texts: Help Wiring Multiple 12 V Batteries for 24 V service

texts:
My question is: If you have 20 12 volt SLA 95 Ah batteries and you need to hook them up to a 24 volt inverter what is the best way to wire these batteries?

Right now I have them grouped in groups of 2 to make 24 volts and those 10 groups are wired in parallel with all matching cables running to a buss bar for the positive and one for the negative.

The charge controller from the solar panels is hooked to those buss bars. Then I have 2 positive and 2 negative cables all matched in length wired to my 8,000 watt PSW Inverter. Does this sound right?

Thanks


texts: Metal sleeve around cassette player motors?

texts:
I have recently taken apart a few cassette players to get motors, and I have noticed there is always a metal sleeve around the main drive motor.

Here is an Ebay product photo showing this on a Mabuchi EG-530AD-2B motor:

The sleeve is not attached to the motor and can be easily removed by sliding it off. I have not seen them on DC motors anywhere else. What is it there for?

The reason I chose an EG-530AD-2B motor is because one of the cassette players I took apart had a 'Mebochi' (not Mabuchi) brand EG-530AD-2B motor with a very similar label to the one shown below, except that the text was blue. I cannot seem to find any information about this online. Does anyone have any idea what it is?


texts: Maximum mid-band gain of s.s. model MOSFET amplifier?

texts:
Schematics

I need to find the maximum possible gain for this NMOS cascode circuit.

Here is the s.s. model:

Work

I used nodal-matrix analysis (basis is KCL) to find the gain (\$A_v\$):

$$
    \begin{bmatrix}
    \frac{1}{r_{o1}}+\frac{1}{r_{o2}} & -\frac{1}{r_{o2}} \\
    -\frac{1}{r_{o2}} & \frac{1}{r_{o2}}+\frac{1}{(R_{L1}\,||\,50)} \\
    \end{bmatrix}
\cdot
    \begin{bmatrix}
    V_A \\
    V_B \\
    \end{bmatrix}
=
    \begin{bmatrix}
    -gm1\cdot V_{in} - gm2\cdot V_A \\
    gm2\cdot V_A \\
    \end{bmatrix}
$$

$$
    \Longrightarrow
    \begin{bmatrix}
    \frac{1}{r_{o1}}+\frac{1}{r_{o2}}+gm2 & -\frac{1}{r_{o2}} \\
    -\frac{1}{r_{o2}}-gm2 & \frac{1}{r_{o2}}+\frac{1}{(R_{L1}\,||\,50)} \\
    \end{bmatrix}
\cdot
    \begin{bmatrix}
    V_A \\
    V_B \\
    \end{bmatrix}
=
    \begin{bmatrix}
    -gm1\cdot V_{in} \\
    0 \\
    \end{bmatrix}
$$

$$
\Longrightarrow V_A = D/C,\quad V_B = -\frac{v_{in}\cdot (r_{o1}\cdot gm1)\cdot (r_{o2}\cdot gm2 + 1)\cdot (R_{L1}\,||\,50)}{r_{o1}\cdot r_{o2}\cdot gm2+r_{o1}+r_{o2}+(R_{L1}\,||\,50)}
$$

$$
V_B = V_{out} = -\frac{v_{in}\cdot (r_{o1}\cdot gm1)\cdot (r_{o2}\cdot gm2 + 1)\cdot (R_{L1}\,||\,50)}{r_{o1}\cdot r_{o2}\cdot gm2+r_{o1}+r_{o2}+(R_{L1}\,||\,50)}
$$

$$
\Longrightarrow \frac{V_{out}}{V_{in}} = A_v = -\frac{(r_{o1}\cdot gm1)\cdot (r_{o2}\cdot gm2 + 1)\cdot (R_{L1}\,||\,50)}{r_{o1}\cdot r_{o2}\cdot gm2+r_{o1}+r_{o2}+(R_{L1}\,||\,50)}
$$

This is the part where I am stuck; I was told that increasing \$gm\$ and \$R_L\$ will reveal the maximum gain but I don't really understand what that entails. Thus far, my interpretation of "increasing \$gm\$ and \$R_L\$" has been:

$$
\lim\limits_{(gm1,gm2,R_{L1}) \to (\infty,\infty, \infty)} A_v
$$

However, I've had trouble finding a reliable/straight-forward method for calculating these simultaneous/multi-variable limits, so I assumed that my interpretation was incorrect. For instance, when I apply this interpretation using Wolfram (the only calculator I could find to compute these types of limits), I receive the following output:

(limit does not exist, is path dependent, or cannot be determined)

If you can provide a better interpretation, please enlighten me.

Remarks

I'd like to know the max-gain but I am more interested in being taught a correct/straight-forward method that is applicable to any similar problem.
Although this is most likely a question of mathematical understanding, it belongs here b.c. many EE's might have already solved this problem or they might bring enough insight about the circuit (NMOS cascode is recognizable/typical) to derive a solution (or provide the final answer at-least).


texts: How can I make a 9V 1A DC adaptor to power this audio mixer?

texts:
I have an audio mixer that is powered by electricity from the wall socket, but I'd really like to power it on batteries instead for greater mobility.
I could not find any ready solution to purchase online so I believe I'll need to DIY it. I am not great with electricity but I know it is possible to connect power sources in parallel or series in order to control the voltage and amperage.
The power input required is only 9V 1A.
Here's some pictures from the power adapter: https://imgur.com/a/rcmQg7J

How could I achieve what I want? Thank you for your time and help.


texts:
I need to interface two PCBs via RS422 (250kbps) in full-duplex mode (4-wire, 2-twisted pairs 100ft cable).  This system will operate in a noisy (CNC) industrial environment, ie, industrial controls and automation.

I realize that RS422 is fully balanced (differential pairs) but the more research I do I seem I get conflicting recommendations about shielding individual pairs or just the (multi-pair) cable as a whole.

In terms of cable selection should I use a cable with each pair individually shielded or go with both pairs shielded as a whole?


texts:
We know the frequency of a direct current is zero. The reason is that there is no repetitive pattern.

But I was stumbled when I noticed, why can't that straight line be cut into smaller pieces, and can we treat it as infinite frequency? I have included a picture below as an example

As you can see, with dc, that straight line can be divided into infinitesimal patterns/cycles, since the cycle can be seen as lines repeating over and over again.


texts: Analysis about H bridge to drive DC Motor

texts:
the picture below shows my design about driving DC motor with H bridge. There is one problem, for example, I turn on the U1B and U1A(use PWM to turn on U1B and the U1A is always turn on when I make the motor run backward), the motor works. But when I measure the signal on pin 2 of U2A, it has noise. That is to say each time(PWM) U1B switches on->motor switches on->the VCC will go a little down->the transistor Q3 will on for a very little time. So it has risk that the MOSFET will be shorted. I have try to make the VCC a little larger(more than 20V), then the MOSFET burnt. If the Vcc not so high, the MOSFET won't burn.

Could you give me some advice?(Make the U2A not be disturbed， so as to protect the circuit) Thanks!


texts: Calculating NTC temperature on Controllino Maxi Automation yields incorrect temperature

texts:
I'm using the analog input on the Controllino Maxi Automation to determine the temperature of a 10K NTC thermistor. At first we thought it was a self heating issue given that with 24V the current through the NTC would make that issue more prevalent.
To verify, I connected the Controllino to only my laptop and used the pin headers to hookup the NTC and series resistor to as shown below.

simulate this circuit – Schematic created using CircuitLab
Following the advice in my previous question I oversampled the voltage to help with noise and attempted to calculate the temperature
#include <Controllino.h>
#include <Arduino.h>
// Thermistor Example #3 from the Adafruit Learning System guide on Thermistors
// https://learn.adafruit.com/thermistor/overview by Limor Fried, Adafruit Industries
// MIT License - please keep attribution and consider buying parts from Adafruit

// which analog pin to connect
#define THERMISTORPIN A0
// resistance at 25 degrees C
#define THERMISTORNOMINAL 10000
// temp. for nominal resistance (almost always 25 C)
#define TEMPERATURENOMINAL 25
// how many samples to take and average, more takes longer
// but is more 'smooth'
#define NUMSAMPLES 255
// The beta coefficient of the thermistor (usually 3000-4000)
#define BCOEFFICIENT 3892 // datasheet - https://www.mouser.com/datasheet/2/240/Littelfuse_Thermistor_Probes_Assemblies_Threaded_U-1372560.pdf
// the value of the 'other' resistor
#define SERIESRESISTOR 9760

int samples[NUMSAMPLES];

void setup(void) {
  Serial.begin(921600);
}

void loop(void) {
  uint8_t i;
  float average;
  long long int values= 0;
  // take N samples in a row, with a slight delay
  for (i=0; i< NUMSAMPLES; i++) {
   values += analogRead(THERMISTORPIN);
   delay(1);
  }

  average = (float)values / NUMSAMPLES;

  Serial.print("Average analog reading ");
  Serial.print(average);

  // convert the value to resistance
  average = 1023 / average - 1;
  average = SERIESRESISTOR / average;
  Serial.print(" Thermistor resistance ");
  Serial.print(average);

  float steinhart;
  steinhart = average / THERMISTORNOMINAL;     // (R/Ro)
  steinhart = log(steinhart);                  // ln(R/Ro)
  steinhart /= BCOEFFICIENT;                   // 1/B * ln(R/Ro)
  steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
  steinhart = 1.0 / steinhart;                 // Invert
  steinhart -= 273.15;                         // convert absolute temp to C

  Serial.print(" Temperature ");
  Serial.print(steinhart);
  Serial.println(" *C");

  delay(1000);
}

That yielded the below results, I should point out the USB voltage is at 4.5V and the actual thermistor resistance (measured outside of the circuit) is 11.63k
Average analog reading 369.96 Thermistor resistance 5529.25 Temperature 39.18 *C
Average analog reading 369.95 Thermistor resistance 5529.07 Temperature 39.18 *C
Average analog reading 369.96 Thermistor resistance 5529.25 Temperature 39.18 *C
Average analog reading 369.94 Thermistor resistance 5528.70 Temperature 39.18 *C
Average analog reading 369.96 Thermistor resistance 5529.25 Temperature 39.18 *C

Which is definitely wrong, my room temperature atm is around 17-20C and the physically measured voltage across the thermistor is 1.8V
Just for quick reference, the pot here is replaced with R1 and the NTC in series and there's no external power supply, just the USB attached.


texts: Vacuum tube stereo amplifiers with an odd number of tubes

texts:
While researching the world of vacuum tube audio amps, I noticed that many commercially available stereo amps have an odd number of tubes. Here's a random example.

How can a decoupled stereo sound be produced using a single tube?


texts: I cant understand how a TVS might absorb voltage. As far as I can see, when a transient is applied to it, it becomes a very small resistor, so the transient voltage will still be on top of him, but all the current will flow through it.


texts:
I'm planning on replacing lights with smart bulbs (e.g. Yeelight RGBW) and replacing light switches with capacitive panels connected to Arduinos which will send data to RPi, which will then control the lights.

