texts: BUZ71 MOSFET seems to be not fully activating

texts:
I'm controlling a coil running at 32V from a microcontroller running at 5V via a BUZ71 N-Channel enhancement mode MOSFET. The coil has a resistance of about 30 ohms and it draws about 0.6A at 32V.

I supply +5V (or about 4.9V according to my multimeter) to the gate of the BUZ71 via a 1K resistor, and I've also grounded the gate with a 100K resistor to ensure it stays off when the microcontroller isn't supplying 5V.

I've got +32V going into the coil, and the coil connects to the BUZ71's drain. The BUZ71's source connects to ground without a resistor.

The whole apparatus seems to "work", and the coil is energising as expected, however when I measure the voltage going to the coil, it appears to initially spike at about 22V and then drop down to about 10-15V. It's hard to see exactly what's going on and when because my digital multimeter only updates about twice a second.

I'm totally new to MOSFETs, and I haven't even really use transistors a great deal. I've looked at the data sheet for the BUZ71 and I think +5V on the gate should fully activate it, but I'm not sure.

Does the setup I've described here reflect how I should be using the MOSFET? Is +5V enough to fully activate the MOSFET? Is the BUZ71 appropriate in this case, and if not then what other MOSFET do you recommend?

Big thanks.


texts: I have a J-link v8 and want to use it, but I can't find its name in Segger homepage, I want to know what ARM core it support and is it support BeagleBone or RPi.


texts: Drive stepper motor using 2xAA NiMH 800mAh (2.4V)

texts:
I am designing a circuit for driving the stepper motor, the link attached (https://www.alibaba.com/product-detail/3v-12mm-2-phase-micro-dc_60641420857.html?spm=a2700.7724838.2017115.17.149a279bsYy1CA&s=p) using 2xAA (2.4V) NiMH 800mAh batteries. Also, I am using a boost converter U1V10F5 (0.5V-5.5V)to step up from 2.4V to 5V to power up the motor as well as the driver (DRV8834). I've found that the motor that runs at 2.7V consumes approximately 70mA. The question is if I am using normal 2xAA(3V) battery or bench power supply (set it to 2.7V) the circuit is working fine and the motor is running. Whenever I set the voltage to 2.6V or 2.4V on the bench power supply or connect the 2XAA rechargeable battery my motor stops working.

Is that the rechargeable battery not having enough capacity? or the step up booster is not able to supply enough current to drive the motor at 2.4V?
Please let me know why the motor is not running at 2.4V and runs at 2.7V. I have attached the rough schematic. I am using two PSU for the microcontroller(5V@3A) and the motor(2xAA(2.4V)) indicated in dotted lines in the schematic. Your guide is much appreciated.

Thanks in advance.

simulate this circuit – Schematic created using CircuitLab


texts: How does a current flow in here if this is not a loop?

texts:
Below is an image from Microelectronic circuits by Sedra & Smith — Seventh edition.

How can a current of 10 mA flow in this circuit (in figure a) if there is no loop for the current to flow in? Is there an implicit assumption that the ground and +10V end of this circuit magically form a loop (which is omitted here)? Not even interested in the diode at this point. How would this be physically possible?


texts: How exactly is the location of contact determined on an analog resistive touchscreen?

texts:
I am doing a physics project for my high school course. My project is to explain how a resistive touchscreen works.I have no engineering knowledge.

From a description I found on computerworld.com (it's the most elaborate one I could find)...

It consists of a top flexible, bendable film and a rigid bottom film (usually glass), separated by a air gap. The two films are lined with transparent conducting materials (usually ITO), perpendicularly placed to one another.

It's analog resistive ("analog"-measures a change in value, not limited to the binary choice between complete presence or absence)

When pressed, the top and bottom films (more specifically, the conducting linings) make contacts, and thus a circuit is formed.

The voltage is measured. Assuming the current that goes through this "circuit" is constant, the resistance varies proportionally with the voltage.

This is the tricky, kinda shaky part that the author just glossed over: with the voltage measured, the X and Y coordinates of the touch position is calculated based on the amount of resistance at the point of contact.

QUESTION

What determines the voltage measured (and thus the resistance calculated from voltage and current)?

What are the conducting layers lined perpendicularly?

If the whole resistive touchscreen is "analog resistive", why then "this analog voltage is processed by analog-to digital converters (ADC) to create a digital signal that the device's controller can use as an input signal from the user"? (ALSO, ISN'T "DIGITAL" THE OPPOSITE OF ANALOG?)


texts: Which battery type for high power and fast charging?

texts:
I'm interested in building a portable PA system (on a small wheely-cart) that's very loud (particularly strong in bass, which uses a lot more power than treble) to be used in short increments of time and then recharged at the wall.

What kind of battery do I want? Li-ion, Li-poly, Lead acid, etc?

The battery should be able to deliver say 200W constantly for 10 minutes.

I realize I will need to learn about capacitive circuitry to "buffer" the load between the battery and the constantly-fluctuating amplifier draw, but that's a different question for a different OP.

....bonus question: if I can afford it, would it be suitable to simply use a large number of identical Li-ion cells in parallel?


texts: Self Oscillating INA with Multiple Feedback filter

texts:
I'm working on a circuit to receive a signal in the 220Hz range.  The signal is created from a small loop transmitter emitting a 50% duty cycle DC square wave of about 4.8 Watts.

The receiver is a small loop antenna (4.69 Henries) with a 0.11uF tuning cap, which should tune the receiver to about 221 Hz.

The problem is when I disconnect both the transmitter and receivers from the circuit, I still get a half wave (positive phase) of about 103Hz. I presume that is some self-resonating characteristic of the circuit.  Can anyone tell me where I might be going wrong with this circuit?  Shunting the inputs significantly reduces the 103Hz output, but does not eliminate it.

Noise does not appear to be coming through the power supply, however I have also added a 1.2uF cap/ferrite bead filter between the +/- sources to GND. (not shown)

Ideally I'd like to have the output produce near 0V when the inputs are shorted together.

Note: the diode D3 is strictly for clipping the negative output portion of the wave, as the output goes to an ADS1015 ADC converter, which is not a bipolar ADC.

All components except R1 and R2 (Trimpots) are 1% tolerance.


texts: High voltage circuit powering Arduino/ESP32 - requesting feedback?

texts:
I have been struggling with this for days...This is the first time using switched power supply units to power an Arduino.
Can you tell me if this is wired correctly? If not, what needs to be fixed?


texts: Do buck converters increase the amp hours of a battery?

texts: I've read that they are 90% efficient compared to linear regulators so given the relationship between volts and amps and I want to power the project off of a 12v battery that has 18Ah and is charged using a small solar cell. The project itself only needs 5v, so if I buck the voltage down to less than half the required voltage, wouldn't the amp hours close to double giving me 36+ Ah? Or am I missing something about the relationships between volts and amps and the mechanism of the buck converter?


texts: HDMI (ADV7511) Output Design on Zynq zc702

texts:
I am relatively new to embedded systems, so please forgive my ignorance. I am attempting to build a hardware design in Vivado which supports console output on HDMI, using the Zynq ZC702 running PetaLinux, and based on the ADV7511 reference design. I have read the guide to HDMI output on Linux, but it does not provide enough information to construct the reference design from scratch, only how to utilize the pre-built reference design for programming applications. Attached is an image of my current block diagram in Vivado. From what I have read thus far, I believe all the neccisary IP is in place (PS, VDMA, clkgen, HDMI_tx, S/PDIF_tx, and AXI interconnect), and the configuration for each IP should also be correct, but the connections between them are very much incorrect.

How can I connect these IP in order to create a functioning replica of the reference design which I can further build upon?

Which ports must be made external and which can be ignored?

Let me know if there is any further information I can provide which would clarify my intentions or my current implementation.

The attached design passes validation and synthesis, but fails timing in the implementation, presumably because the clocks are hooked up wrong.

Thanks in advance.


texts: How to detect pin state change in pulled up pins

texts:
I am working on Toradex module and developing a simple application where I am detecting the input and displaying it on UART. Now the application requirement is that we give 12v as input but the processor pin cannot take 12v as input so I am using below circuit to convert it to 3.3v using PC817 Optocoupler. The below circuit is working fine.

(3.3v and GND on the transistor side of PC817 is from the processor side and 12v supply is from the power supply side, to provide isolation)

Now there are few pins in the processor which are pulled up. That means they are by default high and giving 3.3v. Now to detect input on these pins I need to pull them down. That means I'll have to connect them to ground to detect change in the pin state. So I'll have to design the circuit in which if I give 12v as input, those pins go down. So what circuit should I make for pulled up pins to detect input change.


texts: Could someone identiy this SMD connector?

texts: does someone know what the part number etc of this connector is? It is used to connect two boards. There are 5 pins on one side and 6 pins on the other. The smallest markings on the tape measure are in mm.


texts: Oculus development Kit 2 headset design, main PCB cutout

texts:
I've been reviewing the Oculus development Kit 2 headset design. Files here

There is a cutout in the PCB that confuses me.  It's 1mm wide and there isn't any notch or anything on the assembly to fit inside.

The U11 is MPU-6500 (3-axis Gyroscope and 3-axis accelerometer) and U12 is LIS3MDL (3-axis magnetometer). They are connected through SPI to the main pic.

My guess is that the cutout is to isolate these chips from any type of noise but I think a simple cutout on the layers would be enough and this is a bit excessive.

Does anyone have another idea about the purpose of this cutout?


texts: Error Propagation and Analysis on a experiment due to Voltmeter Constraints

texts:
I got a situation: at the moment I am unable to access both channels for Keithley 2182A nanovoltmeter using LabVIEW. However, for some odd reason, while I cannot access the channels at once, LabVIEW does give me the ability to access channel 1 and the ratio between the two channels - from which I use those points to find channel 2.

However, again, because of my hardware, it appears I would need a minimum of two measurements (the minimum size of my buffer is of two), so I am wondering if the following decisions are sound with experimental good practices:

Given that I get two measurements for channel 1 ($V_1$), I cannot just pick one of them (either at random or deliberately) so I calculate the mean of the two measurements and keep the mean measurement of $V_1$.
Likewise, given two measurements of the Ratio of channels 1 and 2 ($\frac{V_1}{V_2}), I too calculate the mean and keep the mean measurement of $\frac{V_1}{V_2}$.
And finally, I calculate the ratio between these two measurements to yield the mean of channel 2 ($V_2$).

Right now this is just a draft, proof-of-concept so I can do some measurements to teach myself basic lab techniques. However, I also know, from experience, that what I just described sounds like really bad in terms of error propagation. For instance, I think I can able to stand by steps 1 and 2 in terms of error propagtion, but the third step, the ratio, I am wondering: how bad is this ratio measurement in terms of error propagation?

Also, any books, papers, etc about experimental techniques in electronics would be greatly appreciated!

Best!


texts:
I created the following circuit in Pspice:

In the simulation profile I made sure that all flip-flops are initialized to 0. When I run this simulation I get the following error message:

I just can't figure out what is the problem... can you help me with that?
thanks a lot...


texts: Connecting a PIC32MZ with an Android tablet via USB

texts:
I have an Allview tablet running Android I want to connect to my board using USB. An application on the Android tablet would control the micro which in turn would control a bunch of relays and read from a bunch of sensors.
I have routed the +5V, GND, USB_ID and USB_DATA1/2 pins to a connector but I am not sure how to set up the pins on this micro USB connector so that the tablet can talk with my micro and also charge its battery from my board.
Some people say it's going to work with an OTG adapter, which basically pulls down the sense pin to GND. But how does the tablet charge its battery? The connection will be long term/permanent so the tablet needs power.
I have seen a lot of tutorials and specs out there but they are convoluted bricks of text with a lot of ifs and buts so I still don't quite understand: Do I pull down the USB_ID/sense pin to GND? If that's the case my understanding is the tablet would supply power to the board which I don't want, I want the tablet to charge from the board because it will run out of battery eventually.
The board can and must supply some 500mA at +5V to the tablet using the micro USB connector.
Would appreciate some tips from someone more experienced with the USB bus architecture.


texts: Connection of center tap for Ethernet transformer

texts: I'm trying to connect an RJ-45 jack with integrated magnetics (Belfuse L829-1X1T-91 datasheet) to an Ethernet PHY chip (Micrel KSZ8041TL datasheet). The TX+/-, RX+/-, and the LED pins are all easy enough to figure out, but I'm not sure what to do with the center taps (TCT and RCT) for the transformers. Should they be connected to 3.3 V power? To the 1.8 V output of the PHY?


texts: Why are rms values used to calculate power in amplifiers?

texts: I am taking a beginning EE course, and it seems like we just use the given peak voltages to find the current and voltage gains of an amplifier. When it comes to finding the power from its source and the power deliver to its load however, we have to use the Vrms and Irms. Why is this necessary to do, instead of just using the peak of a sinusoidal voltage?


texts: Zener Noise Generator - NPN BJT Amplifier Analysis

texts:
I'm interested in creating a low voltage white noise generator by means of a zener diode, as detailed here: Zener & BJT Noise Generator.  Specifically, I want to use the circuit here, in order to minimise PCB real estate and number of components: .

I'd like to replace some of the parts (D1 & Q1) chosen by the original author, as the article was written in 1990 and better/smaller parts are now commonly available.  Hence I'd like to be able to analyse the circuit, rather than just take a guess at suitable values of components.

I'll use the following circuit for the discussion:

simulate this circuit – Schematic created using CircuitLab

VSS = 3.3V and V_Zener = 2.0V.  I want to know the power dissipation of the BJT in order to determine what is a suitable choice (I want to use a small SMT BJT, not a 2N2222).  I've kept R1 & R2 to be the same value as the original circuit, simply for the sake of the analysis.

My understanding is that the zener is reverse biased and results in a reverse current flow (that is noisy) that is determined by the voltage to which it is reverse biased - is this correct?  Do I therefore find the reverse current flow (into the base of the BJT) in Fig 4 of the Data sheet?  If this is the case, then is the current flow through the collector then = IBE * gain of BJT?

Or does the analysis start by saying that the voltage at V_Zener with respect to ground is V_zener (2.0V) + VBE (0.6V) = approx 2.6V.  Therefore steady state voltage(ignoring noise) at node 'Noise' is calculated by the divider R1/((R2 + R_zener) paralleled with R_Q1)?  Not sure where I would go in the analysis after this?

It's been a very long time since I did this sort of stuff, so any tips would be really helpful.

Having worked out ICE, power dissipation in the BJT = V_collector * ICE?


texts: Interrupt level and Task Level Notification in Microcontroller

texts:
Recently I have come across the two terms in call back functions(Which will notify the User) in particular Project i)Interrupt Level ii)Task Level.  My understanding is,

  Interrupt Level

    The user will get a notification Instantly, though other Task is running.

  Task Level

 The user will get notify if Running Task is Completed.

If above is Correct, then how we can Configure the Interrupt Level in MicroController. I know there will be GPIO Interrupt, UART Interrupt. My question how it will notify in interrupt level. Can we change any reserved Interrupt Table? or how it can accomplish.


texts:
This is my PCB layout:

My problem is:

When i tried to Access SDRam with my example code (Memory test Code) everything seems ok. All the SDRam Data changes what i need. But when i tried to Access bunch of a place on SDRam, Data corrupts. Code is OK, i have tried the code on my eval. board and no problem ocurred. I could understand that if all the data corrupts on my every try.

Here are the codes with problem and without problem:

I will Show how memory has been effected.

First Photo Shows Successfull Read Write:

Second photo shows Faulty Datas:

And interesting one is Third Photo. I have changed nothing. just scroll up and down. And faulty data changes and move to the other places. if there is a read problem exist why doesnt it occurs when i use scroll, on memory window with successfull code tray. I hope photos can be helpfull.

This is my ground :

here is my working code simply. with no fault. Every time it Works perfectly.

   SDRAMInit();

wr_ptr = (uint32_t *)SDRAM_BASE_ADDR;
char_wr_ptr = (uint8_t *)wr_ptr;
/* Clear content before 8 bit access test */
_DBG_("Clear content of SDRAM...");
for ( i= 0; i < SDRAM_SIZE/4; i++ )
{
  *wr_ptr++ = 0x00;
}

/* 8 bit write */
_DBG_("Writing in 8 bits format...");
for (i=0; i<SDRAM_SIZE/4; i++)
{
  *char_wr_ptr++ = 0x11;
  *char_wr_ptr++ = 0x22;
  *char_wr_ptr++ = 0x33;
  *char_wr_ptr++ = 0x44;
}

/* verifying */
_DBG_("Verifying data...");
wr_ptr = (uint32_t *)SDRAM_BASE_ADDR;
for ( i= 0; i < SDRAM_SIZE/8; i++ )
{
    if ( *wr_ptr != 0x44332211 )    /* be aware of endianess */
    {
        /* byte comparison failure */
        _DBG_("Verifying fail, testing terminated!");
        while ( 1 );    /* fatal error */
    }
    wr_ptr++;
}

/* byte comparison succeed. */
_DBG_("Continue writing in 16 bits format...");
wr_ptr = (uint32_t *)SDRAM_BASE_ADDR;
short_wr_ptr = (uint16_t *)wr_ptr;

/* Clear content before 16 bit access test */
_DBG_("Clear content of SRAM...");
for ( i= 0; i < SDRAM_SIZE/4; i++ )
{
    *wr_ptr++ = 0;
}

/* 16 bit write */
_DBG_("Writing in 16 bits format...");
for (i=0; i<(SDRAM_SIZE/4); i++)
{
    *short_wr_ptr++ = 0x5AA5;
    *short_wr_ptr++ = 0xAA55;
}

/* Verifying */
wr_ptr = (uint32_t *)SDRAM_BASE_ADDR;

//wr_ptr -= SDRAM_BASE_ADDR/4;
for ( i= 0; i < SDRAM_SIZE/4; i++ )
{
    if ( *wr_ptr != 0xAA555AA5 )    /* be aware of endianess */
    {
        /* 16-bit half word failure */
        _DBG_("Verifying fail, testing termintated!");
    while ( 1 );    /* fatal error */
    }
    wr_ptr++;
}

/* 16-bit half word comparison succeed. */

_DBG_("Verifying complete, testing terminated!");
    while(1);


texts: Black Pad. Will heat remove the gold from an ENIG finish?

texts:
I have a batch of new PCBs with ENIG (electroless nickel / immersion gold) surface finish. My assembly house has had two unsuccessful attempts at populating the boards. We're trying to troubleshoot the situation.

The assembly house is suggesting that it is Black Pad [1] [2], which is caused during PCB manufacturing but isn't exposed until assembly/soldering. This would, of course, shift the responsibility away from the assembly process.

With ENIG, the nickel is the bonding surface whereas the gold is simply there to protect the nickle. During reflow, the gold dissolves into the solder. You don't know there is "black pad" until the underlaying nickel is exposed.

In my case, we have a 15-up array but we are only populating a few of the individual boards. The remaining boards do not have solder applied to them; all that happens to them is that they go through the oven twice.

We are seeing something that looks like black pad on these post-oven boards:

My question: Will the gold get burned away somehow when exposed to reflow conditions, even if there is no solder applied to the pads? Or might this be an entirely different problem?

Additional info: The image makes it appear that if might be soldermask on the pads, but in real life you can see that it isn't. Here's the best image my equipment will give me. You can (kind of) see that the discoloration is different that the intentionally-placed soldermask.

Another edit. I was able to get a better image, shown below. I think I know what's happening, but I don't want to influence any upcoming answers.


texts: Supercapacitors for transient power-out for RPi

texts:
So I found a RPi Hat (https://juice4halt.com/products) with supercapacitors as a short term UPS for RPi, however it's on the pricey side. I don't necessarily need the communication with the RPi to do power-off detection or what not, just need some brief power-loss detection for 5 or 10 seconds.
Can I just put a couple of bare supercapacitors in-line with the 5V input, no other circuitry/resistors/etc needed? Or is there more supporting components that I need?


texts: Unexpected LTSPICE Output - Voltage Mode Buck Convertor

texts:
I'm trying to simulate in LTSPICE a simple buck convertor taking 34V -> 20V @ 2.5A and I'm not seeing what I expect. Here is my circuit and some waveforms:

The top half of the circuit is the convertor, and the bottom half is the controller. I'd like to use this circuit as a pre-regulator to a linear supply, so I can confidently specify the minimum load. For the actual device specifications, I've calculated:

Vin - 34V-28V
Vout - 20V @ 2.5A
max ripple = 50mV
Ipeak = 3.5A
fsw = 100kHz
Lmin = 135uH

Now for the problem. If I remove the compensator circuit and directly drive the MOSFET, then I can get the correct voltage out by setting the duty cycle correctly (about 70%). With the compensator connected though, I get weird results which seem to center around R2/U2.

For the waveforms, the green trace is the output voltage, the blue trace is the voltage from the feedback resistors, the red trace is the voltage reference, the light blue is the output of the error amplifier and the purple trace is the ramp voltage into the comparator amp.

The first oddity is the feedback voltage. With the output essentially 0V, I would expect the feedback voltage to be 1/5 of this, or 0V. Here the feedback voltage is consistently sitting at about 2.4V.

The second oddity is the output of the error amplifier. With Vref higher than Vfb, I would expect the opamp to drive high but maintain a "constant" value (ie not sawtooth shaped). I've included the ramp voltage to show that the output of the error amplifier is synchronised, even though it shouldn't be (the only place the switching freq appears in the circuit is at the ramp generator). The net result of this is that the FET is only driven for the period that the purple trace is above the light blue trace - so maybe a 1% duty cycle, which is why the output is almost 0V.

Any suggestions as to why the Vfb and Verr traces are not as expected? Why is the ramp voltage affecting the output of U2?

Also please note - I've tried modifying all the parameters here with no luck. The system is uncompensated at the moment as I'm trying to measure the uncompensated loop transfer function (which currently starts at -120dB and decreases from there). I've tried adding type 1, 2 and 3 compensators but there is minimal change.

Cheers!


texts: Control one circuit from a separate circuit

texts:
What I am trying to do today is control one circuit using another, with no common ground or voltage between the two circuits. Basically what I am looking for is some way to have my Arduino, powered off of its own battery, control a 24V led circuit without using a voltage regulator.

It seems like I am looking for somewhat of a hybrid between a relay and a transistor, the relay providing the ability to control current in a circuit from a separate setup, and the transistor providing a solid-state variable current setup (in this case, hopefully also with signal amplification. If need be, though, I could always just use BJTs)

I apologize if there is something like this already on the forum but I could not think of what I should search for, and my searches turned up nothing.

Thanks in advance,

Trevor


texts: Serial Monitoring of DB25 Parallel Port Data

texts:
I would like to examine the string of data being outputted from an industrial equipment's DB25 connector that is being sent to a printer. I was thinking I need to convert this 25 pin parallel connection to USB type A, which would then be plugged into my PC and then examined using a serial monitor.

My question is what kind of hardware could I use to convert this parallel data to USB?

Do I only need the data 0 - 7 pins and ground pin on the DB25 connector to analyze the data on my PC?

Is there any arduino library out there that could convert this data?

I appreciate any help. This is my first time dealing interfacing a DB25 connector to USB. I've done some research on the parallel communication and seem to have hit a wall.


texts: What sensors are commonly used for vehicle detection?

texts:
I want to make a vehicle detection prototype. I find there are multiple choices of sensors that can be used to detect a vehicle, such as acoustic, ultrasonic, infrared, magnetic inductive sensor.

I am only familiar with infrared sensors, which are low cost, can be a good choice of detection of approaching objects, whereas the acoustic and ultrasonic are much more expensive.

However an infrared sensor is not a complete solution. In order to find whether the approaching object is either a vehicle or any other objects, I suppose I need either a magnetic or an inductive sensor. I learned that scalar magnetometers are suitable for the vehicle detection, because it measure the total strength of the magnetic field to which they are subjected.  However then I learned that magnetic sensors can be also divided into DC and AC sensors.

  in wiki, it says "AC" if they measure fields that vary relatively
  rapidly in time, and "DC" if they measure fields that vary only slowly
  (quasi-static) or are static. AC magnetometers find use in
  electromagnetic systems (such as magnetotellurics), and DC
  magnetometers are used for detecting mineralisation and corresponding
  geological structures.

Can anybody explain the difference between DC and AC based magnetometers? Currently my idea is to use a magnetometer with an infrared sensor. What do you think of this approach? My evaluation criteria is performance first, then power consumption, and cost last.


texts:
In Microelectronic Circuits by Sedra/Smith, the authors perform small-signal analysis on a basic active-loaded MOS differential pair amplifier. In attempting to find the amplifier's short-circuit output current, they reason that it is appropriate to assume that the common source node of the input transistor pair is a virtual ground even though the circuit is not symmetric. They explain that because the drain of Q1 is connected to ground through the low impedance of a diode-connected MOSFET, the drain of Q1 is a low impedance node and therefore must be close to ground potential. This approximation makes the circuit symmetric and greatly simplifies the analysis. Reference pg. 639 for anyone who has the book.

So, the question is: under what circumstances are we able to claim that a low impedance node must measure nearly zero volts?


texts: Li-Po Charging from automotive supply and powering load at 3.6v

texts:
This question is very similar to many other threads, but with some additional constraints.

I require a 2.7v to 3.6v supply derived from an automotive supply (typically 7 to 33v) at maximum of 1 amp. When the external supply is connected it must also correctly charge a single Li-Po cell. When the external power is disconnected, the Li-Po must automatically / transparently take over supplying the load.

The Microchip application note AN1149 for the MCP73837 shows as similar solution, but the output voltage to the load is too high, and the maximum input to the 73837 is only 6v. See http://ww1.microchip.com/downloads/en/appnotes/01149c.pdf

I have a solution which uses an LM2595S-ADJ to pre-regulate the input down to 4.5v, which is fed to the 73837. The output from the 73837 is further regulated down to 3.6v with an LDO regulator. Diodes are used to route the supply current.

Although my existing circuit works ok, it seems crazy to need three ICs, several diodes and a handful of passive components.  Any suggestions as to how to simplify this would be very welcome  Thanks.


texts: Dividing down a VHF signal in a 4046 based PLL loop

texts:
I've decided to build a a PLL based synthesiser to produce the Local Oscillator(LO) signal for my DIY transceiver.  My aim is to try to use commonly available (preferably inexpensive) parts in what is a mainly educational exercise.

I'm a total newcomer to the world of frequency synthesis and PLLs, but what I've read so far suggests I'm looking at a multi-loop configuration (two in this case) to achieve a step size suitable for SSB (around 10Hz) with a fast lock time.

This question is centered on the course tuning loop with a VCO output frequency of 34.5 MHz to 36 MHz (the VCO is a standard double varactor tuned Hartley).  The reference frequency will be 125 KHz (produced from a 4 MHz crystal divided down by 2^5 using a 4060) and the phase detector will be the venerable 4046.

The output frequency is a challenge as it's tantalizingly just out of range of many commonly available divider ICs (the oft quoted 4059 is one example, but its maximum clock is around 30 MHz).  I figured this might be an issue, so I ordered some difficult (but not impossible) to find MB501L dual-modulus prescaler ICs (which have a useful 10MHz lower limit).

I figure I'll need to divide my 34.5MHz output by 276 to get a 125KHz signal for the phase compare, so that's N=4 and A=20, which I'll handle using a microprocessor (the 530KHz odd divided down signal should pose no issues).  I've glossed over a lot of detail here, but the design of the loop itself isn't really the issue.

What I'd really like to know is, are there any commonly available alternatives to dividing down the 34/36 MHz signal?  I know I could simply use a cheap si5351 module and be done with it, but I'm doing this for educational reasons, so I'd like to crawl a little first before I sprint!


texts:
I am trying to make an electronic appliance.
My circuit has 8Nos 5V components and 1Nos 12V component. (2 of them being Arduino Pro Minis).
I have 3 questions regarding this circuit:

Q1: How do I design the power supply for this circuit? I can have only 1 adapter (wall wart) to wall mount this appliance.

===

Edit:

Following is the list of my components:

Arduino Pro Mini 5v/16MHz (Master)
Arduino Pro Mini 5v/16MHz (Slave)
DS3231 RTC
16x2 LCD + I2C
Keyes 040 Rotary Encoder
Relay (5v) - For Solenoid Valve
Relay (5v) - For Flow Sensor
Flow Sensor (5v)
Solenoid Valve (12v)

Q2: Is it wise to mount everything on a single prototype board?

The circuit worked well on bread-board - behaves sporadically when all components are mounted on a proto-board.

 Q3: Connected Question - How do I deal with memory leakage?    Question to be dealt with later - once power supply issue is resolved.

===

Can someone please help me "unhold" this question?


texts:
We are designing an image processing pipeline on an FPGA which will need the use of memory interfaces at various pipeline stages. Because of the size of the memory required we decided to go with a DDR3 design.

It would be really useful if the pipeline stages can access there own memory in an independent manner so that I can minimize arbitration. I was thus hoping to implement multiple "narrow"  DDR3 modules (16 bit wide for instance) each with it's own controller on the FPGA so that the stages' memory interfaces can be completely separate.

My other option is using multiple DDR3 modules in a single rank with one controller.

Does anybody have any experience in using multiple controllers on an FPGA? Or would the single controller be the safer bet?

We will be using a mid range Kintex for the implementation.


texts: In Verilog , if the always@ block is executed sequentially , how do non-blocking statements work since they are executed parallely?

texts:
I am getting totally confused because contradictory things are given.

https://class.ece.uw.edu/371/peckol/doc/Always@.pdf

In this pdf, it is said that whether the 'always block' will be executed sequentially or parallelly will depend on the assignment used. If nonblocking->parallely else sequentially.
But many answers like this

Are Verilog if blocks executed sequentially or concurrently?
Says it is always executed sequentially.
So I have two doubts

Is the 'always' block executed sequentially or parallelly?
If sequentially, how do nonblocking statements execute?


texts: Difference between overload and short-circuit protection

texts: What is the difference between overload and short-circuit protection for motors? I do not understand the need for SC protection when a motor has overload protection. Shouldn't the overload protection trip under SC conditions (and really fast due to the inverse time characteristics)?


texts: What is the theorem behind the basic BJT biasing strategy (divide Vcc into three parts)?

texts:
I have learnt that there are strategies say, $$\frac{1}{3}\cdot V_{CC}=R_C\cdot I_C$$
and
$$\frac{1}{3}\cdot V_{CC}=V_{R2},\frac{1}{3}\cdot V_{CC}=V_{CE}$$
finally, $$10\%\cdot I_E=I_{R1}$$
Ignore $$I_B$$ then, $$10\%\cdot I_E=I_{R1}=I_{R2}$$
Where did all these strategies  come from?

Thank you!


texts: Smooth switching between 12 V batteries, with a toggle switch

texts:
I have a number of instruments (12 volts, drawing a few hundred milliamperes) that occasionally need to be switched between one of two 12 volt lead acid batteries.

The toggle switch is break-before-make, so there's a fraction of a second interruption to the supply that causes a couple of the instruments to re-boot.

The instruments are black-boxes, and I don't know what's in them or how they work.

How can I smooth-out the power drop during the switchover and prevent re-booting? Will a capacitor and resistor in series across the load side of the toggle switch be adequate?

The internal characteristics of the instruments are unknown to me (that's part of the problem), so I don't know what sort of interruption to the supply is acceptable. Also, there are several instruments that may or may not be switched on at the time, which adds to the complexity of the issue, so I'm looking for the simplest most generic solution that doesn't require much sophistication - that's why I was thinking of just a 12 V capacitor and resistor across the switch.


texts:
I have a mysterious component covered with yellow "glue" or something. It has very hard surface, but it seems its been poured into the plastic "cage". The shiny cover on the top is some kind of paper, I can rip it off.

Any idea how to remove this goo from the PCB? (Without damaging the components underneath)


texts:
I have this idea for a project I'm working on but I'm not sure where to start.

The ideia is quite simple: there will be platforms on the ground, and when people step on them a musical note is played. Each platform produces a single note.

I was thinking about using a piezoelectric sensor along with a digital keyboard, but I'm not sure if this is the right path or if there's an easier way to do it.


texts: Why voltage sensors are reading these values

texts:
I've tried to make the following circuit (both physically and simulated):

simulate this circuit – Schematic created using CircuitLab

Not sure if its correct but below is the simulink model (same as physical one):

There is one thing I can't understand, I tried measuring voltage across R1 and R2, I though it would be the same, but instead as shown in simulink, the R2 voltage shows ~4.8V and R1 shows ~4.3V
(on physical model multimeter has shown 5V and ~4.3V

Why would voltage across R1 be less 5V (4.3V) as if I was measuring the voltage drop on base-emitter of Q1?
On physical model the C4881 transistor was used. While on simulink some standard settings were there.


texts:
I've been trying to understand how these safety relays from Weidmuller work. But since I can't find any useful resource on the internet, it has remained unclear for me. Here is the link to data sheet: SIL3 RELAYS

This is the internal diagram:

(Source: Weidmüller)

The datasheet says these relays are used in areas that require functionally safe deactivation or activation. But how?

Are they different from a normal relay?
And why some contacts are connected in parallel and some in series?
And then what are test inputs? (The data sheet says that these inputs are for testing relay contacts, but how?)


texts:
I'm wanting to nicely balance some unbalanced inputs to a power amp for good CMRR, and because I'm feeling too lazy to start trying to closely match pairs of resistors, I'm looking at using a hi-fi balanced line driver IC like this.

I know this can do the job for me, but is it appropriate or overkill?  It's designed to drive balanced outputs of a device, including long cable runs, and this is obviously not needed because I'm using it to buffer / balance the input of a device.

Is there a more appropriate monolithic IC for me? (again, ignoring the obvious op amp solution that requires matched resistors)


texts: STM32 'Connect under reset' suddenly stopped working

texts:
For the last few months I've been working on a project that used an STM32F030 microcontroller. Due to a shortage of GPIO I've had to use the SW debug pins for other functions. Until recently this wasn't a problem, since I just made sure to hook up the reset line from the ST-linkV2 and set it up as 'connect under reset'.

In the last few days I've been unable to reprogram the board though, all of a sudden it just started saying 'no target detected' any time I try to program it from Keil uVision.

I thought at first it may just be the ST-link that was playing up, so I tried a couple of others with no avail. Similar situation with multiple other target boards. Then I thought maybe something I had done accidentally in software, but nothing should really stop it from resetting itself and being able to program..?

The only way I've found I can reprogram them is if I pull the Boot0 line high, then power the uC up, and proceed to program. This is a total pain though since it means retrofitting every board I have with a boot0-high jumper.

Does anyone know what's going on here that might be stopping my programming this system the way I always have in the past?


texts: Low pass filter on PSU and target amplifier

texts:
we are designing a LLC resonator PSU to feed a class D amp

The switching frequency of the LLC PSU is 80-140Khz. At the end of the PSU we are thinking to add a LPF ( PI filter ) with a cutoff frequency of 50Khz

This AMP board will be fed by 2 PSU...one as discussed above second we want any laptop brick to be able to feed it (usually sw frequency of those laptop bricks are 500Khz to 1.2Mhz) so we are thinking to add a second LPF (LC) with cutoff frequency of 400Khz

Can we have a second LPF (LC) on the AMP ? In case of using the LLC resonator there will be 2 filters..one on the PSU PCB (cutoff frequency at 50Khz) and second on the AMP PCB , cutoff frequency at 400Khz
In case that we power the AMP PCB using a laptop brick , there will only be 1 filter (400Khz cutoff) should we use a LC or PI filter ?


texts: Identifying motor type and guidance on how to build controller

texts:
Currently trying to fix my old coffee grinder. The PCB is pretty useless so i have to build new controller myself. However, my googling has come to a halt as i first need to identify what motor i have. There little to no documentation on the product so i figured id ask some experts..
Please see the attached picture
The sticker attached to the motor has some details, but what motor type these are properties of i have no clue..
If you have any idea of what type this might be, please do tell me how you were able to tell!

Thanks!
Edit:
Per comment, here are some more picture hopefully showing required details:

More information from comments:
Problem with old pcb is that it was programmed to trigger a small relay at a fixed interval. Essentially switching the motor on and off about once every second. I need it to run continuously.. Please see my updated post with new pictures. I imaging i could bypass the relay entirely, but what points to connect where i'm not too sure of.
The grinder is of the "automatic type", meaning that its programmed to cycle on after x amounts of portions have been dispersed. This was a primitive and effective system with switches attached to the dispersing system. All of this has been removed, but the programming remains. As i can no longer "toggle" the switch i simply want the grinder to turn on when the power switch is flicked. Simple as that. Would i be able to jump what i assume is a relay? As noted, the one second interval is way too short for what these are rated for(i presume). Could this be signs of a faulty capacitor?


texts:
I salvaged a motorized pot from a stereo receiver which I want to use between a CD player and a power amplifier (both devices sit on the same shelf at my workplace). Currently, the line out jacks feed a volume pot through 30+ feet of (cheap) cable, and then another 30+ foot run back to the amp. Nobody at work thinks there is anything wrong with the sound (except for the ground hum), but I was nonetheless able to convince my boss to let me "have at" the sound system.

I like the motorized pot idea because the audio cables will be very short, and noisy environments shouldn't be a problem when driving the motor remotely over long cables (plus multiple control points are possible).

My question concerns the pot's value which is 50k, versus what the vast majority of the audio circuits I've found use, which is 10k. In How do I determine if I can safely substitute potentiometers?, general guidelines are given and I seem to meet them all. All except for: try to stay within a factor of 2 (or 1/2) from the ideal. But this doesn't satisfy; I'm after a more definite answer for my specific application. Then, in What potentiometer should I choose?, I was dismayed to read, "As a rule of thumb, for audio, pots generally range from a resistance of about 10K to around 1 megohm." (I thought we were talking 10k to 50k?)

Since I've found 10k to be the "consensus" value, and 50k to be the "exception" value, it seems reasonable (to me) to make this post. So I ask, "What's the deal with the 10k and the 50k audio pots?" I guess my question comes down to one of degree: how much difference will this make, and in what circumstances? Sound quality is my top priority. If there is a trade-off, I don't want to give up more than 2% to 5%.


texts: Proteus doesn't show the value of float variables and does not attribute values to them

texts:
I have an issue with Proteus Isis.

The image below illustrates the problem. I can't see the values of a struct's fields and I think that Proteus can't see the struct too.

Full Resolution

Anyone know how to deal with this?


texts: Understanding the effect of bit depth and sampling rate on SNR

texts:
I know the meaning of a 16 bit ADC sampling at 1kHz, but I cannot relate it to SNR contribution to the signal. I also know the concept of aliasing. But even though no aliasing the resolution and the sampling rate of the ADC matters when it comes to SNR.

Is there a way to comprhend how these two relate to SNR with an example? How/why does the bit depth and sampling rate contributes to SNR? Maybe bit depth can make sense because ACD cannot resolve more than causing quantization error.

Most importantly why SNR is increasing with increasing the sampling rate even beyond the Nyquist freq.?


texts:
I have a pair of ATH-M50 headphones where the right side has stopped working. I took them apart and measured the resistance at the L/R terminals on each driver. The good one measures about 35 ohms whereas the bad one is around 200 ohms. Another set of good ATH-M50 measures 35 ohms on both drivers.

Does this make sense for a blown driver? This guy's bad driver showed an open circuit.


texts: I have heard of using the ground for communication with extremely low frequency waves. They said 100 watts gives you a km and 1000 watts gives you 10 km. How can I go about pumping the waves into the ground, and what would be a good frequency to operate?


texts: The error "requires SystemVerilog extensions" while declaring an error

texts:
What's wrong with the following code? The array "FIFO" is declared correctly, but an error appears. Can you please help how to fix this?

module fifo(
    input clk,
    input [7:0]data_in ,
    output reg [7:0] FIFO [0:8]
);

integer i;
always@(posedge clk) begin
       for(i = 8; i > 0; i=i-1) begin
          FIFO[i] <= FIFO[i-1];
       end
       FIFO[0] <= data_in;
end
endmodule

Error (10773): Verilog HDL error at fifo.v(29): declaring module ports or function arguments with unpacked array types requires SystemVerilog extensions


texts: what does the reverse voltage rating on an optoisolator mean?

texts:
i am using a 4n25 for a high voltage detection circuit. it has a maximum reverse voltage of 5V. does this mean that the LED inside it can only take in a maximum of 5V in the reverse direction before burning out?
in the below picture, i am using the high output (10.5V) from the TL072 to trigger a low output from the 4n25. a low output from the tl072 will ground the led inside the 4n25 and trigger a high output. whereas, the high output from the 4n25 will not ground it and thus the led will be off and the 4n25 output low.
but this creates a negative voltage of 0.51 across the led. does this mean this negative voltage is safe as long as it is not above the max reverse voltage of the 4n25 which is 5v?
should i put a diode somewhere for more safety?


texts: Observe if terminals on a PCB became connected. Know nothing about the PCB, except it is powered with the same power supply transformer

texts:
I have a PCB with terminals I have access to, otherwise it's an unknown. I want to observe with my microcontroller (uC) if they become (dis)connected.

The PCB is powered by a 24 VAC transformer, the same powers my uC. I have build a rectifier for my uC, so they have different ones.

On the PCB's terminals, I measure 34 V when open.

There is also another kind of terminals, command terminals, those I can control (make them connect) with my uC. I plan to use an optocoupler for that.

But for observing the terminals, I cannot use an optocoupler, as surely it's not possible to drive a diode with them, right? EDIT: I measured 3.85 mA when shorted the terminals.

I could use a transistor, but then I would have to have a common ground between the PCB and my uC.

I believe there are two possible situations: 1) the rectifiers are in sync (I could connect the terminal I observe \$\text{0 V}\$ relative to my uC ground, or will I even observe that?), or 2) they are shifted in phase by \$\pi\$, so I would just switch the wires that lead to my rectifier.

Is it safe to connect uC ground with a terminal, if by multimeter I measure 0 V? I don't know if there are resistors or other components on the PCB in the way and if that even would be a problem.

If this common ground method isn't safe (and it'd better be, I cannot destroy the PCB, not cheap), is there another way to observe the (dis)connected state of terminals? (A mosfet operating a battery driven optocoupler, in case connecting a battery lead to a terminal is safer.)

Additional information (may not be relevant):

The terminals to observe are normally closed

Description for the image:

\$\text{COM60, IC 1, IC 2}\$ are command terminals, \$\text{COM60}\$ is common for the others, if \$\text{IC 1}\$ or \$\text{IC 2}\$ become connected with \$\text{COM60}\$, a command is issued to the PCB. These I plan to control with an optocoupler.

\$\text{COM70, SAFE1}\$ are the terminals I want to observe if they become (dis)connected. Actually there's a third device that taps into those terminals (probably a photoresistor), but it has to be connected to the PCB the way it is.

Between the common and the others, in open state, I measure 34 V (common being positive).


texts:
I want to step up my power supply from 3.3V to 5V.
For this I choose the MAX756 for his price and his availability.
But I don't understand the pinouts...

Pin 1 : I can leave it on fly ;
Pin 2 : To ground ;
Pin 3 : to GND with 0.1µF capacitor ;
Pin 4 : On fly ?? ;
Pin 5 : Connect to Vin so directly to my 3.3 input voltage ? ;
Pin 6 : My output voltage ?? ;
Pin 7 : Ground ;
Pin 8 : ??? ;

There is also this schematic that I don't really understand too...

Here you can find the datasheet : MAX756-MAX757.pdf

Thanks!

EDIT

Okay, so thanks to your help I have this now:

It should be okay.

I have doubts about the capacitor (C2), do I still need a 100uF capacitor tied to the ground just after my schottky diode (on pin8:LX)? Same question about the capacitor of 150uF tied to the ground between Vin and pin5:LBI ?

Otherwise everything seems okay to me can you confirm ? Huge thanks to you guys !

EDIT2

Here my final schematic:

I think everything is okay now !


texts: I need a + and - 200vdc (common ground) at 100ma max power supply. Regulation of 2% is fine. Input is 120vac. I know how to build a bridge supply but I haven't found a transformer cheap enough. They are all > $50. I'm not asking anyone to do my work. Just wondering if anyone here has already done this. It will be used to power a 24vdc supply used in a UPS system for testing. Won't be on for much longer than 30 seconds. Cost of $20-$30 for parts would be cool.


texts:
I find my self using a function which returns the number of bits necessary to represent an integer value a lot in my designs.

I define this function in each of my modules:

function int_width(value: integer) return integer is
begin
    return integer(floor(log2(real(value))));
end function;

Example use:

entity vga_sync is
    generic(
        TOTAL_WIDTH: integer := 800;
        TOTAL_HEIGHT: integer := 525;
        -- [...]
    port(
    -- [...]
    );
end vga_sync;

architecture arch of vga_sync is
    signal horizontal_counter: unsigned(int_width(TOTAL_WIDTH) downto 0);
    signal vertical_counter: unsigned(int_width(TOTAL_HEIGHT) downto 0);
    -- [...]
end arch;

It seems to be a common issue to me. Is there a standard function in VHDL to do this ?
Should I always use a large enough (ie, always 32 bits) unsigned is these cases ?


texts: Altera Quartus "Warning (18236): Number of processors has not been specified...", how to suppress?

texts:
My Altera Quartus builds show this warning...

Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.

How do I suppress this warning?


texts: Why is the three-phase voltage 440V, if single-phase alone is 230V?


texts: I'm looking for a smallest design of a frequency counter time base uses a crystal with lower frequency that can give rates of 1Hz, 10Hz, 100Hz after dividing, I intend to use it in RF circuit, the reason for a lower frequency crystal is trying to avoid interference in the RF circuit, for example can the 32.768khz crystal, is it a better choice for the time base ? if not any other suggestions with help of a better design diagram ? I would appreciate it, thanks


texts: I'm trying to build the circuit shown below. This is a VCA, application taken from Nuts & Volts magazine I think (don't have the article). I know very little about OTAs in general but from what I could understand the limits of the control voltage are the supply voltages so the max control current is about 0.4mA. How can calculate the output from that given the circuit below and given a known input voltage? Also, would it be possible to supply control current via a lower voltage and smaller resistor?


texts: What's with the minimum voltage rating on *some* IEC 60947-2 MCBs?

texts:
It seems that some, albeit not all, miniature circuit breakers have a minimum voltage rating under the IEC 60947-2 scheme (often 12VAC/DC).  For instance, see the Sprecher/Schuh L8 series (PDF page 8) as compared to, say, a Schneider Electric Multi9 C60SP which has no documented minimum voltage rating under IEC 60947-2 (I'm using the C60SP here as it's UL1077/IEC, like the Sprecher/Schuh L8, but the C60BP UL489/IEC breaker lacks a minimum voltage rating as well.)

Why is this? Is this a limitation of testing, or of certain breaker designs compared to others, or of the external environs?


texts:
I do not understand the following memory map regarding the NVIC registers in Programming Manual for STM32f103 page 129. It says that the offset address for NVIC_IPR0 is 0x300 and that of NVIC_IPR20 is 0x320. I do not understand how is this possible?! I think that the offset for NVIC_IPR20 should be 0x350. Indeed, assuming the registers follow one after another one obtains something like this:

NVIC_IPR0 -> 0x300

NVIC_IPR1 -> 0x304

NVIC_IPR2 -> 0x308

etc.

NVIC_IPR20 -> 0x350

What am I doing wrong?


texts: Driving an opto isolator where ground can swing between 30V and 0V

texts:
I have a motor controller that outputs a fault by pulling down its I/O pin (PIN 10). It will also go into fault if you external pull the pin down too.
The MC has two configurable pullups:
A: The output pin is pulled high by a 100K resistor @ 30V.
B: The output pin is pulled high by a 1K resistor @ 6V.
I require an isolated method of monitoring this voltage, my solution is to use an optoisolated that is supplied by the motor controllers 5V output via a 510R resistor.
When the motor controller goes into fault, it will pull down to the ground and turn on the opto.
A diode prevents backfeeding of the 6V (B)/ 30V (A) into the motor controllers 5V rail.
I have tested this and it is working, but is there any negatives, or better solutions?


texts:
Consider a simple common emitter amplifier

Here I will set r1 = r2. Now I think this is what you call a class A amplifier,  with the base voltage being half of vcc . I have a feeling this is not a good idea as it cannot be this simple.

The idea is that if I keep the base voltage at half of vcc, the voltage source will be able to pull half way and push  half way if it ever needs to.


texts: Is putting a board inside an anti-static enclosure enough to make it Ex ib ready?

texts:
A year ago, we made a handheld PDA based on RPi0 for a client. Now they have asked us to certificate it as Ex ib IIC T4.
Here is the PDA's spec:

RPi0 as processing board
4.3" capcitive LCD
A 3500 mAh LiPo battery
Our own custum-made battery charging board based on TI's BQ24160 IC.
An 13.56 MHz RFID module.

We reached a certificate body and this is the test list they have asked our device to pass:

So, my question is, if we build a compeletly non-metallic anti-static enclosure without any protruding or conductive parts (according to thermal/impact criteria), does the device pass the tests? In other words, should I change the RPi0 board because of conductive/inductive curves?


texts: Correct way to control 12V relay from a Raspberry Pi

texts:
I am working on a project where I need to control a couple of relays from the GPIO header on a Raspberry Pi. I tried getting a PCB with the layout like the right version in the image below, but I cannot switch the relay by setting the GPIO pin high/low.

After some more studying I came up with version 2, which is the left version, using an NPN instead of a PNP transistor - is it correctly understood that it looks more correct than the first version?

VCC is 12v and H1PXX is the GPIO pins which are 3.3v. P1/P2 are used to determine what to switch and are not relevant for this

Can I somehow make the right version work? I already have the printed circuit boards, so if it is just a matter of soldering on a wire/resistor somewhere I could do that without too much of a problem.

The board has a 5V regulator for the Raspberry Pi, so GND on the circuit is shared with the Raspberry Pi


texts: Using Constant Current Power Supply to control Load Output of a Grid-Tie Inverter

texts:
tldr: How do I adjust the power being dumped by my grid tie inverter? Is it possible to use a constant-current power supply to do so?

I am planning create a PV system that will help reduce my electric bill. However, here in my place, net metering is not really a thing which means that there's no use injecting power back into the grid. I was planning however to monitor my power consumption to closely match it and let the grid tie inverter output the power that I am using. For example, if my house is using 300w, I will adjust my 1000w grid tie inverter to output 280~300w of power. However, if I see that the house is using 1500w (for example, a water heater running), I will just let the grid tie inverter output 1000w and get the extra 500w from the grid.

I was originally thinking of connecting the batteries directly to the grid-tie inverter and use some kind of DIY solution to increase-reduce the voltage but based on my research, I don't think the inverter would like it, as they are usually designed to be connected directly to a constant-current power supply i.e. solar panels. Is this true? Will I be forced to use a constant current power supply (that has to deliver up to 1000w of power)? Or am I missing something here?


texts:
What does com mean on a circuit diagram (source)?

What are com 1 and com 2 representing?


texts:
Here’s my issue. I would like to turn bright starlight into voltage. Here’s what I have done.as you can see I have placed a photodiode in a telescope eyepiece tube. I have it below the lens because this is where prime focus is, the place where the scope’s light comes to a point. Here it is on the scope My problem Is that I am not able to generate voltage. The diode I am using is this one.

The scope is an 8 inch f-10. Would a zero bias diode be better than a reverse bias. If your suggestion involves a diode with more than three pins please advise how wire.


texts: L293D driver module taking current from USB

texts:
I bought an L293D driver shield for Arduino.
Upon trying to run my 2 stepper motors I found them struggling to run, voltage drops and all.
I replaced my 1.2A 12V adapter with my 7.2V LiPo battery, the motors seem to be working. The problem is when trying to run the motors from 1.2A adapters, my Arduino stopped working on that USB port.  It works on another port, also the port works fine with other components.
Later I got this warning on my laptop:

I assume the laptop blacklisted the Arduino.
Why would the driver module use current from the laptop USB even though I had removed the jumper from driver.  Does this mean that the L293D could use current from the laptop USB and isn't safe to use?
Is that the module's default behaviour or is mine broken? I read on the internet that it is also a very old module and I shouldn't be using it - but then why is it so popular?


texts: How is quality/damage control done in large circuits?

texts:
There is apparently more than 28 billion transistors in the recently released Nvidia GeForce RTX 3080.
First, when you manufacture such a circuit there must be a decent chance of botching some of these. How do the plants make sure that they all work?
Second, after prolonged usage surely at least one of these transistors must fail. Does the circuit somehow recognize this and redirect the workflow?


texts: Will this circuit work? AND Gate behaving strange?

texts:
I've just built a circuit using Yenka, and it's meant to be a system that basically senses light, and whether a switch is on or not, and when both of these are true, the buzzer will, buzz.

I'm quite bad at electronics in general, but I'm trying to get the following to work (ref. Circuit diagram)

What it's trying to do is basically (in code-like-terms):

IF(LDR SENSES LIGHT && SPST SWITCH TOGGLED) { BUZZER ON }
ELSE { BUZZER OFF }

From my low-level understanding of electronics, I think there might be a need for a transistor just before the buzzer to push up the voltage, and possibly more resistance on the AND gate, because this diagram made in Yenka keeps 'blowing up'.

Basically what I think it's going to do: LDR senses light, compares this output resisted voltage against baseline voltage with op-amp, resists the output value if true, send to AND gate. AND gate checks whether op-amp is true, and whether switch is true, if they are both true, activate buzzer.

Will this circuit work? And if not, what's wrong with it? :S


texts:
A 12V battery monitor circuit is available on this page.

What can be done to modify that circuit to alarm when voltage goes below 15V ?

http://www.eleccircuit.com/low-voltage-battery-monitor-by-lm339/


texts: Is the intensity of light shone onto a solar panel proportional to its power output?

texts:
Is there a linear relationship between the two?

I ask because I'm investigating the effect of a different variable on the power output of a solar panel, and intensity is meant to be one of my control variables.

However due to insufficient apparatus I could not control the intensity of light.

For example, say I wanted to control the intensity at 40 lx. However in one of my tests the intensity of light was 120 lx. If I were to divide its power output by 3, would I get the (approximately) same value as I would if the intensity were truly 40 lx?

If any clarification is needed let me know. Thanks in advance.


texts: Running a Peltier directly from a transistor

texts:
New to post, but I come here often. So I am working on building a small fermentation chamber and i want to control the temperature using two Peltier's. One for hot and one for cold.  I'm using two to help prevent thermal shock, and also use the way temperature works with heat rising and cold falling.

I have read a fair bit from this forum and others, but I can't find the answer to my basic questions.

Can I use a transistor as a switch to turn on and off a Peltier without any real problems?

I've seen a few posts about using a h-bridge ,or a variety of tec controllers. But none of the posts go into good detail, and I'm not that good on programming.

My basic design is to use an Arduino connected to a temperature sensor and the two Peltier's connected to the transistors and the power supply. Add a bunch of fans to circulate air, and program it turn hot on below x point and cold on above y point.

If there is a post that does answer my question sorry for the double post. But any help is appreciated. If you have questions about my project please feel free to ask. Thanks for the help.

EDIT: I am on working on the theory right now. I have not committed to any parts yet. I have been looking at easily available Peltier's usually running on 12V and varying amps. Everything else was gonna be commonly available parts.

My end goal is to have a controllable fermentation chamber, with commonly available parts, that's easy and cheap enough others to build. Most of the things I've seen are lacking information, or have too much complexity.


texts:
My Breville oven display shows some missing characters and some dimmed characters, after 2 crosstown moves. I have  disassembled other devices in the past, but those were repairs for other people.
I can still use the oven now. I am worried that on this display I might make it worse, then I can't use it at all.
On the other hand, I could do a regular routine fix.
Can I clean the mating surfaces with alcohol? Is there a reason the strips are acting up?


texts: Measuring positive and negative voltages using ADC

texts:
I came across the simple solution for the said problem posted by Transistor (Transistor (https://electronics.stackexchange.com/users/73158/transistor), circuit for measure positive & negative voltage + Vref resolution, URL (version: 2018-06-05): https://electronics.stackexchange.com/q/378320) but when I implemented it, I got some unexpected results. It measures pos and neg voltages very well, however I'm using it in an electrochemical setup measuring the potential between the anode and the cathode and sometimes the polarity swaps (hence my desire to measure pos and neg voltages). The open circuit voltage is constant, and I'm measuring that constant voltage with a logger (Arduino) however when I use the voltage divider set up the OCV is no longer constant and the voltage changes as if the anode and cathode are shortened with a particular resistance between them.
Can anyone explain to me what is happening?
The voltages are small between 0 - 1V. The R1 and R2 I'm using are 1K Ohm.
The output impedance is about 14.8kOhm. It changed from about 3.3KOhm but settled on 14.8kOhm after some time.
See enclosed the schematic.


texts: Power consumption of Nucleo L432KC board

texts:
I'm currently developing an IoT LoRa node using a Nucleo L432KC.
I want the node to be alive more than a year, so I want to test its energy consumption very carefully.

I intended to cut off any unnecessary devices on the Nucleo board, starting with:

R22 to cut-off LD2 LED (power supply)
D2 to cut-off +3V3_ST_LINK, so the ST-LINK is not supposed to be powered

I power supply the board through Vin (9V).

I did some tests and the whole board is consuming 19 mA when running (idle) and 6 mA in stand-by mode. I don’t understand where those 6 mA are coming from.
The STM32L432KC is consuming few uA so it’s not up to the microcontroller (tested with an amperemeter on JP1).

However, the 3V3_ST_LINK voltage which is supposed to be 0V is at 0.85V when the L432 is in sleep mode and 2.65V when it’s running. I don’t know what the origin of this voltage is and I don’t know either where the 6 mA are coming from.

Any idea? :)

Thank you!
You can be my hero of the day, maybe of the week!

NB: sch of the board page 29-31 of this doc => http://www.st.com/content/ccc/resource/technical/document/user_manual/e3/0e/88/05/e8/74/43/a0/DM00231744.pdf/files/DM00231744.pdf/jcr:content/translations/en.DM00231744.pdf


texts:
I'm working on a SIM908 module using GPIO mode (my rx pin contact is lost when soldering).
I have interfaced it with a PIC16F73 and while using GPIO mode I'm not getting any response. I have included an LCD to print the response. Is there any AT command or pins I should enable on SIM908 to activate GPIO mode or is it because there should be a delay between writing and reading on the ports?

I have included the code:

   char x[20], y[20];
   TRISB = 0x00;
   PORTB = 'A';
   PORTB = 'T';
   PORTB = '\r';
   TRISB = 0xff;
   x[0] =  PORTB;

   LCD_Print_String(2,1,x[0]);

    if (x[0] == 'O')
    {
        LCD_Print_String(1,1,"done");
    }
    else if(x[0] == 'E')
    {
        LCD_Print_String(1,1,"error");
    }

    while(1);

sim908 datasheet:http://www.synes.co.th/nicupload/20111109110456.pdf


texts:
I bought 2 center tapped transformers because I need to make 30V 2A center tapped transformer equivalent and I couldn't find anything with a 120V input.

So I got a 18V 2A center tapped transformer and a 12V 2A center tapped transformer.

18V, 2A Center Tapped (9-0-9) Transformer
12V, 2A Center Tapped (6-0-6) Transformer

How can I connect the secondary together so I get a 30V 2A center tapped transformer equivalent?


texts:
I found this truth table for a 4-to-1 MUX:

(circuit for context)

I know (I think?) that if I were to make a truth table with 2^6 variables and simplified it I'd get the same SOP as I'd get with this one. My question, how was the big truth table simplified with don't-cares to become like the one in the example? What was the thinking behind it?


texts: fast Fourier Transform difference with discrete Fourier Transform

texts:
I'm a french student in engineering and I'm given a kind of mandatory technical project to work out on until February.

I must investigate the following article: Precise and fast spatial-frequency analysis using the iterative local Fourier transform and implement the same kind of iterative algorithm on MATLAB.

Actually I'm not good at signal processing either that much, only have the basics, however I don't understand why they say "the inherent frequency interval limit (of fFT) can be overcome using discrete Fourier transform". In my opinion that is non-sense because fFT is basically just the same as dFT, you just have to sum the sampled values an other way with their odd and even indexes. Therefore I don't really understand what do they apply dFT for...

If someone could help me please he would be more than welcome !

Thank you


texts: Can someone please go over my Arduino design?

texts: I've decided to design a custom Arduino in order to learn about EAGLE and electronic design. I referenced Arduino schematics off of various sites so I think my design is good, but I'd appreciate some feedback before I go onto PCB layout.


texts: I bought my cat a robot dog for Xmas. He loves it! I currently have taken it apart to clean some accumulated hair out from around some of the rotating parts. It plays music that is kind of loud and shrill and annoying. If I removed the speaker from the circuit, would I need to replace it with a diode to produce a voltage drop similar to the induction of the speaker? Does the voltage drop of a speaker change with the amount of sound being produced. Do speakers produce a voltage drop when they are idle? Am I just speaking a bunch of gibberish due to my lack of knowledge on the subject? Do I need to provide more information in order for my questions to be answered?


texts: What are the most reliable pins for stepper driver (Enable Step Dir) for ESP32?

texts:
Uploading code to ESP32 cause noise on motor pins with undesired motor movement until upload started, Probably due Z state of pins. Some capacitor on ESP32 EN pin or pressing button on the ESP32 board made this period faster.
Is there any good pins or must I solder some external pull-up or pull-downs?
I use motor shields with ESP32 @ DOIT devkit v1. I did not got this problem on arduino avr boards with mega328*.
Pins GPIO 36-39 are INPUT only , also both RX TX 0 and 2 are bad.


texts: Detecting hardware watchdog reboot on bootup

texts:
The CPU on my embedded linux system (Armada 370) does have a hardware watchdog.  It does not appear to have any way of checking at bootup time whether the bootup is a normal cold boot or a reset from a watchdog timeout (does not have a reset cause register).

Given this limitation, can anyone think of how I can determine if a hw watchdog timeout event occurred?


texts: How to make affordable DIY low-res absolute rotatory optical encoders with fibers?

texts:
I have zero knowledge of optics and want to make a very low resolution (~10°) absolute rotary optical encoder using rapid manufacturing (I have 3D printers, laser cutter, and desktop CNC). Digging the internet I realized that one can use some sort of code-disk with some slots in an angular/concentric pattern [Fig.1], and putting a light source and sensor on both sides of the disk to count the number of steps. This is called an incremental encoder.

    Fig.1 - Simple relative encoder measuring only the steps with no sens of direction.
                    (image courtesy of [Hydraulics&Pneumatics][1])

Now if you want to have a sense of direction you may have two tracks of slot patterns (e.g. at different radii) or have a mask in front of the disk, plus two sets of light source and sensor [Fig.2].

                 Fig.2 - A relative encoder with the sense of direction.
                           (image courtesy of J.P. Trevelyan [2])

For example, as shown in [Table.1] if the current state is [00] and the following state is [10] we are in CW direction (or vice-versa).

                           |    |  00 |  10 |  11 |  01 |
                           |:--:|:---:|:---:|:---:|:---:|
                           | 00 |  -- | CCW |  -- |  CW |
                           | 10 |  CW |  -- | CCW |  -- |
                           | 11 |  -- |  CW |  -- | CCW |
                           | 01 | CCW |  -- |  CW |  -- |

     Table. 1 - Columns are the current state and the rows are the subsequent state.

This is called an incremental quadrature encoder.

Now I have some issues:

I don't want to have the light source and sensor in the encoder but to use optical fibers to transfer light to and from the encoder to my electronics. The reason is that I can not have any electronics in the nevironment I want to use the necoder. However, I'm being told that if there is an air gap between two ends of optical fibers, a lot of light will be lost. I want to know what is the limit? does it depend on the sensor or source or the quality of the fibers?
I do not understand how absolute encoders work. Do they also follow the same rationale of a disk-mask plus light sources-sensors? Is their design simple enough to be built DIY?
What light source and sensor should I use to emit light into the fibers and read it back? is there some sort of off-the-shelf sensor and source connected to fibers already available which I can plug into an Arduino for example?

Sorry for my novice questions I but I would appreciate if you could help me through. Thanks in advance.

Refrences:

[1]: https://www.hydraulicspneumatics.com/200/FPE/Sensors/Article/False/6440/FPE-Sensors

[2]: https://www.researchgate.net/publication/228362381_Mechatronics_Control_Devices


texts:
In 8085 whatever address the stack pointer holds, we always start storing bytes from one less than this address .
Eg. If SP holds 2008H. We will store 16-bit data at 2007 and 2006H.
Why don't we store at 2008H itself?
Aren't we wasting a memory location .
Is there any specific reason behind this design ?


texts: Wiring up ATX PSU to power (several) 12V LED strips

texts:
(In advance, please pardon my ignorance; I'm still learning)

TL;RD. I want to power N number of 12V LED strips using a PC ATX PSU.
Is it safe & what bits do I need to add to make it function as intended?

Some context:
I'm basing my work on 2 pretty decent articles on the subject:

https://www.makeuseof.com/tag/connect-led-light-strips-arduino/
https://learn.adafruit.com/rgb-led-strips?view=all

What I hope to achieve is to control an arbitrary amount of 12V (common anode) LED strips, & from what I can tell they seem to be in the region of 14.4W per metre (x 5m = 72W), based on LT12560-RGB 12V, 60 LEDs @ 4.8 or 14.4 W/mètre x 5 mètre = 24 or 72 Watts and 300 LEDs, although in the end I'll be going with cheaper units as I need to run close to 16 of these 5 mètre strips concurrently.

I bought some Arduino-friendly MOSFET boards (duinotech XC-4488) to do some prototyping before risking frying larger devices (such as the Mega I bought for this project), then some manual bread boarding using NMOS for PoC & testing, but soldering & running 48+ MOSFET is cost-prohibitive & there's probably a better way of achieving this outcome by using an IC, thinking 3x MAX6971.
Effectively I'm making use of them as glorified relays attached to PWM pins.

I've sketched it out via Fritzing & went as far as running a simulation via TinkerCAD (although due to limitations I couldn't recreate it 1:1).

https://www.tinkercad.com/things/kN1ScLYQq0j-matariki-lights/editel?sharecode=5q0MPWD_CtxPdoZchDBTG-QbR4Et-id8wHuahMLpFvI=

& the final build looks like: (keeping it simple, since relevant resistors are build into the MOSFET boards from what I can tell)

I did some basic tests before firing up & it seemed to have checked out OK, but I was VERY much mistaken, since once I plugged into the ATX PSU, it wasn't long before I got the LOUD POP, flash, magic smoke, funky smell of ozone & the lights went out in the house.
So I'm unsure if it was my ATX PSU that's faulty, but it seems far more likely that I screwed up somewhere.

Needless to say I'm very reticent to pop another ATX, and worry that my invention may be a danger to myself & others.
Luckily I wasn't running my Arduino from the same PSU via Vin (is that legit?)

I'd really appreciate some help here, as I suspect I'm not officially out of my depth.


texts: PIC32 How do I find group number for peripheral

texts:
From my last question I made a mistake on thinking SCK was under PPS control.  I see that now but I still don't understand how to figure out group number for a function with PPS by reading the datasheet.

Let's say I want to bring out MOSI, or I think that's SDO2 in PIC land.   On my board it's connected to Pin 22, SDO2_RPB11.  And I'm still using a PIC32MX210F016B.

Using their macro:  PPSOutput(2, RPA1, SDO1);

I have to specify a group as the first input, then pin, then function.  For some reason I'm not seeing where the datasheet specifies what group to use.

I'm guessing by reading the pps.h header that it's something like this:

PPSOutput(2, RPB11, SDO2);

I'm not sure though that does compile.


texts:
If I have the following circuit and I apply the KCL to the red surface, the algebric sum of the currents in the surface should equals zero.
So ix=-4A. Why isn't that right?


texts:
I have a portable nebulizer that can be powered by either an external power supply with a round plug or two x AA batteries.  On my last nebulizer AA only lasted 12-15 minutes and AA rechargeable about the same.

Would it be possible to safely use a power bank to operate (not charge) the nebulizer?  The neb operates on DC 3v and most power banks I've seen are 5v.  Or any other suggestions on battery operation with longer life?

Found more power info.
Power consumption: 2.0W
Power configuration: DC5V/1000mA
USB power adapter cable or 2*1.5V (2 AA alkaline No. 5, product does not contain battery
cable has USB A on one side and pin on other. See attached image.


texts: How do I edit part SchLib file from SchDoc file in Altium?

texts: Right now my only method to edit library files invovles searching in the Windows file explorer.  There has to be a better way to edit the part directly through Altium.


texts: Why do digital controllers need A/D and D/A converters?

texts:
One of the questions in our final exam will be "Explain the need of A/D and D/A converters in digital controllers".

I could not find the reason anywhere why the Plant part of a block diagram requires a continuous signal. Isn't it supposed to receive a digital signal and output a digital signal? What inside process needs an analogue signal and why? This lack of understanding is probably because I do not understand what Plant is for at all.

I also do not understand why A/D converter is not immediately after the Plant block, but only when it returns back to the start of the block diagram. Isn't a digital controller supposed to output a discrete signal?

Here is a general block diagram of a digital control system [1]:


texts:
I'm looking to control an automotive relay over a cat 5e cable. The run is about 1500 feet. Would there be a way to set up some capacitor resistor coupling at the end to give the relay the initial boost in amps for it to charge or could I do something complete different.

The set up is, 800 feet of run into the woods to a tank where 4 float contact switches are inside. There's also an LED light that uses one pair which isn't a problem ( it flashes when another tank, which isn't in the woods, is full). Of the 4 floats, they use a pair for the power and then individual wires for the signal line out from the float.

The relay I currently am using is a solid state coil and of course it won't energize. However, the pairs still have continuity.  Although the relay is 12v, would only having 10.8 volts not make it trip?

Considering I'm using cat 5e, could it be possible to set up some form of networking switch or a raspberry pi..

Anything..as long as I can monitor the level of the tank from the Sugar Shack. Hopefully I can use the cat5e.


texts:
As I understand it, a non-contact voltage tester works by creating a capacitive connection from a power line to ground, via the detection circuit and the operator's hand/body. This connection passes a tiny amount of current which the detection circuit can pick up.

I'd like to use my Arduino to detect the presence of mains voltage (120v) in a wire without actually connecting to the conductor (for safety and isolation reasons). Because there may not be any current in the wire, current transformers/hall effect sensors would not work.

Is it possible to use a similar approach to the non-contact voltage testers to detect the voltage? I couldn't find any schematics online for commercial testers to see and understand how they work.


texts: How to calculate the safe AC frequency at high Voltages?

texts:
If someone wanted to build some kind of machine which produces HUGE and completely safe electric arcs, how would you calculate the frequency of the AC current in relation to Volt to make it safe?
Why is it extremely dangerous to produce arcs in high voltages in DC (assuming the electricity flows through your body) but also relatively safe if it is done with AC (assuming you have adjusted the frequency of the circuit to make it safe)? I am very sorry if this question is a duplicate, but I couldn't find anything in the internet.


texts: What does 'isolation' mean in a radar antenna system spec text? How to measure it?

texts: It says "85 dB minimum at 18 inch centerline-to-centerline over the OFR". What does it mean? How do I measure that isolation value? in this Text


texts: Bandwidth of CW modulation (morse code)?

texts:
How can I relate the bandwidth required by a morse code signal over RF to:

the length of a dash, and the length of a dot
the time between dots and dashes
the speed of keying?

Are all applicable to the bandwidth of the channel?  Can I model this as a function?


texts: What should my priorities be in designing a home generator?

texts: I have a few basic electrical engineering questions. My purpose is a home wind/ hydro electric project to sell back to the grid. My questions are these: 1. Which generates greater power: running at a faster RPM, or building a larger generator? 2. Is there a limit on RPM usefulness in building a generator? 3. If I can make a generator run at 20,000 RPM (yes, I believe I could achieve that rotational speed), will that produce a useful current gain over the same generator running at, say, 3,600 RPM? I am also not sure if I should construct an AC generator, or a DC generator hooked to a DC to AC inverter. Any input would be greatly appreciated, thanks!


texts: What type of polarized surface mount capacitor should I use?

texts:
I am having a PCB printed by OSH Park and then I will hand-solder surface mount components onto it. For my design, I am using two polarized capacitors; one is the timing capacitor for a 555 timer and the other "slowly" charges and discharges to create a changing reference voltage for a part of the circuit. Both caps will be 4.7uF.
In the past I have used 1206 nonpolarized capacitors for these functions and they seemed to work without a problem. However, for this new design I have some questions:

Should I be using polarized capacitors for these functions mentioned above? I don't believe there is any reason I need to.
If I get polarized capacitors, I think I will get 1206 or 0805 tantalum capacitors from Mouser as they are a convenient physical size and price. I'd like to spend less than $1 per cap. Would these caps be a good choice/is there any reason not to use them?


texts:
I am planning to design Rshunt basis current measuring. My current measuring range is 1A~2A. I need analog output of 0~5V analog with 1% accuracy. How can I do this?

I found conversion circuit here. Will it serve my application? I tried with these Hall effect current sensors from Sparkfun (1) (2).

But with these models, I found accuracy is not good; gives 5% error. Output is not stable even with load not connected. I tried with moving average and SD to filter, but distortion was greater.

Kindly give your suggestions for building shunt basis current sensor module.

Can I use this technique? Or a different one that uses an Allegro Microsystems ACS712?


texts: PIC32MZ bootloader without development board

texts:
I would like to put a bootloader in a PIC32MZ2048ECG064. I found AN1388B, but in table 9 (available bootloader workspaces) it lists only PIC32MX devices as compatible. The datasheet doesn't mention 'bootloader' anywhere. I didn't find anything in the other application notes either, nor did a Google search yield anything useful.

Is there a PIC32MZ bootloader? I would prefer an official one (although probably none exists), and one that works over serial port or USB - preferably not ethernet / SD card / USB host. Does something like that exist? I do not own a development board.


texts: How does noise affect an unbalanced signal on a balanced cable?

texts:
With regard to audio and balanced signals with XLR connectors, how does noise affect an unbalanced signal on the same cable that normally carries a balanced signal?

To give some background, I have a five metre cable run from an unbalanced source to a balanced amplifier that isn't using very good cable and is picking up a lot of audible noise.  I can either replace it with better shielded unbalanced headphone-style cable, or move the RCA to XLR adapter closer to the source and then run two long balanced cables to the amplifier.

The better shielded headphone cable will improve the noise, and of course a balanced signal the whole way would be even better, but what about an unbalanced signal over the balanced cable?

Will the noise be worse, because the balanced cable has less shielding?  (I'm assuming it has less because the balanced nature of the signal allows noise to be better cancelled.)  Or will the unbalanced signal still benefit from the noise reduction applied to the signal at the destination?  What if the source ties the unbalanced audio GND signal to the same chassis GND used for the cable shield - does that reduce the noise in one of the balanced lines, resulting in less noise reduction when the two "balanced" signals are recombined?

The reason I am asking is that I'm not sure exactly how an unbalanced signal is presented on a balanced input.  There doesn't seem to be any active conversion taking place in many of the adapters you find online, so I'm not sure whether the amplifier needs to be designed to accept an unbalanced signal, or whether any balanced input can accept an unbalanced signal without any problems.


texts: How to bypass or replace a defective SMD switch?

texts:
I have a wireless keyboard with a defective on/off switch. The switch has a little play, and it's closing the circuit only when it is almost pushed to the extreme position for on. If 0  represents the leftmost position and 1 the rightmost one, it's closing the circuit for a number around 0.8.

So I decided to disassemble the keyboard and see whether it's possible to repair this. Here is a photo of the circuit:

The keyboard currently uses four 1.5V AA batteries, and I also intend to use an external power supply instead. So I would like to permantently close the circuit at SW5.


texts:
So I have found this Op-Amp tester on Google here link and while it works on a 741 it doesn't on my LM4250 (Programmable operational amplifier). Is this supposed to work on any op-amp or have I just fried another 4250? I've read that it is a programmable op-amp, I don't know if it means anything or not.
Thanks for reading!


texts: Can the EasyPIC PRO™ v7 from mikroe be used with CCS compiler or MPLAB

texts:
I am not aware if any developments have taken place here. Is it possible for me to use my EasyPIC PRO™ v7 PIC development board (http://www.mikroe.com/easypic-pro/#mikroprog) with Microchip's MPLAB or the CCS C compiler? Does it only work with tools designed by mikroe themself?

The idea is to be able to put firmware on the PIC and also carry out ic circuit debugging.


texts: How does conduction angle through a bridge rectifier affects generator performance (vibrations, etc.)?

texts:
Consider this scenario:

A 3-phase permanent-magnet generator is being driven by a strong force and at varying speeds e.g. 1000-6000 RPM
Its output is rectified via a 3-phase bridge rectifier
The resulting DC is fed to a DC-DC converter which powers something (e.g. charges a battery) - consider it a constant power load.

You'd have some capacitance in front of the DC-DC converter (e.g. it may be needed for stability). In this case the classical conduction angle issue of bridge rectifiers emerge, especially if the capacitance is large, and this setup specifically exacerbates this:

when you increase the generator speed, the amplitude of its output voltage increases (so the amplitude of peaks and valleys of the rectified waveform increases)
the period between peaks is smaller
higher voltage = less current drawn by the DC-DC, thus the capacitor can hold out for longer

I've made a simulation of what happens electrically:

the three dim traces are the phases of the generator
the red trace is the rectifier output (what it would look like if it were unloaded)
the cyan trace is the capacitor voltage
the yellow trace is the generator current

I'm simulating winding resistance and cap ESR, but not winding inductance. Values taken from a specific application I was considering.

Question

I'm worried that this pulsating current causes uneven load to the generator, and may cause issues with the generator itself - e.g. vibrations, uneven load to the bearings, or similar. On the other hand, rotor inertia may be capable of smoothing things out. Is my concern well founded, or I'm worried about the wrong thing?


texts: Switching RCA composite video, under uC control - circuit ideas & suggestions

texts:
Trying to use Arduino TV-Out to switch feed to a TV set, s.a. ones found in Clinics, to display some information, s.a. next patient, expected delays etc. The TV is normally playing regular programming fed by a cable STB, but say every 5 minutes, switches to Arduino's TV-out, to display such info, for say 30 seconds, and then switches back to regular programming.

So, the question is --

What might be a very "economical" (circuit / device cost wise) way to switch the input of TV between multiple RCA type composite video feeds (s.a. old'ish set-top-box, teletype box, VCR...) ? If it can switch Audio feeds too, great, but priority (and absolutely must) for me is video switching.

Also, note that I'd like this to happen, under uC control (s.a. Arduino), i.e. the uC decides when to switch to which A/V feed. At the moment, I am looking for capability to switch between one of the 2 feeds.


texts: How does QAM retain the phase of the signals?

texts:
QAM is a modulation technique where amplitude modulation is performed for two signals, one sine signal and another cosine signal. Since the signals are out of phase, the information in these signals is independent and can be fully recovered.

However, recovering the signals requires knowing the phase of the sender. If the phase is known incorrectly, it is for the receiver possible that the sine signal will be treated as cosine signal and the cosine signal will be treated as minus sine signal. Or worse, the signals can be mixed up.

How do practical implementations solve this problem and have the same phase in the sender and in the receiver?


texts: Is this normal Buck Regulator behaviour?

texts:
I recently got around to trying out buck regulators, my results weren't what I was expecting though. For one the ripple voltage seems a little high to me, It's about 800mV with no load and goes up to 4.5V with a constant 1A load. In fairness it's only short spikes that create this ripple. Here's a capture of the regulator with no load:

At 1A the output voltage drops about 100mV and the voltage spikes get fairly big:

I'm using the XRP7664 in the setup given in the data-sheet but changed the output voltage to 6V (Schematic on page 1 with R1 changed to 56k). The circuit was built on a breakout board and connections made with wires. My question is this: Is this normal operating behavior for a buck regulator?

R1 changed to 56K


texts: How to find stepped frequency continuous wave gpr range?

texts:
As far as I know, the range of a sfcw (stepped frequency continuous wave) GPR is affected by bandwidth and number of frequency steps. However, when playing with Matlab's Radar Waveform Analyzer, I noticed that range changes proportional to PRI and pulse width (both are the same value since continuous wave). Is that normal?

In the images, you can see that changing that value only affects range drastically.


texts:
For a couple of days, I have been trying to build Hartley oscillator on my breadboard based on this schematic:

(Original source of schematic diagram above)

Redrawn with components I chose:

And here is the scope output:

Yellow signal - point X of original schematic

Blue signal - point Z of original schematic

Purple signal - OUTPUT

Theoretically we have sine wave on the output, and the voltage on the two inductors is 180 degrees out of phase, but I feel like this is not OK. First of all, the amplitude of the output is too small and second, even more important, I expected about 800 Hz no 100 MHz (as you can see on the scope).

So the question is: What is wrong with my circuit?


texts: What is wrong in this connection diagram.  I had provided pwm with 20kHz and 5volts. But at the R3 I am not getting results


texts: Why do higher frequencies mean higher data rates, and why do we even need frequencies to begin with?

texts:
This is regarding wired connections.  I have heard that higher frequencies mean higher data rates since there are more cycles per second you can fit more data in per second.  That makes sense but I don't understand why we need them in the first place.  Couldn't we have a data scheme that just relies on the presence of voltage being a 1 and the absence being a 0.  Just imagine a very long wire and a battery.  When I touch the wire to complete the circut it's a 1 when the circut shows no voltage it's a 0.  Now imagine I alternate this very very very fast.  Other binary schemes can be:

"Low frequency pulse" = 0 "high frequency pulse" = 1, no sound = wait or next bit (imagine pressing 1 vs 9 on a touch tone phone as your coding scheme)

+Voltage = 1, - Voltage = 0, No voltage = no bits yet (To send 1001 you would touch positive, unapply voltage and switch wires, unapply voltage and touch them again, unapply voltage and switch back to the original position).  Once again imagine a machine doing this very very fast.


texts: Circuit with dependent & independent voltage sources - Why not matching?

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I've just solved this exercise by hand and then I have compared the results with PSIM Simulator and there's a difference of e-006 in the Voltage Vo. I just can't understand where's the mistake, I have tried to do it as a normal KCL circuit; then I have also tried to solve it as a Thevenin & Norton... but I just can't see what's the mistake. I suppose it's conceptual.

Furthermore, my results are negative and the Simulator gives them positive... why? I have supposed the current accross the dependent voltage source is negative as it's + to - ...

Please I would appreciate you could find an answer to this question, I'm not asking you to do my homework...

Many thanks!


texts: Diode behavior when reverse biased with small voltage

texts:
I'm designing a simple circuit to use a lithium-metal coin battery as a backup power supply, and I'm considering something simple like this:

simulate this circuit – Schematic created using CircuitLab

However, during normal operation, \$V+\$ is expected to be at a higher voltage than the coin cell, so I expect some reverse current through D2. According to this source, this absolutely can damage the coin cell if it is too high - coin lithium batteries can't be guaranteed to work after subject to a total reverse charge of 3% total capacity, and a 1μA current will do that in a few months.

My question is, how can I find out how much current will go through D2? Most diode datasheets are completely uninterested at the currents going through the diodes when a small reverse bias is applied, mentioning only maximum reverse current when operating very close to the maximum voltage of the diode. Others have graphs like this, that show reverse current growing roughly exponentially, but don't show any details when close to the origin:

So my question is, is there a good model for how diodes behave when subject to a small reverse voltage bias? Can I have a better estimate of reverse current than simply using the maximum value?

(before you mention, assuming I take Shockley's diode law seriously, the reverse current would be close to the saturation current \$I_S\$ for a large range of negative voltages, but if that were the case I'd expect datasheet graphs as the one provided to look a lot different, and for \$I_S\$ to be mentioned in every single diode datasheet. Since this is not the case, I am assuming the diode law doesn't hold very well for reverse bias)


texts: Why there is no decoupling capacitors in analog IC

texts: Here is a CMOS two stage amplifier. As you can see there is no decoupling capacitor at all. Also I don't see decoupling capacitors that are used in CMOS integrated circuits. Could you explain why? Thank you for help.


texts:
I need a suggestion on a good amplifier design for a current sensor. The requirement is:
Operating voltage between 2.7 to 6.0V
Able to output 3.3V when a 10A current is flowing through sensing resistor (maybe 0.011 ohm).
Able to output 1.65V when 5A and so on.
Able to output 0V when 0A.

Is this possible without a -Vs?

My source will be at ~30V

(It would be nice if it could handle voltages as low as 0.4V and current 3A also)