texts: Using CP antenna for receiving and LP for transmitting

texts:
I've set up two antennas with Linear Polarization (LP) in both sides, in 2.4 GHz no more than 4 meters each other, but they are facing strongly obstruction object (like a big steel wall in they line of sight) so they EM waves are constantly reflecting. Even though I'm able to see signals in LP but they are too weak, (-80dBm according to RSSI) so I've been reading about Circular Polarization (CP) and how satellites uses this for accounting a lot of reflection along the path. Even if antennas distance is few meters I want to improve this communication and one thing that I have in mind is using CP in the receiver (can't use CP in the transmitter because of limited space). But CP could have advantage in multipath fading which is likely the environment I have.

The currently set up have antennas with 5 dBi gain in transmitter and 16 dBi in receiver. With vertical monopole 8 shape in the transmitter and Directional in the receiver.
What do you recommend me for improving this communication? What things to account for?


texts: Error Real Time Clock implementation AVR microcontroller

texts:
I want to create a real-time clock using ATmega328p microcontroller.
The microcontroller's frequency is 1 MHz. So, I think I should use timer interrupts in CTC mode to generate interrupt every second.
I have calculated the value for timer CTC mode:
`n = t * f - 1

n - number of cycles for CTC mode.
t - target time.
f - frequency.
- 1 because it takes one cycle to reset the counter.

I set the frequency divider by 64 for the timer.
n = 1 s * (10^6 Hz / 64) - 1
n = 1 s * 15625 Hz - 1
n = 15625 - 1
n = 15624

So, I have code:
#include <avr/interrupt.h>
#include <util/delay.h>
#include <time.h>

static unsigned long t = 0;

ISR(TIMER1_COMPA_vect) {
    t++;
}

static void InitializeTimer() {
    cli();

    OCR1A = 15624;
    TCCR1B = (1 << WGM12) | (1 << CS10) | (1 << CS11);
    TIMSK1 = (1 << OCIE1A);

    sei();
}

[[noreturn]] int main() {

    InitializeTimer();

    LCD_SetUp(PC_5, PC_4, PC_3, PD_0, PD_1, PD_2, PD_3, PD_4, PD_5, PD_6, PD_7);
    LCD_Init(2, 16);

    while(true) {
        tm* time = gmtime((time_t*)&t);

        LCD_Clear();
        LCD_Printf("Time: %02d:%02d:%02d", time->tm_hour, time->tm_min, time->tm_sec);

        _delay_ms(100);
    }
}

This code prints number of seconds since the start of the microcontroller to an LCD display.
It really does, but since even 3 minutes time error is 2 seconds, since 10 minutes time error is 5 seconds, since 45 minutes time error is 30 seconds. I checked the time error using my phone's stopwatch. Why there is a time error? Error during calculation? What are the reasons for this?
Thanks in advance!


texts:
After complex math and right wiring on my ESP8266, I finally light up my 4x7 segments display, one segment at a time. All the 4 selectors are connected to the 4 GND pins, so all four are lit up.
Do I need a MC or transistors to better select which display is lit up? Or is it possible with only the ESP8266 (I doubt)?
EDIT
Here is the schematic of the 4x7 segments display (source: https://osoyoo.com/wp-content/uploads/2017/08/cathnode.jpg)

And the NodeMCU ESP8266 (source: https://i2.wp.com/randomnerdtutorials.com/wp-content/uploads/2019/05/ESP8266-NodeMCU-kit-12-E-pinout-gpio-pin.png?ssl=1)


texts: What is wrong about this application of Kirchhoffs Current Law?

texts:
At a recent exam I had this very simple problem concerning Kirchhoffs Laws:

I am concerned with problem c

Now my understanding of this is:

I can combine both nodes, and since all currents in the node need to cancel out, \$i_c\$ should be 2A. Now my professor marked this problem as wrong and told me it should be 8A instead.

Am I doing something fundamentally wrong here?

Update:
The professor reviewed the answer sheet because some other answers were wrong and did not mention the 8A again, and accepted the solution ♂


texts: What is my firmware, software, and operating system?

texts: I have a BLE Nano device: http://redbearlab.com/blenano/   It comes with something called MBED on it.  I think this helps us flash the code that we write onto it.  We are using a library called Nordic SDK to program the device.  What I am wonder is what is my firmware, what is my software, and what is my operating system?


texts: ON-OFF MOSFET Switch for Induction Heater

texts:
The induction heater was tested using a relay as an ON-OFF switch before and worked so i just want to focus on the MOSFET switch part of the schematic.

When i tested the circuit using a MOSFET switch it worked but after a few tests the OFF state just stopped working. After taking a look at the P Channel MOSFET I noticed that it was always ON even with everything turned off. I suppose something must have burned the MOSFET.

And my question is what may have caused this to happen?


texts: Error in transfferring multism design to ultiboard

texts:
I have this problem in multism 14, I'm trying to transfer my design in the ultiboard but when I do, these red circles on the edge of the pcb layout keep appearing.
What could be causing this?


texts:
I tried to export sub and sym file on an other PC. I decided to copy the sub files that I created in the "LTspiceXVII\lib\sub" and past it into the same folder of the other PC. I did the same for the sym files. When I tried to simulate the same file which worked on the original PC, it does not work "Could not open library file". I do not want to redo all the files that I created... And actually I do not know why it would change. I will just redo the symbol file. It probably miss a link between the symbol file and the sub file ?
Have a nice day.


texts: How to know when the resault of subtraction is incorrect in a 4 bit binary subtraction circuit?

texts: This is an image of a binary subtractor for unsigned numbers. Some times the output of binary subtraction is not correct and needs to be complemented to give the correct answer, how can I find out when those times are?


texts: Clock termination considerations, single clock driving multiple loads

texts:
In the following example, a single clock is driving two loads.
The traces to the loads have different lengths (10mm and 30mm).
It is not feasible to make the individual routing lengths equal.

Clock specification:
Frequency: 25Mhz, Output: HCMOS, Current: +/-24mA, Load: 15pF, Rise/Fall Time: 3ns

What would be the best approach for the clock termination in this case?

option 1. series termination

simulate this circuit – Schematic created using CircuitLab

option 2. parallel termination

simulate this circuit


texts: What variable-IF tuner IC can I use for UHF applications?

texts:
What. I'd like to build a multi-channel tuner that will pick up, say, two [known] channels, one at 156.3 MHz that's 50 kHz wide, and one at 855 MHz that's 25 kHz wide. Demodulation will be done in a Software-Defined Radio such as GNURadio.

How Rather than have one broadband tuner that picks up and downconverts this wide spectrum, I'd like to have two tuners - one that will pick up and downconvert the first channel to one low-IF, say 1MHz, and a second tuner that will pick up the second channel and downconvert it to another distinct low-IF (using a different LO of course), say 2MHz. Then I want to merely sum the two IFs, and then pass it through an ADC before feeding it to GNURadio where I have the channel selection and demodulation pieces. The advantage will be that the sampling rate can be kept much lower than if I used a wideband tuner to pick up everything in the 150-900 MHz range.

Questions (1) Do the RF experts see any problems with this idea? (2) The Elonics E4005 was a tuner chip that allowed user-selectable IF. Is there any similar variable-low-IF chip I could use since that chip is no longer available? (I'd use one such chip for each channel to be received).

Alternative approach. After reading up on some modern chips available it does appear that the chips available today are pretty much geared towards Zero-IF direct-conversion architectures and it would be simplest to build something with one of these. If I used one of these, then, would it be a valid approach to convert BOTH of the above channels to zero-IF, then UPconvert to two low-IFs, say 100kHz and 200kHz, and THEN sum the IFs before the ADC? That way much of the complexity is handled by the one chip, post which I only have to deal with low-frequency design and layout issues.


texts:
I have the following circuit:

How to determine the waveform of Vout, maximum values for positive and negative half-period segments, and the average value of Vout?

Input voltage Vin has a sinusoidal signal of frequency 1kHz and amplitude 10V. Diodes are ideal.


texts: Common Mode voltage for AC coupled mixed signal circuit clocks

texts:
I am confused by the wording used in the clock sections of a couple Analog Devices and Texas Instruments datasheets. My main confusion surrounds the use of AC coupled differential clocking. I know that after ac coupling (and assuming no bias after the coupling capacitor) the result will be approximately a square wave that oscillates around zero volts, meaning that these chips' pins will be exposed to a negative voltage. I plan on using LVPECL clock signals in my design, meaning that these chips' pins will be exposed to approximately -400mV every clock cycle, and on a transient basis -800mV (startup). I am unable to determine from the datasheets wether or not this is acceptable. Included below are some relevant screenshots from these datasheets, and links to the entire documents.
Parts: AD9911, AD9434, LMX2491.
From the AD9911 Datasheet:

enter image description here

From The AD9434 Datasheet:

From the LMX2491 Datasheet


texts: Does it mean that you need 9 V to make the motor start, or is this the max voltage before it is damaged?


texts:
I'd like to build a prototype of simplest possible GSM device - a simple modem with SIM holder, capable of logging on to the SIM's provider network and nothing else. It's meant to be used as a GSM localizing beacon in larger application. It's meant to be as small, as simple and as cheap as possible. Being crude or rough doesn't matter. I'm aware of >50$ GSM modules/modems, but they are too big and too pricey, and I'm looking for a better solution. I'm also wondering if the cheapest way is actually through the disassembly of an old mobile phone? I can get one for about $10 (or even for free from some junkyard) - the only problem with them is that they have a lot of unnecessary components and board space that's difficult to remove without damaging the GSM module.

Also, is it possible to craft such a device with some simple parts/engineering samples?


texts:
I am trying to understand this op-amp circuit that came from one of our suppliers. The input on X9 connector is a speed sensor (magnetic pickup sensor.) Its voltage amplitude is proportionnal to a motor speed (up to 7500 Hz.)
From what I understand, the op-amp IC11 plays the role of a differential amplifier circuit. With the voltage dividers made of R282, R306, R283 and R305, there is an offset of 3V on both inputs (probably because it is a single supplied op amp) so the signal coming from X9 is shifted up. I have three questions:

What would be the input impedance of this circuit (seen from the sensor?)
What is the role of D515 and R281 + R318 + R308 ? I assume that D515 is here not to disturb the 5V supply but why are there resistors?)
Is Z1 acting as a voltage limiter? If so, are D516 and D517 not enough?

Thanks!


texts: How to connect a phone battery with DC coreless motor?

texts:
I have this phone battery with 4 pins

And a coreless DC Motor

They work together(I've tried to attach them with my hands) however I'm noob and I don't know how to connect them and don't want to waste money on stuff I don't need.

If anyone could give a guideline it would be much appreciated.


texts: OpAmp VS Voltage Divider VS Buck Converter (Current Sensor Output)

texts:
I'm working on part of a project and I need to build the circuit that reads the current through a phase of a motor using this IC from Allegro.

Assuming there will be no more than 5A, and using a VCC=5V, the IC will output between [0.5;4.5]V.

