texts: How to read datasheets for TTL logic gates regarding maximum output current conditions

texts:
From what I have been reading, the input stages to BJT TTL logic gates are emitter terminals of transistors. As such, when the input to these gates is logic low the base-emitter junction of these input transistors will be forward biased and source current (sinking into the first stage). Further, this is the reason we find that tables similar to the following in some datasheets :

I am referring to the polarity of the current when considering polarity of logic levels. Specifically, the fact that maximum operating condition of -800uA for a logic level high is non-intuitive. Should it not be that when a gate is driven LOW the second-stage gate actually sink current into the first-stage? That is, shouldn't sinking current (logic low output state) be negative and sourcing current (logic high) be positive?

My concern is how this maximum current sink metric is related to the maximum current that may be sourced when the output of a gate is driven to a logic high state. Specifically, I had the following condition as of late:

I was recently designing a circuit that used a 74LS163 counter where the outputs were fed into some second stage logic. However, I placed some LED indicators temporarily at counter output while prototyping this circuit in order to see what the count value was at a given time. I used series resistances of 1k to severely limit the current in order to not load the output driver too much, but saw a very significant output voltage drop anyway.

Specifically, The LED I was using had a forward voltage of 2.5V. The nominal, unloaded, output of the counter was 4.5V. With the 1k series resistance we find that a mere 2mA would be drawn to drive the LED. I found that the LED indeed was dimly lit, but the output voltage dropped 1V to 3.45V despite such low current demand.

tl;dr : This led me here. The maximum current when the output is driven high is given as a maximum sinking current, but obviously the counter sources some level of current at this voltage. How do these values shown in the datasheet relate to sourcing current at logic HIGH and sinking current and LOGIC low?


texts:
The datasheet says that an External Reset is generated by a low level on the RESET pin. And after reset all my conditions and values will be set to initial values.
I have connected the Reset(bar) pin to ground via a switch. After running the code for some time, I press the switch and give ground to Reset. But, nothing happens.

Can anyone tell me why this occured ?? Do I have to write a code?


texts: How exactly are the phase shift and cutoff frequency defined for a filter + amplifier circuit?

texts:
Say we had a voltage source connected to a Low Pass RC filter and that this filter was connected to the negative node of an Operational Amplifier, so we would have a filter followed by an inverting amplifier topology.

Please keep in mind that I understand this circuit may be incorrect, I just built it as I had it pictured in my mind as the simplest way to illustrate my question.

In this case, how can I define the cutoff frequency of the filter, as well as the phase shift that the signal experiences? I know that the Low Pass filter delays the signal in 45º, and that the inverting OpAmp inverts the signal in 180º. Then, would the phase shift be -45º-180º=-225º?


texts: Understanding bootstrapping in analog active filters

texts:
"Bootstrapping" is a common technique in (analog) active filters, where the output of the filter is fed back to a node that would otherwise be connected to ground.

For example, the Sallen Key topology begins with two RC L-sections followed by a unity-gain buffer.  Then the output of the buffer is also connected to the base of the first L-section (C3 in the following schematic).  This is said to "bootstrap" that node.

Here is another example, from an old National Semiconductor app note, in which the ground node of a Twin-T notch filter is 'bootstrapped' in order to greatly increase the Q of the filter:

How can I understand the operation of the 'bootstrap' intuitively?


texts: Could anyone explain me how I can use DCM of Virtex 4 fpga to get divided clock-50MHz of the system clock-100MHz?


texts: NPN Transistor Behavior with Base Voltage higher than Collector

texts:
Lets say I have this circuit:

simulate this circuit – Schematic created using CircuitLab

I think if I apply a 0 to the base of Q1, I'll develop something like 4.3V at the collector of Q1, right? In that case with the Base of Q2 sitting at 4.3V which is higher than its collector voltage of 1.8V to 3.2V, what will be Q2's behavior. Will current flow through R4 sourced from V1?


texts: Is it safe to use SMPS instead of LIPO battery to work with BLDC(rated:1400Kv) with ESC(Rated:20A)?

texts:
I am planning to build a high speed centrifuge.

Does the discharge rate really matter for low speeds of BLDC(around 50%)?

Can I control the current consumption(strictly less than 10A) by the BLDC motor unit with the help of pwm control to the ESC itself without blowing up my SMPS??

 BLDC Motor: 1400Kv  ESC: 20A SMPS: 12V 10A


texts:
Can anyone please explain what is the difference in ODT and ZQ technique used in DDR2 and DDR3??
Which method is very useful for DDR2 termination? whether ODT or External parallel termination??

Regards,
M.Arun kumar


texts:
Surely there is some software that lets you draw a simple circuit diagram (DC voltage source and resistors) and then tell you the voltage, current, resistance, and power on R1, R2, R3, etc as well as totals.. instead of having to do it by hand, right?

The only things that seem to be able to do this  that I've found so far are enterprise level software that look like they were designed in the 90's. Places like docircuits.com and circuitlab.com don't tell me the resistance total (for example in series-parallel circuits), or they would be decent.


texts: Unusual power consumption - audio amplifier

texts:
I bought a 50W*2 stereo amplifier from eBay (i believe the values are overrated, though) and i wanted to use it on my motorcycle.
It works just fine, but then i wondered about the power consumption:
I tested the power consumption with my trustworthy digital multimeter (UNI-T) at 1/4 of the volume.

I set it on 10 Amps thinking that it may be much, but the meter broke.
I figured i made a mistake, so i used an analog 15A ampere meter (the panel type) which went all the way up to 15A and stop there, because of the plastic limitations (it hit the plastic really hard as soon as i hook up the amplifier).

It would rarely reach 12A, and every time the led of the bluetooth module of the amplifier blinked it would go back to 15A, which is weird...no bluetooth module should use 3 amps of power.)
Then i sensed something was wrong...again.

I had some car fuses laying around and i decided to test it with those.
I first started with a 15A fuse. The amp worked properly...
Then i tried a 10A fuse. Again, no problem, then i used a 8A fuse, which didn't blow.

Then i noticed i had a 2.5 A fuse among the rest of those.
I hooked the amp up as usual. The fuse was fine. I let it play music for a minute at 1/2 of the volume and the fuse did not blow...

Now i am wondering what is the actual current that the amplifier draws from the battery...15A can't be right. It barely gets 4-5 degrees hotter after intense use ( i used it for 2 hours with a computer PSU).
This is the amp
I used two 4 Ohm speakers (rated for 60W), with the engine off, and the battery was at 12.4 volts.


texts:
SOLVED: I put here my code, I hope it helps someone! ^^
TIP: My problem was because I was comparing if PORTBbits.RB3 == 0 or == 1; the solution has been comparing a variable instead a state.

#include <xc.h>
#include<plib/timers.h>

#define _XTAL_FREQ 40000000

unsigned char config1;
unsigned int timer_value;
unsigned int tpr;
int counter=0;

void main(void) {

TRISBbits.RB3 = 0;
PORTBbits.RB3 = 0;

   // 1/1 prescalar
   T1CONbits.T1CKPS1 = 1;
   T1CONbits.T1CKPS0 = 1;

   // Use Internal Clock
   T1CONbits.TMR1CS = 0;

   // Timer1 overflow interrupt
   PIE1bits.TMR1IE = 1;

   // Enable Timer 1
   T1CONbits.TMR1ON = 1;

   INTCONbits.PEIE = 1; // Enable Perpherial Interrupt
   INTCONbits.GIE = 1; // Enable Global Interrupt

   while(1)
   {

   }
}

void interrupt high_priority lowISR(void) {
if (PIR1bits.TMR1IF == 1) {

    if(counter == 0)
    {
        PORTBbits.RB3 = 1;
        counter = 1;

    }
    else if(counter == 1)
    {
        PORTBbits.RB3 = 0;
        counter = 0;
    }
    TMR1 = 0X00;

    PIR1bits.TMR1IF = 0;
}
}

First of all, I introduce myself! I'm Manuel and as you can see I'm new on this web. I will help as much as I can!

Second of all, I'm working with PIC18F2520 with XC8 compiler and I want to receive an infrared code. For that, I need to work with Timers for the signal's reading, but I dont get it working. I've been looking for this topic and I haven't find it.

Tip: Pragma settings are written in other file.

When I run this code in proteus, seems to do anything. What could be the problem?
Btw, actually I'm using my PIC18 with an external oscillator.

Thank you very much!.

What could be the problem? could be the pragma definitions?

EDIT: code updated in main post, sorry for all the inconvenients!


texts: Solar panel to charge 9 volts batteries, but need to power 120 volts pump

texts: I am making a very simple circuit that takes charges 9 volt batteries from 18 volts solar panels. Then, there is an interrupter to let the the batteries power a water pump that requires 120volts. How can I transform 9 volts of the batteries into 120 volts? I can not find anything online about that.


texts:
I have this project to build an instrumentation system to measure the respiratory rate.
We decided to use a thermistor to measure the variation on the temperature of the air inhaled and exhaled. To measure the variation on the thermistor resistance we decided to use a Wheatsone bridge as shown below.
Since the variation was pretty small (the temperature varies between 25ºC and 28ºC) we needed to amplify the signal. For that we thought about using an instrumentation amplifier - INA128. However it wasn't available in the simulator we were using (which is TINA-TI) so we built the equivalent circuit.
I wanted to know if this is a good option to aquire and amplify this signal, and if this circuit is correct.

To be able to simulate the signal, we measured the signals on the points that were connected to the opamps, and used voltage sources with similar signals.

As you can see, the output has a DC component.
I wanted to know if there is something wrong with our Wheatstone bridge that could be causing that.


texts: How do I troubleshoot a broken SAA3004 Remote control transmitter used in a remote control?

texts:
I'd like to troubleshoot and fix a broken remote control for a Guldmann ceiling lift that uses the SAA3004 remote control transmitter (documentation below in link).  Can someone explain the tools required to do this, and the steps necessary to troubleshoot such a device?  I just replaced the 9V battery being used in the remote, which powers the a circuit board (SAA3004).  I've used a multi meter and I know the CPU is getting power.  I've put the black part of the multi meter on the battery and the red onto Vss (page 10 below), and is showing 8.9V.  I can provide additional information if necessary, and some images of the circuit board.  And I have a remote control with a functioning circuit board, in case we need to compare with the broken circuit board.

http://www.datasheetcatalog.org/datasheet/philips/SAA3004.pdf


texts:
While reading the RM0008 reference manual I got confused about how to use the NVIC to configure interrupts. The manual basically redirects the reader to the PM0056 programming manual which, in my opinion, doesn't do a great job in explaining how to use the NVIC functions provided by CMSIS.

So, I'm trying to set up an interrupt for GPIOA pin 1 using EXTI Line 1 in a NucleoF103 board, and I want to setup priority and subpriority bits, but I'm not sure how to do that. The RM0008 manual states that the NVIC has 4 bits of interrupt priority.

CMSIS provides functions such as "NVIC_SetPriorityGrouping" and "NVIC_SetPriority" to choose priority and subpriority bits, but I can't seem to find a good explanation for what the arguments do in these functions.

