FX-5U PLC for controlling Sg-90 Micro servo(hobby) which rotates 0 deg for 1 ms PWM and 180 deg for 2 ms PWM.
The PLC's output is in sink mode hence I can't connect it to servo directly.I am using and Op-amp OP07CP by Texas in inverting configuration(please find the attached diagram)

I have shorted the supply ground and op-amps common terminal and then used as gnd for the servo.I have tried using both different supply so that their must be sufficient current available for servo to work.

I have verified the Op-amps output on Oscilloscope and verified so that it exact matches with the Arduino's PWM output. The motor runs neatly on the arduino board and external supply(by shorting their ground).But i am not getting why its not working on the op-amps outbut when:

Vcc is 5.5 v
all ground and common are shorted and connected to motor
control signal verified on oscilloscope is given

on switching power supply the motor gives small jerk(means the circuit is complete).Then it is not moving at all.I have kept the wave frequency much below 50Hz still not getting o/p.

servo datasheet:
Weight: 9 g

• Dimension: 22.2 x 11.8 x 31 mm approx.
• Stall torque: 1.8 kgf·cm
• Operating speed: 0.1 s/60 degree
• Operating voltage: 4.8 V (~5V)
• Dead band width: 10 µs
• Temperature range: 0 ºC – 55 ºC


texts: HF characteristics of Liquid Electrical Tape

texts:
Some self-wound toroid inductors from a HF-radio kit are sitting a bit too loose on their PCB for my liking; they stand upright and are only held in place by the thin enamel-coated inductor wire that wraps around the toroid.

I'm thinking of applying a dab of Liquid Electrical Tape to glue the toroid to the PCB, but apart from the Dielectric Strength (of about 1200V/mil) there's no mention of any AC characteristics on the product's website.

Can Liquid Electrical Tape be used for HF purposes without degrading the electrical characteristics of the components around it? Is hot-glue or clear silicone from a hardware shop just as good?


texts: LTspice counter component how does it works?

texts:
I find this component on LTspice but I have some troubles to know how it works. It asks me to enter 2 parameters. I could understand that It needs to know the "divide" number but what is the second parameter ? I supposed one of the outputs is the complementary of the other

Thank you very much,

Have a nice day !


texts:
There appears to be several options out there when it comes to isolating analog signals.  This topic has been addressed on this website in a few forums as well.  The problem for someone such as myself... I'm not convinced some of the solutions discussed apply to my application.

It would seem that the favorite is an isolation amplifier.  But the output would be differential?  I guess my hang-up is the output and does that work with my micro.  The micro is single ended input.  But also my inputs into the amplifier inputs.  Can the geniuses here take a look at what I'm thinking and comment?  Feel free to insult my intelligence if you so choose, just don't insult my mom.

simulate this circuit – Schematic created using CircuitLab


texts:
I am currently working on a portable speaker and still have to figure out some of the electronics.
Specifically I am stuck with the following setup.
The battery pack that I use is a 6s 18650 Li-ion configuration.
There is obviously a charge port and a power switch.
Also there is a LED to indicate when the speaker is charging and secondly an indicator for how much charge is remaining
which should be powered when charging OR when the speaker is turned on.
I don't know how to achieve this since the charger and the battery have to be connected for charging and I have no clue how to seperate the two.
I thought about diodes and relays, but frankly I'm just not very good at electronic circuits.

Thanks for your answers in advance!


texts: 555 soft latch triggers when voltage applied and turned off

texts:
I have built a LM555 based soft latch (toggle) with single push button according to the schematic, and while on protoboard everything seemed to work fine, the pcb version is triggering when voltage is first applied.
So when I first connect 220VAC to the pcb, the trigger latches on. After that the circuit behaves normally, every press of pushbutton toggles the relay on or off. If I disconnect 220VAC and the latch was off, it toggles on for a split second before shutting off.
There is a 9V transformer followed by a rectifier bridge and 100uF which provides around 15V when latch is off, and 12,5V when it is on. I measured the middle point between two 10k resistors and it's 7.5V (off) and 6.2V (on).
I already tried a few things:

Adding a startup delay with 2,2k (or 10k) + 10uF connected to pin 4 and GND - doesn't help on its own
Suspected the 100uF cap is staying charged so added a bleed resistor (1k and 2,2k) - doesn't help on its own
Removing 100uF cap renders the circuit unusable (obviously the ripple from he rect bridge is too high)
Increasing the C1 to 4.7uF and 10uF - doesn't help
Adding a 0.01uF from pin 5 to GND - no change

All of the above doesn't fix the problem, although 1. and 2. together seem to make it appear less frequent.
I want the circuit to stay off until I press the button, so what am I missing here? I'm suspecting some kind of circuit instability but can't figure it out.
Any help appreciated.


texts: UART doesn't transmit all characters when using UDREn interrupt

texts:
Note: I am beginner :) MCU: Atemega328p
In Method 1, I am using a UDRn data register empty interrupt once the transmit buffer is empty and inputting characters from snum into the UDR0 register within the ISR. I want the serial monitor to print "65534" repeatedly. However it shows this:
Method 1 Code:
#define F_CPU 16000000UL
#define BAUD 9600
#define BRC  ((F_CPU/16/BAUD)-1)
char snum[20];
int num = 65534;
int i;
sei();
int main (void)
{
    uarttransmitenable();
    while (1)
    {
        utoa(num, snum, 10);
    }
}

ISR(USART_UDRE_vect)
{
     for (i=0; i< strlen(snum); i++)
     {
         UDR0 = (char)snum[i];
     }
}

void uarttransmitenable(void)
{
    UBRR0H = (BRC >> 8);
    UBRR0L = BRC;

    UCSR0B = (1<<TXEN0)| (1<<RXEN0) | (1<<UDRE0);
    UCSR0C = (1<<UCSZ01) | (1<<UCSZ00);
}

My thinking was that the while loop would covert the 65534 into an array of characters and then every time the interrupt occurred the next char in snum would be sent, and would be sent in order, so 6 first, followed by 5,5,3,4.
In Method 2 I do the int to char conversion and poll the UDREn bit to see if the transmit buffer is ready within the while loop. I don't use ISR at all. This shows "65534" fine on the serial monitor.
Method 2:
#define F_CPU 16000000UL
#define BAUD 9600
#define BRC  ((F_CPU/16/BAUD)-1)
char snum[20];
int num = 65534;
int i;
int main (void)
{
    uarttransmitenable();
    while (1)
    {
        utoa(num, snum, 10);
        for (i=0; i< strlen(snum); i++)
        {
            while (( UCSR0A & (1<<UDRE0))  == 0){}
            UDR0 = (char)snum[i];
        }
    }

void uarttransmitenable(void){
    UBRR0H = (BRC >> 8);
    UBRR0L = BRC;

    UCSR0B = (1<<TXEN0)| (1<<RXEN0);
    UCSR0C = (1<<UCSZ01) | (1<<UCSZ00);
}

I wanted to use the UDRE interrupt as I thought it would result in better performance, but the figures have come out differently.
I understand that using FIFO buffers would be a good idea for this task in general but I just wanted to understand why method 1 does not work.


texts: How do memory seats keep track of their position?

texts:
I was wondering how do memory seats keep track of their position. Since this kind of equipment existed in 1990's cars, it must be simple yet ingenious. I have been thinking about this for quite a time now and cannot figure out how it works (without tearing apart a donor car).

So as to keep it simple, let's only consider the forward / backward position of the seat. Usually, we have buttons for 3 memories.

Seats could be using a default position as a reference paired with a duration of movement of the electric motors, but they would need to go back to this position when you press a button to recall a memorized position before moving to the right position. Since they go straight to the right position, I guess it's not how it works.

Any idea?

Thanks


texts: I need help connecting 2 solar panels in paralel

texts:
I'm new to Electronics but I love solar panels and hiking.

So, I bought 2 of these and one of these
and I connected them.

I cut 2 USB Cables, connected + with + and - with - from each Cable and connected it to the DC-DC booster. The amperage is not doubled and the output Volts are lower than 5V which should be the constant output of the booster. The panels were solar oriented and the output was only 0.02 A with Bright enough sun from those 2 solar panels. The panels separately work fine, it is only when I connect them to the booster that they act weird.

And this is roughly the scheme I'm using, except solar panel specifications and MPPT:
Charging Powerbank with Solar Panels better with converter or mmpt or without?

Is the problem in booster or is it me doing something wrong?
Thank you!


texts:
I've just bought a very bad quality D1 mini board. While soldering pins, I made rookie mistakes and I had to desolder, then (really bad) pads got detached from pcb. I certainly don't have experience replacing pads and keeping through connected holes right, so I figured why not connecting ESP23F directly to JP, bypassing PCB tracks.

By simply visually checking the tracks on the PCB, I can't tell if all ESP12F pins are directly and one-to-one connected to each pin hole, moreover, the top side of the board seems simple enough but I'm not so sure about the bottom side.

So, I definitely can send the board to the trash and buy a new one (why not, they are cheap even in Argentina), but where is the fun in all that?

That's why I'm asking for any advice on how to solder JP given the missing pin hole pads.

I'm might be wrong, but if this can be performed by soldering ESP12F JP to pin hole/headers on the top side, and soldering the unconnected tracks in the bottom side with thin wires to the right JP on the top, it would be helpful to know which are the correct connections.