We need this to be turned into 3.3V to enter some microcontroller.

I thought a simple voltage divider would suffice but I was suggested opamps. This is what I came up with. I picked this OpAmp so I could use the same 5V rail that powers the Allegro IC.

The first OpAmp turns [0.5,4.5] into [-3.3,-0.3667] and the second one turns it into [0.3667,3.3].

I understand a buck converter would not be ideal here because it takes a bit to get into steady-state again and the purposes for which this will be used may need a faster transition.

But why not a voltage divider? Surely with the limited amount of current (aprox 10mA, max 14mA) coming out of the sensor, it wouldn't be wasting any considerable amount of power. Each phase of the motor has ~125W of nominal power.


texts: What is mean by fuse rating of 2A 8V 0.02ohm?

texts:
In of our partner's access control devices they're using MF-MSMF200-2 Bourns Resettable Fuses - PPTC 2A 8V 0.02ohm for protection. However their boards have gone burned and reasons we received is 'Voltage Spike or Short circuit from external body'. How much current & voltage above fuse will bear in open circuit & close circuit states?

As partner is not ready to cover damaged items in warranty to I'm trying to put back on them that. However their devices is supposed to work on 12Volt, 0.7A.


texts: In search of revision to 555 Monostable circuit to create a resettable timer

texts:
First of all I am getting back into electronics after a LONG pause and am going back to the 555 roots.  I am attempting to create a simple circuit that will light an LED after a period of time.  In the circuit I have a reset, that I would like to...reset the operation.
The problem is, my current circuit is doing the exact opposite of what I want.  I feel that I am so close to an answer as it works perfectly....just the direct opposite result I am looking for :)  Any help would be greatly appreciated.
I am looking for simplicity so if something is part of the circuit that can be simplified, I am all ears!
Link to tinkercad design:
https://www.tinkercad.com/things/2vyzH4CGXoF-problem555-monostable

Intended logic:
LED remains off for a period of X seconds/minutes.  After time elapses, LED will turn on.  User can press the switch to reset the LED again for time period.


texts: NRST Pin pull-up resistor on STM32F303RET6

texts:
The datasheet from the STM32F303RET6 shows that a pull-up resistor (a weak one?) is already included in the device itself. Rpu.

But my knowledge tells me I have to add one myself in front of NRST, along with the .1uF cap, but to VDD which is 3.3V in my system.
Based on this tutorial: https://www.electronics-tutorials.ws/logic/pull-up-resistor.html and table 69 in the datasheet of the STM32F303RET6 and the IIH of 400uA

VIH = 0.445*Vdd = 0.445 * 3.3V = 1.4685V

I would need a pull-up resistance of (3.3 - 1.4684)V ⁄ 400uA = 4.57875kOhm
Is my observation correct? what would happen if I chose a resistor of higher value? Do I need this resistor or am I mis-interpeting the datasheet?
What is common knowledge on this subject?


texts: Reading data from digital pressure sensor (Pressure sensor SPD100GD)

texts:
We need to read the digital output from a Pressure sensor SPD100GD with an AVR micro (Atmega128). According to the datasheet we must estimate transmission speed.
The datasheet is saying:

  The transmission speed depends on the update rate and ranges up to 8 kHz.
     The software has to determine the digital output speed by the “Start Bit”.
  This Start bit is 50% low and 50% high.
  Based on this in formation the speed of the incoming data can be interpreted. The parity is defined as even meaning in case the number of 1’s in the word is even the parity is zero and in case the number is odd the parity bit is 1. Between the high and lower byte there is a stop bit, level 1, with the length of half the data cell (not drawn in picture).

So how we could estimate the transmission speed, and after that - is there any similar C or C++ Code for this kind of digital sensors.


texts: Does a step-up power converter cause move volts but less amps?

texts: I have a 5v 10,400mAH battery. I'm wondering if it would be possible to power my laptop charger with this. The laptop charger is 20v 3.25a. Is this possible? If I use a step-up voltage converter, won't it drop the amps?


texts: Can a Wifi device be made to output a continuous 2.4 GHz wave?

texts:
I wanted to do some energy harvesting experiments involving wifi-frequency microwaves and wanted to see if there was a way to make a Wifi-enabled microcontroller devboard (something like the esp32) output a continuous, "blank" (no data) ~2.4 GHz (one of the channels) signal. I assume Wifi is similar to bluetooth with brief, intermittent transmissions. I'm not sure if this is even possible but assumed it was worth an ask.

Thanks!


texts: lowering voltage of high frequency signal

texts:
One of the parts I have is RAM (1.5V logic level).

The hardware communicating with it, is at a 1.8V logic level. The RAM signals are sent quickly - around 350-450Mhz.

So I am pretty sure I can't just blast the ports with 1.8V - or can I? The reference voltage of the RAM IO ports is set according to the datasheet (.6 * 1.5V).

Do I need a voltage divider to drop the voltage? And if I do, will standard chip resistors be alright at that frequency?


texts: What is the significance of the standard form of 1st and 2nd order transfer functions?

texts:
A standard form of a first order differential equation is:

(1) $$\tau \frac{dy}{dt} + y = k * x(t)$$

The laplace transform of this:

(2) $$G(s) = \frac{Y(s)}{X(s)} = \frac{k}{\tau s+1}$$

but sometimes it is given as

(3) $$H(s) = \frac{1}{\tau s +1} = \frac{a}{s+a}$$

A standard form of a second order differential equation is:

(4) $$\tau ^{2} \frac{d^{2}y}{dt^{2}}+2 \tau \zeta \frac{dy}{dt} + y = k * x(t)$$

The laplace transform of this:

(5) $$G(s) = \frac{Y(s)}{X(s)} = \frac{k}{\tau^2s^2 + 2\tau\zeta s+1}$$

but sometimes this is given as

(6) $$H(s) = \frac{\omega_n^2}{s^2+2\zeta \omega_n s + \omega_n^2}$$

Here are my questions:

What is the physical meaning of "first" and "second order"? (apart from the fact that the highest power of the differential in the first is 1 and in the second is 2). How do I know if a system is first or second order?
Where do equations (1) and (4) come from? Why were these decided to be the "standard form"? What is so special about this form and how were these equations derived?
When given a first order system, why is sometimes equation (2) given, and sometimes equation (3) as the transfer function for this system? Likewise, when given a second order system why is equation (6) usually given, when the laplace transform is actually equation (5)?


texts: Which 9 V DC Adapter Need for MB102 Breadboard Power Supply

texts:
Easy question. I'm a noob... I bought a MB102 breadboard power supply unit. But, it doesn't come with a manual. I need to get a 9V adapter for it.  So, I'm not sure what I need.

Does the 9V adapter's current matter or will any 9V wall wart work? What is the max. input mA for the MB102?


texts: Using a 100W External Power Pack to Run / Charge an Old 19.5v Laptop

texts:
I have just ordered the new Flash 2.0 battery pack. Specs are here, but briefly:
100W USB-C Power Delivery 3.0 Output: 5V/3A, 9V/3A, 12V/3A, 15V/3A, 20V/5A (PPS)
I've also got an old HP Pavillion whose output from its AC adapter is 19.5v / 3.33A - 65W. It does not have a USB-C port.
I'm trying to figure out if there is any way I can use the external battery pack's USB-C to charge the laptop using off the shelf components. I've searched for converters and adapters, but nothing is looking promising. It seems like it should be doable. Thanks in advance.


texts: Keeping power to arduino after mains shutdown

texts:
I have had ideas for an arduino-controlled led-lamp for a while now. It's mostly fancypants stuff, but could be fun.

The lamp is made up of several individually controllable leds. And on power-on I want these to light up in order. So far I think my mostly-software skillset is enough. However, I want the reverse thing to happen when the power is cut. So in essence, the arduino must detect that the power is gone, and then trigger a subroutine that shuts down the leds in some order.

Can I do this with some kind of capasitor-setup? I know my car uses a cap to keep the lighting inside on for a few seconds after i shut of the ignition.


texts: Driving a 74HC series chip with a 74LS series

texts: I made a mistake and accidentally bought a 74LS AND gate: this one.  My other chips are 74HCs. I need the output of one of the AND gates to drive the clock signal on a JK flip-flop: this one.  Unfortunately, the LS chip floats like crazy and I get random clock signals.  Is there anything I can do to make sure that the LS chip behaves (that is, doesn't float and cause spurious signals) or do I just need a new chip?


texts: Is the following N-FET circuit sufficient to act as a power switch for an IC?

texts:
I'm trying to build a circuit which will turn an IC on and off using a MCU signal voltage of 3.3V. This is for a low-power circuit, so every coulomb is critical.

I selected the BSS816NW N-type MOSFET for the job. One can see that Vgs minimum is 1.8V for this FET, which worries me with the following circuit:

simulate this circuit – Schematic created using CircuitLab

One can see that as the chip saturates in voltage, the FET will increase in resistance, which is problematic, as there will always be a voltage drop between the gate and source, which may cause brown-outs for U1.

How can I use simple FETS or BJTs to improve this low-power toggle for U1?
There are no other voltage rails besides ground and 3.3V pos.


texts: How to calculate the feedack resistor in this configuration

texts:
I try to simulate the input stage of the ADC feeding circuit. ADC is 0-3.3V.

The circuit:

The Vin input signal:

The output:

The signal is shifted properly but the gain is lower than I expected.
My question is how to properly calculate the value of the R12.


texts:
Where can I find the source of routing guidelines for DDR4.  I'm talking about things like DQ to DQS timing, maximum length difference in ps for address and command and maybe maximum parallel run lengths.

In my search, I see various articles talking about what you should do but no definitive source.  I looked in the DDR4 JEDEC spec but didn't see much mention of PCB routing.


texts: How do you determine how much flash/RAM you need for a microcontroller?

texts:
Let's say you are starting an embedded project with some known functionality. When you select a microcontroller how do you select how much RAM you need?

Do you use a developer board and code your project first and then see how much memory you have used and then select an appropriate microcontroller that fits that memory?

Do you just pick a beefy microcontroller for a prototype and then scale down after you have a working product?

Do you just pick something that you are sure will be enough and if you run out of space, just upgrade to a higher memory density one otherwise, you just keep the existing microcontroller?