It seems that the "NVIC_SetPriorityGrouping" changes some values in the AIRCR register, which does have some bits to configure number of priority and subpriority bits.

So, for instance, is this code correct for setting up and EXTI interrupt on Line 1?

#define RESET_WITH_MASK(reg,mask) reg &= ~(mask)
#define SET_WITH_MASK(reg,mask) reg |= (mask)

[...]

//Configure EXTI Line1 to not be masked
SET_WITH_MASK(EXTI->IMR,EXTI_IMR_MR1);

//Configure a rising edge to trigger an interrupt
SET_WITH_MASK(EXTI->RTSR,EXTI_RTSR_TR1);

//Configure EXTI Line1 multiplexer to listen to port A
SET_WITH_MASK(AFIO->EXTICR[0],AFIO_EXTICR1_EXTI1_PA);

//Choose type of priority bits: 3bits for priority, 1bit for subpriority
NVIC_SetPriorityGrouping(1);

//Set priority of EXTI Line1 to 0 (highest priority), subpriority to 1
NVIC_SetPriority(EXTI1_IRQn,0b0001);

//Enable EXTI Line 1 interrupt
NVIC_EnableIRQ(EXTI1_IRQn);

//Enable interrupts
__enable_irq();

Here I am assuming that the argument for the "NVIC_SetPriorityGrouping" chooses the number of subpriority bits, and that the "NVIC_SetPriority" takes the priority bits, the most significant being priority and least significant being subpriority.

Obviously pin 1 of GPIOA needs to be configured as an input for this to work, but aside from that, am I missing any configuration stuff? Also, is "__enable_irq()" truly necessary?

Any help would be appreciated as I was not able to find any good examples of this, and I'd like to avoid doing the configurations using all those shifts in the NVIC registers when CMSIS already provides functions for this.


texts: Low Jitter and Latency on signal trigger using WFI / WFE on STM32F405

texts:
I have a hobby project using a STM32F405 MCU, which is intended to respond to a fast clock signal (~1Mhz) connected to Pin 1 of GPIOA. For every transition of the input (both rising and falling), I need to execute a short program which accesses address and data on the bus, and takes the appropriate action. The MCU is running at full speed (168 MHz), which gives me approximately 84 clock cycles to process each phase of the external clock.

I've looked into several approaches, and determined that using an Interrupt is not feasible. There is at least 24 clock cycles overhead of servicing an Interrupt, which would waste close to 30% of my available cycles.

The next approach is a polling loop, which works fine and only wastes 5-8 clocks. Basically the cycles needed to poll, plus GPIO latency as it runs at half the CPU speed. The main problem with this is jitter, as the change can happen at any point during the 5-8 clock cycles it takes to do a poll. So the result is that the response to the signal will have a jitter of up to 8 cycles (10%). This is doable, but I need to compensate to the varying jitter by burning off some more cycles using NOPs. This is needed in order to insure the response does not happen within the acceptable time frame.

However, reading a guide on interrupt latency, this guide claims that WFI or WFE can respond very quickly to an event or interrupt. The idea is to have the EXTI generate an interrupt or event (what ever works) on each transition of the external clock. Then I simply use __WFI() or __WFE() to wait for this event, and then immediately start processing. The guide I mention claims a wakeup from a WFI takes 4 cycles, but the point is that the number is consistent, giving me a very low number of wasted cycles and as little jitter as possible.

Now my problem is that I cannot make this work correctly at all. As mentioned, I do not want the ISR to be executed, so I disable all global interrupts before I start waiting.

First I tried WFI; Setting up the BASEPRI register to only let through interrupts of priority 1 (set it to value 2), and further set the priority of the EXTI interrupt in NVIC to 1. But if the interrupt is in fact generated by the GPIO when WFI is called, it does not wake up the CPU. I did a short test by setting the Systick IRQ Priority to 1, and this DOES wake it up. So it seems the EXTI interrupt signal is not working when WFI is called.

Finally, I've tried to use WFE instead, by setting up the EXTI line to generate an Event instead of an Interrupt. However, this exits immediately on the first call (apparently due to a unintended pending event?), and then hangs indefinitely on the second call. It does not respond to transitions of the GPIO pin.

So my questions are as follows:

Has anyone successfully used WFI or WFE on this (or a similar) MCU for a similar purpose and made it work?
The STM32F4 documentation does not provide any information about the time (clock cycles) it takes to wake up from a WFI/WFE (if it was working). So I don't even know if this will actually achieve my goal of a fast response and predictable jitter. Does anyone have any information on this?


texts: Low leakage current methods of initializing pin inputs at power up

texts:
Suppose I have an IC that has a standard level triggered input pin. I need this pin's state to be setup immediately at power on at a time when my MCU's GPIOs may not have established levels. What are my options for accomplishing this while still being able to control the pin level at a later time?

My way that of course comes to mind is using a pull up/down resistor however that can have high leakage current. During the times my MCU is online I will have no use for the resistors as the pin state can be set by the MCU so this leakage is highly undesiable. Are there any options i'm not thinking of?

simulate this circuit – Schematic created using CircuitLab


texts: Why is there seemingly no delay in a block ram read

texts:
I am trying to learn Verilog and was curious why my FPGA's block ram seems to provide the data that I request instantly. I was expecting that there would be some number of clocks that I would need to wait before my results would be available.

On a traditional computer's CPU, the only data available immediately is whatever is stored in a register correct? Data stored in caches or in ram would need to be fetched into a register before it can be operated on right? Are these block ram objects just implemented via registers on the chip?

Thanks


texts: Sending a divided clock through a non-dedicated clock pin?

texts:
I'm moderately new to FPGA's, and right now I'm working on code to interface with a DAC. I'm using this PMOD DAC , and a Nexys 4 DDR fpga. Right now, I'm connecting them through the JB PMOD header.

The DAC requires a clock pulse (I'm sending in a 50MHz one, which I've divided from the FPGAs 100MHz clk), which I'm sending in through pin 4, following the reference manual. However, once I try to synthesize and implement it, I get an error.

"Poor placement for routing between an IO pin and BUFG. If this sub-optimal condition is acceptable for this design, you may use the CLOCK_DEDICATED_ROUTE constraint in the .XDC file to demote this message to a warning. However, the use of this override is highly discouraged. These examples can be used directly in the .XDC file to override this clock rule.
"

There are two possible problems:

The fpga doesn't like that I'm outputting a clock signal through this PMOD pin
There may be an issue with Mset_enable, but it has nothing to do with a clock (right now it's an input assigned to one of the on-board buttons), and I see no reason why there should be difficulty placing it.

My question is: which problem is it, and should I go ahead and use this workaround?

Mset code:

module tuning_word_set(
  input [3:0]data_in,
  input clk,
  input Mset_enable,
  output reg sin_LUT_rst,
  output reg [3:0]data_out
  );

//if enabled, M will change to data_in, otherwise it will stay the same
always @*
begin
  if (Mset_enable)
  begin
    data_out <= data_in;
    sin_LUT_rst <= 1'b1;
  end
  else
    data_out <= data_out;
    sin_LUT_rst <= 1'b0;
end

endmodule


texts:
I have the following problem.
I want to read an -5V Signal using my Microcontroller.
I have the following circuit setup, but it does not work.

My problem is that the the signal is high while the signal is not there (0V).

Thank you for every hint! :)


texts: Maximising the strength of an electromagnet

texts:
I am attempting to create an electromagnetic propulsion system (and no it is not a perpetual motion machine I am not that thick) and for that I need an electromagnet capable of producing a very strong electromagnetic field, currently I am getting a moderately strong field however it is insufficient and I want to know if there are any ways I can increase the strength, I am using a MOT with the secondary removed.

I know that there are three main factors which influence the strength of an electromagnet, 1) Amperage
2) Coil Density
3) Permeability of the core

The core seem to be very permeable and its unlikely I can get anything better than that taking into consideration funds.
I also can't really change the coil density

So I am mainly considering amperage and I used http://www.daycounter.com/Calculators/Magnets/Solenoid-Force-Calculator.phtml
to do some calculations and it seems like this will definitely work but the trouble is I am currently (pun intended) unsure of how to increase the amperage as while I have connected a 400A power source to it, it obviously isn't absorbing even close to that and I estimate it is getting under 8A so my main question is is there a to make it absorb more amperage? I am not overly concerned about Overamping (not the drug one, the electrical one)as it is unlikely to instantaneously destroy it and I have a spare.


texts: Total length of cable to connect 1-wire DS18B20 sensors without problem

texts: Based on this topic and the connection that is proposed I would like to make two questions (if somebody has face the same problem/task). So can I connect the data cable to a raspberry GPIO and then the voltage and GND to an external power supply or I would have problem with the pull up resistor? Also, is it ok the last sensor to be 30 m far from the raspberry? or I would have reflections problems? I am thinking of using cat5 cable. Is it a good choice?


texts: Simple NMOS simulation error. High voltage drop across the nmos when trying to make a MOSFET switch

texts:
I have this simple NMOS configuration in ltSpice.  I would imagine that when V2 (Vg) goes high, Vds would go close to zero. But this simulation suggests that there is a very high voltage drop across the nmos, which is strange to me. What is my error in this simulation? I want to have the nmos act as a "short", or switch when Vgs>some Vth.

(Vn002) is the node just below the 1k resistor


texts: Ohm's law of a circuit which has both a voltage source and current source

texts:
The voltage source has a specific voltage through it regardless of the circuit's current and its resistance while the current source has a specific current through it regardless of the voltage through it and its resistance.

My question is:

When there's a circuit which has both a voltage source and a current source with a load, a resistor R for example. How can people apply Ohm's law on it. The sum of both voltage and current must be reserved.

For example, the circuit has a current source and a voltage source connected in a series with a single resistor which

The voltage source supply 10V
The current source supply 3A
The resistance of the resistor is 4 ohm.

How can Ohm's law be applied in this case.

If we take 10V then the current will be 2.5A which is lack of 0.5 A to make the sum of current equal 3 as the current source supply while if we take the current through it is 3 A then the voltage through it wil be 12 V that over the one which voltage source can supply. I have seen many circuit which have both of these source without knowing how to apply Ohm's law on it.


texts: Transistor setup for large motor circuit

texts:
I am building a relatively simple circuit which essentially consists of two lead acid batteries rated at 12V and two motors rated at 12V. My original plan is to wire them all in series, and control them with a motor driver of some sort using a pwm signal. However, all of the motor drivers I can find that can handle this are rather expensive, and it seems as though it would be just as acceptable to do it with one or two mosfets. I am not sure of what quality/type of mosfet to get, and where to place them within the circuit. I am thinking it would be easiest to do just one high quality one before both motors, but would I be able to control the speed of the motors using a pwm signal that way though? Any advice is appreciated.

EDIT:  The mosfets will be controlled by a simple microcontroller such as a pic or avr.
Here are three N-FETs I have found that may work. 87A 100A 104A

Added [RM]:

Copied from a comment - extra data should be in question for easy reference.