Edit: Pictures of the repair process


texts:
I added a string in PCB Editor and it is on Top Layer, which is good. But when viewing in 3D, its tinted. Its behind the color layer and not appearing clearly as it should like pads(the carbon part).

I couldn't find any setting to remove its region from color layer. How can I make it appear clear ?

Edit: added screenshot


texts: Terminating bidirectional data lines and clock for memory-mapped devices

texts:
I am wiring up an STM32H743 to an SRAM or an FPGA to memory map it (i.e. I would like to be able to re-use the schematic). This SRAM operates at a maximum of 50MHz. The FPGA can operate at 50MHz all the way up to 200MHz, I believe.

It would be nice if I could run the bus to both SRAM and FPGA on the same PCB and only populate one as required (or populate both but only activate one as required) but I am not sure that would be feasible as far as signal integrity goes; mainly because I don't know how you can terminate bidirectional lines that drop off at taps along the way, even if the taps are stubless since some of the taps in the middle of the line end up being drivers.

I had some trepidations about the general approach to memory terminations. Can anyone confirm that how I have gone about things is generally okay?

Namely:

Series termination on the driver end for the unidirectional address lines.
Series termination on both ends end for the bidirectional data lines.
Parallel termination a little past the "tap" for the receiver for the clock.


texts:
I'm working on a project to turn on and off an LED using my phone (android OS). I use DOIT ESP32 devkit V1 board hich is connected to an LED and is controlled by Blynk app via Wifi. I want to automatically send log files from Blynk server to my PC (Windows 10 OS) but I don't know how to access the server and work with it using C++ on Arduino IDE. I tried reading online, but I'm not able to find any function which can be used to tell the server to send reports to my computer. How can I access the Blynk server? is there any documentation about it's functionalities? Is there a better alternative to keep log file about all the different states of my board?
Thank you.


texts:
I'm trying to figure out if i could use 16 white 5cm 12v 5050 led strip with the TLC5940

The Array/paralell setup on the strip is something like this:

+12V
+   -|>|-   -|>|-   -|>|-   -/\/\/\-    +   R = 150 ohms
+   -|>|-   -|>|-   -|>|-   -/\/\/\-    +   R = 150 ohms
+   -|>|-   -|>|-   -|>|-   -/\/\/\-    +   R = 150 ohms

Using the http://led.linear1.org/led.wiz to calculate the values i came up with this:

each 150 ohm resistor dissipates 43.35 mW the wizard thinks 1/4W
all resistors dissipate 130.05 mW together
the diodes dissipate 489.6 mW total
power dissipated by the array is 619.65 mW
the array draws current of 51 mA from the source.

This is probably correct as with a regulated 12v led driver i measured 15cm and it was around 120-130mA

The TLC is able to sink 120mA (with a proper heatsink).

So i guess that it could handle 51mA..... but it's at 12v

Reading  the TLC's datasheet and the following post http://forum.arduino.cc/index.php?topic=143539.0 i probably found what i need.

  At 120mA a 15 Ohm resistor will swallow 1.8V.

  So...if the LED takes 2.4V, the resistor takes 1.8V, that leaves 0.8V
  for the TLC5940.

  0.8V*120mA*16=1.536W total dissipation - that's within spec.

and

  My LED's use 3.2V at 120mA so 5V-3.2V = 1.8V.... 1.8V * 120mA ==
  0.216W per channel. 2.5W/ 0.216W = 11.57 ..... So I can run 11 of these LED's.

So:

9.6v (3x3.2v) @ 51mA so 12v-9.6v = 2.4v * 51mA = 122.4mW * 16channels = 1,958W.

"2.0 Watt on the TLC5940NT" is this calculation correct?

Do i need a heatsink for 2 watt on the TLC5940?

The TLC5940NT is nice because you just need one resistor to impose the resistance on all leds. but as on those 5cm strips the resistors are already soldered in place what should i put on the iref pin (20)? no resistor ? to ground? a small resistor?

IF the above does not work

Most examples using transistors and mosfets to increase the wattage use PNP / P-type transistors. While the official datasheet suggests NPN transistors or N-Type Mosfets.

Using TLC5940 With Higher LED Supply Voltages and Series LEDs

Using NPN transsistors it's probably inverted at the end.... but more efficent ... right?
But also with PNP transistors it's inverted right?
Why are there more examples with PNP transistors?

If the above calculation is correct i probably need to use transistors.

The mosfets i own are all n-type but i have not enough power to fully saturate each mosfet considering 5v . so i think i go for transiostors.
i have some p2n2222a NPN. those can sink 500mA each.. that should allow me to not overheat my circuit. this also would allow me to use 15cm per channel.

In that case how should i setup the TLC5940NT?
Looking at the TI pdf it looks suspicious that the emitter goes directly to the ground.
it says that using an NPN allows to do all the math based on the transistor, so it would actually be able to sink 500mA(with proper heatsink on NPN)?
Vcc comes from 5v or 12v? and what resistor should i put at the base of the npn?


texts: Home made PCBs - chemical temp questions

texts:
I'm trying my hand at making my own PCBs.  Using the positive photo development method and ammonium persulphate for etching.

Does anyone know how long the etchent can be kept once mixed before it becomes useless?
Also, what are the optimum temps for both the developer and ammonium persulphate to function at their best?

Videos online show the etching happening quite quickly and my boards are taking a long time.  Wondering if temp is to blame.  Doing it in the garage so the etch bath is slightly warmer than body temp[40-50C].  Photo development is cooler than body temp like about 25C.


texts:
I just took apart an old dishwasher for parts. The large motor I got from it seems to be an induction motor. It has 4 wires. Green, yellow, red, and blue. I know for a fact that the green one is ground, so it can be ignored. It also had a 15uF capacitor for the motor, but I'm not sure how it was connected. The dishwasher is at a different house so I can't look now, but if I need to know how the cap was connected I could look next time I'm there. How can I figure out how to wire this motor? In case this helps, it is model 5kcp122e1bx, but I can't find much info about it online.

I just measured the resistance between the leads. blue to red is 16 ohms, blue to yellow is 4 ohms and yellow to red is 20 ohms. 16+4 = 20, so that means there isnt really a winding between the yellow and red. This makes me pretty sure that blue is a common, red is main coil and yellow is a start coil. That is what I would have guessed just looking at the wire colors. But having a second differently sized start coil, wouldnt that usually mean that the motor is resistive start and doesnt use a capacitor? I guess I am wrong as i obviosly has a capacitor. So how do I wire it up?
Thanks!


texts: PIC18F26K80 ADC calibration using Bandgap

texts:
The PIC18F26K80 errata sheet mentions that the ADC has an offset error as high as 25 bits and discusses one workaround copied from the errata here:

A/D Offset
The A/D may have high offset error, up to a maximum of ±25 LSBs; it can be used if the A/D is calibrated for the offset.

Work around
Calibrate for offset in Single-Ended mode by connecting A/D positive input to ground and taking the A/D reading. This will be the offset of the device and can be used to compensate for the subsequent A/D readings on the actual inputs.

I have an existing circuit where connecting the AD input to ground is going to be difficult - so I was looking for alternatives.

The ADC has provision for connecting the positive input to an internal bandgap voltage reference (Channel 31)

Pg 358 in datasheet

My Question:
Would measuring the bandgap voltage serve as a way of identifying the offset error also or would each channel have a different offset?


texts:
I want to send information from my Attiny85 to my Raspberry.
For the moment.
Attiny and Emitter work on 5V
Emitter have a 433 Mhz 1/2 waveform antenna
I'am using virtual wire

Raspberry receiver work on 5V with 430 ohm resistance for data.
I use vw.py python program

All this work fine 0-1 meter, badly (10%) at 2 meters and not at all more far away.
Problem, my desk is about 4m far away the Emitter. How can I improve this range ?

My idea : Using 12v input for emitter  with 7805 for Attiny and a low cost NPN transistor between Attiny data pin, 12v and data of emitter.

Is my idea good ?
Do you have other idea ?

Thanks


texts: Impedance matching open collector output

texts:
I am designing a circuit that will receive a 20 MHz square wave (LVDS), convert the LVDS to single ended, and drive a 75 Ohm line.  I've found some 75 Ohm drivers from TI, but the applications engineers are telling me they are not sure if they can handle those speeds at that load.  I've decided to use a Darlington Array type of driver with open collector outputs based on some feedback from the applications engineers.

Some transmission line calcs (not my specialty, correct if needed):

λ = 300 / fMHz = 300 / 20 = 15 meters

Transmission line if:

≥ λ / 8 = 1.875 meters ~= 6 feet

So, if I use greater than a 6' BNC cable, I need to worry about impedance matching, correct?  Assuming the BNC cable is 75 Ohm, the receiver is 75 Ohms, I need to make the source (open collector output) 75 Ohms as well?  I get confused about the ability to drive a 75 Ohm load (i.e. current drive capability) with the need for impedance matching.  If this is the case, how do you impedance match an open collector output?


texts:
I'd like to know why there are no mains-powered chargers that can charge multiple usb devices at, say, 2A and 1A?