What is considered to be good practice?


texts: I do not know what chip/driver to use for a 7 segment 4 digit display

texts: I am looking to start a new electronic project. For this project i will be learning to code a 7 segment 4 digit display, however i am not sure what chip to use  or how to approach the start of this project. Does anyone know what chip i could use?


texts: Would an LCD monitor still work if both polarized films were rotated equally?

texts: I am making a transparent computer monitor which can only be seen when using polarized glasses. Most commercial glasses are polarized vertically but the monitor that I'm working with seems to be polarized at a 45 degree angle. I've removed the front polarized layer and the monitor works wonderfully with a pair of polarized glasses but i have to crook my head to the left in order to see it at it's brightest. I'm wondering if I could replace the back polarized layer with a horizontally polarized film in order to display my monitor best with a straight head. I can't think of a reason that this wouldn't work but I'd rather not total an LCD to try it.


texts: What is the formula for cutoff frequency for LCL filter?

texts:
I have an assignment for school and one of the questions is asking me to find the "bandwidth" of a "pi filter." This teacher miss words things sometimes and I know it's actually a T filter and a low pass filter so the bandwidth is really cutoff frequency. But I can't find a formula to find it any where. Does anyone know the formula to calculate cutoff frequency?

edit: some of these answers really helped thank you. This particular assignment is about thermal noise in power supplies. But I was stuck on one question asking me to "calculate the filter's bandwidth." The filter had no resistors in it and I didn't think the rest of the circuit was very relevant. But here is a picture of the entire thing for anyone who is curious.


texts: Will a light bulb work the same on a car battery?

texts:
So I have an incandescent light bulb that is rated for 100W at a voltage of 220V. So, I calculated that the resistance of the bulb is 484Ω.
I wanted to connect it to a car battery (24V). I know most incandescent light bulbs work with both AC and DC so this shouldn't be a problem. I calculated that at 24V, the current will be about 50mA. Multiplying, I got that the power from the battery would be 1.2W, which is not enough for it to light up.
I still connected it and the bulb got destroyed (filament broken), so the current must have been very high. Can anybody help me understand what happened?


texts:
I want to put LEDs into my shoes, specifically the Nike Air bubble (by drilling holes at the inside of the shoe and dropping them into the bubble).  I also want the ability for it to light up when dancing. I was thinking a Force Sensitive Resistor at the heel.
Im hoping to use a high mAh rechargeable battery too, for usability. But they tend to have a 8.4V rated voltage. Will that work?

Ive tried simplifying the layout. Ive added in AAs instead of the 9V to allow for longer mAh. Removed the mini controller. And switched the LEDs to 3V's. Will i need resistors if both the battery and LEDs are 3V? The FSR is rated up to 22lbs, so anything over 22lbs should provide max current? The rechargable AAs are rated at 1.2Vs, will this still power the LEDs?


texts: Help Identifying Parts of a Battery Management Board

texts:
I am currently way over my head in a personal project to design and create a 5 cell battery protection system. I'm fairly confident that I've correctly cloned the cell balancing section (section C) of the BMS in the picture.

My question is what is the name / purpose of sections A and B in the picture below. I know section A has to do with the maximum current capacity of the BMS, but I don't know what to google to find out more about what specifically it does. This particular board is rated for 60A continuous, but each of the 8 HY4306P MOSFETs is rated for 230A continuous, which is throwing me off for reverse-engineering it's purpose.

I'm sure section B is all pretty specific use-case stuff that would require actual part numbers to understand what it does, but I'm pretty stumped on that as well.

If needed, I can add another picture of the back of the board, but there's basically nothing on it. A bunch of heatsinking under the mosfets, and a few passives under section C.

Thank you for your time


texts: Limiting logic gates input current with serial resistors reading their electrical characteristics

texts:
My application, shown in the diagram below, will have 12V/GND control lines that will arrive at the gate input pins as 'high' state or 'low' state. Datasheets has two values for input current: 10mA (max rating) and 0.1uA (as static characteristics).

The external board switches belong to a board that has been used for many years and cannot be modified. The switched signals (between ground or high Z) will are connected to the gates board by a connector. Every gate input has its own pull up resistor that will connect to the switch after boards interconnection.

I focused the discussion on any pins input current. I would like to know the correct way to understand this information and whether I am handling it correctly.

My question is:  What is the proper pullup resistor value in order to limit the current as is needed.

simulate this circuit – Schematic created using CircuitLab

I have chosen logic gate devices in order to work with input voltages as 12V: NOR, AND, NOT, etc. When reading datasheet I can see the maximum ratings and electrical characteristics tables. This is an OR datasheet information:

Table is From here

I'm worried about max input current Iin that datasheet tables tell us to be 0.1uA.

Does it means that I must be limiting the input current to this value: 0.1uA?
I have been testing my logic function. As max Vin = 12V, I put a serial resistor between 12V pin and logic gate input pin. So current will be limited to R = 12V/I. I test different values for R allowing to work with 2mA, 1mA and 0.6mA and application stills working normally during the tests time. But I wondered if the correct way is to get Iin less than 0.1uA. So this means a too much bigger resistor value, more than 20 megaOhms! Has this approach any sense? Please if my argumentation is wrong let me know.
Taking datasheet and calculations into account; what input current value would you allowing to be driven through input pin? What resistor value would you choose?

NOTE: I have chosen this Texas Instruments families looking for family that allows working with 12V control signals at their inputs and their outputs as high state. I also choose devices that have more than one gate. I will use these outputs for activate reed relays, but I will connect the outputs to a driver, and driver outputs go to the coil relays (concretely to the coil negative terminal). Image is from CD4073B and CD4081B datasheet. Datasheet here


texts:
I'm trying to make a current buffer for high currents, using an LM324 and BUZ70. This is the circuit:

simulate this circuit – Schematic created using CircuitLab

I've noticed that this circuit starts to have a little oscillation (at least 100 times more the Vs frequency) overlapped to the gate voltage if a gate resistance of around 10Kohm is used. Removing this resistance, will remove the oscillation.

Just for completeness, there is also an evident miller effect, in which the initial ramp before the miller plateau is enlarged if a gate resistor of 10K is used, and this should be coherent.

The oscillation disappears also if the led is fed at 5V.

If Vs is a DC voltage, the oscillation takes place too, showing that it is NOT a transient ringing.

It is a breadboarded circuit, but in any case, I think that I have a very little phase margin, but this circuits should have a very large bandwidth.

Any opinion?

edit: when the LED is turned on, fraction of this oscillation is present in V_Power. I may solve this by putting a cap here and there and not using an high gate resistance, but I'd prefer to understand why, if it is possible.

edit1: as stated in comments, I need a compesation if the source resistance is less than 50 ohm. I don't understand, because modelling the system using this circuit:

simulate this circuit

I obtain

$$V_{out}= \frac{R_s G_m}{1+R_s G_m} \frac{1-\frac{s}{z_1}}{1-\frac{s}{p_1}} V_{oa} = k V_{oa}$$

with $$z_{1} = -\frac{g_m}{C_{gs}}$$ $$p_{1} = -\frac{1}{C_{gs}\frac{R_s}{1+g_m R_s}}$$

and this does not affect the stability of the opamp, which is an LM324 with a limited band. The Cgs used is the provided Ciss, the gm = 2 (because of the limited current used now, see datasheet of BUZ70).

In fact, this MOSFET stage have the Vout/Voa with a bode of:

Therefore I can consider the system with the OPAMP asa voltage follower. Why I need to add compensation with low Rs values?


texts: Configuring ADC on Nucleo-F401RE in Arduino IDE gives erratic values for input freq greater than 100Hz

texts:
I want to configure ADC on STM32(Nucleo-F401RE) using Arduino IDE and transmit the values through SPI to Basys 3 FPGA(End Goal).
The ADC works for input signal frequency only below 100Hz.
How do I increase the throughput rate? My project requires conversion of analog signal between 500KHz to 900Khz.

 #include <f401reMap.h>

float analogPin = pinMap(31); //PA0

float val = 0;  // variable to store the value read

void setup() {
  Serial.begin(115200); //  setup serial
  analogReadResolution(12);

}

void loop() {
  val = analogRead(analogPin);  // read the input pin
  Serial.println(val);          // debug value
}

In the past,I have used Keil and STMCubeMX. It did not sample the input signal below 100Hz which was achievable using Arduino IDE.
I have tried increasing the sampling cycles, the issue persists. Configured ADC without DMA with HAL_ADC_Start function and transferred the values to PC through UART,still unable to retrieve the original signal.
I'm unable to isolate where the problem lies. What am I missing?


texts: Did anyone build an accelerometer-based mouse?

texts:
To save my hands from CTS (Capal Tunnel Syndrome), I want to have a mouse that uses an accelerometer, connected to any limb in the body, to replace the conventional mouse that you move with your hand.

In other words, I want a mouse that I can move with movements of my body that do not require me to move my hands away from my keyboard.

Did anyone make such a project? Is anyone selling such things? I could try to build this myself, but if someone already built one before, I prefer to rely on existing knowledge.

EDIT: What would be really nice is a link to a video of such a project that is built well enough to be used every day, not just a proof-of-concept.


texts: Combine two 8bit EEPROM to make 16bit EEPROM

texts:
I am working on building a computer out of logic chips.
I want to use an EEPROM as the instruction memory. However, my EEPROM's only has 8bits data output, but I want my instructions to be 16bits long.
How would I go about combining 2 of them to double the output length?
Thank you


texts: I have a project, But the required IC is available in my home is in SOP design. How do I use SOP ICs on breadboard?


texts: How to detect glue without surface contact

texts:
I am currently working on a project that requires a section of "release liner" to be removed and a clear plastic to be put in its place after a few holes are punched out of the paper. What I am trying to figure out is how to detect if the plastic did indeed cover all of the glue or if there is glue present. An addition to this would be to check and make sure that the release liner is also removed in the current section.

It would be preferred to do this without contact since there is very little room to test if there is glue present (on the surface) before it goes into the next stage of the process.

The materials used are as follows:
light-brown chipboard (type of cardboard/heavy paper) that is backed with glue on 1 side
White (semi-glossy) release liner that sits on top of the glue
Clear (PET) thin plastic backing which is very reflective

Thoughts that I have had, but do not know what avenues to pursue are bouncing a laser off of the surface and measuring the amount reflected back and also ambient reflection to detect if it is bouncing off of a white surface.... Any and all avenues, tips, and/or help will be greatly appreciated.


texts:
Since some of you may already read some of my posts here where I wrote that I preferred AVRs/ARMs may wonder why now I want to know something about PICs.

Though one may like them or hate them, they offer many advantages at [very] low prices (CANbus and Ethernet, RTCC, many I2C & SPI & UART ports).

Finally they seem to be among some of the most widely MCUs used in the industry (beside for instance the 8051 which although old is still widely used), so learning them might be positive for a job.

Therefore I wanted to ask: what MCU architecture would you choose among the many available?
PIC16/PIC18/PIC24F/PIC24H/dsPIC30/dsPIC33/PIC32?

I ask that because it seems to me that their architectures is very different one from the other. Therefore assembly instructions will differ significantly. I don't really if in C these differences are less important.

I know you can't really give me a "general" answer since each MCU is best suited for one specific application, but I hope you can give me tips to maybe avoid using some deprecated MCUs and choose newer ones for ~ the same price.

