texts: Unable to supply FONA 32u4 3.5 v through circuit

texts:
I am relatively inexperienced when it comes to circuitry and electronics. However I am trying to create a simple device in which with a press of a button, the device turns on and calls a specific number.

My parts list -
 - Fona 32u4
 - Logic Level N channel Mosfet
 - 10k ohm resistor
 - 220 ohm resistor
 - push button
 - LED
 - Wires and such
 - 3.7 v 3000 mAH battery

For Prototyping purposes, I am currently designing this on a breadboard -

Here is the circuitry -

Whenever I run this program -

#include "Adafruit_FONA.h"

#define FONA_RX 9
#define FONA_TX 8
#define FONA_RST 4
#define FONA_RI 7

#define number "###"

int LED = 11;

#include <SoftwareSerial.h>
SoftwareSerial fonaSS = SoftwareSerial(FONA_TX, FONA_RX);
SoftwareSerial *fonaSerial = &fonaSS;

Adafruit_FONA fona = Adafruit_FONA(FONA_RST);

uint8_t readline(char *buff, uint8_t maxbuff, uint16_t timeout = 0);
uint8_t type;

void setup() {

Serial.begin(115200);

pinMode(12, OUTPUT);//This is the MOSFET gate
digitalWrite(12, HIGH);//Immediately activate the MOSFET gate
pinMode(13, OUTPUT);//This is the LED
pinMode(LED, OUTPUT);//This is the LED

fonaSerial->begin(4800);
if (! fona.begin(*fonaSerial)) {
while (1);
}

type = fona.type();
Serial.println(F("FONA is OK"));
Serial.print(F("Found "));
switch (type) {
case FONA800H:
  Serial.println(F("FONA 800H"));
  Serial.println("Connected");
  break;
  }

while (1) {

digitalWrite(LED, HIGH);       // turn the LED on
delay(100);                    // wait for a second
digitalWrite(LED, LOW);    // turn the LED off
delay(100);

    uint8_t n = fona.getNetworkStatus();
    Serial.print(F("Network status "));
    Serial.print(n);
    Serial.print(F(": "));
    if (n == 0) Serial.println(F("Not registered"));
    if (n == 1) Serial.println(F("Registered (Online)"));
    if (n == 2) Serial.println(F("Not registered (searching)"));
    if (n == 3) Serial.println(F("Denied"));
    if (n == 4) Serial.println(F("Unknown"));
    if (n == 5) Serial.println(F("Registered roaming"));

    if (n == 1) break;
}

delay(250);
Serial.println ("Ready to call");
callPhone();

}

void loop(){

digitalWrite(13, HIGH);delay(50);digitalWrite(13, LOW);delay(50);

}

void callPhone() {

delay(250);
fona.callPhone(number);
Serial.println("called the POPO");

}

It does not work due to a lack of voltage. The battery supplies 3.7 volts, but by the time the circuit is put in use, the chip is only being supplied 1.2 volts. As stated before, I am limited in knowledge. I ask someone to help me understand why the supplied voltage is so low and how to fix it.

I suspect it is the breadboards fault, perhaps the wires lower the voltage, or the mosfet. But I have no way of understanding.


texts: RL circuit: How to determine the equivalent resistance of the circuit?

texts:
So I'm working on an RL circuit and the solution is stated to be that R1 and R3 are in series, but I didn't think that was the case because they don't have the same current through them. Given solution says to add R1 + R3 in series and then use that equivalent resistance and add to R2 as if it were in parallel.

TL;DR: How do I find the equivalent resistance of the circuit below so that I can find the time constant for this RL circuit?


texts: What is the net magnetic flux density in the center of a four-pole stator and other multiple-pole stator?

texts:
According to this ppt,
if the currents are given as
$$\left\{
\begin{aligned}
i_{aa'}=I_M\sin{(\omega t)} \\
i_{bb'}=I_M\sin{(\omega t-120°)} \\
i_{cc'}=I_M\sin{(\omega t-240°)} \\
\end{aligned}
\right.$$
the net magnetic flux density in the center of the two-pole stator will be
$$\vec B_{net}=\vec B_{aa'}+\vec B_{bb'}+\vec B_{cc'}=...=1.5B_M(\sin{(\omega t)}\hat x-\cos{(\omega t)}\hat y)$$

However, there was no similar formula given for the four-pole situation. I searched online but I couldn't find any source that mentions it.
Personally, I think \$\vec B_{net}=\vec 0\$, since all B cancel out.
If I'm right, how would this four-pole stator make the rotor inside to rotate?
If I'm wrong, what are the detailed steps that lead you to the result? The answer I'm expecting is in the vector form:
$$\vec B_{net}=...\hat x+...\hat y)$$
Further question: what about the cases with more poles?


texts:
I'm currently designing a circuit using Alpha RV141F-40-20BL-B50K Potentiometers which feature a clear shift into which a 3mm LED can be inserted.

My initial plan was to just fit a WS2812B underneath each chip for simple RGB addressing of each potentiometer. Unfortunately, there is only a 0.9mm gap underneath the pot, which won't fit the 1.6mm 5050 package. Additionally, I am worried about light leaking from one pot to another if the led is not properly inserted into the shaft.

My second approach was to use an external driver (e.g. TLC5940) and a 3mm RGB led until I realised that "real" 3mm RGB LEDs don't exist.

Does anybody know about an equivalent of a 3mm led as an smd package, any other widely available clear shaft potentiometers or does anybody have any other thoughts/ideas regarding the problem?

Thank you.


texts:
I'm quite new to the topic but I would like to conduct an experiment on how RFID wristbands in a hospital setting affects patient satisfaction compared to a control group that will not have RFID wrist bands. Currently, a lot of patient verification is required, resulting in asking the same patient (possibly) up to 10 times their name and date of birth.

To conduct this experiment I will need some equipment, and I hope to find some assistance in this forum.

My guess is I will need:

Printed RFID wristbands (or at least an RFID transmitter with a
unique code to identify the patient by)
RFID reader

I'm very familiar with PHP and back-end programming, so my first goto would be some restful API design the RFID reader transmits the data to. Perhaps, it is also possible to link the RFID reader with e.g. a smartphone or iPad?

Then there is a practical question I have: will the RFID reader react on the RFID wristband nearest? Or how will this work?

I hope you guys can shed some light on the hardware requirements I need. Thank you for your time and insights.


texts: Can I safely use rectified 120VAC to keep a 120V lead acid battery charged?

texts:
I want to experiment with some 120V BLDC motors.  I will need hundreds of amps at times.  The controllers can typically take a bit more than 120V input, say 136V.  I don't want a huge battery bank and complicated (expensive) charger.  I'm thinking of ways do something cheap and easy.

Let's say I use 10 "12V" lead-acid batteries in series.  Normally they'd be charged to 135V or so.  I'll switch a full-wave rectifier with an SCR and connect the output directly to the batteries.  If the voltage gets over 130V(?), I'll simply cut the SCR for awhile. This should keep it below "float charge" range of the battery.  (I'll also need to limit current in case I pull the battery way down.)

I understand that this is not optimal and it wastes much of the potential of the batteries, but would it be safe?  Is there a simple way do better?


texts: Unexpected noise at low pass filtered output

texts:
I am trying to capture and filter a PPG signal using a simple phototransistor and an IR led. I have hooked the emitter to a Bessel low pass filter so as to get rid of high frequency signals. Below is the full schematics:

simulate this circuit – Schematic created using CircuitLab

Cut-off freq: around 3.31Hz

I observed the signals on the oscilloscope and the signal at emitter seems fine (observable PPG signal with noise: at emitter (Yellow).) I am expecting the output: opamp out (Blue) to be a much cleaner version, but it is appearing noisy with no improvement:

the signal is fine until the non-inverting input of the opamp and is filtered due to the low pass configuration, Blue: at opamp(+); Yellow: at emitter

About a month ago, I had used the exact schematics and tested the circuit which worked straight away without any issues. Blue: at emitter; Yellow: at opamp out:

So far I have re-breadboarded the circuit, replaced parts, tried different power sources, but nothing is helping.


texts: How can I troubleshoot stuck/flipped bits in a serial connection?

texts:
I'm working on reverse engineering some scrap vaccuum fluorescent displays from Noritake that lived their previous lives inside a payphone. No datasheet exists for it since it's a custom part; Noritake themselves couldn't help out. Some sibling parts are available but they all use different interfaces.

I figured out that the VFD boards use RS-232 thanks to a DS14C232CM level shifter right next to the main connector. Some prodding with a continuity tester later and I came up with this schematic and testing setup:

The second pair of lines looks to be used for flow control.

An extremely fortunate find was a dip switch on the reverse that triggers the module into a debug mode where it lists baud rate, parity, packet size (based on the other dip switch settings) as well as the contents of some registers; a printout of every character in ROM; and a demo of markup support (e.g. scrolling/flashing); it even has an RTC. This tells me the boards are functional and how to talk to it.

The interface is a standard RS232 terminal with some display control done via escape codes. I tried using a USB-RS232 adapter to send some characters to it using RealTerm, but here's my issue: some characters display reliably, while others show consistent flipped bit errors. Here's an example, I'm sending lots of '2's to the screen:

'2' is ASCII 0x32 or 0b00110010. ':' is 0x3A or 0b0011*1*010. Bit 3 is flipped. Similarly when I send 1, I almost exclusively get 9; same bit 3 error. Printing : or 9 displays reliably. This is what printing the alphabet looks like:

I swapped in a second screen and it too has similar problem. Printing f results in an occasional 'v' or 'd'. Other characters have other issues.

How do I troubleshoot this? Is this indicative of some sort of timing error or failed hardware? There is no obvious damage to the boards that would make me suspect the latter.

I've verified the USB-RS232 adapter is functional with a Tektronix Logic Analyzer.


texts: High Speed Data Acquisition with SD Card Write

texts:
I am collecting data from several dozen sensors over an 8 MHz SPI bus at 400 Hz. It is critical that the sensors are sampled at this rate with no lost packets. In order to do this, I have a timer (which I will refer to as TimerA) which raises an interrupt every 2.5 milliseconds. To store the large amount of data, I am using an SD card.

Here is my current program flow

Within the TimerA ISR, data is collected from all the sensors. This takes approximately 1 millisecond.
This data sample is stored in a FIFO buffer. The buffer can store up to 400 samples (1 second of data).
Each time a sample is written to the buffer, an index k is incremented. k keeps track of the number of samples in the FIFO buffer.
The main() loop watches the index k. If k > 0, it pulls an entry from the FIFO buffer, processes it, then stores the result in the SD card write buffer. k is decremented.
Once the SD card write buffer reaches 512 bytes, the SD card write buffer is written to the SD card.

I know that having the data acquisition within the TimerA ISR is a no-no as the ISR code should be short and sweet. I originally had the TimerA ISR raise a flag that would be handle in main(), but during long SD card writes I would lose several data samples.

