texts: Copying sub unit of an old schematic to a new project in Proteus

texts:
I copied an old schematic to a new project in proteus but when I tried creating the corresponding PCB design on ARES, the components/parts section didnt show any of the components used in the schematic diag. And when I again tried looking up those parts in the library and placing them on the ARES working area it Displayed a message "components cannot be placed because the design is locked"
IN short PCB design is not mapping the schematic design.


texts: Measure human voice for ambient noise level

texts:
I need to develop an ambient noise level to measure the loduness in an office. Sometimes during the day people raise their voice more than they should and a lot of confusion is created. So this device should be installed somewhere, like on the table or on the roof, and it should light up an LED when the noise is too high.

I thought of doing it in this way:

-Connect the electret to a band-pass filter to isolate only the human voice, which has to be analyzed
-Connect the output of the filter to an operational amplifier (is a x100 amp enought?)
-Connect the output of the amplifier to a microcontroller (like arduino) and read the voice level.

Should that work? I am expecting to read a value from 0 to 1024 from the microcontroller, is that possible?

Thank you very much!


texts: How to measure remaining lithium battery charge accurately (destructively)?

texts:
I want to measure the remaining charge in batteries and my requirements may be somewhat unusual. I do not need to preserve the charge left in the battery and it doesn't have to be quick. All I want is to measure how much is/was left in a battery. It's okay to fully discharge it in the process.

The type of battery I am most interested in is 1/2 AA, 3.6 V, Li‑MnO2, CR14250. "Normal" size AA 3.6V/3.7V, 14500 would also be interesting.

mAh values would be great but I can live with having to sacrifice (discharge) a full battery as reference for relative values. Is there an easy way to do this accurately (+- 10 mAh? +- 1%?) and cheap (< usd 50?) ?


texts: Creating a verilog code for 4-bit multiplier using lookup table

texts: I am having trouble creating a verilog code for a 4-bit multipler using a lookup table.  I am still trying to grasp the concept of a lookup table. If anyone could help me it would be greatly appreciated.I am just lost.


texts: Why is it possible to replace part of a BJT circuit with thevenin equivalent?

texts:
I know it's possible to replace the left side of this circuit with a thevenin equivalent, but on the left we're able to find the base voltage by the voltage divider Vcc * (R2)/(R2 + R1), which is the same as the thevenin voltage.

Doesn't this change the base voltage of the transistor since there's some base current that goes through the Rth?


texts: What are the "poles" of a signal (after it's reflected perhaps)

texts:
I desire to learn about "estimating the poles of a resonant signal", specifically the complex natural resonance of objects.

However, I don't know what "poles" are. What would you suggest I look up for better resources? :)


texts: Correct note frequency for STM32 based MIDI synth

texts:
I have been playing about with the EasyMXPro for STM32 dev. board from Microelektronica. I am trying to create a simple monophonic wavetable synth using the DAC, playable via. a MIDI keyboard, however, I have the following problems:

I have a loop that cycles through the wavetable values (at the speed of the MCU clock). The rate at which the program cycles through the array obviously gives me an incorrect frequency to that of the fundamental frequency of the sine wave in the wavetable. What is the best way to delay/speed up the execution of the program for each sample in the array, given that I need to cycle through the array at different rates for different notes on the keyboard? I have tried using a simple delay, however for each change in note frequency, the delay amount has to change specifically. Is there an easier way to do this that I have not thought about (perhaps using timers)?

Thanks in advance for any helpful answers!


texts: Motherboard backside traces touching antistatic mat. What happens?

texts:
A certain quantity of these traces is connected straight to the ground-plane.
What happens when an unpowered board (and completely disconnected from any peripheral) is on a grounded antistatic mat?
Will the ground-plane reach equipotential with the mat, because the GND traces make contact with the mat?
Or nothing happens, because both the V+ traces AND the GND traces touch the mat?


texts:
Is there IC fabrication services?
You upload the IC design you want and pay.
They send you physical IC of what you ordered.

Something like 3D printing service, such as shapeways.com for example, but for Integrated circuit.

Do such service exist? Why not?

EDIT:

I want to build SoC that I would use to build a server/super computer. I'm trying to build a computer like raspberry pi. But want it smaller and faster. If I get to design my own CPU. I could build something that is much better, then existing systems, because server on chips would take less space and power. At least for my programs.


texts:
I'd like to make a circuit that essentially produces very brief bursts of an RF signal, for example RF at 10MHz to 200-300MHz bursts of tens to hundreds of nanoseconds.  For example this could be just one half of a sine wave at 10MHz, or for a few cycles of a 100MHz signal.

I'm familiar with some techniques for doing amplitude modulation (eg: varying the supply voltage of a linear amplifier), but I don't know of any way to do amplitude modulation this fast, or with 100% modulation depth.

The output should also be synchronized with the phase of the RF carrier in a predictable way, so it could always get a complete half-sine, rather than a random portion of a sine each time.

At the moment I'm imagining some kind of fast switch that diverts an RF oscillator to the output or to a dummy load.  This is unfortunately not synchronized.  Is there a better way of doing this?  Perhaps something from ultra-wideband (UWB) type circuits?


texts: Is it practical to use separate MOSFETs for PWM and direction control?

texts:
I have an idea for a design which I'm curious to get some feedback on. Without worrying about support circuitry, consider the following MOSFET h-bridge:

The idea is that Q1 is a high-speed, high-efficiency device such as an IRF6, while the remaining devices can be cheaper FETs, for example, a pair of FDS8984s.

My questions about this concept have to do with the behaviour and properties of MOSFETs:

What are the consequences for power consumption and heat? My understanding is that most of the losses in a MOSFET occur during switching. If Q2 and Q5 are continuously conducting, does that mean that the losses mostly occur in Q1, or are the others effectively "switching" too, when the upstream supply is being switched by Q1?
Similarly, what are the consequences for the timing attributes of the devices? Will the rise and fall times be just that of Q1, or is it the max of Q1, Q2, and Q5, or worse, some sum of them?

The specific application being considered is a class D amplifier, but I'm looking to understand these things better generally, as the principles apply to power supplies, motor controllers, etc.

Thanks!

Edit to add: The reason this design (if it works) would be particularly excellent for an amplifier is that the PWM for an amp must be 200kHz to 1MHz to achieve accurate sound reproduction, but the direction will only need to be capable of changing as fast as the fastest sampling rate (48kHz). A full-bridge design also enables building an amp with a single power supply.

This design is a way to sidestep the usual objection to full-bridge amplifiers, which is that it takes twice as many of the expensive, audio-grade FETs.


texts:
I've been having some issues diagnosing the relationship between writing to the registers through SPI commands and stepping the motors. That is, it seems like when I write SPI_STEP=1 (and STEP=1) to register CTRL3, pins AOUT1, AOUT2 and BOUT1, BOUT2 produce a PWM when I expected just a single-step.

So my question is, are the outputs to the DRV8889 chip pulses despite the inputs being a single write command (which I have as 0x50 for CTRL3 register)?


texts: How does one calculate the values of LF1&2 and C93?

texts: I am learning about USB circuitry and one of the example schematics uses this lc low pass filter. I want to understand where these values came from? Thanks in advance. Link to article


texts:
I'm working with a TH3122 I/K-Bus transceiver with a built in 5v/100mA regulator. I'm trying to use my PIC24FJ1024GA606 to pull the EN pin of the TH3122 up/down in order to enable and disable the regulator.

Per the TH3122 datasheet, the regulator works this way:

  The regulator is active and can only switched off with a
  falling edge on EN. The regulator remain with EN=high in
  active mode and therefore also the VCC voltage is active.
  The input EN has an internal pull down resistor. If
  EN=high, the internal pull down current is switched off to
  minimize the quiescent current.

I have the EN pin pulled up to 5v through a 10k resistor and the regulator turns on as expected. However, when I pull the EN pin down (via the PIC's LATCH for the pin), the regulator drops to 2.75v. I have verified that there are only a couple mV on the EN pin when it's pulled down.

What am I missing? For what it's worth, if I wire EN directly to 5v, the regulator drops to zero voltage as soon as it starts floating (5v removed).

Here are the electrical characteristics for the EN pin (min/typical/max/unit for the last four columns):

P.S. I'm not an EE, so I apologize if I have missed any details.

P.P.S Here's the schematic around the part (GND4 floating isn't an issue anymore as I solder bridged it to another ground):


texts: Switching left/right audio with a DPDT relay

texts:
Is it possible to switch the left and right channels of the 3.5mm inputs below to the output with a AZ850P2-5 DPDT relay (given a 5V power source)? I have a hard time reading the pinout of the relay. How would one go about wiring this circuit, and connecting an Arduino to control it?

I have previously used a 2-channel relay module, but I am hoping for something more compact.


texts: Correct use of op-amp to amplify photodiode in reverse bias

texts:
So I have a photodiode in reverse bias, from which I intend to measure my pulse.

Currently, my schematic looks as follows:

simulate this circuit – Schematic created using CircuitLab

Weirdly, this produces a perfect curve with a good amplitude and a response around 380mA (Systole) to 420mA (Diastole).

From my schematic, I understand that I'm not using the operational amplifier correctly, hence why I have tried doing something like this, as it would make better sense:

simulate this circuit

The following schematic still produces a pulse, but the amplitude is not good and I can't see the dicrotic notch as in the previous. (Don't mind the motion artifact)

What am I doing wrong here? How do I correctly use the operational amplifier? If I attach my analog read directly to the output of the Op-amp I get around 0.5V, i.e. close to nothing.

Lastly, when I drive my non-inverting input high, I actually do get some response at my output that looks okay.


texts: Not understanding Level shifting +/-3.5V analog signal for ADC with analog input of 2Vpp and common mode voltage

texts:
I am trying to design a very basic oscilloscope and my first PCB schematic and I am having trouble wrapping my head around how to level shift the front end analog signal so it can be accepted by my ADC. I am using a AD9238 ADC with a 2Vpp input and I want the scope to accept a signal of +/- 3.5 V.
I have a level shifter that feeds into a differential op amp to give me a differential input in my ADC. What I am having trouble understanding is how much gain to give at the differential op amp, and what to level shift to.
I have set the Vocm pin on my differential op amp to Vdd/2, and my voltage source is 3.3V so that gives me a common mode of 1.65V I believe. So since my ADC accepts 2Vpp and common mode is 1.65V does that mean I am looking to level shift from +/-3.5V to .65 to 2.65V? The ADC also has an internal Vref that can be set to 1V, and if I instead use that for Vocm pin on the differential op amp would I then be looking to level shift to 0 to 2V?
The op amp for level shifting I am using is the lf351, the differential op amp is the THS4121CD and the 40msps version of the AD9238 ADC.


texts: Why is center frequency of a bandpass filter is given by the geometric average of the two cutoff frequencies?

texts:
In electronic communication systems, there is a concept called center frequency. A bandpass filter has upper cutoff and lower cutoff frequencies. Center frequency supposed to be in the middle of these.