I want to make the panels by myself, like here. They will contain some round slider for RGB color and sliders for RGB brightness and White brightness, as well as bulb selection and power button.

My question is, can I use single sheet of copper (or tape), with multiple connection points, to make a single panel, where Arduino will calculate the coordinates from the multiple points? It's in case I want to change the layout, the only thing I would need to do is replace one sheet of paper and some layout file for the Pi (it will decide what to send according to the layout).

I've seen some Instructables for single-dimensional sliders, where they connect each end of the slider to a pin, so I think it will be possible.

How many points would be ideal? Could I just triangulate it from 3 values? Or would one for each corner be better? Or even 5 like one in the middle?

Also is the capacitance linear with distance? Is there any formula?

And another question: I have lots of copper tape left from guitar shielding, but it corrodes over time. Will the capacitance change with it corrosion, rendering it useless?

Thank you for all your answers.


texts: How does electricity pass through a surface (or more generally, conductive material with complex geometries)?

texts:
I was reading this article on how the breaking mechanism of a Sawstop works. For those who might not know, Sawstop is a table saw fitted with at least a conductivity sensor that detects changes in current passing through the blade as it comes into contact with something other than wood (the table saw operator's fingers, for instance).

This got me thinking about how electricity flows through a circular plate. If we connect wires to the plate (see attached diagram) and assuming the wires form a conductive closed loop, would the current change if we changed where the 2 wires were connected to that plate? I'm guessing no since Kirchoff's junction rule states that same current drawn through one wire must leave through the other wire. We can just treat the plate as a resistor.
If a person touches the plate and assuming he doesn't form another closed-loop path, would he change the current flowing through the wire? I'm guessing no since he'd just be a floating conductor/resistor, in principle.


texts:
I don't understand it...

When I tried developing a presensitized PCB, I never get perfect results for large boards.

If I use a small board (less than 6cm by 6cm) in a picture frame and use the picture frame clamps and expose the board for one hour, I get good results.

If I use a large board (15cm by 20cm) with the same method, then the middle section of the artwork on the board looks like it has disappeared, yet the rest of the artwork seems fine. It makes me wonder if picture frame glass can bend.

Now this time, I took the traditional method of using the same picture frame for a medium size board (9cm by 12cm). Like the professionals, I decided this time to not use the picture frame clamps and leave the glass just sitting on top of the artwork (because people assumed the glass presses the artwork down) and this time, I reduced the exposure time from 60 minutes to 30 minutes (where as in the last two cases, the exposure time is 60 minutes).

The problem with the last method is that when I examined my board, quite a few tracks were faint and some tracks looked like they're cracked to the point where an open circuit was present where there shouldn't be one, so I had to use a super-fine marker to fix the mistakes (a pain!).

I'm curious, does super-heavy glass exist where UV light can pass through it, because it seems in all these scenarios I have difficulty in keeping the artwork down (where every line touches the PCB).

Yes I have sanded the sides of the pcb prior to exposing it in order to elimate the copper bumps produced from sawing it to size (yes I saw smaller pieces of board with a utility knife from a larger board as that method is cheaper than buying multiple small boards).

I have also tried adding extra transparency sheets without much success. In fact, those transparency sheets seemed to add a few random copper dots to my board which don't wreck the circuit (thank god).

So does a super heavy/thick sheet of glass exist or should I stick hundreds of sheets of glass together in hopes enough UV light passes in one hour?

What can I do glass-wise?


texts: Whats the difference with Carry Look Ahead Generator & Block Carry Look Ahead Generaor

texts:
Whats the difference between this 2 CLAG (Carry Look Ahead Generator)

CLAG

Block CLAG

I mean, the way Carries of 1st 3 bits are the same and the last carry is actually \$G*\$? The difference is use of different gates and the additional \$P*\$ bit?

Equation of 1st image (I'll use 0 index. eg. \$P_0 \text{ to } P_3, C_{-1} \text{ to } C_3\$). Where \$C_{-1}\$ is carry into circuit

\$C_3 = G_3 + P_3 \cdot G_2 + P_3 \cdot P_2 \cdot G_1 + P_3 \cdot P_2 \cdot P_1 \cdot G_0 + P_3 \cdot P_2 \cdot P_1 \cdot P_0 \cdot C_{-1}\$

\$C_2 = G_2 + P_2 \cdot G_1 + P_2 \cdot P_1 \cdot G_0 + P_2 \cdot P_1 \cdot P_0 \cdot C_{-1}\$

\$C_1 = G_1 + P_1 \cdot G_0 + P_1 \cdot P_0 \cdot C_{-1}\$

\$C_0 = G_0 + P_0 \cdot C_{-1}\$

Equation for image 2 ("Block" CLAG)

\$C_1 = (G_1' \cdot (P_1 \cdot G_0)' \cdot (P_1 \cdot P_0 \cdot C_{-1})')'\$

\$= G_1 + (P_1 \cdot G_0) + (P_1 \cdot P_0 \cdot C_{-1}) \rightarrow \textrm{ DeMorgans}\$

So aren't they the same, with the addition of a \$P*\$ bit, or did I miss something?


texts: Confusing ratings of maximum current sunk/sourced by a pin in PIC24E datasheet

texts:
I started a new design based on a PIC24EP256GP202. I was interested in finding how much current can a single pin sink/source, but the datasheet looks a bit confusing to me:

The Absolute Maximum Ratings:

Is the current sink/source capability of a pin 3.5 mA (= 15 mA / 4) or 3.125 mA (= 25 mA / 8)?


texts: Serial Connection Not Working on Modified Router

texts:
I have a Sagem F@ST 2504 router. Following the advice from OpenWRT wiki (http://wiki.openwrt.org/toh/sagem/fast2404) I managed to solder the header pins in the correct place. I've attached pics below. My soldering isn't the best, but I'm working with a gas iron that I'm not too comfortable with.

The pins from right to left are:

...................o Pwr
...................o Rx
...................o Tx
...................o Gnd

I am using this USB to serial cable: http://www.adafruit.com/product/954

I am using Minicom 2.2 on the Mac to connect to the router via serial.

These are the steps I follow:

Connect cable to header pins. Pwr -> Pwr, Rx -> Tx, Tx -> Rx, Gnd -> Gnd.
Open terminal on mac and type: /opt/minicom/2.2/bin/minicom -s
In Minicom I've tried various baud rates. I use, but the recommendation is  9600 8N1
Minicom initializes the modem, but when I press CTRL + A mincom says Offline. Nothing is displayed in the terminal.

Note that when testing I do not plug the router into the mains. I use the 3.3v header. I've tried with power though, which didn't solve my problem.

I'm at a bit of a loose end here. Any ideas on what I'm doing wrong or what I'm missing?


texts:
I am trying to measure distances with the 3 axis accelerometer that is part of the LSM9DS1. I measure the acceleration in X-axis and Y-axis every 5ms and double integrate it over the time.
I can already correctly measure the movement along the X- or Y-axis with a precision of +-1cm.
The problem is that when I move the module in which the sensor is contained along one axis, the data shows me that there is also an acceleration along the other axis.
Because of this I get wrong distances when I move the module freely around the table.
Has anyone experienced such behavior before and knows an answer?
The data sheet of the LSM9DS1


texts: What are the steps to design an instrumentation amplifier using lm741 with gain=100 ?


texts: Introduction dates of different 74xx or 40xx chips?

texts:
The 74xx family debuted in 1964 with the 7400 chip, and the 4000 family debuted in 1968, but not all chips with 74xx or 40xx part numbers debuted anywhere near that time.  If one wanted to invent a hardware design that was period-correct for e.g. 1976, how would one find out which 74xx, 40xx, etc. parts would have been available at that time?  Some chips would seem to be in just about every way superior to others, suggesting that people probably used the generally-inferior chips because they were available first, but perhaps there were other reasons such as fabrication cost, speed, or power consumption.

Is there any easy way to determine which parts that are reasonably available today (if not still manufactured) would be suitable for period-correct designs?


texts:
In my project I have to operate DC motor. For this I am using Arduino as controller and MOSFET for switching. I have connected MOSFET GATE pin to Arduino's pin 12.

I have used this schematic....

Main problem is as I give +12v supply to one end of Motor and other end of Motor to Drain of MOSFET and other  connection same as Image.
But without connecting Arduino output pin to Gate of MOSFET motor staying on continuously.

In my case I am controlling GATE pin using pin 12 of Arduino,which will send pulse to MOSFET to control motor(ON/OFF).

What wrong am I doing?


texts:
I'm trying to learn how to program a battery charging IC (BQ24193) via the I2C communication protocol. My goal is to write the correct values to it in order to gain the proper charging input and output current (I will be using an arduino to program this if that matters).

When going through the datasheet, what I don't understand is the actual address of the slave and the address of the register. Talking to a Texas Instrument engineer, he said that the address given in the datasheet is the address for the register 6BH (which I am assuming is just 0x6B). He also said the the slave address is sent after the start condition. So I have no idea what that means since I always thought the slave address value was given in the datasheet.

Datasheet: http://www.ti.com/lit/ds/symlink/bq24193.pdf

So the questions I have:
How on earth do I, the programmer, get the slave address in order to write to the IC?
How do I write to a specific register if all of the registers have the value 6BH?

Any help would be appreciated. Thanks.


texts: Replacing a 220V single phase motor with a 220V split phase motor

texts: I am replacing the motor on a whole house fan. The old one was 1/3HP 220V single phase. The new one is 1/3HP 220V split phase. Will the low, high and common connections be the same or is there different wiring for the split phase motor?


texts: Negative voltage on both inverting and non-ínverting inputs of a differential amplifier gives non-zero output

texts:
I used an LM324 op-amp for my differential amplifier, in which the inverting input voltage is constant and the non-inverting voltage varies between the range -1.30 V to 1.30 V.

I am having an issue when I give -1.30 V to the non-inverting input. The op-amp produces a very high output voltage, instead of 0 V. Is there any mistake with the sample circuit below? Does anyone know how to rectify the error?

simulate this circuit – Schematic created using CircuitLab

PARAMETERS
V1 =  -1.30 V
V2 =  1.30 V to -1.30 V
Vcc and Vdd  connected to 12 V and Gnd


texts: Electromagnetic coupling on printed circuit board traces

texts:
When I applied the following damped signal in the proximity of my product (the magnitude is around 10 kV and the frequency is around 400 kHz) through a cable of 4 meters, the microcontroller sees a signal normally at 3V3 (HIGH LEVEL) which goes down to a LOW level (this appears very few times, I would say 1/100.)

