texts: Peripheral Driver Libraries on TI TM4C123 / Keil uVision

texts:
I am trying to use the peripheral driver library for the TIVA TM4C123 development board instead of accessing the registers directly. I have tried to copy the programming example in the GPIO section (page 280 of this attached link, See Link to TIVA library PDF) but I have an error message.
I have downloaded the driver libraries and they are saved in the same location as my code files. I have included them all in my C file and I can see they are included in my source file targets.

In the attached code below, every time I pass GPIO_PORTA_BASE into one of the GPIO library functions, it says "error: use of undeclared identifier".

I don't see GPIO_PORTA_BASE inside the GPIO header file (or any others that I checked), which maybe explains why but I am unsure of how to fix this.
Any ideas?

EDIT, ADDED MCU DATSHEET: This is the datasheet for my MCU

#include "include/tm4c123gh6pm.h"
#include <stdbool.h>
#include <stdio.h>
#include <stdint.h>
#include "include/driverlib/cpu.h"
#include "include/driverlib/gpio.h"
#include "include/driverlib/interrupt.h"
#include "include/driverlib/pin_map.h"
#include "include/driverlib/sysctl.h"
#include "include/driverlib/sysexc.h"
#include "include/driverlib/systick.h"

int32_t i32Val;

 int main()
    {

//Enable the GPIOA peripheral

SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);

//Wait for the GPIOA module to be ready.

while(!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOA))
{
}

// Register the port-level interrupt handler. This handler is the first
// level interrupt handler for all the pin interrupts.

GPIOIntRegister(GPIO_PORTA_BASE, PortAIntHandler);
// Initialize the GPIO pin configuration.
// Set pins 2, 4, and 5 as input, SW controlled.

GPIOPinTypeGPIOInput(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_4 | GPIO_PIN_5);

// Set pins 0 and 3 as output, SW controlled.

GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_3);

// Make pins 2 and 4 rising edge triggered interrupts.

GPIOIntTypeSet(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_4, GPIO_RISING_EDGE);

// Make pin 5 high level triggered interrupts.

GPIOIntTypeSet(GPIO_PORTA_BASE, GPIO_PIN_5, GPIO_HIGH_LEVEL);

// Read some pins.

i32Val = GPIOPinRead(GPIO_PORTA_BASE, (GPIO_PIN_0 | GPIO_PIN_2 | GPIO_PIN_3 | GPIO_PIN_4 | GPIO_PIN_5));

// Write some pins. Even though pins 2, 4, and 5 are specified, those pins
//are unaffected by this write because they are configured as inputs.
//At the end of this write, pin 0 is low, and pin 3 is high.

GPIOPinWrite(GPIO_PORTA_BASE, (GPIO_PIN_0 | GPIO_PIN_2 | GPIO_PIN_3 | GPIO_PIN_4 | GPIO_PIN_5), (GPIO_PIN_3 | GPIO_PIN_4 | GPIO_PIN_5 | GPIO_PIN_6 | GPIO_PIN_7));

// // Enable the pin interrupts.

GPIOIntEnable(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_4 | GPIO_PIN_5);

 }


texts: How and when does a regulator draw energy?

texts:
I’m working on a wearable battery project and I think I need to use a regulator on the battery output.
Let’s say I were to connect the battery to an LM317 (detailed here) or an LM7812 (see figure 1) circuit with nothing else connected to the output. Would there be current flow through the circuit? Would the battery discharge more quickly than it would in storage?

Figure 1: LM7812 Circuit
Furthermore, does the current draw (in amperes to clarify) from a voltage regulator depend on the requirements of the components connected? If I connected two LEDs in parallel to the output of a voltage regulator, would the current be greater than if only 1 LED was connected?
Does the power draw (in watts to clarify) from a voltage regulator differ from the current, or does the current change in direct proportion to the power?


texts: I recently used accelerometer ADXL335 in my academical project, this sensor gives analog output. I interfaced this sensor with microcontroller PIC18F458 using ADC module. It was successfully interfaced and shown correct readings. But later I noticed in datasheet of controller that "The maximum recommended impedance for analog sources is 2.5 kΩ" and datasheet of ADXL335 shows that its output impedance is 32kΩ. I have not used any signal conditioning circuit between sensor and controller. I am wondering how I am getting correct output even if source impedance requirement for ADC module of controller is not satisfied.


texts:
ESD protection are really expensive for hobbyist like me.

I have a grounded wrist strap but do you think a simple non-treated wood workbench surface can replace a really expensive ESD tabletop ?


texts: Which type of 100nF capacitor is best for 78xx regulator output?

texts:
I use 78L12 or similar voltage regulators in a few power supplies. I use them in their basic setup, see the picture:

This diagram is common for all 78xx and 78Lxx regulators. It says that output capacitor should be 100nF. I am able to obtain these 100nF capacitors either ceramic, or tantalum, or film for almost the same price (near to nothing) so I'd like to know which type of capacitor is the best for this particular case.

Note: I know that a tantalum cap is recommended for SMPS output, but 78xx isn't switched-mode.


texts: How to measure energy of 120/250V DC, 100 ampere system

texts:
I am looking to build energy meter with 100 A and up to 250 V DC voltage. I have few queries/questions :

How to select proper shunt for this rating?
What all types of shunt available any suggestions? so that it would be easy in selection.
Is DC CT is available/ can use for this parameters?

I want to make complete DC energy meter with above specification


texts: How well should you know electromagnetism before studying Antenna Theory

texts:
There are 3 main books in electromagnetism from "easy" to "hard": Griffiths, Purcell and then Jackson's. I will start the study of Antennas in the next week. However, I'm a bit worried because even though I got a decent understand of Maxwell's equations, I didnt get to study electromagnetic waves. How in depth should I go to be prepared for Antenna Theory by Balanis?

EDIT: Found a good alternative. Sadiku's Elements of Electromagnetics. I've had a good time with Sadiku's book on circuit analysis so I'm a bit biased. However, his treatment of EM waves seems to be geared towards engineering, contrary to the other books mentioned.


texts:
I am making a PCB with Eagle and I need to place some leds SMD size 1206. Looking components, I see two different types of LEDs in this size: SML and SMT. Eagle components are LEDSML1206 and LEDSMT1206. Could anyone tell me the difference between them exactly?

Also happens something similar with resistors. In this case are R-EU_R1206 and R-EU_M1206.


texts:
I need a step up converter for a 5.1A, 120V vibration motor I have in the US that I need to use in Ireland. The motor runs at a fixed frequency of 30Hz in the US. If I step up to 230V for Ireland will the frequency change?

Here's the unit for those interested: Technical details of the motor

I didn't think I would get a response from the company but I did and they replied that it would not work in Ireland. The frequency change causes overheating issues.


texts: Pulse transformer in LTspice giving DC offset

texts:
I wanted to simulate a pulse transformer in LTspice.
It steps up the input 12 -12 pulses to 120V -145 pulses means it has some dc offset. How to correct it?


texts: How do series connected lamp dimmers/electronic switches work?

texts:
How does a series connected electronic LED lamp switch operate when it has switched the lamp off and there is no voltage reference. And how does it work when the lamp is switched on and the voltage drop on the switch is different with different power lamps?

For example: VL-C701


texts: UART single-wire half-duplex level conversion

texts:
I have a single-line transmission device, I use the oscilloscope to check the waveform
Always keep high potential (12V) and low potential (0V), change to logic analyzer test and find that it can be decoded by UART, baud rate 115200
A little search to know that this is a single-line half-duplex working method
I want to use the computer's COM port to interact with it now, but my UARTtoUSB device only supports 5V or 3.3V level, what level conversion chip or circuit can convert 12V level to 3.3V? Single line half-duplex Does the worker's working method only need to short the TX and RX and then connect the signal?


texts:
I wish to transfer a large array of data to 8 output pins that are all on the same port. E.g. a 500 element 8bit array where each bit of each element represents the pin status.
So 500 independent transfers to the port would be required.

I have been looking through the examples that ST have but none of them seem to do this.
There seems to be a lot of 'DMA to PWM' examples which transfer to a pin that has a timer connected to it but this isn't useful to me since I want to transfer to a whole port.
How would I do this? Are there any examples similar to this which I could modify to my need?

Thanks


texts: Confusion with interpreting leading and lagging concepts for given electrical quantities

texts:
I have a confusion interpreting the lagging leading concept when it comes to time plots.

I think in phasors I can see which one is leading or lagging. For example in the below phasor diagram:

How I interpret the above diagram is that A is leading B; and B is leading C. And I think it is because we imagine the phasors are rotating counter clockwise and the reference point is the green line (positive x axis) the first phasor we encounter is A then B and then C.

But what should be the practical way of thinking if we are only given time plots as shown?:

Above in the first plot there are three voltages with 120 degree phase shifts. And in the second plane voltage and current plots are given for a single line.

For these plot what is leading what? What should be the way of thinking here? Do we have to see the plots from the time zero or?


texts: Can a 2-prong AC/DC converter switch polarity based on inverting the plug?

texts:
I got an electrical engineering degree 15 years ago that I barely use.  Although I bought a fairly fancy multimeter, I will freely admit to having only a vague recollection of what I did back then... which was mostly discrete math and signal processing  (as opposed to circuits).

A friend of mine who has a lot more real-world "electrician" experience was trying to figure out what was wrong with some cameras he owned.  They were powered by cheap wall-warts and failing.  We were trying to check these power supplies to make sure they were working, as we didn't know if the problem was with the power or the camera.  Sure enough, some of the supplies were dead.

We tried to substitute in some switchable supplies to get them working.  In the process, I noted with the multimeter that the polarity was different on the switchable supply from the adapters we were trying to replace.  As we were plugging in these 2-prong plugs haphazardly into 3-prong outlets, I wondered out loud if we might have the plugs in upside-down.

He looked at me condescendingly and said "Oh, I see.  You have a degree in this, do you?"

Well firstly, it's been 15 years, and secondly...while he may know a lot about being an electrician I know about the diode bridge inside the stupid wall wart.  And yes, diodes can tell the difference between electron source and electron sink.  But if the power is an AC sine wave then it spends as much time in an up cycle as down cycle and so the decision about polarity is in the circuit post-rectification, etc.

(So it was; to change the polarity on the adapter you just changed the terminals on the plug once it had been converted to DC, not before.  Fine.)

But the hypothetical question kept nagging me.  Given that one of the terminals is ostensibly true ground, would it be possible to build an AC/DC converter whose DC polarity would flip based on which way you plugged it in (and I'm talking about no connection to 3rd prong)?  Do such things exist?


texts: Better way to selectively enable memory chips

texts:
I'm designing a computer using a Z80 CPU. I have one EEPROM chip and two RAM chips, so far. I have to do things like this:

To ensure that this specific RAM chip is only enabled when the 13th and 15th bits of the address are high, and the 14th is off.

