texts: Why don't flyback diodes in H-bridge damage power supply?

texts:
I'm currently learning about driving a small DC motor (~ 5V). My research so far indicated that a L298N might be a good choice to quickly get something up and running. However, I'm also trying to understand what is exactly happening (i.e. the internal H-bridge) and there is something which isn't really clear to me. The example circuit in the datasheet on page 6 uses four flyback diodes in a configuration that seems to be common for H-bridges (since other sites recommend similar H-bridge circuits). The configuration, neglecting the L298N for a moment, essentially looks like this:

Now, if I understand it correctly, these diodes provide a path for the motor to keep the current flowing when the MOSFETs get switched off to prevent large voltage spikes. The path for this current however seems to go right through the power source in the reverse direction. That is, reversed relative to the direction of the current that a power source normally supplies. This is indicated in the figure below.

Since I'm relatively new to the world of electronics, this seems like a weird thing to do. I get that this works on paper if the power source is a ideal constant voltage source. But is this actually safe in real life? Let's say I'm using a few alkaline batteries to power my project, then this reverse current seems like recharging. And the Wikipedia page about alkaline batteries says:

  Attempts to recharge may cause rupture, or the leaking of hazardous liquids which will corrode the equipment.

Or what if I'm using a lab power supply or even a voltage regulator as a voltage source? How these reverse current are handled doesn't make a lot of sense to me and I'm worried that I might blow up my equipment..
Could somebody enlighten me about why the circuit above is actually safe? And if it isn't safe, then why are a lot of sites recommending it and what circuit should I use instead?


texts: I was wondering about the copying/moving of data in RAM and I couldn't help but thing about the possibility of having the RAM process basic memory operations such as copying/moving of memory, if there's no need for the CPU to know about the data that's being copied/moved, wouldn't we benefit from having a single instruction that could communicate with the RAM like this?


texts:
I have an Arduino pro mini connected to a Lipo 3.7 battery. I am using a pizzo buzzer connected to a Ultrasonic sensor, the buzzer only makes small clicking sounds, I assume this is due to lack of current, how cany I amplify this.

The Arduino program increase the 'beep' as something gets closer, this is done by setting the pin to HIGH/LOW at increased rates.
I have sampled setting the Pin to High for 1000 ms and I still only get a faint click.
On an Arduino Uno it is much louder.

The final project has to get pinned on to the ear part of glasses (its a school fun project!). So it needs to be small.

Here is a layout of the breadboard I am using.

thanks


texts:
Disclaimer: I'm a total beginner here.

As explained in other answers here, current in a circuit doesn't flow from negative to positive and the direction doesn't matter.

So what should I make of diodes, which are supposed to make the current flow only in one direction?


texts: nRF24L01+ module channel sensitivity and directivity

texts:
I want to start a project where I distribute many nRF24L01+ modules across the house. I am pretty sure someone has done that before. But before I wanted to begin I evaluated the modules using two Arduino UNOs and noticed two things:

Despite the possibility to select one of 126 RF channels. I get no reception on most of them.

First I thought that is because of interference with other WiFi and Bluetooth devices. So I performed a scan using the RF24/Scanner sketch. But it wasn't it.

I made a setup where I placed both transceivers on a table with 1m distance and played Ping-Pong. For each channel I sent out 1024 messages, counted the received messages on the other node as well the returned ACKs and ACK payloads.

The result was rather surprising. Less than a half of all the channels are reliable.

The sad thing is that those channels are also the most commonly used by WiFi networks.
That brought me to the second point. I thought the PCB antenna on the module might be not optimal for all frequencies but for one. So I made some research on PCB antennas. A PDF from Cypress on p. 13 suggests that the PCB antenna is emitting most of its energy to the right. But on my setup I had them facing away from each other.

I rerun the test with a different orientation of the modules. This time facing each other. I expected to get a wider range of channels that are usable this way. But it turned out the other way around.

So now I'm wondering if someone ever noticed the spectral sensitivity and directivity of nRF24L01+ modules and/or can point me to.


texts:
I am rewiring an old used guitar, typically you solder all the grounds to the switch or the pot case, connecting also all the cases to have a common ground.  Has anyone tried a pcboard strip with screw connectors on it to make a single ground?  this would avoid heating the components while soldering.
would the copper strip pick up noise?


texts:
V1=10 V(peak to peak), frequency of voltage source = 1kHz, D1 is a standard 1N4007 Silicon Diode, R1=10 kilo ohm (the load resistor)
In our electrical lab, we were given the circuit shown in the diagram.
I haven't been able to perform this lab due to the pandemic. So I don't have a clear idea of the equipment and what the question means. The question is:
Assume that a BNC cable is connected across the resistor(R1) and fed into the DSO. To get the best possible bandwidth (limited by the scope), we should pick an impedance of 10 k Ohm for the BNC cable?
Yes or No
Could you explain the terms used and what the answer would be?
What I know: In practice, there are 50 ohm and 75 ohm BNC cables.
DSO is an instrument that is used for continuous measurement of properties of signal like voltage and current(unlike the multimeter which reports average values of AC currents). It has a certain range of frequency of input signal that it can measure.


texts: Time Difference between 120 degrees phase shift signal or a 3 phase signsl

texts:
I am trying to create an Arduino 3 phase square wave code, and I wanted to know the time difference between each 120 degree phase shifts.

With some effort I could calculate it to be 6.66 millisecond.
Please let me know if I am missing something, or is the result correct?

Thanks in Advance!


texts: What is this vintage 1979 IC: General Instruments PB8300 in PDIP 14 package?

texts:
In one of the drawers of electronic components I've accumulated since middle school (late 1970s), there is one integrated circuit I have so far been unable to identify (yes, only one* thanks to the internet).
Markings are:
PB8300 - [GI Logo] 7947 TAIWAN
Here's a photograph of the mystery IC:

There are no markings on the underside.  The logo is General Instruments.  I presume that "7947" is the date code, so I located online copies of several catalogs from GI from the 1978-1983 era, and none of the listed product codes start with "PB".  Any ideas what it is?
One possibility:  Some of the parts I have were unused samples that my father got from colleagues at the Zenith Radio Company (later Zenith Electronics), so they might be television-related.
*Transistors are another story entirely.  I have heaps of TO-92 and TO-5 that I have no data on.


texts: Can I attach a nichrome wire to a copper wire using a crimp connector like this ? is there an easier way to achieve this ? Like soldering? The nichrome wire is expected to get as hot as 70 degrees.


texts: Battery voltage changing drastically after use

texts:
I have a NiCd 2000mAh 7.2V battery that drives two motors. If I run the motors for 30 seconds, the voltage reduces from 7.60 to 5V. Once motors are stopped, it takes a minute to come back to 7.50V at most. What's happening? Is there a problem or is this fine?

Guys sorry I forgot to mention one thing,  I designed my own charging Circuit and I think there's not enough current output from the charger. Can that be a possible reason ? What happens when you charge a battery with low current ?


texts: Why do we send some dummy data before sending any command to a microSD card?

texts:
I am interfacing a microSD card with a microcontroller. The following code snippet is taken from Application note 189 (AN189), MMC DATA LOGGER EXAMPLE on page no. 30. The MMC_Command_Exec() basically implements the details to send the appropriate commands to the microSD card.

// Send the SEND_OP_COND command until
// the MMC indicates that it is no
// longer busy (ready for commands).
do
{
    SPI0DAT = 0xFF;
    while (!SPIF) {
    }
    SPIF = 0;
    card_status.i = MMC_Command_Exec(SEND_OP_COND,EMPTY,EMPTY);
}
while ((card_status.b[0] & 0x01))
    ;

I am not able to understand what is the need of sending FF (instruction SPI0DAT = 0xFF;) prior to sending the command using MMC_Commd_Exec?

I have checked that if I remove SPI0DAT = 0xFF;, and put a delay of 200 ms and even more then I never get a correct result.

Also, I can see at other places that this type of dummy data was not sent, for example:

// Read the Operating Conditions Register (OCR).
do
{
    card_status.i = MMC_Command_Exec(READ_OCR,EMPTY,pchar);
}
while (!(*pchar&0x80))
    ; // Check the card busy bit of the OCR

So the simple question is when to send and when not to send.


texts: How to communicate between 8051 microcontroller and PC

texts:
I am working on a project of mine in which I am getting data from multiple sensors into an 8051 microcontroller.

I'm building a car simulator in which I have various car components such as a steering wheel, brake, accelerator and clutch paddles and some other components. I have some sensors attached to each of these components.

The data from each sensor won't exceed more than a byte. In total I have 8 sensors, which makes a total of 8 Bytes data and the data should be transmitted at least 100 times in one second.

Now, I have to continuously transmit the data coming from these sensors to the PC via micro-controller where it would be further processed. Is there any way I can communicate this data to the PC in parallel as I have data coming from a number of sensors?


texts:
I'm using a relay for a PCB, but have trouble understanding some of the specs for the recommended hole drill sizes.
As shown below, the spec sheet indicates a "6-1" diameter hole.
What is the meaning of this 6-1?
It should be something with a diameter of less than 2.22 mm, but it would be helpful to know an exact dimension in case the drawing was not to scale.

https://omronfs.omron.com/en_US/ecb/products/pdf/en-g5v_1.pdf


texts: transient analysis with time varying Resistance

texts: As we know in frequency domain V(s)= I(s)Z(s) then in time domain it should be V(t)= I(t) Convolution Z(t) instead of V(t)= I(t)Z(t) ?


texts: I am trying to make a digital switch for a high frequency digital signal. As it's a voltage controlled switch, I am thinking of just using a MOSFET for it. What I am confused about is the bandwidth of the drain to source path. I mean, what effect it will have on the signal integrity. How can I determine it for a specific MOSFET?


texts:
I'm having a problem using two xbees communicating over a kilometers that I can't solve.

Three weeks ago we checked that these two xbees communicated correctly using two xbee explorers. But last week when we went to install the sensors and boards communication only went from coordinator to router, but not in the other direction, the only difference in these two weeks has been a slight growth from the surrounding vineyard.

My question is:
why would i get 1 way communication only? I'm using same antennas and xbees on both points.


texts: Stepper motor and ULN2803 connected to PSoC4

texts:
I`m a beginner in the microcontrollers world.

I have PSoC4, a stepper motor and ULN2803 and I want to make the stepper motor control. The stepper motor is NMB PM35L-048 unipolar, 5 wires, 24 V motor. In the motor specifications I found that the current is 600 mA.

As far as I know, this current would be too much for the PSoC4 therefore I need to use ULN2803.

I understand that the output current of the microcontroller is much smaller than the current that the motor draws, but why that can damage the microcontroller?

How can I calculate value of the current at the output of the ULN2803? How can I be sure that the motor wouldn't draw too high current even if I use ULN2803?


texts:
Assume I have a system with open-loop gain G = (s+1)^2/s^3. This system has a negative feedback with feedback factor 1.
I plot the open-loop gain by Bode and see that the phase margin Pm = 21.3877 at frequency 1.4656Hz.

