texts:
I'm looking for help determining what size of solar (PV) I should use to recharge my Li-po battery after discharged.

Battery Characteristics :Capacity:1600mAh

Nominal Voltage: 3.7V

Charging Current:0.2CA=(320mA)

Charging Voltage: 4.2V

Charging time (std):6 to 7 hours

Charging time(max): 2 to 3 hours.

Solar (PV)
I have looked at a couple solar cells like the Digikey solar SM101K09L.
This is a MONOCRYST SOLAR CELL 198MW 6.22V
can anyone help determine how long it would take to charge this battery with the solar cell I have mentioned above? Is there any other product you would recommend?

Solar panel spec


texts:
I would like to "save" a program into my spartan 3AN, I explain :

Currently, I can program my FPGA and use it but when I shut down the board and power it, the program isn't there yet and I've to program my chip again...

Can someone tell me the solution to save my program somewhere in the FPGA?

Thank you !


texts: How does one prototype with SMT chips where the layout must be kept tight to avoid parasitic inductance?

texts:
Is it necessary to go straight to ordering a professionally made PCBs when one wants to test a surface mount component circuit involving high rates of change of voltage (dv/dt) and current (di/dt)? That is, this question refers prototyping SMD PCBs when one must minimize interconnect length to avoid parasitic inductance. Does this requirement make readily available breakout boards useless? (http://www.futurlec.com/SMD_Adapters.shtml).  I've etched my own PCBs, but, I have found that soldering fine pitch parts without a soldermask difficult. Have people found this to be a viable option even with leadless packages with 0.5mm pad spacing and a big thermal pad such as the QFN?

For a particular example I refer you to this question: What is causing large oscillations in my DC/DC boost converter? Is this ground bounce or some other effect?
This was my first attempt at SMD circuit, a DC/DC converter, and in dealing with parasitics. It was based around a small QFN and I couldn't think of any way to prototype the circuit other than to go straight to getting the board done professionally. A very tight layout  was indeed critical to getting the board to work. I found that my layout wasn't sufficiently tight and I will need to make another board revision.

Did I have a better option to getting the board done professionally? I am asking in case there is another option I don't know of.

Does anyone try to solder 30 gauge wire wrap wire onto the small pads and wire the chip up somehow?


texts: I need some help with analysing this differential amp

texts:
I'm having some trouble with analysing a differential amp. The amp and its associated operating parameters are in this link (question 1)

http://imgur.com/iS6fD5N

What have I done so far?

Well I've tried using large signal analysis to get the bias currents in M5, M3, M4 and M6. I can find them for M5 and M6, but can only get expressions containing \$V_{o1}\$ and \$V_{o2}\$ ( i.e. \$V_o = V_{o2} - V_{o1}\$) for M3 and M4 bias currents. I also know that I know that the sum of all these bias currents is equal to 5mA.

I thought this was a pretty good start. What next?

Well, the next thing I looked at was a small signal analysis. I was hoping to draw my model up and derive some equations that I could piece together the voltage gain with - that's how it works normally.

My small signal model is drawn correctly, but I can't seem to get any traction in deriving expressions with \$v_{o1}\$, \$v_{o2}\$, \$v_{i1}\$ and \$v_{i2}\$.

I've been at this for a while now, could anyone point me in the right direction?


texts: Connect an ATmega microcontroller to the HDMI CEC bus

texts:
i need a little help with a proper circuit for a connection between a microcontroller and the HDMI CEC bus.

Here is the whole plan:

Basically I want to use an ATMega microcontroller to decode the CEC bus signal and communicate via the CEC bus with other coneccted devices (TV/BD-Player/AV).

The current state:

I connected the CEC line to the input capture pin of my microcontroller. And the CEC ground to the ground of the microcontroller. The CEC bus works at 3.3V (max 3.63V) and my microcontroller at 5V. This isn't much of a problem and works fine (due to the switching threshold). A C-program is doing the job of decoding the signal and currently sending it out via UART. This works great and I can read every signal of my CEC capable devices.

Now the problem:

In the current state I can only read signals, but I obviously also want to write something. How do I need to connect my microcontroller to change the state between high/low on the bus?

Maybe the Solution?!:

Because of the different logic levels (3,3V <-> 5V) I first need some level shifting. I would use a simple voltage divider (10k and 6,8k) and connect it on to the CEC line from some output pin (other than the pin I am using to read the signal). Would it work like this? If the line is HIGH and I am applying also a HIGH state with my microcontroller, does this cause any problems? How would I minimize the current going out?

I don't want to damage anything here and my electrical knowlage is just the basic stuff :D


texts: Fast-blow instead of slow-blow fuse in consumer hifi power supply

texts:
I have a power supply unit for a hifi pre-amp. The power supply takes a slow-blow fuse (T2.5A/250V).

If I use a fast fuse (F2.5A/250V) instead, how likely is the fuse to blow during normal power-on?


texts: Audio Transformer output straight into an opamp?

texts:
Below is a circuit I'm working on.
It's a guitar input buffer featuring transformer isolation.
The transformer I'm using is pretty expensive and should be fairly linear, but I decided to add a graphic equaliser to the circuit to correct any small non-linearities in the transformer.

In an ideal world there would be no 'volume' control, only 5 eq faders. But that would probably involve some form of compression, which I don't want.
So instead I decided to add an overvoltage indicator which will flash when the output goes above 1V. The user can tweek the eq, and then attenuate the output to keep the volume under 1V using the indicator for guidance.
Does that sound wise? Is it necessary?

I probably don't need the input cap and pop resistor on the eq input.
But is it safe to remove the cap? Can I put the output of the transformer directly into the opamp?

The warning indicator opamp comparator output is normally at -9v but the output is grounded, meaning under normal conditions there's 9V across that LED arrangement. Is that ok?

Thank you in advance good people.

EDIT : I'm aware that both sides of the circuit share the same power supply. That's just for ease of simulation
In fact, placing the EQ before the transformer gives exactly the same simulation response, and requires only one power source.


texts:
I have a simple LT3663 circuit that I'm using to regulate 15v down to 13.8v.

("24v" is actually 15v in, and "15v" is 13.8v out.) This works almost perfectly. It current limits properly, etc. However, for some reason, the LT3663 only outputs 10.4v, at any current draw below the limit. It regulates perfectly at this voltage. Messing around with R18 and R20 values didn't change anything at all.

Layout:

It's...a bit ugly. However, I think it's pretty close to the reference in terms of placement and grounding and routing.

Why is this?

EDIT:

Something very odd is happening, indeed. I just pulled R18 off the board completely (grounding FB), and the vreg still maintains 10.2v.


texts: Microcontroller writes additional data on high-frequent writes

texts:
I'm using C-Control Pro 128 which contains a atmega processor. I've connected the rs232 interface with my PC and read the incoming data, having the following program executed on the controller:

void main(void) {
  Serial_Init(0, SR_8BIT | SR_1STOP | SR_EVEN_PAR, SR_BD9600);
  Serial_Write(0, 1);
  Serial_Write(0, 2);
}

I'd expected the controller to output the bytes 1 and 2. Instead, I receive the following:

1
2
119
119

If I write e.g. eight bytes instead of two, 119 is appended eight times to the actual data. If I write only one byte, only the one byte is transmitted, so all works correct.

The number 119 is independend from the value of the bytes and from the baud rate.

If I add a sleep instruction between the write commands (about 50ms), the problem does not occur.

Has anyone had a similar problem or any idea where the problem could be located?


texts: No previous knowledge of programming, considering electrical engineering

texts:
I am still at school and wont finish until 2015 but i have seen people control doors, toy cars etc with their iphones and i really want to get in to something like that.

I have a lot of spare time and was wondering where i would start, i want to try some projects that help my understanding of electronics and also help me decide if this field is really for me.

I have no idea how they control toy cars, doors, tv's so i would really appreciate it if someone could guide me in the right direction.


texts: What happens when a LIPO drops under 3V? WeMos in DeepSleep doesn't start up again?

texts:
I have a Lipo (18650) which is charged by a solar panel (6V/6W + TP4056 charger).  It's feeding a WeMos D1 Mini which is put in DeepSleep every 10 seconds.  When it's awake, it sends something to Blynk.  By connecting pin D0 to RST it works perfectly, until the voltage of the battery gets too low (< 2.8V).

The WeMos doesn't wake up at all after that. I have to manually reset the WeMos, then it works again.

I also noticed the battery doesn't get fully charged after the WeMos is 'dead'?

Sorry for my basic explanation: I'm really new to the world of ESP8266...

Thanks for your insights!

As far as I understand, the voltage regulator is automatically used by using the 5V-pin.  I was using the 3.3V pin, but I changed it to the 5V pin.  All is working OK for a few hours.

Andreas Spiess recommended the TP4056 charger in one of its great videos.  Normally it handles the charging of the LiPo and the power of the Wemos.  I'm using the TP4056 with protection, so normally it protects the battery from damage (?).

In other posts people suggest to attach the Wemos directly to the battery, while the TP4056 is handling the charging of the battery.  But it wasn't clear if they are using the unprotected or protected TP4056.

I'm monitoring the battery by connecting it to the A0 pin and reading the RAW-values so I know the battery voltage.  I can test it in software and if it gets too low put it in an endless deepsleep (esp.deepsleep(0)) but this will not wake the Wemos when the battery is charged again.

Maybe this is a solution?

https://www.sparkfun.com/products/10617

  The SparkFun LiPo Fuel Gauge connects your battery to your project and uses a sophisticated algorithm to detect relative state of charge and direct A/D measurement of battery voltage. In other words, it tells your microcontroller how much ‘fuel’ is left in the tank. The LiPo Fuel Gauge communicates with your project over I2C and an alert pin also tells you when the charge has dropped below a certain percentage.

But again: Will this restart the ESP8266 when the battery is filled again?


texts:
I built a controller with FOC for BLDC motors and it works well for most motors I tested so far, but as it comes to motors with low resistance and inductance, I hear a noise, that sounds like water in a pipe. For motors with higher resistance (>1Ohm) and Inductance (>1mH) I cannot hear anything. The PWM frequency is 32kHz and clearly out of the audible frequencies. I uploaded a video of the noise on youtube:

BLDC Noise

By using a spectrum analyser, I found the following picture. I measure between phase A and GND.

I further used an acoustic spectrum analyzer app, which gave me a different image with two peaks at 2400Hz and 4800Hz:

What I already tried/analyzed:

I used different PWM frequencies, also in the audible spectrum, but
this did not change the noise frequency.
The PWM signals itself look very clean, and it also works on different motors without any noise at all.
The gate drive is a DRV8304H (Datasheet), such that dead time handling works just fine.
The ADC current measurement triggering works also fine and triggers when the low side is open. I also adjusted there different parameters to test if something changes, but nothing did.
I also tried to apply a constant PWM timing to the motor, also here
the noise is the same.