This, however, seems very messy. Is there a standard way of doing this, which involves minimal (or no) logic gates?

EDIT: Here's the schematic I came up with, if anyone's trying to work this out in the future:


texts:
I bought two SN7489 because I wanted to learn how the memory chip works. I followed the datasheet. I don't seem to be able to get it to work.

After playing around for some time with the IC, it got really hot and I am afraid that I ruined the chip. So, I would like some help understanding how to properly hook up the IC before I ruin the second IC that I have.

I use V_cc at +5V.

I have, for now, fixed the address pins 1, 13, 14, 15 directly to ground to fix an address.

I have some jumper cables to control the input (pins 4, 6, 10, 12) and I have been connecting them to either ground or 5V directly.

I realized after some time that the outputs are "open collector", but I am not 100% sure what this means. From what I can Google, I am guessing that I would attach, for example, a 470 Ohm resistor and LED to +5V to the output pins. That way when the output pin goes HIGH (or LOW?) there should be a circuit from ground through the led and the resistor to +5V. Have I understood this correctly?

Pins 2 and 3 (the write and memory enable) I have (with jumper wires) attached to ground and/or +5V. I assume that the memory enable should just stay low at all times, but I did try moving it around.

My question is: What am I doing wrong? Do I need some resistors somewhere in all of this?

I would like to see a schematics for how connect the IC with resistors and other things needed.

I don't know a bunch and I am just trying to learn.


texts: Can i double max current drawn, putting batteries in parallel?

texts:
Im dimensioning a quadcopter,and from my math, everything will draw a maximum load of 58-63 A.
I need to choose Lipo batteries that can handle that current draw.
From what I know: Max current: Capacity*C-Rating.
For example, i cant use a 2200mAh 25C battery, because max current drawn will be 55A, but if I put 2 of those in parallel, I will maintain the 11.1V of 3S and will double the capacity. From that, my max current will be 4400*25=110A and I will be safe.
Is my thinking right? Can I do this?


texts: What is the purpose of input protection on USB (or at all)?

texts:
I have seen quite a bit where reverse biased diodes are used to clamp input voltages when spikes occur.

What is the typical reverse breakdown voltage for a diode used in this type of application?

It appears that these protection diodes are in place not to protect against a large applied voltage by the user, but rather are in place to snub voltage spikes that may arise from static discharges.

Why might a static discharge occur, where would this excess charge come from in-circuit (on a PCB, not bread-boarding where a person may introduce discharge), and what is the typical voltage magnitude?
Why would one not also consider the possibility of a potentially large negative voltage and also place reverse diodes from the input line to Vcc?

I am designing a simple breakout board for a controller that will output data through a USB interface. Through my research I found that many designs incorporate these reverse biased protection diodes on Vusb, D+, and D-, however not all do.

Again, if all of this is mounted on a PCB, why might a sudden static discharge occur and where might it originate?

How frequent is this kind of event and without these diodes is it likely to damage circuitry?
Is it best practice to always include these protection diodes or are they not necessary at times? If the latter, what special cases deem them unnecessary?
Will any diode work or should one with a specific breakdown voltage be used?

EDIT:

Looking over those App notes, one shows

While the other shows something similar but without the "top" node connected to anything. Is this a misprint or is it implied to be connected to Vbus?


texts: How is FM modulation is achieved using a single BJT

texts:
I want to understand how this circuit achieve frequency modulation. The BJT is a 2N3904. I found that millers effect comes into play and varies the frequency of the tank circuit about a center frequency of the tank circuit.
I want to understand this in details and how to design circuits like this. How to calculate the parameters and their roles.


texts: Crystal oscillator using 7404 is unstable

texts:
I am currently building a small Z80 microprocessor system and require some kind of clock generation. It is not my first design: Earlier I used an Arduino pin that generated a slow clock or a 555 timer. However, earlier designs only included the Z80 and some RAM and ROM.

Now I want to expand upon that and include peripherals. That's why I chose a 3686.4 kHz Quarz, so that I can divide it later via a frequency divider to not only generate my processor clock but also my UART clock.

I did some research on the internet, read some books and schematics and found out that most use a pierce oscillator or a series resonant oscillator. For my design I want to use plain 74xx or 74LSxx chips, because I have them around and ready to use. Fortunately, most books for the Z80 and websites also built them using 74xx chips. So I tried to rebuilt them. My pierce design did not work at all, so I quickly changed my setup to a series resonant oscillator.

For my oscillator I use a single 7404 inverter that has a 100 nF decoupling capacitor attached between 5V and GND. Then I simply copy-pasted the circuit from "Build Your Own Z80 Computer" page 94. I added the capacitor after seeing it on many schematics and without it, it didn't start oscillating anyways. I attached my schematic below (it does not show the decoupling capacitor between 5V and GND)

Now when I apply some voltage to this circuit it indeed starts to oscillate. However, the frequency is not stable at all, seems to be 200 kHz below the stated one and the duty cycle is not at all 50%. You can see my logic analyzer output below.

Whereas the logical high state seems to be quite stable with one unstable cycle seeable at the right end of the graph, the off state varies quite a bit.

Frankly speaking, I do not know how to fix this as I have not much experience with oscillators. However, I have a feeling that the capacitor does have quite an influence. When I changed it from 100 pf to 22 pf the frequency was completely unstable. When I changed it to a higher value, I didn't see much difference at all. I also tried to exchange the 7404 with an 74LS04 as some schematics use it, but that didn't change anything.

If somebody can point out my mistake to me I would be very glad.

Additional Info: The data sheet of the crystal calls states CL=20pf and Rr < 120 Ohm.


texts: Precision voltage reference for load cell and ADC

texts: I want to know what could I use to have a stable 5V excitation voltage for my load cell(wheatstone bridge) which I could also use to have a stable 5V reference voltage for my arduino adc. Would a LM7805(positive voltage regulator) could be applicable for this or I need to use a precision programmable reference like a TL431?


texts: Capacitive discharge excess being used for battery recharging

texts:
I am currently designing a circuit similar to a cattle prod that is intended to be attached to a drone. The cattle prod is powered by a lithium-ion battery, charging up a capacitor and then quickly discharging through a material. It will be delivering approximately 1 J of energy with a 10 kV voltage, at about 7 kHz. I am trying to make the system more efficient.

I know next to nothing about power electronics or batteries (I am studying computer science), and was wondering if it is possible to use any residual current from the discharge to cycle back through and recharge the battery without any mechanical components? If not, can you please explain why? I am currently looking at the MAX8900 IC, and if it is possible I would like to know what I would have to do to process the current so it could be the input to such an IC.


texts: I am trying to test IGBT switching using the following circuit but the IGBT smoked out. I am using MSP430 with g2553 chip, NMK0505SAC dc-dc converter, FOD3184 optocoupler and IRG4BC20UD. Please help me if you find anything wrong with my circuit connection.


texts: How to connect a headphone jack to this lm386

texts:
I would like to attach a headphone jack to this board but I'm a bit confused as to how since the jacks I find have 5 pins but this only has 2 places for the headphone cables.

Thank you in advance for your help!


texts:
I'm trying to understand the ADC pins on an ESP32-WROVER, I can't seem to figure out the values I am reading. I've been trying to read the voltage of a battery but haven't been able to get any good results, I've tried using ADC1 channels, ADC2 channels, via Arduino analogRead and esp-idf toolchain adc1_get_raw, adc2_get_raw but all give me readings I can't seem to interpret.

I ended up taking the esp32 out of the circuit I am trying to build just to test with so I put in the bare minimum, e.g. GND(1), VCC(2), EN(3), GND(15), IO0(25) and the ADC2_7(12). I then applied voltage to the ADC pin in increments of 100mV.

The mappings I got were:

ADC_ATTEN_DB_0: 0-1.09V = 0-4095

ADC_ATTEN_DB_11: 0-3.09V = 0-4095

From my understanding (and it is very limited), I would have expected that +3.3V would equal around 4095 with ADC_ATTEN_DB_0 (a 1:1 mapping). What am I missing? How come the readings aren't what I'm expecting?

The code I use to read the ADC2 channel is:

// .. called once during init
adc2_config_channel_atten(ADC2_CHANNEL_7, ADC_ATTEN_DB_0);

// .. called in a while loop with a 2ms delay
// ADC_SAMPLE_COUNT = 64
uint32_t result = 0;

for (int i = 0; i < ADC_SAMPLE_COUNT; ++i)
{
    int v = 0;
    adc2_get_raw(ch.first, ADC_WIDTH_BIT_12, &v);
    result += v;
}

result /= ADC_SAMPLE_COUNT;

Also, just to note, during my poking around, when I apply voltage to one of the ADC pins it would affect the reading of another pin that was not connected to anything (I don't remember which ones now) but is this normal?

Update 00

In the esp32 datasheet I found the following:

Atten=0, effective measurement range of 100–950 mV –23 23 mV
Atten=1, effective measurement range of 100–1250 mV –30 30 mV
Atten=2, effective measurement range of 150–1750 mV –40 40 mV
Atten=3, effective measurement range of 150–2450 mV –60 60 mV

Atten=0 = Db0 and Atten=3 = Db11 these are pretty close to the readings I was getting.

Also, after more searching I found someone that did some tests and came to the conclusion that using 11 bits for the capture width and Db6 for attenuation along with a capacitor give a much nicer linear set of readings.

By simply probing at the low range and high range I was able to map the adc reading to the voltage reading. Once I got the mapping correct, I then changed the attenuation back to Db11 and re-probed, updated the mapping and it was quite obvious that the readings were no longer linear.

I couldn't create an ADC characteristics to produce an accurate voltage, so I went back to Db6 and the manual mapping, it works, which is fine; I suppose.

Update 01

After much reading and poking around, the esp32 ADC is a all over the place, not sure if this is normal as this is all still new to me and first time using ADC.

