texts:
I'm trying to build a simple guitar tuner using MSP430G2452. The guitar's signal will come through its pickups, via an amplifier and 1kHz filter that I built using LM358.

== Context ==

Now, my concept of pitch detection is loosely based on zero crossings. I'm counting the number of peaks that I get by keeping track of 3 samples at a time. If the middle sample is greater than the two on the sides, it's a peak. This way, I count the occurrence of the peaks and find the pitch (which can either be the fundamental or one of the harmonics).

I've tested this using recorded guitar notes and Python on my PC, and it seems to work in theory.

== Now, my problem ==

I want the ADC to be triggered at my desired rate of say, 2kHz. For this, I'm using a timer interrupt enables and starts the ADC conversion. The ADC interrupt processes my sample and sets the timer again. This cyclic process is supposed to give me a sample every 1/2000 seconds.

However, I've noticed that the timer doesn't work as expected for very low counts.

Let's say I have the timer clock at 12kHz (VLOCLK) and the count as 6 to get an interrupt every 1/2000 sec. I set an LED to toggle in the timer interrupt to be able to view it. Naturally, the frequency is so fast that the LED should appear to be completely glowing. But instead, the LED blinks once at 4 or 5 seconds. It seems as if the timer is counting all the way up to the highest value, and coming back to the 6, and only then an interrupt is generated.

This only happens if the value of the counter is too low. I have a rough code below. This is a slightly older version that the current that I have. But it should give a good idea of what I'm trying to achieve. (In the code below, the timer has been set interrupt once per second, but doesn't work quite well for the low intervals I want)

#include <msp430g2452.h>

#define TIMER_COUNT 12000
volatile unsigned int value = 0;

void configClocks();
void configTimer();
void configADC();

void main(void)
{
    WDTCTL = WDTPW + WDTHOLD; //Stop Watchdog

    P1DIR = 0xFF;
    P1DIR &= ~BIT5;
    P1SEL |= BIT5;

    configClocks();
    configTimer();
    configADC();

    TACCR0 = TIMER_COUNT;
    TACTL |= MC_2;

    __enable_interrupt();

    while (1)
    {
    }
}

void configClocks()
{
    //Set basic clock
    DCOCTL = CALDCO_1MHZ; //DCO 1mhz
    BCSCTL1 = CALBC1_1MHZ; //Aclk 1mhz
    BCSCTL2 = SELM_0 + DIVM_0 + SELS + DIVS_0; //Master 1 Mhz, SMCLK = VLO = 12
}

void configTimer()
{
    TACTL = TASSEL_2 + ID_0 + MC_0; // SMLCK, No div, Stopped
    TACCTL0 = CCIE;
}

void configADC()
{
    ADC10CTL1 = INCH_5 + ADC10SSEL_1;
    ADC10CTL0 = SREF_0 + ADC10SHT_3 + ADC10ON + ADC10IE;
    ADC10AE0 |= BIT5;
}

// Timer A0 interrupt service routine
#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
    P1OUT ^= 0x01;
    ADC10CTL0 |= ENC + ADC10SC;
}

//ADC10 interrupt routine
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR (void)
{
    value = ADC10MEM;
    P1OUT ^= BIT6;
    TACCR0 += TIMER_COUNT; //Set timer count
    //__bic_SR_register_on_exit(CPUOFF);        // Return to active mode
}

== Another approach I'm thinking ==

There could be something I'm overlooking, or my idea itself might be fundamentally flawed. The other plan I thought was to have everything inside a while loop. Something like below:

while (1)
{
    //delay for 1/2000 time
    //enable ADC
    //SLEEP (will be woken up by ADC interrupt
    value = ADC10MEM
    //do something meaningful with the value
}

I have the try to above one. But I've put that in just in case one of you can capture any flaws in it, or point me to a better way of doing it.


texts:
What's the purpose of this capacitor here? I certainly don't think it's for decoupling but maybe bypassing? I presume we don't want any of the amplified RF which might have sneaked by the inductor getting back into the GNSS module.

Antenna is tuned for GPS / GLONASS at 1590 MHz.
Maximum input power at RF_IN will be 15dBm.
VCC_RF typical current rating from datasheet is 50 mA (Max 100 mA). - I dont have specifications from Active antenna yet.
VCC_RF typical is about 3.2 volts for this application.
The inductor I'm using is the recommended (in hardware integration manual provided by supplier) 27nH (LQG15HS27NJ02) with impedance at GPS freq > 500 ohms.
There is no recommended value for the capacitor however.

*Note: The recommended 10 ohm R bias resistor is relatively beefy at 1/4 watt.

What's the best way to determine it's capacitance / parameters?


texts: Impedance matching 2MHz clock 2m cable PCB to PCB

texts:
I am starting to design one of my first instances where I think impedance matching/ reflections might be an issue.

I want to daisy chain a clock from four seperate PCBs with a distance between PCBs of 2m using this 2MHz clock and this clock buffer to allow four separate PCBs to be synced to the same clock source.

I plan on using a four layer board, signal, gnd, power, signal with ground pours and vias.

Using the rule of thumb of 1/10 wavelength, at 2MHz the 1/10 is 149m, which is well below my 8m distance but I would rather tread on the safety side:

I used this trace impedance calculator aiming for 50 ohm impedance. Is this the right impedance to aim for? Is this calculator suitable for my four layer stack up?

Development boards, such as this one , seem to use SMA connectors, but in the interest of reducing BOM cost and number of cables is there a signal connector that can be used for this differential cabling at this frequency. I cannot find one spec'd for this application or maybe because of the 'relatively' low frequency it doesn't a special cable. I am currently thinking, shielded with a differential pair but the cable with 50 ohm characteristic impedance.

Any help would be greatly appreciated!


texts: Create Nixie tube pin connector socket in eagle cad

texts:
I am unsure how to properly layout a socket for a nixie tube in eagle cad. I'm especially unsure how to match the exact dimensions and what tool in eagle to use to create a hole with copper on both sides to house the pin connector.

The socket I'm trying to layout is for the recreation of the z568m tube. The socket is specified here (http://docs.daliborfarny.com/documentation/tube-socket/) with dxf file which can be imported into eagle cad. The recommended pin connector is https://www.digikey.com/products/en?keywords=H3161-01. The recommended hole diameter for the connector is, accoring to the socket spec, 1.95mm for ENIG surface finish, which my pcb manufacturer uses.

How would you create the socket? I started importing the dxf file onto the tNames layer. Then I created VIAs on the VIA layer with a drill diameter of 1.95mm and tried to match the positions of the imported dxf file by hand.

Anyways, this didn't feel like the proper way to do. Neither was I able to perfectly match the imported layout, nor am I sure whether using VIAs is the right choice. According to http://docs.daliborfarny.com/documentation/tube-socket/ the pin socket is pressed into the pcb and soldered from the bottom. Is that even possible with VIAs?

Thanks for any advice


texts: Current limit control using microcontroller

texts:
What I want is to open the MOSFET once the current passing through it exceeds 3A. A fuse is already being used, but more protection is needed.

There are some options to do it. I could measure the voltage in the MOSFET since its resistance does not change so much (it is around 130mohms). That could be done using a subtractor circuit and reading it with the ADC of a microcontroller (STM32F030R8).

Also it could be used two ADC to measure the voltage directly, just passing by a voltage divider.
But it is better to avoid this last option since the uC is almost at its full capacity.

I could also use a gate driver for the MOSFET, but I am not really sure which do use, since I have never worked with one before. Do I need to use one specifically for the p-channel?

If you have a different idea about how to solve the problem, please share with me. But keep in mind I need to solve this using the option with the best cost-benefit.

simulate this circuit – Schematic created using CircuitLab


texts:
What do the different coloured dots on microswitches mean? I see white, pink, blue, yellow "dots", the colour of the switch button itself, on a microswitch.
I'm looking for a Himake microswitch for my Logitech M185 mouse; will all "white dot" microswitches work - ie will they have the same height from the circuitboard-facing base to the top of the switch, the same travel, and the same (approx) resilience? Assuming I can interchange, is there a particular make that's known for longevity?


texts: What are the behaviors of capacitors and inductors at time t=0?

texts:
Do capacitors act as an open circuits or closed circuits at time t=0? Why? What about inductors?

I tried it out, and what I got was this: Initially when I opened the switch, the capacitor acted like a short circuit.  That should not be happening, right?  A capacitor should block DC.  I tried with a couple different caps.  I am very confused.


texts: securely storing and using keys in an embedded system

texts:
I'm using a microprocessor - PIC32MZ2048efm144 MCU that receives commands encrypted with a specific key, decrypts them and executes the command.
The encrypted commands are stored offline, so I cannot just change the key whenever I want. The key is FIXED.
The commands are encrypted by a server, and donwloaded by a phone. The phone sends the encrypted commands to the MCU at a later time, when it's not online. The commands are encrypted before the phone communicates them to the MCU, so a session key is not possible.

I am allowed to connect an external encryption / decryption module to the PIC, but then  the data will pass decrypted in at least one direction..

The solution brought here:
Storing a secure key in an embedded device's memory

uses one-time keys to encrypt, but I need to store a single super-secret key

What My employer requires is for the keys to not be accessible, so physical protection besides the one offered by secure memory modules and the MCU, is not considered.

Assuming no military-grade equipment is used, are there any know solutions you guys know and can recommend?

Thanks in advance!


texts: Unable to set the initial conditions for a capacitor or an inductor in PSpice?

texts:
I'm new to PSpice and working on setting up my initial conditions for a capacitor and an inductor in a series RLC circuit. However, whenever I try to set up my initial conditions, the IC box is greyed out and I can't edit it.

The circuit I'm trying to implement is:

Any help would be appreciated!


texts: Replacing mechanical 8-throw switch with a digitally controlled implementation

texts: I have 8 independent resistive loads on a 1P8T mechanical switch that I use to test a power supply on a circuit board (the switch is connected at the power supply output). I want to replace the switch so that I can programmatically change the loads using an onboard PLC. I have considered an analog mux and then connecting the select lines to the PLC. However I am concerned about the effect of ON resistance tolerance, and ON resistance variation from channel to channel, on the accuracy of the test load resistance. In addition, the low ON resistance models are limited in voltage range (I need 40V). Any suggestions on a more effective implementation?


texts: Using an optical switch with 5 terminals as a sensor

texts:
I am currently working on using a slottet optical switch like this OPB4xx one as a sensor for my project. The sensor going to send its output to my Arduino which then will process the data. According the to the data sheet it has 4 input wires and 1 output wire.