The motors rated power is 337 Watts (at 2655 rpm, 172 oz-in, and 68 amps). The load is present at all times, and should stall minimally, but I have a current sensing ic in place to monitor the current and reduce the voltage if it starts getting too high. I don't care too much about bidirectional control, and the current measuring circuit is a 180 A rated attopilot chip.


texts: What are the main culprits for frying a mosfet?

texts:
I have a bunch of FDN335N mosfets. They works great until i manage to fry them so that they never properly turn off(current leak i guess?).

I Have heard that you should use a protection diode when switching inductive loads, I am switching an mp3 module which contains an amp but is not directly connected to a speaker so i wouldnt have thought it was required(there is a current spike of about 80mA when the module turns on...)

I am not currently using a resistor on the gate, could this help?

But yes if anyone could help with the main culprits for breaking mosfets and give some advice on how to avoid it it would be much appreciated, thanks.

(simple circuit included)


texts: Fuses on both lines of an isolated AC/DC converter

texts:
I'm redesigning a board made from another person. This board have several AC/DC converters (like Traco TMP07 Series and similar) and some screw connectors to connect external devices. Neither the converters now the devices have any connection to the Earth, though they are all isolated.

The board have two fuses for each converter output: one on the positive line and on on the "negative" (actually the 0V).

I'm wondering if it's worth to have two fuses on the same current path or it's enough to put the usual one on the positive line.


texts: How to set fixed bias on transistor 2N2222 for certain specifications?

texts:
I'd like to ask how to set fixed bias for this transistor.. It doesn't seem to be working. If anyone know how to calculate it, please tell me.

I wanna adjust two resistor values so that Uce = 5,44V, Ube = 0,655V, Ucc = 12V and Ic (collector current) has to be 2,43 mA.

I tried R2 = (12 - 5,44) / 0,00243 = 2,7kOhm.

But in the second part where I wanna find R1, I don't know Ib (base current). Or can I find it out? I tried looking for BETA, but didn't find anything.

I tried editing Beta in Multisim but I couldn't click Edit Model because it was unclickable.

R1 = (12 - 0,655) / Ib

Any ideas? If yes, please add calculations if you did some and explanation. Thanks forwardly for every sensible comment!


texts: Why is there a resistor in this circuit?

texts: Why there is a 220 ohm resistor in this circuit? Can't we just connect the thermistor directly to the base of transistor?


texts: Equivalent sequence/stepper relay to "FINDER - 20.21.9.012.4000"

texts:
I am currently looking at this relay: FINDER - 20.21.9.012.4000. Which is step relay, that makes contact AC output active with coil input DC (12V) [which i need]; and disconnects output when coil is triggered again. Which works like this GIF animation: http://www.homofaciens.de/bilder/technik/relay_002a.gif.

Q1: It says that Un=12VDC (coil input), coil resistance R=27Ω and current over the coil must be 400mA. Have I read this data correct? --Coil specifications, PDF, page 2-- So if I needed to switch 16x same relays at the same time, input current consumption would be 7A?

Q2: Where in the specification is the info, that tells me how much time must the coil be on high state, to activate/trigger the contact output?

This relay is kinda expensive for me, since I need around 30 pieces...

Q3: Does it exists equivalent relay, that is described, which:

contact doesn't need to have 16A output, it can easily have max 1A, since burden will only be simple lights, that will probably have max 0,5A consumption;
I need DIN-rail package, but it can be for PCB, and I will find PCB to DIN-rail socket (example);
and has some kind of reasonable coil current.

Thanks


texts: Fuses: What are the practical differences between Ceramic and Glass cartridge fuses

texts:
What are the practical differences between ceramic and glass tube cartridge fuses?

I am trying to find new fuses for a piece of consumer electronics. The original fuses are going out of production.

The fuses the original BOM called for are ceramic cartridge fuses.

It is my understanding that ceramic-tube fuses are significantly more durable, and are able to break a higher-current fault.
However, in this case, both buses have identical markings (CE, UL, etc...) and are sufficiently rated for any fault-situation the device could reasonably be expected to endure.
Also, this is a piece of tabletop-equipment, so durability is not relevant (if you drop the thing, lots more then the fuse will break).

As far as I can tell, the originally specified ceramic fuses are kind of overkill. What should I be concerned about if I switch to glass-tube fuses?


texts: Passing data from Python to Arduino over ethernet

texts:
I have an Arduino with Ethernet shield handshaking with my machine over Ethernet, and now I want to send data between them. My problem seems to be correctly parsing the different data types.

For example, after connecting to my Arduino server, my Python script runs this

msg = "255"
print "Sending %s" % msg
data = s.send(msg)
s.close()

and all I'm looking to do right now is print it to serial on Arduino (I'll eventually do different things based on the input).

Here is my run loop on the Arduino.

void loop() {
     Client client = server.available();

     if (client == true) {
          int recv = client.read();
          if (recv == 255)
               Serial.print("Received ");
          Serial.println(recv, DEC);
     }
}

For some reason it's only printing a single blank character and I don't get any "received" message.


texts: Inverting input causing current draw on non-inverting input?

texts:
Problem: unexplained current draw on non-inverting input when voltage on non-inverting input is above the inverting input.

Background:
I have been playing around with an RC timing circuit from pg. 24 of "The Art of Electronics" (Horowitz and Hill, 2015).

The idea is to charge a capacitor, and then slowly drain it using a resistor. A comparator op-amp is comparing the voltage on the capacitor against a reference voltage, and turning on an LED while the capacitor voltage is above the reference.

simulate this circuit – Schematic created using CircuitLab

I breadboarded up the circuit using a 100 uF capacitor and 1 Mohm resitor. I used a TLV2462CP op amp (because that's what I had in my box), and a LM4040-based precision voltage reference (Adafruit P/N: 2200) in place of the voltage divider.

Confusion:

My plan was to experiment with RC times, but I found the LED was shutting off far too early. When I probed the circuit at the testpoints above, I got this strange behavior. Notice the kink in V_CAP near V_REF. This kink moves upwards if I use V_REF = 4.096 instead.

What gives?

I'm clearly getting some sort of increased bias current while V_CAP > V_REF, but why? The TLV2462CD is not a comparator, but this behavior is still strange.

Solution: I took suggestions 1 and 2 of @dannyf. When the capacitor is fully charged (i.e. 5 V), the discharge current across R2 is 5 uA. According to the datasheet, the worst-case bias current for the op-amp should only be 25 nA.

However, I decided to add a buffer op amp to the capacitor (luckily, the TLV2462CD is a dual op amp!), and the circuit behavior is now as expected.

simulate this circuit


texts:
I have salvaged some parts that I can't identify myself. I would appreciate it if someone could tell me what they are called so I can look them up.

I took some better photos of the first 3 parts, and added a 7th at the bottom.  Sorry about #3, but it is convex from all sides, and I don't have a light diffusor (yet).

1:

2:

3:

4:

5:

6:

Sorry for the low quality of the photos.  I'll get better with more experience with my camera.


texts: What does 'Braked Voltage' mean on a charge controller?

texts:
Here is the complete specs of the controller.

Battery rated voltage: 12v
Wind turbine rated power: 300w
Wind turbine braked voltage: 15v
Recover voltage: 13.5v
Quiescent dissipation: <8ma
Pretection grade:IP67

Does the braked voltage imply protection for voltage spikes thus braking the wind mill by applying some type of shorted load? Thanks!


texts: Maybe this is a stupid question to ask, but I am still wondering. I have this kit, I mounted the LCD on the UNO and connected their headers. After downloading the sketch, I used a power line to see the display content as I needed to picture it. But after a few photo shot, the UNO became hot. Is it normal? Or the power too high?


texts: Comparison between FMCW radar modulation techniques

texts:
In designing a Frequency modulated continuous wave (FMCW) radar system for target detection, there is a possibility of choosing the modulation technique amongst triangle or saw-tooth modulation. What are the parameter which make the base for the selection.

Comparison between these two modulation techniques for FMCW radar will be appreciated?


texts:
Could someone tell me if I've used the right approach for this problem?

Assuming IDEAL DIODES:

I am aware this is not a practical application and that it would not work in real life, but I just to follow the right process in analyzing the circuit theoretically.


texts: Can we explain the differential pair in terms of resistances?

texts:
It has always been a big challenge for me to find the most general ideas behind great circuit solutions that can be illustrated by simple electrical concepts... and even by non-electrical analogies from our daily lives.
The differential (long-tailed) pair is such a legendary solution that deserves to be completely demystified. It is usually explained by electrical concepts (such as "current source")... which in themselves are not simple and clear enough.

The question arises, "Cannot we explain this strange topology with something even simpler, such as a resistor circuit?" If so, we can explain it to any electrician... and even to a 6-year-old (A. Einstein)...


texts: Error due to GNU ARM toolchain usage in IAR workbench

texts:
I recently started programming with STM32F4Discovery board and am using IAR workbench as the IDE. I am supposed to use an already developed program in Eclipse as a part of my project. When I imported this into IAR Workbench, I get the following error and warnings:
Error[Pe020]: identifier "_impure_ptr" is undefined
Warning[Pe223]: function "_REENT_INIT_PTR" declared implicitly
Warning[Pe223]: function "_reclaim_reent" declared implicitly C

I have realized that the _impure_ptr, _REENT_INIT_PTR, _reclaim_reent are a part of the reent.h file which are present in the GNU ARM Toolchain. This is being used as a part of the using FreeRTOS functionality. With Eclipse, this is not a problem, but when using IAR workbench, is there any other file similar to the reent.h for IAR Workbench that I am supposed to include?

I know it is a naive question but I am a beginner to embedded programming and still in the initial stages of setting up this project.


texts: About generating positive and negative voltage from the same power supply

texts:
I have searched the internet on how to get positive and negative voltage from the same power supply and I found the attached circuit.
When I measure between the points A and B, I get +5V.  When I measured between C and B, I get -0.5V.
What is the reason or what is the error in this circuit?


texts: Simple playback audio with FFT not working (dsPic33F)

texts:
I wrote a simple playback audio application (you speak on the mic, it plays on the speakers, just to test), it works. However when I added an FFT + inverse FFT, it doesn't, I only hear noise whitout reaction to when I speak on the mic.

Please, do anyone see an error  ?

#include<ADCChannelDrv.h>
#include<OCPWMDrv.h>
#include<sask.h>
#include<ex_sask_led.h>
#include<ex_sask_generic.h>
#include<dsp.h>

int AdcBuffer[ ADC_CHANNEL_DMA_BUFSIZE ] __attribute__((space(dma)));
int DacBuffer[ OCPWM_DMA_BUFSIZE ] __attribute__((space(dma)));

int main(void) {
ex_sask_init();

fractcomplex Frame[ 128 ];
fractional Output[ 128 ];
fractcomplex twiddleFactors[128/2];

/* FFT config */
int i = 0;
fractional *p_real;
fractcomplex *p_cmpx;

TwidFactorInit (7, &twiddleFactors[0], 0);  /* We need to do this only once at start-up */

/* Instantiate the drivers  */
ADCChannelHandle adcChannelHandle;
OCPWMHandle     ocPWMHandle;

/* Create the driver handles    */
ADCChannelHandle *MyADCHandle   = &adcChannelHandle;
OCPWMHandle     *MyDACHandle        = &ocPWMHandle;

ADCChannelInit (MyADCHandle, AdcBuffer);
OCPWMInit (MyDACHandle, DacBuffer);
ADCChannelStart(MyADCHandle);
OCPWMStart(MyDACHandle);

while (1) {
while (ADCChannelIsBusy(MyADCHandle));
ADCChannelRead  (MyADCHandle, (fractional*)Frame, ADC_BUFFER_SIZE);

p_real = &Frame[0].real ;
p_cmpx = &Frame[0] ;

for ( i = 0; i < 128; i++ )/* The FFT function requires input data */
{                   /* to be in the fractional fixed-point range [-0.5, +0.5]*/
        *p_real = *p_real >>1 ;     /* So, we shift all data samples by 1 bit to the right. */
        *p_real++;          /* Should you desire to optimize this process, perform */
}                   /* data scaling when first obtaining the time samples */
                        /* Or within the BitReverseComplex function source code */

p_real = &Frame[(128/2)-1].real ;   /* Set up pointers to convert real array */
p_cmpx = &Frame[128-1] ; /* to a complex array. The input array initially has all */
                        /* the real input samples followed by a series of zeros */

for ( i = 128; i > 0; i-- ) /* Convert the Real input sample array */
{                   /* to a Complex input sample array  */
        (*p_cmpx).real = (*p_real--);   /* We will simpy zero out the imaginary  */
        (*p_cmpx--).imag = 0x0000;  /* part of each data sample */
}

FFTComplexIP (7, &Frame[0], &twiddleFactors[0], COEFFS_IN_DATA);
IFFTComplexIP (7, &Frame[0], &twiddleFactors[0], COEFFS_IN_DATA);

for ( i = 0; i < 128; i++ )  /*Convert back */
{
        Output[i]=Frame[i].real;
}

OCPWMWrite  (MyDACHandle,Output, OCPWM_FRAME_SIZE);

}
return 0;
}


texts: Switching relay with a PNP and TTL levels

texts:
I can not wrap my head around the fact how I can drive a relay (24V, 160ohm) with an tip32a PNP transistor which has TTL inputs from a controller.
I can easily calculate my resistors when I use the NPN variant (tip31a), but I cannot conceive how to switch the transistor off with just TTL.
The relay will be powered from 29.4V and has a resistor in series to give the appropriate 24V for the relay. And of course there is a diode over the relay.

Any tips will be greatly appreciated, but please note that I at the moment can not use any transistor but the tip32a.


texts: Measured voltage is lower than set on bench power supply

texts:
I'm trying to identify the issue with my portable monitor. While testing it I noticed a weird (at least for me) thing that I can't understand.
I set voltage on my power supply to be exactly 7.2V. When I measure it on the power supply terminals it indeed shows 7.2V. Now when it's measured on the battery connector (where I inject the voltage) it measures only 6.8V.
Does it mean there is a voltage leak to the ground? I'd expect my power supply to show 6.8V on the screen but it shows 7.2V as set.


texts: Resonance in LTSpice using a real op amp in non inverting configuration

texts:
I was trying to use the LTC6269-10 in non inverting configuration in order to filter the high frequencies around 400 MHz, but when i plot the bode diagram in LTSpice it shows a resonance around that frequency. Also, if i try to change the values of the resistors in the circuit the resonance tend to shift and increase in value. What could it be?

These are the two circuits that i have tested:

And this is the bode diagram:

(The green one is the circuit on the left, the red one is the circuit on the right)


texts: Selecting proper vales of Rb, Re and and Rbe in a NPN transistor emitter follower configuration?

texts:
I need to gate a TTL Tx pin @115000bps as the chipset that drives the RxTx lines do not implement UART BREAK for arbitrary time periods.

As a quick hack I have come up with the following configuration that I will connect to the TTL Tx pin of the said chipset, at TTL.TX.In.

The Tx output from the whole device will be tapped from TTL.TX.Out

BREAK is the gating input that controls whether TTL.TX.Out will be in BREAK condition or not.

The TTL levels can be ~5V DC or ~3v3 DC.

My questions are:

What should be the proper value of Rb, Rbe and Re?
Is this a proper design that will allow me to implement BREAK for arbitrary time periods without affecting the "usual" transmission?

My fears are:

i. The Vce drop, typically 0.7V can degrade the output signal quality (although   I measured 0.05V Vce drop - are these old transistors that efficient now?)
ii. By driving the transistor too hard and @115000bps, the UART signal outputs could become severly degraded

Of course, in this case the transistor really should not affect TTL.TX.Out as it acts like a simple switch that either grounds TTL.TX.In or not, but I would like to ally any concerns that this design can cause problems down the line.


texts: Why do we use Laplace transforms to analyse transient circuits?

texts: I just learned transient circuits and we solved them both in the time domain and the Laplace domain and I can't understand why we would use the Laplace domain as it seems it is a lot more simple to use the time domain especially in series RLC circuits.


texts: Why are transparent latches discouraged / encouraged in digital design?

texts:
I have come across material per review from my past encounters with digital sequential logic and I wanted to pose a specific and hopefully general question for the community to help shed some light.
I have found reference to the term "transparent" latch and I discovered that it permits the output to get the input to flow through the output of the latch.
However per my understanding I see that use of a latch (specifically "transparent") is discouraged in digital design, specifically sequential providing any sort of clock should not be used in this process.
What is the effective disadvantage of using a latch instead of a flip flop, and where are they effectively used?
Why is the left good, and the right is bad?


texts: How do I get rid of the red mesh on the left view in Eagle. So that it looks plain like on the right side.


texts:
I'm trying to make a integrator output the velocity receiving an accelerometer signal based on the next design

But the output seems to be fixed on a certain level as showed here

I'm thinking the values of the components are way off the proportions, but even so, I was expecting a signal that changes as the integral of acceleration i.e. something with a period,
not something fixed.
What is missing in the design?
PD: the in1 was intended to reach a bode plot but at the end it wasn't used, but this should have no effect in the process.
EDIT: As noted by jsotola and Sanmveg saini there was a shortcircuit but when it is corrected, it still does not give the expected output signal


texts: How to replace Momentary & Maintained switch with Teensy?

texts:
I've got a LCD driver board (with some push buttons to open menu/+/-) and a bi-directional HDMI switch (with a latch button to redirect HDMI output to one or another) where I want to remove those buttons and command them via a teensy 2+ I bought. Do I just need to wire board GND and switch GND to teensy and do: (let set PIN_D5 is connected to the lcd board button menu and PIN_D6 to the latch button)

In loop function:

pinMode(PIN_D5, OUTPUT);
digitalWrite(PIN_D5, LOW);
digitalWrite(PIN_D5, HIGH);

to simulate a momentary push

and

pinMode(PIN_D6, OUTPUT);
digitalWrite(PIN_D6, LOW);

to simulate a maintained push ?


texts: What is the difference between peak-power, average power and true RMS power in RF measurement?

texts: What difference between peak-power, average power and true RMS power in RF measurement? I have read a peak-power measurement can calculate average power measurement also. Does any of these needs signal to be demodulated?


texts:
On the expanding area of glass?
Is inside of expanding area metal?


texts: I'm searching for a ramp generator circuit which is using only op amps (I guess I need an integrator & differentiator for that). The output should be like in the image below.


texts: Matched termination of a microstrip using absorber foam

texts:
I have open ended microstrips in an RF circuit (operation freq. 18 GHz) and they cause unwanted back reflection into the rest of the circuit.
Now, I wonder if it is possible to eliminate / reduce these reflections without having to solder anything on there (there are a lot of these open ends, so if possible I would try to avoid this) by placing some RF absorber foam on there. In theory, it is made to match air at the top then have a gradual transition to something heavily absorbing. So, if placed "on its side" should it not do the same thing that it normally does to free space radiation to the signal propagating on the microstrip - namely absorbing it while preventing reflections due to some abrupt termination.
Any advice on / experience with this?


texts:
I'm getting some errors when I try to compile my design in Aldec's Active-HDL.

# Warning: ELAB1_0026: BITADJ128.bde(BITADJ128.vhd) : (79, 0): There is no default binding for component "buf". (No entity named "buf" was found).
# Warning: ELAB1_0026: BITADJ128.bde(BITADJ128.vhd) : (157, 0): There is no default binding for component "INV". (No entity named "INV" was found).
# Warning: ELAB1_0026: BITADJ128.bde(BITADJ128.vhd) : (277, 0): There is no default binding for component "GND". (No entity named "GND" was found).

I have added these items to the library multiple times, and in different ways, but it still gets hosed up. I'm wondering if anyone else has had a similar issue? I inherited a large design I'm converting from EDIF to VHDL and switching from Virtex-4 to Virtex-5, and there seems to be a symbol resolution problem.


texts:
Find the differential equation governing y(t), t>0.

$$u(t) = 2U_0(t)      Amps$$

.

KVL (clockwise): $$2*I_c + \frac{1}{4} \frac{dV_c}{dt} - y(t)=0$$

$$I_c = 2- \frac{y(t)}{6}$$

I am having a hard time figuring out what my next step should be.


texts: Arduino + Android : Communicate with a JY-MCU Module

texts:
I am trying to turn ON and OFF a LED with my Android Device through a Bluetooth module (JY-MCU V1.05), I can connect to the module with the key "1234", but when I send a command to the module through the "Bluetooth Terminal" app, there is no respond, no action from the LED.

Here is my installation:

http://uppix.net/HOIKli.png

Here is the Arduino code:

char val;
int ledpin = 13;

void setup()
{
  pinMode(ledpin = 13, OUTPUT);
  Serial.begin(115200);
}

void loop() {
  if( Serial.available() )
  {
  val = Serial.read();

  if( val == '0' )
  {
    digitalWrite(ledpin, LOW);
    delay(1000);
    Serial.println("13 off");
  }

if( val == '1' )
 {
    digitalWrite(ledpin = 13, HIGH);
    delay(1000);
    Serial.println("13 on");
  }
 }
}

(Also tried with a serial of 9600)

Any idea why I can't communicate with the Arduino ?


texts:
I make a simple circuit with the use of Arduino and it works well, having an IC like ATTiny is good but i have a small space on my PVC Tube for DC-DC Step Down.
My goal is to make a flashlight that have a secondary switch

Switch 1 (Toggle Switch) - Turn Lights On or Off
Switch 2 (Momentary Switch) - Turn Lights On even if switch 1 is Off, Turn Lights Off
even the switch 1 is On.

I have this code
    void setup()
{
  Serial.begin(9600);
  pinMode(2,INPUT_PULLUP); //
  pinMode(13, OUTPUT);

  pinMode(3,INPUT_PULLUP);
}

void loop()
{

  int sensorValue = digitalRead(2);
  int sensorValue3 = digitalRead(3);
  //Serial.println(sensorValue3, DEC);
  if (sensorValue == HIGH){
    //OFF via toggle
    if (sensorValue3 == LOW){
     // ON via button if OFF via toggle
        digitalWrite(13, HIGH);
    }else{
      // OFF
        digitalWrite(13, LOW);
    }
  }else if(sensorValue == LOW){
  //ON via toggle
    if (sensorValue3 == LOW){
      digitalWrite(13, LOW);
    }else{
      digitalWrite(13, HIGH);
    }
  }

}

Ive seen an Oscillator with a relay but cant make it work.


texts: Understanding current flow in this converter

texts:
See below a picture from this Reference Design.

I’m trying to understand the min and max current that can flow to Vin pin. This is what I think:

Imin = 235/1.88M = 125 uA

Imax = (914-500)/1.88M = 220uA

Am I right?


texts:
I need to generate a variable voltage ranging from +10v to -10v in order to control a motor driver.  What are ways to generate this voltage?

To clarify: the motor driver takes +-10V as an input. +10V is full forward, -10V is full reverse, with voltages in between being differnt speeds, and 0 being stop.


texts: In PSpice, how can I fix the current with respect to resistor?

texts:
The textbook's problem is;
The current of R4 and the voltage source are 1A and 2V respectively.
If the current source is 1A:

a) Find the mesh currents.

b) Find the power dissipated in each resistor.

c) Find voltage of current source.

d) ...

I drew the scheme using PSPICE, exactly same as the textbook.

How can I make R4 have 1A?

I drew


texts:
Has anyone been able to debug/program using SWD over a Olimex USB-JTAG programmer and the ARM-JTAG-SWD adapter? If so, please share how you did it :)

Specifically, I'm looking for what the OpenOCD configuration files would look like.


texts: Does 3.3v ground and 5v ground connected will affects circuit?

texts:
I have a wifi transciever(ESP8266) which should be connected to 3.3v and microcontroller connected to 5v(PIC16).

For establishing the communication between the microcontroller and wifi they should share a common ground. So while working on the circuit sometimes wifi is consuming more current and the chip is getting heated and no communication happens.

If I reconnect the power of wifi and microcontroller again the circuit is fine.

This problem(heating up the wifi) occuring multiple times while giving 3.3v regulator(AMS1117,3v3 reg). So to reduce that I gave two separate power sources one 3.3v and one 5v power supply.

uC circuit:

WiFi circuit:

Where will be the problem of current consumption?

Is it wifi problem or ground problem?


texts: Where does this decibel equation come from, why a factor of 20?

texts:
For sound levels, it is said that decibels follow this equation:
$$
dB = 20 \log(\frac{p_s}{p_0})
$$
Where \$p_s\$ is the pressure of the measured sound wave (in Pascals) and \$p_0\$ is some fixed reference pressure.
But where does the 20 come from in this particular equation?
I know that the 10 comes from the equation when relating quantities of power:
\$dB = 10 \log(P / P_0)\$ for measured power \$P\$ and reference power \$P_0\$.
So for something like voltage, where \$P = V^2/R\$, you have \$dB= 10 \log((V^2/R) / (V_0^2/R)) = 10 \log((V/V_0)^2) = 20 \log(V/V_0)\$ so I understand that if you have some squared quantity in there you can pull out the exponent of 2 in the log function and that gets you the multiplier of 2 on the outside, hence the 10 becoming 20 in the case of voltage rather than power.
But in the sound equation I can't derive the origin of the 20 by somehow relating power to pressure. I imagine power is proportional to the square of pressure but I can't figure out where, when it comes to sound waves.


texts: Electrical Safety Guideline for LVD Compliance

texts:
We are making a product -a warning light- with 220V rated voltage. The product has a non isolated offline buck regulator. The 220V part can be accessed without the use of a special tool (there is a "turn to open" type cover). Moreover, there are parts on the same side of mains voltage which are used for adjustment of unit (buttons and trimpots).

I think that this product is unsafe, therefore not compliant to LVD. I want to persuade my boss that the design needs to be changed for compliance.

1) Are my concerns rightful?

2) Is there a standard/document which is generally about electrical safety in electronic products, which will solidly support my concerns:

mains voltage parts should not be accessible to end user
non isolated regulator creates a safety risk

Or let's ask with a different perspective; let's say that someone is checking the product for CE compliance. How will he decide that the product is unsafe? Will he rely on a document or just say "hey this is obviously wrong, someone can get shocked"?


texts: Beyond board power, understanding multiple power supplies and loads in a circuit

texts:
I have a project I am looking to power where the secondary load is more than my Arduino can provide amp-wise. I need to know the simplest way to power the whole system. I will be powering the Arduino and a 5v 1.2amp load. Diagrams I have seen show a common ground with two power supplies but I don't know the math for anything beyond a simple circuit. Links to other resources are welcome with all answers. I am looking to learn more about power and circuits in general so more info is better.

EDIT

If I use one supply, how should I design the circuit? e.g. Series or Paralell. Also, how would I go about determining the requirements for that power supply?


texts: How to control squarewave oscillator with comparator output? (LM339)

texts:
I have LM339-based resistive water detector, which produces nice (almost) rail to rail output (see Schematics for device, which reacts to water?), and also LM339-based squarewave oscillator, taken from National Semicondactor document "LM139/LM239/LM339/LM2901/LM3302 Low Power Low Offset Voltage Quad Comparators", year 2000.

Both circuits work separately, but now I need to switch oscillator ON with high output of the detector, and OFF, when there is no water. (R3 is in series with control LED, but its probably not relevant to the problem)

The idea is to use one LM339 IC, where I have four comparators.

I have tried R8 output on + and - of U1b, without any result.

I have also tried to power the oscillator from U1a output (U1a output to U1b GND), and it worked, consuming 18mA, but I want one IC solution.

My idea (maybe, there is a better one!) is to somehow shift U1b comparator balance, when no output is needed, and restore the balance when detector output is high. Maybe I need an inverter  or transistor in between?

This problem is very typical for me, as it seems I do not understand the principles of aligning cascades. There are a lot of ready circuits, but there rarely are explanations on how to use digital output to switch something on and off.

What could be a solution to this?

UPDATE: I know how to do it with 555, but the design goal is to use comparator in square-wave oscillator setup (in simple case, for continuous one frequency output, but maybe I make beeping by deploying third oscillator).

UPDATE 2: Final result, thanks to Andy aka. Changes: swapped (+) and (-) connections of U1a, changed pot to 47k (in hope this will drain battery less), removed R3 (and LED), added R8 1k from U1a output to U1b (-) input. (My mishap with pin number also corrected: gschem has slot attribute, which gives pin numbers automatically).

Follow-up, describing overload problem: Troubleshooting ready board with LM339 IC?


texts: Is the dielectric layer under the top or bottom copper layers always prepreg or can it be a core?

texts:
On a PC board is the first dielectric layer looking into the board from the top or the bottom layer of copper always prepreg or can it be a core?
Here "can" would mean conventional. If not then why?

I asked this leaving work for the weekend. This week I asked the board house this question and they said generally prepreg is always used under the outer layers. I didnt ask why though. If no one will do it then the why doesnt really matter.


texts: Identify that connector - Is it reusable?

texts:
I have an Asus Zenfone AR which has had the screen replaced 3 times.  Last time I replaced it myself, Asus the first 2 times.

Screen replacement went fine but once together I discovered up volume button didn't work.  Upon further investigation, I have found that playing with the 7-conductor flexible PCB cable, I can get the up button to work but not the down button, and sometimes, if I'm luck, maybe both but then not the power button.

I'm quite confident that the problem resides with the flat cable connection to the motherboard.  During assembly, the little white connector, which folds up and down like a lever to press the flexible PCB cable against contractors, popped off, and I've had trouble getting it to stay on.  I wonder if maybe the locking connector, what I'm calling this:

Is maybe fatigued?  Also, due to its very small size (~5 mm wide) it's hard to even understand what orientation it goes in.

I'm hoping somebody can help me ID/source the white connector.  It's my hope that a new connector that didn't pop off will put enough pressure so the cable stays in good contact.  Here are some more photos:

And here I took the liberty of drawing up the connectors because they're so hard to photograph:


texts: Why do these circuits have different output signals, please explain in detail. And how does the envelope detector work?


texts: suggestions for a ~20cm 2 way wireless communication between arduino like devices

texts:
I am trying to build a system where, when and only when someone is within close proximity, about 20 cm or so, two arduino like devices can communicate wirelessly.

I want to be able to communicate data from the device back to the human, and data from the human to the device, probably with some kind of antenna mounted in the back of a glove.

I was looking into nfc, but it appears that nfc is one way.

What are your suggestions?

For clarification, I would like to add that there would be many devices that the user may or may not choose to use.


texts: RC Lawnmower: Joystick emulation: RC PWM to _custom_ DC conversion

texts:
TL;DR I need something to map 0-5v PWM signal to 4.6v-7v DC (~10mA), kind of like what an RC speed controller does.

I'm trying emulate a 2-axis, hall-effect joystick so that it can be controlled by PWM from a RC receiver. (The only part of the power chair I'm using is the 24v motors, batteries, wheels and controller.)

Now the joystick is a hall effect 2-axis joystick. I want to emulate the signals it is sending out. I already measured its outputs. It has five wires:

Red: 11.88v steady
green: 6v steady
blue: (left/right axis) 4.6v-6.95v, depending on joystick position - slight, static pulse
yellow: (forward/reverse axis) 4.6v-6.95v, depending on joystick position - slight, static pulse
black: ground

What I know so far:

Arduino: can't output more than 5v, slightly overkill anyway
RC speed controller: overkill in $ and performance, and not typically
customizable enough to allow for ~4.5v center, 7v forward, and 4.5v
reverse
custom circuit: Very time consuming - we would much rather use something off the shelf

Do you know of a path of lower resistance for solving this problem?


texts: Aluminium electrolytic capacitor information, top marking 9h - 100 - ELA

texts:
I'm looking for information on this SMD aluminium capacitor:

On top of this one : 9h - 100 - ELA

What is the equivalence?

Thank you :-)


texts: How to increase power of a wireless power transmitter circuit?

texts: I designed this circuit for a frequency of 2MHz, but I get an output of 7mW. I need to increase the output power up to at least 10 to 20W. Help me to redesign the circuit. Consider the transformer T1 (not an actual transformer, just two inductor coils) is a combination of transmitter and receiver. The primary is the Tx and secondary is the Rx, and there would be a distance of one meter between primary and secondary. A minimum output of 5W is needed in the receiver side (at the secondary). The transformer inductance is 10uH.


texts:
When we take a clock and a signal, the D flip flop output always gives "clock edge" AND, and the state will be high unto to the next clock cycle.

Now I want my output like like a latch, but timing will be determined by the corresponding clock signal.

If we think about the case 1 (input 1 = D), we do not get any higher state because the clock is not on. But latches gives output (case 2 when D = input2) in this case when both state is high, i mean the clock and input. But the problem is that latches don't give the clock leading edge time.

Is there any way I can get the state high from the corresponding clock leading edges all the time, while it works like a latch? Like the last output that I have added in the diagram.


texts: Battery power to 5v led strip and 3.3v controller

texts:
I'm trying to build a wireless led strip using the esp8266 controller and ws2812 addressable led strip using battery power, but I'm a bit stuck on how to build the circuit.

After a bit of research I'm seeing that step-down converters are rather inefficient due to heat loss, so I'm thinking I could use a 2 AA batteries in series, with the positive connected in parallel to one 5V boost converter for the led strip and one 3.3V boost for the controller. These are the converters I've found:

https://www.pololu.com/product/2565

https://www.pololu.com/product/2563

Here's a sketch of the circuit (sorry if my symbols are not quite right):

Would this work as intended? I want to keep the price as low as possible, and the converters essentially double the cost of the project (~$15 for the strip and controller). However, if I use 4 AA batteries and step down converters then efficiency drops, and I want the battery to last as long as possible.

Any suggestions are greatly appreciated!


texts: Identifying unknown transformer from a computer PSU

texts:
I was recently using an old 375 watt PSU as a benchtop power supply and managed to break it trying to disable the short circuit/overvoltage/undervoltage protection. Meh. Anyway, naturally I took it apart and started desoldering the components. I pulled a transformer out that was mounted to the board with screws with 3 wires coming out and being soldered to the board elsewhere. The transformer had a sticker on it that reads on 2 lines "37-C6371104 ROHS HP OK/0706 SC REV.B" I did a quick google for the hyphenated number but didn't come up with anything. It was taped up with yellow tape and under the first layer was some thin copper foil wrapped around in a single layer, under that was the coils and iron core. There are 3 wires, blue, black, and white. It looks like the blue and white wire goes to one of the coils and the black wire goes to the other, which confuses me. I'm trying to identify the rating of it and I'm nervous to just hook it up to 120VAC and use a multimeter. If anyone could help me figure it out, that'd be awesome. I can take a picture of it if that would help.

Hopefully someone can shed some light and thanks in advance!


texts: Can anyone understand why my USB 1.1 full speed HUB not work, electronic issue

texts:
Our USB ports design include one USB transiever(STOTG04EQTR) and USB HUB(TUSB2036VF).The circuit drawing as below

But even the USB1.1 doesn't work. I tested the data line , the waveform really bad as below

I did not found any layout problem and we ask the USB differential pair 90 ohm as well(Not sure if the factory really followed)

Thanks

Hui


texts: Where is the input and output of this simple circuit?

texts: I was instructed to put in a voltage probe at the input and the output of this circuit. Did I place the probes correctly?


texts:
I have a problem interpreting 2 different representations of Fourier transform and proving their property.
In some texts Fourier transform is represented as :
.
While in other texts the complex number j is omitted in X(jw). The problem comes when we try to prove things where the 2 notations don't work likely for example d/dw (X(jw)) = jX'(jw) and d/dw (X(w)) = X'(w).
I faced this confusion while proving the Duality property of Fourier transform, which is this :
,
in one representation and

in other representation.
I believe that in duality result of the former representation X(jw) should contain additional j, i.e. X(t)---->2*pi*j*x(-jw), when i tried to prove it. But now I am confused.
Here is my proof, can someone validate that this is correct or correct it?
Notice the extra j I am getting.

Lot of articles or tutorials on google search uses this X(w) notation instead of X(jw).
I have found X(jw) notation intuitive lot of times. Can some one please explain ?


texts: Recommended PCB layout understanding - ADM2572 datasheet

texts:
I have problem with understanding and applying this recommended PCB layout to my design (image from datasheet, page 18):

This is isolated RS485 transceiver with integrated isolated high frequency DC-DC converter (200MHz?).

There is a trace connecting pin 11 and pin 14 that crosses the other trace. How should I do this crossing on PCB? Should I create this connection on second layer?


texts: How do I install a KiCad schematic or footprint library?

texts:
After I download a KiCad schematic library or footprint library --
such as the ones from http://kicadlib.org/ --
how do I use it in my schematic and layout?

Should I install that KiCad library file somewhere in the KiCad program folders ( C:\Program Files\KiCad\ ), or a copy of that file in each and every project that uses anything out of that file?

Then what do I do to get the things in the library to show up on my schematic or my layout?
I don't see "using 3rd party libraries" in the KiCad FAQ or the tutorials it mentions. Is there a "using 3rd party libraries" tutorial on the KiCad wiki that I'm overlooking?


texts: WWVB Antenna Reciever 1st Amplifier stage, no signal

texts:
I made a high input impedance JFET CS amp as the 1st amplifier stage for a 60kHz Loopstick Antenna. I am using an RF JFET (J211) and ceramic capacitors.

The only signal I see is a 60Hz sine wave that is present even when the amplifier is turned off.

I am unsure what to do at this point. I dont know if a I need a larger Antenna or if I am doing something wrong in trying to detect this signal. WWVB is particularly weak where I'm at as well.


texts: busted WS2811 LED strip by overpowering, totally useless now?

texts:
Powered a 5V WS2811 LED strip with 12V by accident. It turned on for a split second, it fried a microcontroller, I noticed the smell and turned everything off as fast as I could.

When i tried powering the LED strip again with 5V (also exchanging for a new microcontroller of course) only the 2nd LED in row turned on. I cut off the first 3 LEDs and soldered the wires on again, but now nothing turns on.

Does that mean the whole 5m LED strip is busted or is it possible some LED+ics further down the line could be salvaged?


texts: What resistor do I need to turn a 6 volt current into a 5 volt current?

texts: I am trying to mod a ECS-10 Modulus Nerf Gun to include a laser sight, and since the laser I am using runs at 5 volts, but the battery is 4 AA, what resistor should I use to convert the power?


texts: Is an Arduino/PI strong/good enough for my application or do I need custom hardware?

texts:
I am entirely new to using Arduinos/PIs and I am currently learning a bit out it in order to build a control unit for my masters project.

My setup:

5 IMUs that measure acceleration and rotation about 3 axes.  Each requires an     I2C.
4 variable DC voltage sources
4 magnetorheological dampers

The IMUs send their data to the Arduino/PI where 26 Non-linear ODEs need to be solved simultaneously.  A fuzzy logic controller will use the calculated values to determine the output voltage of each source and this is then sent to each damper.  And the process continues.  The model will be built in Simulink and exported via their toolboxes to the arduion/pi.

My questions:

Is there a way to connect the 5 IMUs' I2Cs to the 3 or so pins on the boards?
In your experienced/professional opinion, are any of the available products from Arduino/PI powerful enough to do my calculations in real-time?

I will be able to get some custom hardware from a company, but I am sure they will charge me an arm and two kidneys for it.

EDIT:
According to a few quick searches, most IMUs have a sampling rate upto about 1000Hz.  The dampers respond to an input voltage in about 15ms.

The equations I will be using are in a pdf from this link:
https://www.pdf-archive.com/2016/11/02/formulas-total/formulas-total.pdf

There are too many for me to type out here.

The fuzzy logic controller will have 6 fuzzy sets for each of the four wheels and 4 output fuzzy sets, one for each wheel.  So in total, 28 fuzzy sets, each consisting of 5 Gaussian membership functions and two sigmoidal membership functions. The fuzzy associative matrix will be 7x7 in size.  There will be 3 of these matrices per wheel, which brings as to the value of 6 fuzzy sets as was stated in the first sentence of this paragraph.

I hope this answers at least a few of the comments' concerns.


texts: How do I calculate the current in parallel branches?

texts:
I've been playing around with an Arduino for a while now, and while I know just enough about simple circuits to get little projects up and running, I still don't know enough to figure out what's going on in all but the simplest of circuits.

I've read a few books on electronics and a handful of online articles, and while I think I understand how voltage, current, resistors, capacitors and other components work; when I see a schematic with lots of them in, I don't know what's going on where.

In a bit to finally get to grips with it, I bought a 300-in-1 Electronics Project Set, however it seems to jump from "Here is a circuit with two resistors in parallel" to things more complex, without explaining how it works.

For example, it shows a simple battery->resistor->LED circuit, but shows that if you wire a button up in parallel with the LED, pressing the button turns the LED off.

I get that the current must be travelling through the path of least resistance, but I don't understand why it doesn't travel through both.

I'm taught that wiring two resistors up in parallel causes the current to flow through both, and so more current flows in the circuit. I've also tried replacing the button in the circuit above with resistors of varying values, and as I suspected, a high value resistor doesn't affect the bulb at all, but lower values start to dim the bulb.

I'm not sure how to apply the E = IR equation to all of this.

Also, how much resistance does an LED have? I tried measuring it with my multimeter, but it wouldn't give a reading.

Sorry if I've waffled on loads here, but I'm trying to paint a picture of what I think I understand and what I want to understand. Not sure I've achieved that!

Oh yeah, and expect lots more of this as I delve deeper into my 300-in-1 project kit!


texts: Question regarding series resistor with potentiometer

texts:
W.r.t above circuit fragment, a 100k linear potentiometer is connected to pins 1,3,4 of J12. Internally my code in the MCU reads the 10-bit ADC from pin P1.3. I am expecting linear ADC values (this is what i need) whereas i find a completely non-linear precipitous voltage drop followed by a long tail when the pot is twisted from high to low values. I am not quite clear how to explain this but feel that R12 (10 ohms) and R17 (10k ohms) have something to do with this. On using a 5k potentiometer i get a almost  linear like voltage change.

I would like to understand how this part of the circuit works and how i can calculate the input voltages from the pot (and thence the expected ADC values) for different values of the pot like 100k, 10k, 5k and 1k.

Appreciate your explanations.


texts:
I am looking to find the transfer function from w to z in this loop. I have been trying for a while looking all the relationships but just don't know how to express w in terms of r,d and n and then express it as a TF with z. I would appreciate a hint on how to solve this.

Regards


texts: Is the peak value received power at carrier frequency in the power spectrum

texts:
Is the peak value of spectrum at carrier frequency received power? I am transmitting the signal with 12 dBm power at 4Ghz carrier frequency. The signal is modulated with 4GHz carrier frequency with BPSK modulation scheme type. The signal is transmitted to the oscilloscope via coaxial cable. For further processing, the oscilloscope is connected to PC via ethernet cable. So when I measured the output signal in VSA software in that PC, then I saw the peak value at 4GHz carrier frequency -3.57dBm which is lower than expected value as there is no attenuator used between the receiver and transmitter. The output is shown as below:

So my question: what is the received power at carrier frequency 4GHz? The peak value is shown -3.57dBm at 4 GHz and measured power at the occupied bandwidth is 9.933dBm. So which one is received power at this carrier frequency?


texts: Control several binary outputs with raspberry pi, CD74HC273 D-type flip flops and 5v relays

texts:
I am using a system with a raspberry pi and multiple d-type flip flop (CD74HC273), its role is to be able to control several digital outputs with a web app.

I use 8 raspbery GPIO bits as data/input bits on each flip flops, and n GPIO bits to select one flip flop and disable the others (with master reset input), so I can control 8 x n digital outputs.

I worked fine when I tested it with leds, so I tried switching to 5v relays, which is the actual goal (below the link to the kind of relay integrated circuit I am using)
https://www.amazon.fr/XCSOURCE-Bouclier-Optocoupleur-Arduino-TE213/dp/B00ZR3B252/ref=sr_1_6?__mk_fr_FR=%C3%85M%C3%85%C5%BD%C3%95%C3%91&keywords=relais+5v&qid=1579683668&sr=8-6

But I realized that those are activated by low state input, which is problematic, because 74HC273 output is low state by default if not activated, so activates relays by default, which I don't want.

I am pretty new at electronics, so I don't really know how to fix this problem.

What would be the best solution ? :

Can I find "active high" relays ?
Can I find another type of flip-flop that works in the same way, "copying" the input level to the output on clock pulse, but with a "master set" input, all ouputs to high state by default ?
Should I use 8-bits inverters on every 74HC output ?
Any great solution I did not think about ? :)

Here is a "sketch" of the circuit (although I don't know exactly what goes on underneath the hood in the integrated relay circuit, that would be the ""?"" bit, but I guess this is a pretty standard component):

EDIT: found the schematics for the "??? relay module":

EDIT :
link to supplier documentation for the electrical lock

Thanks a lot !!


texts: A 13.8 volt radio battery from 18650 cells

texts:
I've dumpster dived and hamfested a whole load of duff laptop battery packs.

I'm going to discharge them all then charge them to get the capacity of all the cells, triage the dead ones and sort into capacity groups.

I'd like to construct a 8000 mAh battery from the 18650 cells.

I thought about a 4S4P configuration, but say a fully charged unloaded 18650 has a voltage of 4.2 V, then 4 times this is 16.8 volts.  This is too high for my radio (Elecraft KX3) which has a maximum specified voltage of 15 V.

The radio draws a few amps on transmit, but I'd also like to run a linear amplifier from the same battery that might draw something like 10 A

I guess there are several possibilities:

A BMS board with a suitable current rating, that gives me 12 or 13.8 V out
Using linear voltage regulators (can I parallel them to give 15 A?)
Switching regulator, like a buck converter.

I believe:

Linear voltage regulators are very inefficient
Switching regulators generate a lot of RF noise which needs to be filtered for RF power supply applications

I guess I could go for 3S4P, the max unloaded battery voltage is then 12.6 V, but I guess when loaded it's going to drop, my radio does have quite a wide operating voltage, so I'd get some use out of it.

So what's the best way to construct a 12-13.8 V battery from 18650s?


texts: How to construct a switch that would switch between two USB outputs, controlled electrically?

texts:
Basically I have a Smart TV, Raspberry Pi connected to it and wireless mouse and keyboard, using a single dongle for connection. What I would like to achieve is to being able to remotely switch where dongle is connected, to be able to operate both devices alternately.

In my research I found a concept of DPDT switch that seems to be exactly what I need, for 4 USB pins, but that switch would have to be remotely controlled. The remote part is out of the scope of this question, I just need something that I could send a signal to from my RPi through one of its pins to change output target of dongle.

I could find pretty much only manual DPDT switches, and I need something that I could control electrically. Would be difficult to build it? Could someone help me with a schematic? I'm willing to try.


texts: RLC circuit and equivalent load resistance of a transformer

texts:
I would like to know when there is no more energy into the RLC circuit with the transformer. (R in RLC circuit symbolized the resistance at the secondary). I tried to simplify this model by doing an equivalent circuit without a transformer.  Then It will be easier for me to do others calculs...

Here are the circuits :

For the circuit without transformer, the quality factor according to my calculs (which may be wrong) is the following :

$$Q = \frac{Rload2*\sqrt{C}}{\sqrt{L}}$$

According to my calculs which may be wrong, the equivalent load resistance at the primary is equal to :
$$Rload2 = \frac{Rload3*Np}{Ns}$$ where Np is the primary turn number and Ns is the secondary turn number.

So the equivalent quality factor Q of the circuit with the transformer is equal to :
$$Q = \frac{Rload3*Np*\sqrt{C}}{Ns*\sqrt{L}}$$

Nevertheless when I adjust Rload2 in the circuit without transformer to have the same quality factor Q, it rings differently.  I could understand that the voltage/current waveform is different but I have some trouble to understand why the same energy at t=0 will take more/less time to be dissipated if Rload2 is really the equivalent resistance of the circuit Rload3 with the transformer

Here are the results :

So what is my mistake ?

Thank you very much !


texts: How do I design correctly ground plane separation for Texas Instruments TPS63060 IC?

texts:
I'm concluding my two-layer PCB design and my last obstacle is ground planes.

Specifically, the problem is the TPS63060 IC that requires Power Ground separation from Control Ground (pin 7). That is a 2.2 MHz max buck/boost regulator that will actually operate between 3.3-7V

The datasheet states:

My design looks pretty the same but I don't understand how to predict the path of the Control Ground return current.

On the basis of what I understood, C2, C3, R2 grounds are connected on that island, then they are switched on the bottom plane.
The return current, however, should return to the device's ground that sends that VIN. But return current could simply pass through thermal vias and come back to the top ground plane and follow an unexpected path: the Power Ground path.

Thank you ;)


texts: Square generator 1KHz to 1MHz with 1KHz precision

texts:
I would like to make a square wave generator which will output a signal with amplitude X voltages and frequency between 1KHz to 1MHz, with the precision of 1KHz (for example: 785kHz, 926kHz, 999kHz, etc ...).
I have tried to do that with Arduino Uno, but I realized that I would need a precision of 1ns to be able to do that. 1ns equals to 1GHz. So, what hardware do I need to be able to do that?


texts: Recent thunderstorm, and a big overhead cloud to cloud lightning flash. Coincident with it, sparks jumped from a metal chair in the house. Would it be possible to get a spark from a loop of cable layed on the floor in the form of a coil with the ends open to create a small spark gap? Or would it have to be more carefully tuned than that? The idea is to get some sparks from lightning that is further away.


texts: Unused gates on Flip Flops best practices

texts: If I'm using a 74LS112 and I only need to use one flip flop, what are the best practices for the other unused inputs? Should I tie J, K, ~SET, ~PRESET, and CLK on the unused JK FF to Vcc?


texts: Need help choosing resistors for difference amplifier

texts:
In the circuit below I am trying to achieve 15.56 gain on IC2.

The following combinations (in kOhms) are fairly close:

20/1.3 or 200/13 = 15.38
47/3 or 470/30 = 15.67
51/3.3 or 510/33 = 15.45
56/3.6 or 560/36 = 15.56

The pair 56k/3.6k is actually spot-on and seems to be OK for OPA548 and required bandwidth (under 200kHz) per this answer. Although it is rather on low side, just as 560k/36k seems a bit too high.

Now, to consider SI8920B requirements I have to look at input impedance of difference amplifier, or maybe at all three impedances according to this answer.

The problem is that I don't understand which one is specified in the datasheet. It says "Output Resistive Load" minimum is 5k. If this is differential impedance then all combinations but 20/1.3 are OK. However an application example in the datasheet has 5k resistor on both lines. If this means datasheet specification is for individual outputs then I am left with high resistance combinations only.

So, my gut feeling tells me to go with 200k/13k.

Question: is this a right choice?


texts: What's the difference (electrically) between AC- and DC-coupled sampling circuits?

texts:
I've noticed that in analog signal acquisition hardware you see two paradigms: AC-coupled and DC-coupled.  Typically AC-coupled hardware is less expensive, and basically has a 20 Hz high-pass filter to remove the DC component.  DC-coupled hardware, which is good for reading sensor signals for example, tends to be in the hundreds or thousands of dollars, whereas AC-coupled hardware like computer sound cards is very inexpensive.

What are the electrical challenges in designing high-quality circuits for sampling DC-frequency analog signals?  I'm trying to understand why there is this huge difference in cost.


texts: I'm using this sensor AIR FLOW METER, but I see on page 11 that the 0-10 V output is not linear, how can I linearize that output?


texts: Hi, I'm trying t0 make a H-Bridge from the ground up and I was wondering if there is a way to deal with my Parallel FET's capacitances? is there any tricky way to reduce the capacitance in parallel at the driver?


texts: Smallest Delay Possible in a really dumb RF communication

texts:
I want to use RF to do a really simple switch over wireless. My design is really simple: a pair of transmitter and receiver, with transmitter sending energy on certain frequency (energy high enough to distinguish from the noise), and receiver detects if there is enough energy on the frequency. I only need to transmit 1 bit of data in my case (energy exists on certain frequency for 1, otherwise 0).
The problem is that I need to transmit it really really fast (in the level of micro seconds), that is to say, from transmitter starts to receive a high voltage and begins sending signal, until the receiver detects the signal and outputs a high voltage (here signal is just energy on a certain frequency), the delay needs to be as small as possible.
I know there is a booting delay on the transmitter side when it gets the sending command (time between standby state until transmitter reaches its maximum sending power state), and there is a detection delay on the receiver side (time between the signal actually reaches the receiver and the receiver outputs a high voltage). I want to know how long are these delays, and what is the smallest possible delay I can get.

Edit:
Here is the background of this problem: I am currently doing a research program, which involves several devices in the space (e.g. in a room), and each of them is equipped with a RF transmitter and receiver. I want to trigger an operation on all of these devices simultaneously (within short time), and the initial triggering command can be sent by any of the devices. Each device is set to repeat the single tone (energy on certain frequency) once it receives it, so other devices that are out of range can eventually get the signal.
Current I am using a pair of OOK RF 433Mhz transmitter and receiver (XCSOURCE), the result is not good enough, the latency is around 30~40us.


texts:
Trying to make a round-robin (time-slice based) array of microphones, which feed to the microphone input of a PC.

There are 2 things I am looking for some ideas / pointers on:-

The distance between mic and pc can be upto 50ft. What can I do to ensure that signal reaches PC with acceptable fidelity ? Do I need to do a pre-amp and feed to line-in of the PC instead ?
I need to run upto 20 mics, all connected to the same PC, with a single ordinary sound-card. The mics inputs are switched near the PC, based on a selection logic which is running on the PC. Clearly, I need only input from one mic at a time. Are there some pit-falls I should watch out for with this approach ?

Any existing schematics for such purpose would be really useful, but I do intend to upload a schematic for community validation shortly.


texts: I was trying to make this circuit on Proteus but this error appears

texts:
I was trying to make this circuit in Proteus as you can see but
"[SPICE] transient GMIN stepping at time=3.12737e-007"
error keeps appearing. How do I make this error go away?


texts: Beginner, how to connect a rechargeable battery to be able to power a 12 Volt Fan and a 5 Volt TEC/Peltier (or 5 Volt Fan/Peltier)?

texts:
Firstly, I want to say thank you for looking at my question. I am trying to make something for my nephew, but I really don't have much experience in electronics, even though I have been researching it heavily.

Basically, I want to make a device in which a slim rechargeable battery (think a phone battery pack) powers all the following:

1) 2 5 Volt Peltiers, (Max 5A, 6.2V @ 19.4 Watts) --> http://amzn.to/2tqHYKM

2) 2 12 Volt Fans with 2 PINS (http://ebay.to/2vwNAo6)  OR 2 4 Pin, 5 Volt Fans

3) An off/off switch would be nice, but a power/speed adjuster is not necessary as I want all devices to run on full speed all the time (19.4 Watts); however,an option to shut the device automatically after a certain temperature is reached is necessary.