The range of ADC input will depend on what the attenuation is configured as; the datasheet lists the values.
Instead of configuring a characteristics to convert from a raw value to voltage, I ended up probing to find the low end and high end of reading and then mapped the raw adc value, which worked fine. e.g. \$\frac{(adc-adc_{min})(v_{max}-v_{min})}{(adc_{max}
-adc_{min})} + v_{min}\$
The higher the attenuation and higher the bits the less linear the values are, e.g. at 12-bits, 11Db the values are non-linear and thus the linear mapping would not work, I suppose this is what the characteristics is for, instead, using < 12 bits and < 11db made the readings mostly linear, (e.g. 11-bit, 6Db)


texts: So as I have understood the logical effort for a 2 input nand gate with only one of the inputs active = 4/3. Furthermore the net logical effort is 8/3 (considering both the inputs). Now given that the logical effort of a logic gate tells how much worse it is at producing output current than is an inverter, I am confused here. With two inputs active in the NAND gate shouldn't the logical effort be low. Also, when we use logical effort to estimate the minimum delay for a multi-stage system why do we use 4/3 as the logical effort for a nand stage (which is just the effort of one input) ?


texts: Opamp output voltage in negative feedback

texts:
Assume we have an opamp in negative feedback just like this:
This is for an ideal opamp which its VCC pin is connected to some positive voltage(15V) and its VEE pin is connected to some negative voltage(-15V).
The equation of Vout=-Vin*Rf/Rin
When working with microcontroller the lowest voltage is GND.
If we connect the VEE pin of the opamp to GND the equation of Vout can't be the same because the lowest possible voltage is GND. Which is the equation for the new 'state' of the opamp?


texts: XBee Power Consumption, RX Current and TX Peak Current

texts:
I'm trying to find out the max power consumption for an XBee Series 2 2mW module so as to pick out a suitable power supply for the system. The docs state that it has a TX Peak Current of 40 mA and RX Current of 40 mA (@3.3 V).

Does this mean that the max power that can be consumed by the XBee is (40 mA + 40 mA) * 3.3 V = 264 mW?


texts: Difference between infrared heating tube coatings?

texts:
I'm converting a toaster oven to a SMD reflow oven and have found the thermal momentum of the resistive elements to be a problem (standard dark-grey type).

So I've been searching online for some cheap IR replacements that I can retrofit. I founds heaps of options including coatings.

What is the difference between clear, ruby, and gold plated tubes? I understand that clear (actually a milky-white) are commonly found in ovens, I read that ruby are 'low glare', and also hear these three types referred to as 'long wave', 'medium wave', and 'short wave'.

Does the coating change the heating/output in anyway? Is it just cosmetic?


texts: If a diode has capacitance, why doesn't it block the circuit after some time?

texts: It is well known that diodes have a depletion region, which in itself has some form of capacitance due to the presence charges on its opposite sides. In RC circuits, the capacitor always acts as an open circuits after some time (when it is almost fully charged). Why doesn't the same phenomenon apply in forward-biased PN junction diodes?


texts: Dimming 6x large LED 8 segment blue displays

texts:
(source: perceptiveart.com)
I am making a clock, using 6 rather large 7 segment blue displays.  I am wondering 2 things.

Do I need a bypass capacitor on the 12V supply for each UDN2981 chip?

How can I control the dimming of the whole thing at once?  I identified 3 options as potential solutions:
A - a transistor at point A (on the schematic), controlled by the Arduino by PWM (which would in turn be controlled by a potentiometer via the Arduino)
B - a potentiometer at point B (12V supply)
C - some sort of voltage regulator at point B.

Any corrections or suggestions to my schematic are welcome.

Any help would be greatly appreciated. Thanks in advance.


texts: How can I calculate the RMS and Medium Voltage in a Controlled Three-phase Full-Wave Rectifier?

texts:
I want to calculate Vrms and Vmedium for the angles of 30º, 90º and 150º on the circuit above with and current source and a resistor load.
I found a variety of formulas on the internet, but them all give different answers.
What are the ultimate formulas for calculating this values? Or how can I find them?


texts: bit bang programming with a 1/222.2ns clock

texts:
I need to bit bang at a 1/222.2ns clock rate.

I am looking a recommendation for the bit banging clock source and "easy" to program means of bit banging at this clock rate.


texts: Different voltage characteristics of CMOS NAND gate for different connections

texts:
Recently, I've played with a simple 2-input 1-output NAND gate realised in CMOS technology as shown in Fig. 1.

Fig. 1. CMOS NAND scheme.

I took some measurements of volteges U(output) vs. U(input). Using two independent voltage sources (constant high level Udd and Uin varying in 0-to-Udd range), I considered three different connection possibilities so to investigate all four input configurations. Those were:

a)  Input terminal A connected to Udd, input terminal B connected to Uin.

b)  Input terminal A connected to Uin, input terminal B connected to Udd.

c)  Both input terminals connected to Uin.

I've obtained following characteristics:

Fig. 2. CMOS NAND voltage characteristics with different connection methods.

As long as a difference between case c) and other cases I could have expected, I was surprised to see a) and b) differ as well. Could someone please explain to me why would changing voltages connection between A and B significantly changes threshold voltage of the gate? Is it a widely observed effect or have I just picked a defective NAND?


texts:
I have a Chinese rip-off game pad, which has an n51802 which is by nordic. I want to flash my own firmware but i’m unable to find any information about it. I can put it in DFU mode, so it is flashable, i have the original firmware from the company - but reversing it would take too much time.

It seems very similar to nrf51822 but i don’t know if they are binary compatible, have same address space etc.

What can i do to find more information about developing for it?


texts: electrolytic cap shelf-life after being mounted on circuit borad

texts:
My question is about whether there would be a problem with aluminum electrolytic capacitors that have been installed in an amplifier, then factory tested (so a current was run through them), then stored for four years.

I know that the shelf life of electrolytic capacitors is 2-3 years. But I have read some say that if they have been mounted on a circuit board and have received a charge during testing at the factory, they can then survive for much longer than their shelf life that with no problems.At the same time, others claim that the shelf life holds also for caps in circuits, when starved of electrical current.

So, the question is: does the shelf life of electrolytic capacitors also apply to capacitors in amplifiers that have in the past received an electrical charge, but have then been put into storage for a long time, at room temperature, in dry conditions? Or does having received a charge make the caps more resistant to chemical degradation in the absence of further charges.


texts: Is it necessary to use resistor when connecting backlight of 16x2 LCD display?

texts:
I wonder if it's necessary to use any resistor when you're connecting backlight of
16x2 LCD module? OR it depends on voltage?
I am using Hitachi HD47780


texts: Replacing 1N4001 for higher current diodes

texts:
We're trying to build a PCB here which originally has several 1N4001 diodes but we only have 1N4007 or 1N4008 diodes.

What would be the consequences of such replacement? Are 1N4001 diodes more "sensitive" than the other ones? What would it be the difference in its specs?


texts: FET - unipolar transistor - Voltage-Divider, question about finding Idss and Id if no Vd given

texts:
If I am not given drain voltage how do I use the formula for Vp to get ID and IDSS current?
So far in testing stuff I noticed that if the two resistors at the right side Rd=8k an Rs=7k are close in value I can get an approximate value for ID or IS since the two are almost the same by doing the following

Close to what the simulator is giving 727.96, and I also tried it with other values and as long as they are close it gives close to correct answer but not 100%.


texts:
I'm new to electronics but I want to make this diagram from "Instructables" :

I have everything I need from a camera... I also realized, using a different transformer, that the sparks are made only when the battery is deconnected and reconected repeatedly, like in this video. So ,I was wandering if that transistor is acting something like an oscillator (closing and reopening the circuit).

Am I right or the transistor is used for something else?
And if I'm right can you explain me how the transistors closes and reopens the connection?

Thanks in advance and sorry for my mistakes(this is not my original language...).


texts: How do I know the direction of magnetic field produced by a bar magnet, assume a electron present side to the magnet ?


texts: Amplifier IC - selecting input (Sound Card/Phone jack) and output(Headphones/RCA)

texts:
Good evening guys!

I'm trying to figure out the solution to my problem, that I have encountered, but I just can't find anything close.

So, first of all, the situation:

I'm trying to build a 5.1 amplifier.
For that, I'm planning to use 4 amplifier ICs:

3 stereo (2 actually stereo, 1 is bridged for center) - TEA2025
1 for the subwoofer - TDA2030

I want to be able to switch between input sources:

Soundcard stereo jacks(1. center/sub, 2. front left/right, 3. rear left/right)
Phone stereo jack, sending the signal for all ICs

And output devices:

Headphones(Stereo Jack)
RCA speakers (6 of them, center, front left, front right, rear left, rear right, subwoofer)

My guess is, to be able to switch input sources, the other source should somehow be denied.
As for the output, the same could be applied.

How can I switch input sources from one audio channel to the next with a circuit?


texts: How to prevent solder getting into through hole during HASL process?

texts:
I think this is an easy enough question - I just don't know how to effectively search for the answer.

I have a PCB that came back and the programming header is plugged with solder. This most likely happened during the HASL process.

I thought about tenting the holes, but that would require me to break the tent when I want to program my boards and that seems like extra work that I'd rather not do.

What can I do on the PCB or documentation (specifically the wording / language) to the fabrication house to prevent it from happening ?


texts:
In this circuit, for which value of CLK will the output Y be high-Z?

Is CLK=0 right?


texts:
I am trying to make an Auto Gain control circuit.

Having any input source's voltage the same.

For example my latop outputs around 1.36Vrms @ 1khz
and my iPhone outputs around 0.962Vrms @ 1khz

Regardless of input source I want the input voltage to be around the same as the laptops.

The idea is convert the input signal into a DC signal to essentially map it out. Compare the DC signal the Vref ~=500mV. The comparator will output from 0V to 1V, depending on that it will turn on the respective transistor. One transistor will be a voltage follower and will not doing anything if (V+ > V-) and if (V- > V+) then it will go to the respective transistor and go through an active op amp with a negative feedback containing a digital pot controlled by an ardunio. Using the negative feedback equation the arduino will calculate a value for the R2 resistor (Digital pot) and make it so the voltage will become 1.32Vrms using the equation R2/R1 + 1.

1 - I am not sure if this will work due to how an audio signal isn't a constant amplitude.

2 - For the full bridge rectifier since the voltage of the iphone out is already so small, I believe the Forward Voltage drop of the diode will ruin the idea of it.

3- Is this even possible?

simulate this circuit – Schematic created using CircuitLab


texts:
Further to a question I asked earlier, I realised that common ground confuses me. I have a USB powered Arduino and a separate Battery supply. The battery supply negative is connected to the Arduino ground. The voltage of each supply is the difference in potential between its two sides and my understanding was that you didn't need to worry what those actual potentials were, just the difference. But when you connect negatives surely the potential is important as the 2 potentials will now "average out" thus potentially (just noticed pun on proof read) changing the original voltages of both supplies.

The fact that it is okay to connect the two supplies means my understanding is flawed. Could someone please straighten me out ?