This is AFAIK where they'd be better suited for:

PIC12/PIC16/PIC18: basic circuits (LED controls, switchs, basic ADC, DAC, SPI&I2C&UART), 8 bits [basically what you do with any AVR] (very cheap)
PIC24F/PIC24H: more complex circuits, ethernet MAC, 16 bits
dsPIC30/dsPIC33: operations involving digital signal processing (I don't plan doing those at the moment)
PIC32: most complex circuits, CAN/CANbus, ethernet MAC, 32 bits (relatively expensive)

Since I already have some projects in mind I'll illustrate what I'd chose for some small applications, so that you may prove me I'm wrong :)

Energy meter: PIC32, since with SPI/I2C it will communicate to a power meter IC, while CAN/CANbus will pass the measured informations to a host (basically a distributed energy meter system with on meter on each [significant] plug)
DC/DC converter, battery charger, ...: PIC12/PIC16/PIC18/PIC24F/PIC24H, basically to do a PWM and negative feedback with ADC

I'll accept any statement on which MCUs to prefer/avoid for one particular application.
I know some of you may want to use AVRs/ARMs/MSP430 and each MCU has its own application field. And, BTW, I'm not saying I only on using PICs. Just that for starters it may be better to use not all architectures at once.

For instance in my opinion:

I'd take a MSP430 for low-power applications or for integrated >= 16 bits ADC
I'd take an AVR for very fast instruction set (most are 1 cycle instructions)
I'd take an ARM for more advanced features and speed/memory

However since PICs are usually the cheapest and with most periferals, I think it's best to know the characteristics of each PIC family. I don't know if nowadays PIC12/PIC16 are deprecated, expecially since I heard some bad things about their "complicated instruction set", but AFAIK nowadays that's a bit better.


texts: is it OK to stack several DC-DC converters with their inputs connected in series to support a larger input voltage?

texts:
Imagine I have a single-IC switching DC-DC converter which supports input voltage up to 16V, for example a LM2727.

Can I stack the inputs of such converter in series, for example 64 of them, and be able to apply up to 1024V across the combined input?

I need lots of stable 3.6V outputs anyway (for charging each cell in a multi-cell battery separately).

And on the output side, can I put a 3.6V cell between the outputs of each DC-DC converter and then connect all the batteries in series - will that be fine, or everything will blow-up?


texts:
I am building a project that requires the pin output for 160 micro seconds.
I will need to delay for 10 microseconds and turn on a sec output pin for 30-40 micro seconds.

I can not find any information on turning on a digital output pin for micro seconds.
I can find it for miliseconds.

Your assistance is apprecitated

Marwynne


texts:
I am learning computer architecture and organization. I have the following doubt. Given below is a question along with its solution but I think that the solution is wrong. You can see the question here question number 5.
Consider an instruction pipeline for the MIPS32 processor where data
references constitute 42% of the instructions, and the ideal CPI ignoring
memory structural hazards is 1.25. How much faster is the ideal machine
without the memory structural hazard versus the machine with the
hazard?
a. 1.34
b. 1.26
c. 1.38
d. None of the above

Correct answer is (a).
Speedup = (Ideal CPI x Pipeline Depth) / (Ideal CPI + Stall cycles per instr)
So, Speedupideal= 1.25 x Depth / (1.25 + 0) = Depth
And, Speedupreal= 1.25 x Depth / (1.25 + 0.42 x 1) = 1.25 x Depth / 1.67
Required answer = 1.67 / 1.25 = 1.34 (approx.)

The solution calculates Speedupideal and Speedupreal and then it divides them. I don't understand how it gives the answer. I think the solution is wrong. Moreover, the solution says that the stall cycles per instruction are 0.42 * 1 which I think it got from the data references but I don't understand how it got stall cycles per instruction from data references.

As I am a beginner my concepts are not very clear so some help will be appreciated.


texts: Two types of LEDs, serial - parallel combination

texts: I am trying to design small DIY grow light for Chilli Peppers. I found ideal to use a combination of Samsung LM301H(https://www.samsung.com/led/lighting/mid-power-leds/3030-leds/lm301h/) and LM351H V2 (https://www.samsung.com/led/lighting/high-power-leds/3535-leds/lh351h-deep-red/). Now I am not sure what is the best serial-parallel combination of these two types of LEDs together. I want to use a Constant Current source. For LM301H(Uf=2,75) I want to use 65 mA and 350 mA for LM351H(Uf=2.2). Is it a great idea to put 6 LM301H together in parallel, series to 1 LM351H? Then I will have a block that will have a voltage drop of 5V and driven with a constant current of 350 mA. Is this correct design, or am I missing something?  Thanks! :)


texts: Do we know what a radio wave looks like?

texts:
In precalculus class we are learning about sin/cos/tan/cot/sec/csc and their amplitude, periods and phases shifts. I've studied electronics on and off for about a year. I would like to know if we actually know what waves look like? do they actually look like the sine and cosines like in mathematics textbooks. Or are those wave functions just representations of something we can't see be can only analyze their effects. And therefore something we don't know what they look like.

Please explain

Thank you


texts: Detecting small AC current signal generated by phototransistor

texts:
I'm trying to detect a small AC signal (~10kHz) generated by a phototransistor on a magnitude of 10nA~1uA using the following circuit by converting the signal to voltage signal first and then filter it:

simulate this circuit – Schematic created using CircuitLab
However, environmental light generates a constant offset of approximately 50uA, which is much greater than my signal. This means that if need to convert the current signal to voltage signal first before filtering, assuming I power the amplifier with a 5V voltage source, R needs to be smaller than 100K Ohm in order to prevent saturation of the amplifier. As a result, the voltage signal would be merely 1~100mV, which is too small for accurate detection due to noise issues. If the 50uA background could be filtered out, I can use a larger R to convert current signal to a larger voltage signal.
In theory, some form of high-pass filter should solve the problem, but I have no idea how to apply a high-pass filter that operates directly on the current signal.
Any hint would be much appreciated! thanks!
Note: phototransistor's collector should be fixed at 0V.


texts: Ethernet.begin() only works with SD Card removed - why?

texts:
When I run this code on my W5100 Ethernet Shield:

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

void setup() {
  Ethernet.begin(mac);
}

it only works when the SD Card was removed from the shield!

It took me days to find this error. With SD Card installed only the full begin setup works:

Ethernet.begin(mac, ip, dns, gateway, subnet);

The official documentation of Ethernet.begin() says nothing about this problem. Why does it only fully work with SD Card removed? Is this a "documentation bug"?


texts: Free-as-in-beer power from neutral and ground?

texts:
I live in a house where each socket has 3 connections,:

hot (phase)
neutral
ground

Where:

The voltage between hot and neutral is about 220V AC.
The voltage between ground and neutral is about 2-3V AC.

Can I use those 2-3V as a 'free' (not paying for it) power source?
Do you know any project using them?


texts: Should I consider systems to be causal or non-causal by default in questions like these?

texts:
Could anyone explain to me when to consider one-sided Fourier transform and when to consider two-sided Fourier transform? Normally in a question, just an input signal is mentioned, without stating anything about the causality. Do we by default consider a system to be causal or non-causal? What's the norm?

For example, let us take this question:

For part (a), I was considering doing a Fourier transform of \$v(t)\$, and then doing the inverse Fourier transform, with the frequencies above \$\omega_c=a\$, and below $w_c=-a$ left out. If the inverse Fourier transform is \$v'(t)\$ (say), then I guess the answer should be either \$\int_{-\infty}^{+\infty}(v'(t))^2dt\$ or \$\int_{0}^{+\infty}(v'(t))^2dt\$. Not sure which.

So, should I do the Fourier transform like

$$\hat{V}(\omega)=\int_{-\infty}^{\infty}e^{-a|t|}e^{-jwt}dt$$

or

$$\hat{V}(\omega)=\int_{0}^{\infty}e^{-a|t|}e^{-jwt}dt$$ ?


texts:
How can I calculate what the current "I" output can i have for determining my  Efficiency.
I am building a simple linear regulator and is it possible to know during design of the circuit , what the efficiency of the circuit would be?

Should I just assume input current to be the maximum current it can out put, or should I put in a resistor for my calculations and see how much current it will draw, if its the second one, then how do I determine the impedance due to other parts in my circuit?


texts: what does "70A moy/arit 90A eff" on a high-current automotive lead-acid battery charger mean?

texts:
I have a huge (28 kg mass) automotive high-current battery charger, and its current delivering capabilities are described like that:

70A moy/arit 90A eff

What do these mysterious abbreviations "moy", "arit" and "eff" exactly mean, and how much current can this beast really deliver, 70A, 90A, what's the difference between the first and second number?

Here is a photo, so you have an idea what kind of device it is:


texts:
I am using an  UCC28C42 in my circuit.

I need a clarification of some resistor. I am converting 48V to 24V. If my load increases to 4.5A then Resistor is getting heated up.(Circled part)

I used higher wattage resistors(1k 2W), too.

PFA of Ckt


texts: Is it ok to use a 110V cable for a 110-220V device on a 220V Outlet?

texts:
The focus here is the cable.  Will the 110V cable be ok if It was used to connect between a 220V outlet and a device that has an input voltage of 110-220V?
Likewise, will it also be ok for a 220 volt cable to connect between a 220V outlet and a device that has an input voltage of 110-220V?
Among the two configurations above, which is better or safer and why? or is there no difference at all?
I'm asking this because I am unsure whether I also need to mind the maximum voltage rating of cables as well. I know its not good to plug a 220V device to a 110V outlet or vice versa however, I cannot find clear cut information yet on the internet specifically with regards to using cables of different max voltage ratings.


texts: Electret condense microphone(ECM), its external circuit design

texts:
I got the external circuit about the Electret condense microphone(ECM), shown as in the below. I would like to know that 1). How it can work out on differential signal to input to CPU? 2). It seems like using so many RC filter, what is its function purpose? 3). What's the filter of blue frame? Thanks.

simulate this circuit – Schematic created using CircuitLab


texts: How to determine a Permanent Magnet Synchronous Motor (PMSM) Nameplate?

texts:
I have already built a three-phase Permanent Magnet Synchronous Motor(PMSM) and wanted to use a VFD in sensorless vector control mode to run it. Now I want to figure out the characteristics of my motor to enter them into the VFD. By characteristics I mean Motor Nominal Voltage, Nominal Frequency, Nominal Current, and Nominal Power.

The information that I have measured from my motor are the following:

Each phase winding inductance
Each phase winding resistance
Voltage/Frequency ratio

Do I need to get more information from my motor to find the parameters mentioned above?
If not, how can I calculate those parameters?

Thanks


texts: What is the difference between vectors and phasors?

texts:
I've seen both the terms vectors and phasors be used when it comes to AC circuits. I'm still kind of confused with how to clearly distinguish the two terms. I get that in a vague sense, the complex quantities used in AC circuits can be referred by using both terms. But I think phasors is more correct? From my understanding, phasors seem to be a subset of vectors. A phasor is a rotating vector and the direction is an angular distance from the reference in the rotation.
I just decided to ask here since I haven't seen any StackExchange question talk about these two words in depth.


texts:
I'm a bit confused about reading current on a breadboard using a multimeter (I'm a complete beginner with electronics).

I'm using a self-powered breadboard which should deliver 5V / 1A. Multimeter is a Fluke 87V.

Voltage is OK, but when trying to read current on a simple circuit with no component (voltage out -> multimeter -> ground), the multimeter starts by giving a reading of ~2A, continuously decreasing (even below 1A).

When placing a single resistor on the circuit, the reading is perfectly correct, based on the resistor value, and stays stable.

So is this something normal (then why), or am I doing something wrong / missing something?


texts: Transformer provides no attenuation for differential transients

texts:
I have read few articles about transformers and they all point to the fact that they are excellent attenuators for common mode transients, but not for differential mode transients!
One of this documents is the following:
https://www.erico.com/catalog/literature/TNCR016.pdf

I am really having trouble to see why this is the case. Could someone please explain why transformers are good for common mode transient filtering, but they are not able to attenuate the differential mode transients?


texts: Why is asynchronous data transfer only suitable for slow devices?

texts:
I have read that asynchronous data transfer is wasteful of CPU time for slow devices like keyboard or mouse.
Then how is it possible that it is suitable only for slow devices like keyboard or mouse for which the data transfer speeds are low?
Moreover I have also read that it cannot be used for high-speed devices.
Why?
Edit: Here is the link to the video DATA TRANSFER TECHNIQUES (9:38 to 13:42).


texts: I have a 20 - 0 - 20 transformer which is giving about +-27V after rectification. I need +20VDC, +16VDC, 5VDC and -20VDC. I thought of regulating from 27 to 20 then 20 to 16, and finally 16 to 5. Will it work using cascaded LM317 or LT1085?


texts: Counter which counts to 5 and then turns on a led

texts:
hope you are all well and healthy during those times. I have a question which I cannot solve. Question is like this:

Design a counter which counts from 0 to 5 and then stops and turns on a led. The process is initiated by pressing start push button. (Please use J-K Flip Flop with preset and reset asynchronous inputs).

I reached at a certain point in the question and I want to share these with you:

When the counter is at 110 (6) the LED turns on. When it gets to 7 LED turns off.

After 111 (7) the counter resets which is natural since I am using 3 Flip-Flops. How can I stop this counter (does my teacher mean resetting by stop?) and turn on the led.


texts:
I'm a software engineer that sometimes has to deal with some electronics. So I'm by no means an expert...

I want to control a BLDC motor and I have added a thermistor to the windings of the motor so I can ensure the motor doesn't overheat itself. The wires of the thermister (Vcc and GND) go over a twister pair cable to a PCB which contains a voltage divider circuit. But I see a lot of noise once the motor has to do work (e.g. current is drawn). There is an embedded encoder in the motor that sends out a differential digital signal to minimize any noise. I wonder if it's possible to create(or an IC exists of some kind) an analog differential signal for the thermistor voltage reading. Or maybe there is some other way to get a less noisy voltage reading?

The thermistor I'm using is a simple NTC type.

Any help is appreciated.


texts: How to control a common-cathode RGB LED matrix with Arduino?

texts:
I have the Arduino Uno board, and I want to create a 17x31 RGB LED matrix. Unfortunately, I wasn't patient enough and already bought the LEDs, and I purchased common-cathode LEDs without doing much research prior.

After the fact, I did my research and found out that the TLC5940 would only work with common-anode LEDs (because they are current sinking). I saw a similar post to mine that suggested to use shift registers with common-cathode LEDs instead, like the 74HC595, because it's current sourcing.

So, is it possible to use multiple 74HC595 drivers to control 527 RGB LEDs with the Arduino? If I multiplex, I think I would only need to be able to control 82 outputs, correct? Otherwise, what would be a better solution?


texts: What are the characteristics of a memristor?

texts:
This is an in-spirit follow-up to my earlier question.

So I'm an electronics hobbyist, and I've been curious for a while about the proposed new component, the memristor. My research has turned up this link demonstrating the creation of one, and now I'm wondering, how do you define and measure a memristor? If a memristor relates charge and flux, how does an oxidized metal perform like this? finally, do all (or most) metal oxides have these characteristics?

I realize that this is probably a lot, but what I've seen out on the internet regarding this has left me very confused.  Thank you for your help.


texts: I am looking for a circuit that will charge 8.1 volt capacitor (3 2.7v 400f in series) using a 24VDC power supply. I want to limit the charging current to no more than 100ma.


texts:
Background: I'm working on a project that would allow a number of people to hook up their laptops to a single monitor through a KVM and use buttons on the desk to control who has control of the monitor. Originally, the plan was to use buttons with microcontrollers to send keyboard shortcuts to the KVM which would then switch to a given input based on what keyboard shortcut was sent. I've run into a problem because the keyboard switching is a little.. off. The only way to do it without installing software is to cycle through the inputs 1 by 1, and it's a requirement that the user not need to install anything. So now I'm wondering if its feasible to interact directly with the KVM hardware. Worst case scenario, we could just plant the KVMs on the table, but that's not quite as user-friendly.

Problem: I want to have a bunch of buttons on a table, ~6ft away from the KVM, which would replace the buttons on the KVM board. I'm not sure how to do this, but I have a few ideas (not sure if they're feasable):

Remove the buttons and solder wires in their place, which would be connect to the buttons on the table.
Connect the wires from the table buttons directly to the leads of the buttons on the board, without removing them.
Some kind of tiny motor or something that could push the buttons on the KVM. (Rather avoid this)

So I guess the question is: which of these would be the easiest, and what's the best way to go about it? Also open to suggestions on entirely different solutions..

First picture is of the top of the KVM, where the buttons are soldered onto the board, the second is the underside of the board. The button connections can be seen sticking out of the board.


texts: Confusion with interfacing a relay according to its given datasheet?

texts:
I'm confused about interpreting a datasheet to interface a relay. In my application, a solenoid-valve is going to be turned on every 30 minutes to drainage water periodically. The control signal will come form an Arduino digital output pin.

I have to use this model, and by reading the data sheet I am very confused how to interface it.

First of all there is this warning in the datasheet:

Unfortunately the model I have Z1D according to the data-sheet does not have surge protection. What is meant by that a TVS?

Here is the schematics I was planing to use to turn on and off the valve:

But I cant infer from the data-sheet whether I need a fly-back diode or not. I cant even find what is the input current the solenoid draws.

Is my schismatic adequate? How can I make this interfacing more robust according to the datasheet?


texts:
I designed a 4-bit JK up/down counter.
I want the circuit to be reset to 0 when counting up when it reaches 9, and to be reset to 9 when counting down when it reaches 0.
Anyone know how ? I tried a lot.


texts: Output stability of step-down regulator connected to vehicle battery

texts:
I do not have access to an oscilloscope, so  I ask here.

Short version: I charged a phone from a motorcycle battery. Phone battery broke.

Question: Can using a running vehicle's battery as a step-down regulator's input cause problems on the output?

Long version: I used this step-down buck regulator connected to a 12V motorcycle battery to charge a Samsung phone. Tested when vehicle was not running, output was calibrated to 5.01V.
A cheap voltmeter was also connected the whole time, but only sporadically verified - all seemed in order.
Half an hour of driving later, phone was found to have turned off. Seconds after being turned back on, the battery started swelling. Phone still works.
Further confusing is the fact the phone has its own charging circuit which I'd expect to handle any instability AND the 2A output.

I am not claiming certainty that the setup caused the malfunction, but it seems likely.

[edit] The question, again, is whether the fact the input is from a running vehicle's battery - being used for the induction coil, etc, and charged at the same time, and whatever else might be important - is likely to affect the converter's output enough to produce the described effect.
[edit2] Connections are simple: From regulator, 2 cables to 12V battery, 2 cables to microUSB plug in phone. The regulator has capacitors on both sides, see the product photo.


texts: Can I use a 24V, 1A fuse for a 5V application?

texts:
I have a 5V power supply which needs protection. I only have a 24V, 1A fuse. Can I use this fuse for the 5V power supply.

As Watt = R * I * I = V * I.
As rated W is constant for a given fuse, will the current at which the fuse blows increase if Voltage decreases?


texts: does the 24 Vdc supplied circuits with metal chassis needs to be grounded to earth?

texts: I used put some electronic circuits together in a plastic box, with a DC power jack attached to the box for a 24V dc supply to my circuit. Everything works fine. However i now plan to put all the circuitry into a metal chassis. I have heard that every metal chassis need to be grounded to the earth for safety reason. I searched online for more info but mostly are AC to the metal chassis box, which i knew it is just connecting the metal box to the 3rd prong. But for my case, can someone please tell how to ground the metal chassis with DC voltage input? I attach some images for understanding.  I tried to make something like a mini PC with metal box shown in figure. Are those mini PC's metal box grounded as well?


texts: Link between Combinational Logic and Sequential Logic

texts:
I always thought that combinational logic circuits could only solve problems that didn't require memory, but then something struck me.
Whenever we are modelling a binary adder with a Finite State Machine, we consider it as a problem that requires memory ( we need to know whether the previous digit addition led to a carry or not ) . That's why we need two states, "no carry" and "carry".

But then we can easily see how binary adders with carriers can be solved by combinational logic circuits, which seemingly don't have memory.

It seems to me that the memory is somehow encoded in the way we put the individual adders in serial ( C_out of the last adder goes into the C_in of the current adder )

Comparing the Finite State Machine solution to the problem with the Combinational Logic solution to the problem , it seems like the former decides to do one digit addition at a time, regulated by a clock and that's why the memory needs to be in form of states . And it seems like the latter decides to do all digit additions at the same time, so there is no need for clocks and somehow the memory for the previous carriers is implemented via a serial cascading connection between the adders.

Just like we can have a FSM as well as a Combinational Logic version for the problem of arithmetic addition with carriers,  i'm thinking whether we can actually convert ANY finite state machine into a Combinational Logic Circuit that does the same job, provided we arrange one subcircuit for every possible job that is done in the FSM in one clock ( one digit addition in the last case ) ,  put all those in parallel, and somehow encode the memory in a serial cascading connection.

Is it true ?

This doubt came because i'm trying to link all concepts i have recently learned in Theory of Computation ( Automata, Turing Machines, Computational Complexity : Time Complexity and Space complexity ) with combinational logic circuits .

Thanks a lot in advance.


texts: USART not working with CP2102 adapter and STM32F1 Blue Pill board

texts:
Having programmed 8-bit AVR MCU's, I bought Blue Pill STM32F103C8 dev board from ebay. It has 8MHz external crystal and I program it with ST-Link on Mac. I saw a lot of options like HAL, etc, but I chose to program using direct access to registers and with core of CMSIS.

