texts: What Formality Am I Using To Isolate This Portion Of The Circuit?

texts:
If I have this circuit in which the switch opens at t = 0 (after being closed for an infinite time, making the circuit steady state), for which I'm trying to find the voltage across R2 as a function of time, I need to determine the current through the inductor as a function of time first. To do this, I need to find the initial current through the inductor. (ignore element values)

simulate this circuit – Schematic created using CircuitLab

I can replace the inductor with a short circuit and use circuit simplifications to reduce the circuit to the following. This is before the switch is opened at t = 0, and use the current through this circuit as the initial current through the inductor.

simulate this circuit

After t = 0, my gut tells me I can simplify the circuit into two parts, one containing the inductor, and the other without.

simulate this circuit

What law states I can do this? Is it because opening the switch means there are no current loops between either side of the circuit?

Thanks for your help!


texts: How does this circuit work with a transitor?

texts:
If the current flows from the left side of the circuit namely positive side
Why doesnt the led burn as the resistor is placed after the LED or if flows from the negative side.Where does the base of thw transistor get current?


texts: Why event flag related functions does not work correctly outside of tasks in keil rtx?

texts:
As you know event flags are very useful (e.g. let task running),but unfortunately their control functions (os_evt_clr/set/wait) does not work outside of tasks bodies correctly(e.g. in interrupt handling functions). For alternative I used a variable ,I initialized it in Interrupt handler when needed ,then used it on another task to running a os_evt_set() function for let MCU entering a task.

    bool Instance_Variable;

    Interrupt_Handler()
    {
    if(xxxx)
    Instance_Variable=1
    }
//--------------------------
    Secondary_Task()
    {
    //This is frequently run task
    if(Instance_Variable==1)
    {
    os_evt_set (0x0001, Primary_Task_ID);
    Instance_Variable=0;
    }
    }
//--------------------------
    Primary_Task()
    {
    Result = os_evt_wait_or (0x0001, 0xFFFF);
    //Task's body
    os_evt_clr (0x0001, Primary_Task_ID);
    }

Any better approach?WBR.


texts:
I have ILI9486 based tft display to initiate via 16bit FSMC. I did gpio, fsmc, and lcd initialization.

    // Interface Mode Control
    LCD_WRITE_CMD(0xb0);
    LCD_WRITE_DATA(0x00);
    // Interface Pixel Format, 16 bits / pixel
    LCD_WRITE_CMD(0x3A);
    LCD_WRITE_DATA(0x55);
    // PGAMCTRL(Positive Gamma Control)
    LCD_WRITE_CMD(0xE0);
    LCD_WRITE_DATA(0x0F);
    LCD_WRITE_DATA(0x1F);
    LCD_WRITE_DATA(0x1C);
    LCD_WRITE_DATA(0x0C);
    LCD_WRITE_DATA(0x0F);
    LCD_WRITE_DATA(0x08);
    LCD_WRITE_DATA(0x48);
    LCD_WRITE_DATA(0x98);
    LCD_WRITE_DATA(0x37);
    LCD_WRITE_DATA(0x0A);
    LCD_WRITE_DATA(0x13);
    LCD_WRITE_DATA(0x04);
    LCD_WRITE_DATA(0x11);
    LCD_WRITE_DATA(0x0D);
    LCD_WRITE_DATA(0x00);
    // NGAMCTRL (Negative Gamma Correction)
    LCD_WRITE_CMD(0xE1);
    LCD_WRITE_DATA(0x0F);
    LCD_WRITE_DATA(0x32);
    LCD_WRITE_DATA(0x2E);
    LCD_WRITE_DATA(0x0B);
    LCD_WRITE_DATA(0x0D);
    LCD_WRITE_DATA(0x05);
    LCD_WRITE_DATA(0x47);
    LCD_WRITE_DATA(0x75);
    LCD_WRITE_DATA(0x37);
    LCD_WRITE_DATA(0x06);
    LCD_WRITE_DATA(0x10);
    LCD_WRITE_DATA(0x03);
    LCD_WRITE_DATA(0x24);
    LCD_WRITE_DATA(0x20);
    LCD_WRITE_DATA(0x00);
    // VCOM Control
    LCD_WRITE_CMD(0xC5);
    LCD_WRITE_DATA(0x00);
    LCD_WRITE_DATA(0x00);
    LCD_WRITE_DATA(0x00);
    LCD_WRITE_DATA(0x00);
    // Power Control 3
    LCD_WRITE_CMD(0xC2);
    LCD_WRITE_DATA(0x44);
    // Memory Access Control
    LCD_WRITE_CMD(0x36);
    LCD_WRITE_DATA(0x08);
    // Set rotation
    DIRECTION(0);
    // # Sleep OUT
    LCD_WRITE_DATA(0x11);
    DELAY(500); // ms
    // Display ON
    LCD_WRITE_DATA(0x29);

Mem. regs:

CMD: 0x60020000
DATA: 0x60000000

Timings:

  Timing.AddressSetupTime = 2;
  Timing.AddressHoldTime = 0;
  Timing.DataSetupTime = 5;
  Timing.BusTurnAroundDuration = 0;
  Timing.CLKDivision = 0;
  Timing.DataLatency = 0;

Wiring is double checked. NE1 is CS, RS -> A16, Reset set high.

The problem is that the display seems to be ON after all (gray background), but it's not possible to draw anything on it.
Practically, doing DRAW_SOMETHING(...) the display just flashes and turns bright gray. I have checked every command and absolutely have no clue why this could happen.
Any help highly appreciated
thanks ~

----------------------[UPD]

correct memory addresses:

CMD: 0x60000000
DATA: 0x60020000


texts: Should right angles at pads be avoided in traces on a PCB?

texts:
I have been told that traces shouldn't bend at 90 degrees or less, because electrons get trapped in those angles. Does the same also hold for when traces meet at pads?

Is the left pad in C2 troublesome?


texts: How can I achieve 5V DC from 230V AC wirelessly?

texts:
I want to step down 230VAC so that I can have a large amount of current that I can transmit wirelessly through the transmitter coil to the receiver coil.

I want to transmit it across 5millimetres between a transmitter and receiver.

Radii of the transmitter and receiver can be at-least 4cm and 2cm respectively.

After transmitting it to the receiver coil, I'm going to rectify it so that I can have a certain amount of DC voltage.

After rectifying the amount received, I'm going to filter it.
Then regulate it to 5V DC and feed it to the battery.

PROBLEM

I want 5V DC at the end of the circuit, but how can I accomplish that ?

What calculations and equipment specifications do I have to use so that I can figure this out?


texts: Home Current Meter - is this a good solution?

texts:
I want to build a simple current meter to measure my power usage at home, and have the data sent to my blog's database. (I know there are similar solutions out there, but this project seems engaging for me to try on my own.)

Is the following specific workflow a viable solution?

A current clamp clips around the incoming mains power + in the breaker box.
A small processor nearby receives input from the clamps and determines power usage. (this will be by the breaker, any idea how to get power to it easily? And I'm thinking about using an arduino unless there's a better solution, thoughts?)
This small computer communicates over the home's wifi and sends my blog's database information at regular intervals.

Is there an easier/more effective way to send my blog power usage data from the whole house?


texts:
I downloaded the driver to connect to mbed via USB. I flashed a serial communications example program on the mbed board.

I've connected to it via Tera Term, at 9600 baud, 1 stop bit, no parity, and 8 data bits. I've also selected LF for Receive under terminal setup.

mbed is hooked via its standard program loading USB. Can I not use this one? I made it printf to both USBSerial serial, and Serial pc(USBTX, USBRX).

Is my mbed device dead? Or am I missing something?

USBSerial serial;
Serial pc(USBTX, USBRX);

int main(void) {
   uint8_t buf[128];
   pc.baud(9600);
   while(1)
   {
       serial.scanf("%s", buf);
       serial.printf("recv: %s", buf);
       pc.printf("recv: %s\r\n", buf);
   }

}


texts: ADS (Advanced Design System) Simulation to fit experimental data

texts:
I am a noob on ADS software. I was just wondering, if I have a given set of measurement data like the following:
And I know a equivalent RLC circuit model for my device, from literature. How do I optimize the RLC parameters in ADS so that the simulated output (say input impedance) can fit my experimentally measured data the best?
Thank you!


texts: A simple Arduino Uno HC-05 system doesn't work

texts:
I have an Arduino Uno, HC-05 module and an LED.
I want to connect the HC-05 to my phone and with an app be able to turn on and off the LED and at the same time sending a message from the Arduino to the Phone that the LED has been updated.

I have built this circuit: (But Rx is pin 12 and TX is pin 13 and with 1kΩ and 2kΩ resistors instead)

The HC-05 blinks properly (so I assume it's not broken).

Here's the Arduino code:

(I tried to put the code using the code sample button but it didn't work properly sorry)

Now, I have two problems with the system:
- bt.println(...) should send text to the phone but the phone side doesn't receive anything.
- Serial.println(LEDState) should print what the phone has sent to the Arduino and it does but it is all ASCII characters and are printed on new lines.

I believe the problems are connected with the baud rate but I tried using 9600, 38400 and both mixed but it doesn't work. I also tried reversing the places of Rx and Tx in the SoftwareSerial initialization.


texts: Identification of unknown peltier element

texts:
I recently found an old, unused peltier element in our lab, with dimensions 40x40x4 mm³. Unfortunately, no type number is visible on it. By connecting it to a power supply I could identify the hot and cold side, but I do not know anything about the maximum current and voltage. Unfortunately, due to a lack of camera I can not add a picture of it here.
Based on other equipment used in the lab I suspect that it could be one of the elements listed here: https://customthermoelectric.com/products/thermoelectric-coolers-tecs/standard-tecs.html?dim_a_group=10&dim_b_group=17
but none of the elements there fit the dimensions.
Are there other approaches to determine the maximum voltage/current and the maximum power of the element?


texts: 5V Relay and Arduino to control a 6v nerf gun

texts:
I am super confused how to hook up this relay
http://www.radioshack.com/product/index.jsp?productId=2062480

The nerf gun has a  spdt switch for the trigger and runs on 4 AA's .


texts:
I would like to have a RTC alarm turn on my arduino at a specified time each day. I know that Arduino has good sleep modes but I'm concerned even with the quiescent power consumption from the voltage regulator due to feeding Arduino with 9V (this is my only option). My preference is to completely shut off the arduino board by removing all power to it.

So my thought is to use a RTC that has an alarm to somehow trigger the Arduino to turn on. I'm completely unfamiliar with MOSFETS and relays but I think these are options for my problem.

Does anyone have any suggestions?


texts: Adding wires to existing board. Not sure where to solder them

texts:
I'm trying to modify a small USB keypad to attach a foot switch to it, that would trigger the enter key.

I disassembled the keypad and figured out which pins I need to contact to make an enter keystroke. It's the 8 and 7 in the image below.

I need to attach wires to these pins (two separate wires, connected to a jack port). Now, I have never ever soldered anything in my life, so I'm not sure what's my best option here.

