texts: Battery Charge and Discharge Time Calculations

texts:
I am performing some calculations but struck with confusion whether I am doing it correct or wrong due to contradictions of these calculations on different calculators websites. I hope here someone will help me with the validation of my calculations.

Battery Capacity            = 150 Ah
Battery Nominal Voltage     = 666 V
Efficiency Charge/Discharge = 0.87
Power Demand                = 100 kW
Current Demand              = 150 A

Battery Discharge Time = (Battery Capacity x Battery Voltage x Efficiency ) / Power Demand
Battery Discharge Time = (150 x 666 x 0.87) / 100000
Battery Discharge Time = 0.87 Hours
Battery Discharge Time = 51 Minutes

Alternative Method

Battery Discharge Time = (Battery Capacity x Efficiency) / Current Demand
Battery Discharge Time = (150 *0.87)/150
Battery Discharge Time = 0.87 Hours
Battery Discharge Time = 51 Minutes

Q1) If above both calculations are correct does it mean that I can constantly draw 100 kW from the battery for 51 minutes?

Q2) This website tells a different story for calculating a run time when you put 150 Ah and 100000 W Load = 0.015 Hour Run time

Q3) What is 10 in the equation given on this website for calculating run time. Runtime = (10 * Ampere Hours) / Load in Watts

Thank You


texts: Junction Potential parameter in Keysight Genesys

texts: In the Nonlinear Diode model in Keysight Genesys there is no forward bias voltage parameter. There is a "junction potential" (Vj) parameter, however. I've never seen or heard anyone use the term junction potential to describe a diode property though. Is it the same thing as forward bias voltage?


texts:
If I am correct in assuming a twisted pair cable is used to provide reduced susceptibility to noise. What is the benefit in having the cable twisted when it is inside a foil screen/shield?
Would shielding around two cables provide noise immunity regardless of whether the cables were twisted or not?

Thank you for any assistance in advance. I am relatively new to this topic so if anyone knew of any good reading materials to help it would be much appreciated.


texts:
I'm trying to implement HDMI to FPGA and vice-versa.

Currently I'm referring with https://www.fpga4fun.com/HDMI.html site.
But I'm confused that "But video signals usually also have an "off-screen" area, which is used by the HDMI receiver (TV or monitor) for some housekeeping. Our 640x480 frame is actually sent as an 800x525 frame."

Especially, how does he know 640x480 is actually sent as an 800x525 frame?
If I want to send 1920x1080 or 2592x1944 frame then do they have some already defined off-screen area size?


texts:
When placing ground vias to connect to my components Altium sometimes removes the via after connecting it with a trace to the pad.

In the following image, if I was to complete this trace. Altium removes my via and leaves the trace there...

(This is a fairly simple design with only two layers. The bottom layer functions as a GND polygon.)

I do not know if this is a known function of Altium, or if I am missing something.

edit: Altium does not always delete my vias.
(I cannot find a pattern in the times that it does happens though.)


texts: Values instead of designators on assembly drawing

texts:
While creating new Altium component for our company's library I started to wonder: why one would place a designator on an assembly drawing instead of value of a component? Wouldn't it be easier to assembly a board with drawing that contains actual values? If you have designators you need to lookup values in BOM to find out what component you need to place on a board. If you had values you know that straight away.

Maybe I am missing something? Please explain.


texts:
I made a simple motor driver as suggested here

+12V ---------+---------+
              |         |
             / \        |
             |M| motor ---  1N4001
             \ /       / \
              |         |
              +---------+
              |
            |/
CTL -/\/\/--|    2N2222 NPN
      1k    |\>
              |
             ---
              -

How do I connect and control this with and Arduino?

Could you please post instructions or direct me to some links I may find useful.


texts: What is Pipeline Flushing in microprocessors

texts:
I am reading the book "Writing Operating System from Scratch" by Nick Blundell. In one of the chapters, it is explained how we make transition from 16bit mode to 32bit mode. It says that before moving to 32bit mode we should ensure that all the instructions in 16bit mode which are currently inside the pipeline (instruction pipeline inside CPU) are executed. To accomplish this it says, we should make a far jump which causes a pipeline flush which the book says is completing all instructions currently in the different stages of the pipeline.
But what I understood about pipeline flushing is removing all the instructions after the conditional branch from the instruction pipeline due to changed flow of the program.
I am confused between these descriptions, could someone please explain what happens during pipeline flushing.
Further, the book says a near jump may not be sufficient to do pipeline flushing. I do not understand this as well.
There is a similar question :
Stalling and Flushing in MIPS Piplining

But could someone please explain about this in somewhat more detail.

Thanks in advance!!


texts: TNT field solver - howto handle 'air' between ground plane and wire?

texts:
I'd like to match the impedance on one of my PCB traces.

For this I chose to use TNT Field Solver.

Suppose that the trace itself looks like this (trace width currently set to 0.8128mm = 812.8 micron):

If I use the TNT like this:

It will iterate the trace width to match 50 Ohms, but in this case trace width is recommended to be 3082 micron (>3 mm) which is really huge so I think this is not the right way to do this.

Now I can add a GND plane also to the top like this, but how can I handle the 'air' between the trace and the top GND plane?

I have 2 questions here:

1.) How can I insert 'air' between the trace and the GND plane? (obviously it is not air, but there is no metallic conductor there)

2.) How to include vias in this calculation?

Update:

I've included now the ground stiching and the top-layer ground plane, however ground plane fills between the stiching and the signal wire which is not correct. For ground planes it is not possible to set the width or position, so I would need to do something around the red circles here:


texts: Do electronic devices like a servo motor need a certification to be sold in the US market?

texts:
We want to start a crowd funding project for our IoT servomotor. It comes with an integrated controller and an ethernet connection (no wireless) and now we are not sure about certifications (FCC, RoHS, etc.) if we send it to the USA.

The device its not an end product (I don't know if this matters). It's intended for makers or students to help them with their projects and not no waste time with motor control.
So its more like a arduino - a device for further development and instructed people (if this matters).


texts:
I have this fairly simple NMOS and it is mentioned that I can determine the Source current \$I_3\$ with the formula \$ I_3 = \frac{K}{2}(V_{GS} - V_{th})^2 \$.

Here they equalize Gate Source Voltage \$ V_{GS}\$ with the Source potential \$ \varphi_S \$ and my question is why? Since the Gate Source Voltage is the potential difference between the Gate potential and the source potential \$ V_{GS} = \varphi_G - \varphi_S \$ this would mean that the Gate potential is zero. And since I don't see why this should be obvious or what am I missing, what circumstances would allow this assumption?


texts: Determining the VA needed for a transformer, when I know the power DC

texts:
I am attempting to design and build my own power supply.  I would like to be able to get ~50VDC, and ~ 5A out of it at max load.

Unfortunately, I'm a little lost when it comes to understanding power transformers.  I understand that VA does not equal Watts, and I understand that 36Vrms is ~ 51VDC (which, after rectifier losses gives me approximately 50VDC).  What I'm missing is how to calculate the VA needed if I know I want 5ADC.

The current is also AC, so is 250VA an rms thing, or a peak thing?  How does the RMS of the current come into play?


texts:
Once an I2C master has been written, the next step is verification. Provided that a BFM for the slave does not exist, how should one go about doing this? Also seeing how I2C is open collector in nature.

Of course in any I2C transaction, the master would transmit the start condition, address, r/w bit and slave would transfer an ACK and so on and so forth. Is there a "standard" testbench for this? I would expect there to be code with flexibility to create BFM for our slave with some modification and then do self checks to verify if our master is working correctly.

Please don't tell me to use an open source I2C master. The purpose of this question is to understand how to do this.


texts:
In LCD Display, I want to SCROLL only one line in and Second line will be constant. I am using 0x1E command but the entire display will move.What commands is using for scrolling one line?
I am using ARM7 LPC1114X301 microcontroller and LCD is JHD162A.


texts: Zero Crossing Detection of ~ 400 kHz Signal with MCU

texts:
I want to measure the frequency of a signal using the digital input pins of the NUCLEO-F767ZI. The signal is sinusoidal with an amplitude of 5 V and a frequency ranging from 100 kHz to around 400 kHz.

1.) First I thought about simply feeding the pure analog signal to the input pin that is 5 V tolerable. I thought about using a serial diode for protection against the negative half cycle and using the internal pull down resistor of the MCU. Then I could generate an interrupt whenever the sinusoidal signal is high enough for the GPIO to recognize it as logical HIGH.

simulate this circuit – Schematic created using CircuitLab

2.) After a bit of research on StackExchange, I also found configurations using opto-isolators:
Detecting Zero Crossing of Mains (Sine and Square Wave)
The advantage is that it would output a sharp rising edge easily recognizable for the digital input pin, rather than the limited slope steepness of a sine wave.

3.) Since the signal does not have a dangerously high voltage, I could also skip the isolation and use a simple BJT or MOSFET instead. This would also output a sharp rising edge.

simulate this circuit

Which of the above options would you recommend? And above all: I hope that the parasitic capacitances of the semiconductor devices do not have any effect below 500 kHz, is that right?
Or do you have a different and better approach?

Best regards and thanks in advance!


texts: Theory and question on using a photo interrupter as a switch

texts:
Edit, answer: I managed to figure it out with help from passerby's answer. I needed a pull down resistor for the PNP transistor. Here's the final schematic:

When the beam of the photo interrupter is unbroken, the LEDs are off, and when you break the beam the LEDs come on.

Original question:

I'm making a money checker, to check for the existence of a security strip in US bills. My project will use UV LEDs, but for the sake of brevity here I'll just call them lights.

Basically, I'd like to build a circuit, without a microcontroller, that turns on the lights when the beam from the photo interrupter is broken. My understanding of them is that the IR detector is a phototransistor which allows current to flow when exposed to IR light, and blocks it when not. Could I use the output of the phototransistor into the base of a PNP transistor to turn on the lights? Again, my understanding is that with a PNP transistor, current at the base blocks current through the connector-emitter, so I could put my lights in series with C-E of the PNP, and the base of the PNP to the C-E of the phototransistor, right? The idea is that when I place a bill in the slot of the photo interrupter, the lights will turn on, and when I remove it they'll turn off. If I've figured this right in my head I shouldn't need much more than what I've mentioned plus a few resistors, right?

I'm on a phone right now, and I don't have internet at home, so I can't make a schematic.

Edit: I'm not sure how I could make what I'm asking any clearer. I want to turn on some LEDs when the beam of a photo interrupter is broken, without using a microcontroller, all of which I stated in my original text... Here's a picture of a hand-drawn schematic...

