texts: Is it truly impossible to tell what a CPU is doing?

texts:
Computer programmers often recite the mantra that x86 instructions are totally opaque: Intel tells us they are doing something, but there is no hope that anyone can verify what's happening, so if the NSA tells them to backdoor their RNGs, then we can't really do anything about it.

Well, I believe that computer programmers can't do anything about this problem. But how would an electric engineer attack it? Are there techniques an electrical engineer could use to verify that a circuit actually performs the operations described in its spec, and no other operations?


texts: Is M1 Chip Memory Considered as Registers?

texts:
Given the following image of Apple's m1 chip, we can clearly see that RAM is so close to the CPU:

does this say that RAM will be much faster when compared to others Macbook models (Since distance is less than by nearly 30x!)

Can we consider and treat the RAM in this case as registers? If they are nearly as close as registers what's the difference between them and registers?


texts:
I was working on building an induction furnace.
What would be the difference in using a metal film capacitor or a ceramic capacitor with similar ratings and values.

From what I know, the ceramic show poor response in terms of high frequency and are highly non-linear in their behavior with frequency. However for this application I plan to run it at around 40KHZ, which isnt a high frequency.
Is it fine to use a ceramic capacitor for this application?


texts:
AC701 Schematics

Refer page 40 of the schematics. Here for Vccint- the regulator is switching at 250 kHz.
page 34 has the sensing signal conditioning for that the inst. amp used is INA333 which has BW of 150 kHz, the BW decreases to 35 kHz when gain is set to 10.
They also are using anti-aliasing filter of ~3MHz cut-off.

Now my question is, considering the cross-over frequency of the regulator be 250/5 = 50 kHz and sampling used here [my assumption] 1MS/s. Using INA333 in the path would degrade the signal isn't it? We should have amp having greater BW than the sampling freq isn't it?


texts: I'm building an LED transceiver to communicate between two computers using serial communication. For this purpose, I'm thinking about using an IR LED bulb to blink according to the 1s and 0s bit stream of messages and receive that from a TSOP17XX IR receiver used in normal TV remotes. I saw in some web sites that TSOP17XX responds to the frequency denoted by XX. So I'm wondering, if I use just an IR LED to generate light pulses, will it be grabbed by the TSOP17XX accordingly?


texts:
I have come across a Bluetooth legacy product or protocol in a meeting at my employer, but I can't quite recall if its name is called BluetoothLC (Bluetooth Local Connectivity). It would be great to know what kind of legacy Bluetooth classes/protocols are out there.

Thanks in advance.


texts: Current Transformer - example (basic) circuit request

texts:
I'm trying to setup an XBee to monitor power usage of a device. At the moment, I'm trying to get a basic circuit setup on a breadboard, without the XBee.

I have purchased a https://www.sparkfun.com/products/11005 Current Transformer to use. Can anyone provide me with a basic circuit to utilise the CT? I'll eventually be feeding it with a 3.3v regulated supply that the XBee requires, but I'm currently using a 5V power supply with the breadboard.


texts: Weird problems with LCD (HD44780 compatible)

texts:
I've been trying to interface with a HD44780 compatible display (16x2) for quite a few hours now, but have run into some weird behavior problems which I can't solve.

My setup:

I'm using the LCD in 4-bit mode (the upper four bits, D4-D7, as in
all the guides I've found, the order is correct - I've checked a few times).
The LCD is running from a 5v regulated supply. (I've tried 3.3v, same result, less contrast)
The R/W line is grounded with a pull-down resistor (fixed in
write mode).
The contrast is set by a pot and I can get the one line of squares visible at startup.
I'm using very slow timings (~200ms wait - enable high - ~200ms - change data - ~200ms - enable low)

My init sequence:

(with RS low)

0x03 - (three times) (sent as one nibble/byte)
0x02 - Enable four bit mode (sent as one nibble/byte)
0x28 - Function set (2 line, 4 bit) (sent as two nibbles, ms nibble first)
0x01 - Clear (sent as two nibbles)
0x06 - Set entry mode (increment cursor on write, no display shift) (sent as two nibbles)
0x08 - Display, cursor and blink off (sent as two nibbles)
0x0F - Display, cursor and blink on (sent as two nibbles)

Here, some things don't happen as expected:

Two line mode doesn't seem to enable (no dark background squares on second line, no chars get written there)
Clear doesn't happen
The cursor is in the 3rd square instead of the first at the end of this init sequence

Next I try to write some characters with RS high, sending 2 nibbles per character.

Here too, I get weird behavior: Instead of writing 1 character per 2 nibbles, it writes 2 (one per nibble). I made it go through the chars 0-15 and I get random symbols (eg slash) and Japanese chars. All of them are from random places on the char table, mostly the bottom row, not in any normal order, but always the same chars in the same order get printed.

My question:
I've really run out of ideas to fix this.
Am I missing anything obvious? What problems could I be having and how can I debug further?

Edit: This is what I see on my screen after init, it may be helpful

Edit 2:

My main code:

GPIOPin lcdEnablePin = PIN_B(11);
GPIOPin lcdRSPin = PIN_B(10);
GPIOPin lcdDataPins[] = {PIN_E(2), PIN_E(3), PIN_E(4), PIN_E(5)};

//Set all pins as outputs
GPIO::pinModeDigital(lcdEnablePin, 1);
GPIO::pinModeDigital(lcdRSPin, 1);
for(int i = 0; i < 4; i++)
 GPIO::pinModeDigital(lcdDataPins[i], 1);

GPIO::writePinDigital(lcdRSPin, 0); //Instruction register
lcdSendData4(lcdEnablePin, lcdDataPins, 2); //Enable 4 bit
lcdSendData8(lcdEnablePin, lcdDataPins, 40); //Function set, 2 line
lcdSendData8(lcdEnablePin, lcdDataPins, 1); //Clear and return home
lcdSendData8(lcdEnablePin, lcdDataPins, 2); //Entry Mode, Increment cursor position, No display shift
lcdSendData8(lcdEnablePin, lcdDataPins, 8); //All off
lcdSendData8(lcdEnablePin, lcdDataPins, 15); //All on

GPIO::writePinDigital(lcdRSPin, 1); //Data register
for(int i = 0; i < 16; i++) //Write test data, 4 bit because that's what seemed to work
 lcdSendData4(lcdEnablePin, lcdDataPins, i);

My SendData functions:

void lcdSendData4(GPIOPin lcdEnablePin, GPIOPin lcdDataPins[], char data)
{
 simpleBusy();

 //Set enable high
 GPIO::writePinDigital(lcdEnablePin, 1);

 simpleBusy();

 //Write data
 for(int i = 0; i < 4; i++)
  GPIO::writePinDigital(lcdDataPins[i], data & (1 << i));

 simpleBusy();

 //Falling edge
 GPIO::writePinDigital(lcdEnablePin, 0);
}

void lcdSendData8(GPIOPin lcdEnablePin, GPIOPin lcdDataPins[], char data)
{
 lcdSendData4(lcdEnablePin, lcdDataPins, data >> 4); //Send MSB
 lcdSendData4(lcdEnablePin, lcdDataPins, data); //Send LSB
}


texts: How to amplify a 3.5mm headphone analog signal?

texts:
I have made a circuit like described at this site

but the sound I receive through the mic sensor is not very high. Can I add some Opamp circuits  to increase the analog data input in android phone?? ( Mine is a Samsung galaxy note 1 )

What is the input voltage limit and power for the smart phone 3.5mm plug?? does it depend upon different models of the phone i.e do they have different max input voltages ?


texts: Improving the quality of an optical audio transmitter

texts:
I wired up a very simple device in which I use an audio signal transformer (EI14) to modulate the intensity of a laser beam (a cheap 650nm, 5mW diode) according to the audio output of my phone. The laser is then received by a photo-resistor (G5528 A205) wired up to the microphone socket of my laptop. With this setup I can transmit audio between the two devices.

Not surprisingly, the results are not astonishing. The audio quality is less than crystal clear, but that was expected. Here's an example.

My main concern that this system may be fundamentally limited is that it's not the data that I'm sending, from which the audio could be recreated; what I'm sending is just some real-time 'amplitude'. I'm actually surprised how well this worked since my intuition is that music consists of a range of Fourier frequencies and each point in the duration of the song comprises of some combination of those frequencies at corresponding amplitudes. At the same time, with a monochrome beam I'm limited to just varying the brightness of my beam and hence only able to send one amplitude at any given time, i.e. only the information about one of the Fourier frequencies (presumably the dominant one?) can be transmitted. Is this reasoning fundamentally correct and does that mean that a monochrome beam can't faithfully transmit a complex sound in real time?

My other questions are: what improvements to my very simple setup are possible to make the audio quality better? What are the limiting factors? Is it even possible to get a reasonable quality in such a system?


texts: Why my hex inverter chips (all three of them) are not producing a HIGH output with low input?

texts:
I wont say I am great at reading datasheets, but I noticed that for 74LS06 chip, Ioh is 0.25 mA and Iol is 40mA. Does that mean it can light-up an LED when its output is low but not when its output is HIGH (a forward biased LED of course)?

If yes, does it mean that all those chips whose Ioh or Iol is lesser than required to light-up an LED can't glow the LEDs even when it is forward biased? Please help. It means a lot.

Also, I have tested with multimeter, the output voltage of three 74LS06 chips with low input is 0.04v.


texts:
I have some doubts about this circuit:

http://hackaday.com/2011/10/28/motor-drivers-half-h-bridge-with-brake-and-more/

Is this schematic correct?


texts: Creating an OATS (Open Area Test Site) for Radiated measurements (pre-CE)

texts:
When building a product with an RF transmitter inside, one of the important things is to ensure that it complies with the CE requirements. So being able to measure the radiated power, both of the carrier and the harmonics, without paying the EMC-test lab every time, would be a great tool.

So I was experimenting with measurements on the soccer field next to our office, but I'm unsure if it is even possible to do within 2-3 dB error margin.

I can see that a "real" OATS needs a metallic ground plane beneath the transmitter and the receiver.

My idea was to place the DUT and the receiver 3 meters apart and 1 meter above ground. Then follow the steps below:

Measure received power from the DUT.
Substitute the DUT with a signal generator + antenna with know gain.
Measure received power from substitution.
Calculate DUT power as difference between 1) and 3).

Does anybody have any experience with this?


texts: DDR2 decoupling/bypassing - 100nF or 10nF?

texts:
I am slightly confused in deciding decoupling/bypass capacitor for DDR2 power supply pins. Some recommendations mention using 100nF and some mention using 10nF. I know that lower capacitance is more effective at higher frequency, but when I think of functions of bypass capacitor, I also think about the sudden requirement of charge during switching, where I believe 100nF can be more stable compared to 10nF (as it can store more charge for more time) in maintaining a steady voltage. Am I correct in my understanding?

I am using a single/discrete DDR2 RAM IC from Samung.

Any advice would be much appreciable.


texts: Best practice for ICT test point locations

texts:
While I have found a few resources (here here here) describing the coverage (strive for 100 %!), distribution (avoid clustering, at least 100 mil apart, away from tall components), and size (40 mil if you can) of test points designed for bed of nails in-circuit testing (ICT), I have not found guidance on the placement of them among traces.
I have seen some pretty ugly placement -- e.g. test points tangential to traces or halfway across the board from their signal's main trace -- but the two options I notice the most are directly inline with the trace or close by the trace/component and bridged with a short trace:

The former (TP-A above) makes the most sense to me while the latter (TP-B) looks to be a technique used among a high density of traces and test points (I'd also be more concerned with acid traps here, but it seems like modern manufacturing techniques aren't as vulnerable).  Are there guidelines or best practices that relate here?


texts: Would this Li+ flashlight circuit be considered safe?

texts:
I recently got an inexpensive (~$4 USD) Li+ 18650-powered flashlight from banggood.com, one of my favorite sources for inexpensive Chinese electronics to tear down and hack for fun :)

I wanted to validate its safety circuit before considering putting it into active service. I'm not liking what I found, but am wondering if I'm being too conservative. I'm having a hard time shaking visions of a Li+ battery charging on my counter bursting into flames suddenly :)

The flashlight takes a single 18650 non-protected Li+ cell. The flashlight won't turn on (draw any more than 10uA) when the voltage is below 2.37V. However, once on, it continues to draw current down to about 1.95V. Also, until it reaches that shut-down threshold, the turn-on "hysteresis" is defeated; that's basically how I've defined shut-down.

Here's my test setup. Only the LED holder and switch assembly are shown; everything else is mechanical (and ground conductor):

Here's a table of the various voltages (on the way down, lower brightness setting):

 V+  I (mA)
---- ------
4.2  65.5
3.8  61.4
3.4  45.2
3.0  22.2
2.7   6.3
2.6   2.5
2.5   165uA
2.4    83uA
2.3    60uA
2.2    46uA
2.1    36uA
2.0    28uA
1.95   0.2uA

And on the way up:

V+   I (mA)
---- ------
1.5  0.0uA
1.7  0.1uA
1.9  0.1uA
2.0  0.3uA
2.1  0.6uA
2.2  1.1uA
2.3  1.9uA
2.4  70.3uA
2.5  165uA
2.6  2.5mA

After this on the way up the V-I characteristics match those on the way down.

So I do note that the current consumption falls precipitously at about 2.5V on the way down (2500 -> 165 uA), and that nothing much happens at all until 2.4V on the way up. What I'm wondering is whether this is enough to constitute adequate protection.

The scenario I'm imagining is that someone places the flashlight vertically, lens down, on a desk, and then forgets it's turned on since the light isn't visible. If left for a couple weeks like this, I'm thinking the battery would discharge to levels that would make it prone to violent misbehavior on re-charge.

What I rather expected to see was the current drop a little sooner, say 2.7V, since the discharge rate wouldn't be great enough to allow much recovery. Then not take more than protection IC current up to about 3.0V on the way up.

Am I being over-conservative?


texts: Struct at overrun error and framing error in USART PIC18F4550

texts:
I'm trying to communicate PIC18F4550 with biomed module. I'm very new to embedded. My module sends a packet of 5 byte information  continuously  at 4800 baud, 1 stop, ODD parity.

I've set my baud rate perfectly BRGH=1, BRG16=1.

My main is:

    void main()
{

    INTCON=0xC0;
    RCSTA=0x80;
    TXSTA=0x24;
    BAUDCON=0x08;
    PIE1bits.RCIE=1;
    IPR1bits.RCIP=1;
    SPBRGH=0x09;
    SPBRG=0xC3;
    RCSTAbits.CREN=1;
}

My ISR is:

    void uart_isr(void)
{
    if(PIR1bits.RCIF=1)

    for(i=0;i<32;i++)
        {
            PORTD=RCREG;
      if(RCSTAbits.OERR)
        { PORTBbits.RB6=~PORTBbits.RB6;
          do{
            temp = RCREG;
            temp = RCREG;
            temp = RCREG;
            RCSTAbits.CREN = 0;
            RCSTAbits.CREN = 1;
          }while(RCSTAbits.OERR);
    }

            PORTD=PORTD-32;
            buff[i]=PORTD;
            myMsDelay(15);

        }

 }
}

I'm getting lots of overrun. Please suggest some method to stop these errors.


texts: Can I connect transformer secondaries with different voltage in paralel?


texts: Sine wave signal at resonant frequency gets distorted

texts:
I am currently at lost on what I need to do to solve my problem.
I have a sine wave signal as my input, and the output is sine wave as well. At resonant frequency, the output of the signal gets high.  I was able to get good signal output using function generator, but I am not getting a similar result using a circuitry. The input signal gets distorted when it is in resonant frequency. From the image below, purple is the output and the yellow is the input. I am currently using an inverting amplifier to output a gain of 10. DDS module outputs a positive sine wave with 1Vpk-pk. With the inverting gain of 10, it outputs 10Vpk-pk. After using AC coupling in oscilloscope, it goes -5V to +5V (yellow) as shown in the image below. At resonant, the yellow signal gets distorted.
What can I do to not have distortion when it is in resonant frequency. Any help is appreciated.

Distorted signal when in-phase

No distortion when out of phase


texts: increasing laser beam without increasing power (and possibly breaking law)

texts:
I bought some laser diodes on ebay recently that were advertised as 5mw which look like the image shown:

To comply with law, I hooked it up to a 9V battery with a 22K resistor.

I made a simple detector as follows with an LM324 op-amp

I connected inverting input to output via 4.7M resistor. Output is connected to cathode of LED via 1K resistor. Non-inverting input is pulled up by 1M resistor and pulled down by the 3mm clear lens photo-diode detector connected in reverse.

The detector works nice if the laser beam shines right at it (which is what I want), but I find that with such a low wattage, I have to be super-precise at shining the beam directly at the detector to get it to respond. If I'm off by even 1mm, the detector won't respond.

I have read about special kind of glass (or something?) that is supposed to scatter laser beam light when hit? but I'm not 100% sure what it is called or if it commonly exists. Can someone shed some light on this? Basically I want my detector to respond if it is in a transparent case and any part of the transparent case that the component side of the circuit is facing is hit with a laser beam.

Can anyone suggest what I should do? and raising power is not an option since laws prohibit lasers more powerful than 5mw.


texts:
I am having trouble identifying some components in this circuit. I am not sure if these are commercially available or not, so that's why I am asking.

The components are shown below:

I believe this would be a transistor.

I believe this would be a diode.

Unsure.

It has a marking like a diode, but really unsure if it is.

I believe this would also be a diode.

Edit:

Unsure about this component as well

Edit2:
Thanks to @Phil G who found both 4th and 6th to be dual transistors. And the meantime i found CY806(1st) to be 2SC881-Y and 5th to be BAS21-O3W.
But if anyone could help me with the 2nd and 3rd, it would be greatly appreciated


texts: Sinusoids and Phasors AC circuit impedance

texts:
Hello. I've been doing problems, and transforming from time domain to phasor domain to find input impedances seems simple enough But I've come across a circuit with a dependent voltage source, as shown in the above figure, and I'm not sure how to approach it. Must a voltage be assumed?

With the assumption, a voltage across the 5ohm resistor is obtained as well as the dependent source. But does that make the value in the dependent source an impedance as well? Thank you for your time.


texts: Parallel MOSFET gate drivers, should I connect all the driver outputs together?

texts:
I'm making a capacitive discharge spot welder. I want to parallel 36 MOSFETs IRFB7430PbF and use a gate driver for each MOSFET. I want quick switching times both on & off and ideally very little gate ringing when I switch the MOSFETs off. The gate driver I'm planning to use is the ZXGD3005E6. I will add a small resistor and ferrite bead to the MOSFET gate to help with ringing when turning the MOSFETs off (See MicroSemi.com application note). I've done as much reading as I can on the subject but I can't find the answer to this specific situation. I've seen other situations where the gate lines are all tied to together (before the gate resistor) but those weren't using a gate driver (See Alpha & Omega application notes). The purpose was to try and have all the MOSFETs turn on at the same time, as much as possible anyway.

Sig_Weld would come from the MCU, Electrode_POS is one welding electrode, with the other electrode being connected directly to the capacitor bank positive. Should I connect "Weld_Gate" to all the other driver chips (to help synchronize switching on time) or leave them separate?  Please let me know if you see any other errors in my approach.

As background information to the functioning of this circuit, I'll try and give an overview. A large bank of capacitors (504 * 5600uF 24V caps) is charged up to the desired voltage (using a seperate charging/discharging circuit). The MOSFETs bank, described above, will discharge the capacitor bank through the work piece creating the weld. I would like to be able to double pulse the weld, hence the need to turn off the MOSFETs with as little ringing as possible. Here is the charging/discharging circuit.

I've built 2 other spot welders. The first was using a microwave transformer, but using thick welding tabs, it simply takes too much time to weld. Too much heat gets into the battery. The second welder was following the design on ZEVA. This is the welder I currently use and it's very functional but cannot do double pulse. This was not a design goal of that welder and it really does a good job. I can't thank Ian Hooper from ZEVA enough for putting his design online for others of us to use.

Thanks.

Update：
I'm going to try and connect all the gate outputs together. This is my best guess as to the best practice.


texts:
I have a 500W PSU that has both 12v and -12v supply rails with the dual +12v rails rated for 360W (20A each) and a single -12v rail rated for 9.6W (0.8A).

My question is; if I was to power something using a +/-12V rail voltage what would the maximum ratings of the supply equate to? If the -12v rail can only sink 0.8A does the entire +/- rail supply then limit to 0.8A and become a 9.6W dual supply (or exceed this and damage the unit)?


texts: Simple question about the difference between Thevenin resistance and non-Thevenin resistance

texts:
In a lecture for an Electrical Engineering course I was taking, the professor did an example on solving a Thevenin circuit.
When he solves the circuit for Thevenin resistance he adds two resistors in parallel between the open circuit "a" port, however when solving to make an equivalent resistor to find the voltage he goes and adds two resistors in series between the same "a" open circuit. I am confused as too how this is allowed.
I would think that for both cases either it could only be added in parallel or series however this seems to not be the case. The only thing that changes is that now there is a voltage source and I am confused on how that has an effect on the calculation of resistance.
Picture for reference of solution:

Edit: Added full solution of the problem using Thevenin:


texts: Is this circuit for Piezo Transducer sufficient?

texts:
I want to drive this Piezo Transducer (https://www.mouser.com/datasheet/2/670/cpt-9019s-smt-1310960.pdf) directly from a pin on my STM32F0 microcontroller. I don't want to use a BJT transistor because the max current consumption of the transducer is so low (5mA). Right now I have the following schematic.

simulate this circuit – Schematic created using CircuitLab

The pin on the STM32F0 can source a max of 3.3V (peak-to-peak). Since the max current consumption of the transducer is 5mA, I want to limit the current going into it to 2.5mA to be on the safe side. Using Ohm's Law, I get a resistance value of R = \$\frac{V}{I}\$ = \$\frac{3.3V}{0.0025A}\$ = 1320\$\Omega\$

Is this circuit correct or am I missing something fundamentally?


texts:
so i have just bought a fan controller(silverstone cpf04) and it is rated with 2200μF and i am planning to connect 7 fans to it.

(NF-F12)4 fans are each rated with 12v operating voltage 3.6w input power and is rated 0.4amp @ 12v.

(NF-A14)3 fans are each rated with 12v also but with 6.6w input power and is rated 0.84amp @ 12v.

I have tried doing some maths myself using a capacitance, charge and voltage calculator but I still am not sure if cant find out whether if it will blow up the fan controller. I know this is a q&a for electrical engineering but I don't know where else to go. Pictures are attached to save your time. Tia.


texts: Controller for a Brushless DC motor (with ESC)

texts:
I have one of those BLDC Motors which are used in quadcopters and also an ESC to control it. I give it a PWM signal and it outputs the necessary condition for the motor to spin (AC signal).

The first question is: I think the ESC's output relative to its input is nonlinear. In other words, multiplying the width of the input pulse by 2 will not increase motor's speed in a factor of two. Am I right?

The second question is based on the first: in case it is a nonlinear system, how can I use a PID to control it? Suppose I want to build a controller (PID) in which I give a specific angular speed and the motors reach this angular speed as fast as it can with low or none overshoot. The input to this system will be something like a RPM value and the output is will be another RPM value (some speed sensor coupled to the motor). But somewhere inside the control loop one should place a gain K which converts the RPM value to a voltage or PWM value.  If this relation is nonlinear, how can this be done?


texts: DIY zero-crossing circuit, how crucial are component values?

texts:
I want to build this circuit, taken from here, and I'm wondering exactly how crucial exact component values are.

I don't have any 220k, 22k, or 4.7k resistors. I'm wondering if I can substitute two 100k in series for the 220k, two 10k for the 22k and a 5.1k for the 4.7k. Of course I could do two 100k and two 10k to make the 220k, but that's 4 resistors in place of one. Will the 20k difference make that much of a...difference?

Also the circuit calls for 1n4148 or equivalent diodes. I have 1n4007. Since those are really just to make a bridge rectifier, could I just use a bridge rectifier component, or just substitute the 1n4007 diodes?

Finally, is a 2N2222 an acceptable substitute in this case for a 2N3904?


texts:
I need several number of WS2813 LEDs (20 LEDs), to be connected to each other in series, to form a strip ring.
Each WS2813 has an input DI (D1) which is generated by MCU and also has an output DO which must be connected to the DI pin of the next LED (D2, D3, D4, ...)

For preventing from multiple component placement, I think It's more efficient to use repeating sheets capability of Altium, but I don't know how implement it in series format.

Is there any way to do it in Altium?


texts: Proteus simulation problem (beginner) - "Power rails 'VCC/VDD' and 'GND' are interconnected in net GND" errors

texts:
I'm a beginner to microcontroller programming and the Proteus simulator. I'm following this "PIC MicroController Volume Adjuster Program(Proteus 8 Stimulation)" Instructables project.

When I pressed the start button to start the simulation, I got the errors shown below. Can someone tell me what the problem is?


texts: How can I calculate resistance from A to C and from A to B in this circuit?

texts:
I've got this circuit, and what I need to do is calculate the equivalent resistance from point A to point C. I've noticed these three resistors are connected in series, but how can I calculate the result? Is it the sum between all three resistors R1+R2+R3, or just the sum between R1 and R3?

Also, the resistance from A to B is going to consist only of R1? Our teacher also told us that we may go through R2+R3, but it isn't the same result as R1.


texts:
As far as I know, you have to put capacitors on most voltage regulators. However, the data sheet for this one specifically says "No external components required" and furthermore goes on to state "electrical characteristics" being "Vi=10V, Io=500mA, Ci=0.33uF, Co=0.1uF, Unless Otherwise Specified."

I'm fairly new to electrical engineering and I don't know what to think of this. Is it saying I should put a 0.33uF on the Vin and 0.1uF on Vout, or does it mean that it already has capacity equivalent to those values built into the IC?

As a bonus, It'd be helpful to know what it means by Vi=10V and Io=500mA because it specifically states that the output is 1A and the minimum input is 7V (dropout 2V, output 5V).

I'm thoroughly confused.

Here's a link to the datasheet: MC7805CT(TO-220)-480029.pdf


texts: Fixed point trigonometry for embedded aplications

texts:
I need to do rotational (and other) transformations in an embedded application, requiring the sin() cos() and tan() functions.  I know you can use look-up tables, and that's the only solution I could find doing my own research, but is there a good fixed point trig library out there?

I'm thinking of using a cortex M3 for the application, so I want to stay away from floating point as much as possible to keep applications zippy.


texts: How can I use an ATX power supply for my own experiments?

texts:
I've been trying to turn on an ATX power supply I had lying around, and I plan to use it for some electronic experiments. Note: I don't want to have to open up the PSU for any reason.

I've tried connecting the green wire (PS-ON) and a black wire (ground), but nothing happens. The fan doesn't come on or anything. I heard something about a SENSE wire and other things. What should I do to make the power supply work?

OK, I got it to turn on now. Apparently it was on the entire time, but the fan in it is super quiet, so I didn't notice it. But still what of the SENSE wires and of minimum loads?


texts: SPI Troubleshooting, Teensy, Arduino, and tri-state

texts:
I'm trying to get my SPI bus devices up and running on a custom circuit board that I've soldered together.  Unfortunately, I neglected to add probe testing spots on this particular circuit board, and don't think I can directly test the SPI bus signals at the ICs.  One is a  20 pin LED Current Sinking Driver in a SSOP package and the other is a microSD card holder.

I can't seem to get either device to work.

My MCU is a Teensy 3.1.  (Arduino-compatible) In terms of firmware, I'm using Arduino v1.06 (highest version supported by Teensyduino), and Teensyduino V1.20. I'm using the SPI library/object for comms with the LED driver, and the SdFat library for comms with the sd card.

Here is the schematic of how my LED driver and SD card are hooked up:

According to the TLC59025 Datasheet, the timing diagram for communicating with the LED driver is as so:

My method of testing thus far, other than software (i.e. trying to open a file on the sd card), has been as follows:

Made sure that the 3.3 V LDO serving the SD card was outputting correct voltage
Attempted to begin serial comms with SD card using SdFat library (this was a no-go)
Measured voltage at various LED Driver out pins, before and after sending two 8-bit words to the LED Driver's MOSI pin and pulsing LE high

If the particular LED output pin is latched and sinking current, then the voltage I measure at that pin should be near 0 V, correct?

My Master SPI clock speed is around 2 MHz.  I know that the TLC59025 says it's operating point is 30 MHz.  I thought that as long as the Master is using a SCK that is lower than the slave's clock, the comms would work.  Am I wrong?

I thought that perhaps tri-state behaviour was to blame for my woes, however it looks like the TLC59025 LED Driver is designed to always be accepting data into it's shift register, even when it is not the intended slave being communicated with.  It looks to me as though it is designed to simply latch the last 16 bits of data sent over the SPI MOSI bus whenever the  LE pin is pulsed high.

I'm stumped as to how to proceed with troubleshooting.  I know that the problem shouldn't be due to the MISO bus, since I only have one device (the SD card) hooked up on that bus.
  Could it be the MOSI bus?  Is it possible that there is too much capacitance on the MOSI bus when I'm trying to communicate, thus degrading the data signal?  If I add a tri-state buffer to the MOSI/CS signals on the SD card, and a pullup resistor on the chip select signal of the sd card, would that help maintain signal integrity on the MOSI bus (ie cut down capacitance of MOSI bus to the point that at least the LED driver should work?).


texts: IR sensor not showing result on serial monitor

texts:
I am trying to display the value received by an IR sensor on the serial monitor.
The sensor blinks the led when I press a button but does not show anything on the serial monitor. I am using my own made AVR test bed based on the Arduino Uno

Sorry for the bad picture quality.

I am pressing the power button of my Sony rm-gd023 remote and the led blinks but nothing on the serial monitor. I have included the source code below.

#include <IRremote.h>

int RECV_PIN = 11;

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()
{
  Serial.begin(9600);
  irrecv.enableIRIn(); // Start the receiver
}

void loop() {
  if (irrecv.decode(&results)) {
    Serial.println(results.value, HEX);
    irrecv.resume(); // Receive the next value
  }
}

You should download the IR sensor library:
https://docs.google.com/folder/d/0B1Hqp8fKfwy4MTlNZzFJdzdoTTA/edit?usp=sharing


texts: polarity of unmarked battery with zero charge

texts:
This battery has the following equivalent part numbers HMA2104, HTPA7W, BKB191210/4, but I cannot find any information on the polarity/pinout of the 3 pins.

Is there some safe way to figure out the polarity of the battery? Maybe the IV characteristic for some small currents/voltages.


texts: wiring ac input to linear DC power supply

texts:
I have a vintage linear DC power supply. Terminals 1 and 2 are labeled just "AC input". Wanted to double check if there is a convention for which pin is hot, or if the polarity is irrelevant in this case.
Thanks


texts: How To Know If a Fuse Will Work Properly?

texts:
I want to know what kind of periodic test we use to test if a current-limiting fuse will normaly open and protect an electronic circuit (a battery charger) if a failure occur (short circuit or over current). Assume that I have a fuse that supports 5A of current and that if current is above this value it will damage the battery cells (venting). If the fuse, which is the last resort in my protection scheme, does not open (stuck) then my circuit will be damaged.

What is the periodic test we can use to be sure that the fuse can safely open in case of short circuit or the current is above the max value (5A in this example)?


texts:
I do not have an L293NE or SN754410 H-bridge chip, but I need to drive a motor in 2 directions using only a pin on a micro-controller to switch between them. I was originally driving the motor with a single NPN transistor, which gave me enough speed and torque for my project (it's a 4 wheel drive robot). However, it became clear that I would need both forward and backward movement. I drew up a simple circuit diagram using a PNP transistor to switch the flow of the motors, however, when I created the circuit, there was no movement when pulsing.

Here is the circuit diagram:

What exactly is wrong with my circuit here?
Why does it do nothing as opposed to maybe frying the board or working in someway?

Most importantly:
How can someone drive a dc motor in 2 directions with transistors? Will my way work or would you need to try something else to get it to move clockwise and counterclockwise?


texts: What would a polar plot or a Nyquist plot of an undamped second order system look like?

texts:
I'm relatively new to control systems.
I got to know how critically damped system looks like in Nyquist plot (same gain and phase cross over frequencies. PS. correct me if I'm wrong) and Bode plot thanks to the Octave online simulator, but I'm really curious to know what a Nyquist plot for a undamped system looks like if it exists. If it doesn't exist, why not?
I tried to plotting plots for
num = [1];
den = [1,0,5];
s = tf(num,den);
bode(s)  # exists
nyquist(s)  # throws error
polar(s) # throws error

PS. I know the system would be unstable, just curious.


texts: Reading signals in a car 9-14.5v and translating to arduino HIGH / LOW

texts:
I have a project that requires me to trigger certain events in an Arduino based on certain electronic devices in the car being switched on and off. I essentially need to read a 12v HIGH state in the car as a 5v high state via an Arduino, but as the cars voltage will fluctuate between 11 & 14.5 v and suffer from transient spikes, I would like to do this as simply and safely as possible.

Currently, my thoughts are a voltage divider with some form of transient spike protection (zener diode?), but I am open to better suggestions!

I need to read 3 separate 12v HIGH events (main beam on, lights on, indicators on) to effect changes in intensity on a set of high brightness DRLs.


texts: Amplification equation for AC coupled Common Emitter stages

texts:
Do anyone can tell me how to get amplification equation for this circuit of coupled common emitter amplifier?

simulate this circuit – Schematic created using CircuitLab

Edit 1

Equation for single transistor only with corresponding circuit.


texts: Plugging in monitor causes floating ground on computer enclosure resulting in shock hazard

texts:
Every connected metallic part of computer cabinet was giving shock. I diagnosed and found out that on switching monitor off stops the current leak and shocks. I fail to understand the reason for it since changing cables didn't worked. This may be a noob question but I am afraid this may damage my connected peripherals and graphic card.
Everything is connected to UPS and plugging monitor on other sockets also didn't worked.

Sorry for my naivness, any quick fixes for the time being? Quickly checked the earthing of building, its faulty so it may take some time to get the whole thing fixed, also power supplier tells they provide earthing from their side also. Tried connecting a short wire from cabinet to floor, didn't worked.


texts: How to determine the highest dominant pole?

texts:
Attached is a circuit comprising two MOSFETs. I am asked to estimate the low midband frequency pole \$f_L\$. It is stated -- "the highest dominant pole determines \$f_L\$. Each pole frequency is just \$1/(2 \pi C_i R_{eqi})\$, where \$R_{eqi}\$ is the equivalent resistance \$C_i\$ "sees" between its terminals while \$C_j(j \neq i)\$ are short circuited. Simply check for the dominant pole (smallest multiplication of \$C_i\$ and the corresponding \$R_{eqi}\$)."
I think the smallest product would be for \$C_s\$, with \$R_{eqi}=2k\Omega\$, which yields \$f_L=79.577Hz\$. Is that correct?


texts: Are circuits damaged by a constant 55°C environment?

texts:
I know that sun like temperatures kill electronics, but what about 55°C if it's constant?

I have a small commercial web camera that is officially rated 0°C to 70°C. It has no jelly capacitors. I intend to heat it to a very constant 55°C so that it's operating characteristics never fluctuate whatever the room temperate. Clearly the device doesn't explode at exactly 70°C, so there must be some form of curve around that threshold.

Can this adversely affect the camera? Is there some form of general life de-rating for all components, not just jelly capacitors?

Are devices damaged by high current, or high temperature? amd What exactly gets "worn out" and damaged by heat? exist but don't quite answer this one.


texts:
I have a 2 layer board that I am mounting directly to an aluminum housing. The circuit contains a temperature regulation circuit to monitor housing temperature by way of an NTC thermistor. As the resistance drops, power is reduced until steady state is reached.
Below is a pic of how I did it. The thermistor pad is connected to the ground plane with some vias. Hopefully the heat conducts from the housing, into the ground plane, and into the thermistor. Could this work? Does the thermistor body need to be mounted to the surface to work properly? Any idea how accurate this might be and is there a better way or standard practice?
I should note this is a little 0805 package thermistor and current is extremely low, it's just a sensing circuit not a power circuit.
Thank you


texts:
I'm building a light device with LEDs connected in series. One device could hold up to 200 LEDs in a strip of 1.5m.

I'm also supposed to take care about the good choice of a PWM frequency (using a microcontroller) to drive the LEDs (via LED driver) as if it's to low you may have flickering (show up easily with video cameras) but if it's to high I'm afraid of EMC so it cannot be certified for selling. Two questions arises then:

1) Who is the biggest problem here? Should I be concerned with EM wave generation somehow or just EMI via circuit?

2) Who should be the main EMI generator? The LED driver (switching), the LED itself, some other component or all together?

Thanks


texts:
I want to build a device using an Arduino or similar that would allow me to detect when particular objects were in a box (things like a TV remote for example).  My thought was that I could use rfid tags on the objects and then put a reader in a box to detect them.  Maybe line the walls of the box with metal or other radio wave inhibiting material to ensure items weren't sitting next to the box but were indeed in the box.

Been doing some research and 2 issues I'm trying to overcome:

1) Distance seems to be an issue with this approach using the rfid readers I have found so far at reasonable costs (lower freq). I would like the box to be at least a foot sq and most of the cheaper readers only read an inch or two.

2) Another issue appears to be that the inexpensive low frequency rfid  readers can only detect a single rfid and not multiple at once.  I want to be able to have multiple different objects in the box and be able to distinguish between them.

Wanted to get your opinion of any other ideas on how I could accomplish my project or if I'm on the right track help refine my thinking a bit.

Thanks,
Jason


texts:
Would introducing a magnetic amplifier to a wireless power transmission system made of two lc circuits increase efficiency?

Would the diode system shown on the website also increase efficiency?


texts: Shunt Current measurement isolation problem

texts: I am using shunt method to measure AC mains Current form circuit, attached image explain the systems. I am using a SMPS to isolated 120 VAC main form other control circuit. By i have some doubt, As i am measuring current using shunt, is i am breaking isolation somehow as per attached image.  Or Do i need op-amp with higher common mode voltage rating ( greater than 120 VAC)


texts:
I have a problem deriving a formula I will be using in my bachelor thesis. It's about eliminating interfering voltages during measurement.

To understand how the interfering voltage is going to be eliminated, I should explain the method of measurement first. So in this measurement we measured the voltage over a resistor induced by a current, where a transformer was used to push the current. Then we switched the current off and measured the voltage again. After that, we switched the poles on the transformer and thus shifted the phase 180°. Now the current is switched on again and we measure the voltage a third time.

We now have the voltage before switching poles (U_1), the voltage during the current-free pause (U_S) and the current after switching poles (U_2).

The voltage without the interfering voltage (U_M) is now given to

$$U_M = \sqrt{\frac{U_1^2 + U_2^2}{2}-U_S^2}$$

It's given in the german DIN EN 50522:2011-11 without further explanation and my brother and I are not able to derivate it from this wikipedia image. The article (german) is the only thing i found online and in all my literature, but even there is no explanation.

Thanks in advance.


texts: Protecting electronics against welding damage

texts:
Users who perform welding on machinery are not necessary diligent in taking precautions like disconnecting the battery from the vehicle.  Apparently, welding can cause severe damage to the electronics.

So:

What is the actual mechanism that causes the welding damage to the circuit?
How can an electronics designer prevent damage to their device which is mounted on the vehicle?
Is there a standard that this can be tested to?

EDIT: The question was referring to arc welding.


texts: Solving the differential equation in control system engineering

texts:
While I am continuing my studies of the Norman S. Nise book about Control System Engineering, and while trying to solve exercises of chapter 1, I noticed that I am out of the scope of solving differential equation. I forgot how to solve a differential equation and what the characteristic equation and how to obtain the variables values from initial conditions.

In one of the exercises, the author asked to solve the following equation:

(dx/dt) + 7x = 5cos2t

The solution started with:

(7C + 2D)cos(2t) + (-2C + 7D)sin(2t) = 5cos(2t)

Then:

7C + 2D = 5

-2C + 7D = 0

Which give: C=35/33 ; D=10/53

He gives the following characteristic equation: M + 7 = 0

And the final solution was:

My questions are:

  How the author solve the differential equation ? I didn't get his technique nor his method of solving.
  IS the following link is good enough to refresh my mind on how to solve differential equation ?
  Does control system engineers still solve differential equation by hand like this, or Matlab is always used to win some time ?


texts:
I have an Arduino DUE, that is based on an Atmel SAM3X8E ARM Cortex-M3 CPU. It has 54 Digital I/O. It works on 3.3V.

I'd like to use it to drive individually 50 LEDs (for instance 50 optocoupler to replace a keyboard).

I know that the total DC Output Current on all I/O lines is 130 mA. So I think I should use a transistor or something to drive such a big amount of LEDs.

I'm not an expert on electronics and I'd like to know which component to use (even I think a darlington transistor should be ok).

Till now I'm driving the infrared led with a BC547 but I think I should replace it… Some hint?


texts:
Can anyone identify this coax connector?  I think it might be an SMA female connector but I'm no expert.  It has threads on the outside and a hole inside.  The diameter (to the outside of the threads) is 5.25 mm.  The pink ruler in the first picture is in cm.  The yellow tape measure in the second picture is in inches.

The connector is on a shaker that I need to connect to an amplifier.  The cable that connects them is missing, so I'm going to get a custom one.  The other end of the cable will have a dual banana plug.  Is there a particular type of cable I should use in this application?

UPDATE: it's not SMA.  Or SMB, for that matter; I took it to a hardware store yesterday and tried both.  They didn't have any SSMA or SMC for me to try, though, so I suppose it could be one of those...


texts: Amplifier input impedance matching to source (low frequencies)

texts:
I'm curious as to what the benefits are of having an amplifier's input impedance exactly matched to that of the source?

For example, when measuring voltages, if the source impedance is between 500 Ohms and 10 kOhms (and varies over time) for a signal bandwidth of 100Hz-10kHz, is there any benefit to having the amplifier's input impedance matched exactly (or very close) to that of the source?

From my understanding, matching impedance exactly is only beneficial when working in the RF range (I may be wrong).


texts: Serial commands not being flushed from Raspberry to Arduino

texts:
I have an Arduino Mega controlling a matrix of 4x4 solenoids via the GPIOs opening/closing mosfet gates used as switches.
I'm trying to send commands via Serial from a Raspberry Pi 4 to the Arduino using the WiringPi C++ library, in order to control the solenoids.
Testing from the Arduino IDE, everything works fine: I read the command bytes from the Serial, and the solenoids respond quickly.
But when I run tests from the Raspberry, and use screen to follow the Serial output of the Arduino, I notice that most of the issued commands are skipped or delayed. I tried to flush the Serial at every loop I run on the Raspberry, hoping it would force the command to be sent, but nothing changes.
So my question is: is Serial communication the best way to handle such commands between the two devices? Or is there another protocol I should consider for real-time control?


texts: I would like to know exactly when we use P-mosfet and when we use N-mosfet? How to know that the circuit should use which type of mosfet? I'm confused as I'm drawing a converter circuit which involved mosfet. Any help is so appreciated.


texts: STM8 microcontroller burns when i plug in the ST-LINK (v1 or v2) programmer

texts:
I am working on a project/PCB that contains the STM8S003F3 microcontroller. Every time I do the following steps, the microcontroller gets burned. The steps are:

I program the STM8S003F3 by using the ST-LINK found in STM8S-DISCOVERY Board (this step i do without any external power supply and it works perfectly);
I unplug the programmer and connect the board to an external 28V power supply (hardware and firmware here are perfectly working);
There are some components that need 28V to run, and, for debbuging the firmware, I need the 28V power supply connected to the circuit;
When my board is connected to this 28V power supply, i plug in the programmer (for programming and debbuging);
In step 4, the STM8S003F3 stops working. Actually, if I measure the reset pin, it oscilattes at a frequency of about 10kHz.
From here, I can't program anymore. I have to exchange the microcontroller.

I thinking about some issues that can be the causes of this problem:

When I was doing this same procedure at my company, there was no problem at all. Now, I am at home and there is no grounding in the power plugs. On the other hand, there is grounding at my company. Is this the problem? Does my USB port have any to do with it?
There is a switching mode power supply (SMPP) on the project board. Maybe when I plug the programmer into it, the SMPP drives more current and burns the microcontroller? How I said before, none of this problems were going on at my company.


texts: How can you tell, remotely, if someone put their SIM card in a new phone?

texts:
On a recent television show, on ID Discovery, 'The Case that Haunts Me' (season 3 epi 4 'Cruel and Unusual') the lead detective finds out that the prime suspect has taken the SIM card out of his phone and put it in his murdered wife's phone...
I thought only the SIM card could be traced/tracked...
How could someone tell, without ever having seen (or seized) the phone(s), if SIM cards have been switched?


texts: What is function of the resistor in series with bypass capacitor in npn transistor amplifier?

texts:
I am new to electronics and recently I was learning about npn transistor as an amplifier. I tried to build one in ltspice XVII.

This is my circuit diagram:

but the output was not as expected as shown below:

But in a video on youtube, the person has a resistor in series with the bypass capacitor. When I tried to do the same the result was as shown below:

So I just want to know why this worked? Why it was not working without it? Usually, all the circuit diagrams on the internet don't have this resistor.

Sorry for my bad english. :P


texts: Hijack/observe RS485 communication data by wire tapping?

texts:
I have some Computer -> LED Matrix Screens system like this diagram:

         ---------------------------------------- RS485 (A / TxD- / RxD-)
COMP >      |       |      |      |        |
SERVER   ---------------------------------------  RS485 (B / TxD+ / RxD+)
          | |     | |    | |    | |      | |
          LED0    LED1   LED2   LEDn   Hijacker

Computer is sending data via the RS485 bus, LED matrix Screens (receivers) act to the RS485 command accordingly.

Now I would like to monitor/observe the raw data transmitting from computer server to my led screens through the wire. and record them into a file or something for debugging purposes.

How do I implement such a hijacker thing. Is it a computer? or oscilloscope? or other hardware? thanks in advance!


texts: What should be the cut-off voltage for charging lead acid batteries through PV panel?

texts:
My solar charge controller allows me to set a cut-off voltage, so that the battery charging is stopped when the battery reaches that voltage. The value I set will probably also be the maximum voltage at which the batteries are charged by the controller.

My battery says:

My question is... is it safe to set the cut-off to 14.40V in the charge controller? I am worried because, once the battery is full, the charger will continue to apply 14.40V which is greater than the popular floating charge voltage recommendation of 13.6V.

My usage of the battery is cyclic. It gets almost entirely discharged in the night, and is fully charged by 1PM the following day.


texts: dsPIC: Link assembler project with XC16 in command line mode

texts:
I have an assembler project that compiles and links fine with MPLABX. Now I am trying to build it from the command line. Attempt to use the command line from MPLABX fails.

When I am calling:

C:\MiscStuffs>"C:\Program Files (x86)\Microchip\xc16\v1.11\bin"\xc16-ld.exe -p30F3012 --defsym __ICD2RAM=1 --report-mem -o Test4.elf -Map Test4.map Test4.o

I get:

C:\MiscStuffs\Test4.o(.text+0x12): In function __reset':
: undefined reference to_PR2'
C:\MiscStuffs\Test4.o(.text+0x18): In function __reset':
: undefined reference to_IEC0'
C:\MiscStuffs\Test4.o(.text+0x1c): In function __reset':
: undefined reference toIC1CON'
....

And so on. When I remove -p30F3012, it starts complaining that Memory region auxflash does not exist. I tried putting wrong processor number. I get: Error: unknown processor 30F3712.  In other words, it understands what the current architecture is. But for some reason still cannot resolve addresses of the SFRs.

Should I specify any additional library? Is there any work around at all? If somebody managed to compile/link any assembler project with XC16, please, drop a line and the command line that you were using.


texts: How to protect P-MOSFET from excessive gate voltage

texts:
I would like to build a DIY solid state relay for my car to enable some circuits (less than 1A current absorption) only when the accessories are powered up (independently from engine on or off).

I have some spare IRF4905 P-MOSFET, some optocouplers, some TVS diodes 18V and various Zeners.

My idea was this one (I found no optocoupler in Circuitlab, I made it myself more or less). I omit from the schematic the diode protecting from inverse voltage.

simulate this circuit – Schematic created using CircuitLab

IRF4905 accepts at most Vgs=20V. In a car I could get short spikes higher than that. Hoe can I protect it using a 18V TVS diode or various Zener I have?

An idea could be to do this, since the IRF4905 requires only 4V of Vgs for complete turn-on.

simulate this circuit

Would that work? other ideas? Or should I really use a traditional mechanical relay?


texts:
Does anyone have / know of a list of all the LM integrated circuit packages available? The EE stockroom at my university recently reorganized and they cataloged several pages of part numbers without any descriptions of what they do. I was hoping to write a script to match them up. Also I need a part that I only know the description of, but am not sure if there is a LM part that does it so this is also for my personal interest.

I've checked out Texas Instrument's parametric search on their site, but it allows for everything except what I need. I was hoping to find something like Wikipedia's 7400 series list


texts:
I am currently trying to build a capacitive touch screen.  My end goal is to create a giant track pad/keyboard for my computer.  Since abnormally large touch screens are quite pricy I have set out to build my own.  Unfortunately it seems as though this has not been done before by regular electronics enthusiasts.

As far as the touch pad goes, I don't need more than one touch to be registered at any one time.

From what I understand, this can be accomplished by using a large conductive plate (I am currently using sheet metal) and four capacitive sensors in the four corners. A set voltage is applied to the plate through a large resistor.  The sensors in the corners continually measure the voltage of the plate.  When a user touches the screen, it will act as a capacitor and disrupt the voltage making it drop.  This will be read as a touch and can somehow be interpreted as x y values.

Designs for capacitive touch screens typically involve a "grid" of sensors that give x y values, but if I am not mistaken, this is only needed to register multiple touches.

So far, just for testing, I am using a small piece of sheet metal. I am using an Arduino Uno to report the raw voltage levels from either side of the metal. When it is not touched the sensors report a value between 1014 and 1023 (the Arduino has a 10 bit ADC).

When the plate is touched the values drop. These values, however, don't seem to be consistent enough for me to get any location information about the touch.

So my questions are:

Does my project seem like it can be done? Is there anything that could be changed about my project to make it better?  Would making a touch pad in this way be possible with reasonably accurate results?

How can I stabilize the readings so I can translate them into x y values and how do I convert them into x y values?

I tried to do research and I think I understand the basics of capacitive touch screens, but I could only find information giving a general description of the science of these devices.  I couldn't find anything that would give me enough detail to replicate the process.

Thanks for taking an interest in this question!


texts: concave conical lenses on 5050 SMD LEDs?

texts:
Is there any way to put plano-convex conical lenses, or something broadly equivalent, on 5050 SMD LEDs?

The lenses I'm talking about are the type commonly built into cheap christmas-tree lights:

As you can see in the second picture, these lenses distribute quite a lot of the light "horizontal" to the alignment of the LED, with fairly little light going normal to the LED. All other LED lenses I've seen, even those meant to diffuse the light as evenly as possible, have a "hot spot" centered directly above the LED.

The reason I'm asking is, I'm trying to build something not unlike what's depicted in this Youtube Video, which depicts an led-backlit art project. I want to make something similar, but much thinner, which means I need to diffuse the light from the LEDs much more evenly - or else, use a lot more LEDs, which isn't practical in my case.


texts: Method required to enable a toy "vehicle" to follow a "target" wirelessly?

texts:
I am trying to create a small robot toy car with the ability to follow a person around, with a range of about 50 m.

Ideally the person will be provided with a small transmitter of some kind, and the car will have a receiver which will allow it to determine the direction to the transmitter so that the car can follow the person holding it.

However,  I understand that systems such as infrared require line of sight to operate, while others like WiFi are too omnidirectional to pinpoint the transmitter direction.

Is there any recommended method or system that would meet my requirement?

Added:

Notes:

To elaborate, it is more for remote photo taking.
A person would hold a remote tag and trigger a command; after which the robot would seek out the person, and position itself in the same direction to take a shot.
Unfortunately GPS not not a solution as for this application is mostly for indoors. I understand RFID tags may work although i am not sure if it has sufficient directionality


texts: apple ipad / ipod lightning connector dock

texts:
I am developing a product that needs to plug a dock in to the lightning connector of current ipads and ipods.

The dock needs to simultaneously pass a charge to the device and monitor the activity status of that device, i.e., if it is in sleep or active mode.

Do you think this is possible?  And if so, could it then have the ability to dictate the mode to "force" the device into active or sleep / lock mode?


texts: How to make a self-recognition socket for diferent connectors (sensors)

texts:
I am working on an electronic device, to which will be a lot of sensors on wires connected to a panel with sockets. Is there any option that will recognise which sensor is connected to a which socket? On the device-box will be a lot of same sockets.

I never made something like this, but I think, that it will be possible with resistivity between some wires and the computer recognise trough this which sensor is it. I will have also Arduino as a slave, so i will be able to use analog inputs/outputs.

May there is an option where three wire sensor is connected to a more pins connector and some pins will be connected together and some logic behind the socket panel recognize what is connected.

Sensors are all digital some of them are using 1-Wire (DS18B20) and some I2C (BH1750)

Datasheets

DHT22.
DS18B20 (1-wire).
MH-Z19.
BH1750 (I2C).

simulate this circuit – Schematic created using CircuitLab


texts:
I have designed a buffer amplifier using an LM358 op-amp, with an input of a 1kHz sine wave and a power supply of +/-6V. whenever I increase the input sine amplitude above a certain threshold, I get a weird output (unlike the normal saturation that we all expect such as the one in Figure 1).

Figure 1 (Above). Normal saturation.

Figure 2 (Above). Weird unexpected saturation.

Why is the saturation in Figure 2 like that? I am used to Figure 1's output but not Figure 2. I guess it's linked to the -+ 6 Volt supply, but I'm really lost.

I've tried looking online for similar waveforms, but I found nothing.


texts:
I'm building a dual rail tracking power supply, for the negative supply because the current is not going to exceed ~200 mA I decided to use LM337 both for simplicity and stability of the circuit (so I thought!).
I have two problems with below circuit:

The output is oscillating and is unstable, with C1 and C2 I managed to make it stable but then again it goes unstable under load.

How can I make the output stable with load or no load?

On the breadboard when I short the ADJ pin (which also shorts the output of integrator) to simulate Q1 activating and current limiting mode, the current draw is tens of mA depending on R4 value (increasing R4 to higher values causes the circuit to go out of regulation). while ADJ pin current is in uA region according to the datasheet.

That amount of current draw in this circuit is unacceptable, how can I reduce ADJ pin/op-amp output current draw to 1 mA or less when the circuit goes to current limiting mode?

simulate this circuit – Schematic created using CircuitLab
I'm just a hobbyist, I'd appreciate it if your answer be simple and understandable for me, thank you.


texts: Purpose of breadboard "studs" on base off micro breadboards?

texts: I recently bought some micro breadboards on Ebay.  Extremely useful little things.  However each have two awkward studs on their bases.  See the attached photo.   What I'm curious about is their purpose?  What might these "plugin" to or be used for?  I think I'm going to file them off.


texts:
I am trying to wire a DH48-S timer to operate a three phase pump.  I have a remote controller/relay for the pump which is located about 1 km from my house.  The remote controller can be configured to close the relay either momentarily or to open and close the relay (in two separate clicks).  It is represented by the momentary switch S1 in the attached circuit.  The load is the coil of a three phase contactor which activates the pump.
The timer, depicted below as a simple relay, does not act in a predictable fashion when connected as shown.  The timer turns on and starts counting when I close SW1, but turns off when I open it. It is as though the switch in the timer does not operate when connected in this manner.  If I leave SW1 closed until the time cycle finishes, the timer stays on and the load stays connected, ie it seems that the time switch activates at the end of the 'on' cycle. Note that with the power connected directly across Pin2 and Pin7, the timer relay functions perfectly.
I have tried connecting Pin2 to the NC contact (Pin5) instead of the NO (Pin6) but this causes the timer to repeatedly count to the set point, then reset and count again.
I could connect the remote in the supply line and have power going straight to the coil of the timer.  However this would mean that I would need to have the remote configured as an on/off switch and would need normally to press it twice to reset (first time to disconnect the timer, and the second time to reconnect it).  By wiring it as shown, I only ever need to switch it once, and do not need to worry about an external power failure triggering the pump on power reconnection.
I could wire it via a separate relay, and that is probably what I will end up doing.
However can anyone please explain this anomalous behaviour of the timer when connected in this manner. Is there any way around this without using a separate relay?

simulate this circuit – Schematic created using CircuitLab


texts: Implementation of boolean function using multiplexer

texts:
Is the following question correct?
Consider the Boolean expression F(A,B,C) = ABC+ AB+ AC.
Implement this logic expression using one 4x1 multiplexer. Do not use C as an input to the selectors of the multiplexer.

Also,Can someone give me a hint or push me in the right direction,as i was thinking of using the above method? Thanks in advance


texts: Relation between thermal conductivity factor(k) and temperature coefficient of resistance(α)

texts:
I'm trying to understand the thermal parameters affecting circuit design. I came across two different parameters.

thermal conductivity factor(k) which is related to thermal impedance. The link to the article i came across is here

http://focus.ti.com/download/trng/docs/seminar/Topic%2010%20-%20Thermal%20Design%20Consideration%20for%20Surface%20Mount%20Layouts%20.pdf?DCMP=mdrvblog&HQS=gma-indu-motr-mdrvblog-150422-thermal-mc-en

temperature coefficient of resistance which is generally specified in datasheets of electronic components.

I'm trying to make sense out of these two quantities. Are they related in some way?
Please help


texts: Piezo vibration sensor board negative values

texts:
I have this piezo vibration sensor module from Grove: http://www.seeedstudio.com/wiki/Grove_-_Piezo_Vibration_Sensor

Using this sensor and an arduino device I want to measure two things:

amplitude (negative and positive)
vibration frequency

Is it possible to measure the negative amplitude with this board? The analog input of an arduino board use a 10bit ADC. So we have 1024 values available. Is it possible to use the value 0-511 for negative measurement and 512-1023 for positive? Normally I would use a voltage devider to set an offset to the negative sensor values. But in this case I don't know how the board is handling negativ sensor values.

Here is the board circuit:

For frequency measurement I want use the amplitude values and do a FFT.

is there any chance to get the negative values?


texts:
There is an extra plastic or wrapper piece at the end of the electrical cables. I asked one of my friends about it and he said its for insulation purposes but he does not know the technical name of it.
Can anyone kindly help me with what the technical name of this is?
See the photo to be more clear


texts:
I am asked to find when Z is gonna be high and which combination of ABCD does it. Book says it's 0100, 0010, 1001 and 1010. What I don't get about MUX is, for example, will 0001 will make Z be equal to I0? Will 0010 make Z be equal to I2?

I appreciate any... inputs. Ba-dum-tss!

Book is Tocci, 12th ed, btw.


texts: Why the voltage across emitter resistor comes out to be Zero while doing the ac analysis of a differential amplifier

texts:
As I am trying to understand the half-circuit method of doing the ac analysis of a differential amplifier by going through the derivation available online, I've found that the voltage across the emitter resistor is zero and depending on this fact, the difference mode gain of the differential amplifier is found out.
Now my question is that why the voltage across emitter resistor of differential amplifier comes out to be zero and I am not able to find any proper explanation or derivation anywhere. Please help me with the Half-circuit derivation process of the differential amplifier ac analysis.


texts: Why does this AC axial cooling fan have 3 wires?

texts:
I'm restoring a 1970s HP Frequency Counter and went to replace the 110V AC tube axial cooling fan on the unit to discover that it has 3 wires. The original fan is a ROTRON 1 PH CAP 0.25MFD fan.

I'm a little baffled by the wiring in the unit which I've shown below.

Why is there both a red lead and green lead from the capacitor to the fan?

And, I can detect continuity between yellow and red - is that likely because of the winding?

My replacement axial fan has only two leads, so I'm unsure where to connect it.

Figure 1. Cooling Fan Circuit

Figure 2. Existing Wiring of Cooling Fan

Figure 3. Existing Tube Axial Fan


texts: How does this Current Comparator Circuit Work?

texts:
I have a quick couple of questions about this circuit:

The schottky diodes are obviously for minimizing slew delay but how exactly do they do this?
If the non inverting input is tied to ground and both the input and reference are connected to the inverting input, how is the current threshold implemented?
Going off of the last question: How is it able to measure and compare the current to a threshold?


texts: What is this resistor strip on my helicopter circuit?

texts:
RM: Smaller photo substituted - larger slower loading one here if desired:
  http://i.stack.imgur.com/RPM8l.jpg

I am building a helicopter and would like to use a linear servo like the one on the right in this picture. The exact same servo has been removed from the left side, revealing two strips, one bare copper and the other one black with variable resistive properties. The black one is connected to positive voltage on top, ground on the bottom.

The back side of the slider on the servo is touching these two strips, causing a variable voltage input on the microcontroller on board. I need to get me one of those black strips, and having searched for membrane resistor/potentiometer, I can not find anything that will suit my circuit. It is supposed to be about 20mm long, and the only thing I can find that actually looks like something I need is this one from SparkFun but that is obviosly to large.

All help on the mather is greately appreciated


texts: UL listing for USB device with battery, detachable cord and transformer

texts:
I want to import a device (for resale) that comprises the following components:

Wall transformer (already UL listed),
USB wire,
LED light assembly,
rechargeable battery (already listed).

The question is this: do I need to get a system certification (from CSA or UL) for the entire device or can I use the existing UL mark for the component that plugs into the mains (the transformer)?

I am getting contradictory information. Some are saying that only the transformer needs the UL listing while others say that the entire system needs the mark (dramatically increasing the cost, especially considering the required quarterly audits etc).

In case this matters, the battery is NOT removable and carries its own mark.


texts:
I'm making my own laser tag and I was checking out existing open source solutions.

The MilesTag protocol uses 600us as the basic pulse length. This however limits the maximum rounds per minute to under 2000 RPM while miniguns reach 6000 RPM (100 rounds per second). Are there any reasons I'm not aware of for the 600us pulse?

Will my own solution be less reliable if I go with, say, 300us pulses? Any lower won't work with the IR reciever I'm working with, because it needs at least 10 cycles in a burst with a 40kHz modulation frequency, but a 300us pulse would let me double my RPM.


texts: Sending resistance values over bluetooth

texts:
I am diving into the deep here, as I am only familiar with audio electronics (guitar related). I thought of an educational project for myself to learn. It should be a miniature solution for the following (basic) problem:

I want to read out the resistance of several potentiometers and send this value to my phone. The total size should be around 2 x 2 x 1 cm excluding battery.

I think I will need the following:

Bluetooth module 4.0
Microcontroller to read out the potentiometer
Battery (coin?)

Upon researching I was overwhelmed with the various chips available. When I thought I found a solution, it turned out it was obsolete and rather power hungry.
So I am turning to this great community. Can anyone give me a pointer where to start looking? The cheaper and smaller the better. Programming a microcontroller is OK with me, can probably look that up somewhere as part of the learning process!

Thanks a lot!


texts:
I have build a little circuit that play an audio file each time a switch is released.
I used a voice board based on an ISD1820
and an amplifier based on LM386.

Everything works fine with a couple of aaa batteries for the amplifier and a button cell battery for the voice board.
Since i want to put this inside a box i'm trying to use only the aaa batteries; but if i connect the two boards to the batteries no sound is played. I can only heard a click sound on the speaker each time the key is released.

Unfortunately i can't find specific datasheet for the boards so i can't figure how to solve this. I hope someone can give me an hint.


texts:
I know the summation equation for two or more resistors in parallel or series, and I know two parallel resistors will give more power.

But sometimes I saw some circuits that used two resistors in series, and I am wondering why that method was used and why they didn't use one resistor with a higher value (equal to total series resistors)?

Such as the following circuit diagram, two 33 kΩ resistors used in series. So why doesn't it use one 68K resistor?

Give it better results? I mean, noise filtering or something else?

Note: This circuit is an AC dimmer for a microcontroller.


texts:
I started studying flip-flops recently and I am stuck at this point:
At some video tutorials, people explain the SR flip-flop like this:

So they use NAND gates, producing a transition table like this:
|     t     | t+1
|  S  |  R  |  Q
|  0  |  0  |  INVALID
|  0  |  1  |  1
|  1  |  0  |  0
|  1  |  1  |  ?

However, some other people explain the SR flip-flop using NOR gates:

(source: startingelectronics.com)
which has a different transition table.
Are both correct? Why do both exist?


texts: Live switching AC loads with TRIACs or SSR

texts: I have been designing a system whose purpose is to provide high reliability to a set of outlets (8), it takes to inputs of diffrent phases mains current, now the purpose of the system is that if the input we currently are using dies (Goes permanently to 0v) we would switch to the second one without or with minimal power loss to the outlets (enough to maintain the device running), now electrical engineering is not my area of expertise (at least at this level) and i cant figure out how to do this, i have tought about using a TRIAC with a zero-cross circuit but i can't know how the outputs will be affected and if it will serve the purpose, could anyone give me an idea about if im going about this the right way or if there is a better way to do this.


texts: Improve RF range with a boost converter?

texts:
This might be a stupid idea, but I will try anyways:

I have a RF 433MHz TX module (datasheet) which can be supplied with 1.5V...12V. My understanding is the range increases with higher voltage as the module can draw more power.

My power supply is a 5V 10W wall adapter. Suppose I cannot simply change that to a 12V adapter.

If I increase the voltage from 5V to 12V using a boost converter, or a charge pump, would that have the same effect as having a 12V supply in the first place? Can the RF TX really draw more power through a boost converter?


texts: Can diodes be used as an OR gate when I use RTL for other gates?

texts:
I have been using RTL (Resistor-Transistor Logic) to build things like NOT gates, or any other types of logic. If diodes control the flow by letting electricity only flow one way, then could I use two diodes to make an OR gate, or would it interfere or disagree with my RTL?

It would be, in my mind, the two inputs have a diode each, and then the output of both is just connected on the breadboard.


texts: Does the type of preamplifier used for a piezoelectric sensor change its physical resonant frequency?

texts:
Two common amplifier circuits used for piezoelectric sensors are voltage amplifiers and charge amplifiers (pictured respectively).

With the charge amplifier, the sensor is shorted but this is not the case with a voltage amplifier. Does this effect the physical properties of the sensor?


texts: How to null op-amp offset in current source?

texts:
I have a current source circuit with an op amp and pass transistor.  The simplified schematic is this:

simulate this circuit – Schematic created using CircuitLab

I would like the output to be adjustable over a pretty wide dynamic range, let's say 4-6 decades (amperes to microamperes), and most importantly I'd like the output to be a true zero if the input is zero.

The problem is the offset voltage of the opamp which introduces an offset to the output current.  The opamps with the right speed for what I'm looking for have offsets of 100-500uV.  This is not much of a problem when the current is 1A (and the voltage across the sense resistor is 1V), but becomes a pretty big problem when the current is 1mA and the sense voltage is 1mV.

The other problem is saturation.  If the offset happens to be positive, when the input is zero, the opamp would try to drive to a negative sense voltage and its output would hit the negative rail.  When the input goes positive (eg at the beginning of a short current pulse) the op amp would take time to get out of saturation, and then to slew from the negative rail to a high enough positive voltage to turn the MOSFET on.  This results in a delayed and slower rise time at the beginning of current pulses in some of the breadboard versions of this I have built.

I could try to null the opamp offset either using the null pins or slightly offsetting the input.  I think drift over temperature and time would make it so this would need pretty frequent adjustments.

I could also add an extra switch on the high side to get a true zero, but that doesn't solve the dynamic range problem (at best I'd have 4 decades of dynamic range, and more likely only 3) and also the saturation problem.

Span errors or deviations from linearity don't matter as much, but zero shift errors are really bad for my use case.

Is there some way to avoid the offset issue in a circuit like this, and have a current source which is essentially exactly proportional over a very wide dynamic range?  Is there some way to use a current feedback amplifier instead of voltage feedback?

(Example component choices: THS4541 opamp, BSS816 mosfet.  R_load is not actually a resistor, it has a nonlinear I-V curve)


texts:
I am using STM32F303VCT6 microcontroller for my application. My question is: Are there any libraries for the GLCD NT75451 which may help me display geometric shapes on the screen?

FYI : LCD interface is parallel with micro-controller.


texts:
I'm trying to get a better understanding of the node method for circuit analysis. I understand the process, but I'm trying to verify that each step in the method is consistent with my overall understanding of what is going on in the circuit physically. I realize that the node method is a way that we can approach circuit analysis abstractly, but I feel uncomfortable using it without understanding the physics behind it.
I'm mainly confused about the voltages (potential differences) throughout the circuit. I understand that the electric field is a conservative vector field so the total potential difference of a closed loop circuit is 0, the potential difference between any two points in the electric field does not depend on the path taken, etc. I'm confused about why the potential difference is constant through ideal wires.
For example:

I understand that the potential difference from H to A is 12 volts since its given and I can see that that the electric field does positive work when pushing a positive charge from H to A assuming that the H side of the voltage source is the low potential (-) and the A is the high potential (+), so it makes sense that the voltage they gave across the voltage source is positive. I don't understand why the potential difference across AB is 0 i.e. the potential at A = potential at B. I thought that since electric potential =  \$ \int_{r_A}^{r_B} \vec{E} \cdot d \vec{r} \$ where \$ r_A \$ and \$ r_B \$ are the magnitudes of the position vectors pointing towards A and B respectively from the origin which I'll let be point H and since \$|\vec{r_A}| - |\vec{r_B}|\$  is not equal to zero then \$ \int_{r_A}^{r_B} \vec{E} \cdot d \vec{r} \$ is not equal to zero. I understand that the total potential difference of the circuit is 0 since \$ \Delta \vec{r}_{total} = \vec{r_H} - \vec{r_H} = \vec{0} \$. I just assumed that the potential difference is different at every point and since some potential differences across certain segments of the circuit are negative i.e. when charges are moving with the field (instead of against it), we can still have it that the total potential difference is 0.
I realize that the path from A to B is an ideal wire with no resistance and I understand that ohms law supports that the voltage (potential difference) is 0 from A to B since \$ V = IR = I(0) = 0 \$ which is why every example shows the potential at A is equal to the potential at B , but wouldn't that go against the definition of potential difference?


texts: Why Does the Input Voltage Drop When a Linear Regulator is Added as Load

texts:
Why does adding a linear regulator to this circuit cause the input voltage (V_c) to drop?

The 9V input coming in is regulated. The voltage measured at the branch between D5 and R22 is ~8.7 V, so it should not be voltage sag due to the load of the regulator.
If I remove REG1 from the circuit, V_c reads ~8.7 V.
With REG1 present, V_c reads ~6.7 V. The drop in voltage is across R22.

The only other place in the circuit where V_c is used directly is to power a 2N7000 MOSFET used as an input buffer.

My best guess is that REG1 is somehow creating a voltage divider with R22, but I did not think this could happen. I don't believe my PCB has any shorts.

Note: I'm actually using a 78L05 regulator. I've tried two different ones (this and this).
The full circuit diagram can be found here (on page 4).

Thanks.


texts: Reversing Polarity on Switch Mode PSU to use on Audio Equipment

texts:
I have a normal 12v 1amp switch mode psu. with positive pin, negative sleeve. I want to use it on a Roland ex3 s keyboard, which I got as a gift, but no power supply.  The PSU specs match those of the Roland according to the manual.
Is it save to change the polarity of the PSU, and use it?
Do you get specially adapted switch mode psu with negative pin positive sleeve?
Much Appreciated
Johann


texts:
Is it safe to touch the ground pin when using this adapter?

Edit: just to clarify, it's from a 60w laptop power brick.


texts: Voltage across a resistor in RC discharging circuit?

texts:
Problem: An RC circuit has a time constant of 68 micro-seconds. The capacitor is charged to 14 V. How much is the voltage across a resistor after 136 micro-seconds of discharge?

Attempt: What I know is that the time the capacitor fully discharge is at 5 Time constant. Then the formulas involved are: Time Constant = R*C and Voltage at the capacitor (Vc) = Vm (e^-t/time constant) but no resistor value were given so:

Time Constant = R*C ; R = (68 x 10^-6) / 14 = 4.86 micro-Ohms. I assumed that Vc = Vm at this time constant. And now I don't know what to do next. I think we have to get the Vc after 136 micro seconds then subtract it from the total voltage.

Question: How to answer this kind of problems? By the way, the correct answer is 1.96 V from the key to correction. Any help would be appreciated.


texts:
I've been wanting try out new microcontrollers and microprocessors other than the very mainstream Arduino and similar. So I want to start by making a inexpensive test board with a minimal test of peripherals - just to see that I can get it working. Can most devices run with just a JTAG connection? Would this be ideal to begin learning a new device?

I've seen a lot development boards on the market, but they're expensive and cluttered with circuits. I'd really rather just start simple so I can understand everything that's going on.

If it makes a differences, I'm interested in testing TI ARM products.


texts: Bluetooth module EGBT-046S vs EGBT-045MS

texts:
I picked up a few of these bluetooth modules recently and was trying to figure out a few things.

Aside from the ability to go into master mode,are there any other differences between the EGBT-046S and EGBT-045MS? I see the 045MS has programmable IO and I was kinda hoping that the 046S might have that as it would save me from needing a micro controller for my project (very simple IO going on).

Is the difference between the two really a firmware issue not a device parts/layout?

I found some dual manual containing information for both,but wasn't sure how to be able to tell which version of the device I had as well. I think I have the 46S, however Looking at the actual pins on the device, there are connections on the pins that the 45MS has.

Module(s) Manual


texts:
What is an accurate manner to calculate the rotational speed of a bldc motor using hall sensors and microcontroller units, considering both floating point operations and length of the observed period (between rising and falling of the same sensor and then 180°, between two rising sensors and then 120°, or 1 electrical cycle and then 360°) ?
I have found this application from microchip where a constant MINPERIOD and the time between two transitions of the same hall are used. Is it a good way? I am doubtful that without averaging with the other sensors the measurement is not really accurate or that maybe the measured period is too short, but I do not have experience with that.


texts:
I am making a project which works on 3.3v. Here I am also using 6 digits 7-segment display so I need large current with 3.3V input.

I am using 6v of a battery which it needs to regulate and generate 3.3v.
I have ld1117v33 and its max input voltage range is 15v. I also got some information about to give Vr = 1.25v.

Here I am confused how can I give Vr at which pin of ld1117v33.
Please help me an understanding of Vr here and how it is different from Vin.
Do I need to give separate voltage to Vr?

Datasheet


texts:
I'm not quite sure what to do with this LED, it's got a forward voltage rating of 5-9V, so I've got a lot of wiggle room and I'm not sure of the ideal (or even if there is an ideal) voltage at which to drive it. Here is the datasheet info. Perhaps someone can tell me how they think I should drive it. I know I'll be using two lithium cells in series, so because of the broad range in this LED's VF I can either drive it directly until the 6V cutoff, or regulate it with a buck to a a certain voltage. Thanks a heap]1]2
[]3


texts: MATLAB:Reducing Transfer Functions using: Append&Connect technique VS Feedback,cloop,series&parallel command technique

texts:
The problem here was when I tried to counter check my answer using algebra and the two techniques above I got three different outputs all together..

The code:

G1=tf([0 1],[1 10]);

G2=tf([0 1],[1 1]);

G3=tf([1 0 1],[1 4 4]);

G4=tf([1 1],[1 6]);

H1=tf([1 1],[1 2]);

H2=tf([0 2],[0 1]);

H3=tf([0 1],[0 1]);

k=tf([2 12],[1 1]);      % H2/G4 - I moved G4 before H2

feedback((series((feedback((series((feedback((series(G3,G4)),H1,+1)),G2)),k,-1)),G1)),H3,-1)

%me checking for errors

syms s;

g1=1/(s+10);

g2=1/(s+1);

g3=((s^2)+1)/((s^2)+4*s+4);

g4=(s+1)/(s+6);

h1=(s+1)/(s+2);

h2=2;

h3=1;

simplify(g3*g4)

series(G3,G4)

simplify((g3*g4)/(1-(g3*g4*h1)))   % so far so good

feedback((series(G3,G4)),H1,+1)

simplify((g2*g3*g4)/(1-(g3*g4*h1)))

series((feedback((series(G3,G4)),H1,+1)),G2) %and here's where it fell apart

%me trying another approach

G1=tf([0 1],[1 10]);

G2=tf([0 1],[1 1]);

G3=tf([1 0 1],[1 4 4]);

G4=tf([1 1],[1 6]);

H1=tf([1 1],[1 2]);

H2=tf([0 2],[0 1]);

H3=tf([0 1],[0 1]);

R=tf([0 1],[0 1]);

t1=append(G1,G2,G3,G4,H1,H2,H3,R);

q=[1 8 -7;2 1 -6;3 2 5;4 3 0 ;5 4 0 ;6 3 0 ;7 4 0;];

input= 8;

output=4;

ts=connect(t1,q,input,output);

tf(ts)  % It gave a whole new different answer

can anyone help point me where I went wrong, any help is welcomed


texts: Series first Vs Shunt First Filter Design

texts:
Im reading Practical Electronics for Inventors by Paul Scherz and Simon Monk and it says that when designing a LPF Butterworth (passive), when the output impedance seen by the filter is greater than the input impedance, it is best to use a T-configuration (series first) filter.

Why is this? What advantages does the T series first configuration have in this scenario?


texts: How to connect to unusually spaced PCB edge?

texts:
I have a TI-84 keypad for the TI-Nspire calculator and I thought it might be interesting to use it in a project as a button matrix. The connector looks like this:

Unfortunately the edge connector has a weird pin spacing - it's a little less than 1.4mm. I can't find any suitable connectors on DigiKey, Mouser, or anywhere else.

How can I connect to this board? I could of course just solder wires to each pin but I would like to avoid that if possible.


texts: Can an IGBT overcurrent damage the driver?

texts:
We are using an hex IGBT module (datasheet: http://www.microsemi.com/document-portal/doc_view/7751-aptgt150ta60pg-rev2-pdf) which is driven by two separate IGBT drivers, the 2SC0108T2D0-07 (datasheet http://www.igbt.cn/UserFiles/CONCEPT/2SC0108T2Dx_Manual.pdf), using two channels on one, one channel on the other module to drive the "bottom" three IGBTs in the module as a DC-DC converter.

During some testing, we had set the current limit too high for the module, and something stopped working. During the de-bug stages, we took the unit apart and discovered that the drivers both had faults. After replacing both drivers, the faults went away, and we could run the circuit to check the IGBTs themselves.

By putting a voltage across each IGBT in turn, we checked that there was no current flowing when the IGBT was stopped, and then that current was flowing when the IGBT was activated again. By this method it looks like all the IGBTs are fully working.

The question is then: how did an over current event knock out both of the IGBT drivers, yet not damage the IGBTs themselves?


texts: Interfacing with SATA in embedded systems

texts:
Would it be possible to use a SATA interface in an embedded system, for example a MP3 player or a video camera? (speed not critical)

What is the typical way to do this? On chip peripherals, external ICs etc... What are important things to consider when implementing such intefaces?


texts: Does putting a car remote on your chin make it more effective?

texts:
Recently asked on Physics.SE:

Why does a remote car key work when held to your head/body?

And also, similar claims abound.

RF engineers know that putting a big conductive thing like a human head near an antenna is going to significantly alter the radiated fields. The argument goes that putting the remote under your chin (or sometimes on your forehead, and sometimes with mouth partially open) not only arbitrarily alters, but improves the remote's effectiveness.

The "experiments" confirming this argument are typically something like this:

  I tried unlocking my car, but it didn't work. Then, I put the remote under my chin, and it worked! Therefore, remote-under-chin is more effective.

This is a textbook case of selection bias. No one ever tries unlocking their car with the remote under their chin, and when that doesn't work, tries unlocking it normally.

Let's skip the speculation and discussion about how it might work. Can someone with access to some proper RF test equipment perform a well-designed test of a car remote's characteristics with and without human-head-in-proximity? Or, can someone cite similar studies already performed by qualified RF engineers?


texts: Reason for two ground planes in PCB for Voltage regulator

texts:
I am trying to expand a PCB I created in the past with EAGLE to add a voltage regulator (LMZ31503). However, in the voltage regulator's schematics provided by the manufacturer, two different ground planes are used, one denoted by the parallel lines sign (PGND) and the other one by the big arrow (AGND). These are eventually connected. What is the reason for these two planes, what would it change if I used a single GROUND plane for both of them?
Thank you for your help!


texts:
I built my first ZVS driver a while ago and had some fun making big arcs before I blew up the mosfets trying to make some alterations for induction heating. When it comes to this stuff I dont know exactly whats going on, but I know how to put it together well enough from a diagram.
So, I'm going to build another ZVS driver and I'm wondering, if I get IGBT's rated at 900V and about 30A, increase the capacitance, the inductance of the choke, and the number of turns on the primary would I be able to rectify 120VAC to about 170VDC (with smoothing caps) and run it all with no transformer?
I know IGBT's need lower frequencies, so I figure upping the capacitance and number of turns on the primary will lower the frequency and I'm hoping that more inductance in the choke will limit the current input at 170VDC.
Everything i see on line says the voltage in the tank circuit is about 3-4 times the supply so i figure 900V for the IGBT should do it. Im just not sure about the current. would 20-30A be enough? I cant draw more than 15 with out tripping the breaker.

Am I on the right page here? I just dont want to order all this stuff and blow it up as soon as I turn it on.

(I have a transformer that can put out 48V and the shorted secondary current is 10A, but with my first ZVS it would not draw more than about 2 amps. Not until i made the alterations and then it was pulling about 8A and it made some funny sounds and POP! there got the mosfets)

Thanks for the help!


texts: High speed memory interface between 2 FPGAs (Virtex 6)

texts:
I have a board with 2 Virtex 6 FPGAs, which are connected to each other through 64 parallel IO lines that can operate up to 400 MHz. One FPGA, let's call it B, also has 2 GB of DDR3 memory connected to it. I also need high speed access to this memory on FPGA A (which doesn't have any DDR3 connected to it). Eventually, the plan is to cache stuff in BRAM on FPGA B and transfer it over to FPGA A.

So, I'm trying to design a high speed interface between the two FPGAs to do just this, but I don't know where to start. I am thinking of FIFOs to buffer the address and data request.

Do you know of any interfaces/protocols that would fit my application? If you can direct me to any papers, that would be great as well.


texts:
Signals can be classified as even, odd, or a neither - in which case they can be broken up into their even and odd components. Theoretically its all very nice to be able to say that yes that function is symmetric about the origin, but practically is this ever actually achievable?

My confusion basically is how can a practical signal exist before t = 0 or x[0] and thus allow for classification? In my naive thinking it would seem that you can never have a purely even or odd signal in practice.

EDIT: To clarify, this is about an INPUT


texts: What is the resistance of a land line telephone

texts: can some one tell me what size resistor would i need to place across a telephone line in order to hold the line open at 6 volts off hook voltage? On hook there is 48 volts, off hook drops down to about 6 volts, i am replacing a standard telephone with a load resistor for a project I am building. Thanks


texts:
I want to use I2C Communication between two stm8s208cb MCUs. I use stm8s standard peripharel library. My code:

Master:

#include "stm8s.h"
#define I2C_SPEED 300000
#define OWN_ADDRESS    0xA0
#define SLAVE_ADDRESS    0x30
void delay_delay(unsigned int mul);
void main()
{
 CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV1);
 I2C_DeInit();
 I2C_Init(I2C_SPEED, 0xA0, I2C_DUTYCYCLE_2, I2C_ACK_CURR, I2C_ADDMODE_7BIT, 16);

while (1)
{
I2C_GenerateSTART(ENABLE);
I2C_Send7bitAddress(SLAVE_ADDRESS, I2C_DIRECTION_TX);
I2C_SendData(0x61);
I2C_GenerateSTOP(ENABLE);
delay_delay(500);
}
}

void delay_delay(unsigned int mul)
{
   for(; mul>0; mul--);
}

#ifdef  USE_FULL_ASSERT
void assert_failed(uint8_t* file, uint32_t line)
{
  while (1)
  {}
}
#endif

/*******************************************************************/
Slave:

#include "stm8s.h"
#include "stm8s_uart3.h"
#include "stdio.h"
#include "stm8s_i2c.h"

#define I2C_SPEED 300000
#define OWN_ADDRESS    0xA0
#define SLAVE_ADDRESS    0x30

void delay_delay(unsigned int mul);

void sendstring(char *s)
{
  while(*s){
    UART3->DR = (u8) (*s);
    while ((UART3->SR & (u8) UART3_FLAG_TXE) == RESET);
    s++;
  }
}

void main(void)
{
CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV1);

UART3_DeInit();
UART3_Init((uint32_t)9600, UART3_WORDLENGTH_8D, UART3_STOPBITS_1, UART3_PARITY_NO, UART3_MODE_TXRX_ENABLE);

I2C_DeInit();
I2C_Init(300000, 0x30, I2C_DUTYCYCLE_2, I2C_ACK_CURR, I2C_ADDMODE_7BIT, 16);

char veri_bas[1];

while (1)
{

I2C_AcknowledgeConfig(DISABLE);
uint8_t data = I2C_ReceiveData(); //-datayy oku
I2C_AcknowledgeConfig(ENABLE);
sprintf(veri_bas ,"%i" ,data);
sendstring(veri_bas);
delay_delay(500);
}
}

void delay_delay(unsigned int mul)
{
   for(; mul>0; mul--);
}

#ifdef  USE_FULL_ASSERT
void assert_failed(uint8_t* file, uint32_t line)
{
  while (1)
  {}
}
#endif

It does not work. Help please, I can't find the error.

Also:
Resistors(4.7K) are okey for I2C Communication.