texts: How to improve this microphone phantom power supply to have better SNR?

texts:
I built this power supply for my Schoeps CMT30F vintage microphones:

It works, but it's not the best I can expect in terms of SNR.

What would do you to ensure the SNR is the best possible?

Use 0,1% tolerance 680 Ohm resistors instead of the 1% resistors I used?
Would this 0,1% one (here in 1k, but I'll find a 680 one) improve something?

1bis. Use 0,1% tolerance 10k resistors as well (right part of schematics)?

Match two 680 Ohm resistors by buying many of them, so that they have exactly same value?
Could this be useful since it's balanced audio signal with interference reduction?
As the output of "2" and "3" are in phase opposition (180°), when subtracting them, we get the signal only and noise cancellates. To have this, is it important that the 2 resistors have exactly the same value?
Buy many 100 µF capacitors and find a pair that matches ESR and capacitance?
Sidenote: I looked on Farnell, but I couldn't find a "matched pair of capacitors". Do retailers sell "matched pairs" of such capacitors? (could be useful for audio)
Change the capacitor type to use? I used electrolytic caps 100 µF, 50V
Use a more complex schematics? (I saw other microphone phantom power supply schematics on internet with many many components, Zener diodes, etc.!)
Something else?


texts: Calculating the number of turns for my inductor

texts:
so i've calculated that I need an inductance of 0.150mH for my inductor. However, I'm trying to figure out the number of turns I need for it. #
I've got an answer of 24 turns but this doesn't feel right to me. Could someone double check my calculations?

below is the datasheet for the toroid I used as well as the graph(from the datasheet) I used.DATASHEET FOR TOROID
***TOROID datasheet (using 3C90)

If anyone is interested what I was following for my calculations.

Many thanks!


texts: A basic question about load balancing and power factor correction in three-phase systems

texts:
I know basically about phasor representation of line voltages and active reactive power concepts in three-phase systems.

But what I'm wondering is the reasons of two things I hear a lot.

1-) What is the main reason for balancing the loads in a three-phase system. Maybe for a three-phase induction motor the reason is more clear. But imagine a house power entry with three line voltages as phase A, phase B and phase C; one neutral and one earth into the building. As far as I know the loads on all phases must be somehow balanced.

Does that mean they should carry same amount of currents? Does that also mean their power factors should also be close? What is the real reason behind all these balancing?

2-) I also hear about PF compensation with capacitors. What is the main reason to make the power factor close to 1? Why is the power factor adjusted?


texts: USB powered IR emitter for night vision webcam

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I had a spare webcam which i turned it into a night vision camera. I have to use IR emitters to be able to see with it ( http://www.instructables.com/id/Night-Vision-Webcam/?ALLSTEPS ) and i don't want to use a tv remote for that. I was wondering if i could power the emitters (4 emitters actually) with the usb port and cable of the webcam? Could you tell me how or give me a suggestion or a link or something? Thanks!

(Btw, i can do some basic soldering and stuff too)


texts: Emulating an electret microphone with a DAC circuit

texts:
Good day,

I'm currently getting into DIY electronics and Netduino programming and there's this one personal project that I want to do but I'm hesitant because of lack of information. Basically this is what I want to do:

Use a mobile phone, in my case an Android tablet (Galaxy Tab) and maybe a WP7 handset in the future, to communicate with a Netduino via a makeshift serial connection using the audio (headphone) port and a custom app. I have found a circuit that I could use and modify for my needs so this part can be considered solved... apart from the app, that is, but that's a different story.
So with that, I also wish to be able to transmit information to the Galaxy Tab via the tablet's microphone input by designing a DAC circuit to emulate an electret mic. Is this even possible? I am no electrical engineer but I do have electronics know-how (although that's with regards to high-voltages) because of my line of work but I have little experience working with digital/analog conversion circuits. I don't want to fry my Galaxy Tab's innards because of assumptions so I've been searching for information around the net to no avail. I hope someone can point me to the right direction. Will really appreciate it!

Thanks a bunch,

Dan


texts: How do I `chain` transistors so that the first transistor `switches` on the second

texts:
I am trying to get more hands-on experience with transistors. I have a simple switch working:

I wanted to find out how to change the circuit so that a second transistor would be switched on by the first one, driving another LED.

I tried connecting the emitter of Q1 to the base of Q2 with and without a current limiting resistor but with this schema, nothing works at all:

I have tried a variety of different transistors too, including S8050.


texts: How good is the idea to place mostly entire copper layer up and down the functional layers in PCB?

texts:
My PCB contains PWM - driven LEDs. The specs says the internal oscillator runs at about 5.6 MHz, with currents of 30 mA per line and there are 56 lines in total. As the indicators are very large (10 cm high), it may be up till 20 cm or about tracks leading from the output of the chip to the indicator.
I am not sure how much it is a problem. But as my design fits into two PCB layers, I have an idea to place two more layers on the top and bottom of the PCB, making all tracks shielded this way. The three closely related question are:

Are the extra layers needed and would it make any sense. If not, probably the other two sub-questions are not required to be answered.
Should the extra layers be connected to the ground or left hanging?
Can I connect one to the ground and another to +VCC and use them to deliver power? 56 lines drawing 30 mA each means there is 1680 mA load the power bus. There are 4 pins on the LED block that are spread evenly around and should handle the load together.


texts: Separating DC Cables and Communication Cables in the same trunking (Solar Installation)

texts:
There is an upcoming project which requires me to install the communication cables together with the DC cables for the PV modules. Each of the PV modules will have an additional communication device added for safety purposes. As we are using a covered GI trunking to lay the DC cables along the rooftop, the supplier has suggested to lay the rs485 cables in the GI conduit (not GI flexible conduit) and to be placed inside the same trunking used for the DC cables. There will be a total 5 communication cables and these 5 must be individually separated as well into 5 GI conduits which is suggested by the supplier. The reason for the use of GI conduit is to prevent the DC cables from interfering with the communication cable and the few communication cables from interfering each other as well (crosstalk).
This is practical but the cost is pretty high, would like to ask if anyone has a better suggestion to isolate the comm cable and the DC cable while having both placed into the same trunking. And if not, any other cost-efficient ways to go about this?


texts: Why can closing a circuit breaker into a short circuit result in an arc flash?

texts:
NFPA 70E 130.6(M) states:
After a circuit is de-energized by the automatic operation of a circuit protective device, the circuit shall not be manually re-energized until it has been determined that the equipment and circuit can be safely energized.

29 CFR 1910.334(b)(2) states:
After a circuit is deenergized by a circuit protective device, the circuit may not be manually reenergized until it has been determined that the equipment and circuit can be safely energized.

My first thought would be, "If the breaker is rated for the available short circuit current, I should be able to close it into a short-circuit without a problem." However, I've heard of cases where it seems that an appropriately-rated molded-case breaker was closed into a short-circuit, which resulted in an arc starting inside the breaker, leading to arc flash injuries.

What is the mechanism of such a malfunction? Age and abuse are possible contributing factors.  Is there more to it?  Is there some aspect of the construction of a molded-case circuit breaker that can result in an arc flash when closed into a short circuit, even if it was a brand new breaker of appropriate rating?


texts: I'm having trouble understanding the logic behind a PID controller used for temperature control. If I were to implement it with a SSR and an Arduino, for example, my aim is to have the PID value be zero, is that correct? Anything different than zero and the relay would activate and make the heating element get hot until the error reaches zero? Is it possible to calculate how much time the relay needs to be activated to reach the temperature or is it better to activate it on really small intervals and check the error?


texts: LEDs flash at the same time and not one at a time

texts:
As you can see on the illustration below, I have a voltage supply (a keyboard made of two piezo elements) with two terminals. Each one drives one LED, but since I've added a buzzer in parallel with both LED, my circuit drives the LEDs at the same time

Do you have any idea on how I could make flash one LED at a time using just one buzzer?
Thanks in advance ;)


texts: How to infer these parameter values from the datasheet for this transistor?

texts:
The circuit below depicts a continuous saturation state and uses 2N3904:

From the above simulation the base current is 11mA, collector current is 14mA and the power is 11mW.

I'm trying to compare this circuit currents and voltages to the max datasheet parameters to ensure the parameters are within datasheet safe range. But stuck with two parameters. Regarding power: in my case 11mW and datasheet states Rja = 200°C/W. So 11mW would correspond only a 2°C increase in junction temperature. So if I'm not wrong powerwise there is no issue. The collector current 14mA is also less than the max continuous rating 200mA.

But I couldn't find the max base-collector voltage(VBC) and max base current in the datasheet. Is there a way to infer these?


texts: Video entry sender has only one signal line for Microphone + Speaker

texts:
I am planning on connecting an off-the-shelf door camera (audio/video sender) to my project.

I've posted an extract from their manual here

The video output is composite which I can support, but only one audio signal is provided by the door camera. I expected two; output from the mic and an input for the speaker. My project has two signals - line in and line out.

How would I connect a single audio line like this to my line in/line out?


texts: impedance matching to mechanical sensors?

texts:
I am working with 40 sensors and almost all the sensors are mechanical. I have some potentiometers converting mechanical displacement into voltage but the resistance of the voltage source is changing dynamically in field. The potentiometers I am using are in the range of 10K to 10M ohm.

It seems that I can't place a passive impedance matching circuit there so anybody tell me what is effective way of impedance matching in this type of case?


texts:
I'm PhD student in CAD/EDA field. My research topic covers VLSI standard cell's layout design and detailed routing. To make my research results more reliable, I would like to test proposed algorithm with some recognizable benchmarks/cell libraries. But, suddenly, I'm not able to find anything of use, except for NanGate FreePDK15.

So, are there any publicly available standard cell library benchmarks, which contain transistor level description of various gates (like aoi222, nand44, fad1)?


texts: Is it possible to securely connect 20AWG wire to CR2 battery terminals?

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I’m trying to securely connect a positive and negative 20 AWG thickness wire to each terminal of a CR2 battery.

From what I understand, they don’t make terminal connectors for these types of batteries as the negative end is flat and positive end has a nub like most small consumer batteries.

For the time being, I am wrapping electrical tape around each end of the battery to hold the wires in place.

I am aware that this is only a temporary solution and would like something that would be much more secure.

Any suggestions/tips would be greatly appreciated!


texts: I have a 1S Lipo battery, and would like to drive a micro brushless motor at upwards of 6 Amps. I'm trying to design the h-bridges using 2 N channel mosfets each, but ran into the issue of finding a high-side/low-side driver that will drive mosfets at low voltages. Am I just completely missing the point here, or does such a product exist?


texts: What circuit I need to lower 20MHz 3.3-0V square wave to 0.01-0V square wave for very low load driving?

texts: My FPGA board outputs the 3.3-0V square wave at 20MHz. I need to convert it to 0.01-0V square wave to drive the very low load (0.1 Ohm). What kind of circuit I need and Is there anything I need to be careful?


texts: What changes when you modify gyro/accelerometer/magnetometer range?

texts:
In hobby-grade MEMS IMUs and MARGS such as MPU-6050, you can change certain registers on the chip and modify the sensor's range. For example 2 g or 8 g for an accelerometer. Of course, because the ADC resolution doesn't change, you get lower maximum accuracy for higher ranges.

