texts:
I have two circuits which I have designed using verilog.One is Counter circuit and other is the debouncing pushbutton circuit.but I dont now how to instantiate a model so that the pushbutton circuit is also included in the main module of counter.Please help me.I am using a Digilent Basys-2 Spartan Board xc3s100e

 Counter Circuit
  module button_binary(
    input clock,
    input reset,
    input button,
    output led,
    output led2,
    output led3,
    output led4,
    output led5,
    output led6,
    output led7,
    output led8
    );

    reg [7:0]count;

    debouncing U1
    (
    .clock  (clock),
    .reset  (reset),
    .button  (button)
    );

 always @ (posedge clock or posedge reset)
   begin
    if (reset)
        count <= 0;
    else if (button)
        count <= count + 1;
    end

    assign led = count[0];
    assign led2 = count[1];
    assign led3 = count[2];
    assign led4 = count[3];
    assign led5 = count[4];
    assign led6 = count[5];
    assign led7 = count[6];
    assign led8 = count[7];
 endmodule


texts: Energy efficient one button on/off with extra function

texts:
(Old) cellphones have a button to turn it on (when off), end a call (when on, short press) or turn it off (when on, long press).

I need something similar for a microcontroller. The device is battery-powered so the circuit should be as energy-efficient as possible. In addition to that, the fewer IO pins I have to use the better. I understand I need at least one as an input to read the state. Size isn't really an issue, but smaller is better.

The microcontroller in question is an XLP PIC16F1829. If I'd use a SLEEP instructions and an input button on an interrupt pin, it would consume about 40uA in sleep, considering the peripherals I'm using. I hope I can get something drawing less current. The circuit should be energy-efficient when on as well.

What are some common energy efficient ways to make a one button on/off function with an extra option for a microcontroller?

As you can see, I already added a circuit myself. However, I don't know how energy-efficient it is when on, and there might be better options.


texts:
I have code below for a counter that sets an output bit high or low depending on the count value being compared with a reference value. It is used to generate a PWM signal.
During simulation, the PWM_Output bit is always high as I think the Count_Value signal in never incremented inside the if statement.
Any ideas as to why this PWM_Output bit is not toggling? (Sorry, I am unsure how to get the code in one snippet, maybe someone who knows how will edit the question).
Below is the code:
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
use work.Data_Sizes_Package.all;

entity PWM_Counter_and_Comparator is

    Generic
    (
        Max_Counter_Value : integer := 20
    );

    Port
    (
        PWM_Comparison_Value    : in std_logic_vector(27 downto 0);
        Clock                   : in std_logic;
        Run_Reset               : in std_logic;
        PWM_Output              : out std_logic
    );

end PWM_Counter_and_Comparator;

architecture Behavioral of PWM_Counter_and_Comparator is

    signal PWM_Comparison_Value_int : integer range 0 to Max_Counter_Value;
    signal Count_Value : integer range 0 to Max_Counter_Value;

begin

    PWM_Comparison_Value_int <= conv_integer(unsigned(PWM_Comparison_Value));

    process(Clock, Run_Reset)
    begin

        if Run_Reset = '0' then
            Count_Value <= 0;

            if Count_Value = Max_Counter_Value then
                Count_Value <= 0;

                if (Run_Reset = '1') and (Count_Value < PWM_Comparison_Value_int) then
                    Count_Value <= Count_Value + 1;
                end if;

            end if;

        end if;

    end process;

    process(Clock , Run_Reset)

    begin

        if (Count_Value < PWM_Comparison_Value_int) and (Run_Reset = '1') then
            PWM_Output <= '1';
        else
            PWM_Output <= '0';
        end if;

    end process;

end Behavioral;


texts: Do we have a peak in an overdamped RLC circuit?

texts:
Consider the natural response of a parallel RLC Overdamped circuit, we're required to find the time it takes for the voltage across the Resistor to reach it's first peak.

I got the equation for the natural response and differentiated it to get a maxima, and the time corresponding to it is the time for the first peak.

But my instructors said that there's no peak in case of an Overdamped RLC circuit? Is he right?

Then what about the value I got after differentiating the natural response equation, that should correspond to something, if it's not the first peak?

The equation for the natural response of the Overdamped case when differentiated and equated to 0, to find the maxima/minima, gives a time at which it happens, if it doesn't correspond to the time when it reaches the first peak then what does it correspond to?


texts:
I am charging a 430mAh lithium polymer battery at 1C using BQ24232 charger IC  (from Texas instruments). The charge terminates within 1 hour 20 min with battery voltage showing 4.17V. On research I came to know that it would take a little more than 2 hours to complete the charge cycle when charged at 1C.

Why does my battery charges so quickly at 1C?


texts: Best way to drive a 20 kg object on a turntable?

texts:
I need to rotate an object about 20 kg's in weight, 360 degrees.

I'm thinking of using a stepper motor with some kind of rubber wheel pushing along the rim of a lazy-susan. Geared or belt solutions are probably better, but I don't reckon I need the accuracy. Mostly I am unsure how to spec which stepper motor I need?

This is the given spec for a stepper motor I can get locally:

HIGH TORQUE HYBRID STEPPING MOTOR, WITH DUAL / DOUBLE ENDED SHAFT
12VDC, 0.31A, 38E5/PHASE, 1.6KG-CM TH, 6-WIRE, 120G-CM TD

Any comments welcome.


texts: What is the signature of ATmega32A PU? I couldn't find it in the datasheet or Atmel's site. Is it same as ATMEGA32?


texts: Connecting LiPo Battery Protection Circuit Modules in Parallel

texts:
I'm working with three 6S very high capacity LiPo batteries (22000mAh each) and I've designed a power circuit that implements them in parallel to provide 25.1V to the load when fully charged. I've passed each LiPo battery through it's own PCM module and I should be expecting 25.1V to the load, however when I measure the voltage available for the load, I read 9.75V. The load for the moment is only pulling 100mA (an idle motor controller), though when active it could pull as much as 24A at max torque. Now, I don't have access to circuit diagrams for my particular PCMs, but I do have a spec sheet provided by the manufacturer. I think the issue could be within the PCM's circuitry since I don't think they were intended to be used in a parallel configuration like this. But I just wanted to rule out any obvious mistakes that I might be missing. I couldn't find much on the internet regarding PCMs in general. Thanks again.

Update: I tried a different circuit configuration, but my results are slightly better but still concerning. Now I'm reading just over 20V from this configuration.


texts: How does a ground node affect this circuits equivalent resistance?

texts:
I'm new to circuit analysis and I bumped into this problem that Im not sure how to solve.
Originally the exercise had two ground nodes at the same ground level but I saw a thread that said that it could be modeled as it is shown in the figure below

I don't know if the ground node affects the equivalent resistance calculation by making R3//R4//R5 or R4 is just in series with R5.

Thanks in advance!

Edit: I'm looking for the total equivalent resistance, from the beginning to the ground node.


texts: How can I reduce the high voltage input for 7805?

texts:
I need to take 20ma from output of 7805.My input voltage is Ac variable voltage (0-300Vrms).I am planning use to pre regulator for 7805 and full bridge rectifier.Maybe I can reduce input voltage of 7805 to 30V from (0-300 Vrms).I can use mosfet for pre regulating.
Do you have a sample circuit on this subject for my inspiration?In summary, I should be able to take 20ma from output of 7805,in (7-300Vrms).(7=5+7805_dropout_voltage).Actually 7 volts can be 9-10volts.(not important).
how can I do it?


texts:
I am asking help to understand the circuit in the black rectangle below.
It’s using a matched pair of PNP, with common Base. I was thinking to a kind of current mirror, but R2 and R3 are different. I have looked in usage of matched pairs and I understand its main properties are equally matched gain.
Any ideas


texts: Minimal distance between silkscreen text and edge?

texts:
I'm maybe going to use JLCPCB to order a PCB (if I get it finished), but I'm wondering about the minimal distance between the edge and silk screen text.

If I look at the capabilities:

https://jlcpcb.com/capabilities/Capabilities

I find regarding silk screen text:

Minimal height (32 mils)
Minimal 'line' width (6 mils)

The only item that comes closest is 'edge rails' (3 mm), but I doubt that's related. 3mm seems big.

I'm intending so place small text and close to the border like below. I used several font types, but I am just playing around with it; I like to use the smallest possible.


texts: Need positioning arms for soldering 0201

texts:
I'm looking for some kind of micro positioning arm to help me solder wires on tiny SMD devices.  Some kind of pantograph mechanism where my hands move much further than the tip controlling the wire.  It would also have to have to hold/release the wire.  Of course, this all has to work without blocking the view of the microscope.

I'm guessing this has been invented, if I only knew what to call it.

I find myself soldering boards with 0201 parts and 0.4mm pitch ICs.  Even with a stereo microscope, my hands just aren't up to the task.  I know of the traditional "helping hands", but they are hard to adjust precisely and the usual alligator clip end is too large (blocks my view).

Update:
I should mention that the board was machine placed and I'm just trying to do rework on it.  If it was up to me, bigger parts would have been used!


texts:
I have already designed a buck converter with the following specifications using an MCP19035:

Vin=14V,
Vout=1.8V,
Fc=63kHz(Crossover frequency),
Vref=0.6V,
Iout=10A
step load High IOH=7.5A
step load low IOL=2.5A
Fsw=600kHz

My design is working perfectly and I got the expected outputs

Now, I want to design the same converter with the same specifications, using MCP1630V. I have used the circuit given bellow, with the same calculated components for the voltage divider network, the compensation network, and power stage network. Unfortunately my design does not work as expected and I could not figure out the problem

The only thing that I think could be the source of the problem is the ramp generator circuit used in CS pin of this component

please, try to figure out what is the problem in my design


texts:
I need to test and maintain a batch of devices which contain GPS modules. I can work on the rest of the device, but when it comes to test the GPS part I have no signal on my desk, no matter how near I try to get to the window. I just need to check that the receivers get proper signal, acquire position and get a S/N Ratio I can compare with other working units.

I could place an antena on the roof (I've actually got one), but the devices have no antenna input (and they don't support active antennas anyway). Since I'm going to do this task for quite some time, I've thought a reradiating GPS antenna is what I needed. However, here in Argentina they're practically unheard of. No specialized shop has them, so I'll have to build my own. Even worse, in Argentina is quite difficult to get most of the specialized electronics components (think of a list of no more than 200 most common transistors), and importing from overseas is practically impossible. Hey, even 1/8W size through hole resistors are getting difficult to find! (only 1/4W 5% are available).

