texts: calculating maximum transmission distance of radio module based on dbm and open air

texts:
I own several HM-TRP TTL FSK radio modules, and every time I turn one on, it reports it as being version 2.

Anyways I did read the manual and it has a setting for transmitter power as follows:

0 = +1 dbm
1 = +2 dbm
2 = +5 dbm
3 = +8 dbm
4 = +11 dbm
5 = +14 dbm
6 = +17 dbm
7 = +20 dbm

How do I convert these values to transmission distance in meters if all of the following conditions are met:

A. The transmitter module and receiver module are powered with a steady 3VDC

B. There are no other objects between this transmitter and an HM-TRP receiver

C. The receiver's noise floor is at maximum

D. Both modules have copper coil antennas measuring about 1cm in length
   and the end is connected to the ANT pin on the module

E. Both modules operate at the frequency 915 Mhz.

F. Both modules use a UART data rate of 38400bps
   and a wireless data rate of 38400bps as well.

So what's the formula?

UPDATE

So I'm trying to understand here... Do I use the formula for path loss and subtract that from the transmission DBM setting I select in my receiver and if the result is not negative then I get a signal?

And I got two different equations for calculating path loss. Which is officially correct?


texts:
Just a quick one. When looking at schematics for a VFD, I see the same circuits as diodes used in the converter (AC to DC), capacitors in the DC bus and transistors or thyristors used in the inverter to produce PWM to simulate AC output.

Question is, to simulate this AC output, the transistors would have to fire at different times. For 3 phase this would be 6 transistors firing at 60 degrees apart. What controls this firing time? Is there something missing from every diagram I've seen or is there something else I'm missing?

An example of the kinds of schematics I've been looking at is
https://www.electronicshub.org/wp-content/uploads/2019/05/Variable-Frequency-Drive-VFD-Building-Blocks.jpg
And
https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQkniY__JYs5TcEJMDSp1t0esI3zMeBTe7ENrK60tw_7PHxrozY

Thanks a lot


texts:
I read how boost converters work and that got me thinking:
Can I use a pass transistor to achieve currents that may be limited by the inductor used in the circuit? This is a bare version of a boost converter as I understood it (correct me if I'm wrong, I'm still learning!)

simulate this circuit – Schematic created using CircuitLab

So what if I did this? Would this give me a current higher than the inductor would have been able to put out?

simulate this circuit

Like the way the LM317/LM78xx series do?


texts:
I am conducting some simulation work where I would like to incorporate the LTC3588-1 component model in LTSpice.

I have an electrical model of a physical system that requires the use of an ideal DC transformer. While I have used the model successfully in Simulink and SIMetrix, such a transformer is not available in LTSpice.

Could anyone please offer some advice about how an ideal DC transformer may be constructed in LTSpice?

For reference, documentation for the component I am trying to simulate is available for
SIMetrix and
Simulink


texts:
So this is my first question here.
I am reading this book, "Digital Electronics & Computer Design - By M.M. Mano". While I was reading the Sequential logic and flip-flops, I found this:

The feedback path between combinational circuit and memory elements(flip-flops) in a sequential circuit can produce instability if the outputs of memory elements are changing while the outputs of the combinational that go to flip-flop inputs are being sampled by the clock pulse.

I didn't understand this statement. So I googled and found a similar statement at circuitstoday.

If a clock pulse is given to the input of the flip flop at the same time when the output of the flip flop is changing, it may cause instability to the circuit.

I tried to get my head around this but didn't come up with any idea that gets me peace. I'm confused especially with this "the outputs of memory elements are changing or when the output of the flip flop is changing. What does it mean? Because the output of a flip-flop will only change if there's a change applied on input signal. It will not change by itself.
So I came up here. Please help me with this context. Any help would be appreciated.


texts:
I have a 12 v dc power supply 36 watt 3 amp
attempting to run 5 12v dc 4 watt led lights in parallel. at first i tried running 5 hallogen lights but figured they were drawing to much power so switched them out to the leds. my question is i am being told i need to put in a resistor to keep from  blowing my power supply. i do not know the led parameters such as voltage drop or how much power will flow through the led. and need to know what size resistor needed?

my led are GY6.35 G6.35 Bi-pin Base LED Bulb 4Watt AC DC 12V Silica Gel Crystal Daylight White 6000k Landscape Lighting,JC Type, Equivalent 25W- 30W Q35/CL/T4 Halogen

please note i am creating a circuit from scratch every time i try power up my lights my power supply kicks off


texts: 555 timer circuit switching automotive solenoid with PNP & NPN switching transistors

texts:
I am trying to design a 30 second timer circuit to switch an automotive solenoid that draws about 0.8 amps, and need some help please.

StackExchange posts have been very very helpful so far, and by reading older posts it has helped improve the design of the circuit with protection diodes D1 and D2, and decoupling capacitors C3 and C4, placed very close to pins 1 and 8 of the 555.

Due to the configuration my control circuit must be above the load, so I am using a PNP transistor (Q2) to switch the solenoid.  The Base of the PNP is connected to ground through an NPN transistor (Q1), which is switched by the output of a 555 chip.

My problem is that the solenoid switches on as soon as the NPN transistor Q1 is connected.  Disconnecting either the 555 output or the connection from the transistor to earth switches the solenoid off.

When prototyping, it worked previously when using BD682 as the PNP transistor and BD681 as the NPN transistor with appropriately sized base resistors, but have now switched to surface mount parts and is broken.  Any advice gratefully received!

In this thread:
PNP to NPN Transistor switch, some of the replies discuss adding transistors between the Base and Emitter of the PNP transistor due to leakage of the NPN transistor, but R5 does that in my circuit, I think?


texts: Bluetooth modules and profiles for audio

texts:
Few weeks ago I started designing a product that requires wireless connectivity, and more specifically Bluetooth audio. I need it to work "right out of the box" with the most popular mobile devices such as smartphones (iPhone, Android, etc) and computers, just like average Bluetooth speakers would (ie. appear in the found Bluetooth device list and directly connect to the device, ready to play its audio content).

However, there seem to be dozens of different Bluetooth profiles that all have their own specificities, but I couldn't find one that is compatible to every device class. For example, I'm aware that Apple requires the device to be a part of the MFi program, and I heard that the iAP Bluetooth profile was required to communicate with an Apple device, etc, but is this profile compatible with Android or windows Phone too ? If not, is it possible to run different profiles at the same time ?

Some Bluetooth modules (like the Microchip RN52) offer support for those profiles but can they be discovered and connected to devices that only support other profiles ?

Thanks for your answers.


texts:
I created an AM modulator circuit with BJT 2N3904 for a school project.

V1 is the modulating signal (sine wave, amplitude 5V, frequency 1KHz)
V2 is the carrier signal (sine wave, amplitude 30mV, frequency 600KHz)
With Tina simulation I have this output:

The oscilloscope show me this situation:

I have calculated the amplitude of the modulated signal (about 1,30V)
Why I have this behaviour? How can I calculate the modulation index?


texts: I've found the memory alignment is always equal to power of 2. Google said that such amount of alignment allows modern computers to perform read more fast. Ok, what exactly problem we would gain if we set amount of alignment is power of 3? To be more specific I would like to know what exact hardware architect aspect require the alignment to be a power of 2.


texts: why there is -ve sign in the phase shift of RL low pass filter?

texts:
why we put negative sign in the phase shift
can someone explain this to me ?
any tutorial or lecture ?
looking forward 4 your suggestion


texts: Connecting separately powered devices via serial

texts:
I have a small issue connecting an FTDI USB to 5V Serial adapter to an externally powered PIC microcontroller. They are connected via serial connection. The USB connection powered the FTDI and a battery powers the PIC.

                 Serial
Laptop --- FTDI ======== PIC ----- 3.7V battery

Currently I have 4k7 resistors in the serial lines. 5V high on the FTDI's TX will be clamped to whatever the PIC is (3v - 4.2v) via the input protection diodes, and 3V from the PIC's TX is higher than the FTDI's input threshold. This seems ok, limiting the protection diode current to 500uA.

My main concern is unplugging the cable from the laptop. Then the FTDI device is powered off and the PIC, via its TX line, will try and power it. Even at 10K, that's 500uA. I've no idea if that's a bad idea or not.

I've a feeling this isn't the best way of going about this given that either circuit could be powered off and damaged by the other. Would it be better to convert each RX side into a pseudo "open drain"?

              +----- Vdd
             100k
+-------|<----+------RX


texts: Z Transform How to Handle the Inital Condition

texts:
I have a question about the Z transform Z{x[k+1]} = X(z)z^1. How do I account for the initial condition? In continuous systems, the analogous situation is L{x'(t)} = sX(s) -x(0). I have a equation from a state space equation,
x[k+1] = (I+TA)x[k] where x[0] = 1. I want to find a closed loop solution for x[k] =?. Normally, I would take the Z transform and solve for X(z) and then convert back. However, the Z transform is not taking into account the initial condition and is resulting in a wrong answer.


texts: What is the sine wave coming from the output of an opamp?

texts:
I'm using opa657 see datasheet for my photodiode, but when I connected the photodiode as the 1st schematic in the data sheet, I got a sine  wave of Vpp=2Vs at the output of the amplifier even without any input on the photodiode.

and when I put an incident light the sine wave will disapear and no signal appears to the output of the amplifier.

Where does this sine wave come from and how fix this problem?


texts:
I am new here so I apologize in advance for any mistakes in the way I am going about this. I had a question regarding a project that I am working on.

I am trying to use a MOSFET as a switch that I am able to control using the digital pins of the Arduino. The switch is meant to control a valve, so I would send HIGH to an Arduino pin and the valve would open. A diagram is below:

Sorry if my diagram is unclear but I will try my best to explain the issue. The supply on the left is meant to represent an Arduino digital pin. The valve is an 8W 12V DC valve that has very simple operation. If its terminals are connected to a 12V DC supply, it opens otherwise it stays closed. Now in this schematic Vdd is 12V (positive terminal of supply) but when I set the Arduino pin connected to the gate to HIGH, nothing happens. I have done the exact same setup except with a LED and it works fine, I can set the pin to HIGH and the LED turns on as expected and turns off at LOW. But this is not true when I use the valve

The MOSFET model and datasheet is here: http://www.mouser.com/ds/2/149/FQU1N60C-246709.pdf

This exact same setup works with a LED. I am wondering what is the issue when I use the valve?

But was unable to use the info there to figure out the issue. I am wondering if it has something to do with the amount of current going through the valve, if that might be too low but I am not sure.

Thank you very much for all your help!


texts: Detecting on- and off-state of a micro switch

texts:
For safety reasons I need to make sure that I am still detecting the correct state of a micro switch and not for example a loss of power, broken cable, etc.