My question is: is my current program flow acceptable? Or is having the data acquisition code within the TimerA ISR going to cause issues?


texts:
I am working at a semiconductor company and we have some issues at the fabrication level.
I see an issue regarding the MIM ratio of a certain data.
What is this MIM Ratio? Is this a ratio of capacitor? Area of the metal of the capacitor?


texts:
I am drawing a schematics in Altium Designer. Based on an old design, there is 4*10k resistor as shown in the figure below. It is actually one component (one Part No in the library) with 4 different parts. So the first resistor is R12A, the second one is R12B, R12C and R12D.

I want to draw this 4x10k resistor in my new design. I found its Part No in the library. Later, I fixed part number to each one. So the first one is 1/4, the second is 2/4 and so on. The problem is coming when I annotate the schematics. Each resistor get a unique designator number instead of one designator number with different parts!!

To summarize my problem:

1)I need one Designator number with four different parts (R12A, R12A, R12C, R12D).
2)when I annotate the schematics, it became like (R12, R13, R14, R15)

Any Tips ?!


texts:
In sequential circuit block diagram ,it is said that some outputs are again feedbacked to inputs,after storing them in memory.
But,where is that memory in sr latch.In sr latch ,it is seen that the output is directly taken to the inputs,and their is no memory.


texts: I'm doing a project for my school which requires harvesting body heat to generate electricity. Now, I've tackled this problem by using TEG, on the chest. Now, the problem is that this TEG is estimated to output as little as 14 mV. This is an extremely low number, and I can't think of a solution to be able to store this power. Is a capacitor gonna do the job?


texts: Altera Cyclone V: Timing issues with routing (interconnect)

texts:
I'm designing an application with an Altera Cyclone V SoC (5CSXFC6C6U23I7N) and interfacing ADCs and DACs at 250MS/s. In the meantime, the design complexity has increased a bit and now there are timing constraint violations near the DAC interface part. This interface uses the LVDS SERDES hardware for the DDR data format. The data clock is 250MHz and hence 500Mb/s data rate. The FPGA is internally clocked at the sampling frequency, i.e. 250MHz, which should not be a problem with this speed grade I7 device.

Now the problem: There are a few registers near the DAC interface to correctly order the data bits. But there are timing violations between such registers, altough there is absolutely no logic between the registers. When looking at the path delays in TimeQuest, I see that there are some 3.5ns delay introduced by routing (interconnect). Together with the other delays, the required 4ns are not achieved anymore. When looking at the data path in the chip planner, I see that it is routed from approximately the center of the FPGA to the I/O section. After seeing this, I thought that I could just insert an additional register stage, so that the data could be retimed somewhere in the path. But the fitter simply places those registers near the output stage as well, always making the same path(s) fail.

I know that the interface itself is not a problem, as this was working perfectly well in pervious compilation runs. Resource utilization is below 5%, so there is also no problem with missing registers/ALMs. Setting the fitter effort to "aggressive" or reducing the target temperature range slightly improves the figures, but there is still negative slack in the range of 500ps to 1ns.

btw: The design as such is working even with the violations when the device is running here at room temperature. I want to have it working reliably though, so just ignoring the violations is definitely not an option.

Any ideas?

Thanks and best regards,
Philipp


texts: Are these standard connectors i.e have a well defined I/O strcuture?

texts:
I have found an FPGA board that contains this in description:
Arduino™ compatible expansion headers
MikroBUS™ compatible expansion headers
PMOD™ compatible expansion connector
Are these standard pinouts? Is their electrical and mechanical layout covered by a standard from ANSI or IEEE?
If these have a fixed pinout, where can I find it?


texts: Is it a good idea to make one instrumentation amplifier with three operational amplifiers for thermistor sensing circuits?

texts: Is it a good idea to have those three amplifiers with LM741 Operational amplifier? Has anyone done this so far? I thought of this as this was a cheapest idea. The instrumentation amplifier costs about $6 but the quad LM741 costs like $2. I know that buying instrumentation amplifier would be most effcient. But does anyone see any huge disadvantage in this making of instrumentation amplifier with three LM741 op-amps?


texts: History of choice of 'Z' to represent high impedance?

texts:
I'm curious to know why 'Z' was chosen to represent high impedance state for types such as used in VHDL and VHDL-AMS's std_logic_1164 logic system:

(image of page 789 of The System Designer's Guide to VHDL-AMS: Analog, Mixed-Signal, and Mixed-Technology Modeling (Systems on Silicon) ISBN: 1-55860-749-8)

"high-Z", "hi-Z" etc. seem to be in common use, but my Google Fu is not up to the task to identify the history. The three state logic wikipedia page does not clarify it, nor does the Use of 'Z' section of the IEEE_1164 wikipedia page indicate the history.


texts: CAN BUS system compatibility? DB9 to M12

texts:
I have a CAN SYSTEM with a M12 5pin male plug that acts as a sensor processor. It runs on 12 volt. I am trying to feed this system with a Raspberry Pi B system using this CAN BUS board: http://bit.ly/1ZGsf2E.
I have found that the M12 having this pinout:

The Raspberry has a DB9 connector with I think this pin-out:

If I measure the voltage on the m12 plug using pin 3 as a ground I get 2.5V on in 4 and 0.05 volt on pin 5 and 9 volt on pin 2.
I am wondering if I am doing the right thing to connect the the DB9 connector the CAN_H and CAN_L together, the CAN_GRND and the Pin9 from the DB9 (CAN_V+) with Pin 2 CAN_V+ on the M12. I am asking myself if I will run into problems because the Pi runs on 5V and the CAN Processor on 12V. Also if the two are actually compatible since I have many more available pins on the DB9 side.


texts: Help identifying components in schematic for HT9032

texts:
I'm new to electronics and hoping to make a caller ID interface using an HT9032C or HT9032D to do the Bell 202 FSK demodulation.  However, I'm having a problem understanding the example application circuits in the datasheet for the HT9032C/D; it's located here: https://www.holtek.com/documents/10179/116711/HT9032C_Dv160.pdf
(Page: Pages 6 and 7, Section: "Application Circuits", Circuit: All four (4) circuits)

Questions:
1) at the top center of EACH of these circuits (left of the HT1050 5-volt voltage regulator), I can't understand what are the two (2) components located above the ground? There's an unnamed white/open input circle, and what looks like a polarized capacitor(?) with the label "9V" below it under the junction.

The symbol for ground wasn't even one I was familiar with:

The HT1050 datasheet (http://pdf.icpdf.com/pdf1/HOLTEK/HT1050_datasheet_280648/457751/HT1050_datasheet.pdf) did not help to clarify—the typical basic circuit at the top of page 7 (of the HT1050 datasheet) shows a polarized capacitor with a capacitance value in uFarads in place of a voltage.

2) what are the values for these components? Is the open input circle the supplied 5V power that is voltage regulated by HT1050 to be VDD? Or is it an input voltage around 9V? I'm not sure what to guess for the queried polarized "9V" capacitor.

Very sorry for the noob question, but thank you so kindly for your help!


texts: Can one use a current transformer with turns ratio of 100:5A instead of 100:1A?

texts:
There is an MV switchgear with a rated current of 100 amps. knowing that a CT with 5 amperes secondary rated current is cheaper than a 1 amperes secondary rated current. In order to cut costs I chose a CT with 100:5 amps instead of a CT with a turns ratio of 100:1 amps.
My question, when is it preferred to use CT of 100:1 turns ratio instead of a cheaper 100:5 amps?
Is there a criteria for selecting the secondary rated current to be 5 instead of 1?


texts: Perpendicular tracks in 2 different layers (PCB)

texts:
Many times ago I heard it's not good to have 2 perpendicular track in 2 different layers of 2 layers PCBs(I mean one track in one side become perpendicular to another track in other side of the pcb) . I can't remember what was the type of tracks (digital signals or voltage or ...)
but now in my recent pcb(it is 2 layers) because of lack of space there is a lot of these perpendicular tracks(some of them are high current- 2 to 5 amp).

Is there any absolute rule for these kind of tracks ?
Is it forbidden ?
How about multilayer PCBs?

Thanks in advance

MA


texts:
I bought a 3 legged Blinking (I have a theory this might be my problem) RGB LED from Radio Shack. I am not quite sure on how to code my arduino to make it emit one solid color constantly.

The closest I have gotten was by restricting the flow of voltage to the LED via resistors but it seems a little bit inefective. I have looked on the interent to find coding examples but winding up with results that do not match my problem.

I wou ld like to be able to control the color by means of coding, I am just not sure of how to code it.

Any help, coding or pointing me in the right direction is appreciated.


texts: Why we use conjugate of current than the original phasor in the calculation of Complex Power i-e S=VI*

texts: i have studied different books and sites for the above question but did not get the right concept that why the complex power encounter current conjugate not the original Phasor.if someone explain it with good example in simple words i would be very thankful...


texts: Is it bad practice to connect wires of vastly different gauges?

texts:
I would like to connect an Anderson plug with 25mm² cable to a 12V AGM battery so that I can easily connect and disconnect different devices which will conduct currents of varying amperage. I may connect 2mm² cable for conducting <500mA, 10mm² cable for charging at 20A or an 800W inverter using 25mm² cable for drawing up to 60A.

Is it bad practice to connect cables of vastly different gauges so long as the thinnest wire can comfortably conduct the magnitude of current required?

Can a wire’s gauge be too low to suitably conduct a very small current or is it a case of the thicker the wire the better the conduction regardless of the magnitude of the current?


texts: Smartphone battery: safe for (further) use?

texts:
I disassembled my smartphone, which required removing the (non-removable) battery. The battery was glued with double-sided adhesive tape to some housing on the board. Further, there was some 'metallic' sticker across the battery and a metallic component on the board.

In order to remove the battery, it had to be bended a bit due to the adhesive tape. Not much, but you could feel that there was some bending going on (few mm)*. Further, the bottom of the battery wrapping seemed to deformed a bit due to the tape. My question is if the battery potentially could have taken some damage due to the removal and might self-ignite, explode, whatever, when I keep using it.
I'm curious if that metallic sticker has some purpose, or if it just some seal. The sticker itself is quite thin, and I couldn't remove it without breaking/disconnecting the battery and the metallic component. I'd like to know if there might result some potential danger if I remove the sticker completely.