I think this is a problem of electromagnetic coupling, even if at this frequency I should have a trace length equal to:
$$trace_{length} = \frac{c}{4*f}$$
Where \$c\$ is the speed of light and \$f\$ is the frequency of the signal.
So the trace length should be equal to 183 meters, which is clearly not the case.  The trace length is equal to around 10 cm. Nevertheless, when I plug a probe on the affected signal, i.e. I add a wire of 1 meter, it clearly works more often!
I would like to know: How can I confirm that it is a electromagnetic coupling and how can I protect my circuit from it? (Other than reducing the length of the trace.)
I think the problem is present on other signals, but the microcontroller is particularly sensitive to the fluctuation of this signal.


texts:
during non contact dielectric measurement of any sample using VNA and patch antennas,should the antenna dielectric be taken into consideration for calculations?
i want to use a ultra wide band patch antenna but i have no idea about its dielectric or material it is  made of. Usually which material is used for making UWB patch antennas operating in GHz?


texts:
I'm attending a university course on real time systems and we are using the STM32F10xxx MCU family for labs and examples. Every GPIO port has an Output Data Register (ODR) and a set/reset register (BSRR). In the manual it says that BSRR should be used to atomically set/reset single bits, "so there is no risk an IRQ occurs between the read and modify access".
If I understand this statement correctly it means that if I do something like GPIOB->ODR |= (1UL<<3) a read and write on the ODR is necessary, so an interrupt might occur in between and, to avoid that, it would be better to use BSRR to set the relevant bits... am I right?
The question is: what if I want to set all the pins on the ODR register in an atomic way? For example does the instruction GPIOB->ODR = 0x00000002 run atomically? In this case there is no need to read the value of the register, I'm simply setting all the bits to a specific value... is this write operation atomical or can it be interrupted? The only thing I found on the manual is "the I/O port registers have to be accessed as 32-bit words", but I don't know if this implies something about atomicity...
Can you help me? I'm completely new to this, so forgive me if the answer is trivial. I've found a lot of similar questions, but none of them clarified my doubts.
Thanks.


texts:
I think I understand left side of the circuit. It is a 2 stages amplifier with positive feedback via C2 and R3, but it's still strange to see how Mk1 and R1 are connected. normally, shouldn't the resistor be connected on the top? and also, what does C3 really doing?

R7 and C4 are used to limit the noise from the right side of the circuit to the left? isn't C4 too large? Will 10uf more than enough?

The right side is very complex. I don't get it at all. it seems like a multivibrator circuit, but it just looks weird. any explanation?


texts: A question about non-linearity of an in-amp gain

texts:
I'm observing nonlinearities in microvolt range inputs on an instrumentation amplifier. Here is the amplififer datasheet and its gain is supposed to be:

G = 1 + (49.4 kΩ/Rg)

And the inputs to this amplifier(from a strain-gage) will be in -/+2mV range in my case.

So I wanted to see the gain at different differential inputs in simulation.

Below the inputs to the amplifier are +/-1mV, so the differential input signal Vsig = (+Sig) -(-Sig) = 2mV and Vout = 1.6V. Here the gain is then around 780. Below is the plot for these:

And this time below the inputs to the amplifier are +/-1μV, so the Vsig = 0.2μV and Vout = -38mV. But this time the gain is around 190k(LTspice shows 19k). Below is the plot for this case:

To see this non-linearity I made a DC sweep for 0.1mV...2mV range and here is what I get:

Am I doing something wrong here? If not would this nonlinearity have bad results for my -/+2mV range strain-gage inputs to the amplifier.

Edit:

Common mode voltage added to the inputs as will exist in real scenario:


texts: I am a type one diabetic and they just released a new advancement in technology. Its a sensor that transmits via NFC to your smart phone. But the range is one inch to be able to read the blood sugar. Is it possible to make a extender to pick up the nfc signals?


texts: Is there an amplifier such that the gain is equal to the ratio of two potential differences?

texts:
I have been toying with some alternatives to transistors in building logic gates. I am particularly interested in the device I tried to summarize in the title of this post. The chip would have 8 pins:
pins 1,2: voltage difference_1=V1
pins 3,4: voltage difference_2=V2
pins 5,6: power=V3
pins 7,8: output=V4

Essentially, I want: V4=(V1/V2)*V3
I would be happy with the following as well: I4=(V1/V2)*I3, with I=current
(and I may ask about that in a separate post)


texts: PCB copper thickness with small pitch SMT components

texts: I typically use 2 ounce copper as rule for all my PCBs.  On a recent board I am using a 0.5mm pitch, relatively large micro, and noticed the pads aren't very flat.  Assembly went fine with the protos, but I'm wondering if 1 once copper would provide for a flatter landing service.  Does anyone have any experience with using 1 and 2 ounce copper with small pitch devices and/or any advice on assembly reliability related to copper thickness for such devices?


texts: butterworth configuration of multi-stage amplifier

texts:
When designing a multi-stage operational amplifier, people usually use butterworth polynomial to set closed loop pole location of the op amp in feedback configuration, and then back calculate to open loop pole locations.
For one example, in this particular compensation scheme, http://repository.ust.hk/ir/bitstream/1783.1-2351/1/200409TCASI_AFFC.pdf, the author states that,

The stability of the AFFC amplifier is achieved by following
Butterworth frequency response to arrange the  location  of  poles.

or in this https://cmosedu.com/jbaker/papers/talks/Multistage_Opamp_Presentation.pdf

Requires p3=2p2=4ωun for stability (Butterworth response)

, or in countless other literatures. It seems it is a common sense that butterworth placement is the assumption, no matter what compensation you are doing.
In butterworth's original paper, he certainly didn't envision people in the future that is going to generalize his idea into multi-stage op amp design.
My question is why use butterworth? how is this generalization done? How is this filter design theory generalize to multi-stage op amp stability design?
For most people that is familiar with two stages design, we do the placement like: based on how much phase margin and how much unity-gain bandwidth we want, we will place the open loop non-dominant pole a cetain factor larger than the unitiy-gain frequency.
For three stages or more stage op-amp, for an amateur like me, I can imagine I will place the poles/zeros like I do in two stage amp recursively, by treating the already-compensated amp as another single-stage, although the phase margin for the intermediate steps may be somehow done in an ad-hoc way.
So I cannot understand why butterworth pole placement strategy is preferred. It would be nice if this can be explained in comparison to other compensation strategies in terms of power, bandwidth, transient overshoot/phase margin or other metrics of interests analytically.


texts: Create delay shorter than a clock period in CPLD

texts:
I have several peripherals that connect to CPLD. They all have different propagation delays, and to compensate that I wish to introduce about 10-15ns delay into the CPLD logic. In detail, clkOUT should be lagging the clkIN by about 10ns. Is it possible to achieve by describing a behavioral model in VHDL? Any suggestions? clkIN = 10MHz.

CoolRunner-II


texts: Photodiode JFET amplifier stage in pinch off?

texts:
In the circuit below, it seems that the JFET is biased in a regime with very low current (pinched off?).

With respect to most designs I came across, this one uses rather large source and drain resistors (factor 10 more than usual). I think it is pinched off by this biasing (datasheet gives cutoff voltage of \$V_{gs}=-1.1V\$ with \$I_d=10\mu A\$).

What are the advantages? (Why is it used rarely? It is a rare configuration, isn't it?)
How can one calculate operating point and amplification factor from data sheet parameters?

I understand that in pinch off, the drain current is exponentially dependent on \$V_{gs}\$, i.e. \$I_d(V_{gs})=I_0\exp\left(\frac{V_{gs}}{n\cdot k_B T/q}\right)\$. But, I never find \$n\$ mentioned in the data sheets. Also most SPICE models seem to fix it to 1. Is this okay? I heard somewhere that it can vary from 1 to 3ish.

simulate this circuit – Schematic created using CircuitLab

(The schematic is adapted from schematics of a lightgun that I found on the web. D1 could also be a phototransistor or forward biased, but I don't think this matters!?)

[Question edited after discussion with FakeMoustache below.]


texts: error 499 in mplab while interfacing lcd

texts: Hi, i was using mplab with hitech c compileri just came across an error[undefined symbol: _lcd_write(testlcd4.obj)] >any solutions pls


texts: Need diagnostic tips for ancient Sanwa YX-360TRe

texts: I need to fix my sentimental value Sanwa YX-360TRe analog meter. It was bought in 1995, slightly used. It can correctly give DC voltage reading. The problem is, it cannot zero-ohm adjust in all ranges, despite using fresh new batteries (9V and two AAA). When short probes, the needle very slightly moves at all. I open it up and here is picture here. I measured each resistors using my Fluke 17B+ DMM and the measured values are here. I suspect the culprit is C2 because I couldn't get a reading on this one. But I'm not sure because it's in-circuit. I searched far and wide, and could not find the schematic of this particular model. I am still waiting my order of the suspected C2 brown ceramic capacitor which is marked F 473Z to arrive. I also cleaned-up with vinegar+salt solution the greenish copper wire as that copper wire no longer beeps when I touch it with my Fluke 17B+ probes. Now that it is clean, it beeps. I also suspect that is the culprit. For the mean time, I appreciate any comments or have this specific model.


texts: Can I load an external file into table for LT spice?

texts:
I would like to load a table (for table instead of editing the table manually) into LT spice, but it's very large (180x2 items). Is there a way that I can load a table into LT spice from an external file?
(I know I can load a PWL file from a csv into a voltage source, that isn't what I want to do, I want to do interpolation from a table)


texts:
I have a 12v motor. I want to operate 12v 7amps relay with lm358 opamp.
when my motor is operate it gives 0.8 Amps, but when it get jammed then it consumes 4Amps, at that time I want to cut down my supply through relay.
I have make a circuit which cuts on 12v-13v but not on 4Amps. Please suggest me a real time circuit.


texts:
I have a DSP kit with a serial connection. Since, I am operating on my laptop, I do not have access to a serial port. So, I would require a Serial to USB converter

How do I create a Serial to USB converter?
Does it work at any baud rate, etc or is it fixed?
Can I access USB using hyperterminal, teraterm, minicom, etc or do I need some other software?
Any other considerations?

Thanks.


texts: How do I design a high powered micro-controlled PID with triacs

texts:
I'm trying to build a micro-controller controlled PID. So far I have found a few recipes for high powered AC voltage ( 10 - 15 Amps ). The first recipe I found involved Using A potentiometer, a capacitor, a resistor a triac an a diac as illustrated below, however this is an analogue controlled system.

The second system involves measuring the 0 crossing with the controller, and using a opto-isolated Triac. The issue with the example shown is that it is designed for control a lamp ( 100 watts ) and I'm looking to control a 1500 watt heater. Can someone recommend a suitable opto-isolated Triac. I was considering using a relay, but I want smoother control over the heat, and I would be concerned that the relay would wear out pretty quick if switching on and off so frequently.


texts: Fuse needed to prevent too much current draw in DC motors?

texts:
I am building a basic Raspberry Pi robot: the Pi controls the enable pins on a dual-bridge motor controller bridge via PWM and sets the input pins for direction. I have a variety of battery options available (a LiOn power pack with a USB out and a 12V out, a double USB out power pack, battery holder for 2x 18650 LiOn, battery holder for 2x AA, etc). My motors say they are 3-6V and have a no load draw of 70mA and a max draw of 250mA.

