texts:
I am designing a circuit which will have some external I2C sensors connected to it and thus I want to protect it from noise - via an optocoupler. I have to say that I am a complete novice to this all and after much searching, I came up with following source: Opto-electrical isolation of the I2C-Bus

The thing is, I would ideally like to see an IC, which would have two sides and I would plug in power + signal lines of the both sides into either side and it would do it all, without any extra complexity. I have looked at RS components but to be honest, it just makes my head spin and I cannot really see which one to choose. Which IC can I use here?


texts: S Bracket Transistors and Reverse Breakdown diodes in Texas Instrument 74LS32 DataSheet?

texts: Hi, I have included the image of the schematic of the Texas Instrument 74LS32. Basically the chip consists of 4 OR gates and the schematic shows the logic how 1 of those gates is set up on the chip. In the figure shown on the LS32 version (the RHS schematic) is a transistor made up of a squiggly S on the body of it where the straight line would normally be, compared to the normal illustration of a transistor illustrated in the 32 schematic(LHS schematic). The same thing again with the diodes the ones on the right have squiggles and the ones on the left don't. I think I remember that this is a reverse breakdown diode? (but would like confirmation) I have a theory that this is illustrating a PNP transistor? But am not sure. Also I was wondering what is that italicized upside down pitchfork thingy right before GND sink? Insights would be appreciated.


texts: Level shifting at the output of a 2:1 multiplexer

texts:
In my design a custom implementation of an Arduino Uno talks to either a CP2104 USB-UART or a bluetooth module, through a multiplexer (74LVC1G3157). Priority is given to the wired connection and hence when the USB cable is plugged in (sensed with the VBUS of the USB), power to the BT module is turned off and hence is inactive.

The CP2104 and the Bluetooth have 3.3V outputs and the Arduino Uno is a 5V device. For the Arduino RX, a 3.3V from either the CP2104 or the BT module works without any conversion and for the TX there is a voltage divider that steps down to 3.3V level to be read into the BT module and the CP2104 has 5V tolerant lines and hence there is no conversion there. However, the DTR line that resets the Arduino should be 5V and I was wondering if the way its wired in the schematic would work ok? (74LVC1G3157 followed by the 74LVC1G17). The 74LVC1G17 is simply a buffer.


texts: What is a good capacitance to use for a low pass and high pass filter?

texts:
First, I am using the minimum components circuit for the LM386

I am going to use the first circuit on this page. I am going to use a potentiometer in series with the circuit to give me variable cutoff frequency, so what should I make the capacitor value?

Similarly, what inductor value should I use for the low pass filter here?

In the minimum parts circuit, there is already a capacitor in series with the output, so do I get rid of it?


texts: Circuit that measures the speed of sound in concrete

texts:
I need a circuit to measure the speed of sound in concrete to 1μs or better. This is for a school demonstration where students who study construction will use this circuit to measure the speed of sound in a sample of concrete to determine the quality of the concrete.

I have two 40kHz transducers: one to transmit the pulse and the other to detect the pulse at the other side of the concrete sample that is about 10cm thick.

I have PIC processors to generate the pulse and then detect the pulse.

However when I look at the many commercial Ultrasonic Concrete Testers on

http://www.alibaba.com/trade/search?sb=y&IndexArea=product_en&CatId=&SearchText=Ultrasonic+Concrete+Tester

It appears from their specifications that they are operating with khz transducers, not mhz.
They do not mention frequencies higher then 200khz. Perhaps there is a limitation of
good transmission of sound in concrete to khz frequencies because mhz frequencies are attenuated?

I have a requirement to build a VERY LOW COST student system, and I can only find inexpensive
40khz transducers. The Mhz transducers that I can find are much too expensive for my requirements.

It appears from the specifications for the commercial devices that they use pulses of 20us to 20ms
and then wait for a receiver detection before sending another pulse. So the shortest pulse would be just
a one complete 40khz sine wave and longer pulses would be several complete 40khz sine waves. Any distortion
may be unimportant because they are not detecting a narrowband frequency, but just the first rise
of the pulse from the receiver?

Does this make sense to anyone? I mean can anybody help me to solve this problem...

Thank you.


texts: In resistive current sensor, can it have two different supplies for the voltage divider circuit and the differential op-amp circuit? Since the op-amp only gets the voltage difference.


texts: Supplying more current to a current limited DC motor

texts:
simulate this circuit – Schematic created using CircuitLab

Added requested schematic. Current circuit is on the left. Proposed additional circuit is on the right. I've never seen two solenoids put in parallel like this and am not sure what problems, if any, would result.

I may have found a solution to the problem below. Albright SW200 main solenoid/contractor works up to 72 V and 400 A of continuous current. It is a SPNO instead of the current SPDT, but leaving the solenoid output floating (so power is removed) should work to stop motor. Worse comes to worse, I'll add a second solenoid to put battery - across the motor (as opposed to leaving motor + floating) if I need it to stop the motor.

I still am interested in why or why not you can put two solenoid outputs in parallel if they have the same voltage levels. When solenoid is closed, it is basically a wire, so I don't see any reason not to, but I also have never seen/heard of it being done. I would still be interested in an answer even though I may have solved the problem with just a bigger solenoid.

Thanks

I have a current limited DC motor.

Current circuit, starting at the battery + supply is to a normally open 586 series solenoid input. The normally closed solenoid input is the battery -. The solenoid outputs are wire or-ed together to the + motor wire. The - motor wire returns to the - of the battery. When the control to the solenoid goes on, the motor runs. When the control to the solenoid goes off, the motor has the battery ground (-) across it and stops. The solenoid is rated for 200 A continuous and the batteries supply 180 A continuous. The motors stall current is 390 A.

The problem is that I have some start up torque issues that are current limiting the motor. For a variety of reasons I can't increase the voltage, but I could put another set of batteries to supply more current (extra amp hours wouldn't hurt either). If this works, the 360 A of current are still below the motors stall current of 390 A.

What I am thinking of doing is putting a second 586 series solenoid in parallel with the first and run a second battery bank through it. The outputs of both solenoids would be wire or-ed together and go to the + wire of the motor. The - wire of the motor would wire or-ed and go to the two battery banks. Rest of the circuit would stay the same (?) I've never seen this done and am not sure that there is a problem waiting to release smoke from some component in the proposed system.

Question 1) Is there some reason not to run two solenoids in parallel to increase the current?

Question 2) Should I use the same control for both solenoids (the control goes to no other circuitry) or generate a second control signal in parallel for the second solenoid?

Question 3) What should I connect to the normally open input on the two solenoids, the wire or-ed - for the two banks of batteries, leave the normally open input floating or something else? I like being able to stop the motor quickly by putting the - battery across it.

Question 4) Is there a simpler way to solve the problem? I couldn't find a larger continuous current solenoid at the voltage I am using (my first thought).

Thanks


texts: diodes selection for MOSFET protection against inductive load

texts:
Hello I would like to design protection for my N and P channel MOSFETS against inductive load. According to this article, Their IC is best but it cannot hanndle my application so i have to use the next best which is to use a TVS setup as to only a free wheeling diode

I will be using the NMOS BUK9K134 and the PMOS FDS8935, My load will be 5v to 60v DC at maximum 2A (befor efuse trips), circuit is in this configuration:

First of all Is the configuration correct? I dont get why you need a clamp on the gate of the PMOS. Next is how do i select the values for diode and zener diode? what would their power rating be?


texts: How do I transform this sinusoid in phasor?

texts:
If it is a signal like this i(t)=5*sin(100t-pi/3)A, I know how to transform.
But how do I do this e(t)=2-√(2)*sin(10t+pi/4) ?
I meant I don't know what to do with "2-"
Thanks for the help!


texts: Audio signal circuit. What is the 200 Ohm resistor doing in this circuit? REDRAWN

texts:
*I tried to draw this on the circuit drawer, it's excellent, but I didn't know the exact pieces to put in. Considering the trouble with my first drawing I thought it worse to use the wrong components than to draw as much as I know carefully by hand.

I don't know much about electronics so I've put a lot of research and testing into making this patch cable. I'm proud I managed to make it work but I'd like to put this out there for other people and I can't just say "it works". To satisfy myself I've actually succeeded I need to understand too.

Can anyone explain this?

Removing or moving the resistor stops the circuit working. My guess is it is something to do with the signal sent back from the iphone to the mic.

Could it be the mic Tip line has a diode in it so when the phone sends out a signal it has to go through both resistors to ground? From my research there is a requirement for the iphone to see 1600 ohms resistance before it shuts off the internal mic.


texts: Simple MOSFET current mirror, Cascode Current Mirror, Impedance and Output Voltage Swing

texts:
Sorry if I don't format this exactly correct, this is my first post on this site.
I am working with a simple MOSFET current mirror and a cascode current mirror and need to determine the output swing and impedance of each. In a DC sweep of Vo from 0 to 5V, I graphed \$ID2\$ and \$\large\frac{1}{D(ID2)}\$ versus \$Vo\$ while \$Vo\$ and ended up with the following results for each respective circuit. I believe that the \$\large\frac{1}{D(ID2)}\$ plot represents the impedance but am unsure. As far as the Voltage output swing from what I have found online the minimum output voltage that can be used for the simple current mirror to operate is Vomin=VGS. For the Cascode current mirror I am also very unsure but believe it to be \$Vomin= 2Vgs + Vt\$.
From what I understand there would be no maximum voltage output limit which makes me think that I may be calculating the completely wrong swing in general. Any help would be greatly appreciated and once again sorry for the format I promise I will improve lol

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Construction of voltage amplifier (nano volts to millivolts)

texts: I want to measure nano voltages (of the order of 10^-7) for a transient hot-wire setup for measuring the thermal conductivity of nanofluids.The setup I'm using is one with a platinum wire incorporated in a Wheatstone bridge setup and the resistance change over the time is measured for the required thermal conductivity measurement.  I don't have a nanovoltmeter with me to measure the bridge voltage measurements over time but I do have Tektronix TDS220 Real-Time Digital Oscilloscope with me that can measure the millivolt region and can be used as a data logger. So I'm planning to construct a voltage amplifier using opamp and the amplified output needs to be at least 10K times higher than the input, also I'm planning on using the IC741 opamp.So is it possible to construct a voltage amplifier with such parameters?Also, I  have Keithley 487 pico ammeter with me and can I use it in some way?I really appreciate any help from anyone.


texts:
A fuzzy area I want to clear up on the MC34063AP is Duty Cycle.

In the MC34063AP datasheet, toff an ton are a result of 1 / f, which is obvious.

toff is calculated by: 1 / f / ton / toff + 1

ton is calculated by: ( 1 / f ) - toff

The timing Capacitor CT is given by: 4.0 x 10 to -5 ton

What I can not find, and seems there is no logical direction, is what component, Resistor Capacitor or Inductor determines the Duty Cycle.

If, for example, I had an existing driver, and I wanted to modify the duty cycle, how would I go about it?

Configuration: Step Down


texts:
I am using pic16f690 and mikroc pro. I want to create interrupt on Rb4 and Rb5 (on those pins I have encoder) and when interrapt came i want to turn on LED.
But compiler gives me a error:
74 317 Operator '.' is not applicable to these operands 'INTCON' MyProject.c
Where i made mistake?
Please help me.

void interrupt()
{
   if ( INTCON.RBIF==1)
   {
        LED=1;
        INTCON.RBIF = 0;        // Clear interrupt flag

   }//end intcon.RBIF if
}//end ISR

void main()
{
    OPTION_REG=0x80;
    ANSEL=0x00;
    ANSELH=0x00;

    CM1CON0=0x00;
    CM2CON0=0x00;

    T1CON=0x00;

    TRISA=0b00000011;
    PORTA=0x00;

    TRISB=0b00111111;
    PORTB=0xff;

    TRISC=0x00;
    PORTC=0x40;

    INTCON.RBIF = 0;     // Clear interrupt flag prior to enable
    INTCON.RBIE = 1;     // enable on change interrupts
    INTCON.GIE  = 1;     // enable Global interrupts


texts: What are the disadvantages of using FPGA dev kits as the 'final product'?

texts: I understand that serious HW firms can manufacture their own boards, but what are the disadvantages of using a development board 'in production', i.e. placing a PCIe card into a server and performing calculations on it?


texts:
I did a lot of reasearch on Relays, Transistors and Arduino GPIO, and I also followed some schematics on other sites. I put my complete circuit into Multisim 11.0 and it worked, but I cannot for the life of me get it to work IRL.

The main problem is, that on the output (collector of the BC547) is a constant 5-6V (even though the arduino pin is set to switch from HIGH to LOW every 1 second), but in reality I need the 12V supplied by my external source to switch the relay.

Here is my schematic (you can ignore the upper part, It's just a AC-DC rectifier):

And here is my breadboard circuit - I checked it multiple times and even tried some other configurations like common emmiter, etc...

P.S.: I'm really new to this SE, so If I did anything wrong please tell me, I have no idea how or what details to post, and what to not post.


texts: Can we use 230V AC 16amp extension lead for 100V AC 16amp output?

texts:
Query: I have an inverter which output 100V and max. Current rating of 15Amp i.e. 1.5kW output. I have some PCs with adapters which takes 100V-230V input and current req. for PC is significantly below limit. Now they are physically quite apart(5 metres approx.) I live in UK and see that we get some extension leads which are specified for 230V and 16amp input. They are generally used for connecting mains at campsite. Can I use them? What could be the issues? I am not worried about sockets type i.e. thier physical shapes.
Thanks


texts: Can I replace an ER107 for an IN4007 or IN4005?

texts:
I am trying to repair a Power Supply where 2 resistances and one diode got burned, that diode was a ER107.

I was looking at the datasheets and the things that change are the Forward Voltage, Peak Voltage and DC Blocking. I dont know if I can use the IN4007 or the IN4005 to replace it or If I shouldn't.


texts:
I am trying to compute the Fast Fourier Transform (FFT) of 16 parallel input data and therefore, I would like to retrieve 16 output data in parallel. The transform size of my project is N=16.

More specifically, if I understood correctly the datasheet, the current Xilinx FFT IP Core allows to load data one-by-one and therefore, they have to come in sequentially. Moreover, after the FFT operation is completed, data come out also sequentially.

Does anyone have any idea about how to solve my problem ?

I thank you in advance.

Edit:

For posteriority, the full code is available here; details and explanations can be found in the paper.


texts: How to find the value on a chart scaled in decibels

texts:
I have the following chart

The blue line is the one I am interested in.

The question is how can I determine the value in LUX if I have the output voltage?

The problem is that I don't have any function to help me calculate this value.

Later edit:

If the light level from my room is indicated by 0.135V, I want to know how many LUX I have at that moment (the moment of conversion).


texts: How do VAC ratings of flyback transformers translate to VDC ratings of flyback converters?

texts:
I am trying to design a 40-50W flyback converter but I am struggling to select an appropriately rated transformer. While most flyback transformers are rated in AC volts, plenty of flyback converters use DC volts (just switched on and off.)
How, then, does one translate the VAC rating of a flyback transformer to the VDC rating of a flyback converter?


texts: How to connect both a bluetooth receiver and a amplifier to the same power input?

texts:
Dear users of this forum,

I am new to this so I apologize in advance for any rookie mistakes.
I am building a portable speaker of which I connected the speakers and the amp already.

I am looking for a way however to connect the amp to a battery pack or accu. I have been told I should use a 12 volt 5 amp battery. The bluetooth receiver I intend to plug into the amplifier needs power too and I have no clue how to wire it to the battery and if I am able to use the same battery?

All your tips are very welcome!

Luke

I will be using a bluetooth receiver similar to this:

http://www.lightinthebox.com/nl/3-5-mm-draadloze-bluetooth-muziek-ontvanger-bluetooth-audio-adapter_p1131211.html?currency=EUR&litb_from=paid_adwords_shopping&utm_source=google_shopping&utm_medium=cpc&adword_mt=&adword_ct=87561882434&adword_kw=&adword_pos=1o4&adword_pl=&adword_net=g&adword_tar=&adw_src_id=1810908567_301588514_21687237914_pla-117284547555&gclid=CLO5yrqOh84CFQ8z0wodalMIMA

And this amp:

https://www.amazon.com/Lepai-LP-2020A-Tripath-Class-T-Amplifier/dp/B0049P6OTI


texts: How is a current controlled voltage source different from a resistor?

texts: A current controlled voltage source produces a voltage that is linearly proportional to a current.  A resistor has the same behavior.  And the gain for a CCVS is measured in ohms, which is the same unit that measures a resistor.  So what is the difference between them?  Is a resistor just a kind of CCVS (and I guess also a VCCS) and if so, how does it differ from an ideal CCVS?


texts: How are objects rendered with a MEMS mirror for AR?

texts:
This question is an intersection of both hardware and software. I am trying to understand the theory of AR technology, but hitting some roadblocks and cannot find any good online resources that talk about this in detail. Please correct me if my understanding is incorrect.
2D MEMS mirrors will reflect a pulse of light from a laser at a very high frequency so it can achieve rendering x pixels/sec (each pixel is a single pulse from the laser). I am using a rendering software, OpenGL to design the actual object I want to render. What I do not understand is the interaction between the rendered object, the laser, and the MEMS mirror.
I think I have an idea. The rendered image in OpenGL can be converted to a PPM file where every pixel is defined with the RGB value. These values can be fed into the laser driver so it can generate each pixel for each pulse. Now the MEMS mirror has to be angled correctly so it can be displayed at a certain position in the coordinate system. In order to actually angle the MEMS mirror, a certain voltage must be passed into the x, y inputs of the mirror at certain times.
By steps:

Render object
Convert to PPM
Generate a “angle” file which maps voltage to specific angles for the MEMS mirror

The coordinate system is a totally different question, but it looks like extrinsic and intrinsic matrices are the right direction.


texts:
What does "parasitics extraction" mean in terms of Virtuoso simulation with Calibre?
I know that this simulation is used to have an accurate model of the circuit.


texts: OK to connect boards perpendicularly like this?

texts:
Are there any disadvantages in using the following method to accomplish a perpendicular board-to-board connection?

(i.e., any disadvantages in terms of

board manufacturing capability/cost
assembly convenience
mechanical stability
contact reliability
and any other potential issues in long-term use of the boards that I am not seeing)

DETAILS:

Since there are only a few contacts needed and within a limited space, I am trying to do this:

Design 1st board with a "pseudo-connector" by shaping copper-pad protrusions directly within the board's dimension
Then make complementary-sized vias on the 2nd board
Finally, insert the conductive protrusions of the 1st board into the 2nd board, and solder

NOTE 1: Each of the two boards will be mechanically bound using screws to the enclosure's top and side walls, respectively.

NOTE 2: Another related solution for the board-to-board connection might be to have castellated vias at the edges of baords, which can be soldered with the boards at right angles, although this approach might make alignment less convenient during assembly. Perhaps this method has some advantages though?

NOTE 3: I didn't wish to use headers/receptacles/plastic-connectors, because they would bring up additional part costs and assembly steps.


texts:
Is there any usable program that could help me organize elements on PCB breadboards? Or maybe some kind of autorouter?

By PCB breadboard I mean something like this:


texts: How to use "Voltage controlled switch" in OrCAD?

texts: In this OrCAD project, I tried to build really basic DC-DC Converter with use of "S"  or "SBreak" parts in OrCAD's Analog Library. But, According to analysis (picture below), the blue DC line should be equal to 5Vdc, but OrCAD says it's between 0V level. I know that the part "S" or "SBreak" is working with "VON" and "VOFF" voltage levels and on their working/closing resistances "RON" and "ROFF"... What and how is it going with "S" switches and how to use effectively?


texts: Convert sonic fuel gauge sender volts to traditional style ohms

texts:
I have a late model Harley Davidson Vrod that uses sonar for fuel level. This sonic fuel level sensor outputs volts 0.9v when full to 3.8V when empty.

I want to change my instrument cluster but the one I have needs Ohms (0-90) for the fuel gauge not volts.

So I'm wondering if there is a way to convert the output volts from the sonic fuel level sensor to a resistive range for the Ohm reading fuel gauge. So basically as voltage increases in on circuit resistance increases in the other.

The gauge is digital bar readout so the resistance doesn't need to be that granular. I'm thinking if I could get readings at a full tank then for every 1/8th of a tank until Empty. So 9 resistance settings in total.

The manual for the fuel gauge states that it has the following options:
"The fuel sender can be a 240-33 ohm sender, 73-10 ohm sender, or can be programmed for a custom sender range."

Not sure what the programmable range is though, the manual doesn't say. So need to map 0.9V full tank to 3.8V empty tank to one of those ohm ranges.

People have made suggestions such as using Arduino with MOSFET's and resistors or use 8 pin PIC12F675 and a bar-graph driver, or a programmable current sink.

I do not know how to use any of these as I'm new to electronics (this being my first project!) so a circuit design and instructions would be awesome.

Edit:
I have done some measurements:
The fuel gauge outputs 4.9 volts.  The setup of the gauge is 100ohms is full tank, 10 ohms empty tank.
I had a bunch of resistors which measured resistance with ohm meter then put ammeter in line to measure mA and I got the following (probably not that acurate as meter was a cheap one):

10Ω       28.6mA     6 bars
12.4Ω     28.2mA     6 bars
15Ω       27mA       5 bars
18.7Ω     27.2mA     5 bars
22Ω       26.7mA     4 bars
27Ω       26mA       4 bars
33.2Ω     25.1mA     3 bars
39.6Ω     24.3mA     2 bars
46Ω       23.5mA     1 bar
47.5Ω     23.3mA     1 bar
55.6Ω     22.5mA     1 bar
68.8Ω     21.1mA     0 bars
74Ω       20.6mA     0 bars

The fuel level sensor outputs 0.9v full tank to 3.8v empty tank.  Ammeter in line with no resisters show 50mA with the tank about 1/2 full @ 1.2V

Edit:  The fuel gauge manufacturer provided me with the following:
The

fuel input is approximately 4.5V through 150 ohm.
73 ohm sender voltage would be 4.5*73/(150+73) = 1.5V
10 ohm sender voltage would be 4.5*10/(150+10) = 0.3V
240 ohm sender voltage would be 4.5*240/(150+240) = 2.8V
33 ohm sender voltage would be 4.5*33/(150+33) = 0.8V


texts:
Im working with a LM3915 makeing a vu-meter. I dont think the LM3915 will directly drive more that 1 LED. I'm looking to find a way that I can hook up more that 1 led to the LM3915. I think that transistors will do the trick but I don't know enough about using them. I made this schematic in eagle, which I just learned, and was hoping someone could look at it and check out if this set up would work and then how I calculate the resistor's value if I'm using X LEDs.

LM3915 datasheet
Info on the LED

Schematic:


texts: Find filter's frequency characteristics from its impulse response

texts:
Impulse response is defined as .

Its plot looks like this:

Now I am basically supposed to say what does filter do with incomming signals based on this formula or plot. How can I approach this problem?


texts:
I need to be able to analyse signals that are 10ns in length. It comes from a PMT (Photomultiplier tube) or an equivalent detector. We need to be able to trigger at a certain signal strength coming from the PMT. Microprocessors like the ATMega328P are way too slow to do this, but I also can't find any fast (100mhz+) a/d converters online. Any recommendations how I can tackle this problem with cheap and easy to use hardware?

Note: This is for a high-school project, the cost needs to be as low as possible.

EDIT: Please forgive my bad English.


texts: In cmos, why connect bulk to source instead of vdd/gnd?

texts:
In cmos, both p and n type mosfets have their bulk connected to their source. Then p-types sources are strictly connected to vdd, and n-types sources to gnd.

1: Why not have bulk connected directly to vdd/gnd for p and n respectively?

and

2: Does having bulk connected to source have any effect on mosfets in series, like in a cmos nand gate?


texts: What is the circuit for the Singing doll that start when touching hands

texts:
If you look at the Elsa singing doll toy, it trigger the music/singing when you touch both hands.
Also, this toy can stay inactive for months on only 3 little battery
I am assuming they are "grounding" the circuit through our body.? can it be?
Toy Video


texts:
I'm using an RN-42 Bluetooth module connected to the serial port of a PIC microcontroller.
The Bluetooth module works great and I'm able to send and receive data but when I send a BREAK (hold TX line to 0) from PC through Bluetooth the RN-42 seems not receive it and the TX line continue to stay at high level.

The data path is the following:
PC -> Bluetooth Dongle -> RN-42 Bluetooth module -> PIC Microcontroller

What could be the cause of this problem? Is this problem common to all Bluetooth modules?


texts: pH sensor with DS18B20 temp compensation on PIC

texts:
I am trying to build a circuit that interfaces a standard pH electrode to a PIC (18F4550).  I need the PIC to also use a DS18B20 for temp reading and use that data to correct the pH reading.  I thought this should be OK with only software coding in the PIC since the temp data will already be digital.  I have seen many schematics for the pH probe amplification but their temperature compensation seems to involve thermistors of some sort and is handled at the ADC end; or they're considering a probe with both the sample and a reference electrode lead (which I'm not using).  My electrode has the single bnc connection.

Any suggestions on how to integrate the DS18B20 data into a correction routine?

Also, any experience recommendations on the ADC Amp would be SUPER helpful too.  There are quite a few in the fA input biasing range, I can't decide.  I'd prefer to avoid the guardrings if possible.

EDIT1:  OK, thanks all for the advice.  I have taken the lazy way out and bought the atlas scientific sensor interface board.  It is a uart board that can do the calculations itself.  I just have to figure out how to get the temp data sent to it by uart.  I posted a separate question about that (atlas code was confusing).  But this process should be much easier.  Also, considering some other advice, I've switched to the 18f46k20.


texts: How to embed a clock oscillator inside a digital block? Specifically, how is this defined for Synopsys DC?

texts:
I have to embed a clock oscillator inside my logic block for layout purposes. It's not an option to leave this block out and just bring the clock port in. Is there any way to define an internal net as a clock for other sub modules? All I want is to use the output port of the osicllator (which itself is am embedded submodule) as my clock for the rest of the design.
Anyone have ideas as to how this is done?


texts: MOSFET gate capacitance in strong inversion

texts:
This lecture (page 4 and 5) said about gate capacitance of a MOSFET in various operating condition.

From the table below, as you can see in strong inversion \$C_{ox}\$  and junction capacitance \$C_{j}\$ are considered to be in parallel.

How is it possible for them to be in parallel here? Could anyone explain that?

Thank you.


texts: Why can't I solder to this micro USB adapter?

texts: I cut the head off a micro USB power supply thinking I could improvise a full micro USB cable. I found only Vcc and gnd wires. So, I decided to tear into the connector itself. Inside the connector was this USB to micro USB adapter. Seems like 5-to-4 wiring with one of the pins on the 5-pin side not connected to anything--how a micro USB to USB should be wired. I tested connectivity with a multimeter, but I can't get any solder to stick on the D+ and D- pins on the 4-pin side. What type of material is this?


texts: How to count number of edges (rising or falling) in a signal in HSPICE?

texts: From an HSPICE simulation, I have a square pulse-like output signal. Suppose, my simulation runs from 0 to 1 second. I like to count how many rising or falling edges are there in the signal in this time window. The square pulse may not be regular i.e., the edges may not occur in regular intervals.


texts: How do I use a 5V relay with a 3.3V arduino pro mini?

texts:
I'm using a couple arduino pro mini's (3.3V) for a home automation project and want to add relays to the final PCB design to switch some stuff on and off.

Since I want to use a 5V relay like this: HF 46F 5V, Miniature HF power relay, 5 V, 1 NO 5 A

I wonder how I can switch this relay with the arduino, since the pro mini only has an output of 3.3V on the pins?
The arduino is driven by a 3.7V Li-Ion Battery.

Another question would be how to use the relay safely with high voltages?
(apart from trace-width and trace spacing between high and low voltage parts on the pcb)
Thanks in advance!


texts: How can a dominant state be the one with bigger voltage difference?

texts:
I am studying about CAN buses, and there is one thing I just can't find an explanation for. I understand that the idea of a wired-and connection is, that if any node is driving the bus to the dominant state, the bus will get to the dominant state regardless of the number of nodes transmitting a recessive state.

However, I find that in CAN the dominant and recessive states are as shown in the image below.

I could easily image an implementation like this, if it was the other way around, and the dominant state was the one where the wires are on the same voltage level:

But this implementation would result in the states being swapped. So how is it possible for the dominant state to be the state with the voltage difference?


texts:
I'm designing an Arduino shield to allow the Arduino to control, among other things, an ATX power supply -- I'm running GPIO pins to the PS_ON and P_OK pins of the ATX.  I would like to be able to run the Arduino off of the 5V_STDBY rail, with no risk of damage if the Arduino is plugged in via USB concurrently with the ATX power supply switched on.  I make mistakes; sooner or later I'll connect them both at the same time and I'd rather not fry my arduino, or worse still my USB port.

I'm designing as a shield, because so many devices these days support the arduino header footprint, that I can swap out for something else if I want down the line.

The basic idea is to wire ground to ground, and 5V_STDBY on the PSU to the arduino's 5V pin.  Now, because different regulators run at slightly different voltages, I don't want to short one to the other.

The fact that this is a a shield puts a new twist on an old problem.  There is no pin corresponding to +5V USB in, so solutions like those in this question OR-ing power supplies (diode or mosfet)  can't be used, because I have no direct way of knowing if the USB cable is connected.

My first idea is to take half of the diode solution from the question I just posted.  That is, put a diode with anode tied to 5V_STDBY and cathode tied to the Arduino's 5V pin.  At 16MHz, the ATMega can handle as low as 3.78V (http://www.atmel.com/Images/doc8161.pdf page 316), and a silicon diode would only drop about 700mV, so even if the PSU only delivers 4.75V, that still leaves me about 300mV of headroom. The hope is to leverage the turn-on voltage of the diode.  If the PSU's voltage is a bit lower, then even if the arduino is drawing no current, we're only dealing with reverse leakage current back to the PSU.  If the PSU's voltage is a bit higher, we'll still have a limited amount of current because the diode won't reach the voltage where it conducts significantly, even if both regulators are 5% off from 5V in opposite directions (500mV).  Hopefully what small effect the regulators have on each other won't hurt them.

Now, since we're talking about a USB port that I don't want to replace, is this a legitimate solution?  Are there any questions I should be asking that I'm not?

If so, should I be concerned about VCC on the ATMega328 being so low that a HIGH signal on the input pins is too high?  There are only a few pins that the Arduino reads, so I could use voltage dividers to shift them down.

Of course, another solution, which might ultimately be simpler, is to use a boost converter to bring the 5V_STDBY up above 7V, and feed that into the VIN pin, and let the onboard arduino regulator convert that back down.  It seems like a kludge, though.

Which solution, diode, boost converter, or other, do you recommend?


texts: Do pieces of wire or metal in general affect the inside of a Faraday cage

texts: Building a Faraday cage and wanted to know do the dozens of metal staples and several small pieces of wire have any effect in terms of acting as an antenna?


texts:
I got a broken subwoofer from a friend of my dad.
It has a build-in amplifier. During testing we came across some problems, most of which we solved. But during these tests, out of the blue, something began smoking.
It was around the capacitors. We tested the capacitor and noticed it was broken and since then I have been searching for one with the exact same "specs" (I'm not really familiar with all the terms used for these parts), but we had a hard time finding them.
I've been doing some research online and found a lot of questions about capacitors for monitors and TVs, where they said you can vary a bit in volts or farad.
Does the same go for subwoofers? I included a picture of the capacitor we took out of the subwoofer.

The reason why I want to know if it can vary in, for example, volts, is that I have found a lot of 6800uf 63 VDC capacitors.
I hope someone here can answer my question. I have been stuck with this problem for almost half a year now because of the capacitors from Amazon.
Kind regards,
Rick
Edit:
I want to thank you all for helping me out. altough i searched a lot I never came across the site of Farnell, where I found one with the same farad and volts. Also thanks to all of you I now understand a little more about these parts. As recommended I will check the voltage of the cap, as well as the rectifiers.
I sincerely thank you all for helping me out and if interested, I can update this question when the new capacitor is attached to the subwoofer.
Edit 2: Hello again,
After attaching the new capacitor we came across a new problem, a part which I think they call an amplifier, began smoking as soon as we turned on the power. So apparantly the capacitor wasn't the part which was smoking. Now again the question, does anyone know where I can buy the exact same one as I took off? A picture of the one we took off is displayed below. I thought I found one but some letters don't match. What do all the letters and numbers on this piece stand for? And does it matter wheter I buy the exact same one or one with little different letters?

Here's the link to the one I found for the people who understand Dutch: https://nl.grandado.com/products/1-stks-partij-tda7293-tda7293v-zip-15-ic


texts: Arduino, problem with displaying RFID ID

texts:
I have recently gotten a Parallax RFID reader and I was trying to make it work with my Arduino uno. I have gotten all the necessary wires attached and I used a RFID reading program I found from Make (I will put the code at the bottom). When I open serial monitor and move an RFID card near it, it spits a series of x's and ø's(eg. xxxxøxxxxøxxøø). I am expecting to see a combination of letters and numbers. I think its a problem with the code, but I dont know enough about it to know whats wrong.

The code can be found at http://cdn.makezine.com/make/28/RFIDread.pde

The RFID reader can be found here http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/txtSearch/rfid/List/1/ProductID/114/Default.aspx?SortField=ProductName%2cProductName


texts:
Question:
Why does yosys mark used sub-modules as unused?
Background:
I am trying to find a rough estimate of the area of a circuit. Some years ago, during my bachelor's, I have used a synthesis tool. IIRC, it was Synopsys. I don't have access to it anymore, so I am using an open source alternative, qflow. This is the first time I have ever used it, or any of its sub-tools, so I do not know its intrinsics. Note, though, that I am open to using other open source tools.
Ultimate Goal:
Compare the area of two modules, A and B. A is composed of 7 (slightly different) instances of module C, and an instance of (an extremely simple) module D. B is composed of 16 (slightly different) instances of module C. It is expected that A is smaller than B.
Detailed description of the problem
I have tried building (synthesizing+placing+routing) A and B, as described in qflow's documentation: qflow build A and qflow build B. Each module was built in its own complete project - i.e., C's source code has been explicitly duplicated. I have located an area dump similar to the one in this question (in place.log); however, the results did not make sense: A had roughly the same "total cell area" as B.
I had my suspicions that the sub-modules were not present in the final synthesis of the top modules; thus, I have built module C by itself (qflow build C). C was an order of magnitude larger than A and B, which confirmed my suspicions that A and B were being built without C. Parsing synth.log confirmed that the instances of C have been removed during the synthesis step (yosys) (for each C* variation of C there was a "Removing unused module C*"). Nonetheless, D had not been removed from A (i.e., it is used). I have no idea why: my testbench files confirm that both modules A and B make use of C to correctly generate output (tested using iverilog).


texts: What is a return line in AC power transmission? Why is it needed?

texts:
This diagram shows V vs. t for three-phase power transmission:

What is the corresponding I vs. t diagram? Would that diagram help explain what a "return line" is and why it is necessary?

(cf. the comment here, which prompted this question)


texts: Looking at conventional smartphone flat flex cable connections, there looks to be a great deal more conducting pins/contacts than on these Project ARA models - Increasing the size of these connections looks great as I understand it could improve their durability, but how did ARA manage to reduce the number of contacts? Any suggestions would be greatly appreciated. I understand that some of these images may be purely promotional, but I believe there are/ were working models out there.


texts: Will putting telephone pair through a DPDT switch affect ADSL / VDSL?

texts:
I'm changing phone providers soon and the new provider is going to connect a new copper pair to the house. Both lines are going to be active for a time and I may switch back to my current provider in future, so I'd like to put a DPDT switch in before the master socket to easily switch between the two lines, but would this affect my adsl / vdsl sync speeds at all?

I'm planning on using gel crimp connectors for connecting the wires together and getting a DPDT switch with screw connectors.


texts: Would a reset IC be enough for this many power supplies?

texts:
Could you please let me know how many reset ICs I'd need for my board?

I'm designing a camera using the IMX225LQR Image Sensor. This sensor requires 3 different input voltages: 1.2v, 1.8v and 3.3v as power source. So I would have 5V source voltage and 3 voltage regulators. For power on/off sequencing a LM3880 would be used. For power on reset I was considering using a reset IC to monitor the Vout of 3.3v regulator. But I heard that people use reset IC for detecting voltage drop in power supply pins(brownout reset). My question is this, do I need to monitor Vout of the three regulators for the brownout reset?


texts:
I have been looking around at 4x4x4 and 8x8x8 LED Cubes and I had a couple of question about them. A few I have seen have a full range of colors from the LEDs which I am assuming means they are using some kind of LED driver with PWM to control them. Looking around though I wasn't able to find many chips that support more than around 8 RGB LEDs and for 8x8x8 cube that would mean 64 chips which would get pricey fast.

So if I were to try to create one of these cubes and control it from my PIC, what would be the best and/or most cost effective way of controlling this many RGB LEDs?

EDIT: Currently looking at the TLC5940.


texts: Matching ground references between computer and small DIY amplifier

texts:
I am teaching myself about audio amplifiers and put together a basic circuit to receive the signal from my laptop and then drive a pair of 32 ohm headphones.

The small amplifier is powered by the USB port on the laptop. The sound signal comes out of the laptop and into the little amplifier via a TRS plug. The small amplifier has a rail splitter on the power input to create a virtual ground at around +2.5 volts above the USB ground. The left and right signal inputs to the amplifier have DC blocking capacitors on them.

My quandary has to do with how to deal with the common line on the audio cable going from the laptop to the little amp. On the laptop the common line is connected with the same ground used by the USB ports (0 volts). I checked this with a multimeter. On the amp, the common pin on the input jack is connected to the virtual ground created by splitting the USB voltage, so it is at +2.5V. Clearly this is not right as it creates a ground loop back into the laptop.

So is there a way to implement this setup correctly? Is it appropriate to place a blocking capacitor on the common line as with the L and R signal lines? Should the common line be connected instead to the 0 volt rail (V- on the amplifier) since it will be at the same potential as the source and the inputs are DC-blocked?

Schematic added:


texts:
I have limited knowledge of switch caps voltage inverters and charge pumps.

I need to generate -2.5V in my system capable of sourcing about 7.5mA.
I have MCU and two rails 3.3V and 5V.

So far, I simulated charge pump in arrangement similar to one above followed by LDO. From what I gathered charge pumps degrade the voltage under the load due to caps now being discharged and not fully “boosting” level and due to diode voltage drops.

Before I consider other approaches, I hope for some suggestions to what could be done to improve in order to get the current up without degrading the output level too much.

Schematic above is taken from: http://chrisgreenley.com/projects/charge-pump/


texts: Driving a 24V isolated load from a 3.3V MCU

texts:
I am looking to drive a 12-24V purely resistive load from a 3.3V MCU.   I would like to use an opto-isolator to separate the circuits electrically.  I've drawn up the following circuit, but I'm not sure about exactly how to simulate it in CircuitLab.   Can someone please tell me if the following circuit will work for my needs or what changes I need to consider?

My concern with driving the MOSFET is that its Vgs max voltage is 20V, so I've put a voltage divider to limit it to ~10V when the opto-isolator turns on.  I know I can use a MOSFET with a higher Vgs voltage, but I couldn't find any with the package size of the FDMC0310AS.

Thanks in advance for your help.

EDITED:

Original Image:

Modified Circuit:


texts: How to correctly address this three digit 7-segment display

texts:
I've purchased a mixed bag of random 7-segment displays and am trying to use a three digit 7-segment display marked as a "ELT-512HDB G C0019). For this I found the a datasheet with the pin diagram: https://www.digchip.com/datasheets/parts/datasheet/158/ELT-512HDB-pdf.php
From what I've gathered, I have eight cathodes per digit plus the dot and one anode for each 7-segment.
I'm quite new to electronics in general, so I struggle to understand how I can correctly display values on all three digits.
One digit is understandable. I have to identify which cathode represents which segment and then power the corresponding cathodes with 5V and connect the anode for the digit.
Do I have to set the regarding configuration for each digit and cycle through all of them in extremely quick succession? Is that achievable with a Raspberry Pi or an ESP32?


texts: Non-contact thermometers used by China in screening for coronavirus (2019-nCoV)

texts:
I'm not sure if this is off-topic, but if it is, then please inform me, and I'll delete it.

In media reports of the spread of the "coronavirus" (2019-nCoV), we often see images of Chinese officials screening people using non-contact thermometers, similar to this:

(https://www.sbs.com.au/news/china-admits-shortcomings-in-virus-response-as-cases-exceed-20-000)

I was wondering if anyone knew what the most common non-contact thermometers being used for this purpose are? I am aware of expensive thermal cameras and non-contact thermometers being used for disease screening, such as at airports and farms, with FLIR being the most common brand, but I think that it is very unlikely that the Chinese government is proving all of these officials with similarly expensive devices. So I am wondering what the most common types ("type" meaning brand, technical specifications, and cost) of non-contact thermometers are being used by these officials for the purpose of human fever screening/detection?

And related to the "types" of non-contact thermometers being used, there is an additional consideration. It might be assumed that these types of non-contact thermometers (whatever they are) are effective for this purpose (that is, effective for disease screening) -- after all, if they were not, then one would presume that they would not be used; but are they? If the Chinese are using lower-cost non-contact thermometers for this purpose, which, as I mentioned above, is likely a good assumption, then are these cheaper thermometers effective at detecting fevers in humans?

As I said, I realize that this might be off-topic, but, since it is a heavily technical question, and within the domain of electrical engineering, I cannot think of any other stackexchange website that would be more appropriate. My apologies if posting it here was a mistake; please inform me and I will delete it. Otherwise, I would greatly appreciate it if people would please take the time to provide answers.


texts: Doubt regarding static timing analysis - setup time check

texts:
I was reading J.Bhasker's STATIC TIMING ANALYSIS book. In that book, he tells that when launch flip flop launches the data & while capture flip flop is capturing data, he says that

  We now examine a simple example, shown in Figure 8-2, where both the
  launch and capture flip-flops have the same clock. The first rising edge of
  clock CLKM appears at time Tlaunch at launch flip-flop. The data launched
  by this clock edge appears at time T launch + T ck2q + Tdp at the D pin of the
  flip-flop UFF1. The second rising edge of the clock (setup is normally
  checked after one cycle) appears at time Tcycle + Tcapture at the clock pin of
  the capture flip-flop UFF1.

Why is he saying that "setup is normally checked after one clock cycle"?

Why can't we consider the clock before the very next active edge?


texts:
I am trying to use some of the IO pins of the dsPIC33FJ128GP802.  The pins in question are RB8 thru RB11.

I have written a little program that reads the input value of one of those pins and outputs it to pin RA4.

All I get is straight 0, which ever of those pins I use.

If I use any PORTB pin from 7 down (i.e., the lower byte of the register), it functions perfectly.

I have scraped through the errata, and found nothing that has any bearing on this problem.

What am I missing?

Test program:

#include <p33Fxxxx.h>

_FWDT(FWDTEN_OFF)
_FOSCSEL(FNOSC_PRIPLL)
_FOSC(POSCMD_HS)

int main(void)
{
    unsigned int x=0;
    // Configure clock and PLL for 40 MIPS from 4MHz crystal
    CLKDIVbits.DOZE = 0;
    CLKDIVbits.DOZEN = 0;
    CLKDIVbits.FRCDIV = 0;
    CLKDIVbits.PLLPOST = 0;
    CLKDIVbits.PLLPRE = 0;
    PLLFBDbits.PLLDIV = 78;

    // Disable the CCP output pins as per a bug mentioned in the errata.
    // Should not apply to this case, but just to be sure...
    CMCONbits.C1OUTEN=0;
    CMCONbits.C2OUTEN=0;

    // Disable all ADC pins (make them digital)
    AD1PCFGL = 0xFFFF;

    // Configure IO pins
    TRISBbits.TRISB10=1;    // RB10 Input
    TRISAbits.TRISA4=0;     // RA4 Output

    while(1)
    {
        // Send input state to output pin
        LATAbits.LATA4 = PORTBbits.RB10;
    }
}

Other useful info:

  Microchip Language Tool Shell Version v3_30 (Build date: Jun 21 2011).

The inputs are being driven by an Arduino, but using that, or hard-wiring to \$V_{LH}\$ or \$V_{LL}\$ makes no difference.

P.S.  I am no newbie to PICs, having spent many hours on PIC16s and PIC18s, so don't bother with the "obvious" answers.


texts:
I am reading an article in which  they consider  a model for charge transport in dielectric.

The following figure can summarize the different procedures done in this manner:

I am new in the domain of electronics, plus english is not my native language, for that I am facing a problem understanding some scientific expressions, that can not be translated word by word. I try to find some definitions in wikipedea, but for some expressions I failed due to confussion  in the domain (same word may have different meaning according to the domain of study).

so would some one help me understand some concepts:
What is meaning of :

Trapping and detrapping ?
why dielectrics have traps ?
Charge injection ?
Barrier height for injection?

Thank you in advance for any help. Any  suggestion for references on the subject  is highly appreciated.


texts: Correctly driving dual 7-segment display

texts:
After receiving some feedback on my other question, I have improved my design.

I am still using a stm32f030k6 to drive a two-digit 7-segment display, but I am using the common-anode HDSM-291C in order to be able to use the STP08DP05 LED sink. Since that IC is specified as being a sink (although source is mentioned in the description?), I concluded that I need high-side transistors to toggle the digits, and since commenters suggested using a MOSFET I chose the dual-channel SQ3989EV.

I am reasonably certain that the STP08DP05 should do the job. It is connected to a set of SPI pins on the MCU, since the protocol (8 bits at a time clocked in through the CLK pin) seems to be compatible with SPI. I've connected the outputs to the cathodes of the display, and as far as I understand I should be able to toggle the brightness of the LEDs by using PWM on the OE pin.

I am far less certain about the transistors. I have tried to research LED drivers and found people using similar setups, but I have little personal experience with transistors. Do I need some kind of current limiting?

I would like to know if any of my assumptions are wrong, if the choice of ICs and transistors is sensible and if I've missed anything else.

Thanks for any help!


texts: Industrial construction of pn-junction diodes?

texts:
I was just doing a project for a website and my team member excavated a standard pn-junction diode to see that inside the ceramic casing, the semiconductors of p and n doping merely abut together in close alignment. Shouldn't the case be that a single length is variably doped with n and p type impurities to form the junction?
If I remember correctly, then textbooks tell that simply joining the two by their boundary does not make it a p-n junction since there are always irregularities on microscopic scale. Any insights on this?


texts: Will this OP AMP work for this application?

texts:
I designed the following circuit in CircuitLab. My question isn't about the whole thing, but rather about the TL081 Operation Amplifiers that circuitlab uses as a default(data sheet found here).

simulate this circuit – Schematic created using CircuitLab

This design is meant to be a low-voltage cutoff circuit for an electric bicycle where there are 3 batteries - each with 4 cells. The first thing I do is use comparators to find the voltage across each cell. At that point, my goal is to use another op amp to determine if the voltage of the cell is below a 3.3V  threshold and then pass either 5V(if the cell voltage is above the threshold) or 0V(if the cell voltage is below threshold) through some digital logic.

I know Circuit Lab isn't the best when it comes to analysis, but I am wondering if the TL081 will work as it does here in Circuit Lab. Im very new to operational amplifiers and the datasheet didn't seem to have any clear answers for me.

Thanks in advance for your help.


texts:
Simple question: Can someone please help me identify this header type on my MacBook Air's (i7 A1369) motherboard. Bottom line is a series of unfortunate events
have led me to have to reset the the chip that stores the EFI firmware password, and this header allows access to it - but I need to make a connector/adaptor.

I know iPhones use this type of connector, but if someone could put a name to it, that would be fantastic. Cheers! (photos below).


texts:
XT90 plugs support up to 90A continous current and up tp 120A for short bursts.

On the other hand the only allow AWG 10 (5mm²) wires. AWG 10 is rated for ~50A
https://www.engineeringtoolbox.com/wire-gauges-d_419.html

https://www.elektromodellflug.de/hochstrom-st.-bu..html

How is this save? Is there some safety margin used? How hot will the wire get?


texts: Where is a good place to start learning about electrical engineering for AVR stuff?

texts:
Can someone point me to a really good tutorial on electrical engineering, mainly avr stuff.
I have looked at alot and none in my opinion really give a complete idiot like my self a good place to start.


texts: Asking if this module is physically possible?

texts:
I am an electronics student and learning Verilog. I had an assignment to build an clock divider for arbitrary frequency. I have made a module that works,
module N_clock(clk_in, freq_main, freq_N, clk_out);

input clk_in;
input [31:0] freq_main, freq_N;
output clk_out;
wire reg [31:0] d;
reg [31:0] counter = 32'd0;

assign d = freq_main / freq_N;
always@(posedge clk_in)
begin
if (counter<=d)
    counter = counter + 32'd1;
else
    counter<=32'd0;
end

assign clk_out = counter<(d/2) ? 1'b1 : 1'b0;
endmodule

My question is, is it possible to implement this module in an FPGA. I'm concerned mostly because of the division I did in line 9. I would like to know if there's any method of implementing physically or any other workaround.
PS: This question is not related to my assignment. The above module is enough for that. However, I am curious.


texts: Connect USB to microprocessor lacking a output port?

texts:
Sorry I'm sure this is a very simple answer but I know very little about how it works beyond serial ports and USB adapters for interacting with PCB circuits.

I've taken apart an old junk flip camcorder, which runs various programs etc. and would like to program it to display whatever such as C code or reconfigure what the play button does. I've been able to locate the microprocessor and searched its datasheet but I still cannot find out how to connect it to my computer by any means. Beyond that and the large chips, I have no idea where to look.

Here is the device itself: see below photo please

And the USB connection:

I can plug the USB into the PC but the issue is camera is buggy and doesn't register as a USB device (otherwise I'd just reformat it) so that's why I was trying to connect to the board itself and not mess with the USB. I know the device works because the load screen shows and a red light appears with only the USB attached. Any ideas?

http://imgur.com/zykkmR9  <-sorry! this is the picture with all the active connections, the other side does not have much

edit: ive got it to appear on the computer somehow, and can read all the .nib files with the variables etc. If say the usb was broken or something else the next way to go about it would be the JTAG as everyone is saying?


texts: STM32 Unexpected reset when a GPIO pin gets HIGH

texts:
I am using the STM32f030C8T6 MCU on a custom PCB. I have 2 inputs on pins PB2 and PB0, wierldy enough, when these pins become high the MCU resets.

I had 2 assumption:

1: this somehow causes the reset pin to go low i.e. hardware problem but I hooked the pin to my scope and it stays HIGH (reset is active low)

2: there is something wrong with the GPIOB register, but i set another pin from GPIOB as an input and it works fine and doesn't suddenly restrart.

I use the HAL library and cubemx to define the state of the pins. the code i put in is as simple as follows:

while(1){
    check = HAL_GPIO_ReadPin (GPIOB, GPIO_PIN_0);
          if(check){
          for(i=0;i<3;i++){
                  HAL_GPIO_WritePin (GPIOB, GPIO_PIN_6, GPIO_PIN_SET);
                  HAL_Delay(1000);
                  HAL_GPIO_WritePin (GPIOB, GPIO_PIN_6, GPIO_PIN_RESET);
                  HAL_Delay(1000);
              }
          }
}

It's just to indicate what happens since there is an LED connected to pin 6. I ran the same code just with a different pin from port B (GPIOB) and it worked fine, I am trying to understand the cause of this unwanted restart. I tried it on both pins PB0 and PB2 and both result in a reset.

Below is the picture of the schematic used:

Any help would be greatly appreciated.


texts: I have several MCU's of which I cannot use the deep-sleep modes, because they cannot wake up on UART data coming in. Are there any components for sale which can solve this? I can imagine something that delays the RX line for a fraction and toggles an GPIO on data arrival, which I can use the wake up the MCU.


texts: Calculate sheet resistance in finite element method

texts:
I have a simulation with several polygonial mesh cells (Voronoi-mesh) and their centers of gravity \$P_i\$, each with its own electrical potential.
Every cell has the same height \$h\$ all over.

How do I calculate the Resistors \$R_{12}\$ and \$R_{21}\$ in the equivalent circuit diagram you see below, if we know the uniform electrical resistivity \$\varrho\$?

One could use the formula
$$
R = \int \frac{\varrho(L)}{A(L)}\mathrm{d}L =  \frac{\varrho}{h} \int \frac{1}{d(L)} \mathrm{d}L,
$$
but in fact I do not know, which area I have to integrate over.

Planar view from top:


texts: Improving Power Amplifier - Digital Bias current set

texts:
In the following power amplifier:

 the MOS bias current is set by VR2. T4 acts as a temperature balance.

The ensemble R15, RV2, D5, T4, T5, R14 act as a current source.

VR1 act as offset adjustment.

My goal is to improve this amplifier to make it more convenient to put in service, removing the needs of manual trim pot adjustment and rather controlling the parameter with MCU (or otherwise).

I still have quite some issue into understanding how T8, T6 and T7 works to set the gate voltage.

I am looking for a solution to automatically set the bias current, controlled by a MCU that would adjust it at power-up and periodically while the amp is not in operation.

I also look to switch off the bias current completely when the amp is not active, to reduce power consumption and heat.

The concept is to replace this group:

By the following, allowing to control the current source from the MCU.

simulate this circuit – Schematic created using CircuitLab

The MCU would also monitor the voltage across R32 during rest state to adjust the bias current. It can also stop any bias current during idle mode effectively disabling the amplifier.

Would that implementation make sense and would be possible to adjust the bias current by measuring across R21, as it is referenced to the ground it would be much easier.


texts: How do you create a folder to hold your custom components? The tutorials I've come across such as the official getting started guide show the creation of only one custom component. Using this approach you end up with several folders... For example in the image below, I have created two custom libraries, ALU_ROM and CONTROL_UNIT. Each appears in its own folder... However, I want instead to have a folder named COMPUTER, where both components (and more in the future) reside. How can I do this?


texts: What is the yellow component shown here? This is off a Outlet USB phone charger.


texts: Lumped Circuit Abstraction extreme cases

texts: When using lumped circuit abstraction, if we consider two ends of a voltage source connected with ideal wire KVL won't hold; and also if we put two current sources opposite two each other, then the node in between won't obey KCL. Since there is no change in magnetic flux or other lumped circuit abstraction restrictions; what causes the Kirchhoff's laws to be wrong?


texts: Fundamentals: KVL in this AC circuit doesn't add up

texts:
I've got the following circuit:

And with it the following meter readings:

In the condition RL, the capacitor has a short over top of it and in RC the inductor has a short over top of it.

My question is this: Why does it seem that the voltage across the components in each condition never adds up to the supplied voltage (100V). I know current for the resistor will be phase with the voltage, inductor will be 90 degrees lagging and the capacitor will be 90 degrees leading. So say if it came to KCL I'd have to use phasor addition instead of just adding the magnitudes. I'm assuming there's something similar at work here? Would I be wrong in saying that the angle of voltage across all components here will be the same? What's the trick?

Thanks, and sorry for the noob question.

EDIT: The resistance here is 300 ohms, cap is 2.2 mic, and inductor is 0.8 H


texts: Can a battery produce more amperes as per Ohm's law?

texts: Ohm's law says I = V/R. So let's say I take a 9V battery and attach 1Ω  resistance across the terminals. So the current running across will be 9A. But the battery rating says only 500mAh. So are there actually 9A running across it? My simple AC switch put on 220V AC line has 5A rating, then how can a 9V battery deliver such amperage? I never understand the concept of ampere. Without attaching any circuit to a voltage source can we tell the amperage of the source?


texts:
I need to create a differential signal using low power single ended op amps(not a fully differential op amp).

Obviously an inverting op amp gets the signal inverted BUT the use of inexact resistors produces a differential error that is not acceptable. I do not have the equipment or quality components to get decent results.

Is there an op amp topology(can use more than one op amp) that can take a signal and produce an inverted signal that is nearly perfect and doesn't dependent on external component values?

For example, a non-inverting buffer is "ideal" as far as I'm concerned. Since there are no external components the gain is exact. Unfortunately the inverting buffer requires resistors which create a variable gain(either due to tolerance, temperature, or whatever).

Basically the circuit topology I'm using is one op amp for gain/drive and another taking it's output to invert the signal. This produces a differential signal but the inverting op amp doesn't produce an "exact" copy which causes problems. (Here the issue, again, comes from the external gain resistors not being exact)

Maybe there is some way to combine the two stages in to one in some ingenious way to get a fully differential output?

Also, the output impedance of the signal to the op amps is a not very high or very low(around 1k-10k) will effect the accuracy of the inverting op amp configuration.

(I'd use a fully diff. op amp if I could find one for my applications... but they don't seem to exist. (low power < 500uA, high voltage(>= 36V)))


texts: Switching capacitors in a guitar effects pedal

texts:
I've built a linear power booster - schematic here:
http://pedalparts.co.uk/docs/LPB-V3.pdf

I did it on veroboard:

You'll note that it gives you the option of having different capacitor values to turn the pedal from a 'clean' boost to a treble booster. Ideally I would like to make one with a 3 way switch - ON-ON-ON (double pole) to be able to switch between capacitors.

Now I just tried this with a 3 way slide switch that looked like this:

Forgive the crude diagram, but it was a 2 pole switch so I used the other pole to do a similar thing with the other cap (C2, not actually electrolytic, just ceramic)

When I tried it, the first position with the high value (100n) cap sounded ok, but the others were choked and thin sounding. It's a guess, but are the other two (unused) capacitors acting like decoupling caps and filtering out loads of the frequencies? The sound is more trebley, but it's very quiet. Is there a better switching mechanism I could use so that I don't have to have 3 capacitors connected to the same place? Maybe a diode or six?


texts: Sharp and Simple Analog Filter suggestions

texts:
I'm looking for schematics of some simple opamp-based analog filter, which has a sharp band-pass functionality. I want it to control small robot with sounds of different pitch.

The matter is like this - to amuse my pupils I already made a robot which is controlled by digital filters. Perhaps this short demo explains better. However some of them asked if they can build similar thing.

My design is rather simple, but makes usage of a small MCU and about hundred lines of code. They complain they are not advanced enough in programming so I'm thinking of proposing "more analog" solution to them.

That is why I'm looking for substituting digital filter (and MCU at all) with analog schematics. I do know how to build first-order low-pass and high-pass with RC chain. And I can use several of them with opamps...

But filtering of 20 or 40 dB per decade seems to be not too sharp for my goal. The main problem is that controlling pitches should not be too far (e.g. I do not want to use 261 and 440 Hz) to ensure that sounds have roughly equal loudness. With simple plastic recorder tones of 784, 880 and 988 are ones of most easily produced and quite loud (indoors) - that is why I used them.

So now I'm looking for schematic consisting of preferably opamps, resistors and capacitors (preferably no coils) which will allow to extract very narrow band. Currently it gives about 0.3-0.4 of amplitude on, say, 784 or 988 Hz filter output when 880 Hz tone is played (and amplitude on 880 Hz filter is about 1.0).

Probably I just do not know proper keywords for googling. What such kind of filter could be called?

Thanks in advance for any suggestions!


texts: The Closest Solder to Radio Shack Solder

texts: Does anyone have an opinion or otherwise 'proven notion' of the closest alternative to Radio Shack solder? Please, only answer this question by your own experience, as tons of options out there say "60/40." Specifically, I am after the kind of Radio Shack solder that says, "PC Work SN 60/PB 40, 60/40 Rosin-Core Solder," "6400006."


texts:
I just encountered the voltage divider a few days back. It was working, yes. But i'm confused that in my circuit,
I needed to output 1/2 voltage so I used equal values for the two resistors. And from what I've read, I could change the ratios to change the voltage. And I tested that, sure enough, it works.

But this is what confuses me, I was taught that resistors don't lower voltage, they lower current. And if they do have some voltage drop, it surely can't drop it by that much. So why does it work?

Any help will really be appreciated.


texts: Why flyback diode is preferred over fwd body diode of MOSFET in case of H-Bridge?

texts:
Why flyback diode is preferred over fwd body diode of Mosfet in case of H-Bridge?
Can fwd body diode of MOSFET can serve the purpose of flyback diode?


texts:
I'm using a b 31855k breakout board (a chinese one at that) with the olimex A20 and a K-type thermocouple (which works OK on another device with the 31855k).
The problem is, that the thermocouple temp reading fluctuates wildly (up to +- 10deg C) and slowly drifts into negative values. Communication with the IC via SPI is ok, because the cold junction temp is correct.
So, for example, once I start the reading after the board has been off for a while, everything seems fine. The thermocouple temp is the same as cold junction around 25 deg C(+- 2 deg C, but that is expected). It then slowly but surely drifts downwards and after 5- 10 minutes it reads max 20 deg C - basically fluctuating around 17 deg C. This is then an "unstable" situation. The temp reading remains at those values as long as the thermocouple is not heated or cooled. Once that happens (I've used a hairdryer and my freezer) the thing goes haywire and starts drifting into negative temperatures at room temperature in a room where there are no drafts or air currents. It also starts reading -10 deg C and +10 deg C within the span of half a second, etc ...
Any ideas what could be the issue?
The breakout board has a capacitor for the max31855 to stabilize VCC.
I'm betting on the 31855k being a cheap Chinese knock off, and if it is only that, it's good.
If it's not however, I have no clue what to do. Any tips would be appreciated.


texts:
I'm using the ADC of a STM32F4DISCOVERY to sample a signal. The sampled values are directly written to the DAC. I tested this and it worked absolutely fine, just as I would expect.

Now I wanted to control the application via a web interface. After the code was added for the ethernet interface, the sampled signal is messy. See picture below. (When I only use the DAC to generate a signal from software this ripple is not present, so it must by ADC related)

The input signal's level is shifted so it lies between 0 and 3V. This signal looks as I would expect. (I don't have a picture of this)

When I tie the input to 0V, the sampled signal looks like the picture below.

It looks like the ripple is added to the ADC pin by the code for the ethernet. Could a signal on a certain IO port mess with other signals on that port?

As shown in above picture, the ADC is connected to Port C, Pin 2. Also connected to Port C are: ETH_RXD0, ETH_RXD1 and ETH_MDC. I suspect one of these signal to mess with the ADC reading, as the signal looks perfectly normal without the ethernet code.

Has anyone else ever had such a problem?

Edit:
Some extra information:

The input signal comes from an 60 Hz AC source, see schematic below.

This is run through a transformer, then it's level shifted and de-amplified. When testing I bypass the transformer and use a signal generator to generate the signal(60Hz, 20Vp-p). This is the input signal from the first picture!

Also, I can produce a neat, clean signal from a look-up-table with only the DAC, the DAC is working fine (no interference on the DAC output).

The input signal is sampled at 50kHz. If the timer runs irregularly, it would not matter, because it has to write the ADC value of that particular moment to the DAC. If the timer was interrupted a few times per second and, let's say, only runs at 48kHz or 40kHz for that matter. This would still produce a decent sine wave. At least it won't explain the oscillations on the output.

When I debug the code, I see the value, read from the ADC, shifting up and down when I tie the input to zero.

I will try some of the suggestions in the answers later today.


texts: How to prevent signal waveform from going towards negative side when increasing gain

texts:
I have managed to design a circuit:
that is able to read an ECG signal where the signal is then acquired through a DAQ called TiePie. From there, the signal is then digitally processed (HPF,50Hz removal,etc), through MATLAB. Everything is fine. However the problem now is that when I tried to increase the gain, the Vpp of the waveform remains the same but the waveform starts to shift lower towards the negative side. A friend of mine told me to put in an AC coupling DC bias level stage,

I added this right after JP3. It works well and maintain the waveform signal at 0 axis when read on the oscilloscope. However, when I tried to increase the gain of the signal, it only increase by a few mV. Can anyone tell me whats wrong or is the so called AC coupling DC bias level is wrong ? Is there any better alternatives ?

Also I am supplying the circuit with 1 x 9V battery where the supply is split to +4.5V and -4.5V.


texts:
I want some experience in designing electronic circuits, and have chosen to build a battery charging circuit for a possible future PCB. I've tried to follow all the advice I can find online about designing such circuits, and would like to know if there's anything I'm missing or misunderstanding in my final design:
The high-level decisions are as follows:

The battery is a single cell, lithium-ion battery with a cutoff voltage of 4.2V
The battery capacity is 2500mAH, and should charge at around 0.2C or 500mA, and discharge at 0.5C or 1250mA maximally.
The load will draw around ~300mAH max.
The voltage provided to power the load should be exactly 3.6V

I will need to choose the following devices carefully:

An appropriate battery management IC
A low dropout voltage regulator

Result

Commentary

MAX1811: I chose the MAX1811 as my battery management IC. It allows up to 500mA of current, which should be enough to (1) charge the battery at the recommended current level (assuming no load) (2) charge even when the load is drawing current (albeit slower). I've connected it to a USB port for power, which should provide 5V and 500mA maximally per the USB2.0 spec. This is within the maximum ratings for the IC. I used the recommended capacitor size on the IN pin, and a larger one for the BATT pin (as there are also other devices connected that I accounted for later)

LTC3025: as my low-dropout voltage regulator. This IC can lower the voltage it outputs. I used the formula provided in the datasheet which is v_out = 0.4 (1 + R2/R1) with R1=24K and R2=3K to get: 0.4 (1 + 24/3) = 3.6V. Of course, this assumes I am getting 4.0V in.

ADP2503: When looking at the application example for the LTC3025, I saw they used this IC with it in order to eliminate unwanted noise coming from the battery. Therefore, I decided to also include this buck/boost IC and configured it to buck mode. The voltage in is expected to be 4.2, and I set it to output 4.0 in accordance with what I expected as input to the LTC3025. Per the datasheet I used the build in (just a voltage divider) formula (V_out = (R1 + R2) / R2 * V_ref) where V_ref is typically 500mV and chose R1=330K and R2=47k because the datasheet asked the total resistance of the divider be around 400K. This gives me just about 4V out.

Criticisms
The only comments I have had so far (in person by a passing friend) is that my design is too complicated and that the ADP2504 is unnecessary. However, I would like to see if I can get some good advice on what I could improve on here from a variety of other perspectives!
I also was unsure as to how to choose the capacitor size to sit on the net between the MAX1811 and the LTC3025 and ADP2503. All of them recommend capacitors be placed on their inputs/outputs. But they all share a common net! I just chose a larger capacitor size of 20uF, and then split it into two 10uF capacitors on a friends direction (faster discharge). This is larger (in total) than all the recommended output capacitor sizes combined for that net, so I thought it would work. But I don't have a proper logical approach for this step.


texts:
I know book recommendations are off-topic here. (Any book you can recommend will soon be out of date.) Rather than asking for a book, I'm asking for how to locate and evaluate potential books.

Last year I read several books with titles like "introduction to digital logic" and similar. As I expected, I already knew most of the material, although I did learn a few interesting new things. Now I'd like to take the next step... but I'm not sure exactly what that is.

All the books I read talked about basic logic gates, De Morgan duality, K-maps, combinatorial logic vs sequential logic, the different types of latches and flip-flops (in varying levels of detail). Most of the books get as far as describing multiplexers, decoders and a simple ripple adder.

However, none of the books seem to go any further than that. For example, nowhere is there a diagram for how to do multiplication in hardware. Certainly none of them describe how an entire processor might be constructed. Now I think I know how to do this — but I'd prefer to read something written by actual experts on the subject.

So what I'm looking for is a book that describes how to design all the major components of a computer system at the gate level. I know nobody does this anymore (unless you work for one of the 3 companies on Earth who still design microprocessors), but I'd like to learn anyway.

If anybody can suggest what search terms I might use and what to look for in a table of contents, that would be great. I imagine if I search "computer design" it will just be books that tell you what ICs to purchase and how to connect them. I don't want that; I want gate-level design principles.


texts: How to produce a middle C on intel 8080?

texts:
This is a example problem in my book. Assuming pin 5 of port 4 is connected to an amplifier that drives a loudspeaker, the solution is given as,

The frequency of middle C is $$f=261.63\ \text{Hz}$$
So, the time period is,
$$T=\frac1{f}=3822\ \mu s$$

The program to produce a square wave with that period is,

LOOP1:    OUT 4H     ;Send bit to speaker
          MVI C,86H  ;Set count to 134
LOOP2:    DCR C      ;Count down
          JNZ LOOP2  ;Test count
          CMA        ;Reset bit 5
          NOP        ;Fine tune
          NOP        ;Fine tune
          JMP LOOP1  ;Go for next half cycle

The number of T states is given as, OUT(10), MVI(7), DCR(4), JNZ(10 if true, else 7), CMA(4), NOP(4), JMP(10).

With a clock frequency of 1 MHz, LOOP2(for half cycles) runs for 1912 microseconds, which is close enough. LOOP1 should run again sending the complement of what was previously in bit 5 of port 4. But I think it doesn't.

When LOOP2 ends, the accumulator has 00H left over from C register. CMA changes the accumulator to FFH. NOP and JMP don't change the accumulator. So then the LOOP1 iterates for the next half cycle, OUT sents accumulator contents to port 4, i.e, FFH whose bit 5 is 1, everytime. So there is not a square wave, it's just a high signal. Then how does it produce a middle C?


texts:
I hope I'm asking this in the right place, I didn't know if it should go on stack exchange or super user instead.

Problem Summary:
I need to configure the baud rate of a USB to Serial bridge device.

What I need to use them for:
I need to send commands to some other serial device at different baud rates through hyperterminal, using a PC without a serial port.

About the bridges: The only identifying marks other than on the IC is a url which has been no help. The bridges have very little on the PCB except except one chip and a few resistors etc, so I investigated the IC, a Silicon Labs CP2102, (datasheet) and came across more information:

What I've done so far:
I bought two to test them communicating to each other. I performed a simple test, (obviously using their default baud rate), as follows:

Install Silicon Labs Silicon Labs CP210x USB-UART VCP Driver Kit
Insert the two USB-Serial converters into a PC, (Running windows XP)
Connect RX pin of one device to the TX pin of the other, and vice versa
Open device manager, note the two new COM ports
Open hyperterminal or similar: two instances, one for each port
Typing in one window appears in the other, and vice versa.

This worked as expected. However, changing the baud rate completely eludes me. I have tried several things:

Device Manager > COM port settings: When I change the baud rate for one of the devices via device manager, there's no change; the devices still communicate as if they were on the same baud rate; so they must both still be on the default. In other words, it seems to do nothing. I didn't even have to change the baud rate setting in hyperterminal.
Downloading something called the "NON-STANDARD Baud rate configuration device" (see below). However, it seems it's for setting a range of possible baud rates, not for selecting a specific one. (As described in the tool's documentation.)

The next step?
Will I have to do some programming to change the baud rate? It seems pretty obsurd! This chip is used in so many USB to serial devices, there must be an easy way of changing the baud rate?

References

Tools including "Non-standard Baud rate" configuration utility (an220sw.zip)


texts: Question about the switching behavior of a transistor as a switch

texts:
I was doing some testing and my intent was to run a transistor as a switch. I was providing an input square wave from a source, and was looking at the fall time characteristics.

Basically this is the circuit I was using to operate it, with the square wave being provided to the base through the resistor.

However while observing the fall time characteristics i.e when the square wave is turning off. I was getting a signal plotted on the scope below.

Basically the green signal is the plot for Vce and the yellow one(falling) is Vbe. Now I would expect to see Vce rise after Vbe falls down, but I was observing it rising a little before Vbe and there is a small kink where the left cursor is, where it gets triggered. Can someone suggest reasons to why it would cause the Vce trigger to soon when its higher than the base voltage to keep it ON ? Thank you for looking.


texts: Why are many 9V DC wall adapter power supply measured as 12-14V by a multimeter?

texts:
I have tried with many (working) 230V - 9V DC wall adapter power supply (of different brands, some of them coming with an electronic Yamaha device, etc.):

they all show a higher voltage when measured in "DC mode" by my multimeter, like 12V - 14V
they even show a higher voltage when measuring in "AC mode" of the multimeter: ~ 30V! This doesn't really make sense: the output of the power supply should be DC, so a theoretic AC voltage should be 0V. Ok, I understand the output of such an adapter is never "perfectly" DC, and there might still be a small sinusoidal component... However, why 30V?

What could be the reason of this higher than normal voltage?

Could it be a ripple after the rectifier?

PS: I don't own a oscilloscope to test the output of the wall adapter, but I will try to borrow one!

PS2: if it was only with 1 such adapter, it could just be a faulty one. But now I've tested about 6 different (working) adapters of different brands...

PS3: it's a cheap multimeter (link) but efficient. All other voltages that I measured have always been correct.


texts:
In my digital logic lecture today, my professor introduced a symbol code called Patty Code. I copied this table off the whiteboard:

     | Symbol | Binary | Odd Patty | Even Patty |
     |--------+--------+-----------+------------|
     | a      |     00 |       100 | 000        |
     | b      |     01 |       001 | 101        |
     | c      |     10 |       010 | 110        |
     | d      |     11 |       111 | 011        |

I did try Googling for both "patty code" and "patti code" with nothing substantial.

I asked my professor after lecture what is Patty Code. He said it's used occasionally. I asked him if it's another name for excess-3 or grey code, to which he said it is different to both of those codes.

Is my professor yanking my class's chain, or is this actually a real code?

EDIT

I want to leave record that the professor that gave me this misconception has a relatively strong accent. He is very knowledgeable and always gives me a satisfactory answer to EE related questions. So I finished that class, and am happy with the result. Hopefully nobody else has to Google this question!


texts: I am newbie, I am looking for a circuit that remaining power for about 5 minutes after switch off the main switch of a 25W fan at 220Vac. Thank you in advance.


texts: Creating Neutral node on Three phase Inverter

texts: I want to create a neutral node at the output of a 3-phase Inverter for ACIM. Is it possible to do that by adding 3 resistors at the Inverter outputs and join them together to get the neutral node? What value of resistor is recommended? I need that neutral node to see the per phase waveforms on the oscilloscope. Can we call it a virtual ground?


texts: Is printf debugging over USB with STM32 possible?

texts:
I've been doing a lot of searching to try find some examples for printf debugging over USB for the STM32 (specifically stm32f1x). I have found a few examples for UART/USART however I can't find any for USB. Can anyone tell me if this is indeed possible and if it is point me to some examples?

Thanks.


texts: Cgs,Cgd capacitor in Mosfet/ problem with measurement unit

texts:
I am a little confused with this problem.

I would like to ask if I have a Mosfet(in saturation)and I have find that Cgs=16fF and Coverlap = 0.5fF/um(this is given in the description of the exercise), how I can calculate the Cgstotal = Cgs + Coverlap and the Cgd = 0 + Coveralp?

The measurement units for the first equation shouldn't have been the same?Also in the second equation for Cgd, units is F/m but I think should be only Farad(F).

Can anyone help I have no idea how I can solve this problem.


texts:
Trying something new out, I'd like to make an 'attachment' PCB that will slot into my mother-PCB, and all the questions here have said to use a kind of edge-to-edge connector or a ribbon connector.

My question is what exactly do I use for high power? Something like 2-3A rectified mains 170VDC.

Basically I know the 'mother' board works, but I don't know if the child board works, so I'd like to 'modularize' it.

Perhaps these things;

Would work? I just have no clue what they are called.

EDIT: Uhp, they're called banana connectors. Still don't know if they're good for high power PCB-PCB connection.

EDIT2: The boards will be side-by-side, edges touching.

EDIT3: pic


texts: Help understanding a full wave bridge rectifier

texts:
I'm trying to understand the workings of a full wave bridge rectifier and would like some help. The output I got is shown below, and I'm wondering with a 6.3V rms input, why is the output amplitude so much less than this? Is there a way to calculate this amplitude?

Additionally, why are there flat spaces between each of the waves? Where do these flat spaces come from?

Thanks!


texts: Solar Charge Battery Low Voltage Disconnecting

texts:
I have a 4.2V 120mA max solar panel and 3.7V 1200mAh battery. I'm trying to make a solar power system for my arduino.

I search through battery management IC's and generally understand the charge concept but at somepoint I'm confused. Lipo battery has a 4.2V overcharge level and 2.75V discharge level. Most of the documents connect battery and system load together on same line but do not explain well, how to cut off at 2.75V low voltage disconnect level.

What is the correct approach for this subject?


texts:
I have designed an op-amp based Colpitts oscillator in multisim. When I press run button it shows- "timestep too smaall error". I've googled and tried everything but it still shows the error.

The link to the Multisim (.ms) file -

http://www.4shared.com/file/bqbr2V_i/Design1.html

Can anyone advise me as to what I'm overlooking and how to make this circuit oscillate?


texts: Encryption library for an 8051 microcontroller

texts:
I've programmed an 8051 microcontroller to send data out through an external transmitter (just a few bytes per transmission). I'm looking to encrypt this data in my microcontroller's program.
I have a 96-bit long key that I'd like to use (ideally) which is known by the transmitter's and receiver's uC.
I’m interested in knowing if there’s any simple encryption technique/library source code in C that you know of and would recommend for this purpose.


texts: Charging a Li-ion battery with a Buck Convertor & ATmega8

texts:
I'm trying to charge a 7.4 V Li-Ion battery following the CC/CV protocol and have a few questions.

I want to use an SMPS from my old laptop that can provide 20 V/3.25 A and feed that to a buck convertor and to the battery. To prevent the battery from overcharging and to limit the current to 0.5C or maybe even lower, is it possible to control the MOSFET of the buck (with PWM from the ATmega) measuring my current from a current sensor and the voltage from the battery?
Then adjust the PWM to not exceed a predetermined current in the CC mode and after that, limit the voltage similarly in the CV mode?


texts: Arduino w/ Atmega328: can't clear the watchdog

texts:
I'm using the onboard software watchdog facility of an Atmega328 like documented here.
My purpose is to limit to 2 seconds the execution of a portion of code that could lead to endless computation.

This is the pseudo-code scheme:

enable watchdog (2 seconds)
run may-be-endless code
clear watchdog
run the rest

The rest of the code should be run if the may-be-endless code manage to run in the given amount of time, otherwise the whole program must be restarted.

This is the Arduino code I loaded into the board:

#include <avr/wdt.h>

void setup() {

  Serial.begin(9600);

  Serial.println("Started");

  wdt_enable(WDTO_2S);
  Serial.println("watchdog ON");

  wdt_reset();
  Serial.println("watchdog OFF");

}

void loop(){
  Serial.println("loop...");
  delay(1000);
}

At this point, the expected output should be an endless printing of loop... messages, after the ones in the setup (Started, watchdog ON/OFF).

Surprisingly, what I get instead is this:

Started
watchdog ON
watchdog OFF
loop...
loop...
loop...
Started
watchdog ON
watchdog OFF
loop...
loop...
loop...
Started
watchdog ON
watchdog OFF
loop...
loop...
[...]

Appartently the watchdog is being set but can't be cleared. How come?


texts: Power supply adapter for Arduino Pro Mini

texts:
First of, i'm not from electronics background, i'm sorry if my question sounds stupid or irrelevant. I recently started a project as a hobby with a help of https://www.mysensors.org/build/irrigation i have purchased all the components and has built the circuit half way but i'm stuck at what kind of power adapter should i use i currently own a mobile adapter with output of 5V 350mA. But the Absolute ration of Arduino Pro Mini is 200mA as per How much current can I draw from the Arduino's pins?
Is it possible to use a 5V 350mA DC input to my chip ? Or would it burn off my chip? if so what kind of adapter or a current regulator should i use ?
A current regulator circuit would be much appreciated.


texts: How to connect a large exisiting code (some simulator) to the AVR Studio Simulator?

texts:
Context

I am working on a brushless DC motor controller project.
And I would like to verify that the interrupt timings make sense in simulation before downloading my code to the board.

Challenge

For that, I have already some C code simulating a brushless DC motor and I would like to run that motor simulation code in parallel with my AVR code.

I wish not to run the motor code in the simulator as well because it makes uses of floating point arithmetic: I want this motor code to run on my PC.

[edit]
I found a way to stimulate the editor. Unfortunately, one must create the input sequence before hand in a file.
This is not convenient because my motor simulator must react depending on the AVR code.
It seems that a good approach could leverage Python debug scripting interface.
However, the documentation seems to be lacking information.
Have you got an idea on how to approach this?

Thanks


texts:
I am working on a project where I would like to use a single pole rotary switch as a mode switch, but also provide power to the MCU. By providing the common on the switch with 3V, I can identify what mode the switch is in at anytime by reading pins 1-4 on the MCU.  Assuming an ideal op amp, one could simply buffer each rotary switch output and then combine the output of all buffers and connect them to the 3V input of the MCU. I would however prefer to use a passive solution to buffer each switch output rather than a active solution like the op amps. To formalize the question: Is there a way to passively buffer voltage? I don't consider myself a hardware wizard, so any suggestions are welcome.

UPDATE 11/19/2016:  So I am trying to implement the circuit (see above) that Majenko suggested.  I am simulating the load of an MCU with the 150 ohm resistor, and I made rough guess for the value of the other resistors (100k and 1k).  The 2.2uF cap on the output is to account for the break before make nature of the rotary switch. In actual implementation, the 3V soruce will be a CR123 battery. Also note that in this circuit I only accounted for one mode.  Imagine expanding this circuit to have multiple modes each with an additional NPN BJTs that all connect to the single PNP transistor base.  Can you see anything wrong with this circuit?  Is there a good way to decrease the total current needed to drive the BJTs?


texts: Driving capacitance with a high voltage level shifter

texts:
I am having issues with a 'high' voltage level shifter I am creating. I need to drive a 28Vpp waveform with specific timings ( <.1us rise time, 1us pulse width), converting from the 3.3V logic that comes out of my microprocessor. I currently have the circuit below:

Which produces the following waveform:

Great! However, I will need to need drive a fairly long cable. When I add 100pf of capacitance to the output:

I get the following waveform:

This waveform doesn't meet my requirements of having a rise time of less than 0.1us. What can I do to overcome this? I have tried replacing the transistor based circuit with an LM139 comparator, but that was still susceptible to capacitance. Are there ICs available that could fix my issue? I can handle about 4us of prop delay if needed. Thanks!


texts: I need a red and a yello LED indicator in my battery operated project. I am looking at specs on Digikey and they list brightness as mcd, viewing angle and test current. Viewing angle I know, but how do I figure how much current and the related mcd so they will be bright enough and still use as little current as possible?


texts: Switching Mixers for LO frequency= 4.25Ghz

texts:
I want to upconvert a square pulse of 250 Mhz bandwidth(250Mhz is the value of the first zero of the sinc ) to a center frequency of 4.25 Ghz , so that the spread becomes from 4Ghz to 4.5 Ghz.

Effectively, the output I want is \$ sin(2 \pi \cdot 4.25 \cdot 10^9 t) * Pulse \$.

Previously it has been done with a switching mixer HMC128 . From my understanding of switching mixer, it basically either allows the signal to pass as it is or blocks it depending on the phase of the  Local Oscillator.

The problem is that the above IC is not available on any of the sites like Digikey etc that ship to India. Can any one suggest some other mixer?
Also can anyone explain exactly how the switching mixer gives the output I desire? Is there some sort of filter to remove the multiplication of the harmonics of 4.25Ghz?


texts:
When choosing an LED Chip for example:3.2V 60mA,I have 2 query..

1) does that mean the LED will draw  60mA ?
If so I can use 150mA instead since it can safely handle more current..

Or

2) LED can handle any current only  upto 60mA above which it will get damaged?

Which is correct?Sometimes I am getting super confused..


texts: Do smartphones and tablets generally use dynamic or condenser electret mics?

texts: I've  heard electret microphones are usually what's in a smartphone, but I've never heard about them. Is it the most common type or is it condenser or dynamic? Or a mixture of the three?