My problem is that I am trying to send symbol from MCU to computer. I am using CP2102 module connected to USART1(PB6 and PB7). LEDs are blinking, but I don't get any output in Arduino IDE serial monitor. Here is my code:

#include "stm32f1xx.h"

void delay(unsigned long delay)
{
    while(delay) delay--;
}

int SendChar (int ch)  {
    while (!(USART1->SR & USART_SR_TXE));
    USART1->DR = (ch & 0xFF);
    return (ch);
}

int main(void)
{
    //Enable I2C2 clock
    RCC->APB1ENR |= RCC_APB1ENR_I2C2EN;
    //Enable the clock to PORT B, PORT C, USART1 and AFIO clocks
    RCC->APB2ENR |= RCC_APB2ENR_IOPBEN | RCC_APB2ENR_IOPCEN |       RCC_APB2ENR_AFIOEN;
    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;

    //use AFIO_MAPR register to remap alternate functions to use USART 1 TX and RX on PB6 and PB7
    //Ref 7.4.2 and 6.3.7 in st manual
    AFIO->MAPR |= AFIO_MAPR_USART1_REMAP;

    //CRL Configures outputs 0 to 7 and CRH 8 to 15, so if you want to configure PC13,
    //you modify GPIOC_CRH register
    GPIOB->CRL |= GPIO_CRL_MODE0_0 | GPIO_CRL_MODE0_1;
    GPIOC->CRH = GPIO_CRH_MODE13_0 | GPIO_CRH_MODE13_1 |
        GPIO_CRH_MODE14_0 | GPIO_CRH_MODE14_1 |
        GPIO_CRH_MODE15_0 | GPIO_CRH_MODE15_1;
    //Set RX as floating in and TX as out push-pull
    GPIOB->CRL &= ~(GPIO_CRL_MODE7_0 | GPIO_CRL_MODE7_1);
    GPIOB->CRL |= GPIO_CRL_MODE7_0 | GPIO_CRL_MODE7_1 | GPIO_CRL_CNF6_0;

    //Enable RX TX
    USART1->CR1 |= (USART_CR1_RE | USART_CR1_TE);  // RX, TX enable
    //Enable USART
    USART1->CR1 |= USART_CR1_UE;
    //Make sure to clear OVER8 bit(15 bit in USART_CR1) to oversample by 16, I dont know if I need this
    USART1->CR1 &= ~(1 << 15);
    ////Configure Baud Rate
    /*USART_BRR = Fck/BAUDRATE*/
    //Set 115200 Baud, 8 MHz crystal
    USART1->BRR = 8000000L/115200L;

    while (1)
    {
        SendChar(35); //Test UART,fingers crossed

        //Toggle led on PB0
        GPIOB->ODR ^= GPIO_ODR_ODR0;

        //Toogle RGB led connected on PC13, PC14 and PC5
        GPIOC->ODR ^= GPIO_ODR_ODR13;
        delay(50000);
        GPIOC->ODR ^= GPIO_ODR_ODR13;
        delay(50000);
        GPIOC->ODR ^= GPIO_ODR_ODR15;
        delay(50000);
    }

    return 0;
}


texts: Two LM317 Based Voltage and Constant Current Regulator Circuit

texts:
I have read some articles on on the following circuit. I was wondering if I can create such a Voltage and Constant Current Regulator for my Power Supply or not.

My Question is - is this circuit Practical? And will 1 Watt power rating's Variable Resistances and 2 Watt Ratings Resistances work?

Here the first LM317 is used as Current Regulator and the Second one as Voltage Regulator. I was also wondering if this ordering is correct, or if this has to be reversed - i.e. first voltage regulator and then Current Regulator to make it work better. Please help.

PS: I need this circuit to regulate Voltage and keep the output current to a configurable Constant level.


texts:
I am new to the use of transistors and couldn't find exactly how to select the right transistor for this type of an application which is to control a 5m 5050 RGB LED strip with an Arduino. The LED strip has 4 pins (R/G/B/12V) so I would need 3 transistors for R,G and B. The LED strip has 300 LEDs (60LEDs/m) and each LED consumes 20mA max current so the max current through any transistor would be 6A. I believe the Arduino outputs at 5V so the input to the base of the transistor would be 5V.

I came across the NPN 2N2222 transistor however its datasheet shows the following which states that its max collector current is 600mA so I am led to believe that I would need a transistor with a higher collector current.

I also found the TIP102 NPN transistor (datasheet) which is has a higher max collector current of 8A which is sufficient for its use. It also has a base voltage of 5V and a max collector-emitter voltage of 100V which is also sufficent.

I also came across the IRLZ34N MOSFET (datasheet) however am not familiar with MOSFETs.

Would the TIP102 transistor work for my use of controlling an LED strip with the 5V arduino?


texts: What is the advantage of using many low-farad capacitors instead of a few high-farad capacitors, when trying to maximize current?

texts: I am working on a high current application, and I am wondering, which maximizes current (over a short period of time), using a bank of small caps, or using fewer large caps?


texts: DC motor voltage drop and high current draw

texts:
I'm quite confident the wiring of my motor-motor controller-Arduino setup is correct. I'm using an L28N H-Bridge motor controller and tested the output voltages to be correct (with 12V input). However, plugging this setup to my motor caused the motor to rotate slightly and the motor controller to overheat.
I disconnected this circuit and connected my motor to a 9V battery for testing. Under load, the voltage across the battery drops from 7.8V to 0.6V and the current is 1.6A, which I'm quite sure is way too high, since the battery was warming up.
My motor controller is only rated for 5-46V and 2A output, and I'm limited on the specs of the motor. What can I do?
L28N MotorController

EDIT: Received the robot details: https://www.banggood.com/Upgraded-WT-500S-Smart-RC-Tracked-Tank-RC-Robot-Car-Base-Chassis-p-1360827.html?gmcCountry=US&currency=USD&createTmp=1&cur_warehouse=CN


texts: Op Amp integrator - limiting +Vsat to zero (ground)

texts:
Part of the Dual Slope ADC consists of an integrator which integrates the input voltage according to Vin/-Vref .
 I am using TL071 connected as an inverting integrator.

Quick summary of operation:
The output of the integrator charges negatively up to a certain count value when Vin is connected.
When the count value is reached, the controller switches to -Vref.
This causes the integrator to discharge and hence increasing output voltage (note due to inverting output).

NOW... Instead of the integrator to continue to integrate towards a positive output voltage while -Vref is connected, I want it to stop at zero voltage so that when Vin is connected as input, the integrator will start integrating negatively instantly.

Is this possible by connecting the op-amp supply terminals +Vcc to ground while -Vcc to -ve supply?
I tried this but observed clipping in the negative rail too, is it a bad approach?
Any other possible solutions?


texts: Input RC filter design for analog pin of ADC

texts:
I am implementing ADC filter for AD7705 ( Sigma Delta ADC - Analog Devices Chip ). Input to ADC is constant DC voltage. So, what will be cut-off frequency I should consider to implement RC filter at analog input.

If we are designing RC filter, then by assuming C value ( typ 0.1uF ) and cut-off frequency above which we are trying to block signals (ripples) , we can calculate R value. Is this a approach which we consider for filter design? Am I correct in my consideration.

So for DC input at ADC pin, what should be ideal or practical cut-off frequency I should consider for designing RC filter.

Thank you in advance.


texts: So I found an HDTV on the side of the road, brought it home, took it apart, and found the problem. A blown capacitor. So I replaced it with another one of roughly the same value (original was 16 V 470 uF new one was 24 V 470 uF) but it's still not working. As I'm new to this I would seriously love some feedback! I think I burnt the board too much, here are a couple pictures


texts: Build output connector for Midi-USB converter in old keyboard

texts:
I'm trying to recover an old keyboard (of about 25 years old). It has all circuitry gone in paradise, but it had a midi output and input line. Moreover, its keyboard mechanics and the transducer work properly. I saw with an oscilloscope that the output from the transducer is something that resembles a midi signal, so I connected this output to a standard 5 din connector following the figure 1; then I connected it to the computer through the midi-to-usb converter in figure 2 (soundsation usmi100), alimenting the keyboard once with the original alimentation  (the one built into the keyboard) and once with the alimentation pin of the 5 din connector.

The connector works great with an other piano midi output that I tried, but when I connect it to the my old keyboard, it doesn't work: I can see it from my computer and I can work with it, but it doesn't send data. Moreover, to work correctly it should be flashing (with the piano, it flashes!), however, when connected to the old keyboard, it does nothing.

Why the converter doesn't see the input?


texts: How to calculate total current drawn by a circuit

texts:
I have been trying a make simple alarm using LM324 and a buzzer. The circuit is pretty simple. I need to power it from my 9V/1000mAH battery. But here is the part am stuck. I don't know how to calculate the total current consumed by the circuit. I need to know this in order to determine how long i can run my alarm using the battery. Here are the few specs i have gathered so far

Buzzer - 5mA at 9V
Output current or Source current of LM324 - 60mA

Now my question what exactly will be the current consumption of IC for this operation. Should i consider only the source current of IC as mentioned above or is there any other current parameters i should consider for making this total current drawn from the circuit calculation.

Somewhere i read that i should also take the account of Quiescent current into account. Is that so? Any guide that helps me to make this calculation please.

For the above setup output frequency will be around 20HZ. Should i take the output frequency into consideration for this calculation as well. Please any possible information will be much helpful.

P.S: Please feel free to edit this question if I haven't put it in the right way. Thanks in advance


texts: Defining Wavefrom as an expression in LTSpice

texts:
Is there a way to define a variable as a function of other nodes in LTSpice so that I can later plot it?

For example V(OUT) = (V+) - (V-)

And then I can plot V(OUT) without having to do the math equation each time in LTSpice? This is useful as I want to keep some measurements for V(OUT) but plan to change that expression.


texts: Deferred callback manager / software timer library for PIC32

texts:
I'm looking for a software timer library for embedded systems, especially PIC32, free or commercial. I'm NOT looking for a full-blown RTOS with threads, I/O, etc. - just for the software timer functionality.

The library should use one dedicated hardware timer, live in the interrupt domain and allow the scheduling of deferred and recurring call-backs.

Is anybody aware of such a library?


texts: Comparing sensitivity to temperature changes of BJT (transistor) circuits in Common Emitter Configuration

texts:
I measured Ic variation with Ib when Vce = 15v kept constant for BJT (NPN) in Common Emitter config and also BJT Common Emitter config with series 47 Ohm resistor connected.

From the experiment I observed less temperature change when I blew on the 2nd circuit Transistor than on the 1st. Can someone please explain to me why the second circuit with the same transistor with series 47 ohm resistor with the emitter is more stable than the 1st circuit without the resistor?

The emmitter resistance provides negative resistance; How does help circuit to be less sensitive to temperature changes?


texts: Regulator design for negative voltage O/P

texts:
In my application, I am generating 7.5V from TPS5430 (Buck) regulator and to generate -5V, I am assigning inductor's one leg to input of 7905 for -5V o/p.

Circuit is shown.
U14 is TPS5430 and U15 is 7905.

Is this a correct implementation to get -5V from pulsating DC?