My motor controller board documentation suggests a 10A fuse on the motor lines and a 15A to/from the battery. Are these fuses going to be necessary? Does that max draw mean that is the max the DC motors would draw at any one time, or is that the max safe draw for those motors? Are motors that small even going to be able to draw more than 10A? Obviously having fuses burn out would be safer than letting the motors burn out... but it seems like it might be acceptable with motors this small/cheap to take the chance.

Will the risks be different based on what kind of batteries I hook up? For example, the 18650 batteries I have are high drain and can deliver 25A.


texts: Are there any cheap air quality sensors?

texts:
I have checked sparkfun and some other websites. It seems that there is no air quality sensors available in the market.

I would like to monitor PM2.5 and PM10. Are there any suggestions?


texts: Increasing the Watch Dog Timeout PIC 16F877A - CCS PIC C

texts:
I have been trying to look around for an example on how to increase the watchdog timer but unfortunately I cant find any. The only example that is included in the example uses setup_wdt(WDT_2304MS)

Could anyone tell me how I can increase this delay to say 5,8,9 or 10 seconds ?
Any suggestions would be appreciated


texts:
I want to use a device who has an USART interface. But my microcontroller has only a UART communication.
Can I connect the UART_TX and UART_RX on USART_RX and USART_TX?

Thanks


texts: Alternate Inductor that can be used for MT3608 boost converter circuit

texts:
I am planning to use MT3608 schematic for my project to boost the voltage from 3.7V to 5V. I am planning on making a customized PCB with all the requirements that are needed for the project.

In the MT3608 module, which is available mostly in the outside market, the inductor used is 22uH. Below are the MT3608 module and  the Inductor component that is used in the MT3608 module.

Link to the Inductor component
However, it is difficult to procure this component as it is not that frequently available everywhere.
In the datasheet, they have mentioned the inductor specifications as seen in the image below.

Can I use any other Inductor of same value of 22uH? Or is there an exact alternative that can be used for this component?
It will be helpful if I can get a component that can be used instead of this one.
Thanks in advance.


texts: How can the dielectric constant of water be so high but water on electric devices can cause a short circuit?

texts: Is it only the fact that pure water has a high dielectric constant and non-pure water i.e. the water that usually causes a short circuit is contaminated and it's the contamination mixture in the water that causes a short circuit?


texts: What exactly will happen if I use 1.2K ohms at LIN master node pull-up? Why does the LIN protocol spec recommend to use 1K typically?


texts:
I've recently been trying to get a custom LCD (ET101005DSAK0) connected to an Embedded System on Module however without any success. When debugging why the LCD is not working I wanted to make use of the BIST (build in self test) PIN of the LCD.
However the datasheet of my LCD doesn't give any descriptions about what the BIST pin should output. I did some research by looking at the BIST output of other LCD's for example:

And eventhough this is similar to what my LCD is outputting it is not quite the same as can be seen in the GIF of my output below.

So in the GIF you can indeed see that the screen is displaying some sorts of RGB pattern. Which according to other datasheets is indeed a common pattern to display when doing these BIST tests. However I would've expected the screen to go from solid red, to green and finally blue. What I am seeing is that the colors for some reason are fading inwards. Also there seems to be this peculiar black stripe in the middle of the LCD. Since this is a Build In Self Test (No clock signals or any signals connected apart from the BIST pin and power) I expected to see the full screen to display solid colors.
Can anyone more practiced in these tests can give any clarity about what the expected outcome should be (E.G. solid colors or not) and can anyone clarify the black stripe through the middle. Or is it safe to assume that this LCD is not functioning properly.


texts: What is the purpose of the stand off on a wall wart?

texts:
I'm making a device that fits best into the form factor of a wall wart. On some wall warts I've seen they have a little plastic standoff that creates a gap between the case and the wall.

Does that gap serve a purpose or is it just a design choice? My device has a ground plug so it would require a larger and arguably more unsightly standoff. Have you ever seen a device with a ground have a good looking standoff? If so can you please share a photo of how it's done?


texts: L293D Brake Doesn't Work (LB1836M good alternative)?

texts:
I have a microcontroller that is supposed to drive three motors (only one needs to be driven at the time). I tried doing this with two L293D's but there's a problem with braking.

The problem is that they don't brake fast enough (the motor just continues going for a while). These motors are NXT Interactive Servo Motors and normally they are driven by a NXT Intelligent Brick but I want to do this with a microcontroller. These motors have two pins to go forward or backwards, ground, 5v for the optical sensor and 2 outputs returning from those sensors to give feedback on how far the motor has gone.

Normally if you put the same voltage on both the driving pins of the motors, they should break but they don't... I found some information on why this is happening on another site and I think I'll have to get another IC to do the job.

I was thinking of using the same IC as the Intelligent brick uses but I want to be sure that these actually brake like I want.

So this is the question: Does the LB1836M make the motor immediately stop if you send 0V to both input pins?

Any suggestions of other ic's or perhaps a solution to make the motors break while using the l293D's are always welcome.


texts:
I have built the following:

simulate this circuit – Schematic created using CircuitLab

In the schematic, the LEDs represent a 12V LED strip with red, green, blue and white channels. I'm using four IRL630 N-Channel MOSFETs (datasheet).

The 12V battery is actually a 20A power supply. The 5V battery comes from a raspberry Pi's GND and +5V pins. As you can see, the negatives (grounds) of both power supplies are connected.

The Atmega328 currently has a very simple program on it that fades colors (from red to green to blue to white, indefinitely), by PWM.

Problems:

With a load of 1.2A (i.e. a LED strip that requires max 1.2A at 12V), everything works smoothly most of the time. Sometimes the Atmega will freeze and the colors stop fading.

With a load of 3.6A, the color transitions are "skippy", i.e. the fading stops intermittently and then jumps straight to the color where it should be and continues fading.

With a load of 6A, the fading works for about 3 seconds and then all MOSFETs seem to enter saturation simultaneously, giving way to a bright white full-on LED strip.

What I've tried:

I tried decoupling, i.e. a 10nF capacitor between the Atmega's Vcc and GND. The effect I observed is a super-accelerated crazy color rainbow with intermitent strobe light effects. I've removed the capacitor.

I tried decoupling as above while separating 12V and 5V GNDs (don't ask me why). It didn't work, the LEDs just kind of lit up a little bit and stayed at one color. I unplugged it shortly after.

I'm a programmer. What am I doing wrong?

Additional details

I'm using 0.75mm² solid copper wires (18AWG according to Google), for everything up to the LED strip.
The connectors to/from the power sources are made out of aluminium, same gauge.


texts: Buffering 5 daisy chained shift registers (MBI5026)

texts:
The circuit I'm trying to make (and eventually make pcb etc.) consists of 1 microcontroller (atmega32 , internal 8MHz clk) sending serial data to 5 daisy chained MBI5026GF (16 bit shift register and constant current LED driver ic). Edit: links added @ bottom.
The whole board dimensions will be 15x15cm (~ 6x6 inches) maximum. And all ics are close to each other (no long wires etc.) And contained in a sealed metal casing.
The questions are :

Will I need buffers between SIPO units?
If so, should all 3 lines (data, clock, latch) be buffered or just data line?
Should the first inputs (MCU to first MBI5026GF) be buffered too, or just the lines between the shift register ICs ?
For this kind of buffering, all buffers should be non-inverting ? (Or I'll have a hard time inverting some of my bits accordingly (second and fourth 16bits) before sending them over serial output, right?)

MBI526GF datasheet : https://pdf1.alldatasheet.com/datasheet-pdf/view/1284473/ETC1/MBI5024GF.html
I'm trying to replicate this common 74hc595 circuit, but with 5 registers, and of course all replaced by 16bit ones (mbi5026gf):
Daisy chain diagram
[Image from hackster.io]
This shift register is very similar to 74xx595, so your experiences and answers for 595s can be useful here as well.
Thanks!


texts: What is throughput as far as processors are concerned?

texts: My teacher showed some algothrims, RR, FCFS and others. In the end he exposed a table with throughput of the algorithms. He explained what thoughput is but he failed miserably. He first said that throughput is like a pipe, so all the students thought, "the higher the throughput the better" after being asked if the higher the throughput the better" he contradicted himself. In another words it was better to give up and search online. I searched online but the explanations seems too complicated for me. What is throughput in very very simple words?


texts:
1) I have 6 4.5V 20mA LEDs and have connected them to a common 9V battery. Doing this I made 3 parallel circuits with 2 LEDs in each.

Now, I see that most pages that describe LED circuitry say that you should always have a resistor in the circuit. In my case, do I need one? Why?

This is a hobby project, but the LEDs are sealed in glue so fixing a blown bulb would be a big hassle. I'd rather have them live for as long as possible.

2) If I happened to have the same circuit as above, but with 3.4V 20mA LEDs instead, is it likely that the LEDs would blow quickly? The LEDs are of a cheap type:

http://www.ebay.com/itm/20pcs-5mm-Clear-White-LEDs-Ultra-Bright-LED-DIY-/190642214244?pt=LH_DefaultDomain_0&hash=item2c63295564#ht_3051wt_1156


texts:
I am trying to understand the following schematic for a differential input pH probe.

here is the link

A1 and A2 role are unity gain opamp amplifying high impedance probe signal, while A3 makes the subtraction.

What does A4 really do? It subtracts tank ground potential to the differential pH signal? Circuit ground and tank ground are connected together?


texts: How to prevent a Lion Cell Phone Battery from Discharging over 20-30 years?

texts:
I'm planning to make a time-capsule that is to be opened 20-30 years from today. In this capsule I want to put a cellphone from todays time. With it I want to include the cellphone battery, which is a Lithium Ion Battery. I'm not sure if the battery or even the electronics would survive that long. I was thinking of putting it into a vacuum sealed bag to prevent anything from going in or out.

Would a vacuum sealed bag prevent a battery from discharging?


texts: Transistor as a switch for 3A collector current

texts:
I am using:

ATtiny10 w/ 10Ohm Resistor in series to drive Base of transistor
Transistor is ZTX688B
Vcc is 5V and 3A source
Load is a Raspberry Pi connected to Collector

simulate this circuit – Schematic created using CircuitLab

The ATtiny is programmed to turn on the Base for 10 seconds and then turn it off for 5 seconds. When I run the circuit it turns on briefly but only manages to 100-200mA (not enough to fully turn on the Pi. How can I make this work? The transistor is rated to handle 3A and up to 12V.

NOTE: I am also open to suggestions of replacing parts. I just need to control the Pis power supply with a MCU.


texts:
I know that capacitors discharge quickly, but it seems like there has to be a way to replace deep cycle batteries. A capacitor with a constant current source that is rated to drain the cap slowly, should allow the cap to act like a battery, yes? Isn't a boost converter a constant current source (or variable but not so high as to drain the cap bank)?