Why is the center frequency of a band-pass filter is given by the geometric average of the two cutoff frequencies instead of arithmetic average?

edit: found a very thorough explanation:
http://www.insula.com.au/physics/1221/L15.html


texts: Will this circuit manage to kill a 2-stroke engine?

texts:
I'm currently building a project that involves a 2-stroke engine. I have tapped into the wires where you would normally place a kill switch in order to get power for some electronics. The voltage is 9VAC. The first half wave is used to supply my battery and logic circuitry with power. The second half wave, I've discovered, that if you draw more than a few mA it will mess with the ignition and stop the engine, so I didn't use it for power.
But then I found the need to be able to use my MCU (an ATtiny84A) running on the first half wave's power to short the other half wave so it can stop the engine if something goes wrong.

I can't use a relay: it draws too much power.
I can't use a MOSFET: the two waves have the opposite potential.
I can't use a latching relay: not in stock where I live (can't buy
online due to shipping restrictions).
I can't use a reed relay because the ones I find are NO but I need it to be NC.
I can't use an SSR: only available for higher voltage range.

What do I do?
I came up with the idea of using an optocoupler with a MOSFET but I'm not sure if it's gonna work. Here's the schematic that I created but if you find a better solution let me know!


texts:
I'm trying to use a ccd linear image sensor (µPD3753) and I'm using the application circuit example in its datsheet, however I'm new at using these type of sensors. Can someone please explain why they're using a hex inverter and not just one (this is needed because the sensor has 2 clocks and they must be inverted in order for the device to work) also why is the pnp transistor needed.

Datasheet


texts: Make 9v ups for router with TP4056 and MT3608

texts:
I am building 9v UPS for my wifi router using TP4056 lithium-ion charging module and MT3608 stepup converter. If USB power is available I want MT3608 to get power from USB (TP4056 Vin Pin) otherwise from battery (TP4056 Vout Pin). I don't have mosfet, So I am using diode Like this

IF USB power is avaliable does MT3608 pull current from higher voltage source (eg: from USB 5v rather then 4.2v from battery). Does this circuit will work?
Any suggestions?


texts:
I'm experimenting with a mic preamp based on NE5532. I'm using the following schematic with some modifications:

The modifications are:

the positive supply is directly connected to the power supply(no noise filtering for the power, but I'm using a chemical battery)
the 4.7uF cap is missing.
NE5532 instead of LM833

The part that is marked with a green rectangle is only for creating a 4.5V reference with low output impedance.

Voltages at the points marked with red circles, with almost no signal coming in from the electret mike:

Battery is 8.5V
1 4.3V (5% metal film resistors, within error)
2 4.27V
3 4.33V
4 1.4V

So it seems that the opamp cannot make its inputs equal. There is too much difference, I guess that cannot be an opamp offset error. Probably it cannot go lower than 1.4V at its output.

If I disconnect the 10uF capacitor from the +input, then I measure these:

1 4.33V
2 4.27V
3 4.33V
4 4.59V

First I thought that the 10uF capacitor is leaking. But it is not...

Here is the input vs. output signal when the electret microphone is receiving a 440Hz sinusodial sound wave:

It is clear that the output signal is clipped, and it is because the opamp cannot go below 1.4V. What I don't get is that WHY it needs to go below 1.44V to make its inputs equal? Does it have to do something with the 4.7uF cap being removed?

UPDATE: The cap was not simply removed but replaced with a piece of wire. Sorry for being ambiguous.

UPDATE2: Replaced 100 Ohm resistor with 1K, so the overall gain is reduced to about 10dB. The I put back the cap, but changed to 10uF. The corner frequecy changed from 339Hz to 16Hz, as it was suggested. Now the output at point #4 is also at 4.3V, and the distortion is not visible:

Conclusion: never forget to eliminate DC amplification when don't need it


texts: When a utility company uses the term "installed capacity" does it mean energy or power?

texts:
This is directly from this website: "The current installed capacity on Ontario’s transmission grid is more than 36,800 MW". Does it mean total energy generated & transmitted in a year OR the grid's capacity to transmit this much electricity in a second?

Also, can I compare this number with the energy generated by 1 litre of biofuel (which is 9 KWH)? i.e. do I need to multiply 36,800 by 3600 (minutes*seconds) to ensure I'm comparing in the same dimensions?


texts: How do I step down voltage and current in a DC application?

texts:
Background
I am currently building a RC multicopter that utilizes an 11.1 V 20 C 2200 mAH LiPo battery as it's main power supply.  This is fine to run the ESC's and motors; however, I also need a 5 V/2 A power source to run a PCB that is laden with an Arduino project consisting of digital sensors, GPS, LED controllers, etc.
Question
How do I produce the proper voltage (5V) and minimum current (2 A) from the primary source (11.1 V/20 C)?  Is it as simple as calculating a correct resistor value or should I do something else?  I don't want to fry my sensors!


texts: Switching and non-switching period in buck converter

texts:
I am using TPS54260 buck converter to step down 10V to 3.3V. Load = 1A.

While measuring the output voltage and switching frequency using oscilloscope, I am observing this:

During no load condition at the output, no switching at the switching node (before the inductor,) but output voltage = 3.3V.
During loaded condition at the output, switching frequency, duty cycle is observed at the switching node and the output voltage is 3.3V.

How come, during the the 1st case, I am not observing any switching waveforms at the switching node, but I am receiving 3.3V at the output?

Please clarify.


texts: Output voltage of op-amp in open loop configuration

texts:
What is the output voltage of op amp in open loop configuration when voltage in inverting input is greater than the one in the non-inverting input?

Is there a technical term for this output voltage?

Do datasheets refer to it?


texts: How to even start solving multi-diode problems?

texts:
For example, in the circuit below there are 5 diodes constant-voltage-drop diodes, I could have 2^5 circuits to solve. Is there something I'm not paying attention to, that would greatly simplify this problem?

PS: The S1 switch is closed. Problem is asking for Vx.
Thanks!


texts: Li-Ion Power Pack vs Deep Cycle 12V Battery?

texts:
I've seen a number of videos on YouTube where people have built a "Power Box" by putting a 12V deep cycle battery in some kind of weatherproof box with a charging equipment and added various switches and ports on the outside.

https://www.youtube.com/results?search_query=powerbox

I'm looking into building one of these for my annual camping trip in the desert, and was considering using this for a battery:

Mighty Max Battery 12V 22AH SLA Battery
Volume: 7.13" x 3.01" x 6.57" = 141 in^3
Energy Density: 22 AH / 141 in^3 = 0.15 AH/in^3
Weight: 13.1 lb
Price: $44.99

However, I also already own a number of Anker PowerCore Li-Ion based USB power packs like this. Which have nearly the same AH rating.

Portable Charger Anker PowerCore 20100mAh
Volume: 6.5" x 2.3" x 0.9" = 13.5 in^3
Energy Density: 20.1 AH / 13.5 in^3 = 1.49 AH/in^3
Weight: 12.56 oz = 0.785 lb
Price: $45.99

Both of these batteries are about the same price and hold about the same number of AH. Yet the USB battery pack is significantly smaller, lighter, and more energy dense.

If I don't have any need for 12V power, and only need 5V/USB power to charge my camera, cell phone, and run some LED lights. Is there any point to even considering using a 12V SLA battery?


texts: Arduino LED 9 V transistor with a common ground

texts:
simulate this circuit – Schematic created using CircuitLab

I am kind of new to building my own electronics.

I am building a stargate with 3D printed parts. When I soldered all the LEDs together, I connected them in series (9 sets of 3 LEDs) with a common ground as that is how I had seen others do it in the 3D printing community. After getting all of the soldering done, I glued the cover on it and when testing realized that in series the rduino doesn't have enough power to light the LEDs completely, they do turn on but barely visible.

It's too late to go back and re-solder them in parallel since I have already glued all the plastic parts together using 3D Gloop which bonds the PLA plastic together chemically.

What I need to do is provide a 9V charge to each set of 3 lights and I understand from my google searches and youtube that I can do that with transistors.

All the videos and information I have seen show the transistor using the ground between the collector and emitter to regulate the flow with the base connected to the digital pin of the Arduino to activate it. Since I wired all the sets of LEDs to a common ground and they need to be turned on individually, I need to run the 9V through the transistors to the 9 sets of LEDs individually and I'm really not sure what type of resistor to use.

The LEDs already have 220 ohm resistors connected inside the stargate if that helps. Any assistance would be appreciated since this is a graduation present for my nephew.


texts: Measure unknown load resistance on battery terminal

texts:
I need a method to measure the load resistance attached to the terminals on a battery.  I want to determine this load before I turn mosfet on to let battery pack discharge.  Most important I want to check for a short at the terminals before turning battery on.  I have a 5 volt cpu to control system.  I am thinking of trying to use a low ohm shunt and current sensing ic along with a current limiting resistor.  Issue is trying to measure difference between a 0.01 ohm load (1500 amps) vs Short yields only a few uA difference, which will be hard to measure be that precise with circuitry.  Without limiting resistor even a 0.001 ohm shunt yields hundreds of watts at high loads.

Is there another method I could use?

simulate this circuit – Schematic created using CircuitLab


texts:
Hope someone can assist me here... I have a 12V DC motor that works fine when connected to a battery source, but when connecting it to a 12V 3A wall adapter, it starts and stops repeatedly.
After a lot a searching online I did figure out its because the "draw current" when starting is too high when starting the motor causing the power supply to cut out. To confirm this I also added another 12v fan in series which causes the motor to work, but of course the 12V is now being split to the motor and fan (also just a motor really) and I both dont want to run both all the time and think it might not be good to run 2 x 12v motors in series with a 12v psu - but I might be wrong - if it is safe and Im happy with the reduced speed can I run it like that?
I also seen it mighty be possible to add one or more resistors (in series) which might also fix the issue, but I have no idea which resistor to use nor how many (Im an out-of-work software developer learning electronics). Should this be the best fix, how do select the right resistors? I have tried a few already but to no avail - I suspect they might not provide enough resistance (could be too much as well - again I have no idea).
Without purchasing an expensive new PSU that can handle the current, is there another solution that someone can possible explain to me please?
Thanks in advance for the help!


texts:
I'm trying to receive data to a PIC24FJ256DA210 from another device using UART communication.

I set up the UART as described below:

void InitUART(void)
{
    uint32_t baudRate = 312500;
    int brg = FCY/(16*baudRate)-1;

     /* Assign UART 1 signal onto pin 4 of PortF (RP10) using PPS */
    TRISFbits.TRISF4 = 1;
    __builtin_write_OSCCONL(OSCCON&0xbf); // clear bit to allow re-map
    RPINR18bits.U1RXR = 10; //Assign U1RX to RP10
    __builtin_write_OSCCONL(OSCCON | 0x40); // lock pin re-map

    CloseUART1(); //disable UART if enabled previously

    /*Enable UART interrupts*/
    IEC0bits.U1RXIE = 1; // interrupt on reception allowed
    IEC0bits.U1TXIE = 0; // no interrupt on transmition
    IEC4bits.U1ERIE = 1; // interrupts on errors allowed
    IPC2bits.U1RXIP = 5; // interrupt level of reception
    IPC16bits.U1ERIP = 6; // interrupt level on errors
    U1STAbits.URXISEL = 0; // interrupt when any character is received

    /* Initialize UART1 */
    U1BRG = brg;
    U1MODEbits.STSEL = 0; // 1 stop bit
    U1MODEbits.PDSEL = 0; //8 bit data, no parity
    U1MODEbits.BRGH = 0; //Standard speed mode
    U1MODEbits.RXINV = 0; //UxRX idle state is '1'
    U1MODEbits.ABAUD = 0; //Auto-Baud disabled
    U1MODEbits.LPBACK = 0; //Loopback disabled
    U1MODEbits.WAKE = 1; //Wake up on start bit detect
    U1MODEbits.UEN = 0; //UTx and URx enabled
    U1MODEbits.IREN = 0; //IrDA disabled
    U1STAbits.ADDEN = 0; //Adress detec mode disabled
    U1RX_Clear_Intr_Status_Bit; //clear RX interrupt falg
    U1MODEbits.UARTEN = 1; //UART enable
}

My problem is that every time I launch debug (I'm working with MPLAB X IDE), the U1 RX Interrupt keeps getting triggered even though nothing is yet sent to the PIC.

Did I do something wrong while initializing UART? It migth be a silly mistake but I really can't figure it out.

Thank you.


texts:
I have a big 500 F 2.7 V capacitor, and a module of six 120 F 2.7 V capacitors. If I calculated the capacitance correctly, the module has 20F total capacity.

If I calculate the energy stored in them by E = 0.5 * C * V^2, I get:

For the module: E = 0.5 * 20 * 16.2^2 = 2624 J
For the big cap: E = 0.5 * 500 * 2.7^2 = 1822 J

So far, so good.

I bought a battery tester device and charged the capacitors to 2.7 V and 15 V, respectively (my DC source only goes to 15 V), and I've connected them like a battery to the tester device. I set 0.5 V as the lower cutoff voltage. The results I got are:

The module yielded about 58 mAh.
The big cap yielded about 220 mAh.

These results are in the ballbark of what an "Ah equivalence" equation, Ah = Farads * DeltaVolts / 3600 gives, but both the measurements and this equation are in conflict with the capacitor energy equation, which shows the energy stored in the module should be greater than in the big cap. The battery tester puts the current through a (constant) resistor, so it should be fairly simple as far as calculations go.

So my question is: how to reconcile the two?


texts:
Could anyone help me out on this, why would an op amp have the curve of X1 with nothing in the circuit, it has a voltage source to the non-inverting input and negative feedback, just like a buffer. I can't figure out why it would have a 1.5v output when the input is 0v, with the shape of the curve I initially thought it was due to rail-rail issue, but that wouldn't explain the initial 1.5v?

The X2 curve is another op amp which has a typical voltage follower curve, but again it seems to have a slight initial voltage and falls just short of 5v.

Any help would be appreciated, I have been going backwards and forwards on this for quite some time now!

*It is a single rail 5v supply


texts: Poor little TO-252 went in a blaze of glory - can you help ID?

texts:
This guy is from a dishwasher control panel.  I'm having trouble finding a replacement for the entire control unit (that will ship to Japan, anyway) and I am handy with a soldering iron.

Can you take a stab at what you think it might be?


texts:
I want to make a Current transformer using toroidal ferrites to measure 220/50-60Hz AC current(40A max). Is it possible? And how can I calculate secondary turns count?
Ferrite properties:
H = 2000, Dimensions: 45*28*12mm.

I'm going to connect a current transformer to a mcu ADE7755


texts: Losses in wire with varying cross section along its length

texts:
Say I have 5 meters of thick wire (10 sqmm), and for the last couple of centimeters, I have to use a piece of 2.5 sqmm wire for mechanical reasons.

When sending a large amount of DC (say, 30 A) through the wire, will the losses / resistance act as if the ENTIRE wire were of the smaller cross section, effectively creating a "bottleneck" and making the remaining 5 meters of 10 sqmm pointless, or is the increase in losses just proportional to the length of the wire with the smaller cross section compared to the length of the wire with the larger one?


texts: How to interface with credit card terminals?

texts:
I am considering doing a project that involves a machine that can accept credit card payment automatically from customers. Think of it as a vending machine, that accept credit card.

I want to out-source the credit card part and just buy a terminal that my machine can interact with. Problem is that I have no idea how this interaction works?

I have seen that in stores, the cash register interact with the credit card terminal when the cashier "sends" the transaction amount to the terminal. Also when the transaction is done, the terminal sends some kind of acknowledge back to the cash register, so that it can log it for sales reports.

It is the same kind of interaction I want my machine to do. Question is which buses and software protocols credit card terminals use (to interact with cash registers for example)? Is there a standard? Or is it different from manufacture to manufacture?


texts: Grounding Distribution Panel Earth Busbar using 'split' cable?

texts:
I'm pre-wiring a distribution panel for future installation into my retirement home in the Philippines. I've read that grounding the DP to an earth rod or equivalent should require a minimum 6AWG/10mm2 wire(?) However in the metal DP which I purchased, the earth busbar only has screw holes large enough for 6mm2 wire. So my question is whether it is ok to split the wire strands in the 10mm2 ground wire into 2 separate bundles and insert each of them into a separate screw hole in the same earth busbar? I would use ferrules to ensure a good contact. It seems logical that it should be ok, but I'm not an electrician (it's undoubtedly obvious!) and wonder if there are any safety issues associated with this?

Thanks all for your suggestions to replace the busbar with one with bigger screw holes. However one (strange?) thing I have discovered is that the DP appears to be coated with a non-conductive paint. I learned this by using a multimeter to measure the resistance between any 2 points in the metal DP enclosure. This also applies to the earth busbar which is attached with small steel screws to the DP metal chassis, but when using the multimeter shows very high (OL) resistance readings using one probe on the busbar and the other probe on the DP chassis.   I suppose I will have to sand off the non-conductive paint to expose the bare metal before mounting the new busbar but wonder if this is 'standard' DP box design?  Thanks for your thoughts.


texts: SPI or I2C: which to use for a longish bus

texts:
I'm contemplating a project that would require several AVRs talking to each other over a bus.  They'd be separated by as much as 6 feet.

It seems like both I2C and SPI can let a series of micros communicate over a bus, but I haven't seen anything talking about how long that would be.  Has anyone tried connecting these protocols over distances of several feet?


texts: Coherence factor in Delay-And-Sum-Beamformer: Triangle Inequality

texts:
I'm writing a delay-and-sum-beamformer in MATLAB that incorporates a so-called and widely used coherence factor CF. Now I'm confused about the math behind that factor!

Given a vector signal of length N consisting of positive and negative real numbers (I will use MATLAB style):

One paper claims that: CF1 = sum(signal)^2/sum(signal.^2) <= 1
Another paper claims: CF2 = sum(signal)^2/sum(signal.^2)/N <= 1

The first statement does not hold i.e. for signal = [2 -5 -4] because CF1 = 49/45!

Is the second statement right? Why? I looked the triangle inequality up, but unfortunately I could not learn anything from it.


texts:
I have this EEPROM IC where I want to check the logic level compatibility with another IC.
But here Voh value is not given. I have observed this in my other IC also.
Why is the Voh value not provided? What shall I take as Voh?
Thanks


texts:
I soldered up a LM2678 for a 5V 1A output with a 12 volt input (Input voltage and current from (12v supply @2A) like shown here. http://www.ti.com/lit/ds/symlink/lm2678.pdf

It outputs a solid 5 volts under low < 50mA loads but experiences significant output voltage drop to ~3.6 volts under loads as small as 400mA. Any ideas what is causing this? It is soldered on perfboard with small distances between components. Mylar and Electrolytic capacitors are used for decoupling are are close to the input leads on the LM2678.

Any ideas?

Thank you


texts: Are there any standard testing methods for bare metal code

texts: I want to know if bare metal code, especially things like device/peripheral initialization code has any testing methods since there is little to nothing that can go wrong when writing to registers (once you know that all the addresses are mapped correctly). Also this kind of code usually has very few branches/paths when the device is being configured for one single function only, so what kinds of testing would be necessary or applicable here?


texts:
I'm doing a few basic load calculations on a 3 phase circuit at work and I stumbled on a concept I'm not sure how to proceed.  Let's say you have a 3 phase load and it is basically a black box.  For many reasons, you don't have any access to the load details (no schematic or circuit) but you know nameplate information like the power draw (in VA), the PF (and that it is lagging), FLA, etc.  Based on these parameters, I proceeded to calculate the 3phase impedance of each phase so I can combine it with other loads on the system, but I'm not sure how the load should be attached to the system, that is whether if the load should be presented as a Delta or Wye load to the power system.  I would think it makes a difference, since if it's Delta, the phase/line currents aren't equal and could throw off my calcs.

I don't do calcs like this very often so maybe I'm missing something very obvious.  What is the best way to model/estimate a scenario like this?


texts:
I am working on a speed controller for a robot and it's for when the robot is balancing on its wheels.
I am designing the controller as part of a project in a linear control design course. However, the controller has to be implemented on a robot and in software delivered by my instructor, so I don't have infinite room of freedom. The way I implement my controller can be seen here:-

As you can see, I can add a gain \$K_p \$, an integrator and post-integrator, a lead/lag-term in both forward and feedback path, a prefilter and a feed-forward. And that's it. I can't change what feedback I'm receiving, I can only add and adjust terms of the controller.
Edit - Finding the new transfer function
Doing what AJN suggests gives me a much nicer bode plot:-

The bode plot is much nicer, but I still have some trouble. I want to smooth out the hill in the phase plot, but I am not sure how to do so.
The new transfer function:
num = [0 0 0 -3.5113e+07 -3.7165e+10 -2.0902e+12 -3.8701e+13 -1.5402e+14 2.5341e+15 2.2109e+16 3.3405e+16];
den = [1 2.4731e+03 1.4491e+06 2.5930e+08 1.2622e+10 9.9503e+10 -1.8488e+12 -1.0302e+13 0 0 0];
G2 = tf(num,den);

Earlier form of the question containing some outdated info
num = [0 0 0 0 -2.3409e+07 -2.4777e+10 -1.3935e+12 -2.5801e+13 -1.0268e+14 1.6894e+15 1.4740e+16 2.2270e+16];
den = [1 2.4738e+03 1.4508e+06 2.6223e+08 1.5442e+10 6.8736e+11 2.6563e+13 5.2944e+14 4.0900e+15 8.1300e+15 3.7708e+15 1.1220e+13];
G2 = tf(num,den);

The open and closed loop bode plot for the transfer function is here:-

As you can see in the closed loop bode plot, there is a big valley in the phase, and this causes the system to be unstable (I think), and I don't want that.
My inital idea was to add a lag-term to the forward path. A lag-term removes phase, so if I place it right where the valley is the peak should get smaller. My lag-term looks like this:-

But even after adding the lag-term the phase still looks very weird. Here is the new closed loop bode plot:-

Is there a way to remove this phase valley and get a proper stable system?


texts:
I built a VOX circuit (Voice Operated Switch) which is an audio activated relay that activates when sound is applied from a USB sound card on my computer.

I am having a problem with the switch, however, every time I touch the input line, the switch activates, even with the largest resistor I could use before the switch was not detecting the audio input from my computer.

R1, R2  10K 1/4 W Resistor
R3  1K 1/4 W Resistor
R4  33K 1/4 W Resistor
C1  1uF Electrolytic Capacitor
Q1, Q2, Q3  2N2222 NPN Transistor
D1, D2, D3  1N4148 Diode
K1  9V Relay

I decided to add an isolation transformer as well as DC removing capacitors in line with the input, and I still had the strange effect, even when touching my aluminum computer, which is isolated from ground.

What are the next steps to eliminate this interference? Here is a link to a video I posted showing the issue.


texts: Why does the capacitance of ceramic capacitors change with test measurement voltage change?

texts:
I faced a problem of measuring capacity in ceramic capacitors.

Measurements did with Smart Tweezers ST5S. It has two output voltage levels that can be selected: 0.45 Vrms and 0.9 Vrms.

The capacitor is 22µF ±20% 6.3V X5R 0603 (1608 Metric).

  Tolerance limits are from 17.6 µF to 26.4 µF.

According to specification test methods are:

  The capacitance/D.F. should be measured at a frequency of
  1±0.2kHz and a voltage of AC1±0.2V(r.m.s.). (Test Methods).

When I set up output voltage level on SmartTweezers:

0.45 Vrms -- capacitance 17.14µF (out of tolerance limits)
when 0.9 Vrms -- capacitance 18.17µF

Why we have so difference? Maybe there is some formula which represents depending on: test measurement voltage VS capacitance?


texts: Are specific impedances for high-speed signals maintained beyond the PCB connectors?

texts:
I found this article that describes the specific impedances that single/differential traces must have for high speed signals (using microstrips).
But what happens to these impedances beyond the connectors which the controlled-impedance traces are routed to? Are the impedances maintained? If not, then is it really necessary to design/route the traces with the specific impedances?
E.g., if I design a parallel RGB interface with controlled 50 ohm impedances and connect a display, then are its ribbon and electronics designed so that they ensure the same 50 ohm impedances? If not, then all the hard work on the layout would be for nothing. In extension, this question refers to every device connected to a board designed with controlled impedances (USB, HDMI, LVDS, Ethernet etc.)


texts:
I am trying to make a discharge curve for one of my batteries that I have. All I know about it is that it is a 1.5V battery. Now if I have to make a discharge curve for it, how would I make one and what load should I use to make one? Should I pick a load with a rating of 1 C? but I don't know how to calculate this 1 C value (of the load) based on my battery.

I am very new to this topic. Any help is appreciated.

Thank you so much!


texts:
I want to build a miniaturized Stargate but I have no clue regarding the electronic part.  The Stargate is a fixed circle with 9 chevrons (see links bellow). An inner circle is spinning inside the main circle and has on it 38 symbols. Let's say someone presses on a symbol on DHD device (see links bellow). Now the upper chevron needs to identify that symbol during the circle's spin, and stop the motor.
The question is how can that be accomplished? I guess a laser reading is to complicated. Is it possible that the inner circle (the one that it is spinning) to have inside one coil for each symbol, and then the chevron to induce a current in each coil during spinning of the circle, and read the value?
Disclaimer: I know almost nothing about electronics and english is not my native language.

Many people might not know what a Stargate is so I put some links.

Dialing a Stargate: http://youtu.be/Qidw0Qqu8h0
DHD: http://en.wikipedia.org/wiki/Stargate_(device)#Dial-Home_Device


texts: Noninverting amplifier; Saturation point?

texts:
I had to design a noninverting amplifier with a gain of 5. I used resistances; R1= 1k R2=4K. Then it asked as magnitude is increased what value of input voltage will it begin to saturate?
Drawing of the amplifier I am using


texts: Will a Schottky diode save my LEDs against reversed voltage?

texts:
Consider the following schematic:

simulate this circuit – Schematic created using CircuitLab

Main question:

1) I am accustomed to use Schottky diodes to protect my circuits against reverse polarity. However, in my current scenario, user may apply voltage in reverse polarity to LEDs directly. After some research, I started to suspect that every Schottky diode may not be suitable, because while their reverse voltage may be rated enough the Schottky to survive, but their reverse current may exceed of LEDs'.

Is it correct?

Other questions:

2) How is the reverse voltage distributed on components? Is it equal, or completely random, dependent on LED/Schottky characteristics?

3) Consider the reverse voltage to be 20 Volts, and shunt the Schottky. Will each LED handle the reverse voltage (approximately) equally, and they will stay functional?


texts: I'd like a basic force balance circuit that I can build on

texts:
I've been messing around with the design of a geophone. This is a sensor that is coupled to the ground (sits on the ground) and records vertical movement.

I will use a phototransistor to detect movement of a suspended weight.
The weight could be a permanent magnet so a coil could act on it.
I'd like to build a circuit that would energize a coil + or - to oppose any movement of the weight.
So I don't have to be concerned about an occilation period of the suspended weight.
I just need to record the current fed to the coil.
I have an lm324 quad op amp I'm planning to use.
Thanks    Peter


texts: STM32L4 drive voltage randomly(?) too low

texts:
Not really sure where to even begin with this one. Last night when I turned everything off, the STM32L432 Nucleo board I've been working with drives high to 3V. When I turned it on this morning--no other differences--I'm only getting a 1V high signal. I'm new enough that I might not be understanding something simple here, but how is this possible?

Today:

Yesterday (lamentably, different code as I didn't save a capture of the current program, but still you can see that the voltage is better):


texts: Why is power so often associated with current and not also voltage?

texts:
I was reading one of my textbooks the other day about linear BJT emitter-follower amplifiers (non-relevant) and came across the following passage:

  Although the small-signal voltage gain of the emitter follower is slightly less than 1, the small signal current gain is normally greater than 1. Therefore the emitter follower circuit produces a small signal power gain.

But I've learned that the power can be expressed:

\$P = IR = \frac{V^2}{R} = I^2R\$

Which means that power is directly proportional to both current AND voltage. Wouldn't this mean that a large voltage gain also provides a power gain?

This is not the only place I've seen this discrepancy either. It seems that whenever people talk about power, they are only really concerned with current and not voltage, even though the math seems to suggest that is not the case.

Can anyone elaborate on this?

EDIT: One explanation I can think of is that there can be voltage across an open circuit, so increasing that voltage would theoretically increase power, even though nothing is getting hot... whereas if there's current flow increasing power by increasing current would make the component dissipate more energy...


texts:
I would like to know how difficult it is to build your own camera module. For instance, how difficult would it be to assemble the Raspberry Pi camera module from scratch?

The reason I'm interested in this, is that camera modules for high quality image sensors often come with horrendous price-tags, and I would like to know why.

.

An anonymous example [to not shit-talk a specific seller :S]:

You can buy a camera modules for a quite good image sensor for 200 bucks + shipping costs online. However, the image sensor cost ~10$ in mass production, and probably ~20$ in smaller bulk orders. If we then factor in the price for some lenses ~35$ and lens holders ~5$, we come to a total component price of 50-60$.

--> So why is the selling price so high? Do I forget important parts? :S


texts: Recommended current for external breadboard power supply

texts:
I want to buy an external power supply for my breadboard (this one). It says that the input should be between 6.5V and 9V, which is easy enough to understand. To power the supply, I planed on buying a wall plug with a barrel jack as an output. There are plenty of wall plugs which supply 9V. However, I found that they differ in the amount of current they output (i.e. ranging from 1A to 2A while both supplying 9V).
My question now is, which one is suitable to power the breadboard, and what the benefit of one other the other is.
Cheers!


texts: Calculate the thevenin resistance with diagonal resistors

texts:
The question is:

Replace the circuit with a Thevenin Equivalent Circuit and find the Thevenin Resistance (Rt) in ohms and find the current in R3.

I've used Thevenin before and solved quite a few equivalent circuits as well.

I've tried to redrawing the circuit, but I getting very confused on you would exactly go about combining these resistors. I found this exercise in a book, however, at the end of the book, it only shows the answer and not the approach. So the thevenin resistance should be 51.61 ohms.

You need to do the Thevenin’s theorem in the orange box.

So my first try was to consider R4 and R6 in series, then in parallel with R5, then in series with R1 to finish in parallel with R2. But obviously, that wasn't the right way to do it.


texts: Easy connectable/click system between enclosures

texts:
I'm planning to make some devices which I want to easily connect together.

Normally cables are used, but I wonder if there exists something like a 'clicable'  connector, where the output of one enclosure 'clicks' into the input of another enclosure. Like a connection without or with a very short and solid 'cable'.

Of course I can use a cable from one component/microcontroller from one enclosure to the other, but than I cannot detach them. I want to have a detachable solution, without the excess of a cable.

Pins needed:

GND (by default)
VCC (that would save an adapter for the second device)
TX (to transmit the signal)
Maybe RX (for some acknowledgement, but maybe not necessary because of the short distance).

So 3 pins would do probably.

The transmission speed is probably 250 kbs, but maybe I extend it later to 1 mbps max.


texts: Why is there a spike in voltage over an inductor double the peak voltage of a square wave input?

texts:
I am trying to understand why a graph looks like this for the voltage over an inductor in an LR circuit. The square wave is an input voltage and the red decaying wave is the voltage across the inductor.

I came up with this graph using step functions and the step response of the inductor.

The only reason I can think of is that the inductor has stored energy, but it seems also that the inductor dissipates that energy after five time constants. Where is this extra voltage coming from?


texts: Source of initial magnetic field in an alternator

texts:
I have been reading about how alternators work and I am wondering where the initial magnetic field comes from when no current is running through the field coils that excite the magnetic field in the rotor. I have found alternators that are using a permanent magnet, where it seems obvious and alternators that apparently do not seem to be using permanent magnets, where it is not clear to me. I can also find on the wikipedia article about excitation that there are such generators:

The magnetic field may be produced by permanent magnets or by field coils.


texts: Is there a standard I2C/SM bus protocol for laptop battery packs

texts: I'm building a laptop with a custom battery pack. I know that the pack has to communicate through an I2C/SM port on the motherboard, but I don't know how to make the bios/os recognize it. Is there a particular I2C address and standard protocol on top of I2C for battery state information exchange? If there is - where can I find the documentation for it? If no - is the protocol just proprietary to the bios manufacturer and then the OS reads it from the bios? I will be bitbanging I2C from the microcontroller that regulates the battery so I can do whatever is needed.


texts: SOT-23 NMOS transistor power dissipation

texts:
I am working on a design of a control system that controls a few small solenoids, each drawing about 200 mA of current and operating at 15-18 V. These solenoids are activated by NMOS transistors. Due to the size constraint that I have for the PCB containing these transistors, I would ideally like to use SOT-23 NMOS transistors.

Now, if one does the math, the power dissipated by each transistor activating a solenoid is P = (0.2 A)(18 V) = 3.6 W. However, it seems that most of the SOT-23 package NMOS transistors can only dissipate a maximum of about 1 W.

My question now is this - is the maximum power dissipation rating primarily due to the heat build-up that could damage the device if it exceeds its rated power dissipation? Or is it the limit of the internal materials that the transistor is made of?

Each solenoid in this system is typically never activated for longer than 20 seconds, and at the very extreme it might be activated for 1 minute, which happens almost never. The average on-time for these solenoids are between 1 second and 10 seconds. Will this relatively short on-time (dissipating 3.6 W of power) have a detrimental effect on a transistor that can only dissipate a maximum of 1 W? Or can one safely assume that the average on-time of the solenoid is short enough that the transistor will not heat up too much to cause any damage?

I have used the 2N7002 NMOS transistor (which has a very low max. power dissipation rating) in a prototype for this system with no problems at all and no evident heat build-up by the transistors. Should I rather get a properly rated transistor (3.6 W or higher rated), or can I safely use a 1 W rated transistor for this system?

Your comments and suggestions will be highly appreciated. Thanks!


texts: ADXL 335, lack of resolution for short angle inclination?

texts:
I am currently working on a project where I would like to measure X/Y inclinations changes, without worrying too much about the acceleration. I decided to use ADXL335 accelerometers in order to measure static changes of g ! To give a little bit of background, the project aims to use the Arduino Leonardo as a mouse, where the X/Y movement will be the readout of the ADXL335 placed on an object.

However, I'm now facing some issue with the reading resolution. In fact the object only provide angle inclination of +/- 10° from its 0 position, and the increments value from 0° to +10° does not provide enough steps to move the mouse from let say 512px on the right (1024 width resolution).

My question is : first, do you reckon any solutions using the actual sensor I have ? Smart coding or anything you could propose would be welcome. If not, what solution would you suggest ? I've been looking into inclinometer, but those 0,0031° resolution sensor are very very expensive ...

Thank you very much for your help !


texts:
I have problem understanding how the following expressions in Altium works, inside a component at the Simulation Spice Functions.IntLib, by editing a Simulation Model,  Netlist Template code:

@DESIGNATOR %1 0 VALUE { @EXP1 ?EXP2|
+ @EXP2| ?EXP3|
+ @EXP3| ?EXP4|
+ @EXP4| }

In Spice I understand the E?T:F is an if else statement taking the expression E as condition and selecting the T or F expressions accordingly. But this is not Spice.

The Netlist Preview (Spice) code, evaluating some parameters is:

E1 V02 0 VALUE { 1
+ SIN(1 2 100k 0.01m 100k)
+ 0
+ 0 }

But this actually don't works, meaning this is not accepting the SIN symbol, or something like that.

Where should i find more information about symbols like @EXP, ?EXP@EXP, @DESIGNATOR and similar?.


texts: Choosing a resistor for balancing lead acid batteries

texts:
I have a solar-panel-and-battery kit with a built-in inverter and what not built into the battery box.  (Goal Zero Yeti 400)  The battery box has Anderson Powerpole connectors for chaining it to external batteries.  As far as I know, these are connected directly to the battery inside.

The battery built-in is a 33 Ah 12V sealed lead acid battery.

Suppose I'm out camping, and someone joins me and brings another 12V, perhaps of different capacity, and at an unknown charge level.  How can I safely connect these batteries together in parallel?

I assume that if the voltage difference between them is too great, the current flow between them will be a lot and potentially damaging to one or both of the batteries.  Therefore, I'm thinking that some sort of resistor is called for, even if just until they're balanced.

Is this a good idea?  And if so, how do I choose what resistor to use in this case?  I suppose I could use something of very high resistance and let the battery trickle up to the right voltage over a long time, but it would be nice if it didn't take days.  What sort of current can these batteries take before they become damaged?


texts: How do I determine the minimum voltage for a buck converter to work? For example, in this Reference Design the minimum voltage is 166VAC. But what if I want to operate it at 100 VAC? What do I need to modify? In general, what parameters define my minimum input voltage? Input capacitance, controller duty cycle, switching frequency?


texts:
I'm trying to obtain BJT characteristics in NGSPICE, but for some reason the plots retrace to origin.

* BJT characteristics

RB 1 2 1Meg
RC 4 3 1k
QBJT 3 2 0 BC107B
V1 1 0 dc 12
V2 4 0 dc 10

.model BC107B   NPN(Is=7.049f Xti=3 Eg=1.11 Vaf=59.59 Bf=381.7 Ise=59.74f
+               Ne=1.522 Ikf=3.289 Nk=.5 Xtb=1.5 Br=2.359 Isc=192.9p Nc=1.954
+               Ikr=7.807 Rc=1.427 Cjc=5.38p Mjc=.329 Vjc=.6218 Fc=.5 Cje=11.5p
+               Mje=.2718 Vje=.5 Tr=10n Tf=438p Itf=5.716 Xtf=14.51 Vtf=10)
*       PHILIPS     pid=bc107b  case=TO18
*       91-08-02 dsq

.dc V2 0 10 0.1 V1 1.5 3.5 0.5

************
.control
run
plot v(4,3)/1k vs v(3)
.endc
************

.end

How do I resolve this issue?


texts: Difference between D-Type Flip-Flop and Edge-Triggered D-Type Flip-Flop

texts:
I need to create a JK Flip-Flop using a D Flip-Flop, a 2-to-1 line MUX and an inverter.  I wasn't really familiar with latches and Flip-Flops, but I understand the difference and how Flip-Flops are edge triggered with a clock pulse whereas latches are instantaneous with input changes.  Now when I was doing some digging into D-type Flip-Flops, I came across two different representations that I'm having a hard time differentiating.  The first is very straightforward and seems to be the standard representation.

This computes fine for me.  I can trace and follow it and fully understand how it works. Most common name I could find for it was simply D-Type Flip Flop.

However when I look further, I cannot differentiate between the name of the previous D-type Flip-Flop and this one:

Everywhere I look this one is defined as Edge-Triggered D-Type Flip-Flop, but I thought where a synchronous circuit uses a clock changes were always edge-triggered? Can someone please explain the difference and how to go about tracing the second one?


texts: Why is it bad to mix new and old batteries?

texts:
I've seen warnings that it's bad to mix new and old batteries -- why?

Is it a matter of a battery's age or a battery's voltage/current (remaining)?


texts:
I would like to replace the BC547 to SM3119NAU on this circuit. I have a several questions for this circuit.

Which resistor Rx value to choose?
Which resistor package to choose 0805 or 1206?

Due to the space on my PCB board, I have to use SMD components.


texts: How to find polarity of terminals of a circuit using meter?

texts:
Title may not me appropriate but i have a basic question that may be a beginners question so forgive me in advance. If we have a PCB and two wires are coming out for the battery connection. One will be connected to positive terminal of battery and other will be connected to negative of battery.
As PCB is a complex circuit most of the times so how we would know using a meter, which terminal of circuit will be connected to positive and which to negative if the positive and negative is not marked on the upper side of PCB.


texts: How can you calculate the transfer function of any parallel circuits?

texts:
I have now seen a few cases where RC in parallel are used as a Filter or just the famous LC filter.
But I am asking my self. How do you calculate the transfer function?

Now Kirchhoffs voltage law says that Ua = Ue. So how would you create the transfer function to calculate the DGL of it? Or is it only possible with resistance in front of the LC?  Or is it because this is just an ideal circuit without any resistance in series?


texts: Why is the resistance of an ideal voltmeter infinite?

texts: Consider an analog voltmeter. I understand that the internal resistance of the voltmeter should be high enough to not lower the actual voltage across the load connected to the voltmeter, but, at the same time, if the resistance was infinite, there will be no current flowing through the voltmeter which means no magnetic field will be produced and the pointer wouldn't deflect.


texts: Is there current flowing through this blank wire?

texts:
simulate this circuit – Schematic created using CircuitLab

Does any current flow from point A to point B?

My guess is no. Because both of those points are connected to a ground symbol by blank wires, they both have potential of 0V.


texts: Measured amperage differs greatly from my math

texts:
I've got the following circuit:

simulate this circuit – Schematic created using CircuitLab

It works. The LED glows nice and bright.

However my math doesn't match the readings I'm getting from my digital multimeter. Using Ohm's Law, I take the voltage rating of the batteries and desired amperage of the LED to figure out how much resistance I need.

This is my math:

V = I*R = 4.8V (4x AA 1.2V/2400mA in series)
I = V/R = 0.02A (1x 3mm Green LED 3.0-3.2V/20mA)
R = V/I = 240Ω (1x 220Ω & 1x 20Ω in series)

These are my multimeter readings:

Voltage across the batteries: 5.17V
Voltage across the LED: 2.93V
Voltage across the resistors: 2.24V
Resistance across the resistors: 238Ω
Amperage on the circuit: 9.56mA

Now obviously I am getting more volts from the batteries than I anticipated but even adjusting for that I still don't get ~9.5mA of current in my math.

Adjusted math:

V = I*R = 5.2V
I = V/R = 0.022A
R = V/I = 238Ω

What am I missing?


texts: Choosing SMPS, buck regulator or controller

texts:
There are thousands of buck regulators I can choose but I can use some good advices. I need fixed 7...8V output, 10...15V input and 2A maximum. The problem is I can't decide because I need smallest board (components) and high efficiency from 0.1A to 1.5A.

Most converters have high eff. starting from 0.5 or 1A. Others have a lot of components, including push-pull mosfets outside. And finally others are exorbitant as price (I found some from Linear Technology, inductorless, in fact component less but hugh price).


texts: Altium: multiple component footprints for the same component on the PCB

texts:
The question is one, but revolves about:

component definition in the library
placement between the schematic and the PCB document so that they remain synced
proper Net definitions and
avoid errors captured by the compiler and
proper BOM list generation.

I am relatively novice altium user and I am designing a fairly simple 2-layer fanout board for a component. I have also created a library for the component.

The component in focus has input, output and IO pins and its default component type is standard, which means that it will be included in the BOM list.

Now what I want, is that the board has pads for this component on both sides, for test reasons. In such a way the test engineer will be able to solder the component on either, but only one at a time, side of the board, leaving the pads on the opposite side unused. Of course the two sets of pads will be electrically shorted and hence, will belong to the same Nets according to specs. This way I will be able to route the board later.

What I did, is that I placed two instances of the component in the schematic: one with "standard" type and one with "standard (no BOM)", which almost brings me to the desired result.

The problem is that I get an error for the output pin from the compiler that "Net  contains multiple Output Pins." I understand the error, but I don't see how to resolve it, as according to the recommendation I should break my library definition, by changing the I/O specification.

Another option would be to place only one component in the schematic and two components in the PcbDoc, but this brings up two new questions:

How to keep the two synced, such that when I am doing a "Update Schematic/PCB document" no changes occur in the Engineering Change Order?
How to place a component with body in Mechanical layer, so that this is not visible in 3D View?

What is the way to do this properly in Altium?

Thank you very much and cheers!


texts: Can the negative terminal of a class B amplifier be connected to the ground instead of the negative supply?

texts:
I have a number of related questions highlighted in italic bold.
Here is a class B amplifier we saw in most of the textbooks (note that the negative terminal is connected to the negative supply. Refer to circuit 1

Circuit 1
Q1: However is it possible to connect the negative terminal of a class B amplifier to the ground instead as illustrated in circuit 2?
Circuit 2
Q2: If the circuit is connected to the ground (circuit 2), can the output voltage has a zero DC value?
(I suppose it cannot. The output in circuit 2 should have a non-zero DC value)
If we want an output voltage with zero DC, there are two possible methods to do it.
Method 1 (circuit 3)

Connect the negative terminal of a class B linear amplifier to the negative supply.
The output voltage at the drains of both PMOS and NMOS already has a zero DC.

Circuit 3
Method 2 (circuit 4)

Connect the negative terminal of a class B linear amplifier to the ground
The voltage at the drains of the PMOS and NMOS has a non-zero DC
Use a coupling capacitor to filter out the DC value

Circuit 4
Q3: Are method 1 and method 2 equivalent if the purpose is to get an output voltage with zero DC?
Q4: What are the pros and cons of method 1 and method 2? Which method is usually preferred? (assume the DC input power for both methods is the same, i.e. Vcc1 in circuit 3 is half of Vcc in circuit 4)
Thanks.


texts: Identifying the logic function of this specific MOS layout

texts:
I am not sure about the functionality of the following MOS layout. I came up with the logic function AND(NOT(AB),C).
Can anyone confirm or correct me ?

PS: The steps I made are attached


texts: GPS for Cubesats - is 8km/sec too fast for consumer chips?

texts:
Satellites in low earth orbit are moving close to 8km/sec. Most consumer-grade GPS chips still invoke the CoCom limits of 1000 knots, about 514 m/s. CoCom limits are voluntary limits for exports that you can read more about in this question and answer and this question and answer and elsewhere.

For this question, let's assume they are numerical limits in the output section of the firmware. The chip must actually calculate the speed (and altitude) before it can decide if the limit is exceeded, and then either present the solution to the output, or block it.

At 8000 m/s the doppler shift at 2GHz is about 0.05 MHz, a small fraction of the natural width of the signal due to its modulation.

There are several companies that sell GPS units for cubesats, and they are expensive (hundreds to thousands of dollars) and probably worth every penny because (at least some of them) are designed for satellite applications and space tested.

Ignoring the implementation of the CoCom limits, and all other issues of operation in space besides velocity, are there any reasons why a modern GPS chip specked at 500 m/s max velocity would not be able to work at 8000 m/s? If so, what are they?

note: 8000m/s divided by c (3E+08m/s) gives about 27ppm expansion/compression of the received sequences. This might affect some implementations of correlation (both in hardware and software).


texts: Esp NODEMCU powered from external 3.3v source and USB

texts:
My project supplies the NodeMCU with 3.3v from a battery source via the 3.3v input pin. I would also like to connect usb input for power and programming and to feed a small battery charger from the Vu pin.
Is there going to be a problem with the onboard regulator conflicting with my 3.3v source?


texts: Common ground between primary and secondary SMPS supply safe?

texts:
Is it safe to use a secondary smps supply in another full-wave circuit (dc side after filtering) by  connecting smps ground to the corresponding ground of the primary?

What if the filtering of the primary is not proper , will the ripple/AC destroy the secondary supply?


texts: Is it possible to know CRT monitor VGA wires that have no color standards

texts:
Actually I know that rgb wires are thicker than the others also they r coax wires.  But how to  destinguish Vsync and Hsync wires   and the respective ground wire for each signal when the wire colors follow no standard.
Wires are as follow:
Coax pink,white and blue and the others are green,orange,white,yellow brown and pink


texts: Raspberry Pi GPIO Pin and BJT Transistor

texts:
New to electronics but having fun.

I am trying to turn on/off a water pump with my Raspberry Pi via 3.3V GPIO pin with a BJT 2N5401 Transistor.

I am having success when I attach the Ground pin to the Base of the transistor and the 3.3V GPIO pin to the Emitter. However this seems backwards to me, shouldn't the GPIO pin attach to the Base and the GND be on the Emitter as shown in my second diagram attached.

My circuit diagrams below.

Thanks for having a look!

A little extra about my comment "I think the Pi is not liking the current". In the working setup I am experiencing a little flicker on my Pi which I think means there is a current related issue.


texts: SIgnal conversion (current -> voltage), robustness of methods

texts:
I do want to read pressure sensors. The output is a 4-20 mA signal. I do have a couple of these low current sensors from Sparkfun at home.

On the other hand, I could go for a more robust solution (money is not the primary concern) and use some of these industrial signal converters from ABB.

With the first option I could go for a small device, together with a small ADC. Everything inside a Box, probably with a Raspberry and touchscreen.

The second solution could be mounted on a "Hutschiene". Probably one of these Controllinos could serve as data aggregator. Data visualization, storage etc. could be done remotely e.g on a Raspberry or desktop PC.

Are the current sensing boards with the ACS712 suitable for this purpose ? Or do I run into some caveyeats ? For which solution would you opt ?


texts: How can I accurately estimate the power consumption of a GPS tracking device?

texts:
I'm building a solar powered GPS tracking device using an Ieik Mini Nano V3.0 Atmega328p Board (based on Arduino Nano), Adafruit Fona GSM module, Ublox GPS module. The GPS module will transmit location data every minute and I want to calculate the battery capacity needed for two days of operation without sunlight. In order to do that I'm trying to get a better picture of the lengths of time the components will be operating at some specified current before I buy the components.

For example the Ublox GPS module's datasheet/manual says that at normal operating conditions, the working current is 40mA max and does not specify a min current. Does this mean the GPS module will draw 40mA 24 hours a day while tracking and transmitting?

The Adafruit Fona claims to draw 20-25mA on "standby", 200mA+ while running, and spikes up to 2A while calling/sending/receiving data. Since it will transmit every minute, it safe to assume it draws 25mA 24 hours a day? or do I have to factor in to 200mA+ somehow?

As for the microcontroller board, the Arduino Uno R3 operates at the same voltage range and has the same max current drawn per I/O pin (40mA) so I am relying on this experiment to perform power consumption calculations. Is it safe to assume that the board draws 40mA (for the GPS module) + 25mA (for the GSM module) 24 hours a day and round up a little?


texts: Logging multiple sensors data to SD card at same time: writing hangs up

texts:
I'm making a data logger project with 5 different sensors which includes a 3-axis sensor runs at 800 Hz. My requirement is to log the data to an SD card.
Here I have to log 3-axis sensor @ 800 Hz and all the other sensors @ 1 Hz.

Since sensors running at different frequencies I used ticker interrupts for each sensor except 3-axis.
I made 3-axis to run in while loop.
Now everything is OK. I should be able to log as per my requirement. The problem is that after logging for 10 mins, sometimes 30 mins, the logging stops.

One important aspect here: fopen and fclose are done outside by using an interrupt. That means initially I open SD card and I write the data for 2 mins; later on, I close that file using tickers and I create a new file.

Below you can see my code sample.

// tickers used to create a new SD file at regular intervals.

 void onFileUpdate(void)
    {
        static int fileNumber = 0;
        if (logFile)
        fclose(logFile);
        char fileName[20];
        sprintf(fileName,"/sd/PCE-DL%03d.txt",fileNumber++);
        logFile = fopen(fileName,"w");
    }

// Ticker object for Light sensor which run at 1HZ by an inturrupt.

void onLight(void)
 {
  LUX = max44009.getLUXReading();
   fprintf(logFile,"\r\n                                 %f  ",LUX);
 }

 // RTC ticker

 void onRtc(void)
 {
    seconds = mktime(&t);
    rtc8564.get_time_rtc(&t);   // read RTC data
    strftime(buf, 40, "%I:%M:%S %p (%Y/%m/%d)", localtime(&seconds));
    fprintf(logFile,"\r\n %s", buf);
 }

// my while loop

 while(1) {
   accelerometer.getOutput(readings);
   fprintf(logFile,"\r\n%i,%i,%i", (int16_t)readings[0], (int16_t)readings[1], (int16_t)readings[2]);

      }
  }

I don't know why it is hanging up. It may be timing problem ...


texts: How to amplfy µA from a fast photodiode with a bandwith of 10GHz

texts: I want to measure faint laserpulses with a step slope (Bandwidth 5-10GHz). I have a photodiode which produces a photocurrent of some µA. Now I need a transimpedance amplifier to convert it to at least 150mV (better 200mV) on 50 Ohm termination so that my time to digital converter can trigger on it. Does such a high gain/high bandwith amplifier even exist? Is there a clever way to use stacked open loop OP-AMPs or a complete different design? What is the highest gain-bandwidth-product achiveable`?


texts: How does a Touchstone (s2p) file indicate whether it should pass or block DC?

texts:
I'm trying to simulate impedance matches for an LDMOS FET amplifier with Touchstone (s2p) files to simulate the device with "real components" before we build it.  I have found that "capacitor" s2p files leak DC current and that "inductor" s2p files don't pass as much DC as you would expect for the milliOhm specification.

Is there something that specifies the DC charactaristics of the s2p model in the file that I could modify?
Are there other ways to solve this?  For example, would an ideal parallel-inductor with a 1e9 nH or an ideal series-capacitor with 1e9 uF across the s2p component help with this in the simulator?
Other thoughts?


texts: Is it possible to drive 4 seven segment display with MSP430G2231?

texts:
I'm trying to teach myself electronics and my goal is to create a digital clock with 4 digits.

I have  an MSP430G2231 which has only 8 available ports as far as I can tell.

I saw some methods for driving multiple seven segment displays, like using a multiplexer or transistors. But it doesn't seem possible with MSP430G2231 because of it's lack of ports.

Am I wrong? Or could it be done? If yes, how?


texts: Could 8V of power be safely put onto the 3V3 input of an Arduino Uno?

texts:
I have permission to access a (borrowed) Arduino Uno, and the documentation says it can be powered with 3.3 Volts from the 3V3 pin:

3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.

http://arduino.cc/en/Main/arduinoBoardUno

However, I would like to use a 24V DC power source.

The safe range is supposed to be 6V-20V.

If I could get a transformer in place to change the 24V DC to 8V DC, could I apply that 8V to the 3V3 input (without frying the board)?


texts:
What is the difference between common-mode and single ended signals?

I hope,

In common-mode signal:We need to have two separate transmission lines and one ground line.
In single ended signal:We need to have one transmission line and one ground line.

Whether my understanding is correct?

Regards,
Azlum


texts: Converting Proteus PCB to Altium PCB file

texts:
Hey all I am converting a Proteus PCB design into Altium and I am wondering what each file is since it asks me in Altium.

My Proteus files are:

And this is what Altium does when I do a PCB Design Check/Fix:

And so I say Yes and I am presented with this:

And this is where I am not sure what to put for each... Any help would be great!


texts: How can I wire a 9-position switch so that each position turns on one more LED than the one before?

texts:
I have a 9-way switch like this guy:

And I'm trying to figure out how I can turn on one LED with position 1, 2 with position 2, all the way up to all 9 in position 9.

Obviously I can repeat all the wiring for the LEDs at each position, but that seems silly.

My idea is that with a layout like below, the switch would represent the circled red line (shown in position 3), which would elongate to the right in each successive position until it connects all the lights. How can I do this?


texts: Current flow through resistor and insufficient source

texts:
In a simple circuit consists of a source and resistor, according to Ohm's law, if 10V is applied to a 10 ohm resistor, the current flow through the circuit will be 1A.

But what if the source in this circuit has a max output of 0.5A? What happens in that case?


texts:
Transistors are always very confusing to me. I read and try to understand the specsheet always but never confident about my understanding :( I have PCB (readymade), which gives me a 2.8V output when I switch on the PCB. The 2.8V is coming out from the MCU directly. Now if I drive a BC109 with that output and put a 75ohms relay in a  common emitter fashion then will the transistor be able to supply enough current to turn on the relay? According to my calculation, the BC109 max collector current is 200mA and a 12V/75ohms relay will require around 160mA current. If I put an additional resistance in serial with the relay's coil, then I can bring down the current more. Can someone please tell me if I am theoretically all correct or not. I am not attaching any drawing as it is really a tiny circuit and can be visualized easily.

=======================================================

After reading the comments, here is the question in a more mathematical way. Please let me know if I understand it correct.

simulate this circuit – Schematic created using CircuitLab

Transistor : BC337
Relay: 12V / 75 Ohms

Connection type: Common Emitter

Input Voltage (applied to base) = 2.8

Required Current to turn on the relay = 12V / 75 Ohms  = 160 mA

Max Ic = 800mA (Safe to drive the relay)

Current Gain to hard on BC337 = 10

Base current required to switch on the transistor (thus the relay) = (Current Gain / Load Current) = 160/10 = 16mA

Vbe = 0.7

Effecting Base Voltage = 2.8 - 0.7 = 2.1

Required base resistor = Vb / Ib = 2.1 / .016 = 131 Ohms (approx)

Transistor's power dissipation: (Vce * Ic) + (Vbe * Ib) = 196mW Approx


texts: Microcontroller controlled pulse current source

texts:
I want to make the laser (Iop < 20mA and Vop < 2.5V) blink with help of MicroController.
I made the following circuit and tried to test it using a 10k resistor instead of the laser in order to check the current flowing through the drain of the transistor.

So when I was measuring the voltage at the source of the transisor it was showing the 1.4V and wasn't change when a signal at the non-inverting pin changed.

When I disconnected  the output of the OpAmp from the gate the voltage at the drain became 0.4V and the voltage at the output of the OpAmp was 2.7V in spite of voltage quantity of the signal pulse (V_pulse = 3.3 or 0).

What was wrong? Is there any mosfet transistor (dip type) that will fit better for my goal? Or do they only work with high current?
Is there a circuit that is better than what I want to make?

UPD: Is the schematics from this answer apropriate how do i create a current source? There are no transistor at all


texts: 74HC14 Schmitt Trigger Oscillator - Weird output at certain voltages

texts:
Recently bought some TI SN74HC14 Hex Inverter IC's to learn and am having weird issues with them. I've looked at many examples online and have tried wiring them the same with the same passive values. Here's one that I tried: http://www.learningaboutelectronics.com/Articles/7414-schmitt-trigger-oscillator-circuit.php

I hooked the output to my oscilloscope and messed around. It seemed like when I turn on the power from my supply to 5V, the output goes high for a period, then the output goes low for a period, then the output goes to a 'middle noisy state' (similar to what you see if you have take out the capacitor). I tried different capacitor values which would extend the pause period but no matter what it would stop working after the first cycle. Its like the capacitor would start low (bring the output high), get charged (bring the output low), and then never discharge again (like having no capacitor there at all).

As a random last ditch effort I tried going down to 2-3V, and the output is what you'd expect - a square wave. Success!!... kind of...

The chip is rated for up to 7V so i'm not sure why this would be happening. I would assume there must be a way to get this to work everywhere within the IC's spec voltage. My circuit is the exact same as the one in the link posted, with the output going to just an LED and to my oscilloscope (i've also tried it just going to my oscilloscope with the same results). Anyone have any ideas?

Thanks,

Andrew

Edit: 1/23/17
Thanks for the comments so far. To give more information based on your comments, I have added a 0.1 uF decoupling cap (I also tried other values). I've tested the circuit with and without the LED, and the resistor on the LED is 330 Ohms (also tested other values). Also you're right about 7V not being the max, the datasheet says 2V-6V operating voltage, I think I just typed the wrong number.

Edit: After trying stuff...

I tried bumping up the LED resistor from 330 ohms to 1-2k, which let me bring the power supply voltage up a few tenths of a volt before the output became unstable. I then tried grounding the unused outputs, and as I ground them one by one it allows me to increase the supply voltage up to the usable 2-6V range! Looks like the issue was mostly just grounding the unused pins. Thanks!


texts: relation between reflexion coefficient and power ratio

texts:
Assume you have an intermediate input/outpout device connected to a coaxial line.
For example, the device may be a DC-bloc, a bias tee, or simply a PCB microstrip transmission line.

Using a signal generator (e.g. YIG oscillators), you can generate a continuous wave and feed the input of the device.

At a given frequency, you have measured the power of the oscillator dissipated in the 50ohm input load of your spectrum analyzer (without connecting the device), and noted the value, e.g. P1 = 20dbm.
Then you connect the device between the oscillator and the spectrum analyzer and measure again the power, say P2 = 15dbm.

I would like a mathematical relation between P1 and P2 and the reflection coefficient (or equivalently the VSWR) caused by the device. Is it possible ?


texts: I want  to upload lines of code (with c files, not sketches). But sadly I don't own any programmers and only possess the Arduino UNO board. Since I want to program in c code, I can't make use of the Arduino IDE. Is there any way can code can be uploaded to the ATmega IC without using any programmer?


texts: JFET Constant Current Source (CRD alternative)

texts: Today I have build constant current source based on J111. To drain I connected VCC it's 24VDC from laboratory power supply, then I connected resitor 470Ohm between gate and source. To source pin i connected potentiometer to simulate load (0-1k). Accordingly to simulation in LTSpice I should get around 6mA of current on my load. I connected my multimeter in series (i have also reading from power supply) and current was much higer than I expected. My current source failed. Could someone point me where I have made mistake? I want to create cheaper alternative for CRD.


texts: What does this part of a circuit with two NPN transistors do?

texts:
My grandmother asked me if I could fix her old portable record player, so I took a look at it and the motor wouldn't spin, so I opened it up and found a schematic inside. Nothing seems bad or broken in the machine, but when I measure the voltage between the motor + and - it's only getting 0.3 volts DC while it should be between 9 and 12 volts.

Upon further testing I noticed that when wiring the motor - directly to ground it works fine, yet in the schematic it goes through a little part of the circuit with two NPN transistors. Why is that part there and what does it do? Why not just wire it directly to ground?

BTW: I already took out and tested both transistors on a multimeter, nothing odd to them

As suggested by Jasen I checked the voltage on R571, and it's 11.09 volts on one side of it and, near to nothing on the other side. It's also a really weird resistor (picture added):


texts: How can a non-sine waveform can equate to combination of DC voltage?

texts:
It has been found that any repeating, non-sinusoidal waveform can be equated to a combination of DC voltage, sine waves, and/or cosine waves (sine waves with a 90 degree phase shift) at various amplitudes and frequencies.

Above excerpt from allaboutcircuits.com. I understand that a non-sine wave can be broken down into a combination of harmonic sine waves. What I dont understand is how it states above that it can also be from DC voltage which isnt alternating like a sine wave.

Could someone help clarify? Thanks


texts: Is it possible to intercept the audio data of voice call in Android?

texts:
To my konwledge, the (voice call) audio data from micphone will be sent to PCM module for resampling, then to modem for coding before sending to air.I am here for asking in Android is it possible to intercept the audio data from PCM to modem? Because I want to encrypt them before sending out.
Thank you ..


texts: Convert low voltage accelerometer to Wake ATTiny Open Source Binary Watch, activate on wrist motion

texts:
I'm working on building a binary watch similar to njeer's binary watch featured on hackaday

I am planning on using a cr2032 3.0V 190mAh battery. So in order for this to run for any length of time I'll need to keep the ATTiny in sleep mode until the user actives the watch. I found this to be a good resource for that.

What I'm wondering is how I can convert the voltage output of a AD22279-A-R2 accelerometer to something that an ATTiny85 can wake up on. And make it only wake up give the right wrist flick or motion.


texts:
I'm trying to set up an APRS station using an old icom HT.  Receiving is fine, but I'm having some trouble with the transmission side.  When I connect all my parts together, the transmit light immediately goes on.

I think I might just not understand the instructions, but the thing I've built works with my testing.

I've got two parts basically.  The first is the standard serial PTT circuit for soundmodem:

I've verified this is working with my DMM.  There's no continuity when normal, but there is continuity when xastir is transmitting.

For the other part, I took wired two 3.5mm jacks onto my breadboard such that the signal lines are directly connected and one (the input) goes directly to ground and the other (the output) goes to ground through the PTT circuit as shown in the diagram from the manual:

Again, I've verified I can hear the output with headphones and that ground is not connected end-to-end except when the PTT circuit says it should be.

Can anyone suggest what I might be doing wrong here?  I've verified repeatedly everything works the way I think it should, so I can only assume there's a flaw in my understanding of how things should actually work.


texts: What is difference between DC current from dynamo and DC current from battery?

texts: Dynamo generate DC current and battery also gives DC current. Here my question is when I use inverter, it worked with battery however doesn't work with same voltage of current from dynamo. Why? Battery gives like 12 volts and dynamo produce and supply 12 volts works same with 12 volts DC bulb, then why inverter doesn't work?


texts: Exactly what is the role of the zero-order hold in a hybrid analog/digital sampled-data system?

texts:
I'll admit, I am asking this question rhetorically.  I am curious what answers will come back out of this.

If you choose to answer this, make sure you understand the Shannon-Nyquist sampling theorem well.  Particularly reconstruction.  Also be careful of "gotchas" in textbooks.  The engineering notion of the dirac delta impulse function is sufficient.  You need not worry about all of the "distribution" stuff, the dirac impulse as a nascent delta function is good enough:

$$ \delta(t) = \lim_{\tau \to 0} \frac{1}{\tau} \operatorname{rect}\left(\frac{t}{\tau} \right)
$$

where

$$ \mathrm{rect}(t) \triangleq \begin{cases}
0 & \mbox{if } |t| > \frac{1}{2} \\
1 & \mbox{if } |t| < \frac{1}{2} \\
\end{cases}  $$

Issues regarding precision, bit width of sample words, and quantization done in conversion is not relevant to this question.  But scaling from input to output is relevant.

I will write my own answer to it eventually unless someone else presents an accurate and pedagogically useful answer.  I might even put a bounty on this (may as well spend what little rep I have).

Have at it.


texts: How to add NFC to a cheap consumer product?

texts:
I want to add NFC (Near Field Communication) to a cheap consumer product with an existing microcontroller.

I need to be able to pass a chunk of static data to a smartphone.

I'd like to be able to pass dynamic data to the smartphone in both directions. (ie. have the microcontroller use NFC as a low speed communication link). But, not if it significantly adds to the system cost.

Low system cost and low power are both important.

There seem to be many different wireless technologies calling themselves NFC, I want the kind that will work with smartphones.

What device(s) would be best for this task?


texts: Mesh analysis equations with dependent current sources

texts:
I can't get the correct mesh analysis equations for the circuit above. The end result I got for \$i_x = 0.111\$... but that does not work in simulation. Iused the equations below, the approximate value that works in simulation for \$i_x\$ is around 8.3A, but I can't get to that value.
$$ i_x = i_a - i_b $$
$$1,5i_x = (i_b -i_c) $$
$$i_a = 2$$
$$i_d = -5$$
$$-(i_b - i_a) \times 10 - i_b \times 20 - i_c \times 25 - (i_c-i_d) \times 5 = 0  \Rightarrow  -30i_b-30i_c = 5$$
And got this for substitution:
$$ 3 - 2.5i_b = i_c \Rightarrow i_b = 19/9$$


texts: Cloning a USB signal - feed two USB hubs with one input port

texts:
I have a schematic for a 4 port USB hub (4 output ports, 1 input port). I'd like to make two of these hubs and connect them together, thus making a 7 or 8 port USB hub on a single PCB.
I know there are 7 port hub ICs, but I find them harder to use, plus I have this schematic already tested.

I can think of two ways to connect these 4 port hubs together.
First way, which I'm pretty sure will work, is to connect one of the hub A's output ports to hub B's input port.
This way however we get a total of 7 usable USB ports.

The second way, which I'm not sure if it will work, is to use only one input port, but clone its USB signals - they go both into hub A and hub B. This way we get a total of 8 usable ports.
But would that work? I know the differential signals are a bit tricky, so I'm not sure if cloning them like this would be acceptable.


texts: How to compare processor speeds based on architexture

texts:
Is there any rule-of-thumb for comparing processor speed based on architecture?

I'm researching single-board computers, and I'm trying to compare ones using ARM processors (e.g. Beaglebone Black, PCDuino, UDOO) to ones using x86 (e.g. Galileo). The ARM ones typically have a higher speed (e.g. the BBB runs at 1GHz whereas the Galileo runs at 400MHz). However, I know the x86's complex instruction set can do certain operations faster, while ARM's reduced instruction set uses less power but also requires more work for certain calculations.

Is it fair to say speed A on x86 is equivalent to speed B on ARM? e.g. Is a 1GHz ARM processor "about as fast" as a 400MHz x86 processor?


texts: Mesh Analysis for circuit having Current Source

texts:
I have the following question: Since the current through the current source is not given (may be error), I assume it to be 2 A. Now since the resistors 6 Ω and 3 Ω are in parallel, I calculate the equivalent resistance and reduce the circuit.

to the following

But to do mesh analysis I need to know the internal resistance of the current source, right? So how can I do mesh analysis? Please advise.


texts: DC/DC buck converter module redesigning for paralleling with higher current

texts:
I am searching to have one bench power supply with two output and have parallel capability as tracking option in commercial power supplies like this:

and found this post to built power supply by ordinary DC/DC converter form the market.

So i prefer use the dc/dc converter which are common in market near the cost of  lm2569 or xl4015 dc/dc converter modules.
So i have seen some post about paralleling power supplies and read suggestion methods like this:

Also i found this post which suggested to have one master and another as slave with one CC mode and another CV mode as said here:

CONNECTING POWER SUPPLIES IN PARALLEL TO PRODUCE HIGHER CURRENT

Two or more power supplies being capable of CV/CC automatic cross over
operation can be connected in parallel to obtain a total output
current greater than that available from one power supply. The total
output current is the sum of the output currents of the individual
power supplies. The output of each power supply can be set separately.
The output voltage controls of one power supply should be set to the
desired output voltage (CV); the other power supplies should be set
for a slightly higher output voltage. The supplies with the higher
output voltage setting will provide constant current output, and will
drop their output voltage until it equals the output of the CV supply.
Connecting two or more power supplies in parallel (Figure 1) provides
higher currents. It is important to follow these precautions:

One unit must operate in constant voltage (CV) mode and the other(s) in constant current (CC) mode.
The output load must draw enough current to keep the CC unit(s) in CC mode.

I have tried to do this work by this kind of modules :

And made this circuit based of this PCB made:

In this topology, i have used the current control part of master converter to the load current line and the slave current sensing part, would be disconnected by pressing the parallel button.
In this topology by diodes in the output of the converter pins, when the current is below the max current set by the current POT volume of master supply, the Mater voltage output converter would be below in the circuit and if the current become over the value of the Mater POT, The master Current sen part act and decrease the output voltage of the master module and it would be disconnected form the load because of the serried diodes in it output with the load, ( no returning current!).
i have reasd some comment about voltage regualtion diffention in real wolrd for every dc/dc converter mudule wich would be problem in praleling this modules like said here, but i think this problem have:

some voltage drop on the load output.

pressure on the load serried diodes which maybe need to choice this kind of diodes by high power range and fast disconnecting type (If that is correct, how much power range and frequency would be enough?).

So i asked here, what problems will have this topology during test? and what more things must be considered?
Thanks.


texts: What wire would I need for 24000 watts (48v @ 500amps max) of DC power?

texts:
I have four batteries in series, 48v and a 500amp controller.

Right now, I am using standard amplifier battery cables, I believe they are 0 gauge.

Operational performance is not as good as suspected and the controller and wires seem to get very hot at peak amps and today a lead terminal sheared itself off under constant load.

I am guessing my wire is insufficient for carrying such a load.

If so, what should I use?

Additional information per comments:

I didn't expect to move to 500 A, I was pushing 200 A for a while and upgraded the controller. The application is a finished electric motorcycle, but I live on a mountainous area so the amperage is sustained longer than usual.

Would you recommend aluminum over copper?

The way each battery is mounted won't allow for busbars to be used.

Really hard estimate the wire length everything is mounted tight, no wire is more than 12", most being around 6"

I do notice voltage drop during higher amp loads but I think that's to be expected anyways during acceleration

The connections are made of lead, they're automotive grade electrical wire, like what connects to a starter. Fine for 200a maybe not for 500.


texts: reverse engineering the Nord Lead 4 control board

texts:
I am reverse engineering a synthesizer named nord lead 4. I want to tap in between the control board and mainboard which has the microprocessor.

i didn’t started with the powered on analysis but i am making a map of the connections and getting to know the IC’s.

I figured out all the pins of the 26 pin cable between the control board(which has potentiometers and two leg switches and 7 segment led displays etc.).

This board has also the IC’s that i am interested 3 ADC ‘s (max1039) a mux/demux(hc4052) 2 octal bus trancievers(lc245a) and probably for the seven segmented displays 6 flipflop IC’s(hct374) and one demux(lvc138a).

I also figured out all the selects and connection between the ADC’s and the mux/demux hc4052. This is mostly all i understand from topology until now.

My question is about the switches. There are around 34 switches in this control board(the ones you press with your finger they are momentary switches) they have two legs when you press there is a connection created between the two legs ofcourse.

These switctches are distributed to 8 busses of the octal tranciever(lc245a) and those busses sent to the other board which has the microprocessor. So multiple switches are on the same bus. Do you have an idea how this machine reads them and know which is which? Does this topology seem familiar to you?

Thank you very much Please tell me if you need more info.

*i hope i put the right tags to the question


texts: How does one know if an 8 bit MCU is sufficient or 16 bit MCU is needed?

texts:
16 bit micro controllers are more powerful than 8 bit ones and the 32 bit ones are on a whole different level. With that being said, while we can decided what peripherals we needed for an application and try to find the cheapest (and easy to use i.e the tool chain) alternative, how does one know if an 8 bit micro controller should be used for an application or a 16 bit one or a 32 bit one?

I do understand the differences between them so I will put the question in a different way.

Lets say I have an application in which I shall have an LCD display used to show bitmap image, a 16 key pad, buzzer, temperature and humidity sensor and a mouse input. A high end 8-bit micro controller can easily do all these things in real time. Now if I move to a colored LCD display, then I may need a 32 bit microcontroller that can update the colored display quickly enough and has more memory. However, I may only find out that my high end 8-bit microcontroller is weak, after I have tried it in the project.

So, before we start working on the project, how do we know what size and how much powerful microcontroller is needed for the project?