I've calculated that with a 3.2Vf drop across the UV LEDs, and 12 in parallel (I know I messed that up in my schematic), I'd need a 5.416 ohm resistor to get 20mA each. If I up the resistance to 10 ohms, I'd get a bit over 10mA each and have 169mW dissipated in the resistor. The 180 ohm resistor is to limit the current of the 1.2Vf IR LED in the photo interrupter to a little less than 20mA. The only thing I'm unsure about is the pull up resistor.


texts:
I need to monitor a high power DC motor with 48V and 600A battery, if it's stalled or not (its a lift truck).
The driver is 25 parallel MOSFET with Rds(on)=7.6e-47 which control by 15kHz PWM.
I think because of high current, i cannot use shunt resistor to check the current.
any bright idea?


texts: Altera Quartus. Technology Map Viewer looks different from expected

texts:
Recently, I've installed Altera Quartus 15.1 and now follow the "getting started" instructions, you can read it here. At the step: to see the resulting circuit go to Tools →Netlist Viewers →Technology Map Viewer (post-mapping). After going there I get the following scheme:

Instead of much more demonstrative diagram from the tutorial:

Here is the code:

// file lab1.v
module lab1(SW,LEDG);
    input [1:0]SW;
    output [1:0]LEDG;
    // input SW*, output LEDG*
    hadd myHalfAdder(SW[0],SW[1], LEDG[0], LEDG[1]);

endmodule

// file hadd.v
module hadd(a,b,cout,s);
    input a, b;
    output cout, s;

    assign {cout,s} = a+b;

endmodule

There are too much groupings and no view of underlying gates. I can't figure out how to adjust the view so it will be similar to what I see in the tutorial. Any suggestions?


texts: Why do I get feedback in my speakers in my car?

texts:
I have a Galaxy Nexus which I have with my everywhere. One of my favorite uses of this device is to play my music. Unfortunately, I have noticed something bothersome and I was wondering if I could get an explanation and suggestions for a way to fix it.

When I use an audio cable to plug my Nexus into my car speakers (via an aux cable), the sound quality is great. As soon as I plug in the charger into the phone (for those long trips), I get a really nasty whine/feedback-type sound. I have also recently purchased the Griffin Technology BlueTrip AUX so I can remove one of the wires in my setup. Sounds is a little fuzzy (assume that's the compression), but I also still get feedback (although it is quieter - more like a light buzz).

First, why am I getting this feedback sound? Second, is this a problem with the car, the cables, my phone, something else? And, third, is there a way in which I can fix this issue. Open to all suggestions.

My preference is that I can use a Bluetooth device in my car and that I do not get the feedback noise at all.

P.S. I am not an electrical engineer in the least bit. Would really appreciate explanations that are more along the "layman" terms so I can understand what's going on.


texts: I'm trying to build an inverter circuit in LTspice using voltage controlled switches

texts:
I'm trying to build a H-bridge inverter circuit on LTspice, but I'm having trouble with getting a correct waveform. The upper and lower switches do not appear to be in sync (i'm not getting a complete square wave as there is an intermediate voltage level that the circuit stops at for a short period of time). There also appears to be no current flowing through the diode (Id1 through  in the picture), which is placed in the circuit to allow for the discharge of the inductor to take place.

For the voltage controlled switch, I'm doing a basic pulsed switch operation with a voltage supply that varies between 0V and 1V, with a Ton of 0.5 and period of 1.

Not too sure what went wrong with my model. Any help or design advice will be greatly appreciated! Thank you


texts: How to power up rfduino and fona from the same power supply?

texts:
I am building a simple sensor device that's using Adafruit Fona to be connected to the Internet.
I want to power up RFduino from the Fona USB 5v power supply. There is a pin on Fona that supplies 5 voltage as far as I understand and I am using voltage regulator to step it down to 3.3v
There is a schematic:

The problem is:
When Fona starts sending data over gprs RFduino gets rebooted. I guess there is a voltage drop or current spike or something. I've tried to put 100uF capacitors around the regulator, but it didn't really help. Although sometimes it works fine... but in most of the cases it does not.
How to fix the circuit that it works and stable?
Thanks


texts: Surface Mount Adapter PCB With Castellated Holes

texts:
I have some prototype boards that I would like to modify. The modification includes removing a section of circuit and replacing it with another circuit. My theory on how to do this is to make an adapter board that will hold my new circuit that will have castellated holes on the perimeter. The perimeter holes will align with existing SMD pads on the main board in order to make the necessary connections.

My question is are there recommended land patterns for castellated holes that I could use to guide the design of my adapter board? In this case I would be designing the castellated holes to match existing land patterns. Of course this is not optimal but I hope that for a prototype it will work. Most of the mounting points on the main board are one side of 0402 resistor lands. I'm guessing that I should use a hole that is slightly smaller than the existing pad. For example, to connect to a 0.024" square pad I'll use a 0.020" castellated hole. Does this sound reasonable?

Thanks.


texts: How to amplify the output of an on NMOS, connected to zero source voltage?

texts:
I am simulating a 3 transistor based XNOR cell using HSPICE. The circuit is shown in the picture.

technology = 45nm

Vdd=1.1v

|Vth|=0.62v

In the case of A=1 and B=1, the output is charged through the N1 transistor. You know NMOS passes the Vs=Vdd to its drain as Vdd-Vth. The problem is when Vth>Vdd/2, the drain voltage becomes less than Vdd/2 and it is assumed as approximately zero, while the desired output is Vdd. So, if I connect this output to the gate of a PMOS, it will be turned on, which is not the desired case.

I want to amplify this output using few transistor and no resistances, just the case A=1 and B=1, to become close to Vdd. How is it possible to amplify this output?

Thanks

simulate this circuit – Schematic created using CircuitLab


texts:
I am an undergraduate and new to electronics. I wanted to know if it is possible to send audio over an infrared LED?

I plan to use a  555 timer to generate PWM output with carrier at around 44 Khz to satisfy the Nyquist rate. On the receiver side I would use a one or two stage active low pass filter to get the output. Is it feasible? What is the maximum range I can get?


texts:
I bought this stripboard on Ebay. It said "Veroboard" so I had thought it would be with some sort of tracks:

http://www.ebay.com/itm/281342062542

Turns out there's copper around the holes but there's no actual copper tracks. I wondered if maybe the holes are connected in a layer below or something (especially since there seems to be row numbers), but it doesn't seem to be the case or maybe my voltage tracing skills just suck ;)

My question is then, what is the point of making a board with copper around the holes, when there's no actual connections anyway?


texts: Should the Quartus programmer find the CPLD wired as shown via JTAG and USB Blaster?

texts:
I apologize beforehand for the elaborate description that follows:
The accompying figure shows an Altera CPLD TQFP chip mounted in a socket-adapter for pin access.
The chip is brand new (i.e. never been programmed before).
I use an STM32 Nucleo dev kit to supply the 3.3V pins connected to the two IO-banks for supplying VCCIO1 and VCCIO2 on the CPLD (there are 6 VCCIOx pins, but I've only connected 4).
I've connected two GND pins along each edge of the CPLD to a GND pin on the Nucleo (there are more GND pins, but I've only connected two along each edge).
The 1.8V for supplying the CPLD internally is taken by voltage-dividing the 3.3V from the Nucleo.
The resistor values should limit the current through the voltage divider to be less than 1mA.
Note that all VCCINT pins are connected to the 1.8V.
The JTAG pins of the CPLD are connected to the 10-pin female connector of a USB Blaster that in turn is connected to the programming PC.
When I press the "Autodetect" feature to scan for the CPLD in Quartus programmer, I get "unable to scan device chain". Can anyone immediately see a problem with the setup ?


texts: How does electricty flow in a flip-flop circuit? I can't understand how memory bits work with NAND gates

texts:
Consider:

simulate this circuit – Schematic created using CircuitLab
The i bit is what we want to store, and the s bit is our setter bit. Each box is a NAND gate.

I am a little confused with how the flip-flop circuit works. Mainly, in what order things are happening.
Say we slowed time down to crawl, could the following happen:

Say s is 0 and i is 1.
0 1 NAND -> 1. so a becomes 1
Now logic gate 3 runs
a is 1, but logic gate 4 hasn't run yet... so c is...0?

If c is 0, 1 NAND 0, o bit would become 1 :<
I am getting tripped up by ordering / speed of light here. Is it possible that the 4 gate, which computes c "did not have time to compute" itself, by the time the 3 gate runs? Is this question nonsense?
How does electricity flow here? Is there some order? If so, what determines this order physically?
I am a software engineer, studying logic gates for some fun. Please forgive me for what is probably a very noob EE question.


texts: Hard drive won't power on, is this the reason why?

texts:
I have a somewhat old, but functional (used to be, actually) hard drive, model Samsung HD103SJ, which I use for backup purposes. This means this is not a fixed unit.

Since a few weeks ago when I moved to a new city, I notice it wouldn't power on anymore. So, upon closer inspection, I noticed one component hanging "loose" in its PCB:

The component is labeled 4R7V. It appears to be actually connected... Here's a look on the opposite side:

My questions:

is it an inductor?
is it the reason why the hard drive is non-functional? Is it reasonable to expect to fix the problem by replacing it?


texts: Do diodes care about current? or only voltage?

texts:
I have a diode, specifically a Zener diode and I connect it in the following configuration:

simulate this circuit – Schematic created using CircuitLab

So that it acts as a voltage clipper. My question is, do I care about current into the diode at all in this process? Or do I only care about the V_f and V_z of the diode? If the forward current of the diode is say 1mA, and I only give it .01mA will it still turn on and conduct? or will the circuit stop acting as a clipper and just pass all voltages?


texts: How do I decide what capacitor to use in a circuit?

texts:
I am using a voltage regulator, and to get cleaner power, the datasheet recommends using a 0.33uF capacitor. However, it doesn't say what type it wants. Stupidly, I went out and bought a 10 pack of 0.33uF 50V Radial Electrolytic Capacitors. After looking up on this site, I found that the symbol means that it is a unpolarized capitator. Will they work because they are polarized? Does this really affect anything in this circuit?

Also, there is a 20% tolerance. Will this affect this circuit?

And so I don't have to ask a similar question again, how did you get that? I know they have different tolerances and ratings depending on the material but does it really matter?

Transistor datasheet:

I can get the voltage regulator datasheet if anybody needs it. Thanks in advance.


texts: Help designing a satellite MPPT board [SPV1040]

texts:
I'm in the process of developing a pocketqube and I am currently working on the power system.
I am hoping to use an SPV1040 MPPT IC to simplify the design and maximize efficiency.
Each side of the craft will have 8 Trisolx GaAs solar cells with an open voltage of 2.6 V and max power voltage of 2.3 V, they have a max current of 14.6 mA. Obviously all these characteristics are in a direct sunlight ideal scenario at ambient temperature. The battery charged will be a 700 to 900 mAh 3.7 V Li-Ion and the output voltage needed is 3.3 V.

The following schematic here displays an output voltage of 5 V though I cant find what resistors I need to change to adjust that.

Here is the datasheet http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00287506.pdf

Input also says 3 V though the IC is rated to 0.3 V, how can I change that?

Also on a last note I plan to use 1 MPPT circuit for each panel, if I put 4 parallel cells in series with another (basically 1 panel) what diode should I use between the series cells?


texts: Measuring USB power adapter quality using multimeter

texts:
I have heard horror stories about poor quality USB power adapter. I have a collection of no less than 20 USB power adapters, most are from cell phone manufacturers and some from small projects.