Here's a portion of the datasheet:

The wires being VCC, ground, output, anode and cathode.

VCC seems obvious it will probably go to the 5v pin on the Arduino,
ground goes to ground on the board. Output goes one the pins on the board.

But how should the anode and cathode be connected to the board?


texts: How to isolate low voltage control circuit from high voltage power circuit?

texts:
Can anyone give me a brief run-down of some methods I could use for this?

I want to drive a MOSFET or BJT with a 12v 555 circuit or oscillator.  The MOSFET will drive a high voltage circuit that can have both large positives and large negatives occuring on both sides of the transistor.  As a result, a MOSFET will require a floating voltage divider to ensure the gate isn't destroyed.  But that won't ensure that my control circuitry is protected.

I'm pretty sure that I really need to completely electrically isolate the control circuitry if possible.  Can anyone throw out some common techniques so I have an idea of ways to go about it? I need this to operate between 50kHz and 800kHz.


texts: Why do we take gain and phase margin from these points in stability?

texts: In the following graph, why do we take the phase margin from -180 degrees and the gain margin from 0 dB in stability?


texts: How to detect a heat emitting object in a distance from 10 - 50cm?

texts:
If I have a heat emitting object like a heater, radiator or hot cup of coffee, what sensor can I use to detect it by the fact that it is emitting heat?

I have hc-sr04 sensors but they use ultrasound and so are not suited to this. I have found this infrared sensor but I am not sure if it detects heat or just distance.

To put context as to what I am asking for, lets say I'm using the hcsr04 as the front eyes of a robot and need something to detect heat from 10cm to 50cm in front of the bot too.

Does anyone know what I can use or is the infrared sensors I provided above suitable along with any other type of infrared sensor?


texts: If a USB Cable is being used between two devices, are the power wires needed?

texts:
I am trying to figure out a way to give power to an android tablet and a DSLR camera at the same time (for a photo booth).

I was able to purchase an AC adaptor "battery" plugin for the camera, but the DSLR needs to be plugged in to the tablet via an OTG data cable (USB).

My question is; Can I open the USB cable and cut the two power cables (red and black), then wire them to a mobile device wall wart charger?

Basically, I want to open the USB cord and not cut the data cables so that the camera and tablet are still connected via data, but I want to remove the red and black wires going to the camera (so the camera does not get power).  Instead, I want the power wires going from the tablet to go to AC power via a mobile device wall wart charger.
will this ruin any data transfer? Does the data need to be transferred with the power for information to be sent?

I think I've over-explained enough, but please ask if I haven't made sense.


texts: Placement of sense resistor on DC-DC converter

texts:
For my design I am using DC-DC converters LTM4620 and LTM4644, which integrate the MOSFETs and the inductor in the chip.

For measuring the output current, I will add a sense resistor in each output with values from 1m to 5m (depending on current range). This measurement is independent of the DC-DC converter feedback loop.

My question is related to the position of this sense resistor, because in some articles, it is placed before the output capacitor, whereas in some designs (for example, KCU105 board), sense resistors are placed after output capacitor.

What should I consider for choosing the correct place for the sense resistor, or is this really not important?

Thank you very much!


texts:
I have a weird problem with the electricity in my house. The house has a three phase municipal supply 400/230V WYE electrical system. The house is old and already I have had problems with water causing short circuits. Before anyone crucifies me, I am going to leave this house in a month or two and leave all the problems to the owner to fix before he rents it out again. But it is unlikely he will fix the current problem so I have to repair it myself to enjoy the luxury of electricity for the last days I will be living here. I am quite capable, but I just need a memory jog. The house is so badly wired that I have been unable to determine how they distributed the loads.
So, during the present rainy season, all of a sudden  on two phases I get 270 volts, the third phase is 230V (Phase to neutral). If I plug in a high load appliance such as a kettle on any phase, the other phases go ballistic, i.e. they either drop to below 200V or climb to 280V.
A while back I was a facilty supervisor and one problem we encontered was a failed neutral line on a WYE system. This puts 400V across all three phases (P-N). So I'm wondering if water has somehow gotten into the cables and caused this? It's obviously not a complete neutral disconnect otherwise I would measure 400V P-N on all of them.


texts:
UPDATE

I changed the top layer to try an other approach. What do you think ? (I didn't implement the vias yet, and didn't change the bottom layer, which is a full ground plane now)

I am designing my second ever PCB layout and I would like some feedbacks.
The circuit is a basic step down converter using 12V as input, and outputing 3.3V.
The maximal output current will not exceed 1 Amp.

Since I'm a newbie in PCB design, feel free to point out any mistake or tips to help me improve my designs.

Here is a link of the voltage regulator's datasheet, and pictures of the design.

Datasheet

Note : Just about the designators, ignore the ones that are badly placed (like the one on holes). It is just to help finding components on schematics, I will rearrange them later)

Thank you very much.

Fever


texts:
I am using 3 PCF8591 ADC connected via i2c to a raspberry pi.

At first all 3 of the ADC worked. All of a sudden I started having issued with them. Occasionally one of the i2c devices stops showing up (i2cdetect -y 1). And now when reading some devices they show up and connect however they always read 0. I attributed this to a damaged ADC so I replaced it but got the same issue. Sometimes is works, sometimes it doesn't. Often after first starting it will work for about 10 seconds then start reading 0.

This is the layout of the PCB I used. I realised I had forgotten the pull up resistors so I jumpered 2 4.3k resistors from the SDA and SCL pins to 3.3V pin.
I haven't had heaps of experience with PCB layouts so I'm wondering if I did something very wrong that is causing the i2c to not work all the time outside of the two pull up resistors I missed. I do not want to get another batch of PCBs made if I have made some other big mistake.

bus = smbus.SMBus(1)

def readADCPin(pin):
    bus.write_byte(address,pin)
    x = 0
    value = 0
    numReadings = 4
    tot = 0
    while x < numReadings:
        value += bus.read_byte(address)
        x+=1
    value /= numReadings
    return value

This is the code I am using. As you can see I'm using SMbus to talk to the different devices.


texts: Why do some multimeters have discrete ranges for measurable values and some just measure based on signal type?

texts:
I have a multimeter in my toolbox that has ranges of values it measures in dc voltage, a lot like the one below which can read DC but reads it by orders of magnitude. In order to get a proper reading I have to select the correct range, otherwise my meter reads 0.00L.

I was browsing some tools on amazon and found this meter which, excepting amperage, does not need to have a range selected discretely. I was curious, it's obviously possible to do as this meter exists -- so why do your regular off-the-shelf wal-meters require you to select the value range?


texts: Why does the USB-C plug shell carry a voltage?

texts: I purchased a Xiaomi laptop PRO computer, which uses a USB-C plug for its power input. I recently measured the plug's shell with a AC voltmeter, and found to my surprise a voltage between 90 to 100 volts (AC)! May be that's why I always felt the sting of a slight electrical shock every time I used the computer. I understand the shell is used for signal shielding and therefore should not be carrying any voltage. Why then is there a voltage? How can I get rid of it? Was this a design or manufacturing error? (The other end of the USB-C cable is connected to a 2 prong non-grounded 60W transformer plugged into the wall.)


texts: Is it safe to short circuit 3 x 9 V block batteries?

texts:
I'm trying to heat up a thin wire like shown in this tutorial. Since short circuiting one 9 V block battery doesn't provide enough amps to heat up the wire sufficiently.

If I take 3 of those 9 V block batteries and connect them together, will the power be so much that the short circuit causes a reaction like an explosion?
Will it make any difference if I connect them parallel or in row?


texts: Can someone help me to find the right transformer for this power supply?

texts:
So my current project is building a replica of the ARP Pro Soloist synthesizer from the 70’s. The project is mostly going very smoothly, but I am having some issues with the power supply section of the synth: Even after many searches, I don’t know what kind of power transformer to select.

As you can see on the schematic, the original unit used a transformer with a center tapped primary and two center tapped secondaries. This seems unusual to me, because most transformers I can find have either only one center tapped secondary winding, or two secondaries, but not center tapped. Other than that, there are almost no other indicators of what kind of transformer was used.
The only other things that caught my attention are that the power supply uses a 250 mA fuse, which means - if I understand it correctly - that the instrument doesn’t use more than 250 mA of total current, because the fuse would blow otherwise.
Also, the 1N4448 diodes used here as a bridge rectifier have an average forward current IF(AV) of only 150 mA.

The power supply outputs 3 individual power rails of + 5 V, + 15 V, and - 15 V, so the transformer must be able to handle that.

Another thing that may help you to help me is something I found in the service manual for the instrument. The section about the power supply mentions what kind of dummy loads should be used to test the power supply. Using Ohm’s law to calculate the current for each rail, I got the following results:

+ 5 V = 1 A
+ 15 V ≈ 0.06 A = 60 mA
- 15 V ≈ 0.05 A = 50 mA

One final thing to mention is that I would like to use a toroidal transformer, since they are less noisy and better suited for audio applications like this one.

So my questions are:

What kind of power transformer should I use?
How can I know the voltage ratings for each of the secondary windings? Aren’t they supposed to be a little bit higher than the needed voltage?
What current rating is the transformer supposed to have?
And most importantly: Where can I buy it?

I really appreciate any help!

Thank you in advance,
Martin


texts: How does a router send different data to different devices simultaneously?

texts:
How does a WiFi router send different data to different devices at the same time? Since all devices connected to it pick up the same signal being emanated by the router, how do they get the data meant for them?
Does the router do something like send addressed data packets and each device filters out the packets meant for them? Or is the router able to send different info/EM waves to different devices simultaneously?
I've googled this a bunch but haven't been able to find any clear answers. Thanks.


texts: Designing a PCB layout without having a schematic diagram (or netlist)?

texts:
Could you please let me know if it's possible to design a PCB layout without a schematic diagram?

I outsourced the development and manufacturing of the ARM board which has 512MB DDR3 RAM and 4GB eMMC. The outsourcing company promised to make it in 45 days, but they didn't give me the product even it's already more than 100 days from beginning of the project. When they said they were manufacturing its PCB last month, I asked them to send its schematic diagram. But the answer was that they didn't finalise the schematic diagram and need 2~3 days to make it. As far as I know, you can't make PCB without importing a netlist from a schematic diagram file, especially when you have two DDR3 RAMs. It has been 1 month from the time and still I don't have the product. I need to decide how to react and would like to know if the company lied.