Next I calculate closed-loop gain Acl = G/(1+G) and then check the step response of this closed-loop function.
The plot in matlab shows that it rings at 0.21Hz NOT 1.4656Hz.
It really made me confused. Why the ringing frequency is 0.21Hz not at the crossover frequency 1.4656Hz?


texts: Can you integrate an electromagnetic coil (torque rod) to a PCB design in EAGLE?

texts:
I am new in using EAGLE and I am currently trying to design a magnetorquer board. I would like to ask if it is possible to somehow create a solid-core  electromagnetic coil (torque rod) that has known electrical and physical values: core (material, size-diameter and length-)and wire characteristics (number of windings, size, max current carrying capabilities, etc) in such a way to integrate it into my PCB design.
Moreover, i would like to create an air coil electromagnetic core in a rounded square for the back side of the same PCB.
For better undestanding, I will link the ISIS Magnetorquer board with images of its top and bottom views. Therefore, succinctly,my question is I can somehow integrate the electromagnetic coils to the PCB design or in the worse case scenario if there exists a library that include any customizable electromagnetic coils or any pre-made ones.
If not, is there any other program that can do this and that can be accessible to a newbie? (I'm running very low on time so I would take just about anything now)
EDIT:As the question is a little bit abstract(i am truly sorry for that), I will try to make it more specific with the help of your feedback.
EDIT4: In the links above, the electromagnetic coils (torque rods) are mounted on the PCB by using a plastic (or another material) support as seen in the links above, so they are separate components. The question above should have been how do I take these coils into consideration when designing the PCB in EAGLE.
I believed that there is an electromagnetic coils library or that I can design it myself as a part somehow and this is the reasoning for the weirdly phrased question.
EDIT2:


texts: Emulating a Doppler Test under laboratory enviroments

texts:
Background

I intend to test the Doppler effect of LoRa. To do so, I actually had to drive a vehicle at varying speeds ranging from 40-110 kmph at different places on the country while using a low performance SDR like RTL-SDR to capture RF information.

Experiment set up
Insert a node into the car and transmit when approaching, leaving. Capture from RTL-SDR and view the chirps later.

The problems
This method is difficult because driving a vehicle at such speeds has many limitations. RTL-SDR is not best at capturing RF data such as a well tested USRP. However, its difficult to power a USRP SDR pheripheral on the road. Hence the choice to use RTL.

The question
How can I, without driving a vehicle, emulate Doppler effect in the laboratory? What instruments do I need to do this? I know this is possible because I saw a post on twitter which had the following photo. But it stopped its explanation there. I attach that photo to the end of this question as it might give ideas to the person who might answer.


texts:
I have breadboarded a 6/12VAC to variable DC power supply that I want to analyze before hard wiring.  It uses the DB207 bridge rectifier chip and I cannot find a LTspice model for it. Does anyone have a link to one.

Thanks, Sam


texts: How to active limit the current from a DC source

texts:
I have a source with variable power output during the time because it is shared with another devices and this source has not enough power to feed my load (a battery charger for a 1 cell 4.2V lipo) so when battery charger try to get a lot of current it downs de voltage of the source sometimes.
To improve efficiency, I converted the source voltage with a buck dc-dc converter to a lower value, so current can be higher at the load, but this is not enough because load keeps asking for more current so source current increases also.

The ideal solution was a circuit so I can say "let pass all the current you can without dropping more than xx mV"(being this mV are setted by DAC).

¿what is the best way to solve this issue?

This is what I have now:

-SMPS buck power supply to convert 9 to 30Vin to 5Vout.

-PNP limiter programmed by non volatile DAC

Drawbacks of this:

-Non linear current selection. Only the first V select the gain of the circuit (amplification of the transistor). But even this first V doesn't have linear relationship with current.

-Digital feedback: Slow and not precise. I need to read the ADC at the input to know if voltage is dropping to extract a little bit less.

-Max current: with 1R at R1, the max current I can have is around 25mA. Can be enough for many of the situations, but it is reduced. I tried with different R1 values and circuit lost precision and I can't select only a few mA, wich is the main goal.

Edit:

This is how looks like after some improvements:

Edit 2:
Go back to an easy solution. Need to fix the feedback loop of the operational amplifier. If at the input of R2 connects DAC directly works well, but it is needed to use digital loop (DAC/ADC) to maintain voltage at the input.


texts:
I am a bit confused related to the concept of common node in a circuit. I know that all voltages are measured with reference to this node. But here's the problem :

I have some big circuit, containing a few IC, common emitter amplifer to amplify their output, followed by op amp filters. Now I want to know that in my circuit, do I need a single common node, which has the negative terminals of all the batteries included( for ic, bjt and op amp) and the ground terminals of ic's, op amp and bjt ?

Or do i need separate common nodes each for ic's, bjt and op amps ? If so, then will I just connect the output of each component to the input of next via a single wire ?

The circuit will be wired to generate a signal from ic's, amplify the signal using bjt and then filter the output.


texts: Adaptability of DALI Click Board for DALI Power Supply 18V DC, 250mA

texts:
I am developing a DALI Control Device using STM32 board. I have already programmed the board and got some basic results, now I want to test my device with industry standard DALI Control Gear. For that, I need to connect my board to DALI Bus Power Supply as shown in the below figure.

I have bought a couple of DALI Click boards long back for my prototype design purposes. DALI Click board has Opto-coupler TPL181, which has the operating range of (5-48)V Supply voltage, 16mA Forward Current, 1mA Collector current and 3.75kV isolation voltage.

Now, I am confused whether I can use this DALI Click board as DALI PHY Board? Initially, I will be testing and re-programming my device for very few DALI Slaves (maybe up to 10) and according to standard, each DALI Slave can draw just 2mA. So, I am guessing that even if I use 10 DALI Devices I will be drawing 20mA from DALI Bus Power Supply which is maximum Forward current of TPL181 and my STM32 board or DALI Click board will be in no danger.

DALI Click Board has following design

My questions are can I use this DALI Click Board as DALI PHY without causing any damage? and Will the each DALI Control Gear (LED Drivers, Lights etc.) draw just 2mA from DALI Power Supply, Is my guess above correct?

EDIT: The figure shows that DALI Power Supply is 18VDC, 200mA but it is actually 18V DC, 250mA! It was a mistake!


texts:
Looking at the L297 datasheet, it references the use of "fast 2A type diodes".

What does that mean?

Would a 1N4001 qualify? Given the application, I'm assuming that it needs to be a higher power part. Not sure about the "fast" part though. The 4001 datasheet doesn't say anything about that.


texts: Replace inverter manual potentiometer with mcp41010

texts:
I have an 3 phase ac inverter that uses standard potentiometer for motor speed regulation.

The speed reference voltage is 0-10v and i need to control it using arduino. In MCP41010 datasheet I couldn't find the maximum voltage between the potentiometer pins only the supply voltage. Has anyone got experience with this digital potentiometer and if it's possible to be used here?


texts:
I do not understand the precise role of the sensitivity list in a process in VHDL.

For instance, consider an architecture with 3 input signals: a, b, c.

I read that if we write: PROCESS (a, b)

we get that the process is activated by any variation of a and b. Now I have 2 doubts:

1) What does the sentence "a process is activated" mean? A process is a hardware component, like a flip flop. I do not understand the meaning of "activation".

2) If we write inside the process something like: "if c = '1' then ...", the process will depend also on c, although we have inserted only a and b in its sensitivity list. What is the difference? Does it determine a different hardware synthesis?


texts:
simulate this circuit – Schematic created using CircuitLab

I want to evaluate the equivalent resistance. For that, I noticed R1, R2 and R3 are parallel connected resistors, which yields

$$\dfrac{1}{R} = \dfrac{1}{3} + \dfrac{1}{3} + \dfrac{1}{3} = 1 \implies R = 1 \Omega $$

R4 and R5 are also in parallel

$$\dfrac{1}{R} = \dfrac{1}{6} + \dfrac{1}{4} = \dfrac{5}{12} \implies R = \dfrac{12}{5} \Omega$$

Now those groups are in series

$$R_{equiv} = 1+\dfrac {12}5 = \dfrac{17}5$$

I believe that my final answer is wrong. Could you point out where I've gone wrong so far?

Regards


texts: Ground loops with S/FTP Cat6 Ethernet cables

texts:
I have an issue with an Ethernet cable causing a ground loop between my router and a raspberry pi, causing noise on the ground of the DC power of the Raspberry. The router/power supply of the RPi are plugged into different wall sockets.

Since to my knowledge Ethernet itself is decoupled, I assume it is the shielding of the Ethernet cable that causes the problem.
How can I avoid this?


texts: Is possible to use wave guide to decrease beam width?

texts:
If I use a normal 1/4 monopole antenna "30 MHz for example" and cover it with metallic wave guide has a narrow beam width, should the gain increasing according to this formula below?

$$G = 10 \; log \Big(\dfrac{32400}{H \times V}\Big)$$


texts: How do transistors replace the electromechanical switch in an inverter circuit?

texts:
Quoting from wikipedia:

"In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding. A switch is rapidly switched back and forth to allow current to flow back to the DC source following two alternate paths through one end of the primary winding and then the other"

Also given in this article was this example image

Can anyone explain how the transistor does the switching part needed to produce the AC current? If the 2 transistors alone are only needed to convert DC to AC what's the need of a 555 timer as shown in this circuit at http://www.electronicsforu.com/efylinux/circuit/IC.pdf

Thank you.


texts: Are the XBee series 2 modules from Digi compatible with other brands complying with the ZigBee standard?


texts: Current capacity of batteries wired in parallel

texts:
I'm wondering what would happen to the mAh when I connect 2 5000mAh batteries in parallel. Would the mAh over all be 10000mAh?!

simulate this circuit – Schematic created using CircuitLab


texts: Full-bridge rectifier not working as expected

texts:
Im trying to create a full bridge rectifier from a step-down voltage source. The circuit is as follows:

simulate this circuit – Schematic created using CircuitLab

The problem is that I'm only seeing a half-bridge behavior across the capacitor. I am doing this in HSpice, the code can be found below. The end goal is to create a +12 and -12 voltage source, but for now, I'm just trying to get the full bridge rectifier working. Anyone know where I'm going wrong?

P.S. - not including the GND in the secondary side causes a convergence error.

Vsource 1 0 SIN(0 339.41 60)

C1 3 4 6m

Etran 2 0 TRANSFORMER 1 0 10
D1 4 2 dp1
D2 3 4 dp1
D3 4 0 dp1
D4 0 3 dp1

.MODEL dp1 D LEVEL=1

.OP
.TRAN .00066 .033
.PRINT V(1)
.PRINT V(2)
.PRINT par('V(3)-V(4)')
.PRINT V(3)

.END


texts: MPU9250 IMU wearable design considerations and device address problem

texts:
I need to use 12-16 mpu9250 IMU for wearable design. Each IMU will be placed different places on the body. Therefore, I want to read data from each device by using I2C interface. However, problem is all mpu9250 devices have same device address -0x68- for I2C. So far I come up with multiplexer yet multiplexing might not be a good idea with I2C.
I also learnt that SPI will not be a good solution due to cable lengths.
I am looking for suggestions for overcoming device address problem for I2C interface and also system architecture.
(Another IMU is not an option)


texts: Forces, on a wire in motion in a magnetic field?

texts:
When a wire is placed inside a magnetic field, and current starts to flow in that wire, and that wire experiences the Lorentz force = \$ I\ell\times B \$, and begins to move, aside from Induced motional-EMF = \$-vB\ell\$, isn't there another force of repulsion/attraction from the magnetic field produced by the flow of current in the wire?

I'm assuming that since the wire's magnetic field is parallel to the exterior magnetic field, there is no effect?

Also, because of the magnetic field induced by the flow of current in the wire, that would cause a change in flux and an induced \$\epsilon\$ to oppose the change? Even though that wire's induced field is parallel to the exterior field?

Diagram:


texts: How to use comparator functions of 74LS181?

texts:
I'm experimenting with the 74LS181 ALU (see here if you like), and it is going well, but I am unable to figure out how to use the A=B, A>B, and A<B comparator functions.

The datasheet states, "The comparator output (A=B) of the device goes HIGH when all four function outputs (not F0 to not F3) are HIGH and can be used to indicate logic equivalence over 4 bits when the unit is in the subtract mode."

This is rather confusing. If I'm comparing A and B, I would think the A=B output would go HIGH any time A was equal to B. (That is the point after all.) Also, I'm not sure what it means by "...when the unit is in the subtract mode." There is no such mode on this chip.

Further into the same paragraph, it says, "The A=B signal can also be used with the Cn+4 signal to indicate A>B and A<B." That sounds nice, but it doesn't explain HOW to do this. Do I have to send the A=B output signal into another logic gate along with the Cn+4 output signal in order to get a result?

What I am hoping to achieve is to have a simple set of output LED's which I will label A=B, A>B, and A<B such that when I have a 0 on the A inputs and a 0 on the B inputs, then the A=B LED will be lit. And when I have a 1 on the A inputs and a 0 on the B inputs, then the A>B LED will be lit. Likewise for A<B.

This chip is pretty nice ... though a bit quirky at times in my opinion For example, why is it A minus B minus 1 as opposed to just A minus B? What good is A minus B minus 1? But otherwise it provides quite a few useful logic functions into a single chip, so I'd like to figure out this comparator thing.


texts: I am sourcing some parts for an Arduino clone. My question is really simple and I am quite sure that I know the answer, but I wanted to clarify my suspicion. Can I swap out the LM7805 with this part ?? 78M05F


texts: Connecting n bit bus from one component to another

texts:
I think I didn't explain myself correctly. Let me tell you in more detail.

I have 64 blocks: A, B, C, D ..... Each of these blocks is a parallel in parallel out shift register of n bits. The task of these blocks is to shift their contents from A to B, B to C, C to D..etc.

I'm having trouble sending the std_logic_vector type of data from one block to the other.

My code is given below. I've put comments on the lines that have the error.

library ieee;
use ieee.std_logic_1164.all;

entity Shift is

generic (
  Block_Size         : integer := 64;
  Entry_length       : integer := 32
);

port(
  new_entry:      in std_logic_vector(Entry_length-1 downto 0);
  clk:            in std_logic;
  reset:          in std_logic;
  done:           out std_logic
 );

end Shift;

architecture Synchronous of Shift is
component ShiftReg
      generic (
           Entry_length  : integer := 32
          );

      port(
          clk:            in std_logic;
          reset:          in std_logic;
          enable:         in std_logic;
          data_in:        in std_logic_vector(Entry_length-1 downto 0);
          data_out:       out std_logic_vector(Entry_length-1 downto 0)
          );

end component;

signal data_Shift_i : std_logic_vector(Entry_length-1 downto 0);
signal enable : std_logic;

begin
  Reg_i: for i in 0 to Block_Size-1 generate
            i_Reg: ShiftReg
            generic map ( Entry_length => Entry_length
                )
            port map (
                clk              => clk,
                reset            => reset,
                enable           => enable,
                data_in          => data_Shift_i(i-1),  -- error: cannot put (i-1)
                data_out         => data_Shift_i(i)     --error: cannot put (i)
              );
  end generate Reg_i;

end synchronous;


texts: Improve input audio signals to car audio system

texts:
I am helping a friend to solve a low and not so clear sound to his car's audiosystem, when using aux-input in particular. He is getting great signals from CD or Radio, but when he feeds the audiosystem with analog in, it sounds "okay" but low. I have tried different quality cables and signal medias such as mp3, flac, WAV and streaming from youtube. Even with high quality cables and high resolution media files like flac, it did not sound as good as CD. I even tried with different phones, but still not satisfied.

And then I suddenly thought of this idea: "What if we transmit the data from the phone to a DAC (with a mini amp inside) and then further to the car's audiosystem." Would not that be awesome? I understand it is not easy to imagine how it will sound untill you try it. Therefore I drew couple of sketches on how to approach to a solution to the problem and also how to supply the DAC and the phone with power while the phone and the DAC exchanges data. All those three components interacting simultaneously. The third component here is a node (power source) from the car which is then transformed with a buck converter from 12V to 5V. Transformer can supply MAX 15 W power. That means it can supply max 3A current, from P = UI formula.

On second sketch I wonder if it would be necessary with a fuse or resistor next to the phone and the dac (in series with each of those to components, just like pointed on the sketch).

According to a article at digitalaudioreview, the DAC is supposed to drain 4-5mA. Let us say i want to allow it to get max 10mA. R = U/I = 5V / 10mA = 500Ω and the phone to charge at max 1A. R = 5V / 1A = 5Ω

My last question is would it be necessary with a resistor or a maybe a fuse or will those components drain as much as they need so I can expect it to go fine? What else would to do or not do to make this idea easier and realizable?


texts: Question on Resistors for use with 5050 LED Strips

texts:
I bought a set of red and yellow 5050 waterproof LED strips for my motorcycle.  I'm looking to add them to my topcase so it has running, brake and directional lights on it.  Right now, there are no lights on the topcase and I feel like it's hard for people to see the bike's lights below the topcase.

These are the ones I ordered - they are the typical strips with 3 LEDs per segment, that you  can cut every 3 LEds.

http://www.amazon.com/SUPERNIGHT-16-4ft-Waterproof-Flexible-Multifunctional/dp/B00BMHP960/ref=pd_bia_nav_t_3?ie=UTF8&refRID=0T7N95KYJ4TASS7Y4CC4

I want to connect about 54 LEDs in 6 separate strips to my topcase (see attached).  Each side of the topcase will have a set of 3 strips:  1x12 LEDs, 1x9 LEDs, and 1x6 Leds.

I was thinking of wiring them up via a serial-parallel framework, using resistors to both my brake light and running light so the LED strips will be dim for running light purposes, and then go very bright when the brake is engaged.

For each strip (+), I was planning to have it connected both:

the brake line with a directional diode
the running light with a resistor and directional diode

I've been researching LEDs for a couple days now but am finding most of the stuff on the internet is for individual LED diodes - not for strips.  I'm confused because I believe the strip segments have resistors built into them already - hence why they can take a full 12v input.  If they didn't have resistors, they would overheat, no?

My big question is - what resistance resistor should I use to dim the LED strips.  From looking around the net, it seems like 1/4 W would maybe work - but I have no math to back that up.

Furthermore, I'm confused by how LEDs react at their forward voltage rates. For example, I believe the forward voltage rate for red 5050 LEDs is 2.0v.  If supplied that voltage, does the LED light up but just barely?  IE:  Is that the dimmest?  And is that for one LED or for the one segment of the strip (3 LEds)?

Any help on this front would be appreciated.  THank you all.


texts: SMD chip identification - top marking "LA" then sideways "4"

texts: Does anybody know this chip? It gets input from a photo-resistor and triggers a solar light circuit.


texts: How to split 5V USB input into 4 rails (+/-5V, +/-15V)? Problem with combining two virtual grounds

texts:
Problem: I have 5V input from USB, I need to split it into four rails with +/-5V and +/-15V.

Currently done: I have built the following circuit in a breadboard.

I have measured the outputs with a multimeter, and it is worked fine until I have tried to connect virtual grounds together for +/-15V and +/-5V. Then the readings in +/-5V changed to - 4.5V and -14.5V.

So the problem I have is combining two virtuals grounds, if anyone could give me any solutions how I can solve it, please let me know.


texts: Net Tie - Design Rule Error in Altium Designer

texts:
I am designing battery charging system. Datasheet of IC's says "Connection of switching ground to system ground, or any internal ground plane should be single-point." on PCB layout considerations. For this reason I decided to use "Net Tie" between GND and PGND.

I created net tie schematic rectangle(pin1 and pin2) and net tie footprint . You can see below.

When I am using Net Tie on my PCB I have seen Design Rule Problems.

  Clearance Constraint(Collision <0.15mm) Between Pad on TopLayer and Track on Toplayer.

  Short circuit Constraint Between Pad on Toplayer and Track on Toplayer.

Picture 1:

Picture 2:

https://s32.postimg.org/u3ttijdut/footprint.png

Note: Track width is 0.255mm (okey for design rule)

Picture 3:

How can I solve the problems? Do you have any advice for this problem?

By the way I checked this pdf:
-Net Ties and How to Use Them-
https://www.smtnet.com/library/files/upload/NetTies-and-How-to-Use-Them.pdf


texts: How to determine resistor value for given voltages

texts:
I'm not sure how to solve the following problem (I'm not asking or complete solutions, just for a hint on where to start!). I'm asked to find the values for R1, R2 and R3. I know it is a voltage divider and depending on the switch's position, R1 and R3 or R2 and R3 are parallel. But just plugging that in gives me two equations for three unknowns.

The problem has the following specifications:
V1 = 10V DC, R1 + R2 = 10kΩ, when the switch is in Pos.1, voltage at VM1 should be 6V, in Pos.2 4V.

Thank you for your help!

simulate this circuit – Schematic created using CircuitLab


texts:
This is an introductory level verilog course. I'm trying to generate a 8 bit output from 4 bit multiplied with 4 bit. Here is the code I have so far.

    // 4 bit x 4 bit operator
    module bit4x4Operator(
    input [3:0]A,        //this code works when A and B are switched to 7:0
    input [3:0]B,
    output [7:0]P
    );
    reg [7:0] ROM[0:224];
    integer i,k;

    initial
    begin
      for (i = 0; i < 16; i = i+1)
           for (k = 0; k < 16; k = k + 1)
              begin
                  ROM [(i * k)] = (i * k);
              end
     end
     assign P = ROM[(A * B)];

      endmodule

So, the assignment has to be done implementing the ROM[], and this code runs and outputs correctly if the input bits are changed to 7:0, but I'm not sure why that works, and why it can't be the way it is now.


texts: Adding noise to examine a circuit's performance

texts:
I am interested in adding noise in two circuits, to examine the filters I designed, and the overall performance of the circuit.

I currently have in mind two cases, but I believe in both cases the way to achieve what I want is the same.

In case 1, I would like to induce white noise on a thermistor.

In case 2, I would like to induce some ripple before a regulator.

How can this be achieved? I do not have a signal generator at the time, but I would appreciate to also know how one will have helped, and how it would have to be connected, for future usage.


texts: What software can I use to simulate I.B.I.S Models?

texts:
I am trying to simulate a switch (TS5A3154) which is made my Texas Instruments but the only models they have available are ones called IBIS Models.

Now I have done a little bit of research and found that it means Input/Output Buffer Information Specification but I cannot for the life of me find any software that will allow me to play around with the model and give me some meaningful results!

Here is the link to the IBIS files that I wish to simulate and if anyone could offer me any insight as to what software to use to run these models and where I could obtain said software, that would be great!

I would preferably like to know about free software options if they are available because I am a bit of a scrounger like that.


texts: How to calculate the reference voltage when a beta value is given?

texts:
I'm having trouble determine the value of the reference voltage. I don't know what's the beta used for.
These is given: Vbe=Vd1=Vd2=0.75V for 1mA and beta=27 for all BJT.

I did the following, but I'm not 100% sure if it's correct:

Vb=-1m*907=-0.907

Vr=Vb-Vbe=-0.907-0.75=-1.65

Any help would be appreciated.


texts: How is power and communication from USB achieved at the same time?

texts:
I am currently designing a circuit which is powered from USB but also requires the ability to communicate (from the PC) to the microcontroller using UART or rs232 over the USB cable. How is this achieved?

[Edit] I am using the BC04 module (http://www.electrodragon.com/w/index.php?title=BC04#Application) I simply want to be able to send it AT commands over the USB cable


texts: I'm trying to avoid putting a new electrical outlet in. I need to be able to directly plug some devices into the strip which directly plugs into the wall. Is there a power strip greater than 25' that exists. Or is there any alternate solution anyone can think of? I must avoid using a extension cord to plug in the power strip.


texts:
We're currently simulating some Xilinx AXI Stream Finite Impulse Response (FIR) IP cores.

https://www.xilinx.com/support/documentation/ip_documentation/fir_compiler/v7_2/pg149-fir-compiler.pdf

The FIR output is not exactly expected compared pen and paper calculation. Instead, the output has some extra oscillations where none are expected. Before I brute force explore the parameter space of the various generics to understand this effect, I thought I'd reach out here and see if anyone can point me to literature addressing this issue.


texts:
I'm trying to connect atmega328P-PU micro-controller to a 9v battery. I added 20M ohm resistor and got the voltage down to 4.8v, which is in the range of atmega, but it doesn't turn on. I replaced the atmega with LED and the LED is very dim, even though I'm getting 4.8v. When I try to measure current, I guess it's too weak and the LED doesn't glow at all.

As far a I understood, the resistor is stripping down current as well. Why is this happening? How can I keep the original current potential and reduce only the voltage?


texts:
I'm going to use MISO/MOSI/SCK pins of 8 bit AVR with ISP and they should connect to shift  register. They are not going to work simultaneously, but the question is how to isolate  register from ISP?

Update:

U7 is ISP header. U1 is ATTiny45/85. U2 is LED display with shift register M512RD, but I'm mostly sure that the question is more conceptual and doesn't require exact parts.


texts:
If One were to have a Linear Actuator like shown below, could you efficiently use that coil as an accelerator for said Coil gun or Magnetic Linear Accelerator.

I use the picture above as it is out of a pinball machine. The flipper from a pinball machine hits pretty hard. Could i for example take one and just use the rod in the center as a projectile?


texts:
I imagine the answer to this question is no, but I'll give it a shot anyway.

Are there any components that can switch (i.e. open and close a current path between two pins) accurately based on an input voltage, while not themselves consuming any current? Like a mosfet with an accurate threshold voltage and a narrower transition between not-conducting and conducting well.


texts:
Hello I have a question on switch mode power supply diodes.
Usually switch mode power supplies have a rectifying diode at the transformer output.
Do these diodes regulate the transformer output or do they just rectify the output?

For example a transformer with a 12 volt output ac when the diode is put on the output and then filtered charges the capacitor at peak voltage will then be higher

so what i want to know is i have a switch mode power supply that has a winding and the a diode i have never seen before (a black diode with a green band)
and there is no voltage regulator just a 35v  capacitor and inductor and then another capacitor like the circuit shown on the output
So is this type of diode a normal diode how would i determine what it is
(also the SMPS is out of a dvd player)
it has a similar winding but negative. which works but this diode is burned out
I know diodes have a voltage drop that why I'm asking this i just want to substitute it.


texts: Demodulate a AM signal from the carrier using Matlab

texts:
So the AM signal has a bandwidth of 5kHz and the carrier signal is 100kHz.
I demodulate the AM signal by multiplying it to a sin function (sin(2000000*pi), same frequency with the carrier frequency).

This is my take in Matlab for the ideal:

%read in the audio
[y,Fs]=audioread('Signal1.wav');
[gt,fs]=audioread('Signal1_gt.wav');

%demodulation
for t=1:1:size(y,1)
    x=sin(200000*pi*(t/Fs));
    y(t,1)=y(t,1)*x;
    y(t,2)=y(t,2)*x;
end

%low pass filter
h=10*sinc(10*(-10:10));
y1=filter(h,1,y);

%down sample
y1=downsample(y1,Fs/fs);

%plot
t=1:size(y1,1);
plot(t,y1,t,gt);

But when comparing to the ground truth signal, it's far from correct.
Any suggestions?


texts: Protection of non inverting opamp circuit

texts:
Hi
We are building this circuit, and we need to protect the + input of the op-amp from over-voltage. We tried to put two diodes connected to the ground and to the supply source (Zener, regular, schotkkey) but the results we got were weird - the zener gave a steady 2.5V, schotkey and regular gave the same result, zero voltage in negative input and linear voltage at positive inputs. We did got good result (voltage clamped at +/-5V) when we disconnected Vref and R2 from the circuit.

Thank you for your help.


texts:
As far as I have read, the I2C pins are Open Drain or Open collector, but in the PIC18F2550 the datasheet doesnt say anything about those pins, and even says they are a digital output if you select them to be one.
Do I need to add a pullup resistor to the pins so to use them as a digitial output?
If I dont, how do they work in the I2C?
Thanks!


texts: Trouble understanding Loop Filter in a PLL

texts: I'm currently trying to understand the function of a loop filter. But where I'm stuck is that I know the output of the charge pump is a series of current pulses whose width is proportional to the amount of time that the there is mismatch between the reference and the VCO frequency. The problem I find is that each pulse can/should only occur at Fcmp right? So isn't it essentially just PWM? But at the same time, I've heard that the purpose of the loop filter is filter out jitter from the reference. But given that the frequency of the reference is pretty much fixed, I can only see it as an "integrator" or a crude A to D. So, I guess ultimately, what I'm asking is, what am I missing?


texts:
So I got me a raspberry pi 2, and a R2FX, both supplied with 5V, R2FX has a power consumpution of less than 1W.

I own several accumulators from old phones & smartphones which got 3.8V .
Maybe a step-up/boost converter might help (but I got no experience with them).
And it would be nice to know how to charge them of course with a 5V power supply...

My question is, how to put 3.8V accumulators together to get a constant 5V output?


texts: 2 voltage measurements same circuit Arduino Uno

texts:
I want to measure a simple circuit. From the battery it leads to an amperemeter to an 1 Ohm resistor to a 5 Ohm resistor and back to the battery.

The voltage that needs to be measured is that of the battery and the voltage drop over the 1 Ohm resistor to determine the flowing current via I=U/R .

If i connect the circuit to Arduino board and do just one measurement, everything works fine (1.2V battery, 6 Ohm resistance, arduino gives 0.2A for current {after conversion} ), if i connect the second one, it seems that a short circuit via GND is created because the current rises to 1.3A.
Is there a way to solve this?


texts: Problem in deriving Noise Figure for Cascaded systems

texts:
I am trying to derive Noise Figure of Cascaded System. I am making some conceptual mistake somewhere in derivation and getting wrong answer. Can any one please help me figure out where I am going wrong?
Noise Figure of one System
Noise Figure (\$F) = \frac{(SNR)input}{(SNR)output} \$
Also,
\$F = \frac{No}{GNi}\$
\$No\$ = Output Noise
\$Ni\$ = Input Noise
Where, \$No = GNi + Np\$
\$Np\$ = Noise produced by system itself
Thus \$F = 1 + \frac{Np}{GNi}\$
Overall Noise Figure of two cascaded Systems
Let 2 systems be in cascade with gains & noise figure \$G_{1},G_{2}\$ & \$F_{1},F_{2} \$ respectively.
Also following is assumed
\$N_{1}\$ : Noise Input at system 1
\$N_{2}\$ : Noise output at system 1 (same as noise input at system 2)
\$N_{3}\$ : Noise output at system 2
\$N_{p1}\$ : Noise produced by system 1
\$N_{p2}\$ : Noise Produced by system 2
\$G\$ : over all gain of system
Now according to my understanding
\$G = G_{1}G_{2} \$
\$N2 = N_{1}G_{1} + N_{p1} \$
\$N3 = N_{2}G_{2} + N_{p2} \$
\$F_{1} = \frac{N_{2}}{G_{1}N_{1}} = \frac{N_{1}G_{1} + N_{p1}}{N_{1}G_{1}} = 1 + \frac{N_{p1}}{N_{1}G_{1}} \$
\$F_{1} - 1 = \frac{N_{p1}}{N_{1}G_{1}} \$ ..........1
\$(F_{1} - 1)G_{1} = \frac{N_{p1}}{N_{1}} \$
\$(F_{1} - 1)G_{1}G_{2} = \frac{N_{p1}G_{2}}{N_{1}} \$  ..........2
\$F_{2} = \frac{N_{3}}{G_{2}N_{2}} = \frac{N_{2}G_{2} + N_{p2}}{G_{2}N_{2}} = 1 + \frac{N_{p2}}{G_{2}N_{2}} \$
\$F_{2} - 1 = \frac{N_{p2}}{G_{2}N_{2}} = \frac{N_{p2}}{(N_{1}G_{1} + N_{p1})G_{2}} = \frac{N_{p2}}{N_{1}G_{1}G_{2} + N_{p1}G_{2}} = \frac{\frac{N_{p2}}{N_{1}}}{G_{1}G_{2} + \frac{N_{p1}G_{2}}{N_{1}}} \$
using (2)
\$F_{2} - 1 = \frac{\frac{N_{p2}}{N_{1}}}{G_{1}G_{2} + (F_{1}-1)G_{1}G_{2}} = \frac{\frac{N_{p2}}{N_{1}}}{F_{1}G_{1}G_{2}} = \frac{N_{p2}}{F_{1}N_{1}G_{1}G_{2}} \$
\$(F_{2}-1)F_{1} = \frac{N_{p2}}{N_{1}G_{1}G_{2}} \$  ..........3
Let Overall noise figure be \$F\$, then
\$F = \frac{N_{3}}{GN_{1}} = \frac{N_{3}}{G_{1}G_{2}N_{1}} = \frac{N_{2}G_{2} + N_{p2}}{G_{1}G_{2}N_{1}} = \frac{(N_{1}G_{1} + N{p1})G_{2} + N_{p2}}{G_{1}G_{2}N_{1}} = \frac{N_{1}G_{1}G_{2} + N_{p1}G_{2} + N_{p2}}{N_{1}G_{1}G_{2}} \$
\$F = 1 + \frac{N_{p1}}{G_{1}N_{1}} + \frac{N_{p2}}{N_{1}G_{1}G_{2}} \$
\$F = 1 + (F_{1}-1) + (F_{2}-1)F_{1} \$ (using 1 & 3)
\$F = F_{1}F_{2} \$

Since I know Actual formula is
\$F = F_{1} + \frac{F_{2}-1}{G_{1}} \$
It means I am making mistake somewhere please Help me out.


texts: Measure PIC's own VDD-in voltage with ADC

texts:
Processor: PIC18F66K22
Compiler:  C18 (XC8 is fine also)

I've just made (and succesfully tested) code to measure the voltage on AN4 analog pin.

Now I want to try something else, not quite sure if it's theoretically possible.

My test-board has a PIC processor, with VDD,AVVD connected to a supply (ranging from 0(if the battery is empty/disconnected) to 4,2(full battery).

Can I use ADC to measure the VDD(-in) of my board?

Why not?:

It's not an ANx pin, not sure how to make the ADC measure it? (Channel?)
If the voltage on VDD(-in) drops, will my ADC reference voltage also drop?
(So when my PIC only gets 3,3V the ADC will still say it's 100% (as the max Voltage on the chip, also the reference is 3,3V).

Why/what do you ask?:

Can I just measure Channel 30 (VDDCORE)?
Could I set my Vref to Vdd and measure a precision voltage reference with the A/D converter. (Not sure how)
Or I could add a wire from VDD-in to an ANx pin?
Will Internal VREF+ (4.096V) stay 4+V when the VDD-in is around 3,4V? Is there some kind of transformator that makes it so?
Internal VREF+ (4.096V) is a bit lower than the max of the battery (4,2V), does this mean I can damage the ADC? Or just that the result will be max when the battery is full. (4,2V out of 4,096V)

Please mind that my knowledge of Electronics is "low".
I've learnt way more about the software part in my education, but I'd like to know more about (Embedded) Electronics as it's a crucial part in Embedded Engineering. (It's sad how my school doesn't see this.)


texts: How to measure -15V to 0V using a microcontroller ADC?

texts:
How can I measure -15V using the ADC of an AVR microcontroller?

I would like to scale my signal so that -15V signal voltage equals 0V at the input to the ADC and 0V signal voltage equals 5V at the input to the ADC. Vref and Vcc are 5V.


texts: Do I need to provide voltages higher than the battery's present voltage to further charge it?

texts:
Take for example currently my battery is at 25 Volts. I need to increase its voltages, to further charge it. Should I supply it with volts higher than 25?

P.S. I can format the question if it is not clear enough.


texts: How to find the fundamental frequency and present harmonics from a graph?

texts:
I'm having a very hard time understanding frequency and harmonics and now that I'm working on problems, I am completely perplexed. The problem reads as follows -

Assume that string of bits 10101010... (Specific pattern) is the data that needs to be
send from computer X to computer Y in a LAN. The transmitted signal (signal leaving
computer X) for this data is represented in the figure below. Assume a periodic signal.
Identify the fundamental frequency of this signal, and the values for the first seventh
harmonics of this signal. Does this signal present all the harmonics? Only odd harmonics? Or
Only even harmonics?

From what I understand, I have figured out that each pulse has a period of 10ms and the duration of each pulse is 1/2f. Thus the data date is 2f bps.

Now using the the numbers I came up with above, 1/2f = .01 and solving for f, would mean the frequency is 50 Hz. This was the best I could come up with. Did I do this correctly? Also if I did, is the 50Hz the fundamental frequency?


texts: UART reception problem when SysTick Interrupt is enabled

texts:
I'm using a STM32F411RE-Nucleo board and generating a project with Cube MX for System Workbench. The problem is that HAL_UART_Receive function doesn't receive input from the user, even though I don't change any UART, GPIO, RCC or NVIC configuration.

Surprisingly, when I comment two lines in SysTick Interrupt Handler function i.e. SysTick_Handler, HAL_UART_Receive starts working but this comes with another problem.

void SysTick_Handler(void)
{
     HAL_IncTick();
     HAL_SYSTICK_IRQHandler();
}

HAL_Delay() function doesn't work when I disable those two lines. I guess it's because the processor can't handle the ticks.

How to work HAL_UART_Receive and HAL_Delay work at the same time? I'm a bit new in embedded programming and I'm sorry if I couldn't get myself clear.

Thanks.

Edit:

I use this function for receiving user input:

  if( HAL_UART_Receive_IT(&huart2, (uint8_t*) RxMessage, RXBUFFERSIZE) != HAL_OK )
  {
      while(1)
      {

      }
  }

I don't want the timer to run while using HAL_UART_Receive() function, which is the same as HAL_UART_Receive_IT() but with an additional TIMEOUT parameter. As the TIMEOUT might call the SYSTICK interrupt, I decided to use HAL_UART_Receive_IT().

Also, the full assert is OFF, if it's necessary to know.

Other parts of my code are as follows:

#define RXBUFFERSIZE        3
uint8_t RxMessage[RXBUFFERSIZE];

void SysTick_Handler(void)
{
HAL_IncTick(); //enabled
HAL_SYSTICK_IRQHandler(); //enabled
}

void HAL_SYSTICK_IRQHandler(void)
{
  HAL_SYSTICK_Callback();
}

/**
  * @brief  SYSTICK callback.
  * @retval None
  */
__weak void HAL_SYSTICK_Callback(void)
{
  /* NOTE: This function Should not be modified, when the callback is needed,
            the HAL_SYSTICK_Callback could be implemented in the user file
   */
}


texts: battery load percentage - concept/definition

texts:
I have two pairs of bluetooth headsets which are used interchangeably on my smartphone. One of them can indicate the battery level and the other doesn't.

I'm curious to know what this feature is called in order to find more details about it, eventually how it's implemented from a hardware point of view.

The price difference wasn't significant at all, so I'm curious to know why not all manufacturers are implementing it.


texts: I have a LCR meter. In the datasheet there is a measurement frequency given for the inductance measurement. But not for the measurement of the capacitance. Is the frequency for the capacitance measurement not important?


texts:
I have an 8-bit Monocrome TFT (240 x 160) that is driven by MCU-A. I have MCU-B (Arduino) that needs to read the TFT Display in real-time.
So far, I was able to 'split' the Flex wire to both MCU-A and MCU-B.
The objective is for the Arduino MCU-B to read the binary data, send it to the web server and have the 'display' replicated in the web page.

I'm thinking that if Arduino can capture the right bits, the display can be reconstructed in the web UI by the use of some scripting language (process? for example).

So far, I'm getting different sets of bits for each screen at different test sets and I need help on how to do this properly.

The TFT datasheet is located here.


texts: What happens if an LM2576 voltage regulator fails?

texts:
I made a circuit with the LM2576 to convert 12V from my car, to 5V to charge my mobile phone.

But what will happen if LM2576 stops working?
Is that possible that it could damage my mobile phone?

My circuit is the same as the circuit in the datasheet of LM2576.
Components are:

100uF input capacitor
1000uF output capacitor
100uH inductor
Schottky diode

The same as datasheet.


texts:
(This is my first post go easy on me)

I'm trying to use an OTA to simulate a floating voltage controlled resister like explained here, but I cannot for the life of me figure out how the mota model functions.

I'm aware of the general idea of an OTA. Differential input, biasing current multiplier, etc. But I cannot get the model in LTspice to function properly. I thought at first that I was supposed to connect a voltage to the bottom left I/O pin, but then I figured out it was a ground reference...

I'm having trouble getting any output from the OTA, and the current doesn't seem to be entering the biasing input.

Any and all help would be appreciated!

Green V(n010): Differential voltage measured from negative input to positive input

Blue V(n015): Output node of OTA

Red I(R10): Current through R10 (supposedly biasing output current, but not working)


texts: Cheap and easy way of coating breakout board/wires black?

texts:
Part of my housing for an arduino based project leaves the back of a screen breakout board and several wires visible through a grill and I need to cover these in black to minimise visibility as the housing itself is black.

The board itself is already conformal coated out of the box, and the only exposed electrical part would be my solder joints between a ribbon cable and the board.

Is there any type of off the shelf paint (brushed or spray) I can safely use to disguise these? I have some Rust-Oleum Painter's Touch acrylic black from another project, would that be suitable?


texts: How is a semiconductor electrically neutral?

texts:
I'm in the process of learning how transistors works, which starts with understanding how doping is used to create n-type and p-type semiconductor materials.

All the resources I've read sort of explain this the same way, and I'm missing something. P-type semiconductors have extra holes and are predisposed to accept electrons, whereas n-type semiconductors have extra free electrons and are predisposed to donate them. This is the fundamental principle of how transistors work, as I understand it.

But every resource emphasizes that in spite of this both n-type and p-type semiconductors are electrically neutral, which is where I'm lost.
If one has extra electrons, and one is missing electrons, how are they electrically neutral and not charged? I seem to have a block about this or something, I just don't get it.


texts:
I am in the process of getting started with electronics, and I have come to a crossroads. Being a complete beginner, should I start with 32 bit microcontrollers (specifically Atmel's UC3 series), or 8 bit microcontrollers (Atmel's MegaAVR or TinyAVR)?

What programmer would be the best option for the UC3 (as there are many models of JTAG to choose from and I can't figure out if UC3 is ISP compatible)?

What is the learning curve for each if programming in C (I know a very small amount, and was planning on using microcontrollers to learn C), and will the extra complexity of 32 bit be too much to handle without being grounded in 8 bit first?

If I end up going with an 8 bit micro, how much of a difference is there between an 8 bit and a 32 bit micro if I step up to 32 bit later on?

I am planning on using a solderless bread board for prototyping. 8 bit AVR's have a large number of micro's in DIP packaging, but 32 bit UC3's don't seem to have any DIP packaging. I found a site for adapters here http://www.proto-advantage.com/store/product_info.php?products_id=2200114 (Sorry if that link isn't formatted correctly), but is there a better way that doesn't involve soldering extremely small TQFP packages into extremely small holes on an extremely small PCB board?

I am planning on learning electronics and programming through robotics; do 32 bit or 8 bit microcontrollers lend themselves better to that?

There are many tutorials for 8 bit, but good tutorials for 32 bit seem much rarer. Where can I find high quality tutorials for each?

On a side note, what are some good low cost breadboards, and what are the differences between them? They all look the same, their datasheets are very similar, and Wikipedia wasn't extremely helpful...

This is my first question, so I hope I covered my bases. I did a quick search for questions like this and didn't find one, so I hope this post isn't redundant. Thanks for your help! :D


texts: What battery to use for a MG996R High Torque Servo?

texts:
This servo’s operating voltage is 4.8v - 7.2v. The running current is 6v @ 500mA - 900mA, and the stall current is 2.5A @ 6v.

Now, I plan on using this servo 24/7 on my door lock ( this might be a stupid idea, but I am trying to experiment).

What are good battery sources ( or battery capacity to expect to buy ) to use if I want to power this for as long as I can, and on average how often should I expect to change or recharge its battery?


texts: Reversing a throttle position sensor signal

texts: I'm very new to electronics, but I'm trying to reverse the signal coming from a throttle position sensor as well as change the voltage range slightly. The throttle position sensor output signal range is 0.325v-4.75v. How can it be converted to a 4.5v-0.38v signal? I found a similar question on here, but I don't know what would need changed to fit my situation (Reversing a .5-4.5V analog sensor output to 5V-0V) or (How to invert a digital signal). I was told maybe a NPN transistor could be used??? But what size and what size resistors in the circuit to get the range to change? Thanks for any help!


texts: Can a high voltage line kill a person without touching it?

texts:
It's common (for me) to hear that a HV power line can kill a person without touching it "if they entered its field." I'm not convinced by this reason and I think it quite naive and that it doesn't clarify anything.

Warning: Video shows people dying.
Video with information about the accident(longer than the YouTube version)

Here's a video of some workers killed by HV but it's not clear if the scaffold touched the line or just "entered the field of the lines."


texts: Is there any way to feed a signal (line-in) into a mobile phone?

texts:
My first post here, so please point out if I say anything silly.

I'm working on an audio application for mobile phones. At this point in time I'm trying to measure audio latency of a mobile device by feeding colored noise into its microphone jack and having it play it back through the headphones, and correlating/deconvolving the two to obtain the time delay.

This all sounds great on paper, but my problem is that the phone will only accept inputs of certain impedance as microphones, or at least that's my guess. I've tried several microphones (actual transducers), and some of them worked while others didn't. As a rule of thumb, headset-like mics worked. Vocal-like dynamic mics didn't. I'm guessing there has to be enough bias current for a microphone to work. When simply taking an audio cable from the output of a computer or MP3 player and putting it into the microphone jack of the mobile phone it never works. What I mean by that is that the device does not recognize presence of an external microphone and does not switch to it as default input.

I don't know a whole lot about current biases and such, but do you suppose there's a way of building a circuit to somehow "trick" the phone into thinking that there's a microphone plugged into it when it's a line in instead?


texts: I am trying to get a couple of temperatures into my computer. In my little lab I have about 50 thermistors that look a bit like this NTC-Thermistor. I now would like to get the temperature of all of them simultaneously and write their temperature into a file on my computer (Linux, Win, Mac doesn't matter). What possibilities would I have? What costs do I have to expect? Is there any board with a USB-adapter?


texts: Using a 36V battery with step up converter for 48v kit

texts:
I have an e-bike motor ( bbs02 48v 750watts ) which requires a 48v battery. I also have a 36v 13ah e-bike battery. Opening the battery and changing cells connection to make it 48 takes a lot of effort.

Is it a bad idea to use a step-up converter? I have a dc-dc converter which claims to have 95% efficiency. Any downside of using one?

If I would step up the 36v input to 50.92 volts using a step converter, will the e-bike motor meter still read the battery as full? Even if the battery goes below 50%, would the output of the step-up converter still be 50.92 volts? Or would the voltage drop?


texts: Stuck in simulation in LTSpice. ESD Generator

texts:
I am trying to simulate an ESD Generator equivalent circuit. My schematic is attached below. I am not getting any voltage. I am guessing there is something I am missing. But cannot think of one. Please help..

I am expecting an output as following:


texts: How can I find the value of these resistors in this power supply?

texts: I am trying to repair this power supply but these two resistors are burned.   How can I find the value of these resistors?


texts: SAR Circuit in Analog to Digital Converter

texts: Hi, I have been trying to figure out which circuit is inside the SAR block. I've looking in the internet but I haven't found anything yet. Does any one know how the circuit inside the SAR looks like?


texts:
It was told me that a signal sent to the circuit can be rapresented by \$V_{sig}\$ and \$R_{sig}\$, where \$R_{sig}\$ is the internal resistance of signal source.

Now, let's consider that we have a waveform generator and we connect it to an oscilloscope. Then, we send the oscilloscope signal to our circuit where there is a BJT that we want to use an an amplifier.

I think that the signal source is the oscilloscope because I sent the signal to the circuit after I have set the signal amplitude thanks to the oscilloscope..

So the internal resistance of signal source should be the internal resistance of the oscilloscope.. or is it given by "internal resistance of the oscilloscope" + "internal resistance of the waveform generator"? Or am I on the wrong way and it is given by the internal resistance of the waveform generator?


texts:
I would like to design an SMPS to feed an electronic circuit that includes a relay. To study the stability of my SMSP I need to model the relay, but when I go through many relays datasheets, they do not include the value of the inductance, but they only talk about the nominal voltage and the coil resistance.

What about the coil inductance? Why don't manufacturers include the inductance?


texts:
I have the following circuit

I have to determine the zones where the BJT transistor is working according to the input voltage (which as you can see is a triangular wave with 4V amplitude). Now here's the thing: I know that if ui is negative that the BJT is on the open-circuit zone. ´
The problem comes when we have ui positive. We know for sure that emmiter-base junction is direct biased. The collector-base junction can however be direct or inverse biased. Do you have any idea how can I determine the values of ui?


texts: Transistor Voltage Switch - Circuit Help Please

texts:
I've been a lurking mechanical engineer for a while, metal fatigue specialty. I could really use some help with a simple circuit design please!

I have two pseudo-constant voltage sources that can arbitrarily vary between 0 and 10 VDC. I need to route either V1 or V2 to an input leg of a CD4051B multiplexer using a normally-closed switch. Vin pretty much needs to equal Vout, that is, very little voltage drop can be tolerated, say 0.010 VDC.

Also there needs to be a smooth transition between the two voltages, no spikes/overshoot upon activation/deactivation. Switching speed with stable voltages upon switching of < 0.5 millisecond would be grand.

Either +10 VDC or +15 VDC is available, but I would prefer to use the +15 VDC source.

Could someone please guide me down the path to success? I'm guessing some 3904/3906 transistors are involved, but maybe I need FET's? Obviously outside my knowledge base here... :(  Thank you!


texts: Variations in Power Transformer Diagrams for multiple primary windings

texts:
I purchased a power transformer with dual primary windings. Reading up on the correct way to hook up the primary coils in parallel for 115V, the proper way is to connect the coils by tying the positive with the positive and the negative to the negative. This is indicated by the dot on the diagram as well.

However, on the datasheet for the power transformer I bought, the diagram looks different. Each of the terminals is labeled with a voltage.

How do these two diagrams map to each other?

Is the correct connection for parallel to connect 115V to 115V and 0V to 0V, (1 -> 4 and 2 -> 3), or is it connecting the 0V terminals to the opposite 115V terminals (1 -> 3 and 2 -> 4)?

Here is the product listing in question.

http://www.jameco.com/z/QC6630-R-54VA-Quick-Connect-Power-Transformer-36vct-1-5A_104417.html


texts: Simple method to find open fault in three wire power cable?

texts:
I have a three wire power cable - live, neutral and ground. My multimeter shows no fault with the neutral and ground wires, but there is an open fault on the live wire. Nothing suspicious upon visual inspection.

How can i find the location x of the fault? The cable is about 1.5 meters.

L-------x---------L

N-----------------N

E-----------------E

Related questions:

How to calculate the earth fault current in a transmission system with no ground wire?
Fault finding (Basic) [closed]


texts: Eliminating motor noise with hall effect sensor?

texts:
I'm trying to build an indexing system for a model railway turntable. I want to use a hall effect sensor as a tachometer for a gear, and control the motor with an Arduino and an H bridge. I have a cheap H bridge motor driver board from Ebay and an Arduino Uno and a latching hall effect sensor from Sparkfun. With the turntable motor I have to use, I am getting tons of electrical noise. It is triggering the interrupts on the Arduino any time it's on. What can I do to reduce this?

Edit:

Here is the schematic for the hall effect sensor portion of the circuit. Sensor Datasheet

simulate this circuit – Schematic created using CircuitLab

I'm using a motor driver board, not the official Arduino motor shield, to drive the motor. It doesn't have a data sheet to my knowledge  but here is an Amazon link.

The motor I am using is an Atlas HO turntable motor, and according to the part number on the side, I found this data sheet. [It won't let me post a link because of my reputation being less than 10. The motor is an FK-280PA.]


texts:
If you have a SPI bus with only one device can you connect chip select to ground?

I'm new to electronics, tinkering with a custom split keyboard design. I have a micro controller in the one half and a MCP23S17 IO expanded in the other. I have a five strand cable to connect the two. I think I need MOSI, MISO, SCK, Ground and 5v+. Do I need a dedicated chip select, or can I connect chip select to ground (pulled low?) if the only spi device on the spi bus in the IO expander?


texts:
I am trying to simulate a transformer with a turn ratio of  1:1. The voltage of the primary and secondary are equal but I am getting a different current in the winding (why?). Also I see some DC offset in the primary current (why?). Please correct me if I am simulating design wrong.
Thanks


texts:
I was looking to run the simulator for an AVR controller, but when I went to set my debugging tools as outlined in this video- http://www.youtube.com/watch?v=9QlDSNeuAdY

I do not have anything show up under the drop down both on my PC and Mac running windows in Parallels.

Below is a screenshot.

Are there any suggestions to resolve the issue?


texts:
simulate this circuit – Schematic created using CircuitLab

Hello i am learning about filters and make this circuit in many circuit simulators.
When i increase the R2 resistance the voltage across is increased and when i decrease it is decreased as well.
Shouldn't the voltage be the same always,since the R2 is in parallel.Or i have understand wrong the series and parallel connections?


texts: Where does the indicated negative voltage terminal lie on this circuit?

texts: Does the negative voltage terminal lie after the 150v source ?


texts: Why does this 7-Segment Display not function properly?

texts:
I've provided details in image.

Although, I'll once again provide in text:

  IC        : 74LS47N (Binary to 7-Seg Display)

  7 Segment : Common Anode

  M.S.B     : D

  L.S.B     : A

This is how absurd OUTPUT is displayed by 7-Seg Disp:

  INPUT (D,C,B,A to IC)___OUTPUT (7-SEG DISP)

  DCBA

  0000_______________2

  0001_______________3

  0010_______________2

  0011_______________3

  0100_______________b

  0101_______________7

  0110_______________b

  0111_______________7

  1000_______________c

  1001_______________ɔ <--- (-_- !) lol

I've edited the pics, so that you may see the wirings clearly.
As you can see the problem in the image itself,(i.e. the output of 7-Seg does not matches with the input to the IC).

  Note: There is no problem with my connections. They are exactly as shown below:

I did the connections 5 to 6 times all over again, but all it shows is absurd and illogical results


texts: I work with SLED (superluminiscent light-emitting diodes). Datasheet said me that I must to avoid electrostatic discharges when I work with SLED. So I want to connect cathode with anode of SLED and will begin to mount SLED. It will be enough for safe operations (without electrostatic discharges) with SLED?


texts: How to find power displacement in transistor npn?

texts: My circuit has a Vcc of 18v and a Vee of -18 ,Rc 330 ,Ic 20 mA ,Vce 8.58V, Re 470, Rb 5.1k, Just want to know the formula for power dissipation for Rc and within the transistor, Please.


texts: Short cables between various Arduinos (I2C)

texts:
I hope this question is not too broad. I am checking for quite some time for cables and connectors to be used on my (future) project.

I checked RS232, 4-pin, molex, etc. but I think they do not fit quite well for what I'm looking for.

What I want is a communication:

Between 1 and around max 5 Arduino's
One is the controller
Others are slave
All messages are between controller and slave (and vice versa)
Communication needs to be fast (small packages, like 4-10 bytes, less than 1 ms, preferably less).

What I want are connectors that

Can pass I2C
Can pass +5 and GND (max 12 V  / 1 A, probably less than 1A), so I can power several Arduinos with one cable per Arduino (from one Arduino to another), with just one power adapter (12V/1A)
Can be built (easily) in a panel/mount/DIY/enclosure box
Cheap if possible

And accompanying cables that:
- are short (I want to stack the Arduino's on top of each other but each in a separate enclosure), so 5-10 cm is enough.
- are cheap if possible

If there is another solution it would even be better.

If there is a better way instead of I2C for such short distances to send messages back and forth between Arduinos I'm also interested to know.


texts: Considerations for a motor resisting a human grip

texts:
I'm trying to replicate this project at home, wherein strings attached to fingers and pulled by servos are used (instead of difficult pneumatics) to simulate an object in a glove as a version of haptic feedback. For example, if I wanted to simulate a cube in virtual space, I would not allow the user to bend the glove past the dimensions of the cube. To accomplish this, I have two ideas.

The first is to use a linear motor to resist on it's own. I've chosen to use a linear motor based off the info found in this question, but if you have other recommendations, let me know.

Alternatively, I'm worried that having a user pull against it will weaken the servo and shorten it's lifetime, so instead I should use a clamping mechanism on the string. However, is this a legitimate concern in the first place?


texts: Electrostatic properties of plastic enclosures

texts:
I'm building a small project and have some electronic (IC) boards I would like to pack in a nice enclosure.

I made an enclosure from PMMA (Acrylic) that looks nice but someone told me that it is not good practice as PMMA is like a 'magnet' to static electricity. I then dug some more and found out there are anti-static PMMA boards for this application. Just when I wanted to order someone told me to use poly-carbonate instead (which is much more expensive).

What would be the right material for building an enclosure? The project should be used inside an office so environment isn't hazardous in any mean.


texts: N-mosfet to disconnect voltage regulator causes wrong V_OUT

texts:
I think I've messed up again with the N-Mosfet.

The idea is to disconnect the stepup regulator (U3 = LTC3525D) when the output of the op-amp (U2 = MAX9015) is low, and viceversa.

The problem is that the LTC3525 V_OUT is a strange 0.98V instead of 3.3V, when the V_IN is 2.2V and the op-amp out is high.
Between GND pin 2 of LTC3525 and GND of C4 (supercap) I measure 1.9V.

I am not sure if I connected the N-mosfet properly.
Do you see any mistake from the circuit in the picture?

Thank you very much for your help.

Sincerely


texts: Can a digital input having internal pull up resistor drive a load?

texts:
simulate this circuit – Schematic created using CircuitLab

I am working on MC56F8006 DSC . On power up or reset the default state of all GPIOs is inputs with internal pullups enabled. I am driving IGBT three phase bridge via PWM chanel GPIO-A0-A5. But if i power up DSC  IGBT driver will gate logic '1' from my Port-A and all IGBTs will turn ON making a short circuit across supply.

So my doubt is even if my GPIO is configured as input and that input is connected to NOT gate output of NOT gate is connected to cathode of LED and anode is tied up to 3.3V. So on power up that LED will glow?
If yes then on power up all igbts will turn on and short circuit will take place


texts: How can a ground loop cause a OSD to flicker / dissapear without affecting the rest of the video?

texts:
I don't know if it is best to ask this question here, or on drones.stackexchange.com, but I think that I am more likely to get a good answer here even if i might have to provide a bit more background.
I experienced this problem on a FPV drone. The drone has an NTSC/PAL camera whose video feed goes into a flight controller (FC) with a built in chip that overlays some important information. The video feed then goes into a video transmitter (VTX) that transmits the signal to the pilot on the ground.
The problem I had was that I powered the camera and VTX directly from the battery via a 5V regulator, while the FC was powered via an electronic speed controller which I assume affects the ground in some way before it reaches the FC.
The problem I had was exactly the same one as this question, and the answer also helped me. I know the problem is caused by a lack of common ground, however what I still don't understand is how a lack of common ground between the FC, camera and VTX can cause the OSD to flicker or even disappear while the video feed from the camera is perfectly fine. I would have thought that the whole video feed would become affected if there was a ground loop.


texts: Is it a practical technique to add a dedicated flash/RAM IC to increase a microcontroller's memory to avoid writing to an SD card?

texts:
I'm working with an Atmega328P microcontroller. This microcontroller will be generating data and will be storing that data onto an SD card. My project will also be battery powered. My research has shown that writing to an SD card is relatively expensive. Especially due to the fact that I'm using a 225mAH battery with a 120mA limited power regulator.

I've read that a common method for saving power is to buffer write commands into a single write. This seems relatively straightforward.

However, I'm now running into the problem that the Atmega328p only has 2kB of RAM. Thus, I really have limited buffer space.

So my question: would it be a viable technique to purchase a dedicated flash memory / RAM IC to increase buffer space? I'm curious about the practicality of this and how difficult it would be to implement.

Any thoughts? I know the obvious answer would be to purchase a microcontroller with more RAM, but I'm trying to stick with this microcontroller such that the project is Arduino language compatible.


texts: Why is NAND flash slower than NOR when it comes to reading?

texts: I have read on several places that NOR flash have lower latency when it comes to reading compared to NAND version but I don't understand is this architectural consequence or due to, often different, interfaces.


texts: Is this circuit and values of component correct?

texts:
I have traced out the PCB of a DC-DC converter (given.)

Is it correct (both circuit and values?)

I need constant 5V output.  What modifications must I make?

updated

In the datasheet of the LM2596  the diode used is schottky diode 1N582, but the DC-DC converter PCB uses a SS34.  Is that OK?


texts: Why Gate voltage must be higher than source voltage in N-MOSFET as High side switch?

texts:
In many circuit, like buck converters, MOSFET used in high side for switching, I've came across the term that Gate voltage with respect to ground must be greater than source voltage by +8V.

For example,
Vs = 60V
Vg = 68V (should be).

We generally implement a bootstrap circuit to achieve this higher voltage.

But, ideally as datasheet of any general MOSFET says, Gate voltage should be VGS = 20V. If I consider this MOSFET.

So, if VGS should be 20V then how MOSFET will work on Vg = 65V?

NOTE: Consider Gate is triggered at 13.5V PWM according to this datasheet.


texts: Arduino/Atmega with TIP120/121/122 transistors: base current question

texts:
I am learning about transistors, and can't seem to find the answer to a few questions which are stumping me. I will be referring to the TIP120/121/122 Darlington Transistor.

As I understand transistors so far, I need to apply a current from
my Arduino to the base of the transistor in order to allow current
to flow between the collector and emitter. What I don't understand
is how a microcontroller is used with the transistor in so many
projects and tutorials. The arduino and other atmegas give ~50mA out
of their pins, but according to the data sheet, the TIP needs 120mA
at the base. On top of that, a resistor is used between the pin of
the microcontroller and base of the transistor, which I would assume
reduces the current going into the base even more. So what's going
on here?
I want to experiment with these transistors, but noticed that the
TIP120 and 121 are more expensive than the TIP122. I am curious to
know why this is, because as per the data sheet, it seems the TIP122
can handle higher voltages (which I suppose is a good thing), with
all other things pretty much the same. So is there a scientific
reason for this price discrepancy and is there any reason I should
select the TIP120 over the 122 to use for my microcontroller
projects?


texts: Multiple temperature sensors - One output

texts:
I'm a plumber and I'm not able to find a commercial product that fits my needs, so I'm wondering if it would be feasible to build it from scratch... I'm familiar with basic understanding of electronic circuits, but cannot find an answer by myself.

I'm designing a heating system powered by a fireplace, and a big hot water tank to store heat for use when fire is off. Heat will be usable in the 55-80°C range, and the water is expected to be fairly well stratified, so temperature sensors placed at different heights would give a good figure of the energy content of the tank.

When fire is on, boiler will push water at 80°C into the top, so the tank will start to "fill up" from top to bottom. When water at this temperature reaches, let's say bottom quarter, the operator needs to be warned that the tank is "full" to stop feeding the fire. If water at 80° reaches the bottom, water out of the boiler will be at a higher temperature, which is undesirable.

On the other hand, when the fire is off, the heating circuit will push water at about 60°C into the bottom. When all water in the tank is at this temperature, it is "half full", and it will take this water again down to about 45°, at that time the tank is "empty". The operator should know the amount of usable energy in the tank with a look to plan lighting the fire again.

So, I need a way of displaying the measurements of the sensors in an easy to read form, accuracy is not important. I was thinking about converting it to a voltage that could be shown by an analog voltmeter with a custom drawn scale, but I have no clue how to sum up the results of the multiple sensors. Other suggestions are also appreciated. The system just has to be easy to implement, reliable and easy to read.


texts:
I want to build a voltage reference based on LM4040 (A series 0.1%), the output voltage is switchable with a selector switch:

simulate this circuit – Schematic created using CircuitLab

Assuming that the op amp have input offset of ~100 uV and resistors are 1% but hand picked to match the values;

How can I calculate the output error?
Which parameters affects the accuracy (only resistors error,op amp input offset voltage and temperature)?
Is there any other downside to this configuration other than lowering the accuracy?


texts: Is there any restriction in the choice of Ethernet PHY, depending on the TCP/IP stack?

texts:
I am new on the forum and am currently working on a project to design an ethernet electronic board. I will have a microcontroller 32-bit with an external PHY.
I wanted to know : depending on the TCP/IP stack I will choose, will there be any restriction on the external ethernet PHY or all the PHY are usable?
The thing is I need to choose the Ethernet PHY before the microcontroller and then I don't know if I will use uIP or Contiki or microchip stack or any other.


texts: Ltspice Full-wave rectified signal issue

texts: I have done a simple simulation with Ltspice with a bridge diode rectifier as shown with the picture below. However I have observed an issue in the shape of the output voltage and not the current output. Has anyone get same issue as me ? I thank you to tell me how can I resolve such issue.


texts: Sorry for my previous vague question. I am setting up a heat generator map for my thermal analysis and I was given that one of the ICs will be dissapating 5.2W. Does this mean that 5.2W of heat will be created into my enclosure? This is my first time setting up a thermal simulation for a pcb so bear with me. In my previous experience if 5.2W was put into something the amount of heat generated was based on the effiency of the item.


texts:
I have a dozen of sources of digital signal, 16-bit signed words. I have implemented very simple mixer where all sample values are summed, and then shifted right to prevent overload. Unfortunately simplicity goes at a cost - if only one (or few) channels are coming into mixer at their full scale, their volume is at least 3 dB down; increasing number of input channels increases attenuation even more.

Is there any advanced (balanced?) way to have digital signal mixed?


texts: Inverted 555 Monostable Timer With a Sustained Input

texts:
I am using a 555 Timer to control a motor for a science team project. I have to make a Rube Goldberg-like machine and I am not allowed to use Arduinos or Raspberry Pis. However I need to trigger the motor and then have it turn off by itself, after a set amount of time. I have been trying to do this with a 555 timer and have had a little luck, but not a ton. So any help in figuring this out (maybe a circuit diagram) would be appreciated.

I want to motor to trigger for about 8 seconds (I know how to do the resistance calculations and figure out the size to use, so this can be worked out later) when I close a circuit/create a high signal. To do this, I have been using an inverted 555 set up, which lets me use a high voltage as a trigger. However, I cannot figure out how to either make this behave as a pulse, maybe using a capacitor, or to configure the 555 timer to use the start of a high signal as the start of the timer.

Really, I just want to know if there is a way to make a sustained signal behave as a pulse for a 555 timer, possible with capacitors, and how to do it.

Thanks!

Edit:

Specifications:
Just a small motor DC circuit motor (I forget what the specifications are, but easily battery powered), 4 AA batteries in series. Other than that, it's your standard series circuit. I can use some small microcontrollers or ICs.


texts: Using Mosfet with seperate Logic Converter and Arduino

texts:
I am trying to use an IRLB3034 with an Arduino even though it is not a logic level MOSFET. I am planning on using an LM2937 12v regulator like the schematic below:

The connection going off the page goes to an Arduino digital pin pulled down with a 10k resistor. I assumed this would work but wanted to check. As a side note, if anyone could recommend a similar MOSFET that could handle 200a and 40v (in TH) that would be great. (Only if such thing excists or is readily available)

EDIT:
I have not made it clear what I am planning on using this for so I will now. It is to drive an airsoft motor and I want to use the LM2937 because I didn't think I could turn the mosfet on and off with the arduinos 5v - because the IRLB3034 isn't a logic level mosfet - so that is the reason I added the 12v regulator.

EDIT (Sorry for the previous incorrect name)

EDIT:
Unfortunately, I have made a mistake, the current is not 200 amps, it is infact 30-40 amps. I don't know how I made this mistake but I think it will be helpful for people trying to follow along. I am currently trying to use busbars/6awg copper wire to carry the high-ish current around. (Only 40 amps now though)

EDIT:
This question is different because it is asking how to convert 5v to 12v to run a mosfet rather then how to use a mosfet with an arduino in the best way like the other post. The accepted answer on this post also answers the other question though.


texts:
I have a question about work-group scheduling on multiple CUs in Intel FPGA. As work-groups are assigned to available CUs, when is a CU considered available? Is it when the last work-item of the previous work-group has abandoned the pipeline or when it is at its second stage (so every stage of the pipeline is occupied by the previous work-group except the first one)? This decision is taken by the hardware scheduler, but I haven't found any public documentation explaining any of this.

Edit: I'm talking about the automatic process that takes place when using Intel OpenCL SDK for FPGA, not a custom design with HDL.


texts: Intuitive way to see pole/zero directly from schematic

texts:
The image below is the electrical configuration and the transfer function of a type II compensator using OTA.

By looking at the transfer function, we can easily see that the circuit has two poles (one pole is at origin) and one zero.

However, I am wondering if there is an intuitive way to see the poles, zero directly from the schematic. In other words, why do these pole and zero exist?

I think we can base on poles/zeroes definition to get some insight.

  Poles and Zeros of a transfer function are the frequencies for which
  the value of the denominator and numerator of transfer function
  becomes zero respectively.

From this definition, I can see why there is an origin pole here. At DC (zero frequency), two capacitors C1 and C3 act as open circuit so the equivalent impedance of the two parallel branches is infinity. This leads to infinite output voltage.

Is there an intuitive way to see the other poles and zero here?
(from poles/zeroes definition or something else)


texts: Quartus II: Suppress warnings by Verilog module

texts:
In my FPGA project I use the Quartus II PCIe megafunction. The number of warning messages this Altera library module produces baffles me.

Is there a way to have Quartus II suppress all the warnings messages generated from within the PCIe megafunction top-level module?


texts: BJT DC Leakage (ICES) dependency with Vce

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I am interested in BJT transistor leakage dependency on Vce.

Specifically: parameter ICES (Collector-Emitter Cutoff Leakage, that is, collector/emitter leakage with base shorted to emitter) is generally specified at some large Vce DC bias (e.g. 50V), and I am wondering whether there is an accepted way to extrapolate the specification limits to a lower bias?

Can anyone point me to a published discussion of ICES dependency on Vce? Or BJT performance in the cutoff region in general?

Most references I have seen tend to ignore cutoff leakage characteristics and focus on forward-active and saturation.


texts: STM32F103C8 resets after a couple of hours

texts:
I have an STM32F103C8 board and my program is switching the GPIOB1 with frequency of 500 kHz.
At first, microcontroller runs the program perfectly, but the main problem is that MCU resets after a couple of hours and stays at reset mode until I disconnect the board from the power supply. If I power the board immediately after disconnecting, MCU will not work but if I power the board a few minutes later, the MCU works properly just for a couple of hours and after that, the same problem is repeated.
I already faced another problem that this issue was happening after 15 minutes. I added a 10 uF capacitor to the VDD3 pin and now, this problem (going to reset mode) happens after about 5 or 6 hours.
Do you have any suggestions about hardware or program?
What should I do with the reset pin? (Currently, I'm pulling up nRST pin with a 10 kOhm resistor.)
Can this happen because of the wrong power-up sequence on VDD, VDDA, and nRST pins?
Is this similar to a clock malfunction?

Figure 1: Schematic (click image for larger size)

Figure 2: PCB layout (click image for larger size)
(This is the original Google Drive link for the images.)


texts: A tidy and safe way to bundle wires and connect them to terminal posts?

texts:
I am building a power supply using an ATX powersupply. There are several wires for each: red for +5V, Yellow for +12V ans so on. The instructions I've seen instruct you to bundle the same colored wires and twist their ends together and then solder them to a binding posts.

I really don't want to do it this way because it is untidy and looks unprofessional. I was hoping to bring all the like wires together and connecting them to a terminal strip and from that strip have a heavier gauge wire that connects to their respective binding post.

Is there anything wrong with doing it this way? Is thereba best practices for auch wiring? Thanks.


texts: ADC is giving fault codes when I touch thermistor attached to it

texts:
I am working on writing a control program for my pellet smoker. I am having an issue with the meat thermometer that came with the smoker.
I have a MAXIM 31865 ADC that is connected to a Raspberry Pi. Attached to the ADC I have a thermistor that is used as a meat thermometer. This thermistor (unknown type/manufacturer) is inside of a metal sheath and has 3 wires that were previously connected to the smoker. There are 2 internal wires that connect to the thermistor and then the metal cable sheath itself was also connected to the original control board on the smoker.
I only have the 2 internal wires that actually connect to the thermistor connected to my ADC. The third wire (thermistor sheath/cable sheath) is not connected to anything. If the thermometer is sitting on the grill or on my desk I am able to get an accurate measurement from the ADC. However, if I pick up the thermistor or touch it more than just lightly brushing it I instantly get an overvoltage/undervoltage error on the MAX31865 ADC that doesn't go away until I put down the probe.
I assume I need to ground that third wire by clipping it to a metal surface on the grill or back through the power supply, but I am trying to understand what is happening here. I tried measuring for a voltage drop/increase while touching the thermometer and I couldn't see anything happening when measuring with a multimeter, and I don't understand why it would be a problem anyway.
(I am not an electrical engineer, just a hobbyist.)
Image of how it is wired I put together before I started.
The black triangles go to a strip of copper on the solderable breadboard. The empty triangles go to a different strip of copper, and then the grounds are merged to a single ground pin on the Raspberry Pi. The small black boxes are ferrite beads. I pretty much just followed exactly what the Max31865 docs said, but since I had a single power source I split it with a ferrite bead between the source and the analog voltage input.
I used a 350k Ohm reference resistor because the thermistor has a resistance of around 300k Ohms at 0 degrees celsius.


texts: Analog circuit to turn on LED for 10 seconds just after power is applied?

texts:
Is it possible to use an analog circuit to turn an LED on for 10 seconds after 5v power is applied, then turn it off until power is removed and reapplied? This would be useful in small battery-powered designs; if a "power status" LED turns on for a short time after you've applied power, you are sure that the circuit is working...no need to constantly keep it on and drain more of the battery.

So, this is what the process would look like:

Plug power in
LED turns on
10 second delay
LED turns off
infinite delay

Is there a simple analog circuit that can do this?

Update: Thanks for the help on this one. I agree that a single big cap and resistor solution would be too expensive/big to be practical. I think I'll use a MOSFET or some transistor array using Olin Lanthrop's schematic below.