Section 7 of this document is basically what I'm doing


texts: Why is my Miller plateau not zero slope (horizontal) but drops down in voltage?

texts:
I am a novice in the field and am currently working on a DC-DC converter and was trying to enhance its performance.

After some research, I found out that the Miller plateau is usually of zero slope (so horizontal) but the measurements taken with my oscilloscope exhibit a negative slope.

Instead of stagnating and then increasing again, the voltage drops significantly and then rises again.

What effects make the Miller plateau drop down?


texts: Where can I use my ammeter to measure the current set by the current limit potentiometer?

texts:
Here is the circuit in question:

(http://i.imgur.com/Jmo6mzL.png)

The circuit is an adjustable power supply that I have put together (can be bought here) and I am working on putting it all together inside of a case now.

One thing that I wanted to do is display the current limit set by the current control potentiometer. The output voltage is easily seen when changed because whatever is set will be the output. It is different for the current, however, because the circuit will only draw what it needs despite what the ceiling is set to. Even though I know I could get by without it, I would like to visually see the current limit change as I turn the corresponding potentiometer.

I have already successfully assembled and tested the power supply. I have one ammeter set to the output and is powering a small fan I pulled out of a dead xbox 360 all through a breadboard. I will be able to test any suggestions so even if you only have an idea of where I should patch my ammeter in, please let me know and I can give it a try.

Note: The current limit potentiometer is linked to the op-amp facing left


texts:
I'm trying to understand a current measurement of a hobby project.

This project consists of several ICs and is battery operated.
At a certain mode (deep sleep) it should consume a very low current, which I estimated around 100μA or less.

To verify low current consumption I'm using the following setup for the measurement:

simulate this circuit – Schematic created using CircuitLab

Since my shunt resistor R1 is 0.5 Ohm, I would expect the current to be V / 0.5.
(Actually I'm using 3 resistors of 1.5 Ohm in parallel, which I consider as a single 0.5 Ohm resistor).

The load R2 is the digital circuit with multiple components (ESP32, BQ21040DBVR, CP2104, M3406, XC61CC3302NR-G, resistors, capacitors, etc) at a deep sleep mode.

And this is the reading I'm getting:

This measurement is consistent. When removing power it goes flat so it originates from my circuit.

Questions

Is the setup I'm using good enough for measuring sub-milliampere currents?
Why Vmin is less than 0? The scope is calibrated and when removing power it goes to 0.
Is it correct to use Vrms as the "average DC measured voltage"? It so, it means that the average current draw is 0.00056 / 0.5 = 1.12mA
Regarding those 7.28Vpp spikes every 500μsec:

I would like to find their source.
The circuit is a printed PCB with SMT parts so I prefer not to rework it, if possible. What would be a good way to debug it and find the part that creates these spikes?
Since these spikes are very short and at a (more or less) steady frequency, my guess is that they come from one of the ICs on the board, and not from analog discrete parts. But looking at their datasheets, I couldn't find any reason why any of them would consume ~14mA every 500μsec when the system is in a deep sleep mode.
Any idea?


texts: Are there command options for Digilent Adept software?

texts:
Recently we started using a Digilent Genesys2 board to emulate our SoC design. To program and control the board, we are using the Adept utility on a Windows 10 PC. This utility allows us to download the bitstream on the FPGA via JTAG, followed by connecting to the chip via an I2C interface.
The "software part" (including downloading the firmware) is done using python scripts from the command line. But it seems like we need to re-program the FPGA every time we want to download a new FW version, or just restart the program.
For automation purposes, I am looking for a way to program the FPGA bitstream from command line as well. Looking at the provided user manual, I could not find command line options for the Adept GUI.
So, is it possible to configure and program the FPGA from the PC command line using the Adept program (or any other method)?


texts: Beacon: dBm power decrease over distance

texts:
I have beacons which advertise their configured data periodically through Bluetooth. The vendor specifies 8 different power options 0 to 7: https://support.kontakt.io/hc/en-gb/articles/201621521-Transmission-power-Range-and-RSSI

With a configured power option 7 (which is equal to 4 dBm) I should receive (RSSI) a value of -59 dBm in a distance of 1 meter.

Is there a formula to allow me calculating the expected RSSI value in 3 meters distance?


texts: Constant current - what is the difference between loads

texts:
This question is more about what terms I need to be using in my search, as I haven't had much luck yet with my searches.
With a constant current power supply, where voltage is set to 12 V and current limit is set to 500mA, if I connect an LED lamp that uses about 600mA, as expected I see it reach the maximum current with a small voltage drop.
If I connect a different load, like a dummy load tester, whenever I turn the potentiometer just above the threshold value, the voltage drops to under 1 V, even though I've set the current to barely above the limit.
I am trying to find out what is behind this difference. Why does a LED or Battery behave differently with a CC source? I feel I have a missing piece here, so would appreciate some direction.


texts: Which pins are power which pins are output?

texts:
We have an accelerometer here are the specs:
http://www.myhoskin.com/newsletters/PDF/7596A.pdf

It has lemo plug but I cant find which pins are for DC power input and which are for output.

The lemo looks like this: http://www.trammicrophones.com/images/equipment/tram/4lemo_pins.jpg

Is there a way to know this without cutting the cable?


texts: Emitter Follower / Common Collector as Negative Feedback Amplifier

texts:
Background
From the wikipedia page on Common Collector Amplifiers there is paragraph describing how the circuit acts as a negative feedback amplifier

The circuit can be explained by viewing the transistor as being under
the control of negative feedback. From this viewpoint, a common
collector stage (Fig. 1) is an amplifier with full series negative
feedback. In this configuration (Fig. 2 with β = 1), the entire output
voltage VOUT is placed contrary and in series with the input voltage
VIN. Thus the two voltages are subtracted according to Kirchhoff's
voltage law (KVL) (the subtractor from the function block diagram is
implemented just by the input loop) and their extraordinary difference
Vdiff = VIN - VOUT is applied to the base-emitter junction. The
transistor continuously monitors Vdiff and adjusts its emitter voltage
almost equal (less VBEO) to the input voltage by passing the according
collector current through the emitter resistor RE. As a result, the
output voltage follows the input voltage variations from VBEO up to
V+; hence the name, emitter follower.

Question
The negative feedback amplifier can be expressed with this equation:
\$Out = (In - Out)*Aol \quad if \quad (\beta = 1)\$
How can the emitter follower be expressed in this way?
My Thoughts So Far
\$ In = V_B \quad Out = V_E \$
As mentioned in the wiki article the summation point IN - OUT is applied to Vbe:
\$ V_{BE} = V_B - V_E \$
WRT Aol
\$ V_E = R_E(I_C + I_B) \$
\$ I_C = \beta I_B \$
\$ V_E = R_E(\beta I_B + I_B) \$
\$ V_E = R_EI_B(\beta + 1) \$
At this point I have an equation relating output to base current (proportional to input voltage) multiplied by a gain but I cant see the step to get from this to the negative feedback amplifier equation
Note
This isnt a question about how the feedback mechanism works. I understand the gain of the transistor causes base current to be multiplied increasing output voltage across \$R_E\$ which in turn decreases base current. This question is only about modelling the circuit as a negative feedback amplifier


texts: Multimeter and clamp give different AC current measurement

texts:
I am trying to measure the power output of an AC permanent magnet motor to a load (a resistor). To do this, I am measuring the current through the resistor, and the voltage across the resistor. To measure the current, I am using two methods: a benchtop digital multimeter which can measure AC current, and a clamp style meter which outputs a voltage that I measure on an oscilloscope.
The current measured by these two methods is about an order of magnitude different. The multimeter gives me ~200 mA while the clamp style meter gives ~ 3 A. I looked through the manual of the multimeter but couldn't find any information on the details of how the AC current measurement works to get an idea of what the problem might be. The output from the motor is ~ 20 Hz, and the voltage is ~ 20 V.
I had the multimeter set to autorange, but also tried all of the ranges individually. I also tried varying the sample rate. The clamp has two ranges, one which gives 100 mV / A output, and another which gives 10 mV / A output (I used the 100 mV/ A setting).
Link to multimeter manual (https://www.circuitspecialists.com/content/235770/siglent-sdm3045x-manual.pdf)
Link to clamp meter manual:
https://www.picoauto.com/download/documents/manuals/ta018-operators-manual-web.pdf
Has anyone on here encountered this problem before? Would definitely appreciate any thoughts on this. Thank you.

Update: called the company that sells the clamp meter (the technical support line) and they said they are not the original manufacturer and basically just read me the spec sheet. So maybe the next step is to try and figure out who makes it and call them.
Update #2: I decided to do a "sanity check" and measure the current drawn by a 75 Watt soldering iron, and I observed ~ 10 Amps drawn during heating, which seems clearly wrong (that would mean it is consuming 1 kW of power). So there it looks like there is a factor of 10 being lost somewhere, which I don't quite understand. I've attached a picture of the clamp meter below, and a picture of the oscilloscope screen. I guess its possible that the clamp meter is just labelled wrong but that seems unlikely too.
Update #3: OK, I was unaware that there was an option internally on the oscilloscope to scale everything by a factor of 10.. this was the problem, and it seems to be in agreement now.


texts: using a magnet to trigger a traffic light

texts:
Here is the link to the Traffic Detector Handbook from the Federal Highway Administration:
http://www.fhwa.dot.gov/publications/research/operations/its/06108/02.cfm
This will explain more about vehicle detection using induction loops.

Here are a few resources:

https://en.wikipedia.org/wiki/Induction_loop#Vehicle_detection
http://www.instructables.com/id/Traffic-Light-Trigger-for-your-Bike/
http://bikeportland.org/2010/09/27/bike-science-making-sense-out-of-signal-sensors-39517
http://www.kjmagnetics.com/faq.asp#pulltest

So the question I have can be broken into parts:

Can a magnet alone (imagine the bike is all plastic) trigger the vehicle detection?
How strong a magnet do I need (dimensions, pull?)?
Are dimensions / shape sufficient by themselves?
Is the grade / pull force important at all for this application?
Significant difference between ceramic, rare-earth, ... for this application?
Let's say I can purchase a magnet, how should I position it on the bike?

There are many different stances on the topic, some calling the magnets just bogus and not working, some swearing by it. I have very little understanding of magnetic field & eddy currents and how a magnet could affect an induction loop, so verbose explanations would help.

Thank you.

update:

I am trying to figure out if sticking a ferromagnetic magnet (rare-earth / neodymium) under a moving vehicle would help at all.

it is ferromagnetic,
it is a magnet,
it moves with the vehicle,
it is lower to the ground than where an engine would be.


texts: 12V LED, Buzzer, and 4 Switched grounds enter a Bar

texts:
First posting so I will try not to step all over the rules. Notice: I am a novice.

My project is 12 volts DC and to have a buzzer activate when any of 4 LEDs are illuminated.

I have a few restrictions:

I do not have access to the buzzer ground
My signal is a switched ground coming out of a Transmission Control Unit
I can not have all LEDs illuminate when one signal has continuity to ground.

I have access to 280 SPDT Micro relays (like this) and an assortment of diodes, resistors, and capacitors.

The LEDs have a 1/4 watt 6.2K OHM resister +- 1%

The buzzer in question.

My research seems to point me to a combination of diodes (like the LEDs), maybe a bridge rectifier, and a 10 contact NAND gate?

I think what I want to do is have a diode tapped off each LED ground that all attach to one side of the bridge rectifier. The other side of the rectifier kicks over (POSN. 86) of a 1.2 watt relay that can supply more power to the buzzer.

Here is a schematic.

simulate this circuit – Schematic created using CircuitLab


texts: PWM Motor speed control using PIC; What mosfet to use

texts:
I have a 5V PIC16f877a controlling the speed of the motor 12V which has a power rating of 8W; the current will be around(600mA) am I correct?

The motor is basically a small water pump commonly used in aquariums.
After much research; I still don't know what is the best MOSFET to use.
As I saw some of the answers use logic-level MOSFETs?
I have IRFZ46N and IRFZ22 in my hand; is the two transistor suitable and enough? or is there any other IR transistor is more suitable. i think IR will be much more available in my country.
Will the 12V 1000mA power supply I have enough?


texts: Suppose we have an nmosfet that is in cut-off. What is it most commonly used for in this operating region? As a switch or as a variable resistor? I believe it makes more sense to use it as a resistor, because it has a long turn-on/off time.


texts:
I'm looking for a thermal simulation tool that can be used for first order viability studies.  For example, I'd be interested in simulating different enclosures with given internal heat load from electronics.

I don't have experience with any thermal simulation software now, so I'm trying to get an idea of what tools are being used by other EEs.


texts:
The schematic beneath is a new project of me.

The theory behind this is: My car has a very fool proof bulb failure detection and warning system. CANbus proof LED bulbs can't fool the car and just a parallel resistor will make a faulty LED bulb undetectable. So when the parallel resistor (wich imitates as a incandescent bulb) can be "switched" off when a short or open circuit LED bulb is "detected", the car will see a faulty bulb.

But... another common fault in LED bulbs is that the LEDs are burned, but without a full open or short circuit. They just take less current/voltage when this happens.
So there should be a third "detection": the voltage/current drop. How can I managa that, without heavily increasing the number of parts and most important, the costs.

At this moment, it is only for the rear brake and indicator bulbs and every bulb needs a circuit as the example below, with 2 circuits combined in 1 box and 1 box for each side.

Thanks in advance.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

Figure 2 by @Transistor. A more conventional drawing with voltage decreasing from to to bottom, chassis symbol used for the vehicle groun and ground symbols all pointing down (towards the ground).


texts: Is my design good enough in terms of noise and EMI as its 80MHz MCU board

texts:
Recently I'm trying to design a PCB board for an MCU. The problem is I haven't considered any noise aspects before. As I'm in a contest for new electronics product run by our university I have to think of all aspects. I have searched a lot about proper grounding, bypassing, and other noise stuff and got a little bit confused. Things that I learned:

Bypassing caps are better to locate as close as possible to power pins of MCU
It's very important to properly design PCB especially on digital clocked devices and frequencies above 50MHz (My MCU runs at 80 MHz)
It's preferred to use power planes instead of power tracks (I'm using a 2 sided board)
Oscillator device should be placed as close to MCU as possible and surrounded by guard traces
The best ground plane is the one which doesn't have traces inside
Supply track should pass from caps first and after to power pins of MCU

Basically it's just a breakout board or PIM board. All nets are on top side of PCB. I'm thinking of using bottom as a ground plane.

Is it a good idea to fill entire top side of PCB with copper polygon connected to + and bottom side of PCB covered with ground plane and have caps under IC connected with vias? Entire board will then act as a capacitor. I read some where that it's a good technique. By this I'll have perfect trackless ground plane on bottom side of PCB but viaed supply plane on top. And I'm not quite sure about the board acting like a cap at all. Is it a good thing to do? Why?

I have read your post, Olin. I'll try to apply local ground plane for caps.

I designed something but yet not sure if its a good one.

By this I connected all VDD pins together. ( This is important for my project). But notice that power pins of MCU are connected to supply bu that track and also directly from header pins. Is it a problem? Does it couse noise and why?:)

Then I filled bottom layer with polygon connected to ground...


texts: Arduino(Nano) Low hertz communication (sound)

texts:
I'm thinking about having two arduino's(nano) communicating with eachother, but I'm not 100% sure how. So I was thinking about the ways that are possible:

Radio
Visible Light
Sound
Wi-Fi
3G

And I believe that the best solution would be sound, low hertz like below the spectrum which animals / humans can hear.

Why do I believe that sound would be easiest?
Because it can bounce on walls and mostly anything to get to a reciever and because it's the easiest way and most likely cheapest way to do it.

The question is: where do I find / how do I make such a device that can send and read low hertz? I don't know what range I'm talking about, but atleast something that won't disturb animals or humans hehe.

I will listen to absolutely anything you've got to say because I've got nothing. So if you got a link / information about anything of what I'm asking for then I'm forever a follower and you shall be my jesus;)

Thanks!
Regards,
Harry


texts:
I am working on the question in the image attached, and I am having trouble with part b)

I found part a by using the formula of resonant frequency for a first order LC filter: w=1/sqrt(LC), and by rearranging for L, and plugging in w=108 x 10^6 x 2pi, and C=25 x 10^-12.

For part b, I have rearrange the same equation for C, and have used the inductance found in a), and plugged in w=88 x 10^6 x 2pi, however this is wrong.

Any ideas is greatly appreciated. Thank you very much.


texts: How to overdrive a 5W IR LED for laser tag

texts:
I am a bit of a noob regarding electronics, but hey, I guess I need to start somewhere.
Here is the premise:
I want to build the Arduino Laser Tag Link: and all went fine until I stumbled upon overdriving the IR - LED to increase the range of the signal transmission.
I got myself a couple of 5W (730nm 2-2,2V, 850nm 1,6-1,8V, 940nm 1,4-1,6V) 1200mA 45mil LEDs by Hotred. As all parts on Aliexpress they come cheap but without data sheets. Since I want to overdrive them I figured a save way would be to double the amperage to 2400mA at max value +0,4V since a comparable LED with data sheet stated it would be within limits if the pulse cycle would be max 1/10 duty cycle , 0,1ms Pulse width.
Now my question is how can I secure the required amperage, powering the module with a 1s Lipo (3,7 V), since the device needs to be portable.
I have looked into DC-DC switchmode current LED driver boards and the LM317. Would the switchmode driver induce noise into the signal transmission (probably sent at 38kHz)?
The LM317 doesn’t support enough amperage but would a similar regulator work regarding wattage, since those a very short burst of IR signals?
I hope you can lead me in the right direction. Google tried to help but here I am - not a bit closer to an answer...


texts: Why does this RAM component have unpredictable behavior in Multisim?

texts: Multisim has a 2k8 RAM component that I was playing around with. Here is how it works. Here is what happens when I simulate this. Let's say I save the value 00000011 to address 00000000. Then, I make all inputs low. Then, I make CS high in order to read the data. My indicators turn on as expected. When I turn CS off, however, they sometimes stay on even if all the inputs are low. Is this what is supposed to happen? Can someone please explain in more detail how to read and write data? I could not find the resource anywhere. Here is a picture of the simulation.


texts: How to protect trade secrets on board with SMD components?

texts:
I have a design which uses a secret technique, and I would like it to remain secret, at least for a period of time.  My plan was to pot the board in epoxy.  Specifically, MG Chemicals 832TC is advertised as providing "superior protection from ..., and analysis".

But then I read on PottingSolutions.com that epoxys can shear off SMD parts due to thermal expansion or contraction, especially below the glass transition temperature.  It seems that the very properties that make epoxy hard to remove are those which are incompatible with fragile SMD parts.

What is the recommended way to protect trade secrets on boards with SMD parts?  I was considering applying a thin coat of silicone and then filling the rest with epoxy.  If it matters, this will be inside of an aluminum box.


texts:
I was learning about the advantages and challenges in scaling down MOS transistors. I came across this statement in Wikipedia :
The main device dimensions are the transistor length, width, and the oxide thickness, each (used to) scale with a factor of 0.7 per node. This way, the transistor channel resistance does not change with scaling, while gate capacitance is cut by a factor of 0.7. Hence, the RC delay of the transistor scales with a factor of 0.7.
Reduction in RC delay means improvement in switching speed.
But as per my understanding, capacitance per unit area is given by the relation C = eps/Tox, where eps is the epsilon and Tox is the oxide thickness. So when Tox is reduced, C increases, which in turn should increase the delay. But what wikipedia says is opposite.
So my question is, how scaling down the transistor reduces the capacitance?
Any good reference or link also will be appreciated.


texts: Design some resistor with operational amplifier

texts:
I will wish that using a variable voltage source (via a potentiometer) whatever happens to my input voltage (it can vary depending on certain conditions between 4V DC and 6V DC) I have 5V output. In addition, I want to have a gain of 2.
So here is the diagram I had thought of, and I would like to know if it is possible to do what I want, and how, because via my calculations I found a reference voltage on the terminal "+" too high compared to to my 5V.

Thus, R1 = 50k, R2 = 100k, the potentiometer is represented by the variable voltage source (between 0 and 5V DC).
I must then determine R3 and R4 so that Vs is equal to 5V by modifying the output potentiometer when Ve = 4V DC or Ve = 6V DC
P.S.: Supply for the operational amplifier is +15-0V single supply.


texts: Using 320QVT TFT display module with stm32f407

texts:
I'm having a bit of trouble trying to get a small 320QVT TFT module up and running. The documentation available is quite vague, but I know the module used a SSD1289 TFT driver, and that 16 address pins are brought out on the module, as well as control lines. Although the module has an SD slot, and touchscreen ability, at the moment I'm just trying to get the display working.

This is a pinout of the available connections on the board.

I currently have pins dealing with touchscreen and SD card left floating (pins 29 - 40). There is one pin (16) labeled F_CS, which I am unsure what to do with, so at present it is also currently left floating.