I just found nothing, which influences the frequency itself. If it is somehow the motors resonance frequency, I don't know why this only occurs at low resistance and inductance motors. Has anyone an Idea what could be the cause of this noise?

Edit When I only apply a constant timing for PWM and then wait in a loop, I get exactly the same noise, so this is definitely hardware/motor related, but I'm not sure how I really can find the noise source. It will be probably the DRV8304H, since at a constant PWM input, the output is fully determined by this driver and the MOSFETs.


texts:
I recently purchased this MPU6050 GY-521 breakout board. I tried it with my Arduino Mega using this Arduino sketch provided by official arduino.cc.
(MPU-6050 Datasheet, InvenSence (producer) Page)

Man, it gives this weird output!!!

InvenSense MPU-6050
June 2012
WHO_AM_I : 68, error = 0
PWR_MGMT_2 : 0, error = 0

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1944, 368, 15608
temperature: 30.576 degrees Celsius
gyro x,y,z : -34, -204, -247,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1952, 364, 15304
temperature: 30.435 degrees Celsius
gyro x,y,z : -38, -216, -274,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1864, 388, 15356
temperature: 30.482 degrees Celsius
gyro x,y,z : -34, -233, -278,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1888, 324, 15260
temperature: 30.576 degrees Celsius
gyro x,y,z : -14, -220, -261,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1904, 392, 15316
temperature: 30.624 degrees Celsius
gyro x,y,z : -34, -241, -238,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1856, 308, 15604
temperature: 30.435 degrees Celsius
gyro x,y,z : -33, -252, -235,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1892, 444, 15528
temperature: 30.624 degrees Celsius
gyro x,y,z : 20, -236, -251,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1924, 356, 15520
temperature: 30.576 degrees Celsius
gyro x,y,z : -19, -224, -251,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 1844, 280, 15732
temperature: 30.529 degrees Celsius
gyro x,y,z : -1, -240, -249,

MPU-6050
Read accel, temp and gyro, error = 0
accel x,y,z: 2004, 372, 15396
temperature: 30.671 degrees Celsius
gyro x,y,z : -20, -252, -255,

(This is only a part of it, it gives this king of output continuously). I know for sure, only the temperature reading is meaningful. But what are those values given for acceleration and gyro readings??

OK, It says those are raw values. If it is so, then how can I convert them into meaningful values. Hoping it can be helpful (as many suggested), I also like to know how to use so called Jeff Rowberg library.

Hope there will be someone experienced with MPU-6050 module. Just give me a point to start. I have no clue on how to use the module... :(

Any help is greatly appreciated. Thanks !


texts: Find the transfer function of the circuit if current I is the measured output

texts:
So there's this problem I am trying to solve:

Consider a series RL circuit corrected to a DC voltage source and an on-off switch. Assume R = 2 ohms, and L = 1H, and applied voltage V = 10 volts.  Find the transfer function of the circuit if the current I is the measured output.   Suppose the switch is closed at t = 0, find the current in the circuit as a function of time.

Based on the problem, I believe the circuit should look like this:

Obviously, when the switch is closed we will have to deactivate the inductor, so the current would be 5A. Now, when the switch is open, the current would normally be zero, so after doing the Laplace Transform of the inductor, I cannot find a way to find the transfer function, and then the current as a function of time.

I would appreciate your help here guys. Thank you.


texts:
I want to know one thing about a fused disconnect. If it's fused for a certain amount of current, would you be ok with not adding additional fuses to protect your loads?

If you have a 30 A fused disconnect and you have 2-5 hp motors and 1-3 hp motor it sounds to me like you might need to add fuses to protect each motor?

I know that for my application since my hp total is less then the 20 hp max that you can have for that disconnect at 480 V. I'm not in any trouble of tripping that breaker.

But would the motors need fusing still?


texts: Looking for a quote on dynamic system identification

texts:
Does anyone know of a quote by an eminent control theorist or controls engineer or book author who I could reference who said something along the lines of the following:

  The process of control system design begins with understanding the dynamic behaviour of the system that is to be optimized.

I'm sure someone did I just don't know who!


texts: Reactive power compensation through grid connected inverter

texts:
I recently designed a bidirectional DC-DC charger for an Electric Vehicle (EV) battery.

I would like to focus on the inverter control. In this application, I designed the inverter to have unitary power factor (cosφ=1 , Q=0, S=P). I have read that in an application like this,  it is possible to make use of the capacitors in order to offer voltage regulation to the grid. In other words, we can offer reactive power to the grid.

So, let's say that I redesign the topology: S=P/coφ in order to have the ability to transfer reactive power as well. So, the maximum power that we can offer to the grid is :

So, in case there is no active power transferred (P=0), the maximum reactive power is Qmax=P. I would like to ask if something like this is realistic. Are there any undesired consequences in the system? Should I take into consideration some parameters (for instance, the capacitor size) during the design methodology?

Also, almost the same topology is used in order to connect photovoltaic panels to the grid. In this case, it is also possible to use the capacitor to offer reactive power. However, in the most cases, I noticed that unitary power factor is desired. I would like to ask why is this happening since topologies like that seem like good solutions for local voltage regulation.


texts: Via stub resonance intuition of insertion loss drop by formula

texts:
Resonance in transmission line occurs when the capacitative part cancels the inductive part.
Why in the case below at resonance does the S-param drop?
Thanks.


texts: Input CLK Keeps Showing As Hi-Z on ModelSim

texts:
I am writing some basic verilog code that blinks an LED at some frequency. The code for the design file is the following:

`timescale 1ns/1ns

module FPGA_Testing(input reset, input clk, output reg LED);

    reg [32:0] counter;
    reg state;

    always @ (posedge clk) begin
        if(reset == 1) begin
            counter <= 0;
            state <= 0;
        end
        else begin
            counter <= counter + 1;
            state <= counter[20];
        end

    end

    always @* begin
     LED =  state;
    end

endmodule

and the test module is here:

`timescale 1ns/1ns

module FPGA_Testing_tb;

     reg clk;
     wire LED;
     reg reset;

     FPGA_Testing test(
                      reset,
                      clk,
                      LED
                      );

    initial
    begin
        clk = 0;
        reset = 1;
        #10
        reset = 0;
    end

    always
    begin
        #5 clk = !clk;
    end

endmodule

When I compile the code, I get these as my warnings and critical warnings:

Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning (292013): Feature LogicLock is only available with a valid subscription license. You can purchase a software subscription to gain full access to this feature.
Warning (15714): Some pins have incomplete I/O assignments. Refer to the I/O Assignment Warnings report for details
Critical Warning (169085): No exact pin location assignment(s) for 3 pins of 3 total pins. For the list of pins please refer to the I/O Assignment Warnings table in the fitter report.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Critical Warning (332148): Timing requirements not met
    Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
Critical Warning (332148): Timing requirements not met
    Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
Critical Warning (332148): Timing requirements not met
    Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning: Warning: File FPGA_Testing_run_msim_rtl_verilog.do already exists - backing up current file as FPGA_Testing_run_msim_rtl_verilog.do.bak11
Warning: Warning: File FPGA_Testing_run_msim_gate_verilog.do already exists - backing up current file as FPGA_Testing_run_msim_gate_verilog.do.bak11

And then when I run a RTL simulation with ModelSim, I get this

As you can see, the clk and reset values in the testbench file are correct, but the clk and reset values in the design module are both Hi-Z(which I suspect is the reason why I get undefined behavior from the other values in my design module). I am pretty sure I did the connections correctly, so I am unsure as to why I get these Hi-Z values.


texts: What components can be placed not to close to the circuit like capacitors and still work fine?

texts:
I read that capacitors(especially decoupling ones) have to be placed as close as possible to their position.
Does the same apply for resistor also? Can resistor be placed not close enough, lets say far, from a transistor for example or from an other circuit that resistor is part of it?
Does the distance of components only apply to capacitors or not only?
I am talking about components and not lets say feed line of antenna obviously.


texts: Can I convert a 2.5W DC to AC with a 120W DC-AC Inverter?

texts:
I want to convert the output of USB to AC voltage, and I come across with this 120W 12V power inverter. Is it possible to step up the 5V DC to 12V, later convert it to AC with a 120W DC-AC inverter? If so, what will I get? As I know 120W is the max. output power, do I need to concern about the input?

P.S. I'm a self-learner.


texts:
Two settings on a system I've got can be changed using jumpers. This is the connector and the pin description:

There seems to be three pins needed to choose between ON and OFF, but how? Do I set them to high/low in some pattern? The documentation is very sparse so I assume this is some standard interface, but I couldn't google it.

  5.3 Jumpers description

  Please note that the two jumpers on the board are PTH (plated-through hole) type and should be easy to
  mount/dismount.

  5.3.1 TARGET jumper

  TARGET jumper controls the powering of the target board. If it is in position ON (check the diagram on the back of the
  plastic cover) it will provide either 3.3V or 5V to the target board
  (depending on the position of the POWER jumper) The default position
  is OFF.


texts: Step down voltage regulator not working with inductive prox sensor

texts:
I am trying to get a fixed 5V output from an inductive proximity sensor. The proximity sensor comes with 3 wires: bn(V+), bu(V-), and bk. A wiring diagram can be seen here on page 2/12. I have available to me both NPN and PNP style sensors and have tried using both.

I am having trouble figuring out why it does not work with a LM2576 though. I am powering the inductive prox sensor's connectors with +24V to bn(V+), bu(V-) to common, and bk to the input of the LM2576 which is then supposed to give a 5V output. I have the bk going into pin 1 of the LM2576 and everything else connected similar to Figure 1 in the LM2576 datasheet. Can anyone give me insight as to why when I connect the bk wire of the prox sensor to the input of the LM2576 it does not output 5V?

I have already verified that all components work by setting them up in other says (such as providing direct power to the input of the LM2576 and verifying it outputs 5V).


texts: USB connector durability: plug vs socket

texts:
I've been searching for information about USB connectors durability and I have found those numbers:

Type-A: 1,500 plug-unplug cycles
Mini-A: 1,000 plug-unplug cycles
Mini-B: 5,000 plug-unplug cycles
Micro-B: 10,000 plug-unplug cycles
Type-C: 10,000 plug-unplug cycles

What this data is lacking is information about which side of the connector has this durability. For example fragile bending parts were intentionally moved in micro-B from socket to plug to put wear on cheap cables instead of soldered elements. Does it mean, that after 10,000 cycles only the plug will fail? When will the socket wear off? If the numbers describe the more durable side, is there any data about type-A socket? Usually it's permanently soldered into expensive hardware, but has waring spring mechanism, so that seems important.


texts:
I am currently developing a small robot project. The motor driver I have uses a L298 motor driver IC. It supports two methods of control, PWM and PLL and it is configurable with on-board jumpers on my board. What is the difference between the two in motor control? I understand how PWM works, but PLL got me thinking. Should I consider PLL?