To be clear, I am wanting to use caps for a datacenter 8 hour backup, but I imagine solar and other enthusiasts want to know.


texts: Standard for document in diagrams the power of motor

texts:
One machine supplier shipped us a motor with a power in its plate so different (800 kW) to the one indicated in the electrical diagrams (500 kW). We calculate the wires using the diagrams information of power, but in the motor plate the power printed is higher.

Did this supplier break some regulation?


texts:
I have a faulty car (bad central locking engines) and a fuse is blowing every time I open/lock the it. I'm looking to do a quick fix, and just replace it with an automatic fuse. The car runs on ~12V, and the fuse is at 15 ampere.

Are fuses designed to operate on specific voltages, and have their ampere "tolerance" rated for the specific voltage?

As I understand it, a 15A fuse for 12V is designed to blow at 180W (the heat produced in the fuse wiring is what makes it melt, right?).

So, if I use an ordinary 16A/220V fuse in my car, it will blow at 3520W, and should really be rated 293A for a 12V circuit...

If my reasoning is right, that fuses blow at effect and not ampere, what I'm looking for is a 0.8A fuse that is designed for 220V (I=180/230), and it would work as a good replacement...?


texts: 10 resistor voltage divider calculations for LM3914 IC

texts: I need to calculate the voltages on the 10 resistor voltage divider (V1,V2,V3...), but i don't know how to work it out. So far I found V1  by doing $$V1=Vs*(R3/(R3+R2))$$ and found V1= 0.5 Volts. Can I get some help on how to calculate the rest?


texts: LED light cycles on and off - Is it a heat or voltage problem?

texts:
I have this LED light that was over the aquarium at my work desk. There's a circuit board (not pictured) that controls when the lights go on and off but, after a power outage a few weeks ago, it seems like something got damaged because it doesn't cycle the lights.
I thought I'd just rewire the lights directly to the power supply (12V at 1amp)  and use a plug in timer to control the on/off cycle. The problem is that, when I had wired them up like that, they'd all power on and then about 10 seconds later, they'd all go off. Then a second or two after that, they'd all go back on again, and then off a couple seconds later.
Was it due to heat? Maybe the circuit board had them controlled to run at a duty cycle lower than 100%? Or maybe the circuit board, which has a backlit LCD display, consumed a significant amount of voltage and now, with it removed, the lights were getting too much?
Or maybe I had wired them up incorrectly. I had the W and B circuits powered in parallel but when I rewired them in series, only a few of the lights came on at very, very low brightness.
What is happening to the lights?


texts:
I use Twi module of AVR Atmega168 to talk to DS1307.

Twi works on the interrupt mode.

It works fine for a few hours and then stops, hopefully losing Twi interrupts further.

Is there any way to fix/resolve/work around this issue.

Any practical tips would be of great help.


texts: How to use measured step response to tune control system

texts:
How does one use a measured step response to tune either a PID or convolution control scheme?
Inspired by this answer*, I'm interested a more detailed explanation of how to implement a control system based on the measured step response.

I would not try to guess all the effects.  There are probably some non-obvious things going on, and you can't know all the parameters.
I would measure the step response.  Find two pump settings that both result in the ball being within the measurable range within the tube.  Then have the controller suddenly switch from one setting to the other open loop.  Meanwhile measure what the ball does over time.  That is the step response.  You can take the derivative of that and get the impulse response.  From the impulse response you can predict the motion of the ball for any history of pump settings, assuming this is a linear system.  It is probably linear enough over the small range of settings to keep the ball within its normal range.
You can use this as a simulation base to find the parameters for old fashioned PID control.  Or you can use the impulse response directly to do a convolution control.  You have to low pass filter the control input enough so that convolution kernel doesn't go negative unless your pump is actually reversible and can suck the ball back down.

How exactly does this work? PID tuning is difficult; I assume "convolution control" is the use of the pole-zero or transfer function, but don't see exactly how to get the parameters.
RELATED: System Modeling for Control Systems
* modeling transfer function of ping pong ball levitation in a tube as a damper


texts: multiple 1.5v devices from one 9v power supply

texts: If I have 6 battery powered wall clocks each powered by a single AA battery, can I wire the clocks in series and connect to a 9v power supply (assuming the amperage is covered)


texts: Using 2 terminal band gap voltage reference

texts:
Specifically, LM385.
Am I correct in assuming that a resistor is chosen to pass a current between 50uA to 10mA through the device from the PSU, and the reference voltage appears across the terminals?


texts: Best practices for a phenolic spacer design to facilitate heat transfer?

texts:
I am making a hand held electronic device that includes a 0.8mm phenolic spacer/electronic insulator between the PCB and the inside/bottom of the case. This spacer is made from epoxy resin and is currently solid save for one 300mm hole.

Since I want to shed heat rather than contain it, what are the best ways I can to improve the spacer and/or PCB to better facilitate the transfer of heat from the PCB to the spacer and case? Specifically, I'd like suggestions for ways to improve the heat transfer capabilities of the spacer (via cut channels, drilled holes, and/or copper panels) from the PCB above it to the aluminum case below it/around the device. The enclosure has 2mm thick walls and should work pretty well as a heat sink. It is not air tight and has a 200mm hole in its lid.

The device in question is a light duty, 12VDC ZVS induction heater, similar in purpose to IHs used to the heat wax carving tools for making dental models. It is operated for a maximum of 5-10 seconds per use. It is passively cooled.

In its current form, the device stays cool enough with the existing spacer that an improvement is not strictly necessary, but since I am making other changes I would like to investigate this piece and see how I can make it better.

This is a hobby-level project and it does not need to be perfect, so what I am hoping to receive as answers are some rules of thumb for maximizing proximal heat transfer, first from the top of a PCB to its bottom side, and then from the bottom of the PCB to the spacer, and out to the aluminum case.

The circuit uses two MOSFETs to power the ZVS heater, and these are the primary sources of PCB heat I need to dissipate. I have room and am currently using 20cm^2 of the adjoining PCB surface as heat sinks for each MOSFET (~10cm^2 for each MOSFET, on each side of the PCB). The PCB uses a 2 oz copper pour and a large number of .5mm x .25mm solder-filled vias to join the two surfaces. I can also coordinate the copper surfaces on the PCB and the spacer beneath it to allow better heat transfer.


texts: Burst mode in synchronous buck converter with current mode control?

texts:
I read this previous question:

The meaning of Burst Mode

It says burst mode happens when the resistance of the load is light and the system stops switching the MOSFETs. However, I just cannot understand how the light load decreases the load current and therefore the inductor current, as mentioned in the link.

As I know \$Vload=Rload*Iload\$ and \$Vload=D*Vin\$. So if we have a low load and highest input voltage, this implies that the duty cycle is small and the current is going high - which means the inductor current must be high as well and never go to DCM!

What I am missing?


texts:
I am using a GSM modem by Simcom SIM 800E. I'm interfacing it over the serial link.

I am passing command AT+CSCB to get the location. But I am not getting it. I just get the response OK.

Can someone tell me the correct way to use this command?

The modem works fine while sending and receiving SMS.


texts: USB 3.0 VS MIPI CSI-2 camera interface on Embedded Linux system. Which one is better from both hardware and software perspective?

texts:
I have a Sony FCB series camera (1920x1080) and looking for a better interface protocol to connect it with processors like NXP, TI or any similar embedded processor.

The camera has a LVDS out port but I have seen that no processor has LVDS input, so we need some converter to connect it with processor available on the market?

Now I'm confused between MIPI CSI-2 and USB 3.0 interface.

Which one faster? from both hardware and software (Linux operating system) perspective.
CPU overhead difference?

Here the camera is not finalized one and I can choose the camera which can give direct CSI-2 or USB 3.0 so I don't have to look for the converter.


texts:
Given a JK flip-flop circuit (using a D flip flop with a 2 by 1 MUX) how can I derive a truth table from this circuit?

D = JQ' + K'Q

Note: This is NOT a homework question. I just simply want to know how to track various inputs to understand the functionality of this circuit


texts:
What is the math behind traces and clearance calculations? I am designing a PCB, which will carry 12V and 6A, what should be trace width and trace clearance?

Similarly, what should it be for 12V 3A, and 5V 3A. Is there a general rule of thumb, using which we can decide trace width and clearance?


texts: 4x 2:1 Multiplexer with multiple select lines. Does that exist?

texts:
I have been checking different supplier websites, and can't seem to find what I am looking for so I am wondering if it even exists or not.

I am looking for a 4x 2:1 MUX IC with 4 select lines. I am trying to create a design for remote control that doesn't require a microcontroller by daisy chaining 2:1's together as shown in the picture below. The digital inputs represent button presses on my RC. I have 8 buttons to work with on my transceiver module and by using two of the MUX's I am trying to get up to 16.

I looked into using 4:1's but I would be leaving one input line empty because I cannot use the case when SEL1 = 1 and SEL2 = 1 because I am daisy chaining them together.

If this isn't the best route to take, can you please share what you might do?


texts:
I'm a newbie,
I need to know the relation between high frequency and circuit size, as I read before that I high frequency transistor size need to be small to deliver the full wave length and I need explanation !!


texts: Can VFD be used with induction motor for regeneration?

texts:
I want to use VFD with induction motor to run it as induction generator (driven by external prime mover).  Does VFD circuit allow reverse flow of electrical power?
Thanks


texts:
I have a radio which uses CXA1619 IC.

I have a question about the oscillator of this IC.

There is a gang capacitor in the circuit for tuning RF and oscillator and there are two different trimmer capacitors: One is parallel with the oscillator cap and the other one is parallel with RF capacitor.

In AM mode, the IF frequency is 455 kHz and this frequency is fixed.

I have tuned the radio and I am receiving waves from a station. Now, I change the oscillator trimmer cap and then I receive another stations, while I haven't changed RF resonant parts.

How is it possible that while RF resonant parts stay unchanged, changing  oscillator resonant parts (that means changing the oscillator frequency) doesn't change IF frequency and it remains fixed at 455 kHz?


texts: STM32F103 Systick Interrupt stopped working when debugging in ram - (Coocox IDE)

texts:
I tried debugging my code in ram in order to increase the flash's life (only rated at 10k writes minimum)

Anyways, I have tied the boot0 and boot1 pins to 3.3v and set the compiler to debug from ram like so:

When I debug my code this way, my SysTick_Handler doesn't run. If I debug from flash everything works just fine.

I can't figure out what is going on, and how can I get my SysTick interrupt to work in ram debug mode ?

P.S: I tried asking this in the coocox forum, but haven't got any help there.


texts: Im trying design this function : (NOT Y)=A+BCD in CMOS my design in pic below now i want to design this function in Pseudo NMOS but i dont know how to design it in Pseudo NMOS.anyone can help please??


texts: I made a RC filter with R=200ohm and C= 2.2uF, I want to filter this PWM in the figure with 10k frequency, and get a Sinusoide with 50hz, but in this case I loss amplitude how i can do this???


texts: I'm building an arduino-based robotic arm which is meant to pick some objects with a two-finger-like structure. The problem is I need to detect the servo stress (the moment when the servo really holds the object) to stop the servo and prevent it from squeezing the object. Is there any way to do this with an Arduino Uno?


texts:
I am working on ultrasound sensors. At the receiving end I have a 2MHz signal of 80mV p-p.
I need to amplify it at least by 10 times. Please suggest an appropriate method.