*edit: Though the bending wasn't much, it was an elastic (rather than a plastic) deformation (battery went back to original shape after stress)

Attached two images showing the battery.


texts: Connecting a current follower to a Raspberry Pi with an MCP3008

texts:
One of the experiments I conduct in an instrumental methods class is the construction of a rudimentary spectrophotometer described in the Journal of Chemical Education (link here if you have access to this journal).  The schematic of the instrument from the paper is:

and we make a few minor changes (fixed resistance for the LED, +/- 9V sources and LM301 op amp).  I'd like to expand this project so that the data is read using a Raspberry Pi rather than a multimeter.  I've had success using these instructions to use an MCP3008 to read an analog signal with the RPi.  I'd like to combine these two projects; however, I recognize that the instrument outputs 0 to -9V which the RPi can't handle.  I've more-or-less reached the limit of my electronics knowledge at this point and would welcome suggestions on how to move forward with this project (including RTFM answers, if you care to tell me which manual to stick my nose in).


texts: STM32 F205VCT6: GPIO B Port 6 and 7 do not work?

texts:
I'm using the STM32 F205VCT6. I have a simple blinking LED program written in C++ with VisualGDB (and VS 2013 Community). It works fine for pins like A1 and E2, but it doesn't for B6 and B7, where I want to plug in USART. Does the processor block it somehow? I have really no idea. Please help, thanks.

UPDATE: Link to the full project on Dropbox:       https://www.dropbox.com/s/jk9r9avg276k6l3/LF-3.rar?dl=1

My program's code:

#include <stm32f2xx_gpio.h>
#include <stm32f2xx_rcc.h>

void Delay()
{
    int i;
    for (i = 0; i < 1000000; i++)
        asm("nop");
}

int main()
{
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOB, &GPIO_InitStructure);

  for (;;)
  {
      GPIO_WriteBit(GPIOB, GPIO_Pin_6, Bit_SET);
      Delay();
      GPIO_WriteBit(GPIOB, GPIO_Pin_6, Bit_RESET);
      Delay();
  }
}


texts: What's the advantage of DMA in byte I/O?

texts:
I have a A/D where signals CPU(Analog Devices Blackfin 706) whenever it has new sample, and CPU reads that through a SPI, which is few bytes. Then waits for new smaple signal again.

My question is, can we use DMA here? Who and how should tell DMA to transfer new data? I can't tell DMA to watch for the signal itself, so somebody has to do it.

Does it make sense to use DMA? This is basically like an interrupt I/O. Everytime A/D signals new sample, main software tells DMA to transfer it. So there is no improvement in efficiency. main is still involved continuously in I/O.


texts: Influence of active area of photo diode on sensitivity

texts:
I am using a photodiode for detecting the laser. I have a question regarding the active area of the photodiode.

Is less active area photodiode is less sensitive? Or it totally depends on the laser spot- if the active area is sufficient enough to capture the spot of the laser, then active area greater than this won't affect or increase the sensitivity of the photodiode. please share your knowledge.


texts: flywheel diode for radio transmitter and receiver need? or not?

texts:
I am a building a device for communicate each other devices via radio signals (VHF) then I want to switch off and on Radio transmitter and receiver driven by 5V max.

transmitter = 24  mA
Receiver = 11  mA

then i decided to transistor switches for this and I heard  flywheel diodes need to prevent effects on EMF s . then radio system generate EMF always when it work.

so transistor switch and radio equip. in same PCB. Actually do we need flywheel diodes for this circuit.if it need,is IN 4007 diode suitable for this?

Transmitter and receiver data sheet -

Data Sheet


texts: Formally determining the minimum number of poles needed to realize some suggested switching arrangement

texts:
Many times, when designing passive switching circuits, one has the following engineering problem:

We know we want to have some number of switches, each with some number of throws.
For each possible switch combination, we know exactly how we want our circuit to look, meaning which nodes we want to be connected to/disconnected from other nodes.
However, we can only get switches with some max number "M" of poles, in real life.

Question: how can we determine, formally, if our switching arrangement is possible to implement, using only switches with no more than "M" poles?

What I am looking for are references to formal methodologies for answering this basic question. A good starting point for formalization seems to be Shannon's "A Symbolic Analysis of Relay and Switching Circuits", and I am wondering if it can be extended for this purpose. Are there any related papers? Or, is there some way to use Shannon's calculus for this situation?


texts: Axial Lead Capacitors - BC 050 - What Are These Markings?

texts:
EE, I am trying to fix a circuit and have come across a group of axial capacitors with markings that I have had no luck deciphering. As best as I can tell, they are marked "BC 050" which doesn't follow any marking scheme I have been able to find.

They appear to go from pins on an IC to ground, if that helps. Here is a photo:

Please help me identify these!

Update:
The IC is MC68HC705JJ7, 20 pin DIP. The caps are connected to pins 1-4:

Pin 1: PB1/AN1 (IC side of cap has a parallel connection to a terminal for an external signal input)

Pin 2: PB2/AN2 (Appears to be nothing else on IC side)

Pin 3: PB3/AN3/TCAP (IC side has a parallel connection to a potentiometer)

Pin 4: PB4/AN4/TCMP/CMP1 (IC side is pretty busy, but appears to connect (through 2 series resistors) to an oscillator, and also pin 7 (non-inverting output) on a LM2904N amplifier...)


texts: What does it mean to "reproduce Morgan's equivalents along with Boolean Algebra"?

texts:
This is my first time attemting anything like this (not posting on the forum, the subject itself) and would like some guidance. It's more of the guidance side. Can someone start me off in the right direction or give me sources? I've done research for a few hours now but can't find any sources that help with my specific topic (or so I think).

So far, here's an image of the page I'm doing for a lab assignment. I don't need help with the few questions at the bottom, I'm just trying to figure out how to "reproduce" equivalents, whatever that means. How do I fill in the small little BAY charts in the image?


texts: MOSFET switching with 5V but latching ON with 12V

texts:
I am having an issue with a control signal.

I have a CEP50P03 P channel trench MOSFET that is supposed to switch a 12v power supply.

I am having an issue I can not figure out. When I power the board with 5V everything works as it should.

However when I add the GND connection to the 12v side to use the 7805DT voltage regulator the Mosfet will come on and latch on and will not turn off.

I then tried removing the voltage regulator and power the circuit with only 5v and the fet does not switch at all. I have not been able to figure out this weird behavior.

I attached the shematic below.
This circuit is used in an automotive rev limiter module where tach signal is a 0-12v square wave used to read rpm that is then converted to a 0-5v square wave the ATMEGA328P reads and if the frequency is above X ammount the Atmega sends a signal to turn the MOSFET off for X time and the mosfet should turn back on.

However like mentioned above when I have 12V coming in the MOSFET latches on and stays on.


texts: Synchronous boost light load operation and general SMPS terms

texts:
What are the differences between the skip cycle, pulse skipping, diode emulation, and forced PWM at general DC DC converter light load operations? How do they work and when do I want to use them? Page 5 of the datasheet on the "mode" pin, page 22 (section 7.4) for device operation modes.

I am looking at the TI LM5122 to use as a synchronous boost. Most of the time I wanted to use it in diode emulation mode for better efficiency in light load conditions, but there could be an instance where my input voltage is slightly higher than the output voltage and I need the bypass operation of the IC. The datasheet mentioned that forced PWM is the recommended operation when bypass operation is required (pg 21,section 7.3.9), but I am not sure I want to do that since most of the time I am not using the bypass mode. What is the reason forced PWM is recommended when using the bypass feature of a synchronous boost controller?

Here is the datasheet link: https://www.ti.com/lit/ds/symlink/lm5122.pdf?ts=1592150669649&ref_url=https%253A%252F%252Fwww.google.com%252F
Thanks!


texts: Dynamic Braking resistor chopper circuit

texts:
I want to design a standalone dynamic braking circuit for AC motor driver , because to deal with regenerative energy that the AC source cannot handle causing a DC bus voltage Rise . The concept is well established in many resources online that senses the DC bus voltage and dissipates the access energy in a " Brake Resistor ".

I want to know what is usually used circuit that is called in the diagram as "chopper module" and design it without micro controller if possible.

I donot know of an IC that is designed for this purpose solely , so what comes to mind is comparator with hysteresis with a low side gate driver to open/close Braking mosfet. but no so sure if this is a decent choice until i test in reality and see how well it will work.

My concept test circuit :

So I would like to know your comments on the subject, and corrections if i am missing something here .


texts:
Is there any equation to find the maximum Locked Rotor current using the motor characteristics values?

The motor I am interested in is ThinGap 7140.

Here is the datasheet:
http://www.thingap.com/wp-content/themes/ndic/pdf/TG7140.pdf

The initial current(maximum Locked Rotor current) is 14.1 Amp, and I know the maximum Locked Rotor torque is T=i*Kt, which is 0.17*14.1=2.39 (datasheet says 2.41 Nm).

I am wondering how the manufacturer obtain the maximum Locked Rotor current. Is this number has to obtain from testing? or it is something I can calculate from motor characteristics?

Also, how come the motor RPM vs Torque relationship is not inversely proportional like other DC motor?

Thank you for all your help.


texts: Coil design for induction cooking system

texts:
I am designing an induction heating circuit using a half bridge, series resonant circuit. Wildly simplified schematic follows (will use IGBTs instead of MOSFETs for the final design, but they were not available in the schematic editor):

simulate this circuit – Schematic created using CircuitLab

L1 will be the induction heating coil, using a spiral geometry similar to this:

The basic theory is explained in lots of materials around the web such as this old ST application note.

Given a value for L1, and a desired switching frequency \$f\$ (say 20-30 kHz), one can calculate a value for C using
$$
f = \frac{1}{2 \pi \sqrt{L_1 C}}
$$

From there we can take \$C_2 = C_3 = C/2\$. The actual switching frequency should be safely above resonance so as to ensure the circuit works in the inductive area.

Of course, all of this assumes that a value of \$L_1\$ is given, and this is the part where I am stuck. I've been searching the internet as well as academic papers, but so far I haven't found a design procedure detailing how to select \$L_1\$ so as to achieve the desired heating power.

In principle I could just build an inductor of the desired physical size (say 20 cm of diameter), measure it with an LCR meter, and then select \$C_2\$ and \$C_3\$ according to the procedure above. However, say I build this circuit and it doesn't achieve the desired heating power; then what should I do next? Increase the physical size of the inductor? Increase/decrease inductance (with a corresponding adjustment in the capacitor to maintain the switching frequency constant)?

In summary: how should I go about actually designing/engineering the induction heating coil, rather than just applying blind trial and error?


texts: Passcode alarm with standby blinking led

texts:
I’m trying to design a basic 4 digit code alarm. If the 4 inputs match the key code then an led will turn on and if they don’t, an alarm will go off. I have this solved, the problem is that I have to add an led that blinks until 4 digits are inputted. I know it might be kinda silly but I would really appreciate any help. Thanks in advance.