What exactly changes when you modify the range registers? Obviously the mechanical and physical structure of the sensor can't change, but I don't know what enables it to measure higher or lower values.


texts: SPI: Can MOSI and MISO line be shorted for data verification

texts: I have developed driver for SPI master which can run at maximum bit rate of 20MHz, but I don't have any SPI slave which can reach 20 MHz. For data verification I have shorted both MOSI and MISO pins and comparing data received with the data which I have transmitted. I just want to ask if this test case will be sufficient enough for data verification at 20 MHz? Also for testing chip select pin, I have tested it with Oscilloscope.


texts:
In terms of drain and source current P-channel JFET is similar to which BJT ? npn or pnp?

kindly tell me about BJT's and FET's relation?


texts: Why do 16340 Li-ion batteries have low volumetric capacity?

texts:
I wonder why currently available RCR-123 aka 16340 Li-ion cells have such low capacity for their volume. The best ones have 800 mAh.

When you do the math and scale down from 18650 cells that can have 3200 to 3400 mAh, you get 1320 to 1400 mAh. Even old 2600 mAh cells would be 1000 mAh at 16340 size.

This doesn't agree with cells you can get, protected or not. We can assume that - due to similar diameter - side wall thickness doesn't skew results significantly, nor would the cap volume, as it's negligible.


texts:
I have a nooby question:
Is it within the range of tolerance to drive a TFT (car electronics 4.3 inch low cost type) which runs on 4.2V internally (12V DCDC-converted to 4.2V by an 'XL1509 adjustable output') by 5V from my Raspberry Pi directly without frying it?

The converter handles 5V as direct input quite well, but if possible I would like to get rid of the inefficiency of the converter and the additional heat. As a last option I would think about replacing the converter by a diode, which probably results in less energy loss...

Thanks for all advice!


texts: New to electronics...so learning as I go. I have a 12vDC 1.5amp power supply that I will be using to power a 12vDC .30a computer fan. I want to use a potentiometer to adjust the speed of the fan but I'm not sure how I go about determining which potentiometer values I need. I've looked at a few of the formulas and calculators online but they're a bit over my head right now.


texts:
I am using a 2A Buck regulator from TI (https://www.ti.com/lit/ds/symlink/tps562202s.pdf?ts=1622136131438&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS562202S), with max input voltage of 17 V. I would like to add some overvoltage protection, in case a higher voltage is connected (> 17 V). I would also like to have some reverse voltage protection if possible. The standard input voltage for the circuit will be 12 V.

Would a circuit like shown above work for this purpose? The TVS diode and Schottky would have a clamping/reverse voltage somewhere between 16-18 V. I have seen more complex circuits involving SRCs and MOSFETs, but I'd like to keep it simple.
UPDATE: After further reading, I found several sources that might help in answering this question. I believe putting a Schottky diode in parallel with the TVS for reverse-voltage protection isn't the best choice, better to put a Schottky in series with the PTC, like shown here: Help designing an inverse polarity and overload (crowbar) protection circuit
Other sources that might be of interest:

Is a Schottky diode appropriate for reverse polarity protection?
'Voltage Fuse' or better


texts: In KiCAD - is it possible to have two nested rings of copper fill?

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I'm using KiCAD to create a nested series of PCB rings - each two layer with copper fill on the front and back.  The problem is when I add edge cuts defining the inner and outer edges of the outer ring, it removes the copper fill from the center area where I'm going to nest the inner ring.

Is there a way to add a nested copper fill area within the inside diameter of the outer ring and still maintain the edge clearance of the copper fill that the fab requires (ie, using the edge cuts layer, KiCAD automatically create a standoff so the copper doesn't go all the way to the edge of the cut, thus avoiding possible shorts).


texts: Can I use serial communication for audio amplifier remote turn on?

texts:
I have a cheap Chinese tablet/GPS/dash-cam in my car. The problem is that I can't hear driving instructions on GPS as the volume is too low. I don't want any external wires for additional speakers and this device doesn't have Bluetooth.

So, I bought PAM8403 small audio amplifier but it doesn't support automatic turn-on via audio input and I don't want this amplifer to be constantly powered when my tablet is turned off. Tablet's circuit board has "free terminals" ED-Rx and ED-Tx.

Can I safely use Rx or Tx as BASE for NPN transistor to remote start amplifier? Or could I directly power amplifier from Rx/Tx (3.3V), amplifier's operation voltage is 2.5-5.5V.


texts: It's an antenna with LC rasonant circuit. What should I consider this circuit? Is it an AC source, inductor and capacitor all parallel with each other or Is it an AC source, inductor and capacitor all in series with each other?


texts: Potential problems if I only ground one probe of my oscilloscope?

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I have found that when I'm probing a circuit using more than one oscilloscope probe, clipping the ground of one of the probes to the board seems sufficient to give me stable readings from all of the probes. And this also reduces the chance of accidentally connecting two different voltage potentials through the ground clips of different probes.

I realize that the longer "ground loop" for the probes not directly connected to the circuit can affect some of the readings, but how? And at what acquisition speed does it become a concern? (I vaguely remember the original, analog scope that I was trained on in the military some 30 years ago only having one ground lead, separate from the probes. But I have no idea how "fast" that scope was.)


texts: STM32 HAL I2C always sends 0xFF as first byte when responding to master using HAL_I2C_Slave_Transmit

texts:
I have an STM32G4 using the HAL function HAL_I2C_Slave_Transmit to respond with some data when requested by a master on the I2C bus. In the image below you can see the device sends 0xFF followed by the actual data it was meant to send (the data I am expecting is 0x11 0x01 0x00).

I have tried this with the minimal test program below so I don't believe it's anything to do with my full program having a delay:
/* USER CODE BEGIN 2 */
  typedef struct {
      char id;
      char payload[2];
  } I2C_RSP_TO_MASTER;
  I2C_RSP_TO_MASTER  I2C_response;

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    I2C_response.id = 0x11;
    I2C_response.payload[0] = 0x01;
    I2C_response.payload[1] = 0x00;

    HAL_I2C_Slave_Transmit(&hi2c2, (uint8_t*) &I2C_response, 3, 10);

    while (HAL_I2C_GetState(&hi2c2) != HAL_I2C_STATE_READY) {
      }
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */

For my current testing the master is an Arduino Nano using the Arduino function:
Wire.requestFrom(ADDR, 4);

I am requesting 4 bytes because the initial byte is garbage (0xFF). The STM32 is clocked at 128MHz so I don't believe it is possible that it is running too slowly to respond to the first byte - I think it may be a problem with the HAL! Is there a way to fix this problem?


texts:
I saw a very strange design of phono stage in Rodec MX180 consoles. 3 generations of those mixers (mk1, mk2 and mk3) have this phono preamp on board!

They have an input filter with 1nF cap then 220 pF cap - the total input capacitance is 1220 pF, that's really a lot. Is it a mistake in the design? I made LTspice simulation with a cartridge model and the response is definitely not flat. Usually input capacitance in phono stages is like around 100-300 pF, sometimes they don't use input capacitors at all! My question is - am i missing something. If not then how it's possible they produced a lot of this gear without noticing?


texts:
I built 2 14S6P battery packs which each have a BMS with a separate port for charging. I am wondering if I should wire a separate charger to each battery or can I create a parallel charging cable which would connect the 1 charger to both batteries?
What are the pros and cons?


texts: Prevent JK-FF Counter to start from beginning after reaching maximum

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how can I prevent a counter based on JK-FF (up-counter, up/down-counter) from jumping back to zero after it reached the maximum.

For Up-Counter:
It should count up until it reaches maximum and stay there until I reset the JKFF.

For Up/Down-Counter
It should count up until it reaches maximum and stay there until I reset the JKFF.
It should count down until it reaches minimum and stay there until I reset the JKFF.

Thanks for your help!


texts: Program AVR EEPROM directly from C source

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When you include the following code in an AVR C source, you can apparently directly program the fuses, without the need for an extra command or .hex file:
#include <avr/io.h>

FUSES = {
        .low =          LFUSE_DEFAULT ,
        .high =         HFUSE_DEFAULT ,
        .extended =     EFUSE_DEFAULT ,
};

Is there a similar trick to program values in EEPROM?
I have checked /usr/lib/avr/include/avr/fuse.h where I can find some comments about a macro, but I can't find a similar comment in /usr/lib/avr/include/avr/eeprom.h and interpreting the preprocessor stuff is a bit out of my league.
It would be really handy if I could include default EEPROM values in the C source code. Anyone know how to accomplish that?
edit1:
This FUSES trick is only executed at ISP-time, not at RUN-time. So there are no fuses being programmed in the resulting assembly code in the controller. Instead the programmer automatically cycles through an extra FUSES programming cycle.
edit2:
I use the avr-gcc and avrdude toolchain on Linux.


texts: the PiFace is advertised as the shield "connecting the Raspberry Pi to the real world" and they claim that this includes things like temperature sensors. I know how to read the temperature using an AVR microcontroller and the A/D converter, but I cannot see that such a converter is present on the PiFace. Am I missing something (I'm not a native english speaker, it may actually be the case that I don't understand what I've found). The inputs I found seem to be just capable of being switched on and off, and the examples I've seen are also restricted in that sense.


texts: How to make logic gate combination using switches and bulbs?

texts:
X         Y         F
  0         0         1
  0         1         0
  1         0         0
  1         1         1

Using min terms F(x,y) = X'Y'+ XY

The logic circuit for F needs And, Or, Not gates.

Using only switch and bulb,

So logic circuit for F will be-

So how to make F using the switch-bulb AND , OR, NOT gates.


texts:
I want to design a low power circuit with stm32l micro and LoRa Module as its radio to send a sensor data to a gateway. The circuit is powered with a non rechargeable battery.

My problem is about its power circuit. I know that in order to decrease power consumption I have to decrease the quiescent current.

I want to turn on the circuit by turning on an LDO STLQ020 once a minute, and MCU in sleep mode is powered with a backup battery.

I  want to know if turning on and off the LDO is harmful for hardware?


texts:
I have a old PDA board, it is not working, but I want to see the content of memory chip for this board, as far as I know there [might be] some interesting software on it, but the PCB is dead, so I thought, maybe I can re-solder the memory chip to USB compatible board (or any other way) to access the contents.

Is it possible, and maybe someone knows compatible device.

The chip is 63 BGA NAND flash K9F1208R0C-JIBO.
Here's the datasheet for it: http://pdf.datasheetarchive.com/indexerfiles/Datasheets-IS86/DSAH00528626.pdf


texts: Converting a battery powered pocket heater into a portable 5V power source

texts:
I bought the attached pocket heater. The elevated element seems to be heater spirals so the red cables seem to lead to short circuit - capable circuitry.

Background: So I built this tight case for my ipod 5G nano and connected it to my suit to not be forced to buy a GoPro or something like that but still have a nice video documentation of my sports activities. Tight means, once the ipod is in place it has almost no space to move in the flat plane. But there is space parallel to it, I found the heater to have optimal dimensions for this. So the video recording using the ipod lasts about 1:39 hours continuously. Then the battery charge is gone. But also in the operating system if being connected to a power source after 1:39 hours recording stops. So my goal is to have a portable power source connected to the ipod via usb-cable. Then each 1:39 hours the alarm of my mobile phone goes off reminding me to get the ipod out and press record again, which is doable. But I also wrote to apple for them to include such a feature in the next firmware update. So this is what the following is for. The following shows the plug. I need to bend it at the dashed line for it to fit inside the case. I have not found another (flat) plug yet, and the current one contains a pcb which won't let me bend it I presume. So I need to find another way.

By attaching a USB-cable the device is being charged. The following image seems to show the battery:

My goal is to use it as a power source for 5V USB. Either by being able to reverse the current flow, ie by pressing the button on the lower left in the following image. It should supply 5V, 500mA at the USB-connection...

... or by drilling holes into the upper plastic being seen here...

... to apply an USB-Plug or Socket externally.

How would you do it given the current pictures, where would you connect what and why? What would you measure where?

My ideas are to replace the red wires, connect one of the wires to the switch for it to only connect to the USB-cable when not charging. Problem is: There is not 5V but something around 3.5Volts in between. Also in how far do I need to take the short-circuit-proof circuitry into account.


texts: MOSFET turn on/off curves misunderstanding

texts:
The MOSFET's turn on/off curves have a part where the drain current and the voltage across Drain-Source are not zero. That's where most of the switching dissipation happens.

The problem I have is in T1-T2 section (see figure below). If the source voltage (Vin) is constant and the current is flowing through the load (ILOAD), how can we still have Vin across Vds?

We shouldn't have the same current flowing through the load when Vds=0 and Vds=Vin ...

Can you please explain what am I missing?

Does this logic differ with a different source type, a different load type ... What are the parameters I need to properly predict the MOSFET's behavior when turning on/off, other than the gate driving?

Image taken from a Vishay application note


texts:
I need to write 16x16 bit data to block memory. I am using RS232 to send data. To get 16 bit data, I send 2x8bit. Now, how can I write my data to the memory?

I have a write signal and 16 bit input but I do not know what I shoul do next.

Thanks in advance.


texts: 56 to 15 Volts Regulator for DC Motor Driving

texts:
I have a project about controlling a dc motor with a very low cost design.I drew a quick schematic for you to understand the circuit better(Capacitors,2576 inductance,bootstrap cap,diode etc. is not included ,+15VDC is the output of the regulator );

In order to drive the motor(42 VDC) our DC Bus voltage is 56 Volts.For driving mosfets and get 5 Volts for microcontroller I need to convert 56 volts to 15 volts with low cost.I plan to use LM2576HVT,for driving I choosed IR2106 that can give 200mA maximum output current.I also planned to use IRF3710 Mosfets.It has total gate charge 130nC and G-S charge 26nC.I planned to drive gate with 100 ohm resistor in order to reduce driving current and reduce the power loss along the lm2576.

Driving with low current will cause slower turn-on but if I change the High-Low Side driver and drive the gate with 1A it will be more difficult to tolerate the power loss the regulator faces.(For example: Using IR2110,15 ohm gate resistance)

Now we have 150mA for driving and we can assume that 50mA current consumption will come from other circuits,total of 200mA.

Regulator has % 83 efficiency at 56 V and 200mA, thereforethe power loss= ((15*0,2)/0.83)-(15*0,2)=0,61 watts right ? ( Calculating Power Loss in Switching Power Regulator?)

If I use high driving current and 1A average at the output of the regulator regulator power loss would be  = ((15*1)/0.88)-(15*1)=2 watts..

If so should I use driver with high output current capability and drive mosfets with high current ?

Also  I wonder to adding a series resistor to input of the regulator can help ?

Also should I add maximum voltage protection  for regulator?  (2576hvt can handle maximum 60 volts input)

Thank you..


texts:
I'm looking for a 25MHz crystal oscillator for the STM32F411. I spent a couple hours today going through the AN2867 Oscillator design guide from ST but still having trouble understanding it and finding something that fits the required parameters. There are suggested LSE oscillator part numbers in the application notes but nothing for the HSE oscillators. I posted a picture of some specs below but when I filter for 25MHZ oscillators on Digikey, I cannot find filter options shown in the picture below.

Can someone suggest a 25MHz crystal oscillator, or a better way to filter/find parts on digikey/mouser/etc that would fit these specs?


texts:
I have a question regarding small-signal analysis of the differential pair with current mirror load.

For Small-signal analysis, why is I(d2) = -I(s1) ?


texts: How is the degaussing feature in the HMC5883L 3-Axis Digital Compass chip correctly used?

texts:
edit/tl;dr: The set/reset strap driver is an H-bridge circuit to deliver 10 mA of DC current to a strap which temporarily produces about a 1.1 gauss magnetic field offset. A change in the measurement before and during this field offset can be used to confirm that the device is functional, as a manufacturing test. However, these straps are also said to work for degaussing, but I have still not found clear instructions how to use them to degauss the sensor. Usually degaussing of macroscopic objects is done with an AC field that slowly decreases in amplitude.

When I hear degaussing I think of the application of an oscillating (AC) external magnetic field to a magnetized ferromagnetic material, then slowly ramping the amplitude of the oscillations field down to zero to remove almost all residual magnetization. Automatic (and manual) degaussing magnetic heads on tape recorders and magnetic shielding on CRTs are some examples.
However, a quick read of that article shows that the term degaussing also applies to the cancellation of the external fields resulting from magnetization of materials through the careful use of one or more coils excited by a DC current to "cancel" the field within some finite region. The example there is large coils on ships to cancel the fields resulting from the ferromagnetic hulls producing external fields excited by the Earth's magnetic field.
In the cases of the HMC5883L 3-Axis Digital Compass chip - or any similar type of Magnetoresistive sensor, how does the degaussing feature work? Are there actually coils inside the chip that are intended to carry DC currents to cancel some fields? How is this done - how are the currents correctly calculated and applied?
Here is HMC5883L_3-Axis_Digital_Compass_IC.pdf where it says:

Feature: Built-In Strap Drive Circuits
Benefit: Set/Reset and Offset Strap Drivers for Degaussing, Self Test, and Offset Compensation

above: screenshot from the datasheet. There are separate  OFFSET STRAP DRIVER and SET/RESET STRAP DRIVER circuit blocks, and they appear to be separately controllable.


texts:
If a DAC has a gain error of +/- 0.1 %FSR and an Offset Error of +/- 1 mV. Operating range 2.7V-5.5V with a reference Voltage of 4.096 V.

How would I convert that +/- 0.1 %FSR to LSB? The datasheet doesn't give it in LSB units.

Is there an equation, the only one I know is:
LSB = (FSR / (2^n -1)).


texts: what are the applicatons of op amp in signal processing?

texts: How op-amp can be used in signal processing applications? Can anyone explain? I know that op-amp can be used for solving linear analog mathematical problems.


texts: DC Supply voltage drop in a Schmitt trigger circuit

texts: I developed a Schmitt trigger using IC NE555P. I supplied a Vcc of +6v from a DC source. My input is a sinusoidal wave (peak-peak = 4V). First I set the voltage in DC source (+6v) and when I connect it to the schmitt trigger circuit,  voltage is dropping to less than 1 V. Then I had to increase the CURRENT in the DC source to increase the voltage to +6V. But it is overheating the IC.  I have to use the same +6V supply in a circuit (an amplifier circuit) along with this Schmitt trigger. Why this voltage drop.  Is increasing the current is safe for NE555P.


texts: Cell Voltage Relaying in a Battery Management System

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Question: If I have 48 lithium cells connected in series as a pack, how would I best go about physically implementing a system to measure, isolate, and relay cell voltages to a centrally managed microcontroller? I am currently considering the usage of analog optoisolators, but I would be grateful for any advice. However, I would need the ICs and other parts to be hand solderable (ie DIP) as these are the only tools I have available. Thank you!

Context:
I am part of a high school electric vehicle team, where we design, build, and test fully electric vehicles converted from gas cars. I joined the team with lots of heavy work already done, but we need a management system for our newly installed LiFePO batteries. Our instructor is considering purchasing a better commercial grade BMS (ironically enough our current one is only consistent in failing), but would rather have our team design a BMS, however rudimentary.

I am looking to design a BMS for a 48 cell LiFePO battery pack. This system would comprise cell voltage readouts and basic cell overvoltage drain functions. I plan on using probes for each individual cell and centrally managing them via some form of microcontroller. In addition to needing to multiplex the data, isolation of the cells and interfacing to a monitor are my major concerns. Because isolation is a major challenge and poses significant safety and reliability implications, I decided to start there.


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I have Nidec Gamma32 D12F-24BS4 15BH2 blowing fan cooler. It has very strange coloring for wires: red-white-black-yellow.

Probably two of wires are GND and +24v and other two are signal and PWM. What is the correct pinout for this connector type?

Below I attach photo of this connector and photo with comparison to standard 3-pin molex connector.


texts: Create my own battery for my electric bike

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I was wondering if it's possible to avoid buying a $400 48V 15Ah battery with an output of 54.6V and 2A, and instead make one by joining multiple 3.7V 5Ah batteries in series and or in parallel? Is a conversion like this even possible with the batteries I have? If not, what batteries would I need?

(The desired voltage and amperage don't have to be exact.)

Thank you for any help or advice you can offer.


texts: why do constellation diagram and eye diagram not show any useful output for FSK? I have tried to find that on Simulink Mathwork, but the progress was negetive.


texts: Maximum CPU Frequency of PIC24FJ256GA705 That I Can Get with 8MHz Crystal

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I'm used to run PIC24 device family (e.g PIC24FJ256GB) at CPU freq 32MHz using the PLL.

Recently I got to use PIC24FJ256GA705 on my new project and when I read the datasheet, I found out that the PLL has mode "PLL8X" (Figure 9-2 page 108)
I've 8MHz crystal at the primary clock input, so if I use this mode I should got CPU freq 8MHz x 8 = 64MHz right?

But last night when I try to blink the LED at 1 Hz using "__delay_ms(1000)", the LED won't blink.

The PLL was locked (OSCCONbits.LOCK) when checked.

So I'm just curious is anybody ever used this device at 64 MHz CPU freq???

Can this device really run at 64MHz?


texts: Testing a PID controller, need equation for PV

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I am writing a basic PID controller for the purposes of a completely in-computer simulation, no hardware to run it on. I only the PID. How can I test it on some simulated physical environment? I have seen some examples in this course years ago.

I need an equation to compute the process variable  in response to controller output, for some fake system.

PV(t,u) = ?


texts: Attaching sensors to PCB to minimize space

texts: In my electronic product design project I need to come up with a completely finished product that can be presented in the market.What i'm designing is a turbidity meter with Arduino components with ATmega328P.My question is,as I'm designing this as a commercial product,I can't use pin headers and attach the sensors to the PCB using jumper cables.What would be  the good approaches to save up space and attach them well.Some  sensor (pads)surfaces are parallel and some are perpendicular to the PCB surface when attaching.


texts: Connecting new and old 18650 in parallel

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Now before everyone start saying how bad or dangerous it is to connect used and new 18650 Li-Ion Cells together - I would like to keep it technical and fact based.

I (like many others) have many used cells ling around and would like to be able to utilize them the best way possible on high current / voltage device (scooter / e-bike etc).

Connecting in series is clearly a bad idea as when one cell voltage drops below the lower limit it will  'permanent damage' point.

Now in parallel (assuming I pre-charged them to a similar voltage ) - what would really happen?

Used batteries will have less capacitance and their voltage will drop more rapidly but they can't because they are connected in parallel so defectively what I would expect is that "each cell will supply whatever current it can" until they all drop together to the minimal voltage allowed (where I would stop the discharge) . I will connect 5, 10, 20 cells in parallel and use a DC2DC Step up to convert them to the needed voltage.

The only thing I can think off is if the internal parallel resistance of one cell is reduced over time - self discharging and leading all other cells to discharge through it. I really want to find a way to maximize my scooter and use so many old yet good cells (ranging from 1200 to 2200mAH left in them).


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I have created a library in Eagle 7.5.0, then I copied it in the folder where Eagle keeps its libraries but and I can't use it. When I try to add new component the library is not among the available ones. When I am in Eagle I can open it and modify it but I can't use it in a schematic. What am I doing wrong?

The custom library is Components


texts: Splitting humbucking pickup coils with a balance pot?

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Is it possible to use a balance potentiometer to blend/split the coils of a humbucking pickup on an electric guitar?
A humbucking pickup is (basically) just two single-coil pickups placed close together in a noise cancelling configuration (single-coil pickups of yesteryear were notoriously willing to accept electrical interference, sending noise to your amp). I've seen many guitars with humbucking coil splitting options, but all of them are single option type, such as deactivating the inner coils of a pair of humbuckers with a push-pull tone pot, or more recently the push-push pot, still used as a tone pot.
Would it be possible to, instead, use a balance fader to control the output of the 2 coils in 1 humbucking pickup?  If, for example, the fader was set in the center indent, it was a perfect 50/50 humbucker. Turned full left would give North coil only, full right giving South coil only, with fade in between.


texts:
Looking at This
datasheet for the LSM9DS1TR 9-axis IMU, there is a pin labeled DEN_A/G with the description "Accelerometer and gyroscope data enable" on page 11.

I can find no further explanation for this pin other than Figure 15 LSM9DS1 electrical connections (Page 27) which shows that DEN_A/G is an input. This is not the chip select pin; there is another pin, CS_A/G, for that already.

The Data Enable pin is not mentioned anywhere in the interfacing portion of the document (Section 5 on page 28). I plan on using this with SPI.

What should a data enable pin do? Does it need to be connected to a digital pin on my micro controller? Could I leave it with no connection? Or should it be directly connected to ground or VDD?


texts: Simulation of the injected noise to oscillator in Virtuoso

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I have a differential LNA that injects current to an oscillator. I want to see the thermal noise injected to the oscillator. This noise is composed of the noise of oscillator + noise of the LNA.
Now in Noise analysis in Cadence i have to specify the output node (port) and the input port.
The output node is the output of LNA. That's where it should be.
But what about the input port??
If i put it in the input of LNA, I'll only be able to see the output noise of LNA (but not the oscillator), am i right?
So how can the noise of oscillator be taken into account?
Should i draw the plot of oscillator input referred noise and LNA output recferred noise seperately and then add up the curves?
And input and output in an oscillator are the same here. actually differential current injected from the LNA is the input and differential voltage of the oscillator is the output of oscillator. So both the input and output for the oscillator are the same nodes.   so how can i plot the curve of noise injected to the oscillator versus frequency in Virtuoso noise analysis?


texts:
simulate this circuit – Schematic created using CircuitLab

I have trouble finding value for I2 current. Would I1 go through NODE1 down and close the loop, so I2=0, or go to the left from NODE1 so I2=-I1, or split (if we assume that both short circuit wires have no resistance) so I2=-I1/2. All explanations seems to me reasonable but I think only one is correct.


texts:
I am designing my own optical rotary encoder with a non-standard number of encoder positions for a specialty application. I have gotten to a sheet of transparent acrylic with the pattern printed on it but now I need to punch out the center hole.
To make things easier, my acrylic has a dot where a smaller hole can be punched:

This small hole could be much more easily punched precisely by hand or machine. I bet my CNC could be fitted with a punch of this size, for example (I am not using CNC/laser cutter because it burns the plastic beyond acceptability).
If a punch could be designed with a small rod in the center, it would align just right with the center hole.
This method could also be used to punch out the whole disk. First a big punch with rod could be used to punch the disk, and then a smaller one to punch out the center hole like so:

The biggest problem that arises is where/how to get a bit that has an alignment rod in the center. Perhaps they already exist, but I just don't know how to search. I don't trust my lathe to drill out the center of a punch correctly, as the punch will likely be made of the same material as my drill bits. How can I precisely punch these holes in thin acrylic sheet?


texts: Reverse current protection on power-switching MOS

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It was suggested in "Select power supply voltage using MOSFETs" that a second MOSFET can be added in series to prevent reverse current flow.

My question is, can I just reverse Drain and Source on the switching MOSFETs and not need extra MOS or diode?

.


texts: Need help in choosing Flash size in a microcontroller

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I need to decide upon selecting Flash size and RAM for a project. The micro controller I prefer to use is TI MSP430 series. Because of its low power consumption and value line series cost. However I'm a complete newbie to deciding on requirements gathering. Most of my programming experience is on Desktop based systems where generally program size, RAM and processor speed isn't much of a concern for common algorithmic tasks.

I have the following questions:

Are there any guidelines or standard practices regarding deciding the RAM and Flash size for a micro controller?
How many lines of code (C) translate to what amount of Flash size on the MCU?
Is assembly language the only way out if the Flash size needs to kept at a minimum?

Regarding General selection of a Micro controller for a project, how do the professionals in this field go about on deciding the most appropriate micro controller for the task? What resources to they search? What guidelines to they follow?


texts: Critical Maximum current for a DC-DC Buck Converter

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I was wondering how one would go about the derivation for the output to input voltage ratio for a DC-DC Buck converter given the critical max current that is found to be
$$ I_{crit} = \frac{V_{in}T}{8L} $$
The final result of the output to input voltage ratio is
$$ \frac{V_{out}}{V_{in}} = \frac{D^{2}}{D^2 + \frac{I_{load}}{4I_{crit}}}$$

Edit: For clarification: T is the period and L is the inductance and D is the duty cycle and we assume the system to be in discontinuous current mode


texts: What is quadruple in integrated circuit gates? Is it just about 4 gates inside the IC or anything else more special?


texts: I'm making my first PCB and would like some advice about ground planes. The pcb it two layer, and all parts are through hole. Bottom layer consists of all the ground pads and everything else is on the top layer. Currently I have a ground plane that includes the input from the 12V batteries, two motors inputs, the mosfets that will drive the motors, two capacitors, and two diodes. The other ground plane includes the rest of the circuit. i.e. microcontroller, 5v LDO regulator, 3.3v LDO regulator, LED's, Bluetooth module, digital sensors, and passives. The ground planes are connected by a single 32mil trace. The 12v battery input is on the motor ground plane and the other battery input for the 5v LDO is on the other plane. Am I on the right track?


texts:
Suppose we want a +/-10v control signal, where 0x0 (to the DAC) = -10v and 0xFFF = +10v.

Firstly, how do we alter the signal so that we can have a negative voltage, dependant on the DAC input?

Secondly, how can we scale the signal so that it fits within the -10 to +10 range?


texts: Clear D flip flop internal logical scheme

texts: I am new in this community and also in logic circuit design and digital electronics. I couldn't find the logical design on the internet for the following D flip flop  and i would like to know how it's made. I would like to simulate its functionality in Wronex and i have to know of what logic gates it is composed and also how they are linked. All i know is that it is part of the SN54175 TTL.


texts: Push Pull Converter Transformer Saturation Rating

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How do you determine the required saturation rating for a transformer to be used in a push pull converter? Can a transformer in this topology pass more than the saturation rating since it is not storing the energy as it would in a flyback type converter?

Some background:
I am building a push pull converter that will take 24V at up to 1A peak and convert it to 15V. I found a transformer (VPH5-1200-R) with a RMS current rating of 1.7A but a saturation current rating of only 0.14A. Will this transformer saturate out before it reaches the 1A through the primary?


texts: Switch-mode power supply, and output voltage range - unregulated?

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This Wikipedia entry specifically on the SMPS part, says:

  Switched-mode power supplies are always regulated. To keep the output voltage constant, the power supply employs a feedback controller that monitors current drawn by the load.

However, I've found a range of mobile phone powersupplies, which claim to be switched-mode, but specify their output as being 4.7-6.5VDC at 900mA max, rated for 4W. Given that these were switch-mode and a range being specified, is what struck me as being contradictory. So, I am wondering if these are fakes ?

In fact, I went ahead and bought one of these, but at the moment, I am far from home and don't have my tools. It seems to be able to charge my Android phone, and is also able to power a RaspberryPi -- though I tried just the boot sequence and then switched-off, afraid of damaging the board. One thing in favor of their claim to being switched-mode, is that they are pretty light weight, and relatively small.

So, is the range, only because their manufacturing is not under tight quality control, and they actually operate at a fixed + regulated output voltage, but there could be variations within that range, from one piece to another ?

Edit:
The power-supply is as such meant as generic / back-market replacement charger for Blackberry smartphones, that expect 5V supply.

My primary use for these supplies is to power a cache of RaspberryPi's (model-B), with minimal peripherals. The supplies available closer home, cost more than twice as much, so was wondering if this could be a good money saving bargain.

Edit2: (Feb 11, 2013)
If the switch-mode power supply output is indeed unregulated, would a LDO as an intermediate step be a good way to regulate the final output to 5V ? Are there any inexpensive (<= $1) 5V LDO's which could do this job ?


texts: Current Mirror - Find Acceptable Range of Vb

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I'm stuck on part A - in particular finding Vb range

Here's what I have so far

Now, here's where I get lost

I have no idea if my method is correct. I'm confident about my value for Vx but no clue about Vb.


texts: Difference between Clock and Operating Frequency

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I am very new to embedded world. I am trying to design a transreciever  system based on RF MCU.

I am looking at ATMEGA64RZAV-10PU from Atmel.

The datasheet says the clock frequency as 10MHz but operating frequency as 2.4 GHz. I believe all frequencies are derived from clock, so is the operating frequency using a PLL to boost the frequency of the clock, or is it something else.

Support will be appreciated a lot!

Best Regards,


texts: PICKIT 3 resets PIC16 three times upon reprogramming

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I am using the PICKIT 3 with MPLAB X with the default setings. When I press F6 to build and run my code, I notice that the PIC16 resets three times:

twice with the previous code (not expected)
once with the recently built code (as expected)

How can I avoid having the two spurious resets with the previous code?


texts:
I need to design a PCB for Linux and use two DDR3.
To have 1GB ram, I'm using two 16bit DDR3 (256Mx16) that are used in fly-by topology.
I have look at some examples, some DDR3 have 16bits address, some 15bit.
16bit ones used all the time where using fly-by topology examples.
Can I use 15bit one DDR in fly-by-topology? If so, what about pin A15?


texts: How can cellphones be charged and used at the same time?

texts:
All of us are probably used to using our phones while they are charging. This is why manufacturers make longer cables – so that the consumer can have the facility of using and charging the question at the same time.

My question is this: Assuming a cellphone consists of battery with the 'phone' (camera, screen, etc) connected in series, how can we charge it (which would require that current flow in the opposite direction of the battery terminals – we were taught this in physics class – you need to apply a voltage more than that of the cell and in the opposite direction to charge it) and use it (which would require that the current flow in the same direction as battery terminals) at the same time.

My attempt: (two possible cases)

The above thinking is wrong and somehow the manufacturers managed to use and charge the battery at the same time.
While charging, the battery does not provide current at all and the current from the wall socket is divided into two currents – one for charging and one for operating the phone.

Which one of the above explanations is correct? Or, is there a third, more complicated explanation?

If explanation #1 is correct – is this achieved in a simple way or do I need to get a degree in electrical engineering to understand this?
If explanation #2 is correct – when the phone is being charged and used at the same time, the rate of charging is noticeably slower. Shouldn't the current drawn from wall socket be increased to make it charge at the same rate?


texts: Powering unknown LCD and connecting to FFC connector?

texts: I recently took apart a dead LCD projector and found some tiny LCD displays inside, I have a total of three of these modules. Their model number is "Sharp G RLCDP0083CEZZ 952B18IK" and I wanted to drive them somehow. Either with an rPi or Arduino, just experimenting with them at first. Does anyone know how or where I could find a 32 pin ZIF flat-flex breakout board or how to drive these otherwise?


texts: How to reduce VOC of solar panels to match the MPPT

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My panels have VOC of 36VDC.
I like to connect 5 panels in series. But in such case the total VOC would be as high as 180V, and damage my Charge Controller.
Is there any dummy load, or  shunt kind of thing which I could attach between the panels and Charge controller, so that at no time there is a ZERO load, and thus keep my MPPT safe.


texts: Inverting Amplifier Circuit using Single Power Rail

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For my homework, we are supposed to simulate an inverting and noninverting amplifier using a single supply and the LM324 opamp. I built the inverting amplifier using a voltage divider, but my output voltage is not a sinusoidal wave rather a square wave that has a cutoff. The output signal should be amplified sinusoidal wave. so, how can I fix this?
Heres the schematic of the circuit:

Here are the screenshots of the results


texts: Discharging 18650 battery at constant rate

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Hello I am planning to do some tests with a 18650.
In these tests my goal is to measure required time to discharge them with different discharge current rates (1A, 2A, 5A and so on...)

The op amp work as a comparator between logical level set by the potentiometer and voltage supplied to the load. If load voltage is lower than logical, mosfet turns on, if lower turns off.

18650 battery nominal voltage is 3.7 V (if not mistaken) so that means maximum current is 3.7 A right? Which will be when mosfet is on all the times? If I want to increase discharge current I need to change the load resistor to a smaller one? Like putting two 1 ohm resistor in parallel?

IRLZ44N datasheet:
http://www.irf.com/product-info/datasheets/data/irlz44n.pdf
LM358 datasheet: http://www.ti.com/lit/ds/symlink/lm158-n.pdf

OP amp will be connected to a bench power supply (+5V and 0 V)


texts: Thinking Through a 6-pin PCIE Splitter Capacity Scenario

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Background:

6 x Goldshell HS1 Plus ASIC miners - each draws 115 W +- 5W (in practice, they usually draw less based on reviews).

3 of them with the accompanying power supplies. 6-pin PCIe from the plug on the ASIC to the brick, and then from the brick to the wall they are standard female electronics cable (IEC 320 C13/C14 I believe?) to a 220v plug (or whichever type they use in most of Asia).  The manufacturer says you can swap these for your normal IEC 320 to 110v wall plug for U.S. use, which is what I did.
3 of them without power supply - was thinking about plugging them into a computer PSU, but then thought maybe I could combine them with the others.

Question:
How can I go about calculating if I can safely split the PCIE side into two and power 6 ASICs from the three supplies?  (E.g. a splitter like the "Cable Matters 6 Pin PCIe Splitter Cable" that you can search on Amazon).  On the back of the PSU brick, it states "100-240V~50/60Hz 3.0A Max. Output 12.0V 15.0A 180W.
Based on the 180 Watts, perhaps it would create an issue if I put two on there?  I'm not sure exactly how to evaluate if this is just the company being cautious, or if this would pull undersupply the ASICs.


texts: Emittors and Collectors in a transistor, what exactly makes them different?

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For my high-school physics class, we are studying the theoretical basics of transistors. I have not been able to understand which side of the transistor is the collector and which side is the emitter by looking the current flow in the circuit. I know that the doping and the size are different, but that doesn't help me when I try to calculate the base current / current at the emitter.

Can you explain me which how I should name Currents I1, I2 and I3 in the drawing? Thanks!


texts:
I'm confused about a couple of things concerning the transistor.. is Vcc the signal to be amplified or Vin? And does the transistor actually amplify the voltage fed to it or does it just regulate how much of that voltage is led out to a say a device that is part of the voltage divider circuit that contains the transistor?

Also why do we use a transistor in the first place? Wouldn't a variable resistor in the divider circuit do the same job?


texts: What does avrdude "programmer is out of sync" mean?

texts:
Lately, I've been getting a lot of "programmer is out of sync" messages while uploading to a microcontroller (ATMega328p). I am very clueless here as the uploading process just randomly succeed and sometimes just doesn't, without any changes. Here's an example of the console from the 'super verbose' mode:

avrdude: Send: V [56] @ [40] . [00] . [10] . [81]   [20]
avrdude: Recv: . [84]
avrdude: stk500_cmd(): programmer is out of sync
avrdude: Send: V [56] H [48] . [00] . [10] . [00]   [20]
avrdude: Recv: . [a5]
avrdude: stk500_cmd(): programmer is out of sync
avrdude: Send: V [56] @ [40] . [00] . [11] . [80]   [20]
avrdude: Recv: . [83]
avrdude: stk500_cmd(): programmer is out of sync
avrdude: Send: V [56] H [48] . [00] . [11] . [91]   [20]
avrdude: Recv: . [a7]
avrdude: stk500_cmd(): programmer is out of sync

What does "programmer is out of sync" mean? What are the possible causes?

P.S. If you need to know, I am using Eclipse CDT with Jantje's Arduino plugin, not the Arduino IDE.


texts:
I have a LM340T15 voltage regulator and want to use it as current limiter (150mA) for a 30V supply line. In the reference design (datasheet) following circuit is suggested

My modified design looks like

Since the LM340T15 has a fixed output voltage of 15V I changed the formula to
\$ I_O = \frac{15V}{R} + I_Q  => R = \frac{15V}{(I_O-I_Q)} = \frac{15V}{150mA-1.5mA} \sim 100\Omega\$
Therefore the circuit draws a maximum \$ 30V\times 150mA = 4.5W\$.
Is this design applicable? Who can I calculate the power dissipation over the resistor R9 and the regulator?
Also: applying a supply voltage (input) will not result in the expected output voltage. At around input=13V the output voltage (voltage over the circuit) is capped at 8.5V. Increasing the supply voltage has no effect on the output. The current rises until 45mA and stops there (as expected). Since the LM350T15 is regulated to 15V, are these 15V still the limit when using it as current-limiter?


texts: How to share a current sense pin on a single GPIO

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The BTS7040 is a 2 channel High Side Switch with diagnostic feature, im planning on using 2 of the IC and i dont have extra GPIOs to spare.
The way you read a fault from the BTS7040 is to select a channel from the DSEL and read the current sense pin IS, if there is a fault IS will be at a fixed value (not sure).
The Internal structure of the IS pin look like this taken from page 4 of it sensing datasheet

I can only allocate 2 GPIOs for the two BTS7040, 1 is used for the DSEL of IC and the other for the IS of both IC. I do not mind not knowing which channel and which IC the fault occurs all i need to know is that a fault occured. I am unfamiliar with the structure on how the IS pin is made thus i know nothing if it is possible to share a GPIO and if it is possible how to do it.


texts: Serial DB9 to Serial 3.5mm over HDMI cabling

texts:
Good afternoon everyone.

I am trying to control a Samsung TV via Serial from a remote processor and I am trying to use spare installed HDMI cabling to do it.

Samsung does not have an open API for IP control of the TVs but this TV does have a "service" (RS232C) port. The processor is located near the AVReceiver and there are 3 HDMI cables between this location and the TV of which only 1 is in use. I do not want to run any new cabling between the two locations and instead want to repurpose one of the spare HDMI cables.

The info I have found on this can be found here:

Questions regarding using an HDMI cable to transmit SPI, I2C, and UART serial data?

http://www.avsforum.com/forum/162-home-automation/1392325-hdmi-serial-rs232c-db9-adapter-projector-control.html

SerialDB9 to USB > USB to HDMI > HDMI Cable > HDMI to USB > USB to SerialDB9 Serial DB9 to Serial 3.5mm  seems like a massively overengineered solution to this problem.
Deconstruction of the HDMI cable is possible. I'd like to avoid it as my hands struggle to manipulate any cabling thinner than an undersea power cable but its a backup option!

I've also got a backup to the backup which is to use an ethernet run. I would very much like to avoid this as ethernet is too useful to waste IMO but at least it's a solid and proven option should everything else fail.

If anyone has had any experience in this then please let me know.


texts: FET level shifter for serial does not work with inline resistor for safety

texts:
For a voltage change on a serial line I'm using a common level shifter design which uses a FET (BSS138 in this case) as so:

I have two of these - one for RX and one for TX. I should add that I'm using this because I have an I2C line pair as well and you can get 4 of these circuits on one little board from Adafruit.

As I was hooking this up to someone else's device and the usual caveat about "RX from which point of view?" applies, I added the 1K resistor on the right so that that miswiring would be less likely to cause shorting issues.

On a proper push pull output this should be fine, especially at 9600 baud. However, with the FETs this does not work. I thought - maybe when the 3.3V side pulls down the body diode is ineffective in clamping. But I had a GPS TX on the 3.3V side sending to the 1.8V RX side and that seemed to work fine, which isn't what I'd expect. Comms with a PIC micro failed though, probably on the TX (1.8V to 3.3V direction) side. When the 1.8V side pulled low, the 3.3V side seemed to pull only half way.

Removing the 1k resistors cured the problem and the circuit translated the serial comms correctly. But I'm confused as to why the 1K caused the problem - what are the dynamics of the issue?

Edit: To explain why I'm considering continuing to use this system - I'd gladly replace the whole thing with a TXS0108 which does push-pull and open-drain level shifting for 8 lines in one device. But that device does not appear to give Vcc isolation (if either 1.8 or 3.3 is turned off for example), unlike the TXB0108 which explicity says it does in the datasheet. Thus I wanted to use two of the FET circuits "back-to-back" to give the isolation.


texts: Understanding Pressure MEMS Technical Information (Relative and Absolute Accuracy)

texts:
In my research, I use smartphones pressure sensor data, and I need to understand their errors and limitations. I found the technical chart for the sensor:

But I don't really understand the meaning of the absolute accuracy of -4 .. +2 hPa in the chart, and what is the difference between the absolute and relative accuracy here.

Can anyone help?

Thank you!!


texts: Does a low level trigger relay module send much current to GND/GPIO LOW

texts:
I have a pre-built relay module and it apparently takes around 70 mA to activate the coil.  However, the relay is a low-level-trigger which requires making a connection from "IN" to GND (or GPIO LOW) to activate the coil.

In my previous builds I have been using a ULN2003 Darlington array which worked perfectly as a buffer for normal relays to protect the GPIO pins on an Arduino(MEGA and Nano), but, as the relays are pre-built and require low level triggering, I wanted to know what current I could be draining from the relays' "IN" pin and whether it would be too much for an Arduino's GPIO pin directly? If this is even a concern in the first place? (They're meant to be safe, but I am having doubts).

Also, if the current drain is too high, what would be the best way to go about this?  Could I just wing it and use VCC as the on/off mechanism instead (with the "IN" pin on the relay module permanently grounded)?

Additional info:

I've not had chance to test the mA being drained (the last relay I ordered was DOA).
There are four relays so far, and each could be on or off at any one
time (0 mA - ~280 mA potential).
The Arduino GPIO pins can't sink much (~20 mA each I think, safely), and as the other pins are
already being used at their recommended levels there's little room for much else without some kind of buffer.

Low-Level-Trigger Relay:


texts:
I've made this circuit to detect de zero cross but in out pin (pin 7) the voltage are about 3,7V fix. I've already measured pins 5 and 6 and the delta voltage ( vin+ and vin-) are inverting. I had inverted pins 5 and 6 and in this case pin7 is fixed in 0V.

Oscilloscope measurement problem:

--First Situation

Probe1 connected only:

Scope img:

--Second

Probe1 and 2 connected:

Scope showing perfectly the signals:

I've already tried to measure with other Scope (TDS 2002B) add caps on various places in this circuit. I will try to put this signal on uC INT pin to see if is a osc problem or a circuit one.


texts: Are resistors the only legal way to tie various power designations together?

texts:
I'm working with a schematic in Eagle and I use IC's with different types of power pins. I connect VDD to VCC to +5V and I connect GND to VSS to zero volts.

When I look at the ERC, I receive warnings as follows:

WARNING: Sheet 1/1: POWER Pin IC1 VCC connected to VDD
WARNING: Sheet 1/1: POWER Pin IC1 GND connected to VSS
WARNING: Sheet 1/1: POWER Pin IC5 V+ connected to VDD
WARNING: Sheet 1/1: POWER Pin IC5 GND connected to VSS

When I switch over to PCB manufacturing mode, it seems that not all the pins are connected.

My schematic has a microcontroller, CMOS IC's and a 555 timer.

Do I need to add resistors between each of the different power supply designations? I'm trying to be legal so that no electrical software complains.


texts: MCU Controlled JFET switch for negative voltage?

texts:
I have a JFET that requires negative voltage to the base in order to close and 0V to be open. I have the following power rails: 5V , -12V & GND (0V).

What would be the simplest way to switch the JFET's base between 0V & -12V using a GPIO pin from the MCU?


texts: A question about preventing reverse polarity for supply rails of an opamp

texts:
Below is an example circuit:

I have some circuits based on opamps similar to the ones above. I want to prevent a situation if one powers supply rails Vcc and Vee reverse way. Normally this would damage the circuit.

Now I want to add a simple interface component or circuitry across one of the supply lines of the opamp which would protect this circuit for reverse polarity situation without contributing much noise.

What is in general used such cases to prevent reverse polarity for the opamp supplies?

edit:

Which way of placing the diode below is better for the purpose of reverse polarity?: For single supply opamps


texts: Why can't two series-connected diodes act as a BJT?

texts:
Another form of the question is: will joining two diodes with wires (pn-np) make a transistor-equivalent?

I read that they are not equivalent, but why?


texts: What is the most common type of high voltage cables?

texts:
I'm building the model of an admittance matrix for the German Grid, most specifically the Transmission grid. I only have characteristics of cables as number of cables, wires and voltage (I'm working with 110kV, 220kV and 380 kV). I would like to know what are the more common types of cables used in order to be able to assign them electric characteristics, as for example, resistance, inductance, etc.

As an example, for 110 kV I have somecables already:
N2XS(FL)2Y / NA2XS(FL)2Y

Ideally a link with the norm or a list of them would be perfect!.

Thanks!


texts: Power a 12V 30A (instantaneous) load. Possible with 18650 cells?

texts:
(novice)

Hi,
I'm driving a 12V load for ~1s second very infrequently, at a draw of about 30A. The load isn't particularly voltage-sensitive. Total mAh isn't that important.

I have a supply of recycled laptop 18650 cells so was looking for a solution using those (I am aware they will be unreliable).
I will charge them individually outside of my circuit, so charge balancing is not a requirement. However I don't think they have over-drain protection built-in, so that needs to be considered. Their positive terminals are flat.

After some searching I think I need a 4 cell holder, wired in series ("4S"), stepped-down to 12V somehow.

Searching eBay reveals hits for "4S 30A 12V balance board". Is this the sort of thing I am after?

  Continuous discharge current: 30A (MAX)
  Instantaneous discharge current: 70A
  Power balance detection voltage: 3.60±0.025V
  Overcurrent detection voltage: 150mV

I looked into using 3 cells with buck-boost converter, but it seems more expensive.

Related:

11.1v to 12v vs 14.8v to 12v (particularly this useful answer)
Best way to power a 12V-2A load using 18650 Li-Ion batteries
Regulating 4s 18650 battery to 12V or use 5s instead?


texts: How do I attach leads to a SOT-227B/miniBLOC package?

texts:
I am reviewing options for full-wave rectifiers for a several thousand watt project, and many of the options are in the SOT-227B/miniBLOC package.  I am not familiar with this package, and when I was reviewing its mounting guidelines, it was unclear how external connections are intended to be connected to the package.

Here is an example of the SOT-227B package:

Do incoming leads go on top of or under the copper terminal tabs?  I have found plenty of information in the application notes about mounting the base plate for best thermal contact, but the guidelines for the terminals reference the tightening torque only.


texts: Coil Winding Sense of Inductor/Transformers and Output Polarity

texts:
Given a solenoidal coil, if it is wound in one sense (say clockwise), would the output from it, in terms of polarity, be equivalent to another coil, wound in the opposite sense (counter-clockwise), with its lead also swapped?  In other words, does switching the leads from an inductive coil produce the same effect as changing the winding direction of the the coil?

For an inductor, this primary instance where this would come into play is if the coil were used as an antenna of an inductive RF signal; would the polarity of the RF signal and the polarity of the voltage coming from it match or not in accordance with the right hand rule?

For a transformer, this is slightly more complex, because now it is the relative winding sense of one coil with respect to the other, the primary to the secondary.  For instance, if both coils were wound clockwise or counterclockwise, would the polarity from one coil to the next would correlate in one way, but if one coil was wound clockwise and the other counter-clockwise, would the polarities correlate in the opposite way?

Here is a diagram to illustrate this question:

A mathematical (or at least graphical) proof of this would be helpful.


texts:
I'm pretty new to avr programming. I'm facing a strange problem that I can't solve so far.

I've wrote a simple code:

#include <avr/io.h>
#include <util/delay.h>

int main(void) {

    DDRA = 0XFF;

    for (;;){
        PORTA = 0xFF;
        _delay_ms(1000);
        PORTA = 0x00;
        _delay_ms(1000);
    }

    return 0x00;
}

I'm setting the F_CPU (the value used by _delay_ms() ) trough the Makefile I'm using to compile and upload the code:

DEVICE     = attiny84
CLOCK      = 20000000
PROGRAMMER = -c usbasp -P /dev/tty.usb* -b 19200
OBJECTS    = main.o dallas_one_wire.o
FUSES      = -U lfuse:w:0x62:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m

######################################################################
######################################################################

# Tune the lines below only if you know what you are doing:

AVRDUDE = avrdude $(PROGRAMMER) -p $(DEVICE)
COMPILE = avr-g++ -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE)

# symbolic targets:
all:    main.hex

.c.o:
    $(COMPILE) -c $< -o $@

.S.o:
    $(COMPILE) -x assembler-with-cpp -c $< -o $@
# "-x assembler-with-cpp" should not be necessary since this is the default
# file type for the .S (with capital S) extension. However, upper case
# characters are not always preserved on Windows. To ensure WinAVR
# compatibility define the file type manually.

.c.s:
    $(COMPILE) -S $< -o $@

flash:  all
    $(AVRDUDE) -U flash:w:main.hex:i

fuse:
    $(AVRDUDE) $(FUSES)

install: flash fuse

# if you use a bootloader, change the command below appropriately:
load: all
    bootloadHID main.hex

clean:
    rm -f main.hex main.elf $(OBJECTS)

# file targets:
main.elf: $(OBJECTS)
    $(COMPILE) -o main.elf $(OBJECTS)

main.hex: main.elf
    rm -f main.hex
    avr-objcopy -j .text -j .data -O ihex main.elf main.hex
# If you have an EEPROM section, you must also create a hex file for the
# EEPROM and add it to the "flash" target.

# Targets for code debugging and analysis:
disasm: main.elf
    avr-objdump -d main.elf

cpp:
    $(COMPILE) -E main.c

Regarding the attiny84's data sheet, it should run at 20Mhz under 5 volts.

Unfortunately the led isn't blinking at a rate of 1 every second but somewhat really longer around a 10 secs rate.

By tuning the F_CPU value, I've reached the 1 second blinking rate by using F_CPU = 1000000 (1Mhz)

Does that means that  the attiny84 is running a 1Mhz or am I wrong somewhere else ?


texts: how do I use a multiplexer to select a logic function to use?

texts:
I have a homework assignment where I'm supposed to use 4:1 multiplexers to select from one of four logic functions in Logisim. However, my only experience with multiplexers in Logisim up to this point was designing a circuit using 2:1's and passing the output of the multiplexer to the output of the circuit

So how do I use a multiplexer to select a logic function? Do I use a splitter at the multipexer's output? Do I set the data bits in Logisim to 4?


texts: Correct way to wire a 5V relay using BC547

texts:
i am trying a relay circuit. I saw one diagram online in google images and another one when i actually test. Here are the two diagrams:

Diagram 1
This one i tried but not worked for me. But its a common diagram available on all over the internet.
Although it did worked once for me. But not sure because if its relay or something else.
Diagram 2
This one is working absolutely fine in when i actually make this circuit on bread board. But not sure if this is the correct way to connect to relay. As my emitter is connected to coil pin 1.
Which one should i refer to? In case if i am making any mistake in understanding something then please guide.
Here is my relay:
5V 7A 5Pin PCB Mount

Any suggestions the right way!
Thank you!


texts: High side mosfet 12V switch from isolated 3V3 GPIO

texts:
I want to switch power of 12V laser sensor from 3V3 STM32H753VI GPIO. I will power on or off for long time (It's not PWM here) I am not comfortable with Mosfet and Optocoupler so I need help to be sure I can route this to my board. I want to go high side because the sensor laser set 12V to output when I cut the ground. I need to be isolated because of isolated power supply.

SCHEMATIC

Laser power is connected to CN1 and draw about 100mA and can work between 10V to 14V.
The STM32H753VI work at 3V3 and GPIO will be set as open drain.
I want to use EL3H7-G (C) Optocoupler and STR2P3LLH6 Mosfet because of small footprint.

DRIVING OPTOCOUPLER
When GPIO is shorted to ground current flow to EL3H7-G led, I get forward voltage from sheet (page 3) and curve (page 4)

GPIO could not handle more than 20mA to the GPIO so I will set If=10mA
R1=(3.3V-1.2V)/0.01A=210ohms
I will go with R1=200ohms
If=(3.3V-1.2V)/200=10.5mA

OPTOCOUPLER Ic CURRENT
I want to When I look into EL3H7-G datasheet (page 3) I can see optocoupler transistor can be saturated with If=10mA and Ic=1ma so Vce(sat) will be at 0.2V max .
(On the curve I can see I can go to 6ma into saturated region)

R2=(12V-0.2V)/0.001=11.8kOhms
I will go with R2=10kOhms
Ic=(12V-0.2V)/10000ohms=1.18mA
Ic=1.18mA

MOSFET Vgs
Vgs is -R2 voltage
VR2=12V-0.2V=11.8V
Vgs=-11.8V
From STR2P3LLH6 datasheet (page 3) I can see Vgs(th)=-2.5V

Vgs (-11.8V) is more lower than Vgs(th) (-2.5V) so Mosfet will turn On.

I can see on STR2P3LLH6 datasheet (page 2) Vgs max is +/-20V
so I will probably not destroy the gate with -11.8V

OUTPUT (VPWR)
On STR2P3LLH6 datasheet (page 5) I can see the Rdson is about 48mOhms for 100mA

Vds=-(0.048ohms*0.1A)=-4.8mV
VPWR=12V-0.0048V=11.99V
VPWR=11.99V
I can now compute Mosfet dissipated power
P=0.0048V*0.1A=480µW
P=480µW
P (480µW) is really lower than Ptot (0.35W)

CONCLUSION

Do you think Mosfet will fully On or Off as I want ?
Do you think I will destroy the Mosfet, Optocoupler or STM32 ?
Do you think optocoupler and Mosfet are about a good choice ?
Do you think It's good to add small value R3 between collector and gate ?

Thanks in advance for your help


texts: Interpreting two wires on 1 pin within this diagram

texts:
I'm trying to interpret this diagram and wondering if there is a way around needing anything special.
I have a Pi that I'm attempting to hook up to this leveler into an RFID sensor.

I notice that this red cable is bridged from the sensor to the Pi, but I don't understand how this link happens. Is there a way around this?


texts: When winding an inductor and you reach the end of the other side, do you jump the wire across to the beginning and continue winding or can you continue to wind from the other side to the beginning for the second layer of wire? Would there be cancellation of the inductance value. I want to make a choke for an Radio Frequency oscillator. It's hard to make my question clear.


texts:
I 'm planning on controlling an RC car via ΒeagleBoard-xM. Pistol transmitter uses ic TX2 encoder.

As image shows, right-left commands are implemented by a 3-part conductive area. Specifically, when area "R" gets grounded, a signal for right rotation is being transmitted. When area "L" gets grounded, a signal for left rotation is being transmitted.

The idea is BeagleBoard-xM to send these signals by two different GPIO ports. Presence of voltage in GPIO port, means signal to be transmitted. However, when I connected two wires for right rotation (one in conductive area "R" and the other to GNG) signal has been transmitted when I powered supply the circuit. This makes sense, as area "R" was already grounded.

The aim is a signal to be transmitted, when wire in conductive area "R" has voltage by BeagleBoard-xM. Is something like this possible?


texts: How to write or generate test cases(or vectors) for automated production testing of embedded electronics?

texts:
My question is following:

Assuming I have developed some embedded controller(board) which has some tens of digital inputs and outputs. It has embedded firmware, which performs some logical functions. I have an automatic test stand which allows functional testing of production boards. It can simulate pretty any input signal combination and read, what controller provides on it's outputs. It can also, for example, switch on and off or swing power supply voltage to check correct operation in different conditions.

Now the point - are there any common methodologies of generating test vectors which would allow 100% testing coverage of my HW and at the best with minimum amount of tests? E.g. I want my controller to be 100% tested.
Currently all boards are tested manualy, but this is time-consuming and I'm sure I don't get 100% coverage.


texts:
I have just seen two Colpitts oscillators from the page as below.

However, the page is not written in English. I tried to translate it into English but I could not understand it.

Could anyone explain why there is a resistor in the first case and a capacitor in series with inductor in the second case?

In addition, if you have a link explaining how each circuit works, that would be great.
Thank you.


texts: What does the number of " single-word instructions " mean on a MCU's memory specifications?

texts:
I have copied the following sentence from a PIC MCU datasheet:

"PIC18(L)F26K22, PIC18(L)F46K22: 64 Kbytes of Flash Memory, up to 37,768 single-word instructions."

the question is what does " 37,768 single-word instructions" mean for a memory ?

does it show how fast is the memory or something else ? what's its meaning and how is it calculated ?


texts:
I feel like this ought to be a FAQ, but because of the abundance of articles on Grade Point Average coming out of the US, it's extremely difficult to search for. I have a micro switch with rather difficult to read labelling on it, but which clearly shows a current rating of 0.1GPA (and 125 VAC):

I'm used to seeing a simple 'A' after current ratings. What does the 'GP' stand for in this instance?


texts: Is it possible to use the Microchip Graphics library for a Single Color GLCD?

texts:
I didn't seam to see the controller for those simple GLCDs on the list of controllers for the microchip graphics library.

Does it support such libraries, or do i have to create a custom controller to support such?


texts: Low operating current, but high stall current. How to pick a driver chip?

texts: I have a motor that normally runs at about 0.65A. When stalled, this current shoots up to about 5.5A (according to the datasheet), which is far more than the low current ICs I'm familiar with (e.g. L293D) can handle. Using a >5.5A chip seems to me like overkill, since it will only rarely be needed (and are usually more expensive). Is there any way I could implement a hard current limit (say at 1.5A) that will cut power to the motor when it shoots up to its stall current? Or are there any good motor driver ICs that anyone can recommend?


texts: Is it possible to perform JPEG compression on a Cortex-M4 MCU? Are there existing libraries that can do this and can accept a 10-bit RAW RGB?


texts: How can I avoid using different batteries to power different components in a circuit board?

texts: I am looking to use MOSFETs as a switch to run a motor and we ran into a slight problem with the power supply to the circuit board.  The main batteries we would like to use output 14.4 V nominally.  However I need to supply 3.3 V to the processor.   I also have an amplifier that I need to supply a +- voltage to (preferably around +14 and -14).   If I had to I could use different batteries to power different components, but that seems silly. The other tricky part is that the solution to this must be rated for operation as 150degC. If anyone has a suggested solution I could look into that would be a great help.


texts: Why has an audio amplifier negative feedback?

texts:
Here is a basic 10W audio amplifier - sorry for the European signs:

Why does the amplifier in this application need negative feedback? What would happen if I'd connect pin 2 of IC1 to ground?


texts:
In a lecture I learnt a BJT VCVS which has gain = 1, i.e a voltage buffer as shown in the figure.

The speaker said that it was the ideal VCVS model of a BJT. My question is that is it possible for a BJT VCVS to have a gain > 1. Thanks.


texts: Will a 950 nm IR emitter work with a 870 nm phototransistor?

texts:
I'm planning to build a simple IR light barrier across a distance of 15 mm.

I plan to use this receiver with this emitter.

The reason is to have some SMD PNP capable components. The emitter and sensor have a slightly different IR wavelength. Will it work anyway?


texts: Measuring input-offset-voltage of an opamp in sim and getting very different result in datasheet

texts:
With the definition of "input offset voltage" I wanted to find it in simulation for LM358 op amp. Here is the definition: "Input offset voltage is the differential input voltage that would have to be applied to force the opamp's output to zero volts."

In simulation by using 5V dual supply, I swept the non-inverting input from -500uV to +500uV and marked the point where the output becomes zero. Below shows this sweep setup and the plot:

I concluded from the sim that LM358 has around 35uV input offset voltage.
Then I go to the data-sheet to verify it.
Here what the data-sheet shows:

Typically the input offset voltage should be 2mV. But in sim I get 35uV.
This is a big difference, so I wasn't sure what I am doing is correct.

1-) Is my way of measuring input offset voltage correct?
If it is correct what could be the reason there is such big difference?

2-) I have found LM358 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT. Where and how is this input offset voltage  is mentioned in these SPICE models? Or is it mentioned at all?

Here is the macromodel:

**************************************
* LM358                              *
**************************************
* LM358 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT
* CREATED USING PARTS RELEASE 4.01 ON 09/08/89 AT 10:54
* (REV N/A)      SUPPLY VOLTAGE: +/-5V
* CONNECTIONS:   NON-INVERTING INPUT
*                | INVERTING INPUT
*                | | POSITIVE POWER SUPPLY
*                | | | NEGATIVE POWER SUPPLY
*                | | | | OUTPUT
*                | | | | |
.SUBCKT LM358    1 2 3 4 5
  C1   11 12 5.544E-12
  C2    6  7 20.00E-12
  DC    5 53 DX
  DE   54  5 DX
  DLP  90 91 DX
  DLN  92 90 DX
  DP    4  3 DX
  EGND 99  0 POLY(2) (3,0) (4,0) 0 .5 .5
  FB    7 99 POLY(5) VB VC VE VLP VLN 0 15.91E6 -20E6 20E6 20E6 -20E6
  GA    6  0 11 12 125.7E-6
  GCM   0  6 10 99 7.067E-9
  IEE   3 10 DC 10.04E-6
  HLIM 90  0 VLIM 1K
  Q1   11  2 13 QX
  Q2   12  1 14 QX
  R2    6  9 100.0E3
  RC1   4 11 7.957E3
  RC2   4 12 7.957E3
  RE1  13 10 2.773E3
  RE2  14 10 2.773E3
  REE  10 99 19.92E6
  RO1   8  5 50
  RO2   7 99 50
  RP    3  4 30.31E3
  VB    9  0 DC 0
  VC 3 53 DC 2.100
  VE   54  4 DC .6
  VLIM  7  8 DC 0
  VLP  91  0 DC 40
  VLN   0 92 DC 40
.MODEL DX D(IS=800.0E-18)
.MODEL QX PNP(IS=800.0E-18 BF=250)
.ENDS
*

Edit:

32V Common mode voltage added; the result agrees with the data-sheet:


texts:
I am using TLC5955, 48 channel pwm driver from TI to drive my LED's. I have chained 4 IC's as shown driven by a CortexM4F STmicro controller.

simulate this circuit – Schematic created using CircuitLab

I believe i am sending the right data, but I have been unable to see even the smallest flicker from the LED's. I tried to feed data just into the first driver to see that it functions. I probed the SOUT of the driver, and it does show activity, which makes me believe that the Driver IC is not dead. The OUT pins of the driver however do not show any activity.

Below are the few waveforms that I captured.

Start section of Control Data

Full Control Data

Start section of DATA

Complete DATA

I would be grateful if anyone could help me with solving the problem...

Microcontroller

TLC5955

A part of the layout, with microcontroller on the left and the first led driver on the right(Sorry, its not the best view)


texts:
I am seeking some feedback in improving the reed switch snubber protection circuit shown below.
The switch will drive a coil of an AC relay. Please note that the AC relay coil is not accessible. Any protection will have to be across the reed contact.
Here is the relay part#
Spec sheet:

Relay coil operating current is 24mA, 115AC.
The reed switch SW1 is Mk23-90C-2

Existing RC values. R=100Ohms. C=5nF
Any value close to 10nF will make the capacitor conduct and causes the relay to activate.

Here is a screenshot showing 3 waveforms.  On the common reed terminal I placed the probe ( blue waveform) 115 AC 400Hz . On the NO terminal I placed the yellow probe.

The purple waveform represents the voltage difference across the reed switch contacts ( the potential difference of the blue and yellow)

Here is a scope shot showing what happens when I activate the reed switch “SW1" with the snubber circuit above R=100, C=5nF. The voltage spike is 180V. The max contact rating on the reed switch is 175V.


texts:
I'm using a 3.5mm male to female connection (images below) to a voltage divider network to measure voltage from a solar panel with an Arduino. 230V to roughly 4V.
My question is whether these connections will be unable to handle the voltage and if so, why? They are rated for 1 amp.


texts:
I'm working with an STM32F4 discovery board and I want to calculate how much time it takes to do some tasks. I'm using Atollic with an SW4STM32 debugger. I cannot figure out how to do it.

I've read something about sending messages to the console and then measuring that time, but don't know how to send messages to the console. Can you help me? Thanks!


texts: Is fractional PLL the key functionality that defines whether a microcontroller is able to generate an analog TV signal?

texts:
I've been researching microcontrollers with the goal of outputting NTSC and/or PAL video signals.
And when I look at the microcontroller specifications, it appears to me that the single most important factor in determining if a microcontroller can generate analog video, is whether or not it has a clock/PLL/timer/counter that can be divided/multiplied such that somehow it is able to output a frequency that matches the required NTSC/PAL video frequency.
And more specifically, it needs the PLL to be fractional so that the clock timers can be divided very precisely because video requires very precise timing.
Is this correct?  Am I on the right track, that basically, a microcontroller with a fractional PLL is able to generate NTSC/PAL video, whilst  a microcontroller without fractional PLL is not able to generate NTSC/PAL video?
Or do I have it wrong, is the fractional PLL not so important, maybe the required frequency can be generated in some other way that would match the analog frequencies?
Clarification 1:
I am trying to identify, when I look at the specs of a microcontroller, if it is, or is not able to generate an analog video signal.  I do understand that many other factors are important in working out if it can do so, but my understanding is, that if you cannot control the output frequency of one of the peripherals to an analog TV output frequency, then nothing else matters - the job cannot be done.  I am trying to confirm if my understanding is correct or not.
Clarification 2:
What I am really trying to understand is whether any given MCU can generate the required frequencies without using external components - such as providing an external clock crystal.
Clarification 3:
I'm talking abut generating a composite signal.


texts: How to Convert 0 to 10V analog signal to 0 to 2.5V for ADC input?

texts:
I have an analog signal which ranges between 0V and 10V.  I want to linearly scale it down to 0 to 2.5V for my ADC.

I'm concerned that using a resistive voltage divider will affect signal quality.  Is this true?  If it's not true, what value resistor should I use for voltage divider?


texts:
I understand there have been quite a few posts asking about the DC motor speed vs PWM duty cycle issues. However, I found those questions different from what I want to ask, so I have to ask this topic again.

I have designed a circuit to drive a small DC motor as shown below. The P channels in the H-bridge are either Full-ON or Full-OFF depending which direction the motor rotates and the corresponding N channel is given PWM drive signals. The PWM frequency is 20kHz, VDC is 7V, T1 and T2 are connected to the DC motor terminals and the gate resistors used are 10 ohms.

In my understanding, the DC motor speed is supposed to be proportional to the drive voltage applied. So, if VDC is fixed, IMHO, the motor speed is supposed to be proportional to the PWM duty cycle because the motor drive voltage is VDC*PWM_dutycycle.

However, this was far from the actual case. Below is the speed vs duty cycle curve I recorded (picture updated).

When I fixed the PWM duty cycle but changed the VDC value, however, the motor speed became proportional to VDC*PWM_dutycycle.

Would anyone please advise why VDC*PWM_dutycycle could have different effects on motor speed when changing VDC compared to changing PWM duty cycle?

[update]

I forgot to mention that the motor shaft was connected to a gearbox whose reduction ratio is 290, and the speed shown in the above plot is the motor speed, not the gearbox output speed.

I started to wonder if this speed vs duty cycle issue was caused by the gearbox friction, which acted as motor load.


texts: Confusion in the difference between DC current gain and AC current gain in common emitter amplifier

texts:
Here is a definition:

It is easy to understand what DC current gain means here. The base current is constant, the collector current is also constant. An their ratio βdc = Ic/Ib. This is the DC current gain.

But I don't get the meaning of the βac AC current gain formula here. Is that the derivative of Ic wrt Ib? I came across the following plot but still didn't get how to calculate this gain.

How would one practically calculate this if one knows the input and output currents? Imagine the base current Ib is a sinusoidal current signal with 10uA peak to peak; and Ic is 1mA peak to peak. If it was DC current we would say the beta is 100. But here since we are dealing with AC, we need to find the AC gain by looking at the Ic Vce characteristics. How can we progress and make a logical derivation of AC current gain from this point?


texts:
What are the main methods the code inside a certain ARM Cortex M4 MCU (TI LM4F120H5QR etc) can be extracted after deployment?

Is it possible to completely stop a third party from stealing the code in it?


texts: How does a 4 pin IR Object/Proximity Sensor work?

texts:
How does this IR Proximity/Object sensor work ? Any resources or tutorials on how this works would be really helpful. I want to use this for my raspberry pi

NOTE : I have searched a lot on the internet and most of them either have 3 pins or a white dome shape over the module. This one has 4 pins.


texts: Does the PLL circuit which is used to increase frequency N times increase also the phase?

texts:
If we have a PLL with the following function:

The output freq. becomes N times the input freq.

But how about the phase difference between the input and the output?


texts: How exactly could you prove the following question about quantum computing?

texts: Consider a function f mapping a bit onto another bit, i.e. f:{0,1}---> {0,1}. The function f is either constant, so f(0)= f(1) or balanced, so f(0)different f(1). Thq qunatum gate for the Deutsch algorithm id given in Figure 1. The second gate f has the following form:


texts:
Is it ok to take the output of a solar panel (no MPPT, but de-rated) and pipe it into a switching regulator at say, 3.45v? The output of the regulator would go into my micro, an STM32F103 and a LiFePo4 in parallel.

I'm hoping that when there is sun, it will float charge the battery and power the micro and when there is no sun, the battery will power the micro.

I will have a diode on the panel.


texts: Should vias be used for every GND connection?

texts:
When making a two layer board with the bottom layer being a GND plane, should every GND pad for ICs and passives be directly connected to the GND plane using a via, or should I route all of the GND pins of components close to one another together and then use a single via to connect to the GND plane?

EDIT: Having a GND plane on the top would dramatically reduce the number of vias needed. However, this answer to a related question says:

  You are right, there is really very little reason to use both the top
  and bottom of a two layer board for ground.

  What I usually do for two layer boards is to put as much of the
  interconnects as possible on the top layer. This is where the pins of
  the parts are already anyway, so is the logical layer to use to
  connect them. Unfortunately you usually can't route everything on a
  single layer. Paying attention and thinking carefully about part
  placement will help with this, but in the general case it is not
  possible to route everything in one plane. I then use the bottom plane
  for short "jumpers" only when needed to make the routing work. The
  bottom plane is otherwise ground.