I want to make use of the USB power adapters or give them away to those who needs it. I wonder if there is a way to determine the quality of USB power adapter using a multi-meter (I have a Fluke 87V clone, which can measure frequency and duty cycle)? I also have various USB cables that I can sacrifice.

What I am looking for is if the power adapter can do a proper job of converting AC to 5V DC, a clean voltage without spikes of noise, can supply the current amperage as stated on the adapter. I don't have access to an oscilloscope.


texts:
I have recently designed and assembled a circuit for a Quectel M95 unit to be controlled by Usart from an Atmel micro-controller. I have a problem with the power supply of the M95, I followed the reference circuit provided in their datasheet, only thing I changed was the voltage divider circuit near the regulator to get 4.5V rather then 4.16, still within the M95 limits. Whenever I turn it on it starts to smoke and short exactly on the Vbat pins, I have been looking at it for a couple of days now trying to figure out what I missed.
Maybe some fresh eyes will notice something I missed.
I have uploaded my circuit below.
Thanks


texts: Device for capturing analogue signal at composite video frequencies

texts:
I am trying to continuously capture and digitise raw composite video signals with sufficient bit depth and sample rate to be able to decode it including the colour channels. I am not looking for a video capture board as i'd like to have the raw signal and decode it in software myself.

So my question: What is the most cost effective way of doing this? i've already looked at digital oscilloscopes (pico etc) which offer capture functionality. but i am not sure if this is the best / cheapest option. it seems to me that capture of analogue signals would be a fairly common requirement but haven't found many easy to use products that do this. Ideally i am looking for a USB connected device with an interface to C++ or similar. any advice greatly appreciated!


texts: Troubleshooting steps for SMPS producing 1.3V instead of 5V

texts:
I have an SMPS based on the TPS563200 regulator. It worked great. Then it parted ways with its magic blue smoke. Why this happened is a separate conversation, not one I understand fully. It was turned on after dozens of other times, and then caught fire, producing this:

The relevant circuit is as follows:

Here's the only thing running off the 5V - two servos:

I replaced the IC with a fresh one, and now I'm getting 1.3V at the output pin. I don't understand smps design enough to be able to figure out what that should be telling me.

What's a logical next step?

The only other components with visible damage on them are the two ceramic caps in the picture, they're input caps and the damage is just soot. Clearly, that's just visible damage and I don't know what else if broken but not visible.


texts:
I am new to PCB design and I want to use a USB-C port instead of a USB3-A port, but in the documantation I have only found how to use a USB3-A port.

I have come up with a sulution, but I am not sure if my solution will work.

(I don't know if it works so please don't use it if you also don't know if it works)


texts: Help to understand this encoder timer tick code

texts:
Could somebody please please help me understand the following code. Its running on atmega128 @ 16 Mhz. Its reading an encoder pulse. Uses timer3. The encoder CHA is connected to PIND2 (INT2) which gets triggered whenever there is an interrupt from low to high. CHB of the encoder is connected to PINE7.

I cant quite understand why TCNT3>>3 in this case.

SIGNAL(SIG_INTERRUPT2)
{
   timer3_stop();
   Right_Odometer_Period = TCNT3>>3;
   right_overflow_occurred = timer3_overflowed;
   timer3_start();

   if ((PINE & 0x80) != 0)
   {
      right_odometer++;
      right_up = 1;

   }
   else
   {
      right_odometer--;
      right_up = 0;
      Right_Odometer_Period = Right_Odometer_Period * -1;
   }
   Right_Velocity = Right_Odometer_Period;
   averaging_array[array_ptr++] = Right_Odometer_Period;
   if (array_ptr == 32)
   {
      arraysum = 0;
      for (int i = 0; i<32; i++)
      {
       arraysum += averaging_array[i];
      }
      average = arraysum>>5;
      array_ptr = 0;
   }
}

void timer3_init(void)
{
   TCCR3A = 0x00;
   TCNT3 = 0X0000;
   ETIMSK = (ETIMSK | (1<<TOIE3));
   timer3_start();
}

void timer3_start(void)
{
   TCNT3 = 0X0000;
   timer3_overflowed = 0;
   TCCR3B = (1<<CS30)|(0<<CS31)|(0<<CS32);
}

void timer3_stop(void)
{
   TCCR3B &= ~(1<<CS30)|(1<<CS31)|(1<<CS32);
}

SIGNAL(SIG_OVERFLOW3)
{
   TCNT3 = 0X0000;
        Right_Velocity = 0;
   timer3_overflowed = 1;
}


texts:
im trying to identify the following 4 transistors, but am having trouble tracking them down.

The one that I think is the dual transistor is marked .1Ft on top of it, and the other three leg one is marked 3BW and then 2b (sideways on). After a search on the internet I found these two as possible replacements :
http://www.ebay.co.uk/itm/271507549901?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

http://www.ebay.co.uk/itm/BC856B-NXP-Transistor-PNP-Sot-23-/360843952989?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item5403f9c35d

but info on these two transistors seems to be really thin on the ground. Is there a way to test the transistors and find out what the rated current etc is, as there are several of them on another board that I have that is identical and still working.


texts: How can a metal object bond to a live object when not touching anything else?

texts:
My electric stovetop developed a fault which caused a short circuit inside the unit (sparks flying and all). The fault occurred as one of the knobs came loose and the metal strut that was supporting it fell down into the unit. The casing of the stovetop is earthed to a nearby power socket, with a resistance of 0.5 ohms. There is no RCD installed on the circuit. No circuit breaker or fuse was tripped during the fault, and immediately after it occurred I turned the circuit off at the fusebox.

Here's the part that confuses me. A clean metal teaspoon was lying on the casing of the stove but not anywhere near the heating element. It wasn't touching anything else. Immediately after I turned the stove off, I realised that the spoon actually got stuck to the casing of the stove - I had to apply quite a bit of force to pull it off, and there was a very small but noticeable ridge that could be felt with my fingers on both the spoon and the stove where they were touching.

My question is, how could the spoon have bonded to the stove if there was no way for it to have a potential difference (i.e. it wasn't touching anything else except the metal casing of the stove?). Is there some physical explanation that doesn't require current to flow through the spoon (and thereby explain heating as a result of resistance?). The spoon was made of stainless steel.

Obviously, I've had an electrician look at it, but apart from checking that it passes the earth test, he couldn't give me a reason why the spoon could have bonded to the stove, nor why the circuit breakers weren't tripped.

I am not an engineer by the way, although have some basic technical and physics knowledge (coming over from stats and data science SE).


texts: How can I interface with these 24 V signals?

texts:
I have a few 24V inputs to my micro controller from Limit switches. I have conditioned the signals as shown. Pulled down, de-bounced and level converted.

I have some signals that are again 24V but coming from a distance of 50meters and going to multiple such conditioning circuits on different boards in the system. Will this conditioning handle such signals? If I have to use high impedance I was about to use comparator ICs. What would you suggest guys?


texts: Controlling audio signal with digital potentiometer

texts:
I am very confused about how to go about using my digital potentiometer to control an audio signal. I have a MCP4231 digital pot and I would like to use it as a MCU controlled variable resistor for gain control of a headphone amplifier. I know there are much better ways of doing this (such as special op-amps) but I would like to try this using the digital potentiometer.

So here is my quesiton. Why in this video there is no mention of biasing the input signal, where as over here it is necessary?

Additionally, the answer to this question about DC biasing of audio signal says that the method mentioned here should not be used due to noise from the input signal!

So basically, I am VERY confused. Do I need a DC bias for the chip I am using? Why can the YouTube lady get away with no biasing? Should I use the method in the first link of the second one? THEN finally, once I choose a method, how do I choose my resistor values?

By the way, this is the circuit I am trying to control. The analog potentiometer that I want to replace is circled in red.


texts: In a NOR gate not connected to any power supply, how can the output be '1' if both of the inputs are '0'?

texts:
I was reading about SR Latches and this very weird (and silly) question popped up in my head.

Here, when A and B is 0, then Q is 1.
Suppose that this NOR gate is lying in air, not connected to any power supply. Then as there is no potential or current passing through A or B, we can say that the inputs are 0 and 0. Then according to the truth table, Q must be 1! How is that even possible? What does it even mean?


texts: Omitting ΔVbe in emitter follower KVL equations

texts:
In the forward active region, if we draw an emitter follower voltage variations as follows:

It seems by using KVL we can say that:

  ΔVin = ΔVbe + ΔVe

Now in many texts they omit ΔVbe and equate ΔVe to ΔVin.

Is ΔVbe caused by the dynamic resistance of the base emitter junction?

If so, how small should that be comparing to the emitter resistor(Re) to be able to omit ΔVbe? Can you give some practical values?


texts:
Is it possible to safely double the current limit using 4 bridge rectifiers? In one forum I found someone wrote:

  Use four bridges, one for each leg. Tie the AC input (cathode to
  anode) connections across on each bridge. This now makes a single
  equivalent diode, at twice the PIV and current. Two diodes in series;
  two in parallel.

I tried to draw a schematics to these instructions but it doesn't make sense to me how it can work.


texts: What is causing my error in executing arm-none-eabi-gcc.exe from Keil uVision?

texts:
I'm attempting to set up Keil uVision to build a simple C++ program for the STM32F3 microcontroller. I've downloaded the GNU ARM toolchain on my Windows computer and placed it into the directory C:\Program Files (x86)\GNU Tools ARM Embedded\bin\. In Keil, I created a project and opened a window Manage Project Items where I was able to select Use GCC Compiler (GNU) for ARM projects and specified the prefix arm-none-eabi-.

When I click Build, the output window shows that it finishes compiling and reaches the linking stage. Here's the output:

Rebuild target 'Target 1'
linking...
--- Error: failed to execute 'arm-none-eabi-gcc'
".\evt-bms.elf" - 1 Error(s), 0 Warning(s).
Target not created.
Build Time Elapsed:  00:00:00

I've verified that arm-none-eabi-gcc.exe is in the bin directory (though I'd be expecting a complaint about g++ since it's a C++ source).

Here's a screenshot of the Folders/Extensions settings page:

Does anyone have any ideas for further debugging I can do? It'd be great if the output window had a little more information, as it really isn't all that helpful by just saying it couldn't run it without any context of the command it attempted.


texts: A very basic question about tuning-word of a DDS

texts:
I have read that a DDS have two inputs one for master clock another for the tuning word. By processing these two inputs the DDS generates the output waveform at a desired frequency.

And if I'm not wrong we need to send this tuning word to the DDS via its SPI interface.

But I cannot find information about the tuning word and is a little confusing.

What I mean is when we program a micro-controller, we code and compile and upload the data to it. And we do the coding part by using lets say C language we know what instructions do what.

But when it comes the DDS, how is the tuning word is sent/uploaded and how it is coded? Do we send it through an IDE? I have no picture about it. Can someone simplify this and give maybe an example how it is done.

That sequence with FQ UD CLKIN W CLK looks complicated to me. Is that about how SPI functions? It also seems DDS has no memory -- does it need that sequence nonstop as an input? The articles I found were too advanced for me. That's why I'm asking primitive questions.


texts: Low power design - switch out voltage divider using transistor?

texts:
I have a very simple voltage divider circuit for measuring the resistance of a platinum 100 Ohm resistor.

I want to be able to switch out the voltage divider circuit from the power supply in order to save power.

Is this possible?

---------------------------+3.3v
              |
              |
          Transistor----low/high
              |
              |
              R1
              |
              |-------to A/D pin
              |
              R2
              |
              |
----------------------------GND


texts: I'm trying design a video transmitter around an 5.8GHz Airwave module. The documentation says the trace to the antenna must have a characteristic impedance of 50 ohms. How do I calculate the characteristic impedance of my trace?


texts: Why does the first pulse have a different duration than the other pulses?

texts: Why does the triggered astable in the next figure have the duration of the logical component "0" of the first pulse lasting 2 times the logical component "0" duration of the next pulses (see the answer below)? Are there any triggered astable that have the same pulse duration even from the moment of triggering?


texts: Why does this two terminal inductor have a polarity?

texts:
The Murata LQP03TN2N0C02D 2nH 0201 size inductor apparently has a polarity marking on the package:

I don't see anything on the data sheet that suggests there's a difference installing it in a circuit one way vs the other.  Even if there are other magnetic fields nearby I expect this to behave the same regardless of polarity.

This is a single two terminal inductor.

What am I missing about this part that makes knowing the polarity and installing it one way vs the other important?


texts:
I've just started making an amplifier for some speakers and I'm completely new to this and couldn't find any information in the documentation explaining it. So I just wanted to know if S-GND and PW-GND can be connected to a common ground back to the negative battery terminal? If not how would I go about connecting the grounds up?

Datasheet: http://www.st.com/web/en/resource/technical/document/datasheet/CD00001048.pdf

Thanks in advance :)
Will

EDIT I'm making the standalone version


texts: Solutions for implementing a USB Mass Storage Device

texts:
I'm trying to figure out a convenient way with which a PC can configure an embedded system. The PC will have a custom app. written that can 'talk' to the embedded uC and configure the various settings and upload some data to it (~ 500 KB). The advantage of this approach is it's simplicity.

My initial thought was to go with a UART to USB bridge and take it from there. However, I'm now considering implementing a usb mass storage device instead. The advantage is that the end-user can simply drag and drop a file which contains the data and the configuration settings. The board will have a flash memory IC of appropriate size mounted on it. The uC will be a low-end STM32 (I have not decided on a specific chip yet).

Since the file will have to be in a specific format for the embedded system, I believe I'll still have to write a custom app. for the PC to write that file from the settings provided by the end-user. This isn't overly difficult.

But what I'm confused about is, how do I mount the flash memory as a FAT disk on the PC? Are there any integrated solutions - perhaps a flash memory which talks to USB directly?

NOTE: I know about LUFA for the AVR. However, I'm not yet sure if I'll be able to use an AVR as I also have to drive a 800x400 RGB display. As a test, I did drive the display using an AVR running at 8 MHz. The update rate was slower than I'd like.


texts: Test current capability of a 24V 15A power supply

texts:
I have a power supply from a broken 3d printer. I want to test if it is still okay. It is specified as 24V, 15A (360 W). It is giving me perfect 24V at idle, but I wanted to test if it is still performing well under (almost) full load.

But what could I use to dissipate 360W at 24V? And: my multimeter is only specified for 10 A, so I will have to use something as a shunt resistor...

I'd appreciate any suggestions avoiding expensive equipment.


texts: Level-shifted push-pull gate driver speed problems

texts:
I am designing a peak detector with a MOSFET as reset switch. I want to drive the MOSFET by the output of a CD4528 monostable multivibrator (voltage vr in the schematic below). When the N-channel MOSFET Q4 is turned on, the hold capacitor Ch is discharged to -10.5 V through the discharge resistor R (I want my peak detector to work at negative voltages as well within +/- 10 V).

The problem is that I need a gate voltage slightly lower than -10.5 to be sure that the MOSFET is turned of, and a gate voltage higher than about -5 V to be sure that the MOSFET is turned on. The CD4528 is powered with 15 V but does not output negative voltages. I then designed a relatively simple push-pull gate driver with a pnp-based level shifter. The schematic below shows the design:

Since I am using a reset pulse of about 1 microsecond, I found the reset circuit to be too slow, especially at turn-off. Adding a Schottky based baker clamp to Q1 did make it a faster, but still it is too slow.

Any ideas on how to improve the speed of this circuit?

The components used is as follows:
Q1 is 2N2907, Q2 is 2N2222, Q3 is 2N2907 and Q4 is the N-channel part of the Si4532 complementary MOSFET pair. D1, D2 and D3 are BAT42. D4 is 1N4148. RB, R1 and R2 are 4.7k. RG and Rd is 1k and Ch is 1n.

By the way: The MOSFET does not like more than +/- 20 V on the gate with respect to the source-terminal, so that is why I want the gate voltage to be within -15 to 0 V instead of +/- 15 V which might be easier to implement.

I have designed a similar reverse polarity peak detector that will detect minimum voltage and is reset by a P-channel MOSFET. In this case I omit the level-shifter and it works fast enough using the same components. So I am sure that it is the PNP-based level shifter that is the problem (SPICE-simulations also confirmed this).

Thanks in advance :-)


texts:
Is it possible to design asynchronous LIFO ( i.e. LIFO with different READ and WRITE clock)

In FIFO , we need to change the write address pointer only on wr_clk while in LIFO we need to change the write_address pointer on both wr_clk and rd_clk. Hence in my opinion we can't design a async LIFO ?


texts:
I have a Jupiter F-2 GPS receiver connected to an STM32 that outputs NMEA messages every second. The GPGSV message indicates that I have 12 satellites in view. At the same time, the GPGSA messsage indicates that I have no fix, either 2D or 3D.

According to the receiver documentation, 5 satellites are sufficient for a 3D fix.

What could explain the discrepancy between the GPGSV and GPGSA messages? Why am I not getting a fix?


texts: My MPLAB X IDE debugger gives me an error whenever I try to debug my PIC24 Explorer 16/32 Development Board

texts:
I am doing a simple program for my PIC24FJ1024GB610 Microcontroller from Microchip, using the Explorer 16/32 Development Board, it has it's own PKOB (Pikit On Board circuitry).

My IDE is: MPLAB X IDE v5.05
OS: Windows 10 Pro, 64 bits,

Whenever I try to download my program into the Development Board, I get this error:

  The programmer could not be started: Could not connect to tool
  hardware: PKOBSKDEPlatformTool,
  com.microchip.mplab.mdcore.pkobskde.PKOBSKDEDbgToolManager

Kindly help me with this issue.


texts: Analysis of a Circuit Simulation with Fault

texts:
I need to simulate this circuit in order to know how much voltage and current will generate the fault at the load.

In this circuit I use a fast blow 7A fuse, a P Mosfet IRF5305 with +- 20V Vgs as maximum, a 10 ohm 1w resistor at the gate and a TVS 1N6376 unidirectional tvs diode with 16.5V max clamp at 70A 1500w. The working voltage of the diode is 12v and the breakdown is 14.1V
The fault I want to simulate as you can see is when you put 25v at input, that voltage will exceed max voltage of the Vgs mosfet so it will fail.
The load is a 85W one (imagine a notebook connected as an example).
I dont know what will happen to the circuit next. The fuse will blow?, the tvs will derivate all current to gnd?, how much voltage and current will see the load?
Maybe anyone with experience in circuit simulation can help me. I recently purchase Multisim 14.0 but I am getting experience till today.


texts:
when a diode is forwards biased can current flow backwards through it?

this question comes from me trying to understand class AB amplifier biasing, so any additional comments about the diodes' use here would be appreciated


texts: Need to get sensor data from a Arduino Pro Mini to a Arduino Mega that is about 150 feet away from each other

texts:
So like the subject line states...

Need to get sensor data from an Arduino Pro Mini to a Arduino Mega that is about 150 feet away from each other (maybe slightly less) both operating at 5VDC.

Do I need to convert to RS485?  I could use XBEE radios but that adds a few more components to go wrong.  Plus the radios would be at least 25.00 each.  Basically I am using the Milone eTape sensors to go to a controller to control a well pump but the lake and the well pump are about 100-150 feet from each other.  To top it all off the "installers" did not bury a conduit when they just replaced the 4" pipe so they put an inline connector on both sides so we can float the wire through the water line.  All fun stuff.  Maybe the radios would be the better solution?  Any guidance, help suggestions would be greatly appreciated here.


texts: Creating led sequence without microcontrollers

texts:
I'm new to electronics and I can work only with transistors. I'm trying to create a circuit that performs action like this:
Let's say I have 10 LEDs. When I supply power first LED lights, 0.5 sec later second LED lights and 0.5 sec later third LED lights and so on. But all the LEDs keep lighting during others light.
I want to know if it's possible or not. If possible please give a link to such a tutorial.
Thanks all for help.


texts:
In KiCad (Pcbnew), and perhaps other PCB layout programs, there is an Eco1.User layer and also an Eco2.User layer.

What does the "Eco" stand for? And what are these drawing layers typically used for, in particular, do they have an "official" purpose?

Google doesn't turn up much on the topic, although I found alternate spellings ECO1 and E.C.O. 1.


texts:
This is the charge pump design from Razavi.
I want to design the opamp for the circuit, a design for which is as given below.

Is the op-amp architecture correct for this circuit, since it requires a rail to rail input swing? Also, how do we increase the gain of that op amp?


texts: Cheap oscilloscope showing 16 MHz square wave

texts:
I own a cheap oscilloscope Hantek DSO4102C. It's rated bandwidth is 100 MHz, and sample rate is 1 GSa/s. Some info about the tool can be found here: http://hantek.com/en/ProductDetail_3_4163.html
Now I have an Atmega328P MCU running from an external quartz at 16 MHz, without any code it it (chip erased by usbasp), only CKOUT fuse bit is set. So I supposed to see a square wave at PB0 pin, but my scope shows it quite distorted:

MCU's datasheet doesn't mention a pin rise time, which was a big surprise to me, so I cannot check if measured 9.5 ns is a valid value. But judging by Pk-Pk voltage exceeding 6 volts (and even going below zero for a good 560 mV), I believe there's a problem with the scope. Am I right?

ADDED LATER, AFTER GETTING SOME ADVICE
I've assembled everything on a  breadboard, rather then using Arduino Uno. I've connected ground clip from the scope to the ATMega's ground pin with a wire through breadboard. I'm measuring directly at the output pin (see photo of my layout below). Now I'm getting better results, also with 20 MHz oscillator.

Obviously, Pk-Pk values are now more close to reality, as well as signal shape. So thanks everybody for the help!


texts: What is that meaning of "This Sensor uses 5v as a working Voltage only"?

texts:
I am trying to understand the meaning of a 3.3v or 5v IC but I don't know how to use the right keyword in search engine to find the explaining   article so I'll explain...

We know Arduino UNO R3 as example have 5v and 3.3v power out pins so I could use to to supply the Sensors or other components in circuit but sometime I read "this sensor is 5v only" or "3.3v only", what does that mean?
Does that mean you should power the sensor with five volt or the 5 volt for IO pins of sensor and if the sensor 3.3v  does that mean this value for IO pins of data like 3.3v that means Logic 1 and if 0V that's mean Logic 0 and the same things for 5V.

I read Arduino Mega difference than Arduino Duo because Duo is 3.3v only, I hope to fine some explaination of how to solve problem like this if we want to run 3.3v sensor on 5V MCU or 5V sensor on 3.3V MCU . Do I need level shifting ?

Second question Seeedstudio say their sensor "Grove - IMU 9DOF v2.0" is  Working Voltage: 5V

http://www.seeedstudio.com/depot/Grove-IMU-9DOF-v20-p-2400.html?cPath=25_134

the schematic for board design

https://www.docdroid.net/qRsbWXl/grove-imu-9dof-v20.pdf.html

show use of 5V to 3.3v voltage regulator for input of chip while the chip used is InvenSense MPU-9250 when I check the Voltage - Supply for Chip in Digi key I found it  2.4 V ~ 3.6 V, can someone explain  if that this 3.3v for IO pins for data because it use I2C as data bus or what?

Thanks for everyone shearing his knowledge in this site,


texts: Agilent 4294A Impedance Analyzer: "Bridge Unbalanced" during calibration

texts:
I am having problems calibrating my test fixture for the Agilent 4294A Impedance Analyzer. The open measurement always works, but with the short measurement I always get the error message "Bridge Unbalanced".

The same problem was described a few years ago (https://community.keysight.com/thread/4715), but never answered.

I changed all parameters like amplitude, frequency, bandwidth etc., but without success. Does anyone have an idea what the problem is or what you could do about it?


texts: Did ESD fry my REF200 current source circuit?

texts:
Last summer I built a current source to power a custom-made pressure sensor. This source uses a REF200 IC and is powered by a wall wart that outputs 5V. The whole circuit is encased in a plastic box that has holes drilled for the energy input (+5V) and energy output (100uA) cables (see circuit).

The circuit worked well for over 7 months and then mysteriously died one day when a friend was using it. He claims he felt a slight shock when he touched a surface that was connected to the pressure sensor. Yeah whatever.

Except that we built another (equivalent) current source and, after a few days of good performance, I felt a slight shock (when I touched a rubber surface connected to the system) and the current source stopped working. Could this shock (which I'm pretty sure is ESD) have damaged the REF200 IC that was inside its own case?

I suppose the charge could have traveled from my hand to the rubber, jumped to the power output (100 uA) cables, then fried the REF200. But I thought that ICs were mostly vulnerable to ESD when not mounted on a board.

So... did ESD fry my defunct current source? And if so, what is a simple way to prevent this? Will grounding the system help? (This is what my friend suggested)


texts:
I'm using HM-11 Bluetooth module and is in layout process currently. One of the concern raised by my friend referring to the datasheet is whether the footprint lead dimension is the same in bottom view?

Another concern was whether the pin numbering orientation is correct, because normally the footprint lead is shown as bottom view in datasheet.

Hope anyone here that has a sample of HM-11 on hand or experience using them can help to verify this for me because I don't want to have my PCB re-fabricated again.

HM-11 datasheet - refer page 12


texts:
I have an old wacom tablet at home, its really big and I'd like to use it but I've lost the pen for it. It uses pens with passive LC circuitry. The board creats an EM-field (I can see it on my oscilloscope) with which the pen interacts and the board can deduce information from the interaction. I looked up the patent and its basically just a coil parallel to a couple of caps.

Is it possible to make a simple LC-pen that would interact with the board simply by trying without more knowldege about the board and pen?

simulate this circuit – Schematic created using CircuitLab


texts:
I would like to buid a trapezoidal (waveform) with the following specs :
rise time : 10ns
VTop : 1V
tTop: 40ns
fall time: 15ns
Linearity is important

Frequency max : 10kHz
Load is has a very high impedance (Op amp input)

I was planning to make a sawtooth first and then clip off the tops. (diodes to have different rise and fall times)
But  I would like to make the rise and fall time adjustable.

so, I would appreciate if someone could help me to find a more elegant and simple approach?


texts:
I'm building current limiter for my circuit, I saw a nice one in Maxim's document (Figure 2a): https://www.maximintegrated.com/en/app-notes/index.mvp/id/2158

I need current limiting for 100mA, so I modified that circuit and simulated in LTspice:

It works, it limits current well, but there is some glitch/spike when power is switched on (current across R1):

Spike in detail (power is turned at 10μs, spike starts at 10μs):

I tried different transistors (Q1 and M1) but it didn't help.

What causes this spike?
Is there any problem in that circuit?
Or is it just some problem in LTspice simulation?
Is it possible to get rid of this spike?


texts: Quartus 2 VHDL Clock Frequency Divider: can't determine definition of operator "+"

texts:
I'm extremely new to VHDL and trying to make some easy projects such that I learn the basics and syntax. I use Quartus 2 at home and ISE 10.1 at the school computer. I wrote exactly the same code in both of them where the code is:

        library ieee;
    use ieee.std_logic_1164.all;
    use ieee.numeric_std.all;
    use ieee.std_logic_unsigned.all;

    entity freq_divider is port(

        clk: in std_logic;
        clkdividedby2,clkdividedby4,clkdividedby8: out std_logic
    );

    end freq_divider;

    architecture karakter of freq_divider is

    signal count4 : std_logic := '0'; --In this line, count4 is initialized as 0.
    signal count8 : std_logic_vector (1 downto 0) := "00"; -- Count 8 is initialized as 0.
    signal clkdividedby2_temp,clkdividedby4_temp,clkdividedby8_temp : std_logic :='0';

    begin

    process(clk)

    begin
    if(rising_edge(clk)) then

    clkdividedby2_temp<= not clkdividedby2_temp;
    count4 <= count4 + '1';
    count8 <= count8 + "01";

    if(count4 = '1') then -- = Tests for equality, not ==
    clkdividedby4_temp<= not clkdividedby4_temp;
    count4<='0';
    end if;

    if(count8 = "11") then
    clkdividedby8_temp<= not clkdividedby8_temp;
    count8<="00";
    end if;

    end if;
    end process;

    clkdividedby2<=clkdividedby2_temp;
    clkdividedby4<=clkdividedby4_temp;
    clkdividedby8<=clkdividedby8_temp;

    end karakter;

This synthesized perfectly on ISE 10.1 in school, but in Quartus 2, I get the error:

  Can't determine definition of operator ""+"" -- found 0 possible definitions

I have no idea why this is happening. I wrote all the libraries and stuff, and it is still not working.


texts: Splitting a cat 6 cable through wire/cable connectors

texts:
There's been a cock-up in the internet wiring at a building I'm helping out at (I'm installing the networking there) and the builder has tried to rectify the situation with a solution I have zero confidence in. I however am no expert in networking/electrics, so I figured I'd ask those who might be.

For context, there's a flat that has one Cat 6 cable leading into it. The problem here is that there are actually two rooms which require an Ethernet port. There's a language barrier between myself and the builder so you can imagine conveying technical details is far from easy.

Upon me informing the builder that this was an error and we needed two Cat 6 cables leading to that flat, he came up with the solution of "splitting" the Cat 6 cable (I think)? He's used this cable connector/one similar to this to do so.

My question is pretty much "will this work?" or do I need to tell him that this is more of a problem than he suspects. I'm thinking that this could possibly confuse the network/cause packetloss/interference but those are all guesses.

I know one solution would be to use one of these but those limit the connection to 10/100 and the connection in the building is significantly faster.


texts: Opamp input voltage divider creates wrong voltage - what could be the cause?

texts:
I'm using above 1:2 differential opamp, when 72V applied to the 30:1 voltage divider, voltage across R1 is only 1.727V instead of 2.4V, opamp output is around 3.4V.

Opamp is LMC6062IN/NOPB
http://www.ti.com/lit/ds/symlink/lmc6062.pdf

I think it's because of bias current, any suggestion on solution?

Follow up question:

Same circuit below but now this time 0V does not connect to circuit main GND, so there is not second voltage divider but i am seeing around 1.5V across R1

simulate this circuit – Schematic created using CircuitLab

Follow up question #2:

simulate this circuit

Switch on both side of V1, top and bottom circuits are identical differential opamp circuit, bottom one is before switches and connect to v1 directly, top one is after two switches.

When SW2 is open, SW1 is closed:
voltage across R3 is 1.4v, output 2 is 2.83v.
voltage across R23 is 0.532v, output 1 is 1.08v.
Seems like R3 is in parallel with a 60K resistor, does that mean two op amps' inverting and non-inverting pin are tied together? I am using a dual op-amp.


texts: DW01 for Lithium Non-Rechargeable Battery Protection

texts:
I'm thinking of using the DW01 IC to make a simple non rechargeable battery protection (over current, short circuit, over discharge). The sample schematic requires two Power fets, one to control discharge and the other to control charge.

My problem is that I don't need the charge control, charging will cause my battery to explode. What I actually want is for the FET to be closed if a charger is present (reverse polarity protection)... is there a way to do this with the DW01 by changing the FET or some other tweak?

Looking forward to seeing what's possible!


texts: Increasing voltage noise but decreasing current noise with rising resistance

texts:
Consider the two (equivalent) formulas for the noise power spectra of a ohmic resistor:

$$W_u(f)=4kT\cdot R~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(1)$$

and

$$W_i(f)=4kT\cdot G~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(2)$$

with the Boltzmann constant \$k\$, the temperature \$T\$, the resistance \$R\$ and the conductance \$G\$  each representing a equivalent circuit source.

General saying is that the noise increases with increasing value of resistance. E.g. in the datasheet for the AD745 it says that the noise contribution decreases with increasing resistance, which holds true for current noise considering formula (2), but is a contradiction considering formula (1).

Now, current noise produces a voltage noise when applied to a resistor with ohms law, but decreasing current noise and increasing resistance still yields a different result than just increasing voltage noise.

The equivalence of the circuits can be shown easily:

$$W_u(f)=W_i(f)\cdot\frac{1}{|G|^2}=\frac{4kT\cdot G}{G^2}=\frac{4kT}{G}=4kT\cdot R. ~~~~~~(3)$$

Please clarify the result in terms of noise of increasing the value of an ohmic resistor and explain the formulas (1) and (2) in the context of the stated contradiction?!


texts: What are the wavy conductive tracks for?

texts:
Consider the following PCB.

I notice some motherboards have such wavy tracks. Are there any purposes?
Or it is there merely for artistic purposes?


texts: How to tell size of Eagle library component?

texts:
I am working on my very first PCB design using Eagle. In my design, I will be using a 10W 10 Ohm power resistor. Since it isn't a "standard" size, I'm having trouble finding the component in Eagle. In particular, it has a width of 47mm.

No component in rcl.lbr is long enough. resistor-power.lbr seems pretty promising, but many  of the components don't have measurements. And I'm not sure what the closest equivalent is. For example, KH216-8 seems like it is roughly the right size. And it happens to have a measurement. So is it, uh, "safe" to go with that?

How could I view the dimensions of a component if it's not in the description?

Are there any other techniques I can use when trying to find a library part that approximates the component I've chosen?


texts: What happens to port isolation in a Wilkinson power divider when source impedance isn't matched?

texts:
Say we have a Wilkinson power divider:

So far as I understand it, if we say port 1 is the input, and the other ports are outputs, then the power is split evenly between the outputs.

If one of the outputs is not perfectly matched, and so reflects some power back, half this power is dissipated in the resistor, half goes out port 1, and none (ideally) of it goes to the other output port.

However, does this port isolation hold true if port 1 isn't driven by a Z0 source? And if not, why and how?


texts: How BLDC motora coils and magnets are mechanically arranged

texts:
I've read some articles about how BLDC motors principle (in my case 3-phase) with something also about linear BLDC. This documents talks about actuation and theory. But looking at drawings I became interested into basics of magnet-coil arrangement.

I can probably say that in a 3-phase, with phases shifted by 120°, a magnet is exactly aligned with a coil every 3 coils. Independently how much coils are used.
If so, center of each magnet is positioned every 1/3 space/degree, I'll have 4 magnets every 3 coils.

I suppose the same applies on linear actuators BLDCs, 3-phase, using same logic up to N phase.

If my assumption are correct, how to calculate ideal magnet dimensions respect to metal core of coils, with which gap? Or if it's a know ration (i.e. 1:1 coil:magnet area and 1/3:1 between magnet-gap/coil-gap)

As reference I post here what looks strange to me:

Where ratio is correct, but magnets seems to me too large for application.


texts:
May I just ask if Class D amplifiers are expected to stay continuously on, flat out, at full power and never have the volume reduced?!

I’ve recently obtained this:

http://www.amplifier.co.uk/images/SDV1042-600_1_ETS.pdf

...It’s my first class D amplifier project and I just expected but I could turn it down with some sort of master volume pot. Am I wrong?

If not then Where would be the best place to connect a master volume on the power amp, please?


texts: How to choose replacement capacitor/inductor in a simple RLC blackbox?

texts:
Assuming there's a circuit that we can't see but we can guess how it works based on what it's made for. We know (or just are pretty sure) it's an RLC circuit with no digital parts. From what I've learned in EE basics, the voltage depends heavily on L & C in such circuits, mainly the inductance and capacitance values. Given the little information, here's what I think:

When changing a capacitor or inductor (just 1) in a blackbox circuit:

The capacitance/inductance value should be the same as the original. Using different values may change the power waveform, which can increase or decrease the maximum voltage and/or make the voltage go up and down, making the system somewhat unstable.
The voltage/wattage rating should be equal or higher. If it's lower, the component may burn out. Having it higher means better tolerance.

Are my assumptions correct?


texts:
I got a digital design problem.  My final implementation of the circuit program didn't achieve the required criteria, so I brought my problem and my works here to be suggested by you if I mis-manipulated any details.

Logic System:  Binary--1,0.

Issue after Simulation and Test on Circuit Board:  LED lighted up at the begining without any switches were turned ON. (Would it make sense?)

Problem Statement:

Use 4 switches A, B, C, D to control a LED.  LED is ON if the following conditions are satisfied,

D and B turn ON,

or A turns OFF while C turns ON,

or A and B turn ON and the rest turn OFF,

or C and D turn OFF,

or all switches turn ON.

End of Problem Statement.

Notations and Circuit Combinations we use:

AND gate:  · (dot)

OR gate:  +

"Not/Invert something":  ~

SOP: Sum of Products

POS: Product of Sums

SOP and POS are equivilant to each other.

My works:

True Table based on the 5 criteria

ON:1, OFF:0.

Collection of LED results is {1011111110001101}.

I can handle operating the software part, but I really want to check with you guys if I use POS method and based on the 5 criteria given in the problem, whether or not my true table is correct.

Please help me to point out my blind spots.  Thanks


texts:
I am currently in the process of making an ultra-low power pH captor and I'm running in a problem. The voltage I get from my pH probe does not fallow the Nernst equation (which states that the voltage should increase/decrease of 59 mV per pH unit). However when I try it, I only get variation of 1 or 2 mV per pH unit which is extremely low. I can make it work that way, but it's not very efficient and I was wondering of someone would know why that is. I am currently testing on a very simple setup similar to this one:

I do suspect that the problem comes from the pH probe, but I'd like to hear other people point of view before buying a new one. Does anyone have an idea why my voltage variation is so low? Even though I know it is not necessary, both amplifier are powered by 3.3 and -3.3 V.

Documentation (the datasheet is not accessible to the public) : https://www.phidgets.com/docs/PH/ORP_Sensor_Primer


texts: Advantages of full Wave Rectifier Compared to Half Wave Rectifier

texts:
I have a homework assignment. Our teacher wanted us to research advantages of full wave rectifier compared to half wave rectifier or just advantages of full wave rectifier. I researched it and found something is like below.
Full wave uses two area, positive and negative ones. But half wave uses just one area, negative or positive one.
Full wave has much less ripple voltage than half wave.
RMS voltage of full wave is higher than half wave.
But I want to know more advantages which is not known so much. Are there any advantages like I said ?


texts: Cockcroft-Walton generator producing unexpectedly low voltages

texts:
I'm trying to build a high voltage DC power supply from AC 220V mains.
At the moment I'm just trying with one stage of the depicted CW generator. The components I'm using are:

1N4007 diodes
Panasonic ECWHC3F103J capacitors (3kV, 10,000pF)
Or:
400V 0.1uF polycarbonate capacitors

When I use capacitors (3), the output DC voltage across one stage is 158V. Two stages is still 158V. What could I be doing wrong here?
When I use capacitors (2), the output DC voltage is 258V. What causes the difference in output voltages when I change the capacitors?
Shouldn't the theoretical output of one stage be 220xsqrt(2), and of 2 stages 2x220xsqrt(2)?
Also, how do I increase the rate at which the high voltage DC output can charge a capacitor bank? The maximum short term forward bias current of the 1N4007 diodes is 30A which seems to be sufficient.
Please ask if you need any photos of the circuit to diagnose the problem. Thanks in advance.


texts: Which wires should I use for stripboards?

texts:
The wire I use seems to break off the stripboard easily. (Typical wire like the wires given with a 9V battery connector).

What is the norm about the wire to be used for stripboards?


texts: Why is a transmitter dipole's ends the max/min voltage instead of the middle?

texts:
If the AC voltage source is connected to the middle of the dipole, I'm confused on why the edges have the max/min voltage instead of the middle.

In my mind, the middle of the dipole is closer to the voltage source, and there is even some resistance between the middle of the dipole and the end, which would imply a voltage drop, making the dipole's end a lower voltage than the middle.

For a receiver, I understand why the ends have the max/min voltage (based on how the wave hits the dipole). However, I'm totally lost when it comes to a transmitter. Any help would be greatly appreciated.


texts: Just what is special about the resist pens used to draw directly on PCBs before etching?   Would a permanent marker work as well, or some other kind pen or marker?  Naturally I have in mind something cheaper but good enough.   This is for one-off handmade projects, single or double sided boards only.


texts:
I'm designing circuit based on a microcontroller, powered by a solar cell. As an experiment, I wanted to add an energy harvesting IC (bq25504). When programming, I'd like to be able to charge the battery through the USB port as well.

I thought of also feeding the current from this port to the input of the harvester.

But the problem is: I can't use a diode in series with the solar cell. The energy harvesting IC is so efficient it can harvest energy from voltages as low as 80mV, so if I add a series diode I'd be losing that ability.

What would happen if I put the V of the programming port in parallel with the solar cell? Will the solar cell get damaged because of reverse-biasing?


texts: Block characters are shown in 16x 2 LCD instead of letters while interfacing with atmega328p?

texts:
I am trying to display some characters in 16x2 LCD (1602 A) using Arduino Uno (atmega328p-pu). I have written my code using embedded C for 4 bit mode. The code is below.

#include <avr/io.h>
#include <util/delay.h>

#define LCD_DATA_DDR DDRD
#define LCD_CTRL_DDR DDRB
#define LCD_DataBus PORTD  //Using PD4 to PD7
#define LCD_CTRL_PORT PORTB

//function prototypes
void LCD_Write(unsigned char cmd, unsigned char reg_select);
void LCD_WriteData(char data);
void LCD_WriteCmd(char cmd);
void LCD_Init();

void LCD_Write(unsigned char cmd, unsigned char reg_select)
{
  char  tempCmd;
  if(reg_select == 1)
    LCD_CTRL_PORT |= (1<<PB0);   //Select Data Register
  else
    LCD_CTRL_PORT &= ~(1<<PB0);   //Select Command Register

  //Mask data/cmd
  tempCmd = cmd;
  tempCmd &= 0xf0;// mask Lower 4 bits

  //Set data/cmd
  LCD_DataBus &= 0xf0;           //Set PORTD LSB to HIGH since we use PD4 to PD7
  LCD_DataBus |= tempCmd;        //Set bits in PORTD

  //Send data/cmd
  LCD_CTRL_PORT |= (1<<PB1); // Send a High-to-Low pulse at Enable pin
  _delay_ms(400);
  LCD_CTRL_PORT &= ~(1<<PB1); // Send a High-to-Low pulse at Enable pin

  //******Send next 4bits

  //mask data/cmd
  tempCmd = cmd << 4; //shift left 4 times so the LSB bit can be sent.
  tempCmd &= 0xf0; //mask Lower 4 bits

  //Set data/cmd in bus
  LCD_DataBus &= 0xf0;
  LCD_DataBus |= tempCmd;

  //Send data/cmd
  LCD_CTRL_PORT |= (1<<PB1); // Send a High-to-Low pulse at Enable pin
  _delay_ms(400);
  LCD_CTRL_PORT &= ~(1<<PB1); // Send a High-to-Low pulse at Enable pin

  return ;
}

//Send data by setting RS=1.
void LCD_WriteData(char data)
{
  LCD_Write(data, 1);
}

//Send cmd by setting RS=0.
void LCD_WriteCmd(char cmd)
{
  LCD_Write(cmd, 0);
}

void LCD_Init()
{
    LCD_WriteCmd(0x02); // to initialize LCD in 4-bit mode.
    _delay_ms(1);
    LCD_WriteCmd(0x28); //to initialize LCD in 2 lines, 5X7 dots and 4bit mode.
    _delay_ms(1);
    LCD_WriteCmd(0x01); // clear LCD
    _delay_ms(1);
    LCD_WriteCmd(0x0E); // cursor ON
    _delay_ms(1);
    LCD_WriteCmd(0x80); // —8 go to first line and –0 is for 0th position
    _delay_ms(1);
    return;
}

int main(void)
{
    LCD_DATA_DDR |= 0xf0;  //set the LCD DDRD to output
    LCD_CTRL_DDR |= 0b00000011; //For RS, E

    LCD_Init();
    _delay_ms(30);
    LCD_WriteData('a');
    LCD_WriteData('2');
    while(1)
    {

    }//while
}

When I run this C code, I get some white blocks in the upper row, instead of letters.
Then, I ran an Arduino version of LCD code but it worked well. Please tell what am I missing in my embedded c code.

I am using the following pins for LCD interfacing,

D4 to D7 = PD4 to PD7
RW = Grounded
RS = PB0
E  = PB1

Thank you.


texts: why does my STM32L412 ADC never reach its full value?

texts:
Im using the ADCs on an STM32L412 but it seems that they never reach their full value - the power is 3.3v and the reference is 3v, but they only ever fill to 3863 and not 4095. Why might this be? I measured the voltage on the input pin as 2.992V and the Vref pin as 3.001V
Is it possible the ADC is using 3.3V as a ref and not 3V? how can I change this?
this is the setup -
static void MX_ADC1_Init(void)
{
 ADC_MultiModeTypeDef multimode = {0};
 ADC_ChannelConfTypeDef sConfig = {0};

/** Common config
*/
hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
hadc1.Init.LowPowerAutoWait = DISABLE;
hadc1.Init.ContinuousConvMode = DISABLE;
hadc1.Init.NbrOfConversion = 1;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.NbrOfDiscConversion = 1;
hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc1.Init.DMAContinuousRequests = DISABLE;
hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
hadc1.Init.OversamplingMode = DISABLE;
if (HAL_ADC_Init(&hadc1) != HAL_OK)
{
Error_Handler();
}
/** Configure the ADC multi-mode
*/
multimode.Mode = ADC_MODE_INDEPENDENT;
if (HAL_ADCEx_MultiModeConfigChannel(&hadc1, &multimode) != HAL_OK)
{
 Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_11;
sConfig.Rank = ADC_REGULAR_RANK_1;
sConfig.SamplingTime = ADC_SAMPLETIME_2CYCLES_5;
sConfig.SingleDiff = ADC_SINGLE_ENDED;
sConfig.OffsetNumber = ADC_OFFSET_NONE;
sConfig.Offset = 0;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
  Error_Handler();
}

}


texts: How do I connect a photodiode to a GPIO?

texts:
I'm trying to read serial data emitted through an IR led with a Raspberry Pi using an IR photodiode, but I'm not sure about the correct way to hook it up.

Unfortunately I don't have a part number for the photodiode, I got them as "generic wide band photodiode".

It will be placed at just some millimeters from the IR led and the signal data is at 4800bps, I'm pretty sure the signal will be good and strong.

After some googling I tried connecting +3.3V to the cathode, a 100kΩ resistor from the anode to ground, and the GPIO to the anode too, but it didn't work so I guess I'm doing something wrong.

I'd like to keep the thing as simple as possible, but it's ok if I have to throw a transistor in there (I have a couple of generic NPN and maybe also PNP lying around somewhere).


texts:
I need help find the the initial value for the following time function:
$$F(s) = \frac{10(s+6)}{(s+2)(s+3)} $$

I've found the final value to be \$F(s)=0\$


texts: Ferrite bead in Ground path of Input Power Supply

texts:
I have been following the schematics of Colibri Toradex Carrer Board. I have used most of the components from their design. However, they have used ferrite beads in Positive terminal and Ground terminal of Input Power supply.

I am unable to understand how ferrite bead in ground connection helps in noise immunity. Please help me as I am planning to remove it as it consumes some space in my denser PCB.


texts:
I am considering using an ceramic antenna for my RF product design, but I am not sure how to interpret some of these antennas' datasheets which specify a ground plane surface.

For example the datasheet of this ceramic antenna from Johanson which specifies an example board with a a ground plane of a certain size:

Here are some of the questions about this design:

Do I really need to have all these vias all around my GND plane?
I have components soldered on top of the ground plane, will it affect the performance?
This is a 4-layer board with two signal layers, a power plane and a GND plane, does this affect the performance as well?
Is the 20mm x 40mm ground plane a recommendation, a minimum, or a maximum? If my PCB is bigger and a different overall form, will it still work?


texts: Total capacitance of two sets of parallel capacitors and resistors in series.

texts:
Assuming C1 and C2 both are rated at 2.5V.

Is the total capacitance of C1 and C2 0.5uF or 1uF?

simulate this circuit – Schematic created using CircuitLab


texts: Real/Complex Zeros for Filter Transfer Function

texts:
So I've been reading into filter design and came across how to determine the transfer function of a filter, when given it's poles and zeroes. I've come across the following question that has me a bit confused about how to determine the zeroes of a transfer function.
Suppose you have a third-order low-pass filter that has transmission zeroes at \$\omega=2,\infty\$, poles at \$-1,-0.9\pm1.1j\$ and a DC gain of unity. Going through the work, I get the following transfer function:
$$T(s)=\frac{K(s^{2}+4)}{(s+1)(s+0.9+1.1j)(s+0.9-1.1j)}$$
where \$K\$ is the gain factor (calculated using the fact that the DC gain is unity).
Here is my issue. The question states that there are multiple transmission zeros, but does not state how many zeros are at \$\omega=2\$. I assumed that the zero at \$\omega=2\$ was complex, leading to a conjugate pair \$(s+2j)(s-2j)\$ and hence how I got \$s^{2}+4\$ for the numerator. But is there someway to show that said zero is in fact a conjugate pair, and not real?
Suppose the question instead stated that there was "a transmission zero at \$\omega=2\$ ". Would the numerator of the transfer function then be equal to \$s-2\$, with a single real zero, since the zero must be real if there is only one of them (i.e. no conjugate pair)?
Seems to me at the moment that I am missing something obvious about this.


texts:
This question relates to this incident here, where a women in Australia died from a faulty USB charger that allowed the full 240V mains voltage through the USB cable.

Now from my understanding you would have to be connected to the mains ground or the earth's ground in order to get an electrical shock. Otherwise there wouldn't be a potential that would allow the current to flow through her.

Now according to the article which cites the police she received the shock because she was touching her phone which was connected to the charger and her laptop which was also connected to a charger, as well as her EARPHONES which bothers me the most, apparently she had burn marks on her chest where the laptop was and in her ears.
Unfortunately there are no details about the devices that were used. So I'm just assuming below.

Here the picture shown in the article explaining the connection:

Now how would this be possible? The phone must have a metal body which is also somehow connected to the power of the phone. The only phone where I can imagine that being the case are the recent iPhone models where the outer aluminum ring on the side is apparently also acting as the antenna (here and here), maybe other aluminum unibody phones as well.
Still, is that even a feasible theory? Wouldn't a metal casing be connected to ground instead? How would a ground in a DC circuit act when suddenly the circuit "becomes" AC?

Then her laptop must have had an aluminum body as well which again must be connected to the ground. Again the only case where I heard about the laptop body be somewhat connected to the circuit is unibody MacBooks where users sometimes feel a tingle when touching the laptop while it is connected to the charger but is that even the case? Again it sounds weird that the laptop's body would be grounded: there is a low DC voltage coming in from the external charger so why would that be needed?

And wouldn't the laptop charger not be faulty as well then? How would it allow the current from the phone charger to flow back into the outlet and complete the circuit? Shouldn't the laptop charger isolate the mains from the DC output circuit?

Then the headphones: WHY would the outer casing of a pair of earphones be connected to the ground in any way and how would electricity even flow through the two sides of the earphones (THROUGH her head to the other side), that sounds like a really unnecessary detour for the current.

If this indeed possible like described by the police would this also be possible by a phone and laptop with plastic bodies?

I would love to see a detailed answer: I'm not that well educated when it comes to mains AC power and safety measures taken to avoid shocks.


texts: I want to carry a voltage along a cable of about 300m, the total resistance is about 2.3 ohms on every conductor, if I have 10 amps of current on the cable the voltage drop will be 23V.My application requires 15 amps so I decided to send through the cable a voltage of about 50V.My question is if it's to send this voltage as AC and rectifies at destination or send this voltage as DC already ?What are the advantages and disavantages ?


texts:
What is the maximum length of cable that could be used to connect two I2C devices (I2C master-> I2C slave)?

Yes, I know that I2C is really designed for intra-board communication.  I have been tasked with a "design goal" of using a common I2C bus for multiple I2C slaves to support a demo.

For purposes of clarity, let's assume the standard I2C bus rate of 100 kHz.


texts: Converting a soldering station from 110 V to 220 V

texts:
i bought this soldering station from the USA and it is 110 V. I need it to be 220 V. Is this possible without external tools?

There are 3 Trimpots: V1 VR1 VR2

This is the inside of the station:


texts: No potential difference between the negative terminal of battery A and positive terminal of battery B?

texts:
I know that if you have two batteries, battery A and battery B, and connect the negative terminal of battery A to the positive terminal of battery B, there is no potential difference. If you consider the negative and positive terminals of the same battery, the potential difference exists (say 1.5V).

I've learned that the potential difference exists because the atoms at the positive terminal have few electrons compared to the negative terminal and so electrons flow to equalize the two terminals. Why does this flow only occur when it is the terminals of the same battery and not opposite terminals of two different (identical in all characteristics) batteries?


texts: Unlock movement/edit of internal polygon layers in altium 19?

texts:
I changed an internal plane to a signal layer and now I want to be able to move objects in this layers like polygon, however I seem to be unable to do so.

How can I unlock polygon move/edit in this layer?
There seem to be no "unlock/lock" like it's for components under properties.


texts: Calculating Back EMF from Torque Constant

texts: I have a brushless DC motor with a torque constant of .0181 Nm/A. How do I calculate back emf (Vpeak/kRPM) from torque constant (Nm/A)?


texts:
Suppose the DC motor has a peak current of 500ma and after that it drops to 100ma, the transistor can switch continuously 200ma.
If I limit the current of the transistor from the base current to 100ma, for some reason could the transistor consume a higher peak than that when starting the motor or would it be limited to 100ma?How effective is limiting hfe gain against inrush currents?


texts:
I am trying to lower the voltage from a 9V battery to 5V for use on an Arduino pin. I bought a 5.1V zener diode from RadioShack. Will this do what I want? Do I have to lower the amps as well? It looks like the battery delivers 9V and 1A. Should I first use a resistor to lower the amps, then use the zener diode to lower the voltage? I tried using a 330 ohm resister directly with the battery and a multimeter just to see how much it lowered the amps, and it got very hot so I am not sure if I should be using it.

Zener Diode:
IN4733A
Voltage: 5.1V
Current: 49mA
Maximum power dissipation: 1.0W

I looked at some example equations here: http://www.electronics-tutorials.ws/diode/diode_7.html but am still not comprehending it. I am not even sure which side the black band on the diode should point. So my question is: Will the diode work to drop from 9V to 5V and do I need to do anything extra?

I wanted to use this: http://www.amazon.com/Voltage-Sensor-Detector-Divider-Arduino/dp/B00S4PCCG8/ref=sr_1_1?ie=UTF8&qid=1424025730&sr=8-1&keywords=voltage+divider+arduino, but don't want to wait so thought I would try something else until I can get this ordered.


texts: It is possible to rotate the PCB view in Eagle?

texts: I do not want to rotate the parts (that is easy by selecting all and click on rotate icon), only the view.


texts:
I have an Arduino with a motor shield and I use it to power 4 different DC motors.
Motors are connected to the shield through a screw terminal.
Since I am in the prototyping step, I am moving them around a lot, connecting and disconnecting them all the time, which means screwing and unscrewing the wires every time.

I was looking for a jack, so I can easily plug in-out. I was going to use the standard 2.1 X 5.5 mm coaxial power connector, however I'm wandering if there is anything smaller.
The flowing power shouldn't be very intense, it's a 12v with a peak usage just little above 1A.


texts: How do I calculate the inductivity of a capacitor with an impedance-frequency graph?

texts:
Lets say I want to calculate the inductivity of one of these capacitors.

I know every capacitor has an ESR ESL

$$ Z = R + \frac {1}{jwC} + jwL $$

Can I use this formula? Im obviously missing the R though could anyone help me here?


texts: Biasing of a circuit with two transistors BJT

texts:
I need to calculate the bias values. So far I have only written these equations, but something is missing. (\$\beta=200\$ for both transistors and \$V_{BE\,on}=0,6\,V\$)

Capacitors=open circuits

\$\frac{20-V_{C1}}{R_2}=\frac{V_{C1}-0,6}{R_1}+I_{B2}\$

\$I_{E2}=I_{C2}\times \frac{\beta+1}{\beta}\$

What equations are missing me?


texts:
I am trying to find external gate resistance value for my MOSFET.

Here are some details:

I am using IRFP4468PbF power hexfet mosfet - Datasheet

80V, 500mA, 3-Phase MOSFET Driver - Datasheet

I had worked out through some formula and found that
 I=0.77A (using I= Qg/ Dt),

T= 702ns ( using ton + toff = T)
so f = 1.4 Mhz

Qg = 540nC
so Cg = 45nC (using Cg = Qg/V) V= 12V

P(power dissipation)= 9.072 watts ( using Cg x Vdd^2 x f)

Now when I find the resistance, I got value 15ohms ( which I dont feel its correct) After reading couple of things online. I thought that it should be around 0.15 - 0.45.
So I want to know where I am going wrong and what is right.


texts: Why do we want gap in the core material while designing inductor?

texts:
In some cases it is necessary that core of inductor should have a gap, unlike with transformer core. I understand the reason with the voltage transformer core; there is nothing to worry about core saturation and we want to keep the winding inductance as high as possible.

The formula for the inductance is:

$$
L = N^2A_L = N^2\dfrac{1}{R} = \dfrac{N^2}{\dfrac{\ell_c}{\mu_cA_c} + \dfrac{\ell}{\mu_0A_c}} = \dfrac{N^2A_c}{\dfrac{\ell_c}{\mu_c} + \dfrac{\ell}{\mu_0}}
$$

And, the formula for the magnetic flux density:

$$
B = \dfrac{\mu N I}{\ell} = \dfrac{N I}{\dfrac{\ell}{\mu}} = \dfrac{N I}{\dfrac{\ell_c}{\mu_c} + \dfrac{\ell_g}{\mu_0}}
$$

Where,

\$N\$: Number of turns
\$R\$: Total core reluctance
\$A_L\$: The \$A_L\$ factor
\$I\$: Current through the wire
\$\mu_c\$: Permeability of the core
\$\ell_c\$: Mean magnetic path of the core
\$\ell_g\$: Length of the gap
\$A_c\$: Cross-section area of the core
\$L\$: Inductance
\$B\$: Magnetic flux density

What I understand from these two formulas is, the length of the gap affects both the magnetic flux density and inductance with the same proportion. When designing inductor, we would like to keep magnetic flux density low, so that the core wouldn't saturate and core loss stay low. People say that they leave the gap in order to keep the reluctance high, so that there are less flux flowing in the core, and the core stays away from the saturation region. However, doing so will reduce the inductance as well. By leaving the gap, we reduce magnetic flux density and inductance with the same coefficient. Then, instead of leaving the gap, we can also decrease the number of turns in the winding as well.

The only reason to leave gap that makes sense to is to increase the number of design parameters to obtain a closer resulting inductance value at the end. I can't find any other reason to leave gap.

What makes leaving the gap an inevitable action while designing an inductor?


texts: Programming Multiple ICs using single USBasp/SPI Bus and Arduino IDE

texts:
Hi and thanks for looking!
Background
After coding and designing a project with the Arduino hardware and IDE, I have been etching my own PCB with a single ATMega328 and related components for the particular project.  I include on my boards a six-pin header to which I have been hooking up a generic USBasp programmer and then flash the IC with new code written in the Arduino IDE.
This all works great.
Problem
I am now building a more advanced circuit that requires five ATMega328 ICs--each with it's own code that is unlike the code on the other ICs.  I need to be able to flash all five IC's from the single USBasp/SPI six-pin connection, but I don't have a clue how.
I realize that it would be easier to just use a single IC with more pins, but that is not an option for now.
Question
Using my single USBasp/SPI six-pin connection, how can I flash multiple ATMega328 IC's with their respective code that I have written in the Arduino IDE?


texts: Can the antenna of a Wi-Fi modem pick up a cell phone's MIN or ESN?

texts:
Specifically: Can the antenna of a Wi-Fi modem pick up a cell phone's broadcast of its mobile identification number (MIN) and electronic serial number (ESN)?

Generally: We are trying to determine if a Wi-Fi modem can detect any unique information from a passive (not during a call) cell phone transmission.  During its periodic outgoing "pinging" to the network, is there any information that is unique to the individual cell phone.  When it searches for an available Wi-Fi signal, is the phone transmitter sending any information unique to the phone?  We don't need to know the cell phone number, just any information that is unique to the unit.


texts: Is there a way I can calculate the magnetic field strength a 5v relay produces?

texts:
So I know this question is rather specific, but im hoping someone can help me answer it.

I have a circuit that i've designed where I have an electromagnet thats switched on at a given point. The electromagnet was made by me and is terribly inefficient to produce. I figured a relay uses an electromagnet to complete a circuit, so the question is such: how can I calculate its magnetic field? I know it can measure it using an iphone app that makes use of the hall effect sensors but im hoping I can work it out roughly before i purchase a batch.


texts: Eagle LBR Connector, Re-designing foot print / placement

texts:
I want to place a connector position on edge on pcb. I don't have this lbr. How can I convert this ?
Currently this is the library I have

And this is the kind placement I want to design

Ignore the pin count. The dimension is same. So I want to make it no drill, double sided solder on the edge of pcb. I hope my question is clear.
BR,


texts:
I have this circuit linear regulator with UVLO so I would like to calculate the power consumption of this block any person can help me, please
Vout = 1.5 V (Iss = 15.2 μA, Vout = 1.5 V, switching = 32.768 kHz, δ = 0.809),
block function A 1.5-V low dropout (LDO) linear regulator Torex XC6215B with quiescent current consumption 0.8-μA. Below 1.5 V, the input of the linear regulator is disconnected from the supercapacitor by a p-type MOSFET (Si-2302) in order to avoid leakage current. An XC6120C voltage detector turns the low-side switch on when 1.5 V is reached across the storage element


texts: How to Check if Micro-USB Cable has a Short?

texts:
Is there a way to test if my micro-USB cable has a short? I've got a multimeter.

I'm having problems programming an Atmel 328 AVR using USBASP with Avrdude, and I want to make sure that my cable is good.


texts: Measure 3-phase Power with Lecroy Waverunner

texts:
Please note that experience with a Lecroy Waverunner Oscilliscope is most likely required to answer this question.

I'm attempting to measure the power draw of a brushless 3-phase motor with a Lecroy WaveRunner 204MXi. I've connected two current probes and two differential voltage probes in order to provide two Wattmeters. I've connected the current probes to Phase A (for Ia) and Phase B (for Ib), and the differential voltage probes across Vac and Vbc. This matches the configuration detailed here by Lecroy:

http://teledynelecroy.com/doc/threephase-power-measurements-using-a-fourchannel-scope-to-measure-threephase-power

And from the link, the power draw at any point in time is:

P = VacIa+VbcIb

This is only, I believe, the real power. I should also be calculating the complex power, correct? The complex power will be draw from the battery, and so it is my actual current draw?

S = Vac(rms)*Ia(rms)+Vbc(rms)*Ib(rms)

The issue I'm facing is that to calculate RMS is, for the Lecroy Waverunner oscilliscope, a measurement (P?). RMS is not available as a math function. Then I need to perform three math functions F1=P1*P2, F2=P3*P4 and finally my complex power would be F3=F1+F2. Here, P1,P2,P3 and P4 are my RMS voltages and currents.

The issue I'm facing is that the math multiplication functions only allow for 1 measure to be included as an input? I can have, for example F1=P1*C1 (where C is a channel), but not F1=P1*P2? Am I measuring complex power correctly? Is there a better way to measure complex power with a Lecroy Waverunner?

Any insights are much appreciated.

Thanks


texts:
I have a big problem with the power supply of a SIM900.
I designed my own board with a 220VAC-5VDC tracopower, an ARM9 CPU, and a GSM/GPRS SIM900 module.
The output of the tracopower is 5V - 800 mA (so 4W).
To supply my GSM module, I use a LDO 5V - 4.1V.
When SIM900 is transmitting its 2A burst, 4.1V GSM supply don’t have any voltage drop. But with the 5V supply, I go from 5V to 4.3V, so the CPU reset.

I know that I did a big mistake when I designed the board because I can not supply the CPU directly from the AC/DC. The best solution would have been to use a AC/DC 9V and then create a 5V for the CPU and a 4.1V (from the 9V source) for the GSM. But I can't change the AC/DC so I need to use this AC/DC 5V-800mA.

So do you have a solution to avoid a voltage drop on the 5V ?
For information, the 4.1V can drop to 3.2 (the Sim900 supports that).

This is my 5V power supply :

And this is the GSM power supply :

Many thanks for your help.


texts:
Apart from the register structure what is the difference between GPIOx_ODR and GPIOx_BSRR?
Is GPIOx_BSRR an abstraction layer for GPIOx_ODR? I know that a change in GPIOx_BSRR "will" change the GPIOx_ODR but how and what are the diferences?

More info:

registers description page-162 of STM32F0advanced ARM.pdf
MCU STM32F051R8
Board STM32F0DISCOVERY
compiler arm-none-eabi-gcc -v gcc version 4.8.3


texts: I'm confused by the formulas for power gain decibels and voltage gain decibels

texts:
I know that my problem with this is some flaw in my logic, I just need someone to point out to me where that flaw is.  According to the Wikipedia article, there are different formulas because power gain is proportional to the square of the voltage (amplitude) gain.  I can accept that and it makes sense except that the formula for voltage gain is only true when the input impedance is equal to the output impedance. That contradicts what I think I know about gain stages - that is, that the input impedance should be very high and the output impedance should be very low in order to drive the next stage.

So my question is, what's wrong with the way I'm thinking about this?  And does the formula for voltage gain in decibels change when input impedance does not equal output impedance?