Additionally, I need to know if normal opamps work with a 2MHz signal? If not, are separate ICs available for that?


texts: MOSFET - calculating heat produced by MOSFET

texts:
from the datasheet which one should I use? Thermal Junction to Case or Thermal Junction to Ambient?
Tj= Ta + Pd * Rth(j-c)
or
Tj= Ta + Pd * Rth(j-a)
when I use Rth(j-a), Tj become way too high, near TjMax.


texts: What type of connector is this? Looks like a kind of shrouded EIAJ

texts: This type of connector is used in some OMRON TENS devices and I'd like to know which kind of connector is this. If you have the reference or a way to get the female connector, it would be really helpful.


texts: Does anyone know what the "Z" lying down symbol is that is in parallel with the normally closed relay contact CRB? I have searched several electrical symbol sites but no luck. The circuit is controlling 24 Vdc power for a motor brake. There is a back EMF arc when this contact opens so the symbol could represent a snubber which in this case may have failed. It will be this weekend before I can physically go in and look for this device. One other bit of info, this machine was built in Japan about 30 years ago.


texts:
If the input of an unknown system is shown by:

\$x(t)= u(t)-u(t-1)\$

which results in the following output:

\$y(t)=u(t)-u(t-3/2)\$

then what can be said about the linearity and time invariance of this system?


texts: How to reverse rotation direction of stepper motor

texts:
Is it possible to reverse a stepper motor's direction of rotation by changing the polarities of its wires?

I'm asking because I have two stepper motors connected to one single driver and mounted on one axle, and I would like to spin the axle from both sides so one motor would have to spin clockwise and the other one counterclockwise.


texts: Why is my buck converter getting hot when voltage is supplied to the output?

texts:
I have a buck converter (LM2596) converting 12V to 3.3V to power an ESP32 off of a 12V battery. When I power my ESP32 via USB and it is connected to the output of the buck converter but the buck converter is NOT connected to the battery, the LM2596 starts to get hot. Is power flowing to the buck converter when this happens? Can I place a diode at the output of the buck converter to prevent this from happening (for my knowledge)?
Thanks!


texts:
I'm trying to control a 12V piezo pump (with an inbuilt driver) and I'm a bit unsure how to use it safely. I'm using an Arduino Uno to control it, with an N-channel MOSFET rated at 60V 30A (with a 10K pull down resistor). I'm powering the piezo pump with a 12V 5A power supply. Looking at the data sheet for the pump, I noticed that it amplifies the signal from 12V to 250V (but doesn't draw very much amperage... about 40mA I believe).

Will the 250V be contained within the piezo pump and not ruin anything? Or do I need a more powerful transistor? I was told it would be a good idea to place a fuse in the circuit, but I didn't really get where it should go. Or which one to use.

I know when you use a motor with a MOSFET, a diode should be used to prevent a voltage spike from coming back and frying the MOSFET, is this the same for high voltage piezos?

The whole 250V amplification thing has me a bit concerned and I'd like some advice before proceeding. So, please let me know if I should be using a higher rated transistor, a diode and/or a fuse. Don't hesitate to let me know I'm missing anything either.

Thanks,

Matthew


texts: How do constant current power supplies work? For example I have a power supply that is constant voltage that can supply up to 5A and I have a 12V motor that takes ~500mA so I crank up the supply to 12v and my motor pulls ~500mA from the supply. But how does this work for a constant current power supply? Would it determine its own voltage output depending on the resistance of the load(ohms law)?


texts: How to keep PWM from "contaminating" analog read values on my pcb

texts:
So I'm designing a PCB for a MIDI controller with a lot of slide potentiometers and push buttons. I'm also backlighting the pushbuttons with LEDs running on PWM and I'm worried that the PWM for the LEDs is going to create a lot of noise in the analog values from the potentiometers. There is also USB on the PCB wich also is the power source.

How do I make sure that the analog values from the potentiometers are as clean as possible?

I guess PCB layout is critical and the use of bypas capacitors is a good idea?

Any help is appreciated :)


texts: Powering a Microchip development board externally

texts:
I have a PIC18F14K50 with a Microchip PICKit2 and the development board pictured below:

Up until now, I've been using the board only for programming using the power supplied by the USB/PICKit, however now I need to use the board a little more permanently as I'm using 12Mhz at 4x for USB and my breadboard has some issues at those frequencies.

I can put my IO Expanders and other supporting components onto this board, however I need external power (5V) to drive everything. USB doesn't supply enough current to run my whole setup.

I originally supplied my +5V to pin 1 circled in yellow, and GND to pin 20 also circled in yellow. When I connected my PICKit to the ICSP1 (green circle), it burnt out my PICKit. I have since bought a new PICKit but I need this external power working.

I noticed the red power header, circled in red. I imagine these are just direct connections to pins 1 and 20 on the MCU, so I'm not sure how these would be any different to supplying power to the yellow circles.

How/where should I be connecting my external +5V such that it doesn't blow my PICKit?
Thanks.


texts: what is the sequence and how it is going?

texts:
I have been trying to understand the hardware implementation for booth's algorithm and here is a diagram i came across trying to explain but i didn't understand this :

How it is going ? I know that B,A,Q are registers.


texts:
I just tried to make my first PCB at home, but it did not work. I don't know what went wrong, so I'd appreciate some advice.

I was using the photoresist method, so I printed my circuit on a transparency using a laser printer and made this template:

Next I exposed my presensitized PCB and developed it to get the following photoresist mask:

The mask looks quite functional at this point. All traces are well defined.

Next, I submerged the PCB in Ferric Chloride to remove the unmasked copper. This is where things went wrong. The copper between the traces on the top side of the PCB just wouldn't come off. I ended up over-etching the board, as can be seen from the fact that the photoresist mask started to break down, yet the unmasked copper between the traces at the top still wouldn't come off! Here are the pictures:

And after removing the photoresist mask:

It seems that something was different with the top of the board, but what? Was it a defective board? Did I do something wrong? I'd really appreciate some advice before I try again.


texts:
I'm working with Micro Controller Mega-32 (SMD). I'm looking for a Wireless module to transfer and receive the data that I created with the micro.

Could you please guide me ?


texts: Schematic Capture: Proteus ISIS Bulk Component Editing

texts:
Is there any way in Proteus 8 Professional ISIS schematic capture to bulk edit components?
I have a sheet full of 0805 decoupling capacitors which I would like to make 0402. I tried all of the commands I could think of, but it only ever edits the last part selected. Selecting more than one part and then pressing CTRL+E doesn't do anything. This is possible to do in OrCAD and is very useful for updating footprints, MPNs, etc.
I tried opening the pdsprj file, and updating the {PACKAGE=...} parameters, but then it crashes when loading the file (suspect the text editor breaks the binary file).
Any advice is helpful. Thanks!


texts: Driving piezo scanner tubes using the driven internal electrode configuration

texts:
I'm planning on doing a project involving a piezo tube scanner (PTS). The PTS will be used for 3 axis manipulation of a sharp needle. PiezoDrive has a few scanners and some info on how to use them. Among that info is a description of how to drive a PTS using a "driven internal electrode configuration". The image below is included in that description.

The description mentions that "Care must be taken not to apply positive voltages to the internal electrode since this can lead to depolarisation". I'm guessing that this is why In5 spans from 0 to -10V, unlike In1 and In3. My problem with this is that there might still be cases where the PTS sees a positive voltage on the inner electrode.
For example, Out1 and Out2 could have a voltage of +25V and -25V respectively, (1V at In1), and Out5 a negative voltage of -2.5V, (-1V at In5). But wouldn't that create a positive voltage between Out5 and Out2? (-2.5V - (-25V) = +22.5V). According to the quote, that should be avoided.
Is this a problem or am I missing something? I hope my question is understandable. Thanks for any answers!


texts: How to measure force that applied on grab bar

texts:
I recently start a project to measure the force on a bathroom grab bar. The force/load is applied by the person who need to the grab bar for assistant. My aim is to do the real-time monitoring of the force and record the data in order to further make decisions in grab bar design.

I am not quite sure about what kind of sensor would be suitable to do the measurement. Right now I am using strain gauge to measure the strain and roughly calculate the force. But I think (might be wrong) there may exists some kind of force/load sensor that can clamp on the bar to do the measurement.

Any sensor types/models or suggestion are welcome.


texts:
I'm looking for the correct temperature compensation equation to use on our project.
We are measuring the output of a detector who's signal is very sensitive to temperature drift. Any external temperature drift is reflected in the output. A cycle due Day/night variation is typically what we see.
So, we apply a formula to the detector's output to try to compensate for the changes in temperature.
The formula we use is: RITC = ((RT - AT) × TC) + I
Where: RITC = temperature corrected output RT = Reference Temperature, AT = Actual Temperature as Read on Instrument, TC = Temperature Coefficient, I = Input (Actual reading from the detector).
This equation works if the temperature variation is constant, say (±5°C) from day to day. However, if the variation isn't constant and it changes from day to day, the equation doesn't work well. Also if there is sudden changes due to maybe air conditioning or Fans turning On/Off, again the equation does not hold up.
So what is the solution? How can the affects of temperature be removed from the detector signal? What is the correct method to deal with sudden dynamic changes and also to deal with the slower variations? I feel a better equation is needed.. just not sure what it is!


texts:
This question, Q1.42(c) has been troubling me for a bit, and I'm unsure of whether my answer is correct or not.

This was my approach:
I just labelled output of first stage as p[n] and output of second stage as q[n]
$$y[n] = q[2n]$$
Also,$$ q[n] = p[n] +\frac{1}{2}p[n-1] + \frac{1}{4}p[n-2]$$
$$y[n] = p[2n] + \frac{1}{2}p[2n-1] + \frac{1}{4}p[2n-2]$$
Since 2n-1 is odd, and 2n, 2n-2 are even, I got this final relation:
$$y[n] = x[n] + \frac{1}{4}x[n-1]$$
Is this correct? My answer doesn't seem to match the ones given in the solution manual.
Edit:
This is what is given in the manual:


texts: Schematic pins shifted over on Altium 16

texts: I am coming across an issue where Altium is shifting pin names to the left. When I updated from 15 to 16, I have noticed the issue come up. When generating the schematic from 16 to 17, the issues go away. No, I did not shift the pin names like that when creating the parts. Comparison between 16 and 17 preferences are basically the same. I have been using 17 to generate the schematic, however, I want to stick to 16 right now. Please look at the examples below. Does anyone have any idea what could be causing the issue?


texts: Where are the UART Rx and Tx pins on a dsPIC33FJ32MC202?

texts:
I'm a beginner to micro-controller and now learning Microchip's dsPIC. I'm trying to use UART with RS232 to communicate with my laptop, but I can't find out where the Rx and Tx pins are on the chip.