The 11 soldered pins you see are about 1,5/2mm wide each, so I'm afraid trying to solder there would end up in me soldering two of these pins together.

There is also the other flat areas, but can I solder something there? Will it hold, and will it not melt the board's coating?

Any other options I'd have missed?

Here's the backside of the board, the pins you see on the front come from the black connector in the bottom left.

And, for those interested, here's the contact sheet of the keys:


texts:
I am an electronics hobbyist and this is my first attempt at an analog circuit of this type. Mostly I stick to arduino and LED stuff or just wiring up kits, etc. This is my first attempt at designing a "real" circuit. I think I have a really good start here, maybe my circuit would even work great without any modification. I have a kit for DIY chrome plating and need a power supply for the chrome bath. It requires very high currents (.75-1 A per sq in surface area of item to be plated). You can of course buy these power supplies off the shelf, but they are extremely expensive for anything that can put out more than 20-30 A. The items that i would like to plate will require 50-60 A. The chrome plating portion of the process only take 2-5 minutes though. So this circuit will only be running for that amount of time. I wanted to see if anyone had any tips or input for what I have so far before I start building. I have all of the components in the schematic and have done a few small tests but have not fully assembled everything and run it. I only have basic circuit test equipment like a DVOM. Here is the schematic.

EDIT: This MOSFET is not rated for linear operation and is not a good fit for this application. I am looking for MOSFETS that would work but I'm not sure what to look for. I can only find one line of products made by IXYS that is specifically stated that it is designed for linear use.
EDIT #2: This datasheet is for a MOSFET that is used by another person to make a very similar circuit https://m.littelfuse.com/~/media/electronics/datasheets/discrete_mosfets/littelfuse_discrete_mosfets_n-channel_linear_ixt_90n25_datasheet.pdf.pdf
This is the link to the project: http://www.kerrywong.com/2017/01/15/a-400w-1kw-peak-100a-electronic-load-using-linear-mosfets/
The MOSFET IRF2804 is something that I have 8 of from taking things apart and saving their components. It's rated for 75 A and 300 W (with a huge heat sink)
The TC7650 is just there to amplify the voltage from the shunt up to a usable voltage so that I can measure the current with an arduino and have it display that on an LCD. I also thought that it would make the 100k pot have an easier time adjusting the input voltage if it was adjusting from 0-5 V rather than 0-.075 V. In the data sheet you will notice that you are supposed to have two 0.1 uF capacitors with it also. I have them but I couldn't find a schematic symbol with the correct number of pins so I left them out in the picture, but I do have them in the circuit.
I went through my resistor bins and measured them all to get as close to the exact numbers as I could find. The values in the schematic are from my measurements. I was trying to get the gain on the TC7650 so that I could use the max output voltage swing without clipping it.
Oh, also chrome plating really like very smooth DC current with very low or zero ripple for the best adhesion and smoothness which I think is what makes the power supplies so expensive. I lot of people have used a car battery in the past with good results and in the old days they would use a salt water rheostat to control the current. A lot of folks commented that it was not very fun to keep the current stable and the plating was very difficult with that method, so I thought I would try this circuit.
Here are the data sheets for the parts.
https://www.infineon.com/dgdl/irf2804pbf.pdf?fileId=5546d462533600a4015355de76f818e3
http://ww1.microchip.com/downloads/en/DeviceDoc/21463C.pdf
https://www.ti.com/lit/ds/symlink/lm324-n.pdf?ts=1591077649948
I also have a giant heat sink and thermal paste and I was thinking that I might put a TEC on there too just for good measure and since I have some 12V 60W peltiers.


texts: Integral and Derivative terms in PID control

texts:
Integral Term
My understanding of the integral term is: Sum of all errors since we started counting.
So, even though we have reached our desired final target position, the integral of the errors should be high (no?) since we started adding all the errors from when we were in our initial position.
And if the Integral term is high at our target position, the controller would still be continually ramping up...? [I understand that the Integral term's value will be a constant at this point since the error is 0. But, would it not still be a high value?]
Derivative term
Say, we are in time instance t1. Can I predict the rate of change for a specific time instance, say t20, and then apply this parameter to the current state? Is that how the derivative term works?


texts:
I am trying to understand the internal circuit schematic of the LM565 phase locked loop IC, on page 6 of this datasheet: PDF Datasheet for LM565 from TI website

In the upper middle, there is a strange little symbol labeled "Q13". Here is a screenshot:

It looks like a PNP BJT, but I am not sure what it is exactly. Can anyone give
me a pointer.

Also, this schematics has quite a few BJT with unconnected pins. I assume that
this is when a BJT is used as a diode, but if someone could shed some light I'd appreciate it.


texts: Measuring phase difference between digital signals

texts:
I have been struggling for some time to come up with a meaningful way to test the phase difference between two quadrature channels of an encoder. I have access to a DPO 2014B Tektronix scope and have been trying to come up with a way to make it do what I want, but have had no such luck.

An ideal quadrature encoder should have 90 electrical degrees of separation between any of its subsequent quadrature edges (A high to B high, B high to A low, A low to B low, or B low to A high). Ch. 1 is A and Ch. 2 is B in this case (see below).

As we all know, the ideal case typically isn't the observed case. The encoder under scrutiny has a specified edge separation that it must meet and I am interested in measuring the smallest of those to ensure it meets the specification set forth. The encoder has 1024 cycles (so 4096 edges) per mechanical revolution. The third channel contains the index pulse which occurs once per mechanical revolution.

That being said, first let me explain the two methods I have tried so far:

Configure the cursors to the known value for the specification that must be met and physically check each set of edges. This method works, but with so many edges to check is highly impractical.
Use the phase difference measurement of the scope. I had high hopes for this one, but after some back and forth with the support team at Tektronix, found that this actually only measures the average phase difference between the first two pulses on the screen. This is signified in the picture by the two sets of vertical lines to the left of the screen.

I would be fine with not measuring the ABSOLUTE smallest edge separation between all of the edges, but I at least need something that could either come up with an average value, or can sample randomly across the entire waveform.

Does anyone have any ideas? Thanks in advance!


texts:
I am trying to build a LC oscillator based on LM393 open-collector comparator, but am having some difficulties. This is the current circuit:

I was expecting to get a nice square wave with one frequency like this:

But insted I got out something like this:

This is just an approximation, but the thing is it contains two different frequencies of oscillations.

My question is, how can I design a square wave oscillator so it will produce only one expected frequency of oscillations? What am I doing wrong here?

Thanks in advance!


texts: Create a simple resistive heating element on PCB with Altium

texts:
I have created a component with a simple pattern using tracks and arcs as shown in the link below.

How to Build Custom PCB Heater Elements

However, Altium DRC is throwing errors since I have used 2 different pads on both the ends of the element track/arc, which are used to power the element.

Can anyone shed some light on how to make a proper resistive element heating component?

Thanks


texts: Connecting PCB power planes and polygons

texts:
i am making a 4 layer PCB board and in that the inner two layers are ground planes between top and bottom signal layers. I want to know do i have to connect the top layer(signal layer) with ground plane (layer 2) and bottom layer (signal layer) to ground plane (layer 3)?
second thing i am very confused about polygons is that e.g if a have a two layer board (only top and bottom signal layers) and i use a polygon on top layer and connect it to ground of top layer, do i need to route/connect ground pins/pads on top layer of my PCB or they will automatically connect to ground polygon on top layer and become grounded??
last thing is if i am routing a board and used ground planes in it. is there a need to add polygon??


texts: Making a phantom powered power switch (not mute switch) with LED indicator

texts:
I want to create an XLR inline power switch (with indicator) so that I can turn my phantom powered microphone on and off as I please!

I have found a few guides online that explain how to create a mute switch, but I'm not sure that will work for what I require.

I've read that an XLR cable has 3 pins, and that you run all of the pins to themselves, 1 - 1, 2 - 2 and 3 - 3 and then you mute the microphone by making a connection between pin 2 and 3, and this shorts the microphone and disables the audio. So this means that when the switch is on, the microphone would be muted.

I want to add one of these these inline to the XLR cable and how I want it to work is that when the switch is on, the microphone and LED on the switch are both on, then when you switch it off, they both turn off.

How would I go about wiring the switch so that when it's in the on position, pin 2 and 3 are disconnected, and then when I switch it off, pins 2 and 3 connect and it shorts the microphone and turns it off?

I'm an absolute novice at electronics, I've learned everything above from researching so absolutely any help would be appreciated!


texts: Understanding the capacitors in an op amp circuit

texts: I am a computer programmer forced to make some circuits for a Langmuir probe our lab is making (the main task is programming the analytic software on the computer, but I have to make a basic amplifier circuit as well). Below is a circuit made by a colleague of mine for a similar problem that I'm basing my work on. I understand everything except for the capacitors. Are they for decoupling, or filtering, or what? Any help would be appreciated.


texts:
I'm learning to use Verilog in a digital systems course. I have a question about value propagation.
I'll use the example below to ask my question.
module sampleModule
   reg a,b,c;

   not g1(d,b);
   and g2(e,a,d);
   and g3(f,c,e);

   initial
      a=1;b=1;c=0;

endmodule

I want to verify that my understanding of Verilog is correct: What I believe will happen right after time=0, when registers a, b, and c are loaded with the appropriate values is

Verilog will notify g1,g2,g3 that the values of registers a, b, c have changed.

In some indeterminate order
g1 will update its output value, d.
g2 will update its output value, e.
g3 will update its output value, f.
Gates will continue updating values until all are stable.

First off, is that right? Secondly, in the example above, the values will eventually stabilize, so Verilog is "happy" to update output values in any order. However, what if such is not the case and Verilog is given a   poorly arranged feedback loop that alternates infinitely between two values? I understand that one can delay output propagation, but if not properly arranged, how does Verilog deal with an arrangement that should theoretically behave this way?


texts: Where is the boost converter in Cypress PSOC 5LP CY8CKIT-059 Prototyping kit?

texts:
I have been using the boost converter (dc-dc converter) of "PSOC CY8CKIT-050 development kit" for a time, but I wanted to use the one in PSOC CY8CKIT-059. Nevertheless, I didn't find the boost converter in the schematics (schematic), thus I don't know where measure to check its behaviour. I thought that this PSOC hadn't a boost converter, but when I programm it in PSOC creator, I can add a boost converter as usual, so I suppose it has one.

I hope someone can help me. Thank you for your answers.


texts:
I have read in a few places about Atmel's support of program traces on their high-end debugger/MCUs. It seems to be that some of the AVR32 processors can be 'traced' by the AVROne! programmer/debugger. See here or this pdf for mentions of the feature.

Initially I thought this was an atmel specific feature, but after reading more it seems that their nanotrace implementation is atmel specific while the concept of a trace is common to many high-end microcontrollers.