EDIT:
I didn't explain what I am trying to do properly so here it goes. I am trying to design a circuit that works as an alarm. The inputs are only highs or lows. As shown in the image below, the Digital Writer has 8 different diodes. diodes 7-4 are the set keycode being 7 the msb and 4 the lsb. Diode 3 does not have any use. Diode 2 will work as a clock, everytime i toggle it it will input whichever value 1 is on. Lastly, 0 will work as a reset button. If the user inputs 2 of the values and decides to start over, presing the reset button will re start the sequence of binary digits. If the sequence of highs and lows matches the key code then the green LED will turn on, if not the red LED will turn on. Before the user inputs the entire code, there will be a flashing LED (not included in any of the images) and it will stop flashing and turn off when any 4 values have been inputted, does not matter if they're correct or not. This might be very easy for most of you but I'm just in my third semester of college and Im really struggling with it. Thanks again.


texts: Minimum EAGLE trace width for PCB etching with glossy paper and a cloth iron

texts: What`s the minimum widht and clearence that's etchable using a photo paper and an iron? I've heard using too small clearence might mess the ink resulting in shorts. I want to have 20V@400mA, will 8mil of width and clearence work for such voltage and current, and will it be etchable?


texts:
I have built the circuit as shown below.
The goal is to power the Arduino by battery and maximise battery life by turning off power when it is not in use. There is no need for the Arduino to wake up periodically or anything like that. The only "wakeup" will be when the switch is closed.

The idea is that an external action (pressing S1) will power up the Arduino. The Arduino will do whatever it needs to do (e.g. report the action) and then power off.

The powering up of the Arduino on press of S1 works just fine.

The first thing that the Arduino will do is to raise D2 high. This also seems to work fine as the LED1 lights up.

However, when I release S1, power is immediately cutoff.

My expectation is that since D2 is high, this will keep the transistor (T2) turned on until such time as the Arduino "does whatever it needs to do" before taking D2 low.

For the purposes of testing, I rapidly blink the inbuilt LED for 3 seconds before taking D2 low. this achieves three things:

I know that the Arduino has "booted up" and that D2 is HIGH (I can also see this on LED1)
The rapid blinking shows me that the Arduino is powered up (which is useful to observe the failure case of D2 going low but for some reason this fails to cause the Arduino to power off).
Gives me time to hold hold S2 closed long enough for the Arduino to "boot up" and allow me sufficient time to release S2 before the 3 second operation (rapid blinking of the builtin LED) completed.

However, as mentioned above the instant I release the switch S2, the Arduino's power is immediately cutoff.

I have tried removing the LED1 - to "force" all power from D2 through the transistor, but this does not seem to change anything.

Following is the circuit diagram. The purpose of the diode (D1) is to protect the Arduino's digital pins from the 9V, but allow the Arduino's D2 signal out to control the transistor. The capacitor C1 is intended to provide a bit of debounce for the switch.

After the circuit diagram is the test program.

Obviously I have no idea why this doesn't work. So my question is why does this not allow the Arduino to take control of it's power supply via the transistor and it's digital output on Pin 2 (with or without LED1)?

Here is the test program. The comments should clarify the intention of the main parts of the program:

#define POWER_CONTROL_PIN   2

void setup() {
  // put your setup code here, to run once:

  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(POWER_CONTROL_PIN, OUTPUT);
  digitalWrite(POWER_CONTROL_PIN, HIGH);      // Turn on the transistor to maintain the power flow.

  Serial.begin(9600);
  while (!Serial) {
    delay(10);
  }
  Serial.println("Arduino Controlled power switch - Ready");
}

// Rapidly blink the inbuilt LED to show that the Arduino is "alive"
void blinkLED(int duration) {
  digitalWrite(LED_BUILTIN, HIGH);
  delay (duration);
  digitalWrite(LED_BUILTIN, LOW);
  delay (duration);
}

void loop() {

  Serial.println("Operations mode - rapid blink");
  for (int i = 0; i < 10; i++) {
    blinkLED(150);
  }

  Serial.println("Shutting down mode");
  digitalWrite(LED_BUILTIN, HIGH);            // Signal that we are about to shutdown by holding the inbuilt LED on for two seconds.
  delay (2000);
  digitalWrite(POWER_CONTROL_PIN, LOW);       // Turn off the transistor to terminate power flow.

  digitalWrite(LED_BUILTIN, LOW);             // We should never get here ('cos the power has been turned off), but just in case,
  delay (250);                                // repeat the rapid led blinking to show that we are still "alive".
}


texts:
First I apologize for my ignorance regarding electrical matters.
I am analyzing a dataset from a smart house.
Some of the power measurements are divided into phase A and B. Their values are somewhat similar (both magnitude and time of occurrence) but different by a small difference.
Some examples: washer machine power has only one measurement, but dryer has power from phase A and B. Oven also has A and B. Microwave has only one measurement.
I tried searching for two-phase power systems and found out that they have not been used since the early 1900s.
So this leads me to a few questions:
Why are there two phases? Does this house have a two-phase power system? Why only a few of the equipment have 2 phase measurements while the remaining do not? Is the total power the sum of the two phases or the average?
Your help and insights are much appreciated.


texts: What type of battery is best to keep in a seldom used flashlight?

texts: I'd like to keep a flashlight by my bed for home safety.  I intend to only use it in emergencies.  Since it's for a home safety emergency, I want to keep the battery stored in the flashlight so it's immediately usable.  The flashlight I have is designed to take a 18650 battery or three AAA cells.  To avoid battery corrosion and keep my flashlight functional in an emergency at least for a short time, what is the best type of battery to use in this situation?  Lithium-ion?  Non-rechargeable lithium?  Alkaline?  Nickel metal hydride?  For how long is it safe to store that kind of battery in the flashlight?


texts: Is the output voltage range of the LMT70 analog temperature sensor fixed regardless of Vsupply?

texts:
The differential ADC on my circuit has 1 channel open, and I decided that to place a temperature sensor IC. The temperature IC is LMT70. According to the output voltage table from the datasheet, the output voltage in relation to the temperature are:

My uncertainty comes from that the table shown is for a 2.7V supply, and I can only provide 3.0V (same as the ADC's supply.)
Would this table still hold true even for a 3.0V supply? The ADC uses an internal 1.2V reference and although that 1.2V on this table is -20 degrees Celsius a situation where my circuit will most likely not be exposed to im worried that the 1.2V Vtao of 3.0V supply would creep to the 20 degree Celsius  where the circuit will be exposed to.
Simplified circuit:

I would hope that I won't have to use a voltage divider to lower the output to not waste the accuracy of the IC.


texts: Is it advisable to try to discover a place to make a ground connection on a board with a separate AC power supply?

texts:
I am building a device consisting of a microcontroller (an Arduino mini) attached to various output devices, which will be triggered using a wireless doorbell receiver. The receiver is a single board device with its own integrated (and ungrounded) AC power supply. In order to tell if the doorbell has rung or not, I need to use the microcontroller to measure some signal from the receiver (possibly just the output going to the speaker), and ideally generate a logic-level signal as an interrupt to wake up the microcontroller when the doorbell rings. My current problem is that I don't know how to measure that voltage unless I have a common ground between the microcontroller and the wireless receiver.

I am considering that it might be feasible to identify the ground used on the board, and to hook that up to the ground coming from the separate power supply which I'll be using for the microcontroller.

My questions are:

Is this a stupid thing to try doing?
If not, what's the best approach? I have an oscilloscope.... Can I just use one of the speaker wires as the common ground?
If it is a stupid thing for me to try, is there a less-stupid alternative?

If the above hasn't already made it abundantly clear, I am a relative beginner at working with electronics. I'll read and study anything I can find, but I haven't been able to find anything yet which speaks to this question in a way that I can identify.


texts: Theoretical calculation of DDR3L transfer speed

texts:
I am not sure if this questions belongs to this stack exchange site but I didn't find other better one. In case it doesn't, let me know and I will move it to some other place.

I am working with a QorIQ T2080 Soc and DDR3L (DDR3-1866 mode, cycle time: 1.071ns @ CL=13 ) memory (model MT41K256M16). The configuration of the DDR3L allows me 1866M/T Data Rate with a 64bits bus-width, so, the theoretical peak achievable data-rate would be 14.9GB/s (1866Mhz * 64bits/8). However, performing a DMA memory copy test, the data-transfer-rate that I obtain is about 4GB/s (2GB/s x 2 because I am copying memory).

I would like to understand where this value comes from.

From what I know, correct me if I am wrong, DMAs normally create the data path when moving memory, and so, data doesn't go through them. Therefore, I didn't consider it as a data-rate limiting factor.

I reached the conclusion that the memory could be the limiting factor and made the following supposition:

The datasheet specify a burst length of 8 transactions of the bus size (64b). It is also specified a CAS latency of 13 for each column access to the memory (cycle time of 1.07ns). As I said before, the maximum peak achievable data-rate should be 14.9GB/s. However, each time we access a new column from the ram, data will only be received during 8 cycles at a frequency of 1866Mhz and then we will have to wait the true latency [3]: CL * 1.07 = 13.9 ns . Hence, I obtain a theoretical worst case:

$$  \frac{64B \: transferred \; in \; a \; burst  }{\frac{8 \: burst \; length}{1.866 \: Ghz}+14ns}= 3.4 \; GB/s$$

In [1] they mention that commonly the DDR controller is able to obtain a higher throughput, getting even close to the peak data-rate.

My question is: Is this supposition right?

Other sources where I looked:

DDR2 data rate and data bus confusion
DDR3 Data Prefetch
Memory Performance Speed Latency


texts: Single versus split power supplies for op amps

texts:
Application is small signal (low mV).
What are the tradeoffs between using a dual supply as opposed to single supply and virtual ground? Apart from maybe the cost of supplying a DC-DC converter to a battery based system.


texts:
i was wondering for a project of mine if i can order components
that are made for a long time of usage. would Mil-spec components fit under this
category?
What i basically want are parts that are good for a very long time, and have a very high reliability, in addition to high life cycle (amount of times it is used)
I can count out electrolytics, as they don't last long. Components with high power ratings are also probably better. Does anyone know if there are companies that manufacture these?

p.s. Is there an alternative to relays that i can use to switch high amounts of power? because relays have a low amount of switchings.


texts: What's causing a bad response time of a phototransistor at 100 Hz

texts:
I am working on a project that involves communicating with LEDs. I need to be able to detect the state of a light source that is flashing at about 100 Hz. I am using the phototransistor that comes with the Arduino Starter Kit, but I am noticing that, while the phototransistor detects a difference between the high state and low state, this is very minimal. Is this simply because of the phototransistor's response time? If so, are there any other components (preferably inexpensive) that I can use to detect light from a source that is flashing at this frequency.

The data sheet for the phototransistor can be found here: https://www.arduino.cc/documents/datasheets/HW5P-1.pdf

Edit:
Thank you to everyone for the responses! I am just a little confused about how I could go about implementing some of the solutions. It appears to me as if the operational amplifier ones just increase the difference between the low and high states. Perhaps I was not detailed enough with my question. I have asked this question on the Arduino forum, which has a little more detail (my apologies for posting on two forums, but this is becoming urgent because of time constraints). The link to this forum is here: https://forum.arduino.cc/index.php?topic=452365.0.