I'm after something that can charge 2 tablets that ask for 2A and 2 phones on 1A, so 6A in total. I've seen 2.5A supplies but nothing higher. Is there a fire risk or something?


texts: Why this inverter is used in the PWM circuit?

texts:
The circuit below is a programmable duty cycle modulator for boost converter in a paper. As from the picture, there are two signals CLK/64 and CLK/64SHIFTED. Could you explain why the signal CLK/64 is inverted by the inverter before connecting to the input of NAND gate?
Thank you.

I have just drawn the output of NAND gate in two cases. The first one with the inverter is Q1 and the second case Q2 is without the inverter.
As you can see the two waveform are similar in T, Ton, Toff. So I am wondering what is the function of this inverter.


texts: What is the output of a PID controller (or any controller in general)?

texts:
I'm new to Simulink and I'm trying to get my hands a little dirty there to get used to using it. I'm working on a speed control of a switched reluctance motor. The input signal is to be fed to a converter (IGBT's gate) to control the speed of the motor.

Consider the general diagram below:

So my controller is a PID , my input is the reference speed of motor , my output is the measured (actual speed) of the motor and the plant is the "converter-motor" set up.

(1) What is the actuating signal obtained from the controller? Is it the control signal to be fed to the IGBTs?

(2) What if the plant input is a voltage (we are directly feeding voltage to the terminals of the motor). Isn't the PID output pretty much the same as the case of IGBTs? The Simulink controller produces a control signal how should I use it to feed voltage instead ?

Thanks ahead


texts:
I am trying to study the radiated and conducted EMI fields of my PCB using ANSYS SIwave. I did the DC IR drop analysis, and that was okay. Next I did the "Compute Near-field" and "Compute far-field" for the same board configuration.
Here is the result I got for far-field (frequency range = 150 kHz to 30 MHz)

Could somebody please help me interpret the results?


texts:
On this page, the two versions of this gyro/accelerometer IC have two different Logic Supply Voltages.

What is the VDD voltage?

Why would one version of the chip also have an option to make the voltage 1.8V?

http://invensense.com/mems/gyro/mpu6000.html

note: not intended to be a dupe of
What is the difference between \$V_{CC}\$, \$V_{DD}\$, \$V_{EE}\$, \$V_{SS}\$.


texts: What is the main difference between SRAM and DRAM in the automotive industry?

texts:
What are the main differences between SRAM(static RAM) and DRAM(dynamic RAM) in the automotive industry?

What kind of memory does the different ECUs use?

I'm interested in the BCM(body control module), but all info regarding the ECUs will be useful for me.

I hope that this is the correct community to answer my questions, if not drop a line, will delete the question.


texts: How can I electronically measure tilt/compression of a pliers or alligator-clip?

texts:
I would like to electronically measure the width (really the compression/extension) to which an object's constituent blades have been stretched. Or alternatively, I could measure some other parameter which I can then map to the displacement by data calibration.

In particular, I am dealing with a miniature tool (a few cm long) whose outline resembles an alligator-clip (or pliers). So consider something like either of the objects in the below image.

How can I electronically track/measure the below spacing to a resolution of about 0.1 mm over a full-scale extent of ~10 mm?

I cannot think of any transducer or phenomenon that I could map to this movement and get such fine resolution. For example:

Perhaps I can measure parallel-plate capacitance -- would that be accurate enough in this scenario?
Or maybe I could place a spring between the two jaws and measure the compression -- but how would I measure the compression of the spring?
CV isn't a viable option because I wish to make the sensor compact enough that that I can log the data wherever I wish.

EDIT: Updated with illustration added based on @Michael Karas's Answer and @Matt Young's suggestion.


texts: Measuring the Current Draw from a LIPO Battery

texts:
I have been working with LIPO batteries to power my portable projects for a while (mostly in RC aircraft), but when using them, I have always had to guess as to how much charge is remaining. Now, I am trying to build a system to provide a more accurate estimate as to how much charge is available.

So, I was thinking, I know how much the batteries get charged to, so, if I can measure the amount of current that is being drawn during its life, I can estimate how much longer the battery will keep operating.

Sadly, I am not to sure how to go about measuring this usage. I have a larger LiPop 4s battery (14.8v, 10000mah), and 4 180w brushless motors. This works out to around a maximum of 50A (each at 12.2A) being drawn by the motors at full power.

So, I want to measure the amount of current being drawn by all the motors. But, all the components I have found have usually maxed out at between 20A and 30A, so not enough to measure the usage if all the motors are going at once.

My solution to that was to measure the current being used by each motor. If I was to get 4 digital ammeters, and connect one to each motor, would that cause any problems? And would it be able to accurately measure how much current is being drawn without interference from the others?

Also, I have been searching several sources for digital ammeters, and there appears to be quite a range, and I don't want to get it wrong and damage my system/waste money, so If anyone could recommend a suitable Current Sensor I could use (the interface doesn't matter too much, as long as I can connect it to an Arduino)


texts: Using chip antennas over a 50 foot distance

texts:
I want to build a coin sized receiver that can operate over a distance of 50 feet. I am interested in using a 2.4 GHz  ceramic chip SMD antenna, like the one described here

http://www.alibaba.com/product-gs/743800172/ceramic_chip_SMD_2_4_GHz.html

I also want to build/buy a transmitter, but because the transmitter does not have the same size and power constraints that the receiver has, I am trying to investigate the receiver first, with the goal of then finding a transmitter to suit the receiver. Due to this, I do not yet know the transmitter strength. Is there any way I can estimate whether the chip antenna will be able to receive over the required distance without knowing the specs of the transmitter?
Can anyone give their opinion on whether this type of chip antenna might be capable of receiving over a distance of 50 feet? (This is an indoor environment)
Does this sound reasonable?
If so, what kind of transmitter specs would you be looking for?
If not, would there be another option I should look at?

I have also found this XBee chip antenna which is claimed to have a range of 300 feet

https://www.sparkfun.com/products/8664

Detailed Datasheet here
http://www.sparkfun.com/datasheets/Wireless/Zigbee/XBee-Datasheet.pdf

This is a little too big, and a lot more expensive for what I have in mind. I just want to use a signal received as an ON command for a connected component, so I am thinking that I do not need to send a lot of data with each transmission.

I have also found lower frequency chip antennas here

https://www.linxtechnologies.com/resources/data-guides/ant-xxx-chp-x.pdf

These operate on 868 MHz, but are of course larger.

Any suggestions?


texts: Multilevel cache effective access time calculations considering cache miss

texts:
I was solving exercise from William Stallings book on Cache memory chapter. The problem was:

  For a system with two levels of cache, define Tc1 = first-level cache access time; Tc2 = second-level cache access time; Tm = memory access time; H1 = first-level cache hit ratio; H2 =  combined first/second level cache hit ratio. Provide an equation for Ta for a read operation.

The solution given was:

  $$T_{a} = [T_{c1} + (1 – H_{1})T_{c2}] + (1 – H_{2})T_{m}$$

I am not able to get this.
Shouldn't it be

  $$T_{a} = \color{red}{H_{1}}T_{c1} + (1 – H_{1})(T_{c2}+\color{red}{T_{c_1}}) + (1 – H_{2})(T_{m}\color{red}{+T_{c2}+T_{c_1}})$$

The reason for H1 is that its the probability with cache hit occurs. We cannot simply add L1 access time.

The reason for Tc1 is that we have already accessed L1 cache before accessing L2 cache, when L1 cache miss occurs.

The same is the reason for Tc1 + Tc2. We have already accessed L1 and L2 cache before accessing main memory cache, when L1 and L2 cache miss occurs.

Am I wrong with my equation or the book is wrong?


texts: Tm4c nested uart interrupts- does each com finishes it's run before the next one executed?

texts:
Board: Tiva™ C Series TM4C1294

EK-TM4C1294XL

My program is listening to 2 UART ports (UART 3 and 7)

I've encounter a problem that I'm losing some bytes received and I'm suspecting that this issue relate to the UART's interrupts.

I understand that UARTs have nested interrupts but does both of them are serial?

For example: I'm inside UART 3 interrupt function and then while UART 3 didn't finish the interrupt (just copy their bytes to buffer) UART 7 interrupts arrives, does the system moves to UART 7 or it will first finish UART 3 and then moves to the UART 7?

Currently I'm suffering from error bytes something like 45-400 bytes for file that his size in 12 Mbytes.

I'm suspecting the above issue cause this issues.

p.s if only 1 UART is sending data I have binary same files on both host and PC.


texts: Looking for an on/off digital toggle signal chip

texts:
I am looking for a chip that will enable me to input 3-12 V DC on 2 pins (+ and ground input), to get as output on 2 other pins, the exact voltage i put in those previous 2 input pins (+ and ground output) and to have a 5th pin, that if i put in a 3-12 V DC signal - Will turn on and off the electricity that goes between the previous 4 pins (+ and ground input and output).

I understand that maybe such a chip can be found on Motorola chip series MC140xx or 74HCxx or on the LMxxx (which is not Motorola, but another manufacturer, that starts with the letter N - i forgot its name).

Anyway - i need the chip to be as less expensive as possible.

Can anyone help me?

Thanks,
Roi.


texts: Why  does the vin=vout takes place at the voltage of (vdd/2) only in the case cmos inverter characteristics? and how to estimate the value of (vout) in every case, so that we can establish  relationship between vgs and vds.


texts: Prevent Lithium battery discharge until USB/Charging voltage is present (for the first time)

texts:
I would like to prevent the battery in a device from discharging (initially) until the usb is plugged in (to keep charge on the battery during storage and shipping).  I am using a typical LiPo protection circuit (BQ2970):

I need to disable the discharge MOSFET until a USB cable is plugged in.  I'm sure this has been done before, but I don't have a common reference voltage to implement any of my ideas (have USB v-divided to drive MOSFET etc.).


texts: Why is there a minimum input resistance?

texts:
I was looking at this multimeter, and it says,

  Output rate:     0.1 V/A (use with a device having a 1 M-ohm input resistance or higher)

Where can I read why this minimum resistance is required?  Alternatively, what would happen if my voltmeter has smaller resistance?


texts:
Im thinking of upgrading some drls on my car.

LED SPEC: 4V max 750mA max.
Daylight white.
http://www.ebay.co.uk/itm/141679345010?_trksid=p2060353.m1438.l2649&var=440967222198&ssPageName=STRK%3AMEBIDX%3AIT

There is going to be 4 leds per headlight.

Im wondering which is the best way to drive these, since the car will give out anything between 12-14.4v.

Ive been thinking about just putting some resistors, but these leds output goes down substantially when voltage is dropped.

Ive also thought about building a C.C circuit to the leds, is it possible to use LM317t for these leds? Would these leds have the same brightness when the car is on / off?

Maybe the best thing is to buy a finished driver from ebay?

I'm sorry for the noob question.

update:

Thank you for answering

There are leds in it right now, however, they arent that bright, they consume around 3w per headlight, they look to be driven with resistors.

Im planning on having the electronics inside the headlight, so, only limited space avalible.

I do have 5 dc to dc step up laying around, maybe i should use those.

i dont have the leds at home yet.

The leds are placed in the bottom, one pointing each direction.


texts: smart doorbell chime module to actuate ac relay

texts:
I'm looking to get an Amcrest AD110 video doorbell and just looking for clarification on hooking it up to my existing (ancient) electronic musical chime.
My current setup looks like this...

The Amcrest doorbell requires up to 24v AC which is more than my chime box currently uses; I don't know how tolerant it would be of higher voltages but I don't want to damage it or shorten its lifespan. Following that, I was hoping to add another 24v ac supply to power the AD110 and then use a relay to keep both circuits separate. Would the following diagram work? ie. would the amcrest chime module be able to actuate an AC relay directly (which would in turn trigger the input on the chime box)?

When looking at relays I found THIS which I think fits the bill?


texts: Identifying pin 1 of Analog Devices REF195

texts:
I have the Analog Devices REF195GSZ, and it doesn't have a circle on either the top or bottom by a pin to indicate pin 1.

Looks like this:

Which is pin 1? The datasheet didn't seem to help either: Analog Devices - Precision Micropower, Low Dropout Voltage References, Data Sheet. REF19x Series


texts:
[Marcel Pelgrom's Analog to Digital Conversion]

Hi,
I came across this section under the "Accuracy" chapter and I'm having a hard time grasping what point he is trying to get across here?

Is he suggesting that all my capacitors should be a 4.5:1 ratio? Or that if I make two capacitors and one is 4.5 times the size of the other that I should make each parameter 4.5 times larger, area, perimeter, etc?

Apologies for this question, just having a hard time figuring it out.


texts: What are the covers behind the terminals for in lead-acid batteries?

texts: Some lead-acid batteries have two extra covers behind the terminals (See the images below). I understand that the 6 holes in the row in front of the terminals are used to water the cells. But what is the purpose of the other two, I've open them and they have only some plastic. What are for then?


texts: UPS in front of an ATS for generator protection

texts:
At the countryside house there is this setup:

And I am trying to protect the generator and house load from brief ~ 1s power outages like so:

It works fine in normal conditions. Trouble is when I turn off the UPS output as to simulate an outage the ATS won't start the generator. I have just thought that maybe by turning off the UPS output then Live and Neutral are left floating and that could somehow impact ATS outage detection?


texts: 3 wires on a (bipolar) DC plug - what are they for?

texts:
If got this cable as a power plug for my DELL XPS 15. I want to hook it up to a different power source.

But what are the 3! wires for on a bipolar plug?


texts: PSOC 4 Bootloader will not work when P4[0] and P4[1] Connected to I2C bus

texts:
I have been desparately juggling the pin allocations on this project in the hope of freeing up the VREF pin, and thought I had managed to do so.
Previously my system was successfully transmitting over the I2C Bus but when I move the SCL and SCA to pins 20 and 21 respectively the bootloader comes up with the message
"The bootloader reported error 'Packet data invalid: the packet sent to the bootloader does not conform to the required packet format, see the Bootloader section in the System Reference Guild for the correct format'."

The strange thing is that when I unplug these 2 wires the bootloader works as normal.
If I bootload the application and then connect the wires the system does not communicate over the I2C bus.
If I can get this to work it will make such a huge difference to my project. Does anyone know what is going on here?  Can I just not use these pins?


texts:
I am trying to implement a rolling average of an array of 12 bit samples in SystemVerilog. New samples are generated and shift into an array via a clocked flip flop. The goal is to have a register that represents the sum of all of the current samples, so I can then take the average with a right-shift.

I've attempted to implement this with the following mix of sequential logic to update the array of data, and combinational logic to total all the array elements. Note that the number of measurements to average will eventually be more like 128-1024:

localparam      numMeasurementsToAverage        =   8'd4;

reg [11:0]  voltages    [numMeasurementsToAverage:0];

// shift in latest voltage measurement on rising clock
always_ff @ (posedge clk)
    if(~rst_n) begin
        voltages <= '{default:11'd0};
    end
    else begin
        voltages <= {voltages[numMeasurementsToAverage-1:0], v2p_out_voltage};
    end

// calculate the current sum of voltages array
always_comb
    if(~rst_n) begin
        sumOfVoltages <= 0;
    end
    else begin
        for (int i = 0; i < numMeasurementsToAverage; i=i+1) begin
            sumOfVoltages += voltages[i];
        end
    end

This runs, but the sumOfVoltages keeps increasing... the new array total is added to the array total calculated on the previous clock edge. I need the sumOfVoltages to only reflect the total of the elements currently in the array.

Because the voltages[] array is updating on the clock, the sum should also only update on the clock edge, so I can see an argument for moving the summing logic to a clocked flip flop. However, I don't think I can use a for loop for sequential logic.

I like the for loop approach because it makes it way easier to modify the number of elements in the array, compared to hardcoding addition operators between each element in the array. Is there a shorthand for summing all values within an array, using sequential logic instead of a for loop?

Or alternately, is there a clean way to reset sumOfVoltages to zero on each clock edge, without creating a race condition between the sequential and combinational logic? The target is a Xilinx Zynq FPGA, so I need synthesizable code, not just test bench.


texts: What is impedance 'masking' and how it is related to impedance 'matching'?

texts:
While reading ECSS-E-ST-20C Standard, I have encountered with a concept named 'impedance mask'. However, I could not find any detailed definition or explanation related to it.

In the corresponding article, it is said that :

"At the point of regulation, the impedance mask of a fully regulated bus, operating with one source shall be below the impedance mask shown in Figure 5‐1."

I would like to know what impedance masking is and how it is related to -if so- impedance matching.


texts: How and when can solar charge controllers be stacked together?

texts:
I run a small business selling solar charge controllers.
Often I have a problem with not having controllers rated high enough amp-wise.

I know that charge controllers can be stacked.
But can all be stacked?
Why? Why not?

Could even relatively simple ones like Chinese-no-name-brands be stacked for higher power?


texts: Impact of PCB thickness to an antenna design

texts:
I have an independent PCB design for a standard SMT-placed antenna. There are large ground planes on both side.

I can understand that the thickness is going to change the values of the matching network but I'm wondering if the thickness impacts the best optimization possible. In other words, is there an optimal PCB thickness for such kind of design? Or can I do as thick as I want? Is thinner or thicker better?


texts: Arduino: How to read sensor without common ground?

texts:
I want to analogRead() the voltage coming from a plasma cutter and serial print it.

The problem is that the serial communication between my laptop and Arduino are breaking as soon as i turn on the plasma cutter, and this is due to high nose on the ground rail (since the ground of the plasma cutter and the ground of Arduino are connected).

Is there a way to keep the grounds separated and be able to analogRead() the voltage?!


texts: How to determine if installed braking resistor is correctly sized

texts:
I have a braking resistor attached to a system with a large rotational inertia. Everything works fine in terms of startup, rundown and normal operation. I would, however, like to investigate whether I could in reality install a smaller breaking resistor.

I do acknowledge the math behind the initial dimensioning of a given system, but would like to measure how much is "left in the tank" of my breaking resistor. Both during start up, rundown, and especially during normal operation (in my case, the breaking resistor breaks the system for each and every cycle that the flyweights rotate due to a very specific control requirement). Is this possible? Measure amps? Temperature? Other things?


texts:
I searched in the "List of 7400 series integrated circuits" on Wikipedia for a open-collector OR-gate, but couldn't find any.

The list looks complete, so I assume there is no such chip in the 7400 series.

Why is there no open-collector OR-gate in the 7400 series?


texts:
I have a 24 pin IC chip that was soldered onto a tiny PCB. I was able to decap the chip and read the label, but I am not finding any information through Google.
Does anyone recognize this label that can help me narrow down either the part number or who the manufacturer is?
Image here: https://i.stack.imgur.com/IV8jx.jpg


texts: Does a package exist to carry out intense string manipulation in VHDL?

texts:
I am writing a VHDL code for a MIPS32. My idea is that for simulation purpose the testbench shall replace the instruction memory with a behavioral model which will read the program instructions from an ASCII file written as assembly instructions and convert them to 32 bit words and store them in a std_logic_vector. Thereafter, the input value from the program counter shall decide which of these values in the vector are output.

To this end the behavioral model shall have to read each line in the text file, determine if it contains an actual instruction e.g add, lw, sw e.t.c and then find out the operands given for that instruction and generate an equivalent 32 bit binary instruction. It shall also have to determine if the instruction is valid or has syntax error during this parsing and token generation process. For this purpose I shall require some serious string manipulation functions in VHDL. However, I don't see them in textio which only contains functions to read/write files and not play with string data type.


texts: What would happen if there is no ground in a PMOS inverter?

texts: I understand why when there is a ground you need a resistor or an NMOS but what if there were no ground at all and simply A goes high, B is 0, A goes low, current flows from VDD to B through the p channel. What's the reason this won't work? Forgive me but I'm relatively new to this.


texts:
I have an L298 H-Bridge, but I cannot, for the life of me, get it to work.
I have connected Vss to +5v, GND to ground, Input 2 to +5v, Enable A to +5v, Input 1 to ground, Vs to +5v, Output 2 to a motor terminal, Output 1 to the other motor terminal, and Current Sensing A to ground. The motor will not spin. I lack a volt meter at present (very short term, I usually do have one), so I tried tasting the wires. There is no electrical tang whatsoever (power supply does taste tangy, so that's not the problem!) This is the simplest circuit I could think of to test this thing and it will not work. Please help me!


texts: Damaged TPL7407LA Transistor Array (*Updated With Scope Testing Images*)

texts:
Application We have chosen the Texas Instruments TPL7407LA to drive groups of LEDs for an automotive lighting solution. The TPL7407LA inputs are connected to +12 VDC input signals to trigger the TPL7407LA’s outputs to turn on. These outputs are sinking current from groupings of automotive LEDs through the TPL7407LA.

INPUTS

BRAKE-IN +12VDC signal from vehicle's mechanical brake switch

TURN-IN +12VDC signal from vehicle's electronic flasher switch OR thermal hazard switch (depending which is enabled)

REVERSE-IN +12VDC signal from vehicle's mechanical reverse switch

PARK-IN +12VDC signal from vehicle's mechanical headlight switch

GND Vehicle's ground

COM Connected to 9V rail. 9V rail is also providing power to LED groupings.

OUTPUTS

BRAKE-PARK-LED-GND (O1/O2) LED common ground from brake light LED grouping

TURN-ON Connected to micrcontroller pin. Pullup resistor to 5V rail installed to preventing floating. 5V rail also connected to microcontroller power supply pin.
REVERSE-LED-GND LED common ground from reverse light LED grouping

BRAKE-PARK-LED-GND (O6) LED common ground from brake light LED grouping. Resistor inline used to dissipate power and ultimately lower LED grouping's brightness.

Application
We have chosen the Texas Instruments TPL7407LA to drive LEDs for an automotive lighting solution. The TPL7407LA inputs are connected to +12 VDC input signals to trigger the TPL7407LA’s outputs to turn on. These outputs are sinking current from groupings of automotive LEDs through the TPL7407LA.

Issue
When applying power to the TPL7407LA on the test bench, the TPL7407LA inputs and outputs work just as expected. Power from the test bench is supplied by a generic adjustable power supply set at 12.5 VDC in this scenario. The TPL7407LA sinks a maximum of approximately 1.0 A total when all inputs into the TPL7407LA are activated with the given +12 VDC inputs.

When installing our product on a vehicle, testing goes mostly as expected except for the scenario where more than one of the +12 VDC inputs into the TPL7407LA goes high. The vehicle provides the switched +12 VDC power input triggers via mechanical OEM  vehicle switches (brake light push button switch, turn signal electronic flasher, hazard thermal flasher, etc).

We notice that when multiple transistor are activated (typically from both the brake and the turn  +12 VDC signal inputs), then after the lines are deactivated  - upon the next activation of the lines, all outputs are activated no matter which singular transistor is activated. I believe this is a symptom of a damaged transistor array and we are unsure why this condition is occurring.

We have since ordered an automotive grade ULQ2003AQDRQ1 equivalent to see if this part is more resilient than the TPL7407LA for this application, but it is still very bizarre to us why this transistor array would be damaged in this type of environment.

TPL7407LA Datasheet: http://www.ti.com/lit/ds/symlink/tpl7407la.pdf

Update

We were able to purchase and make use of an oscilloscope and here were our findings:

TURN-IN Active (electronic flasher), No Diode On Input

TURN-IN Active (thermal flasher), No Diode On Input

TURN-IN Active (electronic flasher), Diode Added On Input

TURN-IN Active (thermal flasher), Diode Added On Input

TURN-IN Active (thermal flasher), BRAKE-IN Active, Diode Added On Input

PARK Active (Headlight Switch), Diode Added On Input


texts:
I'm planning on buying this audio amplifier for a project:

Everything about it is great, except for the fact that volume is controlled by two tact switches for volume up and down. I want to replace it with a wheel potentiometer, so I found this one.

Can this actually be done, and if so, how?


texts: UART Data Transfer Across Modular Boards

texts:
I am trying to create a modular system that uses UART to broadcast the same data to each microcontroller that gets added to the system. It could have 3 or it could have 10 modules added to the system.

Each PCB module is separated by no more than 1 inch of space (i.e most of the trace length will be running on PCB, the 1 inch is just the jack to make the connection from one PCB to the other). The total length of the system would be about 6ft.

What signal protocol would you suggest that could easily be designed onto a PCB system that is modular? RS485 uses twisted pair, which would be difficult to achieve on a PCB from what I can tell. I was considering hooking up all the Rx's of the "slave" microcontrollers to the Tx of the "master" microcontroller. This would allow instantaneous transmission to all of the slave microcontrollers as needed. I do not intend to use UART to communicate back.

What things should I consider in the design? Could one microcontroller output handle the inputs of up to 10-15 microcontrollers? Will I need to add signal boosters?

It is important to clarify that these devices will be modular, so virtually identical. I can't have some components on boards 5-6 that aren't on boards 7-8 for example. The speed I hope to transmit at is ideally 1Mbps.


texts: 'Inverted' voltage follower with an opamp

texts:
I'm trying to figure out how I can achieve an 'inverted' voltage follower.

That is if I'm feeding 1V I output -1V, if I feed 2V, -2V etc.

I'm only going for positive tension to negative, I have +15 and -15 rails.

I'm used to the TL072, but any opamp should do I guess.

Thank you!


texts:
I am working on 12V 30A smps that has only 1V output. I haven't got board's schematic but I found one same like mine (Schematic Link).

I measured high voltage capacitors (C2 and C3 on the schematic.) and bridge rectifier. They are working.
Also checked power switching transistor on board they seem fine. (Q1 and Q4 on the schematic.)
Checked PWM transistors on board. They also fine. (Q2 and Q3 on the schematic.)
I measured PWM IC's Vcc pin(pin12) and it is 2.4V.

I think, there could be a problem with D12 and D11 but not checked( because they are located under transformer).
Also on this link, the author says this circuit has the self-starting capability. After I read it, I become suspicious of C10 also.

Update1: I checked D12 and D11 both working. I read 110V DC over C10(Input 220V AC)

I attached pictures both front and back.
Please help me with this issue.
Thanks.


texts: Connect two boards together after removing Screw Terminals

texts:
An adapter board (to a card edge connector like PCI Express x1) is needed to be designed to for the breakout board below. This should involve replacing the board's screw terminals with some male rectangle connectors, with will be soldered to the adapter board as well.

However it seems that the screw terminal have a pitch of 3.5mm, but no rectangle connectors with a pitch of 3.5mm can be found (at least on Digi key). Do such connectors exists, or is there a better way to make the connections?


texts: Push-Push SIM card holder ESD protection required?

texts:
We are using this SIM card holder in one of our designs. The SIM card can be inserted into the slot and fixed/released by gently pushing it in. So the contacts are protected from touching.

Would you still consider adding the common ESD protection that is suggested in almost every related application note? I don't see the point in this case, but maybe I am missing something.

EDIT: I forgot to mention the fact, that the case of the device has to be opened to insert the SIM card. This normally happens only once or a few times during device life time. So ESD test equipment wouldn't even come near the card holder.


texts:
to every one. excuse my poor english.
may someone help me resolve this problem. What does RT level means?
A,B,C,D,W,X,Y and Z are register of n bit.
project the RT level of this function just using on adder.

Z=AW + BX + CY + DZ

update:  I have tried this.

According to the problem I should use just one multiplier and one adder.  I used multiplexer and decoder.


texts:
I'm reading the datasheet of a DAC (see page 6), and the "Output Noise Spectral Density" has units V / Hz^(1/2).

The Wikipedia article on noise spectral density however states that the noise spectral density has unit Watt / Hz.

Those two units are not equivalent. Why is there a discrepancy in the units?


texts: How to wire an old single phase AC brushed motor to be reversable

texts: I have searched several forums and found a lot of interesting stuff, but nothing yet that really applies to my situation.  I have an old Westinghouse FH motor 1 1/2HP single phase brushed AC motor.  There are four wires coming out of it.  The wires are labeled T1, T2, T3, and T4.  It is currently being used as a motor for a lathe.  The T1 and T2 wires are joined together.  And the T3 and T4 wires are joined together.  I have the leads connected to a drum switch, but no matter what polarity is provided the Motor always spins one direction CCW.  I don't see how reversing the polarity doesn't cause the direction to change.  It doesn't appear to have a capacitor.  I inherited the motor wired in this condition and have poked around on it a bit with swapping leads and other stuff but cant get it to run in any other configuration.  Any knowledge is appreciated.


texts: Measure the the impedance of a 'black box' under two symmetric frequencies

texts: I often see some equipment measure the impedance of a 'black box' with symmetric frequencies (the black box may be a complex high order network, but not only a simple one order). Such as if we want  to know the target circuits impedance under utility frequency, but in order to minimize the utility frequency interference, they may measure it at fu+5 and fu-5, then use their average as a result. I think there may exist some 'approximation'. Any one can give the math in detail?


texts: How to classify power electronics components in 2 main groups?

texts:
I'm working on preparing a course about power electronics, and with my basic search conclusions. I thought that if it's possible or acceptable to classify the power electronics components in 2 main groups.

Group1: Controlled/Uncontrolled rectifiers

Includes: Power Diode, Thyristor, GTO, TRIAC and DIAC.

Group2: Power Transistors

Includes: BJTs, MOSFETs and IGBTs.

My questions, is my dividing power electronics components in 2 main groups, acceptable; as:

Controlled/Uncontrolled rectifiers
Power Transistors

Also, I don't want to add more components, because I want to keep it simple and just studying the basic and most important things.

Any ideas?


texts:
Does a TLV1391 Need a Pull-up Resistor on its output to Provide a logic level output?

Datasheet: http://www.ti.com/lit/ds/symlink/tlv1391.pdf

Is it Open-drain Or Push-Pull?

Or is this just the wrong comparator for the job of providing a rail-to-rail 5v output?


texts: Why is 7:1 video serialization required?

texts:
I am trying to migrate portions of a ZYNQ design from one platform to another. Part of the project is based on Avnet's ALI3 touchscreen kit. From the docs:

  The 7-inch Zed Touch Display Kit includes a WVGA (800x480) LCD panel.
  To better understand the memory storage and bandwidth involved with
  this video resolution, let’s perform some calculations:

  Video Resolution:

  Active area = 800 x 480
  Frame rate = 60 Hz
  Pixel rate = 33.333333 MHz
  Pixel format = 24 bits RGB

  Video Storage Requirements:

  (800 x 480) pixels x 24 bits/pixel = 9.2 Mbits

  Video Bandwidth Requirements:

  (800 x 480) pixels x 24 bits/pixel x 60 frames/sec = 533 Mbits/sec

  The LCD panel has a serial LVDS interface. This means that the 24 bit parallel video interface must be serialized by a factor of
  7:1, before being transmitted on four LVDS differential pairs. A
  fifth LVDS differential pair is used to transmit the clock.

Notwithstanding the significant rounding down of the Video Bandwidth Requirements result, it is not obvious to me why the video "must" be serialized by the specific factor of 7:1.

Is this an industry standard video thing, or does 7:1 follow from the numbers given? What am I missing?


texts:
I was trying to understand this circuit under DC conditions, but can someone explain to me why the voltage across the capacitor is 8.1 V? I can't seem to understand. This voltage however does go down to 4.2 V if I increase the simulation speed and wait for couple of seconds but how can it start of it at 8.1 V. Am I missing something?

Here is the circuit I drawn using falstad simulator.


texts: Help with determining the open circuit voltage

texts:
Can someone go through why Vxy= -84mV?
Given the values off VB=180mv
                     R1=22ohms
                     R2=68ohms
                     R3=150 ohms.
Many thanks


texts: Proper soldering iron wattage for working with uP scale electronics?

texts: I need to solder some headers onto an Arduino shield - what's the recommended wattage for working on that scale?  I ask because the shield is already populated with ICs and I don't want to burn them out.


texts:
A wire of length 100cm is connected to a cell of emf 2V and negligible internal resistance. The resistance of the wire is 3Ω. The additional resistance required to produce a potential drop of 1 millivolt/m?

The answer is 57 ohms.Could someone explain?


texts:
Designing the power supply for an radiation detector, need to supply up to 1500V at 2 mA from mains (170 Vdc).

I've largely considered a flyback converter, but cannot find a flyback transformer with a gain of N=~16 (for a gain of 8 at 50% duty cycle) rated for 1500V at the output winding.

Looked into charge pumps/voltage multipliers some but not in depth yet.

Also just recently learned about CCFL inverter transformers, but still need some time to understand them better.

This project requires a small size and weight, so using a large transformer is not preferred.

What are other ways to step up voltage which I may look into?


texts: Effects of increasing current on external noise and SNR for analog transmission

texts:
This is a conceptual question about long analog signal transmission exposed to capacitive coupling and EMI noise as shown in below figures:

simulate this circuit – Schematic created using CircuitLab

In Figure1 the input impedance of the differential amplifier/instrumentation amplifier is 100Meg Ohm. And in Figure2 the input impedance of the differential amplifier/instrumentation amplifier is reduced to 100k Ohm by adding it as shunt.

I can say that since the source resistance is 1k, in Figure2 the DC error is larger which can be calibrated out as well.

But I'm wondering the what happens to the effect of the capacitance coupling(like 50Hz power supply leakage) and common mode EMI(coupling to the cable wires) when we insert that 100k shunt resistor as in Figure2. If we decrease the input resistance by adding that 100k the amount of current looping is increasing. Does that affect the SNR or provide better noise immunity for EMI or capacitive coupling?


texts:
I have designed a 32-bit adder using a hierarchical carry look-ahead design.  I'm now trying to run a spice simulation of this adder and am wondering what inputs will provide the best and worst-case delays.  I am unsure exactly how to determine what these inputs will be.
The design I have implemented looks something like this:
SPG blocks

4-way CLA Block

2-way CLA Block

all connected in a scheme like this:

Any help determining what the best and worst-case inputs would be extremely welcome.  Thank you.
Edit:
To clarify, I have a rough estimate for the delay along the critical path of the circuit I have designed.  What I am confused about is how different inputs would affect the delay.  Seeing as the design is just a bunch of blocks cascaded together I would think that any input would result in the same output.


texts: Amplifier output wattage and speaker wattage

texts: I have a Creative Inspire M2600. The Satellite speakers have broken and I have to use another 2 speakers. A note here says the RMS Value of Satellites is 6 W each. It is bit difficult to get speakers in my area. Can I use speakers with wattage more than 6W (10 - 15 W) without damaging the amplifier circuit ?


texts:
I am designing a 1kHz inverter in a push-pull configuration with KA3525 and IRF540N MOSFETs.

Input - 12V
Output - 110Vac - square wave filtered to sine wave
Power - 15W at 1000Hz

When I fire it up on load I get some noise on the gate pulses.

Also note that the gate pulse is only about 8V peak instead of 12V.
I have a feeling that the gate noise is causing the MOSFET to switch on and off very fast and cause circulating currents and heat up the MOSFETs.

I built this on a perf board to test before going for a proper PCB, but I don't think that should cause any problems at such a low frequency.
I have tried changing the IC but that did not change anything.
Gate resistance is 100 Ohm and gate to source pulldown resistance is 1k.
Any advice is appreciated.
I have tried to keep the layout as clean as possible.

edit-
Power loss:

Ipeak = 1.25A
Duty = 50%
I_rms = 1.25/sqrt(2) = 0.88
R_ds = 52mOhm
P_loss = 0.04W
Rthj_A = 62 Deg/W
T_rise = 2.5 Deg C (The MOSFET is overkill for this application)
Deadtime is about 40us. These waveforms are at max dutycycle.

I tried using shorter ground paths to eliminate external noise - no change.

No change - (blue is the new setting and yellow is the older setup.)

The negative pulse before was most likely due to improper setting of the base line.
The gate signal starts off clean but soon gets noisy. Check time stamps on the video.


texts: Multimeter experiment with 10A setting -- what happened?

texts:
I have a little experience with a multimeter, but I had never used the 10A setting.

I was messing around with an old stereo tuner that has four fuse-type lamps used to the light the dial.  They are each 6.3V, 250mA.  So I switched the cable and selector to 10A.  Then I put the probes on either side of one lamp, and all four of them went out!  Took the probes off and the lamps came back on.  Suddenly got a sick feeling, thinking I had fried it, but everything appears to work fine.