For reference, it seems that they work in the same way: http://www.dfrobot.com/wiki/index.php?title=Arduino_Motor_Shield_(L298N)_(SKU:DRI0009)#Sample_Code

Also, here is the L298 datasheet, but it doesn't mention anything about PLL: http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00000240.pdf


texts: Switching between two power supplies to power bluetooth board

texts:
I have a Bluetooth board in which I wan to have the option to power it  by a battery or power it by a wall adapter. The power input is a 5mm x2.1 mm plug with two wires (positive and negative). I have both a wall charger and battery available (24v). I want to use a 3 way slide switch (on,off,on). One position would power the board using the wall adapter, One position would be completely off and the last position would power it by the battery. but I am not sure what I need to do, how to wire it or what Rating the switch would need to be. I've found some switches but they are rated for a lot higher voltage than 24v. Would that be okay? Any and all information would be great appreciated.

Link to sample switch shown below
https://www.amazon.com/gp/aw/d/B008DFYNX4/ref=mp_s_a_1_14?ie=UTF8&qid=1490924981&sr=8-14&pi=AC_SX236_SY340_QL65&keywords=on+off+on+switch+dpdt

Thank you in advance.


texts: Inexpensive field deployable non-invasive current sensor

texts:
Is there an inexpensive way to MacGyver a non-invasive current sensor together in a field (yes, a literal field), assuming some prior planning?

The context here is an event similar to EMF Camp or OHM, at which they run a couple of large diesel generators and distribute power around the camp via Commando plugs and consumer socket breakouts inside porta-loos.

I'd like to be able to turn up to an existing system, non-invasively attach or wrap a sensor around a cable (possibly up to 1.5" diameter) and measure the current being pulled on that line. The sensed current would then be transmitted by a LoRa module to a base station which then maps the power usage across the site.

Accuracy isn't particularly critical as I'm mostly looking to track the variation (deltas) of power, so a constant offset of even several amps is perfectly acceptable.


texts: Difference between low impedance fuel injector and high impedance fuel injector

texts:
In my recent project ECU, I'm working with 4 stroke auto rickshaw. Here, when I check fuel injector properly, then I found out something like 3 Ohm written on it. So, I basically google it then I found, my fuel injector is low impedance fuel injector. And there are other high impedance fuel injector also available and it's resistance range is between 11-13 Ohms.

Now, what this resistance indicates ? And what is difference between this low impedance and high impedance fuel injector ?


texts: I have to design a bootloader for Kinetis E series controller. What are the prerequisites to write a general bootloader code ?

texts: To write a C code, the priori knowledge about main function, function declaration and definition, variable declaration and initialization is required, similarly to write a bootloader code what all priori knowledge is required.Say that code should toggle an LED when system starts booting.


texts: Is it always safe / reasonable to replace a power supply brick with one rated for more amps?

texts:
I am specifically looking to replace a 12V 3A power supply that seems to have disappeared from a backup HDD. I found a 12V 5A power supply with the right connector on Amazon, and ordered it without hesitation as I've always "understood" that as long as the power supply was rated for at least the peak current the device might draw, it was fine.

But now that I've had time to consider it a bit, I'm less sure… Having tinkered a bit with TI's designer tool it seems there is considerable room for optimizing the supply circuitry with the expectation of a particular range of loads. Will a "typical" off-the-shelf, switching power supply brick rated for 5A deal gracefully with all loads from 0-5A?

A little knowledge is a dangerous thing, as they say… Is my "understanding" that the higher-rated supply is safe / reasonable actually correct?


texts: What determines the colour temperature of a bulb?

texts:
There are various bulb products in the market, the temperature of the bulb determines the colour of the light emitted by the bulb.

For example

3000K is warm white (yellowish)

6000K is daylight (white)

Is there any correlation between energy used and colour temperature? Does colour temperature determine energy consumption?

Is it possible to get a different colour temperature by putting a filter in front of the bulb? For instance is it possible to put a filter in front of a warm white bulb to get daylight?


texts: Off-line, half bridge. Weird primary voltage

texts:
I'm working with this circuit:

I only show the power section, which is not working well.
It is a SMPS working in open loop, so that I can manually adjust the PWM signal. The capacitor C10 is not mounted on the board.

The parameters of the circuit are:

VDD = 15 V
VD = 311 V
Vo = 24 V @ 2,5 A (approx 50 W output power)
Switching frequency = 80 kHz

For the test, I connected a load of 25 ohms and gradually increased the PWM level.

The following figure shows the voltage on the transformer primary on the TP6, taking the TP7 as a reference point. I think the signal has an acceptable shape. Corresponds to an output of approximately 3 V

I set the control signal so that the output voltage (Vo) is 7 V, and I get the following signal as voltage in the primary:

In addition to the "hump" that appears in the zone of zero voltage, the asymmetry in the amplitude of the pulses is notorious.

Taking the output voltage to 17 V, an oscillation is observed:

And this is the waveform for 24 V at the output:

My question is: why this behavior? What would be a possible solution?

At first I thought that it could be a magnetizing current (transformer) too high, but increasing the output current level (by varying the connected load) does not change the effect.

I apologize for the quality of the images, I hope they can serve as reference for the description of the problem.

EDIT: Here is the input rectifier block with reference to point PRI_MID


texts: Why is the output (in the truth table) inverted in a ic 74154 used as a demux?

texts:
I am studying Digital Principles and Applications from Malvino and Leach. I have a doubt in the demultiplexer section. This is the image of a 1 to 16 demux. I understand how it works.

So, if ABCD = 0000 and STROBE = L and DATA = H, then Y0 will be active and it should be H, while rest all inputs would be L. Also, if DATA = L and STROBE = L then all the outputs Y0 through Y15 should be L.
But when we try to implement a demultiplexer using a TTL 74154, this is the truth table that is given in the book:

Here, G1 = STROBE; G2 = DATA and outputs are Y0, Y1, Y2 etc.

Why are the outputs inverted? Is the hardware implementation circuit different than the one explained in theory?


texts: Why does the forward voltage drop in a diode vary slightly when there is a change in the diode current?

texts: I was going through Basic Electronics and Circuits by David. A.Bell and there it mentioned that the forward voltage drop in a diode varies slightly with a change in forward current - but there is no reason there as to why it happens.


texts: How to identify an ordinary coil? Can I use some tools do identify its value?

texts:
I did a big mistake and damage an electronic coil in my PCB. The only information I did have is the coil itself! There are two identical coil in it.
This is my PCB. It is the UCD-210M.

This is the broke coil

And this is the another good one in PCB.

Click this link to see more images.
So, what you can see is the three colors (clockwise):

Red
Violet
Yellow

This page show how to identify this colors. But it don't show the value of every color, maybe for every series, it change the value. I don't know what is the 1st or 2nd color dots, so I have this:

1st (Yellow) - 2nd (Violet) - 3rd (red)

Luckily it has this exact configuration, so it give 4700 nH

1st (Violet) - 2nd (Yellow) - 3rd (red)

It don't show the values…

Edit…
The manufacture finally answer the mail. It is a coil of 4.7 µH. He don't give any other detail.
Everyone was correct. But… The second problem: can any 4.7 µH coil work for it? The size of my coil is: 2.63mm x 2.35mm (I measure it with a digital calipers). So, with this size, I get this list.
I am really afraid about it because all other electronic details. No model look like visually equal to mine. The best option in this list is the 0603PS-472KLB because it size. But if I buy it, will be a trial and error…
So the question is still the same:

Because I have a good one, I can use some tool to measure its value and electric details. What tools is it?
And how can I identify the exactly manufacture of this piece? If I use a generic one, can it cause problem? Maybe I can get this piece from another device, what kind of device use the same coil?


texts: What does it mean for a power supply to have an output range?

texts:
I had a power supply blow and I replaced it with one from the same company with the same model number. The new supply has lightly different specification than the old supply. Oddly (to me) it gives the voltage as a range.

Old Supply:
U in: 120V 60hz (AC)
P in: 600W
U out: 18 V (DC)

New supply:
U in: 120V 60hz (AC)
P in: 600W
U out: 12-24 V (DC)

Same company, same model number, but it has a voltage range... I get that you can have dual output supplies but that is typically written 12/24 volt, come with an amp rating at each voltage, and have some clear way of hooking up either 12 or 24 V. So my questions are

How does it work for a power supply to output a range?  I wouldn't think that possible.
If it is outputting 24 v is that going to damage an 18v DC motor?

Edit:
This is a Linak power supply for a standing desk powering 3 Linak legs/actuators. The old supply had a button control pad that connected via an RJ45 cable - it also had a mysterious unused small molex port on the board near the RJ45 port. The control pad for the new supply has a small digital LED screen on the button pad to display height and it has a small cable plugged into that port. There is a small secondary transformer on the secondary "fuse board" for stepping 120V to 11V and powering that LED. The tags on the torroidal transformer for the two units are identical output voltages (31 V). So, the 12 V is for the LED output, the 24 V.... still not sure why it says that. Both Boards have a pair of 2200uF 63V caps that appear to be in parallel dumping 21 V into 3 sets of 4 mosfets (1 set for each leg). Consumption by the board probably drops it down to 18V by the time it hits the legs.


texts:
I have designed a wearable device and added a MAX30102 to it (MAX30102 home page, datasheet). The datasheet says the maximum current drawn by the IC (excluding the LEDs) should be 1200uA or 1.2mA.
The switching regulator can provide up to 200mA of 1.8V, and I have tested that. But as soon as I solder the MAX30102 back on it, the 1.8V drops to 0.8V and current increases from 5mA (of the whole PCB) to 95mA. So that's a 90mA increase caused by the MAX30102. The only thing using 1.8V rail is this IC.
I have attached the schematic of my PCB, as well as the typical application circuit in the ICs datasheet. and I cannot figure out why this is happening.


texts:
I need to crimp the 18 awg wires into the 3-pin female JST VHR connector, but have no clue as to how to do it. How would the crimp latch onto the JST housing? Can somebody point me to any helpful resources?

Thanks!


texts: Which type of DC electric motor is the best suited for driving a mechanical clock?

texts: I want to drive a clock mechanism with a motor. In order to get acceptable accuracy I need a motor that can deliver a certain rpm very precisely, is low on vibrations, noise and power consumption, and has a certain longevity. I don't need "production grade" accuracy, this is just for the learning experience, but I want to come as close as feasible. So far what I found out was that it should probably brushless and be able to operate at a low voltage. Still there is a staggering selection. Which other criteria should I pay attention to?


texts: Does somebody know about a tool to design filters for DSPIC?

texts: I have to make a filter with DSPIC33 and I want a program that design the filter (there are a lot), yet export code to DSPIC (in c, any compiler or assembly).


texts:
Could somebody explain how rolling code protocols such as KeeLoq work? I understand the basic premise that they use a different code each time so you can't just use replay attack, but I don't understand how one side verifies the correct code etc.

Furthermore, how do they perform an initial synchronization if the index into the rolling codes isn't known/shared beforehand?

If you have to use Keeloq as an example to explain that is fine, but I would rather a general explanation of rolling codes.


texts:
I built a two-stage amplifier as shown below. I have already built the first satge (R1-R5 & C1-C2) such that If I apply a signal of 1volts peak-peak, the output (at collector of Q1) would be 8 volts peak-to-peak (without the second stage). I wanted to get an overall of a smooth outupt voltage (at collector of Q2) at least 18volts peak-to peak when introducing the second stage (C3-C4 & R6-R10) [applying same signal; i.e. 1volts peak-to-peak]. However as seen below, the output is distored due to incorrect biasing levels (dc quiescent voltage needs to be shifted up I guess).

Anyone could help me resolving this issue. What modifications should be done to the second stage to get correct biasing levels (changes of values of R6-R10, or introducing extra components, etc)? It might be due to the insertion loss when combining two stages as well.


texts: Phase Locked Loop: Confusion in Lock Range

texts:
For Phase locked loop (PLL), we can  have two types of Phase Detectors (PD): Type-1 and Type-2. The Type-1 PD has an analogue multiplier (which is simply XOR for digital inputs) whose low pass filtered output is a signal which varies at a frequency equal to the difference between the input and Voltage Controlled Oscillator (VCO) frequency. The voltage v/s phase plot of such a PD looks like this:

For this PD, the rising slope provides a negative feedback for the PLL loop but the falling slope provides a positive feedback. Why is that? And, as shown in the figure the PLL locks on the rising slope, so what parameters of PLL decide where on this slope the PLL would lock? Does it depend on the input frequency as well?

The Type-2 PD has a digital circuitry of flip-flops whose output depends only on the relative time shift of the input edges and has the average voltage v/s phase characteristics as shown below:

Why would a PLL with this type of PD not lock if the phase difference input to the PD is greater than \$2\pi\$?


texts: Error interfacing GSM with Atmega32 using UART Interrupt?

texts:
I am interfacing GSM with atmega32 using uart interrupts. I am using an external interrupt which is fired when a user press a switch and uart receive interrupt to receive the response of GSM.

CODE:

int main(void)
{

   DDRC = 0xFF; //output led
   PORTD = 0x04; //PD2 high for switch interrupt
   serial_Init();
   GICR = (1<<INT0);
   sei();
   while(1)
    {

     }
}
ISR (INT0_vect)
{

   serial_Tx("ATD<number>;\r\n");
}

ISR(USART_RXC_vect)
{

}

My question is that whenever I press the switch, ISR is fired and command is executed but I didnt get any call. What could be the error? IS this because when I press switch, on my terminal I get a series of ATD command instead of single command. And I am also confused why I get series of ATD command instead of single command.

My next question is how can I receive response from GSM. we can only read single , byte that means do i need to use for loop to store it in a char array.?

Serial_Tx function:

void serial_Tx(char *str)
{
for (unsigned int i=0;str[i]!=0;i++)
{
    UDR=str[i];
    while(!(UCSRA&(1<<UDRE)));
}
}

Serial_Rx function:

char serial_Rx()
{
while(!(UCSRA & (1<<RXC)));
return UDR;
}

OUTPUT:


texts: Square Wave Voltage Level Shifting (Take 2)

texts:
After my question before, I tried to design a circuit with zener diodes and transistors for this issue.

It seems to work in simulation. Am I overdoing it? Are there any other simpler ways to do this, if so, could you please give any example or pseudo circuits?


texts: How to generate positive and negative square wave with frequency of 1Mhz?

texts:
im planning to generate a square wave with positive and negative voltage, so basically, i create a 1Mhz square wave from a microcontroller, and send the output to a circuit which will convert the 0-5V square wave voltage to +20V and -20V square wave. I have successfully created a circuit by using BJT transistor but it only worked on frequency below 100Khz. here's the circuit (the voltage on the circuit below is 12/-12v, but it will do on 20V/-20V):

Is there any way i can create the square wave with the specifications above? please help me. Thank you so much.


texts: Piezo signal amplifier using LM358 opamp

texts:
I was trying to amplify the signal of a piezo, which is very low and amplify it so that I could use it to latch a flipflop. I had the LM358 opamp so I made a differential amplifier by a gain of 50 so that the output would reach 5 volts which is a high logic level.
I got the design of it from internet, I just changed the gain.
I was measuring the output with my multimeter (I do not own an osciloscope,) but the output was never what was expected. The maximum voltage I measured was 1volt, but it should have been 5volts.
No matter what I tried, the output was same.
I do not know if the opamp is not working or if I am measuring wrong.
Please tell me what am I doing wrong or what the problem is.


texts: What is this diamond-shaped voltage source symbol, and how can I solve this puzzle?

texts:
One of my friends sent me this question but I have never seen anything like that, anyone knows what is it or how can I solve it? Question asks: what's the value of alpha and calculate the power of current source using alpha?

Also what's that thing in the middle?


texts: Minimal electronics to interface a solar cell to a battery powered system

texts:
I've got a bunch of solar cells whose maximum power point is at around 18V and a battery-powered system that uses 3S LiPo batteries (9-12.6V). I would like to interface these solar cells to the system in order to increase the endurance (i.e. operation time from battery full to battery empty) compared to the battery-only setup.

What are the minimal electronics required to achieve this?

I'm aware that the proper way to go is to use a MPPT, including possibly one that support recharging LiPo batteries. What I'm after is the minimal effort required to a working prototype where part of the system's power requirement is provided the solar cell. In particular, I don't require battery charging capability and it would be ok if the solar cells don't operate the maximum power point (i.e. it would be ok if it operated at battery voltage instead, which would yield about half the efficiency). Also, since the solar cell can provide only ~30% (~8W) of the total average power (~25W), the battery cannot be completely replaced and the power supply cannot be simply switched from either battery or solar cell depending on battery charge or lighting condition.


texts:
I read everywhere on the Internet that voltage levels in the color components of a VGA cable should go from 0 V (dark channel) to 0.7 V (maximum brightness for that channel). However I tried to measure the voltage coming out of two video cards that I own and I obtained levels between 1.4 and 1.6 V. At the same time I measure the expected output impedance (75 Ohm), because the voltage drops of the right factor when putting a resistor in parallel.

What might be the cause of this discrepancy? Is there any easy error that I might be doing or should I expect that a VGA card may emit higher voltages than the standard 0.7 V?

I am rather sure that the oscilloscope is correctly calibrated because it agrees with at least two testers I have.


texts: I am building an Arduino based project with DS1307 RTC clock module and storing an offset value, rarely updated though, in its EEPROM. But I am observing drift in the time as well as the offset value in the EEPROM over time. The stored value of -18 in the EEPROM changed to 104 after 3-4 days. I suspect the time is changing more rapidly, about one minute in a day. I am also using AltSoftSerial to communicate with a GSM Mini 900A module. I suspect some issue in the Arduino, as the project works flawlessly in some other hardware. I wrote two bytes on address 0 and 1 and after the drift I tried on address 100 but no improvement. The change in the EEPROM stored value is very surprising. What are the general characteristics of a faulty Arduino UNO board?


texts:
Suppose we have an alternating signal and another signal is produced in the loop which is DC. Is there a circuit which tracks down the DC signal even if it is mixed with an AC signal?(somehow removes the AC signal from its output)
I am asking this question to find it so I can begin studying it.


texts: Efficiency of a centre tap full wave rectifier(qualitative analysis)

texts:
In a centre tap full wave rectifier the output voltage is half of the input(secondary coils voltage) voltage, so the power is half of power of secondary. Also in half wave rectifier the only half of the cycle is rectified but the voltage amplitude is full so the power is half of power of secondary coil. Thus I conclude that the efficiency of both half wave and full wave rectifiers are same since both of them deliver almost same power per cycle.
 Is my reasoning and conclusion correct?


texts:
I am building a board based on a working reference design. I've obtained the assembled board based on my design but the '3V3_OUT' signal is failing to carry power anywhere on the board.

The issue seems to be with the power mux (TPS2113ADRBR) as this is where the 3V3_OUT signal is distributed. I am measuring no voltage on the OUT pin (pin7). The two voltage input pins (battery and USB) are both measuring 3.2V (pin6 and pin8 respectively).

I am very much learning this stuff and may be in over my head but I do notice that there is no via under my mux, I am not sure if that may be of concern. Ground planes are used for both layers.

My design which is not producing voltage out on pin 7:

The reference design which is correctly working:

The schematic used for both designs:


texts: How do I perform ac analysis of common emitter with voltage divider feedback?

texts:
I'm working towards understanding voltage-shunt feedback. I'm about halfway there, and stuck.  I am  building a simple common emitter with voltage divider feedback.

I managed to get it biased to put the collector at 6V and have 3.4mA quiescent current.
I modeled it with hybrid-pi and have what seem like reasonable values for gm and r-pi.

Unfortunately, the basic algebra I used to solve voltage-series and current-series problems doesn't seem to work here.  What analysis method could I use to help me answer a question like "for an input current of 100uA, what output voltage/current should I expect?"
As I said, I was able to solve questions like this without too much trouble when it was the common emitter with degeneration or the emitter follower.  But that pesky \$R_F\$ resistor messes with my feeble mind!


texts: Switching power supply noise and grounding

texts:
So I have a +-15 V and a neutral switching power supply. As far as I can see the outputs are floating. The power supply has no earth connection. Voltage from negative terminal to neutral and to positive are 15V and there is a small Ac component of 0.8mV at 50hz.

What confuses me is if I measured from any of the outputs to earth taken from the mains I observe a 114 V Ac at 50 hz. This worries me a bit since I don't fully understand it. I measured the same for a different power supply and it was around 5 volts ac. I thought the DC side is meant to be insulated from the AC side and I read somewhere it could be something to do with decoupling capacitors inside but I don't understand it ?

So my question why have 114 volts AC and can I pull down the negative or the neutral to earth safely? I.e. ground the PS.

I'm using the power supply to power a number of opamps used for transimpedance amplifiers of photodiodes. Currently the power supply injects a lot of noise. My PCB ground plane is connected to the virtual ground of the opamps ( non-inverting input) and also to the neutral of the PS. My feeling is that if I connect the neutral of the PS to the mains earth I'd solve some of my problems but I'm not sure it's safe ( for my components) currently.


texts: Generally speaking at same voltage level and same current which, current is more dangerous AC or DC or are they the same?


texts:
Is the Arduino ground or the common ground the same as Earth ground? Why or why not?
Is the Arduino ground or the common ground the same as Earth ground? Why or why not?


texts: How fast cpu clock do you need to control camera?

texts:
I'm making a camera system with CMOS image sensor and micro controller. But I don't know yet how fast cpu clock I need. Assuming that I use 5MP cmos image sensor and take just still image with 1fps, 2592x1944 and RGB format(8bit for each color), how fast cpu would I need?

Thank you


texts: For a voltage reference providing a reference to multiple devices, ADC, DAC, instrumentation amp... would there be some benefit in placing bypass caps right at the reference input to these devices even though they have high input impedance?


texts: Voltages for connecting ds18b20 to Edison breakout board

texts:
It appears that the upm library provides support for reading temperatures from a ds18b20 on an Edison via uart. They also provide this hookup diagram. However, it looks like the ds18b20 can only operate at 5V while the UART TX and RX on the breakout board are at 1.8V (table 28). This upm diagram seems to suggest they should be directly connected though. I am hesitant to try it for fear of damaging the board or module.

Do I need to step the voltage up and down between the Edison uart and a 1-Wire bus?

If so, what would be the appropriate way to do that?


texts: How to configure PIC24H for 20MHz external oscillator?

texts:
The basic addition of a 20MHz external resonator is becoming much more painful that I thought.  I've got a breadboard setup with a DIP package of a PIC24HJ128GP502.  Nothing fancy, and it has been able to blink an LED with the internal FRC for the clock.  My configuration bits are set in code as follows:

// General Segment code-protection configuration:
// leave code protection off,                       GSS_OFF
// disable code protection,                         GCP_OFF
// disable write protection,                        GWRP_OFF
_FGS(GSS_OFF & GCP_OFF & GWRP_OFF)

// OSCillator SELection:
// Primary oscillator (XT, HS, EC) w/ PLL           FNOSC_PRIPLL
// enable two-speed oscillator startup              IESO_ON
_FOSCSEL(FNOSC_PRIPLL & IESO_ON)

// OSCillator configuration:
//   enable clock switching but not monitoring,     FCKSM_CSECMD
//   allow the RPn pins to be continually remapped, IOL1WAY_OFF
//   leave OSC2 pin as clock pin (not digital I/O)  OSCIOFNC_OFF
//   High-Speed (10-32MHz crystal) Oscillator,      POSCMD_HS
_FOSC(FCKSM_CSECMD & IOL1WAY_OFF & OSCIOFNC_OFF & POSCMD_HS)

// WatchDog Timer configuration:
//   disable the watchdog timer,                    FWDTEN_OFF
_FWDT(FWDTEN_OFF)

// Power-On-Reset configuration:
//   map I2C pins to SDA1/SCL1,                     ALTI2C_OFF
//   use the smallest power-on-reset value of 2ms,  FPWRT_PWR2
_FPOR(ALTI2C_OFF & FPWRT_PWR2)

// Debugger configuration:
//  JTAG is enabled,                                JTAGEN_ON
//  communicate on PGC1/EMUC1 and PGD1/EMUD1,       ICS_PGD1
_FICD(JTAGEN_ON & ICS_PGD1)

int main(void) {
  // STAYS HERE FOREVER, NEVER LOCKS!
  while (!OSCCONbits.LOCK);         // wait for the PLL to lock
  ...

The only knobs (or places I can go wrong that I know of) are in _FOSCSEL() and _FOSC().  I've tried nearly every iteration of those configuration bits that made any bit of sense (even just a wee bit..ok even the ones that made no sense).  I've also tried programming it in debug mode as well as release mode.

Environment: MPLab v8.88.00.00, C30 compiler

Relevant Research:
- section 39.13 on two-speed startup: http://ww1.microchip.com/downloads/en/DeviceDoc/70308B.pdf
- Section 2.7 of the datasheet
- the header file in general, p24HJ128GP502.h, to find the correct macros and configuration masks.

Circuit:
3.3V power supply
the middle pin of the resonator goes to GND, the outer two pins go to OSC1 and OSC2, there is a 1MOhm resistor connecting each of the outer two pins for the 3-pin resonator (for stability)
resonator: ZTT 20.00MX
http://www.ecsxtal.com/store/pdf/zttr.pdf
http://www.digikey.com/scripts/DkSearch/dksus.dll?lang=en&keywords=ztt-20.00mx&WT.term=ztt-20.00mx&WT.mc_id=Crystals%20and%20Oscillators&WT.medium=cpc&WT.campaign=Crystals%20and%20Oscillators&WT.content=text&WT.srch=1&WT.source=google


texts: Boost regulator: Using inductors with greater value than datasheet suggests to improve performance?

texts:
I want to get the best performance out of the Boost Regulator MCP1642B, specifically highest output current at 5v output for low voltage input (0.9v).

The datasheet says :

  the inductance value can range from 2.2 μH to 6.8 μH. An inductance
  value of 4.7 μH is recommended to achieve a good balance between the
  inductor size, the converter load transient response and the minimized
  noise

But it does not explain any further.

It seems obvious that the lower the DCR, and higher Isat the better, (even if there are diminishing returns), and I'm wondering if it's the same for the inductance? For example: would using a 20uH inductor cause problems? And what sort of performance increase, if any might I expect?


texts: FPGA configuration - Multiple Device SelectMAP - sharing PROG line

texts:
So I wanted to program multiple FPGAs (different images) by using a processor over SelectMAP interfaces. I plan on sharing the PROG and INIT lines across the multiple images like this:

This issue I see is that it says in this user guide that when prog is pulsed low, the FPGA configuration is cleared and a new configuration sequence is initiated.
So how does that work with multiple devices? I see the chip selects will be unique to prevent configuring both at the same time, but if I pulse prog low, won't both devices clear the config memory and I will have to program both and not just one?


texts:
We know that ADC 1LSB=Vref/(2^N) where N is the resolution of the ADC.

We know that ADC Effective number of bits (ENOB) is always less than the resolution "N".

When calculating 1LSB do I need to take 1LSB = Vref/(2^ENOB) or I need to take  1LSB=Vref/(2^N)


texts: Cas Latency vs Cpu to Memory Access Time

texts:
I'm so confused between cas latency and access time between cpu and memory.

According to this wikipedia page, reading 8 word from ddr3-1600 sdram takes 15~ns,so between memory controller and sdram there is only 15~ns latency for reading 8 word.

But according to this and other sources mention that access time between cpu and (local)memory is 60-100ns?!

So where that extra 40-80ns comes from?


texts:
Figure show a RC phase shift oscillator using Op-Amp with gain 5(Vo/Vi).

My assumption : Circuit is generating a sine wave with a peak to peak voltage of 10v.

Consider positive maximum point (+5V) at the output. A fraction of this voltage is feed to inverting terminal of Op-amp with a 180 degree phase shift. ie -1V ( 180 degree phase shifted value 1/5 of 5 ie barkhausen criteria) reaches negative terminal of Op-amp. This -1V is again amplified by the Op-amp and we will get +5v at the output. That means this is a stable condition.

Then why output voltage is oscillating ?


texts: Field geometry of external magnetic core?

texts:
If there is a coil with an external core, would the polarization of the magnetic field inside it be the opposite of an internal core?

For example, in the image:

If DC current were applied to the wire (black) would the two ferrite core/shell portions (red and blue) contain magnetic fields which added together or which ran in opposite directions?


texts: Can I determine if my Electro magnetic field (EMF) measuring device is in very close proximity to the source of EMF?

texts:
I am trying to solve a problem of identifying programmatically if I (or my measuring device) is in very close proximity to an EMF source.

The situation is, I have an EMF emitting source (sorry if I got the terminology wrong, I am not a physics student) and I also have a device which can measure the EMF in milli Gaus.
The device gives the value of EMF in x, y and z direction and also the total EMF (don't know how it gets this value).

Based on this setting, I am trying to figure out if I can find if my measuring device is in close proximity of the EMF source. By proximity, I mean lower than some preset distance from the source. So a distance measure would be useful. My questions are

Is there a way to know if I am close to the source by getting a measure of the EMF values from my measuring device?
Given that there is lot of interference, what is the best way to tag a set of EMF values for the source so that I can detect when I can (programmatically) determine if I am in close proximity of the device?


texts:
I've noticed that some Altium PCB Libraries contain a designator in a Text field using the .Designator parameter. I've duplicated this in my own libraries, however if I attempt to place a component on the PCB, I have two designators displayed (the default, and the one I added to the library). Is there something I'm missing?

The reason why I ask is I've been working on using some smaller components lately, and the default designator is too large. At the very least this would save me some time in the Inspector.

Any ideas?


texts: RJ11 pinout (serial) for Amplus AM03128-H11 LED display

texts:
I've got an Amplus AM03128-H11 LED display, without the documentation and serial cable.
I found the programming manual online, but I have no idea what the pinout on the serial RJ11 connector is supposed to be.
Anyone out there who knows ?
Or who has one of these devices and is willing to check the wiring for me?


texts: This is a circuit that takes 220V DC as an input. I understand how the 220V AC changed to 10V AC and changed to DC by whole-wave rectifier. But why is it 12V??


texts:
In many cases, it is demanded that filters have a linear phase response (like in the case of FIR).

Why is linearity so important? Why not a constant phase response, or anything else (any other shape)?


texts: Why do electric companies measure in watts, when they be measuring in joules?

texts:
1 Joule is defined as 1 Watt of power working for 1 second.

When the electric bill comes, it says "you've used 5000 Watts, therefore pay us $100".

However, from what I understand, if I turn on a 5000 Watt oven for even three seconds, you can say I used 5000 watts. However, for the purpose of measuring how much energy I used, wouldn't it be more correct to say I used 1500 Joules?

Why then does the electric company measure in watts when really they are charging you based on a combination of the power used and the amount of time you used it for?


texts: understanding p-channel MOSFET unexpected behavior

texts:
I'm fairly inexperienced and while I have an understanding of classic npn and pnp transistors, I'm shaky when it comes to MOSFETs.
I'm looking for an element to act as a switch. This element would be normally ON, when no stimulus is applied. The trigger needs to be a positive voltage, and is intended to turn OFF the element (open the circuit).
After a bit of searching I figured that a P-channel JFET transistor might solve my problem.
There would normally be continuity between Drain and Source, unless I applied a positive voltage to the Gate.
I'm talking about a low power application:

Drain-source voltage: 5V or less
Drain-source current: a few
milliamps are enough
Gate trigger voltage: 5V or less

Maybe hurriedly, I got a FQP27P06 MOSFET and set up a simple test circuit with a LED. I understand this is a MOSFET and not a JFET, but I thought it would work anyway.
I'm using a voltage divider to keep the gate voltage in the specified range (2 to 4V). TBH I don't understand why that's actually specified as a negative voltage: -2 to -4 V.
In my intentions, the LED should always be on unless the button is pressed.

simulate this circuit – Schematic created using CircuitLab
What I'm observing is:

the LED is normally ON
when I press the button the LED goes OFF
when I release the button the LED STAYS OFF. Or maybe it just glows very dimly and then turns OFF again. Sometimes it gets brighter and brighter but never reaches full brightness. This behavior seems to be randomic.
in order to turn the LED back ON again, I need to short the Gate to ground!

I do not understand what's going on. Can someone please help me out?
Thank you


texts:
I'm wondering as to how a system like this:

acts, when their thyristors are controlled in various ways.

The converters are simple enough, but I'm wondering how the graph made around the voltage going over the resistor \$R\$ would look like when the thyristors are set top \$0^\circ\$ and \$90^\circ\$ respectively.


texts:
Would like your help to clear my doubt and confusion for this circuit http://nil.rpc1.org/wordpress/?p=31.

I don't get a sense that how possible the RS232-pin3 TX signal is converted and transmitted out from the IR tx.

As you look into the photo, the RS232 TX is direct connect to anode of Zener and the cathode is connected -> IR transmitter anode -> resistor ->gnd. That's all.

If saying that, it translates from "-12 -> -0."6 and "+12 -> +3.3v" (1n3138 assuming) then transmit out, how would it be possible?

I am thinking ,the connect orientation should be Zener place from ground with anode and cathode -> IR transmitter -anode? Am i right? With this orientation only the voltage translator able to work.

Can some1 explain further?


texts: Difference between clock cycle, machine cycle and instruction cycle of the CPU

texts: There is a lot of ambiguity between the definition of these three terms. So, I wanted to know what is the intuition behind these terms and how all three are connected to each other.


texts:
I've never done contract work before so I'm a bit lost here.  Hopefully this is the correct place to ask such a question, if not.. let me know.

I have the experience necessary to come up with an accurate quote for the development of the electronic product in question, but I'm not sure how it should be presented (email, legal document...) or how payment should be specified.  A lump payment upon completion of the design and delivery of a prototype scares me a bit.  What if the customer decides to back out after all my work and investment in prototype development?  I also think it would be unreasonable for me to ask for total payment up front.  I was thinking of specifying partial payment up front, with the remaining payment upon approval of the delivered prototypes.  Is this reasonable or standard practice?  If so, what would be a reasonable up front percentage?  Does anyone with experience with this type of thing have more knowledge on standard contract engineering quoting practice?

Also, If anyone knows of a good resource for information regarding the business side of things related to contract engineering, that would be greatly appreciated.


texts: Help for a small project for a small electrical circuit?

texts:
I just want to know that if I connect a fan with a dc motor, then as the fan rotates with the help of wind, will it generate power? and how much?
my second question is if it does then how can I use the power for charging a battery?


texts:
i have following doubts about capacitive power supply or transformerless power supply...

what will be real power drawn, will it be 230 x (current flowing through C1) or 6 x (current flowing through LED)...and explain how it would be...

how it is different that if resistor is used of equal impedance instead of C1...i mean resistor will just take power as heat... but wont it be the same with capacitor which dont take power as heat but consuming the same amount as a resistor...

can i assume C2 and zener diode open circuited and why...


texts: Should I use this powerstrip with different voltage on it?

texts:
pic of label: https://i.imgur.com/gKfhmZ3.jpg

See how they marked off something there? The voltage i think. here in this country the normal voltage is 220. The powerboard is imported from germany, and they have it at 230 V. Would that difference affect anything? I bought this without no box, its how its sold. Its the only brand of powerboard sold here thats not generic. its cheaper than APC or alike, for some reason its cornered the market. It also has its plastic pealing off in places for some reason. The other alternative to this from same company is an aluminum one, i guess that one comes without the plastic pealing.

pic of powerboard: https://i.imgur.com/npP4CeY.jpg


texts: Is the Nyquist plot useful in actual electrical engineering?

texts:
I am currently doing a course on linear control theory, and we are covering Nyquist Plot to study phase and gain margin.

I find myself unable to appreciate this concept. One, the proof of the Nyquist criterion is very non-intuitive to me, something about encircling the origin however many times. Secondly, it is almost never used outside of a course on basic control theory in any other courses I have taken so far. I have asked the teaching assistants for the course and they told me they have never seen any application of the Nyquist plot in real life or in their personal research.

I quickly looked up some potential applications on the Nyquist plot on databases such as IEEE Explore. From 1948 - 2018, only 272 instances where Nyquist plot was used in a published paper

Similarly for Nyquist Diagram

And we are only talking about papers, which are theoretical in nature, and very few of these papers go on to become a useful engineering hardware. Not to say many of these papers are extremely low quality.

By comparison, the much later concept of Linear Matrix Inequality (also used in control theory - which we are not taught) is cited over ten-thousand times.

Some commenter also said that my search result for LMI is biased, because it is more like a math property than a control tool, which may include papers that are not control related. How about "model predictive control"?

I can't help but wonder whether or not the Nyquist plot is even that useful in modern electrical engineering.

Sure, if I wanted to design a circuit with a single capacitor and a single inductor, I could potentially use the Nyquist plot to set the parameters to ensure stability. But in the era of supercomputers, GPUs, CPU with billions of transistors, this entire concept seems to be out-of-date and to put it bluntly, useless.

Has anyone seen a Nyquist plot in the design of an actual control system such as a humanoid robot? For a swarm of quadrocopters? Have anyone used a Nyquist plot in the design of self-driving cars, or rover to Mars? It seems that what we are taught in school have not caught up with real world applications.

Can someone please point to some realistic application of the Nyquist plot and the Nyquist stability criterion (if any)?


texts: Can an open loop system replace a close loop system

texts:
I'm thinking about a mathematical possibility how an open loop system can replace a close loop system so here is my explanation
Let's say I have a plant with transfer function as given in image (1)
But to achieve a desired output with minimum effect of disturbances ,I Make it a close loop with unity feedback and it works very well (image 2)
this time I make a Cascade connection with plant such that overall transfer function is same as close loop transfer function (image 3)
Since transfer function in this case is equal to previous close loop transfer function so for the same input output should be same in both conditions , so we can say an open loop replaced a close loop system?
Problems-
1.but intuitvily it feels that it cannot possible , so there must be something that I'm missing , so where I'm going wrong ?

Why close loop system cannot be replaced by open loop system although mathematical conditions are satisfied(as I shown by example)


texts: STM32 USB device is not recognized by PC

texts:
I have a Nucleo-F746ZG and an F429ZI board, both of the board can be recognized by PC as a USB device via ST-LINK USB port.

However, due to project space limitation, I have to detach the ST-LINK and use the other USB connector(CN13 USER USB).

When I use the CN13 USB connector, I gave the board external power supply 12V to VIN as manual described, but there is no response on PC, not even the 'Unknown device', am I missing something there? Thanks.


texts: RF power changing with different bandwidth selected

texts:
I am trying to measure a radio TX power that is plugged directly to my spectrum analyzer with a -40db attenuator to compare to what the manufacture claims it be and I have few question.
The manufacture claims that the RF power is 30dBm regardless of the bandwidth that is selected. The bandwidth can be selected from 1MHz to 8MHz at frequency from 1.8GHz to 1.85GHz. I understand with higher bandwidth my sensitivity decreases.
However, I am not measuring 30dBm on all BW or I am measuring it wrong so I need some clarification of how exactly to interpret the data I have gathered.
I have tested that radio in all 4 BW (1MHz, 2MHz, 4MHz, 8MHz) all have the TX power output selected at 30dbm. With 40db attenuator I know that I should see -10dbm with some losses in the cable.
Here is the results I got from setting the spectrum analyzer to hold max value and looking for peak:
@1MHz BW: -10dbm
@2MHz BW: -12dbm
@4MHz BW: -14.9dbm
@8MHz BW: -17.8dbm
My question is, when they claim a 1W radio, do they look for a peak of the signal or is it an integration of the entire bandwidth that is 1W. Because if it is the latter then the radio might be as advertised. Since the area under the curve most likely is the same since with higher bandwidth the average power looks the same (I didn't do any math to verify this I am just assuming based on what I saw on the spectrum output)
However, if it is the peak power that is supposed to be 30dbm regardless of the bandwidth used and we just lose receive sensitivity with higher bandwidth then perhaps something is not right here.
The manufacture is a small company and I have been having difficult time getting in contact with their engineers so that is why I am here hopping some one that has had some experience in this kind of thing that can shed some light on it.
Thanks


texts: Why Collector-to-Base currents ratio in a BJT transistor always greater than 1?

texts:
According to this answer:

  Note that the holes injected into Emitter are supplied from Base
  electrode (Base current), whereas the electrons injected into the Base
  are supplied from Emitter electrode (Emitter current). The ratio
  between these currents is what makes BJT a current amplifying device -
  small current at Base terminal can cause a much higher current at
  Emitter terminal. The conventional current amplification is defined as
  Collector-to-Base currents ratio, but it is the ratio between the
  above currents which makes any current amplification possible.

First off, Why collector current increases as base current increase? Is the former causes the later, or the later causes the former, or something else (voltage on electrodes, maybe) causes both?

And here is my question, Why collector current always increases more than the increment of base current? Say after something changes, a extra holes are "injected into" emitter region, and b extra electrons are injected into base region. Then why b is greater to a?


texts: TP4056 and li ion battery charging that never ends

texts:
I have designed a circuit with a Nodemcu ESP8266 (something similar to an arduino nano, requiring 3.3V to work) and I would like to have a backup battery to be robust to main power interruptions.

So far, it seems that one approach is to use a li ion battery and a charger. Therefore I bouth a 14500 Li ion battery (AA sized, rated 1200mAh but, you know with chinese batteries this is not reliable) and a TP4056 circuit that comes with OUTPUT + and - pins. This is supposed to be able to charge the battery without overcharging it, while giving stable power to my circuit.

This is the charging module:

battery connected to pin B+ & B-
input provided to pin input + & -
output taken from OUT+ & OUT-

Basically, this works. The problem is that, after some times the battery is on charge, the board switch to "full charge reached" (blue pin), and, in a few seconds, switch back to "charging" (red pin), then again "charged" and so on.

The firmware used by the nodemcu has a deepsleep cycle of 2 sec, than it wakes up for ~40ms, then back to deepsleep.
In the current version, the deepsleep uses 15 mA (please note, this is a terrible value for deepsleep, in the real use case it uses 200 uA) while taking 30-40mA when wake up.
It seems to me that the charging board switch from "charged" to "charging" when the nodemcu wakes up.

A final note: I'm giving the 5V input to the charging module from an isolated 220ac-5vc converter, which is supposed to be able to provide 800mA. The charging board is supposed to manage and input current up to 1A. Could it be the problem?

15/12/2018 Edit: I realized the following circuit thanks to @RussellMcMahon comment below:

simulate this circuit – Schematic created using CircuitLab

TP2104 datasheet

This circuit work as intended:

The voltage drop on vbat is reduced (with respect to using a diode)
When PSU is available, no current is drawn from the battery

Well, actually "sort of"! When PSU is on, a very small amount of current (2.5uA) is drawn from the battery. Is it correct? Should I change something in this circuit, or given the fact this current is so small, should I just ignore that?
May it be useful, the battery I am now using is rated 2200mAh.


texts: Why do some capacitors leak and other capacitors hardly leak at all?

texts:
I just found out that some capacitors hardly leak whereas other types of capacitors leak a lot of current through the dielectric. I’ve looked at Wikipedia and found several links (Leakage and Capacitor plague) which does not really described the current leakage (to the best of my understanding). The capacitors we used worked well and were not damaged in any way that I could see.

Questions:

What causes capacitors to leak?
Which type of capacitor leak more: electrolytic or non- electrolytic capacitors? Does the direction of the electrolytic capacitor matter for current leak?
From my experience, does one get more leakage current if the electrolytic capacitors is reversed? If so why?


texts: Switch-mode power supply output voltage manipulation via feedback node

texts:
I'm trying to design a cheap way to pull current from the feedback node of a SMPS in order to dynamically control the output voltage, as explained in this application note:http://www.ti.com/lit/an/slva861/slva861.pdf. The DAC of my microcontroller is unable to provide enough current to drive the BJT so I'm using an op amp to drive the base of the BJT.

Here is what I have so far:

simulate this circuit – Schematic created using CircuitLab

I want to control Q1 in its saturation region so that it behaves like a resistor that decreases in resistance as VDAC increases, but I'm not sure which resistance values to use for R3 and R4. I tested the circuit with R3 = 500 and R4 = 500, but the saturation region of the BJT only lasted between VDAC = 2.28V and VDAC = 2.35V, at which point the BJT enters forward active mode. My question is this: what resistance values for R3 and R4 should I use to increase the range of values of VDAC in which the BJT will operate in saturation mode?


texts:
Every laptop has one - a touchpad/trackpad - for controlling the mouse.

I'd like to build my own, external one. I've looked around and I cannot find a tutorial. I have come across 1 example where a webcam is used, but this is an optical touchpad, whereas I want a capacitive touchpad. I don't want to build a tiny one like on laptops; I want to make one at least the size of a mousepad.

Work by Yang Zhang is great and I'd love to do this, but unfortunately I cannot find an demo (checked his github for code, too).

Can anyone point me in the right direction or provide some information? Thanks.


texts:
I am trying to get the pwm working on the Atmel Xmega256A3BU. I am not getting the desired PWM on the port pin. Here's my initialization for the PWM generation in the code.

void pwm_init()
{
 PORTC_DIR = 0x01;             //Set PC.0 as the output port
 TCC1_PER = 0xFFFF;            //Set the period of the waveform
 TCC1_CTRLB |= 0x03;           //Single slope mode
 TCC1_CTRLB |= 0x10;           //channel selection CCAEN
 TCC1_CTRLA |= 0x02;           //clock selection clk/2
}
void main( void )
{
  pwm_init();
  TCC1_CCABUF = 0x7FFF;                      //set the duty cycle as 50%
  while((TCC1_INTFLAGS & 0x01) == 0);     //wait for the new compare value to be loaded
  TCC1_INTFLAGS = 0x00;                   //clear the interrupt flag
  while(1);
 }

Here, I have just provided the snippet of my code which is running at 32MHz. So what else am I missing here ? Any help would be much appreciated. I am doing this in the AVR IAR workbench. So if anyone can share your PWM code that would be helpful too.


texts: Changing frequency of input clock port (FPGA)

texts:
I', using xilinx ultrascale FPGA (xcku025-ffva-1-a)

I am referring to application notes provided by xilinx.

I am going to use the reference code provided in xapp1315.

In this reference code, an external clock of 100 MHz enters to FPGA, passes IBUFDS_DIFF_OUT, and then goes to idelaye3.

I am going to design my top file containing this logic as shown in the picture below

The reference code  should receive 100 MHZ external clocks (go to IBUFDS), but my top design has only 50 MHZ external clocks.

What's the best way to solve a case like this?


texts: Found a particular chip, now I can't find it again

texts:
A couple of weeks ago, I stumbled on a particular chip. At the time I didn't need it, but now I do and I can't find it again.
The chip was a 4-16 line demultiplexer, but its input came from an I2C interface, not from 4 input pins. You send it a 4-bit address, followed by a 1-bit setting, and it sets that pin to the value specified, without changing any other pin. For example, if you sent 3, 1 it would set pin 3 high. If you then follow that with, say, 7,0 the chip would set pin 7 to low, but leave pin 3 alone.
Other details about this chip that I remember is that it has a QSOP package, and I believe it uses a 3.5v supply. Neither of these are critical specifications for me, those are just details about this particular chip that I remember.
I've tried searching DigiKey, and replicating my previous Google search, but to no avail. Can anyone give any hints on how to find this chip? Or if you recognize the chip, could you please let me know its part number?
Much appreciated!
EDITED TO ADD:
It isn't an I/O expander. This chip is an i2c peripheral device, with its own i2c address block (0x20 if I recall correctly, and yes I've searched for chips with that address block :) ).
It is somewhat similar to a 74x154 decoder/demultiplexer, in that it has 16 distinct output pins (see 74x154 datasheet). The major differences between it and the 74x154 is that the chip I'm looking for has an i2c input interface (instead of 4 dedicated input address pins, enable pins, etc.); each output pin can individually be high or low (the 74x154 can have at most one output pin low at any given time; all others must be high); and changing the value of one output pin does not affect the other output pins.
I want to use a couple of these with an Arduino, to control somewhere around 25 distinct outputs. I'd rather use 2 Arduino pins for i2c interface, than 25 dedicated output pins.
EDIT 2:
On closer examination of I/O expanders, I realized I misunderstood what an I/O expander is. It does sound like an I/O expander, so I'll check those out.


texts:
first of all:
I know that a completely discharged battery is damaged permanently. I know it experiences irreversible chemical changes. I know it might blow up if you try to charge it. But that's not at all relevant to my question:

Is it safe to discharge Li-Ion to 0V and short it permanently afterwards?

Point of this question is: I do recycle lot of old batteries (Smartphones, Laptops, ...) and of course I also have to dispose some of them from time to time.
But before I dispose them, I have to store them... And I personally want to store them in the most safe state possible.

Storing them "discharged" to ~3V with the device they were used in still preserves lots of energy in the battery. If I store it with ~3V and, let's say, accidentally drop a huge nail on it, it might still go bang.

Discharging it to 0V and shorting it out, I feel a lot safe - at least I think so. This ensures there is no electrical energy in it left and thus no short circuit current might get it to explode.
However, I know pretty much nothing about the chemical changes in the cell and what actually might happen if the battery discharged to 0V (and shorted) might get damaged by a nail or if it even might blow up by its own.

So, is it safe to discharge a Li-Ion battery to 0V and short it? Is it even better than disposing it with 3V charge left (if you have the know-how to discharge it properly of course)?

Thx!


texts:
What I've:-
I'm using MCP3909 energy metering chip ,
I'm setting this chip in pulse output mode which gives output pulses proportional to the real power .
The used shunt resistor is 200 u Ohm .
Here's the full design:-

What I did:
1- Fully testing the circuit --No connection errors
2- Applied AC input (220 V) with load (lamp ) -- worked
3- Applied DC input(5V -USB ) with load(LED) -- worked
4- Removed the MCU , to check if there's a programming error or something
Circuit behavior:
In all previous test LEDS (D1 -OFF ,D2 & D3 -ON ) respectively (HFOUT ,FOUT0 & FOUT1 )
My questions:
1- MCP initially works in Pulse output mode , right ? this means that LEDS should toggle
in case of any load
2- Why there is very small  voltage drop on the 200 u ohm shunt resistor ? I applied 4 A load on it ? but no pulses from MCP is out ?
3- Am I operating the MCP 3909 right in the pulse output Mode ?
4- Why FOUT0 & FOUT1 are always ON ?
5- I checked the Pin Input Ref in/Out , the voltage on it was 0.5 V , it has a 100 nf cap to ground


texts: Testing the RF properties of an enclosure

texts:
I need to measure RF (cellular) blocking properties of an enclosure.

Is there an off-the-shelf set of tools for doing this?
I'm assuming a MHz signal generator and an oscilloscope with an antenna would do, but is there something more suited for the task?


texts: ASIC gate count estimation and SRAM vs flip-flops

texts:
I'd like to be able to estimate gate counts of different designs for the purpose of architectural exploration.
Below is what I found out. Please feel free to correct, comment, expand.
Logic gates
Two input NAND (NAND2) = 4 T(ransistors) = 1 gate
NOT = 2 T = 0.5 gates
Two input AND = NAND2 + NOT = 1.5 gates ?
N inputs NAND = 2*N T = N/2 gates ? Max reasonable N ?
XOR = 4 gates
Half adder = 5 gates
Full adder = 9 gates
Muxes
MUX 2 :1 = 4 gates or 3 NAND2 + NOT = 3.5 gates ?
Multiple input muxes can be built from MUX2_1 or with multiple input NANDs (see above)
If anyone has some more data points for MUX 4:1, 8:1, 16:1, etc
Mux 2:1 with transmission gates = 4 T = 1 gate
How do I extend this to multiple input muxes ? What's the trade off with gate muxes ?
From this discussion, muxes tend to be transmission gate.
Flip-Flops (FFs)
Synchronous D FF = 6 gates
Enabled, synchronous D FF = D FF + MUX2_1 = 6 + 4 = 10 gates, 6 + 1 (transmission gate mux) = 7 gates, 6 + gated clock = 7 gates ? Which one is more common ?
RAMs
RAMs made with D FFs => 7-10 gates/bit + suitable muxes (see above).
RAMs cell = 6T/bit = 1.5 gates/bit, dual port = 8T = 2 gates/bit
Now, this is the important part for me. From the above, RAM cells seem so much better but I remember a friend of mine telling me years ago, for a 256x8 RAM that "it wasn't worth it, might as well doing it with FFs".
I assume that there's some overhead here. In my designs I often consider small memories such as 64x8 or 128x16 and I'd really like to understand when one method is better than another. Some simple rule such as "when the number of bits is < then...", "when the depth is <, then...." etc.


texts: Can "over rated" cable impact power drain?

texts: I am rebuilding an eGo-T (3.7v +/- 0.5) and wanted to replace the sub-standard wiring that was starting to show signs of heat damage. For some stupid reason I got rid of most of my supplies to save space earlier this year. I have a length of cable which was designed to carry mains voltage (UK so <>230v) at lower amps (3-5, but not entirely sure it is industry standard any more). It is significantly thicker copper than the wire I will replace. Will this wire create a non trivial resistance increase or any other problems that I should be aware of?


texts: What is the box at the end of a USB cable?

texts:
Not the cylinder that hangs onto the cable itself; the actual box at the end that you grab onto in order to pull it out or push it in. They often have the USB logo on them.

Is it some sort of circuitry to handle serialization or timing? Or just to make the cord easier to plug/unplug? They're prohibitively bulky for some applications, and I can't seem to find cables that have smaller ones or none altogether (at least not without knowing what they're called or what they're for).


texts: slayer exciter(tesla coil) circuit modification to allow better audio input

texts:
So I have the circuit working with a kit but the only thing is the audio aux has this offset voltage or some high voltage output I suspect. So when I plug my phone to the tesla coil through the audio jack, there is strong interference. Can anyone offer a solution to the interference? The coil can sing fine, but this interference is really annoying making my phone glitch and I'm worried it might break it. My phone only glitch and the touchscreen becomes odd and non-responsive when the aux is plugged into my phone.

Thanks


texts:
I'm doing a bit of reverse engineering on my Das Keyboard Model S Ultimate. I'm beginning to develop a pretty good understanding of the circuitry, but I am confused about one type of component on the board.

There are 4-5 components on this board with the reference designator of LB. This isn't a standard refdes that I'm aware of and I can't think of anything that I would label as LB. What might this component be? You can see one of them pictured here near the smaller connector.

Description: They look to be about the same size as an 0805 capacitor but gray instead of that brownish color of a cap. It isn't as dark as a resistor either.


texts:
I was analyzing the below circuit. In this circuit an opamp supply voltage (V+ − V) = 16V is powered by using a 45V supply and a -5V supply.
I understand the circuit to some extent.
Here U1 is supply voltage is varied such that V+ - V- is always kept as 16V.
I need a few clarifications

What is the role of the capacitor C3?
Why is the U1 output connected to the junction of R2 and R3?
How do I do design calculations for circuits like this?
How can I perform a stability analysis?


texts: I have this project in MIPS and I read in user input of 10 integers into an array of length 10. After reading them I need to iterate through the array and add the odd numbers (not odd numbered elements, any number in the array that isn't even) together and return the sum of the odd numbers. I believe that I am correctly reading in the array but I am not entirely sure(correct me if I am wrong). I need help checking which numbers are odd. I am thinking to use modulo but I don't know how to implement it. Maybe there is a better way that I am not seeing?


texts: What is the correct replacement for this mosfet?

texts:
I'm trying to repair a broken DC-ATX power supply that I have.
After a bit of searching for faults I believe I have tracked the problem down to one of the MOSFETs.

I would like to try replace this MOSFET and see if doing so fixes the supply.
The problem is that I'm not 100% sure how to identify the correct replace
If I search 50N03 I find various different manufacturers components often with a "-11" or similar appended, though a few without, and all of them seem to have slightly different specificaitons.

How can I ascertain the correct part to buy here, also I'm not sure anyway local (nowhere I've looked so far seems to) has any 50N03 at all - are there any possible substitutes that anyone knows of that would do the same job?

Can anyone tell me what the "64B8F" code means, I can't seem to find much if I search for this?


texts:
I'm looking for a mechanical on/off rocker or toggle switch that can be reset to a default state and position upon the removal of power.

The application is in a vehicle where I want the switch to return to a default position once the ignition is turned off.

I know how to make such a switch using some digital logic and a momentary action, but the application requires better tactile feedback (and the ability to operate the switch without looking at it).

Does such a mechanical switch exist?

I found: Resettable latching switches
and http://en.wikipedia.org/wiki/Relay#Latching_relay, which are close, but do not physically put the switch back in the original position.

EDIT: To clarify, the switch is to control a GPS tracker.  I want the tracker to be "on" whenever the vehicle is powered up, but the operator needs the option to toggle the GPS unit on/off while they're moving around.  I don't want someone to accidentally leave the switch in the "off" position and have the next operator forget to activate it.  It's vehicle-voltage (24V in this case), low current (10's of mA).


texts: How to add hundreds or thousand I/O pins to a microcontroller?

texts:
Suppose that there is a normal microcontroller with i2c port (for example Arduino or Raspberry pi) that we want to extend its i/o ports to  hundreds or even thousands. What ways are there to extend the microcontroller?
there are some solutions which some people says:
Solution 1: connecting 9 pins of micro to a DEMUX (for example 1-256 DEMUX, 8 bit for address and 1 bit for data) so we have 256 I/O lines. but by this solution we can set only 1 line of 256 lines using the address lines; how to access all 256 pins to read and write from/to them simultaneously?
Solution 2: using i2c GPIO chips. but GPIO chips have limited number of pins (for example 100 pins); how to use them for hundreds or even thousands pins?
Solution 3: i think (but i dont know is it possible in electronic industry or not?) by creating a microcontroller like a cpu chip in the shape of surface with thousands pins.
Please simply help me about these 3 solutions and if there are other solutions.


texts: Why does reflection only applies to transmission lines?

texts:
Why does the concept of wave reflection seem to only apply to transmission lines? For example, for a simple circuit with two resistances R1 = 50\$\Omega\$ and R2 = 75\$\Omega\$, is the voltage wave coming from the first resistance reflected by the amount:

\$ \Gamma = \dfrac{75-50}{75+50} = 0.2\$ ?

Then it would mean a \$(0.2)^2 = 0.04 = 4\%\$ power reflection and a \$1 - 0.04 = 96\%\$ power transfer. But then what is the incident power?

I guess you could brush it off as "transmission lines and resistances are different things" but then what IS the fundamental distinction between them? You kind of have a "wave" of electrons "travelling" in a resistance, and I guess that if they hit another resistance with a different ability to let electrons "travel", then they should partially go back, hence be reflected.


texts: How does one position control a voice coil actuator?

texts:
I am looking at trying to position control a voice coil actuator (something like these).  On the end of the voice coil actuator will be a small load (let's just imagine a 10 oz cube), screwed onto the end of the shaft.

Here is where I come from.  When position controlling a spring-return solenoid with a feedback sensor, it's relatively simple: to move the solenoid out to position X, you control the power based on the feedback signal's value.  The more power you input, the further out the shaft moves.

I am wondering, how does one actually conduct position control on a voice coil actuator?  In other words, to hold the shaft static at position X, does it require a constant voltage/current?  Or, can you remove the input voltage/current, and have the shaft not move?


texts: Blinking an LED as a function of signal frequency

texts:
I wrote a function for interacting with my 'PIC16F1788'. The code sends pulses out the 'RC4' port at a specific frequency, to make an LED blink according to that frequency. So the LED will blink faster or slower depending on the magnitude of the frequency. I decided to take a blinking code and vary the delay time according to my input frequency as follows.

void blink(int frequency){
/* starts the LED blinking at a particular frequency */

     PORTCbits.RC4=0XFF;  // RC4 on
     __delay_ms(1000/frequency);   // time in ms dealing with frequency values in kHz
     PORTcbits.RC4=0X00;   // RC4 off
     __delay_ms(1000/frequency);   // time in ms dealing with frequency values in kHz

}

would this code work, is this a good idea ,and is there anyway that I could improve it?

Update #1

I changes my code based on some of your inputs But still no luck running it. it compiles just fine but the LED doesn't Blink =(

#include <htc.h>
#include <pic.h>
#include <pic16f1788.h>
#include <xc.h>
// Config word
#define frequ  100000
#define _XTAL_FREQ   20000000

void main()

{

   // output

TRISB5 = 0;

// configure CCP3

CCP3CONbits.CCP3M = 0x0C;   // set it to PWM mode; and active high

// configure Timer 2
PR2 = ((_XTAL_FREQ)/(4*16*frequ))-1;  // Timer 2 max value is (20MHz / 4*16*f)-1 = max duty, fosc=20MHz, prescaler of 16
CCPR3 = 0.5*(PR2+1);        // CCP3 compare value is 50% duty cycle
T2CONbits.T2OUTPS = 0x02;   // Timer 2 prescaler 16
T2CONbits.TMR2ON = 1;       // Timer 2 on

}


texts: What is read latency in ram summary in VHDL

texts: Hi I am using a single port ram which is constructed using block memory generator in Vivado. When I am reading its summery, something caught my eye. In summary it says total port a read latency: 2 clock cycle(s). What does that mean and how does it affect my operations??


texts: I'm trying to think of the best way to convert a PWM signal into an analog signal. I could use an RC filter, but that requires a very high PWM frequency to create a faithful reproduction of the signal. In my case I'm dealing with audio frequencies for the analog signal - up to 20 kHz. So, what other options are there?


texts:
I can't figure out why exactly the no. of comparators is (2^n)-1 in a parallel type ADC.

The truth table (shown below) for a three bit priority encoder say that there must be at least one HIGH input for the valid output. But as I was reading the Digital Fundamentals by Thomas L. Floyd, the figure shows that the pin 0 of the priority encoder is grounded(it's a reference point and can be any level of volts but I am taking it to be zero as a common practice). So when every output of comparator is 0, all the inputs of the priority encoder are 0.

Is this input valid? Or is it me that is taking the ground to be 0V, rather than some +ve volts to keep this pin high every time?

Here is a screenshot of the circuit shown in the book I am going through.