Note: this question was initially written with the assumption that the device is a photoresistor. It was later updates to avoid confusion when searching for questions on photoresistors.


texts: pragma directives to set frequency for dsPIC33

texts:
currently I set the frequency of my dsPIC33EV with following code:

int j=100;

// setup internal clock for 80MHz/40MIPS
// 7.37/2=3.685*43=158.455/2=79.2275
CLKDIVbits.PLLPRE=0;        // PLLPRE (N2) 0=/2
PLLFBD=41;                  // pll multiplier (M) = +2
CLKDIVbits.PLLPOST=0;       // PLLPOST (N1) 0=/2

__builtin_write_OSCCONH(0x01);     // now the PLL is configured. set the value for {COSC, NOSC} with this function to switch to FRC with PLL
__builtin_write_OSCCONL(0x01);     // Tell the CPU to perform the clock switch.
while(j>0)                         // This loop is here to guarantee that the clock PLL has stabilized before program operation continues
{
   if(OSCCONbits.LOCK) j--;
}

Now I found this can be done also without this piece of active code just by some pragma-directives configuring the related registers on start-up.

So: what pragma-commands correspond to my way of setting the clock? Is there a manual available somewhere describing them?

Thanks!


texts: What is a Schmitt Trigger and its application exactly?

texts:
i would like to ask about what is a Schmitt Trigger and about its application.

I searched a lot but still didn't understand it.  Please explain step by step and hope you help me in its applications in real circuits.


texts: is it normal for a usb device o reset when windows enummerates the device

texts:
I have brought myself a prusa I3 clone(3d printer).

I had my 3d printer printing directly from sd card however I switched on my pc to research something then the printer restarted itself when windows booted up. Am assuming its because windows emmerated the usb device? It has a ft232rl serial interface.

Is this normal?

Is there anything I can do to prevent this from happening again? There potential I could of lost hours of printing. It so happenes I'd just started the job so not reall a big deal but ery ANNNOYING none the less.


texts: Using volatile in embedded C development

texts:
I have been reading some articles and Stack Exchange answers about using the volatile keyword to prevent the compiler from applying any optimizations on objects that can change in ways that cannot be determined by the compiler.

If I am reading from an ADC (let's call the variable adcValue), and I am declaring this variable as global, should I use the keyword volatile in this case?

Without using volatile keyword

// Includes
#include "adcDriver.h"

// Global variables
uint16_t adcValue;

// Some code
void readFromADC(void)
{
   adcValue = readADC();
}

Using the volatile keyword

// Includes
#include "adcDriver.h"

// Global variables
volatile uint16_t adcValue;

// Some code
void readFromADC(void)
{
   adcValue = readADC();
}

I am asking this question because when debugging, I can see no difference between both approaches although the best practices says that in my case (a global variable that changes directly from the hardware), then using volatile is mandatory.


texts: Thermoelectric cooled Avalanche Photodiode sensor PCB

texts:
I'm designing a small PCB (max 5x5 cm) to bias and readout from an Avalanche Photodiode. Since the APD response varies greatly with the temperature, I want to use a cheap 12706 TEC together with a MAX1979 driver to achieve some kind of temperature control (0.1 is enough). However, I'm having trouble finding the best thermal pathway for the whole board - I was planning to use only one side for ICs and components, using the opposite side to place the TEC. However,

1 - Would I need to use via near the APD to conduct heat? Being a noise sensitive application, wouldn't cooled bias rails reduce signal noise?

2 - Can a thermisthor placed near the APD be enough for efficient temperature measurement? Or should I use a direct connection e.g. to the APD ground (I wouldn't want to disturbt the APD circuit)?

2 - With the number of R/Cs the layout requires, I could greatly reduce size PCB dimensions if I used a double-sided approach. Would there be any inconveninece in having the underside cooled (some rails would be cooler than others)?


texts: Separating lithium ion cells for charging

texts:
I have a large set of circuits to make using Lithium Ion cells for power.  The circuit requires ~12V, which is easily achieved by stacking three cells in series, but the charging circuits I've obtained are little TP4056s which (AFAIK?) can only charge one cell each.

I'd like to avoid having to decouple or remove the batteries for charging, so I thought up the circuit below, basically adding some diodes to separate the cells when they're charging (and the circuit is switched off).  I'm basically asking for a sanity check: does adding diodes this way correctly separate the cells?  Or am I missing something about how voltage/current will work out, given that all the IN+ and IN– will be paralleled to a 5V supply?

simulate this circuit – Schematic created using CircuitLab


texts: LTspice filter giving same output voltage from every input voltage and frequency?

texts:
I'm investigating different active filters using LTspice. I've done 3 different circuits of slightly different designs. With each circuit, I use LTspice transient analysis to check the output voltages over a range of frequencies, and use these voltages to produce a plot of the magnitude of the circuit.
With my first 2 circuits, this worked fine and all my calculations matched up correctly with the magnitude plot Ltspice gives from AC analysis.
I've now created a new circuit which introduces feedback (R4 and R5 in the image below) and now I'm getting this issue. No matter what input voltage or input frequency I use, the output is about 22.5V every single time. This is really confusing me. AC analysis of the circuit still produces a valid magnitude plot, but transient analysis is just not right. The only changes to the circuit is the feedback loop and different resistor values.
Is this a bug or have I done something wrong? And if its a bug can someone help me fix it as I need to finish this asap.
The circuit in question:

This is transient analysis with a 5V, 1kHz input. Output pk-pk voltage is 22.5V

And this is analysis using a 5V, 10kHz input. The output is different at first but then goes to 22.5V again.


texts: Why do parallel memory chips in a DIP package have a disorganized pin arrangement?

texts:
I'm looking at datasheet for old RAM's and EEPROMS, and one in particular I'm using is part AT28C256. Why is it that the order of the address lines do not correspond with the actual pin number. An example of mis-alignment is that on a AT28C256, the first 10 pins are labeled A14, A12, A7, A6, A5, A4, A3, A2, A1, and A0. Why don't the engineers of the chip make it so they can be labelled as A0, A1, A2, A3, A4, A5, A6, A7, A8, and A9? and just saying to label the lines yourself isn't an answer because some chips use a special timing where if you write data to the first n bytes in a certain period of time, the write supposedly executes faster (at least thats what the AT28C256 datasheet claims).

Also, Why are the control signals (such as the OE and CE in AT28C256) assigned to the middle pins of the chip instead of the outer pins?

I ask this because I'm having a hard time routing everything without resorting to multiple extra long jumpers (or double-sided board which I'm not ready for yet).


texts: 24 to 96V Boost Converter independent from the load

texts:
How can i build a boost DC/DC Converter that can boost from 24 to 96V without the output voltage depending on the load?

Why? Because i need to charge a battery system that has already been designed and i cant know what is the load resistance...

Basically, i need to charge some batteries using a solar panel to get the energy, it is for charging an electric car, and i cant find a charge regulator for the panels that outputs the 96V needed, i also cant change the battery system in the car to meet the 24V i get from the charge regulator, so what i thought about was this type of converter that would probably reduce the maximum output current but i dont really care, because it doesnt matter how long it takes to charge, it just matters that it charges something so we can use the sun as a power source, anything is better than nothing, which is our current setup.

How would i proceed with the calculations? I've designed some boost/buck converting systems before, but none where i dont know the load resistance, but im assuming there is a way of making the output voltage the same or with a reduced change depending on the load...


texts: Triggering a LED and interrupting it quickly (with a PIR sensor). What do I need for this?

texts:
I'm an artist working on a interactive installation. I'm a beginner in electronics and I'm feeling a little bit lost here, can you help me?

I have a 5v circuit with a PIR sensor activating a LED and a sound module. The minimum output from the PIR sensor is HIGH for about 3 seconds and then LOW for another 3 seconds. I need to flash the LED quickly, not stay on HIGH for 3 seconds.

The LED is just to demonstrate what I am trying to do. This is actually to trigger the sound module that I am using, which is triggered only by a short pulse. If it stays HIGH for 3 seconds it doesn't trigger it (just changes the volume). Basically, I'm trying to use the PIR sensor as a momentary button.

I know I could use an Arduino for this, but I need very cheap pieces for this project (cheaper than Arduino) as I will have many copies of the same circuit. What do I need for this? A timer or switch module, capacitors?

I really appreciate any help from the community!! Thanks!


texts: How does one properly strip coaxial cable to nonstandard strip lengths?

texts:
For my job, I need to put SHV connectors on a couple lengths of RG-59. I have the cable, the connector, and the crimping tool, but I've hit a snag: I don't have the slightest idea how to properly strip the cable! The datasheet gives me some lengths, but every coaxial stripping tool I can find either has a preset strip length intended for a more common connector (BNC or F, mostly) or an adjustable strip length, but only less than about 3/4 of an inch--and SHV (being a high-voltage connector) requires a total strip length of over an inch to achieve proper isolation distance.
I managed to get one connector crimped on by stripping the cable with very careful application of side cutters and an x-acto knife, but I'm sure there's a better way out there. How do people normally strip coax for unusual connectors?


texts: Unidirectional current and bi-directional voltage device

texts: Which is that device which can take in current in one direction irrespective of the voltage polarity across it? ( We can rule solid state switches - diode, SCRs etc).


texts: How to combat voltage drop on a 5v addressable led strip

texts:
I've been trying to make my LED strip work but with no success. It is a 5 meter WS2812B RGB LED strip (60 LED's per meter).

I did some research and it turns out that one LED draws around 60mA at full brightness, so the entire strip would take around 18A at full brightness. I use an old PSU from my computer which is capable of delivering 20A at 5V. The controller for the strip is an Arduino Uno. Below is the circuit I have:

The problem is, when I execute a program that sets all LED's to WHITE, the further away from the start of the strip, the leds become yellow and red at the end. If I set them all to WHITE but at less brightness, the first 20-30 LED's glow white while others just blink random colors. Same thing happens with any other script, for example the rainbow fade works on first few LED's while others flash random colors.

Now I suspect that's due to the voltage drop, I measured the voltage at the end of the strip (~5V) and at the end it was only around 3.5V.

My question is, how do I inject voltage into the strip without making the design look like overhead power lines? Do I need to inject the data line too?

I bough a 2.5mm^2 wire but it looks too overkill, can I use something a lot thinner to use the strip as an actual flexible strip?


texts: In March of 2003 Circuit Cellar published a feature article on using position sensing detectors (PSD). The project builds a 2D position sensor using a PIC16F873 as the microcontroller, an Aculux PCB set and a Hamamatsu PSD. Since that project is now over 10 years old, what modern project or device configuration can I use to get the same or better functionality?


texts: What are typical track lighting track profiles used in Europe?

texts:
In the U.S., the typical track lighting track profiles are known as "H", "J" and "L". Their cross-sections can be easily found by googling them.

Are these same cross-sections used in Europe? If not, what cross-sections are used, and are there any standards that give the dimensions? As much as I can figure out, IEC 60570 unfortunately doesn't give standard track profile dimensions, only general requirements that place limits on some dimensions.


texts:
I am currently working on a MIDI based project and would like to use rotary encoders. However, due to the nature of my project I need to multiplex a total of 64 encoders with 8:1 multiplexers.

Is this possible or will an encoder just not work in this way due to pulses possibly being missed while the code is scanning elsewhere?


texts: Maximum effective range of RG-6/U in CCTV

texts: How long RG-6u i can use in my cctv? what's is the effective range using RG-6u?


texts: Logic gate directly driving power MOSFET

texts:
Art of Electronics, 3rd Ed, pg. 164-165 give an example of naively using a 4000-series CMOS logic gate to directly switch a power MOSFET, disregarding the significant gate current required to charge the MOSFET capacitance. They give the following values: VDD = +10V, C_mosfet = 200pF, maximum current source/sink capability of logic gate = +/- 1mA. Their conclusion is that it will take approximately 50us to switch the MOSFET on/off. I don't see how they come up with this number. If the logic gate is slew-rate limited, then it will take t = CV/I = (200pF)(10V)/1mA = 2us to turn on the MOSFET.

I checked the second edition and although they use different numbers, I'm still not able to come up with the provided answer. What am I doing wrong?


texts:
I have asked a similar type of question previously.
This one is a little different.

Assume, we have the Bode plot of a Control Loop System. In this case, DC-DC Converter.

I measure the Gain Crossover Frequency and Phase crossover Frequency.
Does the difference between the gain cross over frequency and phase crossover frequency, provide any meaning or make any sense? Any insight can be drawn?

  Does this difference make sense or provide any insight = Gain
  Crossover frequency ~ Phase crossover frequency?

And can someone give me some concept or idea about the relation between the crossover frequency and the switching frequency of the DC-DC Converter? An analogy might be helpful.

Thanks.


texts: Switch between battery and dynamo to power bicycle lights

texts:
Voltage produced by the bicycle dynamo varies depending on what speed your traveling at. I have two 12 volt bulbs mounted on the bike at the front and at the rear. I want to power these bulbs using a 12 volt battery until the dynamo produces a voltage greater than 12 volts then I want to switch to the dynamo to power the lights.

How would I do this?

Update

For those interested this is the circuit I built. http://dcaclab.com/en/experiments/7662-battery-and-dynamo-bicycle-circuit/


texts: Would an electric fence be able to detect being bypassed?

texts:
In the Flashpoint episode "The Farm," there's a scene where you can see one of the officers run a jumper cable from one contact on an electric fence to another, then cut the line of the fence (not breaking the circuit, mind you). Based on context clues, one could assume the fence surrounds a large, multi-acre plot of land. Another bit of information: the cable they used to keep the circuit complete was longer than the original cable on the circuit, which would mean it would have a higher resistance when the circuit was rebuilt.

I have two questions:

How feasible is this?
And would a (powerful, that is) fence controller be able to detect the change in resistance? Or would it be so small that it's undetectable in the grand scheme of things?

From my (limited) electronics/electrical schooling, adding the cable to jump between the contacts would change the resistance, as resistance for parallel circuits is modeled as:

$$r_{total} = \frac 1 {\frac 1 {r_{a}} + \frac 1 {r_{b}}}$$

Which means the addition of the extra cable would have an impact on the resistance of the circuit itself (although very minimally).

If I recall correctly, another one of the officers was counting down to when the first officer should splice into the circuit. I don't know enough about electric fences to come to any conclusion, but are electric fences constantly charged? Or do they have a delay between pulses?


texts:
I wanted to transform a differential signal to a single-ended signal using a differential amplifier. When I am reading the datasheets for fully differential amplifiers there are just single-ended/differential to differential cases shown.

Is this possible with fully differential amplifiers?


texts: LCD driver program in Verilog for Altera DE2 board

texts: I need to display the characters and numbers on a 2x16 LCD on the Altera DE2 board using a Verilog program. Any advice?


texts: LTSpice, setting multiple PWL FILE="..." Voltage sources

texts: I am trying to design a circuit for a three phase power generator with an unusual waveform, and the first step is to combine each of the component phases into a single signal. When I set one of the voltage sources (say V3 for example) to a PWL file which models the waveform, all the other voltage sources automatically change their input PWL file path to the file path I just typed (Entering a file path for V3 will change the file paths of V1 and V2 to V3's file path). Is there a way to simulate multiple custom wave forms?


texts: PTC Fuses and Low Current Circuit Protection

texts:
I would like to have some overcurrent protection in a circuit that normally does not draw much current (~100mA max.) I like the idea of PTC fuses, but they seem to be extremely slow in disconnecting power from these types of circuits.

Why do PTC fuses exist with low trip currents if they are slow to react? Wouldn't that make the protection ineffective?

Assuming I were to use a PTC fuse, how does it behave when the current is between the hold current and trip current?

Are there any alternatives to fuses for overcurrent protection?


texts:
Background: I did an "A" level in electronics 25 years ago; now been a professional programmer for nearly 20 years. I want to build some very basic circuits to interact with an Arduino but I've forgotten a lot, apparently :)

Question: I am playing around with the below circuit, and it is confusing me. The values below are taken from a website, and they work fine and as expected. However, they clip the bottom half of the waveform.

Reading that the gain is only set by RL and RE, naively, I though that biasing the transistor to half the supply would move the waveform up so that it would be amplified the same in both directions, so I altered R1 to 11k.

However, this seems to completely stop the circuit amplifying at all; in fact the gain is now ~-0.5. Now, I'm willing to accept that my change didn't do what I wanted, but if the load is only set by RL and RE, why did this have such a dramatic effect?

NOTE: I have read all the many Common Emitter questions on the site and I'm afraid the answers are a bit over my head, so if you could aim your responses at my beginner 17yo self, that'd be good :)

NOTE TWO: RE should be 470R, not 5R. Screenshot is wrong.

(Also I cannot get it to run in Circuit Lab for some reason, so here it is in PartSim - http://www.partsim.com/simulator#76064)


texts: Problem with the code for MSP430F5529 I2C Master communication

texts:
First of all, thank you in advance for the attention and the time dispensed understanding my problem.

So, I am developing a system that includes an MSP430F5529 communicating with an AD5933 via I2C. Previously, I did the same thing with an MSP430G2553 everything went smoothly and my code worked perfectly. I did check with an oscilloscope and every data was being sent. I started with that code for my new system and did all the necessary changes, ports, interrupts, registers, from G2553 to F5529.

No matter what, my code stop in verification loops. Especially this one:

while (UCB0STAT & UCBBUSY);

When I check the bus with an oscilloscope, the SCL is always high and SDA always low. So nothing happened on the bus.

I blink a LED during the code, and that works fine.

My code is bellow, please check it and let me know if you find something wrong, or if you have some idea for me to try out.

#include <msp430.h>

#define SLAVE_ADDRESS 0x0D /**< Address to AD5933. */
#define BAUD_RATE 0x12 /**< Baud Rate value. */
#define SDA_PIN BIT0                                    // msp430F5529 UCB0SDA pin
#define SCL_PIN BIT1                                    // msp430F5529 UCB0SCL pin

signed char byteCtr;
unsigned char *TI_transmit_field;
unsigned char *TI_receive_field;

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;                   // Stop watchdog timer

    //LED configurations
    P1DIR |= BIT1;
    P1OUT |= BIT1;
    P1OUT ^= (BIT1);   //turn on LED

    //MSP configurations to transmit
    P3SEL |= SDA_PIN + SCL_PIN;                 // Assign I2C pins to USCI_B0

    UCB0CTL1 |= UCSWRST;                        // Enable SW reset
    UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;       // I2C Master, synchronous mode
    UCB0CTL1 = UCSSEL_2 + UCSWRST;              // Use SMCLK, keep SW reset
    UCB0BR0 = BAUD_RATE;                         // set prescaler
    UCB0BR1 = 0;
    UCB0I2CSA = SLAVE_ADDRESS;                  // Set slave address
    UCB0CTL1 &= ~UCSWRST;                       // Clear SW reset, resume operation
    UCB0IE = UCNACKIE;
    UCB0IE |= UCTXIE;                           // Enable interrupts

    P1OUT ^= (BIT1);                            //turn off LED
    while (UCB0STAT & UCBBUSY)                  //wait for previous traffic to clear
    ;

    //Configuration of the slave registers (SEND DATA)
    unsigned char field[2] = { 0x80, 0xB1 };
    TI_transmit_field = field;
    byteCtr = 2;
    UCB0CTL1 |= UCTR + UCTXSTT;                 // I2C TX, start condition
    while (UCB0STAT & UCBBUSY)
        ;

    while (1)
        ;
}

//INTERRUPTS
#pragma vector = USCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
{
    switch (__even_in_range(UCB0IV, 12))
    {
    case 0:
        break;                           // Vector  0: No interrupts
    case 2:
        break;                           // Vector  2: ALIFG
    case 4:
        UCB0CTL1 |= UCTXSTP;
        UCB0IFG &= ~UCNACKIFG;
        break;                           // Vector  4: NACKIFG
    case 6:
        break;                           // Vector  6: STTIFG
    case 8:
        break;                           // Vector  8: STPIFG
    case 10:                                  // Vector 10: RXIFG -- I am not using it yet (but I'll)
        if (byteCtr == 0)
        {
            UCB0CTL1 |= UCTXSTP;                    // I2C stop condition
            *TI_receive_field = UCB0RXBUF;
            TI_receive_field++;
        }
        else
        {
            *TI_receive_field = UCB0RXBUF;
            TI_receive_field++;
            byteCtr--;
        }
        break;
    case 12:                                     // Vector 12: TXIFG
        if (byteCtr == 0)
        {
            UCB0CTL1 |= UCTXSTP;                    // I2C stop condition
            UCB0IFG &= ~UCTXIFG;                 // Clear USCI TX int flag
        }
        else
        {
            UCB0TXBUF = *TI_transmit_field;
            TI_transmit_field++;
            byteCtr--;
        }
        break;
    default:
        break;

    }
}


texts: Simple security Alarm incorrect schematic diagram

texts:
I am a student and my Applied Physics teacher gave an assignment to create a schematic diagram of a security alarm. The main Components are,

Switch (Simple on/off)
SCR C106B (Silicon Controlled Rectifier)
10 KΩ Resistor
Buzzer
9 V Battery or DC power supply

(Note: A combination of npn and pnp transistors can be used in place of SCR as Follows)

I created a circuit diagram but my simulator does not seem to work, so i cannot verify it. Please Confirm it that is it correct. The schematic is as Follows,

If There is any error in this Diagram or there is a better and easy way of doing it, please tell me.