What happened?  Did I steal current from the lamps or short them?  The second-highest setting on my MM is 200mA, so I thought that 250mA would blow the fuse on the meter.  Hence my thinking that I should go to a higher setting.


texts: I want to know how to reduce an AC voltage of 175 V to 110 V using a resistor. The device I am using is 200 Watts, 110 V but the voltage from the source is 175 V. What value of resistor should I use to shed about 60 volts AC?


texts: First chip with 1000 or more transistors?

texts:
I am wondering what was the first chip ever with over 1000 transistors?

I already am aware of the following:

The Intel 4004 was the first commercially available single-chip
microprocessor and it was released in 1971 and had 2300 transistors.
The MP944 (designed for the Tomcat) is also considered the first
microprocessor and was designed in 1970, but largely kept secret so
the details are fairly uncertain (including transistor count), also
it wasn't a single-chip microprocessor, it was part of a chipset.
The TMS1000 was designed in 1971 and had 8000 transistors, but
wasn't comercially available until 1973.

Basically, I would like to know what came before these chips that had 1000 or more transistors?


texts: I have voltage signal which is 0V-1V square wave and i desire to see it with a LED which will be on when 1V comes and be of when 0V comes. I used a BC817 npn and a LED (min:3V, max3.5V, 20mA). I am not sure whether 1V is enough to activate BC817. This is the datasheet of BC817. If you share your idea, i will be happy. This is my circuit;


texts:
I am wanting to know,

At what voltage input do I need to produce between 40 and 44 kHz using two quartz crystal resonators?

Just looking to the volts required (oscilating) for AC input, also what is the formula to converting how much power you need, I guess to collect a sound file of this grade of resonance if you would call it that

Thanks


texts: MOSFET as a Switch - When is it in Saturation?

texts:
I have the following circuit hooked up on a breadboard.

I vary the gate voltage using a potentiometer. Here is what confuses me: according to wikipedia, the MOSFET is in saturation when V(GS) > V(TH) and V(DS) > V(GS) - V(TH).

If I slowly increase the gate voltage starting from 0, the MOSFET remains off. The LED starts conducting a small amount of current when the gate voltage is around 2.5V or so. The brightness stops increasing when the gate voltage reaches around 4V. There is no change in the brightness of the LED when the gate voltage is greater then 4V. Even if I increase the voltage rapidly from 4 to 12, the brightness of the LED remains unchanged.

I also monitor the Drain to Source voltage while I'm increasing the gate voltage. The drain to source voltage drops from 12V to close to 0V when the gate voltage is 4V or so. This is easy to understand: since R1 and R(DS) form a voltage divider and R1 is much larger than R(DS), most of the voltage is dropped on R1. In my measurements, around 10V is being dropped on R1 and the rest on the red LED (2V).

However, since V(DS) is now approximately 0, the condition V(DS) > V(GS) - V(TH) is not satisfied, is the MOSFET not in saturation? If this is the case, how would one design a circuit in which the MOSFET is in saturation?

Note that: R(DS) for IRF840 is 0.8 Ohms. V(TH) is between 2V and 4V. Vcc is 12V.

Here is the load line that I plotted of my circuit.

Now, from what I've gained from the answers here is that in order to operate the MOSFET as a switch, the operating point should be towards the left of the load line. Am I correct in my understanding?

And If one imposes the MOSFET characteristic curves, on the above graph, then the operating point would be in the so called "linear/triode" region. Infact, the switch should reach that region as quickly as possible in order to work efficiently. Do I get it or am I completely wrong?


texts: Thermal Paste on Cold Side of Peltier Freezing and not transferring "Heat", what gives?

texts:
I am running a peltier element, and on the cold side an aluminum heat sink to effectively spread out the cool surface to the maximum possible surface area.

I just bought this new thermal paste: Coolermaster Nano, and whenever it touches the cold side of the peltier (less than 10 Fahrenheit) it freezes into a rock, while thermal paste such as Arctic MX-4 does not.

I had a hunch that this freezing affect was causing problem as temperatures using the Coolermaster Nano thermal paste were far far higher than the Arctic MX-4 (16 Fahrenheit vs 0). So, I ended up removing all thermal paste and saw that even with no thermal paste between cold side and heat sink, the temperature was lower than with using Coolermaster Nano, at 10 Fahrenheit.

I was wondering if someone could explain this to me: are some thermal pastes not designed or suited for low temperatures? Is there something I should look out for when purchasing a thermal paste (carbon based?)


texts: Current problems with Buck-Boost Lipo loader evaluation board

texts:
recently I have found an interesting  MPPT Lipo charging IC with an integrated 3.3V LDO

So I have bought the Buck-Boost eval. Board(Datasheet) for few tests.

For my tests I used a 6.2V power supply, deactivated the LDO and connected a 3.7V Lipo to see how high the charging current is. With my Ampere meter I measured 30mA battery charging current which seems to be a little bit to low. So i put a 2.2Ohms resistor in series to the DC/DC inductor to measure the current of the inductor(schematic page 4 and 5).
The pic below shows the voltage across the resistor.  My calculations for the inductor current are

$$\Delta I=\frac{376mV}{2,2Ohm}=170mV$$

$$I_{DC}=\frac{1}{2}\Delta I=\frac{170mA}{2}=85mA$$

Now as you can see, my battery is charged with 30mA but my DCDC converter provides about 85mA. So how comes the difference and what happens with the remaining 50mA?

any ideas?


texts: Simulation of distortion from output inductor in class D amplifier, e.g. inductor non-linearities modelling

texts:
I'm new around here :)
So, I am doing a university project regarding the effects of the output filter of a self-oscillating class D amplifier for low frequency audio signals, e.g. subwoofers. The project is mainly simulation based.
The overall idea is to use a powder core inductor driven into semi-saturation. The pros of this is that you can choose a smaller inductor and that the amplitude dependent change in inductance due to saturation will help stabilize the feedback loop, thus enabling higher gain in the loop and lower distortion. The main con is that the distortion is expected to increase as the core is saturated. So the goal is overall to maintain distortion performance with a smaller inductor.
My question is which effects (aside from hysteresis) will affect the distortion generated from the output inductor? I am thinking polarization and hysteresis, but frankly my knowledge in magnetics is fairly superficial.
Next question is which software can I use to simulate this?
Effects such as the hysteresis loop is easy with a normal spice simulator, but I am unsure of other effects.
Any thoughts in general on the project?


texts:
I am using two timer interrupts:

TIMER0_OVF triggered every 12 ms, with its ISR only polling a pin, conditionally setting a flag and incrementing a value, so it should complete pretty quick
TIMER2_OVF triggered at a rate of 4 kHz, with its ISR only toggling an output pin to make a piezo speaker beep

Since the TIMER2_OVF interrupts are blocked for a short moment every 12 ms by the TIMER0_OVF ISR, the beep doesn't sound clean, it is overlayed by a "rrr...".

Adding ISR_NOBLOCK to the TIMER0_OVF ISR solves this and the beep sounds clean, and the rest still works fine.

However I am unsure if this is a valid use of ISR_NOBLOCK and if there is a more elegant way to generate a "clean" beep?

Reading about ISR_NOBLOCK in <avr/interrupt.h>: Interrupts leaves the impression to me that it is intended for rare cases where nested interrupts are needed and should be used with care.


texts:
I understand that PLLs can be used to modify the phase of a clock signal for various purposes. I have also heard that PLLs are often used to multiply clocks.

How can a PLL be used to multiply a clock?


texts: In this semi-ideal photodiode, what would be the physical interpretation of this current?

texts:
A real photodiode can be expressed as a circuit made of several ideal components, it looks something like this:

simulate this circuit – Schematic created using CircuitLab

I copied it from here and I added a voltage source in reverse bias because it's a photodiode.

Now, lets lump the current source, the capacitance, and the shunt resistance into a semi-ideal photodiode, it would look something like this

simulate this circuit

It was all well and good until I thought: "Wait a second... what is \$I_D\$?". It sounds simple until you consider that the series resistance is the resistance of the diode itself, of the crystal, the current flowing through that resistance is also flowing through the entire diode.

Perhaps this image will help:

I got it from this page.

As you can see, the terminals of the diode are directly connected to the voltage source, just like in the circuit diagram, and yet the voltage drop across the series resistance is not \$V_1\$. But the most pressing issue here, is what is \$I_D\$ in physical terms?.

I imagine all the available electrons flowing from one side of the crystal to the other, and that's \$I_O\$, right?.

I'm considering that \$I_D\$ is not physical just as the Shunt Resistance or the Junction Capacitance are not physical, but rather arise as properties of the crystal, but I don't know.

I'd also like to understand why the Series Resistance is not in parallel with all the other elements of the real diode.

Thanks for reading.


texts: Parasitic Capacitor current of an inductor

texts:
I am doing a double pulse test on SiC MOSFETs from 100-800 V and current from 20-80 A. The schematic is shown in figure (the values are not correct though).
In my first round of tests (Figure 2), I was getting rather oscillatory switch current for lower switch (measured with rogowski coil of 30 MHz bandwidth). When I replaced the inductor in circuit to an option with lower parasitic capacitance (had more distance between winding turns), the switch current curve improved considerably (Figure 1). This made me believe that a part of those oscillations were because of parasitic capacitance of the inductor.
To confirm this, I wanted to check the inductor current difference in both the situations, so I probed with another rogowski coil at the inductor with each inducor but IL wasn't really oscillatory and there was no difference in IL with either of the inductor. I repeated this with a current probe (50MHz) but still no difference. The figure with load current is not attached.
Is this a bandwidth issue? My ride time and fall time are ~50 ns


texts: Qucs simulation of quarter wave microstrip stub doesn't match ideal calculaton

texts:
I'm trying to simulate the resonant frequency and insertion loss of a 3 mm open stub on a 10 mm microstrip transmission line (50 Ω) on a FR-4 PCB (εr = 4.0, height = 0.1 mm).  I calculated that the microstrip width should be around 0.188 mm.
Ideally, it should resonate and produce a deep null in the insertion loss graph, exactly at 1/4 wavelength, which is \$ f = \frac{v}{4l} \$. And ideally, the speed of light is \$ \frac{c}{\sqrt{\epsilon_r}} \$, so it's \$ f = \frac{c}{4l\sqrt{\epsilon_r}} \$. Since \$ l= 3 \text{mm}, \epsilon_r = 4.0\$, we have f = 12.5 GHz.
Next, I setup the following simulation in Qucs.

I found the resonant frequency is approximately 14.2 GHz, almost 2 GHz above the ideal result.

I also tried to terminate the open end of the stub via a 10k resistor to ground, or to add a "microstrip tee juction" or "microstrip corner" between the main transmission line and the stub, but they don't have any significant effect on the simulation result.
Why does my Qucs simulation diverge from the ideal result? What are the higher order effects that Qucs is modeling here?


texts: Why does an oven plug burn out when all knobs are on full-setting?

texts:
I'm having serious trouble understanding this. If a component burns out when too much current is flowing through it, then how does turning on all stove-tops to their full setting burn out the oven's wall-plug?

Shouldn't turning on all the stove-tops increase resistance as you're adding more components to the circuit? Can someone explain (in simple terms) why this happens, also referring to mains supply and wall plugs and series/parallel phenomena. A diagram would help too I guess.


texts:
I have read the following paper (the link at the end), and I have not understand the schematic, which is included in the picture below. To be more specific, there is a feedback integrator, denoted by AMP2, which is said that:

to increase CMRR.
to be low pass filter.

The second point is clear, but the first point I have not understood well. Another thing: how does AMP1 work, if the negative feedback has a integrator circuit? I understand if it has a resistor which is given that it works as an amplifier, but how it will work, if it configured as "an amplifier with integrator circuit feedback"!

This is the link of the paper: http://www.biosemi.com/publications/artikel7.htm


texts: Is it possible to program a AT89S51 chip with a USB to TTL(UART) converter cable or Arduino?

texts:
Recently, a have a chance to get a AT89S52 chip, but I do not have a suitable programmer for it. I am new to microcontrollers, especially the MCS-51 series , but I've heard that MCS-51 is the "right way" to do microcontroller stuff, and I would like to try about learning it.

I have a USB to TTL (UART) converter (using the PL2303HX chip), an Arduino Uno board, and a Raspberry Pi board.

I've searched on the internet about how to program the chip, but most of the information and circuit diagram involves serial RS-232 port, or parallel printer port, or some other expensive commercial programmer products.
As I don't have a RS-232 or printer port on my computer, I can't follow these diagrams or tutorials.

I've discussed to a friend of mine that is familiar with 89C51, and he told me that according to the Atmel's datasheet of serial programming of the 89S51 chip, it's actually technically possible to program the chip with Arduino or Raspberry Pi, but he's not sure if it's doable with USB to TTL(UART) converter.

I haven't found any clear information of the protocol of the 89S51 serial programming (some say that it's SPI, but some say it's not), which maybe is because my lack of English ability or knowledge about electronics stuff, I'm like completely confused.

So, is it possible to actually program an AT89S51 chip with USB to TTL(UART) converter or some simple circuit with that?
If can't, is it possible to program it with an Arduino board or Raspberry Pi?
Has anyone ever done those things?

If the above is all not possible, then can I use a USB to RS-232 converter with a serial programmer like this?

(I get this diagram from here)

Thanks in advance.

P.S. A lot of the commercial products are not usable for me because I don't have a Windows computer anywhere within my reach.


texts: Do I really need a flyback diode when using a power mosfet?

texts:
I am using one of these IRF1404 Power Mosfet and looking at the datasheet I see that the continuous source current (in the Source-Drain ratings section) is rated at 202A!!

I will be using it to drive a wheelchair motor. Do I still need a flyback diode? I mean the internal diode should be more than enough to handle current when the motor is turned off etc?

Edit:
I will post the datasheet link here: http://www.irf.com/product-info/datasheets/data/irf1404.pdf

Edit: diagram


texts: How to wire a system for Nios 2 in Qsys?

texts:
I've managed to reduce the number of errors but I still have some:

Error: System.nios2: Reset slave sram_0.avalon_slave_0 not connected to instruction_master.
Error: System.nios2: Exception slave sram_0.avalon_slave_0 not connected to instruction_master.
Warning: System.leds: leds.avalon_slave_0 must be connected to an Avalon-MM master
Warning: System.sram: sram.conduit_end must be exported, or connected to a matching conduit.
Warning: System.jtag_uart_0: Interrupt sender jtag_uart_0.irq is not connected to an interrupt receiver

Can you please tell me how to handle the errors? The background is these questions:

https://electronics.stackexchange.com/questions/80516/how-to-resolve-these-errors-in-qsys

How to assign clock/reset to sram in Quartus?

How to upgrade a Quartus II project from SOPC to QSys?

Can't synthesize my VHDL in Qsys

It is unclear why I'm getting this message:

Error: System.nios2: Reset slave sram_0.avalon_slave_0 not connected to instruction_master.

Since it seems that the connection is actually there.


texts: Question About Arbitrary Sequence Counter and Changing the Sequence

texts:
hope you are all well. I have an homework which wants from me something like this:

    Design a counter that counts 0 4 6 8 12 14 0... (mod6) and when to counter shows 14 it is going to stop and wait
for 3 minutes. After 3 minutes counter is going to count 0 1 2 3 4.... 14 15 0 ...
There is going to be 6.667 seconds between every count. (You need to use JK Flip Flops to do so.)

So far I tried to find what each J and K input of the Flip Flops should be in order to achieve the sequence. I made table which looks something like this below:

I only wrote 6 rows because I am tasked to show only 6 numbers. Q' represents the configuration of Q outputs for numbers 0 4 6 8 12 14. J(0:3) and K(0:3) represents the configuration of the J and K inputs to change the corresponding Q outputs in each state.

I then drew Karnaugh Maps to find the equivalent logic expressions for the J and K inputs. Here are what I have come up with:

J3 = Q2 + Q1.Q0
K3 = 1
J2 = Q1'.Q0 + Q1.Q0'
K2 = 0
J1 = Q2.Q0
K1 = Q0
J0 = 0
K0 = 1

Then I designed the circuit. The fact that J0 = 0 made me sceptic about the functionality of my circuit; however I still gave it a chance (I checked my table and my Karnaugh maps twice, if I haven't overlooked any detail the tablo and Karnaugh's must be correct.) I simulated my circuit but counter does not increases, it is stuck at 0. I believe that it is because of the jact that J0 is 0. But this is what I found with the calculations I done. Is there some point I am missing? Or should I try a different approach?

And I want to ask something more. I am assuming I completed this part. What I should I do next to change the sequence of the counter back to normal (0-1-2-3-4)?


texts:
I have an issue related to Baker Clamp application for PNP Transistor. I know how to implement the Baker Clamp for NPN Transistor. However I do not know how to do it for PNP. So could anyone can suggest me a schematic?

Secondly, can the Baker Clamp reduce the turn-off time of PNP transistor?

Thank you very much in advance.


texts: which is the difference between magnetic flux and magnetic field

texts:
greeting

confuses me  this definition of electromagnetic induction  .

Electromagnetic induction,
which states that whenever a conductor cuts through magnetic lines of
flux, a voltage is induced into the conductor.

Why flux rather than magnetic field flux has a different meaning


texts:
After looking at the schematic for this particular darlington transistor (see picture pasted below) I had some questions about basic functionality.

First, the diode at the top right of the picture has its cathode leading towards the postivie Vcc voltage supply, wouldn't this reverse bias the diode and prevent any current from flowing even when current is applied to the base of the transistors?

Second, the output is not in series with the supply voltage so when the the transistors are switched on, what prevents the current from just following the path from directly from Vcc to ground (emitter)?? I guess I just don't understand how tying a load to the output terminal would do anything if the supply voltage has a direct path to ground like that.


texts: One button circuit with thyristor, controling power suply

texts:
Please forgive my lack of knowlige.
I need to make circuit with one button(normaly OFF, ON while pressing) using thyristor.
This circuit will be connecting and disconnecting raspberry pi and bunch of LEDs(16x16 ws2812b panel) from power suply.
I was imagining something like: pressing button first time: supply is connected, pressing button for second time: supply is disconnected and so on.
I cant use switch instead( it has to be a circuit).
I want one other led to indicate if its ON or OFF.
I also dont know what values should i use for components.
I will probably use 5V 10A supply but I dont know if resistors and thyristor survive that.
Here is my wild guess:

I will appreciate any help.
It shouldnt be mutch more comlicated than this(i found some alternatives with 2 buttons but i will prefere with 1 button).
I am also sorry if missed something similar and this is a duplicate.