What are cheap and reliable ways of doing this?

To be clear, I need three kinds of signals (examples in parenthesis), on (I=5 mA), off (I=1mA), cable broken/etc. (I=0mA).

If possible I'd prefer some theory behind the solution(s), a book with the basics of such circuits for references would be greatly appreciated.


texts: Parallel in serial out Verilog Shift Register, odd behavior during clocking

texts:
Hello I am trying to implement a parallel in serial out shift register based on the data sheet for the 74LV165A 8 bit parallel in serial out shift register

the spec sheet may be found at datasheet for 74LV165A

If I make my test bench begin by shifting in serially, then try to latch data on the parallel input the data does not appear. If I begin the test bench in with parallel latch enabled then the data appears on the Q and will clock through once shifting is enabled.

My goal is to shift several sets of data through this register however currently this behavior is preventing this. Any help would be very very appreciated, event if its just a hint :)

Currently I am monitoring the set and reset information and the Q lines.

module nand3(input one, input two, input three, output out);
    assign out = !(one&two&three);
endmodule

module nand2(input one, input two, output out);
    assign out = !(one&two);
endmodule

module DFlipFlop(input clk, input reset, input D, input set, output Q);

reg Q;

initial
     Q<=0;

always @(posedge clk or negedge reset or negedge set)
begin
    if(!reset)
            Q<=0;
    else if(!set)
            Q<=1;
    else
            Q<=D;

end

endmodule

module control_mux(input [7:0]set_bits, input CP, input CE, input PL, output [16:0]bus); // bit 16 is clk, bits 15 -> 8 are set, bits 7 -> 0 of bus are reset

assign VCC = 1;

nand3 control(!CP, !CE, PL, bus[16]);

nand2 set1(!PL, set_bits[7], bus[15]);
nand2 set2(!PL, set_bits[6], bus[14]);
nand2 set3(!PL, set_bits[5], bus[13]);
nand2 set4(!PL, set_bits[4], bus[12]);
nand2 set5(!PL, set_bits[3], bus[11]);
nand2 set6(!PL, set_bits[2], bus[10]);
nand2 set7(!PL, set_bits[1], bus[9]);
nand2 set8(!PL, set_bits[0], bus[8]);

nand2 reset1(!PL, bus[15], bus[7]);
nand2 reset2(!PL, bus[14], bus[6]);
nand2 reset3(!PL, bus[13], bus[5]);
nand2 reset4(!PL, bus[12], bus[4]);
nand2 reset5(!PL, bus[11], bus[3]);
nand2 reset6(!PL, bus[10], bus[2]);
nand2 reset7(!PL, bus[9],   bus[1]);
nand2 reset8(!PL, bus[8],   bus[0]);

endmodule

module testbench;

    reg [7:0]set_bits;
                  reg [7:0]set_bits2;
    reg CE, PL, CP, D;

    wire [16:0]bus;
    wire [7:0]Q;

    always
        #5 CP = !CP;

    initial
    begin
        CP = 0;
        D = 0;
        set_bits = 8'b11001011;

                                     PL = 0; CE = 1;
         #10 PL = 1;  CE = 0;
    end

    initial
        #500 $finish;

    initial
    begin
        $display("CP,      CE,        PL,       b16        b15        b14       b13        b12        b11        b10        b9        b8       b7       b6      b5      b4      b3      b2     b1     b0  Q7  Q6  Q5 Q4 Q3 Q2 Q1 Q0");
        $monitor("%b            %b            %b           %b            %b            %b            %b            %b            %b            %b            %b          %b        %b         %b         %b         %b        %b       %b       %b       %b      %b    %b    %b    %b    %b    %b    %b    %b", CP, CE, PL, bus[16], bus[15], bus[14], bus[13], bus[12], bus[11], bus[10], bus[9], bus[8], bus[7], bus[6], bus[5], bus[4], bus[3], bus[2], bus[1], bus[0], Q[7], Q[6],Q[5],Q[4],Q[3],Q[2],Q[1],Q[0]);
    end

    control_mux CM(set_bits, CP, CE, PL, bus);
    DFlipFlop FF(bus[16], bus[7], D, bus[15], Q[7]);
    DFlipFlop FF2(bus[16], bus[6], Q[7], bus[14], Q[6]);
    DFlipFlop FF3(bus[16], bus[5], Q[6], bus[13], Q[5]);
    DFlipFlop FF4(bus[16], bus[4], Q[5], bus[12], Q[4]);
    DFlipFlop FF5(bus[16], bus[3], Q[4], bus[11], Q[3]);
    DFlipFlop FF6(bus[16], bus[2], Q[3], bus[10], Q[2]);
    DFlipFlop FF7(bus[16], bus[1], Q[2], bus[9], Q[1]);
    DFlipFlop FF8(bus[16], bus[0], Q[1], bus[8], Q[0]);

endmodule


texts: SPI to Numerous Chips on Different PCBs with FFC Cables?

texts:
I want to drive numerous chips on several different PCBs with SPI from a microcontroller over FFC cables.

Here is a crude diagram:

UPDATE: Green wires are ground scheme

I have never attempted such a layout and someone has warned that capacitance could be a major issue. As illustrated, there could be 5-10 chips (depending on the combination of boards used) on the digital bus.

The cables are are 8 conductor, 1.0mm pitch, 0.27mm thickness, 1.2A, 60V (like Molex 15267-0237). The pinout of the cables will all be the same since all of these lines are to be connected together to the SPI pins on the uC.

So for example, in the above illustration, the SCLK line would be connected to 8 chips on ~600 mm of cable.

So is this even possible? Or is the combined capacitance of 8 inputs and 600 mm of cable going to destroy my data signals?

Is there anything I can do to limit problems?

I was thinking about a pinout for the cable like:

Cable - uC
------------
SCKL  - SCK
SDI   - MISO
SDO   - MOSI
LE3   - D1
LE2   - D2
LE1   - D3
VL    - 5V
RST   - D4

Ground wires will run separately from each board to a central point next to the bypass caps of the power supply.

I was thinking that maybe if I put VL between SCLK and SDI and RST between SDI and SDO might help limit crosstalk but I don't suspect that will help with the overall issue of parasitic capacitance.

Fortunately none of this has to run at terribly high speed as it will all be ultimately interfacing with a human being. So 2MHz would be just fine and I suspect 125 kHz might even work.

Ideas?


texts:
I am looking at this relay part: FTR-LYCA012Y.
I am tasked with finding a relay part with contact ratings of 5A for both 250Vac and 30Vdc, even better when UL approved.
The datasheet has a table at the end (Safety Standards) which seems to state the contact ratings as approved by UL. From this table, I can conclude that this relay satisfies our needed specs.
However, upon looking at the contact ratings at the start of the datasheet (non-UL table), I see that it seems inconsistent with the UL approved ratings. In fact, the UL approved ratings are higher. Also, looking at the max switching power for DC (144W), I can compute that for 30Vdc load, I can only pass 4.8A. However, the UL rating specified it for 6A/30Vdc.

Can anyone clarify or correct my understanding. Thanks.


texts:
While tinkering with audio amplifier chips, I occasionally find myself testing op-amps that need voltages upwards of +-32V to really push them to the limit. However, off-the-shelf variable bench PSUs that can supply both +32V and -32V seem rare, and would be extremely expensive if one could be found.

However, I have one of these - an SMPS800RE from Connexelectronic. (Datasheet here, PDF). This is a high power SMPS designed for audio applications. The version I have has fixed outputs of +50V and -50V, and is capable of delivering 10A constant (14A peak).

I never found a permanent use for it, and was wondering exactly how I might go about converting it into a variable bench PSU.

Would it just be a matter of feeding the output into, say, a buck converter together with some potentiometers to control the desired output?
...or would I need to modify the SMPS itself, perhaps including some adjustable regulation before the output stage?

Any advice in how best to achieve this? While I've made small variable supplies out of old ATX PSUs and smaller projects, I've never tackled one quite this monstrous. So the simpler the better. But I also value efficiency, and not dying.


texts: Why are crystal oscillators used in clocks instead of RLC circuits?

texts: The timing of quartz clocks is regulated by a crystal oscillator.  This crystal oscillator effectively forms an RLC circuit.  If this is so, what properties does a crystal oscillator have that makes it advantageous over an RLC circuit?


texts: What does this capacitor do? (Microwave biasing circuit)

texts:
I'm wondering what \$C_B\$ attached to the bottom of \$R_{C2}\$ does.  This is a screenshot from a textbook called RF Circuit Design: Theory and Applications by R. Ludwig And P. Bretchko.  Looking at 8-36a and 8-36b, \$C_B\$ doesn't seem to ever get used (the one at the base of the \$Q_2\$ does though).

The book does say somewhere else, though, that often the RFC is replaced with a \$\frac{1}{4}\lambda\$ line which converts the short created by \$C_B\$ to an open circuit, so would that imply that that cap is redundant if an RFC is used?


texts: Allowable current in Ni-Cr 80 20 gauge wire?

texts:
I am creating a small oven for curing composites out-of-autoclave, and have some Ni-Cr 80 20gauge wire lying around.  I need to put up to 8.6 amps through the wire at maximum.  The current is controlled with a PID bang-bang controller, so the duty cycle is not 100% at that current.

I know that 20 gauge Cu wire is rated for ~7 amps, but since Ni-Cr has a higher melting point I figured I might be able to get away with using my left over wire.  The one problem that might knock down the amount of amperage allowed even further is that the ambient environment of the furnace will be at 200 C at maximum steady state conditions, but the duty cycle on the wire will be much lower than on ramps up to steady temperature.

Any insight would be greatly appreciated.


texts:
Two part question.

If I take the 11v and 5v, with diode to prevent 11v to flow to the 5v, will I get 16 volts? And will it charge a 12v battery?

Last how can prevent overcharge?

Also this is an older power supply. 1999 old.

Adding: this an ATX Power Supply. Internet searching info says if you connect the +12v to the -5, you get +17v.


texts: Can you place vias inside a QFN footprint?

texts:
I am designing a very dense PCB containing a 0.4mm pitch QFN chip. In parts it is proving very difficult to fan out. It is made all the more difficult by the huge thermal pad that all QFNs have for some reason.
It is reasonable to place tiny vias 0.45mm OD, 0.2mm ID between the land pads and the thermal pad, like this?

I can't think of a good reason why not: they're covered in solder resist, and the sizes and clearances are within spec for our PCB shop. But I don't think I've ever seen anyone do this before.
Add
I just wanted to add some photos for people interested in these small vias. Here's two from a board we had made recently. Some of the drills are bang on, and some are slightly off.


texts: LDO Voltage regulator output unexpected Voltage drop

texts:
I have a circuit using LD39015 1.2V Low Drop-out voltage regulator.

