texts: Sanity check my first project: to control my air conditioner with a Nest

texts:
I have a window air conditioner. It works well but is a bit old — new enough to be electronic, have a remote and a digital display, but not new enough to turn on from my phone or do anything smart with its thermostat.

I'm dipping my big toe into electronics by hooking up a Nest smart thermostat to this air conditioner, and it's proving to be an adventure:

The air conditioner's electronics run on 16V DC. A 68k microcontroller switches the negative sides of some SJ-S-112DM relays via a darlington array on an IC to control the fan and compressor. I'd like to bypass everything except the relays (but leave the rest functional if I want to go back to basics).
The Nest wants 20-30V AC (24V is standard for residential HVAC). It switches the hot side of the HVAC's relays. It can power itself by running a small amount of current through the relays (but not enough to activate them), or you can connect a dedicated neutral wire.

So, not so compatible. Anyway, I'm a computer programmer by trade, and this is my first electronics project since high school. I'll take an elegant solution over an easy one — especially if I can learn a few things along the way.

I assume that the Nest uses solid state relays to pass voltage out to the air conditioner's compressor and fan. I further assume that that path is agnostic to DC vs. AC. I even further assume that some kind of rectifier is used to power the Nest's guts, and that it will be equally happy on DC.

I've partially tested the last assumption by hooking the Nest up to the 16V out from the air conditioner. I thought that maybe it would just work — that 16V was close enough. Alas, it refuses to operate the system, giving me a "power wire not working" (E24) error. But it didn't blow up! And it even shows the correct voltage on its debug screen. Encouraging. DC might be fine.

Here's my current plan:

Buy a small DC/DC buck converter to boost the 16V coming out of the air conditioner to 24V. Connect this to the Nest. Its outputs will be 24V, too, though, so…
Buy two (or 200, turns out they're super cheap) 2N2904 transistors. Connect the Nest's outputs to the bases of the transistors.
Connect one 2N2904 to the compressor relay, and the other to the fan relay.

So the Nest gets the 24V it wants (but DC instead of AC), and its 24V outputs drive the transistors. The transistors switch the negative sides of the relays.

Here's a schematic. It's my first so be harsh with your criticism:

simulate this circuit – Schematic created using CircuitLab

The questions I could use help with are are:

Is it safe to drive the Nest, which expects 24V AC, with 24V DC? If not, why not?
If the Nest expects to switch AC, will it switch DC too?
The relays don't seem to be specced to use much current. Is it okay to switch them with transistors like this?

If you see any other big holes in my story, I'd much appreciate you pointing them out too.


texts: What method can be used for outdoors circuit protection when transmitting DC or analog signals?

texts:
For long time I have been looking for a source for this but I dont know how to articulate it. Sometimes I need to send analog signal or DC voltage for hundreds of meters by using STP cables. But the projects sometimes outdoors where it is on the top of a bridge where lightings or other phenomena might cause interference on the transmission lines.

I juts need to know if there is any way I can investigate what in industry or in practice used as method as protection for possible high transients.

So below is an example where a 12VDC supply voltage is sent to a far end electronics which has no protection and can be a electrolytic capacitor followed by a voltage regulator:

I marked the nodes as A B C  and D. How could the type of the component be figured and the location considering the above scenario? For instance would placing TVS diodes across A B and C D be a way to protect both sides frrom possible high voltage spikes?


texts: Servo control using dsPIC33's Output Compare and Timers

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I am trying to control a single servo using output compare and a couple of timers. Timer 2 provides the 20ms period and it controls output compare 1 (OC1). OC1 is running in continuous pulse mode, where it uses Timer 2 to count from 0 to anywhere from 0.8-2.2ms. In my code, I have a function called servo_pos() that calculates the needed value for this time, which is placed in the OC1's OC1RS register.

I am able to set the servo position to whatever angle I want at initialization. Currently at initialization, the servo is set to rotate to the neutral 90 degree position and it stays there. However, I want to be able to change position when I tell it to and my servo won't let me do that. For example, I am using a different timer, Timer 4, to create a 2 second delay. Each time Timer 4 reaches its period count, an ISR is called that is supposed to change the servo position using my servo_pos() function. I know the ISR works because I have an LED blinking every 2 seconds. When the OC1RS register is written a new value, my servo seems to try to move to the new position but it seems as if it is fighting to stay at the neutral position (or whatever position I assign it at initialization). My code is given below, if anyone could please try to help me figure out my problem. I've never used a servo before.

#include <p33EV256GM102.h>
#include <xc.h>
#include <stdio.h>

#pragma config ICS = PGD3
#pragma config FWDTEN = OFF

//Fosc=7.37MHz
//Fcy=Fosc/2=3.685MHz (No changes to PLL)
#define Fcy 3685000

void __attribute__((__interrupt__, __auto_psv__)) _T4Interrupt(void);

void servo_pos(int stop_time);
int pos = 1500;

int main(void)
{
    TRISBbits.TRISB6 = 0; //LED output

    RPOR0bits.RP35R = 0b010000;     //remap pin rp35 as OC1
    ANSELBbits.ANSB3 = 0;           //sets RB3 to digital
    TRISBbits.TRISB3 = 0;           //RB3 output for OC1

    // set servo to neutral position at startup
    OC1R = 0;                    // pulse start time
    servo_pos(pos);             // move servo to neutral position
    OC1CON1bits.OCM = 0b101;    // continuous pulse mode

    // Configure Timer 2 (default timer for output compare)
    PR2 = 9213;             // Timer 2 period (20ms) Fcy x 20ms / 8
    T2CONbits.TCKPS = 0b01; // Timer 2 prescaler 1:8
    T2CONbits.TON = 1;      // Enable Timer 2

    // Configure Timer 4 for controlling how long the servo performs each action
    IPC6bits.T4IP = 1;
    IFS1bits.T4IF = 0;
    IEC1bits.T4IE = 1;
    PR4 = 28789;                // Timer 4 period (2s) Fcy x 2s / 256
    T4CONbits.TCKPS = 0b11;     // Timer 4 prescaler 1:256
    T4CONbits.TON = 1;          // Enable Timer 4

    while(1)
    {

    }
    return 0;
}

void servo_pos(int stop_time) //stop time in microseconds
{
    // Configure Output Compare channel 1 (OC1)
    OC1RS = ((float)stop_time/1000000.0)*Fcy/8; // pulse stop time (1.5ms) OC1RS = Fcy x 1.5ms / 8
}

void __attribute__((__interrupt__, __auto_psv__)) _T4Interrupt(void)
{
    // Clear Timer 4 interrupt flag
    IFS1bits.T4IF = 0;
    // Toggle LED on RD1
    LATBbits.LATB6 = ~LATBbits.LATB6;

    servo_pos(pos += 50); //every time ISR is called, change the servo position

}


texts: Dual rail power supply for audio needs to drive LED too, unsure of design approach

texts:
I have a +17V, -17V power supply for a headphone amp I am building, I would like an LED to indicate when the amplifier is turned on, but don't want to negatively effect the audio output by drawing current from the same source.

Does someone maybe have some advice on how to power the LED?

Best regards
Andre


texts: How does this Audio ADC know which rate to sample the audio at

texts:
The part under question is PCM1808. This device needs an external system clock on the SCKI pin. From the master device it shall need LRCK, BCK & DOUT. The LRCK chooses the left/right channels. BCK is the clock signal sent into the ADC to drive the DOUT bits out. The component has 24 bits resolution.

Now assume that I have a 16.384 MHz crystal. According to Table 1, this could mean sampling frequency of 32KHz or 64KHz. The datasheet says that "The PCM1808 has a system clock detection circuit which automatically senses if the system clock is operating
at 256 fS, 384 fS, or 512 fS in slave mode.". I am lost, how does the device know if I want it to sample at 32KHz or 64KHz, automatically!? This appears ambiguous to me, almost like magic.

Then, does the master device need to read the ADC continuously? I mean, there will be times when reading samples will not be needed. What happens if I am not reading the ADC at all? Do I need to send some command to make it sleep and wake up?

The master device is fed by the same 16.384MHz clock. However, obviously it does not send out the BCK signal at the same rate of 16.384MHz. If one is using I2S data format, at what rate does the master device read the ADC to get all the samples by sending out BCK and reading data on DOUT and how is this ensured? Is it by using timer interrupts or special built-in hardware for I2S data transfers?


texts: Which minimization for the KMAP is correct

texts:
In the KMAP shown below, I can think of three different ways to minimize it. How can we determine which is correct? I have listed the minimized equations and why I think each one is acceptable below.

I believe this case is acceptable because it has the fewest number of groups, and the largest possible group.

I believe this case is acceptable because it utilizes the overlap rule and doesn't violate any other rule.

I believe this case is acceptable similar to Case 1.

They all are within the rules, so what makes one more correct than the other?


texts: Design of a Buck Converter with LC Input Filter

texts:
I am attempting to design a circuit from an exercise:

I am stuck at point (c). I attempted to calculate the voltage and current ripple in the LC filter using the small-ripple approximation, but this yields constant inductor current. This is what I attempted to do:

This exercise is proposed in a section of a book that is supposed to be introductory, so probably no advanced techniques are required to solve it, but I wasn't able to find a solution so far.
Thank you for any help.


texts: Replace some LEDs with diodes in relay circuit

texts:
I need to know if I can replace the input LEDs (IN1, IN2, IN3, IN4) by a diode or resistor and if this can help me to reduce the voltage consumption generated by these LEDs.

The circuit is a 4 relay module for use in Arduino and RPi projects. I have this module connected to my RPi, but the RPi show me a "LOW POWER" message when I connect the module to GPIO pins. The RPi is powered with their appropriate power supply.

(*) All pics taken from SUNFOUNDER. For more info about the relays module visit SUNFOUNDER.


texts: Design a cheap 1.5V / 12V DC motor driver for high school students

texts:
I am introducing electric circuits to Grade 9 high school students as part of a dedicated engineering subject. The students have no prior exposure to electric circuits.

As part of this module I want to design a motor driver for the students to build, either using a breadboard or a soldering iron. The motor driver is needed to drive some mechanical doodads later in the course.

The motors in question are the DC hobby motors shown below. My choice is driven by price (these motors are going for $1/ea on clearance.)

1.5VDC, 650 mA M-13-2270-1.5V

12 VDC, 650 mA MF-26CS-18165-12.0V

Requirements

My problem is to design a DC motor driver to the following specifications:

Bi-directional (forwards and reverse drive)
Control by pushbuttons / toggle switches. Either a pair of "forwards/reverse" buttons, or a "forwards/reverse" direction toggle and a "go" button.
Drive either of two kinds of motor - 1.5VDC, 650 mA M-13-2270-1.5V or 12 VDC, 650mA MF-26CS-18165-12.0V. I am planning to use the 1.5V motors to actuate small geared mechanisms, and the 12V motor as a "winch" for a model elevator.
Cheap - less than $5 in parts. Cheaper is better. A class size of 30 students may be presumed, so I can order bulk parts in lots of 50 or 100 which should help with cost.
Preferably breadboard-able so the parts can be re-used for next year's students.

Possible solutions

I have considered a SN754410 Quad Half-H Bridge IC which is cheaply available ($0.80/ea in bulk from eBay, i.e. Hong Kong.) However this has an output voltage of 4.5-36 VDC. I believe this may cause the 1.5V motor to emit smoke.

On the other hand, I considered a H-bridge built out of cheap discrete transistors like the 2N2222. However, I am uncertain as to the power limits of such a H-bridge. It also involves at least a dozen parts, which may be a bit difficult for students who have never dealt with electronics before.

The problem

What transistors, IC's, or other switching components can I use to build a DC motor drive that handles 1.5 & 12 VDC motors? If I can get an idea of the main components, I can design all the auxiliary stuff (switches, biasing resistors, what have you) myself.

It must be cheap (we need 30 of them) and buildable by Grade 9 students and their teacher. (I am not the teacher.)

If the output voltage of the SN754410 could be reduced to be friendly with a 1.5VDC motor, that would be a very easy way to solve my problem.

I myself have very little practical electronics experience but I am willing to RTFM if directed.

The school can make basic PCB's on a milling machine if required.


texts: How to determine if a signal path needs to be treated as a transmission line?

texts:
I remember reading this somewhere but cannot find the ratio of the rise time vs. the propagation time (i.e. the trace length?) of a signal when transmission line effects come into effect?

For example - if I have a SPI bus running at 12.5MHz. If it runs a few inches through the PCB trace, it is not a transmission line - but at what length goes it become a transmission line (at least in theory). How to calculate that?


texts: How to wire a relay for 12v car lighting

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I would like to reconfigure the current wiring of my daytime running lights.

The relay is currently switched on via an accessory power wire with inline switch.

I would prefer the relay to turn the lights off when the headlights are switched on.

How can I wire the relay to switch off the daytime lights when power is applied to the headlight wire?

Thanks


texts:
For one of my electrical engineering labs, we are required to build an lm386 circuit with a gain of 40, then measure its frequency response. I have successfully done the first part - I get a gain of 43 at low frequency (~100 Hz).
Diagram:

The problem is that when I increase the frequency to about 20k Hz the signal becomes distorted:

66k Hz:

and after that the waveform is basically unreadable. Is an lm386 even capable of amplifying at these frequencies? I thought it is since the datasheet gives a bandwidth of 300k.

Anyway, I have tried replacing the lm386 twice (same result) as well as the capacitor. The lab tutors say they don't know what else could be causing this. Any ideas?


texts:
I am using Xbee series 2 modules to handle communications between my home automation modules. As my base station, I am using Raspberry PI with Xbee coordinator attached to it.

It all seems to be working well, however, after around a week of flawless functionality, the xbee module just freezes. It does not respond to anything and appears disconnected. The only way I can bring it back to life is to remove it from the socket and put back (or power-off the whole board).

I've tried both using an addon board to inteface the xbee directly with Raspi's serial port and using a USB-based XBee adapter. In both cases, the problem is the same - after few days the xbee module just stops responding.

I suppose I could detect this state and device a way to perform the reset using GPIO but it "should" work as it is.

Anyone experiencing similar issues?


texts: Correct AT Commands sequence for Quectel M95 GSM module

texts:
I have easily managed to connect the M95 GSM module to an Arduino and can communicate. I want to have a very basic way of posting data to a website from the Arduino. It seems the AT commands are suppose to be easy to use.

I can send basic commands like AT etc very easy and get the reply. Now I want to post data and it does not work. Here is the sequence I use, in Arduino code:

Serial.println("Talking to Modem: AT");
mySerial.println("AT");
delay(1000);

// I get correct response: OK

Serial.println("Check if SIM is locked");
mySerial.println("AT+CPIN?");
delay(1000);

// I get correct response: +CPIN: READY

Serial.println("Setting up URL");
mySerial.println("AT+QHTTPURL=31,30");
mySerial.println("www.somedomain.co.za/api/");
delay(2000);

// I get response: OK. Not too sure if the /api/ must be in the URL

Serial.println("Sending Data");
mySerial.println("AT+QHTTPPOST=31,30,10");
mySerial.println("usersID=2");
delay(2000);

// Get the response: CONNECT

Serial.println("Read Response");
mySerial.println("AT+QHTTPREADS=30");

// Get the response: CME ERROR: 3 (Cause for PPP/IP Stack)

I'm not too sure what next to do:

Why do I have to send string lengths before I post the URL? Why can't I just post the complete URL? Is there an AT command to just post an URL?


texts: How to compute resistors values in bipolar transistor circuit?

texts:
In the attached image, I have this circuit and I need to make the D1 and D2 diodes to work complementary to D3 and D4 based on button status. The problem is that I don't know how to find the resistor values for R3 and R4. So far I have tried guessing some values for them but with no success. I don't really get how to use Kirchhoff law when bipolar transistors are in circuits ( just getting to learn how to analyze such circuits ). Any help will be much appreciated.

P.S. The VCC is 9V.


texts:
I have a PID controlling a DC motor. I am attempting to control the speed of the motor very precisely. My controller allows me to change the direction of the motor and give it a pwm for speed. Therefore, I have a PID that has a plus and minus maximum and minimum. In order to speed up the device and slow down the device quick enough. The output of the PID is for the pwm and therefore is a absolute value of the PID, just changing a direction pin when PID < 0. I am using the opposite direction of the motor only as a braking system. Thus the motor should always be going in one direction but should slow it self down faster by applying reverse torque.

I am writing C firmware in MCUXpresso. The graphs come from sending data over UART to an Arduino to graph data easily.

My problem is that sometimes when the process variable hits 0 or close to it, the PID inverts and needs to go negative and thus spins the motor at full speed in the opposite direction. The two pictures below show the certain cases of when it happened. The red line is the set point and the blue line is the process variable.

The code controlling the device and PID is below.

I am having a hard time understanding why the PID would run away like this. Any help would be amazing. Thank you!

Main Control

int dir = FORWARD; //Controls direction of motor

motorPID.setpoint = vehicleSpeed;

motorPID.input = SM_GetRPM();

motorPID.input = motorPID.input * speedConversion;

UART_SendPID((uint8_t)motorPID.input, (uint8_t)motorPID.setpoint);

PID_Compute(&motorPID);

if(motorPID.output < 0){
    dir = BACKWARD;
}

if(motorPID.setpoint == 0){
    motorPID.output = 0;
}

if(motorPID.input > 60){
    MC_SetMotorSpeed(0, dir);
    int test = 0;
}

MC_SetMotorSpeed(abs(motorPID.output),dir);

PID Code

//Find all error variables
self->lastError = self->error;
double input = self->input;                         //Only so input can't change during compute
self->error = self->setpoint - input;
self->integral += self->error;
double derivative = self->error - self->lastError;

//Anti-integral Windup
if(self->integral > self->Outmax)
    self->integral = self->Outmax;
else if(self->integral < self->Outmin)
    self->integral = self->Outmin;

//Calculate PID
self->output = (self->Kp*self->error) + (self->Ki * self->integral) + (self->Kd * derivative);

//Set limits
if(self->output > self->Outmax)
    self->output = self->Outmax;
else if(self->output < self->Outmin)
    self->output = self->Outmin;

EDIT: Turns out this was a combined error of the problem described and a hardware issue.


texts:
is it possible to program PIC 16F877A using arduino uno?
if it is possible, please tell me how to this;


texts: Which standard dictates how reference designations should be formed in the EU?

texts:
I'm studying electronics in college (I live in Europe), and they are teaching us we should form our reference designations of elements when designing a circuit as according to EN 81346.

This seems absurd to me, because it might be OK for a meat grinder and a generator to have the same designations (G) in some sort of a big automation system, but in a small electronics circuit to name both a diode and a resistor with R, just because they do something to current.. i can't accept that. After looking it up on wikipedia, it seems to me that the classical designations R for resistor, D for a diode, etc. are from the American (ANSI) standard.

I know this sort of thing is entirely voluntary, but I just want to know: Does that standard (EN 81346) really apply to every type of electrical circuit? Are there any other European norms or ISO standards relating to reference designation?


texts: Impedance Matching between Source and Load

texts:
I am having this basic doubt

In the basic crude basic block diagram, we have a source, transmission line and load, all having an impedance of 50Ohms. But according to maximum power transfer theorem, we need the source impedance to be equal to the load impedance for maximum power transfer. But there is a transmission line in the middle of 50Ohms.

This would mean that the source is looking into a 100ohms load (As the transmission line and load impedance get added as the resistances are in series). And the load is also looking into at a source impedance of 100Ohms.

So, how can we achieve maximum power transfer here?
Or, is there something that I am missing?


texts: when to use auto correlation and when to use fourier transform

texts:
In communication, if we don't know any prior information about the signal, we perform an auto correlation say Rx(T) and take the Fourier transform of Rx(T) to analyze the power spectrum.

Supposing if my signal is known do i need to perform auto correlation , or simply i can take a Fourier transform,  and then calculate the power from it.?

Am I seeing it right? or am I missing something here.?

thanks in advance
phani tej


texts: OrCAD Capture Question: Two traces in same plot - where do they cross?

texts: If I have two traces in the same simulation plot, is there a way that I can determine when they are equal to each other?


texts: How to attach/interface an ARM Cortex SoC with an stm32 processor

texts:
I'm trying to work out the best way to attach / interface an stm32f processor with a Linux based ARM SoC?

Is it possible for the stm32 to communicate with the ARM SoC via I2C ...are there any examples of stm32 acting as an I2C client talking to a Linux controller/Kernel Device Driver?

Ideally, I would like be able to upload new firmware to the stm32 from the Linux ARM SoC.

All links, tips and flaming appreciated.

Bruce


texts: Generating dual rail power from a MAX3232?

texts:
I've seen several electronics devices using MAX3232 or similar devices to generate dual rail power supplies. In my instance, I have 3.3V going in and need regulated ±5V outputs. I have three four questions.

How much output current can they sink or source?
Are they regulated or do I need an LDO?
What noise do these give? Through an LDO, would any noise be tolerable for high speed (85 MHz) op-amps?
What other solutions are there for this problem (dual rail power)?


texts: Confused about how I can obtain the State Space Representation of an Electrical Network

texts:
I'm trying to find the State Space Representation of the above Electrical Network.
The transfer function that I derived is of the fourth order:
$$
\dfrac{i_{1}}{i} = \dfrac{\dfrac{1}{C_1 C_2 L_1 L_2}}{s^4 +\dfrac{C_1 L_1 (L_2 +L_3)+L_3 C_2(L_1 +L_2)}{C_1 C_2 L_1 L_2 L_3}s^2+ \dfrac{L_1+L_2+L_3}{C_1 C_2 L_1 L_2 L_3}}.
$$
A fourth order transfer function indicates that the system has 4 inputs. However I can't figure how I can produce a State Space Representation with four inputs, it looks like it can't be done without introducing the current of L3.
$$
            \dot{x_1} = \dfrac{1}{C_1}i_{C_1} = \dfrac{1}{C_1}(x_4 - x_3),\\
            \dot{x_2} = \dfrac{1}{C_2}i_{C_2} = \dfrac{1}{C_2}(i - i_3 - x_4),\\
            \dot{x_3} = \dfrac{1}{L_1}V_{L_1} = \dfrac{1}{L_1}x_1,\\
            \dot{x_4} = \dfrac{1}{L_2}V_{L_2} = \dfrac{1}{L_2}(x_2 - x_1).\\
$$
my main issue is how can I get rid of the current of L3 in the following equation:
$$
            \dot{x_2} = \dfrac{1}{C_2}i_{C_2} = \dfrac{1}{C_2}(i - i_3 - x_4)
$$


texts: When to use the word inductance and when to use inductivity?

texts: I sometimes need to fill in revision tables for inductive components and i always stumble upon whether it's "Turns changed. Inductance updated." OR "Turns changed. Inductivity updated." .


texts: L7805C/L7812C Voltage Regulator with 22V Solar Panel Not Outputting a Constant Voltage

texts:
First, here is my solar panel:
http://www.amazon.com/Instapark%C2%AE-Black-Mono-crystalline-Charge-Controller/dp/B005LR9IOG

And the regulator:
http://users.ece.utexas.edu/~valvano/Datasheets/L7805.pdf

And the Schematic:
http://freedatasheets.com/blog/uploaded_images/7805datasheet-730098.gif

So here is my predicament, whenever I connect the solar panel to the input, the output is not 5V (or 12V for the L7812 regulator) UNLESS the solar panel is outputting its max voltage.  So for instance, when the solar panel reads about 14V, the regulator outputs about 3.5V.  These values are tested under no load.

Now I know that it is not the regulator because when I connect a 9V battery in place of the solar panel, the regulator outputs 5V like a charm.  I also read that there is a 30V upper limit on the 5V regulator so that can't be it either.

My only thought is that the regulator somehow recognizes the max output of the panel and regulates linearly with that voltage so if the panel outputs less than its 22V the regulator will as well.  That is just a shot in the dark and does not make sense to me.

If anyone can let me know how to fix this problem, or why it is happening that would be great.  This is for my senior project in college which consists of a solar tracker and battery/usb charger.  I got the tracking working and the chargers working, but I am trying to self power the system using the solar panel.

So again, any insight would be a great help because I am kind of stumped and when I asked my teacher about it he just said check to see if the regulator is over-heating which it isn't.

UPDATE:
I just checked it now with the panel outputting 18.5V and it did output 5V, so I'm guessing there is a cutoff voltage or something.  Another thing I just tried was measuring the resistance of the panel versus the resistance of the battery.  This was actually pretty interesting.  When the panel read ~10V, the resistance of the panel jumped around in the kilo-ohms (I have an auto-ranging meter).  When I went to test the battery ohms, a little battery symbol came up and it would not give me the ohms.  Here is the key part, when I read the ohms of the panel at 18.5V, it came up with the battery symbol on my meter as well.  This probably means that the panel only acts as a battery above a certain voltage.  I am still kind of curious as to why though, so if anyone has any thoughts that would be great.


texts: How does the gain factor adjustment on this current sense board affect the output voltage range?

texts:
I'm looking at buying this simple current sensing board: http://www.sparkfun.com/products/8883. Here is its schematic: http://www.sparkfun.com/datasheets/Sensors/ACS712%20Low%20Current%20Sensor%20Board%20v12.pdf.

The current sense chip outputs a voltage between 0 and 5v, depending on the current. The op amp on the board can then be adjusted to detect "very small current" changes. The op amp can be adjusted to have a gain between 4.7 and 47, but what does this mean? What is the minimum amount of current change the chip (link below) can detect?

The current sense chip is this one: http://www.allegromicro.com/Products/Current-Sensor-ICs/Zero-To-Fifty-Amp-Integrated-Conductor-Sensor-ICs/ACS712.aspx.

Edit

I'm using the Arduino Uno's ADC, which has the same range as the output to this chip. So, win!


texts: Can I make the space bar act as left click in Altium?

texts:
In a few CAD systems I've used over the years there's the been option of using/redefining the space key as the left mouse click in a finger-saving, RSI-busting option. In the days of modern over-clicky CAD systems this is so good.

So, the simple question is: can you do the same thing with Altium? I've seen various tutorials showing you how to bring up the key shortcuts such as this, but I can't even get that to work on my system. I can redefine other things by doing the CTRL-click option on the menus.

Using version 16.1.0.


texts: RC Circuit - Differential equation (beginner question)

texts:
In a circuit like this one, I was wondering how could one etablish a differential equation:

Because the intensity splits at the node, we would have :

\$R.i_2(t)+R.i(t)+L\frac{di(t)}{dt}=E\$

But how to get rid of \$i_2\$?


texts: will too many inductors in DC power distribution cause instability?

texts:
I'm designing a circuit with different blocks, I used LC filters to isolate power in different blocks. this is how it looks:
pin+ and pin- are connected to a 24VDC supply, possibly from long wires in a noisy environment. a TVS diode is placed in parallel for protection in another sheet. U22 is a switching regulator (LM2576) with fixed 5VDC output. U22 is a 3.3VDC linear regulator (TPS796). I remember from a control course in university that each stage move phase margin closer and when it reach a certain value which makes the system unstable. most of the current drawn is from 5VDCl other blocks don't use more than 100mA. I searched a bit and didn't find anything particular about this problem but then again I didn't find any circuit with this much inductors for DC filtering. pointing out anything else that I might not have considered is welcomed. Thank you.


texts: Convert Single OPAMP PID to Software implementation

texts:
I have a number of analog PID implementations that I need to convert to software. In an typical example (given below), the summing junction is used to get setpoint-measured error. In decoding the P and I coefficients for software implementation, I am confused as to what input resistance should I consider, R1+R2 or R1 parallel with R2.

All help is welcome :)

simulate this circuit – Schematic created using CircuitLab


texts: Can Arduino UNO R3 act as both keyboard/mouse at same time?

texts:
I know that the UNO R3 can be flashed with FLIP to enumerate as a keyboard OR a mouse. I've successfully done this.

My question here is, are there any methods that allow it to perform like the Leonardo in the respect that it can send raw mouse/keyboard commands at the same time? Rather than requiring special firmware for one or the other?

I currently have a a piece of software just decoding serial communication from the Arduino, and sending strokes/movements to Windows... but it's far from what is desired. Mostly because a lot application and games will restrict the keyboard strokes from being automated....

So, is there any possible way to do this type of solution? Or am I stuck with:

  Buy a better board
  Build better keyboard spoofing software


texts:
My proposal for a final project.

  My uncle is making his own smoke house, and to make the smoke he
  decided on using a water heater element. Over the Thanksgiving holiday
  we were discussing this, and it gave me the idea for my final project.
  So, my final project will be creating a controller/display for a water
  heating element. The goal is to use the DE0 to control the power
  source to the heating element, so that the wood chips used for
  smoking, will burn and smoke but not catch fire.

  Thermocouples will be connected between a DE0 (on the GPIO header) and
  the water heating element. The DE0 will read and display (the later on
  a 16x2 LCD add-on) the temperature of the heating element. The power
  source for the heating element will be connected to a relay and the
  control of the relay will be connected to the 5v pin on the DE0’s GPIO
  header. Upon flipping a switch on the DE0, a LED light will turn on,
  indicating that power is being sent to the relay and that the element
  has power. Once the heating element has reached the desired
  temperature a 15-minute timer will start. This timer will be displayed
  on the LCD. Once this 15 minutes has passed, the 5-volt signal going
  to the relay will be cut, the LED turned off, and a new timer will be
  set for 15 minutes. Once this 15 minutes has passed, the heating
  element will be given power and upon hitting the desired temperature a
  15-minute ON timer will be set. This sequence will be repeated until
  the original switch is flipped off, or until 4 ON-cycles have passed.

As for reading the temperature of the thermocouples I have found that I will require a digitize of sort. This is what I have picked out, MAX31855. My concern is the relay. I am not sure if I am understanding the terminology correct.

What I need is the 5v GPIO of the DEO to send the 5 volts to the relay when called. I am correct in thinking that this particular relay requires 5 volts to turn on and can pass upto 220volts?

http://www.jameco.com/z/TC-5VDC-C14-5-VOLT-2-AMP-8-PIN-DOUBLE-POLE-DOUBLE-THROW-DPDT-RELAY_2158338.html

If I am correct, is there anything special I should know about hooking up it at the FPGA?

Lastly, does anyone have a recommendation of relay for my needs?


texts: What does changing the throttle to a BLDC ESC actually do?

texts:
Background: I understand how the standard 50 Hz PWM protocol for hobby electronics works: varying the on-time from about 0.5 ms to 2.5 ms will throttle an actuator from roughly 0% to 100% thanks to embedded controllers inside the servos or electronic speed controllers (ESC) connected in series to a motor.

In the context of a BLDC motor, I understand that the ESC generates a trapezoidal voltage to 2/3 phases of the motor. The ESC looks for the zero-crossing point of the back EMF on the third phase to energize the next pair of phases with a built-in lead (30 degrees IIRC).

I don't understand how the electronic speed controller (ESC) acts upon these throttle commands.

My questions:

Does changing the throttle change the duration of the trapezoids? Using a standard multimeter, I measured the RMS voltage and current between an ESC/motor running at ~50% and ~75% throttle. I know the meter probably isn't rated for such high frequencies, but I trust the fact that RMS readings increased from 50% to 75% throttle. This suggests the ESC is modulating the duration of the input voltage trapezoid to the motor since the peak voltage value is fixed by the battery (unless the ESC also somehow modulates that?). Note, I just realized I can test for this with an oscilloscope. I will do this tomorrow!
How does the ESC maintain unity power factor? Does/how does it also control current? I'm assuming it aims for PF = 1 since this maximizes torque.
Does changing the throttle setting below a certain point change the \$k_{t}\$ of a motor? The second plot linked below compares changing input voltage at 100% throttle to changing throttle at constant voltage. I understand that decreasing input voltage (input RMS voltage would be correct, yes?) shifts the torque-speed curve down and to the left, but why does the torque-speed response also start "drooping" at lower throttle settings? Re-arranging the DC-equivalent model for torque as a function of speed, \$T = [Vk_{t} - {k_{t}}^2\omega]/R\$, the only way slope can change is if \$k_{t}\$ or R change.
Slightly unrelated to hobby BLDC motors, but do the similar sinusoidally-driven BLACs (aka PMSM?) energize all 3 phases at once? If so, then one cannot not sinusoidally drive a BLAC motor with sensorless control based on back-EMF measurements, correct?

Plots from ARL technical report 6389.


texts: What kind of transistor do I need to amplify an Arduino's PWM outputs?

texts:
I'm planning on having 30 incandescent lightbulbs be controlled by my arduino uno on 3 channels (10 bulbs to a channel in parallel).  I've used the arduino before to control a number of red, green and blue LEDs - I used a simple schematic using three transistors.  I'm just not sure which transistors to get this time considering I'm running the bulbs from 120vAC and not a smaller DC power supply.

Here's a schematic for what I want to do - http://i.imgur.com/BzhM3.png

I've tried controlling just one incandescent bulb with an MJE3055T transistor but all I was able to do was slightly dim the bulb, not turn it off completely.  I doubt the power rating was enough, so I tried wiring two transistors together in a Darlington configuration without any luck, nothing happened at all.

I know I should use more than one AC supply to run this - does that mean I'll also need more than 3 transistors?

Do I just need a transistor with a higher power rating?  Would this be the right one?

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=106696146&uq=634559326654518595

Thanks!!!

Dennis


texts: Why does an automatic bluetooth connect fails after some time?

texts:
I am not sure if this is the right place to ask my question. If not, please let me know a better place to ask it.

The question: I have a phone with bluetooth and is connected to a car, so you can use the phone hands-free. And when entering the car with the phone and bluetooth activated, the connection is made automatically.

But after some time, this connection is not made any more automatically. You have to pair them again. As far as I know there has neither been a system upgrade on the phone nor a new app was installed.

I am not asking for a solution, but for the possible reasons why you have to re-pair the car with the phone after some time (happened already a couple of times, after some months or so). What could be the reason for that to happen?


texts: Advantage of using the DEN and DTR control signals on an 8088?

texts:
What is the advantage of using the DEN and DTR control signals on an 8088? The answer isn’t “they enable and control the direction of a bus transceiver, such as an 8286 or 74245”. I know that’s their stated purpose.
While some 8088-based systems use DTR and DEN, there are several that don’t and just rely on RD and WR - sometimes effectively ORed together to enable a transceiver or similar transfer circuitry and with RD to set the direction.
I’m familiar with the cycle timing of these signals, and that for a Read operation DEN goes high at the end of T3 and RD goes high quarter of the way into T4, while this order is reversed for a Write operation with WR going high at the end of T3 followed by DEN going high quarter of the way into T4. But what is the benefit of this slight timing difference? The CPU will already have sampled/output the data before DEN (or RD/WR) goes high.
Why wouldn't a bus transceiver simply use RD (plus INTA) and WR to control its operation? Here's one explanation:
This would work for a RD cycle, where the CPU will sample the data well before DEN or RD goes high.
But perhaps not for WR. At the point when WR goes high and the data is captured by the target device, the same WR transition is disabling the transceiver and so the data captured could be invalid. In this scenario, the additional gate delay from ORing RD & WR at the transceiver is probably helping it to remain enabled for just long enough.
Does this sound right?


texts:
On an STM32F103C8T6 (72MHz) I want to use a delay in range of 100's of nanosecond (to create a LED strip driver, WS2813B).

Since HAL only provides a ms delay, I found at various places code to use the ticks/debug counter as timer.

I have the code below:

Initialization:

volatile unsigned int *DWT_CYCCNT = (volatile unsigned int *)0xE0001004; //address of the register
volatile unsigned int *DWT_CONTROL = (volatile unsigned int *)0xE0001000; //address of the register
volatile unsigned int *SCB_DEMCR = (volatile unsigned int *)0xE000EDFC; //address of the register

unsigned int count = 0;

Within main():

  *SCB_DEMCR = *SCB_DEMCR | 0x01000000;
  *DWT_CYCCNT = 0; // reset the counter
  *DWT_CONTROL = *DWT_CONTROL | 1 ; // enable the counter

  int ticks = 1;

  while (1)
  {
      unsigned int start, current;
      start = *DWT_CYCCNT;
      do
      {
          current = *DWT_CYCCNT;
      } while((current - start) < ticks);

  if (count++ % 1000 == 0)
  {
         HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_6);
  }
}

When I connect a logic analyzer, I see a PWM signal of 0.53 ms per toggle. Since it is toggled every 1,000 counts, this means 0.53 us (530 ns).
However, with 1 tick, I would expect something like 1/72,000,000 = 14 ns (plus some overhead for the while loop/counter).
(note: the counter for 1,000 I used because my logic analyzer can only handle 200 kHz).

I'm not sure if the addresses in the initialization are correct (found them only for STM32F103VET6).

So my question: What is the mistake in the program above?

(side question: is this method good anyway for a LED driver, or should I send the data by interrupt or DMA?).

Update

The reason I need these kind of delays are for the T0H, T1H, T0L and T1L times which can be found at WS2813B datasheet, page 5.

  Data Transfer Time (TH+TL=1.25µs±300ns)

  T0H 0-code, High-level time 300ns~450ns

  T1H 1-code, High-level time 750ns~1000ns

  T0L 0-code,  Low-level time 300ns~100us

  T1L 1-code,  Low-level time 300ns~100us

  RES Frame unit, Low-level time 300µs or more


texts: KiCad PCB Layout Editor - Selecting entire component/footprint instead of a particular element

texts:
In KiCad PCB Layout Editor, I'm trying to arrange and place the various footprints. But when I click on the component, instead of selecting the entire component/footprint, it selects the closest element of the footprint, like a label, pad, throughhole etc. Is there a setting that allows me to default to select the entire component? This has potential to ruin my design without me realising it if one of the pads is moved accidentally.

I can't find anything in the preferences or settings, so any help is appreciated!

EDIT: Here is a screenshot of a resistor. When I click on the pad, I want the whole component to be selected and not just the pad. You can see that right now, it only selects the pad.

EDIT2: As @dylanweber mentioned, I was mistaken about the pads. But it's still a problem when I hit the M key over a piece of text then it doesn't select the whole footprint, but just the text.


texts: Scenario in which the opamp Input offset voltage is more than inverting input?

texts:
we are designing a circuit with inverting inputs in the order of millivolts. The aim is to build an amplifier so that the signal can be raised to a digital level (3.3V)

Now, the question is this: What happens if the inverting signal is below the input offset? How does the op-amp gain behave? Will it be predictable?

This circuit is part of a pressure sensor. So if the transducer is designed with a resolution of say 10mV per Hg delta in pressure, do we need to factor in the input offset voltage?

Another related question is whether the CMRR too becomes a criterion in this design.

Please help.


texts: What happens if doping concentration is less than Intrinsic concentration? Will the semiconductor act as intrinsic or extrinsic? Please Explain

texts:
Si has intrinsic conc of 1.08*10^10
If it is doped with conc less than intrinsic concentration what happens


texts:
I am teaching myself electronics. I designed this circuit to use a photoresistor to trigger a transistor when I hit the photoresistor with a laser pointer. On the Arduino side, I want it to look like a push button. That worked so I wanted to add an led as visual feed back that the laser is hitting the target.

The only way I could figure how to do this was to add a 2nd transistor. It works, but is this the correct way? I don't want to use another pin on the Arduino.

In the pic, pin 11 is supplying the 5V and pin 8 is reading the port.


texts: How can I plug my homemade Yagi Antenna into a wifi USB dongle?

texts:
I have made my own Yagi antenna and I would like to see if it works or not. I made the antenna based of these instructions: Easy to Build WIFI 2.4GHz Yagi Antenna

So I have soldered a coax cable to the pin 2 (the driven element). The center connector to one side and the shielding to the second side of the paperclip. But I have no idea how to actually connect it to my wifi dongle.. Does the center connector of the coax go to the "on board antenna" and then the shielding to the USB ground? also is the antenna the trace to the left of the dongle? The wifi dongle is an old Netgear w111v3. Any tips for me? Thanks!!


texts: Did I wire this correctly? Trying to understand Thevenin and Loading of circuits

texts:
So right now I'm learning about RThevenin and VThevenin of a circuit and how to calculate what the voltage will be once you load the circuit. I am trying to build this circuit:

I am not using these values though. I am using Vin 12.8 volts from a 8AA battery pack. I picked this power supply because I wanted something that I know could fluctuate. For R1 and R2 I am using 1k ohms. For my RL load I am using 100k ohms. The Vout is 6.4 volts with the voltage divider of R1 and R2. Now here is my question... If I put the Rl load (100k ohms) also with the voltage divider shouldn't the Vout or the Vin become a lot lesser than 12.8 or 6.4?
Here is how I wired up the circuit:

Thank you for any help guys :)


texts: Any side effects when substituting bigger capacity battery in place of smaller capacity?

texts:
I have a car key fob whose batteries recently died.  The coin slot says it accepts two cr2025 coin cell batteries.

But I was thinking, since a majority of coin cell batteries run at 3v, I should be able to simply substitute the battery with the biggest capacity available.  So in this case I could use a cr2032.
Fortunately, the bigger batteries fit in the key fob.

But are there any side effects to using bigger capacity batteries in place of smaller capacities?

I heard rumors that bigger batteries demand more current consumption from the load, or else the chemical reaction inside the battery will slow down, thus making the battery life shorter(assuming the load has a p-channel MOSFET to cut power from the load and a button to turn on the power).


texts:
So after my inverter Cut off, I concluded the batteries were no good, as soon as the inverter the total voltage (of the 2 Trojan 6v batteries in series) dropped to 2v and when switched off slowly rose back to around 10v. So I bought 2 brand new 90ah 12v batteries to achieve 180ah. Previously with the trojans I had 250ah. But 180ah should be enough.

My question is that on the internet a lot of people suggest against using 2 12v batteries in parallel, please can anybody suggest why? And a possible solution.

If I do go ahead with this, what would be the best way to charge the 2 batteries, (whilst the are connected to each other, or disconnect them from each other and then charge.


texts:
I am trying to build a transistor computer, and I want to save as much resources as possible. However, I also want it to be practical, so I am implementing a binary-decimal conversion. In order to convert binary to decimal, you must first convert it to BCD(binary-coded decimal). I am working on a machine that converts a 4-bit value to BCD, using a previous post as guidelines. I popped the truth table into Circuitverse's Combinational analysis feature, and it gave me a solution that had 45 transistors in it. Since then, I have compacted it to include only 38 transistors, but I hope that I can go farther and make the converter even less costly. Here is my current design in logic gates:
Hyperlink: Circuitverse
Image:
Truth Table:
Could someone help me make this device even smaller in terms of transistor count? It would be great!


texts:
I am trying to use vias on a fill to connect copper in Altium, but I keep getting unrouted net constraint errors. I have the following:

The red square and blue rectangle (which extends fully underneath the red square) are fills on the top and bottom layers, respectively. Why would I get an unrouted net constraint here?


texts: Relay arcing protection for analog input

texts:
I need to measure the voltage of a Li-ion battery that is connected through a relay, on the NC pin, to the rest of the circuit (so BAT+ -  relay  -     circuit).
The coil of the relay is connected to a usb 5v port used for charging the battery. Basically when charging, the battery is disconnected from the circuit (relay open).
The analog pin of the arduino is connected downstream of the relay.

I know that a mechanical relay arc when opening and closing the contacts.

Relay: 5VDC, 3A, SPDT

Max current through contacts at opening: 2.5A

Unknown value for voltage spikes when arcing; i would assume max 50-100v

Do i need to worry about arcing affecting the analog pin on the arduino (both when opening and closing the contacts)? Do those voltage spikes also carry high current?
If so, would a RC in parallel to the relay contacts be enough?
Do i need a voltage divider on the analog pin? What would be the resistors values?
Would a 5v 700mA TVS diode between analog input and ground be better?
Sorry for asking dumb questions, i am new to electronics.

Thank you


texts: This clamping circuit output is -ve compared to what is expected?

texts: Clock Pulse of Vpeak =10. Providing that the first cycle is -ve why does the output in first is -20 then 0 then -20 and so on? I expected it to be 0 and 20.


texts: How to calculate size of dynamic braking resistor

texts:
I'm running an RC car which has two zytd520 12V 150rpm dc motors run through an L298N motor controller. I'm going to use reverse current braking to save on weight and complexity of mechanical parts. I'm just not sure how to calculate the size of the dynamic braking resistor I'll need to attach to each motor circuit.

Any help?


texts: Short XLR connections via XLR 'cables' or separate wires?

texts:
I'm intending to create a so called patch box (for audio signals), with 16 channels. Each channel has 2 female XLR and 2 male XLR connectors which are tied together (all 3 wires).

The distance between 3 of the connections is about 2-4 inches, the distance to the fourth is about 8 inches.

Is it recommendable to use the (shielded) XLR cable for all these short distances, or can I (especially for the 3 short distances) use 3 separate 24AWG wires?

In schematic form:

XLR Female 1, pin 1      XLR Female 1, pin 2       XLR Female 1, pin 3
       ^                          ^                         ^
       |                          |                         |
    2 inches                   2 inches                2 inches
       |                          |                         |
       V                          V                         V
XLR Female 2, pin 1      XLR Female 2, pin 2       XLR Female 2, pin 3
       ^                          ^                         ^
       |                          |                         |
    2 inches                   2 inches                2 inches
       |                          |                         |
       V                          V                         V
XLR Male 1, pin 1        XLR Male 1, pin 2         XLR Male 1, pin 3
       ^                          ^                         ^
       |                          |                         |
    8 inches                   8 inches                8 inches
       |                          |                         |
       V                          V                         V
XLR Male 2, pin 1        XLR Male 2, pin 2         XLR Male 2, pin 3

We probably will never going to use phantom power (48V), but don't want to rule it fully out. Both microphone level (few uV?) and line levels (max around 1 V?) are used.

We use both microphone and line level instruments.

Or more as a generic question? For what maximum distance it is not needed to use shielded wiring (regarding XLR)?


texts:
Problem Design a controller in the feed-forward path to minimize the effects of the two pairs of dominant poles. Use the pole-zero cancellation technique via the root locus diagram.
I have a 5\$^{th}\$ order system with two pairs of dominant poles,
   Poles =

   1.0e+02 *

  -9.9990 + 0.0000i
  -0.0004 + 0.0344i
  -0.0004 - 0.0344i
  -0.0002 + 0.0058i
  -0.0002 - 0.0058i

Design specifications are overshoot \$<5\% \$ and settling time \$<2s\$. Using the sisotool() function in MATLAB, the white region represents where I need my new poles to be, to obtain the desired specifications:

To compensate the system, I need to get rid, or perhaps more realistically minimize the effect, of the two complex poles. Then I need to re-shape my root locus.
This pair of dominant poles des_poles = [-2.6+2.329j; -2.6-2.329j], give a closed loop response to get overshoot \$<5\%\$ and settling time \$<2s\$, and can also be seen to fit in the white area above.

However, I am stuck when it comes to canceling out the complex pair of dominant poles. Should I add complex zeros, for instance,  0.0004 - 0.0344i and 0.0002 + 0.0058i? These don't seem to yield desired results. Or should I only cancel out the poles which go unstable to the right hand side? How can I cancel out the pair of dominant poles to add the poles which bring about a closed loop within desired specifications?

Any help is appreciated.

My thought process so far (Outputs are still not making sense) I proceeded to add two pairs of complex zeros, to cancel out the complex dominant poles to end up with something like this

I then add the pair of desired complex poles, and another pair of complex poles to the left to make the compensator realizable.


texts: Tesla Coil audio music player circuit analysis

texts:
Here is the circuit:

Here is it being powered up and wirelessly turning on a lamp.

Here are my questions:

How does it actually work?

I do know that 1T ( The red wire ) is being switched ON/OFF by Q2, BD243 which induces a voltage to 350T, which is about (VCC-18v) x 350 = 6.3kv. (I don't think 6.3kv is high enough to wireless powering on a lamp.)
What is the purpose of Q1? It's a N-channel 68 V, 0.0082 Ω, 98 A Mosfet.
LED1 is a red led diode. If it's blocking the 350T, how does circuit oscillate? ie, how does 350T turn off Q2?
I don't know how the audio-in work either, but it does work quite well.

Last but not least, After googling about Tesla Coil circuits, I either find very complex or very simple circuits. Is there a middleman out there?


texts: How to choose and wire a Variable Frequency Drive

texts:
I have a 1.5 HP 3PH 240V Leeson motor that I want to drive my lathe, but I want to vary the speed. I asked a question on this site about a month ago about how to do that and the recommendation was a variable frequency drive.  I'd ideally like to buy a used VFD on ebay to save me some cost and wire it myself. A few questions about what VFD to choose:

I only have 110V available, but this motor is 208-230V input. When I asked on this site before, I discovered that some VFDs take 110V 1ph in and double it in the output. I'm thinking that any 110V 1PH input, 3ph 220V output is going to work for me, but confirming.

Do I need a VFD that is rated exactly 1.5 HP (same as my motor) or would something rated for more (2HP or 3HP) work?

Any other considerations I should be looking for in a VFD?

When I wire it, would a heavy duty extension cord work for the input or should I get something else? What kind of wire would I want between the VFD and the motor?


texts: How to restrict power output to a USB client?

texts:
...or, how not to charge my phone when I'm using it as a GSM modem in USB tether mode?

I've asked this on Unix&Linux but it seems there's no simple way to do it in software.

The problem:

In USB tether mode, the phone wrecks the netbook battery by charging from it. I'd like to be able to maintain the data connection while restricting the current fed over the power lines; let the phone and the netbook use their own batteries without draining each other.

It seems I can't cut VBUS entirely, as device detection won't work. But I ponder the case where I allow the OS and the device to negotiate the power as they desire, then simply fail to deliver - some kind of current-limiting circuitry in the USB cable, so that the phone draws some 100mA or even less no matter how much the host allows to source. If that worked, detection should still work, data lines are unaffected, and the trickle doesn't put much strain on the netbook batteries.

Would that work?
If it would, what would be the best way to restrict the current - simple, robust and preferably not wasting the excess...


texts: Powering the output side of a voltage regulator?

texts: Would powering the output side of a voltage regulator cause any damage to it? (The ground pin would be attached as well) It will not be normally, but I am making a multi-voltage power converter and would like to know if doing such would cause any damage. The regulator would not be the only way for electricity to pass through the circuit, but would be a way. Looking at the schematics, I don't think so, but would like to clarify if there would be an issue.


texts: Are there any way to get (75V 1A) output from 78V input

texts:
Is there any way to get 75 V 1 A output from 78 V input?

I found the TL783 high voltage adjustable regulator. But this can supply only 700mA output current.

I had forgot to tell the details.

Main purpose of this power supply is high precision sensor circuit.

Previously, when required 5V : Step down to 8v with a switching regulator first, then step down to 5v with linear regulator.
It is for the sake of stability of the power supply voltage.

When required 12V : Step down to 15V with a switching regulator first, then step down to 12V with linear regulator.

When required 24V : Step down to 27V with a switching regulator first, then step down to 24V with linear regulator.

This time required 75V and step down to 78v with a switching regulator first, then step down to 75V. I've tried...

This way I have wrong?


texts:
The questions that I'm about to ask will likely "paint very broad a stroke" and open-ended, so feel freed to give whatever that may come to your mind, in full detail or with some rough ideas.

XTR105 datasheet

See the picture attached and please try to answer:

Q1: What's the purpose of component 1?
Q2: What's the purpose of component 2?


texts: Winding EI core Stepup transformer for inverter

texts:
I want to learn the method or concept for winding Inverter Transformer(12V to 220V),
How to select

Core size
Wire gauge
Bobin Size
Turn Ratio and/or number of turns

for different VA ratings on EI type core.


texts: Which side to do the PWM in a H-Bridge, High side or Low side?

texts:
as the title sugests, I am wondering, is there a better side to do the PWM? I believe the high side is better, because the current will flow through the lower part diodes in the Off cicle, which means, the H-Bridge TVSs will help the MOSFETs diodes with the current circulation.
Is there something else I am missing?
Thanks!


texts: The more ICs I add, the less stable my circuit is. Why is that?

texts:
I am making a simple circuit. It has 5 x 74ls161 4-bit counters, and 4 logical ICs (2 x and, not, or). Regardless the logic of my circuit. After I added the last IC (bottom, 74ls32 quad and), the 2nd 4-bit counter stopped working. After 10 seconds, it worked again, then stopped after a minute. It happened before with the other leftmost 74ls161 counters. Sometimes they just stop working, or the increase count by 2 (lsb is always 0.)

I added these 47μF to each IC, but it didn't make a difference.

I am missing something here and I don't know why.

More importantly, how do I check that this won't happen again?

Thank you!!


texts: Inverting Amplifier Not Giving Gain of -2.2

texts:
A LM358N op amp is used with R_f = 220k and R_i = 100k, which should give a gain of -2.2 in a inverting amplifier. It is powered by a regulated +5V supply.

However while the input voltage is 1.000V as read by a multimeter, the output is 0.032V. Why is the gain ~1 and the output not inverted?


texts: How do I calculate the input voltage based on an ADC reading?

texts:
+UB is a 12V power supply. I have to find the voltage on U_KL30.

I take this U_KL30 as an input at PortA<1> of my MC9S08DZ60 and use an ADC to get a digital value. Now I need an equation to reverse engineer the digital value received from the ADC to the actual voltage on U_KL30. What equation can I use?


texts: Can anyone give me some examples of one port network, explaining its significance? Actually I just want to know whether or not such one port network exists? If they do,what are they used for.


texts: Designing a current limiting circuit for my project

texts:
I've got a small DC brushless motor for which I would like to set a current limiting circuit as a protection against over-current.

I thought I could pull it off with a simple fuse (or those current limiting fuse-like chips) but I can't. The fuse would only work to protect against short circuits because I want to set my limit just 20% (max!) above the nominal current draw of the motor.

I didn't design the motor electronics, and my competence in electronics is not great but I was basically wondering if I could use a circuit similar to those:

(source: wikimedia.org)

and if so how I would select the correct components (like transistors and resistors)?

The nominal current draw for the motor is 1.5A. I'd like the circuit to cut the power off when the current is 1.8A or more.

The reason I need something like this is because the load on the motor can vary greatly and would sometimes bring the current draw to 1.8A and more (which I consider unsafe - it's very subjective but that's what I'd like to do...)

Any idea?

edit: clarification: I want to switch power off when the current exceeds a certain value, which has to be about 20% max higher than the nominal power draw of my motor.

edit: how about that second schematic?


texts: How to efficiently design the opcode for a CPU?

texts:
I am building a simple 16-bit CPU in Logisim and have the ALU ready and the opcodes that I want to have.
Now I find it really hard to find the right coding for the commands so that the different subcircuits (e.g. logic, arithmetic) don't need all control wires (that build up the coding) as input, but as few as possible.
Are there any strategies or methods that help with an efficient opcode design?

thx in advance


texts: Split power supply for a multiple op amp circuit

texts: I'm working on a 9V VCO (synthesiser) that has three op amps, of which two needs virtual ground. So far I've been using voltage divider with a couple of caps and it works. I wonder if I need a separate power supply for each op amp? Is the TLE2426 any better? Do I need two of the TLE2426 for the two op amps?


texts: How can I tell how many watts a toroid can transfer?

texts:
I am trying to get general idea of what size of cross-sectional area I would need on a toroidal core to use it as a step-down transformer of a given power rating.

I am aware that the answer depends on frequency. I'm told that as frequency increases, the core-size can decrease and still transfer a given amount of power.

Note: It might be worth noting that I have a very specific need for a transformer in which primary impedance is completely irrelevant. I know most power step-down transformers have a high impedance primary winding to reduce no-load current.  But in my case, I am going to use the absolute minimum number of primary windings, because a no-load condition will never occur. My step-down transformer will always be assumed to be 100% loaded. So I want to know how to figure out how big of a toroid I need in order to transfer a given amount of power at a given frequency or frequency range.

As a matter of example, how I would figure out much power the following toroid can transfer when operated at 260 Hz:
Amico Toroid Ferrite on Amazon


texts:
I am interested in learning more about how SPI works in general, but with the raspberry pi and py-spidev library in mind. I am very technically savvy, although not so much on the EE side of things.

I am attempting to communicate to a piece of equipment via SPI and have been given only a spreadsheet with some information regarding the byte commands and timing. I have already determined that the SPI mode is 1, clock speed should be 300kHz, and word length is 8 bits. A snapshot of the command sheet is seen below. They should be joined end-on-end.

I have attempted to communicate using the py-spidev library and have seen some hopeful numbers (I think). Example:

import spidev
spi = spidev.SpiDev()
spi.open(0, 0)
spi.mode = 1
spi.max_speed_hz = 500000

spi.xfer2([0x03, 0x00])

I am under the impression that this should turn ON the digital pot, which it does not. However, I do see the values [3, 0] returned, which leads me to believe that something is happening.

What is the difference between Bytes(s) out and Byte(s) in? I am under the assumption that if I send the command xfer2([0x03, 0x00], 500000, 9000) I should receive the bytes 0xF3 and 0x03. Is that correct?

I am really at a loss for how to proceed and would love references to good tutorials/descriptions.

After finally receiving my Saleae Logic Analyzer, I have an update. It appears the chip select pin isn't working? Does anyone have tips for debugging this on a Pi specifically?


texts:
I'm having troubles calculating the characteristic impedance of USB/Ethernet traces for a pcb. The Saturn PCB design program calculates values where I'm not sure if they are correct. I want to use a 4 layer pcb of this kind:

The outside copper layers will be 70µm thick instead of the 18µm from the picture (the manufacturer confirmed that they can produce it). Also, εr=3,8 on outside layers.

The calculation with Saturn PCB Design gives the following values for USB:

The conductor width and conductor spacing values seem to be a bit odd. Especially the spacing is really huge, right? (TI: "Route DP/DM traces close together for noise rejection on differential signals".)

The program also shows a S/H warning in the picture.

Are these values indeed correct? Or are parameters wrong? I'm not sure about the base copper weight and plating thickness. As I want to have 70µm on outside layers, I summed the copper values (18+52=70).

What is this warning telling me? Or did I make a mistake?

Thanks!


texts: Why are INTERRUPT CONTROLLER SPECIAL REGISTERS in arm different from others?

texts: For example, in s3c2440, it clears only the bit positions of the SRCPND corresponding to those set to one in the data. The bit positions corresponding to those that are set to 0 in the data remains as they are.


texts: Is there a way to permanently assign 0 to one of an array of registers in verilog?

texts: Is there a synthesizable way to permanently assign the value to a particular memory location? I need a reg that is fixed at 0 and cannot be written to. All writes should be ignored and the register must remain 0.


texts: Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

texts:
I recently encountered a scenario where I attempted to use a Energizer EN500 modified sine wave inverter to provide power to a Dell 180 watt AC adapter. The circuit powering the inverter was 12 volt, 15 amps DC. The AC adapter input is 100-240V ~ 2.34 amps, 50-60Hz, and output is 19.5V, 9.23 amps. I wasn't able to find any more specs online, but it's Dell part # 74X5J, and Dell Model # DA180PM111.

12 volts * 15 amps = 180 watts, and I (incorrectly?) assumed that the adapter wouldn't necessarily need a full 180 watts all the time, and that the worst case would be a blown fuse if it attempt to draw more watts than could be provided. As I'm reading the input on the AC adapter, though, I'm realizing that if it truly can draw up to 2.34 amps, at 110 volts that's over 250 watts...?

When I connected the inverter to the AC adapter, the "power light" on the AC adapter came on when I plugged it into the inverter (indicating connection to AC power), and when I then connected the adapter to the laptop, it started flashing on and off. There was a USB phone charger plugged into another DC power outlet, with a smaller "power light" that also flashed on an off simultaneously, in parallel with the light on the AC adapter. Ever since, this AC adapter has not worked to charge the laptop battery, even when plugged into household AC current. I don't know how many watts it's putting out, but it's just enough to power the laptop at severely reduced operating speed, and the battery won't charge at all.

So it appears that this fried my AC adapter. While it's (presumably) too late to do anything to fix the adapter, I would like to understand possible causes. Could it be due to the inverter putting out modified sine waves? From looking it up online, modified sine waves hardly look like sine waves at all:

Everything I've found online suggests that a laptop AC adapter should work fine with modified sine waves. I did check with Dell and they advised that I use a pure sine wave adapter, but a modified sine wave adapter would still work, although I was "looking at a possibility of shortening the lifespan of the ac adapter." Shortened lifespan indeed!

Or is it likely that the failure was due to the AC adapter trying to draw more current than the inverter, on a 12 volt, 15 amp DC circuit, was able to provide? I wouldn't have thought that insufficient power could kill an AC adapter... could it?

Or is it a combination of the fact that the inverter was providing modified sine waves, and was perhaps "pulsing" on and off due to the excess current requirements? In my question about topicality on meta, DrFriedParts suggested that the failure might have been due to the input clamp circuit failing. Would the input clamp circuit be more likely to fail if the AC adapter experienced a rapid number of "on/off" cycles?

Getting some education on this will impact what I do next. In reviewing my vehicle's wiring diagram, I see that one of my three DC power outlets is a 20 amp dedicated circuit. I could get a pure sine wave inverter and connect it to that 20 amp circuit, providing a "theoretical" maximum output of 240 watts; I know that in reality there are losses and I can't expect a full 240 watts out of the inverter. If insufficient power was the culprit this time, I'd hate to fry my replacement AC adapter again in the same way! If the root of the problem, however, was a modified sine wave, then I can fix that with a better inverter.


texts: Given specific requirements one usually has a very wide choice of matching microcontrollers. Other than avoiding tags like "not for new designs" and such, is there anything one can do to ensure that the product one chooses is still available several years from now? Are there some manufacturers that are known to have longer lifecycles than others, or is that completely unpredictable in advance? Or is it just that I would have to order huge amounts of the part I plan to use for a long time?


texts:
I have attached the problem and the solution I have for the problem.
Is the solution ok ?
The current through 1kohm resistor will be 9.2mA?
And the remaining current 9.2mA-2.1mA=7.1mA will come from the base right ?
Isn't that too much of current as Ib>3Ic ?


texts: Are small clay capacitors pose any health hazards?

texts: I'm making a small activity with children where we will be using capacitors and resistors to make jewellery like earrings. Do they contain any materials that pose a skin or otherwise health hazard?


texts:
I am designing a circuit using an IC, LTC7004, which is a high-side MOSFET driver. There is one pin (10th) marked as NC.

  NC (Pin 10): No Connect. This pin should be floated.

In my PCB design, I'm pulling out a track from the 8th pin which is the pin to connect the source of a FET as in the figure below.

If I can pass the bootstrap (9th) track over the 10th pin, I can have a wider track for the source connector than the one I currently have.

Since the 10th pin is a no connect pin, will it make a mess if I bend and break away the 10th pin from the IC? (Then I can design a custom foot print to have only 9 pins with the MSOP10 package dimensions). Should NC pins need to be soldered onto a PCB with isolated pads by any means?


texts: what type of armature i should use in 12v dc magnetic 2 pole motor to get more than 8000Rpm

texts:
i m trying to wind a motor but i am new at this so can any one can tell me how can i wind an armature to get more than 8000 Rpm in a 2 pole magnetic motor
of 12 volts


texts: What is a decoupling capacitor and how do I know if I need one?

texts:
What is a decoupling capacitor (or smoothing capacitor as referred to in the link below)?

How do I know if I need one and if so, what size and where it needs to go?

This question mentions many chips needing one between VCC and GND; how do I know if a specific chip is one?

Would an SN74195N 4-bit parallel access shift register used with an Arduino need one? (To use my current project as an example) Why or why not?

I feel like I'm starting to understand the basics of resistors and some places they're used, what values should be used in said places, etc, and I'd like to understand capacitors at the basic level as well.


texts: No port matched and or doesnt connect to anything

texts:
Good evening,
I'm having some issues with some verilog code, or quiet a lot to be honest. Or with Lattice's software actually.. This was tried in Lattice Radiant.
First off, I'm getting these warnings(I know they're called 'error' I moved their severity up to make them stand out more). The other 106 errors are related to the .ldc file statements and some severity list statements missing

but when viewing the netlist analyzer they all seem to be connected.

In the Device Constraint Editor they'll show up as unconnected and I cant assign any pin locations to VSync_In and HSync_In.

It's programmed in lattice Radiant, with atom as the text editor, the selected FPGA is the UP5k-SG48(ice40 board) and the verilog version is 2001. I tried; adding the complete pin declaration in the module definition, removing the 'wire' statements, going with different names and more things I can't remember anymore. But alas, nothing worked so far. I included a trimmed version of the code below, I removed all block which aren't related to the pins or only after another module.
// Made by yours truly with the intention of learning Verilog and VHDL
// The idea is to convert the DMG video output to VGA and optionally even CGB video.
module DMGtoVGA(
    // MCLK,
    RST,
    EN,
    BTN_Down,
    BTN_Up,
    HSync_In,
    DMG_CLK,
    VSync_In,
    Data_In,
    Vsync_Out,
    Hsync_Out,
    B,
    G,
    R,
    spi_ssn
);

/*  SPI-Flash pinout  */
// output wire spi_sck;       //SPI Slave ClocK
output wire spi_ssn;       //SPI Slave Select Negated
// inout wire spi_cs;         //SPI Chip Select ~duplicate of spi_ssn
// output wire spi_mosi;      //SPI Master out, Slave in
// input wire spi_miso;       //SPI Master in, Slave out
assign spi_ssn = 1'b1 ;                   // Disable SPI Flash after configuration

// input wire   MCLK;
input wire RST;
input wire BTN_Down;
input wire BTN_Up;
input wire EN;
input wire HSync_In;
input wire DMG_CLK;
input wire VSync_In;
input wire [1:0] Data_In;
output wire Vsync_Out;
output wire Hsync_Out;
output wire [3:0] B;
output wire [3:0] G;
output wire [3:0] R;

wire    Frame_Sync;
wire    VGA_CLK;     //40MHz VGA pixel clock
wire    CLK_HF;      //internal oscillator output(48MHz)
wire    CLK3DIV;     //Custom devision of the internal HF oscillator
wire    [0:4]PSMode; //pallete selection control input

//Button debouncing
wire Deb_Up, Deb_Down;
FILTER
Up_deb1 (
  .FILTERIN  (BTN_Up),  // I
  .FILTEROUT (Deb_Up)   // O
);
FILTER
Down_deb1 (
  .FILTERIN  (BTN_Down),  // I
  .FILTEROUT (Deb_Down)   // O
);

//Pallete selection
PalleteSelector PS_inst(
    .Up(Deb_Up),
    .Down(Deb_Down),
    .Err(1'b0),
    .MODE(PSMode)
    );

    wire [15:0]DMG_PixelData;
    wire [15:0]VGA_PixelData;
    wire [13:0]VGA_PixelADDR;
    wire [13:0]DMG_PixelADDR;
    wire RAMRDWR_1;
//Decode the DMG input to synced Pixel_Data, any custom pallettes are applied here
DMG_Decoder DMG1_inst(
    .CLK(CLK3DIV), //MCLK
    .RST_n(RST),
    .EN(EN),
    .VSync(VSync_In),
    .Hsync(HSync_In),
    .DMG_CLK(DMG_CLK),
    .Data_In(Data_In),
    .Sync(Frame_Sync),
    .Wren(RAMRDWR_1),
    .Data_Out(DMG_PixelData),
    .Ram_Addr(DMG_PixelADDR)
    );

//PSRAM buffer between VGA and input, should be big enough even for the CGB ':)
//for now only 1x 256Kb bank(32KB is needed)

SP256K SPRAM_inst1 (
  .AD       ((RAMRDWR_1) ? DMG_PixelADDR : VGA_PixelADDR),  // I
  .DI       (DMG_PixelData),  // I
  .MASKWE   (4'b1111),  // I
  .WE       (RAMRDWR_1),  // I
  .CS       (1'b1),  // I
  .CK       (CLK3DIV),  // I
  .STDBY    (1'b0),  // I
  .SLEEP    (1'b0),  // I
  .PWROFF_N (RST),  // I
  .DO       (VGA_PixelData)   // O
);

endmodule

Lol, and this isn't even everything. Apparently, the SPRAM module doesn't want to be initialized. But that can wait, I've been at this for a whole week now and it's getting annoying.


texts: Do I have pseudo three-phase power at home?

texts:
I get three live wires and one neutral from the mains. Different rooms in the house are connected to different circuits which terminate at a changeover panel. The changeover switches allow each circuit to be connected to any one of the live wires at a time. I can even connect all the circuits to a single live wire which puts the entire load on it and no load on the other two.

The power company also randomly switches off one or two of the live wires whenever they feel like it and I must changeover to another live wire.

Is this probably even a three phase system? Are they 120 degrees apart? Could each wire be just one of three independent single phase systems since the power company hase no control over people unbalancing the loads?

I assume it's useless for running three-phase equipment even if it was three-phase since some of the phases are randomly switched off. This is in India.


texts:
I want to use the electric signal from the headphones (2.5mm) of a NOKIA E51 phone as an input to Arduino. My intention is not to process the audio signal but rather to be able to detect when there is a signal, specifically to detect when the phone rings. I want to use this to activate an elektromotor by calling the phone. I am new to arduino so I would like to know to adjust the proper voltage levels so they can be used as an analogue input. Suggestions to what circuits should I use wold very much be appreciated.

Thank you!


texts: Internal oscillator drift and its effect on UART

texts: I am eager to know whether a 150kHz drift of internal oscilator clock (mentioned in a STM32 MCU operating with 8MHz internal clock) could destroy a UART connection?


texts: I was wondering if a Device connected to a speaker via Bluetooth drains more energy while sending high volume compared to the same sound on low volume. This might not be the perfect question for this forum as there might be a more computational aspect.


texts: How long does it take (in seconds) to burn a fuse with high surge current?

texts:
Like the title says, how long does it take in seconds to burn a fuse?
Of course it will depend on what type of fuse and the one
I'm using is 61NM 250V/8A but looking at datasheets I could find
on them, they usually have numbers only up to 200% of rated amp.
My question is, would something like a quick surge current of 50A
that last 1 micro second burn the fuse? Right now, there is a surge
protection before the fuse which when I asked the manufacturer should
kick in in few nanoseconds (which seems little too fast to be honest but)
but I'm wondering even with surge control, if a very short duration but
high current could potentially burn the fuse.


texts: why does household ceiling fan electric motor hum?

texts:
I'm interested in the technical reasons behind why an inexpensive ceiling fan in a home would hum, such that when in your bedroom above your bed on low speed is annoying.

Is there a better type of electrical motor to look for?  My existing fan when new basically did not hum and was satisfactorily quiet at night when on low speed.  Now ~5+ years later it is awful.

All I really know is it's a 120VAC brush less electric motor, can run on 3 speeds (low/med/hi).

What causes this kind of hum specifically?  And is there a way to get a ceiling fan with a specific type of motor that would not be susceptible to a droning hum when on low speed?


texts:
I wish to use a 12v deep cycle battery (I used to use this for my CPAP, when camping) put it on a constant charge, preferably a cheap trickle/float charge circuit, like found at Harbor Freight.

I want this to power two devices:

will run on any voltage between 7v and 12v. (an Arduino UNO)
a 12v liner actuator, that has a max draw of 5A, and will run for just a few minutes, twice a day.

Keeping in mind the trickle charge, and my understanding the battery will run higher than 12v itself, I'm expecting I'll need to regulate the voltage to keep it at or just under 12v.  This is not something I've ever done, and I've spent some time googling it, but there seem to be so many variables in other people's projects, I got a bit confused.

Please advise.  I wish to learn.

The actuator I'm looking at is this:  https://www.amazon.com/dp/B07KPPZP6X but it has no data sheet listed.  The charger:  https://manuals.harborfreight.com/manuals/62000-62999/62813.pdf  Neither of these have been purchased, so I'm not dead-set on these models.   No, not a car door lock.  Application is to close a chicken coop door at night, and re-open in the morning.  Want to use the battery so it still runs in case of power failure.


texts: Why do inductors release a high voltage when disconnected

texts:
I take a 12 volt battery, take a strong electromagnet, and fire it up.

I then touch the two terminals that are currently connected, one terminal of the battery, and one terminal of the electromagnet.

When I disconnect the terminal of the electromagnet to one terminal of the battery, while still placing my thumb over the terminal of the electromagnet and the battery, I receive a little shock.

I know that the inductor releases a higher voltage when disconnected, but why?

•The magnetic field is induced with an inductor with X amount of turns when the battery is connected.

• The battery is now released, and the magnetic field closes down, and induces a current on the inductor with X amount of turns.

Heres where I am confused- both X's are the same amount of turns, therefore a 1 to 1 ratio. Why are different voltages present with the same voltage source, a 12 volt battery?


texts: Direct connecting 5v relay interface board to usb

texts:
I'm absolutely noob in electronics but I have this relay and I want to connect it to USB.
When PC switches on usb VCC has +5v. Can I connect USB VCC to Relay Board "VCC" and "IN" wires to open relay (and GND to GND)? I need open relay when PC switches on and close relay when it switches off.

upd:
1-Channel Relay interface board info:

Each one needs 15-20mA Driver Current
Equiped with high-current relay : DC30V 10A AC250V 10A
Standard interface that can be controlled directly by microcontroller (Arduino , 8051, AVR, PIC, DSP, ARM)


texts: Detecting the type of surface/medium a robot is on top of

texts:
I am looking for a way to detect what sort of terrain a bot is travelling on. To keep it simple lets start with grass vs sand vs tarmac.

It is to be used with arduino, and for a hobby project so cant cost an arm and a leg. I figured it could be done with a camera but hoping to find a better way. maybe with sonar or something.

tx

Edit:
Im taking this info to do some more research on the problem. Will be back with some more info and hopefully and answer. i think bouncing light/sound off the ground and somehow measuring the amount reflected/absorbed, maybe with the color filters to aid the readings as the start.

1) I think this is a start. http://embedded-lab.com/blog/?p=1671 sending out light and reading how much has been returned. that would just be picking up the highs and lows.


texts:
Hello All ,

In the Above circuit , TL431 is used to regulate the output voltage which is set by resistors RH1 and RL1. resistor RB is bias resistor to provide the current to regulate the output whenever output is not at rated value. the purpose of capacitor CF1 and RF1 is not getting understood. when Vout goes down will the CF1 provide the bias current to the TL431 ? whats the application of CF1 and RF1 here . kindly help me understand this .


texts: I'm interested in building AM and FM radios from discrete components. Has anyone ever used an RLC meter to precisely create the inductors and other elements used in these radios? I know cheaper RLC meters measure parameters at 1kHz to 10kHz (100kHz if lucky). Is this still applicable and useful in trying to create the right components for the radios?


texts: Motor that has at least 50in-lbs of torque and 200RPM

texts:
I need a motor that has at least 50in-lbs of torque and turns 200 times in one minute (200RPM)

THIS screw driver has inside the motor that I need.

I do not want to buy the electric screwdriver I posted on the link because I only need the motor.

When searching for DC motors on the internet I am not able to find a motor with 50in-lbs of torque.
50 in-lbs = 6 Nm = 57 kg-cm

What could I be doing wrong? Do I have to search with a different criteria? The motor that I have found with most torque and that size is THIS one:

That motor has 1/3 the torque of the electric screwdriver. It also spins 4 times slower (50 RPM). The price is doubled. Am I reading the specs wrong? Where can I find a motor that has 50in-lbs of torque and is not that slow? What do I have to search for?


texts: Is it safe to use a lower rated cable to power a higher amperage device if it isn't constant?

texts:
I'm designing a breakout kit for an open source standalone ECU. The ECU has a 40 pin IDC male socket which has all the pins required to run the engine.

One of the components will be injectors which use around 3 - 4 amps. Each injector actually uses two of the pins to help with the load. The only 40 pin, 1.27mm ribbon cable I can find for a reasonable price is rated at 28awg. 26awg is apparently recommended.

Now since each injector will only fire for a fraction of a second, every second, is there any issue to using 28, or even 30awg wire?


texts:
So I have aquired 1 light of a traffic light that I salvaged from a local dump. I want to try and connect the light to use it like a lamp, however I am a little worried by it as the connector only has live and netural wires.

Basically I want to know if it is possible to earth the system or is it safe without earthing? I read into double insolation but cannot tell exactly how it works.

Sorry if this is very basic or been answered somewhere else, I wasn't exactly sure of how to find an answer.


texts: Linear regulator operating point over input DC Sweep analysis

texts:
I'm sweeping the linear regulator input voltage on DC using Spice from 0V to maximum expected Vin. However, as the OTA that makes part of LDO is internally supplied by the output voltage, the simulation will never turn on the OTA and it will find a very stable point of operation in 0V. it is like the dilemma of chicken and egg.

How I could force to start the OTA and calculate the minimum input voltage required to work properly?

Thanks


texts: Identifying this USB-A female to something connector

texts:
I have this USB-A female connector which has three pins on the other side (images attached). Need help identifying what type of interface that is.

My best guess for now is that it is either a 3 pin mini DIN connector or a 3 pin mini XLR connector, but I do not know for sure. If possible, a link to where I can find them would also be greatly appreciated.


texts: UART Issue - Communication stops working when board reset button is pressed

texts:
I am using a NUCLEO-F401RE board as a master and a B-L072CZ-LRWAN1 as a slave communicating over UART.

Slave is configured to receive in interrupt mode using HAL_UART_Receive_IT.
Master is programmed to request data to the slave with a blocking function using HAL_UART_Transmit inside a timer interrupt callback.

Master is asking for data to slave every minute and the protocol is working fine, but I want the code to work no matter what happens with the boards, so I am turning off both boards (one at a time) to see if everything works fine when they turn on again (to recover from any sort of error in the system).

Communication between them stops working when I turn off the slave (let me explain). If master tries to communicate when slave is off, it gets stucked in HAL_UART_Transmit function so even when I turn on slave, communication never happens again.

Does anybody knows what is happening?

Here is pin configuration:

Master

/**USART1 GPIO Configuration
PA9      ------> USART1_TX
PA10     ------> USART1_RX
*/
GPIO_InitStruct.Pin = GPIO_PIN_9;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_10;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

Slave

/**USART1 GPIO Configuration
PB6     ------> USART1_TX
PA10     ------> USART1_RX
*/
GPIO_InitStruct.Pin = GPIO_PIN_6;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
GPIO_InitStruct.Alternate = GPIO_AF0_USART1;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_10;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
GPIO_InitStruct.Alternate = GPIO_AF4_USART1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);


texts: Other ways to solve this other than Delta Star Transformation

texts: I solved this using delta star transformation (Zeq = 2/3 ohm), but I can't find other circuit analysis techniques to find the Zeq & Io, any help?


texts: Are "functional units" the same as "issue slots"?

texts: I study computer hardware and a multiple issue system. I'm told there are "four functional units" but I don't understand what that means.


texts:
I am trying to pick a wifi module that would fit what I am trying to accomplish. My application is pretty basic: I have an application on a IPad/tablet that communicates over wifi to my product. Basically it is just a wireless wire not connected to a router or anything else, just direct communication to my end product.

I've been looking at a CCC3120MOD which seems to fit but it looks to have a lot more then what I want compared to what I am using it for.

First do you think i should use WIFI at all, sinc I am using it for is a direct connection?
Should i maybe go with a bluetooth module using SPP instead?

Any input is appreciated, thanks.


texts: Interpreting bode plot of type 3 compensation network for buck regulator

texts:
I'm struggling to design the type 3 compensation network for a simple buck PWM controller. The controller is a Richtek RT8110B. According to the datasheet, half of the type 3 network is in-built and cannot be changed:

Note Rs, Cs, and Cp are internal. So my first step was to analyze the stability of the controller without the "optional" C3 and R3. My background in basic control theory is very spotty, so please point out if I'm approaching this way off base.

The poles and zeros are given in the datasheet: a zero at \$F_{esr}\$, a zero at \$F_{z1}\$, a complex conjugate pole pair at \$F_{LC}\$, and a pole at \$F_{P2}\$. Since I'm leaving out the optional C3 and R3, I don't believe I need to consider \$F_{p1}\$ and \$F_{z2}\$ at this time.

My inductor is 15uH, Cout is 100uF, and capacitor ESR is 1mOhm. Based on these components, I came up with the following values for the poles and zeros:

\$F_{esr} = 1.6MHz\$
\$F_{z1} = 796Hz\$
\$F_{LC} = 4.1kHz\$
\$F_{p2} = 319.1kHz\$

Using Octave (a Matlab clone) I used the zp2tf function to translate zeros and poles into a transfer function:

[n d] = zp2tf([Fesr Fz1],[FLC -FLC Fp2],1);
H = tf(n(length(n):-1:1),d(length(d):-1:1)); //zp2tf() outputs the coefficients in reverse order to the way tf() expects them

which gave:

      1.23e+09 s^2 - 1.601e+06 s + 1
H:  -----------------------------------------------
      5.364e+12 s^3 - 1.681e+07 s^2 - 3.191e+05 s + 1

And finally, this Bode plot:

The main thing that stands out to me is the crossover frequency is very nearly 0Hz. In fact, everything interesting in the bode plot happens before 0.1 rad/s. It makes me think I did something wrong in my procedure. Or is this behavior perfectly acceptable?

Also, what does it mean when the Phase plot never crosses 180 degrees? Does that mean the gain margin is infinite? What's the physical interpretation of that?


texts: What to focus on when looking for a good GPS Antenna?

texts:
I am using external active GPS antennas for my application.  These Antennas typically have 5m cable with SMA connector that connects to the receiver, while the Antenna is mounted outside.  The receiver I am using a U-Blox type module with a built-in LNA and SAW filter.  However, the Antenna also includes a single (sometimes 2-stage) LNA and usually a filter as well.  The Antenna is magnetic mount and placed on top of a vehicle roof (assume its metal).

In terms of what to look for in an Antenna, I have found that in general most of these Antennas have the following baseline specs:

Antenna Gain:  5dBic (zenith)
Antenna VSWR:  1.5
Antenna Axial Ratio:  3dB (max)
LNA Gain:  28dB
LNA Noise Figure:  1.5
LNA VSWR:  2.0
Filter Insertion Loss: <3db

However, I could purchase more slightly expensive antennas, which change the specs to:

Antenna Gain:  2dBic (zenith)
LNA Noise Figure:  1.0
With everything else the same.

I also have the choice of omitting the SAW filter in the antenna, and thus avoiding a potential 3db insertion loss of a filter.

In general antennas have excellent directivity.

My goal is to maximize signal to noise and maximize satellite reception.

Which Antenna would be a better choice?  Would the second antenna yield better performance?

Which of these fields are more critical?


texts: I am currently using Vivado to develop several FPGA designs, and I am wondering if the components numbers given during Synthesis are optimal. I mean, are there some ways to optimize the synthesis, in order for example to reduce the number of LUT or FF used by the FPGA ?


texts: Typical half-wave dipole antenna parameters

texts:
From my bachelors degree, I have learnt the fundamental theory behind antennas. One of the main types is the half-wave dipole antenna. We've studied its radiation pattern (isotropic) and how it varies with the elevation angle. But we never used practical values (we didn't have labs on this).
The theoretical aspects behind its radiation pattern were the following equations:
$$
\widetilde{E}_{\theta }=\frac{jI_{0}lk\eta_{0} }{4\pi }\left ( \frac{e^{-jkR}}{R} \right) \mathrm{sin} \theta
$$
$$
\widetilde{H}_{\phi }=\frac{\widetilde{E}_{\theta }}{\eta_{0}}
$$
Where \$I_{0}\$ is the current within the antenna; \$ l \$ the length of the antenna, \$k\$ thewavenumber, \$R\$ the distance from the antenna; \$\theta\$ the elevation angle; \$\eta_{0}\$ the intrinsic ipedance of the medium (usually free space); \$\widetilde{E}_{\theta }\$ the electric field phasor; and \$\widetilde{H}_{\phi }\$ the magnetic field phasor.

\$\widetilde{E}_{R }\$ is assumed to be negligble. Also:
$$
\widetilde{H}_{R }=\widetilde{H}_{\theta }=\widetilde{E}_{\phi }=0
$$
The average power density at a given point is given by (using the Poynting vector):
$$
\overrightarrow{S}_{av}=\frac{1}{2} \mathrm{Re}\left [\widetilde{\overrightarrow{E}} \times \widetilde{\overrightarrow{H^{*}}} \right ]
$$
My question is what are typical values for \$I_{0}\$, and other parameters, specifically for \$2.45 \mathrm{GHz}\$?.
I want to use this to approximate radiation density of these antennas:

2.45 GHz antenna 1
2.45 GHz antenna 2


texts: Understanding this 8Mhz on-off keyed reception circuit

texts:
This circuit takes an 8Mhz on-off keyed signal and down converts it to 128kHz double ended for an analog front end. "MIXER CLK" is 8.192kHz

One thing I don't understand is why the "Enable RX" turns on an npn transistor and pulls the receive antenna (Cap. PAD) through 100ohm to ground. Wouldn't this kill the weak 8Mhz signal? What does the C33 cap do? How does the pi network convert the signal from single-ended to 2 signals? What are these signals now? I have been asked to copy this signal chain but there is so much I don't understand about this circuit.


texts:
I need to use a SN754410 motor driver with a 4.5V microchip and 12V motor all running on batteries.

I want to power the microchip with 3x1.5v AAA batteries. The motor requires 12V and I want to use a larger 12V battery for this.

I'm reluctant to use a voltage regulator because testing the voltage drop from 12V to 4.5V I seem to use excessive current converting the voltage when the microchip is doing nothing.

Here's where I'm confused - do I need to connect the two ground (-ve) terminals of the 2 sets of batteries together?

Picture attached from the SN754410 data sheet.

image of circuit http://jimsrobot.com/wp-content/uploads/2013/2-battery.jpg


texts:
My dsPIC33FJ128GP706A is being powered by a PICkit 3 at 3.19V. I can program the chip perfectly - it is recognised by my programmer.

I felt it and it is quite warm. Not hot, just warm. I measured using my infra-red thermometer and it is at 37°C in a room which is around 23°C at the moment. Not anywhere near the limit, but I'm curious as to why it is getting warm. Is it normal? Or is there a problem on my board? (which is rather poorly soldered.)

The Vcore voltage measures at 2.58V, which is within the allowed tolerances. It's being powered from the dsPIC's on-board LDO.