texts: Imagine having a broken radio transmitter, and I need to make it work by building a solenoid with an inductance of 100 uH. How can I do it?

texts:
This is a problem made by my professor.
Imagine having to repair a radio in a rural area, without any high-tech instruments, and I need to build a solenoid with an inductance of 100uH, a cross-section area of 1.00 cm2 and a lenght of 3.00cm.
Do I need to find the number of turns and their diameter, explaining also the type of material I would use?
I found some formulas, such as L  = [d2 n2] / [18d + 40l] , or this L = u0 * (n2/l) * S . What's the difference between them?
https://www.electricaltechnology.org/2014/03/inductance-air-core-inductor-calculator.html (This is the link to the first formula, while the second one was found in my physics' course book).
I know that I have to find the number of turns and their diameter, the only thing I don't know is which formula do I have to use.


texts: I'm playing around with STM32F4 Discovery board and libopencm3. I want to send data acquired from ADC channels over usb and display some charts on the computer. After doing some research on USB class codes I'm a bit confused: which one should I choose for my application? At first I was thinking that USB-CDC it the way to go, since it's easier to implement but I don't think that it's the optimal solution.


texts:
I have had great success in the past using the reflow soldering method, using a syringe and needle to apply the paste to the board. However, I found myself repeatedly making the same boards so I decided to purchase some stencils.

I purchased a framed metal stencil for one PCB design and a 4 mil mylar stencil for the other.

They have worked well, until one day I forgot to clean the stencil after use. Now the solder has hardened and it is not wiping off.

Is there something I can use to dissolve the solder so that I can wipe it clean? Also, do I use different products for my metal stencil and mylar stencil?

NB. I am using no clean solder paste by AIM: http://www.aimsolder.com/products/No%20Clean


texts: What exactly is SVPWM? Is it used in grid-tied inverters?

texts: I've been doing some research on ways to drive the half-bridges in a 3-phase, grid-tied, pure sine wave inverter. I knew about SPWM but not about SVPWM. Based on what I've read, it's superior to SPWM in multiple ways, but what exactly does an SVPWM waveform look like compared to SPWM? Is it even used in grid-tied inverters? Everywhere I've seen it so far, it was in the context of a motor speed controller, and the output waveform didn't look exactly like a sine wave (like on the image in Shameer N's response to this question). Lastly, are there any other alternatives to SPWM and SVPWM?


texts: Connecting Lora and FSK clients to a single server

texts:
I need to connect a Raspberry Pi (as the server) to some different Arduino devices as clients. Some of the clients need to connect using Lora SX1278 modules, and others use NRF24L01+ (or any similar low cost radio).
They will form a local network and not going to be connected to LoraWan. My SX1278 modules are from AiThinker.

Can I use the SX1278 module on RasPi to connect to both types of clients?
I could not find any stand-alone SX1278 library for RasPi, most of them are for building a LoraWan Gateway by RasPi.
The most commonly used Lora library for Arduino is SandeepMistry's. Is there any more feature rich library having AES encryption?

Edit:

Till now I found out two mistakes on my side:

I was wrong about NRF24, its frequency range doesn't match. I just need to use a cheap radio module, so my client devices' price remain low. Something like SI4432 seems to be good and supports FSK, GFSK, and OOK.
The client devices need to do simple sensor reading and relay switching tasks, and I need to keep client devices' cost as low as possible. So I need to find the cheapest micro-controller capable of AES encryption; Arduino or not.


texts: Op amp rectifier : transfer function and output impedance

texts:
I'm working on an EE student project which uses a rectifier to keep the peak value of a sine wave.
You can find a PSpice pic of the schematics below (Ve is the input (1kHz), Vs is the output).

Op amp rectifier:

I really have problems to analyse this pic. It is quite easy when I replace the diode by a short (and forget about the capacitor for now), then I just have Vs = (2+R3/10k)Ve (the potentiometer R3 gives a variable gain) by considering the op amp is ideal. Until now, it is okay.

When Ve is positive, the diode is on and the upper relation between Ve and Vs is correct, knowing that the 0.6V voltage drop accross the diode is compensated by the op amp.
When Ve is negative, the diode is off and the op-amp saturates at -Vsat behind the diode.
Until now, is it correct ?

Everything becomes more complicated when we put on the capacitor. It works perfectly to keep the peak value but I don't understand everything yet.
When the diode is on, the time constant should be very small, isn't it ? The output impedance of the op amp should be near zero, so the time constant tc = RC is very small, right ?

And when the diode is off, all resistors in the feedback loop (R1, R2 and R3) come in the time constant and tc becomes high, isn't it ?
Well, then why isn't the capacitor just following the signal when it is positive ? And stay at zero when it is down ?
I'm sure I'm missing something simple, but I don't know what...

And, when the time comes to find the total transfer function Vs/Ve (for both cases when the diode is on and off), I'm completely lost.
Just the same when it comes to find output impedance...

Hope I expressed myself clearly (and my English wasn't too bad).
Any help would be greatly appreciated.


texts:
I have a card with a MC74HC125A used to buffer some SPI lines coming from a CY7C68013A USB controller. There are testpoints in place at the output of the buffers. I would like to tap into and supply "my own" SPI signals from an FPGA on another board. There is a latch to remove the power to the CY7C68013A, but there is no way to cut power to the MC74HC125A except for de-soldering and removing it.

Question: Is it possible to drive the lines connected to the outputs of the MC74HC125A with "my own" signals?


texts:
I have been studying the derating effects of temperature on voltage rating of capacitors (ceramic). Something like the image shown below:

The image is the derating curve for a tantalum capacitor. This means that the voltage rating of the tantalum capacitor varies w.r.t temperature. But, does this behaviour also happen in ceramic capacitors?

I had a discussion on the same topic (Capacitor derating).

There I was told that such a behaviour does not affect ceramic capacitors as it does tantalum. But, I just saw a European Space Agency (ESA) document stating the derating curve for ceramic capacitors. The document is in the
ESA documents database, and the document is ECSS-Q-ST-30-11C-Rev1.

So in this document a similar derating curve (similar to the tantalum) is shown on page 22.

Now, I have looked at quite a few space-grade ceramic capacitors, but none have such a derating information. So, what is this paramenter that is being shown in the ESA document?


texts:
I seem to be struggling in locating a replacement set of LEDs for my DRL board.
The manufacture is in China and will not help me out
The led is an RGB chip but every replacement I have found so far only offers 1 red, 1 green and 1 blue diode, where as these appear to run 3 of each providing more light output but in the same size dimensions.. could it be they have custom made these rather than them being available on the market?
I did consider a COB led however even the smallest of those are far too big


texts:
I have a bag of old unmarked PICs, possibly PIC18, but could be PIC16, and want to try to figure out what exact type they are and if they have already been programmed or not. Not even sure if they are of a EPROM or flash variant. Hoping to do this using an Arduino to write/read the PIC pins.
Methods that are potentially destructive to the PIC itself are acceptable, if that makes it easier, but would prefer to not connect it in a way that can fry other things around it.


texts: UVC Compliant H264 Encoder for PAL/NTSC Analog Camera Modules

texts:
I've been looking for some weeks on a part/module and haven't found anything so far.

I've been experimenting with streaming techniques using Logitech C920 webcam.

This webcam has an embedded H264 hardware encoder and through the USB Video Class (UVC) driver, you can retrieve the H264 stream and control the internal encoder (bitrate, etc..) which is particularly convenient for low latency streaming.

I'm trying to industrialize a system but I cannot use the C920 webcam and I'm looking at a more 'OEM' solution.

I'm looking for a small footprint device which fullfills this requirements :
- Takes PAL/NTSC camera as input (this way, I can connect any module camera from Omnivision for instance or Sony's block cameras, or even Infrared cameras).
- Has an internal H264 Encoder
- Outputs video as H264 through USB Video Device Class driver (UVC).
- Control of the internal encoder through the UVC driver.

I have seen several existing devices but these solutions are way too 'big' for my needs (mostly, external encoders for live streaming on DSLR like Teradek...).

If this does not exists, to your knowledge, is there any circuit/component I could use in a custom design, and what complexity does it require to design a custom solution for this problem ?

Thanks a lot for your help !


texts:
I'm back to diagnosing power supply failures, in an LLC resonant SMPS based on the L6598, from a 400 V PFC supply with ostensibly 400 W output.  I'm new to SMPS, and learning this all as I go, and the manufacturers don't know what they're doing, either; they just copied the design and modified it for more bigger power.  The circuit is basically like Figure 3 in AN-9425, but the OPOUT overcurrent detection triggers EN1 (latched) instead of EN2 (soft-start reset).

The failures happen during overload, when the supply is making audible screaming noises and the output voltage has dropped (because it's switching below the resonant frequency, right?)  Sometimes it can withstand a prolonged overload (without triggering EN1), sometimes it can't.  Sudden transient overloads are usually what kill it.  Not sure if it's a progressive damage thing that eventually results in failure or a random spike that exceeds a limit.  Theoretically, it should handle overloads by shutting off momentarily or otherwise protecting itself, not by exploding.

Theoretically, I could change the overcurrent protection so that it detects when it's being overloaded and triggers the soft-start EN2 protection mode, shifting the frequency up high to drop the output voltage instead of dropping below the resonant point.  I tried modifying the circuit to match the app notes so OPOUT drives EN2, but that just made it blow up even more quickly when I overloaded it.

The L6598 controller IC always fails, the STW20NM60 MOSFETs fail sometimes (high side short across all pins, low side short from D to S), so I think the IC is failing first and taking the MOSFETs with it?  The MOSFETs don't have built-in gate protection, so I added Zeners externally and they haven't failed since (yet).  New ICs measure open circuit from any pin to any other, but after I remove a failed IC from circuit, some of the high pins will have kΩ between them (12 Vsupply, 14 Vout, 15 high side driver, 16 bootstrap cap).

Today I was manually triggering the EN2 pin, which worked fine at low loads, changing to a high switching frequency and output voltage dropping.  At about 200 W out, it worked fine when I enabled EN2, but when I let go of EN2 it would shut down (overcurrent protection triggering EN1 is the only way I know of) and then another time failed.  After it failed, the low side driver would still switch at fmin (no output voltage to drive the feedback loop), but the high side driver just had spikes and weird shapes on it, not a square wave.  The MOSFETs measure normally with an ohmmeter and didn't explode.  So some kind of spike is killing the high side section of the IC and I need to prevent that.

I certainly don't see any pins going higher than the 618 V absolute max rating.  I do see tiny spikes going down to -3 V before the rising edge on Vout and VHVG, which are rated for -1 V.  I don't know if that really matters.  I'm not sure about the ratings for Vout or VHVG, or how I would even measure those (differential probe?), or what conditions would cause them to go beyond the stated limits.  They seem to track each other, as would be expected if the high side driver is floating relative to Vout.

What am I missing?

Update:

There are huge bursts of oscillation(?) ±25 V on the gate driver while overloading, 100s of ns after the rising or falling edges, which coincide with the audible noise.  These could easily break through the gates and destroy the FETs, so they are the prime suspect.  They originally had ferrite beads on all the FET pins, which did not prevent this, nor does removing them.  I've added Zener protection to the gates, though, which should prevent them from being destructive, but I'd like the eliminate the bursts themselves first.


texts: I'm building a DIY pedal effect for my electric guitar and I have to connect the input and output jack connector, but I don't know how to do it. The connectors have 3 pins, one is the tip which it is connected to the tip of the male jack and one I guess it is the ground, but I don't know how to connect the third one. My question is: can I use two mono jack input? In internet I saw stompbox with only one mono jack as output and one stereo jack as input. If yes, how do I have to connect them?


texts: Control systems composed of several different parts just as program blocks

texts:
We're having a course on System Software this semester and we're covering the chapter on Assemblers presently. Our professor gave us some questions to think about. One of them is this:

  Control systems maybe composed of several different parts just as program blocks. Is this good or bad for the assembler? If this creates a problem, how can it be solved?

I find this a bit weird. Presumably, control systems can indeed be written in terms of "program blocks" but I'm not sure whether anything can be said about its suitability (good or bad) for the assembler. Can someone provide some hints on this question?


texts: What is the effect that makes components on a circuit board move into place?

texts:
I am going to apologize ahead of time if this is a really simple question. I started learning to solder during my internship but I had no EE knowledge prior.
When I was working with surface mount soldering my internship adviser mentioned this property or effect, the name of which I'm blanking on, that would cause the pieces when heated to move into place on the pads of the board. Does anyone know what the name of that property or effect is?


texts: Using distribution transformers vs direct connection to primary switch gear

texts:
I am trying to learn more about transformers and low voltage electrical distribution.

Say you have a medium sized industrial building with a primary switchboard feeding several load centers elsewhere in the building feeding localized loads.

Is it more efficient* to use one voltage through out the system, i.e. the power feed into the building would be 120/208v 3phase which would be distributed through out the building, or distribute a larger voltage and hence smaller current through the building to the load centers and then transform the voltage to the desired voltage at that point.

*note: more efficient can either mean electrically, as in am i wasting more power by using more transformers vs larger cabling, or monetarily, as in is the smaller copper distribution wire going to outweigh the price of the transformers.

thanks in advance.


texts:
Take a look at this popular circuit for a fridge alarm based around the 4060 binary counter (http://free-electroniccircuit.blogspot.co.uk/2012/02/refrigerator-alarm-schematic.html):

One thing I notice is that the diodes connected to pins 3 and 6 are "reversed".  I think I understand why this is the case: that when these pins go high, after a time interval specific to the output pin (and adjusted by the RC arrangement at pins 9 and 10), the current is blocked from flowing through the diodes and instead flows through the transistor base pin causing the buzzer to sound.  My assumption is that when pins 3 and 6 are not high that current freely flows through R4 and the diodes and into the "output" pins 3 and 6.

My question is this: is it "healthy" to pass current though IC pins that are specifically output pins?  Is this a common arrangement?


texts:
[![enter image description here][1]][1]I accidentally punctured just the very first (pouch?) layer on my MacBook lithium ion battery. A smell came out of it but the battery still works fine and holds charge. from what I've read, this is just the solvent being released from the battery and I haven't actually damaged the battery cell itself. But I can't find the answer to is this in danger of exploding? Thanks!

enter image description here


texts: Why would a motor manufacturer offer multiple coil winding types?

texts:
I'm currently looking through a part catalog from a motor manufacturer and notice that you can purchase this motor with different motor winding types. Specifically, you can order the motor coil wound either delta or wye configured.

Why would a manufacturer offer multiple winding type? What are the pros and cons for each style?


texts: Where to get a USB type E front panel motherboard header?

texts:
I'm designing a product that will need to have USB type C ports on its front panel, and due to physical constraints with the design, I would like to use a USB type E connector in conjunction with a front panel cable (like this one) to accomplish this.
However, searching various online suppliers, I'm unable to find an actual manufacturer, part, part number, or any kind of datasheet for such a connector.
Here's an image of the connector I'm after:

(Note that while I'm primarily interested in the female surface-mount connector on the left, if you do happen to know where to get the bare cable-end connector on the cable to the right, that would certainly be helpful as well.)
The official specification for this connector calls it the "USB 3.1 Front-Panel Internal Connector", but that term isn't turning anything up for me either.
What manufacturers are currently making this connector, and what part numbers should I be searching for?


texts: What semiconductor materials are used in the 2N3904?

texts:
The 2N3904 type transistor is manufactured by a number of companies, using different layouts, but the characteristic requirements are the same for all of them. Do these requirements imply the usage of a particular semiconductor material? For example, simple group IV semiconductor with silicon or more complex materials such as III-V or II-VI materials? One would assume silicon-based material but I am curious if there is a source of information on this?

Thanks in advance.

Sam


texts: Olympus TG-Tracker : What does this data stand for?

texts:
I'm sorry if this comes to wrong forum, but here goes.

I got this new action camera which tracks the following kind of data (edited):

$OLTIM,20170224,045641// Time obviously, no probs here
$OLCMP,23.7 // Compass
$OLPRE,963,421.2,1389.9 // Pressure
$OLTMP,20.5,1,0 // Temperature in F's, no probs here
$OLACC,-1007.1,-3.6,4.7 // Acceleration
--
$OLTIM,20170224,045712
$OLCMP,24.2
$OLPRE,963,422.0,1392.6
$OLTMP,20.5,1,0
$OLACC,-1007.1,-3.6,8.5
--
$OLTIM,20170224,045743
$OLCMP,23.2
$OLPRE,963,419.5,1384.4
$OLTMP,20.5,1,0
$OLACC,-1003.1,-3.6,4.7
--
$OLTIM,20170224,045814
$OLCMP,24.3
$OLPRE,963,422.2,1393.3
$OLTMP,20.5,1,0
$OLACC,-1007.1,-3.6,4.7
--
$OLTIM,20170224,045846
$OLCMP,24.5
$OLPRE,963,419.3,1383.8
$OLTMP,20.5,1,0
$OLACC,-1007.1,-3.6,4.7
--
$OLTIM,20170224,045917
$OLCMP,256.5
$OLPRE,963,423.4,1397.3
$OLTMP,20.5,1,0
$OLACC,274.5,-901.2,-116.8
--
$OLTIM,20170224,045938
$OLCMP,273.4
$OLPRE,964,415.8,1372.2
$OLTMP,20.5,1,0
$OLACC,405.5,-878.4,168.1

I've maneged to solve this:

first digits (963) of $OLPRE must be the average air pressure in hPa

For this, I've got a hunch:

$OLACC could refer to x,y & z accels

Conditions when data was captured:

Outside, ~ -7c
~95m (312ft) over sea level
Clear sky

So the question is:

Any ideas what $OLCMP and the second digits of $OLPREwould stand for? And the rest too actually.


texts: DC boost converter output voltage problem when load is connected

texts:
I have successfully finished one part of the DC converter. Now I came across a certain problem which I can't solve myself.

When I didn't connect a load to the output of the dc converter, there was 50V at most. But after I connected a load, even if I have my feedback code completed, it still drops to like 5 or 4V according to the load. I have searched some videos on YouTube and did exactly they did.

Here is my schematic:

I have also corrected Arduino code which was suited for ATTiny85 chip to be suitable for ATMega328P. But I'm not sure by one thing - my potentiometer is 10k and every is displayed 100k, so it means that they used this 100k value to do its purpose. Can this be the problem that I have only 10k potentiometer? If yes, should the code by fixed somehow or not?

#define F_CPU 8000000
int pwm = 9;
int potinput = A0;
int feedbackinput = A1;
int potinputval;
int feedbackinputval;
int pwmval;

void setup() {
  TCCR1B = TCCR1B & 0B11111000 | 0x01;
  pinMode(pwm, OUTPUT);
  pinMode(potinput, INPUT);
  pinMode(feedbackinput, INPUT);
  digitalWrite(pwm, LOW);
  pwmval = 0;
}

void loop() {
  potinputval = analogRead(potinput);
  potinputval = map(potinputval, 1023, 0, 255, 0);
  feedbackinputval = analogRead(feedbackinput);
  feedbackinputval = map(feedbackinputval, 1023, 0, 255, 0);
  while (potinputval > feedbackinputval) {
    if (pwmval == 230) {
      potinputval = analogRead(potinput);
      potinputval = map(potinputval, 1023, 0, 255, 0);
      feedbackinputval = analogRead(feedbackinput);
      feedbackinputval = map(feedbackinputval, 1023, 0, 255, 0);
    }
    else {
      pwmval = pwmval + 1;
      analogWrite(pwm, pwmval);
      potinputval = analogRead(potinput);
      potinputval = map(potinputval, 1023, 0, 255, 0);
      feedbackinputval = analogRead(feedbackinput);
      feedbackinputval = map(feedbackinputval, 1023, 0, 255, 0);
    }
  }
  while (potinputval < feedbackinputval) {
    if (pwmval == 0) {
      potinputval = analogRead(potinput);
      potinputval = map(potinputval, 1023, 0, 255, 0);
      feedbackinputval = analogRead(feedbackinput);
      feedbackinputval = map(feedbackinputval, 1023, 0, 255, 0);
    }
    else {
      pwmval = pwmval - 1;
      analogWrite(pwm, pwmval);
      potinputval = analogRead(potinput);
      potinputval = map(potinputval, 1023, 0, 255, 0);
      feedbackinputval = analogRead(feedbackinput);
      feedbackinputval = map(feedbackinputval, 1023, 0, 255, 0);
    }
  }
}

Thank you for any sensible response :)


texts: Vhdl Error (10500) near text "when"; expecting ";"

texts:
this is the error: Error (10500): VHDL syntax error at Bin7SegDecoder.vhd(15) near text "when";  expecting ";"

It may be simple but I don't know what's the error.
Thanks in advance!

library IEEE;
use IEEE.STD_LOGIC_1164.all;

entity Bin7SegDecoder is
    port( enable   : in  std_logic;
            binInput : in  std_logic_vector(3 downto 0);
            decOut_n : out std_logic_vector(6 downto 0));
end Bin7SegDecoder;

architecture Behavioral of Bin7SegDecoder is
begin
    process(binInput, enable)
    begin
        if (enable = '1') then
            decOut_n <= "1111001" when (binInput = "0001") else --1
                            "0100100" when (binInput = "0010") else --2
                            "0110000" when (binInput = "0011") else --3
                            "0011001" when (binInput = "0100") else --4
                            "0010010" when (binInput = "0101") else --5
                            "0000010" when (binInput = "0110") else --6
                            "1111000" when (binInput = "0111") else --7
                            "0000000" when (binInput = "1000") else --8
                            "0010000" when (binInput = "1001") else --9
                            "0001000" when (binInput = "1010") else --A
                            "0000011" when (binInput = "1011") else --B
                            "1000110" when (binInput = "1100") else --C
                            "0100001" when (binInput = "1101") else --D
                            "0000110" when (binInput = "1110") else --E
                            "0001110" when (binInput = "1111") else --F
                            "1000000"; --0
        else
            decOut_n <= "1111111";
        end if;
    end process;
end Behavioral;


texts:
I have a old motor driver board, for which I don't know the current capability.
So I tried to find the datasheet of the MOSFET on the board.
But without success (Bing search in various variants)
This are the information:
Package: SO8
Marking:
first line 2N604L
Second line 2 Mosfet is marked with 23D another 2 with 2AN
Third line 61744
No other markings or symbols.


texts: What is the maximum acceptable soldering temperature for a MOSFET?

texts:
I need to manually solder with a soldering iron an LFPAK56, Power-SO8 package MOSFET. I am reading that the maximum junction temperature for the device is 175C.
Soldering iron go way over that temperature but of course the Tj temperature is define for when the MOSFET is in operation. Soldering max temperature must be much higher. Wave soldering has a max temp of about 260C for some 10 seconds. The MOSFET drain is quite a massive piece of metal and must be heated enough to permit solder melt. Is it even possible to solder such a device manually without overheating to destruction?

So, the Question:  What is the maximum device temperature possible before a MOSFET start degrading and or destroy during manual soldering ?

And how long can it endure such high temperature ?


texts:
I'm building a small circuit with an arduino bootloaded ATMega328 chip.

The project will be housed in a small box, and is intended to be stuck to the side of a fridge using a magnet.

Everything in my brain tells me that magnets and chips do not mix well. What is the likelihood that the sketch loaded onto the chip will become corrupted, or that something else will happen as a direct result of the magnetic forces, causing the chip to cease operation/ operate incorrectly?


texts: Motor Mechanical Torque vs Motor Electrical Power

texts:
Let us say there is a constant load which is driven by a geared 3-phase ACIM (AC Induction Motor) of 5kW power rating. The mechanical load and its speed is constant.
If I would need to replace this ACIM motor and gear with a BLDC motor and gear so that it could drive the same load with same speed as before then would I need to use a BLDC motor of 5kW power or is it possible that a lower power BLDC motor will also be able to drive the same load with same speed? The reason I think that a lower power, say 3kW BLDC motor will also be able to drive the same load is that BLDC are more efficient but I am not sure if my understanding is correct or not.
If my mechanical load is same then is it possible that a different type of motor will have different electrical power to drive the same load with same speed?


texts: Is it possible to split USB 2.0 control requests?

texts:
I'm developing an application for microcontroller with onboard USB. The application is supposed to be as portable as possible, so I can't just point to one family in particular.

I'm in the process of reading a device's configuration descriptor, however, it is too long to fit in my internal buffer.
I can't use dynamic memory for this, so a buffer for control transfers needs to be statically allocated and I really want to minimize its size given that it won't be used much. So assigning it a couple Kb just for this cfg descriptor is not an option.

I haven't found it in the standard, but maybe I just haven't looked good enough... is it possible to split control requests into multiple ones? For instance, request 128 (or whatever) bytes of the cfg desc, then request another 128 bytes of the same descriptor, of course, these would have to be returned with a 128 offset to account for the ones already read, and so on.

Is this possible?

Thank you all for you time.


texts: Flyback Transformer Active Snubber Design

texts:
I'm using a flyback transformer along with the LT3750 controller by Linear to charge a capacitor. I'm wanting to increase efficiency and improve the circuit. I began with looking into an RC snubber to relieve some of the voltage stress on the mosfet. In reading about the trade-offs of using snubbers I ran into what's called an active snubber.

(source: sanantoniowebagent.com)
From what I understand an active snubber diverts the leakage inductance energy back into the Vin line. The circuit requires a second mosfet, an inductor and a diode. I'm trying to research this solution but cannot find any additional information. I would think repurposing that lost energy and putting it back into the Vin line would be much more efficient versus dissipating through a resistor.
Any thoughts on active snubbers for efficiency?
Any insight on how to design such a circuit?


texts:
I've had a look around at all the various different ways to build a Full Adder and decided to have a crack at it myself. I looked at what it consisted of (2 XOR gates and a few AND gates) and built a model from diagrams of the gates that I managed to find. After having built this model I tested it and funnily enough it doesn't work.

Now, I can't see where I went wrong in this as according to my logic it should work perfectly. The only thing that I see that could be happening is that there is a leakage from the base to the emitter of all my AND gates.

This is the diagram of what I've built:

I've used 2N3904, which are BJT NPN transistors. I'm not using a ACS713 on the real thing but that was the only image that I could find that was close to what I wanted. The input voltage is 5V with a 1k Ohm resistor.

Can someone please help me to figure out what is wrong with this model and potentially give me some improvements?

Thanks in advance.


texts: Heart Rate Monitor Schematic: Somethings Wrong

texts:
I am trying to get an analog circuit design for a heart rate monitor and eventually create an output to some graphing tool either on PC or phone/tablet.

I have put together the following circuit yet there is something wrong. I can not determine what. I am assuming it is one of two things:

1.) Maybe the Photo Diode must be reveresed?
2.) Maybe the Op Amp is saturated

The circuit schematic is as shown:

I am receiving random values from the Arduinos serial monitor and noticing no change when I completely cover up the emitter.

Is there something wrong with this circuit design?

I have followed this tutorial ( Link to Tutorial ) closely and rebuild the design 4 times. The transmitter is revieving power and the Photo Diode is showing voltage when I measure it.

I have access to both a Multimeter as well as a Scope.

Should I take measurements from the output using the scope, any advice?


texts:
This is my first question on stackexchange so if I do anything wrong, please let me know :-)

So my situation is the following:

I am working on a power supply module where I need 7 separated +28V DC outputs up to 25A. My current design incorporates of a small transformer-rectifier-regulator module with adjustable output that I want to use as a "pilot module". Then feed the output voltage of this "pilot module" into 7 "power modules" where on each of them it will steer a NPN transistor. The NPN transistor I'm thinking of using is the 2N3771 in TO3 package, rated at 50V, 30A, 150W.

Now I need to convert the 230V AC from my mains into a lower DC voltage for the power transistor emitter. Traditionally I would do that using a transformer, followed by a rectifier and smoothing cap. However, in this case I could see that getting very costly and hard to obtain, both using 7 different transformers or 1 big (huge) transformer.

So I was thinking about replacing the mains-transformer-rectifier-capacitor with mains-rectifier-capacitor-MOSFET and control the MOSFET with a pwm signal. Would this work? What would be the advantages and drawbacks of this approach? If I use a transformer, the output current will be lower then the input current while with a MOSFET this wouldn't happen. So could I double the load on the MOSFET given it will only be switched on half the time? Or would the peak current damage the MOSFET?

Thanks to everyone taking the time to read and answer this already :-)


texts: Need advice on my simple solar powered lighting system

texts: I'm building a simple circuit in which a solar panel will charge a 12 V battery during the day and then switch over to battery power during at night to light up a few bulbs. I'm using an LDR which will trigger the NPN at night and switch the relay, as shown in my circuit schematic below. I'm very inexperienced so I'd like if you can tell me what is wrong or what could be done better. I'm also wondering if there is a better approach to activating the relay than using a 9V battery. Thank you.


texts: Is this calculation for an optocoupler's resistor correct?

texts:
I'm trying to calculate what resistor to use for this optocoupler.

Per the datasheet, it drops 1.3v at 50mA does this mean I should try choose a resistor that gives me 50mA?

My supply is 3.3V so my calculation was set out as follows:

R = V / I

V should be the supply voltage minus the drop over the diode, so 3.3V - 1.3V = 2V, and per the datasheet I should try get 50mA:

R = 2V / 0.05A = 40 Ohms

Is that correct?


texts: What does the impedance look like around a small resonant loop?

texts:
Say I have a hoop of conductor, broken at the top, with a capacitor across the gap. The inductance of the hoop and the capacitance form a series resonant LC circuit:

Now, say this loop is excited by a distant transmitter. What will the currents and the voltages look like in this loop? At what point are current and voltage in phase? How does the phase angle change as I move around the loop? Is there a point at which \$|Z| = 50\Omega\$ ? Can I predict where it will be? Can I predict what the phase angle will be at this point?

(The objective, you might guess, is to match an electrically small, resonant loop to a transmission line. I've read many ways to do this, and I can get it to work through trial and error, but I desire a better understanding of why it works, and what's happening inside the loop.)


texts:
I'm attempting to port discrete schematics into a FPGA. In the schematics some AND gates function as short pulse generators, when input goes low output is enabled, until input propagates down an inverter chain and disables the gate (Similar to the answer described here.)  Thus a short pulse is produced every negative edge. I'm new to Verilog, and am not sure of the best way to recreate this effect in Verilog. Would the code below work and is it a proper solution?

module pulser(input in,output out);
    reg mem;
    assign out = mem & !in;
    always @(negedge in) begin
        mem <= 0;
    end
    always @(posedge in) begin
        mem <= 1;
    end
endmodule


texts: Getting rid of electrical noise produced when one touches amplifier and amplifier's dials

texts:
I purchased a Lepai LP-2020A+, which is a pretty good little amp for the price, but I've modified it to make it much better and decided it deserved a better casing to look the part, too. So I constructed a little elegant wooden housing for the amp, to get rid of that carry (an attempt to adjectivise the noun car!) appearance.

I assumed the amp's original aluminum housing worked as a sort of Faraday's cage to avoid external electrical signals from coming inside the system, so I covered the inside of the wooden housing with several layers of aluminum tape that's in contact with the original front and rear aluminum panels (which I kept, because they looked rather good on the finished product), thus effectively closing the Faraday cage of sorts.

So everything's generally fine. There's no outside signals getting in, no more noise than there was before, at any rate. However, when one touches the amp (even when one touches the wooden housing, which is strange), normally when one's turning up or down the volume, turning the device off, one gets some electrical noise.

One thing I thought might work was connecting the front and back panels to the device's ground (as you can see in the photo, the potentiometer is already connected to the device's ground). I've tried this, however, and the noise is still there.

I'm wondering if anyone might have any idea of how I can get rid of this noise that only appears when one touches the amplifier.

I'm including a photo of the LP-2020A+'s PCB as it arrived (yes, the noise was there even before I modified the components). Hope someone out there can give me a hand! Any info will be greatly appreciated!


texts:
I've been doing some work lately with the DRV103 IC by Texas Instruments (datasheet here, essentially it creates a PWM signal of variable duty cycle and frequency, preceded by an 'ON' signal of variable time), which is a pretty cool chip, but I've hit a snag with it.

For a particular application, I decided to control the duty cycle with voltage rather than resistance. According to the datasheet, this should be straightforward.

I found the right resistors and potentiometer for the values needed, selected somewhat arbitrary delay and frequency values, then set it up as per this schematic:

P1 and P2 are generic wire-to-board connectors, the transistor is a PMF170XP,115 P-type MOSFET which I used to invert the output.

Parts arrived, I soldered it up, hooked up the power, but when I switched it on, rather than the expected PWM, the output went straight to 12V and stayed there. The voltages everywhere seem correct (including the potentiometer range), there are no shorts that I can see (and the benchtop power supply I used shows almost 0 current draw) and I replaced the chip as a sanity check; no luck.

Have I missed something obvious? There's no flyback diode, but the chip is only driving the signal input of another piece of hardware; adding one is the next thing I'll check, along with a pulldown resistor.


texts:
Here is Wien oscillator with amplitude stabilization:

I know how this oscillator works in theory, but I'm interested how it would behave in practice. Voltage at Vout node would be sine wave. If we put some load between Vout and ground, it will affect amplitude of Vout, right?
Is it because of limited output current of opamp (LM741 in this case)?
I simulated this circuit in Multisim. Firstly, I connected 100k resistance on output and I didn't notice any change in amplitude of Vout.
Then I used lower values of resistance, and for example, for resistance of 10 Ohms on output, amplitude of Vout is about 0.13V.
What are applications of Wien oscillator?
Thanks in advance


texts: Passing greater of 2 voltages using 5V signal

texts:
I need to output the larger of two voltages (Va, Vb) (both of which could be in a range 0-30V), but drive the circuit using a 5V supply. A simple solution (using op-amps, FETs) is needed.
I have looked at solutions using just an op-amp in comparator configuration, or an op-amp driving 2 MOSFETs, but since my Va, Vb could be smaller or greater than 5V, MOSFET switching does not seem to be an option (atleast with a trivial circuit).


texts: Power amplifier input source current path

texts: Can anyone draw (or write in text) the small-signal path from signal source XFG1 at input of Q1 base to amplifier load for positive and negative input signal swing?


texts: Toggle poles of DC using single port switch

texts:
I need to toggle the poles of a DC battery using a switch.
can you make such a circuit for me? please ...


texts:
I'm making a power board for my robot and I am looking for some advice regarding LiPo battery protection ICs.

I might need to draw a fair bit of current (9A), though if I get the programming right, it shouldn't be a problem (will probably be around 3A max).

Anyway, I was looking at using DS2764 from Maxim (datasheet), and it seems nice aside from the fact that I don't think I can use the 14.7V packs (need 12V output) I wanted to get :) Plus the current is limited to 2.5A. It also has the 2-Wire Interface that I don't plan using, so it's a bit of a waste.

Next, I started looking on Digikey for some LiPo protection devices, and now I'm confused: let's say I have a 14.7V LiPo battery, which means it's 4S I think. So technically there are 4 cells in there, but I don't have access to all 4. So when sorting the ICs, should I look for ones that say 1 cell (because that's the number of connections I have) or 4 cell? The 4 cell ones seem to always want inputs from all 4 cells...

Do you have any suggestions for something that can handle the current (I'm using a fuse anyways, so just as long as it has a fairly high limit it's probably ok) and the voltage? I know it's quite vague, but I don't really know where to look.


texts:
I'm designing a wearable with a ESP32 and three drivers, everything works with 3,3 V and the drivers consumes 15 mA each one.
I'm powering it with a lithium battery of 400 mAh, (4.2 V max). So I thought to use an LDO the AP2112, but I have several questions about the LDO. For example, the ESP32 in sleep mode consumes only 50 mA more or less, but when its in booting or some transactions it consume 300 mA and when you are in "RF mode" (transmitting with BLE) it consumes 250 mA. I would like that the wearable operates minimum two hours without charging it.
So this LDO has an output current of 600 mA, and quiescent current of 55 μA.
My question is if the LDO only consumes 55 μA and it is giving to me 600 mA "for free". But it doesn't make too much sense because I only use 55 μA for power a 500 mA (max) circuit. So it will be switched on like too much hours. With a 400 mAh battery.
And the second question is: if my ESP32 is consuming only 50 mA but the LDO gives to me 600 mA it could be some "overload" in circuit?
I read a lot of documentation but I don't know yet how it really works.


texts: Need detailed working or explanation of SCAN register in DSPIC

texts: I am not able to figure out the working of SCAN register in DSPIC30F2010.I need to read 4 analog inputs in ADC and for that need to set the sampling and conversion


texts: Separately excited DC generator as a constant current source

texts:
Is it possible to operate separately excited DC generator as a constant current source using the following method?
Keeping torque due to prime mover and field winding constant, reduce armature reaction close to zero using compensating windings and interpole windings.
Is this method practically possible and can it be implemented or is there some flaw in this method?


texts: Cancel resonation impedance of a speaker

texts:
In a speaker there is a resonance impedance. Now I am trying to cancel this out in order to create a flat impedance graph for all frequencies.

I know this can be done by using a parallel Zobel network.

The problem lies in the resonance impedance. I think this can be flattened using a RLC circuit parallel to the speaker. I would like to simulate this using Pspice but I cannot seem to find the right values for the resistance,capacitance and inductance.

Would this work?
How can I calculate these values for R,C and L?


texts: What is the best way to evaluate GPS antenna performance by receiver data only?

texts:
I'd like to test GPS Antenna performance, but I don't have access to any expensive RF equipment.  What is the best way to evaluate GPS antenna performance by using only standard NMEA sentence type data?  The Sirf and U-blox based receivers I am using allows me to enable almost any standard NMEA sentence.

One crude way of testing an antenna is seeing if it actually gets a lock -- however, that's the most basic test.  I'd like to evaluate further.

Some ideas that I have:

Measuring number of satellites it can lock to
Looking at all the signal strengths of all satellites
Adding up all signal strengths of all satellites that it can lock to.
Look at the HDOP and VDOP values -- however, perhaps this is not helpful or meaningful as this only depends on the geometry of the locked satellites.


texts: If I have a BJT with a max Ic rating of 200mA and I drive in a base current which when multiplied with hfe, results in a theoretical Ic value of more than 200mA, will the collector actually draw in more than 200mA and get damaged, or will the collector keep drawing a max cap of 200mA? Is it safe to drive a transistor using base currents which would normally generate Ics higher than the data sheet cap recommendations?


texts: Need design best practice: microcontroller controlled, variable, DC voltage source

texts:
I need guidance on designing a Variable DC power supply with the following characteristics:

Microcontroller controlled
DC output ~ 1V - 30V
Current handling: ~5 amperes
Power handling: ~50 watts

I am an electrical engineer but I don't really design power supplies.
I plan to commercialize a product however I am currently just breadboarding and getting a feel for what works.
Can anyone point me to how get started quickly?
I've tried working out a concept already:
microcontroller --> potentiometer --> Switching voltage regulator (the voltage regulator receives voltage from a bench top power supply. I don't really know how to design things that tap directly off mains power yet)


texts: Can anybody help me with identifying this connector? It’s  off a battery that goes into turtle beach i60 headphones. Thanks a lot.


texts: Recommended BMS Parameters for 18650 lition 7S 24V Battery Pack

texts:
I want to build a 24v 7S 3.7-4.2 18650 lion pack. My concern is the parameters my BMS should have to keep in balance all the 7 cells, not over charge them or over discharge them. cells from laptops: ICR18650-26c.

Please open /check this spreasheet  with the values I think the BMS should have to be on the safe side.  If values are incorrect , kindly provide feedback and correct values.

BMS specification

Thank you!


texts: How to ensure an LED is completely off when pin is set LOW?

texts:
I have a situation where, when the associated pin is set LOW, the LED still glows faintly.  As this is to be used in a darkened area, it is quite noticeable.

So far, I have encountered this only with one of my Arduino boards, and only when the LED colour in use is pink, as opposed to yellow or blue, which are the only other colours I have tried.  Increasing the resistor from pin to LED to 1K ohm does not resolve the issue. Also, the use of a different pink LED does not affect the outcome.

I realize that setting a pin "LOW" does not imply zero current, so how should I handle this problem?  Though I am quite familiar with the Arduino, my knowledge of Electronics in general is quite shallow, and ask that any response take this into consideration.


texts: Understand 2 transistors (NPN & PNP) flasher circuit working

texts:
I implemented this circuit on a breadboard and it works.
However on Proteus ISIS it doesn't (I have to change the 330k to 1500k for it to work on Proteus). I have two questions related to it.

1- Why does the positive pole of the capacitor face the positive pole of the battery and how come that while oscillating the voltage of the capacitor oscillates positive and negative.

2- Can anyone explain the functioning of the circuit. It is a bit confusing. the reason for the 22R resistor is quite obvious. However I cannot understand on which bases we use 330k resistor and what happens if we change that value. (which course should I attend or which book should I read to understand this kind of circuits)


texts:
I'm trying to drive a LM317T with a PWM signal coming from my Arduino UNO.
Here is my circuit:

simulate this circuit – Schematic created using CircuitLab

The PWM frequency is about 500Hz and I'm using a TLC2272 op amp and a LM317T regulator.
If the V_ref of the regulator is 1.25V, shouldn't I get an output voltage 1.25v greater than the adjust voltage?
When I measure V_out - V_adj I get about 2V.

What's wrong with my circuit?

Thanks


texts: finding NM by writing formulla in hspice

texts:
I want to calculate Write, hold, and read static noise margin of an SRAM block(WSNM, HSNM, and RSNM). but in order to do so, I want to write a command to do it, so I need to find input voltage when its differentiation is equal to -1 for calculating V(IL) and V(IH). Does anyone know the command to do so?

pictures are from "Analytical Review of Noise Margin in MVL: Clarification of a Deceptive Matter" paper


texts: 3.3V / 1A boost converter TPS61025 drops to 330mV when loaded with 5.5 Ohm - why?

texts:
I made power supply using TPS61025. It's a 3.3-V Output, 1.5-A Switch Boost Converter.

I have chosen relatively large capacitors as my circuit drives a power hungry WIFI chip. I have two new AA batteries (2.7V). Without load, output voltage is 3.4V. But when I use a 5.5 ohm resistor as load, the voltage drops to 330 mV and current is about 60 mA.

My inductor is rated for 1.6 A. Per IC data sheet, it can deliver over 1A. I checked soldering and it seems OK.

What's the possible cause?


texts: How do I wire a motor driver power supply?

texts:
I'm trying to wire and control TB6612FNG Dual Motor Driver Carrier, but am doing something wrong. Why is the motor not running?

I have the vcc and gnd connected to a 5v power source, and ao1 and ao2 connected to my motor.

When connecting the power source directly to the motor, the motor runs.

pwma, ain1, ain2, and stby pins are connected the pins as expected from the sketch. I also have the gnd pin on the logic side of the board connected to a gnd pin on the arduino(uno v2). PWMA is connected to pin 5, which is a digital pin.

const int stby=2;
const int in1=3;
const int in2=4;
const int pwm=5;

void setup() {
  // put your setup code here, to run once:
  pinMode(stby, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(pwm, OUTPUT);
  forward(255);
}

void loop() {
}

void forward(int speed)
{
  digitalWrite(in1, HIGH);
  digitalWrite(in2, LOW);
  digitalWrite(stby, HIGH);
  analogWrite(pwm, speed);
}


texts: Connecting both brushed DC motor and brushless DC motor to a battery

texts:
Warning: I am robotics beginner!!!
Hi,
I am working on a robot car in which four tyres are connected to brushed DC motor controlled using Arduino and Arduino motor shield. Also it has one brushless motor for another part. Brushless motor is NOT controlled through Arduino motor shield.
I am using 8000 mAh, 11.1 V LIPO battery. I am planning to connect Arduino motor shield and brushless motor in parallel to battery.
I have following doubts in case I make above mentioned connections.
If brushless motor draws more current will Arduino motor shield also get more current? I am worried because Arduino motor shield has max current limit way less than brushless motor can need. So can such
connections burn my Arduino board and motor shield?


texts: How the pin2 of 555 timer triggers this simple circuit?

texts:
First of all, I will go through my concept which make the doubt.
When we connect positive side of LED to a positive terminal of a battery and negative of LED to floor (not to -ve of battery), current will not flow, as -ve of battery is not at a potential equal to that of floor (0V). But if I hold by standing on floor of phase line of commercial electric circuit, I get shock because neutral line is at same potential as ground. (Correct me if I'm wrong.)
Now look to this circuit:

(source: circuitsgallery.com)
Figure above shows a touch sensor using 555 timer. It work only if a low pulse applied to pin 2. But how when we touch the plate it get low pulse? Although we consider -ve terminal to be 0v, in practice, I think it is not. As like my first example, I expect the current never flow and pin 2 stays at high voltage. But it is not so.
Then what is my mistake?
Pls help me I am a beginner.
Sorry for my English.
EDIT
Some answers tell me "how the 555 works" or "how sensitivity of circuit increase". But my question is different from that. May be this is due to unclear data from my question. My question is how the pin 2 trigger (or the voltage at pin 2 become less than \$\frac{1}{3}V_{cc}\$ ) when I touch the plate?


texts:
I am trying to mix a mono microphone into both channels of stereo audio. The output of the microphone amp is yellow. The stereo in is red. I am using 2 schottky diodes in order to mix. Is this an imporpor way to mix audio/is there a better way?
Also, this device is low power, but I am using a lm386 to amplify the electret microphone. Are there better alternatives or am I doing it right?


texts:
I was considering buying a Nexys board to learn about digital electronics. The famous ones I see are the Nexys3, and Nexys4. Can someone suggest based on usage, which is better.

Also, some other sites seem to carry FPGA boards like Mojo, and Cyclone 4, Papillo .

What factor should I keep in mind before placing an order?
Thank You for any help!


texts: Is it possible to put SMT components on both sides of the board with the pads touching? I don't want the pads to be electrically connected, but my PCB program (gEDA PCB) warns that they are shorted. Is there any way to avoid this?


texts: 433MHz quarter-wave length antenna: longer is better?

texts:
I am trying to conduct an RF project using XY-MK-5V / XY-FS modules:

link here

My problem is that even though most blogs and Google searches for these modules use a quarter-wave length antenna (roughly 17.2cm), my transmission is worse than when I use a longer antenna. When the antenna is longer than 30 cm (close to 1/2 wave length) I actually get better reception at longer ranges. (7 meters vs 14 meters)

So my question is, how bad is it to use longer antennas? Is there a reason for the 1/4 wave length antennas being recommended?


texts: Does a baudrate in serial communication (USB or RS232) need to be exact?

texts:
In serial communication, does the baudrate mean we have to use the exact clock speed or is it a range of speeds that we can use?

and if it's an exact value, how exact should it be ?
for example, can i use 555 as the clock of a serial communication circuit ?


texts: What are these pull-ups for on BLDC driver reference schematic?

texts:
I'm trying to design a simple BLDC motor controller using L6234 driver IC. Looking at its application reference schematic I came across some weird pull-ups (highlighted in green, I assume these function as pull-up resistors but please correct me if I'm wrong).
https://www.st.com/resource/en/application_note/cd00004062-l6234-three-phase-motor-driver-stmicroelectronics.pdf figure 12:

What are these pull-ups for? I understand the use of pull-up and pull-down resistors when they are used to prevent say button input from floating. But in this case control logic IC outputs PWM signals to control L6234 IC. If these are here to prevent floating enables and inputs while control logic IC is booting then why are these pull-ups instead of being pull-downs?
I'm rather inexperienced hobbyist, am I missing something more fundamental here?


texts:
Taking the following circuit:

The path on the left will be on and the same, whereas the path on the right is dependent on what is connected to the base of the transistor (not shown in the above schematic). Is there a differentiation between a path and current through it that is independent (the one on the left) vs. one that is more dependent (the one on the right)? How are these usually distinguished?


texts: Strange behavior: NE555 + 7493 Ripple Counter + 4 to 16 Decoder

texts:
I have implemented the following with TTL 74LS chips:

A NE555-based timer generates a clock signal every second
The clock signal is fed into a TTL 7493 4-bit binary ripple counter.
The 4-bit binary counter value is fed into a 4-to-16 decoder that I have built from TTL 7408 and TTL 7404 gates.

When I connect the timer and only the 4-bit ripple counter, the ripple counter outputs the correct binary value. When I use the 4-to-16 decoder with a hand-coded binary value, it also produces the high-signal on the correct output line.

But as soon as I feed the output from the 4-bit ripple counter into the 4-to-16 decoder, the ripple counter produces an incorrect binary counting sequence. I'm already struggling with this problem over a few days, and I have no idea how to troubleshoot it nor I have no idea why this behavior happens.

As I have said, the 4-to-16 decoder and the 4-bit ripple counter are working perfectly when I use them on their own, but as soon as I chain them up, the strange behavior occurs.

Every help and tip is appreciated :-)

Thanks & nice greetings,


texts:
I would like to measure pin PC1 and compare it to Vref to get current voltage. This code below worked on L152re. I changed pin number, ADC1 address and DMA channel. It measures something but I am sure not correct. It oscillates between +/- 300 units. At least Vref should be stable. I am pretty sure that the problem will be with configuration of ADC or DMA. Can someone take a look? Thank you very much.

#include "init.h"
#include "stm32f4xx_rcc.h"

__IO uint16_t ADCConvertedValues[2];

void init_DMA(void){
    DMA_InitTypeDef DMA_initStructure;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);

    DMA_DeInit(DMA2_Stream0);
    DMA_initStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
    DMA_initStructure.DMA_Memory0BaseAddr = (uint32_t)&ADCConvertedValues;
    DMA_initStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
    DMA_initStructure.DMA_BufferSize = 2;
    DMA_initStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_initStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_initStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
    DMA_initStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMA_initStructure.DMA_Mode = DMA_Mode_Circular;
    DMA_initStructure.DMA_Priority = DMA_Priority_High;
    DMA_initStructure.DMA_Channel = DMA_Channel_0;
    DMA_Init(DMA2_Stream0, &DMA_initStructure);

    DMA_Cmd(DMA2_Stream0, ENABLE);
}

void init_ADC(void){
    GPIO_InitTypeDef GPIO_initStructure;
    ADC_InitTypeDef ADC_initStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

    RCC_HSICmd(ENABLE);
    while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET);

    GPIO_initStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_initStructure.GPIO_Mode = GPIO_Mode_AN;
    GPIO_initStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOC, &GPIO_initStructure);

    ADC_DeInit();
    ADC_initStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_initStructure.ADC_Resolution = ADC_Resolution_12b;
    ADC_initStructure.ADC_ContinuousConvMode = ENABLE;
    ADC_initStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConvEdge_None;
    ADC_initStructure.ADC_NbrOfConversion = 2;
    ADC_initStructure.ADC_ScanConvMode = ENABLE;
    ADC_Init(ADC1, &ADC_initStructure);

    ADC_RegularChannelConfig(ADC1,ADC_Channel_11, 1, ADC_SampleTime_144Cycles);
    ADC_RegularChannelConfig(ADC1,ADC_Channel_Vrefint, 2, ADC_SampleTime_144Cycles);

    ADC_DMARequestAfterLastTransferCmd(ADC1, ENABLE);

    ADC_DMACmd(ADC1, ENABLE);

    ADC_Cmd(ADC1, ENABLE);

    ADC_SoftwareStartConv(ADC1);
}

void init(void){
    init_DMA();
    init_ADC();
}


texts:
I have built water level indicator circuit as shown in this figure.

If the inputs of IC 74148 is connected directly to negative supply through pull up resistor it works, but if it is connected to negative supply through wires immersed in water it doesn't. Any Suggestion?


texts: what methods could I use to step-up 700VDC to 5000VDC(approx)?

texts:
The input into my circuit is 5-15VDC; this passes through a digital potentiometer so that it can be controlled. Then there is a mini DC-DC converter which steps the voltage up to 700VDC. Now I need a way to get from that 700VDC to around 5000VDC.

I'm using a DC-DC converter as well because I thought with a voltage of 700 it might be easier to boost that compared to a lower voltage.

Also, if you know of a way to boost the voltage from the input value up to around 5000VDC, without using a converter to raise it to 700VDC first, then please suggest it.

Any help is appreciated.


texts: transformer magnetizing inductance vs magnetizing current

texts:
I have 2-switch forward converter operating at 83khz frequency.
Load current must be 10A
maximum D=0.5
I2=Iload*sqrt(D)
I2=7.1A
transformer turns ratio is 2:1, so I1=3.55A

The voltage applied to primary is 300V (220*sqrt2)results in value ner 300V.
I have ETD59 core.
lets calculate E per turn:
Assume that flux swing is 0.2T (Br is 0.066T, Bmax is 0.266T, so dB is 0.266T)
Lets calculate E per turn:
E(1 turn)=dФ/dt=deltaB*S(core)*f/D

D max for forward converter is 0.5. OK

So, E per turn looks like 12.21 V. Ok.

Lets calculate primary turns: 300/12.21=24.57 turns of primary (assume Np=26 turns). OK

The transformer must be 2:1, So there must be 13 turns of secondary (Ns=13)

The next part is the part that i dont understand:
magnetizing current depends on value of magnetizing inductance, right?
And magnetizing inductanse is Al*Np^2 (Al for ETD59 core is 5300+-20%). OK.

If i assume that we have the worst case, Al(worst)=4240nH/turn
So, calculating magnetizing inductance gives me Lm=Al(worst)*Np^2=2.86mH
Is this value ok?
I have also found a formula for calculating minimum value of magnetizing (primary) inductance:

Here, Drmin is minimum Duty ratio, Vsmax - maximum supply voltage, fs is a freqeuncy and delta ilmag is a swing of current flowing through magnetizing inductance.
Is value of magnetizing inductance so necessary?
If i have a transformer which has 26 turns of primary and 13 turns of secondary, is magnetizing current a concern?
Is it a  good idea to increase the number of turns to get higher value of inductance? This should reduce magnetizing current...
Where am i wrong?
If i assume that Drmin is 0.15 (i just assume - i am not sure), Vsmax=400V, f-83kHz and delta i(lmag)=0.355A (its 10 percent of rms primary current), it gives me Lmag=2mH So, is it ok?
If i would done calculation i described before for a transformer which operated at 100kHz of frequency, I get 16 turns of primary and 8 turns of secondary...
So, if i calculate value of magnetizing current the same way (it is MINIMUM inductance required?) i get inductance value L(100kHz)=Al(worst)*16*16=1mH
So, it looks like according to formula for Lmagmin, this value isn enoght to provide 0.355ma of magnetizing current
Im totally stuck. And does the value of magnetizing current affects core saturation? If it is MINIMUM required value of inductance, more is better?


texts: LM2733 boost circuit - inductor current requirements

texts:
I do not have much experience with boost circuits, and am having a hard time picking a suitable inductor required for my LM2733 boost circuit. I have done a lot of research on the actual boost circuit, including how to implement a "true shutoff" using the PNP, but I am unsure of what the current requirements for the inductor would be?
I guess it comes down to I don't understand of the actual current flow is through the inductor or through the LM2733? I also found some other places online that indicated I need an inductor in the 2A range, but the LM2733 is only spec'd to 1A current. Is this because of the boosted voltage, a safety margin or what?
Also, I am lost as to if I should choose a coil-type inductor as I see on a lot of cheap amazon/ebay boost circuits, or if I can use any of the "multi-layer" SMD variants I have found on mouser that look like just any other 0805 (or similar standard SMD footprint). Is cost the only factor?
For what its worth, my application will only require around 100mA of actual 12V current. My VCC is from a 500mA 3.3v source off my microcontroller board. Any other red flags or things I should know are very much welcome! :)


texts: Buffered voltage divider vs inverting amplifier

texts:
To divide an input voltage by about 10 as well as reducing the impedance , I came across 2 possibilities: a buffered voltage divider (top) and an inverting amplifier (bottom).

simulate this circuit – Schematic created using CircuitLab

It is not a problem to invert the signal (the input voltage is itself both negative and positive) and both circuits are using the same components, so they look the same for me. What should I consider to pick one of those circuits in my design?

To give a little bit more information about my requirements:

Input voltage: -25V to +25V
Bandwidth: DC to  10kHz
Op Amp supply: probably +3.3V and -3.3V


texts: Help needed in understanding why a circuit invovling a FQU13N10L mosfet is not working

texts:
I am a relatively new to circuity and have had issues selecting the right mosfet for my circuit(see below). I am attempting to control the flow of 12V at 1.5A, from the source of my mosfet using 4.5V from some batteries to control the gate of the mosfet.

simulate this circuit – Schematic created using CircuitLab
This simple circuit has not worked at all and in certain configurations got the mosfet far to hot to touch. I have failed to buy the right mosfets for this circuit once already but I feel sure that I purchased the right one this time. I welcome anyone to double check this however, here is the data sheet.
But I believe that I must be doing something extremely wrong in this circuit. Is it possible I have put the mosfet the wrong way around? (Do mosfets even have a wrong way around?) Or do I need to apply some charge to the body of the mosfet, which I have attached nothing to?
I'm looking for either large errors with my circuit design/common errors I might have and/or a specific reason why the mosfet purchased will not work. Really appreciate any help, thank you


texts: Embedding python interpreter in the TM4c1294XL

texts:
I have a python file that I want to run on the board. Hence I want to embed the python interpreter (written in C) in the board. I managed to write separate C project that runs the Python file. It compiles and runs as I want to. Here's the makefile for same:-

CC=gcc
CFLAGS=-I python3.5 -I config -I . -c -w
LDFLAGS= -lpython3.5m -lpthread -ldl -lutil -lm -Xlinker -export-dynamic -Wl,-O1 -Wl,-Bsymbolic-functions

all: classifier trainer test link

test:
    $(CC) $(CFLAGS) test.c

trainer: Trainer.c
    $(CC) $(CFLAGS) Trainer.c
    $(CC) Trainer.o $(LDFLAGS) -o Trainer

.ONESHELL:
classifier: Classifier.c
    $(CC) $(CFLAGS) Classifier.c
    # $(CC) Classifier.o $(LLFLAGS) -o Classifier

link:
    $(CC) test.o Classifier.o $(LDFLAGS) -o test

clean:
    rm -f Trainer.o Trainer Classifier.o Classifier

http://dpaste.com/3BCY2RE is my entire directory of project "hello" (It is not the one from the examples).

I included "Classifier.h" in my "hello.c" and I am getting the following errors: http://dpaste.com/3KKCF84

Compiler include options (No preincludes):

"${CG_TOOL_ROOT}/include"
"${workspace_loc:/${ProjName}/TerrainPredict}"
"${workspace_loc:/${ProjName}/TerrainPredict/config}"
"${workspace_loc:/${ProjName}/TerrainPredict/python3.5}"
"${SW_ROOT}/examples/boards/ek-tm4c1294xl"
"${SW_ROOT}"

Linker file search paths:

"libc.a"
"${workspace_loc:/${ProjName}/TerrainPredict/libterrainclf.a}"
"${SW_ROOT}/driverlib/ccs/Debug/driverlib.lib"

and:

"${CG_TOOL_ROOT}/lib"
"${workspace_loc:/hello/TerrainPredict/libterrainclf.a}"
"${CG_TOOL_ROOT}/include"

Am I wrong with some of my configurations? Or is this some problem with python interpreter? Any help is greatly appreciated

EDIT:-
As @KevinDTimm suggested, the problem is that there is no pyconfig.h for my environment. This file is required by python to define important variables like source of system clock. I tried removing safety checks in existing pyconfig.h. The first error I am getting is in pytime.h as :

"_PyTime_t need signed 64-bit integer type"

Which was further because of the following code block:

#ifdef PY_INT64_T
/* _PyTime_t: Python timestamp with subsecond precision. It can be used to
   store a duration, and so indirectly a date (related to another date, like
   UNIX epoch). */
typedef PY_INT64_T _PyTime_t;
#define _PyTime_MIN PY_LLONG_MIN
#define _PyTime_MAX PY_LLONG_MAX
#else
#  error "_PyTime_t need signed 64-bit integer type"
#endif

It appears to me that it needs a variable that stores time. I need help in assigning that variable.


texts: Although the question is general, for discussion purpose let us assume TI's OMAP platform and Linux. If I connect a JTAG device to debug it (or a JTAG tool runs on OMAP platform) , how the system performance will be affected (Do the bus will be more loaded and thus the OS performance will be affected ?).


texts: Which kind of Flash supports "Bit-alterable write operations" right now?

texts:
I'm very desperate not to find any suitable alternative for a discontinued PRAM (Phase-change memory) Flash. My colleague has developed a device which uses this PRAM  Flash and especially its "Bit-alterable write operation".

So my problem is to find any other Flash type which supports this operation. The whole PRAM Flash technology were discontinued in 2013... The specific IC to replace can be found here:

http://www.digikey.de/product-detail/de/micron-technology-inc/NP5Q128AE3ESFC0E/NP5Q128AE3ESFC0E-ND/4316956

Main Features for an alternative:

Bit alterable write function
128 Mbit space
About 100.000 write cycles
About 30 MHz clock frequency
SPI Interface

Thanks in advance!


texts:
I've been working through this schematic for a Nixie Clock and I'm having a hard time understanding how the power supply (for the nixie tubes, not the digital logic) works. Afaik, the power supply is a boost converter that uses a Mosfet and Inductor to raise the voltage to ~180V. The increase in voltage is dependent on the duty cycle of the input to the mosfet (this info found here). The duty cycle is produced by an astable 555 timer. The duty cycle is required to be around 95%.

The ratio between R1 and R2 on the 555 does not create a 95% duty cycle. I'm assuming that the resistor values are chosen to create a specific frequency for the mosfet, and the duty cycle is altered via the control input. Is this correct? And, if so, how is the duty cycle affected by the control input?
R24, the 1kTrim Potentiometer, is used to vary the voltage around the 180V mark to make minor adjustments to the power flow to the nixie tubes. Does it do this by altering the voltage to the control pin? Or by sinking some portion of the 180V output power to ground?
In either case for the previous answer, why is a pin on the potentiometer connected to the control pin via a transistor? Wouldn't that sink the control pin to ground once the threshold voltage for the transistor is reach? If so, why?
Is there a reason why the schematic doesn't specify an input current?


texts: Can roles of primary and secondary windings be reversed?

texts:
Is there a practical reason that the roles of the primary and secondary of a simple single-phase transformer cannot be swapped?

Say you have a transformer (from the old vacuum tube days) that has rated for primary 120 VAC 1 A and secondary 12.6 VAC 10 A (so there is about 0.120 kVA for this transformer).

Is there any reason that one cannot take that transformer and drive the secondary with 12.6 VAC and up to 10 A and get from the primary power at 120 VAC up to 1 A?

I cannot imagine a reason that, as long as the specs on the windings are kept that the roles of the primary and secondary windings of a simple power transformer cannot be swapped.  But I would be happy to learn differently.


texts: If I have some cars going around a track and I want to measure their speed if I put two IR sensors up at a fixed distances can I accurately calculate the speed the cars are moving using an Arduino?


texts:
I stared out with the 28byj-48 motor and got it to rotate one direction with one button and the other direction with the other button using Arduino pins 2 and 4, respectfully. When the new motor, pictured, is plugged in, I can only get it to rotate one way and it's made to go both ways. Pin 4 no longer responds when using this new motor.
How do I get the new motor to turn both ways?
Do I need to reorganize the 5 wires in the new motor and use a multimeter to determine the correct order or is the issue with some other part of this project?
I'm using the uln2003 driver board.
Thank you!


texts: Flip signal values in verilog simulation

texts:
I use "force" command in modelsim to force an internal signal to a specific value (not primary inputs). Sometimes, the value I force is the same as the original value.

Is there any command that can flip the signal value in modelsim or any other verilog simulators? In that case, I will definitely change the value of the signal.


texts: What size of conductor I have to use to ground the shield of a high voltage cable? I would guess that the size of the grounding conductor is related to the size of the cable, but I'm not sure.


texts:
I will promptly provide any detail or revise my question aimed at any feedback.

Does the profile of phase-noise power spectrum density (PSD) vary with time?

The conclusion may be that it won’t basically vary with time or it won't do that within a specified period of time?

The phase noise originates from modern communication transceiver considering the direct-conversion architecture.

Hope to be answered and explained detailedly.


texts: Motor speed controller generating noise on DC source

texts:
I am working with a speed controller for a 3-phase brushless DC motor.
That motor is taking a 6-12S li-ion battery as input. I have additional electronics that is connected to the same power source through a 5V voltage regulator. I have tried several different types of regulators but I am unhappy with the noise that it's picking up from the switching circuit of the PWM controller on the speed controller.
I am trying to either find a better suited voltage regulator, or to add filtering on the output of the voltage regulator.
As it stands I am measuring up to +/- 5V of noise on the battery when the motor is running. On the output of the regulator I am seeing up to +/- 1.5V of noise which of course is a problem for the electronics on circuit powered by the regulator.
I have not looked at the FFT on the output of the regulator yet, but I think I will do that next.
Edit:
The motor controller is based on the TI DRV8301 (schematics below)
That board also has an MCU for PWM generation, and currently this controlled by a development board, but eventually everything will be integrated on the same PCB, which hopefully helps.
Anyway, the motor controller board supplies 3.3V to the Nucleo board as well as 5V to a sensor (encoder).
Communication between the Nucleo board and the motor controller is proper, however communication between the Nucleo board and sensor goes south when the motor is being controlled.
Right now, my best root cause for this issue is a noisy 5V.
As you can see from the schematics, that 5V is generated by the buck regulator on the DRV8301. I knew the voltage out of the buck reg wasn't great which is why I add that low noise 5V regulator, but obviously that's not enough.
The Nucleo board is connected to the motor controller through 3.3V and GND, and the encoder has 5V and GND wired to the motor controller. I have tried a GND to the Nucleo which doesn't help. Those connections are done with dupont wire... for now.

thanks
edit: Also note that I have tried powering the Nucleo and Sensor with external power and tied the ground from the external power supply to the DC power supply with no success.
edit: Is the following diagram a good simplified representation of what a Star Ground arrangement would look like? i.e. a single ground trace linking the control ground to the power ground. Is it important to make this trace going as close as possible to the GND terminal? On revised design I've been working on I have a single trace joining the 2 grounds, however this trace was not directly under the (-) DC connector but more like 1.5" south.


texts: Detecting Switch input in ARM 7 and multiplexing two seven segment displays

texts:
I am trying to multiplex two seven segment displays, once a switch input is detected.

If a switch is pressed then the seven segment displays should show 1
If pressed again, 2, then 3 and so on.

My problem arises when I reach number 9 since the next switch input will show 10. 1 on the first SSD and 0 on the second SSD. Below is a snippet of my code with regards to how I am detecting inputs from 1 - 9.

   int k = 0;
   unsigned int SW1;

   PINSEL0 = 0;                             //Set P0.0 - P0.15 as GPIOS
   PINSEL1 = 0;                             //Set P0.16 - P0.31 as GPIOS
   IO0DIR  = 0xFFFFF9FF;                //Setting  P0.9 as input for SW1

    while (1)
   {

    SW1 = IO0PIN & 0x00000200; //switch connected on P0.9
    if ( SW1 != 0x00000200 )  //when pressed
      {
        k++;
        IO0SET = T1;
        IO0SET = T2;

        if (k == 1){
        IO0SET = T1;               //switching on left seven segment display
        IO0CLR = T2;               //clearing the right seven segment display
        IO0CLR = a;
        IO0SET = b;
        IO0SET = c;
        IO0CLR = d;
        IO0CLR = g;                //displaying number 1
        IO0CLR = e;
        IO0CLR = f;
        small_delay();
        }
       }

I am following the same structure for the 10th switch press:

        else if (k == 10){
        IO0CLR = 0x000000FF;        //turn off all the segments as well as both common anodes. Then your outputs will be ready for the new segment patterns to be set up.
        IO0SET = T2;                //switching on first display
        IO0SET = b;
        IO0SET = c;                 //displaying number 1
        small_delay();              //calling short delay
        IO0CLR = 0x000001FF;

        IO0SET = a;
        IO0SET = b;
        IO0SET = c;
        IO0SET = d;                 //displaying number 0
        IO0SET = e;
        IO0SET = f;
        IO0SET = T1;
        small_delay();
        IO0CLR = 0x000000FF;}

The problem with the second code I provide is that the seven segment display only displays 10 once. That is, first 1 is shown on the left display and then 0 on the second display as required, however this is performed only once and does not go on until the next switch input is detected.

One solution this problem which I have come up with is that I included a while statement after the if else such that:

    else if (k == 10){
        while (k == 10) {   //rest of code

This actually does what I want it to do, and keeps multiplexing both seven segments, showing number 10, however the problem in this case is that it does not step out of the while loop to accommodate for the next switch input.

How can I multiplex both displays until the next switch input is detected? Any ideas/suggestions would be greatly appreciated.


texts: OP-AMP RC multivibrator not producing a sine wave across capacitor.

texts:
I have built my first ever OP-AMP RC Multivibrator using the schematic above. It produces a square wave, but it is somewhat problematic. The square wave has a duty cycle of only ~25%, and has a non-zero base value. To inspect this, I put a probe up to the points on the schematic labelled PROBE + and PROBE -. This is what my scope read:

What seems to be happening here is that the capacitor seems to be both charging and discharging through the resistor. This is problematic because the duty cycle also based on the capacitor discharging to a non-zero value.

Here's a picture of the output (yellow) compared to VCC (blue).

The second problem is that the capacitor is charging to only 350mV, which results in a 350mV peak. Is this supposed to be the case? how would I amplify this? My first Idea was to hook up the output to a second OP-AMPs inverted in, and the positive rail to the non-inverting in, which should produce the inversion of the wave. I would then hook that up to a NOT gate to get the original waveform. The result of hooking this up to the OP-OP AMP is Shown above. The yellow line is the output of the multivibrating OP-AMP, the blue line is the result of the secondary OP-AMP. As you can see, the secondary input messes with the first output signal. I'm not sure why.

Any help with this would be appreciated.

OP-AMP datasheet: http://www.ti.com/lit/ds/symlink/ne5532.pdf


texts: Common ground after voltage dc-dc converter

texts: I have a 7.4V LiPo battery that I use to power an ESP8266, some relays and a servo. The LiPo battery is split into a 7.4V rail and using a dc-dc voltage converter (LM2596) into a 5V rail. The 7.4V is for the servo(s), the 5V for the remaining components. In order to make sure that the signals from the ESP8266 are relative to the same ground, is there a need to connect the ground of the 7.4V rail (directly from the LiPo) and the ground of the 5V (after going through the LM2596) or do they share the same "floating" ground?


texts: Which one is the better way to feed analog input to my ADC?

texts:
I am planning to use an AD7730L analogue to digital converter (ADC) chip, with a quarter bridge circuit. Everything was on the track until I realised something, which indicated that things were perhaps not on the track as much as I thought after all. Basically, I forgot to take into account the fact that I have a quarter bridge with a strain gauge not a load cell. This means that I also need to think about the cases where I have negative output voltages from my bridge.
I thought that the easiest way to go around this is to use an inverting Op amp or a voltage divider and a buffer before the analogue input terminals of the ADC. Does anyone know of a chip which inverts only negative voltages to their equivalent positive voltage and also send a signal (i.e. set a digital output high or low) to indicate when it inverts a negative voltage? I am thinking of feeding this output to my micro-controller input and account for it in software (i.e. indicate that there was a compression on the strain gauge).

The alternative way (based on what I understood from AD7730L’s data sheet and considering that I am using a 2.5V reference voltage chip ADR431), is for me to supply a negative voltage to the AGND pin (analogue ground) which needs to be smaller than -1.2V (because the absolute input voltage range as mentioned on page 24 of the AD7730 data sheet is AGND+1.2V to AVDD-0.95V and the differential between AVDD or DVDD with AGND must not exceed 5.5V). Therefore, I think I have to go with the setting on page 42 of the data sheet. This means DVDD has to change and all the digital logic inputs to the AD7730 should be leveled down and my 2.5V reference excitation voltage will also disappear and some extra components will come into action. I am not completely sure if I am correct, but I think the first way is easier than the second one, but I am not really sure how much noise and inaccuracy it will introduce, but I think it may be more than the second approach.
Here is a schematic of the circuit I would like to put together.


texts: Understanding current, voltage and resistance

texts:
I'm still trying to wrap my head around current, voltage and resistance, and slowly I have the feeling that I start to get some things. Hence, I would like to describe my understanding so far and ask whether it's correct so far.

Current, voltage and resistance

First of all, inside of a circuit there's a stream of electrons. While technically they go from the negative to the positive end, we usually consider it to be the other way round.

Now since it's a stream, we can count how many electrons pass an arbitrary point in the circuit in a specific amount of time. This is what is called current, and it's measured in Ampere.

So: 1A is so and so many electrons per time frame.

Something has to make the electrons move. The force that makes them move is the voltage, and it's measured in Volt. Finally, there is resistance, and it's measured in Ohm. While voltage "drives" electrons, resistance slows them down.

We have: 1V is the force needed to move 1A over a resistance of 1 Ohm.

If we increase the voltage, we get a higher current; and if we increase the resistance, we get a lower current. If we multiply current and voltage, we get the actual power, which is measured in Watt.

Is this correct so far?

Short circuits

Now, if we have a 9V battery, and we connect both of its poles directly using a wire, there is almost no resistance. Using Ohm's law, we get a very high current due to the extremely low resistance. This results in a huge amount of energy moved in a very short time, hence the wire and the battery heat up, and this is what we call a short circuit.

Adding an LED

Now let's make an LED brighten up. Since an LED is a diode, electrons can only flow through it in one direction. So let's connect the LED's anode and cathode to the battery's poles, and see what is going to happen.

The LED causes a voltage drop of, let's say 2.5V, and is able to handle a maximum of 20 mA. Now if we connect it directly to the battery, yes, well, what is going to happen?

I know that we should add a resistor, and I even know how to calculate it, but I can not explain why this is, or to put it another way round: What would happen if we did not add a resistor.

Let me explain this:

I know that if we have a 9V battery, and the LED drops 2.5V, there still need 6.5V to be dropped. Since the LED handles 20 mA, and current is everywhere the same in a circuit, we need to calculate:

  6.5 / 0.02 = 325

Hence, we need a resistance with 325 Ohm. Since the resistor now drops 6.5V voltage, overall we drop

  6.5V + 2.5V = 9V

which is exactly the potential of the battery. Also, it doesn't matter whether we put the resistor before or behind the LED into the circuit, as all that counts is the drop overall. So everything is fine.

Open questions

But what happens if we do not add the resistor? In this case I have some questions that I am not able to answer:

The LED drops 2.5V, but the battery's potential is 9V. What about the "missing" 6.5V? Where are they? What happens to them? What happens to the battery, and what to the LED?
If we do not add a resistor, I guess the current will be way too high for the LED, so I guess we will have a short circuit, but now with an additional blowing LED, right?
What is the actual current in the circuit?


texts: Why does a sallen-key low pass filter not work with virtual ground?

texts:
I've been reading an article discussing single-supply op-amp design. Regarding Sallen-Key low-pass filter circuits, the author states that:

  A few filter topologies, such as the Sallen-Key low pass (see section 1), require a resistive divider to DC bias the input. Addition of this network negates the requirement of a Virtual Ground.

By virtual ground, the author is referring to ICs such as the TLE2426 virtual ground chip. Can someone explain why Sallen-Key requires a resistor divider? Why won't biasing the AC-coupled signal (i.e. put a capacitor in series with the input) to Vcc/2 (provided by e.g. a TLE2426) work?


texts: most resistant substrate layer to embed a specific wire

texts:
I am in process of embedding a wire in a choice of substrates. I would apply voltage so much as to heat it (the wire) to 220 degree Celsius max. What are the best choice of substrates I can use so that if an element which has shock resistance of 180 degree Celsius will be efficiently heated  and not crack down when kept on it?

Please assist me


texts: Brushless DC motor model for model-based design

texts:
I have seen this diagram or something like it being used to model a DC brushed motor:

With a resistance, inductance, input voltage and load inertia basically specifying the motor.

What would be the approach to model a brushless DC motor, or would it be similar?

I am here referring to the 3-wire brushless motors that are used in the hobby industry and typically controlled with Pulse Width Modulation (PWM) through a Electronic Speed Controller (ESC)


texts: Operate Arduino Nano using variable voltage

texts:
How safe/dangerous is it to operate an Arduino Nano 5V with a varying voltage source?
I have a circuit that provides a duration of power with a starting voltage of 5.3V and an ending voltage of 4.5V. I'd try it myself but the time and money of ordering another chip is rather disincentivizing.

Will a higher or lower than rated voltage affect the processor speed? How will a varying voltage affect the I/O pins
I've read on forums that people say that sections of the chip will 'brown out' if not given enough voltage what does that mean?
Please help.


texts: Measurement of an inductor not accurate at all

texts:
I'm trying out a method of measuring the inductance of inductors with a following circuit:

I'm using a signal generator to create the input voltage, and an oscilloscope to read the output across both the resistor and the inductor, as well as across the inductor only. I've found from multiple sources that when you tweak the input frequency such that the voltage across the inductor is one half of the input voltage (across both components), the inductance is given by the formula:

$$L=\sqrt{3}\frac{R}{2\pi f}$$

Here is a picture of my circuit:

The voltage across the inductor is half of the input when the frequency is around 90.9kHz:

As you can see on the right, the peak to peak voltage of the yellow channel is 5.12, while the voltage of the blue channel is 2.56. The frequency fluctuated a bit, but it was around 90.90kHz. The series resistor has a value of 98Ohms as measured by my multimeter.

Using the formula for inductance, I get an inductance of roughly 300uH. However, the actual value of the inductor should be 100uH! So the measurement is completely wrong. What did I so wrong here?

I've read that the method only really works when the series resistance of the inductor is low. I measured it using my multimeter:

It seems to be around 3.3 Ohms. The reactance of the inductor (100uH) at 90.0kHz should be around 57 Ohms, so the series resistance should not cause this much error. I also thought that the output impedance of the generator would make a difference, but I don't see how as the measurement is taken outside of the generator. So what is wrong here?


texts: 12VDC relay suitable replacement for 18VDC?

texts:
I have inherited a fairly old Sharp amplifier which does not power on anymore. After poking around with a multimeter we notice that power stops flowing at a DEC Type DG1U TV-5 relay which is rated 8(2)/60A / 18VDC. My plan is now to replace this, however, there only seem to be relays of this type with 8/60A / 12VDC for purchase online.

Would 12VDC be a suitable replacement? We don't plan on driving a huge sound system (nor very loud) with this - at most a couple smallish tower speakers "rated for max. 90W" (what the sticker says).

I should also maybe note that I'm in Austria where we have 230V.


texts: How to Prevent CD4017 from Resetting to Random Count on Power On

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I'm working on a project using a couple of CD4017 decade counter chips sharing a clock signal from a 555 oscillator.

The ideal behavior I would expect is that the chips would all start on count 0 when given power. They do this most of the time but sometimes they start on a completely random count and the synchronization between the chips is thrown off. I've tried to get around this by putting a capacitor on the reset pin of the 555 and the enable pins of CD4017s like so. This adds a small lag between the 555 clock being enabled when the device receives power, and a small lag for the CD4017 clock inputs being enabled.

However, the CD4017s still start on a random count occasionally when given power. Is there any standard, cleanish method I can use to assure they all power on to count 0?

I'm sure I could figure out something hacky with the  but I'm trying to keep a low part count.


texts: Basic question - multiple solenoids in parallel

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Please excuse my ignorance - I am first and foremost a software person, and I only fool around occasionally with hardware...

I want to get 5-6 solenoid valves working in parallel. The solenoids are 12v DC, 500mA. I have a single 12v DC, 1A wall adapter. I would like to wire up the solenoids in parallel. To my understanding, with respect to voltage, it doesn't matter how many solenoids I have in parallel: Kirchhoff's law states that the voltage will always be 12v over each solenoid, even if I turn them all on at once. However, it is also my understanding that the current (amps) will be 'distributed' across each of the solenoids in parallel. That is, the 1A will be distributed across the N solenoids such that each has a current of 1A/N on it.

If I am understanding correctly, then, I would need a new 12v DC power supply with N * 500mA to adequately power all my solenoids?

Thanks!

EDIT: And as a more general question... What should I "watch out for"? Would too much current, or too much voltage damage the solenoids?


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I am trying to drive this RGB using the GPIO of STM32F072. The GPIO can source around 25mA and the LED consumes around 20mA.
Would there be any issues?


texts: Metal enclosure grounding for audio project

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Fellow engineers,

For various reasons I picked extruded aluminium enclosure for my current audio related project. All exposed metal connector chassis are connected to earth, which then goes to ground trough ceramic cap (100pF 10% 2kV 1206) for ESD protection.

Schematic:

Render:

My gut feeling says there might be artifacts (like spikes) and noise if a consumer touches the enclosure, which will result in audio distortion. How can I make sure my audio ground is totally protected against this scenario?

Note: I do not have a separate audio ground. All I did - carefully splitted ground plane to divide analog and digital parts, no components in between, directly connected to each other close to the LDO.


texts: Is connector 50PS-JMDSS-G-1-TF symetrical?

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I'm looking at a design using connector 50PS-JMDSS-G-1-TF and the pin numbers do not match. They are symmetrically switched. So they would match if I could plug the connector the opposite way. Looking at the documentation for 50PS-JMDSS-G-1-TF it looks like it could be plugged both ways.

So my question is whether the 50PS-JMDSS-G-1-TF is symmetrical?


texts: Could I make the strength of a magnetic field oscillate up and down, by having the voltage increase and decrease while current remains the same?

texts: I know that because of v=ldi/dt, that if I repeatedly lower and raise the dc current of an inductor at high frequencies, the magnetic field generated will be weaker, so If i instead raised and lowered the voltage at high frequencies, would the magnet be workable for higher frequencies? I need to create a magnetic field about that goes up and down in strength at a frequency of 30 ghz, for an device I'm working on.


texts: Sensor supplied by MCU - sink or source what is most energy efficient?

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I'm building a tiny system for fridge door monitoring. AVR (Attiny13A) is used which is connected to a linear hall sensor OH49E, the complete system is battery powered and I'm trying to minimize power consumption as much as possible. Right now the sensor is powered by a pin from the AVR (+3,6V, 3xAA rechargeables) but there is also a 100nF bypass capacitor connected to the supply of the sensor. The sensor is sourced by the AVR to be able to turn it off completely, saving 4,2 mA.

My concern now is if I should sink the sensor instead of sourcing it. By doing that I will prevent the capacitor to discharge every time the the source pin is going to low state.

So what is the most power efficient way of using an external sensor? Sourcing or sinking it? Or are there other better alternatives?

simulate this circuit – Schematic created using CircuitLab


texts: large current through power mosfet in LTspice

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I use some mosfet and BJT for a simple power path management in circuit. When Vprimary is larger than zener(indicate primary battery is healthy), Vprimary is connected to Vsys through M1 and M2 to supply power. When Vprimary falls below zener voltage, Q2 and M3 is biased so that Vbackup is connected to Vsys through M3 to supply power.
The problem is that the current throught the three mosfet seems very large, why?

I think maybe LTspice's modeling about mosfet body diode not correct, however, use one mosfet from TI, the result is almost the same...

update

Thank you. The large current is caused by M1&M2 and M3 both conduct, shorting Vprimary and Vbackup. Followed by your advice, M1&M2 no longer conduct during M3 conducting.
However, there's still momentary large current which is caused by Vpri->Vbak or Vbak->Vpri power source switching. I think it is caused by zener diode and the finite voltage source impedance. For example, during Vpri rising from 0 to 12V, the 9.1V zener diode will conduct when Vpri reachs 9.1V, causing M1&M2 conducts and shorting Vpri and Vbak through M1&M2&M3. Because of the 0.5ohm source impedance, the voltage on zener may below 9.1V. The large current will disapear once Vpri rises much larger than 9.1V. The duration may decrease if source impedance is decreased from 0.5 to 0.1ohm.


texts:
We are building a PCB that we are about to sell for DIY users worldwide (with components). This PCB is microUSB powered, contains a charger chip, and a battery (probably 18650).

I heard that there might be airplane shipping restriction for devices containing batteries. What are they exactly?

How to be able to send an electronic device worldwide without restriction because it contains a battery?