.

The value of VCC is 3.3 Volts. The goal is to supply an ADC channel with a constant stable voltage so I can use that to reverse calculate the VCC. And yes I have looked at both Vref IC and Vreg IC options. But while testing the Volt Reg option, I am seeing a 1.189 volts at the output of the voltage regulator with R2 = 10k, 1.191 V for a R2 = 1k and 1.11V for R2 = 100k Ohm. First of all why am I not getting exact 1.2V rated output from the regulator given it satisfies the min input voltage and the dropout voltage. Secondly how does changing the resistance value change the output of the regulator even when the voltage regulator gets sufficient input voltage.
Thanks.


texts: Basic question - LM833 single power supply

texts:
simulate this circuit – Schematic created using CircuitLab

I am testing an active lowpass filter based on the LM833 Opamp.
Basically I am testing different values of power supply to see how they affect the output.

I first tried the 5V from Arduino, all ok except the signal gets distorted.

In an attempt to improve the output signal I connected the opamp with a 9V external DC power supply. I thought it should work, since 9V is far below the Max VCC accepted by the LM833.
Well I was wrong. The device started to smell very bad.
It's because of the current? The power supply can supply up to 1A. What am I doing wrong?


texts: Diagnosing cause of electrolytic capacitor failing

texts:
I am hoping somebody could help me diagnose the cause of failing electrolytic capacitors in a circuit. The context is a charger circuit, more specifically its power supply unit:

Given a diode bridge rectifier that is connected on one set of terminals to the mains via a filter circuit and on the other side to two electrolytic capacitors connected in series. Parallel to each capacitor are two discharge-resistors. (And of course the actual consumer circuit.)

The problem is, one of the two capacitors in series, the one connected to the - terminal of the diode bridge, explodes. This fault occurs since the device was subjected to intermittent AC-supply: unstable frequency, probably over- and under-voltages.

I am wondering where to search for the problem:

diode bridge? - I played around a bit with spice and the only way I could get reversed polarity on one of the capacitors was to assume two diodes short-circuited and the other two became isolators. This does not seem a very likely failure mode...
circuit fault after the power supply unit? - Any hint on what to look for? The consumer circuit is non trivial...

The capacitors in question were 200Vdc, 1000uF for a device to be plugged into 230Vac. I replaced both after the first failure, plugged it in and immediately the same capacitor blew again.

Unfortunately I do not have access to an oscilloscope at the moment but only a digital multimeter.

Many thanks!

Edit 1

I took a closer look at the PCB and got the following partial schematic. The main transformer is in the top left hand corner. The PWM IC chip etc. are connected to the hanging MOSFET the the bottom of the schematic.

The TRIAC is part of a STR 81145, which automatically switches to voltage doubling mode if input is 115V. (It takes it's supply from the positive rail as well.)

After removing the capacitors in question, C7 & C8, the resistance to the positive and negative rails are equal to the 50kOhm set by the voltage divider.


texts:
Let's consider any circuit which contains a differential pair, for example a telescopic cascode single stage OTA:

In every circuit like this one, my professor and every book compute the small signal differential gain by assuming a perfect differential input couple of signals. Thus, as far as regards our example, we have:

and the small signal differential gain, exploiting the symmetry (i.e. the ac grounds on the nodes on the axis of symmetry which allow me to consider just half circuit), becomes:

This procedure is general: every time we have a circuit with a differential input pair, under the hypothesis of differential input signals, we can simplify the computation of the differential gain by exploiting symmetry (half circuit).

The question now is: why do we always compute the differential gain in the particular case of differential signals as input? In the most general case, indeed, we don't have differential signals. Consider for example this basic circuit:

In every book I've read, we pretend that the gain of the op-amp is the differential gain calculated before (i.e. assuming differential input signals). In other words: in order to use the previous expression of the differential gain, we should have the following situation in which the inverting and the non-inverting terminals of the op-amp receive differential signals (in red in the following picture):

But actually those red signals are not present: indeed the non-inverting terminal is fixed to ground, whereas (assuming large differential gain) the inverting terminal is almost zero.

In conclusion: why do we always calculate, in circuits containing a differential pair, the small signal differential gain assuming perfect differential signals as input? Why do we wrongly assume that the gain found in this way is also the differential gain of op-amps used in negative feedback?

Thank you


texts:
Here's a diagram of a logic level indicator and NAND gate.

Now I'm supposed to use this in conjunction with some basic logic circuits. However I cannot find out what voltage I should have at the input for the LED to light up, assuming positive logic. Does anyone have an idea of how I could find it via calculations? I'm afraid I've got no idea.

EDIT: Added that it is assuming positive logic.


texts:
I want to use this clock oscillator

http://www.ecsxtal.com/store/pdf/ecs-2100x.pdf

It does not require loading capacitance.

However, it says "3.3V operation (optional)", yet on the same page it says "Supply Voltage: 5VDC +/- 0.25".

I was considering just throwing it in a breadboard, giving it 3.3V, and scoping the output pin to see if it worked.  But I was wondering if I would have any problems since the output pin would be unloaded, except for the scope.


texts:
I am trying to connect 6 LEDs on to a 3 V battery.
It is 1 mm LED’s with colors 2 x red, 2 x yellow and 2 x white. Each color connected in series.
Problem is once red and yellow light up, the white pair shuts off.
What is the best way to connect? What resistor or value do I need? A diagram would help me much.
Thank you.


texts: New PSU will not Start - Only flashes when the switch is turned on

texts:
I purchased a shiny new Tier 4 power supply, a RaidMax 500W Cobra Power.

I have dismantled it to use as a power supply for my mini-cloud project.  I am porting the +12V rail to power 4X Intel NUC 5i5MYBE blades through a 12V to 18V 285W step-up DC transformer, the 5V rail to power my managed 5-port gigabit network switches and thrift store wireless router using 5V to 12V step up transformer modules, 3X 500GB USB3 hard drives for Cinder storage on the 3 compute blades, 3X Raspberry Pi 3B units (Swift Object Store w/WD Labs 333GB PiDrive kits,) and 1X Raspberry Pi 3B MaaS controller.

I have connected the brown "sense" wire to the 3.3V rail inside the PSU case and shortened the leed, although I should probably keep it full length and attach it to a full length 3.3V leed, while I do not think this is the source of my issue.

I have connected +12V Power indicator and +12V power-on indicator leads to colored 3mm LEDs as indicators, have wired the green power leed to a switch to turn the supply off and on, and have attempted turning the unit on and off with and without 10W dummy load resistors on the +12V or +5V rails.  I have attempted the following resistor combinations:

1X 10ohm
2X 10ohm parallel and serial (5ohm/20ohm)
1X 50ohm
2X 50 ohm parallel (25ohm)

The power supply power indicator LED stays lit when the unit is plugged in and stays on well after power is removed as it drains the capacitors.  The power-on LED flashes when i hit the switch, as do the connected components, but does not stay on when I turn it on.  I am not sure what I am doing wrong, but am running out of things to try.  I am not confident that connecting the sense wire to the +5V rail is a good idea, but that is the only other thing I can think of to try.


texts:
I am not familiar on how to calculate the stepper motor resolution to operate with multi-turn absolute rotary encoder.

Stepper motor details as follows,

Total step - 600;
speed - 160 pps;
Motor type - Biploar;
Step mode - 1/8.

Please advise.


texts: is it possible to load a transversal wave with a longitudinal wave

texts:
like in communication engineering for sending information what we do,

we take a high frequency carrier and modulate it with the message signal

so can we do the same thing like take a high frequency carrier (transversal wave)

but the message is not transversal wave rather the message is longitudinal wave

say a sound wave

so can we modulate or load a transversal wave with a longitudinal wave ??

also if there is any work on this regard .. kindly post the link also??


texts:
I built a ZVS flyback driver a couple months ago, and it worked great and amazed people with the arcs it managed to create. I used 2 IRFP250 MOSFETs and the results were great. One day I was wanting even bigger arcs, and I combined two 12 volt batteries and a 12 volt car jump starter, for 36 volts and the arcs were giant. They worked for a while until the inductor started to get hot. The driver still worked (even with the hot inductor) until I turned it off and back on, when I had to replace the MOSFETs. The arcs stopped oscillating and it seemed like all of the current from the batteries was going to the inductor. The inductor got red hot and melted. I just recently replaced the MOSFETs and everything worked just like before. I  started out at 12 volts, and no problem, but when I added 24 volts, the same thing happened as when I added 36 volts previously. The inductor got very, very hot, and when I switched it off and back on, the same thing happened. The MOSFETs are 30 amps, 200 volts! so I don't know why they would have failed with just two 12 volt batteries.

How can I prevent this from happening again and what possibly could have gone wrong? (I really don't think I was drawing 30 amps, but I guess if they failed, it did.)

I want to identify my problem because I don't think it is good to keep replacing my MOSFETs just for them to burn out again!


texts: Does one of the battery failure damages the UPS DC capacitor bank?

texts: Last day i found the DC capacitor bank of the 300kva UPS was burst/damaged.Upon further inspection one of the battery in the battery bank found damaged .My doubt is whether the failure of battery can result in the capacitor bank damage ??


texts: Why is so8 test clip causing read errors with 93C56 eeprom (TL866 programmer)?

texts:
I am trying to read an Atmel 93C56B eeprom, so8 surface mount package, with this programmer. When using the so8 adapter in the zif socket it works perfectly. However when I use the test clip, it is giving me read errors on every other bit. The errors are consistent and seem to happen with every bit value except FFFF.

The test clip works fine when writing data also.

In every case (except FFFF), the even numbered bits (0,2,4,...) return the correct value, and the odd ones are wrong.

I am guessing this has to do with the length of the leads, however I even shortened the lead length by 75% and still have this problem. I have also tried 8dip versions of this eeprom in this same programmer and they never give errors so I must assume it is the clip. I have checked the pins of the clip and they are all correct (and if they weren't it shouldn't be able to write to the eeprom)

If this were a serial port I might try slowing down the bitrate, but this programmer seems to have no settings at all.

The reviews for this clip dont mention this problem, and it is sold by the same company that sells the programmer.

edit: btw the chip being accessed with the test clip is not soldered to anything


texts: PIC32 programming successfully but not working

texts:
I am designing my own PCB around a PIC32MM0064GPL028 microcontroller. Breaking down the steps below-

I have built a simple breadboard version first, inspired by PIC32MM curiosity development board.
Here is the schematic of the prototype programmed using PicKit3.
The prototype connects and programs with no issues. And the same code works perfectly on the curiosity development board. This indicates that the issue is in the schematics or components.

Links to the components I am using - PIC32, crystal, 18pF capacitor for crystal, 10uF capacitor for Vcap, Reverse Protection mosfet.

I am not an electronics engineer and have been playing with arduino and similar boards for quite a while now. However, this is all very new to me and probably the issue is a silly one.
It'll be super helpful if you could help me debug the issue. I can upload the code if it helps? Thanks.


texts:
I'm new here, so forgive me if I breach any forum protocols in the asking of this question.

I have designed a voltage regulator scheme for a guidance system on an aerial drone.  All components require either ~4V (they have an input range) or 3.3 V exactly.  My solution is pictured here in a schematic and a board layout.  I used the TPS53318 switcher to regulate my battery voltage down to 4 volts with roughly 3 mVpp noise, then used an LP38502 LDO to convert that into nice clean 3.3 V with as little wasted power as possible.  Datasheets here: TI TPS53318 and TI LP38503.

Schematic:

And board layout(image isn't very good, but I figured I'd include it just in case it helps):

So, my problem: It doesn't work.  The output from the switching regulator is a very small oscillating negative voltage, which I assume is caused by some sort of LC oscillation in the absence of any real output.

I've isolated the LDO, and it does it's job fine when supplied with 4V from an external supply.
I have tried reflowing my solder, even replacing the switcher itself (I always order 3 times as many as I think I'll need) and I still see the same problem.
I've done my best digging around with a multimeter and a scope trying to find a resistor with the wrong value or something, but I'm coming up empty handed.

This is my first time trying to troubleshoot this type of circuit, or any electronics this small on a proper board, so I'm hoping that someone here might point out errors I might have made or possible bugs I can attempt to diagnose.  The oscillating negative voltage output still seems odd to me, and I'm not entirely satisfied with my idea that it is caused by LC dynamics, so I'm also hoping that someone might be able to suggest a possible cause/solution for that effect.


texts: Is this Arduino regulator power switch circuit okay?

texts:
(Okay so I've been informed that you're supposed to edit your existing post and not make a new one even if you want to change the question, so just FYI for anyone reading the comments, this is slightly different than what was originally here.)
This is a new version of the old question that should be more specific/answerable. I think I gradually figured most of this out, and the schematic has more notes in it now to explain.
P-Detect and P-Hold go to the Arduino. First, the PWR button is pressed, turning on the active-low enable line to the regulator. Then after a specified hold-time to turn the device on, P-Hold holds the power to the regulator on, and finally, P-Detect detects if the button is pressed again once the Arduino is on.
However, the problems come in with that pull-up R24, which I can't really skip. It pulls the line up to the battery voltage, which could vary from 18V up to 50V depending on number of batteries (24V/36V/48V).
Unfortunately even the lowest of those voltages is way too high for the Arduino (the enable line of the regulator can tolerate Vin fine.)
I managed to protect P-Hold with a small N-MOSFET, but as for P-Detect, well I can only find MOSFETs that can handle a Vgs of +/-20V, which is a problem for connecting gate to 50V.
So instead I'm thinking of using a Zener diode voltage regulator. If I use a 5V Zener backwards from P-Detect to GND, that would pull the voltage down to 5V at P-Detect, correct? But it will also basically short 5V-EN to GND unless I use a very large value resistor between the Zener and D5/R22.
From what I calculated, 3M ohm should work (I'm using a 3M ohm resistor elsewhere in the circuit so it'd be convenient.) Would reading the state of the button through that large a resistor have disadvantages?


texts: 30A Relay resets Atmega8A MCU as it engages. Are these PCB layouts to blame?

texts:
I am designing a PCB that uses an ATMega8A MCU to switch two high power relays (Songle SLA-12VDC-SL-A). I have used 2 separate approaches with the same disappointed result: the ATmega8A will reset as soon as either of the relay engages, even with no external load.

To eliminate the possibility of EMI caused by the relays’ coil, I have done an experiment with the same setting using an external Arduino UNO powered by the 5V from the PCB. The result is the same: the UNO resets even when it’s like 50cm (1.5 feet) from the relays.

So I reason that it may be because of the power supply, but I have used the LM2576-5V in many project and it’s very reliable. Also ground paths of the signal side and the relay side are separated. 12V and 5V power lines are also separated. Please see the photos.

Approach 1: use Optos to isolate the relays and switch them by a transistor

Approach 2: like 1 but the opto+transistors switch smaller relays (Songle SLA-05VDC-SL-A) which in turn switch the big 30A relays.

So I am at my wit’s end as to how to use these 30A relays. I saw some commercial relay module that use the same relay and though I don’t have the schematic, I can see that they just use an opto and a transistor, just like in my first approach. Or is it the ATmega8A to blame? I remember hearing somewhere that it’s very sensitive to noise.

I’d appreciate any advice!

Dave

UPDATE 1

Please see the complete Eagle schematic and board for both approaches here: https://drive.google.com/open?id=0B_JjLISYz2JHM0t4SzBaQkhZUEE

UPDATE 2

I have added the schematics in PNG for your reference.

UPDATE 3
Attached is my re-design incorporating your advice so far. Here are the changes:
- Since I don't use the 5V relays to switch the 12V relays anymore, I shrank the board to fit a smaller enclosure
- No more optos, the relays are switched by BJTs connected to MCU
- BJTs resistor value has been changed to 470R
- BJTs are close to their respective diode and the coils' pins
- More ground vias
- Added a 100nF at the AVCC pin of the Atmega8A
- There are 2 separate pairs of GND planes: the upper pair (top & bottom) is for 12V and the lower pair is for signal. They meet at the point where battery GND is connected
- BJTs' emiters are now part of the 12V GND plane

Please let me know if you have any further advice, before I have this fabricated and see how it goes. THANKS!

NEW DESIGN


texts: VBIC Mextram Transistor Spice Models Parametrization

texts:
Under LTSpice, for the VBIC (level=4 or level=9) and MEXTRAM (level=504) Bipolar Transistor Options, as some people pointed me, I dont know how to simulate an e.g. 2N3904 under VBIC or MEXTRAM?

The single reference, suggested by Dietmar Warning (if he is the real) is in sourceforge.net from 2010.

IS the situation still the same?. Or there is a better reference?


texts: Test an LCD for missing segments without looking at the screen?

texts:
I have a product with an LCD screen that sometimes fails with missing segments.
I will test the product for a long time to replicate the failure.
I will test many at once.
I don't want to sit watching the displays with my eyeballs.
I write computer programs to control lab test equipment.
I can make the screen display arbitrary patterns at will.
Is there an instrument that can monitor whether a segment is out while I'm not looking?
Thanks.


texts: Relationship Between Number of Coil Turns in DC Motor and the Efficiency of Energy Retrieval From Regenerative Braking

texts:
When learning about regenerative braking, I began to ponder as to what the relationship between the number of turns in the coil of a DC motor is to the efficiency of kinetic energy retrieval from the rotating wheel.

In math terms, what is the relationship between N and eta where:
$$\eta = \frac{E_E}{E_K}$$

If you can cite some references as well relating to your answer for further reading, that would be extremely helpful.


texts:
I am learning about source transformations in my circuits class and I had a couple of questions regarding them.

Question 1: Is a source transformation a law? By this, I am asking if I am able to do it at any time and still yield the same results as far as power dissipation, current measurements, voltage drops, etc.

Question 2: Why doesn't this source transformation problem yield the same results? I use source transformations until I had one source and some resistors. Then I used a source transformation and tried keeping it the same; in the end, I got different results. The voltage drops across resistors were correct though.

The first three images are just using source transformations to get one power source. Then from 3-4 and 3-5, I tried it with a current source and voltage source and got different results.

But, if I find the voltage across the 8ohm resistor, I find that it is 48V. (Which is what the book says is correct). Is this all that source transformations are good for?


texts: Designing an ultra-thin battery holder (CR2016)

texts:
We are designing a miniature electronic device and run into an issue. The suitable battery holders we were able to find are 2.6 mm thick. But the battery is just 1.6 mm thick. It is a huge difference for miniature devices.

So we are looking to design a battery holder, probably a custom one. The holder should add just a fractions of mm to the battery size. Do you have creative ideas on how to achieve this result? One of ideas is to use some contact pins, but we were not able to find a viable solution.


texts: Is there a reason no one uses an opamp when using the LM35 sensor?

texts:
In most examples I've seen so far I've noticed that people connects directly the LM35 output to the Arduino's analog port. At room temp a reading from the sensor is 0.25V, which is 5% of total Arduino's analog range.

My question is if there is a good reason not to use an opamp so that the sensor's ouput spreads over the range 0..5V instead 0..1.5V. A good engineering practice is to spread the analog's input voltage as much as possible, but if no one is using it there should exist a reason.

Thanks!


texts: Driving LED using SN74HC164 and transistor. Apparently this schematic works but I don't understand why!

texts:
I am trying to create a project based on TI chip BQ78412 (Pb-Acid Battery State-of-Charge Indicator With Run-Time Display). There is an evaluation board whose schematic is published in this pdf on page 18.

I am struggling to understand why part of this schematic works (see below the one in question).

My main problem is that the VCC is 3.3V (and all signals) but the LEDs are switched on/off by the transistor through 12 V from a separate battery that has a common ground with the rest of the schematic. I assume that when I have logical 0 on the output pins of the IC the LED will be on as it will be connected to ground. But if I have logical 1, it would be still 3.3V so I will have effective voltage of 8,7V that would be sufficient for the LEDs to be on - the current would be about 66 mA! So I guess I am missing something very basic and important...

I also don't get why the current limiting resistors for the LEDs are 100 ohm - the current should be 20 mA (limited by the IC) and the forward voltage should be 2,1V if I am not wrong (see datasheet for SML-LX0603YW-TR) so according to Mr. Ohm it should be around 495 Ohm.

Regards,

Evgeni

EDIT: In my question I have made some false assumptions due to lack of knowledge and experience:

I didn't recognize that the transistor is acting as emitter follower which was a very important fact.
I have also assumed that the driving current of the serial shift register is max 20 mA rather than 5 mA - I am still not sure how to interpret the data sheet - I'l ask a separate question on this.
I have assumed that 1-3 mA would be quite insufficient for the LED to emit light as it's forward current according to the data sheet is 20 mA.
I have also underestimated the HC164 Vlow assuming that it is always 0 V which apparently is not true either.


texts: Interfacing a STM32 MCU with an external ADC (and reading the data via SPI)

texts:
I want to use a STM32 microcontroller to read data from a multi-channel ADC.
The microcontroller that I intend to use will most likely be something from the F7 series (such as STM32F746ZGT), whereas the ADC that I currently have my eye on is LTC2358-18 from Analog Devices.

The project that I'm working on requires me to simultaneously read 6 analog channels (with a reasonable data rate). As far as I understand, the particular ADC chip can output its conversion results on different serial data output (SDO) channels that can be read out in parallel (the serial clock is identical for all of them):

I was wondering if it is possible to use a single STM32 MCU to read the 6 channel output data via SPI (I don't really need the two remaining channels). In general, I would assume that I need to configure 6 SPI interfaces that are available on STM32F746ZGT, as follows:

One of the SPIs acts as the master and provides the serial clock (SCK) for all the slave devices (5 remaining SPIs on the STM32 chip and the ADC) and the serial data out (SDO) for the ADC configuration. The master would (I'm guessing)  pull down the CS for all the SPI slaves.
The remaining 5 SPIs on the  STM32F746ZGT share a common SCK line and each are linked to a SDO channel on the ADC.

Or, in other words, it would look something like this:

Would this kind of configuration actually work or am I missing something?


texts: What are types of connection between metallic conductors and glass part of an LCD?

texts:
I know that elastomeric connectors are being used to connect metallic conductors to the conductive paths on the glass part of an LCD but there must be other ways being commonly used. For example in iPhone there seems to be no space for the elastomeric connector. See the fifth image here: Can an ordinary Joe replace a busted iPhone screen?

What are other commonly used types of such connections and how difficult is to disconnect and reconnect them at home?


texts: How to connect a PIC32MK 100-pin Motor Control Plug-In Module (PIM) for programming

texts:
I recently got a PIC32MK 100-pin Motor Control Plug-In Module (PIM) I have been trying to prgram it but I have been running into the following error:

Target voltage detected
Unable to connect to the target device.
Failed to get Device ID

I am currently connecting my 3.3V source to pins:

PIN 2 (IN THE MICROCONTROLLER) as VDD (connected to + side of the source)

PIN 15 (IN THE MICROCONTROLLER as VSS (connected to the - side of the source)

I am conneceting the pickit 3 to the following:

Pickit Pin 1 (the one with the arrow): PIN 13 (IN THE MICROCONTROLLER) as MCLR

Pickit Pin 2: PIN 16 (IN THE MICROCONTROLLER) as VDD

Pickit Pin 3: Pin 36 (IN THE MICROCONTROLLER) as VSS

Pickit Pin 4: Pin 27 (IN THE MICROCONTROLLER) as PGD

Pickit Pin 5: Pin 26 (IN THE MICROCONTROLLER) as PGC

Pickit Pin 6: Not connected

Here is the source of where I am getting the values: (Note I have the 100 pin so I am using the diagram in page 5) http://ww1.microchip.com/downloads/en/DeviceDoc/PIC32MK_GP_MC_Familly_Datasheet_60001402G.pdf

the code I am attempting to upload to the Pic is the following:

https://drive.google.com/drive/u/0/folders/1irJj6f744SAhsiNDJO9QxzUNfxEsFJPe file called PWM-centered-interrupt...

Am I connecting to the wrong pins? any help would be appreciated.


texts: Is this the correct way to make a temperature activated fan?

texts:
This circuit is being used outside a PC.

simulate this circuit – Schematic created using CircuitLab
EDIT: @SupaNova The speed will increase with temp and the cutoff temp is 75℉.


texts: How to control a Water Valve through a circuit using latches or flipflops?

texts:
I need a circuit that can "simulate" opening/closing a valve for a water tank.
The circuit has only 2 inputs, 'm' (minimum) and 'M' (Maximum), and an output 'V' (valve). The valve is only open if V= High(1).
The tank has a floating water meter that goes up and down with the tank water level.

When the tank is emptying, as soon as the water meter reaches a certain level, minimum(m), the entry 'm' is Low and the valve should open to fill the tank. As soon as
water meter reaches minimum(m) again in the rising direction, 'm' will become High but the Valve should remain open (=1).
When the tank is filling, as soon as the water meter goes above a certain level Maximum(M), the entry 'M' is High and the valve should be closed. If the tank starts emptying again, 'M' will become Low but the valve should remain closed.

m=Low(0) and M=High(1) will never happen simultaniously.

I need to make two versions of this circuit: one using only NAND gates, and another using a  JK Flip-Flop.

I tried using http://logic.ly/ for simulation purposes. One of the answers has a working NAND gate implementation, but I just can't wrap my head around the circuit with the JK flip-flop.


texts: I have a device that is 1 ohm and it consumes 3Amp. I want to run my device in both ways and I have only one voltage supply. I want to switch ground to Vcc and vice versa with a control bit from mcu. I considered cmos invertes, but I am not sure if the resistance of cmos inverter gate is high or not. Because voltage supply can supply limited current. And is it possible to use only 1 control bit to handle this situation, or 2 control bits are needed?


texts: I am working on a simple audio mixer project. The op-amps I am using (LM741) take +9V and -9V inputs. I am currently getting this by wiring two 9V batteries together, connecting + on one to - of the other, and grounding the pair. This seems to work, but I would now like to switch to a power supply. I can find a bunch of 9V power supplies, but they all only have the one polarity. Is there an easy way to get +9V from a center-negative power supply? I figure I probably need an inverter circuit or something, but I don't really understand what I'm doing.


texts: Signal Strength to ADC quantisation levels

texts:
According to the excellent site of AB4OJ, the Icom 7300 in summary has a 14bit analogue to digital converter with a 1.5 volt peak to peak input (LTC2208-14).  I make this to be 91.5uV per quantisation level. There is a 20db gain amplifier (LTC6401-20) ahead of the ADC so best case this would give 9.1uV per quantisation level.

Wikipedia gives for HF a S5 signal to be 3.2uV (rms relative to 50R). Equivalently this is 9.1uV peak to peak, resulting at best in a S5 signal at most only changing the Least Significant Bit of the ADC. Not much can be hoped to demodulate from this surely?

By the same logic, S9 would only move between 15 levels. Again how much can be demodulated from this strong signal?

As the 7300 works very well, clearly I am missing something but I
 don’t know what. Can anyone fill me in?


texts:
I would like to sample the logic on the pins out out of a toy robot's processor and the MCU is an 8 bit processor that operates a max clock speed of 5 Mhz.

Does anyone have any recommendations on how to approach this without burning it out, I have an oscilloscope but its only two channel.

SPC252A Data Sheet


texts: Which software is used to design this Cirucit?

texts:
Could you help me with the name of the software used to design the circuit below?

I have used Eagle (Easily Applicable Graphical Layout Editor) but I want to design my circuits with looks something like this below.


texts: What do we need the op amp for in this current-to-voltage converter?

texts:
I'm still very new to electrical engineering and at the moment trying to get my head around the concept of the ideal op amp.

In Fundamentals of Electric Circuits by Alexander and Sadiku the following diagram is given as a "current-to-voltage converter".

simulate this circuit – Schematic created using CircuitLab

The reader is asked to prove $$v=-IR,$$ which I think I did. But what do we need the op amp for? Wouldn't the following diagram be exactly the same?

simulate this circuit


texts:
I have a basic question regarding the constants of a motor. I want to know the name of the constants and their SI unit.

Torque (T) = Kt x Flux x Ia

Back EMF (E) = Ke x Flux x speed

When flux is constant,

Kt x flux = Ki

Ke x flux = Kb

I want to know the following defined names are correct or not.

Kt - motor torque constant, motor armature constant (N. m/A)

Ke - feedback constant, motor voltage constant, electic constant, back emf constant, counter emf equation constant (V. s/rad or V/rads-1)

Ki - what is the name of it and SI unit?

Kb - what is the name of it and SI unit?

And what is motor gain constant and motor constant?


texts: Interfacing LoRa SX1301 IC to third-party RF front-end

texts:
I am reading the datasheet of SX1301. I got struck at SX1301 RX operation using a third party RF front-end topic (Page 22). The page (22) says:

  In that mode the SX1301 expects a stream of 4 bits samples at a 32 MSps rate. The “Sample valid” input should pulse every 8 clock cycles to delimit packets of 8 samples. From those 8 samples representing 32 bits, the first 24 MSB are kept as I/Q 12bits sample information and fed to the internal sample 4 MSps sample bus.

and in the next page, they have written:

  The RF front-end must provide a 32 MHz clock. ”Sample valid” and data bits must change state on the rising edge of the clock. They are sampled internally in the SX1301 digital IC on the falling edge of the 32 MHz clock.

There are only two pins to transfer samples to SX1301 from RF Front End (A_IQ_RX and A_QI_RX pins) and they have mentioned above that One sample is of 4 bits and 1 clock cycle transfers one sample. How can they transfer 4 bits in one clock cycle.

The data (I/Q samples) are transferred once (falling edge) in a clock cycle. How is it possible to transfer 4 bits then considering transferring occurs once each clock cycle?


texts: What is needed to control 200 LED's from an Arduino

texts:
I am new to Arduino and want to use two 74HC595 shift registers to control 200 leds. What will I need to consider / get to make this possible?

These are your average starter LED's.

Thank you!


texts: Minimum solder mask ridge (sliver) for DFN package?

texts:
What is better:
No solder mask at all under the fine pitch component with thermal pad or shrink the thermal pad to leave room for a solder mask ridge around the thermal pad?

I  am making the layout for a surface mount DFN 12+1 pin package (Dual Flat No-lead 3x3mm) from Linear Technology (similar to QFN). The recommended pad layout leaves a clearance of 0.225 mm (8.9mill) between the thermal pad and the periphery pads. With a solder mask expansion of 0.1mm (3.9mill) this leaves a ridge of solder mask (solder mask sliver) of only 0.225mm-2*0.1mm = 0.025mm (1 mill) - clearly not a size which can be produced. In fact the PCB fab house has 0.1mm (3.9 mill) as minimum ridge width.
I see two options:
1: Keep the solder mask by: Shrinking the thermal pad's copper land pattern in order to increase the solder mask ridge to >0.1mm (3.9mill).
2: Remove the solder mask entirely (ridge width=0). This is already the case between the periphery pads them selves (pitch 0.5mm (20mill))

I am in doubt as to what is the best option. With option one I have a solder pad which is smaller than the components pad.
With option two there is effectively no solder mask at all under the 12+1 pad's of the component and I would fear short circuits.