What I know

I don't want you guys to think I don't know anything, so I know that I need some sort of circuit board that allows me to output and take in either 12V and 5V, or just 5V, and then I need the same circuit board to be able to take a 2, 2 Pin fans (or 2 4 pin fans) and 2 Peltier devices; although I might only need one.

I have been researching and have come across items such as "PWC controller" for a 4 pin fan, yet they have all only been able to take in 12 Volts. I know that circuits exist in which both 12v and 5v power outputs from a 12V power supply .

Furthermore, I know that the board for for power input and output is called a "charging board", but connecting the puzzle pieces in which a rechargeable battery powers what I want is so beyond me.


texts: Uncertain of 8-bit vs 32-bit alternatives to AVR32

texts:
I was browsing a distributor to find options for simple 8-bit and 32-bit RISC uCs and came across AVR32. After some searching on the web, it seems that AVR32 is a bit dated and possibly not a good choice for long term sustainability. (I am unfamiliar with what’s popular in 2021)
As someone with limited experience, mostly in C with Arduino development kits, what alternatives exist to AVR for 8-bit and 32-bit that are 1) not near end-of-production life cycle 2) have strong support via communities & examples and 3) do not require an OS? (not looking for a microprocessor)
Context: I am eventually looking to design a custom PCB for my project. Also, my project is a simple feedback loop that uses some basic sensors and a motor... I believe a microprocessor is certainly an overkill for my project in terms of infrastructure and cost, so I am specifically seeking microcontrollers.


texts: How to build a true ultra low power binary counter

texts:
I'm looking for a true ultra low power binary counter of ~10 bits (can be longer)
The frequency is not important, I will count pulses, almost static events but I need 10uA max. at 3V

This one for example can be ok at 25deg (with 4uA) but at higher temperature can reach 40uA which is 10x worse than normal.
https://toshiba.semicon-storage.com/info/docget.jsp?did=15759&prodName=74VHC4040FT

Another idea (taken from here I believe) is to use some cascaded D-flips (74AUP series) like this one
https://assets.nexperia.com/documents/data-sheet/74AUP1G74.pdf

But will be 0.9uA per device x 10 bits = 9uA (over temp) + additional cap. loading.
This is the most pro missing solution I found so far.

I'm curios if there is other way to build it.

Thank you in advance,


texts:
I have a (750w) psu that takes up to 60vdc and would like to plug it in a 230vac 50Hz (domestic power outlet).

There are two solutions I thought of immediately, but am not sure which one is best :

1 : 230Vac -> transformer to 60Vac -> rectifier bridge -> bank of capacitor -> DCDC psu

2 : 230Vac -> rectifier bridge -> switching regulator -> bank of capacitor -> DCDC psu

1-> Rare and expensive transformer needed

2-> complex circuitry needed to switch the gate of a mosfet (to drop voltage down to 60vdc).

Of course the easiest would be to buy the converter but it's pretty difficult and the challenge could be interesting :)

(NB. I didn't take into calculation the rms, and other voltage drops for all of these values, the DCDC psu handles up to 50V 15A, I'd like to get the most out of it :) )


texts:
So today I want to make it a little bit strange...
I'm working on a project and there are 4 outputs controlled by 4 relays and the relays' outputs are coming out of the board with phoenix so the user can use them like a switch.
But I'm thinking of putting it in a higher level so the user can choose what every output should be, like this output I want it to be controllable +5V DC (the output set as +5V DC and can be switched on and off with relay) or I want it to be controllable 220V AC so that he can switch on or off this 220V AV output. Notice within just one controllable output we can decide whether it's +5V DC or 220V AC (with a microcontroller).
I'm thinking of using TRIAC.
I don't know if I made my point clear or not but I need your help, if you can help me please don't hesitate and if you didn't get my point tell me which part is not understood so that I make it more clear.


texts: Why can't my 555-based DC-DC boost converter supply even 3 milliamps at 12V?

texts:
I hope someone can help me. I've been tearing my hair out for the past couple of weeks trying to make a simple DC-DC boost circuit.

It puts out a nice 12-ish volts when not loaded, but as soon as I draw even 3mA, it drops down to around 6.7 volts. It's just too weak to supply any current whatsoever.

I initially tried a microcontroller, but then switched to a 555-based design, thinking that maybe the firmware was the cause of the problem. Turns out it wasn't.

My current design looks like this (and can be simulated here):

I laid it out on a breadboard using Photoshop. The red dot is the output, and it's missing the second zener (because I added it later).

Here are some pictures of my breadboard:

Without any zeners, and without any load, the output naturally floats up to around the 20V mark. With only the first (13V) zener, I get around 14V at the output. With the second zener, I get about 12.2V. Until I try to draw a couple mA, that is.

I need it to supply around 15mA at 12V, from a 5V source, with no more than about half a volt of ripple. That is all I require. And I simply cannot achieve this.

I have tried changing to a 1mH inductor; I have tried putting out a nice clean square wave from a microcontroller; I have tried frequencies between 8kHz and 40kHz; I have tried duty cycles from 40% to 80%; I have tried changing the resistance of R2; and I have assembled the circuit on actual PCB instead of breadboard. All to no avail.

Can anyone explain to me why I'm having so much trouble?

EDIT: The inductor is known to be suitable for the task, because I used one successfully in another project:

Granted, this one had a schottky diode, rather than a normal signal diode, but that wasn't the problem either.

EDIT:

Here is the other project happily supplying 9.2mA at 11.5V:

EDIT: There has been some debate as to the 555 being unsuitable for the task. In response to this, here are some pictures of my first design. As you can see, it was microcontroller-based, and located on a PCB. Frequencies of 8kHz to 40kHz were tried, and duty cycles of 40% to 80%.

EDIT: Oscilloscope readings for the output pin of the 555:

Oscilloscope readings for the transistor emitter (before a 2Ω resistor):


texts:
I was reading about SCRs and I'm trying to simulate 2N5060 SCR but having some issues when I plot the currents and voltages:

First by looking at the datasheet, I set the R4 to keep the gate current a bit less than 200uA.

For V2 I set the on time for the 5V gate pulse as 50u and 100us period.

I set a load which does not exceed 0.8A rated.

And here is the current through R1:

and here is the zoomed view:

And here is the plot of the voltage at the gate node:

Why is the load current has so many spikes?(it even gets worse with the shorter pulse ON times)

Is the gate voltage normal? It doesn't go to zero volt even I put a resistor between the gate and the cathode.

Why doesn't this SCR rectify the current? It passes the current both way, see my first plot.

I might be doing something fundamentally wrong but couldn't figure out the source of the issue.

edit:

The gate current:

Edit 2:

I increased the gate current as suggested and it still doesn't work.

And here is the SPICE model:

**********
*SYM=SCR
*SRC=2N5064;2N5064;SCRs;TECCOR; 200V 0.8A
.SUBCKT 2N5064   1 2 3
*    TERMINALS:  A G K
QP  6 4 1  POUT OFF
QN  4 6 5  NOUT OFF
RF  6 4    400K
RR  1 4    267K
RGK 6 5    80
RG  2 6    9.09
RK  3 5    0.112
DF  6 4    ZF
DR  1 4    ZR
DGK 6 5    ZGK
.MODEL ZF   D (IS=3.2E-16 IBV=100U BV=200)
.MODEL ZR   D (IS=3.2E-16 IBV=100U BV=200)
.MODEL ZGK  D (IS=3.2E-16 IBV=100U BV=5)
.MODEL POUT PNP (IS=320F BF=1 CJE=402P TF=102U)
.MODEL NOUT NPN (IS=320F BF=100 RC=0.45 CJE=2.01N CJC=402P TF=3.74U)
.ENDS
**********


texts: Clarifying some doubts regarding PUPDR register of the GPIO [STM32]

texts:
Might come off as a trivial question but when does one use Pull up and Pull down as PUPDR register of the GPIO? I'd guess it's used to define the default state of the pin.

The following includes the image the push button on STM32F401 nucleo board. It's apparent that PC13 IO is pulled high via a pull up resistor in case the button isn't pressed.

So the IO pin as shown below is already pulled high, isn't it? Does it matter if PC13 is configured to be in Pull up or Pull down mode event?

Secondly, for the LED (LD2) that's connected on PA5: if the PUPDR of this pin is set to pull down, there's a pull down resistor (as shown in the IO image above) that's connected to PA5 and for pull up, there's a pull up to VDD? Assuming that's the case, shouldn't LD2 be "on" on start of the program if PUPDR is set to PULL UP? (doesn't seem to be the case with me)


texts:
I'm trying to connect Simcom SIM900 to Nucleo-F411RE using the following configuration for USART1:

void MX_USART1_UART_Init(void)
{

  huart1.Instance = USART1;
  huart1.Init.BaudRate = 9600;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  HAL_UART_Init(&huart1);

}

Also the GPIO initialization is as follows:

        GPIO_InitStruct.Pin       = GPIO_PIN_9 | GPIO_PIN_10;
        GPIO_InitStruct.Mode      = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull      = GPIO_PULLUP;
        GPIO_InitStruct.Speed     = GPIO_SPEED_FAST;
        GPIO_InitStruct.Alternate = GPIO_AF7_USART1;

        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

Now I'm trying to send "AT\r" command and receive the "OK" or "ERROR" from the modem but it seems that I get nothing from it. I've tried sending "AT\n" "AT\n\r" too but neither was giving the proper result.

I use the oscilloscope to see if the binary bits are transmitted to the modem and it works fine. What can be the potential issue?

I think there's a configuration mismatch between Nucleo and the modem but couldn't figure it out yet.

Edit:
My main function looks like this:

#define TXATMESSAGESIZE       (COUNTOF(Message) - 1)
#define RXBUFFERSIZE          10

#define COUNTOF(__BUFFER__)   (sizeof(__BUFFER__) / sizeof(*(__BUFFER__)))

uint8_t Message[] = "AT\r\n";
uint8_t aRxSIM900Buffer[RXBUFFERSIZE];
UART_HandleTypeDef huart1;

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();

  /* UART TX and RX */
  HAL_UART_Transmit(&huart1, (uint8_t*) Message, TXATMESSAGESIZE, 1);

  if( HAL_UART_Receive(&huart1, (uint8_t*) aRxSIM900Buffer, RXBUFFERSIZE, 10) != HAL_OK)
  {
      while(1){

      }
  }
}

Edit 2:

When I step into the HAL_UART_Receive function in debug mode, I see the program stuck inside static HAL_StatusTypeDef UART_WaitOnFlagUntilTimeout() function. To be exact, it goes inside this first if and waits for the next character to be received:

/* Wait until flag is set */
  if(Status == RESET)
  {
    while(__HAL_UART_GET_FLAG(huart, Flag) == RESET)
    {
      /* Check for the Timeout */
      if(Timeout != HAL_MAX_DELAY)
      {
        if((Timeout == 0)||((HAL_GetTick() - tickstart ) > Timeout))
        ...(otherstuff)
  }