So, what can I do? I've got a couple of commercial PCB active and passive GPS antennas. I tried feeding the active antenna with 5V through an inductor, and connecting the output to the passive one through a small capacitor (1nF). The active antenna is supposed to have a gain of 28 dB, and I've got (by spec) at most 2 dB of losses in the cables and connections. I'd thought it would work but I cannot see any improvements in the received signal at all. The active antenna is on the roof, completely obscured from the room I'm into, so I don't think the antennas could interfere with each other. The power supply is a 7805 fed from a 12V battery (so I know that no strange noises are coming through the power rail).

The active antenna is not the problem. I can make it work connecting it to a receiver that does support active external antennas and it acquires position all right.

Perhaps I should install a second LNA stage, near the radiating antenna? What should be its gain? I have barely any measurement equipment. I certainly have nothing useful to measure a 1.5 GHz signal at all, so I'm working blind here. A sample circuit with very few components would be specially useful.

Any help would be appreciated.

EDIT: Added schematic

EDIT2: Added crappy photo of my board


texts: Taking the absolute value of a DC source (getting the magnitude of the voltage)

texts:
I found a circuit online that claimed it was an absolute value circuit, plugged it into the simulator where it worked and tried to implement it on a breadboard. I could not get it to work. So my question is this: How does one take a DC input, like a battery and output the magnitude of its voltage regardless of the polarity of the input?

I want to be able to compare some measured voltage of a 9-V battery to some reference where the polarity of the leads don't matter for someone unknowingly connecting them the wrong way...

EDIT: In order to clarify, I'm just asking how one would go about designing a good absolute value circuit. However, the problem with my circuit might be the parts I used. I know it's wired right because I've done it several times over on the breadboard and get an output that's incorrect, of course. I also have plenty of these ICs and switched them out. Basically I've performed all the debugging you can think of.

My refined question: How would one go about making an absolute value circuit with LM324AN op-amp ICs, 1N4004 diodes and resistors aplenty.


texts: single pole roll off model for an operational

texts:
I need to ask this question regarding my tutorial for signal processing. So the basic theory that I have come to understand regarding this is that the output of an operational amplifier will be as determined by circuit analysis except for when the input voltage frequency exceeds the cutoff frequency. And so for a single pole op amp the model equation is given as follows:

A(s)=GB/(s+ωa)

Where A(s) = gain, GB= Gain bandwidth product and ωa is the cutoff or -3dB frequency. I have this problem with a difference amplifier where the gain is defined to be the output voltage divided by the difference of the two input voltages and for this tutorial I need to be able to derive the modelling equation for this single pole difference amplifier as given by the attached image below:

Can anyone please show me how this derived. My lecture notes have been confusing me with regard to this because they say that at 0Hz frequency A(0) = A0, where A0 is typically 100dB that A0=(k/ωa) and so k = A0ωa and so k is the bandwidth product. But in the equation for the gain given above gives K as the ratio of R2 and R1.

Could anyone show me how this is derived?
Thanks,
Simon.


texts: What kind of tools would I need to analyze 1000BASE-T/gigabit ethernet waveforms?

texts:
I'm an EE student and I'd like to get some visibility into the 1000BASE-T Ethernet waveform. My goal is to induce jitter to learn more about real-world error correction, possibly resulting in research down the road.

I have no experience with analyzing real differential signals, and obviously most Ethernet-specific test hardware is extremely expensive (and I have no lab access). Can PC-based scopes/logic analysers capture Ethernet and do basic decoding (8/10b)? What other recommendations do you have? This may be a long shot, but I'm aiming for a solution < $2k.

So, my question is: What kind of tools can I use to look into 1000BASE-T Ethernet waveforms that are not extremely expensive (less than US$ 2,000)?


texts: Positioning of Air Gap in a Magnetic Core

texts:
We are making a rotating machine where we need to measure the flux in the air gap, however, the flux sensor is too thick to fit in the airgap so a slot will need to be cut into the face of the pole so the flux sensor can slide into it.
But before we do that, we need to determine how much those modifications will distort the flux readings so I was going to make a mock-up.
There would be two setups:

The control setup would consist of a UI core with a DC-excited winding and an air-gap machined into it that would fit the thickness of the flux sensor.
The second setup would be identical except it would have a slot machined into one face of the airgap that the flux sensor could rest in.

Then we would compare the readings of the flux probe at the same DC excitation. Our only goal is to see how much a slot would throw off the flux readings of the flux in the air gap. In this mock setup, we can make the airgap large enough to fit in the flux probe to compare, but on the actual machine the airgap is too small so we would have to make an inset/slot for the flux probe to nestle into but we have concerns about the slow affecting accuracy.
My question is this: Does the location of the airgap in the middle or at the corner of the core matter? Because if the airgap could be at the corner, we could put the coil on a bobbin and on to an I-core and move it back and forth between the two setups (an unmodified U-core and a U-core with an airgap machined into it), rather than needing to wind two separate cores.
I suppose we could do it share a bobbin and coil either way, but if the airgap should be mid-length then that's three fiddly pieces and we might choose against that.

simulate this circuit – Schematic created using CircuitLab


texts:
I have a LED voltage vs current graph. The forward current is represented in a log scale.
Suppose my value is 120mA.  Where should I place my point and what would be my forward voltage with respect to the below graph?

Like, should I split the box between the 100mA and 200mA in normal decimal scale (point A) or log scale (point B)?


texts: DC sweep analysis not matching transient analysis for amplifier

texts:
I'm building a little sound amplifier for something and can't quite understand why it's not a powerful as I though it might be. This is the circuit, and a simulated DC sweep is shown below:-

Vdrive is the meeting point of the output transistors Q1 and Q3.  (Don't know what happened to Q2). The op amp is an LT1006.  You can see that there is the possibility of a 1V to 11V output swing which makes kinda sense allowing for the op amp approaching it's rails. And it's linear wrt the input signal, symmetrical about a 6V mid point.

This these are the transient analyses for signals of 1.5V (4Vp-p) and 4V (8Vp-p):-

You can see that the first graph is slightly clipped.  And the clipping just increases as the input signal increases above 1.5V, as in the second graph. Nevertheless the 4V signal should still fit into the output range as calculated by the sweep analysis.  The clipping also occurs independently of the signal frequency. Why?  Shouldn't that output signal range be identical to the sweep analysis? Otherwise what's a sweep analysis for?


texts:
We are trying to implement a battery monitor circuit in our project. We have a regulator in our design that supplies 3.3V. The logic we want to implement is to monitor the voltage and glow an LED if the voltage is less than 2.7V.

We are using a MSP 430 controller and we use the internal default reference for ADC which happens to be 2.5V. Now this became a challenge and so we put a voltage divider with a 1K and a 300 ohm resistor in series. We are trying to tap the voltage across 1K and feed the ADC through that. When the battery is full, the voltage drop across 1K was 2.5V as expected in the open circuit condition but as soon as we tap the voltage from across 1K resistor and connect to the ADC pin ,there is a substantial drop of 0.8V across 1K and hence my detection algorithm is not working as expected. Am I missing something here?


texts: What makes cables suitable or unsuitable for a given purpose?

texts:
I've been working on a homebrew set of VR Goggles w/ head tracking, and am just beginning to plan the cable that will connect the parts on the user's head to the electronics on the main unit (which will be mounted under & behind the seat the user will be seated in) I'm expecting about a 4ft cable run between the two units, and the connection will need somewhere between 6 and 10 wires (depending on how many ground wires I share):

Manditory wires:

+12v for the video display in the goggles
GND
I2C SDA (3.3v)
I2C SCL (3.3v)
Composite Video
Mono Audio
Optional wires:
+3.3V for the headtracker sensors  (Could be obviated with an LDO regulator from the 12v
GND (paired with +3.3v)
GND (Video-)
GND (Audio-)

Other requirements:

the cable needs to be flexible, light weight, and possibly coiled to handle head movement without discomfort or tangling.
the cable needs to be commodity (this is a personal project)
the cable needs to be reliably disconnectable/reconnectable

I think I understand the various factors in play (crosstalk, emf, capacitance, etc.) but I don't have any perspective on their importance for a 4ft cable run.

My back-of-napkin guess would be to use an ethernet cable (CAT 5), wired like this:
Pair 1: Audio+/-
Pair 2: Video+/-
Pair 3: I2C SDA/SCL
Pair 4: Power +12V/GND

(Use an LDO for the 3.3v on the sensors.)

Is this sensible?  What factors should I be most concerned with?  Which signals will be most impacted by connectors and wiring choices?


texts: Function of solid plane in the NFC antenna

texts:
Below picture shows 2 NFC antenna designed by NXP for their NFC chips .
As you can see there are square planes in the middle of antenna,these planes have no Nets(does not connected to any where ).
Does any one here has any idea whats function of these planes?

EDIT:
there are 2 separate antenna in the picture.


texts: Safety when experimenting with large currents

texts:
I am experimenting with large currents from ultra capacitor discharge.

For example with 500 A (at 2.8 V) you get a very impressive demonstration of the magnetic field of a straight conductor using compass needles or iron chips (compare: http://iopscience.iop.org/article/10.1088/0143-0807/31/1/L03/pdf).

Another example is the Thomson ring experiment http://www.rose-hulman.edu/~moloney/Ph425/0143-0807_33_6_1625JumpingRing.pdf where you may get up to 9000 A for a very short time.

Suppose all voltages used are below 60 V. What do you need to consider about safety in this case?

Here is what I think:

Since the voltage is too low, there should be no danger from current through the human body.
There might be a danger from sparks and lightening when if there are contact problems.

This may be dangerous because of UV light
and because of sparks hitting directly the eye

Also the there might be heat problems which makes thinks to vaporize which you may inhale
A capacitor discharge generates an EMP which may affect pacemakers for example

I am not sure if I mentioned all possible dangers concerning this. My question is:

Under which conditions (minimal current, discharge time...) which danger will become relevant
What to do to make it safe


texts:
Hi
I'm trying to build a PSU based on a design which has it's maximum input voltage 15v. However mine is rectified from 200VA 24Vrms centre tapped transformer. I need to use a zener diode to ensure the voltage doesn't go above 12V for the TLC272 precision opamp. The original design only had 15V so it wasn't a problem. I was wondering if connected it up as in the schematic, would I get a maximum of 12V but full 34V for regulator. I chose 12V because it's easy to obtain and it was the as low as Vin could be on the original design.


texts: RC Circuit, finding time it takes for Voltage across capacitor to rise from 0 to 5V

texts:
For the circuit shown below what is the time it takes for Vc to rise from 0 V to 5 V in (second). Assume Vc(0+) = 0 V

The answer is \$ t = 2\ln{2}\$, but I am unsure why. What I have so far:

$$ V(t) = [V(\infty) + V(0)]e^{-t/T} \qquad \text{where $\;T = RC$}$$
R = 2e3 and C = 1e-3 , so T = 2

$$ V(t) = [V(\infty) + V(0)]e^{-t/2}$$

at t= infinite, the capacitor acts like a broken circuit so V(inf) = 0
but the problem also states that V(0) = 0 so that would set whole thing to 0

Am I doing something wrong, or am I even on the right track here?


texts: Vivado/VHDLOutput signal only for simulation?

texts:
I have an output status signal, that is needed only for simulation. But Vivado 2017.2 doesn't like that it not physically connected (unconstrained):

  [DRC UCIO-1] Unconstrained Logical Port: logical ports have no user assigned specific location constraint (LOC). This may cause I/O contention or incompatibility with the board power or connectivity affecting performance, signal integrity or in extreme cases cause damage to the device or the components to which it is connected. To correct this violation, specify all pin locations. This design will fail to generate a bitstream unless all logical ports have a user specified site LOC constraint defined.  To allow bitstream creation with unspecified pin locations (not recommended), use this command: set_property SEVERITY {Warning} [get_drc_checks UCIO-1].  NOTE: When using the Vivado Runs infrastructure (e.g. launch_runs Tcl command), add this command to a .tcl file and add that file as a pre-hook for write_bitstream step for the implementation run.  Problem ports:  ready.

So is it possible to leave it unconnected? Or alternatively, that is used only in the simulation but not in synthesis and implemention?
I know, I could separate sources for simulation, but is not convinient, especilly if I need to make corrections as result of the simulation.


texts: Why can't I see bouncing of a switch on an oscilloscope?

texts:
I'm trying to view the bouncing of a simple switch on an oscilloscope.

I have prepared a simple breadboard circuit (power → switch → resistor → ground). The problem is, it is displayed as a perfect square/rectangle on the scope. I have attached a photo of the scope screen and the circuit.

Why can't I catch bouncing of the switch on the scope? I don't think it this is a non-bouncing switch.

Here is a photo showing a zoomed-in time scale (50 µs/div). As you can see, it is rising from 0 V to 9 V within 150 µs and staying there. I have tried a few different switches. The resistor in the picture is 220 ohm, 0.5 watt.


texts: Pass a signal in low-level entities and update it back in top-level entity in VHDL

texts:
I have tried a lot to pass a signal that is in a top-level entity, to a low-level entity as an in-port and do some operations on that signal and let the changes happen to the main signal.

Here i just used inc_tb.vhd (as a top-level module) that has a signal named PC and inc.vhd (as a low-level module) that gets the PC and increment it by one at clock edge. But whatever i do, PC gets the 'X' value.
How can i do this?

This is the inc.vhd (low-level module):

library ieee;
use ieee.numeric_std.all;
use ieee.std_logic_1164.all;
use work.types.all;

entity inc is
    port(
        clk : in std_logic;
        pc_in : in std_logic_vector(11 downto 0);
        pc_out : out std_logic_vector(11 downto 0)
    );
end entity;

architecture behav of inc is
begin
    process(clk) is
    begin
        if(rising_edge(clk)) then
            pc_out <= std_logic_vector(unsigned(pc_in) + 1);
        end if;
    end process;
end architecture;

This is the inc_tb.vhd (top-level module):

library ieee;
use ieee.numeric_std.all;
use ieee.std_logic_1164.all;
use work.types.all;

entity inc_tb is
end entity;

architecture sim of inc_tb is
    -- inputs
    signal pc : std_logic_vector(11 downto 0) := x"004";
    signal clk : std_logic := '0';
begin
    -- DUT
    CPU_1 : entity work.inc(behav) port map(clk, pc, pc); -- i want this to just increment pc

    -- clock event
    clk <= not clk after 5 ns;

    process is
    begin
        wait for 10*100 ns;
        wait;
    end process;

end architecture;


texts:
I am looking to build a circuit board that can take a multi segment LCD display signal from a ZIF connector, relay it, and split it to another LCD while having the original and seperate LCD display.

Anyone have experience on this, and are their chipsets that do this already?


texts: Rapidly reverse polarity of electromagnet

texts:
Please forgive my zero knowledge of electronics.

I have asked my people what I thought was a simple question but I just get bogged down with endless questions which I can't answer.

Expressing the situation as simply as possible.

I wish to use a couple of electromagnets about 2 or 3 inches long.
I wish to change the polarity of both magnets simultaneously about 20 times a second.

Question: Can anyone advise what device I require?


texts:
I'm planning to build a few 8x8 LED matrix using 1,7/2,3V and 20mA LEDs, and for controlling them, I have purchased a PCB mounting a MAX7219 with an included LED matrix that you can easily detach.

Checking the specifications of the PCB, I see it uses a 10k resistor, what makes me doubt if it is a valid one for my matrix.

According to the Arduino page (https://playground.arduino.cc/Main/MAX72XXHardware) I should be using something around 26/27k resistor, but I don't see such a big difference between the mounted led matrix and the one I'm building.
Should I change the PCB resistor or is it ok to keep the 10k it already mounts.


texts: Signal differences into Labview to those measured before Multiplexer

texts:
First off, I'm not the programmer.  I am however trying to help him out with my limited knoweledge of IC's and Labview.  But I am reaching the limits of what I know so really need some help. ;)

We have (for example) a gas temperature signal coming into an OP, that is being increased by a factor of 30.  To increase it from the uV into mV.  It is a thermoucouple sensor.

This signal is passed on to a Multiplexer (HEF4051BP).

When attaching a K-Type simululator and measuring the incoming signal into the the Multiplexer, all is well...the signal is 1:1.  For example, by 20C the signal is 29.3mV (0.798mV x 30 through the OP).

Now, this signal gets passed (along with others connected to the Multiplexer) to a MAX110 A/D converter.  From here to an Atmega 168 to be read into Labview.  The Atmega also controls the Multiplexer switching signals and timing.

So, reading the incoming signals in Labview over the COM port from the Atmega, I see differences. The converted signal coming in does not match 1:1 with the signal going into the Multiplexer.  Accounting for error tolerance and all, it still is a large difference.  For example 0.0v in LabView shows as 0.003 and 0.760mV shows in Labview as 0.754mV(I forget the exact value).

This is a problemas we cannot linearise the incoming signals with the LabView K-Type scaling methods as the cuvre appears different to what is to be expected....If we took these signals directly before the multiplexer it would work as these follow the K-Type Industry Standard Table.

Fact is, we have used the OP, Multiplexer, MAX110 configuration many times before and have never had a problem.  So my guess is the Atmega controlling the show, is doing something it shouldn't.  As I know very lttle about the Atmega I thought I would as you guys for some ideas.

Any ideas?


texts:
I'm working with ALD1106 as part of a circuit I'm testing, but looking at the datasheet for the part, I'm confused by the addition of the V+ pin. It doesn't look like it's tied to anything in the pin out (unlike the V- pin, which seems to just be the NMOS body), so am I supposed to just leave it unconnected?

Datasheet of ALD1106


texts: The real equation for quenching frequency

texts:
I found this super regen circuit from http://www.vk2zay.net/article/129

The author stated:

Best over-all performance was achieved with 10 K (for R1) and 6.8 nF (for C1) in the source circuit.

and in his notes:

Typically the quench is set around 30 kHz.

Applying the basic RC equation doesn't work and someone who did the same also posted his findings in the circuit comments as follows:

You mentioned that the optimal quench frequency should not be below 15Khz. According to your design, your quench frequency is defined by R1 and C1. In your circuit, R1 is 10K and C1 is 6.8nF. According to my calculations, your quench frequency is 2.3Khz. Shouldn't C1 be more like 1nF or am I doing my calculations wrong?
The formula I'm using is 1/(2 * pi * C1 * R1)

Then the author responded as follows:

The 1/(2.Pi.R.C) formula is for the cut-off frequency of a simple 1st order RC filter. The RC time constant is how long it takes to charge the capacitor through R to (1 - 1/e) times the supply voltage (about 63.2%), or discharge it down to 36.8% of its initial voltage.
In most RC timing circuits (and this particular circuit) the quench frequency is not determined by the cut-off frequency. There is generally a fixed reference voltage at which point the charging (or discharging) will be stopped and the cycle repeated. How long it takes to reach that point and how quickly it is re-estabilished determines the frequency. Generally the full solution involves two differential equations (one for the charge, the other for the discharge part of the cycle) with boundary conditions determined by other circuit parameters which are often constant voltage/resistance or constant current approximations. A completely analytical solution, even for simple models can be truly nasty!
I haven't modelled this circuit extensively so as to give a nice formula for the quench frequency as a function of the emitter RC values. It would not be a simple thing to calculate, and would be an approximation at best as the quench frequency changes with the transistor operating point (emitter current changes, temperature, noise/signal forcing of the oscillator start-up, etc).

So where do I get such differential equations from and how do I apply them to the circuit? I want to be able to properly calculate the quench frequency. And if it means factoring in source voltage and/or any transistor properties such as junction capacitance, I'd like to know. If I can get answers then I won't have to constantly replace capacitors in my circuit with different valued ones. I want the equation to be compatible with BJT transistors since my superregen uses an NPN transistor.
My superregen is more similar to this circuit:


texts:
I am looking for a photodiode with a peak reception in the 630nm range. I really want high rejection of the 450nm band. However, this doesn't appear to be easily found, for sure not for low cost.

So my options are:

Use long-pass filters on more standard photodiodes.
Use an LED for a photodiode.

So the real question is: What are the drawbacks/advantages of using a standard LED for a photodiode? Speed? Reliability? Bandpass filtering? Linearity over temperature and input light intensity?


texts: Reg opamp circuits with no input signals

texts:
In circuits where there is no input signal shown explicitly as in the figure shown below, how do we determine the behaviour of the circuit? I understand that the power supply given to the opamps drives the circuit, but don't know exactly how we consider their effects initially.
I'd like to know how we take initial conditions into the equations at different nodes(say Vout, here)


texts: What's the difference between consumer and industrial grade strain gauge adhesive?

texts:
Can I just use normal super glue and epoxy resin to attach a strain gauge?? What am I sacrificing by doing so?

Also, how are load cells so cheap and what kind of adhesive / covering do they use?


texts:
I need to draw approx 4 amps for 10-15 hours at a minimum of 18V.

I have hooked up two 300 watt power supplies in series:

+12V on one and +5V on the other: the output is only +15.8V rather than the 17 point something that I was expecting
+12V from each: then one power supply shuts down.

Why does this happen and how can I get the +18V (or more) that I am after?


texts: A basic question about oscilloscope probes

texts:
I have recently acquired a Tek 460A scope and a mixed bag of oscilloscope probes.  I have a very basic question about the probes:

One of the probes is a Tek P2200.  This is a 1X/10X switchable probe with a simple BNC connector on the back.  If I connect this up to a 16V power supply and set the probe to 10X, the scope reads 1.6V.  No surprise there.

The other probe is a Tek P6121, which has a chunkier BNC connector on the back that includes an additional pin on the outside ring (that is obviously engaging with some contacts on the scope).  The probe is labelled 10X, but when connected to the same 16V power supply the scope registers 16V.  Is this because (a) the probe is somehow communicating its attenuation factor to the scope, or (b) is this really a 1X probe?


texts:
I've been looking at the PCB layout for the LT3045, a high PSRR LDO. The datasheet of the LT3045's demo board, the DC2491A, includes a recommended PCB layout. One section of the datasheet mentions that the output capacitor, C2, should be mounted on the PCB using a "split capacitor" technique. I'll attach sections of the datasheet that mention this, as well as an accompanying image from the datasheet.

I don't understand how to achieve the capacitor mounting style for C2 in Autodesk EAGLE.

As a side note, why does this PCB design include the vias in the bottom right part of the board? These don't seem to connect to anything.


texts: MOSFET Oscillations when bringing gate to same potential as drain

texts:
I was messing around in the lab today looking for a clever way to make a single FET oscillator. I made this circuit, which is basically a high side switch using an n channel mosfet. I have it oscillating but I am not sure if my explanation is correct. If someone could help explain why it is oscillating or prove my theory, I would greatly appreciate that.

As you can see in the second picture, the gate is connected up to the drain which is connected to Vcc. Let's say it is at 10 volts. The source then connects through a load to ground. My explanation is as follows:

The fet turns on because the source is pulled down by the resistor to ground and the potential difference between gate and source is > than Vth (2volts).
Once the transistor turns on, the drain is now pulled up to Vcc.
The gate is no longer 2 volts above the source, because they are both roughly at the same potential.
The transistor then turns off because Vgs < Vth
Source is then pulled back down to ground.
Goes back to step 1.

Does this make sense? Thanks! In the pic below I used 10 volts, you can see that the source comes up to 8 volts (input minus Vth) which makes sense. The oscillation frequency is 360khz and p-p voltage is 0.5v


texts: Dual Power Supply for single 10m LED Strip Run

texts:
This is my first time here so sorry for any wrong formatting.
I am currently creating a project where I will run my wall with 10 meters of addressable LED strip (Made up of 2 x 5 meters rolls). I have two 20 amp, 5 V power supply for the project. After calculating 60 LEDs/meter at 5 V it would consume around 18.8 W/meter meaning that at 10 meters it would be 188 W, 5 V = 37.6 amps.
I searched a lot but don't have the necessary understanding of electrical engineering to safely conclude what I am going to do. Below I made up two different scenarios which I could wire up, my two questions are:

Are my scenarios safe? / Would they work?
Is there any recommendations or changes to my schematic?

To control the addressable LEDs I am using a microcontroller board called NodeMCU, which would acquire 5 V from the power supply and send the data signal through the LEDs.
Case 1

For the first case I would have each power supply connecting at one end of the strip and both strips connected together in the middle for power and data, meaning I would not have any voltage drops. The NodeMCU would acquire 5V from the first power supply and send data through one end.
Case 2

Case 2 is similar to Case 1 but the only difference is that there wouldn't be a connection between both strips and the NodeMCU would transmit data at both ends otherwise one strip wouldn't receive data.
I appreciate any opinions and suggestions to my schematic, thank you!


texts: Circuit Diagram: How are these capacitors turning on these transistors?

texts:
This circuit has the LED columns alternate by the capacitors turning on and off the transistors (from a toy christmas tree).  I've been trying to visualize it for a day now. I cannot understand how the capacitors are actually switching the transistors.

Care to help a beginner?  P.S. Does this setup have a certain name?  I can read up more on it myself in that case. Thanks.


texts: Microphone input buffer circuit not behaving as in simulation

texts:
I have designed a circuit to interface the SPW2430HR5H-B microphone into a dsPIC33 ADC pin.

The circuit has an active LPF and uses the AC coupling capacitor as a HPF to get an output on the frequency range between 500Hz to 3KHz.

According to my simulation, I am getting exactly what I need:

However, when I test the real circuit already built on a PCB, the lower frequencies seem to be much more amplified than the high frequencies.

I have checked the mic datasheet and it has a flat response in the band of interest so I suppose the culprit is something else.

Could it be excessive parasitic capacitance from the PCB? Acoustics? Something wrong with my circuit?

Thank you


texts: LTSpice Transconductance Amplifier Simulation

texts:
I'm trying to simulate a band-pass transconductance amplifier in LTSpice, which looks like this:

I used the recommendations of this post - https://electronics.stackexchange.com/a/278870/87695 - and used a G component with a table to represent the voltage controlled current source in my LTSpice schematic.

I have done some estimations on the locations of the poles and zeros:

However, my simulation is not displaying the result I expect to see at all:

I suspect that I set up the voltage controlled current source incorrectly. Here are the parameters:

Any idea of what I did wrong? Thanks in advance.


texts:
i'm actually doing some hardware selection about RS485 trancievers. There are a lot of different suppliers, drivers, etc...
So, i've selected these two trancievers: ADM2483 from Analog Devices and ISO15 from Texas Instruments.
They seems rugged enough to be used in a harsh and noisy industrial environment, basically my decision is to go for an isolated solution in order to mitigate those problems, my MCU is an ESP32 (so USART levels are 3.3V) and i can supply without any problem 3.3V and 5V.
There is a specific reason to go between one and the other?
There is a distinguishable difference?
I'm planning to go for the ISO15, because between the two, the datasheet says:
"These devices are ideal for longtransmission lines, because the ground loop is broken to allow for a much larger common-mode voltage range. The symmetrical barrier of the device is tested to provide isolation of 4000VPK per VDE and 2500VRMS per UL and CSA between the bus-line transceiver and the logic-level interface."
Is that only marketing or it's really optimized for that conditions?


texts:
I'm doing UART communication over a single wire using voltage and current modulation with an STM32F0. The problem I'm having is when I transmit, it feeds back into my Rx circuit an I receive a bunch of junk.

I'd like to disable the Rx UART completely while I'm transmitting, then reset my Tx analog circuit (flip flop state) and then renable the Rx.

Currently when I try to do this, any delays I insert seem to break my firmware flow and I get stuck in a UART interrupt loop.

/* Disable Rx UART during message transmission */
USART_ITConfig(PMIC_COM1, USART_IT_RXNE, DISABLE);

/* Reply over CCIF if message 0x28 is received, reply is enabled and
current state is LiIon */
//TODO: Reply Enable might not be necessary if checking for this in LiIon STate
if (replyEnable == 1 && currentState == STATE_LIION)
{
    CCIF_Send_Reply();
}

/* Reset Flip Flops */
PMIC_Output_On(FF_RESET);

Delay(5);

PMIC_Output_Off(FF_RESET);

/* Enable Rx UART */
USART_ITConfig(PMIC_COM1, USART_IT_RXNE, ENABLE);

void CCIF_Send_Reply(void)
{
  TxBuffer[0] = 0x55;
  TxBuffer[1] = 0x66;
  TxBuffer[3] = 0xFF;
  TxBuffer[4] = '\0';
  USART_ITConfig(PMIC_COM1, USART_IT_TXE, ENABLE);
}


texts: microSD card,looks initialized,but single read block returns 0xFFs

texts:
The 2GB micro SD card i'm working on looks initialized,all commands are giving the correct answer(i.e. CMD 8 returns the echo of the argument),command ACMD41 returns 0.At that point i try to read 512 bytes with command 17.I checked on PC that the bytes are all 0 until the MBR address,but on scope i have the SD Out stuck high.
So i read lot of 0xFF .
How can it be?
Many thanks.
Diego


texts: what does nominal numbers of electrical machines mean

texts:
I got confused about rated numbers of generators and motors like rated voltage and rated power .
I know nominal numbers of electrical machines are numbers which the machine is designed to operate but for example I don't know what the nominal power of a generator is , is it the provided electrical power or required power to operate or what ?
To be specific , in dc generators and motors , what do these factors represent :

Voltage
Power
Rotational speed

thanks


texts: Why is there no tri-state during T2 state of this machine cycle?

texts:
My teacher provided this as part of printed notes where he writes there is no tristate during the T2 state of Memory Write Cycle. I am quite confused about why it is so.

After a short search in the internet, I didn't find any such statements anywhere. Can the tristate exist in T2 too or is this optional? If it is true, why is it so?


texts: How is procedural code converted into a circuit?

texts:
With non-procedural code, the digital circuit the code represents is relatively obvious.
However with procedural code, it's hard/impossible to see how it translates into a circuit.

The only method I know to convert a function into a circuit is to describe it in canonical disjunctive normal form. However doing this to implement even small amounts of procedural code would require a massive number of gates.


texts: Simulating PMOS differential amplifier in Cadence

texts:
I am studying about rail-to-rail opamp design and I am trying to recreate the Itail vs Vgs (in this case input common voltage) curve from the link bellow (pages 5 and 6):
https://mixsignal.files.wordpress.com/2013/03/689-604rail2rail.pdf
I am having trouble to recreate the plot for the PMOS input stage. My VDD and VSS voltages are 1.8 and -1.8, and bias current is 30uA and the passive load is enough to keep the PMOS in saturation.
I have a feeling I am missing something basic with how I instantiated the current generator...

And here's my plot of the mosfet current vs input common voltage (you can see the drain current is a bit off, it looks as if I swept the Vds instead of gate voltage, and I didn't, I double checked):

And finally, I tried putting it all together in one schematic cellview but again, I think I am using the bias generators wrongly because now I can't seem to see the correct current in the NMOS branches even thought there's the current generator...

I would appreciate some help.
Thanks!

EDIT:
Taking a hint from the comments, I replaced the ideal current source with active current mirror source for both NMOS and PMOS differential input.
I managed to get correct plots of drain current vs input common mode voltage and gm vs input common mode voltage but I still have troubles putting it all together into a rail-to-rail input stage (page 7 of the linked pdf).
Here are my tests:

The MOSFETs in the current mirrors are all the same, and what bothers me is that the NMOS M3 is not referencing the correct current from the current generator. My bias current is 40uA, and in individual cellviews where I simulated the PMOS/NMOS differential inputs separately everything worked fine.
Putting it all together now I seem to be having an issue with the PMOS branch again. You can see the simulation results in the next picture.

From the looks of it it seems my PMOS pair is always on and with fixed current through them.

EDIT2:::
After close inspection I realized my input common mode voltage generator was not properly grounded but connected to VSS (-1.8V). It kept my PMOS gate voltage always sufficient to drive them in saturation.
After correcting that mistake I was finally able to have my basic simulation set up and running.


texts: Latch-up and ESD protection for power supply and RS-422

texts:
I am designing a power supply board that has a switching regulator and four LDOs. Now, I understand that layout details or practices will help reduce switching noise from corrupting the ground and so on and so forth.

I have been asked to do a study on latch-up and prevent latch-up of the board in question. As far as I understand, latch-up is a behaviour that corrupts or damages ICs and that preventive measures are taken care of in silicon by the VLSI designer to prevent latch-up.

How can I make my design latch-up proof? I also believed that in case of PCBs, it was ESD that was the killer. How or what are the things that I can include in the power suppy (regulator and LDO) design that can make my design more stable?

The board also has an UART-to-RS-422 level shifter as well. It will take single-ended UART signals and convert them into differential RS-422-level signals.

I understand that EMC or ESD analysis and protection is a vast subject. But any pointers that shall help me begin are appreciated, please.


texts: Are multiple groundplanes a good idea on a 4-layer pcb?

texts:
I'm working on a design of a 4-layer PCB. The stackup is like this:

Top: signal
Inner 1: power distribution traces and copper fill
(VCC) in some areas
Inner 2: signal
Bottom: ground plane

There is a lot of unused space on the signal layers. I'm tempted to fill this to give the board fab a break.
But, should I leave these unconnected? Or connect them to ground? Or should I just not fill these spaces?


texts: Why would I want a 3.5mm stereo audio socket ground designed so they connected to the casing?

texts: It seems most audio sockets have the the ground pin connected the outside of the socket so that when it's fitted in a casing it will be contact with it. Why?


texts: Will resistance of wire increase with age due to some effects?

texts:
Today I had an electrical problem at my home not yet resolved. I will explain the problem.

The switch for water motor and switch for lamp are nearby in same board. When I turn ON the lamp switch, the lamp is glowing untill the switch for motor is OFF. When the motor switch is turned ON the lamp despite its switch turned ON stops glowing and motor is also not operating. When the motor switch is turned ON with lamp switch OFF, the motor is not operating. The performance of other electricals in home  is not disturbed.

What may be the reason?

As a school boy electrical enthuiasist I suspect there may increase in ohmic resistance at wire (due to some effects) series to the parallel combination of these two switches. So lamp which has high resistance able to grab some enough voltage despite that unknown series resistance. But motor which has lower resistance cannot.

Can you explain technically?

Edit: The motor was working well for years with same electricals undisturbed. This fault occured today.


texts: What's the logic behind the load simulation in Simulink's power_microgrid example?

texts:
I'm trying to understand the Simulink example "Simplified Model of a Small Scale Micro-Grid" in order to build something similar. If it's included in your Simulink version you can access it by writing power_microgrid in Matlab.

I get how they simulate the behaviour of the solar panels and the battery using a controlled current source, but my problem comes with the simulation of the houses.

The circuit is very similar to the one inside the battery and panels. I understand that this way they can change the power dissipated inside the resistor and simulate the loads of the house, but isn't the current source introducing "free" energy into the system, that can flow into the battery and charge it, or modify the voltage of the system?


texts:
Is there a benefit to the utility company, or potentially to me, for balancing the loads across the two 120V legs in my mains power? this About page suggests some benefit, though the explanation seems suspect. I understand that, on my end, whether I am drawing 100A on one 120V leg, or 50A across both 120V legs, I am still going to be paying for 12kW.

Given that, does balancing the loads have any impact? I don't know quite enough about center-tapped transformers to say how the center tap affects transformer performance on either the high- or low-side.


texts: Wiring a transformer with two primary windings

texts:
I'm building a circuit that involves the use of multiple transformers. I've mainly used transformers that had one primary and one or two secondary windings. However, this time, the transformer I'm working with has two primary windings and two secondary windings, like in the diagram below:

simulate this circuit – Schematic created using CircuitLab

What is the proper way to wire such a transformer? Do both primary sides have to be wired to something in order to work? In my simulation, I'm only using one primary winding and one secondary as a bridge-rectifier, so the other one is not used at all. If I decide to make S1 and S2 center-tapped, will I have to use P2 as well?

EDIT: More info, I'm working with 115 Vrms. This is a signal transformer. If I have to give it a model, it's the 14A-56-28


texts: Is a Wifi antenna both a transmitter and a receiver?

texts: I only have one antenna on my Wifi card so I am assuming it is both the receiver and the transmitter, but I can't quite wrap my head around it. Does it constantly switch between being a receiver to being a transmitter ?


texts: Are there methods apart from ECC, to detect and possibly correct cache errors?


texts: What does the current distribution look like on an antenna?

texts:
This is more of a conceptual question, but I am struggling with understanding the current distribution on a radiating antenna.

I understand how it travels, but how do we know? Is there some paper or textbook I could read that proves where the current is on a radiating antenna?

Reason I am asking is because maxwell's equations include a current distribution term that I am curious about.


texts: PWM disables charging battery after heavy load on inverter

texts:
I have 2 batteries 12V 80Ah deep cycle lead in series for a 24V system.
I connected an invertor directly to the battery pack.
I have ~600W (~44V) of solar panels connected to the PWM charge controller.

As soon as I use like in this example 1000W on the system, the charge controller just stop transmitting Amps to the battery. (And voltage drops.)

Resulting in a voltage drop like that (captors on battery pack 24v) :

Black line is battery full + voltage added from solar panels. ~28.8V
blue line is battery full. (At night should be around there) ~26.8V
red line is maybe ~23.5V

It seems to restart the charge after few hours.

Is there something wrong with my Charge controller ? With my setup ? :/
Thank you.


texts: Can I generate 56kHz signal with MCU running at 1Mhz

texts:
I am new to embedded systems designing. I have to generate a 56kHz signal with a MCU running at 1Mhz. I want high accuracy. If I just use a timer, it gives me 55.55kHz.

Is there any way I can divide the clock frequency to a high value and using that, generate a 56kHz signal?


texts:
I am currently having a lot of trouble with noise being picked up by load cells.

The strain gauges on the load cell are configured in a full-bridge pattern. In a noiseless environment (ie far away from any micro/power supply lines) the system performs admirably.

However, the four wires that come from the load cell I believe are picking up noise. If these wires lie close (within 75mm) of a USB cable they pick up noise, or there is a WIFI/3G module nearby the wires also pick-up the EMI noise.

In an attempt to mitigate these problems we have twisted the wires coming from the load cell to reduce the inductance loop and therefore reduce the noise problem. This has no helped.

Therefore we are now looking into types of shielding, and thus brings me to the question.

How effective would copper (or aluminium) tape be if I were to wrap it wrap the end of the load cell, all the way along the wires and over the PCB that has the ADC chip mounted on it?

Before you ask about is it coming from other noise sources, I have eliminated the power supply as the noise as I am using a heavily filtered vref design specifically for the low noise applications.

The signal level that exists between the S+ and S- lines is at a maximum 3mV therefore any noise very quickly ruins the signal.

When I twisted the wires coming from the load cell I twisted all four at once and not as twisted pairs, would this have any impact on the result?


texts: Working principles of an LDR Light Switch

texts:
This is a simple circuit which dims the LED according to the light recieved by the LDR or simply a light switch.

Can anybody explain how two BJTs opearete in the circuit, or simply how the system works?


texts: I have a 240 inline fan that can be speed controlled, would it be safe to run the 2 hots to 2 seperate 120v outlets that are both on seperate breakers?  or could I run the  two 240v hot wires to the one hot wire of 120 with just less power?  the fan will be used 3 hours per week


texts: The voltage over the person is 250V. Why does he receive a shock? Doesn't the earth have a very big resistance so the current will be very small?


texts: How do I trigger a MCP2200 / FT245RL chip

texts:
In my original post I thought I had this turkey nailed, sadly not :(

I've got a pnp laser distance sensor and a Denkovi USB relay board.
I'm planning on using the laser to trigger the IOs on the Denkovi board so that I can detect it with software.

The Denkovi Manual is here

The Chip Manual is here

The Laser Manual is here

Denkovi tell me...
4 Digital I/O Port: Inputs - 0-5VDC TTL levels, with pull-up 200kOhm
resistor. Each can be configured as digital output (0-5VDC).

My sensor has either
Normally open 4.5VDC to switched 12VDC
Normally closed 12.5VDC to open 4.5VDC

Does anyone know a way I can active one of the inputs directly without using a relay?

Think Im going to need a relay :(

EDIT
When the sensor is powered up using 12.8VDC (sensor will operate in the range 12 to 30 VDC)
In the NOT switched state, measuring between white (NC) and Blue (0VDC) we measure 12.7VDC. (assumed transistor loss)
In the switched state white to blue measure 4.6VDC

As mentioned below 5VDC has to be the maximum the denkovi board is subjected to.

Hence I propose the folowing


texts: How to make IGBT/MOSFET gate driver circuit (5-10V) using push pull with transistors

texts:
I was trying to drive the gate of 25N120 IGBT (2800pF gate capacitance) with the help of transistors. The working voltage is 10V. I have tried with BC548 NPN and BC558 PNP.
Everytime I apply PWM, the voltage level just remain 8V - 10V. The LED at output stays on. With positive trigger at base it shows 8V (seems NPN conduct try to ground the OUTPUT) and with negative trigger it shows 10V (seems PNP conduct and does its job.) The problem with the NPN why doesn't ground to 0V.
Even though I checked the output by implementing a 10nF capacitor, but the response is the same whether the output is connected or not.
MOSFET)IGBT drivers are not available here. The whole project was almost done, and now got stuck at this last part. My NPN and PNP configuration is in the photo.


texts:
I am developing a 4 layer PCB using KiCAD. It got 4 layers; Top, bottom, L1, L2. Setting copper zones for the top and bottom layers is common practice. I'm wondering, should I add zones to the intermediate layers as well (L1 and L2).

Also is it bad to create a zone which is not attached to any net? Just copper islands? Because KiCAD gives a warning saying it will create copper islands.

Thanks in advance ! :)


texts: What kind of circuit is required to increase amperage with variable input voltage?

texts:
I am new here and will try to be as specific as possible.

I started doing all kinds of stuff in my car, and wanted to add some led stripes in the interior. I want however that the led stripes are dimming with the rest of the interior lights.

I have found the dimmer line, the voltage varies from 0V (lights out) to 10V -> lights at 100%.

I have tested this with simple LEDs and 4.7 kOhm resistors and everything works correctly. However a whole led stripe will consume considerable more power and I want to make sure that the dimmer doesn't overload / burn.

So I thought I'd build a current amplifier connected to the main 12V of the car (battery line) which takes whatever input voltage the dimmer gives, routes that to the output but with increased current. I've measured the LED stripes at 12 V (10 A should be more than enough to ensure good operation at all voltage levels).

My question is :

How is this circuit called? Can you give me the correct search terms?

Searching for 12V DC amplifier points me to audio amplifier which isn't what I need.


texts: How to calculate CR2032 battery life with LED

texts:
I want to power an LED that has a 3.3V forward voltage using two 3V CR2032 coin cell batteries to create a 6V supply. I set the resistor for a 20 mA current. For my application, the LED will be turned on for about five minutes a day.

The CR2032 has a capacity of 235 mAh (Energizer datasheet: http://data.energizer.com/pdfs/cr2032.pdf)
The datasheet only has a "continuous discharge characteristics" curve for a 0.19 mA drain.

How do I know what the capacity is at the current draw level of 20 mA? How can I estimate the battery life, besides dividing the mAh capacity by the current draw?

It's confusing because on some sites I've read that coin cell capacity seriously degrades if you continuously draw more than a few mA... but I've seen many keychain LED flashlights that even use the smaller capacity CR2016 battery.


texts: if voltage is too high but current too low, then is it dangerous for humans?

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voltage=1000V,current=1/1000Amps, so power=1watt
now is this the same as 1V with 1Amp which is not dangerous to humans.

Does voltage not have any any effect if the current is too low?

Because voltage is energy consumed /charge , so voltage is dangerous independently or not?
why/why not?

  Or is it current that is dangerous, regardless of voltage?


texts: I have a fluctuating DC voltage in the range 8.5-9.5V coming out from an adapter. How can I convert it to a stable 9V?


texts: Red resin in-between closely spaced PCB pads

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Closely positioned components on this one sided PCB have red resin separating solder connections and underneath surface mount components.

What is it?
How is it applied and why do only some components have this resin separation?


texts: How to get the LC from a transfer function while given a crossover frequency (low pass RLC filter)

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I have made the transfer equation for a low-pass RLC filter, but I'm having trouble on what to do next to get L and C. (I also have a bandpass and high-pass filter I need to do, but I just need one explained, then I think I can manage the rest.)
For sake of simplicity, let's say R = 10 ohms, the lower crossover frequency is 100 Hz, and the higher crossover frequency is 1 kHz.
I'm a bit confused if it's possible to get L and C from this much information, or if I simply need to make a reasonable choice for L or C (like L = 1 mH or C = 10uF) and go from there.


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I came across an on-line ad claiming to save "90%" or even 100% on my electricity bill. Wow! And "power companies hate this trick"!

I gathered some courage, clicked through the ad, and this is sort of how it's explained:

Appliances always draw more power than they need to run due to inefficiencies and noise on the sine wave. Voltex reduces this noise therefor decreases the amount of electricity wasted. It does not change what the meter reads or steal extra power from anywhere, it just uses the energy more efficiently therefor needing less of it. Voltex is your power company's worst nightmare. They have been trying to hide Voltex from the everyday consumer and have even banned it in retail shops.

An accompanying figure in the sales material appears to show a power factor correction and noise reduction:

And the plug-in device is nothing like a DC magnet as shown in the ad. Here's the touted "Voltex Power Saver":

(If you really must read it all, it's here )
Now, all hype and scam aside, and purely from an EE perspective, what exactly is a "Power Saver" that "cleans up" the noisy sinusoid of your household power, which then somehow translates to savings on the electrical bill?
Is this merely an (adaptive) power factor correction, or is it something else?
Most utility companies do not apply surcharges for minor PF deviations, so the savings -if any- can't really be that high.
Note also the other claimed function: noise reduction. Are real or reactive power savings to be had by filtering a noisy supply? And if so, how is this quantified?
I can imagine that power delivered outside a narrow band around 50H or 60Hz may be wasted. Perhaps a minuscule amount is even billed for but not effectively used, but is this even a real problem?
Another possibility is that the device is just a fixed shunting capacitor to improve a guessed power factor. And that the noise clean-up is a side effect of shunting, with no benefit other than that it provides an air of scientific sophistication in sales copy.
Your thoughts?


texts: Eagle: Removing unwanted bits of copper pour

texts: I have lazily made a copper pour in Eagle by highlighting a rectangle around my irregular shaped board. How do I then selectively remove the copper pour from outside the board boundary and the little unconnected pointless bits between some components?


texts: How to mux audio signal output if power is applied

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I have the following inputs on an audio device:

DAC audio signal
Secondary audio input signal

The device has one analog audio output.  I want the output to source from the DAC when powered, and to source from the analog input when powered off. Originally I used a mux IC, but the power off condition does not work (DUH). How should I switch between these two audio signals based on the device's power state?


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Given my mom's car, I measured a voltage in an electric connector equal to the voltage across the car's battery. This is when the multimeter is connected to the connector supply pins. If I take the negative terminal and put it on the car body the reading is now 0. Somebody told me on the phone why this is happening, I didn't understand very clearly so I came here to ask for help. Can someone please explain to me why is this happening? Why is the multimeter giving me that voltage measurement even though it doesn't truly exist?

Thank you in advance and sorry if the answer is obvious.


texts: Identifying PCB components with metal tops, no other markings visible

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I am trying to troubleshoot a broken PCB and I am struggling to identify these 6 components with metal case.

What are they, and is it possible to test them without removing?


texts: Use of different formulas for capacitor impedence (phasors)

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I'm confused about why I see two different formulas for calculating capacitor impedance \$Z_{cap}\$ using phasors.

For one formula in my text, I see:

$$Z_{cap} = \frac{1}{jwC}$$

And another I see:

$$Z_{cap} = \frac{-j}{wC}$$

Where \$w\$ is omega (angular frequency) and \$C\$ is the capacitor value.

Will someone enlighten me, or am I incorrect to assume these are equivalent and can be substituted for one another?


texts: Single phase 2 speed blower motor controller

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I burn wood and salvaged an old 1/20 hp 1550 rpm two speed GE single phase motor (5KSM59CS12K6AS if anyone can find more info, curious what speeds are). I'm trying to make a digital fan controller that will kick onto low as stove heats up, high while hot, and then step back down.

I found some pretty slick (from my limited knowledge of chinese) dual relay controllers Inkbird ITC-2000 that has 10A hot/cold and an alarm relay.   I'm not sure that it shuts off the temperature relay when the alarm relay is powered.  Ie low and high would be simultaneously powered.

What I'm wondering is how exactly is the speed decided on this motor (three wires)? Right now I'm running the stove the stove on wire nuts choosing which coil/speed to power, but the other day I powered the black AND red wire and nothing blew up and the speed remained unchanged on high.  I'm just looking for a some sort of confirmation that I won't burn up the motor or some knowledgeable person telling me I'll eventually burn it up as motor is fighting itself.

Thanks in advance


texts: How to tell what fraction of current is passing through which BJT

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In the circuit given below we have to find output voltage.

No specifications about any of the transistors are given just that all the components are "discrete". Can we find out how much current is passing through which BJT? Also how to tell how much voltage is dropped across MOSFET i.e. VDS ? What is the procedure to do analysis of such circuits?


texts: How to implement programmable Schmitt trigger?

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I am trying to build a Schmitt trigger that would allow adjusting High and Low threshold values with a microcontroller.

simulate this circuit – Schematic created using CircuitLab

I could replace R1-R2 with a DAC, but how do I adjust the feedback resistor R3? Is the trigger going to work properly if I replace R3 with a digital potentiometer?


texts: I am trying to run five vibration motors rated at 3.7 volts each on one switch. The power will come from a 12V, 40 Amp relay on my Jeep (SPOD). How can I wire the motors all together to turn on at one time. I have no experience with this.


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For a system level project I want to estimate the impact having a single vs. multiple PLLs.

Is there a first order estimate that relates power, jitter (total integrated phase noise) and possibly tuning/range and settling time?

For example, one spec is a tuning range of about 800 MHz around 2 GHz and less than 300fs jitter, settling in ~200ns.

I browsed through some datasheets but I am looking more for a first-order model that I can plug into system equations.


texts: Buck Boost Converter / Controller: 2.8 - 5V Input, 3.6V Output, 5A Load

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I'm designing a buck-boost which needs to provide 5A @ 3.6V, and work from an input varying from 2.8 - 5V.

After having a look at the different non-inverting topologies, it looks like the relatively conventional 2/4-Switch Buck-Boost is the way to go. I can't find any parts with integrated FETs at this load current, so it looks like it will be Controller + External Switches. My question is regarding Max Output Current. Is this independent of a controller with external Switches, Inductor etc?

This value is rarely specified in relation to Controllers, and yet things like Gate Drive Strength are specified sometimes, suggesting that there is a Max Output Current limitation related to the controller itself. Is this true?

And if so,
How do I go about determining the Max Output Power a controller can handle, based on it's drive strength or any other parameter?


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Im going to be working on a project where I will need 2 nodes and one base station. To communicate with each other. I am going to be using an Atmel AVR for the processing on the base station. I have thought about playing with the Atmel raven stuff(for development) and then building my own circuit for the project. Just need to transmit data from the nodes to the base station when some inputs go off. Range is an issue about 100m needed(note this is a maximum Minimum that might be needed is only 2 or 3m). Due to the unknown length each time these will be used I don't want to wire them in. I would like low power with the possibility of the nodes being run of a coin cell.

Is this a good way to go?
Are there any alternatives to the Atmel Raven technology(Do microchip have an alternative)?
Should I consider bluetooth or anything else for the wireless communications?


texts:
I wonder, is there a table somewhere where I can find out impedance of drivers of various HCMOS series?

I am specifically interested in AC, ACT, LVC and HC series. I guess input impedance is very high for all CMOS-based series, so I am interested in drivers impedance only.

I need that to properly terminate long trances, and I guess different series would require a bit different termination.


texts: Can we proof a scavenged transformer of unknown specification?

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This step-down transformer was scavenged from a power tool battery charger.  It was designed to take 120V AC current and it outputs 20V AC.

I can't find any specs for it, so I'm wondering what assumptions one can make about using it.

Since the wires are 16 AWG can we assume it's safe to run at up to 10A?  Or could it be internally more constricted?  Can we "proof" it for a current X by running it at X for a few minutes and confirming that voltage and current don't drop significantly, and that its temperature stays below, say, 40C?
The input contacts are separated by one inch.  Is it safe to run the transformer in reverse (step-up): I.e., can we connect the output to 120V AC and take 720V off the other side?  Or without knowing its rating does that risk arcing the windings on that side and destroying the transformer?  If we're willing to risk destroying it does running it successfully at that voltage for some "burn-in" period confirm that it is safe to operate at that voltage?


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We know for a fact that the initial state of a NOR SR latch is indeterminate until either the SET or RESET pin receives a digital HIGH. I am using an SR latch in my circuit, and I want to initialize the latch such that the SET pin will receive a digital HIGH pulse upon powering up the circuit.
Will a monostable multivibrator be able to do the job, or are there simpler solutions or methods that I do not know of?


texts:
We all know that the For-loop and Repeat are synthesizable, they get converted to blocks, for example:

for (idx = 0; idx < 4; idx=idx+1) begin
a = a + b[idx];
c = c + 2;     //You can change more than one variable in a for loop
end

In that example, the resulting hardware will be a chain of adders, summing the values from four array indices.

So my question is what if the For loop iterates over a huge number let's say 10000 ? Will it create a 10000 adders ?!


texts: I am having trouble trying to create this graph using vector signal analyzer. I am still new to using this device and any help with setting it up would be helpful. The first and second photo are what I have right now and I wish to change it to Trace A: Ch1 FM main time just like the third photo. Also, how do you change the x-axis and y-axis same from the first/second photo to third photo?


texts: Building electromagnets and general pointers

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I’m in the process of sketching up and collecting knowledge on electromagnets for a project I’m working on. It’s basically going to be a organ-sounding electro-acoustic instrument. It’s an array of metal tines, taken from an old toy piano, where each tine has its own dedicated electromagnet, driving it and ressonating it. It’s more or less the same principle as this tine organ by Matt Steinke: (https://www.youtube.com/watch?v=xzoJBfUODbA). I’ve tried to get a hold of him, but got no answer.

I’ve built various electro-acoustic instruments based on driving electromagnets with homemade pwm-modules, but I need these to be stronger and more precise, so  I need to gain a proper understanding of how to build my own. Eventually the whole thing will be controlled through an Arduino and should accept MIDI input and so forth, but as of now, I need to get electromagnets down before I move on.

I’ve made an electromagnet recently, that works and will make the tine sing when hitting its fundamental frequency, but it’s not powerful enough and seems to heat up quite quickly.

I’ve made a less than ideal one recently using the following:
An iron bolt as a core (M8 size), plastic washers, nut, a single layer of insulation tape around the core, enamelled cobber wire (unknown gauge, taken off a small transformer), wrapped in one or two layers of insulation tape.
It’s wound using a hand drill, probably not ideally, since the wire had some twists and turns here and there coming off the transformer shell, but I tried to wind the coil in the same direction every time. I can’t be sure about amounts of turns using the method.

1: Bolt core and washers, no wire. 2: Transformer shell I took the wire from. 3: Wound and insulated electromagnet.

First off, I can’t say why I added insulation tape to the core before wrapping the wire around. Is this something I should stick to or avoid? I’ve thought about getting some small, industrial sewing machine bobbins, but I wouldn’t really know if that is preferable to just using an iron bolt for this project. Size is something of a factor, as the magnetic field of each electroamgnet has to, preferibly, only affect one tine each.

I want to order some cobber wire for the project, but I struggle to choose a gauge, as I’m unsure of what size fits my cores the best, how much current it will actually draw versus how much current the wire can actually handle before heating up too much. It will most likely be run through a mosfet being switched by an Arduino, so I can only assume I will have to supply the electromagnets with an external power supply, since 5v (or however much the Arduino can supply) isn’t nearly enough to get the power I need - I would think.
In the project I linked to earlier, he says that he used a darlington transistor array, ULN2803, to power it and ramp it up to send 30v pulses. I would assume that is the way to go, correct?

Is it absolutely crucial that I know the amount of turns on the coil to find out how much current it can handle or is it possible to determine a safe margin through trial and error and rough calculations?

How much heat is expected? What constitutes overheating? When things start to smell and actually burn? Will slight overheating have any significant effect on the magnetic field?

What material is best to wrap around the coil after winding? As mentioned, I just added insulation tape, but I’ve seen other kind of tapes used. Is it for cooling? To ‘glue’ it down and hold it in place?


texts: Capacitor dielectric: Is X7R a direct upgrade over 2C1?

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I'm trying to replace a capacitor with an IECQ-CECC 2C1 Dielectric. The supplier has offered a comparable EIA X7R Dielectric. Viewing this comparison document, they are largely identical. However, the X7R is not given a "Rated DC voltage applied" value.

Is this due to differing test procedures, or is it related to performance (or both?)


texts: Voltage regulator does not start if driven by mosfet

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I've created a dual source energy harvesting board to store energy from small energy sources, like a 3V 15mA solar panel, into a 3F 2.7V supercap and to power  a small wireless node (3.3V, 30mA),  but I am having trouble with the mosfet.

Schematic is below:

The voltage regulator LTC3125 (U1) gets the energy from the solar panel and steps the voltage up to 2.65V to charge the 3F 2.7V supercap.

The supercap is the input for the 3.3V voltage stepup regulator LTC3525D-3.3 (U3) and its output (3.3V) goes to the load (wireless node).

This regulator should get cut from the circuit  when the voltage of the supercap goes below 0.9V and be reconnected if the supercap goes above 2.5V.
This is done by the non-inverting op-amp with additional hystheresis, the MAX9015 (U2), that drives a low side N-Mosfet SI2312BDS-T1-GE3 (Q1).

The op-amp is powered by two sources: if the sun shines, it is powered by the 2.1V regulated voltage from the LTC3105 (LDO, pin2). If no sun and supercap >0.9V, the power comes from the LTC3525D-3.3 output. If no sun and  supercap <=0.9,  then  the opamp is off and so is the mosfet. Usually the supercap is >1V.

My problem is, that even in best conditions, the LTC3525 does not turn on.

Here my test:

instead of solar panel I used a power supply 3V@70mA
no load on 3.3V output
I let the supercap charge from 0.2V. The supercap goes to the multimeter with 60cm (1.96ft) cables to measure current. Current is about 35mA going to the supercap.
when supercap reaches 2.5V, the mosfet turns on
Supercap voltage starts to drop quickly, discharge current from supercap is 40mA, instead of few uA.
While the supercap was discharing, I measured: Supercap: 2.3V. Op-Amp: OUT = 2.1V. Mosfet: V_GS=2.1V; V_DS=0V; V_GD= -2.1. LTC3525: V_IN = 2.3V; V_OUT=2.1V. LTC3525: LDO=2.1V, V_OUT=2.65V
Supercap kept discharing until about 1.78V, then LDO of LTC325 started to drop to 1.8V and op-amp turned off (min V_IN = 1.8V). I don't know why LDO dropped, the power supply was still on.

The LTC3525 seems not to start. The 2.1V on its V_OUT comes from the LDO, not from it.

The mosfet can conduct 4A with 2.1 V_GS and R_DS=0.03 ohm.

Older version of the board that had no mosfet work correctly.

I had to use a mosfet to disconnect the LTC3525 and its load, because it tented to oscillate around the SHDN when starting while supercap at 0.7V:
If the supercap was charging from 0V, at 0.7V (SHDN threshold of LTC3525) the LTC3525 would start, drop the supercap voltage to 0.65V, the LTC3525 shutdowns, supercap goes to 0.7V and so on… even with bigger (330uF) cap on V_IN of LTC3525 same problem.

To prevent this, I though, a mosfet could cut the LTC3525 completely until the supercap is at 2.5V. At this voltage, the LTC3525 can start safely without oscillating around its SHDN threshold voltage.

I am not sure why the LCT3525 does not work, maybe are the mosfet connections wrong?

All the caps are very close (1mm or less) to their depending IC, except the supercap, as already explained.

The components have been used before already, except the mosfet.

I've already removed and resoldered the LTC3525, to be sure the connections were ok.

Any idea?

Thanks in advance for your help

Sincerely


texts: Is it OK to manually charge a single cell of a 2 cell LIPO battery?

texts: I have a 2 cell LiPo battery and my project involves charging it from a rectified and regulated voltage source. My question is, is it OK if I charge only a single one of these cells instead of both? Or should I connect my 3.7V output into both cells?


texts: Is it possible to power an arduino-like device from soil?

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I am exploring some IoT applications I could work on. One of them is a sensor that does some periodical measurements of soil and saves it into inner memory or broadcasts over low-power radio channel.

I'd make the device as low in power consumption as possible, e.g. small size, low-voltage transmitter, long periods when the device runs measurement (say 2 times a day).

I know there are many factors that can impact it, but is there a chance that soil around the device could give it enough power to function or is it impossible to count on it as a source of energy in a real world project and I should abandon this idea and use batteries?

The idea comes from the article about "earth batteries", which creates a battery by burying two electrodes in the soil.


texts: Extending Output of a fixed Linear Voltage Regulator

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I am working on extending output voltage of a fixed linear voltage regulator.Yes, I accept I could go for the variable voltage regulator.But I am in need to use a fixed voltage regulator.
My query is regarding the derivation of Output Voltage (V0) given  in
Datasheet
Can you help me to figure out how this equation rolls out?


texts: suggest a current booster circuit DC-DC 1uA to 3mA

texts: I have a source of power which can provide up to 1.2uA at 1.5 V DC, however, I would like to power a circuit which uses 3 mA at 0.6 V DC. What would be the easiest way to do this? Is this even possible to achieve this kind of circuitry?


texts: Low pass filter target frequency for a mixed signal frequency synthesizer

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I'm building a frequency synthesized local oscillator with coarse and fine tuning to span 30.5 to 32MHz.  The design follows the following block diagram (bits not essential to this question removed for clarity):

Coarse tuning is done through the ADF4002 phase locked loop (PLL) IC in 5KHz steps.  For fine tuning, I'm using an AD9851 DDS module.  The DDS signal is mixed (NE612) with the VFO to produce a 25MHz IF, which is filtered through a BPF (3rd order Cheby) centered on 25.25MHz.  The PLL will divide the 25MHz signal and lock to the 5KHz reference signal (derived from a 20MHz crystal by the PLL.)
I elected to use the Analog Devices ADISim tool to choose the component values for the LPF and I opted for a 4-pole active design where the target frequency was 30.5 to 32MHz.  I chose the fast settling time option and the tool returned the following circuit:

Unfortunately, I'm having a problem where the PLL won't lock.  I can get it to lock (but with an extremely jittery output) if I apply a voltage to the VCO input that puts the VCO somewhere in the 30.5MHz zone.  When I remove this voltage, the PLL will remain locked providing it's coarse setting is tuned to the upper part of its range.  If I lower the range setting, it unlocks (and the jitter stops.)
Now here's the thing, in a previous incarnation of this circuit I had the coarse tuning part working driving a VFO from 34.5 to 36MHz.  I had used the exact same low pass filter design but with different component values (as dictated by ADISim for that particular target frequency range.)  So, I know there's no issue with my PLL board.  I've tested the 25MHz band pass filter independently and its bandwidth is wide enough to cover the frequencies of interest.
I think the issue is with the PLL LPF and here's my question:
Should I have asked ADISim to design the filter based on a target frequency of 24.5 - 26MHz rather than the VCO frequency of 30.5 to 32MHz?
In other words, where a mixer down-converts the VCO frequency in the loop, what loop frequency are you really working at?
If you need any more detail I'm happy to post it up.  This is a complicated circuit, so I've left out bits that I suspect are working fine.


texts: resistor selection for TPS3700DDCR undervoltage circuit

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I am designing an undervoltage circuit for a lipo battery project. I found this tutorial here which lead me to the TPS3700. I am wanting the undervoltage condition to be 3 volts. The part that I am hung up on is choosing the right resistors for the under and over voltage conditions. At the bottom of page 16 of the datasheet, it says Rt=R1+R2+R3 and Select a value for RT such that the current through the divider is approximately 100 times higher than the input current at the INA+ and INB– terminals.
I'm having trouble figuring out this value. The max current that would be going through the power rail is 650 milliAmps.
Also the equations for R3 and R2 have a term Vit+ which is defined as Positive-going input threshold voltage. Texas Instruments also says it's The input threshold voltage when the input voltage is rising., but this doesn't really give me much detail on how to calculate it. I calculated Vit+ from the tutorial and found this value to be around .4001 I used this value along with their Rt for my resistors and assembled the circuit below:

boost gate just leads to a mosfet that controls a 3.7 to 5V boost circuit. Will these resistors cause the undervoltage condition to be 3V? The specific values for the battery I am using is 3.7V 800mAh.


texts: How to calculate latency of integrated product?

texts:
Is there a standard model for estimating the additional clocking latency which needs to be applied based on product interconnects?

For example: Lets say a DDR memory has a switching time of 1 ns.

However, if I want to put that product on a board, the signal path goes from a microcontroller pin through to a PCB board, across a trace, through some connector, through another trace, to a package pin, and along a wire bond before it hits the actual die of the memory.

Each of those parts in the signal path have propagation delays, parasitic capacitances, and inductances that might form which degrades the signal and lengthens the time before a signal can reach its max, so I would need to add more clock time the longer that path is.

Is there a standard for how such setups are evaluated, to estimate what those capacitances/impedances are? I'm aware that traces on PCB have their propagation time determined by the length of the trace and the permittivity of the substrate, but I'm not sure how other considerations factor in.


texts:
I've hooked up my arduino to a 7 segment display with a common anode..

At first I thought it wouldn't work at all because I was setting the pins on the cathode side of the LEDs to high.. then I discovered when I set the pins to the cathodes high the LEDs turn off..

Which is good, because I just needed to do a binary NOT (pretty much) on the output.

However, I don't really understand what's going on.. when the cathodes aren't set high, how is this the same as them being ground? Can someone please tell me what's going on here? I don't quite see how the circuit is complete..


texts: Measuring Wind Speed Using Ultrasound Transmitter and Receiver

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I am currently trying to create an system to measure wind speed, and I know ultrasound is a good way to do it. I want to make my system be lower cost, however, still maintaining 0.5 m/s precision or better.

There are a few ways I thought to do this.

Measure time of flight into the wind and time of flight with the wind, and calculate the difference to get wind speed.
Measure the shift in phase from the emitted signal to the received signal
Use an ultrasound transducer array to determine how much the transimtted sound wave has shifted due to the wind (system oreinted perpendicular to the wind)
Measuring intensity of sound with and against the wind.

For method 1, I think I could disassemble and HC-SR04, placing the transducer opposite the emitter. Then I could measure time of flight without reflections. However, the precision is not quite good enough. I want something ~0.5m/s, and it seems like this method will give me ~5m/s. I am wondering if there is a way to improve the precision of this device. Or perhaps there is another device, or other pieces I could use to build my own more accurate version.

For method 2, I'm not sure what electronics I would need to use measure the phase difference. Is there a simply way to measure the phase difference between the output signal and the received signal?

For method 3, I could not find any sensors that are low cost.

For method 4, I believe it should be a 1/r^2 decay, but this may not be a precise enough method.

Please let me know if you have any insight on which methods would work best and how to implement these. Perhaps I would need a combination. I thought about using time of flight to get a coarse measurement and phase shift to refine the measurement

Thanks for the help!

Alex


texts:
The output of a magnetic synchro are two signals A and B:

$$ A= 100 sin(2 \pi 400 t) + E sin(T-120)sin(2 \pi 800 t) $$

$$ B= 50 sin(2 \pi 400 t) + E sin(T-60) sin(2 \pi 800 t) $$

The magnitude of second harmonic E is about 6~8 volt and parameter T is changed from 0 to 310 degree.

I need a practical circuit for extracting parameter T. in fact two signals A and B are changed by varying parameter T and for every pairs of signals A and B I want to know value of parameter T.

I have two idea for this problem :

1) Attenuating both signals level with a transformer for processing by a
    microcontroller such as ARM.

2) Using a passive band pass filter with 800 Hz central frequency for extracting
   second harmonic signal and then parameter T is extracted by processing using a microcontroller.


texts: will this timer/delay circuit works as intended with almost equal opamp inputs?

texts:
I just saw this video about a so called delay circuit using opamp in comparator configuration. The author mentions to use a pot as a voltage divider to feed the (+) input and the node between a series R and C to the (-) input.
however the assembled circuit on the breadboard is missing the connection of the pot to ground (like the schematic I included bellow).
so basically after some amount of time the comparator should see almost equal inputs thus the output is indeterminable. I hooked up the circuit using same values but a TL082 and I got white noise as expected, yet I can't understand does this circuit really outputs a steady low output? the SW1 is meant to restart the timing. does the pot and internal input resistance forms a divider? the author confirms that only two terminals of the pot are used in the comments.
do i miss something else?

highly appreciate your help.

simulate this circuit – Schematic created using CircuitLab


texts: Capacitors: 200 mOhm ESR @ 100 Hz, attainable?

texts:
The MLCCs in 0805 case seem to have one or two orders of magnitude higher ESRs at that frequency. Are there any such low ESR caps out there, preferably 0805 MLCC but not compulsory? It is a 220 nF cap I am after.
edit
My datasheet does not hint to polarity though. How would I be using an electrolytic? I suppose solid aluminum would also be better.


texts: Why does NAND erase only at block-level and not page level?

texts: Below is my understanding of how NAND flash memory is organized, with this design it should be possible to just erase a single page and program it instead of erasing an entire block. My question is, why don't NAND implementation erase at a more granular page level? Intuitively, all that needs to be done is to present the word line representing the page being erased, with a high voltage to remove electrons off of the floating gate while leaving the other word lines untouched. Any explanation about the reasoning behind this is appreciated.


texts:
I would like to make a PWM fan controller that uses a 555 timer and be placed in a Gen 2 PCI Express x1 slot, while pulling the power from the slot as well.

I'm not looking to send or receive any signals to the PCI Express bus. I only want to pull power from the 12V.

Is this possible? Will there be any protection mechanism that prevent me pulling power from the slot without sending anything to the bus?


texts:
I’m new to batteries charging and discharging and I have some general questions:
If for example you have AA batteries being charged in parallel do they behave similar to how a load resistor would do (meaning that the battery with less charge (State of charge-SOC) would get the higher current)?
Also in the parallel section of this forum https://www.reddit.com/r/AskElectronics/wiki/batteries#wiki_parallel it suggests that baterries should all be balanced (have same SOC) before being charged but does not mention why is it dangerous, why is the reason? Since the batteries are in parallel wouldn’t they self balance anyway?
Thanks


texts:
I'm working decoding some house intercom devices to know when someone is calling and also be able to open the door.
To do this I buffer the signal (some models has 15v, others 24v...) to a 3v3 level for mcu reading and later counting the pulse length of each transition. After this I got the following for example while I pulse the call button: 13 "messages", and this is one of them:

And, after pulse length counting:

Anyone knows what protocol can be? This is not manchester encoding because there is some 3T pulses (manchester has 1T and 2T pulses only).

Greetings


texts:
(I am mainly from a software background and just started to work on an embedded platform. Excuse me if this is a naive question...)

I am planning to write a driver for an EEPROM which is connected to the MCU via an I2C bus. So I am reading a tutorial about the I2C bus.

The tutorial says:

  Both SCL and SDA lines are "open drain" drivers. What this means is
  that the chip can drive its output low, but it cannot drive it high.
  For the line to be able to go high you must provide pull-up resistors
  to the 5v supply. There should be a resistor from the SCL line to the
  5v line and another from the SDA line to the 5v line. You only need
  one set of pull-up resistors for the whole I2C bus, not for each
  device, as illustrated below:

The red part in the above image is added by me. I guess that's how the whole picture is.

My questions are:

Is my adding of the red MCU correct?
The bold part the chip is the red MCU, right?
Why is it true that the chip cannot drive  it high? Is it unable or forbidden to?
What does open drain mean in plain English?

I searched a bit but seems cannot find a clear explanation...maybe an analogy will help.


texts: What is the theoretical throughput limit of DDR SDRAM read only

texts:
I wonder how fast I can read from a DDR SDRAM (known as DDR1) clocked at 200MHz. The controller will be implemeted on an FPGA.

I have 8 bit data interface to the DDR. Each data pin reached 400Mbps. Therefore the total throughput is 3.2Gbps = 400MBps. However there will be an overhead for read commands to the DDR.

Including those what is the practical maximum READ throughput I can reach?

Regards


texts: Stripboard layout for a 16x16 dot matrix display

texts:
I've been planning a Veroboard/stripboard layout for four dot matrix LED displays. Most of the complexity is due to the daft way companies break out the pins on the 8x8 modules. This is what I have so far:

The fat lines are wires, and the striped orange bits represent stripboard. The colored dots are the pins of the 8x8 dot matrix displays. I only intend to use the red dots, not the green ones
I've got a couple of questions concerning this layout:

How can I physically connect the strips of perpendicular stripboard at the top and bottom (which will have male headers attached) to the main board? Hot glue? Overlap the boards and "sew" them with wire?

Is this really an achievable thing to do? Should I be looking into PCBs?

EDIT:
Looking into PCBs. Board design: