texts: Isn't there a mistake at the correction? Bas shouldn't turn on when V1 > 0

texts:
So there a table depending on the values of V1, the book solved it like this:
+----+---+---+-----+------+
| V1 | S | R | BAS | HAUT |
+----+---+---+-----+------+
|V1>0| 1 | 0 |  1  |   0  |
+----+-------------+------+
|V1<0| 0 | 1 |  0  |   1  |
+----+-------------+------+

I don't get it. Is this correct? I have questions about this:

When V1>0: Why Bas = 1 when S = 1? It doesn't make any sense. Isn't Haut supposed to be 1 instead since S = 1 and R = 0? I have the same question about when V1 is negative.

Why S = 1 and R = 0 anyway? Isn't it supposed to be 0 for each of them? Since the result of F1(when V1 is positive) = 1, then it should pass to S = 1(Then it becomes 0 since it's inverted) and R = 1 too(Then it becomes 0)


texts: Super Capacitor Charge and Discharge Circuit

texts:
I am working on adding a super-capacitor to one of my 5V lines. Foolishly I tried adding the super-capacitor directly to the 5V line, but it over stresses my regulator to charge it all at once.

I am trying to design a very simple charging/ discharging circuit. Would this be the proper way to charge a large (2.2F 5.5V) super-capacitor?


texts: Reading from file in every rising edge of the clock in VHDL

texts:
Hi I am trying to read data from a file which contains 62500 lines of 12-bit binary numbers in order to instantiate my 2D array(sort of a RAM). However, my problem is that this process happens in one clock cycle, which puts extreme amount of pressure on the hardware and synthesis does not end. I want to read one line of data from file in every clock cycle. However, I cannot because the function I call is not very open to modification. How can I read a single line of data in every clock cycle??

Here is what I have so far after weeks of research and experimentation

 type RamType is array(0 to PICTURE_WIDTH_HEIGHT - 1, 0 to
 PICTURE_WIDTH_HEIGHT - 1) of bit_vector(11 downto 0);

 impure function InitRamFromFile (RamFileName : in string) return RamType is
 FILE RamFile : text is in RamFileName;
 variable RamFileLine : line;
 variable RAM : RamType;
 begin
 for y in 0 to 249 loop
 for x in 0 to 249 loop
 readline (RamFile, RamFileLine);
 read (RamFileLine, RAM(x,y));
 end loop;
 end loop;
 return RAM;
 end function;

 signal RAM : RamType :=
 InitRamFromFile("\\ASUS\Users\AsusPc\Desktop\project_son\pictureData.data");

I tried to replace nested FOR loops above with nested IFs and convert variables above to signals in order to make this process suitable for my purpose but I received errors which simply says RamFile and RamFileLine must be variable. I have already run out of ideas. Please help me. I am using BASYS3 board and Vivado2017.2 environment.

By the way, picture_height_width is 250 and I did not do what I said above in function. I got rid of function decleration and tried to do it in classic manner.

pictureData.data contains pure binary data and nothing else.


texts: I'm looking for free software to create drawings of communication cables eg. DE-9, RJ-45, Ribbon Cables, and Molex. I can't seem to find any software that comes with images of the connectors that can also be used to show how the cable is wired. I've done some cable drawings by hand, but I'm really looking for a way to create more professional looking drawings without spending days creating the connector drawings myself in AutoCAD. I’d like to find software like Fritzing, but with a bigger collection of parts. They have DB-25, but not DE-9. What software do people use to create drawings of a cable?


texts: I need circuit able to detect the minimum value of a positive signal

texts:
I'm asking if there is a circuit configuration able to store the minimum positive value (Vmin) of a stochastic signal like in the picture.

I don't know its main value since what i need is a real-time detection of an acquired random signal, therefore i need something similar to a peak detector able to store Vmin (I repeat, it's always a positive value).

Can you help me?


texts: Programming ARM Option Bytes using Assembly Directives

texts:
So, having a look at the datasheet for a specific ARM controller, we find the address space to be mapped out as follows:

There are number of ways to accomplish this, one of which is through an auto-generated file that has the following (condensed) contents:

; Option byte organization
;-------------------------
;   Address     [31:24] [23:16] [15:8] [7:0]
; 0x1FF80000       -     nRDP      -    RDP     (0xFF5500AA)
; 0x1FF80004       -     nUSER     -    USER    (0xFF870078)
; 0x1FF80008     nWRP1   nWRP0   WRP1   WRP0    (0xFFFF0000)
; 0x1FF8000C     nWRP3   nWRP2   WRP3   WRP2    (0xFFFF0000)

FLASH_OPT       EQU     1

RDP             EQU     0xAA
nRDP            EQU     RDP:EOR:0xFF
WRP00           EQU     0x00
WRP01           EQU     0x00
WRP02           EQU     0x00
WRP03           EQU     0x00
nWRP00          EQU     WRP00:EOR:0xFF
nWRP01          EQU     WRP01:EOR:0xFF
nWRP02          EQU     WRP02:EOR:0xFF
nWRP03          EQU     WRP03:EOR:0xFF
USER            EQU     0x78
nUSER           EQU     USER:EOR:0xFF

IF      FLASH_OPT <> 0
    AREA    |.ARM.__AT_0x1FF80000|, CODE, READONLY
        DCB     RDP,   0x00,   nRDP,   0xFF
        DCB     USER,  0x00,   nUSER,  0xFF
        DCB     WRP00, WRP01,  nWRP00, nWRP01
        DCB     WRP02, WRP03,  nWRP02, nWRP03
ENDIF

It appears as if this file is simply giving a nicely configurable way to set these option bytes, but how is it being done? I did a bit of research and it turns out that the AREA directive tells the assembler to generate a new area, in this case a code area that will be read only.

Further, the DCB directive allocates memory, in this case 16 bytes, and initializes them with the respective values given.

My question, then, is where is the specification regarding this newly allocated memory block's location? Namely, how does the value of this 16 byte block get written to the appropriate registers (0x1FF80000, etc) ?

The only mention of this address is given by the |.ARM.__AT_0x1FF80000| argument passed to AREA. However, this first argument is only the name of this new area according to the documentation.

Or maybe the better question is: How can we specify where an AREA will be stored in memory?


texts: How is this circuit a voltage regulator?

texts: I understand how the v_o expression is found, but I don't really understand how or why it's a voltage regulator.


texts: MBED Controller Module Datasheet and Pin Details

texts: I want to connect the output pins of NXP MBED controller to 16 electromechanical relays,and 32 LEDs,what is the best way to do this?The relay would require a current of at least 300mA and LED would be 1.5-2.5V rating LED.And where can I find a datasheet that gives the input and output voltage and current specifications of each of the 40 pins in  NXP MBED contoller's DIP package?When I look for it in google only the datasheets for the LPC1768/65/67,etc. turns up but not for the 40 PIN DIP MBED controller


texts: If one were to use a transformer to increase the voltage to a motor, while at the same time decreasing the maximum current to the motor. Would this have a similar effect as moving to a higher gear in car. Whereas the angular velocity of the motor would increase while the maximum tourque decreases.


texts:
How would one go about handling errors in AVR interfaces that do not specifically provide any acknowledgement scheme?

For example, I have an I2C temperature sensor which I poll every 1 hour. So every hour my AVR sends a TWI start condition to the sensor and gets the temperature at the end of it.Now
tet's say for some reason the sensor does not respond. Maybe it's been taken out, burned out etc.
So how can I check for such in my code and inform the user?

Right now I am using the polling method. Infinite loop till TWINT is set in the TWCR register

while ((TWCR & (1<<TWINT)) == 0){};
return TWDR;


texts: Need to make sure Thyristor switches off with rectified AC

texts:
So I have full-wave rectified AC from mains and the following circuit which is basically a AC dimmer that takes slices of that for a much lower total average voltage.

(Voltage source is labeled as an offsett-ed "triangle" below as I thought it approximates it best for now, damn simulation kit doesn't even have a bridge rectifier...)

Now, it's important that the Thyristor turn off at 0V of the rectified AC, so the cycle start anew of turning the Thyristor on and off. But I'm utterly unfamiliar with rectified AC and don't know if the current will absolutely 0A at 0V, though I know a resistor on AC is perfectly phased with voltage... I don't know, even maybe C1 or C2 might change the intended results...

Or, is it enough for me to pick a Thyristor whose Holding Current is in the hundred microamps range (or higher), so it cuts off??

EDIT:

Also, does C1 and C2 both have to have rating of at least 120V?? Don't they get charge on max up to 30-34V? That's specifically why I chose this design... I can choose lower rating capacitors...

simulate this circuit – Schematic created using CircuitLab


texts:
I have been learning(trying to at least) how to work with pic microcontrollers, and I have noticed this behavior that I am not sure whether it is just my fault or is supposed to happen. I wrote the below program with hopes to make an led blink. It does blink just fine, when connected to the pin labeled RA2, but when I connect the led to pin 15 (labeled RA6/OSC2/CLKO on datasheet) the led stays on, as though I had connected it to Vdd. Then when I put it back in RA2 where it belongs, it is off. The only way to get it back on again is connecting a 10k resistor between Vdd and MCLR (like how it is when programming). What is happening here? MCLR is also needed when tapping it to some other pins. Am I causing damage?
The circuit is 3 AA batteries powering the pic, with a 330 resistor and 3mm led in series running from pin 1 (RA2) to pin 5 (ground).
pic16f88 datasheet
Code:

#include <xc.h>

__CONFIG(MCLRE_ON & CP_OFF & WDTE_OFF);

void main(){

    TRISA = 0x0000;
   // RB6 = 0b000010;
    for(;;){
        RA2 = 1;
        Wait();
        RA2 = 0;
        Wait();
    }
}
int Wait(void) // gives me a delay of 1/3rd a second or so
{
for (int i = 0; i < 50; i++)
 {
 }
}


texts: Unusual Surface Mount Package (with notches) - how to mount / solder?

texts:
I have recently acquired an electronics component that I was expecting to have a "normal" surface mount foot that I could solder.

Instead, what is has is a very thick section that has a 0.50mm semi-circular notch (see picture):

What is the appropriate way to mount a device like this? Are the notches designed to take a pin of some kind?

The notches are a standard 2.54mm pitch, and the row spacing is 19mm - I haven't found any kind of socket that would take a component of this size, so I'm assuming it would need to be soldered directly to the PCB?


texts: Ultrasound transducer at different frequencies

texts:
An ultrasound transducer is specified to have two standard frequencies; 820 KHz, and 2.5 MHz, does this mean that any frequency in-between can be used?

If not, what would happen if a generated signal with a different frequency, let's say 1.5 MHz, was connected to the transducer?


texts:
I'm trying to make DC load up to 20A with 1mA precision.
Current sense resistor is 5mΩ, so the voltage on this current sense will be from 5μV to 100mV.
I picked LTC2050HV (datasheet) which have very low input offset (±0.5μV).

This is my circuit:

First opamp (U4) just multiplies voltage on current sense (R21) by factor of 40, so Vout1 can be from 0.2mV to 4V. Second opamp (U2) compares this with voltage set by potentiometer (RV1) (it will be replaced DAC later) and controls power mosfet (Q6).
There is only one power mosfet IRF540N, I am about to add more parallel mosfets later. This is just a testing circuit.

Problem is that there are some oscillations and I'm not able to remove it.
I tried this this circuit with and without capacitors C1, C6, C12. It had impact on shape and magnitude of oscillations, but it is still there. What I am doing wrong? Or how to improve the stability?
My intention is to stabilize current flowing through current sense, and voltage Vout1 which I will push to 16bit ADC.

I tested my circuit with 500mA load. Control voltage (by RV1 potentiometer) is set to 100mV, so load current is 500mA.

C1 and C12 removed, C6 in circuit.
Vshunt:

Vout1:

C6 removed, C1 and C12 in circuit.
Vshunt:

Vout1:

C6 and C12 removed, C1 in circuit.
Vshunt:

Vout1:

So, the best result I get by removing C6 and C12, and keeping C1 in circuit. But Vout1 is still unstable. How to improve it? I would need it under 0.2mV.

Layout:

UPDATE:
My goal is 0.5% accuracy. That is why I picked this opamp.
So measure 1mA is really 1mA. Measured 20A could be between 19.9A and 20.1A.


texts: PCB Design - Simple USB Radio Transceiver

texts:
I'm designing a small USB radio transceiver with 3 main components:

Sparkfun's RFM69HCW 915 MHz Transceiver. [Datasheet]
Microchip's MCP2210 USB-SPI Bridge. [Datasheet]
A simple USB port from Digikey.

However, even with just these three components, there are a huge number of things I'm uncertain about even after scouring the datasheets! I hesitate to ask them separately, since they are all closely related and it would be a waste of space to do so. Any and all help/answers is greatly appreciated.

Here is my current working schematic: J3 is the USB port, U2 in the middle is the MCP2210, and U1 on the right is the RFM69HCW.

MCP2210 Questions:

Page 6 of the datasheet states that VUSB should be bypassed with a .22uF to .47uF capacitor. Will any value from that range work? What design considerations are there? (C8 in the schematic)
Page 6: What value bypass capacitors should I use for VDD? (C3 in the schematic)
Page 6: How do I know if I meet inrush requirements before building any of this?
Page 6: Do I really need to implement a Low-Power Suspend mode? Is it possible to just turn off the option so I don't need to worry about it? If I do need to implement it, what does that entail?
Page 8: What is the logical high voltage of the reset pin? 3.3V or 5V? I'm not sure which rail I need to connect the pullup to.
Page 9: Section 1.9 Oscillator, Note 1 states: "A series resistor may be required for quartz crystals with high drive level." This is the one I'm planning on using: ECS-120-20-5PX-TR. Does it have a "high drive level"? If so, what resistance should I use?

RFM69HCW Questions:

I can't tell whether or not the SPI lines on the radio are OK with being 5V rather than 3.3V (since the MCP2210 datasheet states on page 6 that VDD sets the logic levels for SPI). How would I figure that out since I can't find it in the datasheet?
Is there anything special I need to do signal- or ground-plane-wise, since I have a radio/antenna on board? I've only done digital logic boards before.
Since the radio chip is the only slave, can I just tie its SS pin low so that it's always active? What pulldown value should I use? (R3 in the schematic)
The radio has three ground pins, but only one 3.3V input. Do I need decoupling caps between only the 3.3V and the closest ground pin, or between the 3.3V and each ground?

USB Questions:

What do I attach the USB case to?
Do I need to do any decoupling/bypass at the USB power pins?


texts: LED- Resistor, does the position matter?

texts:
I was reading the MAKE AVR programming. One of the chapters suggests to solder resistor to the cathode side of an LED.

But in our uni labs it's said to connect the resistor "before" the LED; that is connect the resistor to the anode.

Does the positioning of the resistor matter at all? In case of accidentally burning out the LED? If so, how?


texts:
I have designed a board that uses the MIC2251 (SOT-23 package) boost converter to boost 5v from a USB charger to 10v, to power some 2 series LiPo chargers.
http://docs-europe.electrocomponents.com/webdocs/1065/0900766b81065118.pdf

(source: think-engineer.com)
I am experiencing a serious overheating issue, when a single battery is connected the boost converter should be supplying 10v @ 40mA (These are button cell LiPo's). The boost converter and the diode get very hot.
When hooked up to a bench supply the boost converter was drawing an expected current of 10's of mA's, but it got very hot, and after ~5 seconds, the current draw jumped to ~250mA and the boost converter cut out for a second, then this cycle repeated... until the boost converter died.  By died, I mean that there now seems to be a short between VIN and GND.
I am using a 10uH inductor, rated at 2.2A, 58mOhm:
http://docs-europe.electrocomponents.com/webdocs/0f90/0900766b80f90d1a.pdf
Both capacitors are 10uF 0805 16v.
R1 is 100K, and R2 is 14K
Diode is S1JB-13-F Switching Diode, 1A 600V:
http://docs-europe.electrocomponents.com/webdocs/104b/0900766b8104bc04.pdf
I did not put much in the way of thermal relief on the PCB, as I assumed that drawing only ~120mA would not be to strenuous for a boost converter rated at 2A. I have just tried adding a small heat sink to the boost converter and the diode, and I am experiencing the same problem.
Have I done something wrong regarding component selection?
Please can someone explain why the components are getting so hot, and what design considerations would effect the temperature, and how I can get this module to run stably and at a happy temperature.


texts:
Can I amplify the voltage of a USB supply?
 I mean can I increase the voltage from 5V for example to 7V.


texts: Are television transmitters designed to broadcast two or more 6Mhz channels? Do commercial broadcasters do it in practice? If so, what are the limits (2, 3, 4... channels)?


texts:
Is there such a thing as a variant of the 4000 series CMOS logic chips which has TTL compatible inputs?

Something like the 74HCT but for 4000 series.

The reason I ask is that I am looking to switch a number of 12V low current signals from a 3.3V or 5V source (the grids and anodes of a VFD, while the filament is running from a 5V square wave), and 4000 series running at 12V would be ideal for that (e.g., the 4069). However, in all the variants of the 4000 series I have found, the \$V_{IH}\$ scales with the supply voltage (as is normal with CMOS logic), which at 12V puts it way outside the range of a 5V logic signal, let alone a 3.3V one.

Alternatively, can you suggest a different family of chips? It wants ideally to be usable by novices, since it's going to form part of a tutorial.


texts: TP4056 reference design 1R resistor function

texts: From the datasheet of the TP456 li-po charging chip, a 1R resistor is added in series to the 10uF capacitor. I am assuming the capacitor is for signal conditioning. But why is the 1R resistor added? I see this on some datasheets and it is omitted on others.


texts: Eagle DRC width errors on only power traces?

texts:
I am designing a circuit in EAGLE 6.4, and when running all DRCs (I have used OSHPark, SparkFun, and default), my power and ground traces come up as width errors. They are 10 mils wide, which is well within spec, and I have many other signal traces that are also 10 mils wide that do not show up as a width error.

Similarly, any power traces with vias show up as a drill error at the vias. However, vias on the signal traces are fine - and they are the same size!

Any ideas as to why this is happening?


texts: Grounding Yourself When Working On Electronics

texts:
I was wanting to discuss if using a wrist strap connected to a in unpainted screw on a pc power supply (this screw is a mounting screw it is not touching anything inside the power supply) that is not connected or mounted to a computer as a grounding device to avoid static electricity damaging components.

Of course the power would be switched off but it would be connected to the outlet.

Would this be an effective grounding procedure?

Would this still cause static electricity to transfer since electrons transfer to what electronic you are working on since the power supply is not connected it it (like for instance a pc)?


texts: How would I solve for the Norton Current of this circuit?

texts: How do I solve for the Norton Current of this circuit? The resistance is easy enough, but the box with the resistor and current source is tripping me up. How could I solve for that?


texts: I need the full range from an LM34DZ, but I don't have an 1N914 diode. Is there a replacement?

texts: I want to read the full range on my LM34DZ, but I can't seem to find any 1N914 diodes. Is there anything I can replace it with?


texts: Calculate resistance of an unknown resistor in a circuit

texts:
I am currently studying some old exams for the upcoming one and I got stuck on this question, I seem to get the right answer by eyeballing the circuit but I want to be able to calculate the value.

The question is as follows: Calculate the resistance of R2.

What I tried doing was to calculate the voltage in the middle using Kirchoff's current law but I do not know where to go from there.


texts:
I would like to drive a pump with a PLC. The PLC generates analog output signal of 0-10V with 0-20mA and the pump runs at the same voltage but 3A current. Is there any solution to this problem?

Thank you.


texts: How to convert c project to cpp in Keil 5?

texts:
I am currently working on an IMU project with C in keil. But it needs Kalman filter source file. The file is in .cpp format. This filter has classes, which are not supported in C.
How to convert all files to cpp and compile all in cpp?
Edit
I added cpp file and compiled.

Warning: You are compiling one or more files of source type C++
and have selected 'use MicroLIB'.
MicroLIB does not support C++!
Build target 'RT5.0' compiling main.c... ....\Readmax imu\Kalman.h(21):
error: #20: identifier "class" is undefined

.


texts: What is the difference between \$g_m\$ and \$g_{FS}\$?

texts: I am designing a 2N7000 mosfet common source amplifier with \$A_{mid}=5\$ requirement. To design this circuit I looked up 2N7000's datasheet (here) and here it is written \$g_{FS}=320 mS\$. And I am using this formula to calculate gain \$A_{mid}=-g_m(R_L||R_d)(1+\frac{R_f}{R_2})\$ May I use \$g_{FS}\$ value instead of \$g_m\$


texts:
I'm looking for a way to build a zero(ish) cost intervalometer for my Canon SLR using only stuff that I have or can get very cheaply (my budget is about $4). I've already managed to "build" a wired remote for the camera, which is basically two wires connected to the ground and shutter release pins of the Canon remote connector. Touching the two wires (manually or via a switch) causes the camera to click.

I also have an old Android phone lying about that I'd like to repurpose for this project, since the phone is fully programmable. A requirement for this project is that neither the camera nor the phone can be modified in hardware (i.e., no soldering to or dismantling either).

Since the only wired interface in and out of the phone is USB (mini-USB on the phone, if that matters), I was wondering if a modified USB cable could be built that can be controlled via the phone's software, such that the circuit with the camera is completed or broken. Mutilating or otherwise modifying the USB cable itself is OK.

I'm willing to modify the software on the phone, so if this is possible, but the software doesn't support it, I'll figure it out.

Can this even be done? If not, is there an alternative way of doing this without buying a microcontroller, board and other associated stuff? I'm not a hardware guy, so please be gentle ;).


texts: How can I decrease noise while maintaining bandwidth and gain in my Transimpedance amplifier

texts:
I'm a photonics student trying to develop a Transimpedance amplifier for use as a drop in replacement in a photo-detection circuit. I've run in to a wall while designing the circuit. I want a Bandwidth from around 5kHz to 2GHz, a 26dB+ gain and a noise figure around 3-4dB, but no matter what I try I can't get my noise figure below 20 when modelling in Multisim.

An help in figuring out what I can do would be greatly appreciated. I'd also like to know how I could get rid of the 10 Mohm resistors, but the circuit doesn't seem to work right without them.

THANKS!


texts: Toggle output lines on a PIC24FJ64GB110 processor

texts:
I am new to PIC processors, but not new in embedded systems, M16, 8051 etc...

I am trying to do some very basic tasks: like toggle a I/O line.

I have a 5K pull-up resistor on Pin 34 (100 pin chip, PortB10). The problem is, pin34 is always high, never goes down.

void main()

{

  _TRISB10 = 0;  // RB10 output

  _ODB10 = 1;    // open-drain

  Nop();

  Nop();

  _LATB10 = 0;  // or _LATB10 = 1

  while(1)
  {}

}


texts:
I am using a high-speed op-amp (700 MHz unity gain bandwidth). I have got two questions.

1) It has voltage supply marked Vs+, and Vs- but no ground. So say I supply with say +5, and -5V. But there is no ground connection. The circuit which will feed this circuit, has a ground reference. But the op-amp does not have one. So how it can judge when the input voltage is negative.

2) To test, I have set the negative voltage supply to GND. and set it up as voltage follower. The diagram is the output. Yellow is the input, and green is the output. You can see lot of jitter in input and output, the moment I connect the sine wave input to op-amp. But before connecting input was smooth. Input frequency is 4KHz.

Can someone please tell me why?

OP-AMP Part  # OPA2652U (Texas Instruments)


texts: How to deal with simulation/measurement discrepancies of simple RF circuits (e.g. matching) without access to expensive equipment?

texts:
Designing a circuit (PCB) operating at low frequencies is fairly straight forward. However, my design includes a simple RF frontend. The frontend consists of usual componenents on a PCB (SMA connector, transmission lines, L-match, RF switches) and a few RF diodes to convert voltages to DC (where further low frequency processing happens).
This node after the diode is the one node that I can verify/measure with my hobbyist equipment (multimeter/scope). What I measure is clearly way off from my simulations (LTspice).
I am concerned about the L-match: In LTspice, I tried to somewhat capture main parasitic sources [*], then simulate input impedance and design proper L-match (L and C) at 900 MHz which gives me good S11 in the LTspice simulation.
The measurements are totally off. Now what I started to do is to first solder different inductor values for the L-match and see which one gives the highest voltage level after the diodes. Afterwards, I solder different capacitor values and pick the one which gives highest voltage/largest bandwidth. The C value is so small (~1's of pF) that equivalently I can just leave it out.
I destroyed already a board because of all the soldering/desoldering (pad got loose from PCB).
Is this really all I can do under these assumptions?
Is it really fair to say that LTspice simulations are completely useless for RF -- even to first order?
[*]: I add a few pF's to packaging (e.g. RF switches) and PCB traces, model capacitors with proper ESL and ESR and model inductors with proper R and C based on resonance frequency.
PS: Did I mention hobbyist setting? I do not have access to a VNA or TDR.


texts:
I am new to your forum although I often read it and find great help.

I have a problem that I cannot resolve. I am using a 5A CT (1000:1) to measure 110VAC (50Hz) currents of 70 to 90mA which gives me a very small window (200mV in a 5V range) and I need to monitor this little window with a 10 bit ADC with some degree of accuracy and reliability. After many days, I ended up using a MAX368 audio amp and half wave rectifier to deliver the best DC result.

What I would like is to expand my small 200mV window to 2000mV biased at about 2.5V in order to be able to digitally track and react when the window is breached.

Please assist by suggesting aa additional DC amplifier that will expand my DC window./

Thank you for the responses.

Apologies, I meant 10 bit ADC! RMS, ave or peak, no matter. It's a DC output to an ADC.

Burden resistor has been optimized for best results.

40% is arbitrary! Gives me some lee-way for excess breeches of the window.

I want to expand my DC window to achieve the above "arbitrary" value.


texts:
Design Criteria

For a project I'm making I want to measure temperature using a 10 bit ADC on a MCU.

I don't care for absolute accuracy but I would like precision down to around 1/10th of a degree C.

To clarify I'm fine with a bias and gain error and even weak non-linearity , as long as the random error (noise) is low and measurements are consistent between readings of the same temperature.

The sensor will be powered and read once per hour so self heat-up shouldn't be an issue.

I expect that the temperatures I will measure are around 10-40 C. However to have some design headroom I chose to use the range [-40,+100] C as my design criteria when sizing the passives.

Chosen RTD

I chose to do this with a RTD. The particular one I'm looking at has:

0C = 100 R
-50C = ~70 R
+100C = ~140 R

Circuit

The circuit I have come up with is shown below. It has four major components:

A 1mA current source to bias the RTD.
A level shift of the RTD sense.
A scaling of the RTD sense.

The goal of the level shift and scaling of the sensed RTD value is to scale the range of [-50C, +100C] to [5V, 0V] to get maximal use of the 10 bit ADC on the MCU.

The TEMP_EN is connected to a GPIO pin on the MCU, driven high prior to measuring the output with the ADC. The GPIO pin can drive 20 mA max.

I have chosen 300R and 5K11 resistors for this design as they are used elsewhere in the project and actually form very close to the required ratios for the voltage dividers by a happy coincidence.

A simulation of the circuit can be found here.

I used WxMaxima to calculate the resistor values:

Where:

Va = sensed voltage after RTD
Vb = negative input to first op-amp
Vc = positive input to second op-amp
Vd = negative input to second op-amp
A = op-amp gain (assumed ideal later)

I expect 150 C / 2^10 = 0.15 C precision on the measured value.

Question

This is my first time working with Op-Amps after my EE course in Uni which was a long time ago. And my first time building a constant current source. I would very much like input on the design of the current source, will it be good enough? Are there easy modifications I can make to make it better for this application?

Can I expect the circuit to have reasonable noise resistance? The environment is a typical home environment and TEMP_AO is connected via a 30-50cm shielded, otherwise quiet cable to the MCU.

Should I decouple the op-amps? There isn't any switching going on here so I'm unsure if they are needed.

I have the shift before the gain. Should I change the order to do gain first and then shift? Which is better?

Any other considerations I should make?


texts: Circuit to boost PWM voltage using ULN2803a

texts:
I am trying to convert 5v PWM signal to 10v using ULN2803a IC. My target device (a dual channel LED light)expects two 10v pwm signal and GND via a 3.5mm audio connector.
The part I am struggling with is ULN2803a is a sink, i.e. all available circuit for LEDs uses ULN2803a's output pin as GND connection to individual LEDs (since its a sink) while the +ve end of the power supply directly connects +ve end of individual LEDS. This does not work in my case, as I have to provide single GND connection and two +ve (PWM) via the 3.5mm audio connector, thus both channels sharing the same GND connection.
I am a novice, but I can pick up from a circuit/schematic
I am following this post: http://www.haberocean.com/2014/11/simple-circuit-for-controlling-led-strip-using-arduino-mega-and-uln2803/


texts: Testing 8 pin P-Channel MOSFETS on Laptop Motherboard

texts:
My laptop died recently and I’m testing the motherboard. I’m led to believe these two MOFSETs on the board may be part of the issue PQ301 and PQ302.

Using a multimeter continuity and diode mode; PQ302 beeps between S and D on continuity mode and 0 resistance on diode mode. I’m led to believe that means it’s defective. PQ301 does nothing on both modes between the pins.

I’ve been testing them in opposite pairs i.e pins 8 and 1, 7 and 2 etc. Am I testing them correctly and if so should I go ahead and replace the mosfet and see what happens?

Here’s the diagram I’ve been looking at. Just hoping for some guidance. Thanks.


texts: Do HDMI/DVI and DisplayPort transfer only differences or full frames?

texts:
Let's assume I have a static computer desktop on my external display that is attached by HDMI (or equivalently, it could be attached by DVI, as DVI and HDMI are compatible). The 60Hz picture doesn't change at all but stays static instead.

Is HDMI transferring the full picture 60 times per second digitally? Or is there some kind of buffer on the display device, so that HDMI transfers only the modifications to the picture?

Does the answer change when DisplayPort is used instead of HDMI/DVI?


texts: Transformer core radius and number of turns

texts:
I'm trying to solve this question.

For a specified input voltage and frequency, if the equivalent radius
of the core of a transformer is reduced by half, the factor by which
the number of turns in the primary should change to maintain the same
no load current I

If radius is halved, area becomes \$ 1/4\$ times. Hence to maintain the same no load current, there needs to be 4 times the number of turns we had earlier.
But the given answer is 2 times the number of turns. Why is that?


texts: How to properly switch between two power sources with a MOSFET?

texts:
In our application, our board can receive +12V from an adapter jack when working in standalone mode. This 12V is fed into a switching regulator to create a 3.3V supply (named 3V3_2 in the schematics below)

The board can also be connected to a host board via an edge connector, in which case, 3.3V should be supplied by the host board (named 3V3_1 in the schematics below)

What we want to do is that, when the user plugs in an adapter jack, we want the board to automatically use the output of the switching regulator. We are using a jack with a switch. The switch is floating when nothing is plugged in, pulled to ground when an adapter jack is inserted. (The switch signal is terminal 2 in the schematics below)

Please take a look at these two circuits. Would any of these work? Do you foresee any problems with either of these circuits? Are there any other alternatives?


texts: Reading the voltage of an energy harvesting coil using Arduino ADC

texts:
Being developed by us is a kinetic energy harvester that harvests energy as its magnets move through a coil. It is our goal to measure the voltage across the coil when the real system is being moved by an actuator. In order to do so, we have prepared a test bed which moves the kinetic harvester at a particular frequency.

It is important that we sample the voltage across the coil at a particular frequency and send it over UART to MATLAB for further processing. We wish to use an Arduino for this purpose.

The voltage produced by the coil is not a constant voltage. It varies and also becomes negative as magnets move across the coils. I understand that the Arduino ADC cannot sample negative voltages.

I attach a photo of the harvester and the linear actuator that moves the harvester below.

Below is an image of the voltage waveform.  Please note the voltage ranges from -3.3 to +3.3. We are able to confirm this with the help of the oscilloscope. I wish to sample at the highest frequency possible. The higher the accuracy the better the readings would be. We intend to use an Arduino Uno.

If all the voltages produced by the coil were positive the ADC can be directly connected to the coil. But it is definitely not the case. Perhaps some circuit / technique to make the output waveform positive is required. We cannot provide a DC shift to this coil as doing so may change the coltage induced by magnets effecting the system.

Whats required is a method we can sample the ac waveform varying from -3.3 to +3.3 with the help of the arduino ADC.

Any advice is a lot appreciated.


texts: How to remove solder bridges on a 6-layer PCB - how to rework a board that won't heat?

texts:
I made my first batch of 6-layer PCBs. On some of the boards I got a solder bridge on an MCU - I know I need to improve my design, my solder mask, and my mounting method.
Usually on 2- or 4-layer PCBs I don't have any problems removing solder bridges with braid and flux, but on this 6-layer PCB it's nearly impossible. I have a lot of difficulty heating the area and it cools almost immediately. My solder "sticks" on the pin or on the pad and forms aggregates. Do you have any tricks to rework a 6-layer PCB ? Do I need a a heating table? Please help me to find a solution to save my board.
EDIT 2021-01-29
I Buy a cheap IR preheating plate, this save all my boards. I rework them quickly without problem. The 6 layers thermal inertia is impressive.


texts: How can I supplement a portable generator during peak load.

texts: I'm contemplating purchasing a 2000W generator, to power some of my tools. One potential issue i that I have a saw that pulls 2500 W at startup and then 1800 w to run. Seems to my that as the generator runs, it's creating surplus power, and it's only those peak loads that overwhelm it. Would it possible to hook up some sort of large capacitor or power storage device, to supplement the the generator during those peak times? would a battery array and power invert potentially work?


texts: How do I isolate an open collector MISO from a non-open collector MISO?

texts:
I'm using an Arduino to control a PlayStation 2 Controller and microSD card over SPI. As usual, they share a MISO, SCLK, and MOSI pin. Each has their own slave select pin.

The PS2 controller's MISO line is an open collector output, so I would guess that I need a pullup resistor there. How can I isolate this from the other non-open collector MISO? If the non-OC device is active, won't the pullup resistor interfere with its non-OC MISO line?

Thanks,

Edit

I suppose I could use a non-inverting open collector buffer to convert the non-OC output to OC?


texts: What is the typical power that is transmitted through NFC from a smartphone

texts:
I think the question is clear. I only need a reference value, like is it in the range of 1mW or 10mW or 100mW. Clearly this will vary among smartphones. Also do you think it is possible to set the transmitter power from an app on android?

The only real reference I found is this article that states, that during each read event, the phone radiates about 200 milliwatts of power


texts:
I want to make a kill-switch pedal with on/off LEDs for my guitar. I tested a simple schematic but every time I ground the circuit like the schematic i put below i get an error:

  voltage source/wire loop with no resistance

Every kill-switch schematic I have seen, takes the Input sleeve to the Output sleeve and to the "off" lug of the switch without any resistor.

Is this something I should worry about?

Schematic:

simulate this circuit – Schematic created using CircuitLab


texts: Physical power connector that does not allow reversed polarity power connection

texts:
I have used those XT60 power connectors to connect from my load to the battery. The battery is a forklift battery with a voltage of 48V.
I have attached the male XT60 connector to the battery pack and the female XT60 connector to the load input via two 2.5mm power cables.
I have also shown a person how to connect the male and female XT60 connectors together. I also know the XT60 is designed not to allow a reverse polarity connector.
However today I find out my system blew. Why you might ask.....
Because that person managed to somehow connect the XT60 in a reverse polarity way. This was not expected. So my question is what other connector can I use to make it completely idiot-proof.
Also, I do not want to make a reverse polarity protection circuit because I can not keep replacing that circuit and it does not solve the problem. Hence what other idiot-proof power connectors can I use to prevent a person from doing this?


texts: Can I substitute a mono potentiometer for a stereo one?

texts:
I have a PCB for a headphone amp that has a 6-hole pad for a single potentiometer. I've only got 3-pin ones in my box o' parts. Can I substitute the mono pot for the stereo pot, tie the sets of pads together with jumpers, and achieve the same results? Or should I order the right part?

Based on how I'm visualizing it (below), it seems like I should be able to. Am I missing anything conceptually? or is this a good solution.

  1   2   3
+-------+---+
| O   O | O |      Jumpers between 1-4, 2-5, 3-6
+-----------+
| O   O | O |    <--  Mono Pot here
+-----------+
  4   5   6


texts: Can I put my battery in the middle of my parallel circuit?

texts:
This is a small project, basically cosplay, four 5mm LEDs wired in parallel. Normally, I put the battery at the end:

But could I put the battery in the middle with the same result? I'm researching simple circuits but couldn't find theory on placing a battery (3.7V Li-Ion battery). This layout helps me fit the LEDs in a smaller space without extra wire. Any online resources appreciated.


texts: How to control thermal printer from micro-controller and choose it

texts:
The project is to print barcode and some text with thermal printer using micro-controller. Initially I chose RP58 which has this command set and serial port.

So to control the printer, do I just have to send bytes according to the command set, only? (Since I'm buying new one, I want to confirm).
And in the document, "2.LF" is to print data in "print buffer", but I couldn't find command to set data in print buffer. But I guess, If I send "ON" using "47.ESC = n" command, printer might receive data into print buffer. How does printers usually receive their printing data (or texts).
Since I'm using printer for development purpose, do you have better suggestions? I'm looking for printers, which are cheap, easy to acquire and work with using controller.


texts: Why Xilinx ISE can't get access to my custom package?

texts:
I am trying to create a custom data type which I am creating in a package using Xilinx ISE 14.5. I am trying to create a generic DEMUX to switch between buses, here is the code of the generic DEMUX:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use work.CustomDataTypes.all;

entity GenericDEMUX is
     -- Ancho del bus de cada salida y número de salidas
     generic( busWidth              : integer := 4;
                 channelsNumber     : integer := 4
     );

    Port (  Output  : out  Matrix(channelsNumber-1 downto 0, busWidth-1 downto 0);
                Control : in     integer range 0 to channelsNumber-1
     );
end GenericDEMUX;

architecture Behavioral of GenericDEMUX is

begin

end Behavioral;

So I created a Package to contain Matrix data type:

CustomDataTypes.vhd:

package CustomDataTypes is
    type Matrix is array (natural range<>) of STD_LOGIC_VECTOR (natural range<>);

end CustomDataTypes;

When I do Check Syntax on the Generic DEMUX I get this errors:

  ERROR:HDLParsers:164 - "//vboxsrv/datos/Datos/Micro
  UTN/FPGA/MaquinaEstados/CustomDataTypes.vhd" Line 14. parse error,
  unexpected NOTCONSTRAINT

  ERROR:HDLParsers:3009 -
  "//vboxsrv/datos/Datos/Micro
  UTN/FPGA/MaquinaEstados/CustomDataTypes.vhd" Line 35. Package
  CustomDataTypes does not exist.

I don't know what parse error, unexpected NOTCONSTRAINT means but I think it could be related to Package CustomDataTypes does not exist. Here is a Screenshot of what my Libraries tab looks like, as you can see CustomDataTypes.vhd is there:

However I don't see it in the design tab:

I tried adding it but it says it already exists.


texts: Audio summing mixer- inverting or non inverting output?

texts:
All the audio mixer circuit examples I see online are based off of the summing amplifier:

This is an inverting op amp configuration so the output is inverted. I built a similar circuit and I couldn't tell that the output signal was inverted by listening to the audio...so is there a reason why you would want to de-invert the output of the mixer, by putting in another inverting op amp stage at the output, like in this circuit:

If the audio output sounds the same whether the output signal is inverted or not, why would you ever need to de-invert the output?


texts: Chip antenna, what to do with power and bottom planes

texts:
I'm designing a board which uses a chip antenna.
According to the datasheet, there should be no copper on all layers under the
antenna. There's also should be some ground plane on the top layer with a know distance between the plane and the chip.

My question is : what about power and bottom layers ? Should I add a ground band
around the clear area or should I just do nothing ?

Datasheet : http://www.mouser.com/ds/2/276/0479480001_ANTENNAS-701294.pdf
(link to app notes and other relateds in the top of the datasheet)


texts: I am wondering, if a sychronous generator has a smaller posibility to be burnt (be destroyed permanently) from a short circuit, that has a dc generator with parallel wound or a seperately excited dc generator, and why?


texts: Attiny85, reading analog values from PIN3, reports 654 on idle?

texts:
At first, I am not a hardware professional (starter) so be kind please.

I try to reuse a DENON operation board of a DVD-player with 9 buttons with a Attiny85 Digispark clone connected to PIN3 (see also picture below)

EDIT: About picture: "Sparkfun" must be "Digispark".

However, I can read the values of the buttons, the values seems to be very close so it difficult to detect which button is pressed.

But that's not the main problem/question, the problem is the idle value of analogRead function which I don't understand. The Arduino (IDE) language manual 'says' that it is a value between 0 and 1023. In this case it reports 654 on idle and above when a button is pressed. Tried also PIN1 and reports 1023 but doesn't detect any input (value doesn't change).

Questions:

Why does the analogRead function reports 654 (also when board
disconnected)
Can I increase the resolution of these values to detect buttons more
precisely/accurate?

Some code ( I made a USB debugger software solution to debug values via keyboard because there is no UART):

#include "types.h"              // Custom types
#include "TrinketHidCombo.h"    // Trinket USB lib

#define PIN_BUTTON_IN 3

void setDelay( uint16_t ms ) // usbsafe delay
{
  if( ms < 10 )
   { delay(ms); }
  else {
         uint16_t iSteps = ms / 4;

         while( iSteps-- )
         {
           usbIdle(); // We need to do this to keep the Windows USB driver 'sadisfied'
           delay(4);
         }
       }
  usbIdle();
}

void usbIdle()
{
  // do nothing, check if USB needs anything done
  TrinketHidCombo.poll();
}

void usbStart()
{
  TrinketHidCombo.begin();
}

bool usbSendDebugHandshake()
{
  TrinketHidCombo.pressKey( 0, KEYCODE_F24 ); // press
  TrinketHidCombo.pressKey( 0, 0 ); // release
  setDelay(20);
  TKeyboardLEDState recLedState = usbGetKeyboardLedState();
  return ( recLedState.caps && recLedState.num && recLedState.scroll );
}

void usbDebug(const char* s, bool bLineFeed )
{
 static bool bUsbDebugHandshake = false;
 static bool bUsbDebugEnabled = false;

 if( !bUsbDebugEnabled && !bUsbDebugHandshake )
  {
    //bUsbDebugHandshake = true;
    bUsbDebugEnabled = bUsbDebugHandshake = usbSendDebugHandshake();
  }

 if(  bUsbDebugEnabled )
  {
    (bLineFeed)?TrinketHidCombo.println( s ):TrinketHidCombo.print( s );
    usbIdle();
  }
}

void usbDebug(const char* s )
{ usbDebug( s, true ); }

void usbDebug( int i, bool bLineFeed )
{
  char buff[10]; //the ASCII of the integer will be stored in this char array
  memset(buff, 0, sizeof(buff));
  //itoa(i,buff,10); //(integer, yourBuffer, base)
  usbDebug( itoa(i,buff,10), bLineFeed );
}

void usbDebug( int i )
{ usbDebug( i, true ); }

TKeyboardLEDState usbGetKeyboardLedState()
{
  uint8_t iState = TrinketHidCombo.getLEDstate();
  TKeyboardLEDState tResult;
  tResult.caps = (iState & KB_LED_CAPS);
  tResult.num = (iState & KB_LED_NUM);
  tResult.scroll = (iState & KB_LED_SCROLL);

  return tResult;
}

// Setup and main routine
void setup()
{
  usbStart(); // First priority, start the USB device engine and enumerate

  pinMode(PIN_BUTTON_IN   , INPUT );
}

void loop() // Main program - main()
{
  // Button pressed?
  int iButton = analogRead(PIN_BUTTON_IN);
  usbDebug( "PRESSED: ", false );
  usbDebug( iButton );
  setDelay(1000);
}


texts: switch load depending on battery voltage

texts:
I have the following set up;

simulate this circuit – Schematic created using CircuitLab

MPPT charge controller: https://www.sparkfun.com/products/12885

Load: Raspberry Pi Zero

Battery is: http://ie.farnell.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=15001&urlLangId=353&langId=353&partNumber=2484233&storeId=10163#techDocsHook

Battery Datasheet: http://www.farnell.com/datasheets/2017383.pdf?_ga=2.166173694.1332281990.1495362248-227627644.1495362211

The battery datasheet states:

Over discharge detection voltage: 2.5V

Over discharge release voltage: 2.85V

Release condition: cut load, release after charging up

What happens is that the load at night drains the battery to 2.5V thus triggering the protection circuitry, upon daylight the battery does not charge nor does the load power up from the MPPT charge controller.

The only way to overcome this is to physically disconnect the battery from the MPPT controller and all works fine again. I assume then that the battery is getting stuck via it’s charge protection circuitry.

I want to avoid the above battery low voltage triggering & manual intervention.

Can someone suggest a circuit/solution that will provide power to the battery & load when there is voltage from the MPPT and disconnect the load when the battery voltage drops to say 2.8v and reconnect the load when the battery voltages charges to say 4V?

How can I implement the following switch in circuitry?

simulate this circuit


texts: Best way to regulate 9/12v down to 5v and 3.3v

texts:
If my source is 9 or 12v should I first us a linear regulator to step it down to 5v and from the 5v use another linear regulator to step it down to 3.3v? The 3.3v will be going to a micro-controller while the 5v will drive some 5v sensors/relays.

Current is under 500mA total, probably closer to 300. The power source for the loads (relay etc) are coming from a separate power source.


texts:
I'm a hobbyist with a few years of practice and managed to make some nice musical instruments for myself, making steady progress over time.
For about the last six weeks, nothing I try to do works. Voltages are all over the place, I'm about to go mad. I'm even unable to replicate circuits I already made with success.
I'm using the exact same techniques and equipment, the only thing that changed is that I bought 'water soluble solder' from AIM.
Could this have such an impact?


texts: Is this network able to be interpreted as a node and apply KCL?

texts:
I've may been asking the really trivial question.

Is above diagram correct?
I interpreted the network as a node and applied KCL.
No such grounded thing is included in the network.


texts:
I am taking basic elec. circuits and I would like to know how to graph the wave forms with phase angles in either desmos, or octave or any other platform.  I am not afraid of doing some coding for octave, just not sure how to go about it.
Can anyone point me in the right direction?
Thank you


texts: Autocorrelation and power spectral density for a time scaled random process

texts:
I have worked out a discussion regarding the autocorrelation function and the power spectral density of a scaled random process.
Method 1 is giving correct results, however method 2 is giving wrong results even though I feel I have approached it right. Can someone clarify what is the mistake in method 2?


texts: Placing the pads of SMD components in different layers (KiCad PCB design)

texts:
I am designing a PCB with KiCAD where components such as SMD resistors and capacitors are placed before and after DC/DC converters.

I am trying to build two different common grounds: one placed on the left side of the PCB (for all the input signals) and another one placed on the its right side (for all the output signals).

In order to do so, I am placing ground traces in the B.Cu layer and the rest of them in the F.Cu layer. Then, in the B.Cu layer, I am drawing two separated filled zones -which are connected to their corresponding ground traces-, one on the left, and another one on the right.

For doing that, I need to place one of the pads of the SMD component in the B.Cu layer (the "ground pad") and the other pad must be placed in the F.Cu layer (the "VCC pad"). The pads of the SMD components are by default both placed in the F.Cu layer.

However, I can edit the properties of the component's "ground" pad, select its layer to be B.Cu, and select B.Paste and B.Mask as technical layers.

If I do so, when looking at the 3D design of the PCB, I notice that the copper for the "ground pad" on the top layer (F.Cu) does not exist. Of course, SMD components can only be soldered to one layer, and thus, I need the top layer to have copper for both pads.

The way I have found to solve this is to select both F.Paste and F.Mask as well as B.Paste and B.Mask in the technical layers list for the component's "ground pad". I reckon that this means that I will be able to solder the component on the top layer, and the VCC pad copper will go down just to the first layer (F.Cu), while the GND pad copper will go down to the bottom layer (B.Cu), thus solving my problem.

Is this correct? I am solving this implementation issue properly?


texts: What is the name for gold plated docking station contacts?

texts:
I design a device that must connect to the docking station which has spring loaded pins. I'm looking for gold plated contact for the device side (sample shown on the picture), so these contact pads would be exposed through the plastic case.

Any idea what name I should be searching for these kind of contacts under from suppliers?  I've been searching for multiple hours for "gold plated contact blocks", but haven't found yet.


texts: Does the charger consume power after charged device is disconnected?

texts:
Quite similar to this one. If I'm not mistaken any impulse mobile device charger is still consuming power, when plugged into socket, but when cable is disconnected from charged device. Correct?

Does the same rule goes for power sockets equipped with USB ports for charging mobile devices (link to Polish seller):

I was wondering, if this kind of construction means that my socket(s) will be continously draining power, 24 hours a day, no matter if anything is connected to it or not? Or do these have some kind of power-off "switch" (meaning stops draining power when everything is disconnected)?


texts: How to sample and hold on very narrow pulse?

texts:
I am looking to construct a simple data logger to record the peak intensity from a flash strobe. When a flash is detected, the peak will be captured (ADC), time stamped and written to memory. The frequency at which these bursts of light arrive would be roughly 0.2 Hz (one every 5 seconds or so).

A typical output from my sensor in the presence of a flash strobe is shown below. The flash intensity is so great with respect to ambient conditions that detecting the flash is not an issue. In fact, I am already doing this to count the number of flashes.

My problem then becomes sampling the peak value. My instincts tell me to utilize a sample and hold IC (LF398 for example). Looking at the datasheet, it seems I can achieve sub 10us acquisition times and that is acceptable to me. If I could then detect the peak (second derivative), I would know precisely when to hold. Problem is... I don't know where to start with that.

Am I going about this wrong? Any suggestions?


texts: Data from an arduino to be transferred to COSM through wireless internet

texts:
I am trying to collect data from sensors through an arduino and send it over to the COSM server. My main problem is that the arduino will be in an environment where it will be impossible for me to provide an internet router and thus must find a way in which i can send the data to the internet through a wireless connection.

I would appreciate it if you could give me an answer that does not involve using a wifi shield coupled with data connection through a cell phone as i want it to run even in the absence of cell phone data packets.


texts: Why does my cutoff frequency not match the 3db down point?

texts:
My understanding is that the cutoff frequency of this circuit can be calculated simply by:

1/(2*pirc)

I get a cutoff frequency of 15.9kHz

But as is shown in the provided bode plot 15.9kHz is roughly 6dB down...  Why does this not match 3dB down?


texts: how to cut off power from usb device using arduino

texts:
Seems like I can't restart USB modem in Linux, so I setup an arduino gig to emulate usb modem plug/unplug.

I have Arduino Uno R3 and several N-channel mosfet https://www.sparkfun.com/products/10213, and used the setup in http://bildr.org/2012/03/rfp30n06le-arduino/ for switching the ground wire of the usb modem on/off.

This works, for a while, then the usb hub started to have problem. I think I have to really emulate USB plug/unplug, that is, cutting off both the power wire and the data wire of the usb modem.

The problem is, while the USB power has +5V and ground, the data has D+ ~+2.5V and D- ~-2.5V, they doesn't have a common ground, to be used with the setup using N-channel mosfet.

What should I do? if I buy another arduino uno just for the data wire, I still have problem, the data ground is not the same with the arduino ground (I think N-Mosfet requires a common ground), I don't know if this will cause problem.

Do I need a DC voltage step-up component? or is there other solution.

I'm thinking how usb plug works, is first connect the power wire, wait some micro seconds then connect the data wire, with unplug the opposite.


texts:
Based on this QAM 32 constellation diagram, how it is possible to have the sam values on I and Q axes for different combinations of bits, e.g. 000 and 011 or 000 and 101, as well as other two bits, e.g. 11 and 10. I thought that the they always need to have the same values on the same axes.

Please help a non electrical engineer.


texts: IRF740 datasheet. Error in the datasheet or I'm interpreting it wrong?

texts:
According to the IRF740 data-sheet from IR or from Vishay (they are nearly the same, the Vishay is better to read), the Qg is specified as 63nC under Id = 10A Vds = 320V and Vgs = 10V.

But at page 4, Fig. 6 - Typical Gate Charge vs. Drain-to-Source Voltage, The graph shows that under the same conditions the Qg is ~45nC. Its 63nC at a Vgs = ~15V.

Is the data-sheet that have a error or I'm interpreting it wrong?


texts: How measure the voltage over a large resistance?

texts:
I know initially this question might come across stupid and obvious but all is not as it seems.

I want to measure the voltage drop over a 10M ohm resistor but my voltmeter's probes have an impedance of ~10M ohm, so if I try to measure the voltage drop the conventional way (i.e. put in parallel with load) but that would then cause the resistor value to half as it would make two 10M ohms in parallel giving ~5M ohm.

This is a similar situation if you just try and measure the voltage either side of the resistor, when you try and measure the lower potential side it will create a voltage divider and just gives me half the input voltage which is somewhat undesirable and highly inconvenient.

  So my question to you folks is, how can I measure the drop over a large resistor without inadvertently putting an extra load on the circuit caused by the measurement equipment?

Some information about the circuit may be of use to you budding electroneers:

Voltage going into resistor = 3V DC
Voltage desired out of the resistor, also = 3V DC (or a little lower)
Resistor is going into a control pin for a 2:1 multiplexer / swtich (the TS5A3154 to be precise)

It would appear I neglected to mention the purpose of the resistor...

It is being used as a pull up resistor either on its own or as part of a transistor level translator (I have not yet decided on that) in order to get this pin to detect a logic 1 without drawing too much current.

Note that the output of the MCU will only be ~2VDC which will cause the chip to drain more current than I would like it to, I haven't yet had time to think fully about how I will have this bit set up but this is the basic premise.
This question is not about the amount of current that will be drawn, just purely about measuring the drop over a  large resistor which is not connected straight to ground and any attempt to use a multimeter in the normal way would cause errors in results dues to probe resistance.


texts: Why does my active low pass filter produce triangle waves?

texts:
So here's what I'm trying to do:

Given a square wave provided by my arduino, use a nth order active low pass filter to modify the square wave into a sine wave by filtering out upper harmonics. This is in the audio range of frequencies, of course.

I've spent a good deal of time trying to do this and I'm pretty close to giving up and buying a function signal generator ic like XR-2206. I don't have any dough for fancy equipment, and may I stress that it's partly a learning exercise.

Maybe part of the problem being is I don't have an oscilloscope, and can't afford one, so oscilloscope is out. It would definitely help to have one, sometimes wishing I could see the signal I'm creating, but here's my thinking: If I can create an audio sine wave that I can hear, then I can change my RC values to work for higher frequencies. Right? (Or wrong?)

But I can never seem to get what sounds to me like a sine wave. I play back a youtube 1000Hz sine wave (or pick your frequency) and compare that to the output of my active RC filter and they just don't sound alike. When I listen to the 1000Hz triangle wave, then that sounds exactly like what I'm hearing from the output of my active RC low-pass filter. But why?

I've read over and over, all over the net and back, that by filtering out the upper harmonics of a square wave produces a sine wave (because of the details of Fourier Transform having an infinite sum of continually doubling frequencies with phase shifts and yada-yada) but the idea just doesn't seem to work. If I filtered out all the other sine waves and am left with the fundamental sine wave, then why doesn't it sound like one? Triangle waves!!!

I'm using n many resistors, n many capacitors, and n+1 many LM358 op-amps. I need the last one to amplify the output signal. I have read that many higher capacity capacitors (like electrolytic) are just too inaccurate for a proper low-pass filter in the audio range, so I'm using 100pF caps with very large value resistors. For example, if I used a 100pF capacitor with 1.62M ohm resistor, then the cut-off frequency is 1/(2*pi*100pF*1.62Mohm) = ~982 Ohms. By using multiple RC filters, you can create a steeper "roll-off" on the upper frequencies, and because the resistance values are so high, the signal needs to be amplified, which is why I'm using LM358 op-amps. The output of one active filter feeds into another, and is filtered again in the next active filter. I'm powering everything with 0 to 5V.

And I know the filter works!! I've modified my filter so that I can hear a crisp 400Hz (triangle??) wave, but by just increasing to 450Hz, the frequency is completely inaudible. Therefore, it's definitely filtering, and pretty damn well! Yet I can still not get a clean sine wave sound. Why? What am I doing wrong? Maybe I'll just torment myself further by trying to make a crystal ladder. Pretty sure I won't do that.

I am not expecting perfection. But I know what I'm hearing and it just ain't sine. Not even close. Any suggestions?

Thanks stack community.


texts: Executing code at diferent speeds, using one timer, and no extra RAM

texts:
I was wondering, will this actualy work? (when timer / prescaler set) It saves RAM by not using extra variables. Are the better ways of doing this?

// Microchip PIC10F222

while (1) {  //main loop
   while ((TMR0 ^ TMR0-1)& 4) {  // execute @ 1/4 speed of TMR0 (whenever TMR0 Bit 3 has just toggled)
   // high speed stuff
   }

   while ((TMR0 ^ TMR0-1)& 128) {   // execute @ 1/128 speed of TMR0
   // low speed stuff (toggle blinking led's)
   }
}

Next idea:

I Don't like the idea of waisting processor time , or being dependent on exact timing

I'm not sure about the TMR0-2. I asume If TMR0=0 TMR0-2 will be 254.

// Microchip PIC10F222

While(1) { //main loop
    // Full speed
    if (TMR0&1) {  //skip, eccept for TMR0 odd numbers.
       // 1/1 timer speed. (Not nececairily used)
       // this code may run in one pass with either one of the loops below.
       if ((TMR0 ^ TMR0-2)& 64) {
          // 1/32 timer speed,(state machines, one step each pass.)
          // do not exceed TMR0 period
          }
       if ((TMR0==255) {
          // 1/128 timer speed. (toggle blinking led's, wachdogg)
          // do not exceed TMR0 period
          }
    TMR0++; //TMR0 will be even, preventing passing trough this loop
            //until the timer increments itself,
            //(Doubeling timer speed in the process)
    }
}


texts:
I would like to measure signals up to 5Mhz, between different ranges -2,2 and -36,36, I could use a differential amplifier with level shifting like here.

What is the best way to change the gain of the amplifier? Is it a good idea to use a mux/switch controlled by the ucontroller?


texts: How to convert SATA power port to Slimline power port

texts:
I want to convert 15 pin SATA to 6 pin Slimline but there is problem the 15 pin SATA contain 3 "+5V" and 6 ground but the slimline one only contain 2 "+5V" pines and 2 ground with 2 additional pines DP and M

Can someone please help me with the wiring.


texts:
I'm trying to interface a device (Opentherm thermostat) that actually supports to be controlled through SMS via a serial connection to a GSM modem.

I'd like however to control it through TCP rather than exchanging SMS.

I've thought to write a fake modem that obey GSM 07.07 specs (or probably reuse some existing code) but I've yet to get the whole picture. I know I'll need a level shifter like a MAX232 and then wire up an arduino to it, or maybe an esp8266 with Ser2Net and than write code from the comfort of a raspberry, but I don't know where to start!

Sorry for any missing detail, I'm a software engineer, just passionated with electronic

Follows connection specs, if useful the instruction manual in english is available here.

TECHNICAL DATA SERIAL COMMUNICATION

protocol RS-232
baud-rate 2400 bit/s
use of AT commands according to standard GSM 07.07 and 07.05
use of 5 conductors (TX, RX, GND, DSR, CTS)

EDIT: What should I use to shift levels from the RS232 level to TTL 3v3 ? How to deal with missing CTR and DTR ?

Note: I know that opentherm is a "kind of open" protocol and I've already put the wonderful opentherm gateway by Schelte Bron, but unfortunatley that device don't support "override", furthermore there are other interesting settings that the device support by SMS but are not part of opentherm spec.


texts: Why am i getting different motor speeds with the same voltage?

texts:
I'm making a remote controlled car for a college assignment and i am testing the motors with a power supply set at 9V. So far so good, it runs pretty smoothly.

The problem is when i power it using a 9V battery. It runs way slower than with the power supply. Some people tried to explain it to me that it had something to do with the current, but i couldn't really wrap my head around it.

Here is my thinking, i need to know where i'm wrong:
Since the motor's resistance doesn't change, and the voltage is the same, than the current should be the same and it should all run the same. What changes?


texts:
I came across a device at home which has the specs bellow written on it:

Rated Power: 30 W
Rated Voltage: DC 12 V
Current: 1200 mA

Since P = V × I, P = 12 × 1.2 = 14.4 W
Why on the specs it says 30 W?
What am I missing?
Edit:
It is mounted now on the wall, but I found online the specs also:


texts:
I have a simple security/alarm system I built for my carport after a thief took advantage of me.
It simply has a strobe light and an extremely loud siren, using photoelectric sensors. When the sensors are tripped, the strobe and siren sound/light up.
What I want to do is turn the system off after about 5 minutes once tripped, then be able to engage itself again if need be. Any suggestions on a simple timer? This is a low voltage dc system.


texts: Are there any disadvantages of having many solder joints on a single wire?

texts: I was working on this project where I have to connect multiple wires from a single supply wire. Are there any dis advantages of having many solder joints on a single wire?


texts: Measure rpm of a DC motor using two timers/counter and IR sensor (atmega 328p)

texts:
I'm trying to measure the speed of a DC motor. I have an IR speed sensor connected to the T1 pin(PD5) of an ATMega 328p. My idea is when there is a change from LOW to HIGH, a counter is incremented and for this I'm using TIMER2 to create a 1 second interrupt and TIMER1 to count the pulses.

First problem is that the TCNT1 is giving me random values even if I pass only one time in the sensor (counts from 0 to 200).

Second problem is that its counting both changes from LOW to HIGH and HIGH to LOW.

My sensor is www.botnroll.com/pt/sensores/957-motor-speed-sensor-module.html

Here is my current code:

#include <avr/io.h>
#include <avr/interrupt.h>

volatile unsigned int overflow;
volatile unsigned int timer_counts = 0;

void conf_timer2()
{
    //prescaler = 256
    TCCR2B |= (1 << CS22)|(1 << CS21);

    TCNT2 = 0;
    // overflow interrupt
    TIMSK2 |= (1 << TOIE2);

    overflow = 0;
}

void config_timer1()
{
    TCCR1B |= (1<<CS10) | (1<<CS11) | (1<<CS12);    //rising edge
    TIMSK1 |= (1<<TOIE1);   //enable overflow interrupt

    DDRD &= ~(1 << DDB5);
    //PORTD |= (1 << PORTD5);
}

ISR(TIMER2_OVF_vect)
{
    overflow++;
}

ISR(TIMER1_OVF_vect)
{
    //overflow1++;
    //no need since it will never reach 65536 in 1 sec
}

int main()
{
    sei();
    config_timer1();
    conf_timer2();
    char aux2[10];
    char aux1[10];

    unsigned int rpm;

    while(1)
    {
    if(overflow >= 152) // for 1 sec
    {
        if(TCNT2 > 149) //for 1 sec
        {
            timer_counts = TCNT1;
            rpm = timer_counts * 60;

            itoa(rpm, aux2, 10);
            itoa(timer_counts, aux1, 10);
            USART_putstring("Rot. per sec: "); //print values
            USART_putstring(aux1);
            USART_putstring("\n");
            USART_putstring("Rot. per min = ");
            USART_putstring(aux2);
            USART_putstring("\n");

            TCNT1 = 0;
            overflow = 0;
            rpm = 0;
        }
    }
}
return 0;

}

Any1 help is valuable!


texts: What's the filter type of these ENB figures?

texts:
In TI's "Analog Engineer's Pocket Reference" p. 45, it gives a table about the ENB (Equivalent Noise Bandwidth) of the filter with different poles count:

But it doesn't mention the filter type. I know the figures for a Butterworth lowpass filter are:

Is anyone familiar with the figures given in Table 15? Which filter type it use?


texts: AC line detection, with or without optocoupler?

texts:
If you want just to detect AC line (220VAC) existence using micro-controller, does using optocoupler has any advantages rather to simple RC circuit? Even if you want to meet EMC/EMI/Industrial considerations.

RC ZCD detector from ST app note AN2263 (GND is connected to main neutral):

Second method (AVR app note AVR182):


texts: Recommendations for using a 240V outlet with 120V equipment

texts:
I have a conveniently placed NEMA 6-20 240V outlet here in my lab. I'd like to use it to power my equipment by using a converter that steps down the voltage to 120V. I've been searching all morning for something that would fit my needs, but so far I have not found the right product.

I'm wondering if this is a bad idea, or if I'm missing something that would prevent this from working. My thought is that the 240V outlet would be great to run my whole bench from since it can supply a ton of watts for all my 120V equipment if I can find a way to set things up ideally.

Edit: I'm located in the US, and ideally I'm looking for some kind of all-in-one power distribution solution that will supply all the equipment on my bench. A combination of a step-down converter/transformer and a power strip might do the trick, but I need be sure that it will handle the wattage of my DC power supply, O-scope, function generator, soldering station, etc. I have a regular 120V outlet, but I'm running so much off of it already that I'm growing concerned. It would be nice to run my computer and other sensitive stuff from the 120V line, and use the 240V line for all the brute stuff.


texts: Signal Comparisons: "Orthogonal functions"

texts:
When comparing two vectors, if the angle between them is 90 degrees then they would be seen as orthogonal and Cn= 0 where Cn is the correlation between these two vectors representing a signal.

What if we had two functions and wanted to compare their correlation. In this case under what conditions would Cn= 0?


texts: What are the different antenna types used by various IEEE 802.11 standards?

texts:
I've been working on an assignment about the IEEE 802.11 standards and I've had some trouble with one aspect of a question. I need to explain the differences between various features of the different 802.11 standards (a, b, g, n, etc). I've been able to find most of the details online, especially through official IEEE documents.

What I've been unable to find any information on is the different "kinds of antennas" used by each standard and how they differ from one another. I know that 802.11n introduced MIMO and thus allowed the use of multiple antennas, and that antennas can be either directional or omnidirectional, but all 802.11 standards seem to be omnidirectional. I don't know what is actually different between the antennas themselves as specified by the IEEE standards.


texts:
How does the amount of watts affect a solar array?

The solar array I found is 14 W, so what would I encounter if I purchased an lower/higher wattage? I'm going to purchase an array to charge my electronics on a trip I will be taking soon and I think I understand how volts/amps affects charging, but watts are still a bit hazy. If a device needs x amps and y volts, it uses xy watts, correct? Does this mean that a 14 W solar array could charge a device using xy watts and another one that uses  14-xy watts?


texts: Does unplugging a television from the wall socket make it safer?

texts:
Does unplugging a television from the wall socket make the electronic safer (against power surge for example) compared to:

Plugged in, button on wall socket is off
Plugged in, button on wall socket is on, power button on television set is off

I've been told that one should always unplug the television besides/instead of using the power button on television. Why should I?


texts: GPIO pins of CC2650 are capable of driving the opto-coupler(4n35) directly?

texts:
I need to drive opto-coupler(4n35) from the GPIO pins of the CC2650 (Pins other than high drive capability).

Are the GPIO pins of CC2650 capable of driving the optocoupler  directly? Will they supply sufficient current required by the optocoupler?


texts: Connecting two Ethernet PHY without magnetics?

texts:
In a (tentative) new design I want to connect two 100 Mbit/s Ethernet PHY similar to LAN8270a, separated by few inches on the same PCB, with same ground plane (but different power supplies). I have the choice of one of my PHY, but the other is embedded in an as-yet-unspecified PCIe to Ethernet IC (perhaps Gigabit but used in 100 Mbit/s mode), and it is critical that this PHY thinks there is a bona fide 100 Mbit/s Ethernet connection.

I could use the following

simulate this circuit – Schematic created using CircuitLab

but I would like to achieve the same without the magnetics, in order to save on cost, purchasing headaches, and if at all possible power consumption.

I can imagine an RC network, perhaps as simple as in this appnote, found thanks to a similar question; or maybe engineered with attenuation and lowpass, but that will not emulate the fact that with real magnetics, when there is a negative pulse on TX1P, there is a positive pulse on TX1M and RX2M. I am uncertain about if that would prevent some PHYs from working normally.

Anything to suggest that one is confident will work for practically any PHY around?


texts: What does C mean in terms of an energy calculation

texts:
I'm a bit of a noob when it comes to EE, so this might be a dumb question, but I find it super interesting and am learning as fast as I can
(1) I saw the following formula on another forum:
"E = 0.5 * C * V^2 = 4 mJ"
Describing the energy that a gag shock pen would inflict on a human.
I am confused how the op got to this conclusion. I read on a different site that energy = power * time
where power equals V(voltage) * I(current), so I'm not sure where the 0.5, the C, and the second V comes in.
Does C stand for current? or is it some kind of constant? any explanation would be appreciated, Thanks!
(2) Also related follow up question, the thing I was initially trying to find out for curiosity and to kind of understand what a safe current is, is how much current a shock pen would have, assuming a voltage of about 50- 70 V


texts: How can I wire an emergency stop that requires a secondary reset before the circuit is closed again? I am working on a CNC, and am brand new to the electrical component of them. The problem I am coming across is if I activate the e-stop which would be connected to the contactor and reset it, the spindle power would resume. What electrical component am I looking for that breaks when power is lost, and requires a reset before continuing? It could also be the actual spindle on/off switch too, if you have an idea with that in mind. Thank you!


texts: I want a small portable monitor (7 in) that can connect to my USB drive for power and picture (DisplayLink). I've found some cheap lcd screens, such as http://www.alibaba.com/product-detail/1024x600-Resolution-7-inch-LCD-Display_60134896431.html . I've been researching controller kits and have been somewhat confused on what I need to connect the lcd screen to the usb port on my computer. I know I'll need to use a displaylink somehow, but I haven't found any kits that incorporate the displaylink chip. Any ideas on where to start on this?


texts: Using 2N3904 NPN for audio amplification

texts:
I use a great library ESP8266Audio for play audio using ESP8266. As the author explained we can use 2n3904 for audio amplification as follow:

                            2N3904 (NPN)
                            +---------+
                            |         |     +-|
                            | E  B  C |    / S|
                            +-|--|--|-+    | P|
                              |  |  +------+ E|
                              |  |         | A|
ESP8266-GND ------------------+  |  +------+ K|
                                 |  |      | E|
ESP8266-I2SOUT (Rx) -------------+  |      \ R|
                                    |       +-|
USB 5V -----------------------------+

It works but still, the volume is not acceptable with 0.5W 8Ω speaker. I also tested with some other speaker, same result. With normal amplifier is much louder.
I'm not very good at electronic. Is there any way to add another transistor to make it louder, having a simple low pass filter behind would be awesome too. Thanks


texts: I'm building a power supply for a product that uses a 5V regulator if external power is connected or three alkaline cells if not. I don't want to waste half a volt or more from the cells by diode ORing the two sources. This NPN emitter OR using low VCEsat transistors appears to work fine - The closest thing to a problem that I see is VBE breakdown. Since the circuit is switching a max of 5V, a spec of 6V min or better should be OK... Does anyone see anything else I may be missing?


texts: Inverters with tied outputs, different inputs

texts:
consider we have two inverters whose outputs are tied together and each inverter has a different propagation delay.
If we apply a periodic square wave to one inverter and a delayed version of the same square wave to the other one, what should the output look like ?


texts:
I have problem with clock signal in Verilog test bench.

I've tried almost every possible ways to create clock, but in the waveform it's U meaning "Unknown".

Here is my code for clock (i_SysCLK is my input clock):

`timescale 1ps/100fs

 module sim_tb_top;
   parameter CLKIN_PERIOD          = 5000;
  reg                     sys_clk_i;

  reg clk_ref_i;
  wire                    i_SysCLK;
      initial
    sys_clk_i = 1'b0;
  always
    sys_clk_i = #(CLKIN_PERIOD/2.0) ~sys_clk_i;

  initial
    clk_ref_i = 1'b0;
  always
    clk_ref_i = #REFCLK_PERIOD ~clk_ref_i;
  initial
    i_SysCLK = 1'b0;
  always
    i_SysCLK = #(REFCLK_PERIOD/2.0) ~i_SysCLK;
endmodule


texts: Unresolved inclusion: xuartlite_l.h in Xilinx SDK

texts:
I am following Xilinx Lab Workbook. On Lab 3 (page 60) I am supposed to have resolved all errors but I cannot get rid of an unexpected error.

"fatal error: xuartlite_l.h: No such file or directory    serialPort_helper.c    /SDKintro_app/src    line 9 "

I have regenerated BSP sources and re-built the project but nothing seems to work so far.


texts:
Why L is calculated using average value and not by the formula
1/L = 1/L1 + 1/L2 + ...


texts:
If i do not use Bit Banding feature on ATSAM3N, this region, it will used by the compiler for the program? Or it will stay unused?

What if my program, randomly (by itself) should need to assign and access this region?


texts: Thevenin Impedance for network with only dependent sources

texts:
If a network has only dependent sources, you need to use a test current source or test voltage source (1v, 1a, something simple) since Zth = Voc/Isc doesn't work.

Is it valid to use a DC source as a test source with reactive components like an inductor and a capacitor to solve for the port impedance?

I need to solve for Z at terminals 1-1'.


texts: MC78M12 voltage regulator without bypass capacitors in a simple PCB with only analog signals

texts:
I have a very simple board, two layers, two gnd polygons, 8 analog inputs incoming from 8 potentiometers and 8 analog outputs. In the PCB are 2 resistors (R1||R2) between input and ouput. So, output just will drive 8 voltage dividers.

Board source supply is 24V, but input signals needs to be fed under 20V, so I used a MC78M12G regulator (12V). As this board outputs will be connected to 8 ADC in a PLC block, 2 bypass capacitors were connected at regulator input and regulator output.

Capacitor components have not arrived yet and board were sold with the rest of components.

Design considerations talks about capacitors will not be needed if it's used in a low current application.

Well, taking this into account, in order to get some advantage, I thougt to do some little and simple tests:

only one active input (only one potentiometer is connected and its current is < 20mA),
without connecting the board to the next block
and then measuring its related output with a tester.

I thought the capacitor will be not needed -according to datasheet- and any signal freq will be passing through the circuit.

After switching on the board I can see how voltage output has unexpected low levels. I put the tester on the regulator output pin and I can see 4.6V.

Can the regulator be damaged due to Capacitors absence during switching on? Or can it be another factors?

This regulator it's able to drive until 500mA. I think the over current can not be the cause.

I let you a channel diagram in a pict.


texts: Placement of gate source pull-down resistor for parallel MOSFETs for BLDC motor

texts:
I am working through various Application Notes for driving parallel MOSFETs for a BLDC motor controller.
The addition of individual gate resistors \$R_G\$ means the gate-source pull-down resistor \$R_{GS}\$ can go on the gate side or the driver side.
The 1kW BLDC Power Tool Kit User Manual from Infineon shows the pull-down resistor on the driver side.

But the Power MOSFET Selecting MOSFFETs and Consideration for Circuit Design Application Note from Toshiba (page 11) shows a pull-down resistor on the gate side for both MOSFETs.

\$R_{G}\$ will be 5Ω to 100Ω and \$R_{GS}\$ will be 10kΩ to 1MΩ.  Pull‐down resistor will prevent erroneous switching from induced noise during dead-time as controller transitions.  Gate resistors are to counter parasitic oscillation from MOSFETs in parallel.
I am inclined to go for a single pull-down for my 3 MOSFETs in parallel.  With individual resistors, \$R_{G}\$ and \$R_{GS}\$ form a voltage divider, but as long as \$R_{GS}\$ >> \$R_{G}\$, this will not have a significant delay on MOSFET ON/OFF.  Am I missing something or does it not matter?
Is there any advantage/disadvantage to the use of individual pull-down resistors over a common pull-down resistor?


texts:
I have a 2:1 MUX. It would be designed by using NOR gates. Inputs are X and Y. S, which is data select. When S is 0  F=X  , S is 1  F=Y. Until here, okey. I've found $$ F = S'X + SY $$
to make NOR, I've rewritten as $$ F = [(S + X') (S' + Y')]' $$  At this point , I'm stuck how I can make(draw) the expression by using just NOR gates. Actually, It can be drawn via softwares.But, I wonder that how I should think to draw. I need its logic.


texts: power from glitches vs power consumed on pinelining

texts:
first let me define glitches as i understand it and correct me if i"am mistaken.
glitches are the propagation of unstable signal through  the system it happens when one of the operand arrive to computational block(adder for example) before the other operand .

ok , so we use a pipe-lined architecture (putting synchronous  registers or latches between every combinatorial block between an adder and a multiplier ) to avoid glitches an propagate only stable results .the other advantage of pipe lined architecture is to reduce  the critical path.

well am working on a low frequency project 30khz so delay is not an issue and the period of a clock is moooore than enough to perform all four operations .

the problem that latches or register are area and power consuming .

i would like to know if the it is a good choice to eliminate the registers between each block. and if am going to loose the power consumption i save from register on glitches


texts: How to properly drive MOSFET in MPP tracking duty cycle above 50% for a synchronous buck regulator at 50-100V input?

texts:
I'm currently building a 10W high voltage (~50V-100V) Maximum Power Point Tracking (MPPT) buck regulator on the side for educational purposes. For the time being, the output is tied to a load. Things are working well, and the circuit properly tracks the maximum power point as expected. So far so good.

I'm using the LTC4444-5 High Voltage Synchronous N-Channel MOSFET Driver to drive the top and bottom NMOS MOSFETs controlling the buck power stage (switching at 100kHz), which introduces an issue. On many occasions, my MPPT algorithm wants to set the duty cycle above 50%. This is problematic for a synchronous buck stage since it starts lowering the voltage on the bootstrap capacitor charged by the synchronous MOSFET driver, to the point where the top MOSFET barely turns on.

In order to have the top MOSFET turn on for duty cycles >50%, I have two options:

Find a high side MOSFET driver that uses a charge pump rather than a bootstrap cap.  The best candidate I found was the MIC5011 from Micrel.  Ignoring the fact that the maximum input voltage is too low, it's biggest drawback is that it turns on too slowly: 25us absolute best case (40kHz), more common case is 50us(20kHz).
Have an isolated MOSFET driver with an isolated power supply, but that's starting to get pricey.

Is isolation the only way to properly drive these MOSFETs?  Are there high-side MOSFET drivers that are high voltage (say >50V), switch quickly (easily support 100kHz) and can handle >50% duty cycle?

Better yet, am I going down the wrong path? Is there a simpler way to solve this issue?


texts:
I understand that what's diffusion and what's drift current but what I don know is how I identify whether a semiconductor is diffusion or drift based? Let's say bjt MOSFET and diode as example. They all have diffusion and drift property for me which makes me confused

Thanks! That clears my doubts. but from my notes it says bjt is diffusion based which mKes me confuse and MOSFET  is drift based. Can I know how we know which will dominant to the other?


texts: Can I switch both positive and negative voltage rails on and off using a Teensy 3.2

texts:
I've been trying to switch voltage rails (both Vcc and Gnd) of a device on and off from a digital pin on a Teensy 3.2. I have made a corresponding Low side switch using BC547 npn transistor and a High side switch using a BC557 pnp transistor with another BC547 to serve as a level shifter as it switches 5V from 3.3V and an inverter since I am using the same digital pin for both. The load is an tiny lcd display that draws no more than 100mA. I've tested the two circuits individually and they work flawlessly.
The reason I want to switch both Vcc and Gnd is because the Teensy goes through a sleep mode and even if I used only Low side switching, the display used to flicker and not turn off like I wanted it to. And I'm thinking that would lower my power consumption but that isn't really a matter to me although I'm not sure if that really does lower it.
The problem I am facing is when I switch both Vcc and Gnd off through the transistors and turn them on again, the lcd is misbehaving, i.e is not intialized properly, it does not behave the way it would when it is powered directly and completely fails its purpose by not displaying anything. I tried adding a delay between turning on the transistors and initialization but that doesn't seem to help. Am I doing something wrong here or should I connect the Gnd before Vcc? I'm pretty sure I'm missing something here but I can't seem to figure it out. Can someone help me out?
Thanks in advance.
This is the npn Low side switch from this same website:
And this is the pnp High side switch also from this website:


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I recently learned how incandescent Christmas bulbs can be modified to continue conducting electricity after burning out thanks to a fuse link that bridges the two leads at the base of the bulb.

  When the filament burns out and stops conducting, the entire circuit voltage is briefly across the fuse link.  This voltage is greater than the breakdown voltage of the insulator on the fuse link, which causes the insulation to break down and turns the fuse link into the new direct path.

I was curious about how something similar could be accomplished with LED bulbs.  If it would use the same system, where in the LED would the fuse be placed?

Side note: I'm new.  If my terminology is wrong, please let me know so I can do better research in the future!


texts: LED ULN2803 thermal / heatsink questions

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I'm intending to use LEDs of 5mm, which have a max forward current rate at 30 mA, or a value of 100 mA, with 10% 1 kHz duty cycle, in a circuit like the one below except some changes:

STM32F103C8T6 instead of PIC
2N7000's instead of UDN2981
3 ULN2803 instead of 1, because they can only handle 500 mA
15 rows instead of 8 (thus 3 x 5 = 15 2N7000's)
8 columns, where each ULN2803 handles 5 rows

I have several questions:

In the ULN280x datasheet on page 5 stands the thermal property:

RthJA Thermal resistance junction-ambient 55 C/W

If I do a calculation: 5 V * 100 mA * 5 leds = 2,500 mW = 2.5 W
This means a temperature rise of 55 * 2.5 = 137.5 C.
The junction temperature is max 150 C, so it will be not working.

Or should I reduce the voltage used by the LEDs? (like e.g. 2 V forward voltage):

(5 - 2) V * 100 mA * 5 leds = 1.5 W, resulting in 55 * 1.5 = 82.5 C
Since I round robin over the ULN2803 array's, does this reduce the temperature maybe?  Resulting in a lower temperature? (I think not, but I'm not an expert)
I assume I would need heat sinks, but from what temperature this is needed?


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Can someone help me with identifying this component please? I was initially under the impression that it is a resistor but when I look at the back, it looks like a resistor with a dab of solder in between. I have tried to find a circuit diagram for the board but failed. I looked up a 5 band resistor but the colors don't match. Thanks in advance.

Edit 1: Here is a circuit diagram I found- the components are at D3.
http://www.lcdrepairguide.com/V5/ak_2017/temp/tempfiles_/PSU_Schematic_Diagram/Samsung%20BN44-00358B%20PSU%20Schematic.pdf


texts: Why is the Tach output on computer fan referenced to the VCC?

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I am working on an electronic field mill with a computer fan, and am following the design on this instructable.

The arduino needs to know what rate the fan is spinning to know when the shutters are open and closed to measure e-field voltage. We are using the tach output on the motor to do so.

When powering up the computer fan, I first tried to probe the device by placing the ground of the oscilloscope to the negative lead on the fan and the voltage probe to the tach output of the fan, but I only saw some spikes, no readable square wave. I only got this square wave when I placed the ground wire of the scope on the VCC wire of the motor and left the voltage probe on the tach output.

Why is this output referenced to the input voltage, and will it still work with the arduino? If this is something not unique to only the fan I have, what is the reason for building the fan this way?


texts: Connecting i2c slaves to master over RJ45 style cable?

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I'm desigining several modules (e.g. sensors, motor controller, etc.) that need to communicate over I²C.
These modules can be up to 15ft (5m) away from the base module (I²C master - Spark Photon) - although most will be less than 5ft away. To keep connections simple, I would like to be able to daisy-chain these modules.

Each module uses an ATTiny84/85 which handles the various functions of each module (e.g. ADC/DAC). Each micro also acts as an i2c slave (configurable address) and responds to commands from the I²C master (Spark Photon).

I'd really like to use (abuse) an ethernet (RJ45) style cable. Given that ethernet cables are widely available in various lengths and relatively inexpensive, they would be ideal. I could provide power (3.3V & 5V) and ground as well as the I²C lines to each module and still have spare wires I could potentially use in a future revision. I could even use two twisted pairs to shield the i2c lines. Maybe? The only downside I see here is that someone might be using a crossover cable, which could potentially mess things up.

Alternatively I could use USB cables (A style female extension cables). If I give up separate power lines and use a voltage regulator on the modules that require 3.3V. I'm not sure if my length requirements would be met here, but if daisy-chaining works, this shouldn't be a big problem.

Are there RJ45 connectors that would allow me to use a wire-to-board style connector (e.g. Molex Mini-Latch)?
I'd really like to not have to deal with the precision milling and the cost through-hole or surface mount style connectors require.

The same would go for USB style connectors.

UPDATE:
It appears that I²C is indeed a viable solution. My biggest concern at this point is the cable to use and if there are connectors available that do not need to be directly soldered onto the PCB (wire-to-board would be ideal).


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This week I am repairing an old Game Gear, suffering from bad video memory. The original IC is a HM65256BLFP-10T: an asynchronous Pseudo-Static 8-bit 32k-word RAM with an access time of 100ns.

I would like to replace it with a similar memory, but I do not understand some of the terminology regarding this type of ICs. Does it matter if my new RAM is rated as a CMOS Static RAM? Can I replace a PseudoSRAM with an SRAM?. Is there any risk (damaging other components or modifying the game experience in any way) on choosing a memory with more capacity or less access time?

I have been reading he datasheets of some ICs. Would either Hitachi HM62256BLFP or Sony CXK58257AM do the job? I accept suggestions


texts: Where is the capacitive coupling in this adafruit soil moisture sensor?

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Here is the moisture sensor:
https://learn.adafruit.com/adafruit-stemma-soil-sensor-i2c-capacitive-moisture-sensor/downloads

It has a large copper area insulated with soldermask that sticks in the soil.

My understanding is that moisture in the soil changes the electrical permitivity of the soil, and thus affects the capacitance. However there's only one copper polygon fill on the pcb to serve as one side of a capacitor, and I'd like to understand what it is capacitively coupled to.

If the rest of the circuit is floating, presumably it needs to couple back to the circuit otherwise the microcontroller wouldn't be able to drive the capacitance. I can't see any provision for this though.


texts: Why do all my NTC thermistor have a PTC curve?

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Suddenly, after testing my NTC thermistor (100k), the thermistor's curve started to turn into a PTC curve. To measure the resistance I am using an Arduino. I think its a hardware issue as I did not change my program at all. Is there a way to check it the resistance's that the Arduino outputs are correct? Could this be the problem, would it be the thermistors? The precision, I think, is also affected, some are too 5C others are to 1C.

#include <Wire.h>
#include <Arduino.h>
int ThermistorPin = 0, reffPin = 1;
int resistance = 10000;

void setup() {
  Serial.begin(9600);
}

void loop() {
  float avg = 0;

      for(int x = 0; x < 10; x++)
      {
        avg += volateToResistance();
        delay(50);

      }
      Serial.println(avg/10.0);
    delay(5);
}
float volateToResistance()
{
  float voltage = analogRead(reffPin) * 5.0/1023;  // takes in ausmmed 5 volts and calulates actutal voltage Ex if analogRead(reffPin) = 1023, then voltage will be equal to exactly 5 volts
  float Vout= (analogRead(ThermistorPin) * voltage)/1023.0;
  return resistance * (voltage/Vout) -1;
}