texts: AT+HTTPACTION=1 not transmiting my datas I downloaded with AT+HTTPDATA

texts:
I'm using a SIM808 with arduino, and I want to send via a post request some data to a server using a php page that receive data via post requests, I'm using this AT commands but whenever I check my server I find a new blank column but not the data I send with my arduino, how can I solve this ? thank you

AT+CGATT=1

OK
AT+SAPBR=3,1,"Contype","GPRS"

OK
AT+SAPBR=3,1,"APN","Free"

 OK
  AT+SAPBR=1,1

  OK
   AT+SAPBR=2,1

   +SAPBR: 1,1,"10.69.65.122"

   OK
   AT+HTTPINIT

  OK
  AT+HTTPPARA="CID",1

OK
AT+HTTPPARA="URL","http://xxxxxxxxxxxxxxxxxx.php"

OK
 AT+HTTPDATA=18,10000
    var1=22D&var3=234D
   DOWNLOAD

   OK
   AT+HTTPACTION=1

    OK

  +HTTPACTION: 1,200,295
   AT+HTTPREAD

    +HTTPREAD: 295

     Notice:  Undefined index: var1 in /storage/public_html/xxxxx.php on line 10

                                                                      Notice:  Undefined index: var3 in /storage     /public_html/xxxxxx.php on line 11

and my PHP script : `

            // Include config file
             require_once 'config.php';
             $v1 = $_POST["var1"];
             $v3 = $_POST["var3"];

             $sql = "INSERT INTO rora (var1,var3)
             VALUES ('$v1', '$v3')";

             if ($link->query($sql) === TRUE) {
             echo "New record created successfully";}
             else {
             echo "Error: " . $sql . "
" . $link->error;
                   }

                $link->close();`


texts: Effect of bad antenna design on chip behaviour

texts: I have designed a PCB for TI's cc3200 using recommended design specifications. The chip performs correctly when i use functionalities like GPIO read/ write, UART communication, but as soon as i use any WiFi functionality the chips goes into series of restarts from the point where WiFi function is called. I am wondering can this be hardware issue, like antenna not properly matched? Though the only change i have from antenna reference design is that the clearance between ground and antenna trace is 18 mil in reference design and 10mil in my design.


texts: Is the Induced EMF additive to the circuit?

texts:
From the following diagram:

Assume that +V(S), is a applied voltage from a power supply, and current I is flowing now in the circuit, and I introduced a (negatively)changing magnetic flied covering a small volume of that conductor, and an EMF is induced in such a polarity above. The circuit as a whole is like so:

simulate this circuit – Schematic created using CircuitLab

Where (D) is the diagram above the circuit schematic, is total applied voltage on the load equal to the induced EMF added to the applied voltage +V? $$V_t = V_S + V_E$$

Because the induced EMF is now in series with the applied voltage?
I guess, my confusion with this is the magnetic field is covering a small area, would the voltage still be additive? Vs. the magnetic field covering a larger area inducing a larger EMF at the same polarity?


texts:
I'm designing a couple of step-down voltage regulators based on a LM22677 chip (datasheet) and following the example:

I want to get 5V and 10V from a 12V supply, but I have concerns regarding the power rating I should have on the resistors: considering a maximum output current of 5A, how much W would I dissipate at max?


texts: What happens if you apply a positive Vgs to a P-MOSFET?

texts: If you apply a positive Vgs value to a P-Channel MOSFET, will the Rds be a high impedance value (assuming that Vgs is within the MOSFET rated spec), or would applying a positive Vgs damage the MOSFET?


texts: Can output current be higher than what the input source can provide

texts:
One basic question.Am controlling a group of LEDs (connected in series and parallel) through a MOSFET switch.The input voltage is provided by a battery @ 5V,2A rating.
The total current consumption of LEDs is about 4A,higher than what the input can provide.
Can output current be higher than the input ? Please provide me insight on this.


texts: Powering a 12V misting pump using batteries?

texts:
I have a pump for my misting system:

The pump is 12V DC - it's powered by a AC-to-DC power adapter:

Unfortunately, I'm trying to use it on my balcony, which has no AC powerpoint.

What are my options for powering this without a mains supply?

Would connecting a 12V car-battery work? Or is there perhaps something a bit more turn-key that could work?

Update: To clarify, the reason I can't run an extension cord is because there are two glass doors between the interior and the balcony, and we need to keep them shut often for various reason (air-conditioning, because of our cat, in case of rain, and also if we go away). There is a lighing socket out there - so a lighting socket to power socket adapter might be an option.

I suppose I could hire an electrician to install a new outlet out there. (I can't think of a way to punch a extension lead out there that's waterproof or wouldn't let water back into the house)


texts: Using a multimeter to see if ground is connected

texts:
I've been diagnosing a problem with a relay on my car. One of the pins in the socket that the relay goes into controls the ground for the throw of the relay. When the car's computer wants the relay closed, ground is available on that pin. When the car's computer doesn't want the relay on, ground is not available.

I want to see if ground is available on that pin.

My understanding is that the best way to do this would be to measure continuity or resistance between the ground pin in the relay socket and the ground terminal on the battery. Continuity (or a low ohm reading) would indicate that the circuit is closed. Unfortunately, the computer only turns the relay on briefly, and my multi-meter is slow, so I never have a chance to see if this happens. (If I touch the multi-meter leads together, it takes 5 or 6 seconds to get a solid 0 ohm reading... and I have about 2 to work with.)

The meter will measure voltage much more quickly. If I put the red lead of the meter on the ground pin for the relay socket, and the black lead on battery ground, I get no reading (really small fluctuating values, as if I had the probes in the air) most of the time. However, when the relay is supposed to be activated, I suddenly get a 5v reading. The positive side of the throw is usually 12v when measured against the ground terminal of the battery, so there's a difference of 7v.

Is this an indication that this pin is being correctly connected to ground? If so, why? I have some basic electrical understanding, but I'm not an EE by any stretch of the imagination...


texts: How can embedded systems estimate their battery status so precisely?

texts:
As I understand it, the terminal voltage of batteries changes a little on charge/discharge, but these changes are minimal compared to other effects (temperature, minor manufacturing differences, recent charge/discharge history, etc).

But even the oldest mobile phones could show a charge icon. And it works correctly even in the case of a battery change.

How is this possible?


texts: STM32F0 - run user program from SPI flash memory

texts:
I'm building an application based on the STM32F030F4P6 microcontroller. During the development of the firmware, I realized that the flash memory of the microcontroller is too small.

Can I run my firmware from SPI flash memory? If yes, how could I do it?


texts: Compare negative with positive, ignoring sign

texts: I need to compare a negative voltage with a positive one, each on the order of a few hundred millivolts each; I want to compare the magnitudes, ignoring the signs, although only for this particular quadrant (I don't need all other signs.) How can I do it? I thought of using resistors to pull the negative voltage positive, but it only gives me a small signal on top of a DC offset, and that is difficult to compare with.


texts:
I use capacitor (on Gate) to open MOSFET slowly to fade in/out LED strip. It works fine except some delay before light starts to show. I understand that it is because led strip didn’t receive enough power while mosfet opens.

I like the slow fade in which I have, but I want to get rid of that delay.


texts: Power for 1 Device, 1 MCU, and 2 modules

texts: I have four things I need to get power to. The first is a device that needs 48V and 30W. The other three include an MCU and two modules. Each have various pins that need either 3.3V or 1.2V. I’ve drawn up a circuit on how to get power from a wall into these four things, but I’m not sure if what I did is completely correct, and I could use some guidance.


texts: Is it practical to use relay contact resistance as a shunt?

texts:
I'm driving a DC motor and in its path is a relay with approximately 100m Ω contact resistance, can I use that resistance as a shunt resistor to measure the motor current?
I don't want to measure the current accurately, just as an indicator to know motor is stuck or not.


texts: Would it be worthwhile to support UART for a serial 'plug-n-play' interface? Or would it be a waste of time?

texts:
I'm currently working on a project where I'm designing a central circuit board that will feature mini plugin circuitboards. The communication between the main circuit board and the plugin circuitboards will be serial. I'm attempting to create a general interface such that the main circuit board can support SPI and I2C communications. I have a somewhat subjective question in need of a practical answer:

Would it be worth while to also support UART? Or would this be a waste of time?

I'll give a little more information regarding my application. The mini plugin boards will typically feature small ICs. I doubt that I would ever try to communicate with a PC with this interface.

Now, when I've been looking at some ICs that could potentially be featured on one of these plugin boards (i.e. an accelerometer), Digikey and Mouser really only list serial ICs with SPI and I2C interfaces. I'm having a difficult time finding any chips that feature UART. Thus bringing me to the question, should I even try to support UART on this serial interface I designing?

I realize this is a subjective question, however, I'm somewhat confused as to what typical applications UART is used for. As it doesn't appear to be used for IC-IC communications. Instead, the only real application I've been exposed to is it being used for flashing microcontrollers and communicating with PC peripherals.

So another question - where does the separation between SPI/I2C and UART come into play? Is SPI/I2C typically used for inter IC communications, and UART is reserved for longer distances because its more robust? Also, I'm well versed in the technical differences between SPI/I2C/UART, however, I'm not well versed in typical applications in which you should use one over the other.


texts: mosfet n-channel high side switching considerations

texts: I know high side switching is normally done with a pchan mosfet but i don't want have to invert my control signal. So i am curious if i want to source 10mA through the 28V rail on a n channel mosfet high side switch as shown, is this implementation kosher? The datasheet says max Vgs 20V so that requirement is met. I realize my source pin is being held at 9.9V and i am cool with that. If i strap a 990 ohm load on the source i get my 10mA sourced from the 28V rail. What am i missing here? Will i violate the package's thermal rating? Am i violating other specs?  Thanks!


texts:
I'm looking to observe magnetizing offsets of various current sensors. The idea is that when you pass a high current pulse (close to the rating of the device) through a current sensor and then return the current to zero, there is some small offset in the device. This is due to some polar magnetization of the core inside of the sensor.

My issue is that some of the devices are rated for 200 amps. I would like to somehow create a current source circuit that is able it apply 50 amps for short duration pulses (20 milliseconds or so). I would fool the sensor into thinking its 200 Amps by wrapping the wire in loops so that it passes through the center of the sensor 4 times.

Note: the reason I cannot do 2 amps and 100 turns (example) is because the wire size begins to stack up and will not fit inside the sensor.

Does anyone have any ideas on this, or can redirect me to a post about this?


texts: Open loop op-amp white noise difference amplifier

texts:
I want to amplify the noise generated by a MAX8069 voltage reference, using direct coupling in order to preserve the low frequency components. The frequency band of interest is from 1Hz to 44Khz. I'd like to be able to measure the power spectrum at different frequencies, so minimising filtering and distortion is important. The output of the op-amp will go to the input of an AVR ADC, which is high impedance. The application is a random number generator.

I had the idea of measuring the difference between two similar noise sources; this should yield plenty of noise whilst allowing the direct coupled design.

The op-amp chosen is LM358, noise is supplied into both inputs from two 1.22v MAX8069 voltage references. These should generate around 20µV noise. Supply voltage is 5v and current into each reference is limited to around 1ma by 3k3 resistors. This should maximise the noise each reference generates - see Terry Ritter's junction noise measurements.

The expected behaviour is to see large voltage noise at the output of the op-amp. What I'm actually seeing is the output steady at 3.75v. This changes to 3.8v if the inputs are swapped.

Schematic http://a.yfrog.com/img741/1007/af9qy.jpg

What is the explanation for the fixed output voltage, and what modifications would be needed to see the expected behaviour?


texts:
I need a way to invert a digital signal i.e. if the input is high, I want the output to be low and if the input is low I want the output to be high.

I think this can be accomplished with a single PNP transistor, but wanted to verify that here.  The voltages that I'm dealing with are less than 5V.


texts:
I have one power source (bicycle dynamo) A.C 5-6V which will be rectified to D.C, and the other source D.C from a solar panel 12V. It will be 2 input source and one output.
what type of power switch would work best for this circuit? MOSFET BJT or any other? The output will be to a handheld device of 12V
Thanks for your time.


texts:
Here's the pinout diagram for an LM358

Here's the pinout diagram for the LM386:

Here's a very basic circuit showing an audio amplifier created using an LM386:

If I built the equivalent circuit using the LM358, would it work in a similar way?  Or would it fail since the chip has no gain?
(I've built the equivalent circuit and it did not seem to work.  Didn't know if I was doing something else incorrectly though.)
Is there a way to compensate for the lack of gain in the LM358?
Is it possible to create a very simple audio amplifier using an LM358 or is it basically not feasible due to its characteristics / abilities?


texts: Circuit Design for 6 LEDs flashing in sequence

texts: I am helping my son with his school project.  He wants to design a circuit which has a on and off button and has 6 LEDS and each LED flashes for 20 seconds and stay on, and then the next LED will follow the same sequence. What would i need to do this ? any help would be greatly appreciated.


texts: How to measure self resonance frequency of coil using CRO?

texts:
I have antenna coil for tuning an antenna. I want to measure self resonant frequency of the antenna coil.

Can anyone tell me how to measure it with an oscilloscope? What will be the experimental setup?


texts: lt4363 - 2 Surge Stopper: Shutdown / MOSFET Gate and Vout

texts:
Good day everyone
I am currently working on the board which uses a Surge Stopper LT4363-2. Without LOAD the circuit works fine but once I use LOAD and force a SHDN to low with a Temperature sensor The MOSFET gets damaged.
IC is powered by +28V and has OV/UV and current protection.
This is the Schematic from the circuit.

I tried to simulate it with LTSpice but I didn´t detect any problem, at least it works as theory says.
However in the lab I was able to measure That even though my device is in shutdown Vout comes back to +36V after 24ms even though normal functioning is +28V. As MOSFET Vgs in datasheet is 20V I think this is what damages the MOSFET. Here you can see measurement results.

I repeated the test on a better oscilloscope and saw the same effect with a better resolution.

I have 2 questions.

I suspect that the problem is the INRUSH protection Circuit. Is the capacitor value makes the Response time from GATE much slower ? Can anyone explain it better?

why the Vout comes back even though I am in SHUTDOWN mode?

If anyone had similar problem or has an idea where should i check this circuit again. Please drop a comment or and answer.
PD: By changing the INRUSH capacitor to 47nF it works, nut I would like to understand the reason why with 10uF it doesn´t work. BR


texts:
I just read about buck converters and boost converters and buck/boost converters.  Great stuff.

But, why is a step-down converter called a buck converter?

I tried to research this myself.  According to Google Book search, the phrase buck-boost transformer was in use at least as early at 1891 in a periodical called Architectural Review.


texts: How to use the AMS1117-ADJ to get variable voltage?

texts:
I have some questions about the AMS1117-ADJ:

I found AMS117-ADJ  but I am still confused as to whether this is actually adjustable since in the datasheet,AMS1117 on page 2 , it says, 1.2112 to 1.2875. Thats why I wasnt sure if they are referreing to the input voltage or not. On figure 2, they have a diagram for R1,R2. Is this for the ADJ only. Then what exactly is the second column on the table ? Why is the MAX limited to 1.2875?


texts: Do I need to care about mounting hole contact oxidation?

texts:
I am designing a pcb which I have some mounting hole with the function to connect the mounted screw to the PCB ground.

I found good resources about this subject in the blog, like this one and this other.

However, there is one point that I am still in doubt: I was thinking about the possibility that, after a long time, the interface between screw head and mounting hole pad goes into oxidation.

Just the correct screw tightening is enough to prevent oxidation process? Or there is specifics combinations of screw's material and pcb pad finalization I should choose to avoid oxidation?

If possible, I would like to avoid golden plating, for cost reasons.


texts: How would I simulate a circuit like this in LTSpice?

texts: I want to simulate this circuit in LTSpice, but I don't know how I would enter in the values for the capacitor and the inductor. Any help would be appreciated!


texts:
I have this buck converter - TPS54260
I was doing this Control Loop Stability test. For this test, we need to place a small 5-10ohm resistor on the resistor divided feedback path of converter Keysight Control Loop Stability PDF. Like below,

But after doing this test, I removed the small 5ohm resistor, but forgot to connect the top feedback resistor to the output voltage line. So, essentially, it was like there was no feedback path connected to the output voltage. Like this below,

I powered ON the buck converter and the IC smoked a lot. I couldn't measure the output voltage at that time. Can someone tell me what is the concept behind this. For all I understand, since there was no feedback path connected, the IC could not regulate.
But I just want to understand and learn more technical details on how this catastrophe happened to improve my understanding.


texts:
I'm confused in using HAL-defined interrupts with FreeRTOS. I'm trying to implement "6.3 Deferred Interrupt Processing" in the guide of FreeRTOS, but I don't know how to do it.

The problem is how to use the peripherals of the STM32 with FreeRTOS. Should I give a semaphore to another task (which read and treat the values) within the irqn "ADC_IRQHandler()" for the ADC or the callback "HAL_ADC_ConvCpltCallback()" for the ADC or just read values with the HAL functions and treat them with FreeRTOS tasks (this one works, but it does not seem to use the RTOS power)?

The manual I talk about: 6.3 Deferred Interrupt Processing (PDF)


texts: Error amplifier with compensation questions

texts:
I'm looking at the design of type 2 error amplifier for a DC-DC boost converter.

1) Why should the amplifier be designed to have a high gain at low frequencies and a low gain at high frequencies ?

2) What is meant by crossover frequency ?

3) What is meant by phase margin ?

4) What is the difference between a type 2 and type 1 error amp ?

5) What would be the simplest error amp I should consider looking into ?

Also how is the frequency changing if both the input voltages to the error amp are DC which is the reference voltage and Vout ?, is it because of the ripple on Vout ?


texts:
I would like to know what would be the effect of placing a Zener diode between the op amp's output and the actual output of the circuit like shown in the schematic. The Zener should be of 5 V.

simulate this circuit – Schematic created using CircuitLab


texts:
I have a LT3508 Dual DC/DC converter with 24V input and 12V and 3V3 output.

However some units are not working as intended, but provide the following waveforms on the 3V3 side:

Red = Boost, Green = 3V3 output, Blue = Switch node. The frequency is only about 600Hz.

Please find the schematic and waveforms of a working unit here: http://imgur.com/a/Liutq (I can only post two links)

Any idea what could be wrong or broken?


texts: Help identifying I2C EEPROM - top marking H250 2GB 2

texts:
I have a Fujitsu server (PRIMERGY RX300 S8) with a failed I2C EEPROM on the front panel PCB. I would like to order the correct replacement components, but I am unable to identify the exact series/capacity of the chips.

I believe the top EEPROM (D3) is an STMicroelectronics 64KB EEPROM, probably from the M24C64 series.
The bottom EEPROM (D2) is completely unknown to me, I can't seem to find anything from a search engine for "I2C EEPROM H250 2GB"
I am certain that D2 and D3 pictured are I2C EEPROMs in a TSSOP8 package, I just don't know the model numbers and I'm hoping someone here can identify them.
I am aware that I could purchase a complete front panel PCB from the vendor or eBay, but that is not my question.


texts:
This is the control stage circuit of flyback, I want to use SIMPLIS to measure the bode plot to prove a theory is matched to simulation, I use Mathcad to draw the bode plot, the SIMPLIS result should be the same as Mathcad, but when I run the simulation, the result is wrong. but I don't know where I wrong, this issue stuck me for a long time.
This is my simulation result.

I want to check the bode plot of Power Stage and Control Stage are correct
Hope someone can give me some help.


texts: Unfiltered square-wave as feedback in class D amplifier

texts:
I found this little circuit that (ab)uses a TL494 SMPS PWM controller as PWM driver for a class D audio amplifier:

(Source article @ Geekcircuits.com )

It uses the unfiltered, but constant amplitude (due to D1/D2), output square wave as negative feedback for the error amplifier inside the  TL494. How does this work? How can a square wave be used as negative feedback to be added to a music signal ?

The source article does not really explain this in any detail.


texts: UART communication bet controller and smart card reader over UART

texts:
I am newbie to UART interface. My query is, in my application, smart card reader is interfaced with controller LPC2138 over UART interface.

Connection scheme:

uP ( TxD) --> reader (RxD)

uP ( RxD) --> reader (TxD)

I want to trap these (RxD,TxD) signals on hyper terminal, if I connect MAX232 to UART pins and if while communication bet uP and reader, MAX232 is interafced on same lines.. Is it possible ? Can I trap signals?


texts: Whether a half bridge SMPS based on MOSFET or another one based on BJT will generate more switching noise at the output?, if other parameters such as output voltage, current, type of transformer core, switching frequency,  etc remains the same. I'm only asking how the type of switching device affects noise, let's assume I drive the MOSFET/BJT via transformer, while MOSFET driving maybe simple and straightforward, BJT drive circuit may have a baker clamp.


texts: I am running a software radio application. I need to measure the power of transmitted ofdm signal. The issue is that FCC has regulations of -50dBM/Hz. So I understand that if i need to send a signal at a bandwidth of 1Mhz, the the maximum allowed power -50dBM*10^6 which is 0.01W or 1mw.So i am trying to measure the power at output of my USRP transmitter. I just brought an oscilloscope and measured the sinusoidal signal peak to peak voltage in the oscilloscope. It was 7.2 v peak to peak. I was unsure how to use v^2/R because i don't know the resistance. when i assumed resistance to be 1, I got the power output to be 39dBM. I then checked online and found that you need to measure power spectrum. So that means I need to know power at frequency of transmission. I need a RF power analyser for the same. How is the power at frequency spectrum related to analog power measured by oscilloscope at the output of antenna? What should i measure and reduce if i need to keep it within  desired FCC regulations? Is the power of the frequency spectrum constant?


texts:
A typical installation is
Load - 400 V net - Transformer 1:25 - 10 kV net
If the load is for example a SPS, the 400 V net can contain harmonic currents and thus have a considerable THDi.
How can the transmission of harmonics or disturbance from 400 V net via Transformer til 10 kV net be described?
Some thoughts:

The Transformer is a galvanic isolation, so no direct current can pass
Via induction and magnetic fields, effect is transmitted, i.e. also disturbances
Turns ratio needs to be considered
The transformer will heat up due to harmonics if not it is a specially designed "K-factor" transformer. This affects the transmission behaviour?
Dependance on "stiffness" of HV net. If a power producer sits right next to the installation, it is hard to insert harmonics. Can this be described via the nets impedance? Power Quality


texts: building an audio amplifier for 2.5 ohm speakers

texts:
I recently dug out of my box o' stuff a pair of seemingly decent 2.5ohm bookshelf speakers. I wired them to an old mp3 player I have and while they sound good at low volumes, I get lots of distortion at high volume. Given that they are only 2.5ohm, I'm assuming that this is because they are trying to draw more current than the poor mp3 player can produce.

Rather than buying one (or new speakers for that matter), I'd like to try and build an amplifier for these speakers. I was looking at using an IC such as the TDA7924 but like all of these chips, the advised load impedance is 4 ohms. It doesn't specifically state anywhere that the absolute minimum is 4-8 ohms, but has anyone had any experience with this sort of thing? Will it still work at a lower load impedance if I just make sure that the volume is limited? If not, will I be able to use this IC if I chuck a big 2 ohm power resistor in series (as much of a waste of electricity as that is)?

I'll probably get some anyway to play with but I am a poor student and I would prefer not to blow up several $12 chips. thanks!


texts:
Is it possible to achieve FPGA-like concurrent functionality on, for example, ARM Cortex-4?

If I have a process which does time-sensitive calculations and at the same time I would like to listen for a button press. Even if I use interrupts for buttons, it will pause time-sensitive calculations for a bit to execute onPress function.

I believe what I am asking is - how to simulate threads on hardware?


texts: Does anyone know the YM2410 pinout (from the PSS-130 and PSS-30 line of Yamaha keyboards)?

texts:
I was recently making modifications to a PSS-130 Keyboard, and before I knew it, the keyboard would cease to make noise. I have narrowed the issue down to the main chip on the PSS-130, the Yamaha YM2410. I have been trying to find the pinout for this chip but I have gotten no results on a pinout sheet from my searching. Does anyone have any knowledge about this chip, and even better, a pinout? Anything will help.

This is the chip in question:


texts: Buck converter stops working with higher power

texts:
I'm developing a buck converter. I need to to change its supply  from 9 V to 12 V. I also need to get more power in it (up to 10 A). I do it by reducing the load resistor.

Here is my circuit:

Note: the low-side mosfet does not have an active role here, but I need it for later development.

My problem is that when I try to gradually increase the voltage from 9 to 12, everything stops working at around 10 V. By stops working, I mean no PWM anymore, a lot of noise, and then no voltage at all at my probes.

Here is a picture of the voltage at the gate of the high-side mosfet (yellow) and source of the high-side mosfet (pink) at 9 V, when everything is still more or less working.

Theoretically, all my components are able to handle a voltage of 12 V.

Here are the datasheets:
Mosfets
Capacitor
Inductor

I tried varying the output capacitor value, but it didn't seem to have any impact at all on my problem. When I decrease the load to smaller values, on the other hand, the circuit stops working with smaller voltage already. That's the reason I think it's less an issue of too high a voltage and more a problem of too high a power.

I searched for stability checks and calculation for buck converters, but all I found is literature about the stability of the converter in a feedback control. I do not have such a thing yet, my PWM is fixed. Plus, my output capacitance is pretty high, specifically to avoid problems with

So, here is my question: Why does my buck converter stops working when I try to transfer more power through it, although all elements are supposed to be able to handle it, and I shouldn't have a stability problem per lack of feedback?

Edit: I also wasn't able to reproduce the problem in LTSpice


texts: Differential pair active load contradiction

texts:
I'm confused about one current-based explanation for why the active current mirror restores a differential pair's gain by letting each differential input reinforce the other.
The explanation (from Razavi) is like this:

The output voltage rises by means of two mechanisms: M2 draws less current from X to ground and M4 pushes a greater current from VDD to X.

My confusion is that while I can see that a drop in potential at F means M4 wants to source more current and the drop at M2's gate means that it wants to sink less current, don't these fight against each other (at least without a load attached to the output?)


texts: What to use to crimp a resistor onto 18awg wire

texts:
I want to crimp a resistor like the one below onto 18awg wire without soldering...

I've seen that bootlace ferrules like the photo below can possibly be used to do this but if I buy 22-24awg sized bootlace ferrules then the 18awg wire won't fit. And if I buy 18awg sized bootlace ferrules I'm concerned it won't properly crimp the resistor in place.

What is the best solution to achieve a connection between the resistor and 18awg wire without soldering them together?


texts: How to detect when an LED has burned out?

texts:
I'd like to have a way to detect when a low power LED burns out (2-3.5v, 200-400mA) that is being driven using PWM from a Raspberry Pi with a MOSFET.

My understanding is that I would be able to accomplish this by measuring the current to the LED and seeing if it is near zero in the middle of an "on" cycle. However, I don't know if that's how this is typically done or if there is a lighter weight solution (considering I would want to do this with ~50 LEDs in total). I've been told a hall sensor can be used to measure the current, but I've also been told that they don't work well at this low amperage.

What would a typical solution for detecting a burnt out LED look like?


texts: What is the difference between JTAG and EJTAG?

texts: I want to know what is the difference between JTAG and EJTAG? I know about JTAG as it's a hardware tool used to examine the memory and registers. Correct me if I'm wrong.


texts: Powering a 12 Volt Air Pump to a 36 Volt Electric Forklift

texts:
I have a 12 Volt Air Pump (300 W) that I use to inflate products. Normally it is connected to a forklift battery with alligator clips and that's how we power it. We have had people ask how to use these pumps with their 36 volt Electric Forklift batteries.

Is it possible to do this? Do I need some sort of converter or reducer installed?

I have no experience in any sort of electrical wiring work, I am being asked questions I don't have the answers too and I am having trouble even being able to word the question correctly. Thanks for any help in advance.


texts:
I have a simple circuit that pumps 5A for 100uSec. (Constant current circuit with Opamp).

This circuit is on a different board. 20V is generated locally on this board from the 4V supply (not shown, using a switcher). uP gives a 3.3V pulse and I observe 5A pass through the LED. The 5A pulse is occasional so, I charge the cap and when I need the 5A, the cap provides the current.

Occasionally, I have seen that the 5A return current destroys the CPU and some other components on my mother board. What am I doing wrong?

The GND of this board is connected to the mother board ground via the connector at a single point, I was expecting the current (5A) comes back to the Cap and hardly any current flows back the the motherboard ground. Apparently, something wrong.

UPDATES

Opamp is TLV2465

Mosfet IRLML6344

Cap is 2x 1.5mF (UHE1V152MHD Nichicon)

Schematic above has a mistake, the -/+ are swapped, the CPU goes to the + terminal and feedback from the sense resistor is to the -.

The board receives 4V which is boosted to 20V. Board has only 4 inputs, GND, 3.3V pulse from CPU (hidden behind a buffer), and blank. Opamp is run from the 4V before it is boosted to 20V. I also have a PTC to avoid inrush current between the 20V and the + end of the Cap.


texts:
Can you help me identify these two components? I cannot find information on them on the web. They appear to be ceramic filters of some kind.

Front of Component 1:

Back of Component 1:

Front of Component 2:

Back of Component 2:


texts: A homework problem tells me to find the equivalent impedance, so I added the series and parallel impedances just like I would a resistor; however, I don't understand how does one go from \$100/(12-16j)\$ to \$3+4j \Omega\$. My book just jumps to that conclusion. Can anyone please explain?


texts:
I have an LDO (TPS7A4101) which has two 10 uF, 50 V ceramic capacitors on the input. The LDO is generating 3.3 V, which is used by MCU to drive the LEDs.

When the system goes into standby mode, the LEDs turn on for 1 sec and stay off for 8 sec. During that time, the capacitors make a buzzing sound which is at 4kHz. The LEDs are driven by the MCU using PWM signal, which is running at 4kHz.

I tried using film capacitors which are too big for the PCB, but that stops the sounds for sure. I also tried different values of capacitors such as 4.7 uF, 50 V and 35 V versions, but the noise remains the same.

Does anyone know how this can be fixed in hardware?

In software I know that if, instead of PWM signal, I use high and low signal then it works, but I am looking for a hardware solution.


texts: Signals not showing in Vivado simulation

texts:
I have the below Verilog code and simulation where I want to view the signals and compare the clocks for each of them.

`timescale 1ns / 1ps
module dff(clk, D, rst, Q);
input clk, D, rst;
output Q;
reg Q;

always @ (posedge clk, posedge rst)
begin
   if (rst == 1)
    Q <= 1'b0;
   else
    Q <= D;
end
endmodule
//////////////////////////////////////////////
// clock divider module
/////////////////////////////////////////////
`timescale 1ns / 1ps
module clk_divider(
input clk,
input rst,
output led
);

wire [4:0] din;
wire [4:0] clkdiv;

dff dff_inst0 (
.clk(clk),
.rst(rst),
.D(din[0]),
.Q(clkdiv[0])
 );

dff dff_inst1 (
.clk(clk),
.rst(rst),
.D(din[1]),
.Q(clkdiv[1])
);

dff dff_inst2 (
.clk(clk),
.rst(rst),
.D(din[2]),
.Q(clkdiv[2])
 );

dff dff_inst3 (
.clk(clk),
.rst(rst),
.D(din[3]),
.Q(clkdiv[3])
);

dff dff_inst4 (
.clk(clk),
.rst(rst),
.D(din[4]),
.Q(clkdiv[4])
 );

genvar i;
generate
for (i = 1; i < 5; i=i+1)
begin : dff_gen_label
dff dff_inst (
    .clk(clkdiv[i-1]),
    .rst(rst),
    .D(din[i]),
    .Q(clkdiv[i])
);
end
endgenerate;

assign din = ~clkdiv;
assign led = clkdiv[4];

endmodule

And the test bench

module tb;

// Inputs
reg clk;
reg rst;

// Outputs
wire led;

// Instantiate the Unit Under Test (UUT)
clk_divider uut (
    .clk(clk),
    .rst(rst),
    .led(led)
);

always
    #5 clk = ~clk;

initial
begin
    // Initialize Inputs
    clk = 0;
    rst = 1;

    #10 rst = 0;

    #10 rst = 1;

    #10 rst = 0;

    #10 rst = 1;

    #10 rst = 0;

    #100;
    end
endmodule

here is the simulation
I want to see the clkdiv(1), clkdiv(2), etc. and add more and check the signals. What am I missing here?


texts:
I am trying to layout DDR3 128MB chip and a Spartan-6 FPGA. DDR signal pins located on specific memory controller pins and could not be swapped.
I've never done DDR routing and went with SP605 Xilinx board schematic as a reference to minimise points of human error. I've search for fair amount of literature but i absolutely have no experience on DDR memory and kind-of scared.
So I've split DDR3 memory signals into this groups(net classes).

net class   L min   L max   vias/trace
sdram_ud    19.905  19.931  2
sdram_ld    20.244  20.293  0
sdram_clk   19.102  19.106  2
sdram_addr  31.775  32.77   0..2
sdram_ctl   31.736  32.082  0..2

sdram_ud (pink):
    dq(15..8)
    udqm
    udqsn, udqsp
sdram_ud (blue):
    dq(7..0)
    ldqm
    ldqsn, ldqsp
sdram_addr (orange):
    a(12..0)
    ba(2..0)
    we, cas, ras
sdram_clk (yellow):
    ckp, ckn
sdram_ctl (green):
    cs, clke, rst, odt

Ground and power planes are omitted on the screenshots.

All classes were routed in order they listed. sdram_ld and sdram_ud routed on different layers.
All of the members of sdram_ctl class pulled to ground via 4k7 Ohm.
All of the members of sdram_addr class terminated to vtt via 50 Ohm resistor pack on the bottom layer.
I've put as many decoupling caps as i could: 0603/0402 ceramic 0.1uf + one big 4u7f polymer.

DDR3 layed out on 6-layer board with this stackup:
L1 signal/power
L2 gnd
L3 signal
L4 gnd
L5 power
L6 signal/power

Signal track width is 0.125mm. With my standard manufacturer's stackup it is around 70 Ohm impedance. Is it enough or I need to quote for custom stackup?

DDR3 signals located on L1 and L3. Termination, decoupling, vref and vtt located on L6. There is 1v5 island on L5 under Memory and FPGA part.

I've tried to follow S/3S rule, but not really worked out for me, I guess. I've layed out and tuned everything by hand. Addr class still looks like mess to me, but this is my best run so far. DQ signals are swapped within DQ[15..8] and DQ[7..0].
sdram_ctl tuned to match sdram_addr. sdram_ud is not tuned to match sdram_ld just so happened.

My questions are:
Is this design will work at lowest possible speed at least?
Did i correctly split DDR3 signals into classes?
Is such difference betwin classes track length ok? As far as i understand DDR calibration is the process of compensation delays of net classes relative to the clock (ckp, ckn).
Is it ok to have some address lines routed on one side, and others on the other?
Do i have enough track clearance?

Also, looks like Altium does not account for vias length, so length tolerances might be +-1.5mm more for addr class.

UPD:
DDR3 Chip is MT41J64M16LA in 96ball FBGA (0.8mm pitch)
FPGA Chip is XC6SLX45T in 484ball BGA (1mm pitch)

UPD2:
Dark red traces at L6 is vref net.


texts: Confusion with winding voltages for a fixed positioned brushless motor

texts:
Below is examples of various commutation forms different driving ways of a brushless motor:

Such a motor can be BLDC or PMSM. My question is: imagine we set the motor position to a fixed stationary non moving angle so that the shaft is not rotating after it arrived to the set position. In this case(when the shaft is fixed and not moving) does that mean the voltages across the field windings will be constant? And if it is BLDC with 6 step commutation does that mean the driver can only set the position at 6 different positions or can it provide more positions by varying the voltage levels at the windings?


texts:
I just learned about the awesome world of synthesizing with an Arduino and a resistor ladder. It makes a nice tone but it has lots of harmonics too! How can these harmonics be reduced? I know a little about filters, but not how to make one.

(Resistor ladder? Just learned what this circuit does.) Anyways my range is about 1000hz to 3000hz. It's loose, as it's just for AFSK. I don't know what the percentages really stand for, but as long as the harmonics are dampened a litte it's fine.

Thanks!


texts: i have to make transient simulation of .wav file signal for my project. I tried to change general options for calculating but no results. I think my circuit is complicated for ltspice and simulation lasts forever. I attach scheme.


texts: 480v Single Phase forklift battery charger wiring?

texts: I recently have been asked to install a battery charger that came along with a forklift purchase.  It is a 480volt 1ph charger.  It has terminals labled L1,N,G.  The plant is wired 480v 3ph, with 277v for lighting, and 120v common outlets.  How do I wire this thing???  I have no 480v neutral.  Thanks!!!


texts:
I now searched the web for about an hour and just can't figure out how these displays are called or where to buy them.
A lot of airports use them for the departure table.
They seem to be just LED-Displays with a really strange dot layout.
Does anybody have an idea how these displays or these dot alignments are called?

(source: thehindu.com)


texts: CPU-Multiplier Overclocking causing (silent) data corruption?

texts:
There have been a large number of threads regarding CPU overclocking and damage to electrical components in the past. Mostly, however, these questions were directed at how increased voltage and the resulting heat can cause component failure and reduced lifetime, if not cooled properly.

Since FSB-overclocking to reach higher performance is not recommended today, if a free CPU-multiplier is available, because the resulting increase of the SATA-Bus clock rate can cause hard-drive issues and the actual memory clock is more difficult to control, I was wondering, if overclocking the CPU-multiplier could cause any similar issues.

Is there any logical scenario (or even research done) in which a CPU that was overclocked solely by increasing the multiplier could produce (silently) corrupted data? I'm not concerned with corrupt data because of a sudden thermal shutdown at an extreme overclock with insufficient cooling, but rather with the possibility of long-term silent data corruption of files on the drives or in the memory, because of unnoticed hardware malfunction, even when running the cpu slightly above specification. (E.g. a 10% multiplier increase without raising voltages, etc.)

Is this even a viable danger, given how CPU-multiplier overclocking works and are there any sources on this topic?

I noticed that it is difficult to find sound information on the potential effects of hardware overclocking, besides of subjective opinions and recommendations. ("I wouldn't run hardware outside of manufacturer specifications, if reliability is demanded", etc.)


texts: FET analog switch example of "The Art Of Electronics"

texts:
I am currently reading the book "The Art of Electronics 3rd Edition". However I am having some difficulties to understand chapter "3.4.1 FET analog switch".
This section is about how MOSFETs can be used for switching analog signals. As an example the circuit in picture 1 is used.
About this circuit it is stated, that

"the gate signal is not at all critical, as long as it is sufficiently more positive than the largest signal (to maintain \$R_{On}\$ low)"
"negative signals would cause the FET to turn on with the gate grounded".

However, I don't understand both statements. I would perfectly agree to them, if the body was connected to the source. But this is not the case, instead the body is connected to ground. Therefore I assume that the electric field between gate and body (which leads to inversion of the semiconductor below the gate) is only changed by \$V_{Gate}\$ and \$V_{Body}\$, but not by \$V_{Drain}\$ or \$V_{Source}\$. But if this is true, the state of the FET should not be affected by the signal voltage, which contradicts both preceding statements...
I would be grateful if somebody could help me with this issue :)


texts: I made a light dimmer from this circuit below but doesn't seem to work. It seems to work with vloggers online but they are using 220V mains, I'm using 120V. I'm guessing resistors values may be the problem. Anyone help please on resistor values I may need?


texts: 20Khz 50% duty cycle PWM generation Problem in atmega 328p

texts: I wanted to create a PWM of 20Khz with 50 percent duty cycle(can be varied within while loop) in timer 0 of atmega 328p with MOODE 7:fast PWM mode with top value as OCROA.I used OCROA register to make 20khz and OCR0B to create 50 percent duty cycle(can be varied) by updating duty cycle in every compare match of OCR0B with TCNT0 register value.Datasheet says that output will be found at OC0B pin(11th pin).I compile the code without any error and sucessfully burn it to 328p.But led is not glowing at all.I  am attaching may code:


texts:
I have a design in which a CPLD (complex programmable logic device) is used to generate two pulse signals at 1.695 MHz. Of course the CPLD does some other tasks but I only need the pulse generation and for that a CPLD is to oversized. Now i am looking for other options to generate two different pulses with following requirements:

1.695 MHz frequency
two Pulse signals
variable duty cycle

My first idea is a microcontroller with a 100 Mhz oscillator, but if anyone knows an already existing IC for this task, I would prefer the IC.


texts: is their a difference between the surface area of the weir that i use for 1A AC voltage source and 1A DC voltage source ?


texts: Best approach for reverse engineering an RF Remote for a newbie

texts:
As part of a larger project, I would like to be able to replay signals of this remote.  It's a remote for a temperature controller, operating at 433MHz and it looks like it's using ASK modulation.

I've bought an RTL-SDR dongle and recorded the remote signal using SDRSharp (see Audacity screenshots).  Each button press (increase/decrease temperature) produces 6 packets that are exactly the same.

From reading a few blogs it seems that the common assumption is that each fat/thin pulse corresponds to 0/1.  Is that a reasonable assumption?  Also, do I need to replay all 6 packets and does the interval between the packets matter?  Any sense in how accurate my timing (ie baud rate) needs to be?


texts: Looking to generate 25 Hz square wave at about 90 V AC

texts:
I am looking to build a square signal generator tuned to ~25 Hz at a voltage of ~90 V AC that can output ~400 mA. I've searched around the internet and tried a few things but I've had no luck. My original idea was to have an Arduino and a LM741CN output a square AC wave and then attach that to a transformer to get it to 90 V AC. I achieved the square AC wave, but it only outputs about 2.5 V AC. Getting that far I was looking into transformers but low frequency transformers are not as easy to come by as I thought, I tried building one but the core I had on hand was not big enough to handle the amount of wounds needed.

My overall question here is: Was I heading in the right direction or is there a better way that I have not found yet?


texts: Conducted Emission Fail at Low Frequency

texts:
I need assistance to understand why conducted emission test performed by one of our Customers using our Filter failed at low frequency of 205KHz.

The filter is a planar capacitive filter of 47K±20% pF which has an insertion loss of less than 10dB at 300KHz. The actual capactive value of the filter is on the higher side at 55 - 56KpF.

As seen in the graphs, the conducted emissions are going high only on the negative side of the battery. Why could this be so? I don't have much detail on the Customer layout or their test setup. And I'm not sure they are much willing to share too much detail on the same.

However could potential causes for this occurrence be identified with which we could discuss with Customer for a resolution.


texts: Safe to drive 24V leds directly via 2SK2049 MOS-FET?

texts:
I have built a simple automatic switch that synchronizes IKEA LED strip with the main light in the room, eliminating the need to switch multiple switches in the evening.

Currently it works like this:

simulate this circuit – Schematic created using CircuitLab

It's a bit simplified but that's the gist of it. Now the relay is a bit noisy, it's a high power relay soldered within an Arduino module that I bought along with the driving circuit.

I have a smaller relay that I could use but if I do, I need a mosfet to switch that relay. And the mosfet I have is rated for up to 60V and 50A continuous current. That's way more than the LEDs use.

So my question is, is it safe to replace the relay and the relay driver with a 2SK2049 mosfet. And if it is, how to connect it properly?


texts: Why do these precision current sinks use both a JFET and BJT instead of one FET?

texts:
I was looking through the AN-31 Op Amp Circuit Collection from National Semiconductor (now TI) and saw this precision current sink:

I understand that the 2N3456 JFET is there to remove the beta error caused by connecting the BJT base directly to the op amp output (as in this circuit). It also seems to be the case that the BJT is necessary to provide enough output current, as the 2N3456 datasheet indicates that the JFET can sink at most \$I_{\text{DSS(max)}} = 1\text{ mA}\$. Why not just use a JFET (or a MOSFET) that can sink more current?

It's not just National/TI that has this circuit -- Linear Tech's LT1001 Precision Current Sink uses the JFET + BJT combination as well:

Again, the datasheet for the 2N3685 JFET indicates that it has a low \$I_{\text{DSS}}\$ and the BJT is needed to increase the output current capability. Is that the only reason why the JFET + BJT is used, or is there some other benefit to using a JFET + BJT instead of a single FET that can sink a higher current?


texts: Variable Frequency-Response analysis (amplifier)

texts:
I'm trying to understand what the book "Basic Engineering Circuit Analysis" by Irwin is saying at the chapter of variable frequency...
It's trying to amplify a signal from 50 Hz to 20000 Hz.
Where it uses this circuit to do that:

So the transfer function is this:
$$G_v(s)=\dfrac{R_{\text{in}}}{R_{\text{in}}+\frac{1}{sC_{\text{in}}}}\times 1000\times \dfrac{1/sC_{0}}{R_0+1/sC_{0}}$$
Which I understand.
Then it says that reorganizing and substituting this equation it yields:
$$G_v(s)=\dfrac{s}{s+100\pi}\times 1000\times \dfrac{40000\pi}{s+40000\pi}$$.
I'm lost here. I understand that it uses the domain frequency \$j\omega\$ instead of the Laplacian domain, and it should be replaced with \$\omega=2\pi f\$. But I don't understand the following:

How does the first equation turn into the second one?

Where did the complex \$j\$ go?

Why does it replace the low frequency in the first term and high \$f\$ on the second?

And my last question within the same example:
How is the transfer function approximated as $$G_v(s) \approx \left[\frac{s}{s}\right]1000\left(\frac{1}{1+0}\right) $$
when the frequency is between the low and high frequencies?


texts: How can I measure TVS diode for Seagate Momentus 7200.3?

texts:
I hope the TVS diode (or something like this) of my HDD's PCB is gone, so I could fix this HDD easily, but I don't know where it is. Can you tell me how to measure it?

I read this but I didn't understand, why 3 pins? I'm measuring the circuit resistance since I'm not measuring specifically the diode so I understand that if it's broken the resistance could be different than infinite, so how much should be the resistance?

My broken hdd history is here:
https://superuser.com/questions/242014/is-my-hdd-dead-forever


texts:
In a circuit I'm making I will be using an Arduino to switch a solenoid using a transistor(TIP120). I know I need a flyback diode as shown in basically every example.
My question is, is there a limit on how close/far away the diode is from the solenoid? I want to place it on the circuit board and then have the solenoid on the end of 2 wires maybe 50cm long at most. Will this pose any problems?


texts:
I am trying to do a power analysis of an IC. It is an I2C isolator.
Now, there are 2 I2C buses (hence bidirectional). I want to analyse the effects of its working on the temperature. The ambient temp is 25Degrees celcius.

Now, I am connecting it between an MCU and a temp sensor (for eg).

The current rating is as shown below -

Now, this IC is being run at 3.3V Vcc.The Iol1 and Iol2 are the current that is supplied from the source .

MCU <---> I2C1 <----> Isolator <----> I2C2 <----> Sensor.

So, the current sourced by the Iol1/2 as 3.5mAmps is nothing but the current sourced/sunk by the MCU/sensor. Now, suppose the data is coming via the SDA line from the MCU. Then probably the MCU sends a very low current. The I2C ASIC then sends a max of 3.5mAmps to the sensor, right ?

Now, the logic high is 3.3, which implies
Power = 3.3*0.0035 =11mW. This is for the data lines.
Likewise for clock. So merely doubling it would give me the power consumption of the said IC.

But, then a small current is needed for the IC to work. Provide power to the logic inside. How much is that ? Is it not the quiscent current ? That info is not given.

Now, I want to calculate the temperature aspect. Now, Vout =3.3 and I = 3.5mAmps.

Power = 11mW per pin (SDA).
Power total = 22mW (power and clock).

Theta-ja = 117C/W.

Temperature = 0.022*117 = 2.577 Degrees C.

The temp of the IC = 25(ambient) + 2.5 = approx 27.5 Degrees Celcius.

Is my analysis accurate ?


texts:
I am working on these PLC Board: http://more-suns.com/product/html/?321.html but I cannot contact manufacturer. The fact is to have it programmed I have realized that I can only do it after a cold reset (power-on reset), but to get a really good cold start I have to turn off power for several hours.
The datasheet of the STC12C5A60S2 MCU inside the board indicates that, I think, some capacitor is charged and needs to get discharged.
How can I get a really cold start without that waiting?. I have installed a pilot light in parallel to the board, but still nothing.
Thanks for your advices.


texts: STM32F303K8 Nucleo Restart ADC For Continuous Scans (Using Interrupt?) STM22CubeMX

texts:
I have a project generated from CubeMX for my STM32Nucleo F303K8.
My IDE is SystemWorkbench.

I am using a total of 8 Analog inputs split between two ADC's

ADC1: 1, 2, 4, 12.

ADC2: 1, 2, 3, 4.

I am not sure how to properly read these. I am using DMA and the frequency in which I check the value is much slower than the scan time. But even if it wasn't, I wouldn't care if I read the same value twice.

I just want to have a continuous scan, when one finishes the next starts.

But whatever I try to do, it seems that the only way I can get continuous scans is by manually starting the ADC scans over and over in my main loop using:

HAL_ADC_Start(&hadc1);
HAL_ADC_Start(&hadc2);

or the _IT variant.

I have tried enabling continuous conversion and then starting the ADC once outside my main loop. But that just does one scan and stops there.

I thought maybe I could just use the scan complete interrupt to restart the scan when it finishes. This works when I restart only one ADC inside the interrupt. However as soon as I add the second to the callback then the system locks up. Obviously there is an interrupt not being handled somewhere.

 /**
 * @brief Callback when an ADC scan completes.
 */
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
    if (hadc->Instance == ADC1)
    {
        //HAL_ADC_Start_IT(&hadc1);
    }
    if (hadc->Instance == ADC2)
    {
        //HAL_ADC_Start_IT(&hadc2);
    }

}

My full code is here: Current commit refid: ef11437

https://github.com/c-herring/Sumo2017_NucleoF303/tree/ef11437f2f21d1beaa2ead0d9f5393c295cf9981

If anyone has any insight for me that would be greatly appreciated.


texts: Settings for multiple variable resistors in a logic probe

texts:
I am building what looks on paper like a really sweet logic probe as a first project.  It includes 3 variable resistors. The site I got the circuit diagram from is translated into english and doesn't make sense.
There is some nonsense about low current measurements.
My question...how do I determine settings for the various resistors?

Also, can I assume VR1 at the top is, by convention, 50K?


texts:
I'm doing a PCB in which I'm using the Beagle Bone Black to interact with multiple I2C devices. I have attached a schematic. Out of the many I2C devices, I'm connecting some using TI's I2C switch PCA9548A (mainly for reducing the line capacitance).

I have the following questions

Does my schematic make sense? Are there any glaring loopholes
For the purpose of de-bugging (to see waveform quality, rise time etc), I bring out the main SDA, SCL lines and the switch lines SDA (1-4) and SCL(104) to 0.1 inch 2 Position headers (as shown in the Figure 2). Does bringing out I2C lines like this hurt the signal integrity and overall performance? Also am I doing it right?
Since multiple devices use the same I2C lines, the section where the lines meet looks as shown in Figure 1. The white circles indicate the intersection of SDA/SCL lines from other devices. Does this make sense?

Thanks

Figure 1

Figure 2


texts: Split a 512 bit numbers into 16 words of 32 bits using HDL

texts: How to split a 512 bit binary number into 32 words of 16 bits using HDL?


texts: Understanding specifications with regard to current draw of components NL17SZ08, 6N137 and 74HC165 and other current-related questions

texts:
I am trying to calculate how much current some components will draw. However, it is not clear to me from the datasheets. I also have several other questions.
Firstly, the NL17SZ08 AND gate
MAXIMUM RATINGS

DC Input Diode Current -50mA
DC Output Diode Current -50mA
DC Output Source/Sink Current ±50mA
DC Supply Current per Supply Pin or Ground Pin ±100mA
Latchup Performance ±100mA

DC ELECTRICAL CHARACTERISTICS

Input Leakage Current ±1.0μA
Quiescent Supply Current 10μA

DC Supply Current sounds relevant but I don't understand the ± or the per Supply Pin or Ground Pin. 100mA seems like a lot of current for an AND gate, which I would expect to be simple and low power.
Secondly, the 6N137 optocoupler
ABSOLUTE MAXIMUM RATINGS

Average forward current 20mA
Enable input current 5mA
Surge Current 200mA
Output current 50mA

RECOMMENDED OPERATING CONDITIONS

Input current low level 250μA
Input current high level 15mA

ELECTRICAL CHARACTERISTICS

Reverse current 10μA
High level supply current 7mA
Low level supply current 7mA
High level output current 1μA
Input threshold current 5mA
High level enable current -1.6mA
Low level enable current -1.6mA

If the max average forward current is 20mA, then will the max forward current is 40mA? What is the High level supply current. That sounds reasonable for an LED + some other stuff
Lastly, the 74HC165 shift register

Absolute maximum supply current 50mA - is this only relevant if this chip was connected in series with something which draws current? When connected "normally" in parallel with some circuit, would this ever be an issue?
supply current 160 μA + additional supply current approx 2500μA = 2.7mA - is it really this low?


texts: Using the neutral instead of the earth to supply electrons

texts:
I'm working on a VAN DE GRAAFF generator and I need to connect the bottom comb to the earth ground.
But in my country we do not have a ground line .
Can i use the neutral line instead and connect the bottom comb to the neutral ?


texts: Should I be able to replace the BC547 with a 2N2222A in this circuit?

texts:
I am working through a particular Instructable to build a simple AC current detector.
Just a hobbyist circuit...

Unfortunately the Instructable doesn't include a schematic so I've recreated here:

simulate this circuit – Schematic created using CircuitLab
Replacing the BC547
I don't have a BC547, but I do  have a 2N2222A.  Both are NPN BJTs.
The BC547 datasheet shows the following:

When I compare the data to my 2N2222A (with my limited knowledge), it looks as though I should be able to "safely" replace the BC547 with the 2N2222A.

Does it look like the max ranges of the 2N2222A should be able to handle this circuit?


texts:
I'm trying to do a pwm amplifier in order to control 3 fans with one pwm signal. Since there are three fans and according to the pwm specs allowed current per each is 5-8mA, I expect current load of around 30mA at max. But my pwm generator (raspberry pi) has 16mA limit, so I need some sort of amplification.

simulate this circuit – Schematic created using CircuitLab

An idea to solve the problem is as follows: when pwm source is low (0V), then the base on the transistor is pulled to the ground, so the transistor's collector/emmiter should behave as an open circuit. When pwm source is high (+3.3V), then collector/emmiter should behave as a short circuit.

If all that is correct then high "pwm source" should pull down the "pwm output" to ground, thus giving low pwm output. And low "pwm source" should do nothing and fans on the receiving side are expected do the rest with pull-up to high (by default, as with no pwm control).

My question — is the schematic above is good and is there any caveats?


texts: LCD Controller receives command whilst busy

texts:
Seems like PIC is issuing command while the controller is busy in operation. here is the screen-shot

Here is the C-code for the above configuration LCD Code

Any help would be appreciated.

Edit: I am not using delays b/w byte transfer to LCD, instead, i used D7 bit to monitor whether the LCD is busy or not.


texts: I purchased a temperature sensor (DS18B20) for my Arduino uno. It came with a 4.7K resistor. Throughout the tutorials and data sheet I don't see this being used with the temperature sensor. Should I be using this resistor as well?


texts:
I need help identifying this 360 degree rotary encoder on my Roland SC-880 rack synthesizer. This one has become 'jumpy' and Roland claims the part is discontinued. So my only choice is to replace it. (or figure a way to open and clean it?)

This encoder has 20 detents and a push switch to select different modes. It's 17mm x 9mm at the base, and about 37mm tall.  The synth came out in 1998 and I'm told Roland used Alps Encoders. What's the best way to go about replacing or fixing this?


texts:
I'm trying to make a flight controller for brushless quadcopters with ESP32 using external sensors like MPU6050(Gyro & accel), BMP180(Baro), HMC5883L(Compass). I've seen lots of people make this kind of flight controllers running the MultiWii firmware and use Arduino Mega, Nano, Minis etc.
But, how do I use the MultiWii firmware for the ESP32? The pin layout is different and I have no idea if just changing the I2C pins on the code would work or not. Writing the entire flight control software from scratch is also probably not an option. I'm not really software savvy and mostly a hardware guy. Is there any existing MultiWii firmware for ESP32? Or any other alternatives? Any resources would be really appreciated. Thanks!


texts: JFET's Understanding - Voltage Controlled Resistor

texts:
If the JFET is supplied from a constant current source (5ma flowing Source-Drain) Will changing the Vgs voltage do anything?

This Image for reference:

Another graph of a 2N5457 taken for the datasheet @ http://www.farnell.com/datasheets/666760.pdf

With reference to this Graph, same question although 0.5mA flowing Source-Drain.

If the current is fixed in the 2nd graph above at 0.5ma what Vgs range would cause the Vds to swing 0-2.5V?


texts: Does using a resistor in series on a breadboard track work as expected?

texts:
I've read up on Kirchhoff's laws of current, however I'm not certain how it applies in this case.  I have 1 10K resistor in series on a breadboard track.  Considering that electrons flow the path of least resistance, part of me thinks that electrons could flow on the rail below the track, skipping the resistor and outputting full current.

Here's an image of what I'm talking about:

It's almost like the resistor is a parallel circuit of its own, however it doesn't run to ground.  So, would the rail + resistor be one and the same?  I know for sure if I hopped the resistor over the bridge in the middle that all electrons would flow through the resistor, yet I can't say for sure in the other case.


texts:
Top graph: voltage drop across the resistor vs. time

Bottom graph: current through resistor vs. time

This is a resistor charging a capacitor.

If the cap is being charged and discharged 2 times a second, what is the power rating I need my resistor to be? Of course, I want it to be as low as possible because of size.


texts: I have encountered a three phase ac machine whose name plate contains following information: Y/360 V/90 Hz/2,3 A. I don't know whether it is an induction machine or permanent magnet synchronous machine. Is there any method how to distinguish between them? For example by connecting the machine to a three phase voltage source inverter? Thank you for any ideas.


texts: Two Different Crystal Resonator on Arduino Mega?

texts:
I'm looking to building my own circuit board based on the Arduino Mega 2560 and looked into their schematic. There are two micro-controllers on there; the ATMega2560 and the ATMega16U2. Both of them have their own 16MHz crystal. But their crystal is slightly different from each other.

The ATMega2560 is connected to this crystal with its built in capacitors  with a load capacitance of 15pF. However, the ATMega16U2 is connected to a different crystal (load capacitance of 16pF) and requires external capacitors. The specs of the two are pretty much the same as far as I can see.

Would it not make sense to just use make both crystals the same model? Is there a reason as to why they are different? I looked at the price of both and they're about the same. Would my design still work if I just replaced the crystal on the 16U2 with the one on the 2560?

Crystal Schematic on the 2560

Crystal Schematic on the 16U2


texts:
Just curious to know what will happen incase I short the Pin1 and Pin2 of my crystal while my board is ON. Crystal is connected to MPC5606S.

What will go wrong and why ?


texts: Is the following information about the diode reverse breakdown voltage correct?

texts:
Regarding the PN junction diode, is the following information correct?:

How come the reverse breakdown voltage increases with temperature according to the above graph? Am I interpreting the plots wrong?: At 75C the break down is more close to the origin which means to me at higher temperature the breakdown happens at a lower reverse voltage. But the above info says the Vr increases with the temperature.
Isn't |Vr| at 75C smaller than |Vr| at 25C?


texts: I have 220V AC to 12V DC with 130Amps output. Could I convert this 12V DC to 5V DC where 130Amps not change?


texts: Sensor Module misbehaving when connected to a voltage divider

texts:
I am using this sensor module with Raspberry Pi 3
http://www.sunrom.com/p/optical-slot-sensor
Since this is a 5V sensor, I connected a Voltage Divider circuit. But the sensor misbehaved. The output wouldn't change. I inserted a diode between the resistors and ground.

simulate this circuit – Schematic created using CircuitLab
Schema of sensor module:

Any idea why this would happen?


texts: What is the input and output impedance of a Widlar current source?

texts:
The Widlar current source is illustrated below:

simulate this circuit – Schematic created using CircuitLab

The small-signal AC model is shown below:

simulate this circuit

I know that if the Early voltage is assumed to be infinite, then the input resistance \$R_{in} = r_{\pi} + \left(\beta + 1\right)R\$. But how does it change (or not change) when the Early voltage is taken into account (i.e., when \$r_{o}\$ is not infinitely large?


texts: How can I simulate a Infineon IR2183 gate driver in LTspice?

texts:
I'm making a boost converter in LTspice, initially with ideal switches and comparators, but now trying to use realistic components.

For the MOSEFT I just picked one from the available ones that has a low on resistance and small gate capacitance.

The gate drives is a bit more tricky, as they don't seem to come included with LTspice. So I went on the hunt on the web, and found that Infineon provides (unencrypted!) spice models.

I downloaded the MicroSim Pspice model for the IR2183 (also used here) from the Infineon product page, and have LTspice generate a symbol by right-clicking in the .sub file.

I made a little test schematic, like in the picture below, but the HO and LO outputs are stuck at respectively 5V and 0V. I have so far tried IR2183, IR2181, and IR2101 based on both the PSpice and OrCad files. All of them produce identical results: nothing.

I'm not tied to any particular driver or even manufacturer, so if there is a way to make this gate driver work, great, if there is another manufacturer that produces gate drivers and corresponding spice files, also fine.


texts: How to calculate number of turns, N for a gate driver transformer?

texts:
Update:
Hi, my TA helped my issue.
Thanks for everyone's help. It turns out, my area should be 12.2e-6.(I accidently wrote 12.2e-5).
And, my understanding for ∆=2Bmax was wrong. The right way for me to choose my Bmax is Bmax<Bsat. And, the right concept was, ∆I=2Ipeak
And I wasn't given any specification for the inductance on the primary side. However, I'm still trying to understand this topic as it is my first electronics project.

I want to build a Switch Mode Power Supply (SMPS) and it requires a gate driver.
My parameters for the gate driver are:
Vin= 15V,
f= 100kHz,
duty cycle= 0.35
I'm using the 3C90 toroid as my gate driver transformer and I need to calculate the number of turns. The formula is:
N= /∆
The VTA used should be the worst case scenario, and for this, I made my duty cycle=50%
My VTA=(15x0.5)/100k = 7.5xe-5

From here, I took my saturated flux density, Bsat=345mT (100 °C)

From here, it said that the peak flux density, Bmax is 100mT
And from the datasheet of the 3C90, the area is A=12.2mm2

So, I calculated my N as below:
N= /∆
= (7.5e-5)/[(12.2e-5)(2)(100mT)]
=3.07
=3
(where ∆=2Bmax)
However, this value is too low, and the TA said that it would cause some problems. He said the same thing to my friend who used N=11.
So, I was wondering if something is wrong with my calculations and analyzation of the datasheet.
Links:

https://elnamagnetics.com/wp-content/uploads/library/Ferroxcube-Materials/3C90_Material_Specification.pdf
http://www.farnell.com/datasheets/650988.pdf


texts: How to set solver for control loop simulation?

texts:
I have been developing a simulation of the field oriented control of the three
phase squirrel cage induction motor (control is oriented by the rotor flux).
I have been using the Xcos which is an equivalent of the Simulink software.
The simulation block diagram looks in this manner

Basically there are three main blocks

IM model
-state space model of the induction motor in the continuous time domain

Observer
-discrete block which calculates the unmeasurable components of the rotor
flux space vector

Vector control
-discrete block which calculates reference values of the components of the
stator voltage based on given reference value of the flux and torque
components of the stator current

I used the default setting of the Xcos solver i.e.

As soon as I start the simulation I receive following error message:
Simulation problem: CVode: At t=0.78087, mxstep steps taken before reaching tout
comming from the IM model block

and the simulation ends. I have attempted to find some information about this error and I have found that it is caused by an algebraic loop detected by the solver and it can be solved by reducing solver tolerances in the simulation setup. I thought that the algebraic loop is broken by the first order low pass filters at the inputs of the S/H blocks. Nevertheless I tried to reduce the solver tolerances

and I run the simulation again. This resulted into another error message -
Simulation problem: singularity in a block again comming form the IM model block. This time from different place

Can anybody give me an advice how to resolve this issue or tell me what is going
on in my simulation? Thank you in advance for any ideas.


texts:
I am trying to make some performance on a memory centric network which has one cpu and multiple memory cubes.(HMC)

I want to calculate the intra HMC latency which means the latency between sending a request to one memory cube and receiving the response. This latency is based on DRAM timings which I should use to calculate the total latency. Let's say I have the DRAM timings which are indicated in the picture below.

Could anyone help me in calculating the total dram latency for a read and write request(each of them is 64B)?

Thanks


texts:
I got questions about the working mechanism and measurement method of SPI and I2C interface.
For SPI, there are several modes.
My question is, how will the data be latched?
Take CPOL=1 and CPHA=0 for example, the bit is latched at the falling edge of clock.
But, why is it the same for MISO and MOSI?
I mean, MISO and MOSI come from different devices(the former from device and the later from master).
But the clock always come from master.
So how would it possible to latch both MOSI and MISO by the falling edge of clock?
For MOSI maybe yes, since the clock and the MOSI output together from master, and arrive device at the same time
(maybe I should say half clock later).
So it's possible for MOSI to follow the timing diagram.
But for MISO, how do we let the MISO be latched at the center of its bit, since it'll travel an uncertain flight time from device to master?
And for scope measurement, which point should we probe? MOSI on device side and MISO on master side?

I got the same question on I2C.
How to make sure the SDA data will be kept high when it's from master to slave, and from slave to master, since the clock is
always from master to slave?

Thanks for any feedback! :)


texts: PC driven PWM for 96 Channel Motor Controller

texts:
I need to build a USB motor controller that can simultaneously manipulate speed and direction of 48 12Volt 15Amp brushed DC motors while having full support for up to 96 motors. This controller will always be PC connected and I prefer not to use arduino. I have some basic electronics and logic circuit knowledge, but most of my experience is in software programming.

I've read up on the basics for PWM circuits and for working with USB for PWM. Since my background is in software, bitbanging seems like an appealing method for handling PWM, but I am not sure how to handle that across 48-96 channels. USB GPIO modules may offer a possible solution, but so far I've only seen 32 channel modules and I assume polarity switching would require double the number of IO channels.

I'm willing to design new circuitry to handle this, but I'm not sure where I should begin. I've never worked with microcontrollers before, but if it's necessary, I am interested in learning how to use them.

Here are my requirements in a nutshell:

USB (always PC connected)
External power supply
96 independent PWM channels
Polarity switching for each channel

Does anyone have suggestions or resources and tutorials for handling PWM motor control over such a large number of channels?


texts: DS1307 : Long term effects, time gets corrupted

texts:
I have designed a PCB which has ATMega328P and one DS1307, along with other sensors on the I2C line. The design is as follows :

Y2 is 32.768KHz crystal, and BT1 is a standard 2032 3v3 coin cell. I am able to easily program the time and the RTC counts well. However, over a period of time, some of my chips start showing 2001/01/01 00:00:00 or 2150/12/22 00:00:00. Some of the chips show time which is consistently 2 hours behind the current time, even though they were programmed to show the current time.

These kind of effects only happen after a long time, easily ~ 3-4 months of operation.

Most of the times, reprogramming the chip works. Is this a voltage issue or something else?

Thanks.


texts:
I need to get the value of an input but only need to get one specific bit. Im porting some software and can't seem to think of a way to get the value from PxIN for the microchip pic it looks like this:

unsigned char idx;
for (idx = 0; idx < 8; idx++) {
    unsigned char byte |= RC1;
}

How would I go about reading the input pin with a MSP430? I am using Code Composer Studio v5.3.


texts: Why does the potentiometer have no effect on the output voltage here?

texts: I have the circuit below, where D and Q are input and output pins (respectively) of a 74373 octal D-type transparent-latch IC. As I vary the pot from 0-10k when D is high, the voltage goes high and changes only very little with the varying pot (\$ \Delta V=0.97\$). Why does the pot only affect the D input by a small amount? The chip is being powered by +5 V.


texts: How can I safely power two 3v motors from a 9v battery?

texts:
I'm making a Sumo Bot from scratch and I had purchased two 1.5-3v DC motors from Radio Shack to run with my Arduino Uno v3. I'm using a 9v battery to power my Arduino alongside an RF receiver, Quad Half-H driver, and the two motors. However, 9v is probably too much to directly power two 3v motors.

How could I reduce 9v to a safer voltage to power my two motors?

Thanks!


texts: Large difference between specced values and real values for LED strips?

texts:
Recently I bought some "300LED/5meter Waterproof 5630 SMD LED Flexable Strip" i.e. High brightness LED strips from China. In the specifications, it was said that the strip consumes 75W @ 12v, which equates to 6.25A @ 12v.

I first tested the LED strips with a 12v 2.5a power supply, seeing as it was the easiest to find. Later I found my 12v 5a power supply, and I was surprised to see very little difference between the two power supplies (in terms of perceptible brightness). Not having any proper test equipment on hand, I bought it over to my local hackerspace which is a little more suited towards doing things like this.

After setting up the LED strip so that it's connected to a 3~20v <10a bench power supply, a voltmeter and an ammeter, I took a video of the readouts from the two meters, whilst I increased the voltage:
http://youtu.be/uX-3r6mrF9A

The results I obtained were... interesting :P

Surprisingly, at 12v, I only got 3.44a (41.28w, 45% less than advertised value!). You can get the results here (google doc).

I then plotted watts against volts, and it turns out that I would need to power this strip at 14.14v in order to get 75w!

Basically, I'm not overly happy with the performance of this LED strip. In order to get the correct power output, you would have to overvolt it by 2.14v, which has the potential to significantly reduce the LED's lifetime. Unfortunately, I was unable to measure the exact voltage at the individual LED level (they were epoxied), but I suspect that they would need at least some heat-sinking if they're to operate for any period of time.

I know that the light output of LEDs isn't measured in watts, but in my mind, < watts specified = < luminous flux specified. I'm still not quite comfortable with all of these conversions, so I am probably wrong somewhere.

Aside from this, I suspect that the values indicated by the multimeters may be a bit off (both are cheap ones), and that there is some power loss from the way I set it up. The values on the PSU matched the values on the multimeters so there shouldn't be too many discrepancies.

Any ideas? I only get ~55% of the specced power consumption @12v, is it O.K to go any higher in terms of voltage?

Cheers,

Sasha


texts: Can I use a cheap logic analyzer as a USB to UART TTL cable?

texts:
I need a USB to UART (TTL) cable for connecting to an onboard JTAG connector. Since I already own a Sigrok logic analyzer, I figure it might function soley as a USB to UART cable. Is this possible?

Here's my Logic analyzer:

https://learn.sparkfun.com/tutorials/using-the-usb-logic-analyzer-with-sigrok-pulseview/all


texts: can use these printer motors to made CNC machine?

texts:
can i use this motor to make a cnc plottor ?
is there any way to make a stepper motor using this motor?


texts:
When I use the .STEP directive in LTSpice to produce a range of plots using different component values, sometimes it displays each step in a different colour and other times it doesn't.

What is the trick to get the multi colour display?


texts: What protocol does a headphone jack use?

texts:
I have 2 questions.  One is simple, the other may be not.

1. What's the official name for the standard headphone jack?  It's universal for all brands of phones, so it must have a name (when you want to go shopping for components).

2. Is it using some sort of a communication protocol?  I know for a fact that it's not only for headphones.  There is a device for scanning credit cards that plugs into the same jack.  I believe Nexus also has a TV-out support from the same jack.  Basically, can it be used for other I/O applications?

Thank you


texts: Why two different coils for one output in this circuit?

texts:
It's a backlight circuit for an iPhone 6s. Previous models only used one coil, one diode for one output.

This model uses 2 coils and 2 diodes. Coils are different values. Can't find datasheet for the ic so I'm curious why two would be used.

Is it for providing smooth current output?


texts:
I need to try different 74lsxxx logic ICs over a FPGA. As examples 4 bit adders, counters, etc which are more complex than primitive logic ICs. And it is time consuming and error prone to code in Verilog. Is there a easy way to directly import 74lsxxx IC gate schematics into FPGA synthesis tool?

P.S. I found Aldec's Active-HDL supports for net-list import. But I could not find a 74LS family net-list library.

And I found there was a very old software called viewlogic which had a 74LX library. Seems it is no loner available.

Thank you..


texts: Are IC sockets suitable for mains voltage?

texts:
I need to derive a low-voltage galvanically isolated 50 Hz signal from 230 V mains. I'll use an opto-isolator for this. I'd like to use IC sockets for all ICs in this personal one-off project.

Opto-isolators are typically suitable for mains voltage, being rated for thousands of volts of isolation between the diode and the transistor. But are DIP IC sockets suitable for mains voltages?

I know IC sockets are made of plastic, but I preferred to ask rather than possibly compromise isolation. I don't think there are any datasheets I could check either.


texts:
I'm designing an homebrew RF spectrum analyzer.

Controlling the analyzer will be done using USB which is converted to UART using an FTDI chip.

My concern is that noise (probably common-mode) will be injected from the PC (USB/UART) and affect the SNR of my spectrum analyzer. I know that PCs are very noisy.

My idea was to use some separation(probably an optocoupler) to completely separate the PC from the spectrum analyzer.

Does anybody know whether this is necessary or not?


texts: Do stepdown transformers use their maximum wattage while in use?

texts:
I recently moved to Australia from the United States and brought a few stepdown transformers to make use of some appliances I didn't want to repurchase down under.

I have a 2000W transformer that I use for my rice cooker and vacuum and was wondering today if the electricity usage function is

kWh = (Hours used) * (Wattage of transformer)

Or:

kWh = (Hours used) * (Sum of wattages of appliances drawing power)

Or possibly neither? At prices up to $0.33 a kWh it's an important thing to figure out!

As well, most of my devices say they operate at 120V but my transformer outputs at 110V, will this cause problems?


texts: Connect Analog Audio Line to analog Amplifier IC

texts:
I have a SoC that uses an Amplifier IC to Output Audio to a 8Ohm Speaker. I want to take the Audio Signal from the IC and give it on the Audio Line of another Circuit.

I am not sure if my circuit is correct. Maybe someone can have a look and maybe did something similar already.

The Picture is taken from the datasheet and the circuit on the right is mine (don`t pay antention to the values of my circuit, they are not correct right now)
I only need advice on the connection between the amplifier and my circuit.

There has to be a load on the VO+/VO- lines or else the IC does not output any audio... just a square wave.

Thanks

EDIT

I had a lot other stuff to do in the past so I could not work on this project. Here is a new schematic of the current circuit. I have a beautiful differential output on the VO+ and VO- Lines but I do not get any output?!?!

Please see these oscilloscope pictures, on picture 1 you can see that before a sound is played, that both lines are pulled to 2V, that is also the reason why I removed the -5V voltage inverter because I thought the sound is in the positive range so I don`t need the negative voltage...

A beautifull differtial signal...

So is it a problem that the VO lines are pulled to 2 Volts or what else is the problem? Why am I not getting any output??

Thanks so much :)


texts:
I'm using 3 MOSFETS in a circuit due to the   large currents flowing         through these MOSFETS. I want to use one big single heatsink for all instead of 3 separate heat sinks. This is because   at one time    only one MOSFET is conducting. I believe that this will reduce the overall heatsink size and reduce temperature cycling .

Is there any problem using this type of heat sink? Can any one please share some links related to this type of heatsink.


texts: Why does the capacitor part of the electret mic have very high impedance and why is a FET used to solve the problem?

texts:
As far as I understand a FET is used for impedance conversion of the capacitor part of the electret microphone. I dont understand the meaning of that.

The reason is given that the capacitor itself has very high impedance(I guess output impedance).

Can you explain why the capacitor itself has a very high impedance and why is that a problem? And how does the FET makes it useful? An answer with simple circuit examples help.


texts: Migrating from the ATMEGA8 to the ATMEGA88PB

texts:
I have a simple project that only requires the UART i/f of ATMEGA8, running off 8MHZ internal RC oscillator. I have the DIP package version of ATMEGA8 and things are working fine. I have code compiled using the Arduino IDE for ATMEGA8 and fuses set using avrdude to select the internal RC (no bootloader). For production, I want to move the new ATMEGA88PB in TQFP package (because of lower cost). My questions are as follows:

The Arduino IDE supports compiling for the "ATMEGA88" mcu - would I be correct in assuming that the same code that works for ATMEGA8 and ATMEGA88 (Arduino IDE compiler options) would work on the ATMEGA88PB (the ATMEGA8 and ATMEGA88 are pin compatible, even if not register compatible - but the compiler should take care of that) - correct?
I am running the ATMEGA8 off a 3.3V supply. I am guessing that should not be a problem for the ATMEGA88PB as well?
Are there any other gotchas in making this switch? My circuit is minimal as I am using the internal RC and only the UART interface. Of course, I route out the ISP pins to a header for programming. I am guessing the way I program, etc would stay the same. Any thoughts / experiences? I could not find much prior discussion on the ATMEGA88PB.

Thanks.


texts: Can the following K-map be grouped with 1s in the corners of a subsection of a 16-cell K-map?


texts: I'm planning to build a 12V 4A circuit, and I was originally going to put it on a strip board. However, the board I ordered came broken (and each piece would be a bit small for building a circuit), and I don't have time to order a new one. Additionally, I'm starting to realize that my circuit setup would be pretty difficult to set up keeping the strips in mind, and I would need to widen some of the holes to fit certain components. Since I have a decent amount of a 16 guage wire to link the components without a board, would it work to stick everything on a sheet of cardboard? Do I have to worry about the cardboard catching fire at a high wattage due to heat from the leads?


texts: Can you stack SMD resistors in parallel to reduce power dissipation per resistor?

texts:
I sent my PCB a couple of days ago for fabrication but just realized a terrible error:
I need to send 70mA to an IR LED with a 5V supply so I would need a resistor of about 70ohm, which means the resistor would be dissipating 350mW of power.

The SMD resistor package is 0805. THE PROBLEM is that I can only get one that dissipates max 125mW in this package : 70ohm 125mW from digikey

So can I get 3 220ohm versions of this resistor and literally stack them in parallel?
Has anyone tried this?

What can I do in this situation?


texts: Why is Kapton film used to hold liquid in waveguide?

texts:
I am working on a project similar to the one described in this paper
MEASUREMENT OF COMPLEX PERMITTIVITY OF LIQUIDS.
Here a Kapton film is used to hold liquids, so that they don't spill. Why is this so? Does this film act as perfect conductor at microwave frequencies ?
Won't it affect the measured S-parameters ?


texts: DC output through PSU not readable by a multimeter

texts:
I am using this 300w 12v PSU for small pool/spa set up. It powers LED bulbs fine but the problem is that I am never able to get reading with multimeter (no DC reading from this particular PSU - the multimeter is working fine for anything else).
Now, I tried to connect the LED strip light that comes with a little control box (that remote "talks" to and the control box is able to change colors, etc.) with no success. I can connect the LED strip directly (bypassing its controller) and it lights up fine. I can also connect the LED strip along with the controller to its original 12v PSU and it works fine.
So, the problem is between the LED controller box and my PSU - it must have the same issue of not able to "accept" the DC signal from this particular PSU as my multimeter does.
Is it possible that the DC signal from the PSU is not "clean" enough and this is messing up my multimeter and the LED controller box? Is there a way to verify and address the issue?
Thank you


texts:
Full transparency, I'm a cinematographer, not an engineer, so forgive my ignorance here!

I'm attempting to make an inline dimmer for small bi-color LED strips and fixtures. I have larger, more expensive controllers for larger more permanent fixtures, but for the flexibility and weight I'm trying to achieve with these smaller accent lights, I want lightweight and simple.

So far, I have had limited success with two high speed (10khz) PWM dimmers that I've wired in succession to control the two channels on the strip individually. However, when it comes to precision control of the color temperature achieved by the on-off-blended nature of the two LED colors, this is less than ideal. What I would like to design is a very simple controller with two knobs:

1 for brightness/intensity.
1 for color control (transition from 2800K to 6000K).

This is beyond my awareness to achieve simply because I don't have the vocabulary of components to design something like this. Any help and thoughts would be greatly appreciated!

The LED strips are these

The PWM dimmers are used in the first version are these


texts: How is my square wave circuit able to turn itself on?

texts:
I built a small 1-to-1 transformer from a ferrite core, to investigate if it could be used as a MOSFET gate drive transformer. I use speaker wire, it has two insulated conductors. I am driving the transformer from a 12 volt DC power supply. The transformer is switched on/off with a 2N5551. The drive signal is generated using a 555 and an additional 2N5551 so that I can have less than a 50% duty cycle. The actual scope trace shows the drive signal, so I won't include the specifics of the 555 circuit.

For completeness, here is my circuit

simulate this circuit – Schematic created using CircuitLab

As I indicated above, CLK1 is not an actual 50/50 square wave. It's generated by a 555. Both DC power supplies are mains transformers feeding full bridge rectifiers, smoothing capacitors, and a 78xx regulator.

The issue I am seeing is that when Q1 turns on current flows in the primary. When Q1 turns off, current stops in the primary. Some time later, a voltage spike occurs on the base of Q1, then turning it on briefly again. This spike is a mystery to me. I call this the "free" trigger.

I noticed this if I add a 472K (4.7 nF) capacitor the primary, I saw the "free" trigger of Q1 move to the right in time. So I installed a 473K capacitor (47 nF) and the "free" trigger disappeared entirely. I'm not really sure what the output of this transformer should look like, but it at least looked normal once I did that.

why does this "free" triggering occur? Why does the capacitor fix the problem? Does the capacitor cause other problems when trying to operate a gate drive transformer?

Picture of the physical setup

CH1: secondary of XFMR1, CH2: base of Q1

CH1: secondary of XFMR1, CH2: AC coupling to V1

CH1: secondary of XFMR1, CH2: Base of Q1

Ch2: secondary of XMFR1, CH2: Base of Q1. 472K  cap. in parallel with primary of transformer

CH1: secondary of XMFR1, CH2: Base of Q1. 473K cap. in parallel with primary of transformer.


texts: Capacitor between grounds: Reason and how to decide the value

texts:
while going through the reference designs, I came across the capacitor between grounds. Is it for RF noise protection?
Is ground for U4 and other part of the circuit is different?


texts:
I am new in this field. I have a problem with conversion of std logic input into real values. I have been using to_float function but it always showed error. When I used package float_generic_pkg, it showed error:

  Cannot find  in library .

I also tried creating new library ieee_proposed but still it showed error.

I tried using IEEE.numeric_std.all, too.

Again it gave error <to_real> not declared.

Do I need to use some other library package?

I am using ISE Design Suite 14.7.
One thing more: its for synthsis too. Please help me.

Here is the code :

library ieee;
use ieee.std_logic_1164.all;
use ieee.float_pkg.all;
use ieee.float_generic_pkg.all;

entity dafsm is
port (x : in std_logic_vector (1 downto 0);
      y : out std_logic_vector (1 downto 0));
end dafsm;

architecture fpga of dafsm is
   signal r,s : real range 0.0 to 15.0;
begin
   r <= to_float(x);
   s <= r * 0.5;
   y <= to_slv(s);
end fpga;

The error messages:

  Line 4: Cannot find <float_pkg> in library <ieee>. Please ensure that the library was compiled, and that a library and a use clause are present in the VHDL file.
  Line 5: Cannot find <float_generic_pkg> in library <ieee>. Please ensure that the library was compiled, and that a library and a use clause are present in the VHDL file.
  Line 12: <real> is not declared.
  Line 14: <r> is not declared.
  Line 15: <s> is not declared.
  Line 16: <y> is not declared.


texts: How to generate an Excellon NC drill file from Altium, as my PCB manufacturer does not require a cam file. The NC drill file generated from Altium is a .CAM file, whereas, my PCB manufacturer requires the Excellon drill file and the tool list. Is there any way to generate the above mentioned data from Altium, or is there any other conversion tool for the same.


texts: High EMI PCB track under transistor or diode package

texts:
Can a high EMI PCB track under a transistor or diode package (in this case TO247AC) be a problem?

To get a better understanding:

Is there any advantage on putting these tracks on the other side (like the image above)?

If these two options might present problems, what would be a good idea? making a "bus" vertical to the board? Using wires (really great dimensioned to reduce stray inductance)?

The same for the diodes:

Note: The transistor case is common to collector, so in two of the switches the PCB track under it is common to the case and I think this is not a big problem. But the other two don't.

Some information about the voltage and current:

DC Link voltage: ~340V.
PEAK current at the IGBT: 75A (at full load on the peak of the switching waveform).
Rectified secondary voltage: maximum of 25V/200A at full-load, and 60V at "no-load".
Switching frequency: ~20Khz maybe a bit more if the switching becomes so audible.

The edges will be rounded, it's just not the final design yet.

The BUS tracks although not easy to see is one on each side, so to reduce inductance and add capacitance, also giving a nice design and space use, based on http://xellers.wordpress.com/2013/03/14/general-purpose-h-bridge-inverter/. Thanks.


texts: Can I wire 6V power packs in series and still use them as individual power sources?

texts: I have 4 x 1Ah Lithium Ion battery packs. These I have two systems, one operates at 5V (usb) and the other requires 20v - 24v. I'm wondering can I power both the 5v system and the 20v system by using one USB port on the unit normally, and the other to wire the batteries in series? or am I misunderstanding the principal. Also, would this affect how I charges the batteries? or could I charge them normally using the micro USB.


texts: So how do control engineers control nonlinear plant with exponential output?

texts:
Say that a system (circuit, pump, population model, etc.) has a exponential output of the type $$y = ae^{bx}$$
What do control engineers do in order to achieve control objectives such as tracking and stabilization around a set point?