(Note: Our teacher just asked us to create a Diagram, So type of SCR or any component does not Matter)

Thank You.


texts:
Why do we have to multiple the complex uniformly distributed random variables by \$\frac{1}{\sqrt{2}}\$, for a Rayleigh distribution. In terms of when we want to transmit data across a Rayleigh distributed channel? (The equation is shown below)

\$ray_{noise}=(\frac{1}{\sqrt2})*(randn(L,1)+i*randn(L,1))\$


texts:
This is a question in relation to USB transmissions crash my software GUI.

I posted this question separately so that I could clarify my question separate from the other one.

I have the same operating code here and I would like to ask: How can we estimate the EEPROM read time from I2C communication running at 100kHz?

main()
{
    usbinit(); // usb initialization
    while(1)
    {
        x=do_eepromread();
        UsbTasks(); // does usb works
        yourtasks(); //sends the buffer
    }
}

I trust reading a chunk of data from EEPROM won't do any damage than doing adc_conversions and calculations.

I don't want a precise time duration. But I trust read will occur quite fast rather than write that will take 5ms minimum.

I could not find any EEPROM read time though is it because it depends upon baud rate of communication (I2C here @ 100kbps).

I would love to have your thoughts and information in regards to this problem.


texts: How does the current draw of an IC change with supply voltage?

texts:
Suppose I have a device with a number of ICs (microcontroller, logic gates, MEMs sensors, etc) which can operate from a supply voltage in the range of, say, 1.7V to 3.6V. Will the current draw be different if I power the devices at the low-end (1.7V) vs the high-end (3.6V) of the operating range? Does the answer vary depending on the specific IC or is there a general rule-of-thumb?

The datasheets I've looked at don't seem to go to this level of detail, and instead only specify current draw at a single supply voltage. I'm interested because my device is battery powered and I'm considering whether to run direct from the battery or to use a LDO regulator.


texts:
Assuming the peak voltage at \$V_1\$, \$V_{1p}=9.25V\$ and ideal silicon diodes (\$0.7V\$ drop in forward bias) and the DC output in \$V_0\$ is \$5V\$. I want to find the \$V_{op}\$, peak voltage at \$V_0\$. Given that the ripple voltage, \$V_r=0.2V\$ Then:

\$V_{DC}=V_{op}-\frac{V_r}{2}\$

And we have \$V_{op}=5.1V\$

I can understand why I couldn't apply KVL and write \$V_{op}=V_{1p}-1.4\$. Shouldn't this be the \$V_{op}\$?

If I apply KVL with \$V_{op}=5.1V\$ the equation doesn't hold true. What's going on? Excuse me because I this question may look similiar to another one I posted a while ago. This exercise is confusing me.


texts:
I have a PV cell the size of 50cmx35cm. The voltage and current it produce on short circuit is around 20.5V and 0.9A. I'm trying to measure the power that I could get from it by measuring the voltage and current it produce across a resistor, but when I try that, the measurement I get from multimeter for current is 0, while the resistor show OL(Overlimit/overload?) when I try reading it with the connection on.

I try covering 15% of the PV cell to reduce the voltage produced to around 18V and then suddenly the current is flowing again. At first I thought that maybe my resistor couldn't handle that much voltage(its 20W and 240ohm) so I change to a stronger one(30W 240ohm), but it still show the same result. I have no idea what's wrong right now, and I don't think its the connection as its a simple connection from the PV cell direct to the resistor.

I'll also include the spec of my PV cell.

this one is not my picture, but its how its connected.


texts: Understanding a transistor configuration

texts:
I started watching this video series on a DIY lab power supply by Dave @ EEVBlog.
On his video he's analyzing mostly simple constant current circuit. However, at the top of the circuit there's two transistors in the op-amp feedback. He explains fairly well how the circuit works, but I'm unsure (I have my suspicions) why there are two transistors as opposed to one.


texts:
I am quite new in embedded system and circuit design. I have designed a system in which I have to add voltage detectors. I need to find the accurate power that the detector can consume in each cycle depending upon the value of voltage provided.
Can anyone please guide me how to get the value of current draw in the detector when the voltage provided is between 1.8-3.6 volts.

Following is the link to datasheet.
https://www.rohm.com/datasheet/BU4811FVE/bu48xxg-e


texts:
I am trying to implement the SPI_SLAVE
module SPI_Slave(MOSI,SS_n,clk,rst_n,tx_data,tx_valid,MISO,rx_data,rx_valid) ;

  input MOSI,SS_n,clk,rst_n,tx_valid;
  input [7:0] tx_data;
  output reg MISO,rx_valid;
  output reg [9:0] rx_data;

  parameter IDLE      = 3'b000;
  parameter WRITE     = 3'b001;
  parameter READ_DATA = 3'b010;
  parameter READ_ADD  = 3'b011;
  parameter CHK_CMD   = 3'b100;

  reg read_indicator; //1 for read address and 0 for read data
  reg [2:0] cs, ns;
  reg [3:0] counter_internal=10;
  reg [3:0] counter_external=8;
  reg [7:0] temporary_register;

  /*integer i=9;

  always@(posedge clk) begin
     rx_data[i] <= MOSI;
     if(i==0) begin
        i<=10;
      end
      i<=i-1;
  end*/

  //State Memory
  always @(posedge clk or negedge rst_n) begin
     if(~rst_n) begin
   cs = IDLE;
   rx_valid = 0;
   counter_internal = 10 ;
   counter_external = 8 ;
     end
     else
   cs = ns;
  end

// Output Logic
always @(posedge clk) begin
     case(cs)
        IDLE:
            rx_data = 0;
        CHK_CMD:
            if (rx_data[9]==1 && rx_data[8]==0)
                     read_indicator = 1;     //read address
                    else if (rx_data[9]==1 && rx_data[8]==1)
                     read_indicator = 0;    //read data

        READ_ADD:
            if (counter_internal==0)begin
                rx_valid=1;
                rx_data=temporary_register;
                counter_internal=10;
            end
            else begin
            temporary_register[counter_internal]= MOSI;
            counter_internal=counter_internal-1;
            end

        READ_DATA:
            if (tx_valid==1)begin
                if (counter_external==0)begin
                    counter_external=8;
                end
                else begin
                    MISO=tx_data[counter_external];
                    counter_external=counter_external-1;
                end
            end

        WRITE:
            if (counter_internal ==0)begin
                rx_valid=1;
                rx_data=temporary_register;
                counter_internal=10;
            end
            else begin
            temporary_register[counter_internal]= MOSI;
            counter_internal=counter_internal-1;
            end
        endcase
end

  // Next State Logic
  always@(cs,SS_n) begin

     case(cs)
            IDLE:
            if(SS_n==1)
               ns = IDLE ;
            else
               ns = CHK_CMD ;

            CHK_CMD:
            if(SS_n ==0 && MOSI==0)
               ns = WRITE;
            else if (SS_n==1)
               ns = IDLE;
            else if (SS_n == 0 && MOSI==1 && read_indicator==0)
               ns = READ_DATA;
    else if (SS_n == 0 && MOSI==1 && read_indicator==1)
        ns = READ_ADD;

            READ_DATA:
            if(SS_n==1)
               ns = IDLE;
            else if (SS_n==0 && tx_valid==1)
               ns = READ_DATA;

            WRITE:
            if(SS_n==1)
               ns = IDLE;
            else if (SS_n ==0 && rx_valid==1)
               ns = WRITE;

            READ_ADD:
            if(SS_n==1)
               ns = IDLE;
            else if (SS_n==0 && rx_valid==1)
               ns = READ_ADD;

       default : ns = IDLE;
     endcase

  end

endmodule

Whenever I do test bench I get zeros in the rx_Data line, I don't know why. Can anyone help with this?


texts: Transformer hum coming in audio amplifier

texts:
I made an audio amplifier with a 6283 IC.
When I power the amplifier with a 12V battery it works fine without any hum.
When I power the amplifier amp with a 12V powered transformer,  hum comes from speaker from the transformer.

What should I do?
How do I fix the hum from the amplifier?


texts: Where to fuse high voltage batteries connected in series?

texts:
I have modules of cells in series each with 48V.

I wonder where is the right place to fuse the modules in series. (The current to trip the fuse is the same on every point).

Version 1:

simulate this circuit – Schematic created using CircuitLab

Version 2:

simulate this circuit

Version 3:

simulate this circuit

Version 1 is the usual one, what points against the other two versions?

There is a difference with a grounded battery for sure:

source: link


texts: Any tricks to generate triangle wave to add to analog signal for oversampling?

texts:
I want to increase the effective resolution of the ADC by oversampling and decimation. Unfortunately the signal I'm realing is too clean, so I would like to add a bit of artificial noise (1LSB peak to peak) to a signal.

I would like to use MCU timer to output a square wave, convert it to triangle-like wave and add it to the signal.

Below is my attempt, but it does not work as expected - the amount of noise added varies with the level of the analog signal.

Can someone enlighten me on this topic? How do I do this properly?

simulate this circuit – Schematic created using CircuitLab


texts:
I´m using a PCF 8583 I2C RTC for one of my projects (i´m not a professional, just an amateur). The clock delays about an hour per day, which I find unacceptable.

I´m using a 32768 Hz, 12.5 pf, 50 Kohm crystal with the RTC. Acording to the datasheet, the capacitance is OK (5 min, 20 max, 10 typical), but the resistance is a bit high. They don´t provide minimum nor typical values for that, but state a maximum 40 Kohm for the crystal.

Can this be the cause?

I personally think something else must be wrong. I used the same components and program code for another project, and it is not as bad as this one (it also delays, but about 3 minutes per day).

My last effort was to add a wire connecting the crystal package to ground. It improved, but not enough.

Any thoughts on how to improve accuracy?


texts: How to use Zener Diode in Parallel RC circuit

texts:
What I'm trying to do is allowing the current to move through only one component. In the circuit shown, DC voltage is running two components (Z & C), also charging the capacitor

When voltage cut, then capacitor give current to Z & C. What I want to do is allowing the current to flow through only C but not Z.
I tried to put zener diode on the line indicated by light blue but the current still flowing through Z (zener diode is not working).

How can I make this work? What can be the problem?


texts:
If I increase the tail current, will the linear range of differential pair (range of Vid when both transistors are on) become larger or smaller?

According to this formula, linear range will increase if I increase Itail.
But intuitively when I increase Itail, the gain of differential pair will increase and the Id vs Vid curve will become steeper, thus the linear range will decrease.
How can I understand this contradiction?


texts:
I have trouble designing an ALU. Here are my logic boxes:

But how can we implement a digital circuit which will choose the operation:If I use multiplexers all the operations will be done at the same time.Is it the way to go? Or is there another way? Also how can we select which operation will be performed?


texts:
I need to design a regulator for my thesis, but I really need help, Please!