Any advice would be appreciated.


texts:
I have a device (small fridge) that runs on a 12V car battery, but I don't know the current it draws.
I connected a multimeter in series with a normal 12V battery to measure the current it draws. The device sometimes starts with 3-3.2 A and quickly goes down to less 3A and continues to 2.5A.
I know the bigger the current in a power supply the better, but currently, I have a normal mains power supply with an output of 12V and 3A.
Since the device only draws 3.2A for a split second will I be able to use my 12V 3A power supply?


texts: Overdrive voltage and Early effect in MOSFET

texts: Can anyone explain to me if there is the Early effect in MOS transistor then the Early effect affects the expression for VOV which is \$VOV=\sqrt{\frac{2ID}{kn'(W/L)}}\$?


texts: Why does the led turn dim gradually and then turn off when attached to a capacitor in series?

texts:
I connected an LED in series with the capacitor (any type of capacitor. I used one of 10 μF) and connected them with the 9V DC battery. I connected the positive pin of the capacitor directly to the positive side of the battery and attached the positive pin of the LED with the negative pin of the capacitor (as the LED and the capacitor are in series combination) and connected the negative pin of the LED to the negative side of the battery. So, The bulb should gradually turn dim and then turn off and it did. I followed a diagram of the circuit but I cant attach it with the question due to the lack of population.

My question is, why does this happen? Why does the light turn dim when attached to a capacitor in series?

I am quite new in electronics. Therefore I am not quite familiar with the complex detailed descriptions but still I am trying to give as much details as possible. Pardon me if there has been any mistakes in  my question.


texts: Characteristic impedance of a transmission line

texts:
characteristic impedance of a transmission line depends on frequency of transmission as can be seen by its expression.

What will be the characteristic impedance of TL if my signal has two frequency components?
What will be its expression?


texts:
My electronics textbook says the following regarding a voltage regulator with a Zener diode:

  For proper operation of this circuit, the diode must remain in the breakdown re- gion and the power dissipation in the diode must not exceed its rated value. In other words:

  The current in the diode is a minimum, IZ(min), when the load current is a maximum, IL(max), and the source voltage is a minimum, VPS(min).
  The current in the diode is a maximum, IZ(max), when the load current is a minimum, IL(min), and the source voltage is a maximum, VPS(max)

(VPS is the source voltage).

I dont get why those conditions follow from wanting to be in the breakdown region and not exceeding the power rated value.

Namely, for example, I want an explanation for why first and second conditions are necessary consequences of proper functionality.

Thanks.


texts: how to configure radio registers of cc2500 and cc2511 to 250 Kbps and 500 Kbps?

texts:
-I'm using  cc2500 and cc2511 transceivers in my project.One in transmitting data, and the other is receiving

-I am using cc2500 at target board and cc2511 at host side.

-I am able to communicate this two device at 2.5 Kbps.

-My question is, how can I get the 500kbps and 250Kbps  transmission rate??

-I tried register value generate from  smart RF studio for both cc2500 and cc2511 but some how i am not able to trans receive .my Xtal frequency for cc2500 is 2410MHz and for cc2511 is 48MHz.

-I tried various setting like change in  filter bandwidth ,deviation ,modulation format but badly i am not able to communicate this two chip at 250 and 500 Kbps.

-Please give me register setting or help to solve this problem.


texts: Separating high- and low-power ground-planes

texts:
I am designing a bi-directional DC-DC converter for automotive use. Therefore, there is some high-power stuff that needs to be implemented on the pcb. The overal layout is as such:

My question is if I should separate the high-power and low-power ground-planes? If so, how would I do this? They do need to be connected somewhere, so I'm not sure where I would do that? For now I have it like this:

So there are two 'big' ground-planes, and attached to each other in the center through smaller tracks. Do I remove the tracks and connect somewhere else entirely, or would this work?

Furthermore, I would greatly appreciate some general advice on my design as this is my first PCB, and I am still pretty inexperienced. The reason for all the pins is because this is supposed to function as a test board.

Here's the schematic:


texts: Detecting a location of the needle inside a cavity having multiple IR emitters , using IR Detector at the tip of the needle

texts:
I am working on a project where I need to find the location of a needle that has the IR detector at the tip of the needle.
These needles are medical suturing needles that would help us to detect the position of the suturing needle while suturing. Normally while suturing, if the doctor is not well trained, a bad suture can cause trauma to surrounding tissues. Currently, it's just an idea and we are working on a prototype. We will also be working with a lot more sensors to get the data while suturing but that has more to do with the software part and not the electrical part.
I need to actuate the frequency of the IR detector-emitter (LEDs) in such a way that I can gauge the location of the needle when the IR detector detects at respective frequency bands (typically 20Hz, 25Hz, 30Hz, 35Hz, 40Hz.)
So something like if the needle is in position A, then the IR detector will detect it as we will actuate it at 20Hz for position A, 25Hz for position B, 30Hz for position C, and so on.
This is an idea that I had but I am struggling to implement it and get its logic right with the circuit.
Could someone suggest to me an electrical design or forward me some examples of electrical circuits that I can view and implement the above idea?
Thank You!
All the help is really appreciated!


texts: STM32 HAL driver for register value update

texts: I am new to HAL drivers and STM32 MCUs. Can anyone tell me how to use HAL drivers to update register values of STM32F407 MCU? I have to programatically update the values of ARR and CCR registers of TIM1 to generate PWM waveforms.


texts:
I wonder what is the difference between high side switch and low side switch. Basically it work the same way (electrically speaking) but I don't know if one is better than the other. Is there any safety purpose? What is the best solution if there is big capacitor in the circuit? Capacitor C1 will discharge through the load in the low side switch mode whereas C2 discharge through the ground.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to figure out the way of debouncing encoders and tact buttons with Schmidt triggers, but I'm confused with 2 existing schematics:

simulate this circuit – Schematic created using CircuitLab

Which of those two options are right?
Values are shown for 5.0V inputs level, would the be the same for 3.3V?
Or for 3.3V I should use another Schmidt trigger IC (not 7414)?

Thanks in advance!


texts: What kind of wire can be used for CAN(Cotroller Area Network) protocol based communication?

texts:
Is the wire used for CAN communication protocol any different or normal. Can normal wires(a pair for CAN LOW AND can HIGH)also be used for communication? I am looking to connect CAN controller 1 to CAN controller 2 in same STM32F407 board.

What kind of wire can be used for this purpose, will any wire be enough?


texts: PID vs Bang-Bang - which one is more stressing on components?

texts:
This question is regarding a 3D printer, specifically its heat bed. The head bed is a PCB heater with a resistance of 0.9 Ohms, so it's drawing around 13 Amps when supplied with 12 Volts.

I recently switched from Bang-Bang to PID controlled bed heating. The stock firmware pulsed On/Off with about 5 seconds each cycle. Now with PID, my bed keeps its temperature much more stable, the frequency is around 7Hz.

Although the total amount of energy used for heating should be less now since the heating is more efficient and doesn't waste energy by cooling down, I am a bit concerned of the fast pulsing of the rather high amperage.

So I was wondering, do the faster cycles cause more stress on the components (I am thinking MOSFET on the board and components inside the PSU) or is this negligible? I am particularly curious since this is a rather low budget printer (Anycubic i3 Mega, $350 printer with a generic unbranded PSU) and I don't want to push its limits too much. I suppose the power supply is a switching mode one. Are those safe to pulse like this at fairly high amps? The PSU is rated for 25A.

The only thing I can observe is a very faint noise with the same frequency as the pulses. Might have been the same on 5 second cycles, I was just not paying attention to it back then.

I'd be very glad if somebody could chime in on this.

Thanks in advance.


texts: Potentiometer signal as a speed reference for a drive

texts:
Over what distance is it reliable/advisable to use a potentiometer signal as a speed reference for a drive ?
I've considered converting it to a 4-20mA, is this necessary ?


texts:
I'm using AD7190 with a 4-wire load cell to build a pressure acquisition board. From ADI reference design(CN0102), I understand that connect sense+- lines of a 6-wire load cell to the ref+- pin of AD7190 create a ratiometric configuration which eliminates the need for a precision reference. However, I only have 4-wire load cell. The CN0102 points out that due to lack of the sense line, 4-wire system is not completely ratiometric.
I want to achieve relative high precision and >100Hz date rate, so I config the AD7190 to 150Hz output data rate.
Whether a precision reference is needed for my 4-wire load cell application? If I use a precision reference, is my performance giong to be better or worse?


texts:
I'm doing my first board in Eagle (first board at all, actually) and am getting a lot of stop mask errors around parts that I'm using out of the Nordic and Adafruit libraries. Every point of intersection across the nrf51822 and the 3.3 coin cell holder gives an error in tStop.

There is space around the route, as seen here, so I'm not sure what more I need to do to make sure that these are ok. Pretty I'm just making a simple mistake but can't glean how to correct it from the tutorials I've been reading. Thanks!


texts:
There are 3 resistive bulbs (60 watts each) in series fed by 230Vrms from the transformer.
If I apply capacitors in parallel with load I will get more Voltage. The more capacitors, the higher the voltage, and the bulbs glow more. If I remove all the bulbs and leave the capacitors, I will get an output voltage which will be more than the input voltage.
If we can increase voltage just applying capacitors in parallel, why do we use huge generators like dams to generate 66kV, when we could just generate a few volts and then use capacitors to increase the voltage to 66kV?
In these pictures this man add capacitors to increase the voltage across bulbs and then he removed bulb one by one and the voltage across the load is more than the input voltage
In this way how much voltage I can increase just by applying more and more capacitors


texts: Height of the substrate in online PCB impedance calculators

texts:
Is the height of the substrate just the non conductive portion between copper layers ?

Using this calculator as an example

In a 4L board, if the top and bottom traces are of the same thickness and width with the same height for their respective substrates, would that imply that the impedance of the trace of the same since, they are both exposed to free air and a substrate ?

Are these calculators assuming that the adjacent layer is a ground plane ?


texts: Simple low power rising and falling edge enabled circuit

texts:
I am working on a project where I use an esp8266 and a reed switch sensor (NO), this is powered by a battery so I need a low power circuit that can turn on the esp8266 when the state of the reed switch is changing.

I have been looking at monostable multivibrator (One-shot monostable) circuits and soft latching power circuits, but I haven't found any that fulfills my requirements.
I have also read through some other peoples questions about something very similar, but there is some information missing and other things that causes me to ask again.

Ref1: Circuit to turn microcontroller on when reed switch state changes (to monitor door lock state)
The answer here states that one should use another low-powered MCU to check the state. This is a good solution since there are many low-powered MCU's available, but this causes more complexity to the circuit and the process of programming the extra MCU. (The esp8266 is "easy" to program, but a PIC or ATTINY needs extra programmers and software)
It is ok to pass current through the reed-switch as long as it is a small current.
I want this to be as simple as possible so I can share it with the DIY community.

Ref2: I need a switch that not only detects open/close, but also sends a pulse to wake up an ESP8266 whenever the (debounced) state changes
This answer gives a "simple" way to solve this problem, and with a discrete circuit. The only problem is that when the reed-switch is in closed state it draws to much power. Also it should been controlling a mosfet instead of the esp8266 directly. (Since the esp8266 draws a bit power during deep-sleep)
This is the circuit I have made out of the answer from Russell McMahon.

So my question(s) is:

What can be done with the schematic so it uses less than ~20uA during a idle state? (If possible even lower)
How could a mosfet or transistor be implemented so I don't have to worry about using deep-sleep on the esp8266? (So the mosfet will power another circuit with a LDO so I can use more of the battery)
Maybe there is a IC or MCU that can be used without any extra programming? If so, witch might be used?
Is there another solution that would be better fitted for my problem that I haven't encountered?

(The last two questions are not meant as a discussion, just to show that I am open to other solutions)

Another thing that is important is that the activation time after a state change should not be more than 500ms. How long the signal will be on after activation depends on the solution.

Let me know if something is unclear or not making sense.


texts: Why prevent high frequency input into the loud speaker using a low pass filter?

texts:
As much information as possible about this figure would be helpful

From what my professor said, "Q2 oscillates when we connect a Loud Speaker, this might generate high frequency signals, so we use a low pass filter to filter them out". I understand that we need low pass filter to filter out high frequencies but (why is high frequency bad for Loud speaker?). Some help please.


texts: Exponential nature of current growth/decay in inductors

texts: Why are the curves for growth and decay of current in inductors of exponential nature i.e $$ 1-e^{-x} $$ and $$ e^{-x} $$ respectively. I understand the mathematical derivation for the current i(t). But I want to know the factors like change in flux, application of voltage across the inductor, etc cause the growth and decay of the current to be of exponential nature.


texts: How to find the intersection point in rootlocus diagram?

texts:
Question:

  Sketch the root locus for the open loop transfer function of a unity feedback control sytem given below and determine the value of K for \$\xi=0.5\$

  \$G(s)=\frac{K}{s(s+1)(s+3)}\$

------------------------------------------------------------------------

I have drawn the root locus diagram like this

Now i tried all possible way to get the intersection point of rootlocus diagram with the 60 degree line.If i get that point i can easily find the value of K for \$\xi=0.5\$.

Is is possible to find that point without any software?


texts:
How long should a 240V 45W appliance run on on an inverter connected to an 18V 5Ah (90Wh) battery?
The appliance is a CPAP connected to a Ryobi 18v lithium battery inverter.


texts: What's causing this high frequency ripple on the output of my LM317?

texts:
I'm using an LM317T to regulate 5 V to 3.38 V for a microcontroller. R1 is 330 ohms and R2 is 560 ohms. There isn't any input capacitor and the output capacitor is 470 µF 25V, because I had that value in a pack of 50. The microcontroller is drawing at least 50 mA, so I'm fairly sure I'm meeting the minimum load specifications. The regulator is being powered from a computer SMPS, but I had a very similar configuration set up last time running off an SMPS without any problems.

Here's a scope trace of an I/O pin to show you what I mean:

The ripple is about 60 mVp-p, but as you can see it also happens when the pin is low. I'm worried it might affect the microcontroller itself (for example, make it unstable.)

What I'm more worried about are these large bursts of noise which occur seemingly randomly about 100 times per second:

It turns out this noise is coming from my power line network adapters; it's leaking through from the power line into the computer SMPS and to the 5 V output.


texts:
I was asked to find the form factor of this voltage wave:

But before getting the form factor, I should know the RMS value and the average value of the waveform. Knowing that the

$$V_{\text{rms}}=\sqrt{\frac{1}{3}\left(\int_{0}^{1}(4t)^{2}\:\mathrm{d}t + \int_{1}^{2} 4^{2}\:\mathrm{d}t + \int_{2}^{3} v^{2}\:\mathrm{d}t\right)}\tag{1}$$

My only problem is I can't solve the RMS by its formula because I don't know what to substitute on integral of \$v^2\$. Please teach me how to find the equation for the parabola so that I can substitute it into \$(1)\$
I also can't understand the "piecewise" mentioned on some pdf's. I found the value $4t$ by using ratio and proportion..

Any help will be truly appreciated. Thanks


texts:
I'm continuing my refresher on electronics, and want to validate a conclusion/deduction that I'm reaching.  Consider the two comparator circuits below:

In both cases:

I have chosen not to picture decoupling capacitors for simplicity/clarity
The input waveform is a 6 Hz square wave that is 3.25 volts peak to peak
The output waveform is a 6 Hz square wave that is 5 volts peak to peak

Question:

Is the primary reason to build a comparator using a voltage divider on the (-) input to set a threshold voltage (2.5 volts, in this case), preventing stray signals from triggering the output?  (My intuition and very foggy memory says "Yes").  If so, is there any other reason to do so?

What I was seeking to accomplish was a level shifting buffer to bring things up to a normal TTL range.


texts: How much/fast is a battery allowed to degrade?

texts:
My friend's Macbook Air battery has degraded almost 21% in just over 2 years. This made me wonder how much a battery is "allowed" to degrade over time. Is 21% in 800 days a lot? Or does it seem like a normal amount? The battery has had 610 load cycles.

It's purely out of interest, because his computer claims he should get the battery serviced, but maybe 21% is very normal on such a timespan. It's a lithium-ion battery.

I have no idea if this is the right stack to ask it, but it seemed most fitting.


texts: What are the technical difficulties of making an accurate digital accelerometer?

texts:
In theory, double integrating accelerometer data with time should give displacement.  However this is not widely practiced due to how susceptible accelerometer is to noise (and other reasons??), and we usually resort to vision based approaches or signaling approaches.

What are the technical barriers that prevent us from creating a digital accelerometer accurate enough to be used to determine displacement?


texts: How Do I Set The Bitclock in a Make File for AVR?

texts:
I'm following Chapter 2 of Elliot Williams' book Make: AVR Programming. I'm on an iMac.

I get a success message in Terminal when I input:

avrdude -p m328 -c usbasp -v -B 10

So, I know that my programmer and micro controller are working.

(If I don't set the Bitclock to 10 then it throws an error.)

My problem is working with the Make file. When I try "make flash" I get an error message.

  avr-gcc -Os -g -std=gnu99 -Wall -funsigned-char -funsigned-bitfields
  -fpack-struct -fshort-enums  -ffunction-sections -fdata-sections  -DF_CPU=1000000UL   -DBAUD=9600UL -I. -I../../AVR-Programming-Library -mmcu=atmega328 -c -o blinkLED.o blinkLED.c avr-gcc -Wl,-Map,blinkLED.map  -Wl,--gc-sections  -mmcu=atmega328 blinkLED.o ../../AVR-Programming-Library/USART.o  -o blinkLED.elf avr-objcopy -j
  .text -j .data -O ihex blinkLED.elf blinkLED.hex avrdude -c usbasp -p
  atmega328  -U flash:w:blinkLED.hex

  avrdude: error: programm enable: target doesn't answer. 1  avrdude:
  initialization failed, rc=-1
           Double check connections and try again, or use -F to override
           this check.

  avrdude done.  Thank you.

  make: *** [flash] Error 1

I think that the problem is that the Bitclock isn't set in the Make file, and I'm not sure how to do so. (If I have some other error, please let me know. I'm guessing.) The Make file can be found on gitHub at:
blinkLED Make File

I have set the MCU = atmega328 (which is the micro controller that I'm using.)


texts: How to simulate an RF power source in LTSpice?

texts: I am testing out an RF power amplifier that I have designed in LTSpice. How do I model the input RF power source to the amplifier in LTSpice?


texts: Why isn't my 5-to-24VDC boost converter supplying enough current to turn a 24 VDC motor?

texts:
UPDATE #2: 2020-03-28 - I ditched the MC34063 solution and just built an 80 KHz oscillator with a 90% duty cycle with a LM339 comparitor, 4427A nfet driver, IR630 fet, and a very larger ferrite core 1mH toroid. Using a 5V/2A wall-wart supply, I can now deliver 17V at ~200mA which is enough to turn the motor. Not sure why my MC34063 design stunk so bad, probably should have used an external NFET driver instead of the internal, or probably due to the Rsc value, I dunno. But it's fixed! The biggest impact to current deliver was, as explained in the app note: frequency of the oscillator. The next limiter was the coil.

UPDATED 2020-03-27 based on feedback. Closing this since it is basically a problem delivering current with a boost converter, and there are many other issues similar.

Problem: I cannot get a 24V motor to turn fast enough using a boost converter to step up 5V.

I have a simple 24VDC motor with a no-load speed of 6600 rpm hooked up to a gearbox that reduces it to 145 rpm (specs on the motor are here). Max torque current is ~180mA. I'm using it to stir a viscous liquid.

I have three power supplies:

Supply A: 120VAC 45W power supply with 24V out rated at 2A max

Supply B: A Jabinco boost converter set to convert 5V to 25V, 2A max... specs are here: https://www.amazon.com/gp/product/B081DKJVBK (site won't let me link to amazon for some reason)

Supply C: A home-made MC34063-based boost circuit I built using a TI datasheet design-guide to deliver a max of 24Vout at 200mA.

Both Supply B & C are powered with 5V 4A wall-wart (20W max).

Experiment 1. Test motor with beefy supply

I connect an ammeter in series with Supply A and power the motor. Motor spins fine, DC current is 180mA continuous.

Experiment 2. Test motor with off-the-shelf boost converter

Same setup as Exp 1 but I use the Jabinco boost converter. Motor moves very slowly, makes a weird sound. Update: voltage drops to ~2.5V.

Experiment 3. Test motor with my boost converter

Same setup as Exp 2, but I use my own boost convert which is supposed to deliver a max 200mA. Same result as experiment #2. Update: voltage drops to ~3V.

Experiment 4. Verify boost converters can deliver enough current

Place a 5 ohm (5W) resister in series instead of the motor and check the max current I get out both boost converts. #2 gives a max 280mA, #3 gives a max of 400mA (clearly my design parameters were wrong, but that's still double the required current).

Summary

UPDATE: The boost converters cannot maintain 24V and are dropping down to ~3V. I need to get more current out of them. So even though the previous summary has been corrected, the question is still valid. How do I get enough current out of a boost converter? The beefy supply provides 24VDC at ~200mA which is 4.8W.

The guide I am using from Motorola indicates Lmin is inversely proportional to Ipeak(siwtching), and Ipeak is proportional to the timing frequency. I will try a smaller inductor and a higher frequency...


texts: check if an unsigned binary number is divisible by 15

texts:
I'm a computer science student and I got stuck on this question for hours.

We have a binary unsigned number X, represented by 12 bits.
We would like to build a system with 1 bit output - Y, that will be '1' if X is divided by 15 without a remainder.

The only components we can use are:

4 bit adder, having also C0 (carry) as input, and C4 as output.
1 single NOR gate with 3 inputs.