I've checked the datasheet and I can't find out where it has mentioned about which pin number it is.


texts:
I am currently designing a new power supply schematic using LM317AHVT and NPN transistors. The base schematic is from this website:

https://sound-au.com/articles/power-supplies2.htm#s10

I wanted to redesign the power supply in order to use NPN pass transistors instead of PNP pass transistors. So I found a schematic which can be used to convert PNP transistors to NPN transistors in the 1980 Voltage Regulator Handbook.

I redesigned the schematic and this is the schematic that I obtained:

All capacitors are rated at 63V and the resistors with value under 1 ohm are rated 5W.

My question is: Is this schematic correct?


texts:
I have a real beginner question;)
I have a small quadcopter that stopped working at some point.
in theory it works like this: I turn on the remote control (so far it's ok) and then I attach the lipo battery to the quadcopter and a flashing LED should light up, when the LED becomes fixed I can operate the drone propellers. unfortunately after connecting the battery the led does not light up.
now I would like to understand where the problem is
with the multitester I checked that the battery is ok
the quadcopter has a small board hubsan  ea4000362 (I attach image)
in the image at the 4 corners of the board there are the + and - connections of the propellers, they also beep if connected to the vcc; in the middle of the board there are other pins: on the left c and D, in the center + e - and a single pin R (I don't know what A, C and R mean) in the red circle 2 pins without name
where can the problem be? how can I do other tests with the tester? which components should I connect?

connect with red wire from VCC to other pins, echo what I read on the tester (continuity mode)
VCC -> GND = 530

VCC -> propellers (both + and -) = Beep!

VCC -> c = 1415

VCC -> d = 1415

VCC -> + = 960

VCC -> - = 540

VCC -> R = 1420


texts:
There are many videos and explanations about dipole antennas and the theory seems to make sense. But when I see closed loop antennas I am very confused. None of the material I can find about antennas goes into depth about closed loop antennas.

Do all closed loop antennas work off of the principals of induction?

I've seen example closed loop antennas that have attached capacitors and it makes me think it is built to behave as an LC circuit.
There are other designs that "appear" to only have a single loop.

What is the significance of the number of windings in the closed loop antenna and how does it relate to the wavelength of the desired frequency?


texts:
I'm attempting to make a Monome clone. (What is a Monome?) Now hardware wise I should be fine. I ordered 64 buttons (4 4x4 Button Pads) and making the PCB to hook it up to Arduino Mega. So I will be able to control the LED states and read the button states. I'm also able to read button numbers in the serial Monitor in the Arduino IDE. My question is how can I make my hardware emulate the actual Monome and use the software built for Monome? Is the serial protocol the only option using the Arduino? I know there is a project that already does this called Arduinome but I'd like to make mine from scratch. Monome Software has a really long tool chain which is giving me a headache.

Request: Can you point me in the right direction?

Question: Would it be hard to write a piece of software that that acts as a bridge between my hardware and Monome software?

Edit (Clarification):

My main problem is that I don't know how to approach the problem of connecting my hardware and the already made software. Basically I need to know what information I need to channel into which location using which protocol on my computer (if that makes any sense).


texts:
I need to send/receive files from/to SerialPort and MSP430F5438A, by clicking a browse button in C# interface, selecting a file (like text, notepad, etc.), and in receive case, to save the file which has been sent from CCS to PC!

I really could not find any related thing on Google or somewhere else. Can anyone at least orientate me?


texts: Shouldn't internal input resistance of a transistor be almost zero?

texts: I am absolute beginner in electronics and the whole transistor thing is not looking very intuitive to me. Suppose this problem, in active region input terminal voltage almost remains constant with change in input current for a transistor. So, in terms of h-parameters, shouldn't \$h_i\$ (i.e. short circuit input impedance) be almost zero instead of a significant (typical 600-900 ohm) value?


texts: 7408 AND-gate IC giving HIGH output without giving any input

texts:
It's my first time working with 7408 chips and I'm facing some issues. The chip I'm using is SN74LS08N.
The working principles of AND-gate chips are as follow.

I give my chip 5V supply at pin 14 and connect pin 7 to ground. According to the truth table, without connecting anything, the input pins are at LOW and the output pins should be also LOW. But the output pins are giving out HIGH voltages. No matter which combination I connect it is always giving out HIGH.
I also tried connecting the outputs to ground and now the outputs are always at LOW, even with two HIGH inputs.
Is my chip broken or is there something I'm doing wrong?


texts: Speaker Cross-Over Network and Power Design

texts:
I have some speakers I want to drive from a single output: a 4Ohm 300W Subwoofer, a 6.44 Ohm 60W Midrange, and 2 8Ohm 3W Tweeters. All ratings are RMS.

I know that if I were to wire all of these in parallel, the equivalent resistance would be 1.52 Ohms, but there is different power at different frequencies, so calculating the max output amp voltage isn't trivial. If my cutoff frequencies would be something like 120Hz and 2kHz and assuming my music follows a pink noise spectral power distribution, my subwoofer is taking something like 40ish times more power than my tweeters. However, this is not reflected if one treats the whole network as an equvilant resistor.

How should I approach this? I would assume that using 1.52 Ohms as the equivalent resistance and using the limiting part of the network in terms of power, the tweeters, to designate the highest voltage would be faulty.
Should I instead use the pink-noise sound approximation to design my crossover with appropriate crossover frequencies and power distributions to each speaker, then just use the equivalent network resistance to calculate the max voltage the network can take? How exactly do I quantify the amount of voltage each speaker will see after all of the filtering?


texts:
I am using ADC122S625 (Datasheet: http://www.ti.com/lit/ds/symlink/adc122s625.pdf).
The ADC has a differential input per channel. My signal is from a RF devide with 3V peak to peak and 1.5V DC offset. I want to use the ADC in Single-Ended Input Operation. So I have choosen a Reference Voltage of 1.5V. Now my question is what should I use for the Inverted ADC input?
First I thought I will pull it to Ground as a normal Single input ADC would use 0 to Va input range. But after reading the Datasheet (page. 15) it seems that I need to feed the Vref (1.5V) to the inverted inputs.
From Datasheet (copied)::
"Single-Ended Input Operation
For single-ended operation, the non-inverting inputs of the ADC122S625 can be driven with a signal that has a maximum to minimum value range that is equal to or less than twice the reference voltage. The inverting inputs should be biased at a stable voltage that is halfway between these maximum and minimum values. In order to utilize the entire dynamic range of the ADC122S625, the reference voltage is limited at VA / 2. This allows the
non-inverting inputs the maximum swing range of ground to VA. Figure 35 shows the ADC122S625 being driven by a full-scale single-ended source. Even though the design of the ADC122S625 is optimized for a differential input, there is very little performance degradation while operating the ADC122S625 in single-ended fashion."

Please suggest to clear my understanding about the Inverted input.


texts:
The ST7580 is a power line communication device that can be controlled with any host controller. The ST7580 has a buil in power amplifier to allow it to send a modulated signal (0Hz to 250kHz) as far as possible down the power line.

I have followed the design guide to the letter apart from using the ST host controller and making slight alterations to the AFE (to choose a specific frequency band @ 100kHz with PSK), such as the transmission active filter, reception filter and the power, but only to the values the equations permitted.

I have a proper connection between the ST7580 and the host controller and I have set all the MIB setting I needed to as per the user manual and the system is running at the appropriate speed.

But for some reason, I can not get a signal out of the power amplifier pin (PA_OUT).

I have a correctly modulated signal being produced from the TX_OUT pin, as shown below in yellow, but the PA_OUT pin remains steady, as shown in red.

I have read through all the application notes available and been in contact with the support at ST, but I am still having this problem.

If anyone has any suggestions or ideas on how to I can get this to work I would really appreciate the input.

PS: I have zero detection implemented and the system is exposed to mains.

I have tested the system with and without mains, as well as a hundred other tests.


texts: Do poles enhance frequency or cause it to dip

texts:
I'm a bit confused about the idea of poles. In some of my courses such as digital signal processing, we are taught that in filter design, you place a pole at a frequency you want to enhance and a zero where you want to cause a dip.

In other courses in which we deal with Bode plots, I notice that a pole causes a -20dB/decade slope decrease?

Why is there an incosistency?


texts: Combined chip with LDO and Buck, what use?

texts:
I am searching for a Li-polymer 1A charger with a 3V regulated output. I have found Linear LTC355x serie but can't, after reading many "LDO vs Switching" debates, understand the use of both on the same chip. LTC3553, for example, offers a 200mA buck and 150mA LDO.

I need to drop the USB 5V and battery 3.3-4.2V to 3.0V with a 170mA maximum draw. Space on the PCB is a premium so I'd prefer a combined chip. The PCB also contains 868mhz and 1575mhz antennas so a linear converter might be better ?

Should I choose between LDO or buck (I couldn't find a only-LDO or only-Buck chip) and disable the other ? Should the buck be the main source and the LDO the backup/standby source ? Is it only used to output different tensions, for example, 1.2V and 3.0V ?

EDIT : Thank you for your answers. They got me thinking about the VINLDO pin and I was wondering if feeding the LDO from the Buck to obtain a clean output is worth a try ? Assuming :

Battery safe tension range is 3.0-4.2V and VUSB is 5.0V.
All devices on the PCB could use 2.8V.
Buck is needed to obtain an efficient conversion from > 4.0V.
LDO is needed to obtain a clean output.
=> The buck could output 3.0V to the LDO which in turn would produce a clean 2.8V ?


texts: LPC1343 evaluation board USB bootloader not working?

texts:
My LPC1343 no longer shows up as a USB mass storage device.

I am using the following evaluation board for NXP's LPC1343:

http://www.embeddedartists.com/sites/default/files/support/qsb/lpc1343/LPC1343_QuickStart_Board_Users_Guide.pdf

I plug in with mini USB, file system opens. I deleted the default firmware.bin and loaded my own based on the code of this library: https://github.com/microbuilder/LPC1343CodeBase (without modifying)

I then pressed some combination of the reset and bootloader buttons. And now my device no longer appears on my Windows PC when I plug in USB (e.g. I can't see firmware.bin in device's folder).

Is it possible I accidentally activated a code read protection mode? I really hope not... http://www.nxp.com/documents/application_note/AN10968.pdf

Thanks for any help.


texts: How can a Li-Ion battery maintain decent characteristics for nine years?

texts:
Turns out Opportunity Mars rover is already working for nine years. It uses Li-Ion batteries to store energy acquired from the solar panels.

In my experience Li-Ion batteries when recharged frequently have about 40% of the original capacity after having been used for three years. I haven't tested, but I expect that in nine years they would barely charge.

Yet the rover batteries seem to have enough capacity left after nine years.