The topic:
- A temperature regulator for a small fridge

Some details:
- the regulator has to control a peltier element which will cool the air in the fridge
- the peltier element functions with 12 V and 5 A
- first I need a circuit which measures the temperature, then its result will be compared to a fixed value, and depending on the difference between the 2 values, the peltier element will be controlled

What I did:
- the picture shows a hand-drawn circuit  which I tested on a test board  the results of the test are written in red
- I measured the temperature through a pn junction (a bipolar transistor connected as a diode)
- since the voltage variation with the temperature is very small (aprox. 2.5mV/deg), I amplified it through an operational amp, realized so that an offset voltage it obtained in order to amplify only the voltage variation of a few mV.
- then there is a comparator which compares the measured voltage with a given voltage (through a potentiometer)
- at the output there is a power MOSFET which controls the Peltier element

After realizing this circuit, I understood that in order to control the Peltier element, I need 5A at the output of the comparator. What is more, the group MOSFET-Peltier has to be powered with 20 V, so that the Peltier element can suck 12 V and it still remains 8 V for the MOSFET.
I simulated the circuit in Spice 4 (using some similar components to those used in reality and simulating the Peltier through a resistance of 2.4 ohm), so that I could then correctly dimension the components. But already after the amp, the voltage is not equal to the one measured on the test board and later on, the differences rise.
I tried to vary the resistances of the comparator so that I obtain 5A at its output, but no matter how much I vary them, the result remains approximately the same.

Another thing I don’t understand: I was told I have to control the Peltier using PWM, but first of all I read on this forum that this is not a good idea and second, I don’t understand why I should need PWM, since the circuit I already realized controls the Peltier.
Anyway, I drew a circuit with a 555 timer under the original circuit.

Please help me modify my circuit so that it works! And also, if you could, help me undersstand how and why I should use PWM.

Thanks a lot!

I just modified everything you suggested and also added the circuit for PWM. Do you think it's ok?


texts:
Hello, I am a beginner at electronics. I have two AC to DC converters ((3),(5) in image). The converter with the number 3 is connected parallel with my room's light bulb. It converts 220v AC to 12V DC 1.2 A. The converter number 5 is a small 220v AC to 12v DC 450mA converter. Devices 4 and 6 are arduinos. Number 7 is a switch. and number 1 electricity mains. The problem is that when I attach the number 5 on the circuit then it draws all the current and number 3 does not light up. Why?

Update:
I have an arduino inside my light switch which takes values from a trimmer and send it to a Central Arduino which send them to the Arduino which is parallel connected to the light bulb and dimms the light using a phase control module.

when I disconnect the inverter number 5 the circuit works perfectly. When I connect it back the LED on the converter number 5 turns constantly on but the LED on the converter number 3 turns on for some milliseconds and fade out. With a result the arduino parallel connected to the light bulb to not work

Update 2:
This is the complete circuit. I use nrf24l01 modules to communicate between arduinos. The dimmer is a circuit that detects the zero-crossing and uses a triac to control current. There is a tutorial on Instructables.


texts:
how do I hook a PNP sensor to a raspberry pi 3?
I know I need an A/D converter, and I've already got a MCP3008.
But apart from that, what else do I need?
The sensor output switches 24v or 0v, I also know I have to bring it down to 3,3V.
Thanks a lot guys!


texts: What to consider when choosing batteries for a project?

texts: How do you choose what batteries to use for your projects? Are there a set of criteria that they need to be able to do in order for you to consider them? If so what are they?. The only 2 that come to mind are size and capacity. So do I need a PP3 or could I use 6 AAs? Then capacity AAs are better as they have better capacity.


texts: Finite parallel impedance network general solution

texts:
Does anyone know if a finite number of parallel-series impedance has a general solution?

I am trying to model a network flow problem that can be described in electrical terms and represented as a finite discrete transmission line with arbitrary impedance.

While it is not difficult to write the equations down for a small number of terms, I'm curious if there are some general solutions or insights into the problem.

It looks like

----Z1---+----Z3---+----Z5---+---...---+
         |         |         |         |
         Z2        Z4        Z6        ZN
         |         |         |         |
---------+---------+---------+---...---+

All the Z's are, in general, different.

I'll need to know the "current" and/or "voltage" at every branch. In this case the bottom is grounded.

What would be cool is to be able to know the voltage and/or current in terms of i, the ith position (the top +).

Any ideas?


texts: How to measure shunt drop with an Arduino

texts:
I'm looking at a schematic like the following:

simulate this circuit – Schematic created using CircuitLab
I understand that this will be a very rough resolution as the drop will be in the 25 to 75 mV range and a single count in the Arduino ADC is around 5mV.  Perhaps I'll look into amplifying the signal at a later stage but that is enough for me as a start.
In my case, my Arduino is also powered from within the load circuit, through a non-isolated buck converter. iIn't connecting its ground to potentially 35.9-something volts going to cause a short circuit?


texts: Choosing PLL Loop Filter Bandwidth and Phase Margin for Frequency Ramp Generation

texts: I am new to PLLs and am trying to use one to generate a frequency ramp between 5.725 GHz and 5.875 GHz. I have found tools online that help design loop filters for PLLs, and all of these tools require that the user know the desired loop filter bandwidth and phase margin. I have not been able to find suggestions for choosing filter bandwidth. Also, I understand that filter bandwidth and phase margin are related, but I don't know how to choose appropriate values for them for this application.


texts:
I am currently attempting to design a LED grow light using the following LEDs but I am having a very hard time finding a sufficient power supply.

8 x Lumileds - SunPlus CoBs
DataSheet
51.7 V, 2250mA

The first complication is that these lights will be powered by a 380VDC system, not your typical 110-220VAC Power.  So I believe that I am looking for a DC/DC CC Driver for each CoB?  I would also like to run these 8 CoBs in a parallel configuration, this way if one LED dies the rest will still function.

I know 380VDC sounds odd but if interested in why that is a requirement here is a great article:
https://www.led-professional.com/resources-1/articles/direct-current-dc-supply-grids-for-led-lighting

Also just for reference here is the link to the External power supplies that will be providing that 380VDC power:
https://www.artesyn.com/power/documents/606/

1: At what current should I run these CoB LEDs? I am assuming that running at max current of 2250mA would destroy the lifetime of the LED as well as produce an insane amount of heat?

2: Does anybody have any suggestions on a dc-dc CC Driver for these CoBs? I would prefer not to have to design my own LED driver but will if absolutely necessary.  Ideally I would like to use a pre-built Driver like MeanWell, Glacial Power, Artesyn, etc, but I cannot find one that, A: V-in is 380VDC and B: Is a CC Driver capable of ~2A output W/ PWM or Analog dimming control.  There are just so many brands out there and I do not want to use anything unreliable, hence why I am reaching out for help!

Anyway Thank you all! Looking forward to your responses!


texts: SAR ADC has non-linearity around the middle of the range

texts:
I'm using a SAR ADC in STM32L433 chip and it exhibits a strange nonlinearity around the middle of the range which I can't explain.

It's a 12bit ADC with 64x oversampling and 2 bit shift which effectively makes it 16bit.
The nonlinearity is around 32768 (2^15) which is in the middle of the 16bit range.
It's almost looks like clamping to the 32768 except that a couple of seconds later it'll cross the line nicely.
It seems like approaching the 32768 line from any side is a problem.

What could cause this?

The red line is the 32768 line for reference.
The green line is the signal. 100Hz sample rate, the measured signal is around 1Hz.

Edit: ADC specifications

Edit2: I did an experiment with driving the input with a ramp.(might not be linear to begin with but it was continuous)
Here is how the looks like when the fit-ed line is subtracted.
The big jump is only at the 32k. Why this is the case it still puzzles me. For now the workaround solution is to avoid this range and I'm setting up the AGC to drive the signal above it.


texts: Relating position sensor voltage input to Arduino PWM % output

texts:
This is a general question, I believe it maybe a math question but it is for the Arduino platform.

I'm doing a ball levitation project that will keep a ping pong ball suspeneded at a setpoint in a tube, the balls position is read with a laser position sensor that gives an analog voltage related to the balls position. The sensor output is pretty linear for the operating range of the tube's length.

Then I have a fan controlled with PWM as a %, this is manually adjusted with a pot, and I marked a scale on the tube in one inch increments.

Basically I made a table of sensor voltage output values, related to PWM% values of the motor for different positions in the tube.

I made a graph relating the two variables and it is surprisingly pretty linear. I did a trendline in excel and got a line equation of Y = 3.0265X + 15.05

X is the sensor position(in volts) and Y is the PWM value in %,

The part I'm having is taking the analog voltage from the analog pin that is a value of 0 to 1023 in the arduino and relating it to a PWM to analogWrite to the motor (A value from 0 to 255).

I know the analogRead() is and ADC so do I convert the 0 to 1023 value to a voltage by (5.0 * analogvalue)/ 1023;

That will give me volts, but I dont understand how how to relate this to PWM, like a change in sensor voltage to a change in PWM to the motor. I think I'm on the right track but not connecting the dots together.

Any help will be appreciated!

Thanks


texts: How does the Bias Drive in TI ADS1299 help in noise reduction?

texts:
I'm bit of a noob in electronics so please pardon me if this question is too basic.

I would like to clearly understand how the signal from the bias drive electrode can help in noise reduction, reducing baseline drift and other artifacts.

As a user puts it in this forum page "This BIAS drive signal drives the patient with an inverted common-mode signal that can help reduce noise and 50/60Hz interference."

I'm not able to understand the above statement on how the inverted common-mode signal can help in noise reduction. If some can explain the intricacies behind this concept, that would be great!


texts: Switching 12V with an active low 5V signal

texts:
I’m trying to switch 12V (max 30mA) with a signal from a MCU that I’d prefer to be active low (so the output voltage is 12V when the control signal is 0V, and 0V when the control signal is 5V).

Since I have plenty of bipolar transistors at hand, I’m looking for a solution using bipolar transistors. For an active high signal, I found an answer on this site which seems to work perfectly, and it seems this can be adapted to an active low signal by adding yet another PNP transistor:

simulate this circuit – Schematic created using CircuitLab

However, 3 transistors for what seems to be a fairly simple problem seems a bit excessive. Is there a better solution?


texts:
I’ve got a MCF5282 that I’m trying to use PDD4 as a GPIO on.  In my setup code, I’ve got:

MCF5282_GPIO_DDRDD = 0x10;    /* cs on dd4. */
MCF5282_GPIO_PORTDD = 0x10; /* active-low. */

And in my main loop, I’ve got:

for( mainloop_cnt = 0; true; mainloop_cnt++ )
{
    MCF5282_GPIO_PORTDD = (mainloop_cnt & 0x10);
    /* other stuff. */
}

Which should give me a nice square wave on the oscilloscope, but the port doesn’t seem to be doing as I say.  Am I missing some setup steps?  I can’t find anything in the 5282 manual about a “Port DD pin-assignment register” to repurpose it from its “primary” role as DDATA.