I managed to find some documents which allegedly contains an initialisation and basic functions for the screen, which I have configured to run on the MCU I am using, which is an stm32f407VG (discovery board). But, unfortunately I'm still not able to get any control of the device. The thing lights up when powered on, but nothing else occurs.

I have included my project code in the link below (after doing my nut trying to post formatted code).

http://www.filedropper.com/tftscreen

I'm wondering if anyone else has used one of these with much success with one of these and can see any problems in the code, or has example code, or just advice.

Cheers.


texts:
I want to create a logic converter to communicate an ATtiny85 (trinket 5V) with my raspberry-pi. I am currently following this guide.

I want to use a written program for ATtiny that only generates a TX UART output on the software side and send data to the raspberry.

In this guide the NMOS BSS138 is used, I would like to know if I could use the NMOS 5LN01SP instead.

Also, I want to communicate in the simplest possible way. What is the difference if I choose to use a voltage divider (two resistors) at the ATtiny85 output to ensure the 3V on the Raspberry input pin or the fact that I lose bi-directional property?

Thank's you for your help.


texts:
I've toying with V-USB for a few days and got a circuit working in a breadboard with a Attiny85 and 3.6 Zener diodes.

However, when I tried to get it done in a stripboard, it doesn't work.

Assuming the soldering is correct, the only think that can be a problem is a modification I did to make it easier to solder.

Is this:

equivalent to this?

Can this modification be the problem?

Thank you.


texts: Why is a connection to Earth implied in this power supply

texts:
i'm trying to implement this SMPS in a design, but i'm not sure i totally understand why there is a connection to EARTH (the E in the input terminals on the left) in the schematic bellow..

Can someone please help me out here?
Thanks!


texts: I have been using an HCPL3700 to detect 24VAC, but they are large and relatively expensive. I have tested the design shown in the figure (AC input to the diode, and measuring output collector-emitter voltage to determine if AC is on or off) and it works fine on the bench.  My concern is that the diode in the optocoupler is not rated for use as essentially a rectifier. I use 12k resistors all around (capacitor is 10uF), so power dissipation maximum ratings aren't a problem.  Can general purpose optocouplers (LTV-816 in this case) handle this duty?


texts:
I am trying to reverse engineer and understand the following circuit found in an LED lighting controller.
The OUTPUT is basically a 12V supply where the polarity can be selected by the MCU (Q7/Q2/Q1 N-MOSFET gate inputs) - almost like an H bridge I guess. Strings of LEDs are connected to this output in alternating polarity.
When the Q7/Q2/Q1 N-MOSFET gates are low, the outputs are 12V/12V therefore 0V between them.
When the Q7 N-MOSFET gate is high, the outputs are 0V/12V therefore -12V between them.
When the Q2/Q1 N-MOSFET gates are high, the outputs are 12V/0V therefore +12V between them.
My question is, what is the point of the middle section (Q2 + zener diode) and why does it have separate MCU control (which always follows control of Q1). I imagine it is some form of protection?
Note: Q6/Q9 are P channel MOSFETs.


texts: What is the difference between charging batteries in series and parallel?

texts:
For example, if I have a charger that supplies 300 milliamps:

Will it take a bit more than 3 hours to charge a 900 mAh AA battery?
What if I have 4 AA batteries in series? Will it still take 3 hours?
How does voltage play into all of this?
I am planning to use a solar panel to charge 4 AA 2300 mAh batteries. The solar panel is 6 volts and 100 milliamps.


texts: How does a capacitor and resistor affect an SCR's firing angle?

texts:
Greetings! High schooler here studying SCRs. I've been looking at sites and books on the concept of increasing an SCR's firing angle, and what I've noticed with these references is that they show you how to do it, but they never really explain why it was able to do that in the first place!

The circuit that is confusing me right now is this one:

My guess on how the firing angle increases: I actually calculated this circuit's firing angle and got 95 degrees!
So what I assume is that because a capacitor lags the current, it takes longer for the SCR (which needs a gate-triggering current) to activate. However! With an angle more than 90 degrees, doesn't that mean all the values of the source voltage have already been tried and not enough for the circuit to produce a gate-triggering current? What more with angles after 90 degrees, which have less voltage values since it passed its maximum?
I think there might be a concept of capacitors I am unfamiliar with? How can an SCR still exhibit a voltage waveform like this:

(Values of circuit if you're curious)
R1 = R3 = Rload = 1kΩ, R2 = 500Ω, C = 10uF, Igt = 10mA, Vsource = 160 Vrms


texts:
I need help identifying an smd diode (see picture)
It appears to have 5423 written on it, but I can't find anywhere a diode by this code. I did however find an smd diode by googling 5243 (I figured that it I might have to read it vertically, not horizontally).
Also, 1 of these reads 0.1 when tested with multimeter and another reads 0.2. I have desoldered them both to be 100% sure and the result remained the same. Does that mean the one with 0.1 voltage drop is the bad one? I also tried switching multimeter leads, both read OL as expected. Also, I measured resistance: the one with 0.1 voltage drop read 200-300 ohms, whereas the other one was OL (that's while probing using the correct polarity). After switching multimeter leads it read OL resistance for both diodes.
Thank you in advance!


texts: Discharge protection circuit for 2S Li-ion

texts:
I'm looking for a overdischarge protection circuit for two 18650 in series. Preferably not a module. Discharge current is max 1mA. Charging is done in a separate charger

My situation is a circuit with a power consumption of avg 1mA@3.3V. I would like to use 18650 batteries for a long runtime and ability to recharge. To use these batteries a undervoltage protection is recommended. Now I'm looking for a way to tackle this. A circuit with self low power consumption that shuts down the battery-connection at a reasonable voltage level.

Can this maybe a solution?

  -The BQ296xxx family has a self-disable function to turnoff the regulated output if any cell voltage falls below a certain
  threshold,thereby preventing drain on the battery,and provides an
  external control to enable or disable the regulated output.

page 15
http://www.ti.com/lit/ds/symlink/bq2962.pdf


texts: What makes the band of an antenna broader than others?

texts:
Even though I'm studying waveguide slot antennas, so the examples that I'm going to give are related to this topic, my question covers a wider range of topics.

I already know about a couple of things:

The concept behind frequency independent antennas like spiral
antennas or logarithmic.
Impedance matching and how to use matching networks.
Parasitic elements and how they limit the bandwidth.
Resonance and that resonant antennas usually have a small bandwidth.

So, leaving aside frequency independent antennas that theoretically have an infinite bandwidth, what makes the band of an antenna or any other RF/microwave device broader than others?
When a broadband design is needed, how should one proceed?

In particular, I was wondering why the H-Shaped slot or the U-Shaped slot have a broader band than, for example, a rectangular slot of the same dimension (even though it's not immediate to compare the dimension of those slots, we might take the area).

One possible explanation might be that there are differences between the equivalent circuit and equivalent parasitic elements of the two designs.

Another explanation might be that the electromagnetic field in the H-Shaped slot as well as in the U-Shaped slot has more degrees of freedom than in the rectangular slot. Therefore, they can "accommodate" in different ways at different frequencies with the result of a broader bandwidth.

The latter seems better to me. However, it's not that by adding degrees of freedom you always get a broader bandwidth...


texts:
For a three phase squirrel cage induction motor (IM,) we can have 2 or 4 or 6 etc. pole pairs on its stator and when these stator windings are energized by 3 phase mains supply then we get a rotating flux inside the motor.

Can we say the same for the rotor of a squirrel cage  IM also?

Please correct me if I am wrong that the rotor of an IM always has 2 poles regardless of the poles on its stator.


texts: Output impedance of a series shunt feedback amplifier

texts:
I am trying to find the output impedance of a series shunt feedback amplifier by converting it to a two port network.

I know the input impedance:

Ri=ri*(1+A.β)

But I dont know how I should find the output impedance.

I only know the answer:

Ro=ro/(1+A.β).


texts: Double DC Motor Compressor Circuit Protection

texts:
I'm a mechanic!

So, please do not blame me for stupid questions.
I did a lot of research using relays for switching DC motors. The following circuit is showing the current version I want to realize this to run a compressor with two motor circuits. One motor is driving one compressor unit.

The right side is powered by 110 AC voltage commutated to 110V DC. The high-voltage side is pretty much the same used in the original compressor.The motor is a 110V/0.9A DC motor.
The low-voltage side is fed by a 12V DC power supply. The motor is a 12V/8A DC motor. I'm wondering if the shown low-voltage side is ok since I had to re-design it. Based on the research for switching DC motor it should be ok.
The original device was using only one side at the same time. Since I would like to switch both side at the same time I'm not sure if the circuit is missing some components.

is it ok to secure both relays with one diode (D6 = 1N4007) only?
if the switch S1 is released is another diode on the low-voltage side needed to handle induced voltage by motor stop?
the capacitor C1 is more or less copied from the original setup. What is that needed for?
Is it ok to have the relay low-power side in the same power supply circuit as the relay high-power side for the 12 V DC motor?
should I spend some components on both relays high-power sides to protect the relay switches from arcing (was not included in the original setup)?

Thank you very much for your support. I really want to make sure to not harm both DC motors. Any advice is appreciated.


texts: I understand that silicon has an incredibly important use in microelectronics, as its semi-conductive properties allow us to make transistors. However, this is only possible after introducing other elements such as phosphorus and boron into the lattice. What I'm wondering is if silicon is able to conduct electricity at all without any doping being done?


texts: Thermal stabilization of TH LED (layout recommendations)

texts:
I have to develop a circuit for LED-based optical reference. Due to specific requirements, only available LEDs are in TO-18 packages with metal cans.

The problem is that LEDs experience spectral shift based on die temperature. I would like to avoid this shift by controlling the temperature. So, the question is - how do I improve heat transfer between the die and the heat exchanger?

I plan to have large pads for anode/cathode with thermal vias to the opposite side of the PCB, which attaches to the Peltier element. Measurement thermistor thermally attached to the anode pad on component side, right next to the pin. I was thinking of thermally coupling the can itself as well. Is there anything else I can do about it, perhaps any other recommendations?

UPDATED:

For all the requesters, particular LED "datasheet": https://www.thorlabs.com/drawings/959aa0deecfcd23f-34F04596-F0E3-080D-BD90C82F6B8EC899/LED910L-SpecSheet.pdf


texts: How to handle polling method in micro controllers.?

texts:
I am using PIC32MX795F512L Micro Controller.

