texts: Circuit with DRV8825 and PCF8574 not working! Will it be a problem with the components itself?

texts:
I'm developing a circuit using a PCF8574 and a DRV8825 to control a step motor.
The PCF8574 is used to control the reset, enable, sleep, modes and read the FAULT line of the DRV8825 using only the two wires from the I2C protocol.

The step and the direction line from the DRV8825 are hard-wired.

Here is the circuit:

However, this circuit is not working as expected. I can observe the following behaviors:

Not all the PCF8574 outputs are going to HIGH state when I send the command through the I2C protocol
Some outputs from the PCF8574 have a voltage below the 5V (the logic power) when are set to HIGH state. Something around 1.7V and 2.2V
Sometimes I can observe a kind of short circuit near to the pins 12 and 13 (VREF) of the DRV8825 when I change the value of the trimpot. I can confirm there's nothing wrong with the board (I mean, traces are not short-circuited to the ground or other signals).
The DRV8825 are going to be hot very very fast even there's no motor movement.
The DRV8825 (when it's "working") is moving the motor randomly in a weird way even I don't send any commands.

Can you guys give me your opinion about this board? What must it be?

It's very important to say that both the PCF8574 and the DRV8825 were desoldered from other boards

Will it be a problem with the components? Maybe too much heat on the chip to desolder it?

Hope you guys can help me!


texts: Reducing the Number of Logic Gates by Gate Sharing

texts:
Truth table :

Circuit :

This circuit is created with K-map so it should have been simplified. Is it possible to reduce the number of logic gates by gate sharing? Are there any rule guiding me to do gate sharing?

Thank you for your help.


texts: If i have \$p^+n -pn^+\$ junctions in series how should the i-v curve look? my guess is that because they have the same orientation in the meaning of forward/reverse bias so it's should look like regular pn junction, am i right?


texts:
I want to use a UDN2981 8-channel source drivers IC (see UDN 2981 datasheet) for a matrix multiplex light.

I connected the UDN2981 this way:

pin 9 (VCC) to 5V
pin 10 (GND) to GND
pin 6 to VCC with a 10K ohm resistor
pin 13 to a 3mm white LED to a resistor (220 ohm) to GND

And I connected another LED not via the UDN: from VCC -> white LED -> 220 ohm resistor -> GND

What I see is

that the 3mm white LED via the UDN gives only 0.1 mA (my multimeter here does not have more accuracy)
that the 3mm white LED directly from 5 V gives 1.7 mA

My calculation for the latter would be

  V = I * R <=> (5 - 3.3) = I * 220 <=> I = 1.7 / 220 = 7.7 mA

This is still a lot more than 1.7 mA, but maybe the forward voltage is higher

However, I'm more interested to know why the LED via the UDN gives only 0.1 mA... I tried different resistors to pin 6 but this does not affect the current through the LED.

(I think it has something to do with the internal diodes of the UDN giving a voltage drop... this means I should use a higher voltage to VCC or less current; I hope I can calculate this easily).


texts:
I have created a series, shunt LC bandstop/notch filter.

https://github.com/promach/frequency_trap/tree/development

I am using gEDA with noqsi gnetlist backend and ngspice simulator

However, I could not obtain the desired inductor value from the gyrator made up of X1 and GM2 circuit blocks.

If all resorts failed, I am thinking of using S-parameter to check the value of the active inductance created from gyrator structure consisting of CMOS inverter and GM2 circuit blocks.

frequency_trap.net

* gnetlist -L ../.. -g spice-noqsi -o frequency_trap.net frequency_trap.sch
* SPICE file generated by spice-noqsi version 20130710
* Send requests or bug reports to jpd@noqsi.com
Ctest X1.IN Vout 1n
Vd Vdd GND 'SUPPLY'
Vs Vss GND 0V
.GLOBAL Vdd Vss
.INCLUDE CMOS_Inverter.net
.INCLUDE Gm2.net
.INCLUDE active_inductor.net
.PARAM SUPPLY=3.3v
.options TEMP=25
.MODEL n1 NMOS
.MODEL p1 PMOS
Vtest Vtest GND dc 0
+ac 1
CL GND Gm2.IN 0.07pF
XGm2 Gm2.IN Gm2.OUT GM2
X1 X1.IN X1.OUT INV1
V_IP_X1 X1.OUT Gm2.IN DC 0V
V_IP_Gm2 Gm2.OUT X1.IN DC 0V
Rs Vtest Vout 1e-6
.control
op
ac lin 10000 100 2000
write frequency_trap.raw
gnuplot vtest db(vtest)
gnuplot vout db(vout)
*plot Vtest Vout
tran 0.1p 400p
plot Vtest X1.IN X1.OUT
setplot
plot i(v.xgm2.v_ip3) i(v.xgm2.v_ip4) i(v.xgm2.v_ip5) i(v.xgm2.v_ip6)
noise v(Vtest) Vtest lin 100 1 10G
setplot noise1
let noise_figure=db(inoise_spectrum)/2-db(2*sqrt(boltz*290*50))
plot noise_figure
.endc

CMOS_Inverter.net

* gnetlist -L ../.. -g spice-noqsi -o CMOS_Inverter.net CMOS_Inverter.sch
* SPICE file generated by spice-noqsi version 20130710
* Send requests or bug reports to jpd@noqsi.com
.subckt INV1 2 1
M4 1 2 Vdd Vdd P1  l=0.4u w=3u         m=25
M1 1 2 Vss Vss N1  l=1.2u w=3u         m=25
*
*
.ENDS

Gm2.net

* gnetlist -L ../.. -g spice-noqsi -o Gm2.net Gm2.sch
* SPICE file generated by spice-noqsi version 20130710
* Send requests or bug reports to jpd@noqsi.com
.subckt GM2 7 3
M4 g3 g3 1 1 P1  l=1u w=3u
M3 3 g3 2 2 P1  l=1u w=3u
M5 3 5 4 Vss N1  l=1u w=3u
M6 g3 7 6 Vss N1  l=1u w=3u
I2 8 Vss 40uA
I1 9 Vss 40uA
Vb 5 Vss 1.8V
Rs 9 8 500k
*
*
V_IP6 6 8 DC 0V
V_IP5 4 9 DC 0V
V_IP4 Vdd 1 DC 0V
V_IP3 Vdd 2 DC 0V
.ENDS

In ngspice simulation, .OP gave me the following:

I am looking at it now. Does anyone have any comment ?

Initial Transient Solution
--------------------------

Node                                   Voltage
----                                   -------
x1.in                                  2.09899
vout                                         0
vdd                                        3.3
vss                                          0
vtest                                        0
gm2.in                                     1.8
xgm2.g3                                2.14857
xgm2.1                                     3.3
gm2.out                                2.09899
xgm2.2                                     3.3
xgm2.5                                     1.8
xgm2.4                                0.649101
xgm2.6                                0.649101
xgm2.8                                0.649101
xgm2.9                                0.649101
x1.out                                     1.8
v_ip_gm2#branch                              0
v_ip_x1#branch                               0
v.xgm2.v_ip3#branch                      4e-05
v.xgm2.v_ip4#branch                      4e-05
v.xgm2.v_ip5#branch                      4e-05
v.xgm2.v_ip6#branch                      4e-05
v.xgm2.vb#branch                             0
vtest#branch                                 0
vs#branch                           0.00280043
vd#branch                          -0.00280043


texts: Does anyone have prior experience with DS90UB948-Q1 FPD-Link III Deserializer deserialiser from Texas Instruments ? I am trying to configure the internal pattern generator block sending I2C commands. This application note describes what registers to be configured. The registers are configured using an indirect addressing method. PGIA is the indirect register for addresses and PGID is the indirect register for data. PGIA has to be configured first, before data is placed in PGID. The problem is that when I write in PGID data register the deserialiser stops sending the ACK bit (found out using a logic analyser) and doesn't respond to commands anymore, a hardware reset needs to be performed.


texts: How to generate positive and negative random numbers in VHDL

texts:
In my VHDL testbench, I have a configurable parameter DATA_WIDTH which is set to power of 2 such as 16-bits.

I want to generate random signed numbers (2's compliment) of bit width as DATA_WIDTH. For example if DATA_WIDTH is 16 bits, then I want to generate random numbers in range -32,768 to 32,768 (all range inclusive).

As of now I am doing following (snippet of VHDL code, not complete):

variable W : natural                := 16;
variable seed1, seed2 : positive    := 1;
variable x_real: real               := 0.0;
variable x_int : integer            := 0;

variable data_vec std_logic_vector(W-1 downto 0) := ( others =>'0' );

uniform( seed1, seed2, x_real );
x_int := integer(floor(x_real * real(2**W)));

data_vec := std_logic_vector( to_signed( x_int, data_vec'LENGTH ) )

However, when I run the testbench simulation, I get following warnings from Modelsim:

  Warning: NUMERIC_STD.TO_SIGNED: vector truncated

There is a related question, however the answer in that post doesn't offer solution using standard VHDL libraries but using Open Source VHDL Verification Methodology.


texts:
I'm looking to build a pretty basic project that relies on several submodules that use I2C for communication. I'm trying to find the smallest, cheapest AVR device that supports I2C. I know the 328P has a built in I2C interface, but I really don't need the 20 something other pins. Can anyone point me towards something more like an ATtiny that has a built in I2C interface?

My goal is the smallest, cheapest AVR without relying on software IC2 implementation.


texts: C Programming for 8051: SFR directions as arguments

texts:
I'm currently making a very simple Tic-Tac-Toe game with an AT89C51RC2 and I am having issues getting the button input right.

Basically, the input is a 3x3 Button Matrix which I want to utilize by scanning through the rows with a pulse while checking the columns for a connection; pretty basic. However, the way I wanted to do this was by making a unique scroll method that received the row parameter and set it to HIGH accordingly.

I already have

sbit R1 = P1^0;

all through the needed inputs, but I'm not sure if this is correct.

Then, on my main method, I run something like

while(TRUE)
{
    scroll(R1);
}

which is named scroll, I have this

void scroll (bit P)
{
   P = HIGH; //Sets the row being checked to HIGH (HIGH is already defined as a 1). Same goes with the aformentioned TRUE
   ...
}

So, this is not working. I know I'm not doing this right, but I had to start somewhere. Is what I am attempting to do possible? Sending a single Pin adress as an overload for a method? If so, what datatype should it be? I was juggling between char and bit but I can't settle.

I hope my question is understandable! If not, I will gladly elaborate and maybe post all the code (although it is quite messy). Thanks, everyone, in advance!


texts: Why does splitting a FPGA critical path work to improve performance?

texts:
Context

I am currently reading the (very good) course material on "Introducing the Spartan 3E FPGA and
VHDL" promoted here (community ads) and I don't really get the idea of splitting a critical path to increase performance:

The example is about displaying the 8 MSbits of a 30-bits counter on LEDs. In the codes below, the first example has a setup time of 4.053ns and the second 3.537ns, achieved by splitting the counter in two 15-bits counters and a carry flip-flop.

Question

Why does it work? Isn't the time to ripple the carry from the LS to the MS counter the same, and even higher from inserting the flip-flop? In the end, MS counter will still need its input from the LS counter to finish its cycle...
Bonus points for those who illustrate their answer with diagrams of the critical path before/after and how the signals propagate.

Code

Before splitting:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity Switches_LEDs is
    Port (
        switches : in STD_LOGIC_VECTOR(7 downto 0);
        LEDs : out STD_LOGIC_VECTOR(7 downto 0);
        clk : in STD_LOGIC
    );
end Switches_LEDs;

architecture Behavioral of Switches_LEDs is
    signal counter : STD_LOGIC_VECTOR(29 downto 0) := (others => ’0’);
begin
    LEDs <= counter(29 downto 22);

    clk_proc: process(clk, counter)
    begin
        if rising_edge(clk) then
            counter <= counter+1;
        end if;
    end process;
end Behavioral;

After splitting:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity Switches_LEDs is
    Port (
        switches : in STD_LOGIC_VECTOR(7 downto 0);
        LEDs : out STD_LOGIC_VECTOR(7 downto 0);
        clk : in STD_LOGIC
    );
end Switches_LEDs;

architecture Behavioral of Switches_LEDs is
    signal counter : STD_LOGIC_VECTOR(29 downto 0) := (others => ’0’);
    signal incHighNext : STD_LOGIC := ’0’;
begin
    LEDs <= counter(29 downto 22);

    clk_proc: process(clk, counter)
    begin
        if rising_edge(clk) then
            counter(29 downto 15) <= counter(29 downto 15)+incHighNext;
            if counter(14 downto 0) = "111111111111110" then
                incHighNext <= ’1’;
            else
                incHighNext <= ’0’;
            end if;
            counter(14 downto 0) <= counter(14 downto 0)+1;
        end if;
    end process;
end Behavioral;


texts:
I'm trying to code BGScript but I have some questions. Can you help me?

I have DKBLE112 which is Development Kit of the BLE112 module built around the CC254x, an 8051 derivative with an on-chip BLE transceiver. And my questions are as following.

I could to blink a LED by using an example code below. But some lines are unclear to me.

The first is below.

# setup port 2 pin 1 for the switch output
call hardware_io_port_config_direction(2,$2)

The comment say pin 1. Why $2 is pin 1?  And how can I change to use P2_2?

The second question is this.

call hardware_io_port_write(2,$2,$2)

Why the setting data is $2? (I changed $1 but not blinked)

Thanks,

dim led

event system_boot(major,minor,patch,build,ll_version,protocol,hw)
    call hardware_spi_transfer(0,16,"  Blinky Light  ")

    # setup port 2 pin 1 for the switch output
    call hardware_io_port_config_direction(2,$2)

    # turn port pin off
    call hardware_io_port_write(2,$2,$0)

    led = 0

    call hardware_set_soft_timer(32768,0,0)
end

event connection_disconnected(handle,result)
    call gap_set_mode(gap_general_discoverable,gap_undirected_connectable)
end

event hardware_soft_timer(handle)

    if led > 0
        call hardware_io_port_write(2,$2,$0)
        led = 0
    else
        call hardware_io_port_write(2,$2,$2)
        led = 1
    end if
end


texts:
Well I have these schematic of a vaccum tube amplifier, and I'm having some problems to understand some symbols.

What are these symbols in red?

What does exactly CW mean? It should be a logarithmic potentiometer but have that strange down arrow.


texts:
I am trying to control two LEDs in reverse parallel, using a signal SIG. SIG is an open collector signal, so it is either high impedance or pulled to ground. The schematic looks as follows:

I am trying to calculate the resistor values such that the SIG can light one LED or the other, and passes 2mA of current given a 2V drop across the LEDs. This gives two states for the circuit to be in:

SIG is high impedance state, so R3 passes no current, and D1 lights:

SIG is pulled to ground, and D2 lights:

Given VCC is 12V, is it possible to solve for resistor values such that the voltage and current drops through the LEDs hold true? After trying to set some values for a resistor and solving for the other values, I keep getting negative voltages or the currents don't add up. Is it possible that the currents through the diodes can't both be 2mA?


texts: Power/Battery Management System Prototype: Custom PCB or Evaluation Modules from TI?

texts:
I am developing a battery/power management system for a medical device that runs off of 12VDC. I notice that TI offers a lot of evaluation modules in power management, and wonder if I should start from there, or if I should look at individual electronic component and try to piece up a prototype PCB.
Any input would be appreciated!!!


texts: What is the behavior of electrons in a highpass filter circuit and what is an equivalent closed loop circuit?

texts:
I am being explained that an highpass filter in a circuit looks like this:

It is hard for me to understand how this circuit works. Vin is AC voltage. I'm wondering what is an equivalent closed loop circuit. I'm thinking that an equivalent closed loop circuit would be the following:

Is is correct to say that the second circuit contains an highpass filter (the capacitor and the resistor) filtering the frequency for the load to receive only some frequencies?
Also, I'm wondering what is the behavior of electrons in such a circuit? I'm thinking that the electrons flow in one way then the other since it's AC. But with the capacitor I'm thinking that half the period will be blocked by the capacitor since it will charge up on the left side and then discharge when the AC will switch side. So electrons will flow in only one direction toward the load that is when the current will flow from the negative node to the positive node.
Also, what are good values for R and C. The book I'm reading (Art of electronics 3rd edition) states that
Vout/Vin ≈  R / (R + X) = ωRC / (1 + ωRC).
What is the meaning of that ratio? Why is it important and what does it mean for the value of R and C? I know that reactance decreases with higher frequency. How does it allow to filter higher frequencies here?
Also won't the current flow through the resistor of the highpass filter wasting some current that the load won't receive also dropping the current value for the load?
The circuits are made using KiCAD.


texts: Confusion with how to ground base of transistor

texts:
simulate this circuit – Schematic created using CircuitLab
To start I am very new to working with electronics, I've read a little theory and thats about it. My goal was to make a circuit with a BC337 transistor in it acting like a switch. My goal was that a logic cell, which outputs 3.3V would be able to control the flow of power for a 12V LED chain of lights.
I hoped to use the 3.3V to control the base of the transistor which would enable the 12V to flow(or not) from the collector to the emitter so I wired the positive end of the 12v to the collector, the 12v ground to the emitter, and was about to connect the positive wire of the 3.3V to the base when I realized I had not figured out a place for the negative end of the 3.3V.
So my question is this: Where do I place the negative end of the 3.3V base on my transistor, so that the transistor can still be controlled by the 3.3V and that the voltage of the emitter will still be 12V(or at least very close)?
I tested several configurations of where the negative end could go but all of them either didn't work or resulted in reduced emitter voltage: 9V or less. I do not know if it is relevant but my 12v comes from a 1.5A wall voltage converter and my 3.3V comes from a coin battery. Any help would be appreciated thank you.


texts:
I m actually reading a section of a book which talks about parralleling MOSFETs. The book talk about "Power supply design". There is a sub section which describes how to design the circuit layout. It finally say : "Finally, to prevent oscillations with paralleled MOSFETs, resistors of 10 to 20  Ohm or ferrite beads should be placed in series with gate leads".

I'm surprised ! I have never seen a power MOSFET oscillates... And I actually do not understand what it means by oscillations. In which case oscillations happens ? And why when we parallelise MOSFET we increase the risk of seeing oscillatons ?

Thank you very much !


texts:
I wanted to build a device to track the stuff I have in my bag. I wanted to use passive RFID tags which I would place on my objects.

The problem now is that I don't have much experience with RFID  and I am not sure how well certain tags can be detected. I've researched a bit and found out that UHF tags are very good for tracking multiple things, but also that they don't penetrate materials as good as lower frequency chips. Do you think a 850 - 960 MHz chip would be readable if it is placed inside a thick book like a novel?


texts:
I apologize if this is extremely simple, but I am trying to design this:

I input 2 voltages, one is 12 V and the other is on the order of .5V.  I want to know if there is something I can set up that will output 12 V if the reading of the smaller voltage is larger than a certain value.

i.e

If small voltage > v_crit ; out=12V

If small voltage < v_crit ; out = 0.

My thoughts are to do a switch controlled by a microcontroller, but I am wondering if there is an easier/cheaper way.


texts: What is the difference between a AC-DC power supply and a AC-DC switching power supply

texts:
I need a power supply for 200W 48vdc brushed motor. It will run at 2300 rpm and need 5 amps to generate 150 in-lbs torque. Will both AC-DC and AC-DC switching power supplies work. If both will work is one preferable?
Thanks,
henrylr


texts: File soldering tip to fit in soldering iron

texts:
I'm sorry for my english, I don't know how to say it better, but it's not actually the tip like in the end- it's the part of it that goes into the soldering iron. That part - can I file it so it fits in my soldering iron? There's a store near my house with a soldering iron and a tip I needed. And I have a soldering station. But the tip is ticker than my soldering iron can have. So I thought on the file idea, so it would fit normally. But I wouldn't touch the end of the tip, only the part that goes into the soldering iron.
Would this be a good idea or would it still damage the tip somehow?
Thanks in advance for any help!


texts: Why is the parasitic inductance placed in series with the resistance in the treatment of a real resistance?

texts:
As seen in the following image, the parasitic inductance is placed in series with the real resistance.

I do not understand that it is the reason for this decision, whether by convention or there is a reasoning behind it. It's probably a trivial question, but I'm starting to study electronics and I'd like to understand this basic thing.


texts: Relay's Flyback Diode - Is it necessary?

texts:
I have four 6V, ~80mA Relays mounted on a Perfboard which are being controlled by the 2N2222 Transistors.

The basic problem is that after mounting everything the diodes can't fit in easily.

Is the Flyback Diode really necessary?


texts: Fastest boot time comparisons between RPi, BeagleBone Black, UlinuXino, etc?

texts: I can find many tables comparing the specs of the latest development platforms like Raspberry Pi, BeagleBone Black, and UlinuXino.  However, as all of them run some flavor of Linux, there is going to be some boot time involved before one can launch an application.  I have yet to find anyone that compares the boot times of any Linux distro on each of these platforms.  Would anyone here be able to point me in the right direction?


texts: Selecting a transceiver module for a wireless communication system

texts:
Possible Duplicate:
  Suggestions for a Point-to-Point reliable Wireless Communication Module

I got a project to design a wireless communication system in order to communicate between the factory and the factory's pump station which is situated about 600m away from the factory. In between the two end stations there's an estate with no any buildings, there are planted coconut trees. But, no line of sight is present between two end stations.

I need to start this soon. As I don't have any prior experiences in using wireless communication designs for my projects, I came here to ask for guidance from the experts..

I have one major question here.

What is the suitable transceiver module that can be used here?

I searched a lot, but couldn't figure out a proper one.

Please consider that I'm hoping to use PIC micro-controllers to handle the modules (can go for Arduino, if needed)..

Any thought, advice is highly appreciated.

Thanks!


texts:
I'm new to electronics, and need some assistance :)

I need to charge a 12v 9Ah lead acid battery from 12v input.
How should I start with this?
1. step up to 14V? how much do I loose if I try to charge it from 12v?
2. is there a chip that can regulate the exponential charging process?

Thank you


texts:
I am confused on this.
We know that P = IV and V = IR. That means P = V^2/R by substitution.
I understand that by that second equation we can say "power is proportional to voltage squared" but what if we had gone with the first one, P = IV? In this equation power is proportional to voltage by itself. What if I had not known about Ohm's Law? Would it have been wrong to say power is linearly proportional to voltage based on P = IV?


texts: EM compatibility of single board computers and laptops

texts:
Like a lot of people on this site, I own some single board computers (SBC) and microcontroller boards (UDOO, Raspberry Pi, Arduino, Atmel boards, etc.).

I wonder about the electromagnetic emissions of these products. Since they don't have a metallic enclosure (or any enclosure at all), they surely emit radiations. On the other hand, I think that they have CE compatibility and that it covers the level of tolerable emissions.

Now, I have a laptop with broken hinges and cracked plastic cover. I am currently building a new case in order to make an all-in-one desktop PC with it. Since I won't use the original shielding, I will have to provide some shielding myself (emi standards/best practices for PC cases) .

The question is: How do SBCs achieve EM compatibility without shielding? Is it because they use carefully crafted designs, or because they run on relatively lower power, or a combination of both?


texts: Calculating resistance and reactance of an coil (motor winding)

texts:
I want to find out the resistance and the reactance of an motor coil. I can measure the magnitude of the current through the coil using a DMM.

For example, If the voltage across the coil is 230v ac and the current through the coil is 10A, Impedance, Z= 230/10 = 23 ohm. Now, how can I find the value of R and X where Z=R+jX?


texts: What causes components to "jump" during reflow soldering?

texts:
I've been using a hot plate technique (with a PID controller / thermocouple / SSR setup) to get into making SMD boards. I had an interesting experience earlier today, and I was hoping some more experienced individuals might be able to help me understand what caused it and what I can do to avoid repeat performances.

I applied (non-lead-free) solder paste to my board using a stencil, put it on the hot plate (with a lid on), and started heating up the plate slowly (maybe 1.5 degrees C / second), to "soak" the board prior to turning it up to the melting point. Way before I got to the melting point (maybe around 110C), I witnessed an incredible phenomenon. A variety (but not all) of my components started jumping off the board like popcorn. Some (e.g. D-PAK voltage regulators) just kind of flipped over, others (e.g. 0603 resistors) literally propelled upward and bounded off the lid.

In my earlier attempts I didn't see anything like this happen, and I'm not really sure what I might have done differently on this particular instance. Can anyone explain the circumstances under which this type of outcome might take place and what one can do to mitigate it?


texts:
I built the TDA 7052 circuit from the datasheet and connected it to my computer's sound card and a 50 \$\Omega\$ speaker.

Here's the circuit:

The \$R_s\$ is the source impedance, which I can't measure and sound card manufacturer isn't providing any useful information. I also used 100 nF electrolytic capacitor, since I don't have any ceramic at the moment.

I already know that the speaker and the amplifier can work well together, because they were salvaged from another circuit.

Now about my problems:

First problem is that the amplifier won't work on voltages above 3.1 V. The minimal voltage listed in the datasheet is 3 V, typical is 6 V and maximum is 18 V, so this looks a bit strange.

The next problem is that I get crackling and noise when I set the computer volume to more than 50%. The speaker is quiet (much more than in the radio I got the amplifier and speaker form) and from time to time it seems as if the amplifier is clipping (I'm not sure if that's the right word. The peaks seem to get distorted).

Here's the effect of increasing volume on a sine wave:

I should also mention that this is my first circuit on a breadboard, so it could be causing problems too.

So where do I start fixing this?


texts: Advice for my Voltage controlled Amplifier

texts:
In class we are designing a VCA together as part of a bigger circuit. The aim is that we have an input of speech and an input of music and when we speak the the music reduces in volume.

The speech input to the schematic below comes from another circuit which is just a basic envelope detector. In the case of simulations I have just been using a DC voltage to represent the output of the envelope detector. The output of that circuit is a negative voltage so that is why it is negative DC source below.

The basic theory is, the first stage, the Voltage to Current converter turns the output of the envelope detector into a current which is set using R1. The current is fed into the current mirror which interns acts as a current sink for the long tail pair. The Q4 of the LTP acts as the input from which the music comes into, Q5 is grounded. So when the speech goes up the current goes up which interns makes the voltage increase after R3 and R3. However the voltage also has the speech voltage present, when the speech goes up so does the R3 and R4 voltages, so as they are out of phase by 180 degrees that gets fed into the subtractor which because they are out of phase, it removes the speech voltage, as its present in both branches but the music is left intact (but doubled) as its out of phase. However the last thing is that it is currently doing the opposite of what is needed so the output of the subtractor is fed into the the middle opamp (which is the unlabeled) block, and it inverts the "gain". The output after this opamp is going to be the final output, the music signal whos amplitude is controlled by the input speech signal.

While in theory it sounds like it should work, and it does, theres some behaviour im not to sure about.

I have built this circuit in LTSpice and it works under certain conditions.

As a test, if the speech is -0.1V and the music is 0.2V then the output I get is 100mv. If I go below -0.1v or above 0.2v, even by a bit the output saturates.
However if I make the speech -0.2v then the output is 40mv, -0.3v then 28mv. Which shows the musics gain is being controlled by the input speech.

However if the music is 2V and speech is -1V then it works, but again the output is 100mv only.

This is what im having trouble working out. You can use any combination but it seems like the maximum output you can get is around the 180mv mark.

Using 5V music and -5.089 speech the output is around 170mV. Any lower than -5.089 then it saturates to 12V or sometimes -12V. Othertimes if I get very close say -5.088V theres some wierd effects such as a small sin wave around 6V for a few milliseconds then it drops to -12V.

So, the input speech / control has to be scaled to fit the music signal. In reality we will be dealing with millivolts and according to simulations its all going to work fine even with a 0V speech signal.

So I would just like to see if anyone can share some extra insight into the circuit and why its acting like this or if theres any advice for improvement.
I was under the impression that the input speech would control the music the same way for all music signals. Such as 1V = gain of -2 for all ranges of music inputs, but obviously thats not the case.

simulate this circuit – Schematic created using CircuitLab


texts:
I wonder, if that's possible to load lpc3154 at LPCExpresso board with custom firmware?

I see that chip supports secure boot, so if AES key was programmed, it is impossible without knowing the key? Or are there any options to boot lpc3154 without knowing the key? (SD, flash, USB, JTAG... Anything?)

Does anyone know if key was indeed loaded?

Just buying new lpc3154 is not an option - they are not in stock here anywhere, and wait times are 4 weeks+ (and a price tag > than a price of this board)...


texts: MPU 6050 Digital Motion Processor Gyro Units

texts:
I'm running into an odd issue with a motion control processor (MPU 6050 / 9150) that is returning raw gyroscope values as specified between the -/+ 32768 which in the way this gyro is configured corresponds to -/+ 2000 deg / sec. This makes total sense as this goes along with the specified documentation.

However, when I process data from the digital motion processor (6 axis sensor fusion) I get a maximum of 1429. I don't think that there's an error reading the data from the MPU buffer as the other measurements look good (reading from the same FIFO buffer). I assume this is likely some units issue that has to do with the 6 axis sensor fusion, and also likely involving radians

Wondering if any of you bright people with your light bulb brains have some insight here?


texts: Safe way to reform high-voltage capacitor

texts:
This week I received an old photographic studio flash unit made in the early 1960'ies. Inside is a huge 40µF/2500V capacitor. I don't know the usage history of the unit; it may not have been used for 20 years or perhaps more, or it may have been used weeks ago.

What is a safe way to bring the unit back into use again? I am thinking of interrupting the mains supply (240VAC) with a relays, operated by a microcontroller, starting with 0.1s pulses and a few minutes waiting time, slowly building up. Would that be a good idea, or should I follow another approach?


texts: MBED + STM32F446RE triggers HARD FAULT when trying to write to flash

texts:
I am trying to write to flash memory from the firmware itself.
It looks like the Erase process hangs for 2 seconds or so but works, but the writing process seems to totally freeze the MCU cause a HARD FAULT. Below is the code I am using. Any idea why?
FLASH_EraseInitTypeDef flashErase;
flashErase.TypeErase = TYPEERASE_SECTORS;
flashErase.VoltageRange = FLASH_VOLTAGE_RANGE_3;
flashErase.Sector = FLASH_SECTOR_7;
flashErase.NbSectors = 1;

HAL_FLASH_Unlock();
__HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_EOP | FLASH_FLAG_OPERR | FLASH_FLAG_WRPERR |
              FLASH_FLAG_PGAERR | FLASH_FLAG_PGPERR|FLASH_FLAG_PGSERR);

uint32_t sectorError;
if (HAL_FLASHEx_Erase(&flashErase, &sectorError) != HAL_OK) {
  error = true;
}
if (HAL_FLASH_Program(TYPEPROGRAM_WORD, 0x08060000, 123) != HAL_OK) {
  error = true;
}
HAL_FLASH_Lock();

EDIT: The microcontroller actually triggers a HARD FAULT
I tried locating some user data to 0x08020000 (sector 5) using linker script and initializing it as follows:
__attribute__((__section__(".user_data"))) char userConfig[4] = {1, 2, 3, 4};

I can check that it is properly located and initialized (&userConfig[0] is 0x08020000 and the values are 1 2 3 4), and properly erased (back to 255 255 255 255 if I just do an erase of sector 5), but trying to write to 0x08020000 always makes an HARD FAULT happen.
EDIT2: I tried to execute the code in the RAM (using direct registers access instead of calling HAL methods) and it doesn't make any difference


texts: Pointer to array gets highest bit toggled by ... compiler? (dsPIC33EP & XC16)

texts:
Brief:

Pointer to a const-int-array, nested in a struct
Using ptr to this struct (type) in various places
ptr-deref causes address-error, because value was changed from i.e. 0x00AE to 0x80AE -> highest bit was toggled.

Detailed:
Declarations etc:
typedef struct {
    const uint8_t *rawDataPtr;
    uint16_t width;      ///<in Bits!
    uint16_t height;     ///<in Bytes!
    } image_t;

const uint8_t image_data_timer_53x56[53] = {
    0x00, 0x00, 0x02, 0xff, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x1f, 0xff, 0xf0, 0x00, 0x00,
    0x00, 0x00, 0xff, 0xff, 0xfc, 0x00, 0x00,
    0x00, 0x03, 0xff, 0xff, 0xff, 0x00, 0x00,
    0x00, 0x0f, 0xff, 0xff, 0xff, 0xc0, 0x00,
    0x00, 0x1f, 0xff, 0xff, 0xff, 0xe0, 0x00,
    0x00, 0x7f, 0xff, 0xff, 0xff, 0xf0, 0x00,
    0x00, 0x7f, 0xff, 0xff}

image_t image_timer3 = {image_data_timer_53x56, 53, 1};

Edit: These definitions (above) are outside of any function-body.
void LCD_draw_image(uint16_t x, uint16_t y, image_t *img, uint16_t fg_color, uint16_t bg_color);

"image_timer_3" is global and extern.
Call of function "LCD_draw_image":
LCD_draw_image(X_WIDTH_FRAME, Y_POS_ICON, &image_timer3, COL_BLACK, COL_WHITE);

...using "img" in the subroutine in various ways. Doesn't actually matter how, because the pointer is already corrupted.
See debugger output:
(Edit: Breakpoint BEFORE calling the subroutine mentioned => deref inside of it is not crucial to this question)

Now, I tried size-changing of the initial int-array and it does have an effect since it did work for a while. But now the error reoccurred and I assume it is a setting of the compiler but I cannot figure out what!
Each time I use the pointer I get ADDRESS ERROR (traps code 2), of course, since it does not exist.
WHAT HAPPENS TO THIS POINTER?
dsPIC33EP64GS804, Mplab 5.4, XC16, ICD3


texts: Is it possible to use a XBee module to controll a quadcopter?

texts:
I'm thinking to design my own quadcopter and wondered if it's possible to use a XBee module to control the drone?

The reason I'm thinking about an XBee module is because I want to be able to plug it into my computer and control it from there.

UPDATE:
Anyone got any other recomondation on "remote controll" modules ?


texts:
What values of the main parameters of an op amp are suitable in a bandgap reference design? The purpose is to obtain a smaller temperature drift in the range -40 to 125 C.

The model I am using now is an ideal op amp with the following parameters:

gain = 835e3;
freq_unitygain  = 1.0e6;
rin = 1e6;
vin_offset = 0.0;
ibias = 0.0;
iin_max = 100e-6;
slew_rate = 0.5e6;
out = 80;
vsoft = 0.5;

The schematics of the design is the one from below.

And the schematics of the op amp is this:

Is the gain the most important parameter? Or the bandwidth?


texts:
OK, maybe not all of them, but by far most of the 5 mm LEDs I've ever handled are rated with I(max) = 20 mA and I've been using them for maybe over 15 years.

Why is this? Is caused by the size of the chip that 20 mA is the max? Is it because of historic reasons? Convenience to remember specs? Does a modern 20 mA chip not fit in a 3 mm package? Is it a dissipated power thing (guess not as blue LEDs dissipate almost double power with respect to a red LED).


texts: Can spray paint or a marker block UV for solder mask/resist?

texts: I am planning to make a PCB and putting solder mask on it but I don't have my own laser printer to print the transparency for the mask. I do, however, live near a printing shop with a laser printer who can print glossy/photo paper but not transparencies. So I am thinking if I can use spray paint or a marker to "draw" on empty transparencies by using a soldering paste stencil as a guide. I have seen this question being answered but its not what I'm looking for. So will spray paint or a marker block UV for solder mask/resist so that the pads won't dry?


texts:
I need to do the stability analysis of my amplifier circuit. I implemented schematic in LTspice, where I did some of simulations, so I would like to keep the same tool also for the stability analysis. The amplifier schematic is the following:

I followed some video tutorial that advices the following steps for stability analysis:

Break feedback loop for the AC signals by inserting large - 1TH inductor between the output and
feedback network (this way we keep the DC bias but block the AC),
Add large capacitance (1TF) between the feedback network and AC stimulus,
Ground the input.

Applying the previous, I got the following schematic:

If I correctly understand, the stability check is based by measuring the phase margin of the closed loop gain (that should be V(out)) on the intersect point of 1/β (that should be 1/V(fb), fb is feedback point) and open loop gain plots (that should be V(out)/V(fb)). In general, we should ensure that the phase shift of the feedback signal is less than 180° when amplifier reaches the unity gain (avoid amplification when feedback signal subtraction become addition, because of phase shift). In practice, as a rule of thumb, the minimum phase margin should be 45°. After simulation I get the following plot:

From the plot, I can notice that the phase margin is about 113° (180° - absolute_value(phase at intersection point)), so I can conclude that the amplifier is stable (right?). This also confirms the transient simulation. However, when I remove the 100pF capacitor at the transistor Q4 (the second differential pair), I get phase margin of 145°, but the transient analysis reveals oscillation, like on plot:

I am definitely missing something, so I need help to make correct setup and simulations (probably and interpretation).


texts: Power over ethernet and common-mode termination

texts:
I have a non-standard Power over Ethernet application (connector, and devices are not ethernet standard but we are using ethernet pairs and protocol for communications). On looking at PoE schematics I have noticed that none of them incorporate common mode termination in the design. Isn't common mode termination needed at all, or does the PoE standard reduces maximum cable runs to compensate?

I was planning to use the following circuit for termination (with its equivalent on the ground side, values are estimates), is this overkill?

simulate this circuit – Schematic created using CircuitLab


texts: What is the name of a circuit that delays powering of another circuit?

texts:
I'm having trouble figuring out the name of this circuit.

It needs to delay turning "on" a 12V circuit and a 120VAC circuit, after a 5V circuit has been turned on.

Example:

Turn on 1x power switch, which turns on a microcontroller (5V), a DC motor circuit (12V) and a large AC motor (120VAC).
The sequence of switching "on" should be 5V, 12V, then 120VAC
Without that sequence the 12V motors and 120VAC motor turn on wildly (for ~1 sec) as the microcontroller is "powering on".

Ideally a passive circuit.


texts: Why does my laptop adapter output nominal voltage with a broken capacitor?

texts:
My adapter broke, so I started my repairs by measuring the output voltage; it was 18V as it's supposed to! So, I figured my laptop charging cicruit was broken, but when I opened the adapter I saw the 400V, 120µF capacitor after the main transformer was broken. I replaced it and my laptop was alive again.

I suppose this has something to do when applying a load, but I cannot understand how the capacitor acts in these cases and give me a good voltage reading even though it is blown. Got any good explanation for this?


texts: Pull signal low using a pic microcontroller

texts:
I'm working with a ADH8066 GSM Module and a PIC16F688.  I want to reset the ADH8066 using the ON_KEY pin which is described as:

Power On/OFF signal. Effective at low. Required 100ms above power level.

The way that I read this is that in order to reset the GSM module, I need to pull the signal low for at least 100ms to reset, and I have confirmed this through testing.  My question is, what is the best way to pull the signal low (i.e. connect to ground) using my PIC16F688?  My first thought is to use a NPN transistor with the base connected to the PIC and the ADH8066 ON_KEY pin connected to through the collector/emitter to ground.  Is this the right way?


texts: Can fitting nails of board connectors be used as regular pins?

texts:
Board-to-board connectors often have 2 fitting nails (name depends on vendor), e.g. Molex 505066-0622:

The product specification includes many properties of those fitting nails, e.g. contact resistance:

Does this mean that fitting nails can be used as regular pins? So a 6 pin connector such as Molex 505066-0622 has in fact 8 pins? Also as the contact resistance of the fitting nails is lower, they are even better suited for transmitting power?


texts:
I'm currently doing a project that consists of testing bio-implants to see if they are still good to use.
For this, I have to measure the impedance of the implant from frequency starting at 10Hz to 1MHz.
I'm using an L432KC from STM to control an AD9833 which outputs the 0.6ppV sien wave at the desired frequency.
The implants can have an impedance from a few ohms to around 100 kohm.
Applying this voltage to the implants will generate current and with Ohm's law, I can find the impedance of the implant at each point.
To do the operation, I need to convert the current to voltage so the 12bit ADC of the L432KC can read it.
Here's a "schematic":

I have struggled doing this conversion. I'm trying to use a transimpedance amplifier but I can only use it with low impedance measurements or high impedance.  I can't size it for both:

Does anyone have a solution to have the biggest range in terms of resistance?
Am I maybe going about this in the wrong way?


texts:
This is induced motor question

Let's say a three-phase induction motor is rated 50HP, 480V, 60Hz and 1150 RPM.

developed torque
frequency of the rotor current

Is developed torque mean initial power's torque?

How do I find the frequency of the rotor current?


texts: Experimental feedback scheme in DC-DC boost converter

texts:
Does anyone know if it's possible to connect the feedback pin of a DC-DC boost converter chip like Texas Instruments' LM2733 in a different manner than the one described in the datasheet, namely on the collector of the output side of a standard BJT current mirror, like so :

simulate this circuit – Schematic created using CircuitLab

In which case

With Vfb=1.23V for this specific chip.
This would allow minimizing losses in Q2 by setting Vce a little bit above 0.7V, without having to know the exact voltage of the LED string at a given current.
However I'm way out of my depth here, so I'm wondering :

Is this worth trying?
Is there a risk that the chip will go berserk due to the nonlinearity of Vce as a function of the voltage across the load?
Where should the forward compensation capacitor be connected? What should its value be?

Thank you very much.


texts: Detecting state of LED to control another circuit

texts:
I need to add functions to equipment I am not allowed to modify in any way.  To do this I need to monitor the status of a Yellow/Amber LED and translate its status into a signal that can be used to turn on or off a loud alarm speaker.  I will use a klaxon for the speaker.  My issue is that I only want to detect the light from the LED and not have sunlight or florescent lighting turn on the speaker.  I would like to be able to still see the original LED, but if necessary to cover it, I could add another LED to the device.  I would power from either 5V, 12v, or 24v dc.  Any help would be great.  Once I get some ideas, I will experiment if necessary.
Thanks,
Bcrumb


texts:
I'm trying control the volume of a small speaker (8Ω, 1/4W) in a 3.3V system using a potentiometer wheel (10kΩ). I've done this in the past using an LM386 in 5V systems, but the project I'm working on is 3.3V only. I've been browsing Digi-Key for a 3.3V equivalent, but of the ones I've looked at so far (LM4864, LM4862, TPA301, TS34119), I can't seem to understand how to control the volume in their typical application diagrams (with a pot or otherwise).

Does anyone have experience with something like this?


texts: Buck Regulator Supply From Multiple Sources

texts:
Hey Electrical Engineerers!
I am currently working on making an LED tail light for an older car.
Overview of the Taillight
Each tail light has 4 inputs connected to it: Park, Brake, Turn, and Reverse.
The 4 inputs are switched 12V. For example, if you engage your turn signal, the turn input will switch 12V on and off each time the blinker or hazard lights are activated.  The most current this circuit could draw is ~2.5A.
When I initially created this circuit, I had a regulator on each of the inputs.  Soon after, I realized that four regulators was much too expensive.  So with that, I created this circuit which aggregates all the power to one buck regulator (LM2596) and uses MOSFET transistors to determine which light should be on.
NOTE: The LEDs for each light are actually an array of LEDs, but I simplified it to just one for this schematic.
Circuit

Questions

Is this an effective circuit, specifically the one regulator being supplied from multiple sources and the MOSFETs being used to switch on the lights?  Is something like this available in an IC?
I would like to add over-voltage and current protection to this circuit, how could I effectively do that?

Thanks in advance, I really appreciate any feedback.


texts:
I have a 40 MHz crystal oscillator that generates a sine wave. If I use a schmitt trigger on the output, would the output of the schmitt trigger be a 40 MHz square wave, suitable for digital electronics? Will a CMOS type oscillator work with digital electronics?
Oscillator is Abracon ACO-40.000MHZ-EK
Schmitt trigger is CD40106B


texts: Can I use SPI for asynchronous serial input?

texts:
I need a second serial async input channel on the MSP430G2553 and would like to use the SPI USCI to do this.

Is the USCI SPI baud rate stable enough to do this at 300 baud, 2400 baud or 9600 baud? I am currently using the 8 MHz clock.

Is there any other option that can save me from bit-banging?

Might it be possible to do asynchronous receive by starting the clock-out when the start-bit is received?

My current thinking for Rx on the SPI at 300 baud is as follows:

start bit interrupt disable
wait for 1/2 bit
do Rx enable
Rx interrupt
start bit interrupt enable

One can use 10 bit receive on some of the other members in the family that contains a SPI.

Please note that this is a similar question to: Can I use SPI for asynchronous serial output? but the answer is much more complex because the SPI clock output must be aligned with the Rx bitstream.

Only half duplex is possible if you want to do Tx the same way.

Thanks.


texts: How do I power/wire something that is rotating constantly WITHOUT extra batteries?

texts: So I want to make a Lazy Susan that is rotating constantly in one direction. I also want to have some other things on top such as neon signs, moving things, and etc. Problem is I want this to all run off of one DC source. Problem is I cannot figure out how I wire it so that things don't get tangled since the entire thing is constantly in motion.


texts: Generating a cutting line from a Gerber outline

texts: Our PCB fab has decided to charge us extra for our PCBs unless we provide them with a cutter tool path on a Gerber layer. Amazingly, Altium doesn't seem to have a tool to automatically generate this cutting path. Does anyone know of any software which can generate this, with tabs?


texts: Trouble understanding overvoltage protection circuit

texts:
I am working on a DALI circuit and came across this app note. App note gives a schematic which is supposed to protect the circuit in case someone connects 220 VAC wires to the DALI lines. Schematic below:

App note gives no explanation about how the circuit will work. I came across this similar question but I couldn't understand the circuit fully.

Here is what I could understand in bits and pieces:

Tracing the + and -:

During transmits, U2 will activate which in turn will activate Q2 which will short the DALI lines. Am I correct?

DALI messages will be received through U1 and the current flow will be like this:

Am I correct about this part?

What will happen when the voltage on DALI lines are very high? Q1 and Q3 appears to be a current limit circuit but I don't know how will they protect everything. When will R2 R3 R4 come into picture and what role do they play? How will the circuit behavior change when the DALI line voltage goes from normal (around 15 V) to something abnormal (above 100 V).


texts:
I recently bought a G10/241E tube and I need a power supply for it. There are no designs of a 330V DC power supply and no buck-boost converters would work with such voltage. The datasheet and example circuit:

Unidirectional Cold-Cathode Gas-Filled Decade Counter - G10/241E (CVX2223)

Is there any easy boost converter or should I just buy a transformer and power it from mains? (I have 220V mains.)


texts:
The background is
Off road motorcycle Radiator fan, temp controlled circuit is powered when key on power is present.
User wants a manual switch to kill the circuit...thats easy enough.
A Power on indicator light would be easy to add, but not what i want..

I want to give him a "Power off" indicator light so he can be warned his manual switch is in the off position.
I think what I need to build in order to make that work is a not logic gate..
A: Do I have that right?
B: If a not logic gate is what I need, what would be the "better" way to build a not logic gate used in a 12-14VDC system, subjected to vibrations, 45-120 deg F
C: Indicator light to be used is an LED

Thank you in advance for your time.


texts: Trigger 3055 Transistor from 100mA 3V base

texts:
I'm looking for an NPN transistor that I can use to switch a 3055 transitor.  The base of the transitor I need should switch using the GPIO output from a Raspberry Pi ~3v @ 100mA.

The 3055 needs to put out 14V at about 1 amp.  Anybody got any suggestions?  Or if anyone could explain the gain I need to be looking for to make this work, I'd be glad to look around.

By the way, a very high speed switching darlington may be worth considering. However the 3055 needs to put out a perfect square wave.


texts:
So I was thinking about building a deep water camera housing. The housing would be filled with a non-conductive fluid to counter the pressure at depth.

Although fluids like purified water or propylene glycol (anti-freeze mixtures) are stated to be non-conductive, they become ionized when in contact with metals and plastics, thus gradually conducting electricity again. There are ion-exchange resin products that are supposed to keep the fluids de-ionized though.
Source: https://www.electronics-cooling.com/2015/12/tech-brief-low-electrical-conductivity-liquid-coolants-for-electronics-cooling/#

So while the electronics might survive being emerged in liquids for a day, what about the 3V lithium batteries that power the camera? Do you expect this thing blowing up in my face in any case, or is there a possiblity that this might work?


texts:
Below is a part from this accelerometer:

For +/-2g the Scale factor tolerance is given as 10mg. There is also 0.25%. This is in parentheses as 1.25(0.25%) V/g. Is 10mg derived from 1.25(0.25%) V/g?

I'm completely lost about what scale factor tolerance is.

Imagine scale factor is x V/g and the scale factor tolerance is %y what does that mean in terms of accuracy? Is this tolerance an absolute value of changes with the g?

I would be glad if someone can explain meaning this parameter in a simple manner associating with accuracy. What can be said about the minimum g can be measured regarding this parameter and why?


texts: Is it possible to limit IR led so sensor detects it only if you aim at it?

texts:
I will have IR led and IR sensor as in TV. As you know, even if you don't point at the TV you are able to change channels.

My question is, is it possible to limit it somehow (maybe by putting the LED into some hollow cylinder)?


texts: Difference in noise levels between inverting and non-inverting inputs of LM386

texts:
An article on Hackaday claims that the inverting input of LM386 is less noisy than the non-inverting one:

We’ve also noticed, and we’re not alone, that the inverting input seems to be less noisy than the non-inverting. See how the datasheet applications ground the inverting input (pin 2) and put the signal into pin 3? Do exactly the opposite and you’ll reduce your noise floor even further.

I'm wondering if this is really true, and if so, is this a peculiarity of this particular chip or manifestation of some more general rule?
My understanding of electronics does not allow me to draw any conclusions from the equivalent schematics provided in TI's LM386 datasheet :

Does it sound plausible? Is there a way to measure this in 'home conditions' (i.e. without expensive equipment, oscilloscope and multimeter only?)


texts:
I was wondering if anyone could help me or give advice. I have an old electric green goods shredder. I want to use the motor to make a wood turning machine. How do I add a simple speed control to the motor?

FYI, I'm a complete novice. I have no experience in electrical circuits but I know the obvious stuff like +/-

Any help would be great.


texts:
I just opened a PC a client brought, with some software problems.

While fixing those problems I opened the case to check if there was something that needed maintenance and I noticed the USB shield of the front panel wasn't connected to the motherboard's ground or the mains ground, and it got me thinking because I thought it was always connected.

I did some research and found several proposals:

Directly connect it to the chassis
Connect it to the chassis through a RC filter (0.47 µF capacitor / 1 Mohm resistor) (The only excuse I saw for using this was "to prevent ESD".)
Connect it to the chassis through a Fe bead
Both options above (RC filter + Fe bead in series)
Don't connect it at all

I don't see why any of the options besides the first I named would be good for a simple PC. Maybe someone could explain the reason for them?

NOTE: Even though I gave a particular example, I'd like a more general answer. I believe these concepts could be applied in a wider range.


texts: Noisy Voltage Rails (Vcc, Gnd) - Noise Isolation for Automotive Circuit

texts:
I have an audio (mic, speaker) circuit that I am currently powering off of a 12V car adapter that is fed into a 10V switching DC regulator to power the rest of the circuit. I have noticed a horrendous amount of noise on the mics and speakers when running off of this circuit, even with the appropriate bypass capacitors from Vcc to Gnd in place, carefully tuning the DC-DC switching converter (buck-boost), and so on.

After breaking out my oscilloscope, it seems there is a lot of noise on the Vcc and Gnd rails that affects the entire circuit, and the noise is not present when I swap out the 12V car power source for an external 12V battery solution.

What would be the best approach to eliminating this noise source entirely? I am already providing a regulated power output, but it seems that the noise on Gnd is impacting everything else in the circuit, even with a regulated power source. I could create a separate Gnd for the rest of the circuit, but am not certain as to how this would work with my switching power supply if it doesn't share the same Gnd as the circuit it powers.

I have also considered using a flyback regulator, as it isolates the circuit it supplies via a transformer, but I'm not 100% sure if this will resolve the case of a noisy external Gnd.

Thank you.


texts: Decoupling capacitors with power pour on top layer of 2-layer board

texts:
This question has been asked before but there are too many conflicting opinions.
For a 2-layer board with a 3V3 polygon pour on the top layer and a GND polygon pour on the bottom layer, how should power connections be made to IC pins and decoupling capacitors?
I know there should be separate vias for the IC's GND pin and the GND pad of the decoupling capacitor, but what about the power pins? As I have it now, the IC pin and the capacitor pad are connected by the polygon pour and a separate trace. Should I get rid of the trace or remove the direct connection from the IC pin to the polygon pour?
Guidelines from TI seem to suggest the power should hit the capacitor first and then go to the IC via a trace (see figure 12 in https://www.ti.com/lit/an/scaa082a/scaa082a.pdf); their advice is "Make sure that the signal must flow along the capacitor." I have also seen people who know what they are doing say not to use a trace (http://www.sigcon.com/Pubs/news/9_07.htm). What would you do?


texts: Read AS3953 NFC EEPROM when the chip is not supplied

texts:
I want to read/write AS3953 (NFC chip) through SPI (MSP430) and PCD (Samsung Galaxy S3 Mini).

No problem for the first part (through MSP430 SPI). but when I want to read EEPROM values trough PCD, I have just a "bip" from my smartphone and the applications I use(NFC tag info, Nfc reader, ....) cannot read the tag.

The same behaviour with the constructor demokit.

Am I missing something to perform PCD-EEPROM read write ? Datasheet

Actual Configuration word is: 7b 48 04 1c


texts:
I'm looking for a simple laboratory procedure (and required equipment) to measure the input capacitance of each IC I/O pin.

Thanks in advance.


texts: What might cause audible noise in an inductive charging system?

texts: I have a pair of Qi-compatible wireless charging pads, and I've noticed that when a device is charging, the pad will emit a quiet but noticeable squeal in a relatively high frequency range. Perhaps it's because the pads sit on my desk near my bed, that I notice, but I'm curious what might be causing the squeal and if there's anything I can try to mitigate it.


texts: When i run this circuit on test board i found that when Q3 led on and then turn power off the circuit and turn it on again the Q3 led remains on and it seems the counter contenue counting .what does it means ?


texts: How does a microcontroller load and execute a bootloader?

texts:
I know that for a regular PC, BIOS executes its handler of interrupt 0x19 to search for a bootable device and if a device is found, first 512 bytes are loaded at 0x7c00 and BIOS starts execute from that address. 0x19 and 0x7c00, although are standard, are defined by BIOS manufacture.

Since microcontroller does not use external device like a hard drive to boot but use its flash memory, how do I know where is it going to load and execute bootloader code in flash memory? And using what interrupt? Is there any document, i.e. I have a TM4C123 microcontroller, what relevant documents do I need to look at to write a bootloader?


texts:
What I understand(FACTS) :

In for example a LC resonance circuit the output can many times greater than the input voltage.
At resonance the impedance of the inductor is the same as the impedance of the capacitor.

At the resonance frequence Xl=Xc

What I fail to understand

If the impedance's are equal, how can the output voltage be larger than the input voltage?
Although not correct, you would almost start to reason that the output voltage is half the input voltage(voltage divider).
Where the output voltage is the voltage across the capacitor.

It seems so counter intuitive.

Why is the voltage higher at the output?
What is a intuitive way of explaining why the output voltage is higher than the input voltage.
Or is it one of those circuit where it only starts to make sense when you deriver the transfer function.


texts: A voltage regulator that is controlling a voltage

texts:
My scenario is that I am having a circuit which having 12V as the input voltage and works beween 8V to 15V. I want to limit this circuit in a way that if the input voltage drops below 12V criuit breaks from the input voltage and if voltage goes above 12V circuit invokes and get connected.

Plz Help.


texts: Will permanent inverted current damage my relay module or even my electronic system?

texts:
So I have an expensive piece of electronic equipment which emits ionizing radiation and I need it to set off a warning lightbulb on the wall.
The support company is asking me an overpriced solution so I decided to investigate my own solution which I figure out can be done for less than 5 bucks:
Radiation is only emitted when the button on the remote control is pressed. This remote control is connected to the main device via a 3 pair cable (RJ12 6p6c) I've measured every voltage differential between the pairs on all states and found a useful pair:
Unpressed button normal state: 24 V
Unpressed button armed state: 24 V
Pressed button unarmed state (not emitting radiation): -1 V
Pressed button armed state (emits the radiation): -22 V
My first idea was just to connect a bulb to this wires but that didn't work 1) the led 24v bulb lights up  in either polarity; 2) it triggers a buzzer and light on the remote command continuously
Since I have some 5V relay modules laying around I've did some testing and noted that the module only triggers if I have the right polarity (+ on VCC and IN and - on Ground) and stays off/untriggred if I invert the current (- on VCC and IN and + on Ground). So my second idea was to buy this:

and can connect the above pair inverted so it will only let a 250V bulb light up when the button is pressed while in armed state.
My questions are:

Is it safe to leave the relay module with inverted voltage for a long time? Can it burn or sth?
Is that setup safe for the equipment? Can the VCC/GND used pairs short or receive voltage from the relay module?

Edit (schematic as requested):

a/b will be:

Unpressed button normal state: -24 V
Unpressed button armed state: -24 V
Pressed button unarmed state (not emitting radiation): 1 V
Pressed button armed state (emits the radiation): 22 V


texts: Diff Op-Amp in current measurement ignores input

texts:
I'm working on a small project which involves current measurement.

I'm using R10 to measure Voltage drop (100 mV) when 10 mA current goes through it.

Next I'm amplifing that signal around 37 times using an op-amp (LM358N) which is powered using 0-5 VDC and works as differential amplifier. There should be 3.73 V on the output BUT...

My problem is:

The op-amp is completely ignoring the inputs and it still outputs a value around VCC minus 1.2 V.

Making a symmetrical power supply does not help. I checked everything about 100 times and can't find any solution... If anybody of you know how to help me I'd be grateful.


texts:
See the full TL866 programmer schematic

Below is the pin driver schematic for the MiniPro TL866 universal device programmer (page 2 of the PDF schematic). The L2, L3 and L4 are powered from VDD, which can be anywhere from 2.0V to 6.0V (from the programmer spec). This limit, as far as I understand, is imposed by the operating VCC range of 74HC373D, which is also 2.0-6.0V. These latches are used to switch a pin of ZIF socket to the VDD voltage.

Now the question: say VDD was programmed to 2.0V, but the supply voltage of 74HC164D is fixed at 3.3V. So now we have L2, L3, L4 supplied 2.0V to VCC pins, but they will receive 3.3V on their D1..D8, LE and ~OE pins. How come the 74HC373Ds withstand that voltage, which is 1.3V above power supply voltage? In the datasheet, the input voltage absolute maximum ratings are specified as -0.5 to VCC + 0.5.

Sorry for a possibly silly question!


texts: What's the difference between a SRAM cell and a D-Latch?

texts: They both seem identical - they both have an "enable" and a single input. When enable is high, the value stored in the element is set to the input. Are they functionally different in any way? (I know they are implemented differently, but I want to know if there is a difference in functionality)


texts:
On an iMac and a Macbook, both running macOS Sierra 10.12.6, I have installed the latest LTspice IV (Build Oct 3 2016, 14:49:11 US Pacific), which prompts me to update on launch. Attempting to do so via either the Model Update or Software Update buttons in the Operation tab causes the spinning wheel for about 10 minutes before finally crashing with EXC_BAD_ACCESS (SIGSEGV).

On Windows I had similar issues when behind a proxy, but there are no such Internet shenanigans here.

Does anyone know a way to update LTspice IV on macOS? I'm happy to do it manually via ~/Library/Application Support/LTspice if necessary.


texts: Is there any possible way of designing robots that can communicate with each other? As in, one of the robot can be programmed to act as a master, while the other robot, situated somewhere else, can be programmed to act as a slave and obey the commands given by the master to him?


texts:
I have an SN74LS08N, and I am connecting 3V to the VCC and connecting the other end to ground. I'm not using any of the AND gates. I am only powering the IC. It reaches 120°+ in less than 10 seconds. The datasheet says that it requires a minimum of 4.75V, yet with less than that, it reaches unreasonable temperatures. I am not using any resistors.

Apologies if I am missing something obvious, I am a first year EE student.

Thanks in advance.


texts:
I'm trying to build an accessory power device for my motorcycle. At the moment I'm using the board from a ripped apart USB car charger for the 5 V part, but I'm trying to build a complete circuit.

I've reviewed this answer, but I still can't work out what values I need to use for each component to get the output I want.

I'll be delivering anything between 11.2 V and 14 V into the circuit. I would like to get 5 V out at up to 1.5 A. Looking at the datasheet it says it will do 1.5 A out. However, when I try and use an online calculator it tells me that the switch peak for the circuit would be 3000 mA and that exceeds the 1500 mA max value. From what I can tell, this is because I'm trying to go from 12 V to 5 V.

Can I do what I'm trying to with the MC33063A or do I need to look at a different component to base the circuit around? If so, which should I be looking at?

For the record, the reason I want 1.5A out of the 5V circuit is that I want to be able to power / charge a GPS (TomTom Rider) and also a bluetooth USB dongle. I would also like the ability to charge a phone (iPhone 4 / 4S / Samsung S3) when not using the GPS and bluetooth dongle.


texts: FET with high current ( power JFET) low VGSoff

texts:
I am looking for a N- channel JFET part number with IDmax > = 800 mA  and low VGS(off) < -15 volts. I dont focus on the frequency As an inherent charactristics of JFETs is high working frequency but I need a good working maximum frequency of 100 MHz or above.
I googled for that but Low vgs( off) jFETs  are rare. The main reason I need such low vgs is its usage as a source follower with a " Large Signal" for current gain
Anyone knows a part number?


texts: Is it possible to buy "resistors in series"?

texts:
Beginner question.
I was reading about "resistors in series".
https://www.electronics-tutorials.ws/resistor/res_3.html
Perhaps naively I thought it would be possible to go buy a component which is already a series of resistors, but such a product does not exist.
Why is this?


texts: What's the difference between IC 74HC04 and IC 74AC04PC?

texts: I am trying to make a simple logic gate simulation for which I require the former IC but I could only procure the latter. Will it still work?


texts: Why shows the effect shown in the video below left-right asymmetry?

texts:
I made this video which shows what happens when I move the point of a wooden chopstick over my TFT-LCD screen, with firm pressure.

It's remarkable that one can see that there is a difference between moving the chopstick to the right and to the left (with about equal pressure).
When moving the pressure point to the right the blue blob is positioned on the right side of the pressure point (and between the two red "wake" circles), and while moving it to the left it's also on the right side (so the blobs are on the opposite sides of the pressure point's direction of moving).
The pattern has a different colored "tail", dependent on the direction of motion, being green when moving to the left and pinkish when moving to the right.
What's a pronounced difference too, are the yellow structures: When moving to the right there is one in front and one behind the pressure point. When moving to the left there are two yellow concentric "circles" of which the outer one is much fainter. And so on.

I'm sure it's got something to do with the distance between the two glass plates in the LCD part (so the polarization vector of the light is changed, which changes the color). It's strange that the pattern is direction-dependent, though at second thought when moving the pressure point on a flexible, smooth, and flat structure, the pressure is of course not symmetrical distributed around the pressure point. So the pressure on the upper plastic sheet is asymmetrical wrt the moving pressure point, and those nice patterns form because the pressure varies in a continuous way, making the distance between the sheets smaller in a continuous way too. I just wonder why the color distribution is different if going in different directions. The pressure distribution will be the same when moving in both directions (see the answer below, where a comparison is made with the movement of the chopstick on a rubber sheet which is obviously direction independent), won't it?

So why is the pattern dependent on the direction in which I move the pressure point with the chopstick?. Shouldn't the same bulge pop up in front of the moving chopstick, and the same stretching behind it, no matter in which direction I move the chopstick? In other words, why does the effect shows no left-right symmetry?


texts: Will lowering voltage increase device running time?

texts:
I'm new to making circuits (and electricity in general), let's say I make something which require 3 volts, if I use a 9 volt battery with 750 mAh, when I lower the voltage down, will I increase my device run time? And would something as simple as a resistor do that?

Note: I know I shouldn't lower the voltage with a resistor, I just would like to know if it would have the same effect as a step-down voltage regulator


texts: Why do we measure \$I_{ds}\$ for CMOS instead of \$I_{sd}\$?

texts: The standard way to write current across a MOS seems to be along the \$I_{ds}\$, i.e. from drain to source. Why don't we use \$I_{sd}\$ instead? I understand both ways are equivalent, but would it not be more natural to think of current as flowing from the source to the drain?


texts: Control of P channel mosfet in buck converter

texts:
I'm trying to design a buck converter to get 3.3v from a 6v solar panel. I am thinking of using this as my p channel mosfet:

http://www.farnell.com/datasheets/196719.pdf

I was thinking of the IRF6218PbF because it has a low Rds and needs only -3 to -5 volts to turn on according to the datasheet. The pwm to control the mosfet in my circuit comes from an attiny85 run at 3.3v with an fsw of 32kHz. I wanted to make sure of two things:

As the mosfet requires a negative voltage to turn on this means that my mosfet would turn on when my pwm wave falls to 0v and turn off when it goes up to 3.3v correct? So whatever I set the duty cycle in my pwm to the actual switch duty cycle be 1 minus that right?
If I'm right about part 1, how likely is it that this switching circuit will be too unreliable with a variable output from the solar panel, requiring me to find a mosfet with a very tight tolerance to avoid the switch not turning on in low light conditions.

If I left out any necessary information or my question sounds just plain stupid please let me know and I'll change or add what is needed, thanks for any help.

Edit:

The buck will be used to charge a 3.7v lithium ion battery which is running some microcontrollers, the overall power draw from the load is small, about 40mA. I believe the attiny85 will be fast enough, it has an 8 MHz clock and looking at the pwm output on an oscilloscope it is very clean at 32kHz. The source V2 is in place of the attiny85 in the schematic.


texts:
I've run into a connection between two PCBs, and it's not giving me a warm fuzzy feeling. The master is a carrier board, and the second board is a standalone sensor that communicates over SPI.  This is more of a thought experiment for me to form a better conceptual understanding of EMI issues. I understand there is a lot more at play here, signal rise time, frequency of the SPI communication, proper line impedance and termination, but I want to focus on cable setup.

In my mind, this is a problem because power and ground are no longer tightly coupled, creating a large loop area that is ripe for high-frequency EMI noise. similarly, the SPI bus forms a large loop area and is also susceptible to EMI noise

replacing the power for a ground line poses the same issue as above, with the added problem of a large "ground loop"

Without changing the design too much, I would imagine the best option would be to remove power or ground from the SPI cable. The issue of a large loop area still stands, but the noise is localized to the SPI instead of the entire system.
Ideally, I would think bring the power across with the communication lines and using a properly shielded cable would be best.


texts: Apply PWM signal to PIN of a Microcontroller

texts:
I am using the MC9S08DZ60. I have been give a circuit diagram according to which i must program the micro-controller. I am using Code warrior with Processor Expert which allows me to initialize the required registers, i don't have to write the code for the same.

Requirement from the code: Detect a PWM pulse on pin 0 of register D. In response, switch on LED and apply PWM signal on pins 3,4,5,6 of Register A. According to the datasheet, i have equated the value of the Channel value registers to the expected pin on the microcontroller. How to apply PWM signal at the required PIN ?I have made an attempt for the same in the following code.

Please refer to the given code:

unsigned int result;
   unsigned int pwmSignal()
   {
   If(PTDD_PTDD0) // to check for the incoming PWM signal.
   {
  PTDD_PTDD2 = 1;  //light up LED.
 do // check Channel for 300ms.
 {
  //my understanding is to latch the values of the channel value registers to the
  //expected pin.
   result = TPM2C0VH;
   result <<=8;
   result = result + TPM2C0VL;
   result = PTAD_PTAD4;
   result = PTAD_PTAD5;
 } while (TPM2C0_CH0F == 0);
 }
 else PTDD_PTDD2 = 0;
 }

The code compiles absolutely fine. but i dont see any change.
At this point i wanna tell, this is my first attempt at doing this.

Also i have one more question, how do i use, for example PIN 2 of Register D, for two different operations in a single main.c ??
Please let me know if i can provide anymore data about all of the above.
Thanks in advance!


texts:
In control theory, how do I find out of which type a system is? P-type or I-type (P = proportional and I = integral)

Consider the following nonlinear system with x as output:

$$
\dot{x} = A(x) + Bu
$$

$$
y = x
$$

Is this system of I-type because of 1/s (integrator)

$$
x = \int\dot{x}
$$

Or is it not that simple to claim of which type the system is?
How is it done?

EDIT

I am using a PI controller. And the complete state space representation using A(x) is (a, b and g are constants > 0)

$$
\dot{x} = -a\sqrt{2gx}+bu
$$


texts:
I'm currently doing some repairs on a project that requires linking 1m strips of APA102C LED pixels in series to form a grid. I've always used bare copper for this purpose, avoiding the tinned copper RGB wire that's available all over the place. In this case, though, I think something like this will make my life a whole lot easier.

My understanding is that this stuff is intended for use with single color RGB strips, but I've found it on the end of just about every reel of addressable pixels I've ever purchased. However, I'm driving my strips at 3MHz, so I'm scared of the skin effect. Can anybody offer some perspective on this?

Thanks in advance!


texts: Li battery charger reference voltage problem

texts:
schematic
datasheet

I have designed a battery charging circuit for a lithium ion battery.When i connect a battery the charging IC seems to do nothing. Only when i use a multimeter probe to measure the drop across VFB pin i.e R16 the IC starts to charge,voltage on this pin slowly climbs up to 3.3V like it should. without the meters measurement the IC does not charge the battery.All the components have been checked and is soldered properly. can someone explain what's going on.
sorry, i haven't updated schematic .Actual resistor i have used achieves 12.8 float voltage. R15 is 976K, R16 is 340K
when i measured across R16 the voltage was 3.22 with battery voltage being 12.6 and it kept increasing towards 3.3 the battery float voltage approaching 12.8, but when i remove the multimeters probe from R16 it stops charging


texts:
I hope it is okay to post a software question here.  Please let me know if not.
I've been learning about Microcap 12 (a SPICE simulator), and have been quite impressed.  However, recently I got stuck.  I am using a transient analysis, and the software for some reason is producing a polar output plot with complex values.  It had been the regular rectangular one that most spice programs produce at first, but I did something, and now I can't get back to the rectangular output no matter what I've tried. I've tried changing almost every relevant setting I could find, but to no avail. I've looked in the user guide and on Spectrum's website, but can't find any fixes.  They would seem to say that a polar plot isn't an option for a transient analysis, so I'm starting to suspect some configuration bit might have been advertently set in error.
Am I missing some setting somewhere?
Thanks for any help.


texts: Bandwidth of low pass filter: measured with the cut-off frequency?

texts:
I have the following Sallen & Key lowpass filter:
$$T(s)=\frac{\frac{1}{R_1R_2C_1C_2}}{s^2+(\frac{1}{C_1R_1}+\frac{1}{C_1R_2})s+\frac{1}{R_1R_2C_1C_2}}$$
The parameters values are

\$R_1=10 k\Omega\$
\$R_2=10 k\Omega\$
\$C_1=150 nF\$
\$C_2=1.65 nF\$

On Mathematica I simulated the magnitude response:

Now I need to find an expression for the bandwidth of the filter. I know that the bandwidth of a low-pass filter corresponds to the cut-off frequency.

How do I calculate the bandwidth in Mathematica?
Is the cut-off frequency measured at -3 dB of the low-pass gain, or the maximum of the filter? I know this spike I see is expected as Q>1.


texts: In an AM radio do the electromagnetic waves cause the antenna to resonate to produce an alternating current?

texts: Looking at Hertz's original experiment with electromagnetic waves with the spark gap how did he know how to build his antenna size to receive the wave that generated the spark ? In what way is the AM antenna like a spark gap receiver? There is no spark from within the antenna is there ?  So then any metal object will produce an AC current when an electromagnetic wave hits it? And an antenna is constructed to resonate at some particular frequencies in order to amplify the signal?  Basically I am trying to understand what makes an antenna an antenna so to speak.


texts:
I am kinda interested in starting to learn something about electronics, I thought a good idea would be to try to reuse those speakers so here we are.
I see they have 2 wires but I don't know how could I connect them to let's say, a jack output, so I could plug it into my computer (if that's even possible)
I would thank any kind of guidance as my googling didn't help me much, thanks!
I Found them on the new flat so I don't have a idea of how they work, they seem to be DCM3020.
Is one cable for current and the other for data?


texts: Can a repulsion motor be connected like a series or shunt DC motor?

texts:
Recently I bought an old repulsion-start induction-run motor made by Asincron in Argentina, exactly identical to the one in this video.
I can't find much documentation and information about how exactly their rotor (repulsion motors in general) is wound.
Is the winding the same as in DC brushed motors?
If it is, would it be possible to connect and use it as a series or shunt motor in DC?
I'm aware it has not been designed for that and will probably work poorly, I'm just curious.
I'm also aware that if it does work as an universal motor then it risks disintegrating the rotor at high speeds it could develop, I won't let that happen.


texts: Building Automated Cat Food Dispenser - Need Strong Servo for Worm Gear

texts:
I have a set up for an automated cat food dispenser where a servo turns a worm gear- which in turn drops the food. However, sometimes food gets stuck between the worm gear and the sides and the only way to turn the gear is by having enough force to crush the hard food nibblet.

I have been looking for a while but am not familiar with a proper torque needed for this. For mechanical ease, I am looking to mount the servo directly linear with the worm gear, and not in a geared setup. Thanks!


texts:
I have an iPhone, and sometimes recharging it from a wall is inconvenient. Maybe I am on a long bus ride. If I am willing to do physical activity/exercise to produce power, how much effort would I need to exert to act as a phone charger, supplying a steady 1–2 amps at 5 V?

This hypothetical device would need to be small and light enough that I could carry it... no point in it if I have to be at home to use it.

For example, there’s a simple hand exercise device that you squeeze over and over to build hand muscle. How much power could that generate?


texts:
I am reading up on (servo) motors to start to play around with them. It seems to be that all servo's are limited in range. Most have a 180 degrees range I read.
This would mean that the shaft of a servo never rotates a full cycle.
Is this really the case or I am missing the obvious here?


texts: l7809cv voltage regulator: heat sink or not?

texts:
I'm using 9v regulator (l7809cv) with 12 1,5v AA batteries in series so that my application gets both 18v and 9v for my Arduino Uno r3 board.

I've been running it for about 15min without any problems, but when I touch the l7809 it feels really hot after 10min or so.

I've measured a current between the batteries and the l7809 to be steadily around 100mah. I haven't exceeded the maximum voltage input ratings, and as far as I can see, neither the current ratings (it says in the datasheet that it's "internally limited")

Maximum temp. appears to be 0 - 150 celcius, which seems to be more than enough.

So my question is, is it OK that the component gets so hot that it hurts touching it although it probably isn't 150 c, or should I make some kind of heat sink for it?


texts:
can somebody explain me how this works please?
I bought a power adapter that has a dual output stated on it: 6.5V DC and 9V AC. There are 4 wires coming out of it. I can measure 9V DC on two of them but can't find anywhere the 6.5V DC that I actually need.
many thanks!


texts: How to protect againt surges if working and maximum voltage are too close

texts:
I have a circuit that I want to protect against surges and eventual peaks (e.g. indirect lightning surges) and I was thinking about TVS diodes or MOV.

The situation is:

-My circuit input is 48V that is stepped down to 12V with a MP24943

-The 48V comes from a standard converter (that I bought) connected on the AC line.

-The maximum voltage accepted by the MP24943 is 60V (datasheet)

-I want to protect the MP24943 and what is after it from surges but I couldn't find any TVS Diodes or MOVs that meet the requirements (for 48V the clamp voltage is something around 75V)

I have already read this, and I couln't find any of the Bourns ICs mentioned here in Brazil (specific components are very hard or impossible to find), and the most cost effective solution for me would still be MOVs or TVS, is there any way I can use them in my circuit? Or to find a replacement for them?

I tried Zener Diodes but no success too, the BZD27C Series (datasheet) for example still have a Clamping voltage too high for me.


texts: Oscillator starts precisely on edge.. ie. synchronous

texts:
I am new to electronics and don't know what I have to Google. I want to build a circuit that oscilates synchronous to a real time capable RaspberryPi.

From the outside, an edge will be sent to both devices. That time is the zero point. All output oscilator edges have to come in a 50Hz frequency as accurately as possible to the zero point. The edge height has to be 5 Volts.

I want to send ultrasonic signals from the device that has the oscilator in it, and catch them with the RaspberryPi. After the zero point is set on both devices they will have no physical connection to each other.

Where do I begin?

I assume that the NE555 is not precise enough.


texts: What's the purpose of diode between high side and low side supply voltage of IR2110?

texts: What's the purpose of the diode between VCC and VB?


texts: STM32F103C8T6 dev board with C and debugging

texts:
I am looking for a cheap and minimalist dev board, and found the above one (Cortex M3 for Arduino). I am used to stm32 but normally their dev boards are a bit expensive if I am going to use them in a bunch of units, so this seemed like a good choise at 3$.

However, I would like to program it in C and be able to debug it. It has a SWD interface, but I am finding very little info on how to set up programming and debugging (almost all links seems to be for AVR based Arduino, not stm32). Will absolutely not use the Arduino IDE.

Anyone knows where to find this info, or any similar really cheap 32-bit dev boards?


texts: Why did relay run when I applied half the nominal coil voltage?

texts:
I'm using a RadioShack 12V DPDT relay, model 275-249.

I applied 6 V across the coil and the switch closed. Why is this? I didn't have any resistors in series with the 6 V power supply (the only limiting resistance was that of the coil). I'm wondering why the switch closed when the relay is rated with a 12 V nominal coil voltage.


texts:
I would like to ask about the difference between Li2YCY and LiYCY TP cables.
As far as I know, the main difference is that the Li2YCY has core insulation based on PE and wrapped screening made from tinned copper wire while the LiYCY cable has core insulation based on PVC and tinned copper braiding.
Why should we choose Li2YCY over LiYCY or vice verca?


texts: Converting between series and parallel circuits

texts:
I have an RCL circuit which which is coupled to an RC circuit via a coupling capacitor, \$C_{c}\$. When the system is on resonance, \$\omega = \omega_{0}\$ the impedance of the RCL is purely resistive, \$R_{p} = \omega_{0} Q L\$. However the presence of the RC component -- itself part of an amplifier circuit modifies the effective resistance of the circuit -- shown in the equation bellow.

I can't seem to derive this equation from scratch, using the diagram

simulate this circuit – Schematic created using CircuitLab

I want to show that the total resistance of this circuit is now described as:
$$R_{total} = \left (\frac{C_{C} + C_{in}}{C_{C}} \right)^{2} \frac{R_{1}R_{2}}{R_{1} + \left (\frac{C_{C} + C_{in}}{C_{C}} \right)^{2} R_{2}}$$

I guess this involves converting between series and parallel circuits for certain parts of the diagram, but I can't see the answer.


texts: we can see the connection at the right hand side between the DGND and AGND! according to my course text,"the real electronic ground of the system is where the point AGND and DGND are coupled." but it doesn't explain clearly why? Why do we need to couple them together?


texts:
Young men in Sierra Leone are making antennas from fluorescent tubes mounted on wooden frames with wire leads.

How would the gain from these devices compare with that of more conventional devices that they replace? Where can I read about how they work?


texts: Cockcroft walton multiplier output both AC and DC?

texts:
I was watching this video
https://www.youtube.com/watch?v=ep3D_LC2UzU
and I noticed that closer to the end he is probing the upper half of the circuit and the scope is displaying square waves , also on the lower side his diagram shows one can take off DC.
start about 14 min in the video you can see it on the board.

Also a separate question, can a CW multiplier be used to step up voltage pulses where one would input a lower voltage pulse and get out a higher one?
Or do the capacitors in the circuit spread out the pulse and flatten its steep rise time?


texts: Problem in redesigning one EAGLE schematic

texts:
In the past I designed a PCB on EAGLE, and now I want to make some changes on it, but it's impossible. You can see it in the picture below:

In the old schematic part I can move and delete nets, but I can't stick a new line or new elements to an old design part. It looks as if my schematic is separated into the old design and the new design, and I can't connect these two together.


texts:
I'm talking about LED lights which are used to light homes from main wall supply
[230V] here.

If I developed a LED driver and its heat sink, is there is a way to measure its
stability against thermal runaway? I mean to calculate whether the heat sink is enough or
the protection mechanism of the driver is enough.

What kind of machines are there to collect these data and measure the integrity in industry
assembly lines? What data should I collect and what model should be used?

I also want to know the benchmarks and standards on thermal stability used in industry.


texts: Identifying a cylindrical SMD component with two banded color markings

texts:
I have been looking at google images of cylindrical smd resistors, but they don't look like the ones on my board.
So my question is: What component is this?

Long story:

This board is a 230VAC to 11.8VAC converter for a lamp which does no longer output 11.8VAC but rather drops down from 8VAC very quickly(~1sec) to 0VAC and I at least try troubleshooting it. The mystery components mentioned also behave strangely when measured by a multi-meter (they each give different resistance values even when measured from different sides ranging from 1kOhm to 150MOhm)


texts: How to calculate amplifier gain (in dB) using frequency?

texts:
I know how to calculate decibel gain using the ratio of power, or Vin/Vout.

However, is there a way to calculate the magnitude of the attenuation and phase angle when you’re given the cutoff frequency and another frequency?


texts: What's the easiest/cheapest variable-frequency sine wave oscillator?

texts:
A Google search will give you a few billion ideas.  Which is the simplest/easiest/cheapest that you know of?

Generating a square wave and then filtering out the harmonics isn't a good solution unless the filter frequency can be varied along with the square.


texts: PNP transistor instead of mosfet to register small clock and data signals

texts:
I have a device that outputs -0.2v clock and data pulse (It works on CR2032 (3v) and I assume it's CMOS), I want to register that signals on arduino in simpliest way. Since no mosfets have threshold this low and since I don't want to use voltage shifter (to create dual supply) and op amp (too many elements), I tried PNP transistor and it works. Is there any sufficient risk of damaging device knowing that output will sink about 1mA of current all the time. Also, why do base have 5v when transistor is closed and how do I chose resistor values.

This is what device instruction says (is it JFET there?):

This is how I do it:


texts:
I got a breadboard with some logic on it. Including it's own power suppply. It is connected to my Arduino Mega 2560 to fill a shiftregister with some bits. Whenevery my arduino is in a undefind state i want the shiftregisters to be dissabled to prevent the hardware from hazards. Undefind means when it is turned off. Since the logic has it's own powersupply it could damage some of the hardware which i toggle with the registers. (toggling transistors with a lot of leds on it)

So i added a pull up to the "blank pin" of the shiftregister(2k 10k 18k). But it does not work as expected. In this case it dows nothing(The test leds still are in some kind of undefind state when i turn off the power of the arduino)! If i delete the gnd line between the arduino and the breadboard it works.

So here is some small shematic (Not compplete but the important things):

What am i doing wrong?

Edit. Sorry i am not that good in drawing this schematics...


texts: How to read / understand spatial RF charts like "XZ Plane Polarization"

texts:
I have been studying about embedded low power RF system on chips. I understand how different antennas, baluns and filters affect the quality and power drain of RF communications.

In all RF documentation there are plane polarization graphs that I do not understand.

Can somebody explain it in layman's terms.


texts:
I want to wire the hotshoe  of my dslr (Nikon D5100) to my Arduino board in order to react to the shutter release of the camera.

I measured a 5 to 8 volts signal between the trigger and the ground lugs when I push the shutter release. So my question is, if I wire the trigger lug to a digital input of the Arduino, where should I wire the ground lug to ? And subsequent question, do you think I should fear for my camera with the current/voltage involved?

I am fairly new to electronics, so I hope my question doesn't sound too stupid.


texts: Transistor heating problem in slayer exciter circuit

texts: i made this project but it is not working and the transistor is heating up very fast, i couldn't find anything regarding this specific project but as far as i understood i should maybe use another transistor, what do you suggest?


texts: Simulation behaves differently in Proteus vs Icircuit

texts:
I'm an electrical engineer student and I'm trying to make an LED Flasher circuit using a 555 Timer.

When I simulated the circuit in Proteus simulator, it's not working! But in Icircuit simulator it works perfectly! It's an identical circuit.

The question is: Why is the circuit not working in Proteus?

Circuit in Icircuit:

Circuit in Proteus:


texts:
Im just a little bit confused wether if LiFe batteries will work the same with an ESC (Electronic Speed controller)

Whats making me confused is that in the description they only talk about LiPo batteries but as I understand LiFe and LiPo work the same, just differences is discharge rate and density.

ESC

In the description it says:

  ... can handle up to 12S Lipoly.

And then in thespecifications it says:

  Input Voltage: 5-12 cells lithium battery or 15-36 cells NIMH battery.

So im a little confused with what they mean.


texts: What is a solution to representing bits physically? (on a cartridge, to be read by the cartridge holder... like a printer)

texts:
I am trying to recreate the sort of microchips that are on printer cartridges so that I can make cartridges that can have their data programmed and read? I only need to store 8 bits, so I was thinking a microchip might be overkill. How can I get 8 bits of data from a cartridge that is plugged in?

I was also thinking of simply connecting power through a switch (0/1), representing the bits. This would be connected through a pull up resistor and so where the switch was closed, you would get some voltage reading.

Another design I thought of can differentiate 16 distinct currents based on 4 switches and 4 strategically chosen resistor values. The switch being open represents a zero. The current was equal to the bit value (ie. switches being closed in 1010 gave 10ma of current). How reliable then is current ADC and would it be easy to repeat this for several cartridge holders?

Anyways, these are the potential solutions I have been thinking of today. Let me know if you all can think of another solution for differentiating between cartridges when they are plugged in.

Excuse the many tags but the solution could potentially be in any of these categories.

Thank you!