Could somebody explain to me what this is, why it it would be more useful than traditional debugging techniques like logging debug over UART or instruction level stepping, and provide some resources on how to use such a feature? I don't care so much if the resources are for the atmel chips I mentioned as I don't plan on actually using the feature in the near future, I just want to be educated and aware of what it can do.


texts: External power for Raspberry Pi USB device

texts:
The Raspberry Pi's USB ports can only supply about 100ma of 5V current; this comes directly off the 5V input power to the board.   The usual solution is to use a powered hub to support devices that need more of that, but I have an application where I have a single USB device, and want to keep the setup as simple as possible, as it will be in an enclosure with other equipment.

Comments in this question seem to suggest that a setup like this would work:

since both devices were being powered from a common source; I'm planning to try this with a USB charger with two jacks and and a cable like this, hoping I can carefully open the cable and identify VCC and snip it.

Is there anything else I should be aware of?


texts: Can't seem to figure out equations in Mesh Current Method

texts:
So I've been tasked to use the Mesh Current Method to determine the currents in different meshes using SageMath, and then compare the values with those obtained in Qucs. My problem is that SageMath is not giving the expected values, and therefore I think my equations are wrong. However, I can't figure what exactly is wrong with them...

This is my circuit (From Qucs), alongside with the results obtained for the current going through each probe, from the simulation :

Meshes are indicated by Red Numbers.

And these are my equations:

$$
EQ_{M1} : (I_1 - I_2)R3 + (I_1 - I_3)R1 = IV_{cc1}
$$
$$
EQ_{M2} : (I_2 - I_4)R2 + (I_2 - I_1)R3 = V_{cc1}
$$
$$
EQ_{M3} : (I_3 - I_1)R1 + (I_3 - I_5)R6 + I_3R9 = 0
$$
$$
EQ_{M4} : (I_4 - I_2)R2 + I_4R4 + (I_4 - I_6)R7 = 0
$$
$$
EQ_{M5} : (I_5 - I_3)R6 + (I_5 - I_6)R10 + (I_5 - I_7)R8 + I_5R13 = 0
$$
$$
EQ_{M6} : (I_6-I_4)R7 + (I_6-I_5)R10 + (I_6-I_8)R5  = IV_{cc2}
$$
$$
EQ_{M7} : (I_7 - I_5)R8 + (I_7 - I_8)R11 = V_{cc2}
$$
$$
EQ_{M8} : (I_8 - I_6)R5 + I_8R12 + (I_8 - I_7)R11 = 0
$$

Where $$ I_n $$ is the current at mesh n and $$ IV_{ccN} $$ is the current going through Vn.

Could you help me figure out what's wrong with my equations?
Thanks in advance!


texts:
I am trying to design a small CNC maching for milling PCBs. I am using unipolar stepper motors driven by a microcontroller, but I am unsure of what tehnique to use to drive them.

I once read that driving a motor with constant current provides a constant torque and driving them with constant voltage provides a constant speed.

But, using constant current source seems more intuitive to me. Since its the current through a conductor that generates a magnetic field around it. Meaning if I drive them with a constant voltage there would be a rise in the strength of the magnetic field untill it reaches its maximum (if I am not switching with higher frequency) generated by the coil. And if I were to drive them with constant current, the coild would immediately generate the maximum strength of the magnetic field and I would be able to drive them with higher frequencies.

Is my logic here flawed, where am I wrong?
What tehnique is usually used in milling machines?
Should I look out for maximum voltage/current rating of a motor when using constant current?


texts: RealTerm buffer problem: When I send a text file with baud rate above 115200, I see in the scope that it transmit 116 bytes with 50mS pauses between any 116 bytes group. No any delay sets. This is not UART setting problem because with another SW no such pauses problem. Why I use the RealTerm? because I need to control the delay between lines (CR + LF). Someone know how to cancel the pauses or a SW with line delay?


texts:
The normal ethernet components configuration: MAC <-> PHY <-> Magnetics <-> RJ45. My RJ45 connector must be mounted on the system box's front panel, so there must be a wire routed from the PCB to the front panel connector. My system box contain many relays, so there may some interference from them. Now, I have several choices:

Locate the magnetics at RJ45 connector side. And using CAT5 UTP wire to the main PCB. Then I can choose a RJ45 connector with integrated magnetics.
Locate the magnetics at the PHY side, that is on the main PCB. Then use wires connect to the connector, which without integrated magnetics.
If I can use two magnetics, one on main PCB, and one on the connector side?

Which method is better?


texts: Use AVR Timer1 for Compare Interrupt AND PWM at same time

texts:
Is it possible to use Timer1 on an ATMega to generate a compare interrupt on OCR1A and PWM output on OCR1B? I've tried with similar to the following, but neither work with everything I've tried.

TCCR1A = _BV(COM1B1) | _BV(WGM11) | _BV(WGM10);
TCCR1B = PRESCALE1_8;
OCR1B = 0;

// set compare match register for 1000Hz
OCR1A = 2000;
// turn on CTC mode
TCCR1B |= _BV(WGM12);

Side note: I know this is extremely similar to another question of my own, but that was regarding PWM on one timer and interrupts on another. This time I'm having trouble getting both out of the SAME timer.


texts: Does the MAX31855 thermocouple converter output accurate temperature values?

texts:
I'm trying to figure out why my MAX31855 thermocouple converter appears to be outputting inaccurate temperature data. I'm curious if this is due to non-linearity in the converter. Link to data sheet: https://datasheets.maximintegrated.com/en/ds/MAX31855.pdf

The accuracy of the thermocouple seems to be okay around room temperature, however, it it becomes very inaccurate at higher temperatures. Around the 400-500F range, it can be off by +80F.

I'm somewhat familiar with the physics of thermocouples, but I'm definitely not an expert.

So my question: does the MAX31855 actually output accurate temperatures? The data sheet states that it outputs in units of 0.25 deg C. From this, I assumed that it would output accurate temperature data since it's using deg C as units.

However, I'm curious if this is a bad assumption. The FAQs page of the MAX31855 states that it does not linearize the results (link to FAQ page: https://www.maximintegrated.com/en/support/faqs/max31855-faq.html). This confuses me, why would it the datasheet say it outputs in units of 0.25 deg C if it's not actually linearized/valid?

Am I required to post-process the data by myself to get accurate temperature values?


texts: Multiple clients listening the UART TX line

texts:
I'm building a DMX device and am thinking about paralleling the workload amongst several microcontrollers. The device has to support 24 PWM channels and I'm afraid, I won't be able to service all 24 channels (software bit angle modulated) in one atmega MCU. Is it possible/right to hook up several Atmegas to listen on the TX line after RS485 receiver or must I put a separate RS485 receiver on every MCU?

My idea is that the first MCU will have an address DIP switch and set addresses to later MCUs via SPI or I2C, then all of them will listen to the same TX line comming from one RS485 receiver and act as they should when they receive their own addresses. (On DMX bus values for all the 512 channels are repeated over and over again)

Is this doable? I think I would have no more than 3 parallel MCUs listening to the same line.


texts: How do I define the voltage drops polarity when applying KVL?

texts:
Let the circuit be:

Question: Find Ix by applying KVL.

Correct Answer: Starting from node ‘f’ and going clockwise, KVL gives: 12 – 3Ix – 6Ix = 0, so that Ix = 12/9 = 4/3 A.

Problem: This seems to be a bit confusing. According to my knowledge, we can choose the signs of the resistor and we'll have the same answer.

It seems that the answerer picked those signs  + --3Ω-- - and - --6Ω-- + . When Ix passed through the negative pole of the battery, we gave a (+) sign, when Ix passed through the positive pole of 3Ω and 6Ω, we gave  a (-) sign.

I picked those signs.  - --3Ω-- + and - --6Ω-- +. Starting from node ‘f’ and going clockwise, KVL gives: 12 + 3Ix – 6Ix = 0, so that Ix = 12/3 = 4A (the correct answer is 4/3 A).

Question: why the answerer chose the signs of the resistors this way? Why is the answer 4A wrong and 4/3 A correct? If it has to do with the passive sign convention, I would appreciate if someone would explain it to me?


texts: What would be a suitable motor controller for this BLDC?

texts:
I'm looking at replacing some steppers with a BLDC to get smoother operation and higher speed.  The BLDC motor we want to use is this one.

It is a small 2-axis robot that requires accurate position control but I also want to have speed control if possible (rather than just a step and direction input).  The maximum motor speed is probably less than 100 RPM. The motor is sensorless and I found some sensorless controllers like this one but they don't incorporate position control.  The encoder on this motor is SPI anyway so I doubt I'll find such a controller.

There will already be another processor (RPi-based) with the main application running, but it's not capable of the high speed requirements of this real-time motor control so there needs to be another external controller.  I figured a motor controller like the one above with a small MCU for closing the position loop might work, but then why not just have the MCU do the whole thing (aside from the extra firmware development required).  I was looking at the PIC18F2431 which includes a motor feedback module.

In this case it's likely I would use UART or SPI to send motion profiles and get position and status feedback to/from the MCU.

Any other options or factors I should consider?


texts: Benefits of using Altera IP in FPGA designs?

texts:
I've just started using Quartus to synthesize a VHDL design that I created a while ago. Inside of this design are things like DFFs, decoders, etc. I noticed that Altera has IP of its own with the same functionality.

Are there any significant benefits to using the Altera IP? I would rather not uproot all of my VHDL files but if there are significant size/performance enhancements then I might consider it.


texts:
I want to make a wire glow using a simple 9V battery. Will a simple resistor prevent this from being a short circuit and safety hazard? How do I decide which resistor to use?

The hazard I am afraid of is an exploding battery. The glowing wire is intentional, and not the hazard I am afraid of.


texts: Is AD7794 a good alternative to Hx711 for multi-channel ADC?

texts:
note: Electronics isn't my main background so I might make silly mistakes. I did read the datasheet but don't understand all the terms despite my effort. Suggestions are welcome.

AD7794 (datasheet) is 6 channel 24 bit ADC with on-chip gain of 128.

Questions:

My load cell outputs +-20mV at FS so 128 gain = 2.56V which is suitable for ADC. But does in-amp has minimum voltage that it can amplify?
Is this chip also able to take -20mV input?
The AVDD = 2.7V to 5.25V. So as long as I supply voltage within that range, will I be okay?
If I look at INA125 instrumentation amplifier(datasheet), it has voltage regulator of 10V, 5V and so on. I can supply load cell with the regulated voltage and amplify the output in mV. But I don't seem to find such feature in AD7794. However there is 1.17V reference which I don't know what it is used for. So do I need to add separate voltage reference for excitation?
Am I overlooking anything if I intend to use this for load cell?

BTW, if you know other ADC with multi-channel ADC, I am open for it also.

Edit: There is also available breakout board at tindie. I don't know if there is any issue with arduino or not. But I hope not.

Regards,


texts: How do I log only received information in RealTerm

texts:
I am trying to test a sensor circuit I'm working on. Essentially, I am using RealTerm to send commands to the µcontroller and it is returning the value read by the sensor. When logging to a file in RealTerm, I noticed the commands being sent were showing up as well as the data being returned. I was wondering if anyone knew a way to record only the incoming data using RealTerm, and not the outgoing commands. Any suggestions would be greatly appreciated.

Unfortunately, there is no way around using RealTerm specifically because of a company policy.


texts: VFA vs. CFA Compensation Capacitor Comparation

texts:
Here, I am referring to voltage-feedback amplifier (VFA) and current-feedback amplifier (CFA). A basic schematic is given below for each.

I.) VFA

II.) CFA

I am curious about the position of compensating capacitor, when both circuits are compared. In VFA, compensating capacitor is connected in parallel between input and output of voltage amplifier (between base and collector of BJT). But in case of CFA, the compensating capacitor is connected in parallel between output (collector) and ground of voltage amplifier. Why is it so? Why not the same in both configurations? How does compensating capacitor has any influence on CFA's frequency plot?

Obviously, in both circuits, frequency compensation technique differs. In VFA, compensating capacitor compensates Miller Capacitance of a BJT. Why isn't the same technique used in case of CFA? On what principle is frequency compensation of CFA through compensating capacitor (between voltage amplifier's output and ground) based on?


texts:
I am working on a project where I have to use string LEDs running on 5V (USB power.)
I had purchased one such string, which is 10m in length and has roughly 50 LEDs inside.
My specification requires me to use 20m of this string light , so I tried to join them together. That didn't work as the brightness of the second string attached was way lower than the first one connected.
I found that at the joint for the second string I was getting 2.4V (starting with 5V.)
This becomes a problem as I need them to be equal brightness.
I am not able to find why this would happen as all the LEds are in parallel and should get equal voltage along the string.
There is another seller selling the same LEDs in parallel and they work just fine. They have 3 wires running instead of 2 , and I can't figure out what the 3rd wire does exactly. (It's too expensive for me to break it apart and reverse engineer it.)
Please help me out.
LED string lights.


texts: How does analog video transmission work in toy drones?

texts:
I'm trying to get a big picture understanding of how video transmission works. How is the video transmitted in FPV transmitters like here?
In the specs, it says FM. So is the analog video (NTSC/PAL) signal frequency modulated with a 5.8 GHz carrier using analog electronics and power amplified to an antenna?
Any reference design, application note, or example circuit would also be helpful. I searched around and couldn't find a good reference.


texts:
I was watching one of Jacob Baker's videos
(http://cmosedu.com/videos/f10/ece5472/lec1_ece5472_video/lec1_ece5472_video.html)

At minute 19:30, he explains the concept behind linear regulation:

His Explanation

He explains it by saying that if the output regulated node is at 1.9V and reference is 1.8V, then the gate of the PMOS device will increase, decreasing current in the branch and a smaller voltage drop across the load resistor hence the output regulated voltage goes down to 1.8V.

My Explanation

The way I see it is that if the gate of the PMOS device goes up and if I follow this graph:

Then we would switch to a Vgs curve which has a less steep slope and thus the PMOS device would actually have a higher resistance, dropping a larger voltage and thus bringing output node down to 1.8V.

Is my understanding valid? (I hate thinking of PMOS devices as fixed resistors(like a lot of authors simplify it to be) since it doesn't satisfy KVL).


texts: Difference between power on Arduino Pin 13 and Other Digital Pins

texts: I am using Arduino Digital Pins to turn on and off a relay. Now I am using the 5V and GND from the board and supplying this to the relay. This power is turned on/off using a NPN 2n2222. This transistor in turn switches on/off the relay. Now I can make this happen by supplying the power from 3V supply on board. Now I want this to happen using the digital pins. This works, but only on pin13 and not on others. What can be the reason?


texts: Do unused relay pins help with heat dissipation?

texts:
I have been using DPDT relays to control high-current loads (~15 A at 240 Vrms) though I am only using them in a SPST, NO fashion; that is, the load is disconnected when the coil is de-energized, and vice versa.  A supplier has offered DPST parts that basically remove the unused NC contacts (top two on the image below).

The copper pour (blue) is on the top and bottom layers in 2 oz copper as well as two inner layers in 1 oz copper.

Is there a benefit of keeping these DPDT relays around despite the unused contacts, or would thermal vias do just as well to keep the PCB trace temp rise down?


texts: Y or Delta connections advantages / disadvantages

texts:
I have been studying three-phase systems for the whole course of a subject (on the first year of the university degree). I have finished now, and I know both "Y" (star) or "Delta" (triangle) connections. I have made a lot of computations with them, however I don't know the different applications they have and I would like to know the following in order to increase my knowledge.

I would like to know which one is better (Y or Delta) for different purposes, they must have its advantages and disadvantages, but I have never been told which ones are them. I have tried to do some research on the Internet, but I haven't found in particular a good answer. I have only seen the advantages and disadvantages of Y and Delta motor startup, but I'm thinking more of the "circuit" point of view.

I'm really interested on the subject, but I just seen it from the computational point of view. I would appreciate if someone could explain me a little bit some of the main advantages and disadvantages of using both connections. Thank you.


texts: Layout and Capacitance of 24/12 Inverter

texts:
Consider below layout:

It is from CMOS VLSI Design Book by West-Harris.

Why it is called 24/12 lambda inverter? I could not estimate its width/length so it match 24 and 12.
Why its capacitance is 9 times of a unit (4 lambda) transistor ?


texts: Why does the self-inductance of a straight wire decrease when its radius increase?

texts:
I made some research on the self-inductance of a straight wire, and many sources cited “Inductance Calculations” of F.W. Grover. So I read a bit of that book but I couldn't find the answer to my question.

As far as I know, the self-inductance is given by the sum of internal and external inductance of the wire. Since the first one is constant with respect to the radius, I assume that the latter decreases when the radius increases.

For the external inductance, I found here (see Figure 1) the formula \$\frac{\mu l}{(2\pi)}ln(D1/D2) \$ with D2 the diamater of the wire, and D1 the diameter of a fictitious wire. It seems indeed that when D1 gets larger, the inductance decrease. However, in my opinion, with a single wire D2 should tend to infinity. So, how does this formula make sense?

Maybe I have this doubt because I don't really have clear what is the external inductance of a single wire. In fact, I don't see what the flux is linked to when the magnetic field is external to the wire and how it can generate an emf across the wire.

Also, other than that formula, the real question is what is the physical phenomenon that makes the self-inductance decrease when the radius increases?


texts: Automatic and manual clock managing. Errors with ring counter but not with 4-bit counter

texts:
I'm building an 8 bit computer and I've just developed the clock.

I used a NE555 (datasheet) with some other integrated (74 series) to manage it.

The operator could stop signal from 555 (with a switch) and use it in "manual mode" using another switch.
No clock signal should reach the output pin if clock enable pin is low.

To achieve this I useed:

74HC00 (NAND) to debounce manual switch
74HC00, 74HC08 (AND) to debounce auto witch and signal from 555
74LS32 (OR) to get the manual clock or the automatic clock (with 555)
74HC08 to get an high value on the output pin if both clock and clock enable are high.

I hope this diagram will be more clear than my words:

simulate this circuit – Schematic created using CircuitLab

Now I'm testing it and what I got is really strange!

First I tested it with a 74HC161 (datasheet), a synchronous 4-bit counter: what I got is ok: I see 0000, 0001, 0010, ..., 1111 as expected.
Then I used a 74HC4017 (datasheet), a 10-bit ring counter with the clock inverted by a 74LS04 as it need to be in my computer:

Unexpectedly at "high" frequencies (2Hz), using the automatic mode, the counter becomes active with bot high-to-low and low-to-high tranistion. Using the manual this behavior never occurs.
Than if I switch off the automatic clock manager and put clock enable to ground the counter continue advancing the high bit. Note: manual clock is low.
On the other hand if I switch off 555 and I use only manual clock the integrated word fine.

So I checked the voltage value between OUT and ground and what I got is 0.07 V . It's a too small amount to be evaluated by the 744017, but it seems to evaluate it anyway.

How to repair my circuit? What is wrong with it?

Any idea/solution/hint will be appreciated.


texts: How can I get SPI SCK line to idle low without wasting current with a pulldown resistor?

texts:
I am using the STM32L475 MCU and am using SPI to communicate with an SD card.
When I configure the SPI SCK GPIO pin, I configure it as Alternate Function SPI in PushPull mode. I set the ClockPolarity to be idle low, which would make me think that the SCK line would remain low when inactive, but this is not the case. Instead, the SCK line idles high until SPI communications are started. This means that if I do a SPI write and subsequent read, an extra clock pulse is triggered, throwing off my communications.
The only way I found to be able to fix this is to further configure the GPIO pin to have a pull-down resistor, but this seems to me like it will be wasteful in terms of current draw. Configuring the pin as open-drain doesn't do the trick either, since I need to add a pull-up in that case anyway. Finally, I have tried writing to the GPIO pin's output register for the SCK pin and setting it to be low, but this does not change anything.
It seems to me like my only option is to place a pull-down resistor on a push-pull pin and constantly waste current in order to have the SCK line stay low. I was wondering if this was the normal solution that people used for SPI communications? I can't imagine that it is.


texts: transformer has continuity but no voltage output?

texts:
I have two old transformers that appear to be fine, however no DC voltage was measured on the secondary coil.

I have measured:

The input voltage: 229 AC
the input coil ohms: 0.015 kOhms
the two parallel output coil ohms: 0.008 kOhms each
the multimeter base resistance when i touch the probes = 0.006 kOhms
resistance between AC and DC coils - no continuity.

The other transformer is similar, continuity between the primary and secondary, AC 230 in, DC 0 out.

What kind of problem affects both these transformers?


texts: Solar-powered 74HC14 LED flasher: oscillators interfere

texts:
I am building a "nocturnal solar engine" with two LEDs flashing independently, following the description at the old Solarbotics website. I am essentially rebuilding the same circuit. The schematic and a photo of my breadboard is below.
I am using two different resistors for R3 and R5 to get a nicely asynchronous blink from the two LEDs. What I am experiencing, however, is that when the two flashes get close to each other (around 0.1 sec), they actually happen in sync, and the two oscillators' phases keep restarting from this shared moment. After a while, the independent flashing even stops, and I am left with two LEDs flashing completely in sync.
Diagnostics so far: When the solar panel is off and the circuit on the right is working, I am measuring 1.99V in the IC's circuit (the bottom power line on my breadboard). I have tried various combinations of R3/R5 resistors, different types of LEDs, and 10uF instead of 22uF for C4/C6, but the two oscillators always end up in sync.
You can watch a video of the LEDs syncing up via this Dropbox shared link. To clarify, here's a table with each flash's timestamps (jotted down while watching the video frame by frame). Yellow's interval fluctuates but seems to be around 1.90 sec. However, when the "synchronized" flash occurs (the two highlights), it flashes over 100msec too early. It should flash later, not in sync with Red.

A similar problem was reported in Q406793, but that question has not been resolved.


texts: Relays to control both directions on tubular motor using Raspberry

texts:
I'm using a Raspberry to control a tubular motor for a window blind and I have an issue whent testing it, the relays used to operate the motor got "stuck" and stopped working after a few direction changes.

The motor has 4 cables. 1 neutral, 1 ground, 2 for each direcction. And work with 220V AC power.

I use a relay board to control the current flow to each direction.

Here is a picture of the relay board:
https://www.openhacks.com/uploadsproductos/are00108sl_1.jpg
I cound't find the direct specs of it but the relay used is:
SRD-05VDC-SL-C
https://www.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf

Here is the motor specs:
alsidoor.com/pdf/NICE/Nice-ERA-M-adapatadores-persiana.pdf
Model E M 3017

So I use 2 relays to control both directions of the motor.
And I made a software to activate one relay, and deactivate the other so I will change direction.
And it works.. but after a few changes one of the relay got stuck and didn't work anymore. I tried with another and the same happend after a while.

In the specs it says that the relay can handle up to 10A of current.. and the motor only uses 1.1 A.. so it shouldn't have any problem to handle it.

What I think it's happening is that when the change is made, the tubular motor has some inertia and consumes a boost of power to change the direction and there is where it get stuck.

My question is.. is there any way to avoid this when changing the direction?
I can make a pause between each change.. but eventually for any problem it may harm the relay anyway, so I would like a more elegant solution.

I don't really have an electronic background.. I'm a software developer so I don't know much about the specs of the pieces, I just connect the cables, but tha's why I'm asking if putting some resistence or change the relays I can fix this issue.

Any ideas?

Thanks.


texts: Connecting a telephone to the computer's soundcard to playback music samples while talking

texts:
Possible Duplicate:
  How to boost audio volume coming from a telephone

Foreword: If you don't know the answer, don't leave. Write your idea where I could find an answer to this as a comment.

I want to connect my telephone to my computer's sound card. I want to connect my headset to my computer's line-in with a mic preamplifier in between. I want to hear my partner on the phone and talk to him using my cable headset connected to my computer.

The reason for me to connect my computer's sound card to my phone is that I want to include music samples into my voice channel so my partner I am talking to via phone can hear my voice aswell as music samples generated by my computer.

How would you do that. Be as precise as possible.

What kind of phone?
This landline cable-bound phone.

What headset?

Something like that

What have you tried?

A lot. I won't share it to avoid influencing the ideas.


texts: What does having the v in the center, with the positive near the top wire and negative near the bottom wire mean in this circuit diagram?

texts:
This is the diagram that I am asking about:

I understand that the symbol on the left hand side of that middle branch is a current controlled current source, and the symbol on the right is a current source.

What does it mean to have the CCCS on the left, the CS on the right, with the v in the middle, and + and - on top and bottom, respectively?

Does the whole branch, having a v in the middle describe some kind of circuit that I don't know about?  Can this circuit be redrawn?  Perhaps as:

I'm sorry for the poor redrawing.

Thanks for any clarification.


texts: Will a device charger with higher current output necessarily charge an electronic device faster?

texts:
Charger specs

Charger type : USB Charger

Voltage : 5V

Amp : 2 Amp

Freq : 60 Hz

Battery specs
Type : Li-ion

Power :  7.4 Wh

Current : 2 Ah

Discharge Voltage : 3.7 V

Charging limit voltage : 4.2 V

Charging limit current : Not specified

Execution Criteria : GB/T18287-2000

Situation :

My present charger deliver 0.750 Amps and it takes 4 hours to charge a mobile phone.

I plan to buy a tablet charger which is fullly compatible with my mobile phone, which delivers  2 Amp.

I plan to do this expecting that the charging time will be 2.66 faster (2 / 0.75) times faster. So, I expect the mobile to be charged in 2 hour 40 mins.

Known issue :

Most electronic devices has a circuit which limits the maximum current that is allowed into the battery.  (I am not aware if my phone has this)


texts: I've scoured the internet for an EAGLE library with the SN754410NE part. I found one, but it's for a version previous to 4.11 and I'm on a Mac and have no way to convert it 55.10. The original file is at http://db.tt/66pnv4Y. Can anyone hook me up with a recent version?


texts: Schmitt trigger using NE555P gives wrong output

texts: I am trying to create a Schmitt trigger using NE555P to generate square pulses from some periodically changing signals. I used the following circuit diagram and applied some sinusoidal waves (3.3v). What I am getting at the output is just the inverted input (not square pulses). What is the problem with my circuit. Any suggestions, please.


texts: How do I detect the pattern of the knock on a door, and use it as a signature to unlock a door?


texts: Is the power from solar panel redirected to load when battery is full?

texts:
When the solar panel attached to a charge controller then to a battery, simply stops the charging when the battery is full or Is the charge controller(MPPT) smart enough to redirect the power directly to the load when the battery is full?

For example: Lets consider that I have a 100 Watt solar panel, The MPPT charge controller is connected to 12V battery and the load is a 12V bulb. When the battery is fully charged does the charge controller transfers power directly to the load instead of battery?


texts:
I'm looking for a certain component - not a concrete shopping recommendation, but rather if this kind of device exists and what it is called.

I need a little actuator that has the following properties:

linear motion (travel ~1 cm)
no intermediate steps required (just goes full to the left or to the right)
fast switching
no high force neccessary (should just be able to flip a mechanical switch)
small package size (say 3x3x1.5 cm)

What I'm looking for is basically this:

I put on a voltage, and the rod bumps out to the left. Reverse the voltage and it bumps to the right. The rod should be protected from fall out by a tab, but there need not be a spring to force it back to the middle. It can remain where it is when there is no current.

If I hold the current for a few seconds, it would be great if it would remain excerting a force, but it would be also ok if the force would be cut - it should just not melt.

I've found solenoid actors, but they are mostly just push or pull type, with a spring, and also they are too bulky:

What I'm also not looking for is the kind of linear actuator where you have a rotating motor, and that pushes a screw out or in. I really just need a "bang a little rod to the left or right" solenoid in a box. Any idea where I can find this (or a suitable replacement)?


texts: Capacitor of choice for low noise applications

texts:
I saw in a schematic a while back that a polypropylene capacitor was used to generate a stable sine wave in an oscillator circuit. I suppose this gave a better 'frequency reference' for the oscillator.

Are some capacitor types better for lower noise applications?


texts: Charging NiMH batteries using a lab bench power supply

texts:
I have a project that requires some battery power and I have a 7.2V 3300mAh NiMh battery pack. I would like to charge it from my lab bench power supply  which is current limiting.

Would this be recommended?

I would prefer not to purchase a charger though if it means the pack will explode then well... Also could I have a recommendation on a good charger around the $50 mark.

This how I have been charging to so far:
  Voltage: 8.1V
  Current Limit: 300 ma
I leave it to charge until the current is almost 0

Would this charging scheme be recommend or safe?

Thanks Jack

By the way this is the battery I am using: https://www.jaycar.com.au/7-2v-ni-mh-3300mah-r-c-battery/p/SB2314


texts: Op Amp gain modification from kenwood krf-7060d

texts:
Hi, I have an kenwood krf-7060d, which has an subwoofer line out that is very very "quiet". The top part of the schematic has the final opamp (sw out) before the acutal output. Can someone tell me what is the best way to increase the gain(modify r227?) and what are the workabouts of the resistors and capacitors connected to the op amp? Thank you!

Mentions: the opamp works at +/- 12V, the gnd line is where r223 and r224 come together. The whole service manual can be found here https://www.manualslib.com/download/953472/Kenwood-Krf-V7060d.html


texts: Suggestions for small and handy connector for in-circuit programming?

texts:
I have many PCBs that use an AVR in SMD packaging, and since I frequently change the firmware in prototype boards, I'm trying to come with the best solution to program the AVR quickly and easily.

The first approach was to have a standard header (2x5 pins, .1") on the board, but since these are bulky (for the size of the boards I'm dealing with), I started to have just the contact holes without soldering the header, and bent the pins of a header with a plier so I could "snap" it in and out the board. Not an optimal solution, but it worked.

The next step was to use gold fingers (i.e. one edge of the board would have some contacts exposed, like those old ISA boards, but with just a few contacts of course). The problem with it is that the board cost increases, and still uses a lot of "real estate".

Any suggestion for small+cheap+clean alternatives? Ideally, without having to solder anything on the board (like with the gold fingers). I was thinking about just some small contacts on the board and maybe two aligning holes, if there's a connector that could fit there and by some way stay in place while the programming is done.

BTW, although the standard connector has 10 pins, only 6 are required.


texts:
I am doing some research about using a LDO as a constant current LED driver and For this project, it is imperative that the LEDs remain as stable as possible. I also need to be able to easily adjust the brightness of the LEDs. I have a few clarification questions about the setup.

I would like to use an LT3085 as a constant current LED driver as described here and in the image below. The LEDs that I am planning on using are red Osram LRW5SM, which have a forward voltage of 2.0-2.6V and a forward current of 100-1000 mA. I am planning on using one LDO to control one LED.

My questions/clarifications:

To achieve a 2.2V voltage across the LED, I should place a 220k resistor at the SET pin, correct?
In order to adjust the current across the LED from 100mA to 500mA (max output of this LDO) with a 220k resistor at the SET pin, I would need a ~4.4-22 Ohm potentiometer (this seems pretty low) at the OUT pin, correct? [LED current = 10uA * (R1/R2)]
What should I power this LDO with? Would a lab power supply work, or should I use a battery? What voltage?
Is there a better LDO option altogether for what I'm trying to do?


texts: SAW resonator oscillator operating principle

texts:
I can't for the life of me figure out how the following SAW oscillator works. I can't see how the oscillation would be maintained since it doesn't use a feedback mechanism I'm familiar with. This post could prove useful.

So here is what I was thinking:

L2 blocks high frequency components from coupling back to the power supply, though I'm not sure why this would happen (150nH from dimensions given).
C3 is a supply bypass cap, which likely has something to do with L2 though I'm not sure what. On some boards this doesn't seem to be populated (unknown value).
L1 presents a high impedance at the oscillation frequency (35nH from dimensions given).
T1 is an RF transistor in a Class C amplifier configuration.
R1 sets the transistor bias and possibly the transmit power.
R2 and T2 enables the circuit.
C2 presents a low impedance path to the antenna to remove the DC component (unknown value).

I'm not sure what C1 is for, and it seems to be unpopulated on some of the boards. For the SAW resonator, the only thing I can think is that when turned on it rings for a bit then dies down, so continuous transmission wouldn't be possible.
I'm hoping someone could shed some light on my assumptions listed above, and maybe on how the component values were selected.


texts:
I have an old VAXstation that has an external SCSI Bus.

When I don't have anything attached to that, I get errors. I was thinking of adding a terminator, but those that I found online are quite expensive. So I was thinking of wiring one myself.

Does anybody happen to know how I should wire them, and what resistors I need?


texts: magnetic rotary encoder 0.3V output voltage

texts:
I have a 24V DC motor with a magnetic rotary encoder. The encoder has a 5V supply voltage. The datasheet states that it has an output voltage of 300-700mV. I have also measured it, and it gives around 0.5V. I want to interface this encoder with an STM32 microcontroller, so I want to convert it (reliably) to 3.3V. But I don't really know how. Since the datasheet states a 300mV minimum voltage, I want to build a circuit, that "turns on" at 0.25V, it is "off" below and "on" above, and gives me a clean square signal.
My first though was a transistor operated as a switch, but 0.3V is not enough for a BJT transistor's operation. Then I was thinking about a MOSFET circuit like this one, with an N-channel enhancement MOSFET:

But I have no experience with such circuits. Could this work with just 0.25V threshold? Or do I have to amplify it? What MOSFET and resistor values do I choose?
Or what other solution would be better in this situation?
Thanks for the answers!
Datasheet: https://www.power-tronic.com/wp-content/uploads/2019/11/Type-Magnetic-Incremental-2019-01-08.pdf
MCU: STM32F101R8T6 (GPIO PC8, PC9)


texts: How do we tell distance to target at the receiver from frequency modulation?

texts: Was thinking about radar and how to tell distance using FM. If you send a wave with a consistent wavelength of 1 meter, and it hits a target 1000 meters away and then comes back, it will have gone 2000 meters and done 2000 oscillations. But how would we know that from the received waveform? I assume that the phase of the wave that comes back would tell us how many oscillations occurred roundtrip? Or if it did 2001 oscillations, the received phase would be a little past the starting point of the waveform? Is this where Fourier transform comes in? Hopefully I am on the right track here, thanks.


texts:
For this LDO circuit design at https://github.com/promach/LDO/tree/development ,

1) which exact circuit node(s) contributes to the zeroes near 1MHz after removing CL ?

2) If I remove "AC 1" from Vref, why the whole bode plot becomes erratic ?


texts: Should I use a snubber or solid state relays on a 24 vac circuit?

texts:
I'm trying to create a smarter controller for my hydroponic systems.
I have an arduino controlling a sainsmart mechanical relay.
The load on the relays are 24 VAC orbit sprinkler valves.
Everything is powered from the same 120VAC circuit using different wall wart transformers.

The problem is that 30% of the time the arduino resets when a valve is triggered.
This happens whether or not the relay board is fully optically isolated or not.
But, this does not happen when the arduino is powered off a 9 volt battery.

I'm guessing that the relay triggering is sending power spikes into 120VAC.

Should I setup a snubber circuit, and if so, what are good specs?
Should I ditch the mechanical relay in favor of the below SSR?

The mechanical relay board:
http://www.sainsmart.com/8-channel-dc-5v-relay-module-for-arduino-pic-arm-dsp-avr-msp430-ttl-logic.html

The solid state relay board:
http://www.sainsmart.com/8-channel-5v-solid-state-relay-module-board-omron-ssr-4-pic-arm-avr-dsp-arduino.html


texts: Driving three high power RGB LEDs with PWM, from a 9v battery

texts:
I'm building some LED juggling balls. I'm planning to power an Arduino with two AA batteries, and power the LEDs with a 9V battery.

I want to drive three of these 3W RGB LEDS in parallel, with PWM. I'll probably need 3 to get an even glow around the sphere. I'm planning to use a 9V battery (perhaps something like the Energizer LA522) to power the LEDs. They say this battery can provide up to 1A continuous discharge, so at max brightness there will be about 100mA through each LED. That would give a power of about 0.65W for reds and 0.56W for greens & blues.

I found the NCP5623T LED Driver with PWM, which has 3 outputs for RGB, and I2C support. I'll be needing about 300mA for each color (3 LEDs in parallel), and the IC can only provide 90mA, so I was thinking to use darlington pairs for each of the colors.

Questions:

Would it be better to use these 1W LEDs at 100mA? I chose the 3W ones because they were $2 cheaper. Or is it likely that I will get the same brightness at 0.6W?
Would you recommend using a different LED driver IC with PWM? (Non-SMT would be easier to breadboard)
Should I use MOSFETs instead of darlingtons? (Maybe NTD80N02-001?)

Please correct me if I've made any wrong calculations / assumptions, and please let me know if you have any suggestions. Thanks for your time!


texts: Electrical impulses in plants_Pulsum Plantae_circuit prototype problems

texts:
HELP!! Where am I going wrong?
I am trying to make a prototype circuit based on the Pulsum Plantae circuit (no longer available to buy) https://github.com/Lessnullvoid/Pulsum-Plantae. The serial read doesn't seem to make any sense though and I’m not sure the circuit is correct. Any ideas would be greatly appreciated.

This is the code I am using:
// number of analog pins to read
#define NUMPINS 6

// read at most 100 times a second
#define READPERIOD 5

// a header for outgoing serial messages
#define MSGHEADER 0xAB

byte serialMsg[7];
int whichPin;
unsigned long lastReadWrite;

void setup() {
  Serial.begin(57600);
  serialMsg[0] = serialMsg[8] = serialMsg[7] = 0x00;
  whichPin = 0;
  lastReadWrite = millis();
}

void loop() {
  // don't read pins more frequent than 100 times per second
  // and only read one pin per loop to avoid noise
  if(millis()-lastReadWrite > READPERIOD){
    short readValue = analogRead(whichPin);

    // send 3 bytes per value: HHHH_HHHH AAAA_VVVV VVVV_VVVV
    // where HHHH_HHHH = 8-bit fixed header
    //       AAAA = which pin [0,15]
    //       VVVV VVVV_VVVV = 12 bits of data [0,4095]

    serialMsg[0] = (MSGHEADER&0xFF);
    serialMsg[1] = ((whichPin<<4)&0xF0) | ((readValue>>8)&0x0F);
    serialMsg[2] = (readValue&0xFF);

    Serial.write(serialMsg[0]);
    Serial.write(serialMsg[1]);
    Serial.write(serialMsg[2]);

    Serial.flush();
    whichPin = (whichPin+1)%NUMPINS;
    // use millis() because flush could take longer
    lastReadWrite = millis();
  }
}


texts:
I'm designing an inverter with a switching frequency range of 10-40kHz. The inverter will run off of a DC power supply at a relatively low voltage (30-80VDC) and low power (~100W) for motor control applications.

I am currently working on the input EMI filter to attenuate common-mode and differential-mode noise. I will use DC link capacitors to reduce the differential-mode noise but after doing some research, have come across additional options:

LC low-pass filter (differential-mode noise attenuation)
Ferrite bead low-pass filter (differential-mode noise attenuation, specifically for high frequency noise)
Common-mode choke (common-mode noise attenuation)

If I were to implement either of the low-pass filters, I plan on using a T configuration to match my low source and load impedances.

I have a couple questions about this design:

The application is not space or price constrained, so I don't see the harm in including all three options on top of the DC link caps. Is this a good plan?
Is a low-pass filter cutoff frequency of 100Hz a reasonable spot to attenuate the worst-case fundamental switching frequency of 10kHz?
How should I design around the resonance in a ferrite bead/LC low-pass filter? The inverter is for testing multiple motors, so I don't know the load impedance of the motor in advance and can't impedance match to that.


texts: Do I need to fuse batteries in parallel?

texts: I have two deep cycle batteries in my Airstream, in the panel there is a fused bus bar (that appears to be faulty) so the solar panels only charge the one battery. Can I just run a heavy gauge wire between the two positive and two negative terminals? Or do I have to put a fuse across them? ... if so do I fuse the positive or fuse the negative? What's the worst that can happen if I don’t fuse them?


texts: Stepper Control using DC Brushed Motor Driver

texts: Is there any way to control a bipolar stepper motor using one or more DC brushed motor drivers?  My only interface to the motors is setting an integer to represent their speed, ex -100 to 100.  I believe this is possible as I saw examples doing this with the arduino Stepper.h library, however I am not using an arduino and cannot use any libraries (answers should be platform universal).  I know stepper motors use pulses to its two coils to advance a tick; is there any way I could simulate this using timed operation to simulate these pulses?  I dont need specific step precision, continuous rotation would be sufficient.  Thanks.


texts: Choosing Component Values for DCO Design

texts:
This is a sawtooth DCO, the comparator U1A resets the ramp at the desired frequency (thus controlling the frequency), and the voltage V7 applied to integrator U2A determines the rate of change of the the ramp (determines the amplitude). I am trying to find the values of RS2 and C1 of the integrator circuit.

Known:

Maximum Integrator Input Voltage V7 = 5V
Desired integrator Output Voltage after 500 microseconds = around 5V

(500us since a frequency of 2000Hz as used in equation below)

Op amp: TL084

Unknown:

RS2
C1
Input current at maximum voltage

I understand that the current flows straight through (virtual ground), so the equations below should apply. My question is, which value of C1, RS2 or max current is chosen first, and why?


texts: Inverting Amplifier Generalized Gain Derivation

texts:
I understand that the derivation of an inverting amplifier's gain is generally treated as \$G = \dfrac{-R_2}{R_1} \$, and have seen many resources supporting this claim. I understand how the proof works by solving for the current flowing to virtual ground at equilibrium, and am satisfied with this expression. However, my EE textbook showed a different, more generalized version of the expression for gain,

\$ G = \dfrac{-A(1 - B)}{(1 + AB)}, \$

where A is the open-loop gain of the op-amp and \$B = \dfrac{R_1}{R_1 + R_2}. \$

In the limit of high open-loop gain, I understand how this expression simplifies to \$G = 1 - \dfrac{1}{B} = \dfrac{-R_2}{R_1}.\$ Can someone provide an explanation as to how this more generalized transfer function is derived, and why the general derivation that follows is inaccurate in some way for low open-loop gain?

Here is a sample of the derivation that I followed - what simplifying assumptions are made?

\$ I  = \dfrac{V_{in}}{R_{1}} \$

\$ V_{out} = V_{in} + IR = V_{in} - V_{in} \times \dfrac{R_2+R_1}{R_1} = V_{in} \times \dfrac{-R_2}{R_1}\$

\$ \therefore  \dfrac{V_{out}}{V_{in}} = \dfrac{-R_2}{R_1}\$

Follow-up: Does whatever correction needs to be made to the closed-loop gain of the op-amp affect the input resistance of the op-amp, or is it always \$R_1\$, regardless of the op-amp gain?


texts: Differential Signals - Why is having an equal impedance an advantage?

texts:
I lately heard in a course that a main advantage of differential signals is that both signals show the same impedance, whereas a single-ended signal, which is measured against ground, has a high impedance at the point of measurement and a low impedance at ground (please refer to the picture below).

I understand why that is the case, but in which way does it matter? Why is this important? Is it because "environmental" noise affects both signals the same way?


texts: Why is an inductive load not desirable for a GTO circuit?

texts: I was wondering why is an inductive load not good for a GTO circuit from a power electronics perspective.


texts:
I am working on a project to count the number of cars in a specified region. I would like to use a Zibee/Xbee module. As far as I've learned, Xbee modules are used as stationary nodes and Zigbee modules are arranged in the car. There is a gateway node that receives the data in terms of RSSI values of the signal received through the stationary node.

1)How to use that data to find the position of the car?

2)A Xbee unit can take how many readings at same time?

3)What is the range of this position locator

For the first question I studied a lot on the web and there is no certain information about how to do it. All I know is a mobile node requires three stationary nodes to locate it and it is measured through RSSI value of signal received. If I am wrong somewhere please correct me.


texts:
I'm currently trying to figure out how to drive a bare 7-segment 4-digit LCD glass (without driver).

Part number of display: VI-415-DP-RC-S

I’m currently planning to apply a (min.) 30 Hz square wave to active segments. With VOn = 3V. The common pin of the LCD is currently planned to be at GND (0V)

Is that valid? Because I have read that DC is the worst thing that could happen to an LCD and I don’t know if a square wave is preventing the display from damage.

If I need a “real” AC source, is it valid to put 1.5V on the common lead of the display via a resistor ladder? This would result in a voltage from -1.5V to 1.5V on Segment pins.

If this is valid, which current should be flowing down the resistor ladder? And I assume that the segment off voltage then needs to be 1.5V —> 0V for the LCD between segment and common.


texts: Is it possible to connect 9 blue leds to a 9 volt battery?

texts:
My plan is to connect 3 series of 3 blue leds in parallel, all connected to a 9 volt battery. Would this be possible to do without a resistor? Because from what i read, blue leds use 3 volts
Here's a rough sketch of what i want to do. Any help is appreciated


texts: Replacing atmega8 with atmega328(arduino)

texts:
I was supplied with an arduino board in a workshop(which is a very old version board) similar to :
 the board comes with atmega8 as a micro controller ..
I wanted to increase the performance and memory of my micro controller, so I purchased an atmega328 IC from ebay

Atmega328 IC Arduino Duemilanove bootloader

After replacing the IC with atmega328, I changed the settings in my arduino IDE to atmega32 duemilanove board ..

When I supplied power to my arduino board, I noticed that the LED on pin13 is keeps on blinking continuosly(Though I pressed reset button many times)

Here's a little video I made after replacing the IC

After replacing with new atmega chip, I'm not able to upload the code

can anyone help me with this

Thanks !

ps : I'm pretty new to arduino & electronics world :(


texts: Mixed logic gates AC or weird multiplexer

texts:
I was thinking of ways to control 2 devices each with 3 bits or more input.
Ideally this can be done with one inverter and 6 AND ports. Or a weird multiplexer. Of course it can be done with 2 74LS or similar, but I was wondering if a single chip that does this exists and what it is named.
Think of the digital equivalent of this ancient device below.
Which leads me to the question: do such mixed gates IC exist? I know about the configurable ones, but they serve a different purpose.
Thanks!


texts: What single board computer (SBC) solution would allow me to cut power instead of powering down?

texts:
I'm building a circuit with a single on/off switch.
"On" turns on the circuit, which includes a SBC currently running on Windows that runs the GUI (Labview).
"Off" powers of the circuit, including the SBC.
I'd like to keep a single switch that turns everything "Off", without corrupting the computer memory / hard disk to ensure smooth startup each time. Is that possible and what solutions exist?


texts: What is the dependance of voltages in a MOSFET on its Performance?

texts:
The Wikipedia page says that (in context of scaling)

  To maintain performance, the threshold voltage (Vth) of the MOSFET has to be reduced as well.

And also, this paper says,

  For high performance operation the power supply voltage must be significantly above the threshold.

How exactly is performance dependent on these voltages?


texts: Arduino watchdog with 555 Timer and a MOSFET

texts:
I want to protect an Arduino from stop running using a 555 timer. I saw some projects that use the Arduino RESET pin to do that but there are cases that my Arduino project still stop working even when I do a reset using the RESET pin.

So I used the circuit below to cut the 5v line of my Arduino. I choose the 5v line instead of the ground because I have only one 5v pin and more than one ground at Arduino.

My problem is how can the Arduino reset the 555 counter? How can I pulse the 555 to prevent it from disable the Arduino? If I connect the D2 Arduino pin to the Threshold/Trigger/Capacitor pin like I saw on some projects, and keep the capacitor charged, it works when the Arduino is running but if it disables  it never turn on again because the Arduino don't allow the capacitor to charge again and it stays forever off.

simulate this circuit – Schematic created using CircuitLab


texts:
I would like to find the expression of voltage across Rsense in the circuit below:

The author says in the book:
"A multiplier generates a current which is a product of the rectified line voltage k.Vin(t) and the error amplifier output level Verr". This current generator feeds an offset resistor Rcs connected to the sense element *Rsense in series with DC low side input terminal. Rcs fixes the maximum peak inductor current allowed by the multiplier. For instance, suppose the the multiplier delivers 300 uA and Rcs equals 2 kohm; then the maximum voltage across Rsense reaches 600 mV
(the inductor is just above the transistor connected in a boost configuration with a diode)

What bothered me in this circuit is the last statement, i.e How does the resistor Rcs fixes the maximum peak inductor current current?
What is the mathematical expression of Vsense in terms of the current entering Rcs and the inductor current entering Rsense from low side?


texts: Full-wave rectifier circuit with non-grounded center tap

texts:
I'm troubleshooting a full-wave rectifier power supply circuit and have come across something I've not seen before and I'm not quite sure how it works.
The center tap of the transformer is grounded through two resistors. The center tap itself provide one voltage node and the junction of the two resistors provides another voltage node. The voltages in this circuit are quite high 250 VDC so I'd like to get an idea of how it works, before I start poking around.  I believe Nodes 2 and 4 are negative with respect to ground and are supplying biasing voltages, hence the polarity of C3.  If anyone has any insights, I would appreciate it.

simulate this circuit – Schematic created using CircuitLab


texts: Can I use Mason's gain formula to find ratio of intermediate node variable to input?

texts:
In the text book of 'Automatic Control Systems' by Benjamin Kuo, I read like this.

Consider the following system.

In some books, I saw they are using Mason's formula to find x2/x1 ? Is that allowed? The above statement from text book says only x3/x1 is allowed to find using Masons formula.


texts: Confused with PC RS232 pin-out for this stepper motor communication

texts:
I'm planning to communicate with the module of a servo motor. The manual is given here. At page 88 there is a diagram for RS232 wiring as shown below:

The manual mentions in the motor side pin3 must be bridged to pin7 for controlling a single motor(non addressed means that I guess). So far so good, but on the PC side the RS232 pins 1 6 7 and 8 seems connected without any explanation. Is this something common for any PC RS232 port? How can we interpret this?


texts:
I am trying to hack a Wireless USB Keyboard (Microsoft Wireless Keyboard 2000) to create an external power button.

The problem here is that, as you could see from the image there are four output terminals from each key centre. What two terminals should be connected to the wires so that they could be directed to an external switch?

Also is it possible to remotely access a key, for example let's take the Enter Key through USB in case of laptop?


texts: Sanity check for current transformer burden resistor calculations

texts:
I'm hoping to use this(CR8420-1000-G) current transformer to detect ground faults of 20mA. Using the formulae in the datasheet:

Here are my calculations:

They say

  For best linearity, choose R such that V < 0.8 VL

I'll go with 0.5:

Now say I'd like to have a 500mV output for 20mA:

35.3KOhm seems way out in left field for the burden resistor. I was expecting something around 500 Ohm.

Did I miss something?


texts: Does an infinite AC bus which gets a load step experience any frequency sag?

texts:
I'd always imagined that the frequency sag experienced on an AC bus was a direct consequence of the mechanical slowing down of the alternator rotor/crank.

But is this truly the case? On an infinite bus, or perhaps more practically on a bus formed by an inverter, does a load step also translate to a frequency sag?

My understanding is that Voltage sag is what fundamentally happens on any type of circuit, but that frequency sag is only the case with mechanical (spinning) voltage sources (i.e. alternators).


texts: Where does return current flow for a differential signal?

texts:
As far as I understand, return current flows the "negative" channel for a differential signal connection. Only if it is not balanced well, there might be unwanted return current in reference GND or power plane.

But some say the return path for both positive and negative are always the reference plane, which get me confused...


texts:
Hey I got a question about switching a 12V supply to a low power circuit with an MCU.

My requiaments are:
 - switching has to be on the High side.
 - switch should stay "closed" when MCU is powered down.
 - MCU is TTl level (Atmega 328P)

After some searching I came up with this shematic but I don't know if it is ok to conect the 12V supply with an Voltage dividor to the MCU.


texts: Can an AND gate be used to toggle an HDMI connection?

texts: I am looking to turn on and off the throughput of an HDMI signal via a microcontroller. Would four ICs such as the SN74LS08N AND gate be enough? Or do HDMI signals need something more complex?


texts: External crystal needed for ATmega328P for multi-master I2C communication?

texts:
I want to connect multiple ATmega328P chips to an I2C bus. Each unit is configured as slave but can send/broadcast messages as master too.

I have this currently working with Arduino Nano units and this works fine.

To reduce cost and more importantly space, I want to replace the Arduino Nano's with ATmega328P chips.

Now, my question is, do I need external crystals for these ATmega328P chips for this multi-master configuration?

I know I2C is not time-critical such as RS232 because the slave follows the clock-line of the master (right?).

The only concern I have is: will collision detection work properly if two ATmega units without crystal start transmitting data at the same moment?


texts:
I have the following board with the below diode:

One diode fails circuit testing and needs replacing, but how do I find out the specification of the diode I should buy to replace it?

(it is for a synthesiser)

Thank you!


texts: Total curent through two parallel resistors

texts:
voltage source- 5V

This simulator shows that the curent in the left wire will be 10A, like sum of curents through two parallel resistors. Is it wrong?


texts: I was just wondering about the frequency domain with regards to bandwidth. I am not sure how to relate the bandwidth of a signal to its frequency. For example, I have a Fourier transformed equation of the form G(f) = rect(Pif/1000) + tri(Pif/2000). Would the bandwidth be 500/Pi for the rectangular function?


texts: NPN transistor as switch - does base resistor matter?

texts:
I'm a bit confused. I'm trying to use an NPN transistor as a switch to control a simple LED circuit.
I assume that if I put it into active mode (emitter to ground, collector to Vcc), it just needs a positive voltage at the base to turn it on. However, if I change the base resistor, there is no change in the brightness of the LED. I thought that by changing the base resistor, the base current would change, and that would affect the collector current according to Ic = beta * Ib. I am confused why the BJT is called a "current-controlled device" when changing the base current has no effect on the collector current. Even with a 1MΩ base resistor, Ic seems to be the same. If base resistor doesn't matter, surely it is a "voltage-controlled device", not a "current-controlled device".
Please tell me what I'm missing. Cheers.


texts: Is it needed a relay snubber in an ammeter?

texts:
I'm designing a picoammeter for an academic project, with different current ranges. To switch between current ranges I should use some relay, driven by a micro. This kind of ammeter should be able to measure current in a bidirectional fashion, and should measure only resistive load, but i would consider it slightly inductive due to wiring.
I was wondering though if it would be necessary a snubber or something else in this portion of the circuit.

What do you think? is it necessary? if yes, what kind of snubber should i use to avoid any parasitic artifact in the measurement?


texts: Capacitors and MOSFET Integrated Circuit

texts:
I have attached a basic Field Strength Meter circuit diagram that I drew. It functions as a basic RF detector. However, I want to try and design a circuit that could fit on a chip, therefore, using capacitors would be far too large. I was thinking that I could use transistors (Specifically MOSFETs) to replace these capactiors and make these MOSFETs behave like the capacitors given.

I was thinking if this is plausible and specifically how I would be able to implement this idea if its plausible.


texts: What's the name of this tamper proof screw ? (looking for screwdriver type)

texts:
I'm trying to fix device witch contain tamper proof screw witch i'm unable to recognize. I have set of standard tamper proof screwdrivers but i'm unable to find any suitable.

Could someone recognize this screw and point me what's the name of it so i could search e-bay for right screwdriver?

Regards


texts:
I'm designing a hardware for a hobby purpose involving SIM900. I'm a newbie when it comes to antenna design. I was wondering what would be the best antenna choice to start with. Even though chip antennas do have some design complexities involves, I'm bend on using them since they're kind of compact. My question is whether chip antennas will be able to radiate enough power to transmit to cellular base stations. I haven't seen any SIM900 modules with chip antennas.

http://simcom.ee/modules/gsm-gprs/sim900/

Thanks.


texts:
I have paired up L297 and L298 together to make a bipolar stepper driver.
My schematics are :

I have hooked up the step and direction pin  number 4 and 5  respectively on Arduino.
I am using a 5V power supply from a DC adaptor

The code I'm using is:

#define stepPin 4
#define dirPin 5

void setup() {
    Serial.begin(9600);
    Serial.println("Starting stepper exerciser.");

    pinMode(stepPin, OUTPUT);
    pinMode(dirPin, OUTPUT);

    digitalWrite(dirPin, HIGH);
    digitalWrite(stepPin, LOW);
}

void loop() {
    int i, j;

    for (i=1000; i>=200; i-=100) {
        Serial.print("Speed: ");
        Serial.println(i);

        for (j=0; j<2000; j++) {
            digitalWrite(stepPin, HIGH);
            delayMicroseconds(i);
            digitalWrite(stepPin, LOW);
            delayMicroseconds(i);
        }
        delay(500);
        digitalWrite(dirPin, !digitalRead(dirPin));

        for (j=0; j<2000; j++) {
          digitalWrite(stepPin, HIGH);
          delayMicroseconds(i);
          digitalWrite(stepPin, LOW);
          delayMicroseconds(i);
        }
        delay(1000);
        Serial.println("Switching directions.");
        digitalWrite(dirPin, !digitalRead(dirPin));
    }
}

I am using NEMA17 bipolar 5V motors , the data sheet can be found here :
datasheet

Motor specs are here

I have also tried L297 with L293d , but the things aren't working the way they should.

Most probably the issues are with the oscillator or the clock pin (may be the pulse is not generating ), before posting the question , I had a quick google search which showed me I was not the only onne facing this issue.


texts: How do I find the coefficients to know if this color combination is realizable? What am I doing wrong in my solution?

texts:
I tried to solve the following problem:

Part A was solved without any problem, however with part B there is a problem:
Second the digital signal processing, to be more specific, image processing, I know that:
$$
\begin{bmatrix}\beta_1\\ \beta_2\\ \beta_3\end{bmatrix} = \begin{bmatrix} \alpha_1(P_1) & \alpha_1(P_2) & \alpha_1(P_3)\\\alpha_2(P_1) & \alpha_2(P_2) & \alpha_2(P_3)\\ \alpha_3(P_1) & \alpha_3(P_2) & \alpha_3(P_3)\end{bmatrix}^{-1} \cdot \begin{bmatrix}\alpha_1(C)\\ \alpha_2(C)\\ \alpha_3(C)\end{bmatrix}
$$
With the data of the problem I got the following conclusion, as \$S_i(\lambda)\$ is constant in the range \$[\lambda_0, \lambda_f]\$ so:
\$
 \int\limits_{\lambda_0}^{\lambda_f} S_i(\lambda).P_k(\lambda) \,d\lambda =  S_i\int\limits_{\lambda_0}^{\lambda_f} .P_k(\lambda) \,d\lambda= S_i\$
So
$$
\begin{bmatrix}\beta_1\\ \beta_2\\ \beta_3\end{bmatrix} = \begin{bmatrix} S_1 & S_1 & S_1\\ S_2 & S_2 & S_2\\ S_3 & S_3 & S_3\end{bmatrix}^{-1} \cdot \begin{bmatrix}\alpha_1(C)\\ \alpha_2(C)\\ \alpha_3(C)\end{bmatrix}
$$
I thought it would solve the problem, but mathematically the result is not doing well. I'm getting very strange solutions, the determinant of the matrix A (the matrix 3x3) is practically 0 and the solutions are something of 10^{34} order. What am I doing wrong, and how to solve correctly part B of this question?


texts: Is there an order in which electricity goes off from the point of disconnection or fault?

texts: Have watched in a lot of movies, in scenes where their is a blackout and the power is going out like lets say for a country, the going off of the lights seems to follow a specific pattern.. so i was just asking.. with the high speed that electricity flows, is that the way it always goes out? do charges continue flowing like for a second or so even after a disconnection?


texts: Does turning a phone on and off deplete battery life?

texts:
First of all, I'm sorry if I had put this question in a wrong place, but I couldn't find a StackExchange site more suitable than this one.
Basically, I'm asking if turning something on and off might be more costly than keeping it on. Let's imagine such situation: I'm in a bus and I have a phone with which I can buy bus tickets. Unfortunately, my phone battery is dying, so I'm keeping my phone turned off. I imagine two scenarios:

1. When I get on the bus, I turn on the phone and use the ticket app to but the ticket. Then I turn off the phone. If a ticket inspector shows up, I turn the phone on, open the ticket app and show him the ticket.

2. When I get on the bus, I turn on the phone and use the ticket app to buy the ticket. Then I don't turn the phone off. In case a ticket inspector shows up, I show him the ticket (the phone has been working all the time).

I think the thing that separates these two scenarios is the risk, that my phone won't work when I'll have to show the inspector the ticket, and I'm looking for the solution with the lowest risk.
I've heard those sayings about the campaign where you turn off all your lights for one hour - people say, that actually turning these lights off and on costs more energy than keeping them on the whole time. Is it true and if yes, does this also imply, that actually the second scenario is less risky?


texts: LTspice diode model parallel capacitance

texts:
Some datasheets define parasitic/parallel capacitance for a diode. MA4E2532 datasheet even list SPICE Cjpar parameter.

But the LTspice D model lacks this parameter. An inductor L model has Cpar parameter but diodes don't. Am I missing something? Is this parameter has a different name or is it inherently useless to define and model it? When I manually add parallel capacitor to a diode it drastically change the results on high frequency.


texts: I inherited a project from an engineer who just left our company. In his  (Altium) PCB Layout, there's a footprint on the board for a 2 pin connector, but it's not in the library. I need to edit the footprint, and I can't figure out how to add it to the library so that I can edit it... Let alone to have in the pcb library... Tried the "Design -> Make PCB Library" option, it grabbed every part but this one.... Where am I going wrong?


texts: LVIT: w/ coil "spoiler": how much impact on inductance and Q

texts:
I've been reading about a linear displacement sensor known as a Linear Variable Inductance Transducer (LVIT).   This uses a movable conductive shield over a coil to modify the inductance.   The shield is referred to as a "spoiler".
Note the spoiler is nonferrous, eddy currents are created in the spoiler, which I assume decreases the inductance compared to a free standing coil.
My question is how much does moving the spoiler onto the coil change the effective inductance?  Is it likely to be approximately linear to the position?
Online coil calculator like Coil32 allow me to model a single-layer coil, but do not assume any sort of spoiler is present.


texts: How do I find this value for the feedback fraction?

texts: How exactly do I find this value for the feedback fraction Beta? Thank you. \$\omega_0\$ here is the natural frequency calculated as \$\omega_0\$ = 1/RC and s is the complex frequency.


texts: Chassis grounding for multiple daisy-chained units

texts:
I'm designing a system that provides power/ethernet/serial for up to 5 daisychained units. All of the boxes will be metal and my initial plan is to run power and signal ground through the 14 pin cables that will connect each unit. Each cable's shield will be tied to chassis ground and the plan is to tie chassis and power ground together in the PSU/COMM box.

My question is A) is this a sound idea and B) should I connect an RC connection (1Meg/100pF or something) from my PCB mounting holes to the chassis ground in each box? Pros/Cons?

The boxes will draw between 5 and 10 amps at 48V. We'll have 100 Mbit ethernet and also rs232.


texts: 3x3 LED grid using NPN transistors to switch (Arduino)

texts:
I am trying to design a basic project to multiplex a 3x3 LED grid in a common anode arrangement. In order to avoid sinking (sourcing?) too much current from the digital I/O pins of the Arduino I would like to uses NPN transistors as a low-side switch for each column.

I understand the case where I use a transistor to switch a single LED with the anode connected to Vs. However, I am having difficulty in designing the circuit for the multiplexed approach.

As my circuit stands I can't understand how to to wire it to source current from Vs and using I/O to control the flow.

Any pointers would be much appreciated.


texts: Redesigning the Arduino Duemilanove and Ethernet shield in to a single board

texts:
I have build a prototype with the Arduino Duemilanove and a Ethernet shield. It works great, now I want to get it redesigned in to a single board with a few extra connectors.

Screw terminal for power,
Screw terminal for a few of the digital pins,
RS232 connection to the serial port.
RJ-45 port
I also want an enclosure for this new board.

Q: Why do I want to redesign the board?
I can't have a barrel connector for power, its a requirement from the site where I want to install this product. I also want a nice metal enclosure ( I couldn't find one for the Arduino that was reasonably priced.

Q: How many units would you be making
100-250 to start and more as time goes on.

My question is; Where should I post this job posting?


texts:
Could someone explain to me what wide function means?
Is it a function with big number of inputs in single CLB or smth else?
EDIT 1
It is from  virtex fpga xilinx, p18
EDIT 2
'planar non planar pipulation', p 35, What is "pipulation"


texts:
Comes with the Arduino Uno

As you can see, it may require soldering. I don't have soldering experience but am receiving a soldering iron soon. Could you explain how this would need to be soldered if that's the case?


texts: Life expectancy of fan with magnetic bearing?

texts:
I asked this on Superuser a while ago, but since fans are often used for cooling electronic devices, I think that the question would be on-topic here too.

So how long is life expectancy of fan with magnetic bearing? I did some looking on catalogs of popular stores and datasheets of some manufacturers, but I couldn't find any information about life expectancy.


texts: I need to build a transistor circuit to go up from 3.3v (output of serial port) to drive some mechanical relays which require 24v input. Thoughts?