texts: How to prevent pH-sensor from maxing out, when pump is turned on?

texts:
I am a bioproces engineer currently working with setting up a pH control system in a bioreactor (basically a large vessel filled with water). Hence, my electronics knowledge is quite limited.

Initially, the setup worked just fine.
However, after installing a recirculation pump, we are having trouble with the readouts from the pH-sensor.

I have tried my best (with only a smartphone available) to depict the setup below:

The problem is, that when the pump is turned on, the readouts from the sensor 'maxes out'.

Observations:

When the pump is turned off, the sensor readings are just fine, when compared to an external reference.
As soon as the pump is turned on, the sensor-readings maxes out. However, when the pump is turned off again, the readings fall back to normal.
If the same probe is inserted into a handheld, battery-powered device, the readings are UNAFFECTED by the state of the pump.
It is not a matter of mixing caused by the pump or a real change in pH-value. (checked by sampling the fluid with a chemical analysis).

So this must be caused by the electronics, but I have no idea why, and how to prevent it.

For reference, the principle behind a pH-sensor is to measure the electrical potential between an pH-electrode which is in contact with the liquid, and an isolated reference electrode (both encapsulated in the same probe).
Hence, any parameters that would affect this potential would also affect the readings.

What am I missing?
I hope you guys can help!


texts:
I have a project in mind, to build an intelligent 3 stage charger from either ardruino or rasberri pi.

I plan to have a voltage and amperage monitor, and via the press of a toggle button have the charger change profiles for different batteries within my home.

12v lead acid battery 7.2ah (alarm battery)
cellphone Lion battery 3.6v (cellphone)
rechargable AAA batteries 1.2v (appliance batteries)
even 12v Wet Cell 102ah battery (car battery)

The question is, what are the amperage ranges which I could work with to electronically switch rate of charge, current, voltage. etc. and what stops regular chargers from charging such a broad spectrum of batteries. Surely if I get a device to work in the volt and amp ranges required by each battery its just a matter of developing the code to switch modes?

I'm not really worried about form factor, just want a one size fits all charger?


texts: Degradation of AC signals as inputs of inverter amplifier circuit

texts:
i recently, did a configuration of an inverter op amp model and i fed it with an analog signal of the form$$S(t)=2sin(1000t\pi)$$

As you may know, the general response of an inverter Op Amp (741), is the additive inverse of the resistance pluggers to the output and the one plugged to the input, times the input signal. When put high values of R2, the oscilloscope wave form change and it looks like a square signal, i wonder if anyone knows why is that, is that behavior related to the system, the IC, the oscilloscope. Is that related with FT in any way?
Thank you very much.

Implemented ciruit: (R2=10k), (R1=100 ohms) (vcc=15)

Input signal:

Output signal:


texts:
Wondering if anyone has tried running an entire program on a PIC32 out of RAM? How would one go about doing that. I understand that you can use the ramfunc keyword to move certain functions to RAM however they still require the copy to be on Flash.

What I would like to do is have a loader program on the PIC32 that can accept a hex file over the serial port etc and rather than writing it to flash have it run out of ram directly.

Ideally I was hoping that by modifying the default linker script you could target a program to run from RAM alternatively if anyone knows how we would patch up a program that was linked to run from flash to run from RAM that could work too

Thanks
Mike


texts:
I calculated the Norton equivalent circuit of a given circuit and I found the result is the same as my book provide, except for the sign.

Here is the circuit:

simulate this circuit – Schematic created using CircuitLab

So the circuit I've to analyse to calculate the Norton current is this:

simulate this circuit

Doing a KCL at the node 1:

\$i_N=-\frac{Av_d}{R}\$

Now, my book says that it's \$i_N=+\frac{Av_d}{R}\$, in fact it draws the current \$i_N\$ in the opposite direction.

My question is: why?


texts: Im trying to understand how a super diode works. I understand that when the input is negative, the opamp output is positive, this forward biases the diode, and sends all of the current to the opamp output. What i dont understand is the simulation results i am seeing. It takes a while for the negative swing to be rectified. This happens regardless of frequency or input voltage. Does someone know why this is happening? I am using an ideal OpAmp in this simulation.


texts:
Assume we are connecting a lamp to a source but line (wire) is so long (for example 20Km):

Will the lamp bright after connecting the source immediately?

how much time it will be?

Can we calculate this delay?

Can the AC or DC source effects on this delay?

The resistance of the wire will increase with increasing the length of the wire, What relation is there between the length of the wire and the resistance?

is there this delay when transmittal of  any resistor in the circuit?(if resistance of resistor be equal resistance of the long wire)


texts:
I am trying to make a logic level converter using transistor BC547.
This is to convert Voltage level of Rpi Gpio from 3.3 to 5V.
I have wired the circuit according to this diagram:

I have done this to convert 3.3V to 5V for  PWM application.
I have connected the circuit to GPIO no 17 and set it high

Questions :

1) why is there no ground in the circuit?

2)I tried to measure voltage at the other end wrt ground, does not show anything.what is the problem?

Thankyou.


texts: Motor choice for a quadcopter, DC coreless or BLDC?

texts:
Ok, I am planning to build a quadcopter by myself. Almost anyone uses BLDCs with ESCs in the tutorials etc. I wonder why a BLDC is more preferable than a similar DC coreless motor. For example I found a 3.7V 50000 rpm DC coreless motor.

Cheaper than BLDCs.
No need to ESC, H bridges are more easy to obtain and use.
Easier to operate.
I am aware a brushed motor will tear by time, however, just ignore
it for now.
Same and even more rpm than a 2400 KV BLDC with a 3S LiPo (2400 * 3 * 3.7)

So, what do I miss?


texts: What is the best way to measure op amp input and output impedance versus frequency?

texts: How do I measure the input and output impedance vs. frequency for an op amp?


texts: SMD solder failure due to probing? How to solve it?

texts:
I was visually inspecting a board that had functional problems, and I have noticed a strange pattern in the pads surrounding the IC.

Upon electrical inspection, there are two pads that are shorted out: the second and third one on the horizontal part right to left.

This is a prototype board and there was lots of debugging and probing the board to solve some problems.

Does it seem to be consequence of mechanical damage, such as external probing with pointy tip, or a defect from the reflow process?

Could just a touch up with the iron reshape the soldering joint? I am afraid the IC pins are bent with the surrounding solder, which would make the repair difficult.


texts:
Can a CSR8645 bluetooth module be used as an A2DP source?

This information is not clear in the datasheet.

Product Page


texts: I want to make an RC skateboard that can easily take my weight and move me around. How do I go about deciding the electric power system?

texts:
Here are the details:
Weight (skateboard + rider) = 75kgs
Required cruising speed = 25kmph
Required range = 15km

Here are my calculations:
To keep a comfy window, assume speed is 30kmph, and since wheel circumference is 23cm, RPM = 2174.

Here is the motor I plan to use:
Turnigy Aerodrive SK3 - 4250-350kv Brushless Outrunner Motor (https://hobbyking.com/en_us/turnigy-aerodrive-sk3-4250-350kv-brushless-outrunner-motor.html)

Thus at 2174rpm, the voltage required to run the motor is 6.2V.

Question 1: Does this mean I cannot go above say 11.1V of LiPo voltage?

Power = (Voltage)x(Current)
Thus this means that at the motor rating of 1000W and our voltage of 6.2V, the current draw will be 161.2A, which is insanely high!

Question 2: What is going wrong in the above calculation?

At the cruising speed of 30kmph, and the corresponding current draw of 161A, the travel time required (to finish travelling 20km) would be 2/3 hours, and therefore the required battery would have to be 108mAh.
Thus, according to my calculations, I will need a 180A ESC and a 2S 110mAh LiPo.
I think I have made a mistake in the fact that I am using a belt drive drivetrain with a 1:3 reduction and I have not accounted for this. Is this the case?

Question 3: Why is the system mass not coming into the picture??
Question 4: How would you design the power system for this project?

It is not necessary to answer all questions, any help will be much appreciated.


texts: How to measure amplitude MHz sine wave with 50 volts common mode

texts:
For a resonant switching power application I need to measure the amplitude of a differential signal that is a sine wave with frequency between 1 and 2 MHz, and amplitude up to about 2 volts. There is also a common mode voltage of about 50 volts to deal with.

I've looked into high voltage difference amplifiers like LT1990, but it seems like the bandwidth is always too low. They cannot handle signals in the MHz range.

It seems like maybe some sort of current mirror circuit might be in order. Maybe someone can point me to an appropriate candidate.

Additional information:

I am trying to build a current monitoring circuit for the resonant tank on the primary side of an LLC converter. The purpose is to monitor the secondary side current by monitoring the peak-to-peak voltage across the resonant DC link capacitor. The LLC converter is driven by a microprocessor with an ADC.

Some of the comments led me to the idea that maybe all that is needed is a blocking capacitor and a half-wave rectifier. Then the peak current could be measured by the ADC, which is probably adequate enough for the purpose.


texts:
I am using a P chan fet as a high side switch.  The data sheet specifies a min Vgs threshold voltage (-0.45V @ 250uA) and a max leakage current (Ids<1uA @ Vgs=0); but does not provide a cut off voltage.    Is there a rule of thumb or equation I can use to estimate the cut off voltage?
Note: The "cut off" voltage is the value of Vgs "below" which the channel is shut off and only leakage current flows. I just need to determine the Vgs required to guarantee the Ids is below some very small number.  It is not practical to get Vgs=0V; so how close to 0V does it need to be?

Maybe cutoff is the wrong term? How can I determine a safe Vgs such that the sub-threshold Ids is small enough, say < 1-2uA?

The question is really about mosfets in general but here is the data sheet link:
NTJD4158C Datasheet


texts:
Many vendors provide both S-parameters and simulation models for their devices. Having encountered device models that when simulated, don't result in exactly the same S-parameters as the touchstone files provided, this leaves me with these interrogants.

What could be the source of the disagreement?
Should S-parameter files only be taken as reference measurements? Or are they valid for simulation too?
Which advantage/disadvantage would the SPICE model present over the S-parameters measurements provided, and vice versa?


texts: Different pin assignment for same regulator

texts:
I got 2 samples of LP2905CZ (TO-92) voltage regulator. First sample is made by TI and second on by On Semiconductor. Links of the datasheets:

On Semiconductor

TI

Due to ignorance, I just read the datasheet of On Semiconductor and started to test the two regulators but later discovered that the TI one does not work. After trying to check all breadboard connections, I thought to check the data sheet of TI one which revealed some interesting finding.

For the On Semiconductor:

PIN 1: Output  PIN 3 = INPUT

For TI:

PIN 1: Input PIN 3 = INPUT

I understand that I should have checked the datasheet before hooking these, but my question is why do the manufacturers don't follow a logic layout (e.g. PIN 1 = INPUT and 3 = OUTPUT like all(!) LM7805)


texts: Using diodes for reverse polarity protection

texts:
I want to protect my circuit against reverse polarity, by simply adding two diodes in parallel between the + and - input cables. So if the polarity is reversed, the current will go through those diodes at high current and blow the fuse. Change the fuse and flip the polarity and everything should be good to go.

The SS34 diode's datasheet says:
Peak forward surge current 8.3ms single half sine-wave superimposed on rated load (JEDEC Method): 80A. I'll be using two of these, so total amperage is then 160A.

That should blow the 20A automotive fuse rather quickly, but is it quick enough? Seems the diodes can only allow such high amperage for 8.3 ms, and I don't know if normal automotive fuses will break so quickly.

Will using two SS34 diodes work?

EDIT: Found this document that has time-current curves for some common fuse sizes.

https://www.littelfuse.com/~/media/automotive/catalogs/littelfuse_fuseology.pdf

Seems a 20A fuse will need a whole 0.2s to blow at 160A. And from what I can tell, normal short circuit current of motorcycle batteries are in this range.

If the fuses really are that slow, then it seems impractical to design a circuit that relies on blowing the fuse for the reverse polarity protection.


texts:
let me say that I have a 40 Years+ experience in digital electronics (I worked for Sperry Univac) but my knowledge of basic analog electronics is almost zero, so I beg you pardon for may possibly silly questions!
I need to build a tool to discharge a lead-acid battery with a controlled current for a specific time. The project is based on an ESP8266 and a DAC, but this is meaningless while, at he very end, I want to control the current through a voltage. I ordered the components to follow this schematics I found somewhere on the Internet:

The theory is that the controlling voltage is fed to the non-inverting input, the voltage drop in R1 is compared and the opamp output controls the gate of the mosfet. The supply of the opamp is 0 and +5V from and independent supply, while the battery is connected to the drain of the mosfet. Unfortunately, the mosfet is always ON.
So, I tested the OPAmp in this way: 0 +5 as supply, 2.5v at the inverting input and a Pot central pin  (spanning from 0 to 5 V) to the non-inverting input. Surprisingly the output of the opamp transitions from ~1.48V to ~4.55V. Almost the same shows (obviously) if I invert the the inputs. My guess was I should have 0-5V (or a bit less), otherwise I cannot figure how that circuit can work. I tested 3 NE5534 but all behave the same, so I assumed I am in fault, not them!
I found in my garbage box a used RC4558 and it too "fails" almost in the same way! Surprisingly, an LM324 works exactly the way I expected: fine, but this totally disoriented me!
While I would like to know why this happens my real and final question is: can an LM324 be used to control the gate of the mosfet? Or, is there an other OPAmp that behaves as I need and is capable to drive the mosfet?
Unfortunately, I don't want to change too many things in this project while I already made most of the hardware and the software!
Tanks in advance!


texts: circuit analysis of DC-source, inductance and modulated resistance

texts:
Here's an interesting problem. Consider a DC voltage source (for bias), an inductor (supply wires, for instance) and a resistor, which changes its resistance as a function of time: \$ R(t) = R_{offset}+R_{mod}\cos(\omega t)\$, where \$R_{offset} > R_{mod}\$. The bias voltage across the photoresistor would cause an AC-current \$i(t)\$ to flow.

simulate this circuit – Schematic created using CircuitLab

Now, to find the unknown AC-current \$i(t)\$, I would solve the following ODE:
$$
V=L\frac{di}{dt}+i(t)R(t)
$$
which can be rearranged to:
$$
\frac{di}{dt}+i(t)\frac{R(t)}{L}=\frac{V}{L}
$$
which enables us to solve the DE using the integration factor method.
$$
i(t)=\frac{\int e^{\int p(t)dt}g(t)dt+c}{e^{\int p(t)dt}}
$$
where \$g(t)=\frac{V}{L}\$ and \$p(t)=\frac{R_{offset}}{L}+\frac{R_{mod}}{L}\cos(\omega t)\$. We get:

$$
i(t)=\frac{\frac{V}{L}\int e^{\big(\frac{R_{offset}}{L}t+\frac{R_{mod}}{\omega L}\sin(\omega t)\big)}dt + c}{e^{\big(\frac{R_{offset}}{L}t+\frac{R_{mod}}{\omega L}\sin(\omega t)\big)}}
$$
which becomes:
$$
\require{cancel}
i(t)=\frac{V}{\cancel{L}}\frac{\cancel{L}}{R_{offset}t + \frac{R_{mod}}{\omega}\sin(\omega t)} + \frac{c}{e^{\big(\frac{R_{offset}}{L}t+\frac{R_{mod}}{\omega L}\sin(\omega t)\big)}}\\
=\frac{V}{R_{offset}t + \frac{R_{mod}}{\omega}\sin(\omega t)} + \frac{c}{e^{\big(\frac{R_{offset}}{L}t+\frac{R_{mod}}{\omega L}\sin(\omega t)\big)}}\\
$$
The first term goes to 0 after briefly going to \$\infty \$ when \$R_{offset}t\$ and \$\frac{R_{mod}}{\omega L}\sin(\omega t)\$ are equal (big L-'hard-start'?). The other term goes to 0 with \$e^{-t}\$ which looks kind of strange, as I would expect some sort of steady-state solution.

Am I asking the wrong kind of question, here? i.e., is the problem badly stated, or am I missing something else?

EDIT: After doing the write-up, I have a suspicion, that:
$$
\int e^{\big( \frac{R_{offset}}{L}t+\frac{R_{mod}}{\omega L}\sin(\omega t)\big)}dt \neq \frac{L}{R_{offset}t + \frac{R_{mod}}{\omega}\sin(\omega t)}e^{\big(\frac{R_{offset}}{L}t+\frac{R_{mod}}{\omega L}\sin(\omega t)\big)}
$$
I will have another look, and correct if needed.


texts:
I am trying to develop a data link on FPGA. The transmitter combines 8 channel input to single output. The Rx has to de multiplex the single channel to 8 bit parallel output.
presently the system is source synchronous. At Rx side I need to find the start of data , for the at Tx side I am sending a frame of "11111111" after every 8 bit serializing.
At Rx side I am trying to detect this pattern , so that Deserialization can begin.
Following is my code:

Tx side:

entity encoder is
port ( data_in : in std_logic_vector ( 7 downto 0);
        data_out_main: out std_logic;
        clk: in std_logic
        );
end encoder;

architecture Behavioral of encoder is

signal s : std_logic_vector( 3 downto 0) := "0000";
signal data_out: std_logic;

begin
 process (clk)
 begin

 if rising_edge(clk) then

    s <= s +1;
    end if;
end process;

process (clk,data_out)

begin

    if rising_edge (clk) then
        if (s = "0000") then data_out <= data_in(0);
        elsif (s = "0001") then data_out <= data_in(1);
        elsif (s = "0010") then data_out <= data_in(2);
        elsif (s = "0011") then data_out <= data_in(3);
        elsif (s = "0100") then data_out <= data_in(4);
        elsif (s = "0101") then data_out <= data_in(5);
        elsif (s = "0110") then data_out <= data_in(6);
        elsif (s = "0111") then data_out <= data_in(7);

        elsif (s = "1000") then data_out <= '1';
        elsif (s = "1001") then data_out <= '1';
        elsif (s = "1010") then data_out <= '1';
        elsif (s = "1011") then data_out <= '1';
        elsif (s = "1100") then data_out <= '1';
        elsif (s = "1101") then data_out <= '1';
        elsif (s = "1110") then data_out <= '1';
        elsif (s = "1111") then data_out <= '1';
        end if;
    end if;

    data_out_main <= data_out;
end process;

Rx side:

entity decoder is
port ( data_in: in std_logic;
        data_out_d : out std_logic_vector( 7 downto 0);
        clk: in std_logic
        );
end decoder;

architecture Behavioral of decoder is

signal s_d : std_logic_vector ( 3 downto 0):="0000";

signal data_out,shift_regi : std_logic_vector( 7 downto 0):= "00000000";

type state2_type is (check2,get_data);

signal state2 : state2_type := check2;

signal convert : std_logic := '0';

signal cnt1 :integer := 0;

begin

process (clk)
begin
        if rising_edge (clk) then
        s_d<= s_d +1;
        end if;
end process;

    process(clk)
        begin

    if(rising_edge(clk))then

        shift_regi(7) <= shift_regi(6);
        shift_regi(6) <= shift_regi(5);
        shift_regi(5) <= shift_regi(4);
        shift_regi(4) <= shift_regi(3);
        shift_regi(3) <= shift_regi(2);
        shift_regi(2) <= shift_regi(1);
        shift_regi(1) <= shift_regi(0);
        shift_regi(0) <= data_in;

case state2 is

when check2 =>
    if(shift_regi = "11111111")then
        state2 <= get_data;
        cnt1 <= 0;
    else
        state2 <= check2;
    end if;

when get_data =>
    if(cnt1 < 8) then
        data_out(cnt1) <= shift_regi(0);
        cnt1 <= cnt1 + 1;
        state2 <= get_data;
    else
        cnt1 <= 0;
        state2 <= check2;
end if;

    end case;

    end if;
    end process;
data_out_d <= data_out;
end Behavioral;

After a lot of try I am unable to get the simulation work properly for this code. Can anyone help me in this regard, I am basically struggling with framing and deframing of data.
The shift register at Rx side is giving correct data but I am unable to deframe it.
Please let me know if i am confusing at any point.
Regards


texts: Powering arduino UNO+microservo off power bank

texts:
Currently, I have a USB powerbank powering my arduino Uno which powers my micro servomotor. I would like to have the motor running for long periods of time (~24 hrs). Sometimes, I am able to achieve this run-time but in most cases the power bank shuts off after about 3-4 hrs of running. I am not quite sure about the variability. It seems that my powerbank has a current threshold (don't know exactly but probably 50-60 mA) and my arduino/servo motor are probably right at that cut-off.

What is the easiest way to handle this problem? Could I program my arduino to draw more current from the power bank (have it calculate pi to many decimal points?)? Or, would just buying a proper grade resistor do the job.

Thanks


texts: MOSFET: How can I find conduction parameter and transconductance based on graphs?

texts:
So I have my graphs (below) with various MOSFET characteristics. I don't know device dimensions or geometry, therefore I can't solve for the 2 directly with an equation. Otherwise I would just do that.

That being said, any ideas on how to solve for transconductance and the conduction parameter based on my graphs?

Conduction parameter:


texts: Transmission lines in USA, household transformers - efficiency and economy

texts:
I want to ask about efficiency and economy of electric power distribution in USA.

I live in Europe and American standards are so weird for me. I was very surprised when I saw this:

See inside main breaker box

Question 1: Every house has separate transformer? 7.2kV overhead transmission lines are present over all streets at small towns and villages? Seriously?

Here where I live - we have 230V and few hundreds of houses are powered from single 3-phase 15000/230V or 30000/230V transformer. Transformers like this have 99% or similar efficiency.

Im sure, that smaller transformer (like American household transformer) wastes much more power, and in addition output voltage is less stable than voltage from high power transformer. By less stable I mean voltage changes with load changes.

Question 2: Is "American standard" much less efficient than European?

I was wondering if 400kVA transformer is cheaper than 20 20kVA household transformers. Other thing is 7.2kV lines everywhere - they need bigger insulators (more expensive).

Question 3: Is "American standard" less cost efficient than European?


texts: Will Kirchoff's voltage law work in a vacuum

texts:
Kirchoff's voltage rule tells us that the sum of voltages around a closed loop in a circuit will equal zero.
If a battery sits on a table, using KVL and treating air as matter with high resistance makes a KVL loop with a voltage gain of the battery's voltage which gets lost to the air.
If this battery floats in a near-perfect vacuum like space that has little matter and no interference will KVL still be applicable to create a "mesh"/loop around the battery?


texts: What mode (CPOL, CPHA) should a programmer of an AVR ATMEGA324PA use?

texts:
I'm using a logic analyser to look at the MOSI, MISO, SCK and RESET lines while an ATMEGA 324PA is being flashed by at Atmel AVR MKII programmer.

The clock starts high, so that makes me think it must be CPOL = 1.

The centre of data bits coincides with the rising edge of SCK.

    -+       +-----
MOSI |       |
     +-------+

    -+   +---+   +-
SCK  |   ^   |   ^
     +---+   +---+

From https://upload.wikimedia.org/wikipedia/commons/6/6b/SPI_timing_diagram2.svg I think this mean CPHA=1.

Is there any documentation which confirms that CPOL=1 and CPHA=1 when programming the ATMEGA324PA?  (I've searched the 600 page PDF and found nothing relating to the SPI for ISP.)


texts: Modbus communication between Arduino and Unitronics Jazz2 PLC

texts:
I am trying to connect Unitronics Jazz2 PLC (JZ20-R16) and an Arduino Uno using Modbus protocol, over RS232 interface. I've got all the required connectors for both Arduino (TTL-RS232 MAX3232 converter as the one below) and Unitronics (JZ20-PRG with JZ10-22-CS10 RS232 connector).

PLC is confogured to be Master, Arduiuno - Slave. Configuration is 8N1. Both units operate very well while connected to ModbusSimulators (from modbustools.com). I connect these devices to the PC using a RS232-USB converter.
The problem is that the PLC require DTR and DSR signals. As you can see from the schematic, the TTL-RS232 converter I've used can not provide such signals.
Here's the screenshot of succesfull data stransfer between the PLC and a PC simulator:
As You can see, CH3/4 (DTR/DTS) are required to be high in order for PLC to communicate over the modbus.But, as I've daid, the TTL-RS232 converter can not give high DTR/DTS signals. Any idea if there is a chance to tweak this ? I've tried to hook DTR/DTS pins of the PLC to +5V ,  no luck.


texts:
In a lot of power supplies the main transformer has several outputs, which are switched via a relay when the supply output exceeds a certain voltage.

Below is a Mastech HY1803 psu schematic - the SK1 relay switches the transformer outputs, while the schematic around the U2A opamp handles the switching after the output voltage exceeds 5V.

The question is - why is that switch needed? Am I understanding it right that it is just to lower the transformer output voltage when the voltage on the psu output is lower than 5V and lower the 2N3055 dropout voltage and, therefore, the power dissipation? Are there any other reasons to do that?


texts: How to code in assembly language for floating point exponentiation?

texts:
I have problem calculating raise a to the power of b (a^b) where b is a floating point number.
In my case, b=-1.45. So the expression is a^(-1.45).
I'm using PIC18F4520 microcontroller and I don't know how to implement it in assembly language or its routine as well.


texts: Reverse voltage PN junction (how it works?)

texts:
I have this block inside my circuit, which is supposed to drawn a current from the main line to the GND whenever there is this signal in the transistor base (simple diagram):

The main line can reach 50V, so I chose a BC546B which has a Vcbo of 80V and Vceo of 60V.

After that I discovered that the main line also could reach peaks of 150V and -50V sometimes. This would damage my BC546. I don't want to put a reverse diode in paralell with the transistor because I really need to block current in both ways. So I thought that maybe putting a series diode with the transistor may help me. So I did this simulation:

It seems to work. Note that when Vce>0 all the main line voltage is accross the transistor. When Vce is < 0 the main line voltage is accross the diode. Since a simple 4148 can hold up to 100V, I could choose a new transistor (MPSA42 for instance) that can hold up to 300V.

Since the diode voltage drop is not an issue because i'm dealing with current direclty, this could do the trick. Although the problem seems to be solved, how can I explain this behavior (that shows the scope)? How can I know where is the voltage drop when more than one PN junction is put in series?

**Corrected picture:


texts: Why the voltage in a circuit changes when the battery has a resistance but not when the battery doesn't has a resistance?

texts:
I was learning the basics of electronics with an interactive simulation of a DC circuit on phet.colorado.edu and I notice this weird pattern.

And also, in real life, with a real battery, what rule applies? Does the voltage between the two sides of a battery also equals the voltage of the battery or does it depends on the resistance on the circuit?


texts: Unexpected plots for active low pass filter response in LTspice

texts:
I was trying to compare the differences between passive and active filters and below is for almost same cut off and by using an ideal opamp:

Above was something I expected.

But then I used a real opamp LM324 and obtain the following outputs:

And for the same circuit if I switch to an opamp called LMC6482 I obtain the following output:

Why with real opamps there is such loss in voltage values or power at very very low freq. unlike in ideal case? Is that something related that Im using single supply? Does the vertical axis show peak-to-peak voltages or amplitudes in LTspice? And why two real opamps give totally different loss?

edit:

The opmap is clipping yes, but why is the amplitude is 0.6V at 0.2Hz in Bode plot which is 1V in transient analysis. And for LMC6482 the amplitude is 0.1V at 0.2Hz in Bode plot which is 1V in transient analysis. There must be a meaning behind these numbers (?) in Bode plots


texts:
I've got a touch sensitive table lamp that dims to three different stages (off, low intensity, mid intensity, full intensity). It has stopped working like that and now just being powered to the mains goes to full intensity, ignoring the touches to the base.

Touch plate connection is good, and I've gone checking connections throughout the circuit, and all seems good too.

I ordered a new dimmer IC and replaced the chip, but the circuit behaves the same. The circuit is very very similar to the one described in the IC sheet here http://www.micropik.com/PDF/tt6061a.pdf

I'm more interested in learning how to debug the circuit than the fix itself. Any help on steps to take would be appreciated.


texts: Jump start car from lithium ion laptop battery

texts:
Building the actual circuits is beyond me at this point, but I'm wondering if it's technically possible to jump start a car from the power contained in a large lithium-ion laptop battery.

For example, I have this laptop battery with the following specs:

11.1V 8.4Ah 94Wh

And I see a car jump-starter product here with the following specs:

Battery Capacity: 12Ah
Gas powered vehicles - 4.0L and lower displacements
Jumpstart your car battery 20 times on a full charge

Would it be technically possible to MacGyver a connection that could jump start a small car (let's say 4-cylinder gasoline for the sake of example) from my laptop battery?

And if not, what is fundamentally different about the type of battery they use in the linked product that causes it to withstand the startup current?


texts:
I'm currently working on writing a simple counter in VHDL, trying to genericize it as much as possible. Ideally I end up with a counter that can pause, count up/down, and take just two integer (min, max) values to determine the appropriate bus widths.
As far as I can tell, in order to get an integer of a given range, I just need to delcare
VARIABLE cnt: INTEGER RANGE min TO max := 0
Where min and max are defined as generics (both integers) in the entity. My understanding of this is that if min is 0, max is 5, for example, it will create an integer variable of 3 bits.
My problem is that I actually want to output this integer. So, naturally, I write
counterOut : OUT INTEGER RANGE min TO max
But this does not appear to be doing what I need. I'm generating a schematic block in Quartus Prime from this, and it creates a bus output from [min...max]. For example, if min = 0, max = 65, it outputs a 66 bit bus. Instead of the seven bit bus it should.
If I restricted the counter to unsigned values I might be able to just math out the output bus size, but I'd like to keep this as flexible as possible, and of course I'd like to know what I'm actually doing wrong and how to do it properly.
TL;DR: I want a VHDL entity to take generic min,max values, and generate an integer output bus of the required width to hold the range of values. How do?
If it matters, I'm using Quartus Prime Lite Edition V20.1.0 at the moment.
Note: I know I can use STD_LOGIC_VECTOR instead, but it is going to simulate significantly slower and is less easy to use than the integer type as far as I have read. I can provide more of my code if necessary, but it's really this one line that's the problem as far as I can tell.
EDIT: It's got to be an issue with the generics, since hardcoding in values gives expected behavior. Here's my generic block in case I've done anything wrong there,
    GENERIC (modulo : INTEGER := 32;
                min : INTEGER := 0;
                max : INTEGER := 64);

EDIT 2:
Complete implementation is shown below
LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;
USE ieee.std_logic_signed.all;

ENTITY Counter IS
    GENERIC (modulo : INTEGER := 32;
                min : INTEGER := 0;
                max : INTEGER := 64);
    PORT( pause : IN STD_LOGIC;
            direction : IN STD_LOGIC; -- 1 is up, 0 is down
            clk : IN STD_LOGIC;
            counterOut : OUT INTEGER RANGE min TO max --RANGE 0 TO 32 -- THIS line is the one generating an incorrect output bus width
            );
END ENTITY Counter;
-- or entity

ARCHITECTURE CounterArch OF Counter IS
BEGIN
    PROCESS(direction, pause, clk)
    VARIABLE cnt : INTEGER RANGE min TO max := 0;
    VARIABLE dir : INTEGER;
    BEGIN
    IF direction = '1' THEN
        dir := 1;
    ELSE
        dir := -1;
    END IF;
    IF clk'EVENT AND clk = '1' THEN
        IF pause = '0'THEN
            IF (cnt = modulo AND direction = '1') THEN
                cnt := min; -- If we're counting up and hit modulo, reset to min value.
            ELSIF (cnt = min AND direction = '0') THEN
                cnt := modulo; --Counting down hit 0, go back to modulo.
            ELSE
                cnt := cnt + dir;
            END IF;
        END IF;
    END IF;
    counterOut <= cnt;
    END PROCESS;
END ARCHITECTURE CounterArch;
```


texts: How can I sync an LED with a camera shutter?

texts:
For an academic research project I need to visualise a fast movement. To do so, I need to sync a small (< 6 cm on the longest side) LED light source with the shutter of a high-FPS camera. The FPS are ~1000fps and the camera offers an 8-pin Hirose connector, of which two pins are described as flash output with optocoupler +/- in the technical datasheet. Space is very limited, so prefabricated solutions like standard flashes cannot be used.
Unfortunately, I am inexperienced with LEDs and camera sync alike, so I'd be thankful if you could point me towards possible solutions to this problem.


texts: SAM-D21 Clock On Demand does not wake up the MCU from Standby

texts:
I am using SAMD21 with FreeRTOS. I am putting the system on sleep level Standby and relying on a TC that works as a systick for the tickless FreeRtos to wake up the MCU however, when the debugger isn't connected (which it shouldn't be) the MCU goes to sleep and never wakes up.

I have tried it with the internal 8M and external 32K and had no lock. The only clock which the CPU can wake up from sleep with is ULP32K which is always on so On Demand doesn't really mean much in that case.

This is the snippets of the TC and my Clock configurations:

// From conf_clock.h
/* SYSTEM_CLOCK_SOURCE_OSC8M configuration - Internal 8MHz oscillator */
#  define CONF_CLOCK_OSC8M_PRESCALER              SYSTEM_OSC8M_DIV_1
#  define CONF_CLOCK_OSC8M_ON_DEMAND              true  // <--
#  define CONF_CLOCK_OSC8M_RUN_IN_STANDBY         false // <--

/* Configure GCLK generator 5 */
#  define CONF_CLOCK_GCLK_5_ENABLE                true
#  define CONF_CLOCK_GCLK_5_RUN_IN_STANDBY        true // <--
#  define CONF_CLOCK_GCLK_5_CLOCK_SOURCE          SYSTEM_CLOCK_SOURCE_OSC8M
#  define CONF_CLOCK_GCLK_5_PRESCALER             1
#  define CONF_CLOCK_GCLK_5_OUTPUT_ENABLE         false

// From tickless.c
void vPortSetupTimerInterrupt(void)
{
    // Struct for configuring TC
    struct tc_config tcconf;
    // Set up configuration values
    tc_get_config_defaults(&tcconf);
    tcconf.clock_source     = GCLK_GENERATOR_5;
    tcconf.counter_size    = TC_COUNTER_SIZE_32BIT;
    tcconf.run_in_standby  = true;                       // <--
    tcconf.clock_prescaler = TC_CLOCK_PRESCALER_DIV1;
    tcconf.wave_generation = TC_WAVE_GENERATION_MATCH_FREQ;

    // Initialize the TC
    tc_init(&tc, TICK_TC, &tcconf);

    // Register and enable callback for freeRTOS tick handler
    tc_register_callback(&tc, (tc_callback_t) xPortSysTickHandler, TC_CALLBACK_CC_CHANNEL0);
    tc_enable_callback(&tc, TC_CALLBACK_CC_CHANNEL0);

    // Set top value equal to one OS tick
    tc_set_count_value(&tc, 0);
    tc_set_top_value(&tc, TIMER_RELOAD_VALUE_ONE_TICK);

    // Enable the timer
    tc_enable(&tc);
}

What I am missing here.

Is this the same issue people are talking here -> http://www.avrfreaks.net/forum/samd21-samd21e16b-sporadically-locks-and-does-not-wake-standby-sleep-mode

Just to clarify, the sleep level IDLE_2 works and CPU can recover from sleep successfully.


texts:
I have the following scheme.

The goal to drive 2 A current through resistor R1.
For example purposes I chose BD743 bipolar transistor which should be half opened and limit current up to 2 A.

Using datasheet I've took hfe as 35.

Using this hfe I've calculated base current:

I = 2 A / 35 = 0.05714... A

Knowing base current I've found base-emitter voltage from datasheet (link above), which is 0.9V

Knowing base-emitter voltage drop I've calculated transistor R2:

R2 = (5.5 - 0.9) / 0.0571 = 80.560

The question: what am I missing? Am I calculating transistor correctly?
With another models of transistors I've had either higher or lower resulting values, but still wrong values.

Update 1

I've made changes in the scheme according to all comments collected. Also I've changed source voltage to mach Vce=4V on the charts for hfe value. Scheme still showing wrong values. New R2 calculated the same way

R2 = (4 - 0.9) / 0.0571 = 54.290

What's wrong now?


texts: Digital Multiplication, Subtraction, Division Integrated Circuits?

texts:
Having a hell of a time finding ICs that offer multiplication, subtraction and division?

Are these functions just a product of adders and not worth the fab?


texts: What is the major difference between the Telegrapher's Equation and the transmission line equation?

texts:
I am confused on when you would use the telegraphers equations vs when you would use the transmission line wave equation.

Telegraphers equations:

Transmission line wave equations:


texts: How to determine direction to read resistor color codes

texts: This resistor can be read either way, so what is the correct value? Does the size of the line have any significance?


texts: Switching a current source with a MOSFET

texts:
Probably is basic electronics, nonetheless every time there is an explanation of using a MOSFET as a switch (both NMOS or PMOS) it is always with a DC source. However, what if I want to drive a LED matrix where the resistances changes?
I know that, if there is an open circuit with a current source, in an ideal case voltage would increase to infinite and there will be an arc to close the circuit. but I can't see how that might affect the circuit.
Here is more or less the idea.

simulate this circuit – Schematic created using CircuitLab


texts:
I am simulating a dense network in NS-3, with around 200 nodes each sending 1MB of data to a single AP/router. Although I have set the CCA threshold to a very low value (so that all 201 nodes are within each others' range, implying that hidden/exposed terminal problems don't occur), I can see that packet loss still occurs (data is not received from all the 200 nodes).

What could be the primary reason for this packet loss? Could collisions still occur in this scenario? One reason could be that 2 nodes stumble upon the same back-off counter, which leads to them transmitting at the same time. Are there any other reasons for collision or any other kind of packet loss?


texts: Find primary current in 3 phase transformer

texts:
I am really confused with the above problem.

I get the logic of the solution

Since,the line voltage ratio is 2. So, current will be half. Thus 50.

But I am confused should we take +30 or -30.

Shouldn't it depend on the connection whether it is Yd1 or Yd11.

Please help me in understanding this concept.

-- EDIT --

I was trying to draw some phasors which I have attached below

Assuming IA winding and Iab winding are in phase

In this case taking Ib = 100 <0 gives me IA = 50 <30

Please help me with current phasors, I am really confused.


texts: Current too low at forward voltage of power led

texts:
I bought some RGB power leds, o.a. a Cree XML.
The spec/description at the (Chinese) site mentioned forward voltage of 3.3-3.9V.
But when driving the led at that voltage I measure much less current than expected. ~0.150mA @ 3.9V instead of ~1A for the Cree led, and something similar for other leds with a max of 700mA.
I need to go above 5V to get the full max current.

Do I misunderstand the meaning of forward voltage? Or is it happening more often that leds are supplied with higher voltage drops (than described).

I planned to use a 5V power supply and a current regulator (mosfet, resistor and transistor feedback) which requires and extra voltage of ~1.2V.
This does not fit if forward voltage is that high.


texts: How does a capacitor resist changes in voltage?

texts:
I was reading about how capacitors work and two sentences confused me:

"A capacitor’s ability to store energy as a function of voltage (potential difference between the two leads) results in a tendency to try to maintain voltage at a constant level."
"When voltage across a capacitor is increased or decreased, the capacitor “resists” the change by drawing current from or supplying current to the source of the voltage change, in opposition to the change."

If the capacitor draws current from the source when the capacitor's voltage increases, how is this considered a form of resistance by the capacitor? I mean - the way I understood it - for the voltage to remain constant in this case, shouldn't the capacitor not draw any current but instead, limit the flow of current through it? I am really confused in here - I feel like I am missing something very fundamental...
Here is the full paragraph:

"Because capacitors store the potential energy of accumulated electrons in the form of an electric field, they behave quite differently than resistors (which simply dissipate energy in the form of heat) in a circuit. Energy storage in a capacitor is a function of the voltage between the plates, as well as other factors which we will discuss later in this chapter. A capacitor’s ability to store energy as a function of voltage (potential difference between the two leads) results in a tendency to try to maintain the voltage at a constant level. In other words, capacitors tend to resist changes in voltage drop. When the voltage across a capacitor is increased or decreased, the capacitor “resists” the change by drawing current from or supplying current to the source of the voltage change, in opposition to the change."


texts: Best practice for anti-aliasing very low sample rates?

texts:
I'm looking to sample a signal using an ADC at very low rates - perhaps once every minute.  What's the best practice for anti-aliasing filtering in this situation?
Obviously, trying to construct a first-order passive filter at the Nyquist frequency produces absurd component values.  Do I use some higher-order (probably active) filter?  Just ignore aliasing and hope it'll go away?


texts: How to create precision reference 2.5 voltage

texts: Can I create a precision reference voltage of 2.5V using 7805 regulator and ordinary resistors(10% error)/diodes or do I need to rely on specific reference voltage generator?


texts: opamp voltage offset balance resistor for varying input Z

texts:
I'm using a non-inverting amplifier to amplify AC signal, datasheet of my opamp say this

  balancing resistor be used to reduce the offset errors, balancing resistor equals the parallel combination of R IN
  and R F

But my input terminal(+) has an impedance (LC filter) which will vary according to the input frequency, now I cant choose the fixed balancing resistor, how to solve this problem


texts:
I recently bought assorted diodes from here, and I'm having trouble identifying part of a reel of diodes. I've taken a few pictures here.

The ruler is in centimeters. The diode markings are all along the diode horizontally. They appear as follows:

(M)K

D35

-20

-08

408

Anyone have any idea what part number they are and if possible a datasheet location? Thanks.


texts: How does this RS-latch with open switches power the lightbulb?

texts:
So I'm trying to learn some of the basics in electrical engineering such that I can better understand how computers work and I'm currently reading about circuits with switches, relays, different gates and how to produce different outputs based on inputs. I don't have a background in electrical engineering and this is the first book I've read related to this stuff so bear with me.

What I'm struggling with is this RS-latch. I understand the logic behind how the output is the input inverted and all that, and how to "activate" the different cords. I think that's basically what the circuit is meant to illustrate. However, what I don't understand is how the lightbulb is lit in this circuit. From my understanding there needs to be a closed circuit with a power source (battery) connected for the electrons to travel through the lightbulb to turn it on. Here, none of the batteries are connected to the circuit and the lightbulb is still lit.

What am I missing here? Is this just an illustration of how the concept of logic gates work and not a complete circuit?


texts: TRS connector for noice cancelling headphones has 5 wires inside cable, instead of 4

texts:
Scenario: 3.5mm TRS audio connector on a pair of Panasonic RP-HC200 Noise Cancelling headpohones is damaged, so I cut it off and I'm going to replace the connector from another pair. After cutting and opening the jacket, I find 5 wires (Red, Gold, Blue, Green, and blue/gold-stripe, as per attached photo). I was expecting a standard 4: one pair for each driver. What is that fifth wire for? Where would I hook it up?

Now, as I understand, "noise cancelling" is usually done with a tiny microphone on the outside of the headphones to sample the environmental sound to produce a "negating" sound via circuitry embedded in the headphones' "cans", but I would have expected all of that to remain inside the headphones, no need to send the signal down the cable. And moreover, since its still TRS (not TRRS), I don't see where it would be hooked up.


texts:
Designing a Relay control from a MCU's GPIO, there are some requirements to take into account.

Coil Voltage: 3V
Coil Resistance: [36-45]Ohm
Relay Voltage: 250Vac // 30Vcc
GPIO Voltage: 3V3
Max GPIO Current 4mA // 20mA (depending on pin)

So, even when relay are THR, I'm looking for SMD transistor instead of THR for controlling the relay.

I would like you to share yout opinion about which would be the best option to make this work.

THR transistor:

BC550
1N2222
1N3704

SMD transistor:

50C02CH

My questions are:

What do you think about used SMD instead of THR?
Will transistor be
able to dissipate power?
MCU, would it deliver enough current to
activate the base?
Do you have any recommendations?

EDIT: Added COIL Resistance [36-45]Ohm


texts: Will this reversible USB-A circuit work safely?

texts:
I'm working on a PCB USB stick with a reversible USB-A connector.  This device should work reversibly with any normal USB host.

I know that it works fine with just the topside, but I realized it could be reversible with the traces added on the bottom.  It is a bit concerning though, because now the "not-used" traces will potentially short to the host-side USB shielding.

I made this circuit that:

Uses diodes to prevent "top" 5V, GND and "bottom" 5V, GND from connecting to each other.
Zener diodes to protect from ESD
The FSUSB42UMX switch to choose between "top" D+/D- and "bottom" D+/D-.  The select is the 5V of one of the sides with a pulldown resistor.

When 5V is present on the "bottom" side, then "bottom" D+/D- are selected.  Otherwise, the pull down will default select to "top" D+/D-.

Is there anything potentially still risky with this approach that I'm missing?

Would the host USB shielding ever normally be something other than Z or GND?

Is there a simpler way to do this?


texts: Help understanding the function of my circuit. (Bug swatter)

texts:
The important thing is the image below. I want to know how it works. Here's what I understand so far.

First I'll identify the pieces:

-The blue "packet" is a capacitor. Its a \$ 0.030 \mu F\$ with 400 V Capacitor.

-The resistance near to LED is a \$560 \Omega\$ resistor.

-The resistor closest to the black diode (close to the capacitor) is a \$22M\Omega\$ resistor; so is the one next to it.

-The resistor next to the transformer is a \$1.2 k \Omega \$ resistor.

-There is a resistor of  \$ 1.2k\Omega\$ stuffed in between the transformer and the diode.

-There is a transistor below the transformer.

-There is a diode between the capacitor and the transformer.

My theory of how this works:

The batteries provide a voltage and this is fed to the transistor. The transistor provides an alternating voltage which is crucial to the transformer. The transformer then intensifies the voltage but this comes out as an alternating current, which is why we need a diode. The diode is connecting to the capacitor. That's all I can tell.

My questions:

What is the function of the capacitor in this circuit and why is it connected to the diode?

My two copper rackets (see first figure) discharge when they hit each other. How does this work?

What function do the resistors have? Are they in series or in parallel?

The product says it could generate a >1000V. Why isn't this harmful to a human being?

Those are my main questions up to now.


texts: How to tell if a capacitor is still good?

texts:
I was replacing a 400 V 120 µF capacitor in a power supply (AC 120 V - 19 V DC 4.62 A).

I tested the dc out end while it was still plugged in and got 0.07 V.

As far as I can tell although being plugged in for 2 minutes (approx) it did not get boiling hot (was barely warm when I reopened it).

Upon visual inspection there does not appear to be any bulging or cracks.

I don't just want to turn it around have it explode, is there a way to check and see its still safe? Is it even likely to be? From what I've read people have mixed opinions but the general consensus is how long vs how many volts, is there a way to be certain?


texts:
This is a circuit with a general, unspecified logic gate fed by a battery. The series \$ L \$ and \$ R \$ represent the wire which carries the current from the battery to the logic gate.

simulate this circuit – Schematic created using CircuitLab

The capacitor is useful during transients, when the logic gate requests more current: it can provide some of the needed current. I have the following expression for \$ I_L \$, the inductor current:

$$I_L = I \frac{\displaystyle \frac{1}{sC}}{\displaystyle \frac{1}{sC} + R + sL}$$

In order to obtain this, I tried to draft the Norton equivalent of the \$ V_S, L, R \$ branch, but it was not useful: given the Norton equivalent current generator \$ I_{NO} = V_S / (sL + R) \$ as the only generator of the whole circuit, the \$ I_L \$ needs the input impedance of the logic gate to be determined.

The above expression instead does not consider that input impedance, even if it seems to be a current divider expression. Even the battery is ignored!

My questions are:

1) can the logic gate be considered as a current source in this situation, as it seems to be from the above expression?

2) Why?

Note: that expression is used to show that \$ I_L / I \$ exhibits a maximum at a frequency \$ \omega = 1 / \sqrt{LC} \$ due to an undesirable resonance between \$ L \$ and \$ C \$.


texts: How to build a simple DSSS (direct sequence spread spectrum) transceiver?

texts:
I have a modern microprocessor (Cortex-M3) with a decent ADC (10-bit 400kSPS or 12-bit 200kSPS).

How to design and build a simple DSSS system for learning purposes? What is the simplest RF front-end that would be needed for this?

The bandwidth is not very important but the system should demonstrate high noise resistance since this is one of the big selling points of DSSS.

EDIT:

I hoped I would get more information on how to proceed on the software side. Like should I do blind correlation of the whole buffer at every sample or are there any "magic" tricks. Maybe I should ask another, more focused question.


texts: Self Resonant Frequency VS Package Size for capacitor

texts:
In general belief, smaller capacitors have better charactristic(more capacitive behaviour) in high frequency than bulky capacitors.

On contrary in one of my RF project (8.5GHz - 9.5GHz) when checking for different package size as bypass capacitor between each of my microwave block (Mixer, Switches and etc) I suspect above rule of thumb

After some inspection on S-Param of Kemet RF capacitors, I noticed that for the same value of capacitor, SRF(Self Resonant Frequency) become higher as package size increases. So a 805 package have higher SRF than 603 and the same rule for 603 and 402 (SRF_603 > SRF_402).

I see the same result in KSIM simulator from Kemet. Here is the summarized result

  10pF C0603 C0G 10VDC-8 C0603C100K8GAC : SRF = 2.089GHz

  10pF C0805 C0G 10VDC-8 C0805C100K8GAC : SRF = 2.399GHz

As can be seen in simulator (and verified by VNA in lab) the SRF not decrease with size instead SRF increases with even more than 300MHz. Why is that the case?

note: I will add the sparam plot soon.
note2: I see same result in reply #11 and other replies on this page.


texts: Help me clarify max ratings and microcontroller pins tolerance

texts:
I use an Arduino Due which is rated 3.3V as a kind of waveform oscilloscope to display signals on my PC. As I knew I had to scale my signals to 3.3V to avoid damaging the analog pins.

Here is the warning on the Arduino Due specifications page:

Warning: Unlike most Arduino boards, the Arduino Due board runs at
3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Applying voltages higher than 3.3V to any I/O pin could damage the board.

Some time ago I used a voltage divider to do this but lately not sure for what reason I used just a 20k resistor.

The Arduino Due analog pin seems fine, I have used it to measure 4.5V (as measured by the multimeter) for quite some time, so can someone clarify to me why the pin or the board is not damaged, what difference makes a voltage with very small current ( 0.265mA in this case ). Does the voltage measured by the ADC on the Due reach the microcontroller? (I suppose yes as the ADC is part of it)


texts: Possible to use external graphics program to design KiCad edge cuts?

texts: Is it possible to create the outline for your PCB using a drawing package and then apply it within KiCad somehow to make your edge cuts? I am designing a board that must fit into a 72 pin SIMM socket and getting the exact dimensions and shapes for the key holes / registration shapes is proving to be a royal pain in the butt!


texts: Understanding available frequencies of quartz crystal from datasheet

texts:
I would like to make an order of crystals from digikey.com. The crystal product series datasheet is at https://support.epson.biz/td/api/doc_check.php?dl=brief_C-2-TYPE_en.pdf

However, I am having hard time to read the data sheet.

I know the crystal has series resonant frequency and parallel resonant frequency.

My targeting frequency should be between them for LC tank circuit.

Here is my question.

I saw the nominal frequency ranges in data sheet.

For example, nominal frequency range : 20 kHz to 120 kHz.

The targeting frequency is 100 kHz.

Then, Is 20 kHz the series resonant frequency?

I would like to know the information of series resonant frequency from data sheet.

Thanks.


texts: Homemade Electromagnet from Microwave oven transformer

texts:
I want to make an electromagnet in order to perform this trick

I have taken the following parts from a microwave oven, and following some instructions i have made the following electromagnet:

I have tried to supply it with power from an 1.5V AA battery then i tried  from 4 x 1.5V batteries in serial then i tried from a 12V motorcycle battery and finally i tried from a 12V car battery. None of them gave enough strength to keep down a spoon inside a soup. They did gave some attraction, but it was too weak for what i needed.

Is it safe to plug it directly in 220V / 50Hz AC?
Is there another way to increase the strength or it is impossible with this equipment?
Is there any safety precautions i need to have in mind?


texts: Understanding how much power a stepper motor draws

texts:
I had a previous question describing a power management system where I was trying to power 7 stepper motors from a wall outlet (with switching power supplies and motor drivers). I realized during this question that I may not understand how to fully calculate how much power, in Watts, a stepper motor will draw.

Setup:

Questions:

1) What is the maximum power that this motor can draw in the described setup? How do the calculations from phase current + suppler voltage + motor parameters (see below) relate to the torque-speed calculations for finding power? E.g. it'd be nice to see something like P = V * I = Torque * Speed so in the future I can estimate missing quantities quickly.

2) Can I limit the power drawn by the motor via the motor driver, by choosing a lower current mode?

3) How does microstepping affect power usage? By default I will probably microstep to 400 steps/rev (by half).

4) Are there any random events (like stalling, first time starting up, etc) that may cause large unexpected spikes in power consumption? And can I count on the PSU + motor driver to protect against it? They claim all sorts of protection features.

References:

Example Motor Specs:

Phase:  3
Step Angle: 1.2°
Holding Torque: 2.0 Nm (283 Oz-in)
Phase Current:  5.8 A
Inductance: 1.85 mH
Resistance: 0.62 Ohm
Rotor Inertia:  0.00818 oz-in-sec2

http://www.americanmotiontech.com/products/productdetail.aspx?model=es-m32320-283-oz-in-3-phase-nema-23-stepper-motor-1000-line-encoder

http://www.omc-stepperonline.com/24-phase-nema-23-stepper-motor-driver-2450vdc-15a45a-256-microstep-m542t-p-293.html


texts: What exactly carries energy in a transformer from primary to secondary?

texts:
Suppose we have applied a voltage to a transformer with an open secondary, we will get a certain flux in the core and a certain voltage at the secondary depending upon the turns ratio.
Now, suppose we connect resistance to the secondary and therefore current will start to flow through it and a reflected current will flow in the transformer's primary winding. But the magnitude of flux remains the same with or without the load.
So my question is: What exactly changes when we connect a load to the transformer, which results in power transfer from primary to secondary? In short, which magnetic parameter is responsible for power transfer between primary and secondary?
As far I understand, change in flux induces a voltage but does not carry any power, and change in flux remains the same with or without the load.


texts:
I am designing a high powered LED driver controlled by a microcontroller.

Now it would be very easy to make a constant current limiter so I don't burn out my LED. I have a bunch of LM317's and putting a resistor between ADJ and OUT gives me a circuit that limits the current.

I can then hook this up to a transistor in series, and use my microcontroller pin to switch it via PWM and get my LED controlled that way.

However I wanted to go a little further to see if I can run my LED's directly and not via PWM (i.e. switching them full on and then full off). This is likely to introduce more complexity into my circuit but I think I would learn something if I can get it to work.

Initially I was designing a variable current source (see here) but I have my LED's on hand now and after some testing I've discovered that they are quite bright even at very low current. It seems to me that linearly controlling voltage via the microcontroller would give me better control over brightness.

How can I provide my LED's with a PWM-controllable voltage? For instance I can get a precisely controlled steady voltage from PWM with a lowpass filter. But I obviously can't supply 1A or more that way. If I make a voltage follower with an op-amp, would I need a specific op amp that is rated for that current? (I have some op amps on order but they are "general purpose")

Could I put the lowpass filter on the side with the load current? (I had always been thinking about connecting the lowpass filter to the PWM signal rather than to the other side of the power transistor)

Any advice that is related to this topic is welcomed


texts: Will NXP NFC PN532 work connected to an antenna grid that is multiplexed?

texts: Can I operate say 36 different antenna monitoring tags against a grid of small 2" x 2" squares by simply connecting the antenna to something like the NXP NFC PN532 through a multiplexer (N-to-1 multiplexer)? Does such a scheme work? If yes, how long will each antenna need to be multiplexed in before a reading can be obtained?


texts: PCB analog and digital split impossible with multiplexers?

texts:
I'm trying to make a PCB that has both an analog part and digital part.

I divided the PCB in areas (sort of), like power supply, MCU (STM32), multiplexers (around 10 ICs, mix of CD4051s, CD4052's and CD4053), and analog components (mostly transistors and capacitors for audio signals).

I know it is advised to keep the analog part away from the digital part, but the multiplexers define all the (flexible) audio routing, so it's impossible to split the PCB in an analog and digital part as all multiplexer ICs handle both digital (the selection of channels) and analog (the channels themselves).

Below is my 'work in progress'... Most ICs are multiplexers (although I want to keep the digital only ICs on the right side, such as shift registers and level shifters).
... and yes, I know I have to move some ICs as they are off the edge now :-)

How can I make sure there will be no noise/crosstalk?

Some ideas I gathered/read about:

Using GND for back (impossible to split in a digital GND and analog GND though)
No parallel digital next to analog signals (also hard, as I use the Manhattan technique, otherwise routing is impossible)
Using GND signals parallel to analog signals (not tried, but cost quite some space to have many parallel signals).
Putting all analog components on one side of the board (not tried, is this a good idea?); not sure how to handle GND in a good manner this way.
Or should I try to separate the board in a digital/analog part, and get long lines from the multiplexers to the analog components and carefully route each multiplexer to minimize crossing digital/analog traces?

Note, I'm mainly using SMD components, and my electronics (as a hobby) skills are not good enough I can do a noise analysis (if there exists such thing practically).

Any better ideas are welcome.

Update

Possibly there is not much of an issue, since the multiplexers only change when the users presses a button (which results in a change of all settings, but this is once per 100 ms in worst case.

So the most 'worry' is that 9V signals (for controlling the multiplexers) close to a (much lower?) audio/analog signal can affect that analog signal. I think not, but I'm not 100% sure.


texts: Why can't I get the expression for this karnaugh map using minterms?

texts:
I am getting ab + bc'd' + ab'c', But I keep failing, it doesn't work for my table.

Can someone explain to me what am I doing wrong? This is using minterms.


texts: Check if a (String) variable is well defined - use preprocessor?

texts:
I am currently developing an Arduino based project involving a password check.

The password is provided as a global variable in the source code. However, the password should only allow certain characters (basically only letters, numbers and just a few special characters).

I want to ensure that no other characters are used - otherwise the code shouldn't compile.

Is there a way (possibly using the preprocessor) to check a String variable for the characters it contains and abort compilation if "illegal" characters are used?

Example code snipplet (probably not necessary, however...):

const String password1 = "test"; // should compile
const String password2 = "%$§~^"; // should NOT compile


texts: Understanding a circuit label in ICSP programmer for atmega

texts:
I am completely new in electronics.  I wanted to make a programmer (or burner) to burn my program in my Atmel16a microcontroller. I found a circuit on the internet:

(source)

Everything is clear, except what is the +5V in the ICSP? Is it same as VCC? Do we have to externally supply 5V to this circuit?

And there are two diodes in the bottom. Are they zener diodes? Do they have special names or characteristics?


texts: When using USB and external power, how should I isolate the grounds?

texts:
I want to connect USB to my ATmega32U4 microctroller, which is powered by an external power supply. I was thinking it might be possible that the USB +5V/GND would be different than the +5V/GND I am getting from external supply. From some reading, this seems unlikely if the external power is a wall wart, but would be possible if the power source was a battery or some non-earth grounded power supply.

The ATmega32U4 has a UGND pin for "USB Pads Ground". Can I connect the USB cords GND wire to this and keep the other GND pins connected to the external power supply? Should I even worry about this if I assume I will never use a battery? (I am planning on always using a wall wart)


texts: How to change input impedance electronically?

texts:
I need to simulate a wire loop in presence of a metal(usually iron) near it and without the metal.
the resistance of the wire is constant (suppose R=20ohm) but the inductance of it changes; The inductance drops when the iron is near. L1=100uH in presence of metal and L2=560uH in absence of it.
I want to remove this loop and use fixed inductors and resistors and a push button to simulate the presence of the metal.
Any Idea that can help?


texts: Noisy top peak of clock signal with CMOS inverter circuit

texts:
I have built this clock circuit (with a 4MHz crystal rather than the 1Mhz shown in the image):

I am concerned about the wave form that I see on my scope. It doesn't look very clean on the top (see image below). I plan to use this as a clock for driving a microprocessor. My question is whether this wave form is 'good enough'? Also, an observation: this noise at the top seems to be caused by some sort of interference. When I physically come closer to the circuit (lean in), the wave form suddenly becomes clean (see second image below). But then after a couple of seconds it starts 'bleeding' the noise and stabilizes into wave form shown in the first image. I am not sure what is going on exactly.

Update
A few comments suggested changing the duration per division on the scope. Setting this to 2ms/div does indeed show some strange ripple:

I disconnected the clock circuit and measured the power supply directly and it too shows a ripple at 2ms/div. So looks like this is a power supply issue? :|
Update 2
It indeed was the power supply. Swapped it out with a 5v Apple iPhone charger and now I'm getting a clean, stable clock signal! Thanks to everyone for the help in debugging this.


texts: Calculating the magnetic flux density in cylandrical coordinates near a neodymium disc magnet

texts:
I am looking for an analysis of a disc magnet, I have heard there are 2D analaysis and 3D. Could someone point me in the right direction of a paper or some academic text on the matter.

I don't mind if the solutions are Cartesian, cylindrical or spherical.

I have seen solutions to solving for the \$Z\$ axis (the axis of magnetisation).

\$B = \frac{M}{2}(\frac{h + z}{\sqrt{r^2 + (h + z)^2}} - \frac{z}{\sqrt{r^2 + z^2}})\$

Where \$B\$ is the magnetic flux density at axial distance \$z\$ from the centre of the magnet, \$h\$ is the height of the disc, \$r\$ is the radius of the magnet and \$M\$ is the remanence field (units in flux-density).

I understand if the only practical solve is a finite element synthesis but an indication of this would be nice.


texts: What would be the process to convert a fan control meant for an AC ceiling fan to one meant for a DC ceiling fan?

texts:
My understanding is that the fan speed controls in wall switches are - unless specifically paired with a DC ceiling fan - meant for AC ceiling fans; and they work by controlling capacitance (I'm a little hazy on that part, but some more detail is over in this answer and this answer.)
In contrast, DC ceiling fans receive full power from the wall, and then utilize some of that power to control the DC motor, and do something after receiving RF signals telling it to adjust the speed and direction.
In particular, my Monte Carlo fan receives RF signals that adjust the dimmness of the light and speed/direction of the fan. The RF controller in the fan uses two wires to talk to the LEDs and 3 wires to talk to the fan.
I would like to explore the possibility of replacing the RF controller in the fan with a thing of my own design that converts 'signal' from the normal wall dimmers (varied capacitance in the case of the fan control, and whatever the dimmer mechanism is for the light) into the 'signal' understood by the fan and the fan's leds.
I presume this would involve measuring what is provided to the leds/fan over those 2/3 wires using a multi-meter (or possibility an oscilloscope?). But I am completely lost as to what thing might be able to turn the signal from the wall into whatever it is that the leds/fan expects.
I recognize that without being able to say for certain what the leds/fan expects this is somewhat difficult to answer, but I am hoping someone would be able to suggest the process by which I can attempt this myself, what additional information to gather, and what device(s) are the most likely needed to do this so I can read up on them.


texts: How to calculate collector current in in a CC amplifier when given current source?

texts:
simulate this circuit – Schematic created using CircuitLab

How do I calculate the \$I_{C}\$ from the circuit above?

I tried using \$KVL\$ using this equation:

$$-100I_{B} - 0.7 +10 = 0$$
$$I_{B} = \frac {I_{C}}{\beta}$$
$$\beta = 100$$
$$-100\frac {I_{C}}{\beta} - 0.7 +10 = 0$$
$$I_{C}= 9.3mA$$

\$I_{C}\$ should be: \$I_{C}= 1.98mA\$

I am unsure on where I went wrong.

Edit: Here is the exact question


texts: 8 layer PCB with Gold plating for each inner layer and immersion gold for all out layers?

texts: it is just a 8 layers PCB with min line 4mil ,6mil holes in a 10 mil pads, Can somebody tell me why we need gold plating for each inner layer while immerison nickel gold for all out layers.


texts: Calculating Power Loss in Switching Power Regulator?

texts:
I am new to the construction of DC/DC power supplies (still a university student) and have built basic supplies using simple linear voltage regulators. I have recently discovered the world of switching power supplies and their increased efficiency (in exchange for higher part counts). This is useful since I am building a project that can use 1.5A peak current at 5V, and I am using ~12V source. Linear Voltage Regulators are, from what I am reading at least, not a good selection for high current applications and heat becomes an issue.

I am wanting to use a TI TPS5420 step down switching voltage converter. I noticed the package (8-SOIC) is much smaller than many high current linear regulators, and that raises the question about heat and power dissapation. Linear regulators can require large heatsinks and larger packages at "higher currents" ( > 1A, but really counts on other factors like input voltage, output voltage, etc).

Can someone help me through how I would calculate the power dissipated through heat on this chip and if I should worry about the IC being too hot to touch? Even though the IC is more efficient than a large linear regulator, its also much smaller and doesn't have a thermal pad -- this makes me worry about how the heat is dissipated. Or am I just overthinking the issue?


texts: Relay: how to calculate the maximum current and switching current

texts:
I need some advices on a design and not values in datasheet.

I know that the carry current is the current that can be supplied continuously to contacts without exceeding the maximum temperature when the contact are not switching.

how can I be sur that contact parts of the relay won't melt or
stick together?
how can I calculate the real temperature at the
contact?
Is the maximum current in a material only determined by
Joule losses?
How can I calculate the maximum switching current possible.

Can someone please gives me some explanations?

thx


texts: Audio amplifier mono operation and power consumption

texts:
I'm looking to use a PAM8406 in Class-D mode, with only the left channel active.

The datasheet doesn't discuss how to handle unused pins for the right channel to "deactivate" that half of the amp.

Should I connect INR, OUTR+ and OUTR- to ground?
If not, what can I do to ensure the right channel isn't operational?

Additionally, I plan to provide 3.3v to the amp to a 2Ω load, which yields about 2W amplification per chart 17:

Given 3.3v at 2.2w, this means an amperage draw of about 666mA (not accounting for efficiency, etc), right?
Is that amperage draw per channel or combined? If it's combined, this means an amperage draw of 333mA in mono mode, correct?


texts: Why does hardware division take much longer than multiplication?

texts:
Why does hardware division take so much longer than multiplication on a microcontroller? E.g., on a dsPIC, a division takes 19 cycles, while multiplication takes only one clock cycle.

I went through some tutorials, including Division algorithm and Multiplication algorithm on Wikipedia. Here is my reasoning.

A division algorithm, like a slow division method with restoring on Wikipedia, is a recursive algorithm. This means that (intermediate) results from step k are used as inputs to step k+1, which means that these algorithms cannot be parallelized. Therefore, it takes at least n cycles to complete the division, whereas n is a number of bits in a dividend. For 16-bit dividends, this is equal to at least 16 cycles.

A multiplication algorithm doesn't need to be recursive, which means that it is possible to parallelize it. However, there are many different multiplication algorithms, and I don't have a clue which one may be used by microcontrollers. How does multiplication work on a hardware/microcontroller?

I've found a Dadda multiplier algorithm, which is supposed to take only one clock cycle to finish. However, what I don't get here is that Dadda's algorithm proceeds in three steps, whereas results from step 1 are used in step 2, etc. According to this, this would take at least three clock cycles to finish.


texts:
While going through topic on ALU design. I came across the point.i.e  Design of Arithmetic Section .But what confused me is what is it's purpose in ALU. I'm thinking it in  terms of performing basic arithmetic operations. I've a picture here. I do understand what is it doing logically but failed to know it's inner.

Illustration of the application.


texts:
I've got a constant current MeanWell LED driver that has 3-in-1 dimming (100k potentiometer, 0-10V signal or 10V PWM), and would like to control the dimming with a microcontroller.

I found a few suggestions online, the simplest one is feeding a PWM signal to an optocoupler connected to directly to driver's DIM+ and DIM- (without any external power supply).

This works because apparently MeanWell dimming circuit looks like this (courtesy of https://www.eevblog.com/forum/projects/mean-wells-2-in-1-dimming/msg1835957/#msg1835957)

simulate this circuit – Schematic created using CircuitLab

However I have a couple of additional requirements

1) I need to limit the maximum brightness to about 75%. Just limiting duty cycle is not enough - I want the driver to never output more than 75% of rated current even in case of software bug/controller failure.

2) I need dimming to be 0% when microcontroller is powered off.

If I was using the single optocoupler schematics, I could use 75K resistor in series with opto output, but  requirement (2) means I have to invert the output somehow with a BJT/MOSFET.

Could you please suggest a schematic and help with components choice?

PWM frequency doesn't need to be high (100-200 Hz is enough). The driver I'm using is ELG-100-C350B
https://www.meanwell.com/Upload/PDF/ELG-100-C/ELG-100-C-SPEC.PDF

FINAL UPDATE:

I created a test PCB that comprises of two dimming channels, one of which is limited by 7.5V Zener diode. The only change from the answer below is that resistor values for R3 and R4 should be > 500K.

It works!


texts: Why should crystal switching be avoided?

texts:
The MC44144 is a gated phase locked loop intended for video applications that is described in its datasheet as "sensitive
to shunt capacitance" and that "crystal switching should be avoided".

What issues might I expect to encounter if I were to attempt crystal switching such as in the schematic below? I understand this would introduce around 5pf to ground in series with the selected crystal, and 5pf in parallel. Would I get non-oscillation, unstable oscillation, drift, ?

Are there any measures I might take to mitigate these effects?

simulate this circuit – Schematic created using CircuitLab


texts: filter between amplification stages of a distortion pedal

texts:
I'm currently building this distortion circuit for a guitar pedal.

I didn't have any 2N5089 transistors so I decided to try using 2N3904s instead. The result has been an extremely harshly clipping output, due to the higher gain characteristics of the 2N3904. In order to tame this harshness, I would like to try and insert a low pass filter before the last stage of amplification/distortion.

So the Blackfire runs essentially:

buffer -> amplifier -> buffer -> dual amplifier -> output

And I would like it to run:

buffer -> amplifier -> buffer -> FILTER -> dual-amplifier -> output

The the stage of the Blackfire that I would like to filter into is based on a canonical multi-stage transistor amplifier circuit, but with the output of the preceding buffer biasing the input of the following transistor such that C1 and the R1-2 voltage divider aren't necessary:

My intuition was to put C1 and the R1-2 junction back in and then add a second capacitor such that C1 would become C1a and C1b. My thinking is that this should further decouple the segment between C1a and C1b, into which I should be able to insert the filter.

However, this has only resulted in a significant loss of signal strength, and no desirable filtering effect to speak of.

I've searched through my archive of guitar pedal schematics and various DIY pedal sites, and haven't been able to find any examples similar to what I'm trying to do. Which leads me to a few questions:

Is what I'm attempting feasible/possible?

If it is, should the filter be active or passive?

How should I go about implementing the filter?

Could someone explain why the filter I've tried to insert hasn't worked?

Thanks much in advance!


texts:
I'm using 220v -> 48v 830 W transformer directly connected to the 220v grid and used to operate my PCB drill.

The issue with transformer is that it's making irregular (with 0.1-2 min interval) sudden "BZZ" noises, accompanies with current spike in input coil and voltage spike in output coil.

Before using it as drill power unit, it was powering a linear voltage regulator supposed to regulare voltages up to 60v, but it was burnt out with one of those voltage spikes.

I wonder what could cause such spikes? Defect in transformer or it is normal behaviour?


texts: How to configure my xbee s2c modules for communicating with arduinos + sensors?

texts:
I have two xbee module (fixed on a development board), these boards does not have a individual access pins to access xbee pins (photo included), but rather a RS232 port.

As for what I have searched, there are two ways to configure your xbee for communication. One is to use software Coolterm from here. Second way is two use XCTU software from here.

Using Coolterm
This requires arduino to configure it. This is the video.
Circuit :

Problem: I am not able to get any reply from xbee, as when i type "+++", result should be "+++OK". But nothing is coming.

Question: Is this the right way to connect arduino and the xbee? I am using single stranded wires, and inserting them directly.

Using XCTU
I do not know if it requires arduino or no. Video I referred
Here I used a RS232 to USB adapter and connected it to the laptop.

My device manager is showing that the COM5 is connected, but in XCTU, it is not able to search my xbee. I tried my both xbees.

Problem: My XCTU is not detecting the xbee connected to the USB port via an adapter which is directly connected to xbee. Arduino is there to provide power only, no other connections are there.

Question: Is this the right way to do it? What do i have to do so that it will be detected.
This RS232 port is creating problems?


texts:
how does this design really improve EFT immunity.

where does EFT come from i guess (VDD) as spike ?
in my estimation i would say (10k+100nF) is more robust from changes on VDD?
in fact the 100pF is low impedance at high frequencies so its shorting reset pin to VDD ?
im really confused ..


texts: ATmega328p Motor circuit resetting the controller

texts: I've made a circuit to run 5V DC motor via ATmega328p  micro controller GPIO as shown below.whenever there is a connection to 5V DC motor, and if it tries to actuate the motor, micro controller will get reset.If there is no motor connection relay will get actuated properly. power supply circuit is also provided. please let me know how to resolve this.


texts:
I want to add a few amps to the output of a stepper motor driver (bipolar 4 wire) with out modifying the interns of the driver.
MY QUESTION IS BEFORE I START I WANT TO ASK IF THERE IS A PROBLEM WITH MY IDEA BELOW AND OR MY SCHEMATIC.
My idea is pull ground +24 and the 4 wires that go to the motor and make them switch some transistors like so. Again I want to know if there is a problem here with component values and what not. I only ask because I tend to dew stupid stuff and i do not want to blow this up.

simulate this circuit – Schematic created using CircuitLab
PS: sorry for caps I keep getting marked down for not having a clear question.


texts: Impedance response of a linear system is independent of the perturbation amplitude?

texts:
I'm studyng electrochemical impedance spectroscopy. On my book there is the sentence: "Impedance response of a linear system is independent of the perturbation amplitude.".

Why? If I have a non-linear system, when I zoom the voltage-current curve, this will be linear and, if I chose a bias voltage \$V_B\$ and if I superimpose a perturbation with small amplitude \$v=v^* sin(\omega t)\$ to \$V_B\$, for the frequency response theorem, I'll get:

$$i(t)=I_B+i^*sin(\omega t+\phi)$$

The impedance is:

$$Z=\frac{\mid V \mid}{\mid i \mid}e^{j(0-\phi)}=\frac{\mid V \mid}{\mid i \mid}e^{-j\phi}$$

Maybe the impedance is independent of the perturbation amplitude because, in the region in which the V-i curve is linear, the ratio \$\frac{\mid V \mid}{\mid i \mid}\$ is constant?

Thank you for your time.


texts: How to replace 6V battery with capacitors

texts:
I have an old motorcycle that runs on 6 volts. There is no electric starter, just a kick starter, and the headlamp is switchable to 'off'. Since this is an older bike that isn't run on the A roads and sits for long periods, I would like to replace the 6V battery with some capacitors. My question is, is it as simple as getting some big capacitors and put them in place of the battery or is there more to this?

I'm aware that using capacitors may result in a pulsating headlamp at low rpm and that it will take a few kicks to get the caps filled up enough to fire the spark plug, but these are all things I'm amenable to.


texts:
I have to start a layout for a PCB soon, and it contains both AGND and DGND. All the components will be on the top layer of the board (micro-controller, voltage reg, SD card, Inst. Amp etc.) so I am wondering is it better to split the top layer to have analog stuff on one side, and digital on the other, with a small 'bridge' over the split, and have a full solid ground plane underneath, or should I also split the ground plane?

At one point I was thinking it might be an idea to have a separate AGND plane and a separate DGND plane, but this doesn't seem like a good idea.

This is my first time dealing with this type of layout, so any advice is very welcome!


texts: How much electric power can we generate at home by use of treadmill like devices and dynamo?

texts: I goto gym to burn about 600-1000 KCal. Instead, can we conserve this and be less dependent on grid for basic lighting and TV and other electrical energy needs at home? What are challenges today?


texts:
I am trying to make separate signal planes in eagle using the polygon tool. The problem is that when I draw the first polygon, regardless of whether I draw it small or large once I name it to GND and hit the "Ratsnest" tool, it will just occupy the whole space of the PCB leaving no space for other planes. How can I fix that?

Also I need one of the planes to be exposed copper, by drawing a polygon on either the bstop or tstop layers, I am getting what I need. The problem is that I don't know how to connect it to another part (say a transistor)?


texts: What module to look for if I want to tell if there's Wi-Fi in the air?

texts:
I'm working on a mobile device. Essentially it has nothing to do with WiFi communication. It doesn't transmit any data over the air.

It has to know however if it's in- or outside of the range of a given WiFi base station. (So basically it must be able to tell whether a WiFi network with a specified SSID is in the air or not, nothing more, nothing less.)

Do I need to put a WiFi module into the device, or are there any PCB components made specifically for this purpose?

(Power efficiency is a very important aspect as the device is pretty small and uses kinetic energy to charge its battery.)

Update: The device has an 8cc harvester that operates around 2 hours a day and is capable of outputting approx. 200 µW during a normal cycle. About once in every second month, the device connects a cellular network and does GPS positioning too. The whole process takes up 2-3 times 30 seconds on average. This results in a total power cons. of ~27mW/h. (If circumstances turn out to be fortunate it might be that this "energy-hungry" operation doesn't need to be done for a whole year or even for a longer period.) WiFi-monitoring described above must be continuous. (Manual charging can be a possible option if necessary, but it would be great to eliminate this circumstantiality.)


texts:
As you see many product and open source using RC servo to build small robot arm.
This question might simple but I think it important to someone that want to build robot arm and decide which type of actuator to use.

1. How RC Servo control position? what type of control used (P,PI,PID)?

As engineer student I learn to control DC motor and learn how it interact with dynamics system like robot arm (manipulator) It take many knowledge about this system and parameter that we try to control to cancel non linear term or at least make it stable. But how RC servo work to control its position? I've try to build robot arm myself (parallelizer type ,15 CM Arm, 3 x MG995) it look stable (not osculate and still actuated) How that possible to design position control that work in wide range parameter?

2. From that type of control, Is that suitable for robot arm or should I use another one?

As you see in many project. it seem to work with manual control. some project make its remember command and repeat it (show some repeatability).
after playing around I see that RC servo cannot compensate steady state error (may be it don't have I term) and it can't read its position it quit dangerous when it start and do rapid move.
In my application I want to control robot by calculate inverse kinematic. after working on it for many days, it seem pretty hard to to tune or calibrate it.


texts: Is this circuit an instrumentational amplifier? Is there an error in the circuit?

texts:
I have found this OP AMPs (ADS1240 from TI) configuration in a datasheet (pg. 21) as an ADC input driver:

simulate this circuit – Schematic created using CircuitLab

Is is supposed to amplify a differential signal coming from a strain gauge bridge. The output is connected to an ADC differential input. I recognize it to be very similar to some part of an instrumentation amplifier. How would you call this circuit? It calls my attention that feedback comes to the positive input of OA1. Is it right? Or maybe there is an error in the datasheet?


texts: Voltage dependent current source in LTSpice

texts:
I'm trying to simulate a voltage dependent current source in LTSpice and I need to have a limited output current. Here is the directive that I am using:

IOUT = LIMIT( K1 * V(1,0), 0.001, -0.001)

In my schematic, IOUT is a regular current source. In this case the current source has a transconductance equal to K1, and samples the voltage across nodes 1 and 0. (And limits the output current to 1mA.)

The weird thing is that my LTSpice directive works fine without the "V(1,0)"

IOUT = LIMIT( K1, 0.001, -0.001)

So does LTSpice not support the V() function or something? How am I supposed to simulate a voltage dependent current source with a limited output current?


texts: Does the length of differential probes matter? Are we possibly measuring something that is not really occurring in the circuit?

texts:
So we're measuring waveforms across certain terminals of an IGBT and noticed that when we extend cables of our differential probes (by about 1.2 meters/4 feet), ringing occurs and we are worried it might possibly destroy the device we are testing.
When we disconnect the said extensions, the length of the cables of the diff probe is about 60cm, and when connected to our test setup, no such ringing is seen.
Did we unintentionally create a tank circuit thru the inductance of the extension cables?


texts: Power switching a higher DC supply from a mcu

texts:
I'm designing a pcb with a 3.3v mcu and some 5.5++V modules on it.
My microcontroller is doing the power-management, turning the 5.5V supply on/off. But I'm not sure how to turn the "high" voltage supply on/off from the mcu(GPIO).

The 5.5V is from a battery and is powering some modules(GSM/GPS) with internal regulators, so supplier encouraged "raw" battery-voltage so they can consume the current they need.
I would like to be able to power these modules off completely(ultra-low-power system) when they aren't in use, often hours/days at a time.

The mcu is also powered from the battery, but via its own 3.3v LDO reg, and should always be powered on.

My knowledge in analog electronics is basic and limiting :p
How to I enable the power-supply to one part of the circuit using my 3.3V mcu?
Is a MOSFET the way to go? I would like to avoid a relay and other large components.

EDIT: Link for the Datasheet(GSM)
The power-off current is 40µA, and would almost triple my idle current consumption if left on.


texts:
I have a rather simple circuit and would like to have it simulated. It uses a Schottky diode from the Misc Devices.IntLib, but it keeps giving me an error. It looks like the .nsx is using incorrect syntax / unrecognised parameter:

Does anyone know why t_measured is invalid or why it is generated?


texts: So I made an error when purchasing a power supply that was far below desired voltage (dc). The power supply I bought certainly produced enough current, however, and I am wondering if it is possible to combine this power supply with a second power supply for the voltage without blowing both of them. I am powering several stepper motors at the same time as well as providing a 10V barrel jack plug in. I don't know if this is possible and instinct is telling me that I will explode one or both of the supplies if I place them in series to the circuit and at least one if they are in parallel but I have no good way of explaining why I feel this way. If someone wouldn't mind explaining if this is even possible, and if not what goes wrong, that would be awesome.


texts: Xilinx ISE - VHDL: Code template to make a ROM

texts:
I am looking for a implementation of ROM using VHDL code.
I´m looking for a piece of code to make this easy example in order to make  a generalization afterwards.
I want to put in the ROM these values: 14,45,67,32,12,64,89,34,54,22
so when the for the address 'x' (the input of the system) you get 'y' (the output of the system):

x  y
1  14
2  45
3  67
4  32
5  12
6  64
7  89
8  34
9  54
10 22

Thank you to all possible references, articles or comments.


texts: How to go about turning on/off a coffee machine with an Arduino?

texts:
I have a coffee machine that has one button. When this button is pressed, the coffee machine will do its thing and automatically shut off after a certain period of time.

I need to use a signal from an Arduino paired with a relay to turn this coffee machine on automatically. I don't have too much experience doing things like this so I need some advice. My instinct is to short out the button in the machine and just turn it on/off with the relay. Would this make sense?

Obviously since coffee machines differ, I'm not asking for the exact process. I would like some advice as to how I would go about doing this on any coffee machine (what to look for, etc). Also, I'd like to know what my other options are.


texts: Correct complementary feedback pair output stage with multiple devices

texts:
I have a doubt about the connection of 0.1-0.47 ohm power resistors in the power stages of an amplifier.

Assuming that the CFP (complementary feedback pair) stage has multiple devices that share the output current, in what configuration should the power resistors be placed?

Another question: are power resistors in a CFP power stage necessary?


texts: understanding a SPI data sheet - FIFO size versus recieve register size

texts:
My question is in relation to the difference between a SPI recieve register size and a FIFO.

For example - I am looking at the SPI datasheet for 2 devices (1) a spi IP for an FPGA and (2) the SPI controller on an MCU.

The datasheet for the FPGA (Altera - soft processor) says that SPI receiving holding register can be up to 32 bits on size. Here is the datasheet for the fpga

Here is the datasheet for the MCU (intel C1000 mcu). It says that it has up to 32 bit frame size.

But it also says that it has "FIFO mode support with 16B TX and RX FIFOs made from 4 entries of 32bits wide" - what does this mean?


texts:
I’m trying to use the interrupts of the 6502 and 6522. I want to read the value of PORTA whenever the “READY” line I have is HIGH.

I think I understood that I have to put the “READY” line on CA1 and that it’ll output some stuff to IRQ when it’s HIGH. Then, in the code, I created a pointer to my interrupt “function” at address fffe and it should execute that code when the “READY” line is HIGH. But it’s not working.

I saw stuff about Interrupt Enable and Flag, but don’t understand how it should work. So if you could explain what I need to do for it to execute code whenever a CA1 is HIGH, it would help me a lot!

I made this project based on Ben Eater's 6502 project and I'm trying to add support for a PS/2 keyboard.

Here's a schematic of the circuit:

I have another 6522 for the LCD screen, the LCD's 6522 is at adress 6000 and the Keyboard's 6522 is at adress 4000.

And you can find the Assembly code at this link:
keyboard.s


texts: Control relay from sensor output when LOW is 0.2V

texts:
I used this circuit as a reference to drive a relay from the digital output of an arduino.          This circuit worked as expected.

simulate this circuit – Schematic created using CircuitLab

Instead of controlling the 2N2222 with the arduino, I then tried to control it with the Panasonic EKMC1601112 motion sensor.  The results were not good: I noticed that the output kept flickering on and off, even with no one in the room.  I measured the output of the sensor and found that it was 5V when "on" and about 0.1V - 0.2V when "off".

I have several questions about this.

1) I'm assuming that 0.1V is enough to turn the 2N2222 on, which causes the flickering behavior.  Does that sound right?

2) I know I can run the output of the motion sensor into the arduino (and I eventually will do that) but how can I adjust the existing circuit?  Is the issue proper transistor biasing?

3) If I'm reading the AtMega328 data sheet correctly, when powered by 5V it recognizes a "low" signal up to 0.3V.  So I should be fine if I use a digital input.  What is normally done...is that "good enough" or would you do something to lower the voltage that appears at the AtMega input?

I'm assuming that the problem totally goes away if I connect the sensor to an analog input on the arduino.  And again I may do that, but I really would like to understand the other issues involved.