I need to develop an application where 4 led's connected to pins of controller will blink continuously at a rate of 1sec and there are 15 inputs connected to controller. These inputs will send some data to UART whenever they get HIGH.
For example:

while(1)
{
if(input1 == HIGH)
{
 putsUART1("input1 HIGH");
}
if(input2 == HIGH)
{
 putsUART1("input2 HIGH");
}

//same for rest of the inputs

LED1 = HIGH
delay(1000);
LED2 = HIGH
delay(1000);
LED3 = HIGH
delay(1000);
LED4 = HIGH
delay(1000);

LED1 = LOW
delay(1000);
LED2 = LOW
delay(1000);
LED2 = LOW
delay(1000);
LED2 =LOW
delay(1000);
}

above technique is polling method and is not giving real time input data to UART. I thought of using UART TX Interrupt but dont have good experience in it.
I have just downloaded FreeRTOS for PIC32 and created few task and using RTOS it is working fine. Should I continue using RTOS or switch to use Interrupts. If there is any other way of doing it,
Please help


texts:
I'm experimenting with compensation topologies for inductive WPT systems and have a small confusion.
The general WPT industry uses compensation networks to cancel out reactive components in the transmit and reciever side and therefore improve efficiency.

What I noticed is that the industry mostly uses Series-Series or Series-Paralell compensation topology.
I did some experiments and it doesnt add up.

So here is the picture for Series-Series topology:

And Series-Non compensated:

In the pictured we see the frequency response at node north of R1 and C2 (or transformer in non compensated mode).

In Series-Series topology we see that the gain at resonance is around 4 dB, but in Series-non compensated at resonance the gain is 9 dB.

Why is it so?

And if somebody has some literature to share on the topologies, feel free to share!


texts:
I would like to use 1 RFID reader (13.56Mhz, protocol iso14443a) with 2 antennas in a way that I can recognize the location of the tags- if they stand on antenna #1 or #2.

For that, I tried to use 2 RF switches that can work from 10Mhz to 3Ghz (or any other option that includes 13.56Mhz in it). I used the RF switches on the TX lines- TX1 and TX2 of the differential output of the reader, and with the combination of the RF switches I tried to control one antenna at a time.

The idea is to switch every X ms between the antennas and by that know where the tag is. the control is with 2 GPIOs (1 & 0 to activate one antenna and 0&1 to activate the 2nd antenna).

From the material I found on the internet, i saw that it can also be done using high-speed RF relays, but I also saw that they are more expansive.

This is the RF switch I checked:
http://www.rfmd.com/store/downloads/dl/file/id/30282/rf3023_product_data_sheet.pdf

And this is my reference design:

After I tested in the lab this RF switch I notice that i keep getting recognition from both antennas in all modes. It seems like the component keep shortened the RFC(5) to both RF1(1) and RF2(3), that it doesn't really disconnects between RFC and RF1 (or RF2).

Please advise why do you think it happens. howcome that this component doesn't fully disconnect the other net?
Assuming I need a very low cost solution, do you have other alternatives?

Thank you!

Dudi


texts:
I'm looking for a part that enables a user to frequently change a configuration. Right now I'm utilizing a SMD DIP switch connected to an I2C I/O expander.

What bothers me is the large footprint of these components (DIP switch combined with IO expander IC) as well at the rather tedious user interface.
Are there DIP switches or something that serves the same function that I can talk to over a digital bus like I2C to read its state?

I'm also open to completely different approaches. All I need is something that can be mechanically altered in a permanent way and allows at least 64 different states.
It is important that the configuration can be made when the circuit is not powered up and provides visual feedback of the exact configuration to the user. The only way where it would be ok to power up the circuit is if the configuration and visual feedback is self contained without the need for control from a microcontroller or SoC.

The question is somewhat related to this question from 6 years ago: DIP switch replacement

Edit: There are some great suggestions in the answers and I think I leave this question unanswered, community votes should decide what is helpful and what is not. If you have the same issue as I have, look through all the answers.


texts:
I am trying to make a motion detector with a photodiode, and I am trying to trigger a 555 when the photodiode goes from dark to light (this will detect a person crossing the detector, and not stay on forever if ambient light changes).

I realized that to detect the changes in the light, I would need an inductor. This is the idea for a schematic I have so far:

The usual positive current during normal operation and the forward emf from the inductor when it goes from light to dark won't trigger the 2-pin of the 555, but when the photodiode goes from dark to light, the inductor will give a back-emf that I hope to capture with the 555 (I have the 555 part down :D).

However, I am worried that if the voltage is too much and the change of light is too slow, then the v=L*di/dt term from the inductor will be less than the forward voltage and the sum will still be positive, not triggering the 555.

My teacher had the idea to put that resistor before the photodiode so I could maybe lower the forward voltage so the di/dt could be greater than it. However, I think that this won't work because this will linearly lower the current, and thus linearly lower the di/dt term (cuz linearity of derivative and all that) thus achieving nothing.

Would this circuit work? What does one normally do to capture the back-EMF? Are there any other pitfalls or considerations for this? Keep in mind that I am very new to this circuitry stuff, so tell me if there is something obvious that I missed.

Thanks!


texts: Connecting Arduino to 10hp 3 phase ac motor?

texts:
I want to connect Arduino to 3 phase 10 hp ac motor. I just want basic functionality that is I should be able to turn it on or off using the code.
Is it possible to do with 3 phase solid state relay?
if yes, can I use 3 relays instead of a 3 phase solid state relay?
If no, how to do it?


texts: Battery management circuit for Nokia BL-4C / 5C Li-ION batteries

texts:
Nokia BL-4C / BL-5C are 3.7V, 700-1000mAh (variants) Lithium-ion batteries, which are available in abundance and at very low cost ($4 - $7 a piece), since these are used in entry level Nokia phones, sold in most developing countries.

These batteries have 3 terminals, as explained here, for battery positive-terminal, ground, and a terminal (BSI) which I believe presents a fixed resistance value, that needs to be measured, to determine battery-type (chemistry, characteristics including capacity etc.)

So here are my questions:-

Is anyone aware of any existing open-source hardware project, that has built battery-management circuit around such batteries ? (PS> In my searches so far, I've not come across any such project).
How exactly, can one accurately measure the resistance offered by BSI terminal of the battery ? A very accurate and stable reference voltage would be required, I believe - but if the battery itself is the source of such reference voltage, it could vary with charge-status and condition of battery, so how could it serve as a good reference ?
Is it necessary to have a temperature sensor in proximity/touching the battery ?
What would be some low-cost battery-management IC's that are not too difficult to source or work with, for hobbyists, which can be used to charge such Li-ION batteries safely ?

Have found this question here related to 'resistance measurement', but the mechanisms described are far too cumbersome, expensive & require manual intervention, to be useful in automated battery-type identification. OTOH, it is possible that I've completely misunderstood the purpose of the BSI terminal.

As for whether "temp sensor" is needed, I think the answer is YES, based on this. However, the question then becomes, without access to proprietary battery characteristics information of this Nokia battery, what can one do with the temp-sensor ?


texts: Can I mix ASC and PSC when analyzing a circuit?

texts: Can I analyze any circuit using Active Sign Convention (ACS) for power sources and Passive Sign Convention (PSC) for resistors, or will this lead to errors? In other words, should I always stick to the same convention when analyzing a circuit?


texts: Engineering Electronics: which approximation is usually good enough?

texts:
I have a strong computational background, so approximations with floating point precision depend on the type of computation. One thing is to know how to make an approximation and another one is when to do one. Sometimes in Chemistry I was asked to use around 4 decimals places. In high school Physics we used somewhere around 3 or 4 decimal places. But we always used the whole formula!

Then I found that in Engineering we can make approximations on the formula. If we are analyzing a diode, then we just go ahead and say that the voltage drop is 0.6 or 0.7. Yet sometimes I feel it might be necessary to use the exact description of the voltage drop. So overall, which areas of electronics require how much precision? I have close to no idea of when to use a certain precision!


texts: Simple transistor resistor amplifier circuit question

texts:
Can someone please help me solve this?  I have tried and got stuck.
In a point that can I apply Kirchhoff's voltage law around R2,R4 loop.

simulate this circuit – Schematic created using CircuitLab


texts: Asking about resistors for a FreeTrack IR clip

texts:
I have been working on a project for a freetrack IR clip to use with some of my simulators, and I had a question regarding resistor values.
The guide I am using is here, and it details the use of 30 Ohm resistors. However finding these has been a pain but I have found 33 Ohm resistors available near me.

I was wondering if there would be a significant difference between using 30 and 33 ohm resistors for this circuit, which has 3 IR leds powered by a 2xAA battery pack.

I look forward to your answers, and thank you for reading my question.

Cheers,
Finn


texts: What's inside a MK 484 radio inegrated cirucit?

texts:
I wanted a functional diagram for the MK 484, kind of like you will see for op amps (http://www.ti.com/lit/ds/symlink/lm741.pdf).

Instead, I only found this:
http://www.datasheetcatalog.com/datasheets_pdf/M/K/4/8/MK484.shtml
This only has applications, but not how the chip works, nor its functional relationship.

How does it work? What's inside.


texts: I have an old laptop power supply which provides 3.5A at 20V. I want to re-purpose this for another project for which I require 3A at 5V. If I cut the output cable I'm assuming I'll find a +20V wire and a 0V wire? If I chuck some resistance on the +20V to drop it down to +5V will this have the desired effect? Will I end up altering the available current or otherwise messing things up?


texts: IC on Breadboard: I have a PCB IC (LTC3115), how to search if it's available for breadboard use?

texts:
I am designing a PCB and am using buckboost converter IC - LTC3115. I have tested the component on the PCB and am not getting the required voltage output. My idea is now to check if it will work on a breadboard for the given configuration; how to check if the component is available on a breadboard? Digikey?

Alternatively, how will I know if my IC is burnt as that might be the issue why it's malfunctioning?


texts: Would using litz wire for an inductor change the inductance compared to regular wire?

texts:
Litz wire is multistranded wire where each strand is insulated from the others along the wire's length, but they are connected together on each end.  This is useful primarily to reduce the skin effect, so that more high frequency current can be carried on less copper, saving cost, weight, and volume.  Inductive cooking surfaces often use Litz wire.

Does Litz wire require different equations for inductance than regular stranded or solid wire?


texts: Can a filter circuit be built for the FM broadcast range to only pass the frequencies not bearing a broadcast stream?

texts:
I want to build a receiver that constantly sweeps the United States FM broadcast frequencies between 87.8 MHz to 108.0 MHz.

However, I want to filter out any frequency that has a radio station broadcasting on it.

Is there a way to dynamically detect a frequency with a broadcast on it and not pass it to the output circuit that has a speaker?

In operation:
1) the circuit receives the first frequency in the standard U.S. radio range.
2) if the frequency has a broadcast on it, ignore it, otherwise send it to the output speaker.
3) If no more frequencies in range, go back to 1), otherwise receive the next frequency in range and go back to 2).

I want to receive only those channels without a broadcast on them, sort of like the opposite of a squelch circuit.

I am a beginning electronics enthusiast and this is an experimental application to prove a concept. I'm asking for help because I haven't the slightest idea whether it would work and if it could, how to go about building such a thing.

Thanks all.


texts:
I am trying to setup a schottky diode oring circuit to switch between my battery and a dc power supply.

I am dealing with some pretty high amperages and a liPo battery, so I need to make sure I get this right or else somthing could go boom. The circuit I am trying to create will be pulling about 20A max from my 11.1v nominal voltage battery and obviously around 10A from my 24v wall supply (if necessary I also have a 12v wall supply that I could use). The LiPo battery charger will hopefully be included in the circuit along with an extra diode to charge the battery.

Iwill attach an image of what I have drawn up, but please note I have absolutely no electrical background so my drawings might be completely off (just note that the triangle things are diodes)

simulate this circuit – Schematic created using CircuitLab

Charger schematic redrawn by kindly neighbour. Note drawing convention of higher voltages at top with general flow from left to right.


texts: 0/10V @ 5 mA input ,translated to 0/10V @0,2A output

texts:
The idea is a circuit where an analog input 0-10V (max current of 5mA input), reflects into an analog output with a minimum current of 200mA. The voltage of the analog output (Vo) must always be equal to the analog input voltage (Vi), ie Vo = Vi (gain = 1) The circuit should be powered on 24VDC, where the current gain should come from this source . The circuit must have terminal necessary for the connection.

Any sugestion ?


texts:
I have a RF device which work on 2.4 GHz and Output power is 30 dBm (1 W), RF output is connected to a whip antenna (gain 2 dBi, omidirection), distance track between RF pad to antenna is kept as short as possible to avoid any losses, 50 ohm independence is maintain all over this track.

So with this antenna actually my transmit power will be double or not since my antenna gain is 2 dbi?

Also the antenna transmit the radio wave, so what really it means if antenna transmit 1 W radio wave or tranmit 2 W of radio wave, how physically this wave behave in air, does both have amplitude difference, or it just like that higher the power and far it can travel?


texts:
I am using the U62256A 32K x 8 bit static RAM. For testing purposes I connected all outputs to LEDs and since they are also inputs to a dip-switch so I'm able to write data.

The write mode works nicely and stores everything correctly. Data rentention in the RAM chip is also working. What doesn't quite work to my satisfaction is the read mode. Stored 1's (high) are properly output at a stable 5V, but 0's are flickering. My cheap voltmeter reads about 2.4V at the output and the LEDs are visually flickering at about half the brightness of a high output. According to the datasheet there should be a maximum voltage of 0.4V when the output is low.

This is the circuit. The right side of the LS245 is there so I can connect the RAM output to a bus. I have already tried removing it and connecting the outputs directly to the LEDs, as well as disconnecting the dip-switches (not shown in the schematic). I'd like for the LEDs to be simply off when the outputs are low, but with my little knowledge on electronics I can't figure out why they are flickering or what to do about it.

I'll appreciate any and all help!


texts: I want to make an auto power cut off for my battery charger

texts:
I have a charger for a 12v battery but it is without auto power cut off.

I know I need a circuit consisting of a comparator and a relay and I drew the circuit but I don't know if there is something wrong with it because when I run the circuit the relay doesn't switch at all.

Is there something wrong with the circuit or is it the simulator that doesn't work right??


texts: Power indicator for circuits with voltages much higher than LED forward voltages (say 15-48V)

texts:
I have a circuit that has a 24V power rail and I put an LED and series resistor on it for power indication. Even at 10mA forward current, over 200mW of power is dissipated, over 90% of it in the series resistor. This is more than many (but not all) SMD resistors can even provide. This seems like a lot of power for a simple LED.

Neon indicators might work at the higher voltage end, but they aren't commonly available in SMD packages and they're bulky, expensive and can have limited life.

I also considered an astable multivibrator to do a low-duty cycle flash to keep average power down, but that needs 4 resistors, 2 capacitors and 2 transistors, or an IC (which would be unlikely to work at 24V) and some passives.

Is there a very simple (low component count, cheap, low-power and low-board-area) way to show power indication in circuits with a rail voltage more than about 10 times the LED \$V_f\$ (say around 15V up to 48V).


texts: I need to measure the impedance of the system, is it better to measure the resistance or capacitance?

texts:
The goal of this project is to measure Retinol levels in the blood. To do this I will be use two electrodes, one of which will be coated in nanowires. These nanowires will then have antibodies that will bind to the Retinol. To determine the levels of retinol, I have to determine the impedance of the system.
Now, I have a colleague that seems to think that it should use an ohmmeter and I am not too knowledgeable about EE but my understanding is that resistance wouldn't change. Rather, I should be trying to measure the change in voltage.
Does anyone have any thoughts or ideas about this? I apologize if this isn't clear enough, as I'm not sure what information is pertinent to this question. Let me know if there is anything I need to clarify.


texts: How can I make an accurate torque/RPM curfer for the random electric motors lying around my garage?

texts:
I am blessed with a garage filled to the brim with all sorts of electric motors, most of them sourced from broken household appliances and the like.

I would like to gather some data about them, like for example how much torque do they output at different rpm.

What kind of tools would I need to produce such a curve? Can I make the tools myself?


texts: How to implement a comparator logic gate in Quartus software?

texts:
Been trying for hours...How do I properly implement the following expressions:
F0 = A0'A1'B0 + A0'B0B1 + A0B0'B1' + A1'B0B1
F1 = A1'B1 + A0'A1B1' + A0A1'B0' + A0B0'B1 + A1B0B1'
I'm using NAND & NOT gates


texts:
I got a circuit for a photodiode, but unfortunately without datasheet and explanation. Now I am a bit confused what the purpose of the different parts is:

simulate this circuit – Schematic created using CircuitLab

As far as I understood, the resistor R1 and the diode D1 are providing a voltage drop, while the capacitor C1 provides a voltage buffer. R2 is doing ?, and C2 is coupling out DC current. Is that correct? And what is the purpose of R2?


texts: Alternate topping up two capacitor banks

texts:
I've implemented a Beam robotics 'solar engine' as detailed in the diagram below

This engine takes a small trickle charge from the solar panel, before discharging the capacitor in one pulse of power. It then starts charging again.

I'd like to power multiple sets of these circuits from one solar bank. The problem I found is that whichever circuit discharges first discharges all the capacitors for all engines. Putting in a diode in the charge lines for each engine results in the engine that discharges first 'short circuiting' the rest of the engines - it essentially takes all the charge from the bank as it cycles whilst the other engines are just below their trigger thresholds.

Does anyone have any suggestions? The simpler the better and preferably very low voltage drop.


texts: How is a modern digital oscilloscope calibrated?

texts:
Old CRT type oscilloscopes were nothing but analog devices. They were filled with potentiometers. All this circuitry would drift over time. When they were calibrated, known waveforms were fed to the scope, the displayed wave form was then compared to the known and if the differences was within a given margin the pots would be adjusted to bring it back to the original spec. This procedure depends on that the scope has a predictable drift. If the difference between the known waveform and the displayed waveform was significantly greater than the expected drift, something was wrong with the scope and it needs repaired.

New digital oscilloscopes don't have potentiometers like the old CRT scopes. The verification process, I assume, is exactly the same. Feed the scope known waveforms and compare them with the displayed waveforms.

With no potentimeters how is the scope adjusted for drift over time?

Is the scope trimmed in software or if the scope is out of tolerance (but still within the excepted drift) it needs repaired?


texts: Does Bluetooth Latency come from the Transmitter or Reciever?

texts:
I'm going to buy a low-latency bluetooth module that functions both as a tramsmitter as both receiver. Should I get just one to connect to my audio interface or do I also need one for my headphones if I want to minimize latency?
The afformentioned module used aptX technology, making it much faster than standard bluetooth (which my headphones use).


texts: Very high current frequency on transistor collector

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simulate this circuit – Schematic created using CircuitLab
I am designing astable multivibrator for homework and I have calculated values for resistors and capacitors (hopefully right) but I just can't figure out why is current oscillating at very high freqency on transistor collector. Any advice?
Analysis:


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I'm trying to read multiple tags 'at once' using a LPC1768 mbed board and a RC522 module. I've spent some time reading about anticollision and I'm still confused about how it works and how it could help me achieve this task. I want to be able to read a maximum of 3 tags located near the RC522 module. I only need their IDs. I don't want to actually read them at once, but rather to find a way to make them respond in sequence if possible.

So far I had interesting results. With the mbed library example here that just prints the tag IDs, if I stack 2 tags and put them near the module, I get no IDs printed. However by varying the distance between the tags, I can find a sweet spot where both tags respond randomly. Can anybody tell me why this would happen ?

I want to know if it is possible to read multiple tags reliably with this module or with other technology (tags and readers).


texts: Measurement setup for power line spectrum

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I've come across a setup for measuring AC power line spectrum.

Here is the spectrum graph which shows 60Hz and harmonics in a power line voltage:

And below is the setup and wiring for this measurement:

If I would do it I would use a step down transformer like 230V to 5V, then connect the primary to 230V mains and then couple the secondary to an oscilloscope and look at the FFT on the scope screen. I guess using a spectrum analyzer gives a better result than a scope's FFT function which I can understand.

But there are some points which I don't understand about the diagram above:

1.) Why are the primary windings are not connected to Line and Neutral but connected to Line and SG? If SG is the safety ground, what is it directly connected to? To the mains earth? How does it work? (Is the spectrum analyser earth grounded?)

2.) What is meant by 10Hz - 10MHz transformer? (I'm not used to see transformers by frequency but by primary and secondary nominal voltages.)

3.) What could be the reason for 1nF capacitor?


texts: Is there a way to secure an 18650 battery pack together without soldering, spot-welding, or an end cap kit?

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I'm putting together an 18650 battery pack for an e-bike. The BMS is specified for 10s 36v 40a. I want to avoid soldering, spot-welding, or an end cap kit if possible.

I thought I would make each group of 10 cells in series to reach 36v, and then those groups would be in parallel. This would allow me to just use dual tubes of 5x2 cells a piece to reach 36v.

But from what I'm reading now, my understanding is that a BMS does not work like this. I should actually connect each group in parallel to reach desired capacity, and then connect the groups together in series.

Assuming this is correct, is there a way to make the pack in a similar way as I was planning before, with tubes instead of a brick?