texts: Confusion with resistor and diode voltages when heated in a series circuit

texts:
Below there are two circuits supplied by a 10V supply. The only difference is the one on the left is 10k in series with 1k; and the one on the right is 10k in series with a diode.

Confusion 1 about circuit (A):

If the resistor is heated its resistance increases. And if the current would remain the same we would say that the voltage across the resistor would increase. But the current will not remain same because the total circuit resistance increase will decrease the current. Will the voltage across the 1k resistor increase or decrease? Which one will dominate? Increase in resistance or the decrease in current?

If the temperature of the resistor increases resistance increases and this yields current decreases according to Ohm's law V = R * I. R is increasing and I is decreasing. In a practice which one dominates and what happens to the voltage across the 1k resistor?

Confusion 2 about circuit (B):

If the diode is heated its DC resistance decreases. If the current would remain the same the voltage across the diode would also decrease. But since the circuit current will increase I'm again facing the same difficulty here. The diode DC resistance is decreasing which immediately should increase the circuit current. Again something is very cloudy for me to decide what happens to the voltage across the diode when it is heated in practice. Which one will dominate? Increase in current or decrease in DC resistance? How can it be explained step by step manner?


texts: Simple 7 segment decoder circuit not working

texts:
I used a cd-4511 decoder for my seven segment display circuit. It was a simple circuit, just to get familiar with how the 7 segment display and the decoder operate. However, upon sliding the switches, nothing happens.

(I have 5 switches and 4 or gates that are unused, but i plan to use them in the future as part of this circuit).
Tinkercad shows the function of all the pins on ICs (power, ground etc..) So I don't think thats where I have messed up...
What is going wrong with the connections then?
Tinkercad simulation link:https://www.tinkercad.com/things/7Y2irqYYjJy


texts: Making a Triangle wave on LTSpice using LM741 opamp

texts:
I'm trying to get a 1kHz, 15V triangle wave on LTSpice. For that, I'm using the following design:

So far, my Square Wave has the desired frequency and amplitude, but my triangle wave has a lower amplitude. How can I correct this so both waves match at +15v and -15v?

I'm using the following specs, sorted out by some formulas but also trying. There are some values that I don't see how affect what I get.

Vcc=15v
R1=150k
C1=3.03361n F
R2=R3=100k
R4=R5=1k
C2=1000n F
R6=3k

Thanks a lot for your help.

EDIT: [UPDATED] here's a caption of the actual simulation i'm running on LTSpice:


texts:
I understand the proof in the link below and how a voltage divider works. This question is about a definition in the proof:

$$V_{out} = I \times R_2$$

If \$I\$ is the current in the series circuit, then I understand that the current times the resistance of the second resistor (\$R_2\$) will be the voltage drop across \$R_2\$ (in a DC circuit).

Will \$V_{out}\$ always be equal to the voltage drop across \$R_2\$? Is this known as a result of experiment or the result of some other math? Or am I just thinking about this the wrong way?

Voltage Divider article at WikiPedia.


texts: Short circuit problem (batteries getting HOT) within circuit

texts:
So I am making a circuit with a simple 12v dc motor in series with an NO microswitch and on off switch conntected to a dpdt switch to reverse the polarity of the motor. The first issue I had was to find a way to connect a microswitch to only work in the reverse position, and through trial and error, I connected the switch between the negative side of the battery and motor, this set up works however the batteries keep draining current (getting hot) I'd just like to ask what am I doing wrong, and is there any other method using the components used, I've attached a simple drawing (apologies for the quality).

simulate this circuit – Schematic created using CircuitLab


texts:
I'm repairing a 250W bass power amp board and one of the problems is that the pads for two ground wires have lifted off the board. It looks like it has had something of a bodge repair done before and there doesn't seem to be much in the way of pad left.

For a tiny pad connecting to a component I can see that repair would not be too difficult, but this seems a bit more tricky given the higher power, bigger pads and the chunky wires. I wondered what the best approach might be to fix this. I thought about a terminal connector, but then that needs to be soldered into place, so perhaps something mechanically attached to the board and then connected to the rest of the ground trace, or am I over-complicating things?

Here be pics:


texts: Controlling Solenoid Valves with ULN2003A, Inrush Current, Arduino

texts:
I want to control a total of five solenoid valves with my Arduino. The solenoid walves operate at 12 volts and have a power consumption of 5 watts per solenoid valve, which equals a current of roughly 420 milliamps.

My idea is to use a ULN2003A transistor array to do this. The ULN2003A datasheet says it supports voltages of up to 50 volts and a maximum current of 500 milliamps per output.

My question is: Is the ULN2003A with its 500 milliamps maximum current rating per output sufficient to reliably switch the solenoid valves? I'm asking because solenoid valves are inductive loads and if I'm not mistaken, they are subject to inrush current that far exceeds the normal current.


texts: Why the base current is zero in B part of this question?

texts: In the B part of this question , i am not getting why the base current is zero. Everything seems to be fine but still not getting ...


texts: NTAG213 Not being picked up by the RC522 Module

texts:
I have been using the RC522 module to read and write things to the tags it came with. But when I tried to use an NTAG213 I bought for a recent project it will act as if it isn't there. I've tried a lot of different code to try to get it to recognize it but I haven't had any success.

I’ve mostly been trying to use the module that the RC522 needs on the arduino UNO

Have I just not been using the right code? Or is it not possible for the RC522 to recognize the tag?

Ok I was just able to scan the tag using a friend’s phone and I have found the manufacturer and the protocol. The manufacturer is NXP and it uses the ISO/IEC 14443-3 protocol
'''c++

    #include <SPI.h>
    #include <MFRC522.h>

    #define RST_PIN         9          // Configurable, see typical pin layout above
    #define SS_PIN          10         // Configurable, see typical pin layout above

    MFRC522 mfrc522(SS_PIN, RST_PIN);  // Create MFRC522 instance

    void setup() {
        Serial.begin(9600);     // Initialize serial communications with the PC
        while (!Serial);        // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
        SPI.begin();            // Init SPI bus
        mfrc522.PCD_Init();     // Init MFRC522
        mfrc522.PCD_DumpVersionToSerial();  // Show details of PCD - MFRC522 Card Reader details
        Serial.println(F("Scan PICC to see UID, SAK, type, and data blocks..."));
    }

    void loop() {
        // Reset the loop if no new card present on the sensor/reader. This saves the entire process when idle.
        if ( ! mfrc522.PICC_IsNewCardPresent()) {
            return;
        }

        // Select one of the cards
        if ( ! mfrc522.PICC_ReadCardSerial()) {
            return;
        }

        // Dump debug info about the card; PICC_HaltA() is automatically called
        mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
    }

'''


texts: A parallel RL circuit being energized by a sinusoidal a.c. voltage of \$v=100\sin(1000t+36°)\$. Find total current in RMS value


texts: Is it good to wire WS2813 LED strip DI and BI together?

texts:
I have so far only worked with WS2812 strips and understood, that the WS2813 have a backup data line. But how do I connect the first LED to my Arduino (acts as a controller)?

Many tutorials said I should just wire the BI to V0, but doesn't this eliminate the backup functionality? So I thought about wiring both data pins to my data source? Is this a good idea?


texts:
I'm trying to know What kind of tracks is this?(What do you call this kind of tracks?)

I mean those soldered tracks. I guess this kind of trick could help to increase the thickness of lines and thus you can draw more current through these lines(tracks).

Am I right?

How much it can help to draw more current? is there any approach to calculate it?


texts: Comparing with short circuit how does a current flow in parallel circuits with different resistances. Shouldn't it just choose the one with lesser resistance?


texts:
So far I've established the following:

Current is the movement of charge over time, measured in coulombs/second.

Charge is the electron in an atom.

Voltage is the potential difference between two points and the energy per unit of charge.

Still, I don't understand why this happens:

How is it possible that at time t=0 the current is present in an RC circuit without the potential difference? What caused the charge to flow in the first place?


texts: How to correctly edit a system to increase per-unit voltage of a bus [PowerWorld Simulator]

texts:
I have created and simulated the following energy system using PowerWorld Simulator 17 (please download the picture if it's not clear).

Now, I was given the requirement that every bus should have per-unit voltage larger than 0.94. So bus number 8 does not satisfy this condition (its per-unit voltage is 0.88) and I want to do something to correct it. I tried the following methods all of which did it but I am not sure if I am in the right direction.

Method 1: I decreased the MW value of the load connected to bus 8.
Method 2: I decreased the Mvar value of the load connected to bus 8.
Method 3: I attached a generator of 1 MW to bus 8.
I am wondering if any of these methods is correct or if they violate the design of the system. Any other ideas?


texts: What might be causing an op amp to fail in a voltage follower circuit?

texts:
I have the following super simple op amp circuit that makes use of the AZV321  single op amp (https://www.diodes.com/assets/Datasheets/AZV321.pdf) in order to balance the voltage on a pair of supercapacitors in series.

The op amp and capacitors are receiving 5V and the circuit works for a period of time before the op amp fails and drives the C2 voltage toward 0V. After that, the op amp is no longer functional.

I have checked the specifications of the op amp for the current that might be sourced or sinked by the op amp and nothing seems out of line but the problem occurs repeatedly.

The battery source Vin, is very stable without any fluctuations and even when the R3 resistor is completely removed so no current is externally driven, the op amp fails. This op amp specs indicate that it can handle 5 volts.

In case there was a problem sinking or sourcing too much current, I even removed R3 so that the voltage would simply match the output of the voltage divider. However, the problem still occurs.

I am now wondering about the resistance of the voltage divider, but could not see anything that might describe what is happening.

Please ignore the pin numbering on the op amp as the diagram was just made with an available drawing package. Pin 7 is connected to 5V and pin 1 to ground. I have observed the death of the op amps both using the battery and an external power supply.

The capacitors were precharged and connected to the circuit with a switch once they had the exact same voltage as existing circuit. No inrush current or voltage transients were observed with a scope.


texts: I accidentally bought a 7.4 volt servo when I should have bought a 5. Seeing that it is already integrated into the project it is being used for, what is the best way to drop 11 volts to 7 or 8 in a lightweight manner?


texts:
I am a software developer and just started my journey in electronics side.  I had this particular idea which I want to do for my project.

Problem statement: In my college every room has fans and light which is powered with normal switches. People when leaving the class don't switch off the fans and lights when leaving the classroom

Solution: I wanted to develop a software which will recognize when the classroom is empty and will switch off the lights as soon as no one is there.

It will have three components:

Sensor: This will detect that there are no people in the room and send a signal to the system
Software system: Which is responsible for taking in INPUT from the sensor do the processing and send either signal ON/OFF command in some form to the electrical main
Main Circuit: This circuit should understand the software command and convert it to signal of some form which makes circuit switch off and switch on

MY PROBLEM:

I am not able to figure out two things.

What circuit should I use which can understand a software command and convert to signal?
How can this circuit switch off the power?


texts:
Hello I have built the 555 delay power off circuit by using these 2 guides:

home.cogeco.ca/~rpaisley4/LM555.html#30

http://www.electroschematics.com/5963/adjustable-timer-1-10-minute/

I using a 10kohm potmeter + I was experimenting with 100 microfahrad - 1000 microfahrad caps. With the 10k + 100micro it switches off after 2 minutes something but not always in the same time and some time it stays on forever.

I have tried another new 555P ics in case it would fry or something but no luck. Can somebody see anything wrong with my circuit on the picture?

The red LED coming from the 2nd example (I think that circuit is bogous), even if I disconnect that part it does not make a difference.


texts: Toner Transfer + GBC Creative 9 Laminator: GBC Mod Question

texts:
After receiving a ton of feedback from this post, I decided to give the old toner method a try once again. I grabbed a GBC Creative 9 laminator off of Amazon for $23 and am now looking to modify it to produce more heat for the transfer.

I ran across UltraKeet Australia where PodeCoet modified a similar GBC laminator for the same purpose. I got the laminator in the other day and quickly took it apart only to realize that my model was slightly different. Unlike his model, I only have one thermal switch in my unit.

Here is a picture of the thermal switch and thermal fuse that comes with the Creative 9 laminator.

One thing that I noticed on PodeCoet's laminator, he has a switch on the front of his unit which allows 3mm and 5mm items to be inserted. He also labeled the two thermal switches noting that one was for 3mm and one for 5mm. This may explain the missing component on my system.

I am wondering if and how I can safely modify my unit to produce more heat for the Toner Transfer method. Also, if anyone can point me in the direction of a component that will put out around 200-220 celcius, I would be much appreciated as I have not found anything cheaper than $35 (on Mouser).

Any help is appreciated. Thank you in advance.


texts: What does it mean when my circuit has an indeterminate/no solution?

texts:
I could not solve this with KVL and KCL equations.
I did arithmetic until I ended up with a single equation with two unknowns 40 + v1 = v2.
I'm going to reread these 2 chapters so maybe I'll understand it my second time around, while now, I would appreciate help.
I get the feeling that v1 and v2 may behave with resonant behavior or switch amplitudes interconnectedly as the resonant RLC circuits behave.
The solution I come with after this will go up on my YouTube video for these solutions, I hope you can do an awesome job of helping so we can help others.


texts: Why I can't get a clean signal from my opto-isolator?

texts:
I am trying to get working my first Mosfet H bridge. My H bridge characteristics are:

12v power supply
3.5A max current
I need to control the bridge from a microcontroller 5V output
About 30KHz PWM

I am driving it from a 4N35 opto-isolator which is controlled by a 5V signal from a microcontroller with a frequency of about 25-30KHz.

As you can see on the left, I use the opto-isolator to drive two BJTs in push-pull configuration that controls H bridge's left side. The problem I can't get a clean signal from the opto-isolator even when my input is a perfect square wave. Also, it never reaches 0V and I think this will heat up the Mosfte am I right?

I have read here about Mosfet H bridges and designed it according to what I read. Am I missing something else?


texts: My question is about an inverter system with the transformer which is controlled by dspic30f, how to sense the mains voltage i.e.,230V 50Hz to the microcontroller?


texts: Searching for a Micro controller with a battery capability

texts:
I am working on a low power design, which will have a MCU powered by my regulated DC power supply from mains(220VAC). But when the Mains fail, I intend to have a battery connected to the chip that puts the MCU in a sleep mode with some specific peripherals working (RTC). It come out of the sleep mode either when the mains is restored, or when an external interrupt occurs (in which case, it has to service the ISR and goes back to sleep).

What MCU can I use for this? Actually, i do not need a very expensive/sophisticated one. Preferably, I will like an 8051 core, 6-8k Flash, at least 512RAM, UART, I2C basically. Internal EPROM will also be nice if available.

But any suggestion, circuit diagram, application notes will be greatly appreciated.


texts: HVAC furnace igniter causing micro reset

texts:
I am using a combination of Microchip PIC18F4520 and PIC16F73 in a controller which interfaces multiple heating systems for different applications. One huge issue I am running into is fossil fuel furnace / boiler spark igniter noise causing micros to reset. Does anyone have experience / tips on how to remedy this? We have isolation relays on the controller to isolate the furnace voltage from the controller voltage.

To this point, we've added another layer of external isolation relays to remedy this, but as you can guess, this is not acceptable for the end customer.

At this point I am thinking a low-pass filter may be a route to look at, but it seems this may end in the same result (system cycling).

Any tips would be appreciated.


texts: Can I make power consumption analysis much harder by temporarily disconnecting the power supply?

texts:
I am thinking about building a dongle that acts as a USB or PS/2 keyboard device and is capable of doing some cryptographic things for me, e.g. provide time-based authentication codes, store passwords and things like that. However, I would like to make this thing at least a little bit secure against power consumption analysis attacks.

One thing I have in mind is to put a small capacitor on the board and have two microcontrollers; microcontroller A talks to the computer and the user, microcontroller B does the crypto. When A requests a computation using a secret key, B would make sure that it has enough power in the capacitor and then disconnect itself from A using transistors before performing the actual computation.

Does this sound like a good idea? In other words, is it likely that this will make power consumption attacks much harder without significantly degrading the usability?

Edit: I'm assuming that the opponent is inside the PC but can't get hold of the board.


texts: Reason for inconsistency with Ohm's Law, of current measurements in resistor connected to battery circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

Connecting various resistors to the same two batteries rated 1.5 V and 9 V as  shown in schematic above returns unexpected results: lower the resistance of R1, lower the current in respect to expected value (as per Ohm's Law).

Would appreciate explanation or hint as to why this happens.


texts: How much current can a standard THT lead support?

texts: Sometimes cutting the lead of a THT resistor can be useful as a jumper or any other connection. Most THT resistors are rated 0.25 W, but if they fail it's always the resistor itself which gives out the smoke, not the leads. This seems to prove that the leads themselves can carry much more. How much more, approximately?


texts: Creating multiple identical outputs for a device and shorting between them

texts:
While looking at existing designs in the company that I recently started working at, I noticed many times that designers take for Example a DC-DC and add extra outputs that have the same name, and then they connect them to the same node:

This is a Richteck DC-DC that has the following Application Circuit:

What is the reason for that?
Note: Notice that the same principle here is applied for PVDD.


texts:
I have some doubts about how to select a voltage regulator.  I am planning to use a Texas Instruments TPS7A05 LDO regulator to regulate my 5V (250 mA) to 3.3V (200mA) to power my STM32 microcontroller. I am using a battery as source.

My input to LDO regulator:

input voltage :5v
input current : 250 mA

Expected output:

output voltage : 3.3v
output current : 200 mA ( to power my STM32 microcontroller)

My doubts:

Dropout voltage :

I understood that dropout voltage is the difference between input and output voltage .
The difference between my input voltage and my expected output voltage is 5V-3.3V =1.75V, but in the datasheet it is given like

So I am getting my voltage drop of 1750 mV. It is more than 230 mV so to get 200 mA of output current my voltage drop should be 230 mV or what then why they have given the maximum input voltage as 5V and maximum current as 200 mA. So based on my doubt I cannot use this regulator or ehat or my understanding is wrong and we can use it.

Ground Current :
I understood that ground current is the difference between input current and output current. So the difference between my input current and my expected output current is 250 mA - 200 mA = 50 mA but in the data sheet it is given like:

It is given like as 6 micro amperes, but based on my input and output current difference is 50 mA it is lot more than the given.So can I use this regulator based on my input and output or not or can I use a resistor connected in series so that I am able to get the ground current as given in the data sheet.

If my understanding is wrong please correct me.

Can I use this regulator for my application or not?

Please find the attached link of Texas instruments TPS7A05 LDO regulator.


texts: Using sr036 only for the regulated output

texts:
I'll start by admitting I am a newbie to electronics. I would like to use the sr036 IC for only the regulated output. So I left out the GN2470 transistor out of the circuit I've built. The problem is that there is no output now on the regulated output pin. Is the bipolar transistor mandatory also for the regulated output? Or could I use something else than a GN2470 / MOSFET transistor in order to have the regulated output as described in the datasheet?

Thanks!


texts: why the stator frame of a 3-phase generator is made up of cast iron?

texts:
I don't have a good knowledge of engineering materials, so please answer the following questions with reasons.

Why is the stator frame of a 3-phase generator made up of cast iron?
Why is the armature ring made of Special Magnetic Iron or some times Silicon steel?
Why is the frame holding the armature made of cast steel?


texts: Viewing netlist on native ltspice for mac

texts:
I have a mac os x 10.9.3 and I run the native ltspice on it.  I cannot seem to access the netlist (the text file version of the schematic) on it.  Looking at the website: http://www.experimentalistsanonymous.com/ve3wwg/doku.php?id=ltspice_dirty_secrets#the_netlist

This website gives instuctions to "select menu “View” and then select “SPICE Netlist”" to view the netlist of the schematic.  However, as can be seen in the below screenshot, I have no option for "View" since it seems that the LTspice mac version has been pared down.  Any advice on how to remedy this would be awesome.  Thanks!

Edit
As @placeholder points out, I could just open it with a text editor.  (See text below)

Version 4
SHEET 1 880 680
WIRE 304 208 224 208
WIRE 640 208 384 208
WIRE 224 288 224 208
WIRE 640 336 640 288
WIRE 224 416 224 368
WIRE 416 416 224 416
WIRE 640 416 416 416
WIRE 416 480 416 416
FLAG 416 480 0
SYMBOL voltage 224 272 R0
WINDOW 3 -285 248 Left 2
SYMATTR Value PWL file=/Users/eriktafari/Desktop/SPICE/Zebra_circuit/Zebra_voltage.txt
SYMATTR InstName V1
SYMBOL res 400 192 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName Zebra_Resistance
SYMATTR Value 1.9
SYMBOL ind 624 192 R0
SYMATTR InstName Zebra_Inductance
SYMATTR Value 69.0E-9
SYMBOL ind 624 320 R0
SYMATTR InstName Load_Inductance
SYMATTR Value 5.0E-9
TEXT 24 200 Left 2 !.tran 0 500NS 0


texts: Weak internal pullups on microcontrollers and EMI susceptibility

texts:
What disadvantages can I run into when using weak internal pullups (100k) on microcontrollers? I'm wondering how susceptible lines (with only parasitic trace/component capacitance) become to EMI transients with these weak pullups.

Digital filtering with a 3-4ms window may decrease the odds of transients having an effect, but is there anything else to keep in mind on a professional PCB?


texts: Relay driver circuit with input referenced to positive

texts:
I built a standard relay driver circuit as shown in the first schematic here:

It works as expected, but I now realized my input is between the positive terminal instead of ground.

How can I adjust the circuit to handle the input that varies between positive (12V) instead of ground?


texts: RC Circuit Simulation gives unexpected transient response

texts:
I am currently trying to find the correct measure of current through the 4KOhm Resistor in a transient response after the switch is closed.

I tried to replicate the switch using AC Voltage Source with pulse.

My issue seems to be that the current that PartSim is giving me doesn't match what I am expecting for the current that flows through the 4KOhm Resistor.

Currently, Partsim returns this:

However, I thought that using the general solution, with initial current of the 4KOhm Resistor after the switch closes being 1 mA, and the final current being 2 mA, which would result in the current through the 4KOhm resistor being:

i(t) = 2-1e^(-3.75t) (RC being 4/3 KOhm)

However when I compare the two graphs (the PartSim result starting at t = 2 seconds), they don't match.

The graph based my my function:

Could anyone please point me in the right direction as to what I am doing wrong?


texts: Op-amp unity gain buffer introduces distortion in the LM386 circuit with high gain factor

texts:
I'm building a simple mixing stage, lowpass filter, and final amp in sigle supply (9v battery). I started from the LM386 circuit on the data sheet. It had a lot of distortion which was solved with the decoupling capacitor (fig.1). As a second step, I introduced an op-amp unity gain buffer to isolate the mixing stage from the filter stage and be able to calculate easily the cutoff range of the pot. I put the input capacitor (C11), matched the input pots with the input resistors (useful?), and used C13 to remove the bias, since the LM386 wasn't working with the biased signal (fig.2).
In fig.1, everything works fine: I tried many input sources and the amp works well from a gain factor of 20 to 200.
In fig.2, it works until the gain factor of LM386 becomes very high. At this point, if I open the filter and let the high frequencies pass there is a significant distortion.
The input and the speaker I used for the test are the same.
Any solution to have the circuit in fig.2 withstanding the same amp gain without distortion as in fig.1?


texts: How continuous phase variation is achieved in MSK scheme?

texts: As per my knowledge MSK(minimum shift keying) is same as FSK with the modulation index of 0.5. Now I want to understand how this 0.5 modulation index helps MSK to achieve phase continuity which was not present in FSK.


texts: Reducing current in a circuit without reducing voltage

texts:
I didn't find a solution in the other similar posts or maybe I don't understand them.

Here is my problem : I've got power supply with an output of 5V and 8A to feed 128 leds drawing 5V and 50mA each. At maximum effort they will draw 6.4 amps from the power supply so, I'm seeking a solution to reduce the output current by at least 1.6 amps.

In the first part of my project I'll only use 42 leds wich would draw 2.1 amps from the power supply, this mean that I have to divide the current by nearly 4 times.

In both situation keeping the voltage as near as possible to 5V is very important.

Thanks for your attention.


texts: Controlling a latching solenoid with the DRV8838: Is this PCB design correct?

texts:
I'm using the following Texas Instruments devices: DRV8838 (Low-Voltage H-Bridge Driver) and MSP430G2553 microcontroller. The purpose of the DRV8838 is to control a 9V latching solenoid. To test it, I have used the the DRV8838 breakout board made by Pololu. As I only need to have between OUT1 and OUT2 9V and -9V and sleep or turn on the DRV8838, the SLEEP and ENABLE pins are connected (see Table 2, page 11 on the datasheet).

I have developed a test code to open and close the solenoid and it works correctly. So far so good. The problem is that when designing my PCB, I made the mistake of not connecting pin 4 of the DRV8838 to GND so it did not work. I contacted the assembler who de-soldered the DRV8838 and connected pin 4 to GND through a wire. However I do not guarantee that everything is correct, because they had to do it by hand and the integrated circuit is very small.

The problem is that it still does not work (I use the same test code which I tested with the pololu breakout board). At this point, I don't know if my design is wrong, or if the re-soldering of the DRV8838 was not done correctly. So, I put the design of the circuit in case you see some design flaw that I'm not seeing.

In figure 1 is the schematic design of my PCB and in figure 2 is how I connected the development board of Pololu. Do you think there is a design error?

simulate this circuit – Schematic created using CircuitLab

I've attached a screenshot of the layout in case it helps to determine if the layout is correct or not. (R1 is a resistor that is not fitted because the DRV8838 already has internal pull-down resistors)

And this is a image with the 4th pin connected to GND through a wire:

If necessary I can upload the code. Thank you very much in advance.


texts: I am working on a project which requires the main usb interface to an atmel chip (32u4) to be USB-C.   In this case If I only connected the traditional usb 2 pins (D+, D-, +V, GND) to the atmel usb driver would this function properly?   I Am worried it might draw power from the device instead of supplying it (because I know USB-C can be used for charging computers on the new apple computers for instance.   I do have a transistor circuit which switches power away from the battery to the usb bus if the usb bus has 5v (and this works with normal usb) but I'm not sure if this would work with USB-C.


texts: How does this BJT biased with a diode work?

texts:
I'm trying to teach myself some basic electronics and I'm stuck on understanding what's going on with this simple NPN transistor circuit that is using a diode for bias.

I've simulated the circuit with SPICE and I get a base voltage of about 0.61 V and a collector voltage of about 0.85 V.  I also built the circuit and get very similar values on my breadboard.

It seems that the transistor is conducting, otherwise the collector voltage would be 9 V, but if it's conducting that means that there's a current through the base and thus the diode, in which case the drop across the diode should be about 0.7 V, but instead I'm getting about 0.24 V.

Something seems to be wrong/missing from my mental model of either how the diode or the transistor (or everything!) works.  I'd be very grateful if someone can help me fix that.

Changing R1 to provide different diode currents and voltage drops (measured from C-B):

1      364 mA  1.14 V
10     13.4 mA 0.75 V
100    521 uA  0.58 V
1k     45.2 uA 0.46 V
10k    4.87 uA 0.35 V
100k   568 nA  0.24 V
1MEG   73 nA   0.14 V
10MEG  10 nA   0.06 V
100MEG 1.65 nA 0.02 V


texts: Why does this circuit start at a very high value?

texts:
I have a capacitor connected in series with a current source. But the voltage remains at 1TV. Why is it not increasing?

Also, in general, if I don't want to connect the other end of the current source to Gnd, how do I leave it so that it supplies enough voltage to allow the current source to operate correctly? Can I tie it to any voltage?


texts:
I would ask for some help with noise figure calculation for circuit attached. It is front end of improvised differential probe that I would like to build. I am aware that simulators such as LTSpice can analyze noise. However, I would much more prefer to understand it.
Since all resistors have capacitor in parallel does it mean bandwidth used in noise formula [4kTRB] is based on RC?
Also, since all the noise sources create potential divider is there any special consideration, I should take adding them or is sum of square roots still valid?


texts:
I'm looking at building an audio amplifier using the following the TDA7385 amplifier IC.

Here is the data sheet: http://www.mouser.com/ds/2/389/CD00002618-109852.pdf

I am confused by the application circuit which is documented in the above datasheet, specifically where it does not mention any voltage lines (apart from the pin labels) like most other data sheets I have seen for similar chips. The below graphic should help describe my query.

Am I correct in assuming that the voltage line is not labelled directly and that the black lines are "chassis ground" ?


texts:
I'm abit confused with the different products, DC-DC converter and Voltage regulators. Can this voltage regulator be used in the same way as this DC-DC converter?
Thank you.
Steffen


texts: Why do designers use op-amps with fractional gains?

texts:
I often find designs like the following

simulate this circuit – Schematic created using CircuitLab

Where the gain is less than one (\$\ R_2/R_1 < 1\$)

Why not simply use a resistive voltage divider? Beyond the inversion (which tends to be irrelevant in many applications), a divider with \$\ (R_1-R_2) \& R_2 \$ would produce the same output with the same input impedance. Plus, it will not have an offset problem, an input bias current problem, a transistor noise problem, or a bandwidth problem (adding a couple of capacitors can make it basically flat in frequency).

Although my first instinct is to regard this as a possible instability (gain beyond the op-amp specification), I see that it is basically a stable trans-conductance amplifier with the input current given by \$\ V_{in}/R_1 \$, so that is not a valid objection.


texts: interfacing pic184f450 with 16X2 lcd in four bit mode?

texts:
I am working on interfacing 16X2 lcd in 4bit mode with  pic18f4550.The higher 4 bits (D4,D5,D6,D7) are connected to PORTA1,A2,A3,A4  , pin RAO as RS, RE2 as RW, RE3 as RE3. i am struck with below code which displays nothing .The below code compiles without any error ,but display nothing (assume no mistake in my hardware connection)?
            /*
              * File:   main.c
              * Author: tamil
              *
              * Created on June 5, 2013, 11:32 PM
             */
      #include

 #pragma config FOSC = HS  // to select external osc
// CPU System Clock Postscaler:
// [OSC1/OSC2 Src: /1][96 MHz PLL Src: /2 = 48 MHz CPU Clock]
#pragma config CPUDIV = OSC1_PLL2
#pragma config PWRT     = ON        // 62 ms waiting at start
#pragma config BOR      = ON        // Brown our Reset enabled (IMPORTANT!!!)
#pragma config BORV     = 2         // Reset level = 2,7 V
#pragma config WDT = OFF  // watch dog timer off
#pragma config DEBUG = ON,LVP = OFF // debugger on , as per pickit3
#pragma config PBADEN = OFF //PORTB<4:0> pins are configured as digital I/O on Reset
#pragma config MCLRE = ON //MCLR pin enabled; RE3 input pin disabled

//lvp should be off

 #define rs LATAbits.LATA0
 #define rw LATEbits.LATE1
 #define en LATEbits.LATE2
 #define lcdport LATA
    void Delay_ms(int ms)
 {
  int i,j=0;
   for(i=0;i<ms;i++)
    for(j=0;j<165;j++);

  }
       void lcdcmd(unsigned char cmdout)
     {
lcdport=(lcdport |(cmdout << 1));       //Send command to lcdport=PORTB
rs = 0;
rw = 0;
en = 1;
Delay_ms(1);
en = 0;
    }
       void lcddata(unsigned char dataout)
    {
lcdport=(lcdport | (dataout << 1)); //Send data to lcdport=PORTB
rs=1;
rw=0;
en=1;
Delay_ms(1);
en=0;
    }
   void dis_data(unsigned char data_value)
   {
unsigned char data_value1;
data_value1=(data_value&0xF0);
lcddata(data_value1);
data_value1=((data_value<<4)&0xF0);
lcddata(data_value1);
    }
    void dis_cmd(unsigned char cmd_value)
    {
unsigned char cmd_value1;
cmd_value1 = (cmd_value & 0xF0);    // Mask lower nibble because RB4-RB7 pins              are being used
lcdcmd(cmd_value1);         // Send to LCD
cmd_value1 = ((cmd_value<<4) & 0xF0);   // Shift 4-bit and mask
lcdcmd(cmd_value1);         // Send to LCD
    }
    void lcd_ini()
    {
dis_cmd(0x02);
    Delay_ms(200);// To initialize LCD in 4-bit mode.
dis_cmd(0x28);
    Delay_ms(200);// To initialize LCD in 2 lines, 5x7 dots and 4bit mode.
dis_cmd(0x0C);
    Delay_ms(200);
dis_cmd(0x06);
    Delay_ms(200);
dis_cmd(0x80);
    Delay_ms(200);
     }
   void main ()
     {
       unsigned char data[]="tamil";
       unsigned int x =8;
       //unsigned int y = 1;
        //unsigned int i=0;
           ADCON1=15; // to configure  all analog pins as digital i/o
           TRISA = 0; // to config port A as o/p
           TRISE = 0;// to make it as o/p
           lcd_ini();
           // LCD initialization

         while(data[i]!='\0')
       {
    dis_data(data[i]);
    Delay_ms(200);
    i++;
        }

}


texts:
I'm trying to make a super simple circuit simulation for a class, and I keep getting the same error:

ERROR -- Must be 'I' or 'V'

Here's the whole log:

**** 03/07/19 15:47:25 *********** Evaluation PSpice (Nov 1999) **************

 * C:\Users\admin\Desktop\FE\Lab1\Schematic1.sch

 ****     CIRCUIT DESCRIPTION

******************************************************************************

* Schematics Version 9.1 - Web Update 1
* Thu Mar 07 15:44:12 2019

** Analysis setup **
.DC LIN V_V1 0 0,75 10m
--------------------$
ERROR -- Must be 'I' or 'V'
.STEP  TEMP LIST
+ 20  35

* From [PSPICE NETLIST] section of pspiceev.ini:
.lib "nom.lib"

.INC "Schematic1.net"

**** INCLUDING Schematic1.net ****
* Schematics Netlist *

D_D2         a 0 D1N4002
V_V1         a 0 0V

**** RESUMING Schematic1.cir ****
.INC "Schematic1.als"

**** INCLUDING Schematic1.als ****
* Schematics Aliases *

.ALIASES
D_D2            D2(1=a 2=0 )
V_V1            V1(+=a -=0 )
_    _(a=a)
.ENDALIASES

**** RESUMING Schematic1.cir ****
.probe

.END

Here's an image of the circuit:

The sim I'm currently running is a DC voltage sweep, from 0 to 0.75, on two temperatures, 20 and 35 degrees.

Any help is appreciated
Thank you all in advance!


texts: How to Implement Clocking Wizard IP into Vivado Project

texts:
I am using Vivado (2017.4) and have been trying to experiment with the Clocking Wizard IP. I understand how to create a new IP but am not sure what to do with the HDL file it generates. I've looked at a lot of tutorials and they all seem to have different methods for incorporating the new clock speed into their project.

Does anyone know of a standard way to use the code generated by the Clocking Wizard in your project? I'm familiar with both Verilog and VHDL so any advice would be helpful!


texts:
I have MAX485 board. MAX485 is a half duplex 485 IC.  There are A&B pins.
The device which i should communicate it has the following pin diagram.

I think this is full-duplex interface. Can i communicate with it using MAX485?
Which pins of TEC3000 device should be connect to A&B pins of MAX485?
NOTE: TEC3000 waits a query like "*IDN?" and response immediately. Do i manage DE&RE pins for switching first TX mode after RX mode?
Installation diagram in the datasheet. There's no specific detail about half/full duplex usage.


texts: Hand crank DC generator - a simple dummy load that won't burn out?

texts:
I'm working on a project that allows a user to crank a hand generator while current and voltage sensors measure the output. After the user finishes cranking, software displays information about how much power was output.

This is the generator we're using: http://windstreampower.com/Human_Power_Generator.php

It seems like it should be a simple problem. However, in the current setup, I've been using the provided 12V voltage regulator and feeding power into 12V incandescent bulbs, and once the rig gets under heavy use, the voltage regulator burns out, and the bulbs blow.

The setup is like this:

Hand Crank => 12V Voltage Regulator => 12V Incandescent Light Bulb (50W)

So, I'm wondering if there is an alternative approach to this configuration (we don't need light bulbs or anything visible). Maybe feeding the crank directly into a 12V battery with some type of charge regulator and a constant drain? Maybe connecting the generator to several bulbs in series?

What is the simplest, most inexpensive dummy load we can attach to the generator, just so we can get current and voltage readings of the user's output while they crank?


texts: What mechanism is responsible for the β/hFE variations in manufactured bipolar transistors?

texts:
It's common sense that the current gain β (hFE) in a bipolar junction transistor is somewhat unpredictable, and one must design a discrete transistor circuit to be insensitive to the variation of β.

In most textbooks and tutorials, the common explanation is something similar to the following: The transistors are not coming from the same batch, so there will be variations in the manufacturing process. Some variations also exist within the same batch. If one wants matched parts, one should purchase hFE-grouped transistors. Better matched parts are selected from the same wafer, and the best possible matching is possible when transistors are on the same silicon die, i.e. an IC.

But none explained what physical mechanism is responsible for the  manufacturing variations, possibly because the question is out-of-scope of an applied electronics book. Question: What precisely is the physical mechanism for β/hFE variations in manufactured bipolar transistors? Is β/hFE an parameter that is intrinsically difficult to control?


texts: Rectifier unit in Neve 33609 Compressor Schematic

texts: Real quick question, I'm analyzing the Neve 33609 schematic (as shown below), and I can't figure out what is responsible for rectifying the AC audio signal into a DC control voltage. If anyone has an idea what components are specifically responsible for rectifying, please let me know. Thanks


texts: Properly rated components for 12V -> 500V booster circuit

texts:
I am working on a pulsed induction linear motor (aka multi-stage coil gun) as a hobby project. I'm more of an electronics kind of guy so this is an opportunity for me to become more familiar with power electronics.

The first component I need to build is a 12V->500V booster circuit to charger a capacitor bank. I found the schematic below here.

I modeled the circuit as well as I could in LTSpice and I'm seeing the expected voltages. However, the currents I'm seeing through the inductor & MOSFET are way over the max ratings. The inductor is rated for 4A (continuous) and the MOSFET is rated for 13.5A (continuous), yet both are seeing currents of 15A RMS. I am well aware how dangerous things get at voltages this high so I am very skeptical about this schematic.

I don't have the exact components in my library but I tried matching everything as closely as possible. I set the series resistance of the inductor to the datasheet value and chose a MOSFET with similar drain-source resistance (ON). I included the series resistance of the 12V battery as well.

So my questions are:

Am I being overly cautious?
Am I forgetting to model something?
If the schematic is wrong, what is the best way to reduce the current? MOSFET with higher series resistance (which I'm guessing results in higher power dissipation), larger inductor?


texts: Optocoupler to drive LEDs (maybe with transistor)

texts:
I wonder if there is some simple solution to drive LEDs powered from single rectified voltage.

Assume AC is 220 V, each LEDs is 3.0 - 3.2 V 150 mA. I reckon series connection made it simpler but not sure if the optocoupler is able to provide the current.

Adding a BJT/MOSFET at the opto output should be OK but I am not sure how to connect it. Protective part can be advised but I wish to have the basic ON/OFF function working first.

EDIT on 2019-01-28 12:34

Actually, my design consists of two 30xLEDs paths and wish to end them with an optocoupler to Neutral.

Thanks to JonRB and Transistor, they discovered several fatal issues, so i retry and hope this would make more sense.

Refer to this active current limiter, i wonder if the optocoupler can attach to it.

Now, with 60 x LEDs (3.0 - 3.2 V 150 mA):

100k Resistor to turn IRF740 FET On.
8 Ohm Resistor with BC817 BJT to limit the current to ~150mA.
Optocoupler PC817 would shutdown both transistors.

I think IRF740((400Vds) should be capable of AC peak voltage and current limiter can save the LEDs from destory as well.


texts: What is the impact of package on SMD capacitor

texts:
Most of electronic component exist in different package for different reason, it can either be power rating, reachable value, power dissipation... As far as I understood, the size of resistor principally impact the power rating.

So, a 1kΩ resistor in a 0805 package will have a different power rating than a 1kΩ resistor in a 0603 package.

If the package has an importance in the selection of resistor, is it the same for MLCC capacitor?


texts: Does Arduino use step down voltage regulators?

texts:
I am designing my first "permanent" Arduino application, and I would like to know if the voltage regulator is linear or step down.

The reason I would like to know is because I am currently powering the prototype with an 11.1V 1300mAh LiPo battery.  If it uses a linear regulator the efficiency would be, best case, 30% and 46% for the 3.3V and 5V regulators respectively.

I would much rather add my own step down converter to drop the voltage to 5V and power via USB port if that would be much more efficient.

I'm not sure if the different Arduino models have different parts or not, but for this application I am using an Arduino Leonardo.

Here is the schematic of the Leonardo.


texts: Is it really possible to obtain a AC signal (voltage/current) from a pure DC signal?

texts:
As one can see that there are circuits in figure 1 which consists of a AC voltage source with \$V= V_m sin(2\pi f t)\$ ,a diode and a resistor.

Now, if I do \$V_{o1}+V_{o2}\$, I will get same bidirectional AC signal, IE. \$V\$

But if I do \$V_{o1}-V_{o2}\$,
I will get a unidirectional AC which is also can be called as DC signal(?).

Now, I want to know that is it really possible to obtain an AC signal ( Voltage/current) from pure DC (IE \$f=0\$) input signal. If yes, what could be the circuitry in the question box of figure2?


texts: How is possible that with same Ibase there is more than one Vce?

texts:
Ok guys, look at this picture:

How is possible that with the same \$I_{\rm base}\$ we have more than one \$V_{\rm ce}\$?


texts: What is the best program for designing circuit diagrams

texts:
I am trying to find a free program for designing circuit diagrams. Is Autodesk's Eagle program any good or is that just for designing PCBs. I've had a look at Microsoft Visio but I don't really want to spend $20 a month. I'm looking for a program that is for making basic circuit diagrams that have symbols.
Thanks.


texts:
(initially using STM32H745 w/ CubeIDE) uSD card was working, but was getting some fifo underrun issues? so I started switching rising/falling edge, and flow control and stuff. Now the card doesn't work at all in any laptop, with an ESP32 over SPI that it used to work with, all yield nothing. After switching everything back to default I'm getting back CRC errors on the STM32 on the attempt to find SCR to switch to 4 bit mode. But still no luck when I switch in the ESP32, I'm getting a failure to go to idle state. Sadly I don't have a great way to debug the ESP32, just print statements in user code.
I am worried that I may have accidentally run the STM32 code with the "transceiver" option, which switches the card down to 1.8v. Doesn't explain why it wasn't working before I started messing with things, but would explain it now. Is it possible that in switching to 1.8v, and still giving it 3.3v signals, I fried something? No pins are shorted to each other and the card doesn't get hot, but it sure doesn't work.
Thank you.


texts:
I am using a MCP73844 dual cell Li-Ion charge management controller to charge a pair of LIR2032 cells, which are rated at 45mAh.

I have breadboarded the circuit according to the schematic in the datasheet, however I am using a sense resistor of 2.8 Ohms to achieve a constant current of ~40mA so I do not exceed the 1C rating of the cells. The only other difference is that I am using an NTD2955 as the driver MOSFET.

I have connected a 10v input to the charging circuit, and a depleted battery, and I am getting unexpected behavior. When powered up, I experience the following.

1 - The circuit draws ~2mA for a couple of seconds. As expected in the charge qualification phase.

2 - The status LED illuminates and the circuit draws ~40mA, (sometimes, and only for a few of seconds)

3 - This quickly decreases to ~20mA, and then continues to slowly decrease down to ~12mA (Presumably as a result of having transitioned into the constant voltage charging phase)

4 - After some time has passed, the current draw drops to 0mA, and the status LED turns off, indicating the charging has finished, but after a few seconds, the current jumps back up to ~12mA, and the LED comes back on. This cycle seems to be repeating indefinitely.

5 - The battery voltage ends up being only 7v

So, the questions that I have are:

1 - Why is the constant current phase not always happening, and when it does, why does it only last for a few seconds?

2 - Why does the charge cycle keep restarting?

3 - Why does the battery not reach the expected 8.4v?
Cheers.


texts:
I am planning to build this circuit below as a electric guitar amplifier.

Source
And I also would like to add

gain control
overdrive channel

to existing design.
I have simulated this circuit on LTSPice as follows:

I have installed 10k potentiometer between gain pins. It worked fine
on simulation but is it an effective way to control gain?
Other question is I
would like to add an overdrive channel to this amplifier circuit
which will clip the input signal after amplification. For this I have
tried placing two opposite directioned diodes parallel to bypass 0.05
\$\mu\$F capacitor but it failed. How could I add an extra overdrive
channel with overdrive control?


texts: Is there any way for me to check that my Thevenin equivalent is correct?

texts:
I understand how to find Thevenin equivalents when the are independent sources in the circuit, but once dependent ones are introduced, I get a little nervous.

Here's what I did:

I found the open circuit voltage which is equivalent to voltage Vb relative to ground by doing the node voltage method. I found Vb = 10V.

Then I considered the circuit in the short circuit condition in which an addition connection from node B to ground is made. In this condition, I found the short circuit current to be 4mA.

Thus, the Thevenin equivalent resistor is given by 10V/4mA = 2.5 kOhms. Therefore, the Thevenin equivalent circuit is a 10V voltage source connected to a 2.5 kOhm resistor.

How can I check to see if my answer is correct though?


texts:
I have 12v peltier modules that I wish to run as a heater and ac unit but they have have a limit of like 27ma I have tried plugging then directly into a 2a car cigarette lighter adapter and they instantly got scalding hot on both sides so I figure it must be the amperage flow
How would I go about reducing the current enough to let this run continuously on 12v without risking damaging more cells in the process...

The intent right now is for heating a van but would hate to destroy the cooling functions of it...I do plan on mounting a cpu fan to this to dissipate heat as quickly as possible.I have successfully used these running off an 18650 cell directly with a cpu fan for about 1hr as a personal body temp control in the summer, only being moderately too cold for continuous direct contact with the skin to be comfortable but kept me feeling good in 100¤ weather when kept on my wrist.

Are these typically only run by some sort of smart switching mechinism in conjunction with a thermostat or what?


texts: Is it possiple to discharge the positive charge only from a capacitor and maintain the negative charge?

texts: Is it possiple to discharge the positive charge only from a capacitor and maintain the negative charge ?


texts:
I have a Hierarchical design in Altium and after compiling I am getting and error about Duplicate NET name wire.... I searched on Altium articles and here on electronics.stackexchange but I can't understand why I am getting the error. Here is a picture of it:

And here is my project settings:

I know I have 2 ports with the same name RX communication that is the port Altium is complaining about but I have other ports with also the same name:

And I am only getting a Warning (and I think I shouldn't be getting that warning). Can't I have ports with the same name in the hierarchy?


texts: Transmit electrical signal across human body

texts: Is it possible to transmit and receive an electrical signal SAFELY using the human body as a medium? For example, I would have a transmitter of some sorts in my left hand, and a receiver in my right. And if it is, are there any commercially available transmitters, if not, any home made assemblies that can be made. Unlike this question: Data transmission through the human body, I'm looking for an actual module that I will be able to use. And if data is too much to be transferred, can I make it so that at least I can transmit 1 bit across (on or off), much like a switch?


texts: Designing custom LED bar as a replacement for standard headlight

texts:
I own an Opel/Vauxhall/Holden astra produced in 2000. Currently it is fitted with standard halogen headlights, however I am looking to improve the looks of the car by customizing the headlights. I am looking to install an LED light strip inspired by the latest Audi models. The catch is that I am not able to take out the entire headlight part, and open it up since the car is heavily used. Therefore I opted for a simpler solution. Here you can see the way the headlights are arranged in my car:
As you can see there is a rather large hole for the DRL, and I believe I can make an LED bar, plug it in the connector where now the DRL is, and manage to manuipulate its way through the hole. Here's what it should look like(made this in photoshop):

I do have several requirements:

The LED bar should be continous
It should also be used as a blinker (pulsating, just like, you guessed it, Audi)

I intend to use a standard RGB, adressable LED strip, fitted into a translucent plastic pipe to act as my LED strip. However, the light from the LED strip would be concentrated, and not continous, so the plastic pipe would need to be sandpapered to achieve diffusion of light. The plastic pipe would be bent to proportions by being previously heated in an oven and being filled with sand beforehand, as to avoid cracking when bending to place. I would use a cheap headlight bought at the scrapyard to work on the fitting, as not to work with the actual headlights on my car. However, I am not sure where to place my control circuit (micorcontroller and LED driver)? The PCB should be sealed  in a box, with only the connectors for the led strip and the car connector accessible. It needs to be able to fit though the hole. The plastic pipe would be attached to that box.

I am not sure which LED strip to chose, so if you have any suggestions they are welcome. Also, what other ways would you suggest to achieve the diffusion of light?


texts:
I'll work for the first time with a Hockey Puck type SCR with a high di/dt application. So far I've mounted it properly, with the proper clamp and heatsinks. Now I'm concerned with the gate drive, since this article is saying the following:

And also:

In respect to the second quote, I see that I have to apply a sufficiently high driving voltage, but I don't know which paramater in the datasheet I should look at.
This application note shows a graph of the gate current with steeply rising on-state anode current:

I assume the curve B occurs because there's a reverse gate-cathode voltage that's opposing to the applied one. Is that correct?
The datasheet of the device I'm working with has the following paramaters for gate:

As far as I understand, I should apply at least 3.5V (Vgt) to gate-cathode in order to trigger the SCR. But since I'm working with high di/dt, I should apply a higher voltage, but not higher than Vfgm (20V), as the previous article explains (I'm not sure if I got it right):

So, how high should be the voltage applied?
Looking into another thyristor datasheet, with similar ratings, I've found that:

In the datasheet, it doesn't specify the Vfgm parameter, but it says that I should apply at least 30V in the gate. So, did I misunderstand the Vfgm parameter? Is that the maximum reverse gate-cathode voltage that occurs during the high di/dt anode current? And so decreases the gate current? If so, I must apply at least 20V.
Finally, is there any problem if I apply a constant current to the gate instead of this shape of the last image? Even if it's constantly strong (say, constantly applying Igm)?
I know that there are some commercial gate drivers like this one but I'd like to use my own, using optocouplers.
The diagram of my circuit is similar to the following:

simulate this circuit – Schematic created using CircuitLab


texts: Crystal Oscillator with OP AMP, or Oscillator circuit built with Crystal and Op Amp

texts:
I've been trying to make a Oscillator circuit with a Op Amp and an crystal (7.68 MHz)
Similar to the one in the schematic below, but for a 7.68 MHz crystal.

Is this possible? (it says low freq only). If so, what modifications do I need?

Ideally I would just make a Pierce Oscillator circuit. However I do not have any NOT gate logic chips on hand, but I do have Op Amps


texts: What do pull-up and pull-down resistors do in an ethernet PHY?

texts:
I've noticed that most ethernet physical layers (i.e. the interface between the MAC/network and e.g. an RJ45 connector with magnetics) have pull-up or pull-down resistors on the TX and RX lines. For example, the reference schematic for the Wiznet W5500 has a pull-up on the differential TX line and a pull-down on the RX line. These have the effect of making the "virtual ground" between the TX and RX differential channels either +3.3V or GND. In addition, the central tap of the TX line into the RJ45 magnetics is pulled up, and the RX line is pulled down:

I've seen other schematics that do the pulling up or down differently - for instance this design pulls both the TX and RX lines down.

What purpose do these resistors serve? And why in the case of the W5500 is the RX line ac coupled (by the capacitor in series) and not also the TX line? I guess the answer is something to do with signal to noise, but I don't understand the reasoning.


texts: differential and inverting op amp problems

texts:
I am trying to offset a triangle signal of 4 volts peak to peak by around 10.2V up with only a +20 volt supply voltage, I do it using a differential amplifier but the output signal is inverted so I tried to invert it back by using an inverting op-amp but instead of just inverting the signal it reduced the output of the voltage to a few millivolts with a very low peak to peak value and move it back to the origin point. Any idea on why this happens and how to solve it?

Below is my schematic diagram, Vin is my input signal and Vout1 is the offset that I want but only being inverted instead, and Vout2 is what happens after it passes thru the inverting op-amp


texts: In the I2C Voltage translation circuit below, does it matter which side (SDA1/SCL1 or SDA2/SCL2) is the master and which side is the slave?


texts:
Soo.. I've been testing my designing limits, trying to learn about Serial Digital Interface, and building a simple reclocker with TI IC's. And now I've run into a small speedbump with the output from the cable driver IC, LMH0307.

As you can see in the picture below (Taken from the LMH0307 datasheet), both SDO and it's complement !SDO are apparently being connected to coaxial cables and transmitted. This seems really weird to me, as SDI is designed for transmitting over a single cable. And as far as I know, it's not supposed to be connected to the shield, because that's straight-forward GND or floating on one side (again, AFAIK), and !SDO is not the same as a return path for SDO.

And when I look at the input of the cable equalizers in the same series (the LMH0394 etc, see below), I see that !SDI is connected to GND, through a cap and a resistor. In other words, this IC does not bother with the complement input at all.

So, what is the best practice on terminating the complement output from the cable driver, when I obviously can't/shouldn't do what's in the datasheet?

-- Thanks, Araho


texts: Why is the Ampere the only SI fundamental unit for electricity?

texts:
According to wikipedia the only SI fundamental unit for Matters Electrickal is the ampere. Don't you at least need the ohm to derive anything? How would you make volts from only amps?

Perhaps I misunderstand the meaning of "fundamental unit".


texts: Voltage regulator using bipolar NPN transistor

texts:
I came across a circuit, and I got some questions about it.

What is the reasoning behind using the NPN-transistor?
What part of the circuit draws the most current?


texts:
Question: I need to increase the capacity and data lines of a EEPROM board using decoder and/or basic logic gates. The EEPROM is Hitachi HN58C1001. it is 128K by 8 bits. Task is to make it 1M by 32 bits.
My guess is to use decoder (3to8) and connect it to CE pins of 8 of this boards, I'll give me 1M of data but also 64 data lines, not 32...
What is the correct way to do this?


texts: Is it possible to limit the address space accessed by a master using the Avalon-Memory Mapped bus?

texts:
Provided that a slave is shared by multiple masters which connect to the same slave's Avalon-MM slave port in Qsys, is there a way to control the read/write access to certain address locations inside the slave for the different masters? This would require the slave knowing which master is accessing at a given time. I assume this might be possible in AMBA buses but is not possible in the Avalon-MM bus. Is this correct?
The basic idea is that the slave has the same Avalon-MM slave port being shared by multiple masters, but some address locations can only be modified by certain masters, also the value read from certain addresses depends on the master accessing it.


texts: Getting output voltage after connecting snubber across Triac

texts:
i am controlling Ceiling fan through Panasonic AQH2332A SSR, but getting voltage across fan terminals even if SSR off. The voltage across terminals is about 35v.

i tried to reduce snubber capacitor to 0.01uf, this reduces the voltage to 18v. How can i reduce voltage further.

1> Further reducing capacitor can increase over voltage across SSR, i guess.

2> increasing resistance of snubber doesn't affecting voltage

simulate this circuit – Schematic created using CircuitLab


texts:
I am working on a performance art project in which I want to track the position of juggling balls as they are thrown in the air. The idea is to output a sonification of the ball's position in the air as an alternative to seeing the pattern being juggled.
Note that because this is not scientific, I am only looking to generate any output which changes intelligibly in response to juggling patterns.

I think that having a beacon/transmitter/receiver resting on the floor would be a good idea, making all the calculations relative to this beacon. The props would be a maximum of 2-3 meters away from the beacon when at the top of a throw.

Props being juggled

Ideally balls, less than 100mm in diameter. That being said I could adapt to using larger ones, or to use juggling clubs instead.

Already tested approaches

Bluetooth accelerometer data from wii controllers embedded in juggling clubs. This didn't produce very interesting results because the acceleration hardly changed once the club was in the air.
Computer Vision detection of colored juggling balls. This approach created very interesting results but requires a large amount of setup, space, and was very sensitive to lighting conditions
Mounted infared sensor detecting closest object. The beam was too small to accurately pick up small juggling balls at a distance

Ideal results

Below are two examples of suitable final results

Wireless distance detection from the props to the beacon (digital)
Props interfering with field which is detected and then output by beacon. (analog)

What suggestions do you have about solutions to this problem?

It could go one of two ways: 1) Each prop generates position data and outputs its own audible output through speaker 2) Each prop interferes with some kind of field from the beacon. All output comes from a speaker connected to the beacon.

Thanks in advance, Max

PS I am aware that this question is very general. I am open to all suggestions about different approaches to the problem.


texts: Effects of impedance mismatch on RF signals from antenna

texts:
I'm building an antenna array that operates at high frequencies (around 2 GHz).

I want to use a SDR dongle that has a 75 ohm input impedance as receiver, I've also bought the coax cable, a 4 way adder and a line amplifier that have 75 Ohms as well as the Antenna.

The problem is I need to connect the antenna to a Low Noise Amplifier (LNA) and the LNA to the adder and eventually to the SDR. but they only sell 50 Ohm input/output impedance LNAs.

My question will this have a huge impact on my signal? what is the effect of this mismatch? is reflection going to be really significant?


texts: Calibrate AC measuring channel using DC input

texts:
I've made a AC voltage measurement board, the structure is simply:

input -> gain -> block capacitor - ADC.

Now I want to calibrate it. Because the input may be sub mVs, so I'm considering calibrate it by using a DC input (sure, I need bypass the block capacitors). And I've heard someone said it's convenient to calibrate AC channel using DC input, because a DC can be measured more precisely. Is it true? How the commercial DMM's  AC measurement channels are calibrated, particularly at small signal input?


texts:
I'm trying to speck out a heat sink for a 3 phase rectifier. The rectifier consists of 3 individual rectifier blocks. I need a heat sink for each block.
The rectifier is for a generator and all the specs I have to work with is that the DC output will be 468VDC at 112ADC.
I will use 3 individual heat sinks. How do I calculate the power dissipated per individual block?

Individual block.

The best i've been able to come up with is that at 112A a diode will drop about 2v which will give a power dissapation of 224W but that seems too high because that is peak conduction and will only spend a small amount of time there.


texts:
I would like to use blender PSU board.

To power motor of the blender. Whole blender consists of this this board, control board (which blew up) and motor itself. I am now trying to hack this board to output power and use arduino (with some mosfets) instead of control board.

I know this is some kind of AC to DC converter (the motor itself is DC, I powered it with my Lab bench power supply and it spinned). I tried to trace all connections with multimeter and found datasheet (LNK362-364) for chip between diodes (left bottom on the picture). All I was able to get was a DC voltage jumping from 2V to 30V, measured from LNK's pins (pin 5 and 7). I imagine that is rectified sine wave (but I don't have oscilloscope to prove it). I wasn't able to get stable DC from this board, I guess I have to plug somewhere around these caps, but where to get reference point? There is transistor under the white goo, I guess it could serve a safety feature for the board.

The pins on the top was where the control board was connected. I tried to measure, connect them, but with no luck. I am kinda lost now, where should I go next, to obtain power from this little device.

One more photo from the back:


texts: My BJT audio amplifier circuit isn't working as expected

texts:
I am trying to design an audio amplifier circuit using BJTs.
These are the requirements of the circuit:

Input signal: 50-100 mV (It's the output of my iphone's microphone.)
2 W - 4 ohms speaker
There is no requirement for DC voltage source. I can choose to feed enough my circuit.

Here's the circuit:

I'm having troubles with impedance matching.
Can anyone tell me how to calculate the input impedance, output impedance and the gain of the power amplifier stage? I want to calculate exactly to ensure that the voltage is not dropped a lot on the output impedance of the CE stage and the power amplifier stage. In other words, I want to maximize the voltage dropped on the 4 ohms Rload. My calculations seem to be wrong, which result in 0.2 V peak at the 4 ohms Rload, while the expected voltage across 4 ohms Rload is 4 V peak and the maximum current should be 1 A to get 2 watts on it.


texts: Replacing 27C256 with 28C256, how to wire /WE?

texts:
I am looking to replace a 27C256 compatible maskRom (nintendo Nrom PRG and CHR if it matters) with a socketed 28C256 in order to make a development cart.

It looks like the pin for A14 is in the wrong place and will need to be wired to hole 27

/WE(pin 27) is active low on the 28C256

Can I just float pin 27(leave unconnected)? Or would I connect /WE to +5v?


texts:
I thought as a first exercise in op amps, even before setting up a feedback circuit, I would determine the gain of the raw op amp.

I tried with an LM324 and an LM358 which should be essentially the same.  I assume the input currents are really small, I believe when I glanced at the data sheet it was nA.  So I used a 4 AA power supply with 6v (not fresh batteries).  To get an input signal, I created a voltage divider from a 1M and 1K resistor (V0).  I can measure .0056mV with the meter.
Then I put a second divider of 1M and 1k across the 1k (labelled V1), which should give roughly 5.5 uV though I can't measure that.

For the LM324, pin 2 is V-, pin 3 is V+, and pin 1 is Vout.
If I set pin 2 and 3 to 0V, essentially 0 comes out (some small noise as expected).
If I set pin3 to Vcc, 4.8v comes out (roughly 1.2v drop through the amp).

But when I set pin 3 to the first stage voltage divider, 5.6mV, the output voltage does max out, but I notice the input voltage does change a bit.  That one I didn't record, see below for more.  Troubling, considering there should be essentially no effect from the op amp.  Worse, once I put in the 5.5uA signal, I expected to see something like a gain of 850,000 or 900,000.  I swear I did this before, and had planned a lab on it.  But now I can't get this repeatably.  When I tried again, this time replacing R3 and R4 by 100k each, V1 changed from 2.9mV to 3.2mV  I don't see how that could possibly happen.

I tried again with positive feedback mode, I can get a gain of 101 using a 100k and 1k resistor.  I used 1M and 1k, and then across the 1k, a second voltage divider with two 100k.  Again, voltage V1 is 2.9mV but when plugged into the + side of the op amp it changes, only to 3.2mV, but I wouldn't have thought there would be any change at all.

I'd like to know whether I am simply using the op amp out of the range in which it behaves well, whether it should work in which case I will try to double check my power supply, my wiring.  The voltage is still 6v, and the LM324N should be good down to 3V, so I can't believe it's the power.  This whole experience is making me doubt my sanity.


texts:
Adafruit Trinket 5v
https://learn.adafruit.com/introducing-trinket/pinouts

I'm really sorry to bother you all with my ignorance but I completely suck at math and couldn't figure out the equation for Ohm's law. I'm at a crossroads and don't know where to turn. This Adafruit Trinket will only produce 20 milliamps from GPIO pins. I need to add a transistor to one of the pins I've programmed to push 20mA to 7.5v.

Per Adafruit's description:

  All the GPIO pins can be used as digital inputs, digital outputs, for LEDs, buttons and switches etc. They can provide up to 20mA of current. Don't connect a motor or other high-power component directly to the pins! Instead, use a transistor to power the DC motor on/off

I'm not trying power a motor. I'm trying to power a self-made cup warmer made from kanthol wire and polymer clay. Can anybody advise what transistor will boost 20 milliamps to 7.5v? Your assistance will be greatly appreciated.

Thanks Again!


texts: I have a 6V to 20V input I want to convert to 12V at 1 amp maximum continuous current. The output must be the same polarity as the input, so that pretty much means a SEPIC is the only way to go... However, I've been looking around and all solutions I've seen thus far require many components and a lot of surface area; I'm looking to minimise surface area as far as possible, and to do this I don't mind sacrificing a bit of efficiency. Does anyone have any suggestions?


texts: Orthogonal Frequency Division Multiplexing (OFDM)

texts:
I am not a professional but I'm trying to figure out how OFDM works. It is clear to me that OFDM works with closely spaced subcarriers with orthogonal frequency. Each subcarrier gets modulated with a conventional digital modulation scheme, let say for the sake of this example QAM-4.

Lets say that I have a stream of data 0101 1100 1111 0100 broken up in four parts to be send with OFDM.

What confuses me is this. I know that QAM requires two carriers and uses symbols with two bits. Does this mean that fow every broken part of data stream, OFDM will actually use two subcarriers?


texts: Duty Cycle Demodulation Distortion Correction

texts:
I'm trying to come up with a system which will reliably convert an arbitrary input to a PWM signal, and then back again. The comparison signal is a 50kHz sine wave, and the result is fed through a window comparator to reject any partial signals.

I've got the duty cycle conversion functioning perfectly, however I'm having difficulties demodulating the signal accurately.

In the picture below the green trace is the input, the blue and red traces are from successive RC low pass filters.

There's a fair amount of distortion. Looking at the FFT it looks like it's being caused by other harmonics.

I'm wondering what I can do to produce a much more accurate output. I was hoping to have a fairly wide usable frequency range with this system. Adding more poles to the output just creates additional harmonics.

Thanks!
EDIT: Result using a triangle as opposed to a sine wave, thanks to tomnexus.


texts:
Good morning,

I am still learning, and often I see a lot of datasheet value that I dont understand. For this case specifically, what is the difference between output current and supply current?

The data sheet is here http://assets.nexperia.com/documents/data-sheet/74HC_HCT08.pdf

1)The ratings on page 3 list the supply current as 50ma, but the supply voltage is -0.5 to 7 volts. Does this mean I must limit the current to pin 14(in this case) to 7 volts, and the current no greater than 50ma?

2)Regardless of voltage, as long as it is within the allowed range(-0.5v - 7v), the IC will out put Vcc at +- 25ma at any of the output pins?

Thank you


texts:
I am trying to control a BLDC motor without sensors using BEMF method and zero crossing detection. I managed to detect the zero crossing point but I am not sure if it is correct. I read that the hall sensors signal and BEMF ZCP have a phase shift of 30 degree.
I measured the output of one hall sensor and the zero crossing point for the same phase (B):

How can I be sure that I really detect the zero crossing point ? Right now the motor runs in open loop, first I want to be sure when to switch to the next state because if I do it wrong it might burn the MOSFETs.


texts: How do I remove this ring around the via?

texts:
I am wondering what this is this ring around the via and how do I remove it?
I am using Altium 20.


texts:
The boolean function I want to convert is: F = xy' + yz'

I will first convert it to canonical form:

F = xy' + yz' ------> (1)

= xy'(z + z') + (x + x')yz'

= xy'z + xy'z' + xyz' + x'yz'

= Σ(2, 4, 5, 6) = π(0, 1, 3, 7)

Now, F' = π(2, 4, 5, 6) (Is this statement correct, why not?)

= (x + y' + z)(x' + y + z)(x' + y + z')(x' + y' + z) ------> (2)

I thought I had converted the function to POS form, but when I checked the truth tables for (1) and (2), they are the complete opposite. Truth table for 1
Truth table for 2

Why is this incorrect? According to this answer, I'll have to complement the input function twice to convert to POS form. But this seems very counter-intuitive because if I complement a function twice, will I not get back the original function?


texts: Modeling a real transformer: why is the excitation branch in parallel?

texts:
In the above diagram, the parallel branch containing Rc and jXm represents the excitation branch.

My question: I just can't seem to understand why the core loss current and the magnetization current had to be modeled using a parallel branch?


texts:
I'm doing a circuit that controls a charge for TRIAC, with zero detection. Whenever I tested the circuit, regardless of what I was sending from the microcontroller, TRIAC always sent all the current to the load.

When I looked at an oscilloscope for the detection of zero, I realized that it only detected zero once in a complete wave (not two). I researched the component I was using and noticed that the 4N35 only has one LED, so since I was not rectifying my wave before, it was only detecting the positive part of the wave.

I can not find any integrated circuit that has two LEDs in my city, so I decided to change the software. This is the function I have been using when it picks up the interrupt:

 int dimtime = (65*dimming);    // For 60Hz => 65
  usleep(dimtime);    // Wait for start TRIAC
  digitalWrite(AC_LOAD1, HIGH);   // Start TRIAC
  usleep(8.33);       // Delay TRIAC
  digitalWrite(AC_LOAD1, LOW);    // Turn off

This 65 came from:
1 full 60Hz wave = 1/60 = 16.6ms
It will reach the zero point in: (60Hz) -> 8.3ms (1/2 cycle)
8,3ms = 8300us
(8300us - 8.33us) / 128 = 65 (Approx) (and 128 was the amount of steps I split)

In my country, i have 220V and 60Hz for AC.

My question is: how can I change my code to control TRIAC by detecting zero only on the positive side of the wave? It is possible?

With this code by now, when i send 128, it simply lets the wave pass completely, and when I say 2, for example, the output wave goes out all "wrong", without following the AC wave.


texts:
I've searched online and found wire gauge calculators but I still can't seem to find a reliable answer.

What gauge wire do I need to carry 36 volts (DC) at 5 amps (peak) for 4 meters?

This cable will be used for a video arcade machine light gun, and the power drives a solenoid which is only active for a few milliseconds.  The current draw should be zero until the light gun is fired which quickly activates a solenoid and then stops but the gun can be fired in rapid succession... (which can cause a fairly steady (?) draw of 5A to continuously activate the solenoid)

Would an 18 AWG wire be sufficient, or do I need to go bigger?  ...or can I go smaller?

Voltage drop isn't too important because the solenoid circuit can use 24 - 36V and will be powered with a regulated 36V power supply.  I just don't want the wire to heat up or catch on fire, heh.

edit: I'm looking to use a stranded wire for flexibility (in case that matters)...

edit: This is related to a previous question, where a cable length of "10 to 15 feet at the most" is mentioned.


texts: In a MOSFET if VGS is kept constant then VDS is increased till entering a saturation mode, a pinch-off accrue near the drain. This indicates that the E field between the gate and the bulk is not evenly distributed due the increasing positive potential at and near the drain region. This phenomena will also affect the resistivity of the channel. Does this means that the resistivity near the drain have the highest value? If so the dissipated power is mostly generated near the drain?


texts: Can I use MOSI, MISO, SCK pings for reading input in AT89S52?

texts:
I am doing a custom keyboard for my project. It has totally 22 keys.

I am using AT89S52 microcontroller. I have allocated P0.0 TO P0.7 AND P2.0 TO P2.7 AND P1.2, P1.3, P1.4 (totally 19 pins) which are completely available for I/O operation.

I have 3 more keys to read input. So, in this case can I use MOSI, MISO, SCK pins which I use during flash programming.

And even INT0, INT1, T0, T1 if I require more inputs in future?


texts: Making a positive edge clock pulse with a button?

texts: Is it possible to have an input, say a button, that does one positive edge clock pulse? So I want to press this button once and it does a 0->1->0. I can't think of anyway to do it because it changes twice with one input.


texts: Verilog : Are there any good sites contains open source projects?

texts:
i was wondering if there are any good sites who encourage open source in the fpga world using code in verilog or vhdl?

since the open source community is very powerful and all the big firms contribute to it with great modules in software, is there any similarity in RTL codes?


texts: PCB layout ideas for multiple voltage power lines

texts:
I am new to designing PCB boards.

I have been working on a data acquisition board and it seems that four layer board will be correct way to go about it.

But there are a lot of different voltages required for different components.

These are mainly

+15V,
-15V,
+7V,
+5V,
-2V,
2.5V, etc.

I can't figure out a strategy on how to get these voltages, and how the power plane fits into the picture.


texts: Which current types can be measured with a Shunt?

texts:
Which of the following current types are typically measured with the help of a shunt resistor?

DC
AC
Impulses (4/10 us, 8/20 us, longer impulses > 500us?)


texts:
I am trying to learn how to use interrupts for a project using an Attiny85. I have written a simple program from what I have learned from tutorials. However when I try to build the program in Atmel Studio, I get this error message:

"Error  2   static declaration of '__vector_1' follows non-static declaration"

I do not understand what this means or where my mistake located. I've searched all around for answers but I haven't found the reason for the error yet. Here is my code:

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>

int main (void)
{

    DDRB = 0b11111011; // set all pins to be output except PB2 to prevent false signals

    GIMSK |= (1<<INT0); //set PB2 to interrupt
    sei();

    MCUCR |=(1<<ISC00);  //set to detect any change as interrupt
    MCUCR &= ~(1<<ISC01);

    ISR(INT0_vect)

    {

    // dot
    PORTB = 0b00001000;
    _delay_ms(500);
    PORTB = 0b00000000;
    _delay_ms(200);

    // dot
    PORTB = 0b00001000;
    _delay_ms(500);
    PORTB = 0b00000000;
    _delay_ms(200);

    // dot
    PORTB = 0b00001000;
    _delay_ms(500);
    PORTB = 0b00000000;
    _delay_ms(600);

    // dash
    PORTB = 0b00001000;
    _delay_ms(1000);
    PORTB = 0b00000000;
    _delay_ms(500);

    // dash
    PORTB = 0b00001000;
    _delay_ms(1000);
    PORTB = 0b00000000;
    _delay_ms(500);

    // dash
    PORTB = 0b00001000;
    _delay_ms(1000);
    PORTB = 0b00000000;
    _delay_ms(600);

    // dot
    PORTB = 0b00001000;
    _delay_ms(500);
    PORTB = 0b00000000;
    _delay_ms(200);

    // dot
    PORTB = 0b00001000;
    _delay_ms(500);
    PORTB = 0b00000000;
    _delay_ms(200);

    // dot
    PORTB = 0b00001000;
    _delay_ms(500);
    PORTB = 0b00000000;
    _delay_ms(2000);

        }

    while (1) {

    }

    }

If anyone could provide assistance it would be much appreciated.

Thank you,

-David


texts: Small feedback capacitor in photodiode amplifier

texts:
I'm designing a transimpedence circuit with a photodiode.

Op-amp: LTC6268 (GBW = 500MHz)
Photodiode: SFH2700 A1 (C_j = 4.6pF, max current = 1.5uA)
Required bandwidth: 2MHz

Using the calculation from this question, I figured out that my R_f = 1.33M => C_f <= 59fF, which is super small. Should I install some 0.2pF capacitors in series there?
Or any other recommendations?
Here is my schematic:


texts: Creating a keyboard with a microcontroller, do I need an input pin for each key?

texts:
I am planning to implement V-USB with an ATMega8 microcontroller. I am interested in implementing an HID device; more specifically, I want to try and make my own simple 26 key keyboard (each corresponding to a letter of the English alphabet).

This may be a stupid question, but do I need an input pin for each key I implement? In other words, will I need to use a microcontroller that has at least 26 I/O pins? Or is there another way to do this?


texts: Matched resistances at inverting and non-inverting diff amp inputs in power amps: why?

texts:
The following is a common input and feedback structure in audio power amps:

simulate this circuit – Schematic created using CircuitLab

What I often see is that the resistors are chosen such that \$R1 + R2 = R3\$.

Why?

Of course, I understand what that does: equal resistances in the + and - circuits balance the voltages due to the input bias currents (typically in the microampere range for BJT input stages).

But thanks to C2, the amplifier has no gain at DC unity. So the DC offset at the output caused by input offsets is tiny.

For instance, if R1 + R2 = R3 = 39K, the voltage across the resistors is only 39 mV due to a 1 uA bias current.

If only about that much offset appears at the output, it seems insignificant in an amplifier that can swing +/- 50V.  The speakers won't dissipate much heat due to this tiny voltage. Why bother with it?

Is there some deeper reason for wanting to null the offset much more precisely, or just it just "neatness counts" esthetics?


texts: Calculate the value of an inductor using an RL or LC circuit

texts:
Given an inductor of an unknown (though magnitude-estimatable) value, and a resistor of precisely known resistance, how can one calculate the inductance of the inductor?

Tools I have at my disposal:

Oscilloscope (both digital and analogue)
Signal generator (can make any waveform up to around 20KHz)
DMM

Some things I have noticed during my experimentations:

If I apply a sine wave I see a phase shift.
If I vary the frequency I see different levels of attenuation.
If I apply a square wave I see sharp peaks at the rising edge and sharp troughs at the falling edge.

Ultimately I'd like something I can sample in some way with a microcontroller - be that with analogue inputs, the use of timers / input capture / output compare, etc, or whatever other means, to then calculate the inductance in use.

I know how to do phase measurement of digital signals, but can this be adapted to measuring the phase of a sine wave?

Alternatively, could I use an LC circuit and use the resonant frequency of that combination in some way?


texts: How to use Arduino Uno to Process Signal from Leuze LV463 Optical Fiber Sensor

texts:
I'm attempting to use an Arduino Uno to receive the output from a Leuze LV463 Optical Fiber Sensor, but I'm a little confused as to which pin to use on the Arduino.

The thing that is throwing me off is that the sensor has an amplifier where you can set a threshold limit, which when passed triggers the switching signal.

Based on the output signal from the sensor amplifier (as can be seen above), which pin on the arduino should I connect the sensor amplifier output signal wire to, and are there any limitations I need to take into consideration i.e. is the switching signal current too large for the arduino or anything like that?

Thanks in advance!


texts: Efficiently powering multiple LEDs from higher voltage than used for microcontroller

texts:
I need to control 12 LEDs that are powered by 6V (4 AAA batteries).  I'm using a PIC18F25K40 microcontroller that will be powered by 3V (2 of the AAA batteries).  Because of the different power supplies, I can't charlieplex.  There are enough IO pins available to individually address the LEDs.

Because I will rely on persistence of vision, the LEDs will be powered ONE at a time, so I'm expecting it to be fine to arrange them in parallel with a single current-limiting resistor.

To turn on an LED, the corresponding IO pin will be set to Output LOW in order to sink current.  To turn off an LED, the IO pin will be set as an input (high impedance).  Schematic shown below.

The issue is that the PIC documentation says that any applied voltage to the pins must not exceed Vdd + 0.3V.  With the LEDs off, a voltage of about 3.8V will placed on the pins.  (6V - 2.2V = 3.8V).  2.2V is the forward voltage of the LEDs, and Vdd is 3V.

In order to address this, I'm adding a series diode to the current limiting resistor, in order to drop the voltage placed on the IO pin to be below 3V. (Shown in schematic).

My questions:

Will this circuit function as intended (over the range of battery life 1.0V-1.5V)?
Will a Zener diode be better for producing a definitive voltage drop?
Are there better ways to accomplish this?  (The PIC needs to remain powered by 2 batteries.  Other parts of the system require 6V, so can't route the remaining 2 batteries to be in parallel with the first pair.).

Additional info:

The use of 4 batteries to power the LEDs is to spread the power consumption, as well as to ensure that the LEDs can still be powered even when the individual batteries deplete to below 1.1V.  Otherwise 2 x 1.1V will barely meet the 2.2V forward voltage.  Please note that the 6V is required for other parts of the system; not just for the LEDs.

Haven't been able to find Zener diodes of 1V.  Using standard diodes will provide a 0.7V drop, which doesn't leave much margin for preventing damage, especially if the initial battery voltage is a bit higher than 1.5V each.

PCB space is VERY tight. Strong preference to keep part count to a minimum. ie. no room for a handful of transistors or additional power regulators.

Thanks in advance for the guidance!


texts: Can I use a transistor, or would it be easier to use a microcontroller?

texts:
I've got kind of a weird project in mind.  I want my project to be able to connect to the headphones jack of an MP3 player.

The mp3 player will either be playing a constant tone or not playing anything at all.  When it is not playing anything, I want to light a green LED.  When a tone is playing, I want to light a red LED.

Is enough power generated through a headphones jack to cause a transistor to switch?  Would it be easier to just use an AVR (ATtiny or something) to listen for analog input?


texts: How are resistor power dissipation calculations performed?

texts:
I'm designing a switching mode power supply to supply 150V at 10mA to a nixie tube that is rated for 150V and 3.5mA. The circuit diagram will be very similar to this design, with the main difference that I'm powering a single tube instead of 6.

If I understand correctly, the resistor is needed to limit the current flow, so as not to blow the tube. The resistor would have to be 42K Ohms (V/I or 150/0.0035). However, only the output current of the resistor is used in that equation. There are 6.5mA of current at 150V unaccounted for. Are these 6.5mA of current "addressed"/used in the power dissipation calculation (P=V*I) as the remaining current is dissipated as heat in the resistor? Or does the power dissipation calculation still use the output current of the resistor?

If the latter, what happens to the 6.5mA of current not used by the load?


texts: Power IR2110 from a low voltage AC Source

texts:
I am trying to power the IR2110 using an AC Source. However, this source is also connected to a full wave bridge rectifier that's going to supply a controlled buck converter.

I tried using a voltage quadrupler that takes a 5V sine from a function generator as input to and outputs around 16V DC. I thought that by adding regulators I can get the required voltages to supply the IC. I am still confused about which point to connect as ground to the regulators. I tried using the ground of the rectified output as the reference point in my whole circuit. I also tried simulating the attached circuit using LTSpice but the simulation was too slow and couldn't be completed.

The problem is that the 15V regulator outputs only 6V. By tracing the circuit I found out that the multiplier output drops whenever the regulator is connected to the circuit. How can I solve this problem? And are there better ways to power this IC from an AC source ? I would really appreciate your help :)


texts: What does number of lines represent in semiconductor's E-K diagram

texts:
After I read the post: E-K diagram in case of semiconductors I have few more question on E-K diagram.

For the Si E-K diagram above, we see 8 lines, 4 lines in conduction band and 4 lines in valence band. Si has four valence electrons.

Q: Is each line for one valence electron?


texts:
I want to learn PID (Proportional–Integral–Derivative) control mainly for temperature.

I would like to learn preferably through an easy project to do.

Could you please recommend something which would take a few weeks to learn?

Edit: I want to control the temperature of a water tank. The heating is done by a resistor.


texts: 8 to 3 Priority Encoder. Answer Verification

texts:
I am trying to design a priority encoder with a given priority table.

Input: I0 I1 I2 I3 I4 I5 I6 I7
Priority: 2  7  6  1  5  0  3  4

Image attached!! Are these correct? Or I am failing?


texts: What noise frequencies is an oversampling ADC susceptible to?

texts:
When calculating the input-referred noise and filtering to a 24-bit sigma-delta ADC (MCP3561), I hit a roadblock. Knowing the noise spectrum density (nV/sqrt(Hz)) of a signal noise source, like thermal noise, the noise in uVrms (microvolt root mean square) is calculated using the bandwidth of the signal. The latter number should be the noise floor that determines the effective resolution. Therefore I need to know what bandwidth (frequency span) applies in my scenario:

The ADC will do internal oversampling to form a single one-shot reading. The signal is from a thermistor where the bias power will be pulsed at 10 Hz for the duration of ADC, hence the signal itself is assumed constant for the measurement period and I suppose the signal frequency is 10 Hz. But 0-10 Hz can't reasonably be the frequency span to calculate noise from, as the ADC is inactive most of the time.

Is the frequency span from 0 to the oversampled sampling time (in the kHz range, but just one sample)?

Or is the frequency span from 0 to the internal ADC sampling rate (in the MHz range)? But I read that higher ADC speeds reduce the noise problem, which isn't consistent with this idea. And while the ADC runs at 4.9 MHz, the sampling time for each oversampling level is specified as 3x the expected (for example OSR=128 takes 78 us = 12.8 kHz = 4.9 MHz / (3 * 128)) so even the internal frequency is unclear to me.

It's also easy to imagine even higher noise frequencies affecting the measurement, but maybe any high-frequency noise is filtered in the ADC and included in the ADC datasheet ENOB? Maybe some Nyquist limit is involved.

The goal is to understand the practical measurement resolution under different Vref values and oversampling levels, and to optimize the filters. It seems to me that the slow signal may be filtered until thermal noise is the limit, but to know this I need the thermal noise of the signal as uVrms.


texts: Safe Power rating of resistor for my circuit

texts:
I am working on circuit shown below

Current flowing through circuit is 88.235 mAmp

I = V/R = 24/272 = 88.235mA

which generates heat of

68*88.235*88.235 =  0.529 Watt

I have used resistors of 1 watt but it generates little heat.

  Will this resistor sustain for longer time?

or

  should I increase the wattage?


texts:
I have a circuit fed by a 5V source which receives audio signals, amplifies them, and modulates an LED so the intensity of the LED changes with the voltage.

Ok so far so good. But what I want to do is to replace the LED with a laser diode. I tried and it behaves as LED.

In many websites I came across they are using a capacitor and diode when connecting a laser diode. Should I connect a laser diode in a different way than an LED? Why?


texts:
I recently study about two stage amp.
In Sedra-Smith, it stays that PSRR for VDD is very small, and ignores this.
To understand this, I set Q6's source Vin and Q6 is acting like a common gate amplifier.
So $$\text{Gain} =  g_{m6}(r_{o6} \parallel r_{o7})$$
I thought like this first. It doesn't make sense.
So next, I set like this; Q7's drain and gate are connected, Q7 acts like diode-connected FET which has resistance \$1/g_m\$, so gain has to be rewrite as $$g_{m6}[r_{o6} \parallel (1/g_{m7})]$$
But this does not make sense too, because the gain is 1. What am I missing?

And I cannot understand this too,

If ground is replaced as VSS, that denotes the Vout caused of VSS.
How it would be voltage divided form? That formula means that Q7 is diode-connected which has resistance \$r_{o7}\$, I cannot handle with this.


texts: Let’s put J=1, K=0, CLK=1; The output of the circuit will be Q=1 & Q(-)=0; But when the feedback goes back to input (Q is attached to K and Q(-) is attached to J). Hence J input will be (0.1.1) & K input will be (1.0.1). Hence output from the first stage Nand gates are 1 & 1. So how it is stable. So feedback is changing the operation of the J=1,K=0,clk=1 operation. Please explain how feedback is affecting the output.