I did find a pattern. If I'll calculate 2^i % 15 for 0<=i<=11 (since it's 12 bits), then for I'll get a sequence 1248 1248 1248.

And if I have 0001 1110 1111 then I can just multiple all the digits, sum them, and check if my number is divisible by 15.

0 + 0 + 0 + 8 + 1 + 2 + 4 + 0 + 1 + 2 + 4 + 8 = 30

The problem is, I have no clue how to implementing it, and if it is even efficient.

I would love some help.


texts: Why can't the earth discharge my DC batteries?

texts:
Electrical newbie here. After watching this video I noticed that in the event of a fault, the AC power in your house can discharge into the earth/ground (which thus causes the house breaker to trip).

If AC power can be discharged into the ground then why can't I drain a standard DC energizer battery by connecting a wire to the positive terminal and placing the wire in the earth/ground?


texts:
How can I connect Full Adders together to form a Carry Ripple Adder?
Here is what I have so far.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity CarryRippleAdder is
    Port ( Carry_in : in  STD_LOGIC;
           input_A : in  STD_LOGIC;
           input_B : in  STD_LOGIC;
           Carry_out : out  STD_LOGIC);
end CarryRippleAdder;

architecture Behavioral of CarryRippleAdder is

-- FullAdder
COMPONENT FullAdder
PORT(
    A_in : IN std_logic_vector(15 downto 0);
    B_in : IN std_logic_vector(15 downto 0);
    C_in: IN std_logic;
    C_out : out  std_logic;
    S_out : out  std_logic_vector(15 downto 0)
    );
END COMPONENT;

begin
 -- FullAdder0
    FA0: Fuller PORT MAP(
              C_in => Carry_in
              A_in
       B_in
       C_out
          S_out
);

end Behavioral;


texts: How can I do two points scaling in electronics? 0.6 V - 3.2 V to 0.0 V - 3.3 V

texts:
I'm seeking a solution how to do a two point scaling in electronics. I have tried an Op-amp, but it did not work very well. So I wonder if you have some ideas how to do two point scaling from e.g 0.6 V - 3.2 V to 0.0 V - 3.3 V?
When I apply 4 mA, I what the output to be 0.0 V or very close to 0.0 V.
When I apply 20 mA, I want the output to be 3.3 V or very close to 3.3 V.
The Zener below is a 3.6 V Zener.
Is that possible?


texts:
I got a strange issue with my Arduino, and more specifically with my breadboard. I got the following circuit:

+5V |----[TMP36]-----| GND
            |
            |
            A0

Where TMP36 is a thermoresistor (datasheet).

When I got this circuit, everything is fine and I got correct measures (temperature of 24°C), which corresponds to a value of 148 (on 1023), namely 0.72V.

Yet, as I would like to add another sensor on my breadboard, I plugged this same sensor between the Power and Ground lines. Here is my schematic:

+5V (Arduino) ------ Power line (+)
                          |
                          |
                       [TMP36] ------ A0
                          |
                          |
GND (Arduino) ------ Ground line (GND)

Here comes the trouble. I got an output value of 81 (so 0.39V). Pretty bad, as corresponding temperature is -11°C.

I can't see any reason for such a difference, but I'm an electronic newbie. :)

Have you any ideas on why such a behavior?

EDIT: adding the breadboard schematic:


texts: 555 timer - large inaccuracies with precision components

texts:
This is a problem I have been slowly chasing down.
At first I was using 10% caps that caused the poor output accuracy. After changing the capacitor to a 1% I thought the problem would be fixed, but it was not fixed.

Here is the circuit ignore values because they are old.
Important values:

R1: 649 1%
R2: 3.24k 1%
C1: 10nf 1% (12063A103FAT2A) (ceramic)
f = 1.44(R1+2R2)C1
Pw = .693(R1+R2)C1

After plugging all of this in I should get (mathematically) f = 20kHz with  Pw = 27u (the values I want.)
In reality I get f = 18kHz and Pw=28us.
This value is completely unusable for the application.
I considered the surrounding circuit to possibly cause issues so I breadboarded just the 555 circuit.
This circuit obtained exactly the same f and Pw as the one on the PCB.
After some more digging I found that a small R1 could be the problem.
I added two pots to the breadboard and picked some random R values. Then checked f and Pw vs the calculation and it had worse accuracy than the hand picked resistors. (I understand the pots could be the reason they were more wrong.)
Is there anything I am doing wrong? Is there a better solution for this?
I have a uC controlling other things, but I want to keep it isolated from this circuit because the load is a flyback circuit (20kV.)


texts: Power 9 IR LEDs 850 nm with a forward voltage of 1.7 V and forward current of 100mA

texts:
I am looking to power 9 IR LEDs 850 nm with a forward voltage of 1.7 V and current of 100mA. i want to make a circuit where i can use a small power supply or could I use the raspberry pi to power it? Can i use the GPIO pins directly without causing harm to my Pi. If not, which other power supply option do you think I could use? I want to make the setup small and portable. I need to turn the LEDs ON for a short duration like 5 seconds.
I would be happy to receive suggestions. I am new to electronics, please help me out!!!!!

Update: I would also like to know if it would be possible to control the brightness of the LEDs to 3 different levels, such that one is just dim, one is bright and the other is in between the two brightness levels. I was wondering if i should use a PWM pin of the raspberry pi to achieve that but i am not sure how.


texts: Can this transistor (2N2222) take 6 V on emitter-base? Am I reading the datasheet incorrectly?

texts:
I have created the following circuit to better understand how to use a transistor as a switch*.

I've been struggling with understanding datasheets for transistors.

simulate this circuit – Schematic created using CircuitLab

Datasheet states EB maximum voltage

According to the datasheet the emitter-base maximum voltage is 6.0 V. In my circuit I am only applying 5 V. From reading the datasheet (below) would you expect that to be too much?

Also, I see that the secondary (output) circuit of collector-emitter can supposedly take up to 40 V(?). Does that mean I should be able to drive a circuit on the collector-emitter side that has up to 40 V on it?

Am I reading the datasheet properly?

I'm wondering because in my other (referenced question) circuit the transistor became very hot with only 5 V -- but that may have been due to being wired improperly, I'm not sure.

You can see the complete datasheet at:

https://www.onsemi.com/pub/Collateral/P2N2222A-D.PDF

* Note This question is directly related to Is it possible to use a NPN BJT as switch, from single power source?. However, I had the original circuit built improperly there, and I'm now wondering if the 2N2222 can take 5 V on its base pin (according to the datasheet).


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texts:
The original network is an square network with two diagonals as you can see here there is no intersection between the diagonals.:

The question is what is the equivalent resistance between points A and C as wel as A and B ?

I rearranged the network to the equivalent network here under (all the resistances which labeled as '1k' below is actually 'R' in original network):

now i see the bridge of Wheatstone so the equivalent resistance is $$\frac{R}{2}$$. The bridge  is in equilibrium and the current in 'r' is zero. Now i want to evaluate the equivalent resistance between the points A and C, if i take exact the same rearrangement and suppose that there is no current in resistance 'r' i would find an expression independent of 'r', but that's clearly false and i wonder why ?

The correct answer is $$\frac{R(3R+(5r)}{8(R+r)}$$. I find it by using the general methode.


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I want to make a 12V battery pack to run an Nvidia Jetson TK1 for an afternoon.  I am new to using batteries and was wondering - will mixing smaller capacity lithium ion batteries with larger capacity lithium ion batteries result in a bottle-neck &/or accelerated wear on the system?

I want to combine the voltages of these batteries to get over the 12V required to power the Jetson TK1, and thought it might be convenient to combine batteries.  The prices per amp-hour are comparable, but I don't want to go way over the 12V (to 29.6V) by combining 9 of the smaller batteries.

2 x LITHIUM 3.7V 6AH (Model: ICR18650 6600mAh 3.7V 1S3P)    [1528-1835-ND]  $4.47 per Ah
2 X LITHIUM 3.7V 2.2AH (Model: ICR18650 2200mAh 3.7V )   [1528-1836-ND]  $4.52 per Ah

From what I can tell by the model numbers, [digikey # in brackets], the candidates below are comprised of Samsung ICR18650 cells, although both the large capacity and small capacity batteries both output the same 3.7 volts.


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I know that operational amplifiers have a stage in which there is an incompatible association (VCCS + VCVS). How do I show that this configuration gives an infinite gain? I am considering general two port networks - ideally, I'd get this configuration, but I can't see how to show mathematically that the gain is infinite.

(EDIT)The original circuit I am solving is this one:


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I need to use a constant current source 20mA, the current flows through multiple diodes and resistors which are in series.
The resistor value can vary from 0 to 1.6k and also a possibility of Open.

As the measuring device can read only upto 10V(Not multimeter, it is a 10V Analog Input Card), and at present 20mA*1.6k=32V+(diode drop). Hence I need to reduce this voltage before passing to the measuring device.

Is there a simple way to do it?(Current Source is a must)
To protect Open Condition of the resistor is a Zener Diode Sufficient?


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I have a project that uses about 200 solderless jumper wires connecting header posts from one circuit board to the next. Now that the whole thing works, I want to ditch the "temporary" connections in favor of a permanent solution, which means soldering everything in place.

The solderless (female) connectors have a small hole in the side that I'd hoped was there for exactly this reason, but some experimentation leveled a zero, and I'm now in the market for anything that would slide over the header pins and be easily soldered in place. The "temporary" jumper wires I'm using now:

These things are very tightly packed, so I don't have any more room than the jumpers fit in. To be honest, I had to sand a mil or two off of some of them to get them to fit. (They're .1" apart.) =[


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The project is to add 2 USB-A ports to my bass amp so I can charge my device(s) during a gig.  To do that, I bought a 2-port USB panel mount connector (intended to connect to a motherboard) and a 2-port plugin charger.  The idea was to cut off the header connector and replace it with 2 USB Males to plug into the charger.  The problem is the charger has 1 USB-A and 1 USB-C port.  Can I just put on a C male end on the bare wires, or put an A male end on the bare wires and use a A-to-C adapter to plug into the charger?
Edit: The "Micro" in the title refers to the cable that goes from the panel mount Type A connector to the actual device being charged.
Edit 2: In talking about this with friends, this question was unclear to them.  The plan is to tap into the AC mains inside the amplifier cabinet and run it to an outlet, also mounted inside the cabinet.  Then I plug the 2-port wall-wart charger into that outlet.  The from the 2 USB ports of the charger, run cables to the USB-A panel-mount.  The question is if I put a USB-C male on the end of one of those cables and plug it into the charger, will I be able to plug my phone into the other end of that same cable and have it work?