I have seen this arrangement somewhere in design and trying to apply in my circuit.


texts:
I have a Motorola MC14011CP Quad-dual input NAND IC in which Vdd = 12v. I'm trying to use it as a NOT gate by tying the inputs of one of the gates together. When the inputs are not both true, the output is changing to ~0.5v instead of Vdd +- 0.5v as listed on the datasheet. Could it be something wrong with the chip or have I perhaps made an error in either my component selection or wiring?

Schematic: The Vdd on my IC is tied to +12v and the Vss to 0v. The load is an electromagnet.

simulate this circuit – Schematic created using CircuitLab


texts: Spice circuit Error : Must be an inductor or transmission line

texts:
Hello I have an error on my spice circuit, I can not understand what is wrong?
able to help me?

ERROR IMAGE:

ERROR:

Must be an inductor or transmission line
Name "kp" is defined more than once
-NONE-
Must be an inductor or transmission line

CIRCUIT:

Mn1 5 1 0 0 mosn L=0.5u W=7u
Mn2 5 2 0 0 mosn L=0.5u W=7u
Mn3 5 3 0 0 mosn L=0.5u W=7u
Mn4 6 4 5 0 mosn L=0.5u W=7u
Mp1 6 4 9 9 mosp L=0.5u W=7u
Mp2 6 3 7 9 mosp L=0.5u W=7u
Mp3 7 2 8 9 mosp L=0.5u W=7u
Mp4 8 1 9 9 mosp L=0.5u W=7u
.model mosp pmos Level=1 CGBO=4.5e-10, CGSO=3.5e-10, CGDO=3.5e-10, tox=8e-9, VTO=-1,
kp=50u, gamma=0.4
.model mosn nmos Level=1 CGBO=4.5e-10, CGSO=3.5e-10, CGDO=3.5e-10, tox=8e-9, VTO=1,
kp=100u, gamma=0.4
VCC 9 0 5V
CL 6 0 1pF
VA 1 0 5 pwl(0 5 10n 5 10.1n 0)
VB 2 0 5 pwl(0 5 10n 5 10.1n 0)
VC 3 0 5 pwl(0 5 10n 5 10.1n 0)
VD 4 0 5
.tran 100p 30n
.probe
.end


texts: Current consumption calculation + Full wave Bridge rectifier

texts:
I am facing to calculate the current consumption in a segment of a circuit as shown in the picture below.I have used the formula (showed in the picture) without considering the impedance of the capacitor C1. I have just considered the resistors components. Can any one tell me if the formula that I have done is correct to determine the current consumption.
Best regards,


texts: Resistance measurement voltage - multimeters

texts: What voltage/current is applied by modern multimeters to determine resistance?


texts:
In a previous question I had this as the given:

  The transfer characteristics of a voltage amplifier are described by the following equation:
  vO = F + G vI with amplifier saturation levels at vO = –3 V and at vO = +5 V.
  The input voltage vI = 0.4 sin(t) V produces an undistorted output with the largest peak-to-peak
  value, which is vO = C + 4 sin(t) V. Find the value of G (in V/V).

By taking the midpoint $$\frac{(L- L-)}{2} = 4V$$ Then we divide by G, the gain we're looking for to get 0.4 V.
$$ \frac{4}{Gain} = 0.4$$

So the Gain = 10 V/V

In the following question we need to find F. The answer according to the key is 1, I've only managed to prove that F = C but that gets me nowhere.


texts: No load connected - damage to amplifier?

texts:
Can turning on an audio amplifier without a connected load damage it?
Can I apply an input signal and crank it up without the load?(for short or long time) Are Valve amps more tricky in this respect?


texts:
Can anyone identify this connector type?

It sticks out of my wall near television area. I suspect it may be some kind of antenna connection, but I'm not sure. Could not find it in any of the antenna connectors listings.


texts:
I want to connect a Li-Ion battery on a GSM/GPRS module expecially this one (http://www.electrodragon.com/w/GSM_GPRS_A6_Module). In general parameters is mentioned operating voltage from 3.3V to 4.2V
A simple Li-Ion battery when is fully charged goes up to 4.2V, somethings slightly above this. The question is, how can I protect the GPRS module from this fully charged battery's voltage? I'm looking for something efficient...


texts: Is there any way to force square header pins into round holes?

texts:
I got a kit in the mail with some PCBs and components to solder to it, but the headers that it came with don't seem to quite fit in the PCB holes they're meant to go in.

The header pins are square, and the holes are round. I can push the pins far enough through so that their tips are just poking through the other side, but they won't go any further.

Can I just solder the pins in if they are just barely poking through? Are there any methods to persuade the pins to fit in the holes that won't impact the connection, or would the solution be to just get new headers that fit the holes?


texts: How can I make 20-200 ohm variable resistor look like a 20-240 ohm resistor?

texts:
I have a fuel sender in my kit car that goes from 20R to earth (full) to 200R (empty). Unfortunately the gauge (constant current source, measuring resistance to earth?) expects empty to be 240 ohms, so displays '1/4 full' when empty.
What is the simplest analogue way to make 20-200R look like 20-240R?

(40R in series gives a full tank showing '3/4 full' on the dial: Still not ideal!).

So, a great suggestion from Transistor (below). I think I'll change R4 in his/her Figure 1 to a constant current source since car volts can vary quite a lot!

I believe the value for R3 (above) will be fairly independent of the transistor specs?

Update: Yes, this works nicely, gauge now goes from full to zero. I put R3 on a little trimmer - 720R for 1.6mA. Many thanks transistor!


texts: Digital vs Analogue Filters From an Non-Audio Perspective

texts:
Recently I have been reading about the use of digital filters. By deriving the transfer function of the desired filter (in the s-domain) and multiplying holds (ZOH or FOH).

What is the general consensus around using a digital filter over an analogue filter? To make things less broad, in the application of an oscilloscope anti-analysing - I want to filter off frequencies 1MHz+ and I'm using a 10MHz ADC. Using analogue components costs money, why use analogue over digital filtering if the processing power is available? (Other than the obvious marginal filter accuracy loss).


texts:
I was studying the L298 datasheet and I noticed something;
So basically an H-bridge contains two PNP and two NPN transistors as shown in the image:

but in the datasheet, there are no PNP transistors used. There were some tutorials out there on how to make an H-bridge with only NPN transistors but the L298 circuit doesn't look like any of them:

What am I missing here?


texts:
I'm looking for a way to build a cheap 1m linear encoder. Precision should be around 2cm (which is not really "precision").

Any advice will be welcome.

@Joe Hass : yes it is moving. Not really fast. Speed is not a concern. 1m per 10s is ok.

Edit : Thanks for help, as asked I give more details.
The device will pick paper in drawers arranged vertically. There's one moving paper picking device, and dozen of drawers on top of each others.
I need accuracy to locate the drawers to pick from. And a good notion of speed and position for the PID system that control the picking device.
I think two laser cut optical rulers will do the trick. (there's a fablab in my city).


texts: how do you know the each parameter values of SDC at the first time?

texts:
when we do synthesis with SDC. we should be used with SDC.
But I want to know what if you are in situation where the synthesis of yours is the first time, also the company does not even did synthesis before.
all of the first time, then your role and responsibility is make synthesis.

Ok, then how do you know the each SDC's commands parameters ? for example,

set_clock_uncertainty -setup ?

set_clock_uncertainty -hold ?

set_clock_transition -rise -max ?

set_clock_transition -fall -min ?

set_input_delay ?

set_output_delay ?

...?

when you first met this, how do you handle?


texts: Is anyone familiar with the term "life tolerance of a resistor" ? I could not find a good read in google. Any link with the explanation will be sufficient.


texts:
I'm using a voltage divider to read the battery level of a wireless sensor platform using STM32L151. I'm shooting to use 20k for R1 and 10k for R2, to be under the 50k limit of the MCU's ADC peripheral.

How do I calculate the current wasted by the divider?

Originally, I was planning on using a P-channel MOSFET to enable the divider when taking measurements to reduce power consumption, but I see that MOSFETs have leakage current and raise the part count.

Can I just set the GPIO to push-pull as the ground for the divider and set it low when I want to measure and high when I don't?


texts: Converting variable voltage to constant voltage / variable current

texts: I'm using solar panels + a micro wind turbine to charge a decent sized LiPo battery using this circuit - http://www.adafruit.com/products/390. The problem is that the solar/wind stuff will produce a highly variable voltage (anywhere from 0 to 30V+). To feed the ada module, should I be looking at just a switching regulator, or are there other considerations given the high variability of input voltage and current?


texts: Isolation for loop powered devices with limited power

texts:
I am implementing 4~20mA Transmitter that consist of a MCU, a current DAC, and an ADC for measuring an analog signal.

I would like to electrically isolate the analog signal from the loop current so that the higher end control system (i.e master system) is not damaged by some outrageous condition on the lower end (i.e sensor) side.

I've searched various solutions on-line and found that I could either use isolated ADC or digital isolator for I2C or SPI.

However, my device is loop powered, so everything must be done within about 3mA to be safe.

The isolation devices I found on major IC makers normally consume more than 1.6mA per channel.

Anybody have better idea or parts that I could use?


texts: Which Approach is Better to Drive Brushless DC Motor with PWM Duty Cycle

texts:
I'm doing a project that use brushless geared DC motor,

the motor is connected to a moving platform.
I will drive the motor with PWM, the motor then move the platform from -a degree to a degree position.

There's an RPM setting for the motion speed need to be achieved,
to do this everytime it reach the peak position (0 degree) I read the angular speed from gyro sensor
that was attached in the platform, then procceed the value to PID controller.

I want to ask which one is the correct/better approach to drive the motor:
(motor initially stop)

(1) Start from a MINIMUM duty cycle (let say ~30% is the minimum to make the platform move),
then I increment the duty cycle at every time interval (e.g. +1% every 100 ms), when it reach 0 degree position
I start braking by decrementing the duty cycle (e.g -2% every 100 ms),
then stop the motor when reach the end position. That will be one cycle, then after every 1 cycle finished,
I will calculate new value for the increment & decrement to achieve the RPM setting.

(2) From the start position, I drive the motor with constant duty cycle, then when reach 0 degree position
start braking just like approach (1) using decrement. Then after every 1 cycle finished, I will calculate
new value for the constant duty used, and also the decrement value when brakaing.

Which one is the better ALGORITHM with pros and cons?


texts:
I'm working on a project that use various analog sensors (load cells, microphone, pressure, etc.) All of them have an analog standard output (mv/V). I'm using a Raspberry Pi. I want to choose a module that can do continuous reading from these sensors.
Based on my search, I found that the HX711 module can do the job (amplification and digital conversion) and it has 24bits precision.

Will the ADS12XX (eg: ADS1263) integrated circuits from Texas Instruments amplify the signal or will I have to use an amplifier circuit?
Is there some IC like the HX711 that can do both things?


texts: I'd like to swap the speaker on an electronics kit for a reed relay

texts:
Morning all, I've built the Velleman IR Light Barrier kit:
http://www.vellemanusa.com/us/enu/product/view/?id=350693

It currently beeps when the light barrier is broken, but I'd like to remove the speaker and replace it with a reed relay to trigger another circuit. I imagine I'll also need to add some resistors in order to stop it from blowing the rest of the board, but am unsure how to work out what to add.

I've got a reasonable multi-meter, which can measure DC & AC current/voltage, resistance and capacitance. If I can measure what I need to using it, could you please describe how - I'm not sure whether I should be bridging the contacts on the speaker, or introducing the meter into the circuit in series...

Please let me know if any of the above makes no sense, I usually keep these projects inside my head, and don't know how many of the terms I've used are correct and how many I've made up.


texts: Should a oscillator's output load capacitor be attached to ground? And how much?

texts:
I have some experience with electrical engineering but there are various subjects I'm totally a noob at.

I'm planning on using the ASE-24.000MHZ-ET and it states that the Output Load should be 15pF

Should this load be connected like this?

Or should the C1151 capacitor be in series with the CLK output? Also if I recall correctly, the length of the trace also affects the total pF load on the line. Is this something I should take into calculation on a small 8x8cm PCB?

Thanks!


texts:
Where should I start when trying to identify this connector on a WaveShare epaper hat? I've browsed through more Mouser pages than I want to think about. The manufacturer (WaveShare) has been downright unhelpful.
Additionally, what crimp ends are appropriate for this type of connector?

I think I've narrowed this down to the following categories which still yields ~400 results:

Connector > Header & Wire Housing
8 Position
1 Row
Pitch ~2.5-2.54
Female

What can I do to further narrow down this search?

Here are a few more pictures of the male and female parts of this connector.

EDIT:
As requested, here are images of the crimp-on ends for completeness


texts: How to wire a single wire alternator to a bridge rectifier?

texts: I'm trying to make a 25cc weed eater generator (for fun) and I'm thinking of using an alternator to take the rotary output from the engine and turn it into electricity. I need a way to take the 12-14V AC from the alternator's output and turn it into ~12V DC to charge a 12V battery and power an inverter. The alternator I have my eyes on is a 35A ~12V output, but it only has one wire for output. I'm thinking I need to use a bridge rectifier to take the AC into DC, but I'm not sure If I can hook the single wire AC to a bridge rectifier. Is there a way to wire it to a bridge rectifier properly, or is there a better way I can go about doing this?


texts: What well-known ICs have essentially no packaging?

texts:
As a kid I once found a calculator whose IC was protected only by a loose plastic cover. With the cover removed, and with appropriate lighting, I could make out distinct features of the IC– including company logos– with a simple classroom microscope.

I'm just a lazy enthusiast; I realize that most ICs are more expertly packaged, and I have no interest in milling, dissolving, or chipping away at anything. How uncommon was my childhood discovery anyhow? Are there any well-known integrated circuits I could buy or find that I can gaze at without much hassle?

(In case anyone cares, the calculator I found was a CVS-branded "scientific calculator", model 185371.)


texts:
I am designing a PCB which has a chip antenna with a coplanar wave guide.
Having a 4-layer PCB (stackup layer: rf signal, GND, POWER, signal) can I run traces across the antenna transmission line on the farthest bottom layer?

here a picture a CPW just for reference


texts:
I'm building a circuit that has a number of servos on it. To eliminate servo chatter, I've seen recommendations to put in a 250uF cap (for the size servos I'm using). That much I can follow.

The question is - if I have multiple such servos, then placing multiple such capacitors seems... redundant, as the GND and VCC lines leading into them are the same line. Should I still place a capacitor per servo, as close as possible to the servo power pin? Should I just have a single larger capacitor elsewhere?

Additionally, my board needs to intermittently shut off its own power supply for a second or two, and then have enough power left to turn the supply back on (the supply has an EN pin that I can control it with to minimize the quiescent current). My idea was to use a .2F - 1F supercap to keep enough power in the circuit to last it through this shutdown, but how does that factor in the capacitor count and placement question from above?


texts: Maximal resistance in series with input of 74LS14 Schmitt-Trigger-Inverter

texts:
I was experimenting with a 74LS14 Hex-Schmitt-Trigger-Inverter (datasheet). I notice that with the input pins are not connected, the output pins are low.
Furthermore when I had a 10k resistor in series with an input, it wouldn't react to any voltage changes at all. To be more precise: when I connected an input to GND via the 10k resistor, the corresponding output stayed low. Then I thought maybe it has some internal pullup resistor, but when I measured the input it was actually at 0V.
Then I replaced this resistor with a potentiometer (as a variable resistor between input and GND) and noticed that the output would go high if the potentiometer was below about 3.5k and it would go low if the pot was about 13k. But during the whole time I measured 0V at the input of the device.
Why is this happening? I thought as long as the input is at 0V the output should go high. And I couldn't find anything about that in the datasheet.


texts: How to make an electronic switch for a current-mode digital to analog converter?

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In a current-mode DAC there is a switch in the current path between virtual ground and actual ground based on width.

How can I design the switch used?


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I'm busy helping a friend with a project involving a cheap mp3 playback circuit based on the WT2003.

The original design is based on an LDR which shorts an amplifier circuit and initiates playback, we are modifying it so that the playback is linked to a switch. The issue that I'm running into is the circuit itself is designed to continually loop the audio track while the circuit is open.
Can anyone think of a convenient way to ensure the audio clip only plays once?
Tl;dr: I'm in need of a circuit which transitions from closed to open circuit in a controllable way


texts: Sending command via phone or mobile phone

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Does anyone knows, how to send a command to microcontroller via handphone? For example turn on the relay, I press numeric one in my mobile phone. You don't have to be exactly right, any references will be appreciated.

How can I make the circuit (DTMF decoder) auto-pick up and receive command?

Please, take a look at following link, it might be helpful here.


texts: 555 Timer won't run at calculated frequency

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I have a 555 timer connected to an LED that I am trying to strobe for 450ms on, 72ms off to replicate an existing strobe light I have. The issue I am having is it is strobing at around 243ms on, 42ms off. According to my calculations, in order to get that timing I would need Ra=37.2k, rb=6.2k, with C=9.3uF. My actual values are Ra=56K, Rb=10K and C=9.3uF, however. According to the formulas found online for Th and Tl, with those values, I should be getting 460ms on and 69ms off, which is close enough for me. I am reading the pulse durations with a light sensor connected to an arduino running on a separate power supply. I've tried replacing the 555 timer with a different one (I bought 5) and it doesn't change anything so I'm really not sure what is happening to make it run the way it is. Is there something wrong with my circuit or am I missing something here?
Edit: the capacitor is a 106 ceramic, which should be 10uF but I measure it at 9.3uF


texts: Producing clean power with multiple switch mode power supplies

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Thanks, I am new to using this site, I apologize for my vague post earlier. Here is a schematic I been working on.

The project requirements are 5VDC, and 20VDC. The 5VDC is to power the microcontroller and 74HC14 IC and MCP3425. The 20VDC powers a 4-20mA loop transmitter.
I'm not sure if it is essential to have an isolated power supply system or not. The supply is  a 12VDC battery from a forklift, which is higher than 12VDC when the alternator kicks on i'm assuming. I chose to isolate it with a Recom RS6-1212S. After that converter I used another Recom (non-isolated) converter to step the 12VDC nom down to 5VDC. To get my  20VDC I used an MC34063 since I couldn't find a reasonable supply elsewhere. I tied the low outputs of the 5VDC and 20VDC together to form a ground on the circuit board, but it is still isolated from the forklift chassis ground/battery (-).

The coupled inductor, c5, and C6 were recommended in the Recom datasheet to reduce common mode noise. D1 was used to protect against reverse polarity when connecting the circuit to power. My problem is getting clean power, and the RS6 power supply is buzzing when I power the device up with my benchtop power supply. The buzzing is audible, and when I connect a dummy load (10k resitor) to the 20VDC output the buzzing lessens and the frequency seems to increase. I don't know what I'm missing.

couple thoughts come to mind:
  1) The 500uH inductor might be too close on the board layout
  2) Is the 20VDC SMPS backfeeding to the other two SMPS's
  3) The SMPS need regulator circuits / filtering

I'm looking for help to try and fix this circuit, make it better, and any helpful considerations that can help me with this project. Also, I don't have access to software for multiple layers for board layout so I did the best I could with the software and limited knowledge of PCB layout that I have.


texts: Virtual ground supply for audio-applications

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The most common solution to provide positive and negative voltage to supply an OP-amp would be to use a voltage divider and another OP-amp. In this way the voltage "on the top" of the voltage divider would be the positive voltage, ground would be negative voltage and the voltage in between would be our virtual ground.
When working with audio-applications it is very important that these circuits do not create noise, so my question is: How do you design these to make sure they don't create noise? What OP-amp should you use?


texts: How subtle or dramatic are the effects of a impedance mismatch by a certain percentage?

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If a trace is designed to be 50 ohms, how much of an effect would 10% or 20% mismatch between line impedance and termination values ?

For instance, a 50 ohm line with 45 ohm or 55 ohm series termination ?
or 50 ohm line with 40 ohm or 60 ohm series termination ?

How much wiggle typically available before you run into potential problems ?


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I'm reading some conflicting literature that suggests R2R has higher "resolution" than Delta Sigma and some literature that says just the opposite. This is both confusing and frustrating.

Can someone offer a more lay explanation of this? These are reputable manufactures and I doubt they're posting erroneous data sheets/tech notes.

Furthermore,I'm mostly interested DACs in the context of audio, which is why I started looking into this,  so perhaps there are different performance metrics that would/would not be relevant in the 20-20K spectrum and change how one might evaluate one vs another.

Finally, i'm not wrapping my head around R2R and string differences.

Analog Devices DAC
TI DAC literature


texts: Multimeter ammeter resistance increasing

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Recently I have been doing some measurements with a multimeter on some new transformers for my company. Lately I have noticed the resistance of the multimeter in current mode (ammeter) has increased. Other multimeters measured less than 1 Ohm across the mA measurement points in mA Mode while the multimeters I am using are now showing 2,4 and 14 Ohm. The A Mode points still have low resistances. I have searched everywhere and not found a thing. I have been measuring mains for some of the tests.

Does anyone have an idea why this would be happening? I have checked fuses and they are fine.

Thanks,
et.


texts: Possible to copy a circuit from 1 Logisim .circ file into another Logisim .circ file?

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I'm using Logisim to experiment with Electrical Circuit design, and I was wondering if it is possible to copy a circuit created in 1 Logisim .circ file and place it into a different Logisim .circ file or instance? I'd really like to reuse some components I've previously put together into a new file for a larger design, but can't seem to find a way to get the circuit from one file/instance to another.

It is possible to copy a circuit within a file and paste into another circuit in that same file, but I can't find anywhere online or in Logisim documentation about getting a circuit from 1 file into another.

Anyone know if this is possible? I'd really prefer not to repeat all the work over if I don't have to...