texts: P-Channel FET Failing in Battery Protection Circuit

texts:
I'm working on a battery pack monitoring/protection circuit! I've got a bidirectional switch, but I'm having some issues with FET_SW2 and I'm not entirely sure why. Seems to be failing short, with a relatively low RGS around 500 Ohms. It doesn't immediately fail, seems to only be happening after the battery pack has been used a few times.
Current theory is some kind of short circuit/over current failure. There is an overcurrent protection circuit, that is tested to be working. But I'm wondering if repeated short circuit might be degrading/damaging the FET significantly over time. There's no visible forms of failure in terms of burning/scorching.
Here's the link to the FET datasheet: aosmd.com/pdfs/datasheet/AOD4189.pdf
Wondering if any of you guys might have any additional insight or ideas why the FET is failing. Any advice would be appreciated!
Thanks!
Vext is the voltage at the barrel jacks.
Ibat is measured across the lowside shunt via an instrumentation amp.
Vgate is gate voltage of the switching fets (fet_gates net).


texts: How to transfer electrical power from stationary to rotational part.that can be used for POV display?

texts:
I have been researching how to transfer electrical power from stationary to rotational part. Some of them showed the means by using slip spring rings like in this website

http://www.luberth.com/analog.htm (under the An Analog & Digital propeller clock section)

But it does not specify how do you actually assemble that?

So how do you connect the slip spring rings in your setup? Do you connect it to the motor's shaft? But only the ground terminal can be retrieved from the motor's rotating shaft? Where can we get the V+? It was not specified in the website. What are other components that are mainly used for this application.


texts: How can I detach a metal ball from a magnet using opposite force with current?

texts:
I am trying to make a very small device which has multiple cylinders and inside each cylinder there is an iron ball (about 2.5mm ball size.) The bottom and the top of the cylinder are magnets, so the ball inside the cylinder is pulled by one of the magnets of the cylinder and the ball stays there.
Once the ball stays on one side of the cylinder, I want to be able to pull the ball to the other side of the cylinder, probably using some kind of magnetic field (using current.)
I have no other idea on how to do this. I thought about servos, but they are mechanical, and they are too big for my project, so I decided to go with electricity.
I have no idea how to actually create this pull force. I assuming that pulling the ball a bit of half way throough the cylinder is enough, assuming the two magnets are equally strong.
UPDATE:
100% of the time the ball is in one end of the cylinder, it's not "floating." I want the ball to be attracted to only 1 end of the cylinder, and stay there without using current. The only time I would like to use current is when I want the ball to change direction to the other side. I guess I mean ferromagnetic ball and not "iron." The point is that I need the ball to be attracted to one magnet or the other. The point is to use the magnet "free" power to make the ball stay in one point
Here is an image to visualize this:


texts: What adhesive is best to glue strain gauges to metal?

texts:
I'm trying to use these strain gauges to measure bending of a metallic cantilever (metal TBD). Does anyone know what adhesive I can use to glue the strain gauges? I'd rather not have to use an oven for curation, unless it is my very last resort.

Thanks in advance!


texts: How to increase range of AM radio waves?

texts:
As a personal project, I made a very simple AM transmitter with an idea from an online tutorial, using a 1 MHz crystal oscillator (plus power source, antenna, breadboard, etc.).

However, when using an 8 inch wire for the antenna, it is only picked up over a couple feet. How would I make it transmit a longer distance (about 1-2 km)?
EDIT: Not 1-2 km anymore, but maybe 50 ft. Either way, I want to understand how it is possible to extend range.

I'm kind of new to electronics and can only understand simple circuits and components like transistor or capacitor, so my online research for this question left me confused. One site mentioned that a good ground is most important for range. If this is true, how do I do this?

Also, I understand that in some countries, there are rules and regulations regarding AM broadcasting. I am doing this in a location where I confirmed that it is okay to do.

Thanks for help!


texts: Connecting a medium sized 1 kVA Inverter with a 2 kVA Generator

texts:
I have a 1 kVA inverter which is using a 12 V battery to generate 220 V AC (battery is connected to a charge controller and is being charged by a PV). In addition I've got a 2 kVA generator.

According to load consumption of power, is there a concept or a design or even a name for a circuit that can smartly switch between the two sources to provide power for the load at any given time? I'll explain further:

If the PV is partially shadowed i.e maximum power of the PV system can not be obtained, is there a circuit that can instantly respond to this change and supply the load from the generator? Thank you.


texts:
Forgive me in advanced if I don't make this question clear enough, I'm just getting my head around this new device and related terminology.

I just got a psoc 5lp with onboard kitprog - (CY8C5888LTI - LP097) and i am trying to do a basic 'hello world' using USBUART (CDC Interface V3.2) to 'print' the state of the onboard button and I am unable to see any of my putstring commands in my teraterm serial reader.

I have been able to create a working program using the RX connection to my output pin with a 'normal' UART, which is my understanding that uses the kitprog as a serial connection. But am unable to get anything from the USB connection that is directly connected to the psoc I am programming. (socket labelled J5 on board, as shown in picture)

Checking my device manager I can see the KitProg showing under Ports, which is how I understand the 'normal UART' connection was working, but that is it.

I feel like I am missing something really simple, but if anyone can give me a step in the right direction, it would be much appreciated.

I am following a tutorial on youtube step by step to no avail.

workspace/code can be found on GitHub here

youtube video here


texts: Practical Issues with Surface Mount Heatsinks?

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I'm considering using surface mount heat sinks for D2PAK devices on a PCB.  These heat sinks are bent sheet metal frames with tin/lead plating in tape/reel packaging which are suitable for soldering directly to PCBs.  I have not personally seen these types of heat sinks on production PCBs previously, but see them offered by several leading vendors.

I'm a little concerned about the thermal mass of the heatsink and the fact that it might shield the part beneath it from any infrared/radiant heat sources when running through a reflow oven.

I'd appreciate if anyone could share their experience with these devices?  Any best practices or precautions?


texts: STM32F103xxxx VFQFPN 36 pin package thermal pad, isolated or tied to ground?

texts:
Currently designing a PCB based on the STM32F103. The package is a VFQFPN 36 pin package, which also has a large thermal pad. The datasheet for this part does not appear to indicate a pin number or function for this pad. Do I assume it's:

a) An isolated  Pad

b) A Ground pad

c) Something else


texts:
how many 7400 can the 74LS04 safely drive ?

74LS04 Specs :

I output low  : 8 mA

7400 Specs :

I input low : -1.6 mA

PS : I know that the answer either 5 or 2. The only thing I am not sure is that do you consider each input for 7400 separately or not. So each 00 would need 3.2 mA or only 1.6 mA ?


texts:
I'm working with Arduino Uno (Rev 3) to interface a DRV2605 haptic driver to control several ERM/LRA motors using I2C.

As I look at examples on the web, I see everyone uses a I2C level conversor to drop the voltage from 5v to 3.3V, despite according to the driver datasheet and the I2C protocol description it is possible to use 5V directly. I understand that the only requirement is that both devices work at the same voltage level.

Is there any reason (apart from power efficiency) to use 3.3V over 5V?


texts:
I am designing a Schematics for one of my big project. I am using Hierarchical Design for my project. My Schematics has one processor which has 5 UART. The UART nets have names like UART1_TX, UART2_RX. I have to move such signals from child sheet to top level sheet and from top level sheet to various other sheets via Sheet Symbols and Sheet Entries.

After reading this article, I got to know Buses should be used only with signals (or net labels) which has sequential names like Data0, Data1 and etc.

But in the past, I was using a Bus to collect signals like UART1_TX and UART1_RX and move from sheet to sheet. The Net Identifier scope was set to Global. I was actually following the way that has been presented on these Evaluation board Altium Projects. I realized now that Bus in my earlier practices weren't actually doing anything as the Net Identifier scope was set to Global.

I want to know is Signal Harness is a right Net Identifier for my signals (UART1_TX and other GPIO signals GPIO_PIN_20)?

Why it is not being used in above Evaluation Projects?

Below is the picture of my harness:


texts: Please explain the circuit (current regulator test circuit with Zener diode)

texts:
my mind needs refreshing so could someone please help explaining analysis of this circuit.

It is used for testing a current regulator (LED driver circuit) ('I' in the image). The regulator current is divided between a resistor and a series connection of a Zener, resistor and a LED. If D2 illuminates the current regulator is supposed to pass the test.

Majority of the current of course flows through the single resistor, but I don't understand the equation how it is exactly divided between the two circuit branches. I would like to replicate this circuit for testing a current source with different amperage, and thus would need the equation how to select proper values for Zener and the resistors.

Many thanks in advance.


texts: 1N5062 is getting hot at only half of its rated current

texts:
I have a rectifier bridge with 4x (GP)1N5062 diodes (body made of black plastic tube - like 1N4007). I have seen that they are getting hot, even if the current passing through the rectifier is 0.95 A.

I can only keep my finger on its terminal for 3-4 seconds, so let's say 45 Celsius.

Is this normal? I think, the diodes are rated for 2A, even though this forum says 1 A.

My digital multi-meter measures 23V DC voltage at the output of the bridge. However, if I switch to AC voltage it measures also about 2.1 VAC.


texts: I have the following lcd (DisplayTech 128x64 COG STN Y/G) unfortunately after reading the data sheet I still have no idea how to hook this up with an arduino. Could someone either assist in explain how this needs to be hooked up and how you would interface with it once connected.


texts: Using the UCF constraints to assign one of two output ports

texts:
I've got a CPLD design which has one spare (Debug) pin. I'm trying to find out if it's possible to use the UCF file to select which output port (NET) that pin becomes.

The problem is however, that I've got two different nets I may want to connect that pin to, depending on what I'm debugging, but the fitter always wants to assign every output port to a pin, and fails because there isn't enough.

For example, I want to connect SIGNAL1 at present

NET SIGNAL1 LOC=P114;
NET SIGNAL2 LOC=Don't connect it please;

But then I might want SIGNAL2 on it:

NET SIGNAL1 LOC=Don't connect it please;
NET SIGNAL2 LOC=P114;

I know I can go and modify the design to remove the output I don't want as an output at that particular time, but, sheesh, this just seems like a lot of hassle. There must be an easier way!


texts:
Are there any guidelines, standards or rules of thumb to follow when designing a PCB with connectors (USB, ethernet, etc.) that will need to fit into a case with a back panel? More specifically, how far should a connector be allowed to hang over the edge of the board?

Is it mostly just season to taste?


texts: A question about Carry-lookahead adder propagation delay

texts:
I'm studying Digital Design and Computer Architecture book, I'm stuck in the section of the carry-lookahead adder because there's something that I don't fully understand about the propagation delay of an N-bit carry-lookahead adder.

The book specifies the propagation delay through the 32 bit adder as firstly to calculate the generate or propagate signals G0 and P0, respectively, and then to calculate the generate and propagate signals of each block, and this is done concurrently in all blocks, and then the critical path goes through the and/or gates which has the carry-in as an input (through every block), so that the critical path delay will contain M * t_{AND_OR}, where M is the number of stages. this is (somewhat) understood and seems reasonable to me. The thing is that the book specifies the delay as:

What I don't understand here is that this equation implies that the number of stages which suffer from the AND/OR delay is \$(\frac{N}{k} - 1)\$, which is one less than the actual number of stages. Furthermore, it says that the critical path has \$k\$ full-adders.
This is indeed what said in this paragraph:

Unfortunately, the book does not explain this further. My question is that why is the last stage is treated like this? Why isn't it treated like the previous stages? In my opinion or understanding, I don't see why Cout is calculated through the lookahead logic so that the number of stages would be \$ \frac{N}{k} \$ (increase by one) and the term \$ k * t_{FA} \$ would vanish away? Especially because the last block is considered a "4-bit CLA block", then why wouldn't I use the generate carry and propagate carry signals in order to calculate the Cout?


texts: Inputs to a Wiimote using a microcontroller

texts:
I've seen various methods of grabbing inputs and sensor data from Wiimotes and Wii Nunchuks as standard Bluetooth HIDs into microcontrollers like the Arduinos, but is there a way of sending button presses (say, for an Intelligent Agent running on an aforementioned microcontroller) to a Wiimote that's connected to a Wii? I would assume opening it up and sending pulses directly to the board would be the easiest way, but I am relatively new to electronics. It would be preferred if I didn't have to open up one to send inputs, though. Perhaps using the I2C expansion port?

The folks over at Wiibrew with more electrical knowledge than me have rounded up some of the more technical aspects of the controller: http://wiibrew.org/wiki/Wiimote


texts:
I am confused as to the complexity of the elements shown below. What is the order of complexity of them?
NOTE- this is a Pre-lab quiz which is NOT assessed, as seen by the multiple attempts allowed.


texts:
I am using traces much wider than the LED footprint to dissipate heat. What design guidelines should I follow when making design like this.

Should I add solder mask expansion between anode and cathode pads for correct placement of the LEDs?. I think there is no need for it on the other sides because even if the solder mask in misplaced little bit, the copper pad will still be complete. but The solder paste will be insufficient at the same time.

what is the best practices to follow in this kind of designs? should I leave solder mask expansion and solder paste expansion equal on all sides?


texts:
Is it possible to read the code that is programmed on an ESP12F/ESP8266? I don't even know which programming language is used.

This is a technical sheet for the ESP12F
http://wiki.ai-thinker.com/_media/esp8266/a014ps01.pdf


texts: Field Flux control and Speed Of DC motor

texts:
I was studying electromagnetism and I tried to link with working of DC motors.

For the speed control of DC motor - The Flux of DC motor is reduced to increase the speed above rated speed.

  I understood that as we reduce the flux density(B) due to field coils the
  back emf produced in the armature coil reduces as per faradays law. So
  Armature current will increase as per KCL applied in the armature circuit.

  Ea= V - Ia*Ra

  This increase in Armature current produces a further increase in magnetic flux density due
  to the armature current.

  Thus overall Magnetic flux density in the air gap increase. This
  results for the increase in Magnetic torque on the armature winding due to
  Lorentz force equation
  and thus the motor's angular acceleration increases and thus the speed increases.

Is this understanding the right one? Please comment on whether this understanding the right one or any deeper understanding is available.

What happens if I Consider the armature reaction?

I also learnt that Flux weakening is commonly used to achieve motor speeds above rated speed.

As the increase in speed is indirectly achieved my increase in armature current Doesn't this make the current in the armature coil go beyond  nominal value or rated value?


texts: Boost circuit outputs a lower voltage than it should

texts:
I'm learning boost circuit and I'm a trying to get a 50~100v voltage output from 3~5v input and 30kHz PWM using boost circuit.

simulate this circuit – Schematic created using CircuitLab

(Using transistor as a switch and diode)

The simulation seems to work, however the real circuit only generate a 10~12v output..

Plus, I'm using arduino to generate a near 32kHz PWM Input with near 90% duty cycle. And it seems to have some problem, too.

void loop() {
    digitalWrite(9, HIGH);
    delayMicroseconds(28);
    digitalWrite(9, LOW);
    delayMicroseconds(4);
 }

(I also tried to change the built in timer and analogWrite, but it cannot generate a PWM with duty cycle greater then 50%. I've no idea about it..)

PS: I'm using this calculator to get the requirements of Inductor and Cap.

Update: I've tried a smaller inductor(470uH) with a higher PWM frequency (125kHz, using another Arduino, using build-in timer). And get only 4.5v on output...


texts: Circuit Requirements for a 30 min continuous on off cycle

texts:
I would like to build a circuit (preferably using components from old common electronics like a VCR or whatever) that continuously cycles on/off in ~ 30 min intervals. Input voltage is from a 12v groundless DC inverter that's plugged into the wall. The 30 min on/off cycle is to power a 12V 0.23amp computer fan. A period of 60 min with a 50% duty cycle would seemingly work fine here.

The optimal answer would include additional information on how I could modify the circuit (if needed) to increase the time delay. Thank you in advance!


texts: Grounding adviseable on tube pre-amp powered by a 9VAC power brick?

texts:
I have an ART Tube MP pre-amp that is powered by a compact but rather heavy power "brick" that delivers 9V AC @ 1A. I use the pre-amp with a large-diaphragm microphone that gets its 48V phantom power from the pre-amp.
I'm getting an annoying background noise with a low-frequency repetitive component superimposed which obliges me to keep the input and output (tube) gain pots lower than I'd like (at 12h and 9h respectively). Two samples (also with both gains maxed out):
https://soundcloud.com/rjvb/sets/noise-from-the-art-tube-mp-pre-amp
I already looked for a quality PSU, but the only lab-style unit I found that does AC output was worth 6x the price of the pre-amp. Reading more user feedback on this and a comparable Behringer amp I picked up a suggestion to try grounding the set-up.
I know that amplifiers usually have their chassis connected to the mains ground wire (which is then also used to ground the turntable). I thus suppose that running a grounded wire to the pre-amp's metal chassis should thus a priori be safe ... but I prefer to be sure and also get some educated opinions whether this could indeed solve my issue?
I also read an evaluation in which someone claims that running the output through a D.I. got rid of the noise. He never answered the question which D.I. he used...
Another observation: there must be a few big capacitors in the system. The unit's power LED remains on for quite a while after putting off the mains power to the PSU, and the mic continues to receive enough phantom power to give off a signal after turning off the phantom power on the unit. It seems to me that that points to the presence of a couple of aggressive lowpass filters which might even remove the need for a line filter?
Noise wave form with auto-trigger. The waveform being triggered on must be the "prrrffftt" sound and is pretty constant. If I'm not mistaken it occurs at a 10ms interval, which seems much faster that what I hear (but I may be hearing a "beat" of course).

FFT spectrum. Contrary to what I mentioned elsewhere I now get a peak at 50Hz systematically, it's even what my tuner app gives. Strangely enough I don't hear the "mains hum" I'm used to hear from an ungrounded turntable pickup...


texts: Sign on range hood light switch says "incandescent or resistive 120V AC Only"; does this mean no CFL or LED?

texts:
The switch includes a standard-looking rheostat; I have read the issues around using dimmer switches with conventional CFSs. I don't value the "dimmer" function on the hood -- just want to see the food that is cooking when the room is not well lit.

Am I okay to put a CFL in here as long as I switch the light all the way on or off? If i get an LED bulb, is this sufficiently "resistive"? I am guessing not...

Thanks for any help. Sorry if this is insufficiently technical. Amazed to find zero hits on "incandescent or resistive 120V AC Only" which is literally on the switch inside this hood (purchased 2003).


texts:
I am working on a 3 phase energy metering project using ADE7752 IC. I am stuck into getting the power supply part in a smaller form factor.

Since energy measurement is being done for all 3 phases, the IC must be able to measure energy even if two phases go down and hence VDD supply must come from all three phases.

After some searching, I came to this schematic:

This involves 3 transformers which will be too bulky in size and hence becoming an issue for me.

Is there some alternative compact circuit which can do the job? I don't need isolated power supply here.

I was thinking about using diodes to rectify all phases and combine them at a capacitor but I think that will end up in smoke if not fire and shock.


texts: Does the drive strength of a GPIO pin alter with change in temperature?

texts:
In low temperatures the functionality of the I2C is being affected, but the slave is working properly and the temperature is also within limit of slave. For that reason I suspect the drive strength.

Does temperature affect the drive strength of a GPIO pin?


texts: How to extend detection distance of computer mouse?

texts:
I recently learned that modern computer mice take tiny pictures many times a second and compares them to understand in what direction it is heading. And that the little light at the bottom is to create shadows for uniform colored, textured surfaces to get a decent image.

I was wondering, is it possible to extend how far away the image sensor can pickup on a surface? Right now, if I hover my mouse over about 0.1" above the surface, I still get movement of my cursor, but beyond it fails to detect. If I were to put a strong magnification lens right after the sensor, would I be able to hover the mouse higher?


texts:
Doing some reverse engineering to a PCB, I drew this part of the circuit. Looking into the datasheets, I found out the comparator (LMC6772) is able to drive the SCR (S6S2) by itself. But the designer used a PNP transistor in between. I see that the comparator is fed with single power supply, so I assume the PNP is to do some kind of shift as the SCR is referenced to -13V. Why would the designer do this? It's like the current from the coil is sinking to -13V instead of the ground, but why? If you need more details about the circuit I can expand the drawing, but that's the basic concept of my question.

Below there's a link which is a follow up of this thread. Some notes:

TR1 in the old thread is U5 in this thread.
V+ in this thread is the point between R2 and R3 in the old thread.
L1 in this thread is the coil in parallel with D9 in the old thread.
R20 in this thread is (R2 + Rds (FET)) in the old thread.
In this thread, I just drew the circuit for simplicity, since in the old thread the path from R3 is bypassed when the SCR is fired.

Understanding this power supply design


texts: Altium polygon doesn't pour to vias of same net

texts:
I am using Altium 17 and try to make a GND pour. On the GND polygon I want to place some vias to GND polygon. But it doesn't connect GND polygon and GND vias. They belong to exactly same net, GND.

I restarted Altium, but still no success.


texts: What is the difference between rated voltage and full load voltage of a transformer? Are the ratings given on the nameplate at full load?  Suppose if transformer is at full load, then are the voltages on primary & secondary side equal to their rated values?


texts:
I'm trying to run this example because I have a DE2-115.

I get this debug output then I don't know what to do

nios2-flash-programmer --debug --epcs --base=0x0a001800 tPad_Selector.flash
Using cable "USB-Blaster [2-2]", device 1, instance 0x00
Resetting and pausing target processor:
OK
Processor data bus width is 32 bits
Looking for EPCS registers at address 0x0A001800 (with 32bit alignment)
  Initial values: 0001703A 04C00074 9801483A 9CFFF804 983FFD1E 0000203A
  Not here: reserved fields are non-zero
Looking for EPCS registers at address 0x0A001900 (with 32bit alignment)
  Initial values: 92400237 4A40100C 483FFD26 90000135 92400237 4A40200C
  Not here: reserved fields are non-zero
Looking for EPCS registers at address 0x0A001A00 (with 32bit alignment)
  Initial values: 108001C4 1004D0FA 002EE03A 003F9C06 002EE03A 003F9506
  Not here: reserved fields are non-zero
Looking for EPCS registers at address 0x0A001B00 (with 32bit alignment)
  Initial values: 00000000 00000000 00000000 00000000 00000000 00000000
  Not here: SPI_SLAVE_SEL has 0 valid bits (should be between 1 and 16)
Looking for EPCS registers at address 0x0A001C00 (with 32bit alignment)
  Initial values: 00000000 00000000 00000260 00000000 00000000 00000001
  Valid registers found
EPCS signature is 0x16
EPCS identifier is 0x010216
No EPCS layout data - looking for section [EPCS-010216]
Unable to use EPCS device
Leaving target processor paused

What is needed?


texts: How is it possible to have a 5W transmitter driving 50 ohms with a 12V supply?

texts:
So let's say you have a circuit, which generates a carrier wave at some frequency (let's say 27MHz) and it's connected to a 50 ohm dummy load (which I gather is equivalent to an antenna for circuit analysis purposes). And it is powered by a regulated 12V power supply.

So imagine the carrier wave is 12 volts peak-peak, which is 4.242 volts RMS. As per the formula \$P = (V_{rms})^2/R\$, this gives a power output of about 0.36W. Even disregarding average power, 12V into 50\$\Omega\$ is 2.88W. And the peak of the waveform is actually 6V, and at 50 ohms that's only 0.72W.

How then do circuits like these output of 5W or more with a 12V (give or take a few volts) power supply?

http://www.rason.org/Projects/transmit/transmit.pdf (This one reports that when built the output was actually over 7W)
http://www.radanpro.com/Radan2400/Transmitter/5-Watt%20Transmitter%20by%20SM0VPO.htm

If you wanted an average 5W out of a 50 ohm load, you'd need a peak-peak voltage of almost 45V. For 100W, you'd need a signal that's 200V peak to peak! Somehow I doubt that people are powering their radios with such high voltages.

What I'm not understanding is how one gets more power out of a circuit with a fixed load and a fixed supply voltage. Even if your amplifier can deliver 100A, I=V/R; With a 12V supply, Ohm's law says that even at the peak, it's only going to be delivering 0.12A, with the load dissipating 0.72W.

I think one could somehow use a step-up transformer to increase the voltage to the necessary level, trading current on the primary for voltage on the secondary, but neither of the circuits above do this. Aside from that, all the impedance matching networks in the world aren't going to get you more voltage across that load.

All of what I explained may well be wrong, and that's why I explained it. Please help me sort out my conceptual misunderstandings :)


texts: Op-amp integrator response to square wave

texts:
simulate this circuit – Schematic created using CircuitLab

I would like to study the frequency responce of this op-amp integrator to a square wave. By setting a frequency of 10KHz and the pp-amplitude of the in-voltage to 340mV I obtain a triangle output wave with a pp-amplitude of 244mV. Now, according to my prevision I should have an output of 161mV, in fact    Vout=(-1/R1 C1)*integral(vin dt)=-(Vin/(2 f R1 C1)) that is the integrator formula for a square wave. I have already checked this value by expanding in fourier series the square wave and by trasforming each harmonic through the transfer function. The op-amp is TL081. Even if it is not shown in the circuit scheme, the op-amp is powered through +15 and -15 DC sources.

Can someone help me out?
[EDIT: corrected the extra  factor 2 as signalled by Olin Lathrop]

Screenshot of the oscilloscope:


texts: does changing UART stop bit number configuration (receiver side) affect message correctness

texts:
I'm using USART on board to display messages on desktop PC terminal using Realterm

I noticed that, when I change stop bit number on Realterm, it does not affect the correctness of the message, contrary to baud rate, or bit number.

why stop bit number does not affect correctness?.


texts: Can a multimeter measuring current damage low voltage devices?

texts:
I'm using an arduino due (3.3V) which its power regulator can deliver 800mA of current.
Can I connect a multimeter in series and get a reading of the current my circuit draws, and can i leave it connected so to measure the current in real time?

(I regularly re-program the Due with the circuit connected is there a chance the multimeter can damage the device in this situation?)

Will such a config affect the circuit?

At last should I break the circuit and connect the multimeter to the positive or to the ground connection?

simulate this circuit – Schematic created using CircuitLab


texts: In Digital Multimeter note accuracy in digits

texts: I have digital Multimeter noted in the multimeter accurcy is range 0 - 1000v at 0.2% +30 digits in this range what is 30 digits?


texts: What happens when an embedded program finishes?

texts:
What happens in an embedded processor when execution reaches that final return statement
Does everything just freeze as it is; power consumption etc, with one long eternal NOP in the sky? or are NOPs continuously executed, or will a processor shut down altogether?

Part of the reason I ask is I am wondering if a processor needs to power down before it finishes execution and if it does how does it ever finish execution if it has powered down before hand?


texts:
This is one of those things that I have always had a really hard time wrapping my head around.

In the horrendously simplified ideal step-up SMPS model below, I have set it up so when at 50% duty cycle, the output voltage is double the input voltage. For the sake of easy math, the current in the inductor is maintained at ~1A.

simulate this circuit – Schematic created using CircuitLab

As you can see, the power transfer is 1W so it operates at 100% efficiency.

But here is the kicker... only half the current taken from the supply ever reaches the load...

Intuitively one's head is telling one it can only be 50% efficient.

Granted an ideal SMPS would not be 100% efficient, but numbers in the 90 - 98% efficiencies in a real world SMPS are not unusual...

What is going on?


texts:
I want to simulate the following PhotoMos in CircuitLab for switching circuit but i didn't find the model for any photomos in CircuitLab. I was preparing a simulation for a switching MOSFET circuit and i need a PhotoMos model in my simulation, but i didn't find a PHOTOMOS model in CircuitLab.

How to insert a photoMos in CircuitLab simulation ?


texts: Is there any problem if one of secondary windings is left floating in a flyback converter

texts:
Is there any problem if we leave one of the secondaries in a flyback converter floating?
I have two secondaries: 24V & 18V.  My application needs only 24V.  What happens if the 18V winding is left floating?


texts: Measuring continuous voltage and current circuit

texts:
I'm trying to make a circuit that measures continuous voltage and current of a power supply, so I'm controlling the load applied to it using a MOSFET controlled in a closed feedback loop. By varying the PWM duty cycle, that passes through a low pass filter (making a DAC), I can control the amount of load.

I thought the R4 resistor would be dissipating most of the power but actually it's the MOSFET that's dissipating most of the power source, so I decided to short circuit the gate, drain and source from the MOSFET with another MOSFET to divide the dissipation power but it started to gain some noise on the MOSFET back to the PWM source making it difficult to control the load.

Does anyone have a guess of what could be happening and how can I solve this problem?

as show in the figure below:

simulate this circuit – Schematic created using CircuitLab


texts: Can I use a N-MOSFET to switch lower voltage signals?

texts:
I'd like to have a 12V signal as an input to a microcontroller, but it can only handle 5V on the input pins. This circuit will be used in a truck, so the "12V" signal can vary by quite a lot.

My question is this: Is it possible to drive a N-MOSFET with a higher voltage than what will be switched? The picture below shows what I'd like to do.

In this circuit, the 5V will be regulated, and stable.

I don't want to use a resistive voltage divider, as the input could be very variable, and this could either damage the MCU, or provide an unreliable signal. I'm open to alternate suggestions as to how this could be done.


texts:
simulate this circuit – Schematic created using CircuitLab

From what I understand, the magnitude and direction from an independent current source is constant. What would happen in the circuit above? If currents flow they way they're supposed to from the current source, KCL is violated. So how would the circuit above behave?

How about this one?

simulate this circuit


texts:
I would like to know what is the inductance (circled in red) of this part of this model? Is the value infinite? And only the inductance (circled in blue) is the value of the inductance of the transformer. So actually when it is written into a datasheet that the inductance is XX µH, the datasheet is actually talking about the magnetizing inductance (circled in blue on the schematic)?

Thank you very much.


texts: Galvanic separation between a microcontroller and a motor driver

texts: Is it possible to achieve galvanic separation between a microcontroller and  this driver . It's a dual full bridge driver and I'm going to parallel it's outputs (consequently the inputs and the sense pins) for higher current output (Figure 7 in the datasheet) to drive a DC motor and sense it's current. Is there a simpler solution without using this driver? A H-bridge made of MOSFETs seems to me to be a higher part count and complicated solution.


texts: How can AM modulation be performed in LTspice by built in MODULATOR function?

texts:
I have been looking for this for an hour and there is no single example or information about it in English language. The nearest ones are like this and there is no explanation I don't even know it is correct. No tutorial, no example, no diagram ect.

I used search still no luck:

https://www.google.com/search?biw=1422&bih=655&tbm=isch&sa=1&ei=kV0EW7fHG8OwsAGa7YyYCg&q=am+modulation+ltspice&oq=am+modulation+ltspice&gs_l=img.3...151628.151628.0.151831.0.0.0.0.0.0.0.0..0.0....0...1c.1.64.img..0.0.0....0.EcFpzqH5i3c

As an example how can we modulate a 1k carrier signal with a 10Hz signal by using the the built-in MODULATOR? (AM not FM)


texts:
A power transistor is used to switch a 25 A, 600 V inductive load at a switching frequency of 100kHz with D=0.5. Turn-on and  turn-off each occur in 100ns and the collector on-state voltage is clamped at 2V. Calculate the total power losses of the switch.

So, I'm not sure how to attack this, so I look for information in a book: Power Electronics by Lander.

According to this book:
$$E=\frac{VI}{6}T$$

So, turn-on loss will be:
$$\frac{25 \times 600}{6}\times\frac{1}{100\times10^3}= 0.025 J$$
And turn-off loss will be:
$$\frac{25 \times 600}{6}\times\frac{1}{100\times10^3}= 0.025 J$$

Hence, the mean switching power loss  \$=(0.025+0.025)\times 100\times10^3 = 5kW\$
Conduction loss \$= 25\times 2 \times 0.5=25W\$
Total loss is therefore, 5025W?

Is this correct? I don't really feel like it is... none of these equations are in my university notes. The only equations in the notes are:
$$P_{on}=I_D^2 R_{DS(ON)} \frac{t_{ON}}{T}$$$$P_{off}=V_{DS(max)}I_{DSS} \frac{t_{OFF}}{T}$$
But these pertain to MOSFETs and I don't really see how I can use these to solve the question...


texts: I have an EEG brain signal measurement device. I need to calibrate it -- i.e., I need to be able to apply known voltages to it and see its output. After doing this many times, I want to be able to determine the relationship between an applied voltage at the terminals and the output it gives. Any ideas on how I could do this? Is there a particular device that I could use to apply the deterministic voltages? I understand the voltages read by such EEG devices are so low and hence susceptible to noise. Would this affect me so badly. I am from CS, no much knowledge on EE


texts:
So I came across this LCD module the other day. The only obvious writing on it is SOLOMON. After typing in every number I could find on it I finally came across this mention online: http://nutsvolts.texterity.com/nutsvolts/200503/?pg=35#pg35 See the lower left on page 35, its the 16x4 LCD.

So apparently it is a Solomon Goldentek #LM1112SYL, but a google search for that turns up almost nothing. Trying to find the product on the goldentek website is a no go either. Anyone know where I can find a datasheet or anything that would tell me how to interface with this guy?

I can't even tell where the power is supposed to be connected...


texts: I'm having trouble figuring out the identity of this QFN-32 packaged component.  I can tell you it has a crystal attached so it's some king of embedded device.  I doubt it's an FPGA because it also has a native USB phy connection (D-/D+).  It also has a SPI flash device connected.  The minimal part marking makes me think it's some obscure brand or a counterfeit imitation of something else.  Thanks


texts:
I am making a simple BCD to 7 segment decoder but for some weird reason, the ICs I am using, 7432 and 7408 are not working properly.

My 7408 ICs (all 5 of them) are always producing high outputs, regardless of the inputs. While my 7432 ICs (again, all 5 of them) are acting like AND gates, i.e. only producing high output when both inputs are also high. I am using a 9V battery to power the circuit. Pin 14 of the ICs are connected to positive and pin 7 are to connected to negative.

Are my ICs broken or have I done something wrong in my circuit that I failed to notice?


texts:
I am trying to debug a UART driver for the STM32F405. It does not work above a certain baud rate (about 50 kBd). I connected it to a logic analyzer with analog capability, and I saw that the signal is rounded; it takes time for the signal to rise. It seems that at higher baud rates the signal does not rise high enough for it to be read.

How can I allow the UART to function at higher speeds? I'm not sure if this is a hardware problem, or if it can be corrected in software.

Screenshot of logic analyzer, MCU transmitting at 38400 baud.

Screenshot of logic analyzer, MCU transmitting at 115200 baud.

More details:

I am reading the serial connection with a FTDI chip connected to my desktop.
I sniffed this connection with a Saleae Logic 8 connected to the same lines as the FTDI.
In the screenshots shown, the board is sending "testing" over the serial.
The MCU is part of an OpenPilot Revolution flight controller.


texts: Inconsistencies between my Nortons and Thevenins equivalent circuits

texts:
Disclaimer i am sure this is super simple, but i am a complete novice to electronics.

I am trying to create thevenins equivalent circuit. For VTH i have been calculating IOC which I believe to be, 12(27/77) = 4.2v

However I am debating whether I should be including the 1 ohm resistor in my calculation.

Next for RTH I have shorted the source and opened the load, to calculate RTH I have thus done 1 + (50 * 27/50 + 27) = 18.53ohms

To clarify, VTH = 4.2v and RTH = 18.53ohms

Nortons. What I have been doing to calculate I nortons is to divide the source voltage by any of the resistors on the route to the short circuit in this case just the 50 ohm.

IN = ISC = 12/50 = 0.24A

Now here is my problem, I have read that VTH = IN * RN so 4.2 = 0.24 * 18.53 which of course isn't correct, 0.24 * 18.53 = 4.4472

I am failing to see where I have gone wrong!


texts: COM port goes down unexpectedly, but Arduino Leonardo keeps running

texts:
I am observing strange behavior with my Leonardo board.

I use 9V AC/DC adapter to power it. Relay extension board is attached to digital pins, and relays are used to control several valves and motors.

I've left only one small 220V 0.2A AC motor for testing. It is connected to the same wall socket as 9V adapater. Arduino connects to the notebook with a short USB cord equipped with ferrite ring.

Now here is my problem: using the serial connection I turn relay on and off a few times and COM port connection dies sooner or later. PuTTY window displays error, the COM port stays listed in Windows Device manager, but I can't reestablish connection unless I plug USB cord out and back in. Surprisingly, Leonardo keeps running. I know for sure it doesn't reboot - I've added buzzer beep to the setup() to hear when it does.

It could be the noise caused by the motor's coils that messes with DC adapter - I don't have capacitors on them. (And it is not the relay board - it has diodes for every relay's coil). My question is different:

I wouldn't be so stunned if it was Arduino UNO. But Leonardo has a single chip for both USB communications and work - so if one fails, the second should, too - right?

How could it be happening?


texts: ratiometric ADC, is it feasible to separate reference voltage and excitation voltage by an amplifier

texts:
I have a variety of bridge transducers (pressure, strain gage) with sensitivity of 1mV/V.  Also, most 24-bit ADCs and analog frontend chips have a PGA with programmable gain between 1-128.  This means that at the highest gain setting, the maximum output is only 12% of full-range.  In other words, the ENOB of the ADC reading is decreased by 3 just as a result of insufficient gain.

Recently I noticed that some ADCs allow a reference voltage significantly less than the excitation voltage of my sensors.  Is it feasible to, for example, reduce the reference voltage and then use a non-inverting op-amp with 4x gain to supply the transducer excitation voltage?  As far as I can tell, I will still have all the benefits of the ratiometric connection, with only slight degradation in noise performance (due to the ADC performance with reduced Vref... the closed-loop output resistance of the op-amp and its input voltage and current offsets appear to be negligible in this scenario) in terms of noise bits -- but the increased resolution more than compensates for the increase in noisy bits.  As a bonus, this can separate the excitation voltage for each channel, so that e.g. a short circuit in one transducer won't interfere with excitation of the others.

I believe I can get very good gain accuracy by using a chip bussed resistor for the feedback -- this way the feedback resistors will be exceptionally well matched to each other and also be thermally-linked, so the feedback won't vary with temperature either.

If this works, any ideas why this arrangement doesn't commonly appear in example circuits?

Diagrams modified from http://www.ti.com/lit/ml/slyp163/slyp163.pdf

The "usual" circuit:

Proposed circuit:

Where the amplifier block looks like (pay no attention to the op-amp model number, it's what CircuitLab supports)

simulate this circuit – Schematic created using CircuitLab


texts: Does an alternating current have surface charges associated with the current charges?

texts:
As alternating current passes along a wire:

Different charges are pushed to the surface in response to the current charges and form an excess electric field, leaving the interior wire neutral.

Questions:

Is this view correct?

This would mean there are two groups of charges.
Experimentally: Is there a strong electric field associated with each half wave even with a low resistance wire?

Does the electric field travel down the wire near the speed of light and, before a current starts, all the positive and negative half waves are established along the length of the wire.  The current charges between half waves can then neutralize each other. All the half waves progressively change together near the speed of light as the alternating electric field refreshes. Charges do not form on the surface in response to current charges.

This can mean there is not an electric field associated with each half wave.  There can still be an electric field from resistance in the wire deflecting current charges to the surface.


texts: Can a pic microcontroller be active all the time everyday?

texts: Can a pic microcontroller be active all the time, everyday, without getting damaged?


texts: Setup and Hold time VS temperature (and temperature inversion)

texts:
So I know that propagation delay and timing inside an ASIC are affected by temperature.   In the old days things went faster when colder and slower when hotter.  Now at 90nm and below there is temperature inversion so things get faster as they get hotter and slower when colder.

If I have a 65nm chip that has a timing problem at high temperature am I looking for a setup or a hold violation?   Or could it be either because it's really just the prop delay that's affected?  An explanation of how/why would be appreciated.

I've done some searching, read some articles, (tried to remember what I learned last time this was an issue) but it's still not really clear to me.


texts:
The condition for using an LC/RLGC model over an RC model is when:

f > R/(2*pi*L)

(see for example http://www.ece.tamu.edu/~spalermo/ecen689/lecture2_ee720_channels.pdf slide 19). This explains why we typically treat every normal twisted pair cable as transmission line (f>32kHz) but still use RC models for IC design (f>1.6GHz).

Why question is: WHY? How exactly is this criteria derived?

I am somewhat missing "C" in this criteria. Shouldn't it matter whether C is tiny or huge?


texts: Q: transistor as a variable resistor for oscillator circuits

texts:
this is my first question,

I want to ask a simple question, I searched but couldn't find proper answer, here is my situation; I want to build frequency generator circuit with op-amp oscillator topologies, but I want to control the circuit with ATMega328p's RC-Filtered PWM Analog outputs, but as you know, oscillator circuits tuned with changing R and/or L (if RL resonator/tuned circuit used) or C ( if RC circuit used for oscillation) values, it is obvious that I cannot change L or C values easily, so I decided to change R values to tuning oscillation frequency (as variable), so I think that I need to implement digitally controlled potentiometer or variable resistor, after that I came up with an idea; when using a BJT transistor at Active region, it acts as a variable resistor (ofcourse there will be some voltage drops due to Vbe)

but I cannot achieved this goal because active region needs small signal input at base, here is my question : can I set the PWM or RC Filtered Analog output's amplitude as needed for active region ( as mV scale, I think) or should I consider another way to accomplish this issue?

thanks in advance, sorry for my bad english


texts: How can I amplify my transmitter's RF signal to open the garage from the 12th floor?

texts:
I live on the 12th floor of my apartment building and the garage door is on the ground level  right below me but is obstructed by trees and a ledge. I do not have line of sight.

My garage door opener uses a 300 MHz RF signal. The exact model is the Multicode 3060 Remote Garage Door Mini Key-Chain Transmitter (see Amazon).

Is there any way I can amplify this RF signal to open the garage from the 12th floor even though I don't have line of sight?


texts: Debugging a nonsynchronous step-down power supply problem

texts:
I'm a software engineer doing some basic (I thought) hardware design. I have built a 5V power supply around an Analog Devices ADP2303 non synchronous step-down regulator. The schematic is from the top of page 25 in their data sheet.

I have three PCBs built, the original prototype and two "second generation". The schematics and parts are the same but the PCB layouts are slightly different (I had to cut traces and add two jumpers on the original to get around a design error). My problem is that the original board works perfectly, holding 5 VDC under load, but in both newer boards, the output drops to 2.4V when I connect a load - a Raspberry Pi. In all three cases, I'm using the exact same 12V 5A AC adaptor as a power source.

I have no idea how to debug this problem and would appreciate any pointers. I do not have an oscilloscope, so I hope that's not a requirement.

In looking more closely at my PCB layout, I definitely did not follow AD's layout at all, in either generation of board. But the two big differences are (a) gen-1 punched the ADP2303 ground pad thru to a full ground plane on the back of the PCB, while the gen-2 did not (I don't know why), and (b) in gen-1 the connections between pin 5 (FB) and the output capacitor and between pin 7 and ground are jumper wires instead of traces. So I'm wondering what the likelihood is that these differences are responsible for the fact that gen-1 can support a Raspberry Pi at 5V while gen-2 output drops to 2.4V when connected to a Pi, and whether redesigning this part of the board will solve the problem.

[update]

As there is a clear consensus that my PCB layout is really pathetic, I am redesigning based on AD's recommended layout:

Thank you all so much for taking the time to explain and recommend. I will update with my results when I get the redesigned board.


texts: stm32 - i2c communication fail after disconnecting oscilloscope probe

texts:
I am trying to communicate with TCS34725 module with NUCLEO-F401R board. The first I tried is to read out ID register of TCS34725, which should be 0x44, to check the connection. Everything works fine when I have my scope probe (gain is x10) is connected to SCL/SDA Line:

BUT, whenever I disconnect my probes (both or one of them), the HAL_I2C_Mem_Read function call will timeout and readout will be 0 not 0x44. I have no idea on how to fix this, so I am here for help.

Here is my hardware connection:

The TCS34725 Module is a product by DFROBOT, the schematic is (Source):

My code is:
#define TCS34725_ADDRESS          (0x29 << 1)
#define TCS34725_ID               (0x12)
extern I2C_HandleTypeDef hi2c1;

void TCS34725_Read(unsigned char subAddr, unsigned char* dataBuffer, unsigned char bytesNumber) {
  subAddr |= TCS34725_COMMAND_BIT;

  HAL_I2C_Mem_Read(&hi2c1, TCS34725_ADDRESS, subAddr, I2C_MEMADD_SIZE_8BIT, dataBuffer, bytesNumber, 1000);
}

uint8_t TCS34725_Init(void) {
  unsigned char readout;
  TCS34725_Read(TCS34725_ID, &readout, 1);
  return readout;
}

Here is my current hardware setup, I have changed another breadboard and redo my wiring to make sure nothing is loose. But same problem still exists.


texts:
I need to sum output A and output B of a PWM (UC3526AN) because each output have a maximum duty cycle of 0.45.

I try with 2 diode and a limiting resistor(R1) for the led inside the optocoupler (4N25)

This is the voltage before R1

This is the voltage after R1

The blue line is the voltage to pin 1 .

This is the PWM block diagram :

Why did you think I got this problem ?


texts:
Can any one please explain me how the convolution of the following leads to delta(t).

To convolve these to function i considered  delta(t+T) as x(t) and
delta(t-T) as the response. Then these two function overlaps only at t=-T and then the convolution should result in only delta(t+T). Then why delta(t) is the answer.


texts:
I can't find type of this connector.
Space between pins is 1.27 mm.
And it has 6 pins.
What type is this connector?


texts:
I'm on a school project that involves, as part of it, the sending of messages to a cellphone through a SIM800L GSM module. This module will be controlled by an PIC16F648A MCU. My problem is: how to make sure the TX and RX power level of either the module and the MCU matches?

As far as I know, data transmission  pins of the GSM module accepts 2.8V as logical level high, while PIC does 5V for TX and RX pins of it.

Considering it, I believe the connection can't be straight, but I have to consider two scenarios:

Arduino's circuits over the internet shows a straight connection between the data pins as shown in a quick search on Google:

SIM800L datasheet recommends a "level matching" circuit between the MCU and the module on page 32:

SIM800L GSM module datasheet link: http://simcom.ee/documents/SIM800/SIM800_Hardware%20Design_V1.08.pdf

I'd rather do what the module datasheet says (although connecting it straight to the PIC would be much more simple), but I'm not sure about what the level matching circuit does or how it works and not even sure if it is really needed. So, please explain me if it is really needed and, if it is, how it works.

It may also be helpful to say that there are a few models of this module in the market so, for instance, mine is that one:

Obs.: Consider I'll be using just Vcc,TX,RX, Gnd/Vdd, and antenna pins of it.


texts: How to set up SPIDF channel bits for high sample rate output?

texts:
The original SPIDF standard supported sampling rates only up to 48kHz, but today much higher sample rates are supported. The sample rate was set by controlling channel status bits, which also contained other information.
Question: For high sample rate 2-channel output that is used for recording purposes, what should the channel bits be set to? Can I simply set all bits to 0 and have an interface accept the output?


texts: What do you call the drawing which contains tracks, pads and drilling points of a PCB layer/side?

texts:
Example:

Does this drawing has a technical name?

I see that people usually call these drawings "PCB". But, PCB is physical object, physical implementation of circuit, isn't it? Is these kind of drawings really called "PCB", or do they have a special name?


texts: MS5611 (barometer / thermometer) returns temperature going up if checked repeatedly

texts:
I have a ms5611 module working fine.  It reads pressure and temperature without a problem.  However I have one condition I have a problem with.

I am calculating out the current altitude using the pressure and temperature, but if I check temperature too quickly and repeatedly, the value goes up like below.

21.66
21.66
21.67
21.67
21.68
21.68
21.68
21.68
21.69
21.69
21.69
21.68
21.69
21.69

*I did a loop sleeping 0.1 second above.
*It keeps going up if I don't stop the loop.

I am pretty much sure it is because the module sensor itself is heated up by the calculations, but how often should I check on the values so that the values won't be affected the heat from itself?

Is there a way to read the datasheet for this?
http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7FMS5611-01BA03%7FB%7Fpdf%7FEnglish%7FENG_DS_MS5611-01BA03_B.pdf%7FCAT-BLPS0036


texts:
I am trying to send a data=40 from matlab gui to pic16f877A  via serial communication.
To crosscheck value is properly transmitted to pic i also transmitted back that data from pic to matlab and displayed that data in edit text in matlab gui.
I noticed that edittext value is 75.
the data received was transmitted as it is without any manipulation then why does the value changed.
can anyone help  me . Is there any problem in my typecasting?

mikroc code:

 unsigned int setPoint;
 char start;

main function

 void main() {
 UART1_Init(9600);
 setPoint=100;       // initially setpoint is set to 100
 .
 .
 .

    while(1){
  if (UART1_Data_Ready()){
       start = UART1_Read();

    }
 if(start=='s'){             // if start button is pressed

  do something....
 }
else if(start=='g'){          // if stop button is pressed
   do something....
}

else if(start=='r'){         // if refresh button is pressed
 UART1_Write(1);
 refresh=1;

 while(refresh==1){
 if(UART1_Data_Ready()){
 setPoint=UART1_Read();      // reads data from matlab

  refresh=0;
   UART1_Write(setPoint);      //transmits back to matlab
 }
 }
 }
 }
 }

Matlab code:

executed when start button is pressed

   function start_Callback(hObject, eventdata, handles)  // start button in matlab

    s = serial('COM2');
    set(s,'BaudRate',9600);
    set(s,'Timeout',10);
    set(s,'ReadAsyncMode','continuous');
    fopen(s);
    handles=guidata(hObject);
    handles.set=s;                         //passed serial comuunication object(s),so that it can be accessed in other callbacks
    guidata(hObject,handles);
    fprintf(s,'%c','s');                // send 's' to mikroc
    i=1;

     do something here....

executed when stop button is pressed

     function stop_Callback(hObject, eventdata, handles)  //stop button in matlab

     setup=handles.set;              //setup is serial communication object(setup=s)
     fprintf(setup,'%c','g');      //send 'g' to mikroc

     do something here.....

executed when refresh button is pressed  (problem lies in refresh button)

     function Refresh_Callback(hObject, eventdata, handles) //refresh button in matlab

     setup=handles.set;
     fprintf(setup,'%c','r');   // send r to mikroc
     refresh=0;
     while(refresh==0)
     if(setup.BytesAvailable>0)
     refresh = fread(setup,1,'uint8');
      end
      end
      setpoint=str2num(get(handles.edit1,'String'));  // take data from edit box (data =40)
       fwrite(setup,setpoint);     //writes data(40) to pic

       setp=fread(setup,1,'uint8');    // receive data from pic
       string1 = sprintf('set = %i', setp);   //display in edit text
       set(handles.edit5, 'String', string1);
       fclose(setup)
       delete(setup)

The output displayed in edit text is 75 how 40 changed to 75. I am new to matlab gui.


texts: Do 100% duty cycle buck converters have no voltage drop?

texts:
I am currently designing a circuit which should be able to take 12-28V DC power in and output 12V DC @ 1.5A.

The question is: is this possible with a 100% duty cycle buck converter (like TPS54302)? What will happen if the input and output voltage are nearly the same?

If this is not possible what options do I have?
If it would be ok to drop up to 1V when the input voltage is below 13V, will this make things easier?

Would it be possible to detect a low voltage and bypass the converter if the voltage is too low?


texts: Microcontroller programming: do I need vendor's IDE?

texts:
I am very interested in the following ARM Cortex-M0 microcontroller:

http://www.nxp.com/products/microcontrollers/cortex_m0_m0/lpc1100/LPC11U24FBD48.html#overview

However I'm turned off at the thought of having to license their development software, which I found here: http://www.lpcware.com/lpcxpresso

Do I have options? My goal is to PCB design a custom development board based off of this microcontroller or similar (Cortex-M0/M3), and be able to program it via (micro) USB. Frankly I'd rather write ARM assembly - and likely be able to find good open source stuff to get me started - than have to use a proprietary IDE.

Thanks for any help; also open to alternatives based on my goals.


texts:
Reading the Space Systems/Loral press release SSL Achieves Milestone, 100 Satellites Delivered based on the 1300, a Platform for evolution, innovation I ran across the sentence(s):

  It was the first satellite to use a 100-volt bus and Direct Radiating Collector (DRC) amplifiers, providing the higher power needed for direct-to-home television.
  It was the first true high-throughput satellite, an advance which now enables millions of people around the world to have access to high speed broadband.
  It was the first to reach 20-kW of power, which enables satellite broadcast of today’s HD and UltraHD television.
  It was the first satellite to provide two-way ground-based beam forming, which increases a satellite’s flexibility to meet changing business requirements.
  (emphasis added)

I'm trying to imagine an amplifier with the collector attached directly to a feed horn for radiation, but I think at these frequencies traveling wave tubes (TWTs) are used.

Question: What is a Direct Radiating Collector Amplifier?


texts: Connect two sections with different grounds

texts:
I have two circuits in two different ground domains GND1 and GND2. These grounds are shorted together at the power supplies which are far away. Domain 2 is a high power system so the voltage drop across the two grounds can be as high as 100 mV and depends on the absorbed current, which is variable.
The signal from domain 1 has to be connected to domain 2. (see schematic. OPAMPs are not TL081s though)
The bandwidth of the signal is about 20 MHz and connection must have no latency, so optocouplers are excluded and INAs are too slow.
I thought a solution like the one in the schematic, a simple difference amplifier.
The current from domain 1 to domain 2 will be in the order of 100 uA so DC current is not an issue, but I am concerned about the medium-high speed current, in the range of 100 kHz - up. To go back from GND2 to GND1 it has to travel back to the power supply which will be an antenna, and a probably big inductance. The only thing it came to my mind is to connect locally the two grounds with a cap, 1 uF, to short them at medium-high frequency.
Is this a good idea or is there another solution I don't know?

Thanks

simulate this circuit – Schematic created using CircuitLab

**My big concern is having net current from system 1 going into system 2, either via Vdd1 -> GND2 or GND1 -> GND2. An INA architecture would probably be the best solution, with GOhm input impedance I'll have neglecting current going through. I can surely make an INA out of three opamps but I was looking for an already integrated solution with only one IC and couldn't find high speed INA


texts: Can I use 2 10uF instead of one 22uF for voltage regulator?

texts:
I am using a switching voltage regulator to go from 5V to 3.3V, 1A of output current.  The datasheet specifies 22uF ceramic capacitors for the input and output.  Can I use 2 10uF capacitors instead of one 22uF capacitor?

Besides the difference in frequency response (10uF has a higher resonant frequency), is there a reason why one 22uF would be better than using two 10uF?


texts:
In High school and University courses, I have only seen active filters made around OpAmps. I'd like to know something about active filters built with BJT amplifiers.

Figure: Example of BJT filter compared to OpAmp version

I can find lots of information in books I have about OpAmp filters, but nothing about BJT filters. I searched a lot also on the Internet, but I found very little information.

My question is how to design filters with BJTs and what are the advantages/disadvantages versus OpAmp circuits (costs, performances, noise...)?

Moreover, can you please suggest me a good book or some lectures to better understand these kind of filters?


texts: Streaming a section of video to an external display

texts:
I want to be able to connect an external display to my Windows PC (in addition to the existing one), and stream a selected portion of the screen to this display. For example, if I have a small terminal window open on my main monitor, then this smaller display will show only that terminal window, not the rest of my desktop. I guess it's like Picture In Picture (PIP) on a TV, but for a PC instead.

Can anyone recommend the easiest way to achieve this? I don't mind getting into the video programming side of it (maybe using DirectShow?), but if there is a hardware solution, eg on a DSP board,then that would be great.


texts: Do 110-250V power supplies waste power at higher voltages?

texts:
I'll provide a standard Mains->USB adapter as an example.

We know that the output of the USB will remain the same no matter what voltage between the allowed range is applied at the input.

If we're using this adapter in the UK, then we'll be applying 230v across the input. Are we wasting any power at this voltage compared to using the device at a lower voltage, say 110V?


texts: Explanation of structure and function of a safety relay

texts:
I am reading a safety guide from Pilz. This guide contain a chapter about safety relays.
A circuit given in this guide is given below:

I know the purpose of all switches and buttons defined in it. But I am unable to understand the circuit completely.
How does it working, and how does the short circuit occur?
What I understand is that positive-guided always wants its switches to be open, but it gets closed for some reason (I don't know which,) and as a result a short-circuit occurs. But I am not sure.


texts: Why charging Li-Ion batteries in cold temperatures would harm them?

texts:
Accordingly to what I've found in several sources (user's manual of electronic devices, various forums, e.t.c.) I shouldn't charge my Li-Ion batteries in cold temperatures because this would harm them. However it's completely unclear which kind of harm they will receive and why exactly would they receive any harm at all.

Is that really true? If it is, then can somebody explain me the nature of electronic and / or chemical processes leading to damage when charging lithium-ion batteries in cold temperatures?


texts:
I have built a simple rlc circuit with a pulse input and performing transient analysis on it. I am interested in the voltage of the behavioral voltage source as shown in circuit.

The system is an under-damped system so the voltage at the behavioral voltage  node is an under-damped signal.

I want to plot the enveloping curve for the same.
It will be really helpful if someone could help me out with it.

Thanks in advance


texts: State variable equations for a RLC circuit

texts:
What are the state variable equations of this RLC circuit? How do I write the final matrix? I tried to write the equations for the capacitor and inductor:

$$L\frac{di_3}{dt}=v_1-v_C \leftrightarrow \frac{di_3}{dt}=\frac{v_1}{L}-\frac{v_C}{L}$$

$$C\frac{dv_C}{dt}=i_3\leftrightarrow \frac{dv_C}{dt}=\frac{1}{C}i_3$$

I tried to apply the Kirchoff's law:

(1) $$i_1R_1+L\frac{di_3}{dt}+v_C=v(t)\leftrightarrow i_1=\frac{v(t)}{R_1}-\frac{L}{R_1}\frac{di_3}{dt}-\frac{v_C}{R_1}$$

(2)

$$v_1=v(t)-R_1i_1$$

From these equations I am unable to reach the final matrix. How could I go on?


texts: Anyone aware where can I find SPICE models for MAX6126, MAX6250 etc? I searched a lot and could not find. If anyone knows, can you please share the link/file?


texts: Is this desoldering hack likely to work?

texts:
I found an interesting YouTube video with a neat de-soldering trick that requires no special equipment.

Essentially you bend a reasonably thick piece of copper wire round into a right-angled S shape, add a layer of solder over the bottom edges, then place it over the chip. By heating the copper from the top, it melts the solder and provides a near perfect coverage of the IC's pins. From there you can just lift it off the board with tweezers.

Is this likely to work without damaging the IC or the board's pads, as described in the video?


texts: what is the digital communication format that the bluetooth module communicates with

texts:
I am using ATtiny2313 microcontroller along with a bluetooth module(HC-05) to communicate with my laptop.
Heres my doubt,
How does the bluetooth module communicate with the laptop. i.e. what is the digital communication format used (whether BASK, manchester ... ?).
How do i calculate the baud rate graphically and read what data is being sent from the waveform (i am looking at the waveform on the TX pin of the microcontroller on a DSO).
Also, should the waveform be very stable or should it be noisy (i am sending a constant byte 0b01010101 over the bluetooth).
If someone can provide me example waveforms, i shall be grateful


texts:
In my vehicle, I have a 27-pin connector with Volkswagen OEM part number 8K0 972 701 (male) / 8K0 972 702 (female). Etched onto it is the TE Connectivity logo and the number 1718872-1. I am looking for crimp terminals for this connector.

The terminals look like this for the narrow pins:

and for the wider pins:

I have found plenty of places to buy the connector housings with the given information. However, how would I go about finding the correct matching crimp terminals to attach to my wires? As you can see, pins 18 - 23 are wider, so I would require two different types of terminals.

Any general pointers to where or how to search, or even an exact answer as to which terminals to use would be greatly appreciated. Is there some type of standard? I have already found some pigtail connectors, but I would rather crimp the wires myself.

Update

To anyone also looking for this information, I have found the OEM numbers of some pre-crimped cables that seem to fit on this connector (not entirely sure).

Male:

000 979 022 (wide pin, 0.35 mm² wire)
000 979 035 (narrow pin, 0.35 mm² wire)
000 979 134 (wide pin, 1 mm² wire)
000 979 160 (narrow pin, 1 mm² wire)
000 979 226 (wide pin, 2.5 mm² wire)

Female:

000 979 026 (wide pin, 0.35 mm² wire)
000 979 034 (narrow pin, 0.35 mm² wire)
000 979 151 (wide pin, 1 mm² wire)
000 979 159 (narrow pin, 1 mm² wire)
000 979 242 (wide pin, 2.5 mm² wire)

Part number + suffix A seems to be for gold-coated contacts and suffix C for silver-coated contacts, from what I can see.

As these parts are kind of expensive I would still be very interested in what type of crimping terminals they use so I can make these wires myself!


texts: I want to drive a 6-volt ignition coil with a DC resistance of 3 ohms, from a power supply of 6.2 volts DC at 2 amps.  I propose to use a 555 timer as the PWM, with a 50% duty cycle at about 5 to 10 kHz, with a totem pole amplifier.  I don't need full power output from the ignition coil. What would be a good power transistor for the output?  (I would like to use a MOSFET, but don't have a grounded working mat or wrist strap.)


texts: Cleaning circuit boards for high impedance

texts:
Colleagues,

EEG signals typically have high source impedance.  Amplifiers in the EEG circuits have high input impedance too.  The signal is DC-coupled to the amplifier.

One problem is that leakages across the surface of the board can distort the signal.  Guard rings help prevent that.  Contamination on the PCB increase leakages.  So, I would like to clean the contamination.  Could anyone recommend a procedure for that and what solvents to use?

The board is FR4 with solder mask and silk screen.  SMT components.

Cleaning will be done in an industrial facility, which is equipped for handling and disposing solvents.  We have fume hoods.

UPDATE: Just added a bounty to this question.  What I'd like to get is a fairly detailed procedure.  Just throwing names of chemicals at this question will not count.

UPDATE: Bounty period had expired.  Still looking for the procedure. Didn't get answers I could award the bounty to. The tips which got posted so far might be useful for somebody in the future.  More tips about board cleaning here (parallel thread on another forum).

UPDATE: Found more systematic insight into PCB cleaning (here and here).


texts: Why to use a BJT transistor instead of MOSFET?

texts:
I read that MOSFET are more power efficient than BJT and that they are capable to handle higher current.
In this case, why using a BJT ?

I see most circuit use BJT to turn on / off some LED with a MCU GPIO for example.
But why not simply use MOSFET instead ?


texts:
I'm designing a go board that can detect where pieces are placed through a raspberry pi for the purpose of game recording. I'm planning to put magnates on the bottom of pieces and do the detection with a matrix of reed switches. The question is how to best read all of the inputs from the 19x19 grid?

I could use 3 MCP23017s or even shift registers but I have a suspicion that there might be a chip specifically designed for this application. I wasn't able to turn up anything googling but I'm probably just using the wrong terms.

So in short, is there a better way to drive a large input matrix than to use a few IO expanders?


texts: Trouble with Peltiers TEC and USB Output Current

texts:
here is the website I will be referencing: http://www.instructables.com/id/5-Mini-USB-Fridge!/

So I was reading from Inscrutables on powering a small Peltier TEC to cool your hand while reading, and so I bought a 5v 19.4 Watt Peltier.

The instruction website got me under the impression that a peltier will run at the 5 Volt and whatever current it receives. So, I set up the peltier element using my USB cable plugged into a USB battery pack and nothing happened. The item and fan turned on for one second, then shut right back off.

I got a current reading of 5v, 3.9 Amps when I plugged the Peltier USB into a USB wall wart which confused me since the maximum output of the USB cable and charger is stated to be 5V 2.4 Amps. So logically, I need to find some way to power the Peltier off of a rechargeable battery 5v 2.4 Amps.

According to the instruction website I should have been totally fine powering the peltier from a USB battery pack as the instructional sheet was using a 12v 60 Watt peltier element powered by a USB cable.

*

Potential Solution and Question

*

I believe the problem lies in that the USB battery pack is shutting off to save itself from outputting a current of 3.9 Amps when it can only reasonably allow a draw of 2.4 Amps.

How can I stop this, how can I make it so that the peltier runs off the USB battery pack at its maximum capacity of 2.4 Amps, 5 Volts?
And why is the peltier pulling 3.9 Amps and not defaulting to the 2.4 Amps I am giving it through the rechargeable battery pack, as did the peltier powered by the USB cable in the Instructables website?


texts: I have some Phillip speakers I got from a friend, but they forgot to give me the amp. I'm hoping to still use these for some projects, but noticed the speaker wire coming out has two terminal, one wire marked with "+" and one wire marked with a number (I have 3 speakers, each is labeled "6", "7" or "8"). There are no colors to these wires. Is it safe to assume its a normal speaker where + is positive and the wire with the number is negative? I've never seen this before.


texts: Push pull converter magnetizing current during both switch off state?

texts:
In a push pull converter during turn on a switch magnetizing current and load reflected current build up. So magnetizing inductance store energy. During both switch off state secondary coil does not carry current. But what about the built up magnetizing current? Current in the inductor can not instantly goes to zero. But when both switch off waveform shows primary current is zero. So my question is where does the charged magnetizing current discharges?

According to this picture, input current/primary current, Iin comprises of secondary current iL and magnetizing current im during sw1 on and sw2 off. What happens to this current when both switch is off? If the current is zero during both switch off, becuase there is no free wheeling path, then how can primary winding of transfromer allow such abrupt current change to zero without creating harm to switch or destroying something?


texts: What is the ampacity of 14 gauge silver wire?

texts:
There is no information I can find (charts/specifications) that gives the ampacity for single core silver wire. But I know this can be calculated, I've found this property list for silver from a [metals supplier][1]

  Thermal Conductivity:  428 W/m * K at 20 oC
                                        356 W/m * K at 450 oC

  Electrical Properties:

  Electrical Conductivity: 108.4% IACS for extremely pure silver

  Electrical Resistivity: 14.7 nΩ * m at 0 oC

  Temperature Coefficient: from 0 to 100 oC, 0.0041 per K

  Cold working of silver considerably increases resistivity: 5% for 90%
  reduction.

Any ideas why this information is not available anywhere? I'd love to know how this is calculated and what it would be for 14 gauge (2.5mm wire).

Many thanks!


texts:
Hi I am trying to design with the TSM104W, which is a 4 package rail-to-rail OpAmps, with a built in voltage reference. This is the package pinout:

I see that the four Op-Amps are supplied through pins 4 and 13, but also pin 13 is the anode for what I think is a Zener diode, I am having trouble understanding how to actually use this voltage reference.

This is the part of the datasheet that tells the reference data:

I want to undestand how this voltage reference actually is and how to design with it, also I want to know if this IC could be used on a single supply application (Vcc- connected to ground).

Does voltage regulation is achieved with a circuit similar to a LM317 Voltage Regulator?, I would really aprecciate some hint on this. Thanks!

Edit:

I think I have found a similar Voltage reference in a stand alone package, TL431 or TL432. Comparing both datasheets is easy to see that the nomenclature used is the same.

TL431 datasheet:

Would it be ok to design with the TSM104W using the schematics shown on the TLA431 datasheet?

For example:


texts: Questions about reflowing solder on a motherboard

texts:
One of my laptop's DIMMs is dead and working with less than my usual 8GB of RAM is brutal. Multiple sources suggest reflowing the board. I quite frequently tinker with/hack my electronics, but I've never attempted to reflow a board, especially whilst putting my beloved computer at risk. I have a few questions before I start:

Temperature? I know it depends on what kind of solder alloy is used, but I don't know how to check it. Is there a de facto standard I can resort to?
Time?
Oven or heatgun?
How come the processor (among its other chip buddies) don't burn out at 200°C+ temperatures while being (essentially) baked, but burn out when operating at near 100°C?
Any advice you can offer on the basis of dramatic/entertaining anecdotal evidence of how this can all go terribly wrong?


texts: How do I properly shield wires to my stepper motors?

texts:
I have a project where I need to run stepper motors within a few centimeters of wireless RF transmitters and receivers. On the breadboard I have experienced some strong interference. I am purchasing shielded wire so that I can avoid it but I am concerned about how effective my shielding will be.

I will have fully shielded wire running from the stepper to the driver but I am concerned about the open soldered connections to the board. Will this also cause interference?

I also will have to attach this shielded wire to the unshielded wire coming out the the stepper. I will make sure I do this as close to the stepper as possible but there will inevitably be some un shielded wire.

Is there anything I can do to further avoid interference at these connection points or am I being nitpicky and it won't matter to much?


texts: Conducted Emissions of EV Charging Electronics

texts:
I'm building an AC-charging device for electric vehicles (the standard calls it an "ICCPD" or an "In Cable Control and Protective Device") and I'm facing some EMC issues due to the PWM Signal on the CP-wire.

Background:

The charging device is connected to the vehicle via the type-2 connector. The cable to the EV looks like this and is approx. 5-10m long:

The CP wire is used for the communication between the vehicle and the ICCPD. Basically it carries a PWM signal and the duty cycle indicates the maximum charging current. The frequency, amplitude and rise-time is defined in the standard.

f=1kHz
positive amplitude = 6/9/12V (relative to PE)
negative amplitude = -12V (relative to PE)
rise/fall time = <2us

Problem description:

The following figure shows the conduced emissions with PWM signal ON (turquoise) and without PWM signal...const +12V (blue) measured on the neutral line. Cable length was 9m. Measured with Rohde&Schwarz Precompliance test equipment (HMS-X and HM6050-2).

Question:

Is there any way to reduce the conducted emissions due to the CP-Signal?

Update 1:

Reducing the cable length and/or shielding the CP-wire is not possible.

Update 2:

According to my understanding the equivalent schematic looks like this!? And the Problem is the parasitic capacitance between CP and N (Neutral), which is approx. 60pF/m based on the dimensions.

Update 3:

conduced emissions according to Andy's suggestion/ thought experiment:

Turquoise line: PWM Signal on CP wire inside the cable
Blue Line: PWM signal connected to a separated wire (no PWM signal on CP wire in the cable)


texts: Co-application of DC field and Microwave Irradiation on Soil

texts:
I am attempting to design/enhance a system which applies direct current to a soil for the electro-kinetic remediation of organic/metal contamination. My current plan is to try enhancing conventional EK-treatment by concurrently heating the soil using microwave frequency radiation distributed in-situ through a co-axial antenna.

My question is whether the microwaves will interact with my DC field in any way, and if anyone could suggest some resources to me for exploring this idea

To help visualize the problem, I plan to utilize an anode on the left of the soil cell, a microwave antenna centrally located in the soil, and a cathode on the right of the soil cell. I cannot seem to find information on how these two components may interact.

(I apologize if this is a silly question, I come from a Civil Eng. background so electricity is quite foreign to me)


texts:
I have 7 NiCd batteries hooked up in series (ordered from china) for a spare time project of rebuilding an old battery drill. Have been trickle charging them with 8.7V and 0.04A. When the battery is full it shows 8.6V
The thing is when I hook it up to the drill the voltage rapidly in like 1-2 seconds goes from that to 8.0 also the amperage goes from 1A to 0.7A drawn from the batteries.
Have been researching these kinds of batteries and it seems that rapid voltage drops are not their thing. Am I doing something wrong or is it possibly a problem with the batteries.

Technical specs:
Drill is a Bosch 8.4V all I could find on the net.
Batteries are NiCd stack of 7 each 1.2V and 600mAh.


texts: Identify this battery-charging connector

texts:
Can anyone identify the connector in the middle/right-hand side of the image below, which is used to charge a battery cell from USB?

I'm trying to find a replacement charging cable.


texts:
if i have the following circuit , what the expected behaviour of the following caps ? , it will be charge and discharge very quickly since we have a low inpedance form op-amp?

simulate this circuit – Schematic created using CircuitLab


texts: Isolated power supply with output on a 2kVDC floating ground

texts:
I am building a system of detectors which are referenced to independent floating grounds. The maximum voltage between each stage is 2kVDC. So I need isolated supplies which can operate continuously at this voltage. I found these Mean Well supplies.

RSD-30G-5     VIN: 9-36V VOUT: 5V
RSD-30G-12    VIN: 9-36V VOUT: 12V
Both are 30W

The data sheet reads:

WITHSTAND VOLTAGE
Input-Output: 4KVDC Input-Frame Ground:2.5KVDC Output-Frame Ground:2.5KVDC

I looked further but I cannot be totally sure the supply wont get shorted in a continuous 2kVDC use. I wanted to know if anyone had a different recommendation regarding the power supply or any thought on using these power supplies at 2kVDC.

I contacted the supplier to clear the rated voltage for continuous operation.

simulate this circuit – Schematic created using CircuitLab

The maximum voltage a detector can go is 2kVDC.

In this link you can find the datasheet and the report of the tests conducted on the device.


texts: EMI determine farfield from nearfield probing

texts:
So I went to the chamber and failed at 900MHz.  Then sniffing around with my E-field probe and my spectrum analyzer I found the source.  Next I made some modifications that reduced what I saw with the probe by 3dB.  My question is should I expect to see a 3dB reduction now when I go back to the chamber?

I'm sure it will be lower but I don't know if it will be linearly lower or not.


texts:
Currently I am using the normal ATmega328P chip with my barebone Arduino I have made.
I am planning to switch it with an SMD version of ATmega328P, since it's smaller in size it will consume less current and will be more compact.

My question is, does anyone know how to burn a bootloader in the chip? And after bootloading it, how do I actually burn the code which I have written on Arduino IDE 1.5.6 r2?


texts:
I want to calculate the resistors required with:

Input voltage = 9.0 volts

Output voltage = 3.0 volts

All the datasheets omit to give the input voltage in the formula:

Vout=1.25*(1+R2/R1)+(near zero term in R2)

Where R1 is the fixed resistance (about 240R) and R1 is the variable resistor.


texts: Philicorda phase shifter vibrato circuit doesnt work

texts:
I have built this circuit in the online editor, but it doesn't seem to oscillate.

My philicorda vibrato broke down and i want to repair it. It should convert 21V DC into a sine wave when i understand it correctly.

But my online circuit simulation does not oscillate, why is that?

philicorda 752 service manual

Solution: I used the wrong capacitor values in the simulation. Also the service manual was showing the output capacitor in the wrong polarity, it needs to go with the negative side towards ground. Thanks for all the help :) ! working simulation

Update: Turns out the cap was shown in the correct polarity in the manual - as on the physical board. I just had a too low reverse voltage set in the simulation. Also: this was actually the cap that was blown and caused the vibrato in my Philicorda to fail. Because its only rated for 4V. I replaced it with a 16V cap that should be able to deal with more reverse voltage.


texts:
I'm creating a speaker box with a 11.1V Li-ion battery pack with a charging circuit.
I'm using this cheap lm2596 module with constant current/constant voltage (https://aliexpress.com/item/32943869964.html) to step my power supply down to the desired charging voltage. To test the module I'm using a laptop power supply (19V, 3.42A) with stripped down wires.
On the internet I've found the following steps which I did.

power up the module
set the multimeter in DC voltage mode and turn the potentiometer closest to the input to 12.6V (full charge voltage), the red "OK" led lights up
set the multimeter in DC ampere mode and turn the potentiometer closest to the output to 2A (I've quite a lot of batteries so this should be high), the blue "CH" (charging) led lights up and the "CC/CV" led lights up
connect the batteries

With the last step I've a problem. On the internet the "CH" led and the "CC/CV" led lights up, on my module only the "CH" led lights up not the "CC/CV" and the measured charging current is ~0.21 A (not the 2A is set).
I don't know whether my module is faulty or if I'm not doing the things wright.
Can someone help me or give an alternative solution?


texts: Can I leave XTAL2 floating when using an oscillator chip with 1 output and no input?

texts:
I'm using a chip that needs a 6MHz crystal on it. All of the regular 2 pin crystals are very large for this application, so I was looking into the smaller profile oscillators. This is the chip in question:
https://www.digikey.ca/en/products/detail/texas-instruments/TUSB2046BIRHBR/1629099
I'm familiar with hooking up 2-pin crystals where they connect to the XTAL1 and XTAL2 pins and have external pF capacitors to ground, as well as the 4-pin ICs with 2 GND pins and the XTAL ones, but all of the 6MHz oscillators I'm looking at seem to be different. They are 4-pin devices with this setup:
1: Tri-state
2: Output
3: Ground
4: VDD
Those connections seem straightforward too, but my question is about the XTAL pins. Can I connect the oscillator output to XTAL1 and leave XTAL2 floating? Or do I need to pull it up or down, or can I even use one of these oscillators with 1 output and no input? One of the oscillators I was looking at was this one:
https://www.digikey.ca/en/products/detail/ecs-inc/ECS-2033-060-BN/1693362
Thanks for any help!


texts: how to change the number of harmonics for THD in LTSpice

texts: I am learning to work with LTSpice. After I did my transient analysis, I established the .four command, but I don't know how to change the number of harmonics from the default which is 9 in LTSpice, any insights are appreciated. Thanks in advance.


texts: Update Facebook Status message using an Atmega16 microcontroller

texts:
How can I access Facebook and post a status message using an Atmega16 microcontroller ?
Or what all things I should know for doing this?


texts: How can I use pull up and pull down resistors in an H-bridge?

texts:
I have to build an H bridge out of the following components

2 PNP transistors
2 NPN transistors
battery 9V
4 resistors for the transistors
a DC motor

I connected the above equipment but, I also have 2 resistors 10k ohm each. I don't know where to put then  because I don't know what they would do in an H-bridge.


texts:
Sorry, dumb one really. I just had the heating out for a couple of days and eventually found a fuse blown in a controller for the (LK) underfloor heating.

I can't tell what rating it has (amps). It has T200H250V embossed around the end, and is made by ESKA with an S on the bottom/top. But that doesn't Google well.

I can see that the transformer it was (presumably) protecting has an output of 2 x 20VA @ 12V, I've found a 3.15A 20mm clear-glass fuse for sale, but maybe someone on here can better guess than me?

End of question.


texts:
I would like to connect a 3.3V (not 5V-tolerant) circuit (a Xilinx XC3S200 FPGA) to a TTL-level 5V asynchronous 16-bit bus (very similar to qbus) with about 30 mostly bidirectional lines. (The bus belongs to a Elektronika BK-0011 homecomputer with a 4 MHz KM1801VM1 CPU, similar to the LSI-11 CPUs).

I was thinking of using the simple FET bidirectional levelshifting circuit from NXP/Philips AN97055. Is this a good idea? What would be a good MOSFET to use? Many of them seem to have rather high input/output capacitances which could be an issue with rise times. Are there any other circuits worth considering?

The FPGA has configurable built-in pull-up resistors (about 3 kΩ) and the BK has 2.2 kΩ pull-up resistors on each line, can I omit the resistors in the level shifting circuit?


texts: I want to generate 500V @100mA from a source of 24V @2.4A. My question is that would it be possible to maintain this current? Any clues please.


texts: Help my off grid solar system is driving me mad

texts:
Please can someone help me with this problem I'm having with my solar system?
Ok I have 7 × 190w 24v panels wired in parallel,
Coming down to a 80A MPPT charge controler which automatically selects whether it's a 12/24/36V and so on. From that I have 16 100A 12V battery bank wired in series, then from the batteries a 12V to 240V AC inverter which is 8000W.

Now my problem is they are not fully charging 11.8 to sometimes 12.3v it goes to only and my water pump need at least 13.5 for it to come on. Hopefully I haven't confused you guys, if u need to no any more info please ask. I'm not a electrician but I have a bit of an idea.


texts:
Given the Verilog description of a chip, what are the steps necessary to implement it in hardware and how would a person DIY something like this?
For a specific reference. I was looking at the wikipedia webpage for MMIX that says:

Hardware implementations
As of July 2010, no known hardware implementations of the MMIX instruction set architecture exist. However, the fpgammix project implements MMIX in Verilog, making it possible to implement using a field-programmable gate array.

How can one go from the Verilog of MMIX to the actual hardware using a home setup? (I have no idea what a field-programmable gate array is)


texts: Problems while using op-amp as a comparator on a single supply

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Here's my circuit: .

Application: The circuit is for ground fault detection. When a fault current of 20mA flows through the primary of the current transformer (1:660), it generates a current of ~30uA in the secondary. This current drops across the 10k resistor to give ~5-6mV. This is amplified and given to a comparator to generate a \$(V_{CC}-1.5)V\$ which will be given as an input to arduino. The arduino will then turn off the relays which will cut off the mains power.

My problem is as follows: I am using a voltage divider network to generate \$\pm2.5V\$ for powering the LM358.
The first part which is the inverting amplifier works correctly and I get a 0.5V output at pin 1 for a 5mV input.
Now I want the second op-amp to generate a high voltage whenever the input to it is \$\ge 0.5V\$. So I am using the second op-amp in comparator mode. I use a 20k trim pot to generate 0.45V reference for the inverting terminal of the second op-amp. Since the trim pot is connected to +2.5V rail in the circuit, it acts parallel to the voltage divider network (which powers the op-amp) and there is no longer a equal \$V_{CC}/2\$ drop across the two resistors. Now that the rails are no longer \$\pm2.5V\$, the op-amp fails to function correctly. Can anyone help me out with this? I know I could go for a dedicated dual power supply but I am trying to operate using a single supply only.


texts: Is it ever bad to run an IC VCC trace next to a ground plane with 1mm clearance?

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Since my last board flopped, I looked at it again and noticed a ground loop (because the DB9 casing completed the loop).

Now I adjusted my board so that there is no loop of any kind. Instead, I'm running a VCC track next to a GND plane with 1mm clearance right underneath the 40-pin DIP AT89S52 microcontroller (on opposite side of course since I'm doing single-sided PCB). I'm also planning to add a couple of 0.047uF decoupling capacitors.

For clarity, I added a picture of part of my circuit. I highlighted the ground wire in red and will convert it to a plane after so I don't waste etchant.

The circled green items are the 0.047uF ceramic decoupling capacitors.

They say ground loops are bad, but is vcc next to ground this close bad as well? and would modifying my clearance between the two planes affect microcontroller operation? and no I won't use 0 clearance or I'll blow the batteries up.


texts: Speed control of 30 amp, 90 volt, 4 hp DC treadmill motor

texts: I have a 30 amp, 90 volt, 4 hp ya Cheng DC motor and I am looking for a way to control its speed. I can match the volts but not the amps, or I can match the amps but not the volts. I am using it on a project that requires speed control.


texts: What is the purpose of MOSFETs in this schematic?

texts:
On the main power line there are two MOSFETs but for what reason?

(source: www.ti.com)
The MOSFETs in question are Q1 and Q2.


texts:
So this was talked about in the comments of a previous question, but not in great detail:

I'm using a 2.4GHz ble chip, with a chip antenna. The recommended layout for this chip has a capacitor and an inductor to convert its output to a 50 ohm feed line. This feed line is going to be less than 1cm long before it hits my chip antenna.

Someone previously said that the characteristic impedance of my (pcb trace) feedline doesnt matter if it's that short (considering that the wavelength of 2.4ghz is around 10cm). Does this also apply to the characteristic impedance of the source, and the antenna? Can I get away with no pi matching network at all?

NRF52832 datasheet showing conversion to 50 ohm


texts: What is the path taken by the back emf current?

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!

Where will the current flow through?

If ON current(back emf "current") will loop through A B and C

If OFF current will(back emf "current") loop through x y and z


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How do I get the ceiling fan motor below wired, and how do I enable speed control?

Our AC outlet supplies 220V, and the motor comes with a 1.5uF capacitor.

I understand I would need an h-bridge controller or something similar?

When measuring the wires, red and brown are connected, and white and grey are connected.

Here's an image of the fan motor:

and its capacitor:

Since @transistors' answer, here's another photo on how I got the wiring done, in order to get the motor spinning in the right direction.


texts: Is possible with SDHC microSD card write 32 bytes of data without loading full block o the RAM? SDHC has for some operations fixed block size to 512 so  I dont know if it is possible. If possible what commands I have to use? If it is not possible is another way to write data to SD card from MCU with <= 512B RAM?


texts:
I am looking for a "water overflow pail detector".
 It basically will make some sound (e.g. beeping) when the water in a pail was about to overflow.
 The detector must also be water-proof otherwise the electrical source to this detector will be short-circuit.

I have a very slow running tap that I used to fill up pail to wash my car.
 However, I don't want to sit down there watching that slow tap to fill up the pail and
 I also don't want it to overflow if I just went to watch the TV.
 Therefore, I need to put that detector on the pail somehow in order to detect if it is about to overflow

I am not looking for a detector to measure the level of the water in the pail or tank or something like in the link - Level of a water tank with a microcontroller