I spent about $6,000 for the outsourcing and now I have no idea what to do.


texts: Why does the A8 have twice as many transistors than the Haswell processor yet runs on less power?

texts:
There's something I don't get - I am always under the impression that the more transistors we pack in, the more energy it consumes and the hotter it gets (assuming we haven't shrunk the die). However, the Apple A8 has around 3 billion transistors while the Intel Haswell has half the transistor count, yet the A8 is able to run cool and takes much less energy to compute.

Can anyone explain the difference?


texts:
I am wanting to control a voltage range of 0-10v across a 10k load with PWM from a micro. Now I was told to use this circuit with an n channel mosfet:

This is what I understand so far:
R1 is to reduce current flowing into the base
R2 is used to pull mosfet closed when its not conducting

I was wondering if I could have help understanding what R3 is doing?

Cheers


texts: Beginner PCB Repair - Voltage Regulator Issue

texts:
During a fault finding mission on my car I found the Vref on a sensor that should be 5V sitting over 7V.  I traced it back to one of the modules and found the pcb mounted voltage regulator was outputting the 7V I'd seen at the sensor.  The reg was a LM2931-5.0 fixed voltage regulator in TO-92 config.

In doing some research on the specs I thought it may have failed due to engine bay heat and replaced it with another LM2931-5.0 TO-220.  I changed to the TO-220 as it had better heat handling characteristics.  The problem is that the new reg is now passing the full 14.5V through.  I tested continuity at the pins and there is no shorts.

Has anyone got any ideas why these regs aren't dropping the voltage to 5V as they should?  The pins are slightly larger on the second reg and took some force to install.  I wondered if I'd damaged it doing this but I thought it that were the case I would see a short between them.


texts: Adding capacitors prevents car peltier cooler from making low battery light flicker, but why?

texts:
I have a Black and Decker Heater/Cooler that I want to use in my Camper as a little drink caddy for in front of my Futon while I have company over and we are playing games, and I just switched to a new Camper and I stripped the old camper of some of it's parts like the converter So I wired the cooler up to the Converter and the "Vehicle Battery Low" Indicator light turned on and started rapidly flickering like it would if it was plugged into the car and the battery was dead.

So I knew this solution would work, but I don't quite know why,
(I guess I was thinking of Automotive Stereos and Amplifiers where you can sometimes buy a big Capacitor and it will prevent the AMP from drawing too much power from the battery and alternator and making the lights flicker during times of High BASS and Volume.)
can anyone explain to me why this would work though?

My solution was to take an electrolytic type 10,000UF  16V Capacitor and put it between the Positive and Negative with respect to appropriate polarity, but all it did was make the cooler blink faster, So I put another Identical Capacitor in Parallel with the first one and ZING the cooler turned on and operates as though it is on a 12 Volt Battery now.

I am great at experimenting with electronics and I have been wiring circuits since I was a little kid, since I can remember anyways, but I am not an engineer.  Can anyone possibly explain to me why or how this worked?

I also know that sometimes if you over volt or over Amp a capacitor it will get hot and it will vent and that will destroy the capacitor.  Could you help me to ensure this will not happen while running this device I have created?

Cooler~
Black & Decker: TC212FRB (Peltier Cooler)

NOTE: My Multimeter says it is only pulling about 3.60 Amperes at 12 Volts 43.2 Watts

Converter~
Phillips: Model Number PC-201-A1, It puts out DC 12 Volt Maximum 20 Amps or 240 Watt Capacity

2X capacitors JRB 10000 Micro farad at up to 16 Volts Vented Large Canister type 105C in Parallel

The Cooler is getting cold, but the Converter is getting slightly warm (there seems to be a Wire wound resistor inside heating up for some reason, but if I remember right it does this normally as old as it is, so IDK if this is a great idea or not,but it seems to be powering it well when it couldn't power it without the Capacitors, and I am really not sure why it couldn't if it can now.  The capacitors are not adding voltage or amperes are they? Capacitors just store and discharge DC electricity right? This is baffling to me.


texts:
I'm doing a sound system for\with a friend of mine (I've done many, many before)....

In the past I've done either simple L\C or LC crossovers, but I've been looking around for something I can build by Sunday with what I have available (Everything but inductors, and very minimal op amps that aren't really meant for audio), but also something that is A-grade work. So I pondered an RC crossover, but evidently you can't do a second order\two stage setup effectively with those.

For a single stage RC high pass crossover at 120Hz, my R value was going to be 13.2KOhms, and C value was 1uF.

But then I found these and I'm highly interested:
http://www.sentex.ca/~mec1995/tutorial/xtor/xtor6/xtor6.html
http://www.radio-electronics.com/info/circuits/transistor_activehighpassfilter/transistor_highpassfilter.php

The problem is either there are no formulas available, or I'm just having trouble with the math (it's not an excuse to be lazy, I actually have trouble with some math at times due to a brain ailment)

So I was wondering if I could just get a little assistance. The crossover frequency is ~120Hz. I'd like a second order filter for a faster rolloff...

Thoughts?


texts:
I'm trying to make a 1-bit computer, and I'm stuck on the registers. I think I am going to have 2 of them, and I want a way to separate their outputs. Let me explain. Let's say Register A has a 0, and register B has a 1. If I want to invert Register A(or do anything else with it), I would need to get a 0 on the bus. But I can't do that as long as the registers are connected, because the 1 from Register B would go into the bus and ruin the entire program. If I want to separate A and B, you would say,

  "Just use a tri-state buffer".

But why can't I just use an AND gate to separate the registers from eachother? It would block one register while letting information from the other register pass. So, are tri-state buffers even necessary?


texts: What should I know about "press fit" connectors?

texts:
I'm looking a particular type of connectors and they are all press-fit style. I've never dealt with such connectors before and to my knowledge they do not require any soldering.

I have a questions about them though..

Here is an example of the type of connector I am looking at

HM2J07PE5118N9LF - Digikey

HM2J07PE5118N9LF  Drawing

Can these be manually inserted or do they require some sort of constant uniform force machine to press all the pins at once ?
Are there special considerations that are required from a PCB design perspective other than that the diameter of the hole should be less than the diameter of the pin ?
Can I just opt for soldering the pins instead of worrying forces and specific diameters ?


texts: Need help identifying this connector from a Pulsar Taximeter

texts:
This is the primary mounting connector for Pulsar 2010, 2020 & 2030 Taximeters.
I have looked many times and have never seen this exact one...

It is symmetrical with 5 pins.  The pins have lip on the outside edge that after they have been crimped cause them to lock to casing.

Hopefully the pictures are clear enough.

Thanks.

Ok, here is a scale as requested.


texts: Why do we need small signal analysis in differential stage?

texts: I do not understand why do we need to perform small signal analysis in the first stage of an op-amp, that is the differential stage (2 mosfets with sources in common and a current generator under them). For example, if I consider the classic non inverting configuration of an op-amp with a constant generator (For esample, 5V), I don't see a sinusoidal signal between the 2 input terminals of the op-amp (the voltage between them is approximately 0)


texts: Which Amplifier Should I Use After my DAC (what are I am doing wrong)?

texts:
I am working on a project "cat projector" which shall "shout" at the cat when she jumps on the table in the living room.

For the logic I use an Arduino board which plays/streams the sound at 22.1kHz from a SD-Card and using the MCP4821 DAC to generate the signal. This works perfectly fine (as you can see on the measurement). The output on the DAC is 0-4V.

This is the schema for the DAC part of my project. R3 and C4 should filter the noise from the Arduino board.

VCC for the DAC is 5V and comes from the Arduino board.

The problematic part is the Amplifier I use. This is the schematic for the amplifier with the LM386N-1 and some resistors and capacitors to filter noise. I actually used one of the usage examples from the data sheet of the chip. The amplifier is powered with 9V directly from the power source.

I drew a yellow and a blue point at the places of the measurements. What I measure at this points is this:

I am just lost at this point. If I try to increase the amplification, I quickly reach the limit and get the shown distortion until there is no hearable sound left.

Note: the 0V line for the blue line is at the bottom of the screen. See the Marker "1" and "2" for the 0V line of the measurement.

I am a beginner with amplifier and do not know what I actually do wrong, or how I could improve this setup.

My final goal would be to get around 40-60 dB in front of a small speaker.

So, how can I improve my existing setup? Or what are I am doing wrong?

Final Solution

Just for documentation, this is the working circuit I ended up with. It is using the LM386N-1 with a 8Ω, 0.2W speaker. The sound quality is usable, with small distortions on high frequency tones.

Using C1/C5, there is no hearable noise if the DAC is turned off (0V level). The actual measurement looks like this:

The yellow signal is measured in front of the speaker. The blue signal is measured at pin 3 (input+) of the amp. Note the different scales: Yellow 1V, blue 50mV.


texts: MOSFET as heating element for a RaspberryPi

texts:
I developed a PID autotuning algorithm that I want to test outside of a simulation environment. For this purpose, I got temperature sensors to send data to a RaspberryPi.

Now I need something to produce heat, but it needs to be controllable with a RaspberryPi, so a Peltier element can't be used (needs to much amps). Someone told me that I could use a MOSFET for this. Does that make sense?

How difficult is it to implement something like this?


texts: Lowpass filter design with transimpedance and difference amplifiers

texts:
I have a DDS chip with complementary current outputs that I need to filter. I'm using a design like this:

I need a different cutoff frequency, however - 2MHz instead of 50KHz. Note that I'm not using the particular opamps specified in that schematic - I'm using the LT6207 instead.

I understand the basic operation - TIAs followed by a differential input amplifier -
and after reading the active filter design techniques chapter for Opamps for Everyone, I think I understand the basics of active filters, but I'm stumped as to how to apply those principles to this design.

Unless I'm mistaken, it consists of a first order filter (the TIAs) followed by a third order filter, which violates Opamps for Everyone's prescription that only odd order filters contain order-1 stages. Thus, their calculations and coefficient tables don't seem to be terribly useful.

How can I calculate the component values to adjust my filter for a new cutoff frequency?


texts:
I have a Ni-Cd battery (8AA) 700 mAh 9.6 V, taken from an RC car. However, is no longer capable of powering up sufficiently the RC car.

Specifically, servo works fine but motor can't spin. Instead, there is a sound came from the PCB (I guess from the conductive area of motor's power cables). In addition, after a while, servo can't turn the wheels.

Battery is fully charged (multimeter is showing 10.2 V). However, I can't imagine that there is something else wrong. Is there any way to ensure that battery isn't working properly? Could this mulfunction be due to the amperage?

Battery neither has been charged for a long time, nor was in operation. Anyway, how should I treat to a Ni-Cd battery?

Thank's in advance.


texts:
I have an upcoming exam in a few days so I'm going trough some problems I found online or in textbooks and just try to solve them.

I have one here where I'm not entirely sure about the initial conditions of the problem and I hoped that maybe someone could help me out a little bit.

The circuit:

The problem:

A LC circuit is driven a long time with constant current \$I_0\$ (switch closed). At \$t=0\$ the current gets switched off (switch off). What are the currents and voltages on the capacitor and on the inductor for \$t=0^+\$? Calculate the voltage on the capactior for\$t\gt0\$.

So basically I have to find the inital conditions for the differential equation I have to setup for the next question where the voltage of the capacitor is asked.

My though process was: Before the switch is openend: $$I_L(0^-)=I_0$$ $$U_C(0^-)=U_0$$
Since \$U_C\$ and \$I_L\$ are continuous it should follow that $$I_L(0^+)=I_0$$ $$U_C(0^+)=U_0$$The thing I'm unsure about are now \$U_L(0^+)\$ and \$I_C(0^+)\$ . My guess would be that $$I_C(0^+)=-I_0?$$ $$U_L(0^+)=-U_0$$ since KVL says that \$U_C+U_L=0\$.

Sadly there are no solutions avaiable so I don't know if I'm doing the right thing here, it would be great if someone could give me a hint or an advice on how to tackle this problem correctly.

Thank you!


texts: How can you increase an antenna's range?

texts: Can you simply increase the voltage going to the antenna, or is it more complicated than that?


texts:
I am currently running a club for kids (9-11) for Arduino and we are making a robot and are moving on from motor/transistor drivers to half-hbridge (so we can go backwards).

The kids are learning to solder and doing well.
We want them to use a h-bridge chip, rather than using a shield, this being:
1. They are so excited about using a chip
2. costs
3. education - shields tend to hide what is going on.

So all works fine on our breadboard, however the crunch comes when moving to something more permanent to place on our robot.

As a novice electronics wise (programmer here!), I am really surprised that I cannot find a mechanism that easily and cheaply allows me to solder a chip and then make the jumper connections (16 for the half hbridge or even shift registers).

Here is what we have tried:
1. Veriboard - great, but expensive (can't buy from china) and still requires you to cut to size and drill out a central reservation.

ProtoBoard (pad per hole), really hard to solder the chip holder, and to connect a jumper wire to a chip leg, also requires the crazy solder jump technique or more jumper wires, the kids maybe get it right once or twice, but 16 perfect, not a chance.

So my question to you all is, what would you recommend we do with a class of 20, all wanting to connect 16 jumpers to a single chip?

I look forward to hearing your thoughts.

thanks

jon


texts:
As I have heard it is a common practice to fill the unused flash memory of a microcontroller with an jump instruction to the reset function. This aids in resetting the MCU in case of the PC is corrupt, faster than the expiration of the watchdog timer.

I am currently interested in ARM Cortex-M microcontrollers. Which is the instruction I need? How to convert it to hex to place it in the linker script, how can I define the jump address I want?

What are the modifications needed in the linker script?


texts: Every time I want to program my ATtiny85 using AVR Studio 6 it has the MyProject.elf file pre-selected in the "Flash" drop-down box in the Device Programming dialog. Obviously I want it to program the MyProject.hex file, but I manually have to select this every time using the drop-down list. Does anyone know a trick to get my selection to stick?


texts: Sensor, ADC, SPI master placement - 1 meter distance with 4 MHz speeds

texts:
I have an accelerometer sensor which must be placed 1 m from my microcontroller.  I can choose whether to place the ADC near the sensor or the controller.

I understand that longer distances from the sensor contribute more voltage fluctuation pre-ADC (noise).
Longer distances from the microcontroller increase SPI errors and limit my transfer rate.

If I need to clock the SPI transfers to 4 MHz, where should I locate the ADC?  Will the 1m distance be limiting my transfer rate?  Will 1 m of pre-ADC wire contribute significant noise?

Notes:

The ADC has a 0 – 5 V input range, I care about steps in the 10 mV range (1/500th of the range).  If my noise peaks are below that the application will be successful.
The wires between the ADC and sensor will carry 3 Vout channels, ground, and 5 V.
The sensor, wires, and (depending on placement) the ADC will undergo impacts as the application is impact characterization.  Impacts will be due to dropping with an estimated peak g force of 150 g for 2 ms.

Accelerometer specs

Update:
I decided to run the ADC close to the pi (~6 inches) and the sensor far from the pi (~0.75m) as the analog noise sounded easier to troubleshoot than the digital errors.  I currently get a baseline of ~61mV from the sensor with a standard deviation of 10mV (based on ADC readings).  Peak to trough noise levels are about 60mV.   This is a decent start but I think I have some improvements to make in the circuit design.  For example, without a sensor attached I get a fluctuation of about 100mV on the scale of 1Hz.  I'm going to improve my Vref and grounding scheme and see if I can remove some of this noise. Thus far I don't think my main issue is cabling, though insight is welcome. Also found this useful reference: http://ww1.microchip.com/downloads/en/AppNotes/00688b.pdf

Update:

My final circuit was drastically improved from the first so it will be hard to say exactly what changes were responsible for the improvements.  My initial design didn't include decoupling capacitors, a dedicated reference voltage, and also had multiple paths to ground.  I eventually designed and got a PCB fabricated for about 20 bucks + shipping.  With this system, a 0.75m length of 10 wire IDC cable carrying the analog voltage to the ADC, and IDC connectors here is my result:

The right axis shows the integer output of the ADC.  The standard deviation of that variance in y is about 3 units (mV) and in z is about 4.1 units. Peak to trough is about 20 units. This is a huge improvement over the first design and I'm very happy. decoupling capacitors and a reference voltage were critical it seems.  Going throught the whole process of getting a board fabricated was super fun as well.

I can't explain the increased variance for the z channel.  It is furthest from my power/ground wires.  It is the last wire on the end of the flat cable, so that could be it.


texts: AC / DC Backup Power Supply For Solar Irrigation Pump

texts:
I think this technology exists but I don't know what the device is that I need to do the job.

I need a DC Power supply that will pull input 110V - 220V AC (for here or international) and will output 48V DC @ 20A. But here's the catch. It's to provide backup power to a solar irrigation pump that currently runs on 48V DC.

Using a timer I'll allow the AC power source to get power from 6 am to 10 pm. I only want to provide the AC power when the solar DC power is absent (like a very cloudy day or after sunset.) But when solar is present and working fine, I don't want the AC to be drawing hardly anything.

So my question is, while I could design a circuit to measure the solar voltage / power input, and then kick on the power supply and disconnect the Solar, I am wondering if that is re-inventing the wheel.

Is there a device that does this already that I should simply buy instead? Like some kind of AC -> DC power supply that can detect the voltage / amperage / power from the solar and can top it off or smooth it out for me?

Remember I don't want to be using AC power hardly at all when solar is available.


texts: How to design an amplifier to meet particular specifications

texts:
I need to specify the (W/L) ratio of transistors and the value of the current source in an amplifier as shown in this picture

so that these specifications are met:

*the height of the input step for evaluating settling time is 0.25v.
I tried to approach it by first using the settling time to evaluate slew rate and wt and then using the approximation of wt = wp*gain but didn't succeed.


texts: Why is there no net current in a wire without a voltage applied?

texts:
Atoms of materials with loosely bound outermost electrons constantly exchange charges between each other over time, and these materials are called conductors. Now, the conducting process is different from the one often described in the electrical engineering textbooks.

This implies that in order for current to flow in the circuit, an electron has to move from one lead all the way to the other, which is simply not true. Reality is something like this:

The electron at the far left coming from the negative lead of a battery, for example, is then colliding at the nearest atom and because of its acceleration it's knocking out the electron which is revolving at this shell level. The knocked electron is heading to its closest atom and in turn it's doing the same, knocking out an electron which creates a chain reaction. So, basically, electrons move just a little bit, but the overall outcome is virtually instantaneous.

What I don't understand is if we take a regular conductive wire WITHOUT applied voltage on it, electrons still constantly bounce from atom to atom which means that literally there is "an electron flow" in the wire, but if we connect the wire to a LED diode nothing would happen. So, what I am really asking is how differs "an electron flow WITH applied voltage" from "an electron flow WITHOUT applied voltage" in a wire.


texts:
I am designing a changeover circuit that will switch the power of attached appliances between two electricity providers. The two AC mains are of 220V RMS voltage and 50Hz frequency sine waves. The two supplies are independent and out of sync. I will be using a microcontroller to control dpdt relays for switching.
I may need to switch between grids every hour or every half hour.

During one cycle of sine wave, what is the best time to switch the load? I did some research and found out that in the UPS, when it's time to switch over from inverter to mains, the controller first syncs the inverter with the grid by varying the frequency of the inverter before switching. But in my case I can not sync the two supplies.

So my question boils down to:
What are the things that I should worry about during switching? I want appliances to remain alive during the switching and I do not want to damage my appliances (due to some weird harmonic) during the switching.

It would be much appreciated if someone points in the right direction.


texts: Energy conservation when adding braking resistor to H bridge?

texts:
This may be a stupid question but I'm missing something fundamental about energy conservation of electrical machines - I am sure I have forgotten something from basic machine theory but I haven't found out what thus far:
Let L, R, E be the equivalent model of a DC brushed motor winding (inductance, resistor, back-EMF).
Say we are braking the motor either by short-circuiting the windings, or applying the reverse voltage, let I be the current value. The mechanical power is -EI right? Energy conservation dictates this power is dissipated somewhere, and here it's RI^2.
Now, I close a switch and insert in series with the winding an additional braking resistor (for example when freewheeling the current goes back to the supply and into a braking resistor when the DC link regulator switch is closed). The braking power is still the same, -EI, since the current has not yet changed thanks to the inductor. However, now both the windings and the braking resistor dissipate more power than before the switch closed: (R+R2)I^2.
What am I missing? Is the inductor providing the power for the additional resistor - meaning the energy dissipated in the winding cannot be reduced for a given mechanical energy to be dissipated?
This is ultimately what I am trying to achieve, my winding cannot handle the mechanical energy I have to dissipate from the rotor when braking.


texts: Finding an unknown resistance with superposition

texts:
I've been given a problem in which I need to calculate the resistance of an unknown resister \$R_2\$ by using the superposition method. The only other info which I have is that \$R_2\$ needs to be such so that \$I_1=I_2\$ and \$I_3=20\text{ mA}\$.

I hope the image is readable:

I've set up the three superpositon cases, but at the start of trying to calculate the solution I realised that I had no idea how to proceed with an unkown resistor.

A sort of idea I had was to solve for \$R_2\$ in the first two cases, but then I don't know what to do with the third case.


texts:
I am not an engineer.  I have researched basic information that can be found on optocouplers.  I understand the theory of 4 pin optocouplers.  I believe I even understand basics of 6 pin optocouplers.  However, everything I have located about 6N137 or 8 pin optocouplers in general, assumes I understand more than I do.  I have located two types of information on 8 pin optocouplers.  Basic info: which does not seem to include the 8 pin configuration, or Advanced info: which assumes I have knowledge I do not possess.

I have the Vishay 6N137 datasheet.  Assume this 6N137 to be used instead of a 4 pin optocoupler or a relay in a simple circuit where closure times must be short.  Small amperage DC input to trigger larger DC amperage output circuit.  My questions are extremely basic.

Q1)  Pins #1 & #4, may be used for what purpose?
Q2)  Pin #5, I understand is Ground, but is it ground back to the negative side of the Vcc Collector DC supply?
Q3)  Pin #6, Vo=Voltage Output.  Is this output connected to the negative side of the circuit you are closing?
Q4) Pin #7 Ve=Voltage Emitter.  Or is this the output connected to the negative side of the circuit you are closing?  If not, what is it for?
Q5)  Pin #8  Vcc Collector Supply.  I assume the positive side of the circuit to be closed when the optocoupler is activated is connected here?

A direct answer to my questions would be wonderful.  Direction to literature that describes specifically what I am asking would be helpful also.

I could understand 8 pin optocoupler layout better if someone had a diagram of the inside a 6N137 optocoupler showing internal routing of all 8 of the pins.  The datasheet does not seem to account for every pin.


texts: Use of schottky diode and tracking peaks of input signal with capacitors

texts:
I am using this instructable to make a VU meter: http://www.instructables.com/id/Mini-Decibels-a-Simple-Volume-Meter-With-an-Electr/?ALLSTEPS

I have two questions.

What's the use of the Schottky diode 'D1'?
The instructable says that the capacitor 'C5' is used to track the peaks of the input signal. What is the exact procedure of this tracking? Also, what would happen if this capacitor and the resistor R9 through which it discharges is eliminated from the circuit?


texts: How to solve this non ideal inverter opamp?

texts:
it is asked to make a non ideal inverter opamp that has an input of 2mV or and get an output of -100mV, so I think the next circuit should suffice.

simulate this circuit – Schematic created using CircuitLab
But later there is  extra questions: the error in the output voltage must be less than 0.1%, ¿What is the gain in open loop of this op-amp?¿What is the error if the gain is 10000?
I understand there should be a Beta parameter
\$A_{v}^{ideal}=\frac{1}{\beta}=\frac{-5000}{100}=-50\$
\$\beta=-0.02\$
and the closed-loop gain is
\$A_{v}=-\frac{R_{2}}{R_{1}}(\frac{A\beta}{1+AB})\$
but then how can be calculated he error or make it is between the limits required?


texts:
I am currently trying to achieve delay of 1 uS using timer in stm32 for my application purpose.

SYSCLk is set to 16MHZ LSI and define same for timer clock.
Timer used is a 16 bit timer.
The logic I am using is this.

void delay_us (unsigned int cnt_val)
{
unsigned long x =0;
unsigned int cnt=0,  psc_cnt = 0;
RCC->APB1ENR |= (RCC_APB1ENR_TIM6EN );

x = (unsigned int)((cnt_val * 1000) / 62);
if(x < 65536)
  {
    cnt = x;
    psc_cnt = 0;
  }
else
  {
    cnt = 0xFFFF;
    psc_cnt = x / 65536;
  }
TIM6->SR = 0x00;
TIM6->ARR = cnt;
TIM6->PSC = psc_cnt;
TIM6->CR1 |= (TIM_CR1_CEN | TIM_CR1_OPM);
while(!(TIM6->SR & TIM_SR_UIF));
RCC->APB1ENR &= ~(RCC_APB1ENR_TIM6EN);
}

Issue is when i tried to achieve the delay of 1 us i am getting 2.5 us.
I checked it by toggling the gpio.

while(1)
{
GPIOA->ODR ^= GPIO_PIN_5;
delay_us(1);
}

can't understand the reason and looking for the solution.


texts:
This is the question I am struggling with

I have found a node equation:

$$ I_3 = I_1 + I_2 $$

I have found two loop equations:

$$ 50 = I_3 + R_1 \times I_1 $$

$$ 50 = I_3 + R_2 \times I_2 $$

I'm not sure what the third loop equation is.


texts:
I need to convert 24V DC to +5V and -5V to power two op-amps (opa2134) and one ATtiny85 with minimal heat generated from the circuit.

What voltage regulator would you recommend ?

//Digis


texts:
I'm trying to glow an led using a microcontroller and switch. I have programmed it to blink
Every 2 seconds.when voltage comes from PB1 switch gets tuned on and led . Circuit diagram is shown here.
It doesn't work. Please help me to fix it.is this how to connect to atmega 8?


texts: Maximum discharge rate of coin cell batteries

texts:
I am trying to figure out the maximum current I can pull from different battery types.  Cursory research suggests this isn't a commonly reported values, maybe it is close enough to the capacity such that approaching it leaves battery life too short to care about it.

Some observations

LR41 batteries shorting across a multimeter provide about 220 mA of current
A single cell, protected, lithium ion battery provides 1.4 A of current

Questions

Is there a way to predict the maximum discharge rate of alkaline batteries?
Maximum discharge rate appears to vary with voltage/use - is there a relationship plotted for this phenomenon?

Specific details

Slightly used LR41 batteries in series have a higher voltage (3.3V) than my slightly discharged lithium cell (3.0V).  Yet, an LED attached to the LR41 batteries is dimmer than the lithium cell. Current seems limited through one out of the three-series-LR41 batteries, though voltage appears to remain appropriately high.  Curious about this relationship between remaining charge, maximum current, and voltage.


texts: Arduino Uno as a programmer for AVR chips

texts:
I am trying to make an Arduino Uno act as an external programmer for an ATmega32 and ATmega 8. I couldn't succeed, I used connections as given at Using an Arduino as an AVR ISP and Arduino Uno as an ISP programmer  and followed the steps.

I used an external 12MHz crystal with the chip to be programmed then I connected XTAL2 of Arduino Uno with XTAL1 of chip to be programmed. The programmer is working but it's not showing the proper device ID. Can anybody help me?


texts: Adding to a circuit the ability to "remember" the last chosen settings when turned off or disconnected

texts:
If you could please bear with me: I'm just starting out in electronics and I've had an idea for a nice experimental mod that will also be useful.

I've recently bought a pretty cool little 8 x 8 LED spectrum analyzer off eBay:

And I'm currently building a container for it. I'm going to add a couple of mods. Among them, an ON/OFF switch, so I can get rid of the USB connection and have it permanently connected, but only ON whenever I really need it.

The thing is, this little device has a couple of configurable settings, none of which are, by default, the ones I prefer. So after installing the ON/OFF toggle, every time I toggle the device off, I'll lose my settings, and have to reconfigure them when toggling it back on... which is of course a hassle, because this is meant to be a little decorative plus when I turn on my music and relax, not a task to complete every single time.

So I've been researching what would be the best (slash-maybe-not-the-most-complex) way of adding the possibility for the device to remember its settings even when disconnected to power (or powered off).

I've read a couple of forums and articles and have come across the terms latching relay and slow-discharge capacitor... but I'm still mostly lost. I'm even wondering if just adding a coin cell at some point will do the trick but I'm almost sure it can't be that easy!

So if anyone could put me on the right track, in other words tell me, based on this specific project, what's my best bet, that'd be GREAT! Because right now, after a couple of days of research, I've turned out nothing, at least nothing I can make any sense of.

Thank you in advance!

P.S. Or... is there a way to reconfigure the WD1088S chip?

P.S.S. I've just had another idea... it might be a bad one, but I'm not sure if it won't actually work OK. This device works with 3-5V and has a "static working current [of] less than 3mA". So what if I attach it to a 3.6V 1240 mAh camera battery and have the charger connected to the battery with the ON/OFF toggle in between. That way, at least, I won't be using the electrical current while the device is not in use. Yes, the device won't really be OFF, but as long as it's kept idle, it should have enough power to not turn OFF during about 12 days. I can even use it with the battery (it should work about a day, with an working current of 30mA). I know it's not an elegant solution, more like a workaround... But it's the only thing I can think of. What I'm afraid is I'll be contributing to shortening the lifespan of the whole thing... Anyway, I'm out to learn, so what do you think of this idea?

Edit: I found the PCB schematic and the IC datasheet. Perhaps that can help...


texts: How to trigger a relay through a USB port?

texts:
I'm more a computer programmer than an electronic specialist so my question might seem simple to you.

I have a speaker and some other devices, I wanted to turn them off when TV is turned off, so I thought maybe it's so easy, I could connect one of USB ports of TV to a 5V relay and when TV is turned off every other device would be turned off too.

But after searching a bit I realized it's possible that relay coil consumes more current than a USB port provides, moreover backlash can be harmful to host device, I know there are some USB modules for triggering relay through USB port but I'm not supposed to do amazing stuffs by that, also I wanted to know if it can be done using a simple circuit by a transistor and a diode?

Can you guide me or offer a link for that at least?


texts:
The following is an image of the AND logic gate from electronics-tutorials and my representation of that in EveryCircuit, where I've used the "Logic input" as the A/B inputs on the left (equivalent to a 5V battery).

Is this the correct representation of the AND circuit? Additionally, what is the usual voltage or current requirement for an A/B input to be considered in the 'on' position?


texts:
I'm trying to build a brushless dc motor driver, which provides the possibility to measure the currents on all three phases of the motor independently.
The driver IC that I'm using (DRV8313) has three pins broken out for low-side current sensing using a shunt resistor.

I'm familiar with the basic concept of a shunt resistor, but I find it hard to select a suitable amplifier (opamp,...) and design the needed circuit around it.

Some information about my project: The maximum current is 2.5A, but most of the time it will not exceed 1A. The ADC I'm going to use has a 3.3V reference voltage. Thus, using an 0.1Ohm resistor would result in a voltage drop of 250mV, which had to be amplified by about 13V/V for the ADC.

My question is, how exactly do I design a low-side current sensing circuit? Which criteria does the opamp have to meet?

Looking forward to any kind of help. :)


texts: How to test an RF attenuator with limited tools

texts:
I have an RF attenuator with the specification:

Freq DC to 3 GHz
30dB attenuation
2W avg power rated
VSWR = 1.2 max
Imp = \$50\Omega\$

How can I test this attenuator without a spectrum analyzer?

I have an oscilloscope which has a 1kHZ, 5V output. Can I use this signal to check the attenuator and observe the attenuator output with the scope?

Will 5V is too high for this attenuator?


texts: USB serial emulation: CDC or vendor-specific?

texts:
When designing a device that requires communication with a PC via a virtual serial port over USB:

When would one use usb-serial port emulation chips with vendor-specific drivers (e.g. FTDI) and
when would one implement a Communication Device Class (CDC) device?

What are the advantages of each solution, what the limitations?


texts: How do I model an EFT Surge wave equation on voltage source with LTSpice?

texts: I am trying to put the following equation onto my voltage source on LTSpice to get the same waveform. The waveforms and equations are attached


texts: How to power two motor drivers and Raspberry Pi with one LiPo battery?

texts:
apologies in advance for the lengthy question.

I'm working on creating a remote controlled rover. It is controlled by a raspberry pi, and driven by two MDD10A REV2.0 motor drivers (one for the left two wheels and one for the right two wheels), which themselves are sent control signals from the Pi. I was wondering how i would power both of these motor drivers with one battery. I would like to use the 25C-11.1V 2200 mAh LiPo battery that I have, but I only have a degree in computer science so my hardware knowledge is pretty limited. Currently I can power one motor driver (2 wheels) with it, but I'm not sure what hardware I need to achieve this.

Furthermore, eventually we want to add the PiCam 360 module, a Particle board for LTE connection, and a DWM1000 module for ranging data, all controlled by the Pi. I was planning to first power the Pi with a USB power bank, and the motors with the LiPo, but what would I need to do to power all of this with one battery?

Thanks.


texts: What Circuitry is needed to charge in parallel, but power in series?

texts:
simulate this circuit – Schematic created using CircuitLab

I've read several other battery posts, and didn't find the answer I was looking for. My question is, can the Diagram I've provide do what I intend it to, or am I missing something fundamental.

I have 2 x 3.7v batteries in series to power an Arduino. I also have a 3.7v charging circuit that I would like to be able to recharge the batteries with. Can I simply use two diodes to block any back voltage/current and then simply switch between connecting the second battery to the charger, or to powering the Arduino.

I don't plan to ever have the unit charging while the Arduino is on, but based on my diagram it would be powered in series while one battery was being charged, if this did happen, could it damage anything?

Thanks, please feel free to throw links at me if there is a place out there that already answered this type of question.


texts: Multiple voltages power suply, high current

texts:
I'm trying to design a battery back-up power supply for my home network devices. I need these:

48 V / 40 A
24 V / 10 A
12 V / 2.5 A
5 V / 5 A

I got a 48 V / 60 A industrial power supply with battery backup (four 12 V car batteries in series) and need to divide the voltages.

After digging through Google and Electrical Engineering Stack Exchange, I want to use a bunch of diodes (like 1N4007, but of a type able to withstand the current) and simply take out needed voltages somewhere between these like this:

The second option is high current transistors like BC547B driven by zener diodes, but I'm not really sure if that would be better than the first option. Is my idea OK, or I should do it another way?


texts: Fundamental component of Sinusoidal PWM inverter output

texts:
It is given in "Ned Mohan Power electronics converters applications and design" that, "sinusoidal PWM output's instantaneous average (over one time period of carrier wave) is same as the fundamental frequency component in the signal."
I am unable to think how, instantaneous average is related to only fundamental frequency component as, instantaneous average may include any slow varying (low frequency signal's contribution) components, as high frequency ones near by switching frequency get zeroed in a time period. 'mf' frequency modulation index when chosen appropriately, odd such that output becomes odd symmetric (only sine components) and half wave symmetric (only odd harmonic components) too, 3rd harmonic may interfere. How can we make sure that output doesn't contain 3rd harmonic, that too if contains, would be less compared with fundamental one ?
Please help me understanding this..


texts:
I'am trying to make an automatic irrigation system using an Arduino, a moisture meter and a water pump.

The issue is that I can't figure out whether there is some relay/contactor type component that can control a 400 V device such as water pump using max 5V from Arduino in the controlling circuit. As far as I have researched it's quite common to use Arduino controlled relays to control contractors, but it seems this approach comes with challenges of its own, so any advice is welcome.


texts: Performing integration using hardware instead of software

texts:
One can compute the integral of a function using software, specifically one can get add doubles to obtain an approximate integral -- this is fast but suffers from rounding errors, or one can use arbitrary precision -- this is precise but generally slower.

I was wondering if it is possible to implement a middle-ground in hardware (thus obtaining something that is fast, and of bigger precision than doubles) by generating in hardware a wave that corresponds to the function to be integrated and using a simple circuit with a capacitor and a resistor to obtain the integral of the resulting wave? Are there implementations of such "hardware integrators" and are they used in practice?


texts: I need to find Vin max(Common Mode) and min(common mode) for given circuit.

texts: please let me know how i can proceed with this circuit


texts:
I'm come across a schematic that uses a switch symbol shown below. This switch is a Kraus & Naimer CA10 Switch (That's all I know). The schematic symbol is shown on the right with terminals numbered 1-6 and lines representing the three positions. The physical location and angle of these positions is shown on the left. Has anyone seen this before and could tell me how to read these or direct me to somewhere showing how?

I'll shown another example below.


texts:
i am currently reading about memory system in computer architecture.
I wanted to know, Is the word length the number of bits input to the ALU?


texts:
I am having a QSPI Interface (operated in SDR mode) from this QSPI chip to MCU chip. QSPI lines :

QSPI CLK
QSPI CS
QSPI_IO0
QSPI_IO1
QSPI_IO2
QSPI_1O3
VSS
VDD

I am trying to validate the QSPI Setup time and Hold time parameters for the Data IO Lines with respect to the clock.

The data and clock lines are connected directly to the Micro with only a 47ohm 0603 resistor in series.

But if you check the Table 65 of the MCU datasheet (page 119), it is given as Setup time for incoming data and hold time for incoming data.

I am using 500MHz scope.

My doubts :

If I probe the data lines, how will I know whether the data transitions in the IO Lines are incoming data or outgoing data?
Apart from Setup time and Hold time validation, what are the other parameters I have to measure for validating QSPI lines from hardware perspective?


texts: Reverse voltage protection diode - necessary?

texts:
I'm designing a system to drive 5 strips of RGB LEDs, it will draw around 25 amps, at 12 volts.

This system is only going to be used by me, and I have the suitable power supply coming in the mail.

In my design I had a Schottky diode from the DC jack to the power regulator to protect against reverse voltage. I'm currently pulling together my BOM and getting ready to order my PCB and the parts, and I can't find a Schottky diode with ratings for what I need. I'm mainly worried about accidentally frying my pre-release MKR 1000 Arduino board I got that I'm using for the project.

My question is, is it worth it to try to find a diode for reverse voltage protection?

This many be too broad or controversial but I wanted to see what you guys think, and if there is any kind of rule-of-thumb that I should be following


texts: Using Switching Regulators to Make Split Supply

texts: I am trying to use two switch-mode regulators to create a split supply, where the first one regulates the positive voltage as per the application schematic in the datasheet and the second one works the same way, but references its output to GND and uses the GND pin as the negative voltage output. Is this valid? Here is my schematic:


texts:
I found 500 mL of hydrogen peroxide. It says 12% and food grade.

Normally, before, what I found was 3% only, and there wasn't any note like food grade at all.

Is this suitable while etching PCB? Is having higher percentage (I guess it is concentration of H2O2 to Water) better or worst?

Such product is this.


texts: Suitable transistors for adaptive motorcycle light project

texts:
simulate this circuit – Schematic created using CircuitLab

I am working on something very similar to this, Adaptive LED Headlights – Model 8790 Adaptive 2 as a hobby project.
I have controller part done, VID_20180728_195351.mp4, and this was the simpler part of the job.

Now I am trying to build a circuit which would light up up to five powerful LEDs depending on the lean of the motorcycle.

LEDs are Cree XPG2, they need 3.5 V and will run at ~1.5 A.
The controller is ESP32 which gives 8  mA and 3.3 V.
Motorcycle gives ~13.5 V and I'd like to avoid using voltage converters and keep it as simple as possible dropping 13 V to 3.5 V on transistor, power waste is not a problem since these LEDs light up only for a short periods of time.

I've tried BD135 as a switch but it cannot handle this load. Then TIP120 it's ok but in order to run at required current it requires ~4.5 V on gate.

ESP32 obviously doesn't have 4.5 V, so in order to stop burning further transistors I am looking for a way to select the right transistor for this project. I've run through many transistors datasheets but I am not sure what characteristics are important here.

On similar topics I saw that MOSFET transistors like IRF520 require 1-2 V on the base to be fully open, but I am afraid that voltage drop may not be as significant as on darlington TIP120 and it won't be possible to select an appropriate resistor between ESP32 pin and transistor's gate to have required 3.5 V at emitter.

CLARIFICATION: the system will have 10 lights in total, 5 items from each side. 1 to 5 leds may be fired at a moment depending on the lean angle.

The whole system runs on a massive aluminium heat sink(about 1 kilo) with active air flow.


texts: Connect Wii balance board pressure sensor to an Arduino

texts:
We have a Wii balance board pressure sensor and were wondering how we could connect this sensor to an Arduino board.

On the circuit board (see picture) of the Wii Balance Board are Japanese characters printed, only those are pointing out which color there must be. The problem is, most pressure sensor examples of the Arduino are with 2 cables, but the Wii pressure sensor got 4 cables. So which cable is for what?


texts: Powering a ESP8266 that needs to be mains-referenced?

texts:
I want to use a ADE7953 power metering IC, and I want to interface it with an ESP8266 wifi module. Since the ADE7953 needs to be referenced to mains, and also I don't plan this module to have any sort of physical user interface, I don't think isolation is a must.

The ESP8266 is very power hungry, so probably 1A of current will be needed, so a capacitor dropper seems to be out of the question here.

What sort of power supply can I use for this project?


texts: Finding transfer function and tuning cutoff frequency of High-Pass FIlter

texts:
I have a schematic for a High-Pass filter that has a cut-off of around 7Hz. I obtained the designed online and want to tune it to have a cutoff of 5Hz instead.

I assumed I would proceed in the following way:
1. Find the transfer function H(s)
2. Equate 20log|H(s)| to -3dB

Would this be the correct approach ?

In any case, I am having trouble deriving the transfer equation and would appreciate some help to solve this.

Thank you


texts: How to connect multiple i2c-interface devices into a single pin A4 (SDA) and A5 (SCL) on Arduino?

texts:
I want to add a real time clock module into my little project. I want to display both time and date on my existing i2c 2x16 LCD module.

Both i2c-interface real time clock module and 2x16 LCD module use the same pin A4 (SDA) and A5 (SCL) on Arduino Uno. After hours of searching on the net the i2c bus can actually take many serial devices. This is possible because each device has its own unique address.

My question is how to physically wire the two i2c-interface devices into a single A4 and A5? Thanks.


texts: Why change the quiescent current in an op-amp? (LM4250)

texts:
I am trying to understand the LM4250 op-amp. Datasheet:

http://www.ti.com/lit/ds/symlink/lm4250.pdf

Main description:

Pin-outs for DIP:

Example circuit:

It appears that pin 8 (quiescent current set) can be used to change the quiescent current, according to this table:

My question is: why would you want to do this (change the current)? My understanding of quiescent current is that this is the minimum amount of current consumed by the device (not under load). Why would you want this to be any higher than the minimum the device is capable of?

Also, what is this symbol?


texts:
I already tried to solve my LTspice problems within another thread here on the forum but I guess my design is bad. So for this reason I decided to start a new thread with some more information about my project. I hope somebody can give me some feedback on how to design this thing.
I'm working for a research group and they asked me to manufacture a "noise generator." It will be used by a university research group. At the university, they have a giant setup with 20 electrical cabinets, each cabinet must represent an industrial building. All the cabinets are connected with a low voltage distribution net. The idea is to generate noise within one cabinet and check how the noise will behave within the distribution net and what it will do to the other users.
They asked me to make a switching device for a high power resistor.  The idea is to switch a 20 ampere load at 230VAC within a frequency range from 2-500kHz. So I thought to use a PicoScope to generate the PWM signal. With this signal I want to switch 2 MOSFETs so I can control the load and generate some noise.
I would like to have some galvanic isolation between the PicoScope and the noise generator. My first idea was to use a simple optocoupler but they are all too slow within that frequency range. I tried different and more complex devices like a HCPL3140 and a 6N137.
I first need to simulate the design within LTspice before I can start to design the PCB, and this is where things get difficult. I'm struggling to get the LTspice simulation running.
Also the design should be as simple as possible since we want to manually calculate all the voltages and currents so we can verify the LTspice simulation and make a good scientific report on this project. For this reason I can't get too complex with the galvanic isolation since this would be too hard to calculate (like the 6N137 which has internal logic gates etc).
For this reason I think an optocoupler or something similar is not the way to go. I hope somebody can give me some tips so I can get this thing to work with the least amount of components.
Our supervisor suggested to work with an optical fiber connection to send the PWM signal from the PicoScope to the noise generator, but I think this will be too complex and I have no idea how to start with this.
Attached you can find my current LTspice simulation which doesn't work and always results with the same error.

EDIT:
As suggested below i tried out this schematic.
We want to PWM an AC load, not a DC load.
So i tried to rework the schematic. The result is good in one part of the sinus but not in the other part. It has something to do with how the coils couple but i don't have enough experience about this topic to get this to work. Any suggestions?


texts:
If I place the probe of my Rigol oscilloscope on the metal casing of the outlet box I can see a lot of noise on the scope. The noise definitely coincides with actions of nearby machines with motors running and stopping. The spikes are repetitive in regards to the specific machine, short, from 5 to 27 u sec and from +/- 8V.

Is this something I should be seeing if the ground really goes to Earth ground?

The scope is plugged into the same outlet, so it has a common ground.


texts: Help me identify this audio connector on a turntable

texts: I have recently purchased a West German NECKERMAN 830 record player (1960s), which requires a separate set of speakers for audio output. Could somebody tell me the technical name for this cable so that I can purchase the correct counterpart?


texts:
So, I'm looking to build an autonomous robot of a sort and want to know what sensors / MCU packages would be good for dealing with lined boundaries?

These would be similar to how dog collars work. Lay a ground line beneath the ground, power it up, and use a sensor (magnet?) of some sort to detect the boundary.

Another way could be to use wireless beaming of a kind (above ground) but would have to work without LOS (Line of Sight).

What are my options? Any suggestions would be helpful too.

Some options explored or being thought about:
Hall effect sensor:
What is a low voltage (approx 5v) hall sensor that could detect up to 8".
I came across: A3144 but spec says it's a discontinued product since 2005.

Inductive sensor.
The few that I could find were around $3 but could only provide up to about 4mm of distance.

AM radio and receiver:
After more research perhaps the best way to go about this would be using a similar setup of how dog collars work. From what I understand the ground line basically acts as a small AM frequency antenna and the receiver (on the bot) picks up that signal when it gets close. By fine tuning the power going to the antenna / receiver, you can have a fairly accurate type of boundary system.

Now only to find what kind of MCU/receiver would be best for the job.

Another part of the problem that I forgot to mention is that there will be a 9DOF MPU-9150 package onboard (or something similar, Perhaps GY-271 HMC5883L). How will the magnetic field affect this? I imagine it's possible to fine tune the ground boundary wire to output as minimal of a field as possible.


texts: Protocol used by IR LED reciever (50W driver)

texts:
I have a 50W LED driver with a IR remote control that i want to controll with a microcontroller. I hooked it up to my oscilloscope to try to decipher the data sent between the IR reciever and the remote, but couldn't recognize the protocol used, and the PicoScope software couldn't figure it out either. Any idea what it is? The short 0 pulses are approx. 0.52ms long

Here is a picture of the reciever:


texts: High voltage OP amplifier circuit analize

texts:
I revised my previous hand drawing schematic to a clear one.

As discuss, Block A seem to be a non-inverting amplifier. But not same with classic non-inverting OPA, the input is at inveting-input at OP, is this works?
Or it's a schmitt trigger?
Block D seems to be a current source, How to calculate the current Id?
How to analyze block B & C?  What is C1 function?

The image from circuit lab looks a litter small. I attached a bigger on pic.

Sorry for many questions, I'm really new to analog circuit.

Thanks a lot for your patience.

simulate this circuit – Schematic created using CircuitLab


texts: MSP430 Bluetooth interfering with USB module

texts:
I have a simple project that basically sends and receives data through USB connection and Bluetooth.  Both the USB module and the BT module share the same UART RX (P1.2) and TX (P1.1) ports.

The problem I am having is that when the bluetooth is powered, I can't send commands to the MSP430 with the USB module.  If I unplug the BT module, I can send just fine over USB.

Am I connecting them incorrectly, or do I need to disable the BT when using USB?

The USB module is based on FT232R:
https://www.sparkfun.com/products/9716

The BT module is based on RN-42:
https://www.sparkfun.com/products/10269

USB connections:

GND --> GND
CTS --> GND
3V3 --> N/C
TXD --> P1.1
RXD --> P1.2
DTR --> N/C

BT connections:

CTS-I --> N/C
VCC   --> 3.3V
GND   --> GND
TX-D  --> P1.1
RX-I  --> P1.2
RTS-D --> N/C


texts: Power supply compatibility - 4.5v and 5v

texts:
I am wanting to replace the power supply for my Dreamplug (too chunky for a power-board and requires a converter to an AU plug). I have another power supply, however I am unsure it will work (without letting the magic smoke escape).

The supplied power supply is rated at 5v @ 3A and outputs 5.16v - 5.18v when measured with a (cheap) multimeter. The other power supply is rated @ 2.5A for 4.5v,6v, 9v or 12v. It outputs 4.90v - 4.93v according to the same multimeter when on the 4.5v setting.

Can I use the other power supply (checking polarity and ensuring that the device does not exceed 2.5A of current)?


texts:
I am attempting to build a circuit to run my HO trains with a common rail.  When I use this circuit LM317 works for a period of time then gets stuck at the input voltage (At that point the LM317 fails and needs to be replaced). The train draws 300 mA.  The input power is a center tapped 16-0-16 transformer.  The voltage adjustment at JP2-1 is a PWM signal.

The input voltage to the LM317 is 17.1 and the output after the failure is 17.0 V. Before the failure everything is operational and the output voltage varies according to the PWM input. The heat sinks are .667" × .654" × .987". The train has only been drawing less than 0.5 A. The max. voltage required by the train is 18 volts but we are only looking for approximately 17 volts as the output.

The PWM source comes from an ATmega2560.  One of the problems I have is that the train layout is broken into 8 sections with separation on only one of the rails.  The other rail is common to all of the tracks.  This is a normal way to create a layout for HO trains, but is not as easy when creating a system of 3 power supplies that can run forward and reverse.  My original plan was to use a power supply and a H-bridge, but that had problems when sending one of the trains in reverse due to the common rail.

The schematic is now black/white and if you right click the image and select view you will get an image that is full screen.

The datasheet for the LM317 does have internal thermal overlad protection and internal short-circuit current limiting.
As to using DCC - the train layout is old with block switching.  It was put away for years but now that the grandchildren are interested I thought that they could have some fun with the old set.  I have read that DCC can be problematic for old trains and also they can be more challenging for the young.  Thense the main reasons I am trying to stay with the common rail system.


texts: Determining the max current through a coil

texts:
I have to light a LED with a NPN, so this is cool, I just pick a base resistor so that i have a collector to base current lower than the led's max rating
But I also have a coil to keep in mind, which is supposed to trigger a relay.
It has that weird rating that does not ring any bell: 12V@100mA
is the voltage at the coil going to vary depending on the current passing through it? I dont understand.


texts: SATA as transport medium for external device

texts:
I have free sata connector in my laptop and I've wondered if is there any option to use SATA as some kind of data transmission, like USB. Will i need to write my own drivers?
Bottom line is: i want to design a device that is connected to laptop in optical bay. Any ideas?


texts: How can I determine if a servo motor is in the commanded position?

texts:
Once I have set PWM to move a servo to a particular angle, is there a way to detect that the servo has finished moving?  I am concerned about situations where the servo is encountering extra resistance and is struggling to reach the desired angle.

Why I need this: I want to prevent certain events from happening until the servo reaches the right angle. I also want to be able to time the servo out and report a failure if it doesn't finish.


texts: Torque output from an electric motor, when a force is applied to it's movemet

texts: What happens to an electrical motor when a force is applied against it's movement?, an opposite force large enough to lower the rotational speed of the rotor to 0, or even larger. Will the motor continue applying a torque-force? will it have the same output torque than when it's spinning? And if the movement is stoped, but the voltage stays constant on the motor, will it burn up?


texts:
I want to link a PIC16F1825 and a TCN75 temperature sensor via I2C. The temperature sensor is about 1m from the MCU. Can somebody enlighten me on whether and what kind of difficulties I am going to face by running I2C over wire? I read that I2C can be quite noise sensitive especially at higher rates and longer distances.

How much of an issue is this really going to be in practice in my case? Does anybody have any experience under similar conditions? I am quite happy so stick with slow transfer rates.

Link will operate at 5V.
What can I do to make this link as simple in design as well as operation as possible?
With standard non-TP signal cables I will not know their capacitance. How do I calculate the pull-up resistors?
Will I need any pull-up resistors or is the PIC16 pull-up current sufficient?

Alternatively, can somebody point me towards an AN that will help me with I2C over wire?


texts: Identification of ribbon cable connector

texts: I need to identify this 15 wire ribbon cable connector, does anyone happen to recognise this? Assuming it’s not easy to find can anyone suggest where I can buy a replacement?


texts:
According to the book "G. Randy Slone: High-Power Audio Amplifier Construction Manual", the current limit protection is utilized inside of VA stage of an amplifier as follows:

simulate this circuit – Schematic created using CircuitLab

Q3 supposed to be a current limiter (C1 and C2 serve as two-pole compensation, which is not relevant here).

Author wrote next (talking about shorting the output signal): "During positive half-cycles, this isn't a problem, because the constant current source is already current stabilized. However, during the negative half-cycles, a short-circuited condition from the collector of Q2 to the output rail will almost certainly "blow" Q2."

I get the point of putting current limit protection to this circuit.

But could, for example, be there another constant current source stabilizing current for the negative-rail in case of short-circuited output? If yes, would it replace R2?


texts: Why do I have to unplug the STM32F4 discovery card to update program?

texts:
I am starting working on embedded programs using the STM32F4 discovery board and the Atollic Lite PC software.

Every time I edit, recompile and attempt to download the revised program,  it tells me the ST-LINK interface won't work unless I unplug and re-plug the USB cable.  This is annoying because my last computer was ruined by plugging and unplugging the USB cables millions of times.

Is there an easy work-around for this, or something I am not doing to keep the ST-link connection between the IDE and the board healthy ?


texts:
Let's say you have a wire connected to a device that you can switch between high-voltage and ground voltage. The wire is not connected to anything on the other end. You're observing the voltage in two places: one (#1 in the pic) very close to the device and one (#2 in the pic) at the far end of the wire. The wire has some load capacitance, so between the time the voltage toggles from low to high or high to low and the time that the wire is uniformly "pressurized", #1 and #2 will have different readings since the signal does not propagate instantaneously.

My question is this: would the voltage change propagate down the wire as a "sharp line", where at some point in time #1 would be close to high and #2 would be close to low? Or would #1 and #2 rise/fall more or less in tandem with just a tiny delay between the two?

I have a (relatively) long wire in a digital circuit where #1 and #2 are gate inputs that I want to act on with a picosecond-scale time gap between them; would #1's signal be stable before #2's was stable in the event of a change of voltage on the wire? Like, is this feasible or am I barking up a silly tree?

I've confirmed that I can delay a signal by a few picoseconds by lengthening a wire from point A to point B (not surprising). But I want to know if I can get (and stay stable enough once I initially get there) from point A to point B_1 in time_x and point B_2 in time_x + time_y just by spacing them out on the same wire.


texts: How to convert logic gates to multiplexer in a circuit?

texts:
In one of my previous questions, I wanted to know what integrated circuit I could use to replace my logic gates in the circuit below:

The accepted answer helps me to redesign my circuit and replace the gates by an integrated circuit.
However, a second answer tickled my curiosity. It is said:

You can wire up a multiplexer to act as any of the standard gate types (AND, OR, NOT, etc.) It's pretty easy to find a quad 2:1 multiplexer chip, and that one chip should be enough to implement all the logic you've shown.

I tried to redesign my circuit using 2:1 multiplexers:

The issue here is I'm using 2 different 2:1 multiplexers and I can't convert them into a 2 x 2:1 multiplexer. Indeed, the selector input is different for the two multiplexers and I'm not able to find a configuration with the same selector.
How can I redesign my circuit to use only one chip? Is there a method to convert logic gates to multiplexers?


texts:
I have an ESP32 Huzzah board from Adafruit and am trying to control a 2.19" flexible eInk display to no avail. While the screen occasionally updates, the full black and white "clear" screens work but then the image is either incoherent lines (makes me think a potential data issue) or garbled static.

The main issue I'm seeing is also that I cannot reliably update the screen. After waiting the necessary 2-3 minutes to hit reset on the uC the screen rarely updates. I cannot seem to reliably force this change and therefore can't reasonably test different code/hardware configs.

So far I've tried:

Checking the electrical connections with a multi-meter
a new eInk display
a new eInk Friend driver
a new ESP 32
different pins for chip selects
different pins for Reset line (both parallel w/ uC and GPIO)
adding/removing the Busy line (uses time delay w/o)

Has anyone else successfully controlled such a display with a 3V3 signal/power? I've included images and my code below as well.

/***************************************************
  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing
  products from Adafruit!

  Written by Limor Fried/Ladyada for Adafruit Industries.
  MIT license, all text above must be included in any redistribution
 ****************************************************/

#include "Adafruit_EPD.h"

#define EPD_CS      4
#define EPD_DC      36
#define SRAM_CS     39

#define EPD_RESET   -1 // can set to -1 and share with microcontroller Reset!
#define EPD_BUSY    -1 // can set to -1 to not use a pin (will wait a fixed delay)

/* Uncomment the following line if you are using 1.54" tricolor EPD */
//Adafruit_IL0373 display(152, 152, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);

/* Uncomment the following line if you are using 1.54" monochrome EPD */
//Adafruit_SSD1608 display(200, 200, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);

/* Uncomment the following line if you are using 2.13" tricolor EPD */
//Adafruit_IL0373 display(212, 104, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);
Adafruit_IL0373 display(250,122, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);
#define FLEXIBLE_213

/* Uncomment the following line if you are using 2.13" monochrome 250*122 EPD */
//Adafruit_SSD1675 display(250, 122, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);

/* Uncomment the following line if you are using 2.7" tricolor or grayscale EPD */
//Adafruit_IL91874 display(264, 176, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS);

/* Uncomment the following line if you are using 2.9" EPD */
//Adafruit_IL0373 display(296, 128, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);
//#define FLEXIBLE_290

/* Uncomment the following line if you are using 4.2" tricolor EPD */
//Adafruit_IL0398 display(300, 400, EPD_DC, EPD_RESET, EPD_CS, SRAM_CS, EPD_BUSY);

#define COLOR1 EPD_BLACK
#define COLOR2 EPD_RED

void setup() {
  Serial.begin(115200);
  //while (!Serial) { delay(10); }
  Serial.println("Adafruit EPD test");

  display.begin();

#if defined(FLEXIBLE_213) || defined(FLEXIBLE_290)
  // The flexible displays have different buffers and invert settings!
  display.setBlackBuffer(1, false);
  display.setColorBuffer(1, false);
#endif

  display.clearBuffer();
  for (int i = 0; i< 50; i+=5) {
    display.drawPixel(i,i, COLOR1);
  }
  display.display();
}

void loop() {
  //don't do anything!
}

void testdrawtext(char *text, uint16_t color) {
  display.setCursor(0, 0);
  display.setTextColor(color);
  display.setTextWrap(true);
  display.print(text);
}


texts:
Hey all I am just wondering before I do this if its possible to connect 2 SFP sockets to each other in order to bring in the fiber connection and then take it back out the same way?

So in the image above, Pin 1 would hook up to Pin 1 on the second SFP socket. Pin 2 would hook up to Pin 2 on the second SFP socket, etc etc...

I'm doing this so that I can bring in the SFP connection into a server case and then once inside the server case I need to hook it up to a motherboard inside there that has the SFP connection.

To better illustrate what I am trying to accomplish:

this is what the ONT fiber hook up looks like that I am wanting to use (green connector).


texts: System-Level Average Power/Current Measurements

texts:
I have a question regarding probes/methods when measuring system-level average power/current.
The system consists of microcontrollers and multiple valves, including solenoid valves. My plan is to use two channels/probes to measure the voltage across a 1-ohm in series resistor on the O-Scope when the system is on, as described using differential probe setup.
I am aware of current differential probes which are specifically used for current measurement. Since the entire system is operating under 12VDC power supply, I do not think current probes are necessary. Would my planned setup with regular probes work for the electromechanical system?


texts: Is frequency of 40 Hz light from Apple/Android tablet as reliable as that from an LED light?

texts:
On this site, I read about the MIT study using 40 Hz light and sound to mitigate the effects of Alzheimer's disease. I am looking for a suitable 40 Hz lighting device, even though the jury is still out on its efficacy in humans.
There are apps like AlzLife which flicker at 40 Hz gamma. However, I have read that the light from a tablet is less reliable than an LED light due to analog/digital issues.
I would be grateful if someone with knowledge could tell me whether this is correct.


texts: Differences between UART receiver STOP bit implementations

texts: Some UART receivers require that the specified number of stop bits are present in the received data.  For example, if the receiving UART is configured for 2 stop bits, the transmitting UART must also be configured for 2 stop bits.  Other UARTs only use the stop bit setting for transmitting, and the receiver is always satisfied with 1 stop bit.  Is there a specification that applies to this behavior?


texts: NPN driving PNP, Diode from NPN Base to PNP Collector?

texts:
I am reviewing some old 12V alarm designs that use the circuit below to activate a siren.  The design has been built on PCB and I have confirmed proper operation, proving the schematic is not flawed (not that I can see anyway).  Simply put, when the MCU pin goes HI (5V), it switches the NPN transistor, which in turn switches 12V to the siren via high-power PNP transistor.  That is easy to understand, but what is the purpose of Diode "D1"?  It's Anode attaches to the Base of the NPN and its Cathode attaches to the Collector of the PNP.  But what does it do?

I am also curious if Diode "D2" is necessary.  Why not tie the NPN's Emitter directly to Ground?


texts: Wafer thickness reduction (750 µm to 50 µm)

texts:
Need some suggestions as to what techniques one could possibly adopt to reduce wafer thickness to 50 µm or less while fulfilling these 2 conditions :

Surface roughmess, Ra < 3nm
Total Thickness Variation < 3µm