How is that possible?


texts:
In vhdl code for synchronous counter, I replaced following part

process(clock)
begin
    if(clock'event and clock='1')then
        count <= count + 1;
    end if;
end process

with

process(clock)
begin
    if(clock='1')then
        count <= count + 1;
    end if;
end process

result remains same. Then why 1st way of coding using clock'event is always recommended. ?


texts: Compensation of forward voltage drop of a diode - software

texts:
In my case I would like to compensate with software a voltage drop over the diode.
I have diode RS2J which supplies DC/DC (50mA - 200 mA) converter at this point with resistor divider I would like to measure the voltage with ADC calculate the input voltage before the diode.
Out of my calculations the compensation with single value  (ex. 800mV) is out of tolerance because it depends from  temperature and input current.

Do you know any kind of software method which could help to reach higher accuracy.

simulate this circuit – Schematic created using CircuitLab

Some simplified schematic.


texts: N-channel mosfet turn constantly on after a while

texts:
Hi;
N-channel mosfet (Q4) work fine for couple of time and suddenly turn on constantly.
I changed Q4 multiple of times and each time it work for couple of time and suddenly turn on constantly.
the output of mosfet is connected to a 2.5 amper 12 volt car windshield washer pump and the reason of C11 and R33 is because of water pump noise that cause microcontroller to dont work normal.
What could be the reason of this problem ?


texts: Will the negative charge on the capacitor be neutralized?

texts: If I have the negative terminal of a charged capacitor, say 3V, connected to the positive terminal of an ideal battery of 5V, leaving the positive terminal of the capacitor and the negative terminal of the battery not connected, will the negative charge on the capacitor go to the ideal battery through the wire between them? If not, could please tell me why? Thank you!


texts:
EDIT: @EugeneSh.  I ment how can I build a hub
Double edit: Sorry everyone, I mentioned how can I build a USB hub...

I'm looking to build a very small USB Y splitter for my Nexus 7 2nd Gen so it has 2 USB ports.
The reason why I'm not buying one from eBay (ect.) is because i don't want a cord and I want to build something like the "sugoi hub" mentioned below.
I WAS going to buy a sugoi hub but those things are nowhere to be found!
Anyways, do any of you guys have an easy wiring diagram for a (micro) USB 2.0 Y splitter?


texts: I am building an ozone measuring device and am getting inconsistent and sometimes non-existent results from the sensor. the sensor is mounted separately on a piece of stripboard on the lid of the box along with a resistor and only 5 wire links. I was trying to work out why I was getting strange results when I noticed that an unconnected track had only about 150 - 300 kiloohms resistance to tracks up to 4 holes away. Once again, I stress that this track is unconnected, it just has a small amount of solder on it which I have quadruple checked is not bridged to anything. I have used acetone to wash away flux residue, but if anything, the resistance has gone down. Is there something wrong with my stripboard, my multimeter or me?


texts: 0-1А adjustable current source IC for dimming battery powered LED

texts:
I'd like to build an adjustable current source for battery-powered LED lamp to dim it so I can adjust its brightness for reading while using it.

It is originally powered by 4V 0.75А PSU but consumes about 500mA max.
I want to power it from a 1S Li-Ion so would be 3-4.2V as well.

I guess linear regulator is a bad choice for that.

But I have troubles to find a switching IC myself googling because some of ICs are too rare, some are not too friendly to be soldered by amateur (DIP/SOIC/TO would be OK), some require too many discrete components.

Could you please recommend me some good old, simple, but efficient chip/solution?


texts: Impedance Matching Long 2000 meter Transmission Line

texts:
My apologies if this isn't the most appropriate forum to ask this question, but I have found the response from users on this form to be extremely helpful in the past with my electrical questions.

I am new to impedance balancing so bear with me. I have a transmitter and receiver with 2000 meters of electrical cable connecting the two. The signal I am transmitting is a 3.3 volt digital signal. I am trying to impedance balance this network and a bit confused where to hook up my VNA.  I drew a diagram below, is this correct?  If I understand it, my VNA connects to the transmitter circuit while it is connected to the 2000 m transmission cable, which is then connected to the receiving circuit. Using my VNA and a Smith Chart, I will impedance balance the TX circuit with some "L" network including a certain value inductor and capacitor.  After that is balanced on the VNA, I connect my VNA at the receiving end and do the same type of impedance balance.

Does this make sense or am I going about this wrong?  Thanks for any input anyone has.


texts: Recommendation of a USB-to-RS-232 chip for an industrial environment

texts:
I have bought a device which has an ATmega microcontroller and an FTDI chip which connects to a computer through USB. The FTDI is used only as an RS-232-to-USB adapter.

My problem is that this device hangs up the PC when some of the machines are running. I changed the cables to thick, heavy-shielded ones. Also the cable is in a steel conduit. And the device itself is inside a 2 mm stainless steel casing. The case connected is to ground.

Amazingly, the problem is not present when working with this device, but with a plain RS-232 version. (The RS-232 version works even with el-cheapo cable. no problems.)

My questions are:

Is the problem related to a poor design of the device or is the FTDI chip fault? I am now confident that it was due to a bad design of the converter.
What would be the best pick for a chip to convert RS-232 to USB in an industrial environment?
How much work is it to use a microcontroller with a built-in USB port, for example an Atmel microcontroller? Will it be cheaper and faster?

The only requirement is that there must be drivers both for Windows and Linux for the converter.


texts: "close range" voltage protection with TVS

texts:
Question about a specific scenario:

In an (vehicle) environment where a "normal" voltage ranges between 24-29V I have a circuit that uses the NCV7805BTG 5V linear regulator to supply 5V for an ATTiny.

I want to protect this circuit from voltage spikes during (jump) starting or when there is heavy equipment being used, for example a winch, that may cause voltage fluctuations. I read that starting may cause voltage peaks up to 180V.

The NCV7800-datasheet is a bit vague (at least to me) about the absolute maximum voltage for this regulator. The way I read it, it's 40V.

I was thinking to use a TVS diode, but, as I understand it (and I'm new to this, so I may read it wrong), I would need a TVS with a working voltage < 29V and a clamping voltage of max. 40V. Correct? However, no such a TVS diode seem to exist. I recon the closest one is a 15KE30A, which starts breaking down at 28.5V and has a clamping of 41.5V.

What should I do? And how bad is it that if it starts breaking down slightly earlier (heat?/power loss)? Perhaps I should use Zeners instead (how?)?

Now, there is a chance that I'm overthinking this, so any field experience on the topic is welcome! Thanks!

-- reason I use the NCV7800 is that it's the only through-hole regulator I could find that can supply 5V and has an automotive rating. --


texts: Marx Generator For Quick Discharge of Capacitors On Inductor

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Hello guys! My goal was to charge these two capacitors with a dc generator as shown in the schematic using a Cockcroft-Walton generator which has worked in the lab perfectly. The capacitors are charged in parallel and my goal was to switch them somehow in series and drive an RLC oscillation. My idea was to use a modded Marx generator with the switch S1 open during the charging phase. When S1 would close then the caps would be in series (60 volts) driving the oscillation. R1 and R2 are both 1 MΩ and R3 is 10Ω. I am having a hard time figuring out why I am not getting the expected outcome. When closing S1 I am expecting the capacitors to discharge however measuring the voltage at their leads does not show that as i am getting 30V continuously. Any ideas would be greatly appreciated!

*PS capacitors are polypropylene 150nF rated at 630 VDC 400VAC


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I am a beginner in EE and I am just studying circuits at the moment, and I have this question about designing an AC Mains Voltage indicator that indicates the voltage level of AC mains by three different LEDs. It takes input from a stepped down transformer and through a circuit that has three led indicators, Red which is on when the input voltage is above (240+5%)V (rms) (+5%), Green when input voltage is in 5% range below or above 240V (rms) and Yellow if input voltage is less than  (240-5%)V (rms)

The problem is, I have just started sinusoidal state analysis and I don't have any idea how such a thing is implemented. Can you give me some leads that would help me design this circuit? It is from a design assignment.


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I bought a cheap string of LEDs in the supermarket (the christmas decorationny type) and just out of curiosity I'm trying to figure out how it works, because I can't understand how it doesn't short itself.

It consists of a basic holder for two AA batteries with an on/off switch, and 20 tiny but bright white LEDs on two wires that lead out of the holder. The wires connect to one end of the first LED, and on the other side of the LED two wires lead to the next LED, so each LED has four "legs". The wires on the end of the very last LED simply connect to each other.

The wires themselves are not insulated, (only the LEDs are, they appear to be dipped in some kind of transparent silicone), which What's weird to me because the positive and negative wires are touching all along the length of the strip. Also, you can scrunch up the wires and touch each bit of wire to every other bit of wire, and it still works. In fact, the two wires that come out of the battery holder appear to be touching. How is it not immediately shorting out the batteries, or causing a short when you scrunch it up?


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Adding some components and a ground plane, all GND pins are connected automatically after a ratsnest command (just like R2 in picture); except those that I added manually in my custom library (like the battery B1 in picture). I wonder why I can't get them connected to the plane...

Update: Adding schematic to make sure:


texts: Why does my comparator not give an output?

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I am new to doing electronical things, so I bought some components and I am just trying thing out.
Now, I am using a LM 2901-comparator, whichs documents you can find here.

Using a power supply of 3V, I measured the following pins,

Pin 3 (V+): 3.0V
Pin 4 (Input 1-): 1.5V
Pin 5 (Input 1+): 2.2V
Pin 12 (GND): 0.0V

according to the documents you would expect pin 2 to be 3.0 V since Vout = 1 if Vin+ => Vin-, but it is not giving an output at all.

Anyone that can explain why this is not working?

simulate this circuit – Schematic created using CircuitLab


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I am doing a project on a door shutter opener where there are two states or signal I pass into the circuit:

0V: Door shutter closed
5V: Door shutter opens.

I plan to accomplish this via motor control. The problem is I need to reverse the polarity of motor to change direction so this basically works like a DPDT switch except that I have to do this via electrical signal.

How do I accomplish this and is it possible to do this via transistors or gates?

I've done basic electrical science course in college till now so I would appreciate it if you can talk at my level of learning.


texts: What is meant by counts of noise in this context?

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Regarding the following paragraph about resolution of a 16-bit ADC:

  Unfortunately, other factors enter the equation to diminish the
  theoretical number of bits that can be used, such as noise. A data
  acquisition system specified to have a 16-bit resolution may also
  contain 16 counts of noise. Considering this noise, the 16 counts
  equal 4 bits (24 = 16); therefore the 16 bits of resolution specified
  for the measurement system is diminished by four bits, so the A/D
  converter actually resolves only 12 bits, not 16 bits.

Above what is meant by “16 counts of noise”? And how does it reduce resolution to 12-bit? Can this be explained in more detail and explicit manner?


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I'm making a water level indicator using an 89C51 for which I need 5 V input voltage. I used a 230 V to 12 V step down transformer and a regulator to get 5 V.

I got the 5 V but then the transformer started giving an output of 4.4 V instead of 12 V.

Can you please suggest the possible causes for this problem?

Power supply schematic: