texts:
I'm trying to install a plasma cutter on a CNC machine, but the problem is that the cutter uses a high-power HF start to initiate the cutting arc, and this causes horrible interference with my control electronics.
The main source of the EMI is the cable from the cutter's inverter to the torch (also the torch itself). With the torch cable disconnected, I measured only some tiny amount of EMI. The cut metal is ground-clamped back into the inverter (the ground clamp is positive in respect to the torch), and this also creates some EMI, but not as much as the torch itself.
By probing a free floating control wire (not connected to anything at either end), I've been able to make some measurements. The cutter creates periodic oscillation bursts every 2.62 ms, and each burst rings at around 2-6 MHz with peak to peak amplitude of above 100V (limit of my scope). When I repeated the measurements at different points in my system (computer output port, machine control board, various wiring and shielding), I measured the same results.

Measurement at higher samplig rate: (some 6MHz oscillations are visible here but not the complete waveform)

I have already wrapped all cables (most of all, the torch cable), the computer case and other electronics with aluminium shielding tape, and connected the individual shields single-ended into a star pattern. I have to admit though, I'm not sure where to actually ground the shields to. I tried to connected the shields to my mains safety ground (yellow/green). I'm using stranded wires everywhere, but the mains ground is solid core, so I didn't expected great results, however, grounding this way actually made it even worse, I measured less interference when the probed cable's shield was left floating. I think the mains ground line itself is picking up interference and not doing a good job of grounding it.
I triple checked the conductivity of the shields, and I'm getting a clear path to the ground everywhere.
I tried to ground the shield to the cutter's ground clamp terminal, but this also didn't appear to help at all, if not also make it even worse.
I also added ferrite cores on every cable, and it helps a little bit, but not nearly enough. Also, all the electronics and control cables are of course as far from the cutter as possible, and there is no physical connection between the CNC machine and the plasma cutter, other then the shared mains power grid.
I also made some other interesting observations. On a control board for the CNC machine, there are several LEDs that pick up enough interference to very slightly light up when the cutter (HF generator) is turned on. I did a lot of experimenting with this and it appears that when the shields are just grounded to my mains ground (described above), the effect is quite random. Sometimes, it made the LEDs light up more, and sometimes it made them light up less. I was not able to find any mechanism behind this, and the effect was very small, so it was probably just some minor details such as cables shifting slightly. However, I noticed a significant change when I added a ferrite ring to the grounding wire where it connects to the shield. It made the LEDs dim almost completely, when connected to the mains ground (compared to when the shield was left floating), but only at a certain number of turns, but it would have no effect with more or less turns around the ferrite ring. I replicated the same results with a ferrite sleeve. One sleeve would dim the LEDs a lot, while adding more than one sleeve would negate the effect.
I probed one of the LEDs and found this:

The peak to peak was around 750 mV.
I'm not really sure how to tackle this whole issue, I ran out of ideas. Any help is greatly appreciated.


texts: How do you tell if an FPGA is capable of running an ip core?

texts: I'm looking at a cheap board to start on and I'm wondering if I'll be able to fit a Picoblaze, LEON, S1, or OpenRISC core on there. Is there any way to tell?


texts: Replace electric connector with different type (from C13 to European)

texts:
By mistake I got a wrong electric appliance and due to the fact that it was shipped from US to Europe, it's not worth returning it to replace with another.

Situation: There is a motor which has a US male connector. And there is a controller for the motor that has a C13 female connector. It should have been a US female connector but by mistake it isn't. As finding a US male to C13 female adapter is difficult and takes too long to be shipped, I thought of the possibility to take it to an electrician and cut the end of the cord and replace the connector with a European female receptacle and then put a US to Europe adapter.

Will this approach work? Is there anything I should pay attention to?


texts: Conductive or insulated motherboard-standoffs?

texts:
AFAIK it's common practice to mount an ATX motherboard to conductive brass standoffs inside the case. There are even metal traces around the screw holes to provide contact between the screws and the motherboard ground-plane.

Are these traces just for the screws or are these traces there to provide a path between the motherboard ground-plane and the case?

What's actually better? Conductive standoffs or insulated standoffs?


texts: Generator voltage dipping at specific loads with observed increase in frequency

texts:
Background
I have an interesting problem at hand on a diesel generator onboard a marine platform. The generator is rated at 380V, 50Hz, 3Ph and 1500kW output.
Problem
While conducting installation trials of the generator in a mixed load bank at 0.8 power factor, it is observed that when the generator is loaded at 1000kW, the generator runs stable within limits of output frequency and voltage. However, within 3 minutes, after settling on 1000kW load, the output voltage drops to 260V and the generator load decreases to ~640kW. Within 3 seconds the voltage is regained and things are back to normal. At the instant the drop in voltage and load is observed, a rise in frequency to 51.5 Hz is observed. The frequency settles to the rated frequency as the voltage settles. In steady state, this phenomenon continues at intervals of about 200 seconds.
Also, interestingly, if you slightly increase the frequency (by 0.6Hz) after generator has settled at 1000 kW, this phenomenon doesn't occur. Additionally, if you tweak the output voltage slightly high at no load (0kW), the 'load shedding' occurs at a lower load and vice versa.
Change of AVR and governor has had no effect on this phenomenon.

Is my generator possessed?


texts:
I refer to the diagram from this thread: What is the use of the capacitor in this relay circuit?, which is also shown below. If I were to use a capacitor for my relay coil (12v latching type) which already has a flyback diode installed, what voltage rating, capacitance and type (e.g. electrolytic, ceramic) should I be looking at?
Also, if I were to use multiple capacitors for my set-up, would combining different types of capacitors be ok (e.g. electrolytic, ceramic), or not recommended?


texts:
How would you generate clock jitter in a testbench?

I have seen these two ways, but I am not sure if they are the best ways:

always #(period/2+$random(-jitter/2,jitter/2) ) clk = ~clk;

always #(period/2+$dist_uniform(seed,-jitter,jitter)) clk = ~clk;


texts: How collector-base junction in BJT works

texts:
I have read some answers about how BJTs work, but I'm still not convinced.

To show my doubts better, suppose we extract base and collector from BJT NPN transistor with all its construction details (thin base, doping things, etc.). Let's treat it like odd diode and connect it reverse biasaed way to a battery.

Would electrons from battery minus clip diffuse through P material (is there chance this strange diode would conduct)? I mean why in diode reverse biasing stops current, but in BJT doesn't do the same? What helps transferring electrons through depletion region?


texts:
I want to read a voltage from 0-30V with an MCU ADC which has a maximum input of 3V.

Initially I thought of using a 100k-10k divider (so 33V translates to 3V) but according to the answers to ADC input impedance on MCUs, this will add a 3% error due to the input leakage current; I'm looking for 0.5% error maximum. However, at lower values for the divider, I risk damaging the MCU's inputs because of overvoltage (the resistors act in tandem with the clamping diodes on the input.) I also increase power dissipation in my resistors, which are tiny 0603 devices, rated for 0.063W maximum. How can I avoid this? n.b. input impedence is not critical.

I'm not worried about sampling speed, it will be monitoring a battery voltage at a maximum of 100 samples per second.


texts:
I designed the first version of a PCB board based on atmega328p to control 2 proportional valves (valves specs: V = 12Vcc, R = 3.7 Ohm, I = 1.80A, PWM 120Hz).

Currently, I'm using a FQP30N06L (datasheet) which is a N-Channel QFET MOSFET with a logic level gate allowing voltages in the 3-5v range.

The FET is working fine, but sometimes the atmega resets and so I'm designing again the board in order to improve the circuit (decoupling caps, mosfet IC drivers, ground plane, optoisolators, isolated power supply for the atmega).

At this step, I'm trying to control the MOSFET with a IC driver and I was thinking to use this driver MCP1407 (datasheet).

Is this driver suitable for my FET?

I never used a driver, how do I have to wire it?

At the moment, I directly connect the FET to the arduino output in this way.

As you can see in the photo, the MCP1407 has 5 pins and I am a little bit confused.

Pin 1: arduino pwm output
Pin 2 and 4: arduino GND
Pin 3: ?? what is VDD? Is it the main power (in my case 12VDC?)
Pin 5: FQP30N06L MOSFET gate

Can you help me, please?

Is the MCP1407 a good driver for this MOSFET?

If not, can you suggest me a good driver for my FET, please?

Do I have to use any resistors between the atmega328p output and INPUT pin 1 and between OUTPUT pin 5 and the MOSFET gate?

Thank you!

EDIT 1:

Are these connections correct?
There are duplicate pins, how to handle the two outputs?
Do I need to wire both of them to the mosfet gate or I need to leave one floating?


texts: STM32 runtime Variable value manipulation

texts:
So basically I am not an expert, altho I think I have a good basis of knowledge.
I am using an STM32 Cortex 4 (discovery) for a hobby CNC machining application.
So lets assume we have a SW under development. The SW is used to control a system, lets say some actuators based on sensor values, using simple PI (lets ignore the rest of signal processing for now).
Now lets assume that I want to try out several P & I values based on the analysis and see how the system performs.
My question is, what kind of mechanism am I looking at here, in order to be able to change the content of a global variable in my SW during the runtime, without re-flashing.
Is SWD (and JTAG) only clean option? Or would be possible to use any other serial com and if yes, could you provide some links or short examples which could point me "How it is done?".
I have checked thinks like IAP and DFU in case I need to reflash it. I also checked STM Studio as an example (here I believe on-board ST link of Nucleo is used?)
Regards


texts: What effect would a hydrogen bomb detonated at high enough altitude have on the power grid and solid state electronics?

texts:
After reading several dozen reports on EMP effects of nuclear explosions and viewing archived government footage of nuclear weapons testing I have come up empty handed.

As for example let us assume 1-5 megaton hydrogen bomb at an altitude sufficient so that the line of sight would be the continental U.S.  I use line of sight as straight lines extending from the fireball.

Some reports say only minor disturbance.  And Other reports say all transformers and all electronics that does not belong to the military with the exception of some automobiles.  With manufacturing electronics , communications electronics and networking equipment destroyed. In addition to all high voltage transformers, nuclear plant cooling transformers and electronic control. All aviation, train , trucking distribution centers electronics. Air and cooling equipment as well as gas distribution , water and sewage treatment electronics.

One source I found said the disturbance would actually be no different than a powerful lightning storm and pale in comparison to a Solar Coronal Event and that the danger has been overblown in the media. While other sources like National Geographic say it would be the end of civilization and no country on earth would have the manufacturing ability to replace even the transformers needed much less the electronics.  They site South Africa's rolling blackouts as an example of how hard it is to get transformers let alone electronics.

Are there any reliable sources  or is this one of those hush hush  topics understood perhaps only by our military people?


texts:
I have a couple of basic questions on three phase generator connections. I am trying to connect a three phase machine (datasheet) as a generator to a three phase load on a breadboard, as shown:

simulate this circuit – Schematic created using CircuitLab
The physical generator has 4 wires coming out of it; three are for the phases A, B and C, while the fourth one is for frame ground. My questions are:
(1) Should the frame ground wire be connected anywhere on the breadboard?
(2) What is the purpose of frame ground?
Thank you.


texts: Can a low side N-channel MOSFET in a DC-DC converter limit inrush current?

texts:
I want to add an NMOS just before the supply negative side and thereby controlling its slew rate so as to create a soft start.

I've seen many examples but mostly with high side PMOS (high Rds on) or NMOS (additional circuitry to drive in high side). I doubt there must be some reason.

Can we use a low side N-channel MOSFET in a DC-DC converter for limiting inrush current? Are there any drawbacks?


texts:
I would like to make a circuit that turns on a power supply to a microcontroller after holding down a button for a period of time (say 2 seconds). To make matters slightly more complicated, if possible, I would like to use this button as an input also. The power off could come from another switch if need be.

I was thinking of something like a latching RC circuit to an zener that switches a MOSFET on to allow power through.
Ideally the solution would not consume power until the switch is pressed.

Thanks for any help


texts:
In many articles regarding transistor biasing I see a circuit like below and I don't really get what is the point of biasing like this WITHOUT emitter resistor Re?

When emitter branch is connected straight to the ground, wouldn't the VB voltage always be around 0.7V no matter the voltage divider output? "The rest" of biasing voltage would only result in greater base current. In other words - it's like we tried to bias a diode.

With emitter resistor it's different story. VB would be then VB=0.7V+VRe - we get a steady VB voltage with any value we want (e.g. 3V).

Could someone please clarify this?


texts: How to remove copper from inner planes on cut PCB

texts:
I'm in the middle of designing a specialized communications device that uses an off-the-shelf radio module.  This radio module is larger than desired and the PCB area that is not needed is easily cut away.

However, the module is built using a 10-layer PCB.  Upon cutting away the undesired area, the internal conductor planes are visible and I need to make sure that the various layers do not have excess copper shards that can short to other layers.

I've used a fine-grit belt sander with the long cut edge of the PCB oriented in the direction of the sanding belt travel.  In other words, the belt travel is such that it doesn't short across the various copper planes.  This does clean the cut edge nicely but I still have copper smearing - the smeared copper from various internal layers is very close to the layers next to them.

I'm seeking advice on how to remove the unwanted copper from the edge of the cut PCB internal planes.  My first thought was to use a high-speed down-cut router bit but, upon reflection, that will probably push the edges of the copper planes together and cause short circuits.

Another thought is to use a flat-bottomed vessel with a very shallow depth of PCB etchant, then stand the circuit board vertically with the edge of the cut PCB held just above the bottom of the vessel.  I'd probably have to have some means of circulating the etchant so that the PCB edge is always exposed to fresh etchant.

Total quantity is quite small - perhaps 150 units or so.

Any thoughts?

[Edit]

The sections of PCB that I'm removing are away from the RF section. The area near the portion that I am removing contains power supply and accessory connector stuff.

One section is bare PCB with a number of test and factory-programming pads, the other section contains an accessory connector that isn't needed.

I've been very careful with my changes - remove a section, clean up the exposed layers at the PCB edge, test. Once I verified full functionality, I'd remove the next portion of circuit board and repeat the whole process.

I was fairly certain that the circuit board material did not contain important traces and my testing seems to confirm that. I have been able to remove all of the undesired board and the module appears to be completely functional.

The reason for doing the modifications in small steps was so that I would destroy at most only one module. As it is, I've lucked out and I appear to be able to remove all of the undesired circuit board and still have a fully functional module.

Now all I need to do is find an easy method of cleaning up the internal copper at the cut edges of the PCB.


texts: Protecting PC parallel port interface when controlling external devices

texts: I need to control two devices with the PC's parallel port simultaneously.  To protect the port and provide some sort of a buffering, I thought to use an optocouplers and two ULN2003 Darlington arrays.  I wonder whether this design is reasonable.  Maybe one ULN2003 could be enough in this situation?  Alternatively, is there a simple solution for the parallel port interface?


texts: Logic Analyzer / Oscilloscope Suggestions

texts:
Possible Duplicate:
  Beginner's logic analyzer?

I am a beginner in electronics. Been tinkering with micro controllers for about 2-3 months now. At this point I find the need for a logic analyzer / oscilloscope to help me while debugging my projects.

The only time I have used an oscilloscope before was in university lab class (instrumentaion).

I was hoping you could help me with what I need to look for in one (specifications .. i am not even sure what specs are there for such tool) and give some suggestions for some good on considering the factors below

Cost - dont want to invest too much at this point
Portability - i dont have a workshop setup so portability is good
Use - would be using it mainly to debug micro controller projects

on a side note, ability to connect and transfer data to a PC would be awesome.


texts:
lets say, i am using a LTC4361 ic to protect an usb device from overvoltage and -current.

Top Left is GND, below is VBUS, +5V is protected output.
How would i deal with ESD protection for the 5V line? Using an USBLC6 would protect the following circuit from ESD, but would also just clamp the voltage down, if it is, for some reason, too high.


texts: How to tell if a battery pack is draining while in water

texts: We currently have an issue where we think maybe water is getting into our battery packs and possibly draining them.  We'd like to setup a battery pack into a similar state an put it into water.  But the question is,  how to tell if the battery is slowly draining out through the water.  How do you measure it? Observe it?


texts: detect VGA port (through pinout) and send a command to microcontroller

texts:
How can i realize that a video project is connected to laptop through a VGA port??
I think I can understand it from the VGA pinout; but i don't know which one??
If I realize it then I can send a command to microcontroller and then do some functions...


texts:
I have a design with a W65C51S ACIA IC, which uses a 1,8 crystal MHz for serial communication. The clock generation example in the datasheet shows an external 1 MOhms resistor in parallel to the crystal.

It seems that the crystal doesn´t produce any clock signal if the resistor is missing. So what does this resistor do?


texts: PMSM motor current calculated by D axis and Q axis current

texts:
Now, I know d and q axis current can be calculated by phase current ia, ib, ic in a PMSM, via clarke transform and park transform.

ialpha = sqrt(2/3) * (ia - ib / 2 - ic / 2)

ibeta = sqrt(1/2) * (ib - ic)

id = ialpha * cos(theta) + ibeta * sin(theta)

iq = ibeta * cos(theta) - ialpha * sin(theta)

Now, if motor running at a steady state, id and iq should be in DC form.

But how to calculate RMS of phase current ia,ib,ic by id,iq.

I think RMS(ia) = RMS(ib) = RMS(ic) = K * sqrt(id^2 + iq^2)

What is the value of K.


texts:
I'm trying to build an oscillator circuit for driving several IR LEDs at 38 kHz 50% duty cycle. The circuit layout I used is shown below.(Source link: http://www.electronics-tutorials.ws/waveforms/555_oscillator.html ) (Pin 7 is not connected to anywhere and I didn't use the resistor R1 in my case) Actually a really accurate duty cycle was not so important to me it could have a value +-10%. But I wanted a frequency which should be as close as possible to 38 kHz. In addition to this circuit my layout has a mosfet on its output for driving the LEDs.

From the same web site I used this formula to calculate the resistor R2 and capacitor C1 values:

I have used R2 value as 39.2 kOhm (1% tolerance) and C2 value as 470 pF (%1 tolerance). So according to calculation the frequency output should be 39152 Hz. However, the frequency that I read on oscilloscope is 35.3 kHz. So, actually my question is not about how to get the desired frequency. I could just change the resistor value by trial and get my 38 kHz. The real problem that annoys me, how I couldn't find any explanation about the 4 kHz frequency shift, which is almost 10% of the desired output. If you have any ideas about it, I really would be thankful.

Here are the components that I used:

TLC555 (digikey part no: 296-1336-1-ND )
470 pF capacitor (digikey part no: 399-8082-1-ND )
39.2 kOhm  resistor (digikey part no: 311-39.2KCRCT-ND )
mosfet (digikey part no: DMG1012UW-7DICT-ND )
10 nF capacitor for pin 5

And here I write down some important facts about my circuit and the things that I have already tried to solve the problem:

First I am aware of the fact that 555 timers are not so accurate for timing. But the 4 kHz shift means that either the R value is over 43 kOhm or the C value is 520 pF. Both cases seems really not possible to me, since both componets have %1 tolerance. I also know that capacitor values tend to change depending on the applied voltage. But the dielectric material that my capacitor is C0G(NP0), which is claimed almost no change on voltage.
I couldn't upload the pcb layout, I can try if needed. I have few vias on the line between pin 2 and pin 6, which wouldn't be a problem in my opinion.
As I have mentioned above, I use an oscilloscope for measuring frequency on the output pin 3. I don't really know if oscilloscope is a reliable tool for frequency measurings. Maybe I should count the steps via a microcontroller.
With a multimeter I measured the R value. It is 32.1 kOhm(within the tolerance range as I expected). The copper traces on the RC line are also not over few ohms. So it seems like the problem is not with the R value. But I don't also know if measuring impedance on the circuit with a multimeter is reliable or not.
I couldn't figure out if the output mosfet has an effect on the frequency. I took out the mosfet and didn't see any difference.
I tried another TLC555, the result was the same.
When I looked at the datasheet of TLC555(TI) ( http://www.sophphx.caltech.edu/Physics_5/Data_sheets/tlc555.pdf )(page 10) I found out some properties that could delay the on off time of the output, which could reduce the frequency. I couldn't use those calculations since my setup isn't like datasheet's standard astable suggestion. So I built the circuit according to that setup on datasheet. I used 10 Kohm for Ra, 39 Kohm for Rb and the same capacitor(470 pF). According to calculations output frequency should have been near 35 kHz but the result was 31 kHz. The same 4 kHz frequency shift!


texts: Connects To The Device That's The Closest

texts:
I need some expert advice or ideas.

Please note I'm not a student nor practitioner of Electrical Engineering.

I'm working on a product idea where a device will automatically connect to another device (via bluetooth?) if it's the closest device within 30 feet range (bluetooth's distance)

Let's say a Television with bluetooth.

In the living room, there are 20 bluetooth remote controls that can connect to the TV.

Is it possible to connect just one remote control because it's the closest to the TV?

Thank you in advance.


texts: difference between a 5 v 1a and 5v 0.65a hd

texts: What's the difference in the ampere of  a 5v. 1A laptop hard disk and 5VDC 0.65A 12VDC :0.50 A PC hard disk for my laptop.


texts: Ambiguity about concept of baud rate and bit rate

texts:
I know that there is lots of questions and answers that is related to this topic, but i can not clearly and distinctively find answers to my questions, yet. In addition i found some answers which seems to be contradictory to each other.

I know that baud is number of symbols per second in a data transmitting signal, As here is mentioned:
https://electronics.stackexchange.com/a/282382/254779, Then its unit could not be "bits per second", right?

But these two answers bellow say that the baud rate unit is "bits per second":
https://electronics.stackexchange.com/a/273817/254779, https://electronics.stackexchange.com/a/117245/254779.

Further more, I have ambiguity about the way measuring baud rate. In some web sites is said to be measured by number of times line changes per second and some where else as signal units per second. But i guess that they are not completely the same, right? Because this really means that every signal unit should be correspondent to only one signal change.

So for example how baud rate is measured for Manchester encoding? I guess that in this encoding number of signal changes per second is not the same as number of signal units per second, right?

And the last one is that i found some answers which said meta data bits like start and stop bits were not taken into account for measuring bit rate, however, I saw somewhere else that all bits were used for measuring bit rate. So which of these is correct at the end? For example is baud rate / bit rate = 1 in the UART protocol?

I have these questions in my head for long, and i decided to ask them once for all.

Thanks for reading.


texts:
At a job site we typically have 10 vehicles connected to a single vehicle (star layout) by a 100m 5 conductor cable carrying power(unused), ground, shield, CANH, and CANL. The shield is grounded on both ends, but the ground is effectively the battery ground, which as far as I know isn't tied to any other external reference.

What (if anything) keeps the shield from acting as giant antenna? My understanding is the shield is meant to block EMI from entering the can bus, and may also be to limit external emissions from the bus, but I thought that to prevent radiation both ends needed to be well grounded; I'm not sure how (or if) a floating battery based ground effects it.

Disclosure: Not a EE/CE major.


texts: PIC18f4550 Timer setup for 1sec Interrupt

texts:
I want to generate Interrupt(on PIC18f4550 using TIMER0) every 1 sec but by using the following code interrupt is generated after every 6 secs.

#include<pic18f4550.h>

#pragma config PLLDIV = 5 , CPUDIV = OSC1_PLL2 , USBDIV = 2

#pragma config FOSC = INTOSCIO_EC
#pragma config FCMEN = OFF
#pragma config BORV = 3
#pragma config WDT = OFF
#pragma config CPB = OFF
#pragma config CPD = OFF

void intinter(void);
void inittimer(void);
void interrupt low_priority timerinterrupt(void);
 void main()
{
TRISB =0x00; // Port B as output for LCD
PORTB =0xff;
intinter(); // Initialise Interrupt
inittimer(); // Initialise Timer
TMR0ON =1;   // Timer 0 on
while(1);
}
 void intinter(void)
{
RCONbits.IPEN =1; //Low priority enable
INTCON = 0b11100000; //timer 0 interrupt enable
INTCON2bits.TMR0IP = 0; //set timer 0 int. low priority
}
void inittimer(void)
{
T0CON = 0b00000111; //prescaler of 256, 16 bit, internal clock
TMR0H = 0xED;  // Set TMRH and L Value
TMR0L = 0xB0;
}
void interrupt low_priority timerinterrupt (void)
{
 if(TMR0IF == 1)
    {
        TMR0ON =0;//Timer 0 off
        TMR0IF = 0; //Timer 0 IF disable
        TMR0H = 0xED;
        TMR0L = 0xB0;
        PORTB = ~ PORTB; //complement  port B
        TMR0ON = 1; //Timer 0 on
        }
}

I am setting the internal clock at 20MHz and I think the problem is in the values of TMR0L and TMR0H. Can someone please guide me, how to set correct values for these and get 1sec interrupt if it is possible. Or there is another way to do it.

Thank you.


texts: Reverse engineer USB HID device: easy way to hack up USB hardware?

texts:
Background:

I want to make a custom controller for an XBox. Either by butchering an existing controller, or making the hardware and firmware from scratch(ish). (Specifically, the goal is to make an arcade machine style driving simulator with steering wheel etc., directly mapped to buttons on a standard controller.)

I have an unbranded Xbox USB controller which seems to be compliant with USB standards, since connecting it to a PC and using USB packet sniffers confirmed that it's recognised as an HID device and the data coming from it seemed to be simple and made sense.

My question: What would be the most straight forward way of making the USB device from scratch(ish)?

I was going to butcher an existing controller: desolder any variable resistors and replace with my own, e.g. for the steering wheel - and the same for switches. Dead simple. But the problem is, among others, the latency of the controller seems to be pretty poor, and I was hoping to improve on it.

Are there any out-of-the-box solutions such as Raspberry Pi, Arduino or similar, which would, for making an HID device:

Have a library giving the simplest high level interface to the necessary USB protocols, with hello-world HID code samples.
Give me good latency (not hard, I'm sure, given it's a simple HID device)
Preferably via a high level programming language such as Java. (My C programming leaves a lot to be desired)
Not break the bank
Come out-of-the-box with 6+ ADC inputs (>100Hz sample rate, >10 bits) and some digital inputs

Ideas:

Raspberry Pi seems overkill
Arduinos' AFAIK have a reputation for being limited given their proprietary language/compiler.
I usually program 8-bit PIC microprocessors, but I've heard their USB stack is limited, hard to use and generally problematic. Also it would probably mean extra circuitry; or at least hassling with non-DIP packages, making PCBs or whatever else
Program an old Android smartphone to act as an HID device. I don't know which, if any OS versions would allow me to do this without writing or modifying a custom ROM. But the only way I can think of getting analog/digital inputs would be via a bluetooth module which would connect to the phone, no doubt giving terrible latency from end-to-end.

All advice welcome!!


texts:
So basically I'm trying to make a circuit for a piezo-electric actuator. I only have access to a single supply at +70V for my op amp, an OPA445AP. Vin varies between 0 and +3V. I've looked at the help given by TI in this PDF and have come up with the following circuit. I've implemented it but when I power it up, Vout saturates at around +68V regardless of Vin. When I've simulated the circuit it indicates that it should work as expected.

Have I messed something with my circuit design up or is the OPA445AP not suitable for use with a single supply? Thanks in advance for your help.

Matt

simulate this circuit – Schematic created using CircuitLab


texts:
I have been learning about the basics of electronics, and reverse engineering hardware using UART connected to my computer. I find it interesting how I can access the busybox which is Linux and then make it perform cool and interesting new features.
My question is how consumer devices used to work before they all got shipped with Linux? I understand there may have been other operating systems for hardware, but I assume that there was a point where there was no operating system to control it, if we go far enough into the past?


texts: What is the clock frequency of 10Gb ethernet?

texts:
I am working with an FPGA that does 10Gb ethernet. As I understand, at the PHY level the  clock frequency is 322.265625 MHz for a 32 bit wide bus, but at the MAC level, the clock frequency is 156.25 MHz for a 64 bit wide bus. The diagram here shows the various frequencies.

The strange thing is that 156.25 * 2 is not equal to 322.265625.

How can the PHY and MAC operate at fundamentally different speeds? What is the advantage of changing clocks (especially that there are latency losses in the clock domain transition)? Will the PHY not receive data faster than it can output to the MAC?


texts: Logic Translation with Different Ground Reference

texts:
I have two chips which communicate with each other using 1.8v CMOS I/O (1Mbs UART). One chip is on the normal 0v ground plane, but the second chip's ground is at .7v (so its I/O operates at 2.5v for high and .7v for low with reference to first chip's 0v ground).

Im trying to figure out the best way to translate these logic levels so I/O works correctly between them. One option is to just connect them with no level shifting, in which case the the first chip would be seeing 2.5v instead of 1.8v for high (it should be able to tolerate), and .7v for low instead of 0v (which would probably not be reliable for 1.8v low logic which is around .45v to be safe).

Other option is to use something like TXS0102, with its ground referenced to 0v. Two questions with this, the low .7v signal from Chip 2 will be fed to the input of the TXS0102, but will this be low enough to trigger a 0v output for chip 1? Second when chip 1 is sending a low signal to Chip 2, since it will be driven down to 0v chip 2 will see that as -.7v. Will this cause issues with the logic gate over time if its logic gate keeps seeing negative voltage for low?

Am I overcomplicating this an is there a simpler way to do this with voltage dividers for slow 1Mbs logic?


texts: Garbage on RS232 and no the baudrate IS correct

texts:
I have a device like this https://www.vaisala.com/sites/default/files/documents/WXT530-Users-Guide-M211840EN.pdf.

Some facts:

I have an FTDI to USB board from Sparkfun which is tested to work with other serial devices, so it's not broken.
The device mentioned above is correctly wired for RS232 and is tested with an USB -> DB9 on 19200,8,N,1 to work correct both on Mac and Windows.
The serial device prints ASCII characters one line at the time which is ended with <crlf>

My problem:

When I wire the serial device to the FTDI to USB and I use the correct baudrate, I get garbage out. I have spent numerous hours to fix this and I can't figure out the problem.

If someone have ideas, that would be appreciated.

Things I have tried :

I tried 2 different USB to DB9 that work fine both on Windows and Mac
I tried the mentioned FTDI from Sparkfun both on Mac and Windows, same problem -> garbage.
On the Vaisala device, I have connected SGND (Serial Ground) with the Vin - no difference.

My ultimate goal is to connect the Vaisala serial device to the serial of an ESP8266, but until I understand this problem I can't continue. Actually I did try to connect it and I also get garbage here too.


texts: Electricity consumption of electrical machines - why do they consume electricity when they are not turned on?

texts:
The question is, why do electrical machines consume power when they are not turned on (they are plugged into an outlet)?
Also, suppose there is a seven-port USB hub with AC power. Is the power consumed by the hub always the same regardless of how I use the hub?


texts: How can I control a "high" voltage charlieplexed LED array?

texts:
Context
I want to design a system that allows me to control different LED arrays that I have, which can be either conventional multiplexed arrays (MP) or charlieplexed arrays (CP), by just plugging them into the board and send the instructions (logic) via a GUI.
The size of the arrays can be very varied, but always being MP or CP. They can be as small as 16 LEDs (4x4 MP) or 144 LEDs (14 contacts CP.)
In order to help myself with an explanation, I'll add a basic block diagram:

For now, the design of the supply stage and which microcontroller I'm going to implement is not yet defined, since what has given me most problems and will probably condition the supply is what is inside the blue square.
The Problem
The "lines" after the connector that feeds every LED have an impedance around 200-300 Ohms, so, in order to achieve a minimum current of 10mA, a voltage of roughly 9 to 10 Volts is required.

In the case of MP arrays it is not a big problem, but for CP arrays it has turned out to be quite a challenge, since I cannot find the arrangement of components that allow me to do that.
Approaches
My first approach was to look for a driver that is capable of sourcing and sinking current from every contact in a small package, I searched and searched and came across to the IS31FL3731 from Lumissil Electronics.  The problem isit can only provide a maximum of 5.5 volts.
After that, I came accross this video from Pileofstuff, where at the end he drives some more demanding charlieplexed LEDs using some optocouplers and transistors. That idea led me to search alternatives for tri-state configurations and the use of buffers, where endevor100 really saved me a lot of time with his hackaday post where he basically covers approaches that I was considering.
TL;DR
How can I control charliplexed arrays that require 10 volts with an Arduino?


texts: Where to find ERNI REL14-A2 1.3 equivalent?

texts:
I have problem to find equivalent of these relays.
During my research I found that "ERNI" has stoped to manufacturer these relays.
I can't find datasheet of the relay and can't find any specifications too.

Here is visual specifications:
ERNI REL14-A2 1.3

Driving side of the relay : 12VDC

Power side of the relay 250VAC 4A

If anyone have some information about equivalent please shere.

Here is some pictures:


texts: What refresh rate do digital stopwatches use?

texts:
We've all probably come across these kinds of electronic stopwatches at some point:
They almost always claim to count centiseconds (although this one counts in milliseconds), but do they really have such precision internally? And even if they do, does their display actually refresh to keep up with its counting speed, or does it use something slower, like 60 Hz (or less)?


texts: I'm working on reading analog voltage from type S thermocouple which is approx 10 microvolts per degree Celsius using ADS1232 TI converter. according to the device datasheet page 19, serial clock positive & negative pulse width must be a minimum 100 nanoseconds which are an important parameter in the data retrieval process. question is if I implement 1 microsecond pulse instead of 100 nanoseconds, could it work? I just got confused any help would be appreciated.


texts: Analog circuit for multiplying in the frequency domain

texts:
I have an idea I want to experiment with - doing boolean logic with analog (OFDM) signals. Each frequency component represents a different 'bit'. A key factor is performing the AND operation. I would like to be able to multiply the frequency domain of two signals (aka convolution), e.g.

$$A(ω)B(ω) = X(ω) \leftrightarrow a(t)∗b(t) = x(t)$$

Essentially, the frequency response of one signal is used to filter the other signal. If A is a superposition of 100, 200, and 400 Hz sines, and B is 200,300, and 400, the output would be 200 and 400 Hz.

Is there a circuit to perform this operation? I know I can multiply the time domain signals with something like a Gilbert cell. Digitizing and using DSP would completely defeat the purpose, I would like to do this solely with hardware (and ideally the simplest circuit possible).

Note: I read Convolution perfomed by an analog circuit before posting this. It does not really have any satisfactory answers (except delay lines, which I've been looking into). Also, I might be able to get by with just being able to very rapidly (~1Ghz) adjust the center frequency of a bandpass filter.

To give a bit of clarity, what I am kind of looking to do is send multiple (i.e. 64) bits down a single trace of copper, frequency multiplexed. It would pass through assorted gates to make up an ALU. A 64-bit AND gate would only need 2 input traces and do frequency-wise AND. Max frequency is less important than bandwith.

Anything to help me move in the right direction would be great. CCD-based delay lines seem promising, but specific implementations / use cases would be most excellent.

Thanks!


texts: Can you build a battery from scratch which is able to make a computer run?

texts:
I'm learning about batteries and I'm really fascinated by this topic.
I saw some online videos on how to build some "Voltaic Pile - like" batteries with coins and other kind of cells in different ways.
The hosts then usually use this batteries to power up simple elctronic devices ( such as flashlights or calculators).
I then saw some videos showing how to replace computer batteries using industrial cells(batteries) in order to rebuild the laptop battery pack.
I was wondering if it's possible to join this 2 processes in someway. Essentially, building some cells (single batteries) from scratch and arranging them together in order to create a laptop battery pack.
I don't know if anyone knows about someone who did it and can link them to me.
I did not find anything like that, and I'm starting to think that If it's not impossible, it is at least very complicated.
Anyway, I don't have the skill and the experience to understand where the complexity actually is, so that's why I'm asking it.


texts:
I would like to know if there is a pattern to name switches board pinout, at least, for these boards.
The boards are parts of a piano toy. First one for some effects buttons and second one is the piano keyboard.
The pins are named as P10, P11,P12, P13, P20, P22, P23, P40, P43 for a 10 switches board.

At the reverse it's easy to see how switches are connected to pinout.

The reason because I ask for the labeling pattern is because I would like to connect the piano keyboard to an Arduino with Midi and, the keyboard, looks with the same labeling pattern:

Here the reverse:

Here schematic pinout for 10 switches


texts: 2.4GHz WiFi module causing interference on 433MHz RF receiver module

texts:
I have a prototype board which has two RF modules on it, a 2.4GHz Wifi module (ESP-01) and a low cost 433.92MHz RF receiver module (Wenshing RWS-371F-6).
My 433MHz transmitter (a remote control) sends data encoded in manchester to be decoded by the receiver, this part is working well. The data rate is 2000 bits per second and I am using 433.92MHz SAW ressonator on the remote control PCB prototype. I have a frequency meter, and its transmission frequency is exactly at 433.9MHz constantly.
When the ESP-01 module is not connected to the board, I can control the relay of the board from 50 meters distance with short presses on the buttons of the remote control, and it almost always work at this distance (to control the relay).
When the ESP-01 module is connected to the board, the 433MHz RF performance is very poor. For example, from only 5 meters distance I have to do a long press on the button in order to control the relay, and sometimes it does not work. And with the ESP module connected to the board, It does never work doing short presses on the button like works when the ESP-01 module is not connected on the board...

As can be seen on the photos, I have tested 433MHz module antenna with helicoidal and straight wire (17,3cm and 13cm), and with 13cm long wire the result is even worst.

This board have 12V (100KHz - LNK626DG) power supply that is generated from the mains, then the 12V is reduced to 5V (7805) and 3.3V (LM1117IMP-3.3), two linear voltage regulators. The board has a ground plane also, shared by all them.

The only thing connected to the 5V output is the 433MHz RF receiver. At the input of 5V regulator I have a 100nF ceramic, and at output 10uF ceramic 0805 16V, and at the two 5V supply pins of the 433MHz module I have a 100nF ceramic.

The ESP-01 is being supplied by a regulated 3.3V (this power supply will be changed by a buck converter of 1.5MHz on the next prototype). At the output of this regulator I have one 22uF ceramic, and very close the the 3.3V pin of the ESP module I have 2x 22uF 0805 10V ceramic capacitors.

In that board it is also possible to connect a bluetooth module like the HC-05 (bluetooth is also 2.4GHz) in place of ESP-01, and when the BT module is connected to the board and working, it does not cause interference on the 433MHz RF like the ESP module do, maybe due to the low-power RF of bluetooth.

I have noticed that the 3.3V output is at one edge of the PCB and the ESP connector is at the other edge of the PCB...

Do somebody know if is it possible in my board, to have a good performance on 433MHz RF and use the ESP module at the same time? Because in my board the ESP module seems to be causing interference on the 433MHz module's receiving capability.

Why is this interference occuring? And what could be done to solve?

Is it layout issue?

Datasheet of the 433MHz receiver module: www.web66.com.tw/_file/C3/31776/Dfile/1402897191832file.pdf?t=2019091807

Regards.


texts: Operational Amplifier Open-loop Frequency Response

texts:
I using an LT1001 precision amplifier and am trying to plot the open-loop frequency response. As I understand it an op-amp can be modelled as a single poled system:

Which from the LT1001 datasheet has the values:
DC open-loop gain = 800,000
Gain-Bandwidth Product = 800,000
Dominant-pole frequency = 1Hz

My query is, is my deduction of the dominant pole frequency at 1Hz correct? Does this mean in the frequency response it will almost immediately start to decrease by 20dB/decade?


texts: Why is the gate phisically bigger than the inversion layer in a MOSFET?

texts:
In other words why does the gate overlap a bit of the source and drain instead of being exactly on the middle, please look on the following diagram

You can clearly see that L is smaller than the gate length, why is this? When doing calculations we ignore the differences and say that they're equal but in reality, it is not equal.


texts: Do almost all modern smartphones use piezoelectric speakers?

texts:
Do almost all modern smartphones use piezoelectric speakers for both the ear speaker and the speakerphone speaker?
The reason I ask is because I rinsed off my waterproof smartphone (which I've done dozens of times) and the speakerphone speaker now sounds horrible: the volume is very low and the sound is exceptionally "tinny".
Its done this before after rinsing it off, and I can usually just make a call on its speakerphone to resolve the issue.  But this time, after making several speakerphone calls and letting a single bass-filled track of music play repetitively for an hour, the sound quality is still poor.
In order to determine how to hopefully resolve this issue, I first need to understand what type of speaker is likely involved.  The brand is Samsung, if that matters.  Is it almost surely piezoelectric?


texts: Simplest way to measure 4 cell LiPo battery State-of-Charge during discharging

texts:
For testing purposes, I need to know an aproximate percentage of the battery charge in order to know when the battery must be recharged. It doesn't need to be accurate at all, p.e. a simple signal (LED) which warns you about low battery level. Easy to implement since I cannot spend much time on this now (after testing I will go for the fancy option), so I guess fuel gauges (unless there is an evaluation board ready to use) are not considered by now.

I'm using a standard charger and I have all this information during charging, therefore I only need a solution during discharging.


texts:
Can we use  Virtuoso Cadence to produce this type of wave(c,first picture)?it is the wave that PZT produced

My schematic and waveform of connecting high pass


texts:
I am trying to figure out how many batteries I will need, in order to power my 4-wheeled robot (based on an Arduino). I understand that it is not practical to power the Arduino and the wheels with only one 7.4 V LiPO battery. So I know that the Arduino power source is going to have to be different than the motor power source.

The specs for the motor are:

Stall Current: 3.6A
Free Current: 0.15A
All motor specifications are at 7.2 volts. Actual motor specifications are within 20% of the values above.

I need to have all four motors run for at least one hour. So the question is: Can all four motors be safely powered by one 7.4V LiPO battery, or am I going to have to have one battery for two motors?

The batteries that I have are 2200mAh, 1C continuous discharge.


texts: Multiple 2kW inverters connected to same 12V battery bank

texts: It seems that putting 4kW over a 12V DC circuit is unwise, given that this would exceed the maximum of 302A for which 0000-gauge wiring is rated for power transmission.  However, is it safe to connect 2 2kW inverters to the same battery bank, running them both simultaneously?  What about more than two inverters?  Would 00-gauge wiring (rated to 190A, higher than the 166A max current for a 2000W 12V circuit) be sufficent for this setup?


texts: What are the concerns when converting single-ended signals into differential?

texts:
Application Description:

We are converting a single ended DAC output into differential. The DAC output composes a DC signal(-10V - +10V) and sine waves running below 100kHz(below 100mVpp). The DAC has an OpAmp voltage follower at the end of it already.

The reason for conversion is because I want to export a larger range of the output. The range of the single ended signal is 20V, while a differential one with same power supply could provide 40V range.

The load which the output voltage will exert on is a capacitor, so with very large impedance. I guess in this case the balanced outputs for differential voltages are not necessary.

Question

Can I simply use a voltage inverter at the output of the DAC? The reason is that I can find small footprint OpAamps with several OpAmps in one chip.
What are the considerations when designing a converter for this purpose? Such as OpAmp selections, feedback resistors and etc..
I saw some applications use differential OpAmps. What are the benefits of them comparing with using OpAmps?


texts: Can a lead-acid battery charger be used for "Gel" type?

texts:
I have a PB-600-24 lead acid battery charger.

Can I use it for the battery type that has an image as below? 4 of the batteries are in series.


texts:
I wonder, what's the best oscillator scheme to use with watch crystals(32kHz) to get optimal stability & precision? (provided that temperature is stable, digital correction is out of this topic).

Typical solution is pierce oscillator, but what's the optimal swing/voltage?
I have a feeling that sine-wave generator should put less stress on the crystal.

So, what's the best & less stressful oscillator scheme for watch crystals?

That is for digital clock, so long-term stability is important (crystal will be temperature-stabilized & corrected for aging).


texts: Replace UR battery by IMR with lower mAh

texts:
I am replacing a shaver’s battery, a Braun Silk Epil 5.

It uses a Li-Ion battery manufactured by Sanyo for Braun.
According to my research it must be a UR Battery like the UR18500L :

Size : 18500
Volts: 3.7V
Capacity : 1300mAh/4.8Wh

My question is pretty simple (and maybe dumb), the UR Batteries are pretty expressive.
Is it possible to replace it by an IMR Battery that has the same voltage but less mAh (Usually used for e-cigs)?

If it is, what would be the consequences ?


texts:
I'm building my first biped robot, using a Raspberry Pi as the brain. My problem is, I want to decouple the battery before I use it to power the Pi.

The reason I want to decouple the battery is because I will have 32 servos connected to a servo controller which is also powered from the same battery, I expect it will cause a lot of fluctuations in the power source.

I understand what a decoupling capacitor does but not how to use it or what types of capacitors I can use.

So I guess my questions are, how do I use a decoupling capacitor and can I just use any type of capacitor?


texts:
I run a Toshiba Digital copier machine in my shop and the machine started showing error codes related to power issues a few days ago. This happens randomly during daytime. There were no problems at night time. So I have transported my copier machine to an another place during the daytime and used it for a long time with no errors reported. I have concluded that there is harmonic distortion in the power lines of my shop area. Also, I have noted that there is a workshop near me which uses heavy AC motors. I suspect that they cause the issue in the power lines because of malfunctioning equipment.

Is there any circuit that can filter these harmonics which I can build? Will using a UPS fix the problem?

I have already complained about this to the power company but there seems to be no action taken by them.


texts: We are currently studying RC, RL and RLC circuit but I am having a hard time comprehending some topics, like what is the function and importance of putting a 0 V source in series with the inductor in the RL circuit below?


texts:
I have a little problem which I cannot understand, control theory is not my specialty but I have been reading on it lately.

I have a buck-boost converter which I modeled on matlab and I am trying to control it with a PD compensator. However, I cannot achieve what is asked in the example namely a crossing frequency of less than 20 KHz and a phase margin of at least 52 degrees.

I suspect I might need to add an extra pole in the PD transfer function but I do not know how to choose the particular pole.

Here is my matlab code so far:

%%Clear
clear all
clc

%%Uncompensated
Tu0 = [10.417];
num = Tu0*[-6.51e-6 1];
denom = [1.72e-8  3.25e-5 1];
Tu = tf(num, denom);

%Compensator (PD)
Gc0 = [0.37];
num2 = Gc0*[5.06e-4 1];
denom2 = [1.54e-7 1];
Ts = tf(num2, denom2);

%Compensated loop gain
Tf = Tu* Ts;

%%Bode Plot
 bode(Tu)
 %bode(Ts)
 grid on
 hold on
 bode(Tf)

%Stability numbers
[Gm,Pm,Wgm,Wpm] = margin(Tf);
GainFreq = Wgm / (2*pi)
GainMargin = Gm
CrossoverFreq = Wpm /(2*pi) %Crossover frequency has to be less than 10% of the switching frequency: fc <20 KHz
PhaseMargin = Pm  %Phase Margin of at least 52

Thank you in advance for any hint!


texts: Finding gain from a transistor datasheet

texts:
I'm trying to work out the gain of a transistor, the datasheet is here, although I have extracted the relevant images here:

The datasheet gives the gain for Ic=5mA and Vce=2V as 25, and the remainder of the results seem to indicate something of a bell-curve of the gain plotted against Ic, which with some rough interpolation would allow you to find a very rough and approximate gain for any Ic value in between 5mA and 500mA; although this is all for a Vce=2.

The graph gives a shape expected of the results, but the tabular results don't seem to match the graph (i.e. 150 mA should be 40, but graph value seems closer to 160 - i.e. the maximum). It seems the graph is plotting the maximum gain rather than minimum - doesn't make the graph useless?

The tabular data, while useful is strictly for the stated values of Ic=50-500mA and Vce=2. Obviously, 2V is quite low, so if this was part of a circuit running at Vce=5 and the Ic pulling say 100mA, then how could this datasheet ever be useful, considering those values can't even be found in the datasheet?


texts: Does a capacitor connected by only one lead have any effect on a circuit?

texts:
A capacitor in my ceiling fan failed. I was hunting for this replacement:

but at first I only found this:

I was wondering if the second one would work if I just capped off the red wire and didn't attach it to anything. With no potential difference across the third capacitor, it never stores any energy right?

Is my dim memory of idealized freshman physics correct? Even if it is, is there some real-world effect that would make doing this wrong in practice? (Don't worry! I found the exact replacement, so I'm not actually going to use the second one. I'm just curious.)


texts:
I've bought a RGBLED stripe with 300 SMD5050 RGBLEDs. These are rated at ~18mA on 5V each, so I have approximately 5.4A on the complete strip. I have to cut down the strip into several parts and have to connect them with short wires of 10-30cm each.

According to the AWG table, I would need to use an AWG14 or AWG13 to be sure, but that seems rather large for the application I have. With a total wire length of approximately 5m, whould it be ok to go for an AWG in the range of 20-24 without having to worry about the wires getting too hot?


texts: Is there any device such as a typewriter or keyboard that is portable and can save data to a USB (other than a cell phone or smarthphone )

texts:
I need a device for take notes

Is there any device such as a typewriter or keyboard that is portable and can save data to a USB (other than a cell phone or smathphone )

please give me a suggestion


texts: How to shield from electro surgical generator in close proximity?

texts:
Looking for help EMI hardening a SERDES interface in close proximity to electro surgical instruments. I believe there may be tips or reference designs from existing pacemaker applications that may assist in my pursuit. Are there any examples or design resources available for this situation?

Thanks


texts: Opamp: capacitive loading when buffering a Reference

texts:
I need to drive a ratiometric current sensor ACS758xCB with a nominal supply current of 10mA. Due to the ratiometric nature of the sensor I would prefer to supply it from the reference voltage of my ADC. Obviously I need to buffer the reference.

However, most opamps, notably those with low offset voltage, require the capacitive loading of the opamp be limited. Since the sensor itselfs contains active circuitry it requires supply bypassing in the range of 100n.

simulate this circuit – Schematic created using CircuitLab

How does one usually cope with this situation? I've looked into tracking regulators such as TPS7B4250 but the tracking performance of +/-5mV does not sound too impressive.


texts: STM32 - How does analog configuration of MCU pins affect the power usage?

texts: When I was creating a new project using the STM32CubeMX, I saw a check box stating that setting all free pins as anlog will decrease the power consumption. I couldn't figure out how it works. How can configuring the free pins as analog decrease the power consumption of an MCU?


texts:
Okay I already read this post which answers the question mathematically
here,

at the end of the top answer the poster said:

"Thus, the only way to keep current from going to infinity is the condition I(T)=0
"
So does this means that the indcutor does not have some property that it magically makes any periodic waveform have an average voltage of zero, but WE are setting that integral equal to ZERO and solving for that case?

So this thing about "average inductor voltage always equals 0" is more of a rule we must impose on it, rather than something it does on its own?

If i apply a voltage to an inductor for 50mS it will rise linearly and i remove the voltage for only 1ms it will return to the initial voltage? thats a periodic waveform if i keep doing it but seems to me it would rise for ever. Which makes me wonder how then is the average zero?

and same would apply to a capacitor?

This highlighted integral.
Basically  , will it always equal zero because of some physical trait of the inductor that makes it always be in a steady state, or is this telling me that we must SET it equal to zero to operate in steady state?


texts: I want use Electret microphone Pre-amplifier described in TI document, with Color light organ. Will the output level of this pre-amp enough to drive LM324 Op-Amps on Color organ? Input signal goes to VR1 "Master level" potentiometer. Also, is the standard Line level output of consumer audio electronics enough for connecting it to VR1?


texts:
Can somebody explain in short terms whats means this from datasheet  TXB0102:

  When the output-enable (OE) input is low, all outputs are placed in
  the high-impedance state.

I dont know how I would connect the OE pin

Thanks


texts: What is the fastest and easiest way to transmit arduino's sensor data to a PC wirelessly

texts:
I have a specific problem :

I'm working on a testing platform. It has to be absolutely isolated, so I cannot wire it back to my PC. I again reiterate it. There is no way to wire it to my PC. IT HAS TO BE ABSOLUTELY ISOLATED
It has about 10 different sensors on it and I need to read sensor's data simultaneously at 100Hz.  It is currently working fine with 16Hz, but I need to improve it further, so I think maybe in future sampling rates higher than 100 is beneficial. 7 Hz is the lowest possible value that doesn't botch the whole things up.
I have a laptop on the platform which reads the sensor data via RS232, then it processes them in a fraction of a second and produce a control signal and send it to the actuators. It has to happen at real-time. Control algorithm is not heavy, it is several PIDs.
It has 6 actuators with the fastest possible reaction time of 0.005 second.
The main sensor currently is Microstrain 3DM-GX1. It is a very good sensors.
I want to add a GY-80 sensor in parallel to 3DM-GX1. I want to test various filtering algorithms on the GY-80's output and compare them to 3DM-GX1.
Platform has 6 degrees of freedom so I think laser transmission is not practical.
Distance between the computer and the platform is at most 3 meters.

For some reasons I am not able to use the laptop anymore. I want to read the sensor's data with an Arduino, preferably Arduino Mega 2560. My problem is that I don't want to load the control algorithm to the Arduino.

IMHO the perfect solution is going to be a Wireless link between the Sensors via Arduino to my PC. This way my PC logs data and also the Control Algorithm can promptly calculate the feedback signal and send it to Arduino which will send them to the actuators. This immensely makes things easier for me.

I think I need a RS232 shield for the 3DM-GX1 & Arduino, + some wireless solution for sending data from both sensors to my computer. Then I need to send back the control signal back to the actuators wirelessly.

Now what is the fast and easy way to transmit the data between PC and Arduino in real-time?

Thank you in advance !


texts: Combining two power outs along with voltage regulator

texts:
I have two seperate solar panels with exact same circuitry connections. This is what I have:

Solar panel -> Sparkfun Buck boost converter (set on 5v) -> TP4056 -> single 18650 AND + and - Power out cables ready for connection (which I'll connect to LM2596 in a way I explain below).

I want to power my board that needs 5v 1-2amp (varies) for as long as possible. My 18650 batteries are 5000mah each.

So I'm going to connect both positive OUTs from TP4056 pins combined together to LM2596 switching voltage regulator and two negative pins from two of my TP4056s to negative IN on LM2596 and set the output voltage of LM2596 to 5V. LM2596 support up to 3A which is great and more than what I need.

Do you see any problems with my board/method? My board will be outside all day, during daytime I think my board will mostly consume the direct solar power and during night it will use power form 2x5000mah 18650 batteries.

If you see inefficiencies, problems, things I can add to improve safety and power efficiency, please share them with me. Thank you

P.S. Each of my solar panels are 6V 1A 6W panels

TLDR:

2xPanel -> 2xBuck Boost -> 2xTP4056 -> 2x18650 5000mah batteries

Outs of 2xTP4096 combined together will be connected to LM2596 and then to my 5V 1-2A board.


texts: I have a non-inverting op-amp circuit with each branch having a resistor and capacitor in parallel. The op-amp I am using is a LM741. The circuit works as expected for sinusoidal inputs up to 10 kHz, but once it reaches 20 kHz, the gain suddenly increases more than expected. Can someone please explain why this is happening? (i.e. why is there the little hump in the bode plot?).


texts: Definitions of elements, nodes, branches, loop, mesh for a network with short circuit

texts:
CONTEXT

This question is intended to highlight the lack of precise definitions of basic circuit terminology that I have found.  For example, consider the following definition of branch.

  "A branch is a connection between nodes. A branch contains an element (resistor, capacitor, source, etc.). The number of branches in a circuit is the same as the number of elements. 1"

Notice that definition says connection between nodes, not a node. In the circuit below, R3 connects between only one node. So is there a branch through R3 or not?

Comments are welcome as are references to more precise definitions that deal with this sort of thing.

QUESTIONS

Given the circuit below:

Q.1. How many elements are there?

There are 4 elements.

Q.2. How many nodes are there?

There are 3 nodes.

Q.3. How many branches are there?

There are either 3, or 4 branches.

Q.4. How many loops are there?

There are either 1, 2, or 3 loops.

Q.5. How many meshes are there?

There are either 1, or 2 meshes.

1 https://spinningnumbers.org/a/circuit-terminology.html#branch


texts: Glass fuse identification - Siran No. F 13 4A

texts:
We have a glass fuse for a 12v lighting circuit that has
"Siran No. F 13 4A" written on paper inside it. The circuit takes 5.5A at the moment with all the lights switched on without the fuse blowing. Can someone tell me what this is rated at? It seems to be a fast blow (F) so can it really be a 4A?

I figure my options are

13A (so what does the 4 mean?)

13.4A

4A (why is it still working at 5.5A?)

Thanks for reading, Steve

Edit: Images added as requested. Fuse shown with left side in holder


texts:
I have an input voltage -10V to 10V from a DAC. The DAC can source approximately 4 mA. I need to scale the voltage as close to 0.1x as possible (source -10V to 10V to output -1V to 1V). The output is then fed into a motion control input.

What is the best way to accomplish this? I have considered the following:

Inverting op-amp to scale the voltage 0.1x and then a second inverting op-amp to invert the voltage again
Simple resistor-divider
Unity gain op-amp -> resistor-divider
Resistor-divider -> unity gain op-amp
Option #1, omit the second op-amp and change the DAC firmware to output the opposite polarity (-10V instead of 10V). Motion control would be the same.

I have no idea what the best way to do this is. Does it matter? I do have +12V and -12V available for the op-amp.


texts:
I'm new to magnetics and apologize in advance if any of these questions are too basic. I'm looking to build an electromagnet array to move around an object placed on top of the array. Something similar to the image below. Based on my understanding the number of windings the core material, and the amount of current and frictional force to overcome define the strength of the magnet.

Would this be the right formula to calculate the force of the electromagnet with N turns, current I at distance D from it's center F = (N * I)^2 * μ0 * A / (2 * D^2)?

How do you decide between bigger core cross-secttional area vs having multiple layers of windings? (From the image it looks like there are multiple layers of windings around the core with N turns each)

Would this be a good core to use, bit unsure if this is even the right type. https://www.digikey.com/en/products/detail/fair-rite-products-corp/4077374711/8600016


texts: Simple question about superposition-theorem

texts:
Which one is correct? (first one is my solution, second one is how my teacher solved it in class as an example when he was teaching superposition theorem).

Red rectangles are where the difference is.


texts: compact fluorescent lamp noise on digital signals

texts:
The answers to this question about CFLs (compact fluorescent lights) in an electronics lab indicate there is some concern about the presence of electronic ballasts and CFLs in connection to radio and audio electronics. It is my understanding that CFLs have a compact electronic ballast in their base. There is the implication that these answers have to do with the switched on steady state noise.

My question is different because I am interested in the possible effect on 3.3 volt digital wires in a prototype circult during the transition of the CFL from off to on and back to off. These CFLs are on 120 volts AC, 60 Hz and they get switched on and off by randomly behaving people. CFLs are at a distance of 3 meters or more from the prototype circuit. The prototype circuit is powered from a cellphone charger and a USB interface. Sometimes a computer is used instead of the cellphone charger.

I am indirectly observing (because I have no oscilloscope) some unexplained rising edges on Arduino inputs where the processor is programmed to pull up with an internal 20K to 50K ohm resistor. The specification states there is a wide range on the value of the resistor. Digital 1 is 3.3 volts. The problem is intermittent and may occur 1 or 2 times within the space of 20 hours. As a prototype the input pins are connected to breadboard jumpers that are 15 cm long and approximately 24 AWG copper. That gauge is 0.511 mm in diameter. The other end of the jumper is a rotary encoder. In the testing period there is no input activity on the encoder so the firmware can be considered to be in a steady state.  A rising edge suggests that noise is enough to drive an input down to digital 0 and the subsequent pull-up brings it back to digital 1.

As a prototype the wires are longer than they will eventually need to be. As a prototype there was no electronics enclosure. I am currently running a long term (24 hour) test with the prototype circuit in an aluminum enclosure. Are CFLs in an electronics lab a known cause of flipped digital signals in a 3.3 volt circuit?

Low is defined as 0.2Vcc-0.1V which I interpret to mean 20% of 3.3 volts minus 0.1 volts, in other words, 0.56 volts.


texts: VHDL iterate over a "list" of external names

texts:
I'm using external names introduced in VHDL-2008 to access a bunch of signals (let's say 1000) in a design hierarchy with many levels.

<< signal dut.signal_1 : std_logic >>
<< signal dut.signal_2 : std_logic >>
...
<< signal dut.signal_1000 : std_logic >>

I want to iterate over these 1000 signals and force them to '0' or '1' to perform some fault testing and it would therefore be convenient to have something like this pseudo code:

alias test_vector : std_logic_vector(999 downto 0) is (dut.signal_1, dut.signal_2, ..., dut.signal_1000)

I.e. I want to construct an "alias-vector" with all my external names in it. With this vector I can do something like this:

test_vector(random_number) <= force '0';

I can't seem to find an easy way of doing this. The only way I can think of is to use one alias and with a script copy the external names one at a time into the file, run the simulation and then repeat for all 1000 signals.

Any help or ideas are much appreciated!


texts: Approach for receiving unknown length of data

texts:
I'm using STM32F407 and I would like to receive unknown length of data.
My current approach uses a fixed known size to receive the data from UART5.

How do I change it to receive unknown length of data.

/**
  * @brief This function handles UART5 global interrupt.
  */
void UART5_IRQHandler(void)
{

    if (!bytesAvailable(&_writeBuffer))
    {
        __HAL_UART_DISABLE_IT(&huart5, UART_IT_TXE);
    }

    HAL_UART_IRQHandler(&huart5);

    /* USER CODE BEGIN UART5_IRQn 1 */

    /* USER CODE END UART5_IRQn 1 */
}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart == &huart5)
    {
        tx_finished = 1;
        HAL_UART_Receive_IT(&huart5, _readBuffer.buffer, expected_replay_length);
    }
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart == &huart5)
    {
        if (!isFull(&_readBuffer))
        {
            uint16_t counter = 0;
            while (counter < expected_replay_length)
            {
                push_single(&_readBuffer, _readBuffer.buffer[counter++]);
            }
        }
    }
}


texts: Can I leave the input pins of an ADC channel in floating state?

texts:
I'm using this 4-channel ADC: MCP3422 -> Datasheet

I only need to use 3 of the available 4 input channels in total.
Normally I would add footprints for pulldown resistors for example in case a floating condition causes problems.
But this time I need the PCB space so I would like to free up some space.

So can I leave the two pins of one input channel floating?
I need channel 1-3, but will leave both pins of the 4th channel unconnected.
Can that cause issues?
Any best practices?


texts:
In thinking about an answer to a different question, I came up with a likely-not-ideal solution to the following:

Given a square-wave input of 125 Hz whose minimum is 0V and maximum is somewhere between 1-7V
Assuming an ideal source with zero output impedance
Not having access to a negative rail
Needing to support an output load of at most 10 mA that varies at the same frequency but between +Vin and -Vin; i.e. zero-centered and with double the amplitude
Wanting as simple a circuit as possible, ideally with only passive, discrete components

The complex and obvious solution is a switching supply to generate the negative rail, and then a comparator. I came up with the following charge pump as a simpler solution, shown at Vin=5V, RL = 5k:

Since it doesn't need to generate a negative rail, it doesn't need an inductor. It works fine, but I don't love it, for the following reasons -

I feel like it can be further simplified
The output is asymmetric - the positive cycle is stable but the negative cycle follows the capacitor discharging

Is there a simpler solution? The alternate one below does work, courtesy @tobalt.

simulate this circuit – Schematic created using CircuitLab


texts: How to read data sheet to get the time diagram of the outputs

texts:
I would like to know how one can read and obtain the outputs for Qa, Qb, Qc, Qd, using this data.

On the third line of the truth table, what does it mean when the outputs for Qa is a, Qb is b etc ? What are a, b, c and d ? Does it mean that the outputs follows the clock ? Why are the inputs for the load are a, b, c and d ?

Thanks


texts:
I am looking to install WS2811 LED Strips inside coving on walls for a down lighting effect. I have drawn up a wiring plan but i am not sure if it is correct / the best way to do it.
Is there any immediate issues with my wiring plan attached? Are there any suggestions / changes that would make it better?
The distance between the two power supplies (and as such the distance of the Common Ground) is about 32 Meters, will this be an issue for the power supplies / signal?
The setup is as follows;

WS2811 LED Strip, each Strip is 12v and 5 meters long
2x 12v 60A power supplies
BC-204 controller (Artnet to SPI), which has 4 LED outputs. Each output will send a signal to 10 meters of LEDs (2 strips per output)
Fused Bus Bars from Power Supply 1 & 2 will be used to provide V+ to the LED strips and controller
Bus Bars will be used to provide V- to the Controller and the other power supply (Common Ground?)
The power supplies will be connected together at V-
All wires will be routed along the edge of the wall (Not ideal as my wire lengths are pretty long, however im using 4 core 1.5mm2 cable and the voltage drop on this should (according to some rough calculations i did online) be acceptable.

The distance between Power Supply 1 & 2, and the other measurements can be found on the other attachment if it is of use!


texts: What is the maximum number of bytes that can be sent through USB-to-serial COM port at one go?

texts:
Suppose someone uses hyper-terminal to send a very long ASCII string at a COM port. This COM port is created by FTDI USB-to-serial port cable. The cable used is http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232RG_CABLES.pdf.

Is there a limitation imposed by the UART driver for PC? For example, Arduino UART tx buffer is 64 bytes only.

What is the maximum number of bytes that can be sent through a PC serial port at one go?


texts: Is the JHD12864E compatible with an Arduino board?

texts: I am using a KS0108 compatible graphic LCD (JHD12864E) and I want to connect it to my Arduino Leonardo board to display some text. I searched using Google and also in the Arduino forum but I didn’t get much information. The examples I found were for a 16*2 LCD. Please suggest connections and a basic program for an Arduino board.


texts: impedance of basic mosfet current mirror

texts:
How to find the impedance looking into the drain of basic mosfet current mirror, including the device capacitances?

Is it like the ro of M2 is parallel to Cgd and Cgs. Do we consider the 1/gm from M1 transistor?? I am also including the small signal model[!


texts: SMDs on bottom side of board with THT components?

texts:
I'm designing a PCB for factory production and I'm not sure if placing SMD components on the bottom side of the board, which also contains THT components (pin headers and buttons, they're all on the top side though), will make the board manufacturable without a special process. Normally I would avoid this, but the board I'm designing is very space-limited, and this could save really a lot of space.

I understand that this is not a problem for hand-soldered DIY-level projects, but this board is factory produced and assembled.

Thanks for any suggestions.


texts:
I need to measure frequencies between 25kHz and 150kHz with a precision of minimum 50Hz. I'm using a MCU 8051(C8051F382 Silicon) with 48MHz clock, and need the measure to be done under 100us, so I can't use CD4040/prescaler to get many counts.
I need a high precision because my reference isn't stable, it drifts during day.
Is PLL an alternative?
I'm using 8051's PCA module so I can get x counts per period, but under 48M clock and 100k target my count is 480 but to get to 481 or 479 it needs like 99.8K or 100.2K, and I needed to get a tick every 50Hz not every 200Hz.
My target will be an inductive loop and it will need to detect a motorcycle above it.
UPDATE: Tried to use the frequency without CD4040, my clock can't handle all the stuff I need, 150kHz is only about 6us to do everything I need, so I'm back to CD4040 using div by4. Tried to oversample but did no good, still good at lower frequencies, still awful at higher frequencies. For now I'll try to lower all my frequencies while I can't think a better way to do this.


texts:
I have this function to read key press from a 4x3 key-board:

uint8_t GetKeyPressed()
{
  uint8_t r,c;

  KEYPAD_PORT|= 0X0F;

  for(c=0;c<3;c++)
  {
     KEYPAD_DDR&=~(0X7F);

     KEYPAD_DDR|=(0X40>>c);
     for(r=0;r<4;r++)
     {
        if(!(KEYPAD_PIN & (0X08>>r)))
        {
           return (r*3+c);
        }
     }
  }

return 0XFF;//Indicate No key pressed
}

Some macro, I missed:

    #define KEYPAD A
    #define KEYPAD_PORT PORT(KEYPAD)
    #define KEYPAD_DDR   DDR(KEYPAD)
    #define KEYPAD_PIN   PIN(KEYPAD)

But I don't understand this code, pretty well, because of those bit shifting operations.

Can anyone help me with this code?

Compiler : avr-gcc

Micro-controller : ATmega328


texts: connecting 3 one phase Generator to get three phases

texts:
I have a big welder machine that needs around 26 kW and three phases. A generator for this power is a little bit expensive and take me a while to import one.
When you are in a complicated situation always you think in stupid ideas and this is one:
I was thinking what if I connect one single phase generator (10 kW than I can get quickly) for each machine phase, could this option works for my application?
Thank you in advance for your attention


texts: Interfacing SIM900A GSM Modem with TM4C123G TI microcontroller

texts:
I was hoping you guys could help me on connecting SIM900A GSM Modem with this TM4C123 micro controller.

I connected the RS232 ports of TX, RX, GND and power ports to GND and +12V. should I connect the RS232(TTL Levels) too? (the yellow pin connectors).
As you can see in the picture, the red LED turns on for about 64ms and off for 3s, which based on this website: https://elementztechblog.wordpress.com/2014/10/10/interfacing-sim900a-gsm-modem-with-arduino/
means its registered to network or SIM card is active. but Green LED should be on to indicate that it is working properly and ready to send and receive messages, right?
Could someone please explain the pin connection for this modem.
thanks in advance


texts: high pincount stackable header separation

texts:
I recently made myself a custom hat for a Raspberry Pi. To connect the Pi and the Hat there is a 2x20 stackable header. However, I find it extremely difficult to separate them once they are mated together. While I don't do it often, I fear that there is an important mechanical stress that is applied to both connectors and this could break the pi in the long run.

Do you have any technique or tool that could ease up the separation process? Is there something that I also need to consider at the design level? Perhaps you might know about a 2x20 header that is looser from experience?


texts: Phase shifting DC+AC audio signal without affecting its DC content

texts:
I have a strongly and asymmetrically clipped audio signal (green signal on attached picture), with DC bias content (blue signal).

In order to obtain the exact DC bias level of this composite signal later, first I would like to phase shift the signal with 180 degrees, without affecting its DC content (red signal on the following picture).

The inverting op-amp configuration change the polarity of the DC content too, it can not be used in this case. Is there any possible solution in the analog signal domain? For the time being I don't want to switch to digital domain.


texts: What are the main causes of Overshoot and undershoot of a signal?

texts:
I'm not an EE major, but I was curious what causes overshoot and undershoot.

Where can i find a detailed explanation of the process? I heard it has to do with the parasitic capacitance, but there were no details.

parasitic capacitance seems to have the effect of drawing more current into or out of the line, but i don't directly see how this would make a signal overshoot.

Also, how does an improperly terminated signal result in overshoot? If the signal is not properly absorbed and reflects backwards, I would expect some of the energy not to be transmitted into the receiver.  Thus, if anything wouldn't this cause the voltage to undershoot because it doesn't receive as much power as it is expecting?


texts: How can I make smaller steps with my servo?

texts:
I've got a Raspberry Pi with which I control a servo. The servo controlls the rudder in an autonomous boat I'm building. I'm using Golang and this gpio library to control the PWM.

The input I get from the program ranges from -100 (full left) to 100 (full right). I've got some code (proof-of-concept) which works great (paste here).

I use:

a frequency of 100
a cycle length of 100
I vary the duty cycle between 3 (full left) and 14 (full right).

This works great, but since the library only accepts ints as input for the duty cycle, I only have 11 discrete steps to which the servo can be set. I would like to be able to have more fine grained control though. I would like to use a minimum of about 25 discrete steps.

So I played around with the numbers of the frequency, the cycle length and the duty cycle minimum and maximum, but I really can't get more steps.

Could anybody give me some hints as to how I can create more discrete steps? All tips are welcome!

So far so good.


texts:
I have a led string like this

I want to power it from batteries and not from the outlet.

The string consists of 3 parallel strings of 28 leds, which I can power separately.

Originally, the output of the controller is 220 v and on the first 5 leds of each string there is a resistor of 4.2k, which gives us ~21k.

From a test with batteries I performed on a single led from the string, it has a voltage drop of 2.01V. It suggests that the operating current was (220-33*2.01)/21k=7.3mA, which seems reasonable - with this current I get a reasonable light from the led and no burning smell. With about 16 mA I get about the same light and a burning smell.

The straightforward solution I think would be to connect 2 leds + 200 Ohm resistor in a series to a 6v battery pack to get ~10mA operating current, and to connect many such units to the batteries. Probably there is a better solution?

How can I drive more then 2 leds in chain with a 6v battery pack?


texts: Upgraded flipflop square wave generator - did I do good?

texts:
I've drawn up a simple multi-frequency square wave generator, based on a astable multivibrator circut, with frequency trimmed by the two ganged pots (both 100k) and the range set by a DPDT switch, which switches capacitors (1uF, 10nF, 100p hard connected). There is an aditional output stage that "squaryfies" the signal and increases possible output current. Should I take the output, to steer a BJT for example, from the emmiter? Can I make the signal AC (-2.5V low to +2.5V high) by adding a capacitor?
Btw, collector R's are 1k and output base is 2k2


texts:
I'm trying to find a suitable high capacity (4-16GB) memory for an embedded application.  Clearly this is going to be some kind of NAND flash memory.  I need to be able to write to it at at least 16.5Mbit/s and I'd like to be able to read all of the data off it within a reasonable amount of time, say 10-20 minutes, so need to be able to read at around 13MB/s.  I've had a good look around but I'm still not sure what the best option is.
Here's what I've come across so far:

SD card memory

high capacity
acceptable speeds
easily obtainable (can buy in stores..)
reasonable price (< $20)
*must pay royalties (~$3000/year, can't really justify this expense)

eMMC

high capacity
acceptable speed
*difficult to obtain unless in 1000+ quantities (only want to buy 10-50 at this point)
reasonable price (< $20)
no royalties, i think?

So is there any way to get around the SD royalties?  Is there any way to get my hands on eMMC chips without having to commit to buying 1000+?  Are there any alternatives to these two options?  I've also looked for other high capacity memory chips however they seem to require purchasing in 1000+ quantities as well (checking on: find chips/octopart/mouser/digikey).


texts: What happens if the input of a voltage regulator gets out of the operating range?

texts:
I know that for a linear regulator to go into regulation, it is necessary to maintain (at least) a specific dropout voltage between its input and output.

But what happens if the input voltage drops so much that it will be closer to the intended output value than the dropout? What will be the "new" output voltage?


texts: How long do electrolytic capacitors last in seldom-used equipment?

texts:
I have a Fender solid-state amplifier nearing its 40th birthday. I've been going through it, replacing some failed logic chips and updating some of the op-amps (gaining about 10dB in S/N ratio!).

The low-voltage (±18V) DC supply has typical 220µF 25V electrolytics. I haven't tried to test them but they seem to work OK. But they're almost 40 years old! The amp has been used only sporadically over its lifetime—I wouldn't hazard a guess as to total hours but it's not many.

Should I replace them? I'm thinking yes, but if total hours are low, is it necessary?


texts:
I  have a toroidal transformer ac 230v  with x2 25v.
 I am trying to power an old ham amplifier  witch takes 28v 8amp (transistor) (blw77).
I have now linked the transformer to an 8 amp bridge rectifier  with a 35v 10000μF capacitor  and are getting 35.7v dc.
What kind of voltage drop would I get as the  transistor (blw77) should only take 28v 8amp.
I don't mind it not being on full power as I do not want to blow it up.


texts:
Normally vias are made with through hole plating. In the past they used to make vias by soldering a piece of wire to connect the top and bottom layers (like a short piece of 24 gauge copper wire). Could the same be done with solder?

Question: Can a VIA in a double sided PCB be connected with solder? Is there any precedent for  such?


texts:
I have a LC meter at hand that I'd like to use it to measure the inductance (dominated by L1) of a circuit branch like this :

simulate this circuit – Schematic created using CircuitLab

The bridge I'm using has the following settings:

Frequency: 100Hz or 1kHz
Assumption: parallel or series
Bias ON/OFF: I don't know what that one does, when activated the unit freezes and the screen shows "Bias"...
Q ON/OFF: Certainly to display the quality factor instead of the value of inductance/capacitance

First, in my case R1 is much lower so I intend to use the series assumption, but in the general case where R2 is the same order of magnitude of R1, what should be used: parallel, or series?

Second, the inductance is supposed to be independent on the frequency, so what's the effect that forces us to test at particular frequencies?

Edit: On request, here are the results of a quick test I've just run:

  Series, 100Hz: 18.8mH

  Series, 1kHz: 18.3mH

  Parallel, 100Hz: 1.4H

  Parallel, 1kHz: 33mH

Please note that I have a LED in series with R2 and a diode "head to toe" across that LED (to protect it against negative voltages), which will certainly change the "seen" resistance of R2. In this particular test case, R1=96Ohms and R2 = 1.5kOhms.


texts: In a shared wireless channel, what are the factors that impact channel gain for each user?

texts:
Assume a wireless channel with bandwidth B is shared among N mobile device users. Let's say the size of data transmitted by each device is in the range [100, 1500] Kbits.

How does the transmission power of each device and the size of the data packets transmitted influence the channel gain for each user?

Can you please explain the channel gain calculation with a simple numerical example (say, with 5 users)?


texts: Understand mosfet conductance simulation?

texts:
I made a simple simulation of following circuit (in LTSpice):

The IRFZ44N mosfet (10v on gate voltage) is switched on and off with 1kHZ 12V 50% duty cycle PWM signal. The "Heavy-load" is just a passive, 1 Ohm resistor.

I got following simulation result:

Why does the vout voltage reach just 7V (I expected something around 12V, since fet should be fully on)? Why is the load current (I heavy load) so much non-linear curved cycle?


texts: Confusion in +v -v and ground in amplifier circuit

texts:
I have an amplifier kit, in which it requires a power supply with +24v -24v and ground, the input is and audio jack which is +v and ground , i.e. both of these grounds are connected, i would be using a laptop charger to test the circuit as it needs minimum 19v but the charger has a pin in which i believe there is a + and a ground or - I dont know how to connect the power supply to the circuit as the cirxuit has 3 inputs(+,-,ground) and my power supply has just 2 outputs(+,- or ground) Im pretty new to the +,-,and ground concept and i am confused if i need to connect the - to the ground or not
This question is reposted from sound.stackexchange which was off-topic


texts: Adaptative Logic Module : Logic Element equivalence

texts:
I have implemented some circuitry with Quartus on a Cyclone 5 FPGA. This has be done for my master thesis. I have to justify wether the number of logic element used by my implementation is "expected" or not. During the class of my supervisor, I had a small example showing how I can build a 8 bits LUT with smaller LUT and multiplexer. I have to do the same things but with a concrete FPGA.

I have looked the datasheet of the Altera Cyclone V and I have found that they use Adaptative Logic Module instead of "simple" Logic Element. However, when I want to check the number of logic element used by this 8 bits LUT, the answer is given as Logic Element. At this point, I have several questions :

In this file, it is written that 2 4 bits independent LUTs can be implemented in one ALMs. Does it mean that 1 8 bits LUTs can be implemented in an ALMs ? If not, how many ALMs are needed ?
When I set only one LUT in my design and compile, the number of Logic Element used is 34. This number is a little bit unexpected since I have read that an ALM should be equivalent to 2 Logic Elements. Is that correct ? In this case, does this value seem correct ?

Thank you in advance

EDIT :

To help you, this is the code of my element (I have removed lines such that the post stays clear) :

module sbox_lu(input logic[7:0] in,
                output logic[7:0] out);
always_comb
case (in)
    'h0 : out = 8'h20;
    'h1 : out = 8'h8d;
    'h2 : out = 8'hb2;
    ...
    'hfc : out = 8'h53;
    'hfd : out = 8'hb4;
    'hfe : out = 8'h6;
    'hff : out = 8'hfe;
endcase
endmodule

As duskwuff suggested, this is some screenshots of the chip planner :
i.stack.imgur.com/WCXL3.png

i.stack.imgur.com/WzX7p.png

The first picture is a "global" view of the chip. We can see that 5 LABs are used. If I zoom on the right top group, I get the second picture. In the left bottom LAB, only one ALM is used. If I go back to the second picture, we can see that 33 ALMS are used. If I add the one of the bottom group, I get the 34 ALMs. When I click on the used ALM, I can see the path and that each ALM can be seen as a 6 LUT. If I refer to the previous document, I would need 4 ALMs for the 6 LUT and 3 2:1 multiplexer to handle the last 2 bits. In this way, I don't really understand why 34 ALMs are used. In addition to that the ALM of the left bottom LAB is empty.


texts:
The circuit below is from a really old device, however I'm trying to understand it. As far as I can see, the comparator U2 is working as multivibrator or astable oscillator, and this circuit works as long as PB1 is pressed. I think the purpose is to cause an AC current through the test coil. When PB1 is pressed and M2 is ON a current flows in one direction through the coil and while PB1 is ON and M2 is OFF the current reverses direction, am I right?

I'd appreciate any guidance.


texts: I've a question concerning the function of a transistor in the saturation state. In a Common Emitter transistor (n-p-n), at the saturation state (when collector current maximum), both junctions are forward biased. My question is how can the electrons coming from the emitter region and enter the collector region (through the collector-base junction) constitute the collector current (you have to note that it is maximum here)?


texts:
I don't understand our professor's explanation for the answer to this problem:

An LED is connected in series to a 150ohms pull up resistor and a MOSFET with drain-source resistance of 3ohms. The Pull up resistor is connected to a 5V source and the MOSFET is connected to ground (say MOSFET is turned on i.e. the gate). Now if there is a 2V drop across the LED, what is the current flowing through the LED.

I calculated the LED's resistance to be 102ohms giving the current through the LED to be 19.6 mA (which is correct).

But my professor says that the LED has no resistance at all and that my method of calculation is wrong (despite there being a voltage drop). And he said something about thevenin resistance which I did not understand.

Do you know what he is talking about?


texts: Looking for layout advice for industrial environment using ATMEGA328P

texts:
I need some advice on the layout of my board.
I'm using Atmega328P and intend to use it in industrial environments.
The purpose is to take a 30Vdc max input and step down to 5V with LM317 to power the Atmega and other IC's.
A relay will use the input voltage and if needed a series resistor, the LEDs will be driven by ULN2003. The main idea is to make a reliable system for monitoring battery packs during charge, up to 65Vdc, and based on the voltage the relay will cut the charge off. The SMD buttons will make the configuration for the relay operation.
On the next version will try to make SMPS power suply instead of LM317, first I need to test the software in use and then make changes on pcb if needed.
Schematic

Layout


texts: MCU: saving data directy on flash. What's the advantage?

texts:
I know on some MCUs its possible to save data directly on program memory (flash memory). AVRGCC compiler uses "PROGMEM" keyworkd, MPLAB C18 uses a similar one with the same effect.
However, what's the advantage of having data on program memory?

Maybe because those MCUs have a Harvard arquitecture and so read data from program memory is faster than read it from data memory? Is it "really so much faster" that it's worth to use it?

Thanks!


texts: Choose "safe" section of DDR memory in ZC702 board

texts:
I can not fully understand what section of the available external memory is safe to assign for a VDMA on the ZC702 board. I need to dedicate 4MB of memory for the three frames (640*480* 4bytes * 3 frames aligned memory). According to UG585
in Chapter4 table4-1 page 113,

it is clear that I should not use any memory for the VDMA in the 0x4000_0000 to 0xFDFF_FFFF. But which of the 0x0000_0000 to0x3FFF_FFFF would be the most "safe" to dedicate for my frames? Does it matter?